JP2011023335A - Electrode for nonaqueous secondary battery and nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a nonaqueous secondary battery with high capacity and high stability and a nonaqueous secondary battery having the same electrode. <P>SOLUTION: The nonaqueous secondary battery has an electrode mixture layer using lithium content composite oxide represented by a general composition formula Li<SB>1+x</SB>MO<SB>2</SB>[-0.3≤x≤0.3; M represents at least two types of elements selected from at least Co, Mn, Al, Mg and Ti and at the same time, three or more types of element groups including Ni; 45≤a≤97, b≤49, c≤49, d≤10, e≤10, f≤10 and 3≤b+c+d+e+f≤55 when the ratios (mol%) of Ni, Co, Mn, Al, Mg and Ti among respective elements composing M are represented by a, b, c, d, e, and f] and having an average valence of Ni of 2.5 to 2.9. In this case, the nonaqueous secondary battery has the electrode for nonaqueous secondary battery as the positive electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery electrode having high capacity and high stability, and a non-aqueous secondary battery having the electrode.

In recent years, with the development of portable electronic devices such as mobile phones and laptop computers, and the practical application of electric vehicles, secondary batteries and capacitors having a small size and a high capacity have been required. Currently, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like are generally used as positive electrode active materials for high-capacity secondary batteries and capacitors that can meet this requirement.

In particular, in achieving high capacity of the secondary battery, it is effective to use LiNiO ₂ as the positive electrode active material, but since the thermal stability in the charged state is lower than that of LiCoO ₂ , It was difficult to satisfy safety. Also, a battery using LiNiO ₂ could not ensure satisfactory characteristics from the viewpoint of charge / discharge cycle life due to the low reversibility of the crystal structure of LiNiO ₂ .

Under such circumstances, in order to maintain the LiNiO ₂ charged state crystal structure, attempts have been made to improve its safety and reversibility by substituting Ni with elements such as Co, Al, and Mg. (For example, Patent Document 1).

JP 2007-273108 A

However, the lithium-containing composite oxide in which Ni is substituted with other elements as described above does not sufficiently improve safety and reversibility when the substitution amount is small, and when the substitution amount is large. Causes a decrease in capacity, and it is difficult to fully exhibit the characteristics of LiNiO ₂ .

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous secondary battery electrode having high capacity and high stability and a non-aqueous secondary battery having the electrode. is there.

  The electrode for a non-aqueous secondary battery of the present invention that has achieved the above object is represented by the following general composition formula (1), and the lithium-containing composite oxidation wherein the average valence of Ni is 2.5 to 2.9 It has the electrode mixture layer which used the thing.

Li _{1 + x} MO ₂ (1)
[However, in the general composition formula (1), −0.3 ≦ x ≦ 0.3, and M is at least three elements selected from Co, Mn, Al, Mg, and Ti; This represents a group of four or more elements including Ni, and the ratio (mol%) of Ni, Co, Mn, Al, Mg and Ti in each element constituting M is represented by a, b, c, d, When e and f, 45 ≦ a ≦ 97, b ≦ 49, c ≦ 49, d ≦ 10, e ≦ 10, f ≦ 10 and 3 ≦ b + c + d + e + f ≦ 55. ]

  The nonaqueous secondary battery of the present invention is a nonaqueous secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode is the electrode for a nonaqueous secondary battery of the present invention. It is what.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous secondary battery electrode with high capacity | capacitance and high stability and the nonaqueous secondary battery which has this electrode can be provided. That is, the non-aqueous secondary battery of the present invention has a high capacity, high safety, and a long charge / discharge cycle life.

It is a schematic diagram which shows an example of the non-aqueous secondary battery of this invention, (a) Top view, (b) Cross-sectional view. FIG. 2 is a perspective view of FIG. 1.

  In the electrode for a non-aqueous secondary battery of the present invention (hereinafter sometimes simply referred to as “electrode”), for example, an electrode mixture layer containing an active material or the like is formed on one side or both sides of a current collector. It is composed of that. The electrode of the present invention has a lithium-containing composite oxide represented by the general composition formula (1) as an active material and having an average Ni valence of 2.5 to 2.9.

  The electrode of the present invention is used for a positive electrode of a non-aqueous secondary battery, and the lithium-containing composite oxide acts as a positive electrode active material for the non-aqueous secondary battery. A non-aqueous secondary battery (non-aqueous secondary battery of the present invention) constituted by using the electrode of the present invention as a positive electrode has a high capacity, high safety, and a long charge / discharge cycle life.

  The lithium-containing composite oxide according to the electrode of the present invention contains at least three elements selected from Co, Mn, Al, Mg, and Ti, and four or more element groups M including Ni. Among these, Ni is a component which contributes to the capacity | capacitance improvement of lithium containing complex oxide.

  In the general composition formula (1) representing the lithium-containing composite oxide, it is preferable to increase the Ni ratio in order to achieve high capacity. However, if the Ni ratio is too large, Ni becomes a Li site. When introduced, it tends to have a non-stoichiometric composition. In the lithium-containing composite oxide, as described above, the average valence of Ni is in a specific range, but since trivalent Ni is unstable, Ni tends to have an oxidation number lower than that of trivalence. For example, it becomes difficult to control the oxidation number of Ni by firing in the atmosphere (a method for synthesizing a lithium-containing composite oxide will be described later). In addition, when the valence of Ni is lowered, the capacity is usually lowered or the reversibility is lost.

