JP4543474B2 - Positive electrode active material, method for producing the same, and non-aqueous secondary battery using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode active material for a non-aqueous secondary battery, a manufacturing method thereof, an electrode paste containing the positive electrode active material, a positive electrode produced from the paste, and a non-aqueous secondary battery using the positive electrode active material.
[0002]
[Prior art]
LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ have been studied from the expectation for higher energy density as a positive electrode active material for non-aqueous secondary batteries. However, LiCoO ₂ has a problem that cobalt is expensive and has resource limitations, and LiNiO ₂ is difficult to synthesize. For this reason, expectations are high for a low-cost and high-performance lithium-manganese oxide-based positive electrode active material, and its development is underway.
However, in a non-aqueous secondary battery using spinel-type LiMn ₂ O ₄ as a positive electrode active material, capacity reduction occurs in a short time when charging and discharging are repeated, and the actual electric capacity is expected from the electric capacity expected from the composition of the positive electrode active material. There is a problem that the capacity is quite small.
[0003]
Japanese Patent Application Laid-Open No. 2-270268 discloses a composite oxide having a spinel structure with little decrease in capacity even when charging and discharging are repeated by adding Li excessively to spinel type LiMn ₂ O ₄ . However, in this case, since Li is excessively added, there is a problem that the initial capacity becomes small.
UK Publication No. 2221213A discloses a secondary battery having a large initial capacity using spinel-type LiMn ₂ O ₄ synthesized at a low temperature as a positive electrode active material. Since the surface area is large, there is a problem in that the capacity reduction due to repeated charge / discharge increases.
[0004]
JP-A-2-278661, in _{Li x M y Mn 2-y} O Z (M is selected from periodic table IIIa or IIIb elements), 0 <x ≦ 1,0 < y ≦ 1,4 ≦ It is disclosed that the positive electrode active material represented by Z <4.5 is excellent in cycle characteristics. However, since x ≦ 1, in the case of the oxide in which M is Al, the capacity retention rate is only about 70%. Further, in this publication, when M is Y, the capacity retention rate of the secondary battery is close to 90%, but there is a problem that the discharge capacity is reduced because Y having a large atomic weight is added.
[0005]
_{JP-A-5-21067, LiMn 2-y M y} O 4 (M are elements other than hexavalent Mn from monovalent) By using the positive active material, a nonaqueous electrolyte battery excellent in cycle characteristics Is disclosed. However, this technique also has a low capacity retention rate of the secondary battery because Li is not excessive as in the invention described in Japanese Patent Laid-Open No. 2-278661.
JP-A-4-28962 discloses a positive electrode active material represented by Li _{x A y} Mn _{2 -y} O ₄ in the range of 0.85 <x ≦ 1.15 and 0.02 ≦ y ≦ 0.5. Discloses that it has excellent overdischarge characteristics. However, in the case of such a compound, since an electrochemically inactive Al compound is added so that y ≧ 0.02, there is a problem that the discharge capacity is reduced.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problem in a non-aqueous secondary battery, wherein the electric capacity after 100 cycles has a large value of 100 mAh / g or more, and the capacity retention rate after 100 cycles has passed is 90% or more. It is an object of the present invention to provide a non-aqueous secondary battery with low capacity reduction, a positive electrode active material for the battery, and a method for producing the same.
[0007]
[Means for Solving the Problems]
The present inventors have made intensive studies with respect to the problem, Li, Mn, in the composite oxide _{Li x Al y Mn 3-xy} O z having a spinel structure consisting of Al and O, the composition formula is 1.0 By using a positive electrode active material in the range of <x ≦ 1.1 and 0 <y <0.02 and 3.5 <z ≦ 4.5 for a non-aqueous secondary battery, the capacity is hardly reduced. It was found that a secondary battery can be provided.
