JP2012104290A - Positive electrode active material for nonaqueous electrolyte battery, positive electrode for nonaqueous electrolyte battery, and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve stable charge/discharge cycle performance by using a positive electrode active material using an inexpensive and resource-rich element in a nonaqueous electrolyte battery.SOLUTION: In a nonaqueous electrolyte battery, a positive electrode active material including secondary particles and having an N-methyl-2-pyrrolidone oil absorption of 25 g/100 g or more and 35 g/100 g or less is used. The secondary particles comprises primary particles of a lithium phosphoric acid compound, and the primary particles are joined via an electronic conductive material with each other and each of the primary particles has a surface at least partly covered with the electronic conductive material, the lithium phosphoric acid compound having an average composition represented by (chemical formula 1) and having an olivine structure. (Chemical formula 1): LiM1M2PO(where, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn) and magnesium (Mg), M2 represents at least one selected from among elements belonging to Groups 2 to 15 excluding M1, and x and s represent a value within regions of 0≤x≤1.2 and 0≤s≤1.0, respectively).

Description

  The present invention relates to a positive electrode active material and a nonaqueous electrolyte secondary battery, and more particularly to a positive electrode active material for a nonaqueous electrolyte battery, a positive electrode for a nonaqueous electrolyte battery, and a nonaqueous electrolyte battery that are excellent in high capacity and high output characteristics.

  In recent years, with the increase in functionality and performance of portable electronic devices, the power consumption of electronic devices is increasing, and a higher capacity is required for batteries serving as power sources. From the viewpoint of economy and reduction in size and weight of electronic devices, there is a strong demand for secondary batteries with high energy density. As typical secondary batteries, lead storage batteries, alkaline storage batteries, lithium ion secondary batteries, and the like are known. Among the secondary batteries as described above, the lithium ion secondary battery has advantages such as high output and high energy density. The lithium ion secondary battery includes a positive electrode and a negative electrode capable of reversibly inserting and removing lithium ions, and a nonaqueous electrolyte solution or a gel or solid nonaqueous electrolyte.

In lithium ion secondary batteries, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), or lithium-containing transition metal compounds are used as positive electrode active materials capable of intercalating and deintercalating lithium ions. A complex oxide partially substituted with an element is used. Further, lithium manganate (LiMn ₂ O ₄ ) having a spinel structure is being developed as an inexpensive material having a high energy density and a high voltage. On the other hand, an olivine compound represented by lithium iron phosphate (LiFePO ₄ ) has attracted attention as a positive electrode active material using cheap and resource-rich iron. In addition, the olivine compound has a strong bond between phosphorus and oxygen, does not release oxygen even at high temperatures, and has excellent thermal stability, so it is used for power tools, hybrid vehicles, electric vehicles, power leveling, power The demand is expected in the future in various fields such as storage and robot.

However, these positive electrode active materials have various problems. For example, lithium cobaltate (LiCoO ₂ ) has been pointed out to be problematic in that the cobalt (Co) itself is toxic, in addition to the problem that the cobalt (Co) reserve is small and expensive. Moreover, although lithium nickelate (LiNiO ₂ ) has excellent charge / discharge characteristics, it is not cheap, and there are many problems such as stability at high temperatures and a sudden deterioration in characteristics due to composition deviation from a constant ratio. Furthermore, it has been pointed out that lithium manganate (LiMn ₂ O ₄ ) and manganese (Mn) are eluted at a high temperature, cycle deterioration due to Yarn-Teller strain of Mn ³⁺ , and the like.

On the other hand, although lithium iron phosphate (LiFePO ₄ ) has an excellent point that there is no problem of toxicity to the human body and the environment, the conductivity of lithium iron phosphate (LiFePO ₄ ) itself is low, There is a problem that the insertion / elimination reaction is slow. For this reason, when it is set as a battery, high output is not obtained and mixing with a electrically conductive agent is examined.

To solve this shortcoming,
(1) Making primary particles in secondary particles of LiFePO ₄ into fine particles (Patent Document 1)
(2) To provide conductivity by controlling the pore diameter in secondary particles of LiFePO ₄ (Patent Document 2)
(3) Uniformly impart conductivity to the entire fine particles, that is, the positive electrode active material having a large outer surface area (Patent Documents 3 to 5)
Has been made, and
(4) Replacing part of LiFePO ₄ with a different element to improve conductivity (Patent Documents 6 to 8, Non-Patent Document 1)
(5) Increasing the packing density of the composite of carbon and LiFePO ₄ (Non-patent Document 2)
Has been reported and proposed.

  Regarding the above (1), for example, Patent Literature 1 discloses a hydrothermal synthesis method and a method for suppressing particle growth. As for (2), for example, Patent Document 2 defines an optimum ratio between the average particle diameter of primary particles constituting the secondary particles and the pore diameter of the secondary particles. As for (3), for example, as in Patent Document 3, there is a method of improving the conductivity by making conductive particles exist around the particles, or as in Patent Document 4 and Patent Document 5, carbon or carbon is used. A method of firing with a precursor is disclosed.

Furthermore, as a method of substituting a part of LiFePO ₄ (4) with a different element (M), many methods such as Patent Documents 6, 7 and 8 are disclosed.

JP 2003-45430 A JP 2009-152188 A JP 2001-110414 A JP 2003-292308 A JP 2003-292309 A JP 2001-307726 A JP 2001-307732 A JP 2001-85010 A

Electrochemistry vol. 71 no. 8 p. 717-722, 2003 R. Dahn, Journal of the Electrochemical Society, 149, A1184-A1189, 2002

However, when the positive electrode active material of the olivine compound is produced by the method of Patent Document 1, the production method is difficult, and a baking time is required for a long time in order to suppress particle growth, which is not suitable for a large amount of synthesis. On the other hand, LiFePO ₄ particles produced without suppressing particle growth are secondary particles in which primary particles are aggregated, and the secondary particles have many spaces (pores) surrounded by the primary particles that have grown. A porous body is formed. Therefore, the LiFePO ₄ particles that did not suppress particle growth have very poor conductivity. As a result, a large amount of a conductive agent such as acetylene black and a binder are required for electrode preparation. When a large amount of conductive agent and binder are added, not only the density of the active material in the electrode is lowered, but also a slurry of LiFePO ₄ particles cannot be formed at the time of electrode preparation, and the electrode is prepared by applying the slurry. Can not. Even if the electrode is forcibly produced, the electrode density is low, and the formed positive electrode active material layer is easy to peel off, and does not constitute a substantial electrode. With such a positive electrode active material, a battery having a high capacity, a high output, and a long life has not been obtained.

  In addition, with the method that defines only the pore diameter of the secondary particles as defined in Patent Document 2, it is impossible to synthesize optimal secondary particles with high accuracy and can be obtained by measuring pore distribution. It was found that defining the pore volume is still insufficient. Specifically, as shown in FIG. 1, the pore volume of the positive electrode active material, and the positive electrode current collector and the positive electrode active material layer in the positive electrode produced under the same conditions using the positive electrode active material of each pore volume The result showed that the relative value of the peel strength varies greatly. Moreover, it was found that the method for forming secondary particles is insufficient and it is difficult to reproduce this method. In addition, the pore distribution measurement using the mercury intrusion method not only requires time for measurement but also requires mercury and a porosimeter, which is not an easy measurement method.

Furthermore, many of the methods for improving the conductivity of the positive electrode active material using a material having conductivity such as carbon as described in Patent Documents 3 to 5 are merely mixed with a conductive agent. There is poor adhesion between LiFePO ₄ and a conductive material. Further, the conductive agent cannot be uniformly dispersed into the inside of the positive electrode active material particles. In addition, a method using a metal as a conductive agent has been devised. However, in this method, the specific gravity of the metal is heavy, so in order to give sufficient conductivity to LiFePO ₄ , the weight is higher than when carbon is used as the conductive agent. Must be added in large amounts. Therefore, light elemental carbon is generally most preferable as the conductive agent. From this point of view, as shown in Patent Document 4, LiFePO ₄ bonded to carbon and complexed is preferable. However, even in the method of Patent Document 4, it is necessary to reduce the primary particles of LiFePO ₄ in order to improve the output of the battery.

When a positive electrode active material in which a part of the transition metal is substituted with a different element as described in Patent Document 6 to Patent Document 8 is not used alone, there is no significant effect of improving conductivity, and a large amount is required at the time of electrode preparation. It is necessary to add a conductive agent. Further, no LiFe _x M _1-x PO ₄ carbon composite treated at a high temperature of 700 to 900 ° C. in an extremely reducing atmosphere in which carbon coexists has been proposed as a positive electrode active material.

Also, the (5), LiFePO ₄ in order to be porous, when complexed with a LiFePO ₄ and the carbon, the carbon is deposited to cover the LiFePO ₄ particles without penetration into the pores of the LiFePO ₄ Thus, contrary to the need stated in the above report, the composite of LiFePO ₄ and carbon has a low packing density. Also, when a carbon precursor is mixed with a raw material for producing LiFePO ₄ (hereinafter referred to as a LiFePO ₄ raw material) and baked, a large amount of volatile matter is generated from the raw material and the carbon precursor, and the generated LiFePO ₄ carbon composite is produced. The body is porous, the particle itself has a low bulk density, and the particle shape is not spherical. Therefore, the packing density of the composite obtained by mixing and firing the LiFePO ₄ raw material and the carbon precursor is much lower than that of the above composite in which LiFePO ₄ particles are coated and attached with carbon.