  Therefore, in the general formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Ni ratio a is from the viewpoint of improving the capacity of the lithium-containing composite oxide. , 45 mol% or more, preferably 50 mol% or more, more preferably 70 mol% or more, and from the viewpoint of avoiding the above-mentioned problem due to the excessive Ni ratio. In the electrode of the present invention, the lithium-containing compound used as the active material is selected from Co, Mn, Al, Mg, and Ti as long as the ratio of Ni is adjusted as described above and Ni satisfies the ratio. By including at least three kinds of elements, for example, stable production of a lithium-containing composite oxide having a capacity of 180 mAh / g or more (when the drive voltage is 2.5 to 4.3 V based on lithium metal). Is possible.

  In addition, the electrical conductivity of lithium containing complex oxide falls, so that the average valence of Ni becomes small. Therefore, the lithium-containing composite oxide particles have an average valence of Ni measured by the method shown in Examples below to be 2.5 to 2.9. This also makes it possible to synthesize stably in the air, and to obtain a high-capacity lithium-containing composite oxide that is excellent in productivity and thermal stability.

  The lithium-containing composite oxide contains at least three elements selected from Co, Mn, Al, Mg and Ti as well as Ni as the element group M.

  In the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Co ratio b is 49 mol% or less and Co is present in the crystal lattice. And the reversibility of the crystal structure of the lithium-containing composite oxide can be mitigated, and the irreversible reaction resulting from the phase transition of the lithium-containing composite oxide by Li doping and dedoping during non-aqueous secondary battery charging and discharging can be improved. Therefore, a non-aqueous secondary battery having a long charge / discharge cycle life can be configured. In addition, in order to ensure the above-mentioned effect by containing Co better, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. In addition, the Co ratio b is preferably 1 mol% or more.

  Co in the lithium-containing composite oxide is preferably such that the average valence is a value lower than trivalent, for example, 2.2 to 2.9, as measured by the method described in the examples below. As a result, the valence of Ni can be prevented from being lowered more than necessary, and the reversibility of the lithium-containing composite oxide can be further increased.

  In the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Mn ratio c is 49 mol% or less, and Mn is contained in the crystal lattice. When present, the layered structure can be stabilized together with the divalent Ni, and the thermal stability of the lithium-containing composite oxide can be improved, so that a safer non-aqueous secondary battery can be configured. It becomes. In addition, in order to ensure the above-mentioned effect by containing Mn more satisfactorily, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. Further, it is preferable that the ratio c of Mn is 1 mol% or more.

  Mn in the lithium-containing composite oxide is a value measured by the method shown in Examples below, and is preferably 3.5 to 4, preferably 3.8 or more. More preferably, by setting the value close to tetravalent in this way, the stability of divalent Ni is improved, and the above-described effects are ensured better. Note that the valence of Mn may be slightly larger than 4.0 in consideration of measurement errors and the like, and therefore, the upper limit value of the valence is “4.0 valence” as a numerical value including such an error. Instead, it is expressed as “tetravalent”.

  In the lithium-containing composite oxide, when Al is present in the crystal lattice, the crystal structure of the lithium-containing composite oxide can be stabilized and the thermal stability thereof can be improved, so that the safety is higher. A non-aqueous secondary battery can be configured. In addition, since Al is present at the grain boundaries and surfaces of the lithium-containing composite oxide particles, the stability over time and side reactions with the electrolyte can be suppressed, and a longer-life non-aqueous secondary battery is constructed. It becomes possible to do.

  However, since Al cannot participate in the charge / discharge capacity, increasing the content in the lithium-containing composite oxide may cause a decrease in capacity. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Al ratio d is 10 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Al more favorably, when the total number of elements in the element group M is 100 mol% in the general composition formula (1) representing the lithium-containing composite oxide. In addition, the Al ratio d is preferably 0.02 mol% or more.

  In the lithium-containing composite oxide, when Mg is present in the crystal lattice, the crystal structure of the lithium-containing composite oxide can be stabilized and the thermal stability thereof can be improved, so that the safety is higher. A non-aqueous secondary battery can be configured. In addition, when the phase transition of the lithium-containing composite oxide occurs due to Li doping and dedoping during charge / discharge of the non-aqueous secondary battery, the irreversible reaction is mitigated by the rearrangement of Mg to the Li site, and the lithium-containing composite oxidation Since the reversibility of the crystal structure of the product can be increased, a non-aqueous secondary battery having a long charge / discharge cycle life can be formed. In particular, in the general composition formula (1) representing the lithium-containing composite oxide, when x <0 and the lithium-containing composite oxide has a Li-deficient crystal structure, Mg instead of Li becomes a Li site. A lithium-containing composite oxide can be formed in a form that enters, and a stable compound can be obtained.

  However, since Mg has a small contribution to the charge / discharge capacity, if the content in the lithium-containing composite oxide is increased, the capacity may be reduced. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Mg ratio e is 10 mol% or less. In addition, in order to ensure the above-mentioned effect by containing Mg more satisfactorily, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol% In addition, the Mg ratio e is preferably 0.02 mol% or more.