[0008]
That is, the present invention
[1] Li, Mn, complex oxide having a spinel structure consisting of Al and O, in _{Li x Al y Mn 3-xy} O z, 1.0 <x ≦ 1.050, 0 <y <0.02 , 3.5 <I range der of z ≦ 4.5, the lattice constant (Å) is less than -0.24x-0.28y + 8.481, be -0.24x-0.72y + 8.481 or more , crystallite size, the positive electrode active material for nonaqueous secondary battery, characterized der Rukoto more and 950Å or less 400 Å,
[0009]
[2] complex oxide having a spinel structure, a positive electrode active material for nonaqueous secondary battery according to item 1, which is less particles having an average particle diameter of 2 [mu] m,
[3] complex oxide having a spinel structure, a positive electrode active material for nonaqueous secondary battery according to item 1 is a granulated sintered particles of particle diameter 3Myuemu～50myuemu,
[0010]
[4] An electrode paste containing the positive electrode active material for a non-aqueous secondary battery according to any one of items 1 to 3 ,
[5] The electrode paste according to item 4 above, wherein the paste contains a positive electrode active material or a granulated product thereof, a conductivity imparting agent, a binder, and a solvent.
[6] The positive electrode active material or the granulated product thereof in the paste, the total solid content of the conductive agent and the binder, the electrode according to item 5, which is a range of 30% to 70% by weight For paste,
[0011]
[7] A positive electrode comprising the positive electrode active material for a non-aqueous secondary battery according to any one of items 1 to 3 ,
[8] A negative electrode containing an active material capable of reversibly occluding and releasing lithium ions, a non-aqueous electrolyte solution or a polymer electrolyte, and a composite oxide active material having a spinel structure made of Li, Mn, Al and O A nonaqueous secondary battery comprising a positive electrode, wherein the composite oxide is the positive electrode active material for a nonaqueous secondary battery according to any one of items 1 to 3 ,
[9] The object is achieved by providing a non-aqueous secondary battery in which the non-aqueous secondary battery according to the preceding item 8 is a coin-type battery, a cylindrical battery, a square battery, or a polymer battery.
[0012]
Hereinafter, the present invention will be described in detail.
The present invention, Li, Mn, relates positive electrode active material of a composite oxide having a spinel structure consisting of Al and _{O, Li x Al y Mn 3} -xy O composition range of x in _z is 1.0 <x ≦ 1. Provided is a composite oxide in which the composition range of 1 and y is 0 <y <0.02 and the composition range of z is 3.5 <z ≦ 4.5. The composition range is preferably 1.005 ≦ x ≦ 1.080, 0.005 ≦ y ≦ 0.018, 3.7 <z ≦ 4.3, and the lattice constant L (Å) is In the composition of the formula, L1 (x, y) = − 0.24x−0.28y + 8.481 is smaller than the value represented by L2 (x, y) = − 0.24x−0.72y + 8.481 Those greater than the value represented are preferred. That is, the lattice constant in the range shown in FIG. 1 is good.
[0013]
In general, it is known that when a solid solution is formed in ceramics, the lattice constant changes according to Vegard's law. For _{Li x Al y Mn 3-xy} O z, since Mn ³⁺ in the crystal has a distortion, can not predict the lattice constant in the Vegard's law, the present inventors have studied, complete It was found that when a solid solution was made, the lattice constant (Å) was in the plane represented by the relational expression (−0.24x−0.72y + 8.481) of L2 (x, y). On the other hand, when the solid solution of Al does not advance, the lattice constant (Å) becomes larger than this surface, and it is greater than the value of the relational expression (−0.24x−0.28y + 8.481) of L1 (x, y). Then, it discovered that the electrical property when it was set as the positive electrode of a Li ion battery worsened (refer FIG. 1). To date, no complex oxide having a spinel structure having a lattice constant in such a range has been found so far.
[0014]
When the lattice constant is larger than the above range, the capacity reduction is increased. In order to prevent this capacity reduction, it is necessary to make x larger than 1.1. In addition, attempts can be made to increase y to 0.02 or more in order to prevent a decrease in capacity, but as a result, the discharge capacity becomes small, the target capacity is large, and the capacity decrease is small. A positive electrode active material cannot be obtained.
The positive electrode active material preferably has a crystallite size of 400 to 950, more preferably 600 to 850. When the crystallite size is smaller than 400 Å, the discharge capacity of the secondary battery is reduced, and when larger than 950 Å, the deterioration of the discharge capacity in the charge / discharge cycle is increased.