In addition to this, since the composite obtained by mixing and firing the LiFePO ₄ raw material and the carbon precursor is pulverized again after firing, the positive electrode active material particles coated with carbon are destroyed and LiFePO ₄ is destroyed. In addition, since the cross section is exposed and the particles become smaller, bridging occurs between the particles, the packing density is lowered, and the conductivity as the positive electrode active material is extremely lowered. Regarding the electrode life, generally, when a large amount of a conductive agent such as acetylene black is used, the produced electrode is easily peeled off. In addition, there is a problem that the surface area of the electrode increases, reacts with the electrolytic solution, the electrolytic solution is depleted, and the cycle performance deteriorates.

As described above, the conventional composite of LiFePO ₄ and carbon is porous, has a low packing density, and has a low conductivity. For this reason, a large amount of a conductive agent and a binder are required when producing an electrode. In addition, this conventional composite has a problem that a high-density electrode, that is, a battery having a high capacity, a high output, and a long life cannot be obtained. In addition, there has been no method for regulating slurry characteristics and peel strength using olivine-type lithium iron phosphate (LiFePO ₄ ) particles as described above. The powder characteristics of olivine-type lithium iron phosphate (LiFePO ₄ ) include pore volume, specific surface area, particle size distribution, crystallinity, etc., all of which are slurry of slurry using lithium iron phosphate (LiFePO ₄ ). It is insufficient as a method for defining characteristics and peel strength.

  Therefore, the present invention eliminates the above-mentioned problems, uses inexpensive and resource-rich elements, and realizes stable charge / discharge cycle performance, for a positive electrode active material for a non-aqueous electrolyte battery, and for a non-aqueous electrolyte battery An object is to provide a positive electrode and a non-aqueous electrolyte battery.

In order to solve the above-mentioned problem, the positive electrode active material for a non-aqueous electrolyte battery of the present application has an olivine structure whose average composition is represented by (Chemical Formula 1), in which at least a part of the surface is coated with an electronic conductive material. The primary particles of the lithium phosphate compound having secondary particles formed by bonding via an electronically conductive substance,
The N-methyl-2-pyrrolidone oil absorption is 25 g / 100 g or more and 35 g / 100 g.
(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. )

Moreover, the positive electrode for a nonaqueous electrolyte battery of the present application has a positive electrode active material layer formed on a positive electrode current collector,
The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder,
The positive electrode active material
Primary particles of a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1), the surface of which is at least partly coated with an electronic conductive material, are joined together via the electronic conductive material. Secondary particles comprising
The positive electrode active material has an N-methyl-2-pyrrolidone oil absorption of 25 g / 100 g or more and 35 g / 100 g.

Furthermore, the nonaqueous electrolyte battery of the present application includes a positive electrode, a negative electrode, and a nonaqueous electrolyte,
The positive electrode has a positive electrode active material layer formed on a positive electrode current collector,
The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder,
The positive electrode active material
Primary particles of a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1), the surface of which is at least partly coated with an electronic conductive material, are joined together via the electronic conductive material. Secondary particles comprising
The positive electrode active material has an N-methyl-2-pyrrolidone oil absorption of 25 g / 100 g or more and 35 g / 100 g.

  The above-mentioned “bonding” does not mean that the primary particles are merely aggregated secondary particles, but at least the secondary particles are 1 when the electrode is formed using this electrode material. It means that it is firmly connected to the extent that it behaves as one particle.

  In this invention, peeling between the positive electrode current collector and the positive electrode active material layer can be suppressed.

  According to the present invention, a positive electrode active material having a high discharge capacity is used, and a high binding property between the positive electrode active material layer and the positive electrode current collector when the charge / discharge cycle progresses is realized, thereby achieving a high battery capacity and a high capacity. Cycle characteristics can be obtained.

It is a graph which shows the relative value of the pore volume of a positive electrode active material, and the peeling strength with a positive electrode collector and a positive electrode active material layer. It is a graph which shows the relationship between the oil absorption amount of a layered lithium complex oxide, and peel strength relative value. It is a SEM image of the positive electrode active material of this invention. It is a graph which shows the relative value of the peeling strength with the NMP oil absorption amount of the positive electrode active material of this invention, and a positive electrode collector and a positive electrode active material layer. It is sectional drawing which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention. It is sectional drawing to which a part of winding electrode body in FIG. 1 was expanded. It is a disassembled perspective view which shows the structural example of the nonaqueous electrolyte battery by embodiment of this invention. It is sectional drawing along the II line of the winding electrode body in FIG. It is sectional drawing which shows the other structural example of the nonaqueous electrolyte battery by embodiment of this invention. It is a basic diagram which shows the other structural example of the nonaqueous electrolyte battery by embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. The description will be given in the following order.
1. 1st Embodiment (About the positive electrode active material of this invention)
2. Second Embodiment (Example Using Cylindrical Nonaqueous Electrolyte Battery)
3. Third Embodiment (Example Using Laminated Nonaqueous Electrolyte Battery)
4). Fourth embodiment (example using a laminate-type nonaqueous electrolyte battery)
5. Fifth embodiment (example using a square nonaqueous electrolyte battery)
6). Sixth embodiment (an example of a nonaqueous electrolyte battery using a laminated electrode body)
7). Other embodiments

1. First Embodiment A positive electrode active material according to a first embodiment of the present invention will be described. In the following embodiments, the average particle diameter indicates the median diameter (D50) unless otherwise specified.

(1-1) Configuration of positive electrode active material [configuration]
As the positive electrode active material of the present invention, a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1) is used.
(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. )

In (Chemical Formula 1), from the viewpoint of high discharge potential, abundant resources, safety, etc., M1 is manganese (Mn), iron (Fe), and M2 is magnesium (Mg). , Calcium (Ca), strontium (Sr), titanium (Ti), zinc (Zn), and aluminum (Al) are preferable. As the lithium phosphate compound having the olivine structure of (Chemical Formula 1), lithium iron phosphate (LiFePO ₄ ) is particularly preferable.

  The positive electrode active material is preferably a secondary particle formed by aggregating a plurality of primary particles of a lithium phosphate compound having an olivine structure whose surface is coated with an electronic conductive material. Of the primary particles constituting the secondary particles, the portion exposed to the outside is also preferably covered with an electron conductive substance. The electronic conductive material contained in the secondary particles is present on the surface of the primary particles of (Chemical Formula 1), and is simply a mixture of the primary particles of (Chemical Formula 1) and the electronic conductive material. to differ greatly. The electronic conductive material is preferably present uniformly in the secondary particles.

  Moreover, it is preferable that primary particles are joined through an electronically conductive substance. In this embodiment, the term “joined” does not mean that the primary particles are merely agglomerated secondary particles, but at least when the electrode is formed using this electrode material. It means that the particles are firmly bound to the extent that they behave as one particle. And in this secondary particle, it is preferable that an electronically conductive substance exists in a three-dimensional network between primary particles.

  As the electronic conductive material, carbon is most preferable from the viewpoint of chemical stability, safety and cost. In addition to carbon, metals such as gold (Au), platinum (Pt), silver (Ag), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir) and other precious metals are preferably used. It is done. The precursor of an electron conductive substance is an electron conductive substance when heated. The precursor of an electron conductive substance includes an organic compound, a metal salt, a metal alkoxide, a metal A complex or the like is preferably used.

  The reason why the lithium phosphate compound having an olivine structure is used as the positive electrode active material in the present invention is that there is a high correlation between the oil absorption of the lithium phosphate compound having an olivine structure and the peel strength. The amount of oil absorption is determined in relation to the primary particle diameter and the way the primary particles in the secondary particles are solidified (secondary particle diameter and pore diameter). The lithium phosphate compound having an olivine structure does not correlate with the peel strength in terms of specific surface area or average particle size. Obtainable.

On the other hand, the characteristics of the layered lithium composite oxide such as lithium cobaltate (LiCoO ₂ ) and the spinel type lithium composite oxide such as lithium manganate (LiMn ₂ O ₄ ) are more specific than the NMP oil absorption, the specific surface area, the average particle size, Since it is affected by various factors such as the chemical composition and the amount and type of the conductive agent, it cannot be simply defined only by the NMP oil absorption. It is possible to obtain a positive electrode active material having a high peel strength by using the NMP oil absorption amount for positive electrode active materials other than lithium transition metal oxide particles having an olivine type crystal structure. However, for example, when the specific surface area is reduced with respect to lithium cobaltate (LiCoO ₂ ) having a layered structure to reduce the oil absorption, charge / discharge efficiency, load characteristics, and the like are reduced.

Moreover, it is also possible to synthesize a positive electrode active material having high peel strength by using the NMP oil absorption amount for a layered compound that generates secondary particles or a spinel compound that is converted into secondary particles. However, the electric power of the layered lithium composite oxide such as lithium cobaltate (LiCoO ₂ ) and the lithium composite oxide having a spinel structure such as lithium manganate (LiMn ₂ O ₄ ) is about 10 ⁻² near room temperature. [Scm ⁻¹ ], 10 ⁻³ [Scm ⁻¹ ], which is much larger than lithium iron phosphate (LiFePO ₄ ). As described above, since lithium iron phosphate (LiFePO ₄ ) is almost an insulator, it cannot be effectively used as a positive electrode active material of a lithium ion battery unless it is finely divided and coated with a conductive agent. Thus, the properties of the layered and spinel lithium composite oxide and the olivine-type lithium composite oxide are greatly different, and it is difficult to define the NMP oil absorption as in the case of the olivine-type lithium composite oxide.