When Ti is contained in the particles in the lithium-containing composite oxide, the lithium-containing composite oxide has a LiNiO ₂ type crystal structure that is disposed in a crystal defect portion such as an oxygen vacancy to stabilize the crystal structure. The reversibility of the reaction is increased, and a non-aqueous secondary battery having excellent charge / discharge cycle characteristics can be configured. In order to ensure the above effect satisfactorily, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Ti ratio f is: It is preferable to set it as 0.01 mol% or more, and it is more preferable to set it as 0.1 mol% or more. However, when the content of Ti increases, Ti does not participate in charging / discharging, so that the capacity may be reduced, or a heterogeneous phase such as Li ₂ TiO ₃ may be easily formed, leading to deterioration in characteristics. Therefore, in the general composition formula (1) representing the lithium-containing composite oxide, when the total number of elements in the element group M is 100 mol%, the Ti ratio f needs to be 10 mol% or less. % Or less, more preferably 2 mol% or less.

  The lithium-containing composite oxide may contain at least three elements selected from Co, Mn, Al, Mg, and Ti as the element group M together with Ni. Specifically, the lithium-containing composite oxide may contain three elements among Co, Mn, Al, Mg, and Ti, and may contain four elements. It may contain all species. In the general composition formula (1), when the total number of elements in the element group M is 100 mol%, the Co ratio b, the Mn ratio c, the Al ratio d, the Mg ratio e, and the Ti ratio The total with f is 3 mol% or more and 55 mol% or less, preferably 50 mol% or less, and more preferably 30 mol% or less.

  The element group M in the general composition formula (1) representing the lithium-containing composite oxide may contain elements other than Ni, Co, Mn, Al, Mg, and Ti. For example, Cr, Fe, It may contain elements such as Cu, Zn, Ge, Sn, Ca, Sr, Ba, Ag, Ta, Nb, Mo, B, P, Zr, W, and Ga. However, in order to sufficiently obtain the effects of the present invention, the ratio of elements other than Ni, Co, Mn, Al, Mg and Ti (mol%) when the total number of elements in the element group M is 100 mol%. When the total is expressed in g, g is preferably 10 mol% or less, more preferably 3 mol% or less, and particularly preferably 1 mol% or less. Elements other than Ni, Co, Mn, Al, Mg and Ti in the element group M may be uniformly distributed in the lithium-containing composite oxide, or may be segregated on the particle surface or the like.

  For example, when Ge is added, since the crystal structure of the composite oxide after Li is desorbed is stabilized, the reversibility of the reaction in charge / discharge can be improved, and the safety is high, and the cycle characteristics It is possible to construct a non-aqueous secondary battery that is excellent in the performance. In particular, when Ge is present on the particle surface or grain boundary, disorder of the crystal structure due to Li desorption / insertion at the interface is suppressed, and a high effect can be exhibited in improving cycle characteristics.

When an alkaline earth metal such as Ca, Sr, or Ba is added, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved. Stability over time is improved, and irreversible reaction with the electrolyte can be suppressed. Furthermore, since these elements are present on the particle surface and grain boundaries, the CO ₂ gas in the battery can be trapped, so that it is possible to construct a non-aqueous secondary battery with better storage and longer life. . In particular, when the lithium-containing composite oxide contains Mn, the primary particles tend to be difficult to grow. Therefore, the addition of alkaline earth metals such as Ca, Sr, and Ba is more effective.

  Even when B is added, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved. Therefore, the active sites can be reduced, and moisture in the atmosphere and formation of the electrode mixture layer can be reduced. Irreversible reaction with the binder and electrolyte used in the above can be suppressed. For this reason, the stability over time when it is made into a paint is improved, gas generation in the battery can be suppressed, and a non-aqueous secondary battery having excellent storage properties and a long life can be configured. In particular, when the lithium-containing composite oxide contains Mn, the addition of B is more effective because the primary particles tend to hardly grow.

  In the case where Zr is added, the presence of lithium-containing composite oxide particles at the grain boundaries and the surface suppresses the surface activity without impairing the electrochemical properties of the lithium-containing composite oxide, thereby making it more storable. An excellent long-life non-aqueous secondary battery can be configured.

  When Ga is added, the growth of primary particles is promoted and the crystallinity of the lithium-containing composite oxide is improved, so that the active sites can be reduced, and the stability over time when made into a paint is improved, Irreversible reaction with the electrolyte can be suppressed. Further, by dissolving in the crystal structure of the lithium-containing composite oxide, the layer spacing of the crystal lattice can be expanded, and the rate of expansion and contraction of the lattice due to insertion and desorption of Li can be reduced. For this reason, the reversibility of the crystal structure can be enhanced, and a non-aqueous secondary battery with a high cycle life can be configured. In particular, when the lithium-containing composite oxide contains Mn, the addition of Ga is more effective because the primary particles tend to hardly grow.

  In order to easily obtain the effect of the element selected from Ge, Ca, Sr, Ba, B, Zr and Ga, the ratio thereof is 0.1 mol% or more in all elements of the element group M. preferable.

The lithium-containing composite oxide having the above composition has a large true density of 4.55 to 4.95 g / cm ³ and is a material having a high volume energy density. The true density of the lithium-containing composite oxide containing Al and Mn in a certain range varies greatly depending on the composition, but the structure is stabilized and the uniformity can be improved in the narrow composition range as described above. For example, it is considered to be a large value close to the true density of LiCoO ₂ . Moreover, the capacity | capacitance per mass of lithium containing complex oxide can be enlarged, and it can be set as the material excellent in reversibility.