[0015]
As a method for producing the positive electrode active material of the present invention, for example, a lithium compound, manganese carbonate having a specific surface area of 10 m ² / g or more and 100 m ² / g or less, and an aluminum compound are mixed, and this is mixed at 350 ° C. or more and 680 ° C. or less. The positive electrode active material can be manufactured by performing a baking reaction at a temperature for 1 hour or more and then heat-treating the product at a temperature of 730 ° C. or higher and 900 ° C. or lower. In particular, in this production method, the raw material is preliminarily reacted at a temperature of 350 ° C. or higher and 680 ° C. or lower, and then re-dispersed by pulverization, and then heated at a temperature of 730 ° C. or higher and 900 ° C. or lower Then the reaction can be completed. In addition, by performing this low-temperature baking step, there is an advantage that Mn is not mixed in the Li site in the crystal lattice at the time of baking at a temperature of 730 ° C. or higher and 900 ° C. or lower so that it can be crystallized. In the present invention, a composite oxide for a positive electrode active material having excellent battery characteristics can be obtained by such a production method.
[0016]
In the production method, the raw material lithium compound is not particularly limited, and lithium carbonate, lithium hydroxide, lithium nitrate and the like are preferably used.
In the production method, the aluminum compound as a raw material is not particularly limited, and an aluminum compound having a specific surface area of 50 m ² / g or more and 200 m ² / g or less from the viewpoint of reactivity at a temperature of 350 ° C. or more and 680 ° C. or less. Anything is fine. Examples of such aluminum compounds include aluminum oxide (alumina such as α, β, γ, δ, ζ, η, θ, κ, χ, and ρ), Al (OH) ₃ , Al (NO ₃ ) ₃ , Al ₂ (SO ₄ ) ₃ (aluminite, etc.), aluminum acetate and hydrates thereof can be mentioned. Preferably aluminum oxide, particularly preferably alumina obtained from a gas phase process (eg γ-type) is used.
[0017]
In the present invention, the _{Li x Al y Mn 3-xy} O z ( where, 1.0 <x ≦ 1.1,0 <y <0.02,3.5 < range of z ≦ 4.5 The composite oxide represented by) is a pulverized particle obtained after pulverization of the fired product (this is a primary particle or a secondary particle in which primary particles are aggregated, and an average particle size thereof is 2 [mu] m or less, preferably 0.1 [mu] m to 1.0 [mu] m, more preferably 0.2 [mu] m to 0.5 [mu] m.
Further, in the present invention, dense granulated particles (particle diameters of 3 μm to 50 μm, which are obtained by adding and mixing a sintering acceleration aid (granulation accelerator) to the pulverized particles having the average particle diameter and mixing and granulating them. (The range of 5 to 30 μm is preferable) may be used as the positive electrode active material. Here, the dense granulated particles mean that there are no or few voids between the primary particles of the oxide, and can be produced by the following method using a sintering accelerator.
[0018]
Wherein the crushing and pulverizing _{Li x Al y Mn 3-xy} O z ( where in the range of 1.0 <x ≦ 1.1,0 <y < 0.02,3.5 <z ≦ 4.5 .) Is not particularly limited, and for example, a medium stirring pulverizer, a ball mill, a paint shaker, a mixing mixer and the like can be used. The mixing method may be either dry or wet. When the composite oxide is pulverized and pulverized, a sintering accelerator aid may be added and mixed at the same time.
[0019]
Sintering accelerating agents that can be used are Li _{x A y} Mn _{3 -xy} O _z (where 1.0 <x ≦ 1.1, 0 <y <0.02, 3.5 <z ≦ 4.5). It is sufficient that the pulverized / pulverized particles of the composite oxide particles represented by (2) can be sintered for granulation, and more preferably a compound that melts at a temperature of 900 ° C. or less, for example, Any oxide that can be melted at a temperature of 550 ° C. to 900 ° C., a precursor that can be converted to the oxide, or an oxide that can be dissolved or reacted with lithium or manganese to be melted or a compound that can be converted to the oxide. . For example, the sintering acceleration aid includes compounds containing elements such as Bi, B, W, Mo, Pb, etc., and these compounds may be used in any combination, and B ₂ O ₃ and A compound combining LiF or a compound combining MnF ₂ and LiF is also used. Among these, compounds containing Bi, B, and W elements are particularly preferable because they have a large sintering shrinkage effect.