FIG. 2 shows the relationship between the NMP oil absorption amount of lithium cobaltate (LiCoO ₂ ) powder having a layered structure and the peel strength between the positive electrode current collector and the positive electrode active material layer in the positive electrode prepared using lithium cobaltate. It is a graph. As shown in FIG. 2, in the positive electrode active material having a layered structure, there is no correlation between NMP oil absorption and peel strength between the positive electrode active material layer and the positive electrode current collector. For this reason, the regulation of the NMP oil absorption amount with respect to the positive electrode active material can be correlated with the peel strength only when applied to the olivine type lithium composite oxide.

  FIG. 3 is an SEM (Scanning Electron Microscope) image of the positive electrode active material of this embodiment, in which a plurality of primary particles of a lithium phosphate compound having an olivine structure represented by (Chemical Formula 1) are assembled. The plurality of primary particles are joined to each other through an electron conductive substance, and the overall shape is a secondary particle such as a spherical shape.

  Here, the average particle diameter of the primary particles of the positive electrode active material is preferably 0.001 μm to 1 μm, and more preferably 0.01 μm to 0.3 μm. If the average particle size of the primary particles is smaller than 0.001 μm, the crystal structure of the positive electrode active material may be destroyed due to the volume change due to charge / discharge. On the other hand, if the average particle size of the primary particles is larger than 1 μm, the primary particles do not form secondary particles densely, and therefore, secondary particles containing many voids are formed. For this reason, the binder is incorporated into the secondary particles of the positive electrode active material, and the peel strength between the positive electrode active material layer and the positive electrode current collector tends to decrease, and the conductivity between the primary particles tends to decrease. The amount of binder used is increased in order to achieve the required peel strength between the positive electrode active material layer and the positive electrode current collector, and the amount of positive electrode active material relative to the entire electrode is reduced. Efficiency). Furthermore, since the olivine-type positive electrode active material itself originally has low electron conductivity, the amount of electrons supplied to the inside of the particles is insufficient, and the utilization efficiency is lowered. As the load characteristic of the battery deteriorates, the cycle characteristic also deteriorates as a result.

  Moreover, it is preferable that the average particle diameter of a secondary particle is 0.01 micrometer or more and 20 micrometers or less. If the average particle size of the secondary particles is smaller than 0.01 μm, a large amount of binder is required to form the positive electrode active material layer, and as a result, the ratio of the positive electrode active material in the positive electrode active material layer is decreased. End up. Further, when the average particle diameter of the secondary particles is larger than 20 μm, voids are likely to be generated in the positive electrode active material layer.

  Furthermore, the shape of the secondary particles is preferably spherical. This is because the spherical shape facilitates the closest packing, the amount of the positive electrode active material per unit volume increases, and the battery volume can be reduced even with the same capacity.

  Further, the content of the electronic conductive material contained in the secondary particles is preferably 0.1% by weight or more and 10% by weight or less. If the content of the electronic conductive material is less than 0.1% by weight, the electronic conductivity may not be sufficiently exhibited. In addition, if the content of the electronic conductive material is more than 10% by weight, the electronic conductive material is contained in an amount more than necessary to obtain the necessary conductivity, and the weight and volume density of the positive electrode active material in the particles are reduced. is there.

[Oil absorption amount of positive electrode active material]
The secondary particles of the positive electrode active material of the present invention have an N-methyl-2-pyrrolidone (NMP) oil absorption of 25 g / 100 g or more and 35 g / 100 g or less. Thereby, the peel strength between the positive electrode active material layer and the positive electrode current collector can be improved.

  Here, the NMP oil absorption is a value calculated by the following operation and conforms to JIS K5101.

(I) The appropriate sample amount shown in Table 1 below is measured from the sample according to the expected oil absorption.
(Ii) The measured sample (1-5 g) is taken at the center of the burette stand, and N-methyl-2-pyrrolidone is gradually dropped from the burette 4 or 5 drops at a time into the center of the sample. Knead the whole thing thoroughly with a spatula each time.
(Iii) The dropping and kneading of N-methyl-2-pyrrolidone on the sample is repeated, and after the whole becomes a hard putty, N-methyl-2-pyrrolidone is dropped and kneaded for each drop. The end point is when the last drop is ready to be spirally wound with the sample kneaded with a spatula. However, if the sample cannot be spirally wound, the end point is the point immediately before the sample kneaded with one drop of N-methyl-2-pyrrolidone suddenly softens.
(IV) Read the amount of N-methyl-2-pyrrolidone dropped when the end point is reached. Specifically, the dripping amount is read from the difference between the remaining amount of N-methyl-2-pyrrolidone in the burette and the amount of N-methyl-2-pyrrolidone initially taken in the burette.
(V) The NMP oil absorption is calculated from the following equation (1). The NMP oil absorption is indicated by the oil absorption per 100 g of the sample.
Oil absorption [g / 100 g] = (N-methyl-2-pyrrolidone (NMP) density [g / ml] × NMP drop amount [ml] / sample amount [g]) × 100 (1)

  When the NMP oil absorption is 25 g / 100 g or less, the viscosity of the positive electrode mixture slurry is too low when adjusting the positive electrode mixture slurry with the same solid content. Therefore, when the positive electrode mixture slurry is applied to the positive electrode current collector, Liquid splashing or dripping occurs. Further, when the NMP oil absorption amount is 35 g / 100 g or more, the viscosity tends to increase, so that application unevenness, perforation, etc. occur when the positive electrode mixture slurry is applied to the positive electrode current collector. If the viscosity is further increased, the positive electrode mixture slurry may not be applied.

  Moreover, since binder particle | grains will be taken in in the positive electrode active material secondary particle when NMP oil absorption amount is high, the peeling strength of an electrode will fall. When using a positive electrode active material having a high NMP oil absorption amount, the binder necessary for bonding the positive electrode active material layer and the positive electrode current collector is insufficient unless the binder content is increased. The active material layer peels off. Increasing the binder content results in a decrease in electrode capacity. Furthermore, since the conductive agent is also taken into the positive electrode active material secondary particles and extra voids are formed between the primary particles in the positive electrode active material, the load characteristics of the battery are deteriorated. As the load characteristic of the battery deteriorates, the cycle characteristic also deteriorates as a result.

As described above, the NMP oil absorption amount of the positive electrode active material is very sensitive to load characteristics and cycle characteristics. The electronic conductivity of lithium iron phosphate (LiFePO ₄ ) is 10 ⁻⁸ to 10 ⁻¹⁰ near room temperature. ^-9 [Scm ^-1 ], which is almost an insulator. If lithium iron phosphate (LiFePO ₄ ) is effectively finely divided and not coated with a conductive agent, it cannot be used as a positive electrode active material for a lithium ion battery.

  Moreover, as shown in FIG. 4, when it prescribes | regulates by NMP oil absorption, since the correlation with peeling strength is high, it is preferable.

(1-2) Method for Producing Positive Electrode Active Material Hereinafter, a method for producing a positive electrode active material will be described.

(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 is at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. )

  The lithium phosphate compound having the olivine structure represented by (Chemical Formula 1) described above is obtained by mixing a lithium (Li) source, an M1 source, an M2 source and, if necessary, a phosphorus (P) source. It is obtained by spraying and heating a solution or suspension containing a conductive material or a precursor of an electronically conductive material.

As the lithium (Li) source, for example, lithium salts such as lithium chloride (LiCl), lithium acetate (LiCH ₃ COO), lithium hydroxide (LiOH), and lithium carbonate (Li ₂ CO ₃ ) can be used. When iron (Fe) is used as M1, for example, iron (II) chloride (FeCl ₂ ), iron bromide (II) (FeBr ₂ ), iron sulfate (III) (Fe ₂ (SO ₄ ) ₃ ) and iron (Fe) salts such as iron (II) acetate (Fe (CH ₃ COO) ₂ ) can be used. Further, as a manganese (Mn) source, a cobalt (Co) source, a nickel (Ni) source, etc., for example, manganese chloride (II) (MnCl ₂ ), manganese sulfate (III) (Mn ₂ (SO ₄ ) ₃ ), A salt such as manganese acetate (II) (Mn (CH ₃ COO) ₂ ) or nickel chloride (II) (NiCl ₂ ) can be used. As the aluminum (Al) source, for example, an aluminum salt such as aluminum chloride (AlCl ₃ ) can be used. Examples of the phosphorus (P) source include phosphoric acid (H ₃ PO ₄ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ). Can be used.

First, a lithium (Li) source, an M1 source, an M2 source and a phosphorus (P) source as necessary were dissolved or dispersed in a solvent to obtain a uniform solution or suspension. As the solvent, for example, water, alcohols, ketones and the like can be used, but water is preferable from the viewpoint of ease of use and safety. The concentration of the raw material component in this solution or suspension is not particularly limited as long as it is a concentration at which the solution or suspension can be sprayed. % By weight is preferred. Subsequently, together with the solution or suspension, ceramic beads such as stainless steel (SUS) metal or zirconia (ZrO ₂ ) are put into a stirring pot, and stirring with strong friction and impact is performed, whereby the raw material components and Grind and mix with solvent.

  The pulverization and mixing time of the raw material component and the solvent may be set as appropriate depending on the size of the stirring device and the stirring conditions. However, in order to reduce the above-mentioned NMP oil absorption amount and sufficiently extract the electrode and cell characteristics. For this, it is better to lengthen the time for pulverization and mixing. Whether the raw material components are sufficiently pulverized can be confirmed by particle size distribution measurement.