When the lithium-containing composite oxide has a composition close to the stoichiometric ratio, the true density increases. Specifically, in the general composition formula (1), −0.3 ≦ x ≦ 0. .3 is preferable, and the true density and reversibility can be improved by adjusting the value of x in this way. x is more preferably −0.1 or more and 0.1 or less. In this case, the true density of the lithium-containing composite oxide can be set to a higher value of 4.6 g / cm ³ or more. .

The lithium-containing composite oxide moderately suppresses the activity of the particle surface, thereby suppressing gas generation in a battery using the electrode of the present invention (the battery of the present invention), and in particular, a rectangular (rectangular cylindrical) exterior. In the case of a battery having a body, deformation of the exterior body can be suppressed, and the storage property and life can be improved. From the viewpoint of securing such an effect, the lithium-containing composite oxide preferably has the following form. First, the lithium-containing composite oxide is in the form of particles, and the ratio of primary particles having a particle size of 1 μm or less in all primary particles is preferably 30% by volume or less, and 15% by volume or less. More preferred. Further, BET specific surface area of the lithium-containing composite oxide is preferably at 0.3 m ² / g or less, and more preferably less 0.25 m ² / g.

  That is, in the lithium-containing composite oxide, if the proportion of primary particles having a particle size of 1 μm or less in all primary particles is too large, or if the BET specific surface area is too large, the reaction area is large and the active points are increased. Moisture in the atmosphere, binder used to form the electrode mixture layer, irreversible reaction with the nonaqueous electrolyte of the battery is likely to occur, and gas may be generated in the battery to cause deformation of the outer body, There is a possibility of causing gelation of a composition (paste, slurry, etc.) containing a solvent used for forming the electrode mixture layer.

The lithium-containing composite oxide may not contain any primary particles having a particle size of 1 μm or less (that is, the proportion of primary particles having a particle size of 1 μm or less may be 0% by volume). Further, the BET specific surface area of the lithium-containing composite oxide is preferably 0.1 m ² / g or more in order to prevent the reactivity from being lowered more than necessary. Furthermore, the lithium-containing composite oxide preferably has a number average particle size of 5 to 25 μm.

  The ratio of primary particles having a particle size of 1 μm or less contained in the lithium-containing composite oxide, and the number-average particle size of the lithium-containing composite oxide (further, the number-average particle size of other active materials described later) are It can be measured by a laser diffraction / scattering particle size distribution measuring apparatus, for example, “Microtrac HRA” manufactured by Nikkiso Co., Ltd. Further, the BET specific surface area of the lithium-containing composite oxide is a specific surface area of the surface of the active material and the micropores, which is obtained by measuring and calculating the surface area using the BET formula, which is a theoretical formula of multimolecular layer adsorption. . Specifically, it is a value obtained as a BET specific surface area using a specific surface area measuring device (“Macsorb HM model-1201” manufactured by Mounttech) by a nitrogen adsorption method.

  The lithium-containing composite oxide particles preferably have a spherical shape or a substantially spherical shape from the viewpoint of increasing the density of the electrode mixture layer and increasing the capacity of the electrode, and thus the capacity of the nonaqueous secondary battery. . Thus, in the pressing step (details will be described later) during electrode production, when the lithium-containing composite oxide particles are moved by pressing to increase the density of the electrode mixture layer, the particles can be moved without difficulty. And the particles are smoothly rearranged. Therefore, since the press load can be reduced, it is possible to reduce the damage of the current collector accompanying the press, and to increase the productivity of the electrode. Further, when the particles of the lithium-containing composite oxide are spherical or substantially spherical, the particles can withstand a larger pressing pressure, so that the electrode mixture layer can have a higher density. .

Furthermore, the lithium-containing composite oxide preferably has a tap density of 2.3 g / cm ³ or more, and preferably 2.8 g / cm ³ or more, from the viewpoint of enhancing the filling property in the electrode mixture layer. More preferred. The tap density of the lithium-containing composite oxide is preferably 3.8 g / cm ³ or less. That is, the ratio of the pores is such that the tap density is high and there are no pores inside the particles, or the area ratio of minute pores of 1 μm or less measured by cross-sectional observation of the particles is 10% or less. By setting it as few particle | grains, the filling property of the lithium containing complex oxide in an electrode mixture layer can be improved.

The tap density of the lithium-containing composite oxide is a value determined by the following measurement using “Powder Tester PT-S type” manufactured by Hosokawa Micron. The particles are ground into a measuring cup 100 cm ³ and tapped for 180 seconds while appropriately replenishing the reduced volume. After tapping is completed, excess particles are scraped off with a blade, and then the mass (A) (g) is measured, and the tap density is obtained by the following equation.

    Tap density = (A) / 100

  In synthesizing the lithium-containing composite oxide, it is very easy to obtain a high purity by simply mixing and firing raw material compounds such as a Li-containing compound, a Ni-containing compound, a Co-containing compound, and a Mn-containing compound. Have difficulty. This is because Ni, Mn, and the like have a low diffusion rate in the solid, so that it is difficult to uniformly diffuse them during the synthesis reaction of the lithium-containing composite oxide. It is thought that Ni, Mn, etc. are difficult to distribute uniformly.