[0020]
Examples of Bi compounds include bismuth trioxide, bismuth nitrate, bismuth benzoate, bismuth oxyacetate, bismuth oxycarbonate, bismuth citrate, and bismuth hydroxide. Examples of the B compound include boron trioxide, boron carbide, boron nitride, and boric acid. Examples of the W compound include tungsten dioxide and tungsten trioxide.
[0021]
The addition amount of the sintering accelerating aid is preferably in the range of 0.0001 to 0.05 mol with respect to 1 mol of Mn in the composite oxide in terms of added metal element. This is because there is no sintering shrinkage effect if the amount added in terms of added metal element is less than 0.0001 mol, and the initial capacity of the active material becomes too small if it exceeds 0.05 mol. Preference is given to 0.005 to 0.03 mol.
The sintering promoting aid may be used in a powder state or in a liquid state dissolved in a solvent.
When added in a powder state, the average particle diameter of the sintering accelerator aid is preferably 50 μm or less, more preferably 10 μm or less, and further preferably 3 μm or less. Although it is preferable to add the sintering promoting aid before granulation / sintering, the granulated product may be impregnated and sintered at a temperature at which the sintering promoting aid can be melted after granulation.
[0022]
Next, the granulation method will be described.
Examples of the granulation method include spray granulation method, fluidized granulation method, compression granulation method, stirring granulation method and the like using the above-mentioned sintering acceleration aid, and also include medium fluidized drying and medium vibration drying. You may use together. Agitation granulation and compression granulation are particularly preferred because the density of secondary particles is increased, and spray granulation is particularly preferred because the granulated particle shape is a perfect sphere. Examples of the agitating granulator include a vertical granulator manufactured by Paulek Co., Ltd. and a Spartan Luther manufactured by Fuji Paudal Co., Ltd. Examples of the compression granulator include Kurimoto Tekko Co., Ltd. Examples thereof include a roller compactor MRCP-200 type. As an example of a spray granulator, Ashizawairo atomizer Co., Ltd. Mobile minor type spray dryer etc. are mentioned.
[0023]
In the present invention, the size of the granulated particles used for the positive electrode is not particularly limited. When the average particle size of the granulated particles is too large, it may be crushed and pulverized lightly immediately after granulation or after sintering, and classified and sized to obtain the desired particle size. In order to increase the granulation efficiency, an organic granulation aid may be added. Examples of the granulation aid include acrylic resins, copolymers of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropyl cellulose, methyl cellulose, corn starch, gelatin, and lignin.
[0024]
The amount of granulating aid, said _{Li x Al y Mn 3-xy} O z ( where, 1.0 <x ≦ 1.1,0 <y <0.02,3.5 <z ≦ 4. The amount is preferably 5 parts by weight or less, more preferably 2 parts by weight or less, based on 100 parts by weight of the composite oxide represented by (2) and the sintering promoting aid.
[0025]
Next, a method for firing the granulated particles will be described.
The granulated particles are degreased by holding them in the air or in a gas atmosphere containing oxygen at a temperature range of 300 ° C. to 550 ° C. for 10 minutes or more. The carbon residue in the defatted granulated product is preferably 0.1% or less. The granulated particles after degreasing are sintered by being held for 1 minute or more in a temperature range of 550 ° C. to 900 ° C. in an atmosphere containing air or oxygen.
In addition, the firing of the granulated particles without using the above-mentioned organic-based granulation aids is similarly performed in the air or in a gas atmosphere containing oxygen to sinter and shrink, thereby densifying the secondary particles. Can do.
[0026]
Next, a method for using the positive electrode active material of the present invention as a positive electrode material for a non-aqueous secondary battery will be described.
The positive electrode is prepared by mixing the positive electrode active material or a granulated product thereof, a conductivity-imparting agent (conductive material), and a binder (binding material) with a paste solvent in a predetermined ratio to prepare an electrode paste. It is applied to the body, and then dried and pressurized with a roll press or the like. Examples of the conductivity-imparting agent generally include carbon powder such as carbon black and graphite such as Vulcan XC-72 manufactured by Cabot, metal powder such as Al powder and Ag powder, conductive metal oxide such as SnO ₂ , and the like. A mixture is used.