  In the present invention, the average particle size of the raw material components in the solution or suspension after the pulverization and mixing treatment is preferably 0.001 μm to 1 μm, and more preferably 0.01 μm to 0.3 μm. Thereby, primary particles of a lithium phosphate compound having the above-described average particle diameter and having an olivine structure represented by (Chemical Formula 1) can be formed. Here, the particle size distribution is preferably more uniform, and the raw material component preferably has a smaller particle size. Moreover, it is preferable that the particle diameter of the droplets at the time of spraying the solution or suspension is 0.05 μm or more and 500 μm or less.

Although the heating temperature at the time of spraying varies depending on the raw material used, it is preferably 500 ° C or higher and 1000 ° C or lower. When the heating temperature is lower than 500 ° C., the decomposition and reaction of each compound of the raw material component does not proceed sufficiently, the crystallinity becomes low, and it may become amorphous. Moreover, when heating temperature is higher than 1000 degreeC, there exists a possibility that a product may melt | dissolve and vitrify. As the atmosphere at the time of spraying and heating, particularly when M1 is iron (Fe), an inert atmosphere such as nitrogen (N ₂ ) or argon (Ar) is preferable, and hydrogen ( A reducing atmosphere containing a reducing gas such as H ₂ ) is preferable.

  In the method for producing a positive electrode active material in the first embodiment, a lithium (Li) source, an M1 source, an M2 source and a phosphorus (P) source as necessary, and an electron conductive material or an electron conductive material precursor In the state where each raw material component is uniformly dispersed in a solution or suspension, it is sprayed as fine droplets and heated. As a result, secondary particles are formed by interposing an electron conductive substance between primary particles of a lithium phosphate compound having an olivine structure represented by (Chemical Formula 1). At this time, the electron conductive material or the precursor of the electron conductive material that has been uniformly dispersed in the solution or suspension is also uniformly dispersed in the droplets. For this reason, when the secondary particles are generated, the electron conductive substance is taken in uniformly in the secondary particles, and secondary particles in which the electron conductive substance is interposed between the primary particles are obtained. Further, the primary particles are joined to each other through the electronic conductive material, the individual primary particles are covered with the electronic conductive material, and the outside of the secondary particles are also covered with the electronic conductive material.

<Effect>
By using the above olivine-type positive electrode active material as a positive electrode material of a lithium ion battery, the positive electrode active material layer and the positive electrode current collector are bound with high electrode peel strength. For this reason, the obtained lithium ion battery has a high discharge capacity, a stable charge / discharge cycle performance even when the charge / discharge cycle proceeds, and a high filling property, a high output, and the like.

2. Second Embodiment In the second embodiment, a nonaqueous electrolyte battery using the positive electrode active material of the first embodiment will be described.

(2-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 5 shows a cross-sectional structure of a nonaqueous electrolyte battery according to the second embodiment of the present invention. This battery is, for example, a lithium ion secondary battery.

  As shown in FIG. 5, this nonaqueous electrolyte battery is a so-called cylindrical type, and a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are interposed in a substantially hollow cylindrical battery can 11 via a separator 23. The wound electrode body 20 is wound. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11.

  The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 20 is wound around a center pin 24, for example. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel (Ni) or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 6 shows an enlarged part of the spirally wound electrode body 20 shown in FIG.

[Positive electrode]
The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on both surfaces of the positive electrode current collector 21A. In addition, you may make it have the area | region where the positive electrode active material layer 21B exists only in the single side | surface of 21 A of positive electrode collectors. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum (Al) foil.

  The positive electrode active material layer 21B includes, for example, a positive electrode active material, a conductive agent such as fibrous carbon or carbon black, and a binder such as polyvinylidene fluoride (PVdF). As the positive electrode active material, the positive electrode active material of the first embodiment is used.

  As the conductive agent contained in the positive electrode active material layer, a carbon material is preferable, and fibrous carbon is particularly preferable. Since fibrous carbon has a longer major axis than carbon materials having a substantially spherical shape, when used as a conductive agent, the number of contacts between conductive agents should be reduced compared to the case of using a substantially spherical carbon material. Can do. Since the conductive agents are connected to each other by the binder, the amount of the binder in the conductive path is reduced by reducing the number of contacts, and an increase in resistance can be suppressed. For this reason, it becomes possible to improve the electroconductivity in the thickness direction of a positive electrode active material layer by using fibrous carbon.

  As the fibrous carbon, for example, a so-called vapor grown carbon fiber formed by a vapor phase method can be used. The vapor grown carbon fiber can be produced by, for example, a method in which an organic compound vaporized with iron serving as a catalyst is blown into a high temperature atmosphere. As the vapor grown carbon fiber, any of the as-produced carbon fiber, the one heat-treated at about 800 to 1500 ° C., and the one graphitized at about 2000 to 3000 ° C. can be used. This is preferable because the crystallinity of carbon is advanced and it has high conductivity and high withstand voltage characteristics.

  The fibrous carbon has an average fiber diameter of preferably 1 nm to 200 nm, and more preferably 10 nm to 200 nm. Further, the aspect ratio calculated by (average fiber length / average fiber diameter) using the average fiber diameter and the average fiber length is preferably 20 or more and 20000 or less on average, more preferably 20 or more and 4000 or less, and more preferably 20 or more and 2000 on average. The following is more preferable.

  Furthermore, for example, when the thickness of the positive electrode active material layer is increased in order to improve the volume efficiency of the battery, it is preferable to use carbon black or the like as secondary particles as the conductive agent contained in the positive electrode active material layer. The major axis of the carbon material formed into secondary particles as the conductive agent is longer than the major axis of the fibrous carbon, and the number of contacts between the conductive agents is reduced. Therefore, it is possible to prevent the conductivity from being lowered by the binder.

[Negative electrode]
The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B provided on both surfaces of the negative electrode current collector 22A. In addition, you may make it have the area | region where the negative electrode active material layer 22B exists only in the single side | surface of 22 A of negative electrode collectors. The anode current collector 22A is made of a metal foil such as a copper (Cu) foil.

  The negative electrode active material layer 22B includes, for example, a negative electrode active material, and may include other materials that do not contribute to charging, such as a conductive agent, a binder, or a viscosity modifier, as necessary. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include a fluorine polymer compound such as polyvinylidene fluoride (PVdF), or a synthetic rubber such as styrene butadiene rubber (SBR) or ethylene propylene diene rubber (EPDR).

  The negative electrode active material includes one or more negative electrode materials capable of electrochemically inserting and extracting lithium (Li) at a potential of lithium metal of 2.0 V or less. Yes.

  Examples of the negative electrode material capable of inserting and extracting lithium (Li) include a carbon material.

  Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, carbon fibers, and activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body refers to a carbonized material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: In addition, examples of the polymer material include polyacetylene and polypyrrole.

  Among such negative electrode materials capable of inserting and extracting lithium (Li), those having a charge / discharge potential relatively close to lithium metal are preferable. This is because the lower the charge / discharge potential of the negative electrode 22, the easier it is to increase the energy density of the battery. Among these, a carbon material is preferable because a change in crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Moreover, non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained.

  Examples of the negative electrode material capable of inserting and extracting lithium (Li) include lithium metal alone, metal elements or metalloid elements capable of forming an alloy with lithium (Li), alloys, or compounds. These are preferable because a high energy density can be obtained, and in particular, when used together with a carbon material, a high energy density can be obtained and excellent cycle characteristics can be obtained, and therefore, it is more preferable. Note that in this specification, alloys include those composed of one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. The structures include solid solutions, eutectics (eutectic mixtures), intermetallic compounds, or those in which two or more of them coexist.

  Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth. (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf). Examples of these alloys or compounds include those represented by the chemical formula MafMbgLih or the chemical formula MasMctMdu. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one of nonmetallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of f, g, h, s, t, and u are f> 0, g ≧ 0, h ≧ 0, s> 0, t> 0, and u ≧ 0, respectively.

  Among these, a simple substance, alloy or compound of Group 4B metal element or semimetal element in the short-period type periodic table is preferable, and silicon (Si) or tin (Sn), or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

Examples of the anode material capable of inserting and extracting lithium further include other metal compounds such as oxide, sulfide, or lithium nitride such as Li ₃ N. Examples of the oxide include MnO ₂ , V ₂ O ₅ , V ₆ O _{13 and the} like. In addition, examples of oxides that have a relatively low potential and can occlude and release lithium include iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and tin oxide. Examples of the sulfide include NiS and MoS.

[Separator]
As the separator 23, for example, a polyethylene porous film, a polypropylene porous film, a synthetic resin nonwoven fabric, or the like can be used. The separator 23 is impregnated with a non-aqueous electrolyte that is a liquid electrolyte.

[Non-aqueous electrolyte]
The nonaqueous electrolytic solution includes a liquid solvent, for example, a nonaqueous solvent such as an organic solvent, and an electrolyte salt dissolved in the nonaqueous solvent.

  The non-aqueous solvent preferably contains at least one of cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC). This is because the cycle characteristics can be improved. In particular, it is preferable to mix and contain ethylene carbonate (EC) and propylene carbonate (PC) because cycle characteristics can be further improved.

  The non-aqueous solvent may also contain at least one of chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC). preferable. This is because the cycle characteristics can be further improved.

  It is preferable that the nonaqueous solvent further contains at least one of 2,4-difluoroanisole and vinylene carbonate (VC). This is because 2,4-difluoroanisole can improve the discharge capacity, and vinylene carbonate (VC) can further improve the cycle characteristics. In particular, it is more preferable that they are mixed and contained because both the discharge capacity and the cycle characteristics can be improved.