  Therefore, when synthesizing the lithium-containing composite oxide according to the present invention, a composite compound containing at least three elements selected from Co, Mn, Al, Mg and Ti, and Ni as a constituent element, and Li It is preferable to employ a method of firing the containing compound, and by such a method, the lithium-containing composite oxide can be synthesized relatively easily with high purity. That is, at least three elements selected from Co, Mn, Al, Mg, and Ti, and a composite compound containing at least Ni are synthesized in advance, and calcined together with a Li-containing compound, thereby forming an oxide reaction. In the above, at least three elements selected from Co, Mn, Al, Mg and Ti, and Ni are uniformly distributed, and the lithium-containing composite oxide is synthesized with higher purity.

  The method for synthesizing the lithium-containing composite oxide according to the present invention is not limited to the above-described method, but depending on what synthesis process is performed, the physical properties of the finally obtained composite oxide, that is, the structure It is estimated that the stability, reversibility of charge / discharge, true density, and the like greatly change.

Here, as the composite compound containing at least three elements selected from Co, Mn, Al, Mg and Ti and at least Ni, for example, at least three elements selected from Co, Mn, Al, Mg and Ti are used. Coprecipitation compound containing at least element and Ni, hydrothermally synthesized compound, mechanically synthesized compound, compound obtained by heat-treating them, Ni _0.7 Mn _0.1 Mg _0.2 (OH) ₂ , NiMn ₂ O ₄ , Ni _0.6 Co _0.3 Al _0.1 OOH, and other oxides of Ni and at least three elements selected from Co, Mn, Al, Mg and Ti or Hydroxides are preferred.

  In addition, a part of the element group M is further added to elements other than Ni, Co, Mn, Al, Mg, and Ti (for example, Cr, Fe, Cu, Zn, Ge, Sn, Ca, Sr, Ba, Ag, Ta). , Nb, Mo, B, P, Zr, W, and Ga. The lithium-containing composite oxide containing at least one element selected from the group consisting of N, Mo, B, P, Zr, W, and Ga. Is a process of mixing and firing at least three elements selected from Co, Mn, Al, Mg and Ti, a composite compound containing at least Ni, a Li-containing compound, and a compound containing the element M ′. Can be synthesized.

  However, in order to obtain a more homogeneous composite oxide, the element M ′ is preferably contained together in a composite compound containing Ni or the like, and a composite compound containing all the constituent elements of the element group M, that is, It is preferable to use a composite compound containing at least three elements selected from Co, Mn, Al, Mg, and Ti, Ni, and the element M ′.

  The amount ratio of at least three elements selected from Co, Mn, Al, Mg and Ti, Ni, and element M ′ in the composite compound is appropriately adjusted according to the composition of the target lithium-containing composite oxide. do it.

  As the Li-containing compound that can be used for the synthesis of the lithium-containing composite oxide, various lithium salts can be used. For example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide , Lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide, etc. Among them, carbon dioxide gas, nitrogen oxide Lithium hydroxide monohydrate is preferable because it does not generate a gas that adversely affects the environment, such as substances and sulfur oxides.

  In order to synthesize the lithium-containing composite oxide, first, at least three elements selected from Co, Mn, Al, Mg and Ti, and a composite compound containing at least Ni (a composite containing the element M ′) are also included. Compound), a Li-containing compound, and an element M′-containing compound used as necessary are mixed at a ratio approximately corresponding to the composition of the target lithium-containing composite oxide. And the said lithium containing complex oxide can be obtained by baking the obtained raw material mixture at 600-1000 degreeC for 1 to 24 hours, for example.

  When firing the raw material mixture, rather than raising the temperature to a predetermined temperature at one time, once heated to a temperature lower than the firing temperature (for example, 250-850 ° C.), preheating by holding at that temperature, Thereafter, it is preferable to raise the temperature to the firing temperature to advance the reaction, and it is preferable to keep the oxygen concentration in the firing environment constant.

  This is selected from Co, Mn, Al, Mg, and Ti because trivalent Ni is unstable in the production process of the lithium-containing composite oxide according to the present invention and is likely to have a non-stoichiometric composition. Reaction of at least three kinds of elements and a composite compound containing at least Ni (further, a composite compound containing element M ′), a Li-containing compound, and an element M′-containing compound used as necessary This is because it is generated stepwise to increase the homogeneity of the resulting lithium-containing composite oxide, and the generated lithium-containing composite oxide can be stably crystal-grown. That is, when the temperature is raised to the firing temperature at once, or when the oxidation concentration of the firing environment decreases during firing, at least three elements selected from Co, Mn, Al, Mg and Ti, and Ni A compound containing at least (compound compound containing element M ′), a Li-containing compound, and an element M′-containing compound used as necessary are likely to react inhomogeneously, resulting in a lithium-containing product The uniformity of the composition tends to be impaired, for example, the composite oxide tends to release Li.

  In addition, although there is no restriction | limiting in particular about the time of the said preheating, Usually, what is necessary is just to be about 0.5 to 30 hours.

  In addition, the firing atmosphere of the raw material mixture may be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (argon, helium, nitrogen, etc.) and oxygen gas, an oxygen gas atmosphere, or the like. However, the oxygen concentration (volume basis) at that time is preferably 15% or more, and more preferably 18% or more. However, from the viewpoint of reducing the production cost of the lithium-containing composite oxide particles and increasing the productivity of the particles and thus the productivity of the electrodes, it is more preferable to perform the firing of the raw material mixture in an atmospheric flow.