[0027]
As the binder, polyvinylidene fluoride (PVDF), Teflon, ethylene-propylene-diene-copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC) or the like is generally used. The solvent that can be used for the electrode paste is any solvent that can dissolve or swell the binder. For example, aromatic solvents such as N-methyl-2-pyrrolidone (NMP), benzene, xylene, and toluene, methanol, ethanol And alcohols such as propanol and butanol; ketones such as methyl ethyl ketone; and ethers such as dioxane. NMP, xylene, toluene and the like are preferably used.
[0028]
As the current collector, a known metal current collector of foil or mesh made of aluminum, stainless steel (SUS), titanium or the like is used.
The ratio of the solid component of the electrode paste is 50 to 95% by mass of the total solid component mass, preferably 60 to 90% by mass, considering the characteristics of the active material and the electric capacity of the present invention. The imparting agent is 49 to 4% by mass, preferably 39 to 4% by mass, and the binder (binding material) is 1 to 46% by mass, preferably 1 to 36% by mass. The solvent amount of the electrode paste is arbitrarily determined from the applicability, and the solid content concentration is freely set to 30 to 70% by mass, preferably 40 to 60% by mass.
[0029]
The negative electrode used in the nonaqueous secondary battery of the present invention is not particularly limited as long as it is an active material capable of reversibly occluding and releasing lithium ions. For example, lithium metal, lithium alloy, carbon material (including graphite) ), Metal chalcogen, etc. can be used.
Examples of the electrolyte salt in the nonaqueous electrolytic solution used in the nonaqueous secondary battery of the present invention include LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiCF ₃ SO ₃ , and LiC _4. Examples thereof include F ₉ SO ₃ , LiI, LiClO ₄ , LiSCN, and the like. Preferably, the lithium salt containing fluorine is used.
[0030]
Alternatively, in the non-aqueous secondary battery of the present invention, a polymer solid electrolyte may be used instead of the non-aqueous electrolyte, and the material is not limited. The polymer solid electrolyte is usually a polymer solid electrolyte (abbreviated as SPE) containing an oligooxyethylene group or an oligopropyloxy group, and has an ionic conductivity of about 10 ⁻⁶ to 10 ⁻³ S / cm. (For example, JP-A-4-211212). For example, this SPE includes polyethylene oxide, polypropylene oxide, polyethylene, polypropylene, polyacrylonitrile, polybutadiene, polymethacrylates, polyacrylates, polystyrene, polyphosphazenes, polysiloxanes or polysilanes, polyfluorides, Examples include polymers in which an oligooxyethylene group or an oligopropyloxy group is chemically bonded to a base polymer such as vinylidene or polytetrafluoroethylene.
[0031]
As the non-aqueous electrolyte solution of the non-aqueous secondary battery, at least one electrolyte containing lithium ions is dissolved in the non-aqueous electrolyte solution. The non-aqueous solvent of the non-aqueous electrolyte solution can be used without limitation as long as it is chemically and electrochemically stable and aprotic. For example, dimethyl carbonate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, diethyl carbonate, ethyl propyl carbonate, diisopropyl carbonate, dibutyl carbonate, 1,2-butylene carbonate, ethyl isopropyl carbonate, Examples thereof include carbonates such as ethylbutyl carbonate. Also, oligoethers such as triethylene glycol methyl ether and tetraethylene glycol dimethyl ether, aliphatic esters such as methyl propionate and methyl formate, aromatic nitriles such as benzonitrile and tolunitrile, amides such as dimethylformamide, dimethyl Examples include sulfoxides such as sulfoxide, lactones such as γ-butyrolactone, sulfur compounds such as sulfolane, N-vinylpyrrolidone, N-methylpyrrolidone, and phosphate esters. Of these, in the present invention, carbonates, aliphatic esters and ethers are preferred.
[0032]
Next, a method for evaluating electrode characteristics will be described.
Positive electrode, negative electrode, non-aqueous electrolyte or polymer electrolyte prepared by the above method, separator (for example, made of polypropylene, other polyolefins including polyethylene and copolymer), and, if necessary, negative electrode In order to prevent micro-shorts caused by dendritic generation, silica fiber filter paper QR-100 manufactured by Advantech Toyo Co., Ltd. is also used as a reinforcing material, coin battery (for example, 2016 type), cylindrical battery, prismatic battery, polymer A battery is produced. Then, 100 charge / discharge cycle tests were performed on this battery, for example, constant current constant voltage charge-constant current discharge, charge and discharge rate 1C (charge suspend in 2.5 hours from the start of charge), scan voltage 3 Performed at 1V to 4.3V.