  Nonaqueous solvents further include butylene carbonate, γ-butyrolactone, γ-valerolactone, those in which part or all of the hydrogen groups of these compounds are substituted with fluorine groups, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran. 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropyronitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, or trimethyl phosphate may be included.

  Depending on the electrode to be combined, the reversibility of the electrode reaction may be improved by using a material in which part or all of the hydrogen atoms of the substance contained in the non-aqueous solvent group are substituted with fluorine atoms. Therefore, these substances can be used as appropriate.

A lithium salt can be used as the electrolyte salt. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), and antimony hexafluoride. Inorganic lithium salts such as lithium oxalate (LiSbF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis (trifluoromethanesulfonyl) ) Imide (LiN (CF ₃ SO ₂ ) ₂ ), lithium bis (pentafluoroethanesulfonyl) imide (LiN (C ₂ F ₅ SO ₂ ) ₂ ), and lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO _{2) 3)} perfluoroalkane sulfonic acids derived such And the like, it is also possible to use them in combination of at least one kind alone or in combination. Among these, lithium hexafluorophosphate (LiPF ₆ ) is preferable because high ion conductivity can be obtained and cycle characteristics can be improved.

[Method of manufacturing non-aqueous electrolyte secondary battery]
This nonaqueous electrolyte battery can be manufactured as described below, for example. First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a positive electrode mixture slurry. . Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is manufactured.

  Further, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21 by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22 by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11.

  After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolyte solution described above is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. As described above, the nonaqueous electrolyte battery shown in FIG. 5 can be manufactured.

  In this non-aqueous electrolyte battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted into the negative electrode 22 through the electrolytic solution. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and are inserted in the positive electrode 21 through the electrolytic solution.

  By using the positive electrode active material as described above, both the conductivity between the primary particles in the secondary particles and the binding property between the secondary particles or between the positive electrode active material layer and the positive electrode current collector are achieved. A positive electrode active material and a nonaqueous electrolyte secondary battery excellent in capacity and high output characteristics can be obtained.

<Effect>
The non-aqueous electrolyte battery using the above-described olivine-type positive electrode active material has a high discharge capacity, stable charge / discharge cycle performance even when the charge / discharge cycle proceeds, and has high filling ability, high output, and the like.

3. Third Embodiment A nonaqueous electrolyte battery according to a third embodiment of the present invention will be described. The nonaqueous electrolyte battery in the third embodiment is a laminate film type nonaqueous electrolyte battery that is covered with a laminate film.

(3-1) Configuration of Nonaqueous Electrolyte Battery A nonaqueous electrolyte battery according to the third embodiment of the present invention will be described. FIG. 7 shows an exploded perspective view of a nonaqueous electrolyte battery according to a third embodiment of the present invention, and FIG. 8 is an enlarged cross section taken along line II of the spirally wound electrode body 30 shown in FIG. As shown.

  In this nonaqueous electrolyte battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is mainly housed in a film-like exterior member 40. The battery structure using the film-shaped exterior member 40 is called a laminate type.

  For example, the positive electrode lead 31 and the negative electrode lead 32 are led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 is made of, for example, a metal material such as aluminum, and the negative electrode lead 32 is made of, for example, a metal material such as copper, nickel, or stainless steel. These metal materials are, for example, in a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, an aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 40 has, for example, a structure in which outer edges of two rectangular aluminum laminate films are bonded to each other by fusion or an adhesive so that the polyethylene film faces the wound electrode body 30. ing.

  An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. Examples of such a material include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

  In addition, the exterior member 40 may be comprised with the laminated film which has another laminated structure instead of the above-mentioned aluminum laminated film, and may be comprised with polymer films or metal films, such as a polypropylene.

  FIG. 8 shows a cross-sectional configuration along the line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by laminating and winding a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte 36, and an outermost peripheral portion thereof is protected by a protective tape 37.

  The positive electrode 33 is, for example, provided with a positive electrode active material layer 33B on both surfaces of a positive electrode current collector 33A, and has the same configuration as the positive electrode 21 of the second embodiment. As the positive electrode active material, secondary particles composed of a lithium phosphate compound having an olivine structure represented by (Chemical Formula 1) of the first embodiment and an electron conductive material are used.

  The negative electrode 34 is, for example, provided with a negative electrode active material layer 34B on both surfaces of a negative electrode current collector 34A, and has the same configuration as the negative electrode 22 of the second embodiment.

  The positive electrode 33 and the negative electrode 34 are disposed so that the negative electrode active material layer 34B and the positive electrode active material layer 33B face each other. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the second embodiment. The configurations of the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23 are the same.

  The electrolyte 36 is a so-called gel electrolyte that includes the nonaqueous electrolytic solution according to the first embodiment described above and a polymer compound that holds the nonaqueous electrolytic solution. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and liquid leakage is prevented.

(3-2) Manufacturing Method of Nonaqueous Electrolyte Battery This nonaqueous electrolyte battery is manufactured by, for example, the following three types of manufacturing methods (first to third manufacturing methods).

(3-2-1) First Manufacturing Method In the first manufacturing method, first, for example, by collecting the positive electrode current by the same procedure as the manufacturing procedure of the positive electrode 21 and the negative electrode 22 of the second embodiment described above. The positive electrode active material layer 33B is formed on both surfaces of the body 33A to produce the positive electrode 33. Further, the negative electrode active material layer 34B is formed on both surfaces of the negative electrode current collector 34A to produce the negative electrode 34.

  Subsequently, a precursor solution containing the non-aqueous electrolyte according to the first embodiment, a polymer compound, and a solvent is prepared and applied to the positive electrode 33 and the negative electrode 34, and then the solvent is volatilized to form a gel electrolyte. 36 is formed. Subsequently, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A.

  Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are stacked via the separator 35 and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion to produce the wound electrode body 30. To do. Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded to each other by heat fusion or the like, so that the wound electrode body 30 is Encapsulate. At this time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, a nonaqueous electrolyte battery is completed.

(3-2-2) Second Manufacturing Method In the second manufacturing method, first, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34. Subsequently, after the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35, a protective tape 37 is adhered to the outermost peripheral portion thereof, and a wound body that is a precursor of the wound electrode body 30. Is made.

  Subsequently, after sandwiching the wound body between the two film-shaped exterior members 40, the remaining outer peripheral edge except for the outer peripheral edge on one side is adhered by heat fusion or the like, thereby forming a bag-shaped exterior The wound body is accommodated in the member 40. Subsequently, a composition for an electrolyte comprising the nonaqueous electrolytic solution according to the first embodiment, a monomer that is a raw material for the polymer compound, a polymerization initiator, and, if necessary, other materials such as a polymerization inhibitor. Is prepared and injected into the inside of the bag-shaped exterior member 40, and then the opening of the exterior member 40 is sealed by heat fusion or the like. Finally, the gel electrolyte 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, a nonaqueous electrolyte battery is completed.

(3-2-3) Third production method In the third production method, first, except that the separator 35 coated with the polymer compound on both sides is used, the same as the second production method described above, A wound body is formed and stored in the bag-shaped exterior member 40.

  Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence.

  The polymer compound may contain one or more other polymer compounds together with the polymer containing vinylidene fluoride as a component. Subsequently, after the non-aqueous electrolyte according to the first embodiment is prepared and injected into the exterior member 40, the opening of the exterior member 40 is sealed by heat sealing or the like. Finally, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the non-aqueous electrolyte is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36, thereby completing the non-aqueous electrolyte battery.

<Effect>
The third embodiment has the same effect as the second embodiment.

4). Fourth Embodiment A nonaqueous electrolyte battery according to a fourth embodiment of the present invention will be described. The nonaqueous electrolyte battery in the fourth embodiment is a laminated film type nonaqueous electrolyte battery that is covered with a laminate film, and the nonaqueous electrolyte battery in the fourth embodiment is the same as the first embodiment except that the nonaqueous electrolyte solution in the first embodiment is used as it is. This is similar to the nonaqueous electrolyte battery according to the third embodiment. Therefore, hereinafter, the configuration will be described in detail with a focus on differences from the third embodiment.

(4-1) Configuration of Nonaqueous Electrolyte Battery In the nonaqueous electrolyte battery according to the fourth embodiment of the present invention, a nonaqueous electrolyte is used instead of the gel electrolyte 36. Therefore, the wound electrode body 30 has a configuration in which the electrolyte 36 is omitted, and the separator 35 is impregnated with the nonaqueous electrolytic solution.

(4-2) Manufacturing Method of Nonaqueous Electrolyte Battery This nonaqueous electrolyte battery is manufactured as follows, for example.

  First, for example, a positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to both sides, dried and compression molded to form the positive electrode active material layer 33B, and the positive electrode 33 is produced. Next, for example, the positive electrode lead 31 is joined to the positive electrode current collector 33A by, for example, ultrasonic welding or spot welding.

  Further, for example, a negative electrode material and a binder are mixed to prepare a negative electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 34A, dried, and compression molded to form the negative electrode active material layer 34B, whereby the negative electrode 34 is produced. Next, for example, the negative electrode lead 32 is joined to the negative electrode current collector 34A by, for example, ultrasonic welding or spot welding.

  Subsequently, after winding the positive electrode 33 and the negative electrode 34 through the separator 35 and sandwiching them inside the exterior member 40, the nonaqueous electrolyte according to the first embodiment is injected into the exterior member 40, The exterior member 40 is sealed. Thereby, the nonaqueous electrolyte battery shown in FIGS. 7 and 8 is obtained.

<Effect>
The fourth embodiment has the same effect as that of the second embodiment.