The flow rate of the gas during firing of the raw material mixture is preferably 2 dm ³ / min or more per 100 g of the mixture. If the gas flow rate is too low, that is, if the gas flow rate is too slow, the homogeneity of the composition of the lithium-containing composite oxide may be impaired. In addition, it is preferable that the flow rate of the gas at the time of firing the raw material mixture is 5 dm ³ / min or less per 100 g of the mixture.

  In the step of firing the raw material mixture, the dry-mixed mixture may be used as it is, but the raw material mixture is dispersed in a solvent such as ethanol to form a slurry and mixed for about 30 to 60 minutes with a planetary ball mill or the like. It is preferable to use a dried product, and the homogeneity of the lithium-containing composite oxide to be synthesized can be further improved by such a method.

  In the manufacturing method, by appropriately controlling the gas composition and the firing temperature according to the composition, the average valence of Ni, Co and Mn satisfies the above range, and the particle size, the BET specific surface area, the number A lithium-containing composite oxide satisfying the average particle diameter and tap density can be obtained.

The electrode of the present invention has an electrode mixture layer containing the lithium-containing composite oxide as an active material, but the electrode mixture layer may also contain other active materials. Examples of other active materials other than the lithium-containing composite oxide include lithium cobalt oxides such as LiCoO ₂ ; lithium manganese oxides such as LiMnO ₂ and Li ₂ MnO ₃ ; lithium nickel oxides such as LiNiO ₂ ; LiCo Lithium-containing composite oxide having a layered structure such as _1-x NiO ₂ ; Lithium-containing composite oxide having a spinel structure such as LiMn ₂ O ₄ , Li _4/3 Ti _5/3 O ₄ ; Lithium having an olivine structure such as LiFePO ₄ Containing composite oxides; oxides having the above-mentioned oxide as a basic composition and substituted with various elements; and the like can be used. In addition, when using another active material, in order to clarify the effect of this invention, it is desirable for the ratio of another active material to be 30% or less of the whole active material by mass ratio.

Among the other active material, the lithium cobalt oxide, other above exemplified LiCoO _2, a part of _{LiCoO 2 Co Ti, Cr, Fe} , Ni, Mn, Cu, Zn, Al, Ge An oxide substituted with at least one element selected from the group consisting of Sn, Mg and Zr (except for the lithium-containing composite oxide according to the present invention) is preferable. This is because these lithium cobalt oxides have a high conductivity of 1.0 × 10 ⁻³ S · cm ⁻¹ or more and can further enhance the load characteristics of the electrode.

Among the other active materials, examples of the spinel-structured lithium-containing composite oxide include LiMn ₂ O ₄ and Li _4/3 Ti _5/3 O _{4 described above} , as well as one of Mn of LiMn ₂ O _4. An oxide in which a part is substituted with at least one element selected from the group consisting of Ti, Cr, Fe, Ni, Co, Cu, Zn, Al, Ge, Sn, Mg, and Zr is preferable. These spinel-structured lithium-containing composite oxides are excellent in safety during overcharge because the amount of lithium that can be extracted is half that of lithium-containing oxides such as lithium cobaltate and lithium nickelate. This is because the safety of the electrochemical device can be further enhanced.

  When the lithium-containing composite oxide according to the present invention is used in combination with another active material, these may be used simply by mixing them, but these particles are used as composite particles integrated by granulation or the like. In this case, the packing density of the active material in the electrode mixture layer is improved, and the contact between the active material particles can be made more reliable. Therefore, the capacity and load characteristics of the battery using the electrode (the battery of the present invention) can be further enhanced.

  Further, when the lithium-containing composite oxide according to the present invention contains Mn, the lithium-containing composite oxide has a surface on the lithium-containing composite oxide when used as a composite particle with the lithium-containing cobalt oxide. By the presence of cobalt oxide, Mn and Co eluted from the composite particles are quickly deposited on the surface of the composite particles to form a film, so that the composite particles are chemically stabilized. As a result, decomposition of the non-aqueous electrolyte in the electrochemical element due to the composite particles can be suppressed, and further elution of Mn can be suppressed, so that a battery with better storage properties and charge / discharge cycle characteristics should be configured. Will be able to.

  When the composite particles are used, it is preferable that the number average particle diameter of one of the lithium-containing composite oxide according to the present invention and the other active material is ½ or less of the other number average particle diameter. When composite particles are formed by combining particles having a large number average particle diameter (hereinafter referred to as “large particles”) and particles having a small number average particle diameter (hereinafter referred to as “small particles”). In this case, small particles can be easily dispersed and fixed around the large particles, and composite particles having a more uniform mixing ratio can be formed. Therefore, non-uniform reaction in the electrode can be suppressed, and the charge / discharge cycle characteristics and safety of the electrochemical element can be further enhanced.

  When forming composite particles using large particles and small particles as described above, the number average particle size of the large particles is preferably 10 to 30 μm, and the number average particle size of the small particles is Is preferably 1 to 15 μm.

  The composite particles of the lithium-containing composite oxide and the other active material according to the present invention include, for example, the above-described lithium-containing composite oxide particles and other active material particles in a common uniaxial kneader or biaxial kneader. It is possible to obtain a composite by mixing using various kneaders such as a machine, sliding the particles together and applying a share. The kneading is preferably a continuous kneading method in which raw materials are continuously fed in consideration of the productivity of composite particles.