[0033]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.
[0034]
Example 1 Production of Positive Electrode Active Material Manganese carbonate (BET method specific surface area: 30 m ² / g) 0.492 mol, lithium carbonate (BET method specific surface area: 1 m ² / g) 0.128 mol and aluminum oxide (BET (Method specific surface area: 100 m ² / g) 0.0016 mol was mixed in a ball mill having a capacity of 0.7 liter for 1 hour, and then reacted in the atmosphere at a reaction temperature of 650 ° C. for 4 hours. This product was crushed with a ball mill for 1 hour and then heat-treated in the atmosphere at a heat treatment temperature of 750 ° C. for 20 hours.
[0035]
The composition of the positive electrode active material was determined by decomposing the sample with hydrochloric acid, obtaining Li with a flame photometric method, Al with an ICP method, and Mn with a potentiometric titration method. The lattice constant was determined by the method of JBNelson and DPRiley (Proc. Phys. Soc., 57, 160 (1945)). The crystallite size was measured from the X-ray diffraction peak of the (111) plane of lithium manganate under the following conditions and calculated using the Scherrer equation. Assuming that the outer shape of the crystallite is a cube and has no size distribution, a value obtained by calculating the spread of the diffraction line due to the size of the crystallite from the half width was used. A device constant calibration curve was prepared using a powder obtained by pulverizing single crystal silicon with a tungsten carbide sample mill and then screening to 44 μm or less as an external standard. However, the measurement device is a Rad type goniometer manufactured by Rigaku Corporation, continuous measurement is used as the measurement mode, and the RINT2000 series application software is used as the analysis software to analyze the crystallite size. It was. The measurement conditions are X-ray (CuKα ray), output 50 kV, 180 mA, slit width (3 locations) 1/2 °, 1/2 °, 0.15 mm, scan method 2θ / θ method, scan speed 1 ° / Min, the measurement range (2θ) is 17 to 20 °, and the step is 0.004 °. The accuracy of the crystallite size by this method was ± 30 mm.
[0036]
Next, a coin-type battery was produced by the following method using this positive electrode active material.
A positive electrode active material, carbon black as a conductive agent, and ethylene tetrafluoride dissolved (or swollen) in N-methyl-2-pyrrolidone are kneaded at a mass ratio of 80:10:10, and this paste is made of aluminum expanded metal. A positive electrode was formed by pressure molding at ² t / cm ² on a current collector comprising: On the other hand, a lithium foil having a predetermined thickness was used as the negative electrode. As an electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / liter in a mixed solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2 was used. Using these positive and negative electrodes, a polypropylene separator, and an electrolytic solution, a 2016 coin-type battery was produced.
Using the battery produced by the above method, charge / discharge was repeated at a charge / discharge rate of 1 C and a voltage range of 4.2 V to 3.0 V, and a charge / discharge cycle test was performed. Table 1 summarizes the composition, lattice constant, crystal size, discharge capacity, and capacity retention rate of the composite oxide.
[0037]
(Example 2-5, Example 6, Example 7-14)
With reference to Example 1, a positive electrode active material was produced in the same manner as in Example 1 except that the mixing ratio of manganese carbonate, lithium carbonate, and aluminum oxide was different, and its lattice constant, crystallite size, discharge capacity, capacity retention rate The results are summarized in Table 1.
[0038]
(Example 15)
Lithium carbonate, manganese carbonate, and 150 m ² / g of vapor phase alumina were mixed by a ball mill so that the molar ratio of Li / Mn / Al was 1.03: 1.957: 0.013. The reaction was carried out at 4 ° C. for 4 hours. Boron oxide (0.4% by mass) was added to the obtained reaction powder, and wet milled with a ball mill using water as a dispersion medium to obtain an average particle size of 0.3 μm. After drying the slurry, the slurry was granulated with a Spartan Luser RMO-6H manufactured by Fuji Powder Corporation. The pulverized powder was granulated by adding 1.5% by weight of polyvinyl alcohol as an aqueous solution as a granulating binder. The obtained granulated powder was lightly pulverized and pulverized with a mixer and sized to 20 μm by air classification. The sized granulated powder was kept in the atmosphere at 500 ° C. for 2 hours, degreased, and then baked at 750 ° C. for 30 minutes to obtain a composite oxide.