5. Fifth Embodiment A configuration example of a nonaqueous electrolyte battery 50 according to a fifth embodiment of the present invention will be described. The nonaqueous electrolyte battery 50 according to the fifth embodiment of the present invention has a square shape as shown in FIG.

The nonaqueous electrolyte battery 50 is manufactured as follows. As shown in FIG. 9, first, the wound electrode body 53 is accommodated in an outer can 51 that is a rectangular can made of a metal such as aluminum (Al) or iron (Fe).

  Then, after the electrode pins 54 provided on the battery lid 52 and the electrode terminals 55 led out from the wound electrode body 53 are connected, the battery lid 52 is sealed. Thereafter, the nonaqueous electrolyte solution is injected from the nonaqueous electrolyte solution inlet 56 and sealed with the sealing member 57. Thereby, the nonaqueous electrolyte battery 50 according to the fifth embodiment of the present invention is completed.

  The wound electrode body 53 is obtained by laminating and winding a positive electrode and a negative electrode with a separator interposed therebetween. Since the positive electrode, the negative electrode, the separator, and the nonaqueous electrolytic solution are the same as those in the first embodiment, detailed description thereof is omitted.

<Effect>
In the nonaqueous electrolyte battery 50 according to the fifth embodiment of the present invention, the same effects as those of the second embodiment can be obtained.

6). Sixth Embodiment A nonaqueous electrolyte battery according to a sixth embodiment of the present invention will be described. The non-aqueous electrolyte battery in the sixth embodiment is a laminated film type non-aqueous electrolyte battery in which the electrode body is laminated with a positive electrode and a negative electrode and is covered with a laminate film. It is the same as the form. For this reason, below, only the electrode body of 6th Embodiment is demonstrated.

[Positive electrode and negative electrode]
As shown in FIG. 10, the positive electrode 61 is obtained by forming a positive electrode active material layer on both surfaces of a rectangular positive electrode current collector. The positive electrode current collector of the positive electrode 61 is preferably formed integrally with the positive electrode terminal. Similarly, the negative electrode 62 has a negative electrode active material layer formed on a rectangular negative electrode current collector.

  The positive electrode 61 and the negative electrode 62 are laminated in the order of the positive electrode 61, the separator 63, the negative electrode 62, and the separator 63 to form a laminated electrode body 60. The laminated electrode body 60 may maintain the laminated state of the electrodes by attaching an insulating tape or the like. The laminated electrode body 60 is packaged with a laminate film or the like and sealed in a battery together with a non-aqueous electrolyte. Moreover, you may use a gel electrolyte instead of a non-aqueous electrolyte.

<Effect>
In the nonaqueous electrolyte battery 20 using the laminated electrode body 60 of the sixth embodiment of the present invention, the same effects as those of the second embodiment can be obtained.

  Specific embodiments of the present invention will be described in detail. Note that the present invention is not limited to this.

<Example 1>
[Positive electrode]
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, iron (III) sulfate (Fe ₂ (SO ₄ ) ₃ ) as the iron (Fe) source, diammonium hydrogen phosphate ((NH) as the phosphorus (P) source ₄ ) Weighed using ₂ HPO ₄ ) so that the average composition was Li _1.05 FePO ₄ . In addition, acetic acid (CH ₃ COOH) was used as a carbon (C) source, placed on the fired positive electrode active material, and weighed so that the carbon (C) content was 3% by weight. The above raw materials were introduced into a stirring pot, and zirconia (ZrO ₂ ) beads and water were added to form a raw material suspension. The solid content concentration at this time was 20%.

The stirring pot charged with the raw material suspension was stirred and mixed for 13 hours. When the particle size distribution of the raw materials was measured, the average particle size was 0.07 μm. The suspension after pulverization and mixing is sprayed under an inert atmosphere of nitrogen (N ₂ ) and heated at 650 ° C. to form secondary particles in which carbon, which is an electronically conductive substance, is interposed between primary particles. did. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by the laser scattering method was 6.0 μm, and the specific surface area of the positive electrode active material secondary particles was 11.0 m ² / g.

  When the oil absorption amount of the above positive electrode active material was measured in an environment of 23 ° C. and an absolute humidity of 0.45%, the NMP oil absorption amount was 27 g / 100 g. Here, the density of N-methyl-2-pyrrolidone (NMP) used for the oil absorption measurement was 1.028 g / cc.

  The NMP oil absorption amount of the positive electrode active material was measured by the method described in the first embodiment. In addition, it shows below again about the NMP oil absorption measuring method.

After measuring the appropriate amount of sample from the sample according to the expected amount of NMP oil absorption, take the measured sample at the center of the burette table and remove N-methyl-2-pyrrolidone from the burette at a time, 4, Five drops were gradually dropped onto the center of the sample, and each time, the whole was thoroughly kneaded with a spatula. The end point was when N-methyl-2-pyrrolidone was dropped until the sample kneaded with a spatula could be wound into a spiral shape, and the amount of N-methyl-2-pyrrolidone dropped when the end point was reached was read. . And NMP oil absorption amount was computed from the following formula (1).
NMP oil absorption [g / 100 g] = (N-methyl-2-pyrrolidone (NMP) density [g / ml] × NMP drop amount [ml] / sample amount [g]) × 100 (1)

90 parts by weight of the above-described positive electrode active material lithium iron phosphate (Li _1.05 FePO ₄ ), 6 parts by weight of graphite as a conductive agent, and 4 parts by weight of polyvinylidene fluoride (PVdF) as a binder are mixed to form a positive electrode mixture It was. Thereafter, the positive electrode mixture was dispersed in 100 parts by weight of N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly applied to both surfaces of a 15 μm-thick strip-like aluminum (Al) foil serving as a positive electrode current collector, dried, and then compressed with a roller press to obtain a positive electrode sheet. Finally, the positive electrode sheet was cut into a predetermined shape, and a positive electrode lead made of aluminum (Al) was welded and attached to one end of the positive electrode current collector to obtain a belt-like positive electrode.

[Negative electrode]
90 parts by weight of powdered artificial graphite as a negative electrode active material and 10 parts by weight of polyvinylidene fluoride (PVdF) as a binder were mixed to prepare a negative electrode mixture. Thereafter, the negative electrode mixture was dispersed in 100 parts by weight of N-methyl-2-pyrrolidone (NMP) to obtain a negative electrode mixture slurry. The negative electrode mixture slurry was uniformly applied to both sides of a 10 μm thick strip-shaped copper (Cu) foil as a negative electrode current collector, dried, and then compressed by a roller press to obtain a negative electrode sheet. Finally, the negative electrode sheet was cut into a predetermined shape, and a negative electrode lead made of nickel (Ni) was welded and attached to one end of the negative electrode current collector to obtain a strip-shaped negative electrode.

[Non-aqueous electrolyte]
Lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solution in which the volume mixing ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) is 1: 1 so that the concentration becomes 1 mol / dm ^3. A non-aqueous electrolyte was prepared.

[Battery assembly]
The belt-like positive electrode and the belt-like negative electrode produced as described above were laminated via a porous polyolefin film as a separator and then wound many times to produce a spiral wound electrode body. The wound electrode body was housed in a nickel-plated iron battery can, and insulating plates were disposed on both the upper and lower surfaces of the wound electrode body. Next, the aluminum positive electrode lead is led out from the positive electrode current collector, welded to the protrusion of the safety valve that is electrically connected to the battery lid, and the nickel negative electrode lead connected to the negative electrode current collector is connected to the battery can. Welded to the bottom.

  Finally, after injecting the non-aqueous electrolyte into the battery can containing the wound electrode body, the safety can, the PTC element and the battery lid are fixed by caulking the battery can through an insulating sealing gasket. A cylindrical battery having a diameter of 18 mm and a height of 65 mm was produced.