  During the kneading, it is preferable to add a binder to each of the active material particles. Thereby, the shape of the composite particle formed can be kept strong. Further, it is more preferable to add a conductive additive and knead. Thereby, the electroconductivity between active material particles can further be improved.

  As the binder to be added during the production of the composite particles, any thermoplastic resin or thermosetting resin can be used as long as it is chemically stable in the non-aqueous secondary battery. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (PHFP), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoro Propylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoro Ethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro An ethylene copolymer, an ethylene-chlorotrifluoroethylene copolymer (ECTFE), a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, a vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or , Ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and Na ion cross-linked products of these copolymers. May be used alone or in combination of two or more. Among these, considering the stability in the non-aqueous secondary battery and the characteristics of the non-aqueous secondary battery, PVDF, PTFE, and PHFP are preferable, and these are used in combination or formed of these monomers. A copolymer may be used.

  The amount of the binder added when forming the composite particles is preferably as small as the composite particles can be stabilized. For example, it is preferably 0.03 to 2 parts by mass with respect to 100 parts by mass of the total active material. .

  The conductive auxiliary agent added during the production of the composite particles may be any one that is chemically stable in the non-aqueous secondary battery. For example, graphite such as natural graphite and artificial graphite, acetylene black, ketjen black (trade name), carbon black such as channel black, furnace black, lamp black and thermal black; conductive fiber such as carbon fiber and metal fiber; aluminum Metallic powders such as powders; Fluorinated carbon; Zinc oxide; Conductive whiskers made of potassium titanate; Conductive metal oxides such as titanium oxide; Organic conductive materials such as polyphenylene derivatives; One species may be used alone, or two or more species may be used in combination. Among these, highly conductive graphite and carbon black excellent in liquid absorption are preferable. Further, the form of the conductive auxiliary agent is not limited to primary particles, and secondary aggregates and aggregated forms such as chain structures can also be used. Such an assembly is easier to handle and has better productivity.

  The amount of the conductive additive added when forming the composite particles is only required to ensure good conductivity and liquid absorption, for example, 0.1 to 2 parts by mass with respect to 100 parts by mass of the total active material. It is preferable.

  The composite particles preferably have a porosity of 5 to 15%. This is because the composite particles having such a porosity have appropriate contact with the non-aqueous electrolyte (non-aqueous electrolyte solution) and penetration of the non-aqueous electrolyte into the composite particles.

  Further, the shape of the composite particles is preferably spherical or substantially spherical, similarly to the lithium-containing composite oxide according to the present invention. Thereby, the density of the electrode mixture layer can be further increased.

  The electrode of the present invention can be produced, for example, by forming an electrode mixture layer containing the lithium-containing composite oxide or the composite particles as an active material on one side or both sides of a current collector.

  The electrode mixture layer is prepared by, for example, preparing a paste-like or slurry-like electrode mixture-containing composition by adding the lithium-containing composite oxide, the composite particles, the binder, and the conductive additive to a solvent. It can be formed by applying to the surface of the current collector by various coating methods, drying, and adjusting the thickness and density of the electrode mixture layer by a pressing process.

  Here, the presence of a conductive additive and a water repellent such as a fluorine-based resin or a silane compound in the electrode mixture layer facilitates the formation of a solid-phase / liquid-phase / gas-phase three-phase interface. Gas absorption is facilitated, and a non-aqueous secondary battery having excellent storage properties and long life can be configured.

  Examples of the coating method for applying the electrode mixture-containing composition to the surface of the current collector include a substrate lifting method using a doctor blade; a coater method using a die coater, comma coater, knife coater, etc .; screen printing, letterpress Printing methods such as printing can be adopted.

  Examples of the binder and conductive additive that can be used for the preparation of the electrode mixture-containing composition include various binders and various conductive aids exemplified as those that can be used for forming the composite particles.

  In the electrode mixture layer, the total active material including the lithium-containing composite oxide is 80 to 99% by mass, and the binder (including those contained in the composite particles) is 0.5 to 10% by mass. %, And the conductive assistant (including those contained in the composite particles) is preferably 0.5 to 10% by mass.

In addition, after the press treatment, the thickness of the electrode mixture layer is preferably 15 to 200 μm per one side of the current collector. Further, after pressing, the density of the electrode mixture layer is preferably 3.1 g / cm ³ or more, and more preferably 3.52 g / cm ³ or more. By using an electrode having such a high-density electrode mixture layer, higher capacity can be achieved. However, if the density of the electrode mixture layer is too large, the porosity becomes small and the permeability of the non-aqueous electrolyte may decrease, so the density of the electrode mixture layer after the press treatment is 4. It is preferably 0 g / cm ³ or less. In addition, as press processing, it can roll-press with the linear pressure of about 1-100 kN / cm, for example, and it can be set as the electrode mixture layer which has the said density by such processing.

  Moreover, the density of the electrode mixture layer as used in the present specification is a value measured by the following method. The electrode is cut into a predetermined area, the mass is measured using an electronic balance having a minimum scale of 0.1 mg, and the mass of the electrode mixture layer is calculated by subtracting the mass of the current collector. On the other hand, the total thickness of the electrode was measured at 10 points with a micrometer having a minimum scale of 1 μm, and the volume of the electrode mixture layer was calculated from the average value obtained by subtracting the thickness of the current collector from these measured values and the area. To do. Then, the density of the electrode mixture layer is calculated by dividing the mass of the electrode mixture layer by the volume.