[0039]
Pure water was added to the resulting composite oxide to form a slurry with a solid content concentration of 20%, ultrasonic treatment was performed for 5 minutes, and the process until the supernatant was removed was washed 10 times and dried at 100 ° C. . The solution was added to an aqueous solution containing 5 mol% of nitric acid with respect to the obtained composite oxide having a spinel structure, and after confirming that the pH of the aqueous solution became constant near neutrality, the solution was filtered and washed to 100 ° C. And vacuum dried. And it heat-processed at 300 degreeC for 4 hours, and obtained the positive electrode active material of this invention.
The obtained positive electrode active material was subjected to battery evaluation in the same manner as described in Example 1. Table 1 summarizes the results of the composition, lattice constant, crystallite size, discharge capacity, and capacity retention rate of the composite oxide.
[0040]
[Table 1]
[0041]
(Comparative Examples 1-10)
With reference to Example 1, a positive electrode active material was produced in the same manner as in Example 1 except that the mixing ratio of manganese carbonate, lithium carbonate, and aluminum oxide was different, and its lattice constant, crystallite size, discharge capacity, capacity retention rate The results are summarized in Table 2.
[0042]
(Comparative Examples 11 and 12)
With reference to Example 1, a positive electrode active material was produced in the same manner as in Example 1 except that the firing temperature was different, and its lattice constant, crystallite size, discharge capacity, capacity retention rate were examined, and the results are shown in Table 2. Summarized.
[0043]
(Comparative Example 13)
With reference to Example 1, a positive electrode active material was produced in the same manner as in Example 1 except that manganese carbonate having a BET specific surface area of 8 m ² / g was used as a manganese raw material, and its lattice constant, crystallite size, discharge capacity, The capacity retention rate was examined and the results are summarized in Table 2.
[0044]
(Comparative Example 14)
With reference to Example 1, except that electrolytic manganese dioxide having a BET specific surface area of 15 m ² / g was used as the manganese raw material, the lattice constant, crystallite size, discharge capacity, capacity retention rate of the positive electrode active material were the same as in Example 1. The results are summarized in Table 2.
[0045]
(Comparative Example 15)
With reference to Example 1, except that electrolytic manganese dioxide having a BET specific surface area of 80 m ² / g was used as the manganese raw material, the lattice constant, crystallite size, discharge capacity, capacity retention rate of the positive electrode active material were the same as in Example 1. The results are summarized in Table 2.
[0046]
(Comparative Example 16)
With reference to Example 1, except that manganese trioxide having a BET specific surface area of 5 m ² / g was used as the manganese raw material, the lattice constant, crystallite size, discharge capacity, capacity retention rate of the positive electrode active material were the same as in Example 1. The results are summarized in Table 2.
[0047]
(Comparative Example 17)
With reference to Example 1, the lattice constant, crystallite size, discharge capacity, and capacity retention rate of the positive electrode active material were determined in the same manner as in Example 1 except that aluminum oxide having a BET specific surface area of 10 m ² / g was used as the aluminum raw material. The results are summarized in Table 2.
[0048]
(Comparative Example 18)
With reference to Example 1, the lattice constant, crystallite size, discharge capacity, and capacity retention rate of the positive electrode active material were determined in the same manner as in Example 12 except that aluminum oxide having a BET specific surface area of 10 m ² / g was used as the aluminum raw material. The results are summarized in Table 2.
[0049]
(Comparative Example 19)
With reference to Example 1, a positive electrode active material was produced in the same manner as in Example 1 except that the mixing ratio of manganese carbonate, lithium carbonate, and aluminum oxide was different, and its lattice constant, crystallite size, discharge capacity, capacity retention rate The results are summarized in Table 2. However, in this comparative example, no aluminum oxide was added.