<Example 2>
The stirring pot charged with the same raw material suspension as in Example 1 was stirred for 11 hours for pulverization and mixing. When the particle size distribution of the raw materials was measured, the average particle size was 0.11 μm. By using the suspension after pulverization and mixing, secondary particles were formed in the same manner as in Example 1 with carbon as an electronically conductive substance interposed between primary particles. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.4 μm, and the specific surface area of the positive electrode active material secondary particles was 12.0 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 30 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 3>
The stirring pot charged with the same raw material suspension as in Example 1 was stirred and mixed for 9 hours. When the particle size distribution of the raw materials was measured, the average particle size was 0.23 μm. By using the suspension after pulverization and mixing, secondary particles were formed in the same manner as in Example 1 with carbon as an electronically conductive substance interposed between primary particles. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.3 μm, and the specific surface area of the positive electrode active material secondary particles was 12.2 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 34 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 4>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, iron (III) sulfate (Fe) as the iron (Fe) source ₂ (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 1 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.04 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.2 Fe _0.8 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.9 μm, and the specific surface area of the positive electrode active material secondary particles was 12.0 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 26 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 5>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 2 with carbon as an electron conductive substance interposed between the primary particles. When the particle size distribution of the raw materials was measured, the average particle size was 0.09 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.2 Fe _0.8 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material secondary particles measured by the laser scattering method was 5.5 μm, and the specific surface area of the positive electrode active material secondary particles was 12.5 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 30 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 6>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 3 by interposing carbon as an electron conductive substance between the primary particles. When the particle size distribution of the raw materials was measured, the average particle size was 0.18 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.2 Fe _0.8 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.2 μm, and the specific surface area of the positive electrode active material secondary particles was 13.1 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 33 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 7>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 1 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.02 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.4 Fe _0.6 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.8 μm, and the specific surface area of the positive electrode active material secondary particles was 12.2 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 28 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 8>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 2 with carbon as an electron conductive substance interposed between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.08 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.4 Fe _0.6 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Further, the average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.4 μm, and the specific surface area of the positive electrode active material secondary particles was 13.3 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 31 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 9>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 3 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.15 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.4 Fe _0.6 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.1 μm, and the specific surface area of the positive electrode active material secondary particles was 13.5 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 35 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 10>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 1 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.02 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.6 Fe _0.4 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.8 μm, and the specific surface area of the positive electrode active material secondary particles was 12.2 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 25 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 11>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 2 with carbon as an electron conductive substance interposed between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.08 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.6 Fe _0.4 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.4 μm, and the specific surface area of the positive electrode active material secondary particles was 12.7 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 29 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 12>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 3 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.15 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.6 Fe _0.4 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material secondary particles measured by a laser scattering method was 5.1 μm, and the specific surface area of the positive electrode active material secondary particles was 13.2 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 33 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 13>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 1 by interposing carbon as an electron conductive substance between the primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.02 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.8 Fe _0.2 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material secondary particles measured by the laser scattering method was 5.6 μm, and the specific surface area of the positive electrode active material secondary particles was 13.5 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 26 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 14>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 2 with carbon as an electron conductive substance interposed between the primary particles. When the particle size distribution of the raw materials was measured, the average particle size was 0.07 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.8 Fe _0.2 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Further, the average particle diameter of the positive electrode active material particles measured by a laser scattering method was 5.2 μm, and the specific surface area of the positive electrode active material particles was 13.8 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 30 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Example 15>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Other than that, secondary particles were formed in the same manner as in Example 3 by interposing carbon as an electron conductive substance between the primary particles. When the particle size distribution of the raw materials was measured, the average particle size was 0.13 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.8 Fe _0.2 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material secondary particles measured by the laser scattering method was 4.9 μm, and the specific surface area of the positive electrode active material secondary particles was 14.2 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 35 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative Example 1>
The stirring pot charged with the same raw material suspension as in Example 1 was stirred for 5 hours, and pulverized and mixed. When the particle size distribution of the raw materials was measured, the average particle size was 0.35 μm. The pulverized and mixed suspension was sprayed under an inert atmosphere of nitrogen (N ₂ ) and heated at 600 ° C. In the same manner as in Example 1, carbon which is an electronically conductive substance between primary particles was used. Secondary particles were formed by interposing. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 5.6 μm, and the specific surface area of the positive electrode active material particles was 13.5 m ² / g.

  When the NMP oil absorption amount of the positive electrode active material was measured under the same conditions as in Example 1, the NMP oil absorption amount was 38 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative example 2>
The stirring pot charged with the same raw material suspension as in Example 1 was stirred for 9 hours, and pulverized and mixed. When the particle size distribution of the raw materials was measured, the average particle size was 0.23 μm. Then, the suspension after pulverization and mixing was filtered, washed with water, and heated at 650 ° C. to form primary particles. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. Further, the average particle diameter of the positive electrode active material particles measured by a laser scattering method was 0.6 μm, and the specific surface area of the positive electrode active material particles was 14.0 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 78 g / 100 g. Except for using such a positive electrode active material, an attempt was made to produce a cylindrical battery in the same manner as in Example 1. However, the positive electrode active material was almost peeled off, and a cylindrical battery could not be produced. .

<Comparative Example 3>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Otherwise, in the same manner as in Comparative Example 1, secondary particles were formed by interposing carbon, which is an electron conductive substance, between primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.52 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.2 Fe _0.8 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material particles measured by the laser scattering method was 5.5 μm, and the specific surface area of the positive electrode active material particles was 12.0 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 40 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative example 4>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Otherwise, primary particles were formed in the same manner as in Comparative Example 2. When the particle size distribution of the raw materials was measured, the average particle size was 0.18 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.2 Fe _0.8 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 0.7 μm, and the specific surface area of the positive electrode active material particles was 13.5 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 81 g / 100 g. Except for using such a positive electrode active material, an attempt was made to produce a cylindrical battery in the same manner as in Example 1. However, the positive electrode active material was almost peeled off, and a cylindrical battery could not be produced. .

<Comparative Example 5>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Otherwise, in the same manner as in Comparative Example 1, secondary particles were formed by interposing carbon, which is an electron conductive substance, between primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.45 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.4 Fe _0.6 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 5.4 μm, and the specific surface area of the positive electrode active material particles was 13.5 m ² / g.

  When the NMP oil absorption amount was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption amount was 43 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative Example 6>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Otherwise, primary particles were formed in the same manner as in Comparative Example 2. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.15 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.4 Fe _0.6 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. Moreover, the average particle diameter of the positive electrode active material particles measured by a laser scattering method was 0.6 μm, and the specific surface area of the positive electrode active material particles was 15.2 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 75 g / 100 g. Except for using such a positive electrode active material, an attempt was made to produce a cylindrical battery in the same manner as in Example 1. However, the positive electrode active material was almost peeled off, and a cylindrical battery could not be produced. .

<Comparative Example 7>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Otherwise, in the same manner as in Comparative Example 1, secondary particles were formed by interposing carbon, which is an electron conductive substance, between primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.42 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.6 Fe _0.4 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by the laser scattering method was 5.1 μm, and the specific surface area of the positive electrode active material particles was 14.7 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 48 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative Example 8>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Otherwise, primary particles were formed in the same manner as in Comparative Example 2. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.15 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.6 Fe _0.4 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 0.5 μm, and the specific surface area of the positive electrode active material particles was 15.2 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 85 g / 100 g. Except for using such a positive electrode active material, an attempt was made to produce a cylindrical battery in the same manner as in Example 1. However, the positive electrode active material was almost peeled off, and a cylindrical battery could not be produced. .

<Comparative Example 9>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Otherwise, in the same manner as in Comparative Example 1, secondary particles were formed by interposing carbon, which is an electron conductive substance, between primary particles. In addition, when the particle size distribution of the raw material was measured, the average particle size was 0.37 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.8 Fe _0.2 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 5.3 μm, and the specific surface area of the positive electrode active material particles was 16.0 m ² / g.

  When the NMP oil absorption amount of the positive electrode active material was measured under the same conditions as in Example 1, the NMP oil absorption amount was 52 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative Example 10>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Otherwise, primary particles were formed in the same manner as in Comparative Example 2. When the particle size distribution of the raw materials was measured, the average particle size was 0.13 μm. The average composition of lithium manganese iron phosphate having the olivine structure thus obtained is Li _1.05 Mn _0.8 Fe _0.2 PO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained. Other impurities were not confirmed. The average particle diameter of the positive electrode active material particles measured by a laser scattering method was 0.5 μm, and the specific surface area of the positive electrode active material particles was 16.3 m ² / g.

  When the NMP oil absorption amount of the positive electrode active material was measured under the same conditions as in Example 1, the NMP oil absorption amount was 83 g / 100 g. Except for using such a positive electrode active material, an attempt was made to produce a cylindrical battery in the same manner as in Example 1. However, the positive electrode active material was almost peeled off, and a cylindrical battery could not be produced. .

<Comparative Example 11>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, iron (III) sulfate (Fe ₂ (SO ₄ ) ₃ ) as the iron (Fe) source, diammonium hydrogen phosphate ((NH) as the phosphorus (P) source ₄ ) Weighed using ₂ HPO ₄ ) so that the average composition was Li _1.05 FePO ₄ . In addition, acetic acid (CH ₃ COOH) was used as a carbon (C) source and weighed so that the weight percentage after firing was 1 wt%. Water was added to the above raw materials to form a raw material suspension. The solid content concentration at this time was 20%.

When the particle size distribution of the raw materials was measured, the average particle size was 0.6 μm. The suspension after lightly mixing was sprayed under an inert atmosphere of nitrogen (N ₂ ) and heated at 700 ° C. to form secondary particles having an electron conductive substance interposed between the primary particles. The average composition of lithium iron phosphate having the olivine structure thus obtained is Li _1.05 FePO _4. As a result of X-ray diffraction structural analysis, only crystals having an olivine structure are obtained, and other impurities are It was not confirmed. Moreover, the average particle diameter measured by the laser scattering method was 6.0 μm, and the specific surface area of the positive electrode active material secondary particles was 2.1 m ² / g.

  When the NMP oil absorption was measured for the positive electrode active material under the same conditions as in Example 1, the NMP oil absorption was 20 g / 100 g. A cylindrical battery was produced in the same manner as in Example 1 except that such a positive electrode active material was used.

<Comparative Example 12>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.2 Fe _0.8 PO ₄ . Other than that, it carried out similarly to the comparative example 1, and formed the secondary particle which interposes carbon which is an electronic conductive substance between primary particles.

<Comparative Example 13>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.4 Fe _0.6 PO ₄ . Other than that, it carried out similarly to the comparative example 1, and formed the secondary particle which interposes carbon which is an electronic conductive substance between primary particles.

<Comparative example 14>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.6 Fe _0.4 PO ₄ . Other than that, it carried out similarly to the comparative example 1, and formed the secondary particle which interposes carbon which is an electronic conductive substance between primary particles.

<Comparative Example 15>
A positive electrode active material was prepared as follows. Lithium carbonate (Li ₂ CO ₃ ) as the lithium (Li) source, manganese (III) sulfate (Mn ₂ (SO ₄ ) ₃ ) as the manganese (Mn) source, and iron (III) sulfate (Fe ₂ as the iron (Fe) source (SO ₄ ) ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) as a phosphorus (P) source were weighed so that the average composition was Li _1.05 Mn _0.8 Fe _0.2 PO ₄ . Other than that, it carried out similarly to the comparative example 1, and formed the secondary particle which interposes carbon which is an electronic conductive substance between primary particles.

[Battery evaluation]
(A) Measurement of Peel Strength Relative Value As described above, the positive electrode sheet was prepared by uniformly applying and drying the positive electrode mixture slurry on both surfaces of a 15 μm-thick aluminum strip (Al) foil that is a positive electrode current collector. The peel strength test was conducted using

In the peel strength test, Shimadzu Autograph AGS-50B (manufactured by Shimadzu Corporation) was used as a tensile tester, and the measurement was performed according to the following procedure.
(1) A double-sided tape having a width of 25 mm and a length of about 20 cm was uniformly applied by roll pressing in the electrode application direction on the measurement surface side of the positive electrode sheet. At this time, the double-sided tape was pasted with the tip folded back about 1 cm.
(2) The portion where the double-sided tape was attached was cut out using a cutter knife and a ruler.
(3) The positive electrode sheet was placed on a dedicated stainless steel plate with the electrode surface facing up, and one end of the double-sided tape attached to the positive electrode sheet was not folded back and fixed with tape.
(4) The electrode was slowly peeled off to about half while pressing the folded part of the double-sided tape.
(5) The peeled electrode was folded back to the upper part of the stainless steel plate (tape fixing part) and the double-sided tape was folded to the back of the lower part of the stainless steel plate.
(6) The stainless steel plate was fixed to the lower chuck together with the folded double-sided tape.
(7) The peeled electrode was fixed to the upper chuck.
(8) The upper chuck was raised with the lower chuck fixed, and the 180-degree peel strength was measured.
(9) From the chart, the average value was read and converted to intensity per mm. At this time, the 180 degree peel strength was measured with two or more cylindrical batteries, and the measurement was further repeated when the variation in the measured values was large.

  Peel strength easily changes depending on the amount of the positive electrode mixture and the type of binder, kneading conditions, application conditions and drying conditions of the positive electrode mixture slurry, and the type of aluminum (Al) foil that is the positive electrode current collector obtain. In this example, the conditions of the example and the comparative example were obtained by unifying all the conditions under which such peel strength can be changed to produce a positive electrode sheet, and measured the 180-degree peel strength. The absolute value of the peel strength is expressed in units of [mN / mm]. In view of the above factors, the peel strength of Example 1 is based on the peel strength value of Example 1 [mN / mm]. The absolute value [mN / mm] obtained was converted into a relative value.

(B) Confirmation of degree of adhesion with aluminum foil In each of the above Examples and Comparative Examples, the positive electrode mixture slurry was applied to both surfaces of a 15 μm-thick strip-shaped aluminum foil, dried, and then compressed with a roller press machine. After obtaining the positive electrode, the belt-like positive electrode was applied to the end of the desk and rubbed 15 times, and the degree of adhesion between the positive electrode powder and the aluminum foil was visually observed.

(C) Initial capacity For the cylindrical batteries of the above-described examples and comparative examples, after performing constant current charging at a constant current of 1000 mA at an environmental temperature of 23 degrees until the battery voltage reaches 3.8 V, 3.8 V Constant voltage charging was performed until the total charging time at constant voltage was 2.5 hours. Next, constant current discharge was performed at a constant current of 1000 mA until the battery voltage reached 2.0 V, and the discharge capacity at this time was measured as the initial capacity.

Subsequently, charging / discharging was repeated up to 1000 cycles under the above charging conditions and discharging conditions, and the discharge capacity at the 1000th cycle was measured. From the following formula, the discharge capacity retention ratio at the 1000th cycle relative to the initial capacity was determined.
Discharge capacity maintenance rate [%] = (discharge capacity at 1000th cycle / initial capacity) × 100

  Tables 2 and 3 below show the evaluation results.

  As can be seen from Table 2 and Table 3, in the nonaqueous electrolyte battery of each comparative example in which the NMP oil absorption is not in the range of 25 g / 100 g or more and 35 g / 100 g, the aluminum foil used as the positive electrode current collector and the positive electrode active material layer The peel strength relative value became low. For this reason, the adhesion degree with the aluminum foil was low, and part or all of the positive electrode active material layer was peeled off by the above test.

In particular, Comparative Example 2 and Comparative Example 4 using a positive electrode active material having a small average particle diameter, in which the granulation step of spraying the pulverized and mixed suspension in an inert atmosphere of nitrogen (N ₂ ) was not performed. In Comparative Example 6, Comparative Example 8, and Comparative Example 10, the NMP oil absorption amount of the positive electrode active material was significantly increased, and the positive electrode active material layer was all peeled off. For this reason, it was not possible to produce a cylindrical battery. Further, in Comparative Examples 11 to 15 in which the amount of carbon (C) source mixed was as small as 1% by weight and the primary particle diameter was large and the particle was grown, the NMP oil absorption amount was small and the peel strength was large, but the capacity retention rate Deteriorated in several cycles and became almost zero.

  Further, for example, when Examples 1 to 3 and Comparative Example 1 having the same primary particle composition are compared, Examples 1 to 3 in which the NMP oil absorption amount is within the scope of the present invention are compared with Comparative Example 1. On the other hand, the discharge capacity retention rate after 1000 cycles of charge / discharge was significantly improved. The same was true for the examples and comparative examples using positive electrode active materials containing primary particles of other compositions.

  Thus, in a battery using a positive electrode active material using a lithium phosphate compound having an olivine structure using cheap and resource-rich elements, a stable charge / discharge cycle even when charge / discharge progresses as 1000 cycles The performance could be realized.

7). Other Embodiments The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention.

  For example, in the above-described embodiments and examples, a battery having a laminate film type, a cylindrical battery structure, and a battery having a square battery structure have been described, but the present invention is not limited thereto. For example, the present invention can be similarly applied to a battery having another battery structure such as a coin type or a button type, or a battery having a laminated structure in which electrodes are laminated, and the same effects can be obtained. Also, regarding the structure of the electrode body, various configurations such as a laminated type and a zigzag folded type can be applied as well as a wound type.

DESCRIPTION OF SYMBOLS 11 ... Battery can 12, 13 ... Insulating plate 14, 52 ... Battery cover 15 ... Safety valve mechanism 16 ... Thermal resistance element 17 ... Gasket 20, 53 ... Winding electrode body 21, 33 ... Positive electrode 21A, 33A ... Positive electrode current collector 21B, 33B ... Positive electrode active material layer 22, 34 ... Negative electrode 22A, 34A ... Negative electrode current collector 22B, 34B ... Negative electrode active material layer 23, 35 ... Separator 24 ... Center pin 25 ... Positive electrode lead 26 ... Negative electrode lead 30 ... Battery element 31a ... Positive electrode current collector exposed portion 32a ... Negative electrode Current collector exposed portion 36 ... electrolyte 37 ... protective tape 51 ... exterior can 54 ... electrode pin 55 ... battery terminal 56 ... electrolyte injection port 57 ... sealing member

Claims (8)

Primary particles of a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1), the surface of which is at least partly coated with an electronic conductive material, are bonded via the electronic conductive material. Secondary particles comprising
A positive electrode active material for a non-aqueous electrolyte battery having an N-methyl-2-pyrrolidone oil absorption of 25 g / 100 g or more and 35 g / 100 g.
(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. ) The positive electrode active material for a non-aqueous electrolyte battery according to claim 1, wherein the primary particles constituting the secondary particles are lithium iron phosphate mainly composed of iron (Fe). The positive electrode active material for a nonaqueous electrolyte battery according to claim 2, wherein the electronically conductive material constituting the secondary particles contains at least carbon. The positive electrode active material for a non-aqueous electrolyte battery according to claim 3, wherein a carbon content in the secondary particles is 0.1 wt% or more and 10 wt% or less. The positive electrode active material for a non-aqueous electrolyte battery according to claim 4, wherein the secondary particles have an average particle size of 0.01 μm or more and 20 μm or less. The positive electrode active material for a non-aqueous electrolyte battery according to claim 5, wherein an average particle size of the primary particles constituting the secondary particles is 0.001 µm or more and 1 µm or less. A positive electrode active material layer is formed on the positive electrode current collector,
The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder,
The positive electrode active material is
Primary particles of a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1), the surface of which is at least partly coated with an electronic conductive material, are bonded via the electronic conductive material. Secondary particles comprising
A positive electrode for a non-aqueous electrolyte battery, wherein the positive electrode active material has an N-methyl-2-pyrrolidone oil absorption of 25 g / 100 g or more and 35 g / 100 g.
(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. ) A positive electrode, a negative electrode, and a non-aqueous electrolyte;
The positive electrode has a positive electrode active material layer formed on a positive electrode current collector,
The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder,
The positive electrode active material is
Primary particles of a lithium phosphate compound having an olivine structure whose average composition is represented by (Chemical Formula 1), the surface of which is at least partly coated with an electronic conductive material, are bonded via the electronic conductive material. Secondary particles comprising
A non-aqueous electrolyte battery in which the positive electrode active material has an N-methyl-2-pyrrolidone oil absorption of 25 g / 100 g or more and 35 g / 100 g.
(Chemical formula 1)
Li _x M1 _1-s M2 _s PO ₄
(However, M1 represents at least one selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), magnesium (Mg)). M2 represents at least one element other than M1 among elements selected from Groups 2 to 15. x and s are values in the range of 0 ≦ x ≦ 1.2 and 0 ≦ s ≦ 1.0, respectively. )