[0050]
[Table 2]
[0051]
As described above, the results obtained in Examples 1 to 5, Reference Example 6, Examples 7 to 15, and Comparative Examples 1 to 19 indicate that X, Y, and lattice constants in Li _X Al _Y Mn _{3 -XYO Z} (Å ), Crystallite size (Å), initial discharge capacity (mAh / g), discharge capacity after 100 cycles (mAh / g), capacity retention rate after 100 cycles are summarized in Table 1 or Table 2. It was. The amount of oxygen indicating the composition ratio Z is difficult to accurately analyze and has oxygen defects, but is usually in the range of 3.5 <z ≦ 4.5. The capacity retention rate was obtained from the calculation of (discharge capacity after 100 cycles / discharge capacity of initial cycle) × 100.
[0052]
【The invention's effect】
Conventional Li, Mn, in the production of the composite oxide _{Li x Al y Mn 3-xy} O z having a spinel structure consisting of Al and O, it is necessary to add a large amount of Al to the solid solution is difficult advances, its As a result, there was a drawback that the initial capacity of the battery when the secondary battery was manufactured was reduced, but the positive electrode active material of the present invention had an Al addition ratio in the low concentration range of 0 <y <0.02. Thus, it was found that the solid solution at the time of production proceeds unexpectedly.
[0053]
Further, the composite oxide having a Li _{x A y} Mn _{3 -xy} O _z structure with composition ranges of 1.0 <x ≦ 1.1, 0 <y <0.02, and 3.5 <z ≦ 4.5. In the object, the lattice constant (Å) is smaller than the value represented by L1 (x, y) = − 0.24x−0.28y + 8.481, and L2 (x, y) = − 0.24x-0. A value larger than the value represented by 72y + 8.481 is preferable.
In the composition range, when a solid solution is completely formed, the lattice constant (Å) is in the plane represented by the relational expression (−0.24x−0.72y + 8.481) of L2 (x, y). For the first time.
In the present invention, by using the positive electrode active material for a non-aqueous secondary battery, the non-aqueous secondary battery has a high practicality and almost no decrease in capacity compared to a conventional battery using a manganese oxide system. It has been found that a battery can be obtained.
[Brief description of the drawings]
FIG. 1 represents a range of lattice constants effective in the present invention.

Claims (9)

Li, Mn, complex oxide having a spinel structure consisting of Al and O, in _{Li x Al y Mn 3-xy} O z, 1.0 <x ≦ 1.050, 0 <y <0.02,3. 5 <range der of z ≦ 4.5, the lattice constant (Å) is less than -0.24x-0.28y + 8.481, and the -0.24x-0.72y + 8.481 or more, the crystallite size, positive electrode active material for nonaqueous secondary battery, characterized der Rukoto more and 950Å or less 400 Å. 2. The positive electrode active material for a non-aqueous secondary battery according to claim 1 , wherein the composite oxide having a spinel structure is a particle having an average particle diameter of 2 μm or less. 2. The positive electrode active material for a non-aqueous secondary battery according to claim 1 , wherein the composite oxide having a spinel structure is a granulated and fired particle having a particle diameter of 3 μm to 50 μm. The paste for electrodes containing the positive electrode active material for nonaqueous secondary batteries of any one of Claims 1 thru | or 3 . The paste for electrodes according to claim 4 , wherein the paste contains a positive electrode active material or a granulated product thereof, a conductivity imparting agent, a binder and a solvent. 6. The electrode paste according to claim 5 , wherein the total solid content concentration of the positive electrode active material or the granulated product, the conductivity imparting agent and the binder in the paste is in the range of 30% by mass to 70% by mass. . The positive electrode containing the positive electrode active material for nonaqueous secondary batteries of any one of Claims 1 thru | or 3 . A negative electrode including an active material capable of reversibly occluding and releasing lithium ions, a non-aqueous electrolyte solution or a polymer electrolyte, and a positive electrode including a composite oxide active material having a spinel structure made of Li, Mn, Al, and O A nonaqueous secondary battery, wherein the composite oxide is the positive electrode active material for a nonaqueous secondary battery according to any one of claims 1 to 3 . The nonaqueous secondary battery according to claim 8 , wherein the nonaqueous secondary battery is a coin-type battery or a cylindrical battery, a square battery, or a polymer battery.