  The material of the current collector of the electrode is not particularly limited as long as it is a chemically stable electron conductor in the constructed non-aqueous secondary battery. For example, in addition to aluminum or aluminum alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., a composite material in which a carbon layer or a titanium layer is formed on the surface of aluminum, aluminum alloy, or stainless steel can be used. . Among these, aluminum or an aluminum alloy is particularly preferable. This is because they are lightweight and have high electron conductivity. As the current collector of the electrode, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials is used. In addition, the surface of the current collector can be roughened by surface treatment. Although the thickness of a collector is not specifically limited, Usually, it is 1-500 micrometers.

  In addition, the electrode of this invention is not limited to what was manufactured by the said manufacturing method, The electrode manufactured by the other manufacturing method may be used. For example, when the composite particles are used as an active material, the composite particles are obtained by a method in which the composite particles are directly fixed on the current collector surface without using an electrode mixture-containing composition. It may be an electrode.

  Moreover, you may form in the electrode of this invention according to a conventional method the lead body for electrically connecting with the other member in a non-aqueous secondary battery as needed.

  The non-aqueous secondary battery of the present invention has the non-aqueous secondary battery electrode of the present invention as a positive electrode, and there is no particular limitation on the other configuration and structure, and the conventionally known non-aqueous secondary battery The configuration and structure employed in the secondary battery can be applied.

  The negative electrode has, for example, a structure in which a negative electrode mixture layer composed of a negative electrode mixture containing a negative electrode active material and a binder and, if necessary, a conductive additive is included on one or both sides of the current collector. Can be used.

  Examples of the negative electrode active material include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, and metals that can be alloyed with lithium (Si , Sn, etc.) or alloys thereof. Moreover, the same thing as what was illustrated previously as what can be used for the electrode of this invention can be used for a binder and a conductive support agent.

  The material of the current collector of the negative electrode is not particularly limited as long as it is an electron conductor that is chemically stable in the constructed battery. For example, in addition to copper or copper alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., a composite material in which a carbon layer or a titanium layer is formed on the surface of copper, copper alloy, or stainless steel can be used. . Among these, copper or a copper alloy is particularly preferable. This is because they are not alloyed with lithium and have high electron conductivity. For the current collector of the negative electrode, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials can be used. In addition, the surface of the current collector can be roughened by surface treatment. Although the thickness of a collector is not specifically limited, Usually, it is 1-500 micrometers.

  The negative electrode is, for example, a paste-like or slurry-like negative electrode mixture-containing composition (binder) in which a negative electrode active material and a binder, and further, if necessary, a negative electrode mixture containing a conductive additive are dispersed in a solvent. May be dissolved in a solvent) on one or both sides of the current collector and dried to form a negative electrode mixture layer. The negative electrode is not limited to the one obtained by the above production method, and may be one produced by another method. The thickness of the negative electrode mixture layer is preferably 10 to 300 μm per one side of the current collector.

  The separator is preferably a porous film composed of polyolefin such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester such as polyethylene terephthalate and copolymer polyester; In addition, it is preferable that a separator has the property (namely, shutdown function) which the hole obstruct | occludes in 100-140 degreeC. Therefore, the separator is made of a thermoplastic resin having a melting point, that is, a melting temperature measured using a differential scanning calorimeter (DSC) of 100 to 140 ° C. in accordance with JIS K 7121. Preferably, it is a single layer porous film mainly composed of polyethylene or a laminated porous film comprising a porous film such as a laminated porous film in which 2 to 5 layers of polyethylene and polypropylene are laminated. Is preferred. When a resin having a melting point higher than that of polyethylene such as polyethylene and polypropylene is used by mixing or laminating, it is desirable that polyethylene is 30% by mass or more, and 50% by mass or more as a resin constituting the porous membrane. More desirable.

  As such a resin porous membrane, for example, a porous membrane composed of the above-mentioned exemplified thermoplastic resin used in a conventionally known non-aqueous secondary battery or the like, that is, a solvent extraction method, a dry type Alternatively, an ion-permeable porous film manufactured by a wet stretching method or the like can be used.

  The average pore size of the separator is preferably 0.01 μm or more, more preferably 0.05 μm or more, preferably 1 μm or less, more preferably 0.5 μm or less.

In addition, as a characteristic of the separator, a Gurley value represented by the number of seconds in which 100 ml of air permeates the membrane under a pressure of 0.879 g / mm ² is 10 to 500 sec. It is desirable to be. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the separator may be reduced. Further, the strength of the separator is desirably 50 g or more in terms of piercing strength using a needle having a diameter of 1 mm. If the piercing strength is too small, a short circuit may occur due to the piercing of the separator when lithium dendrite crystals are generated.

  Even when the inside of the non-aqueous secondary battery is 150 ° C. or higher, the lithium-containing composite oxide according to the present invention is excellent in thermal stability, so that safety can be maintained.

  As the non-aqueous electrolyte, a solution (non-aqueous electrolyte solution) in which an electrolyte salt is dissolved in an organic solvent can be used. Examples of the solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, 1, 2 -Dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, Sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone, etc. Aprotic organic solvents, and the like, may be used these alone, or in combination of two or more of these. Also, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can be used. Among these, a mixed solvent of EC, MEC, and DEC is preferable. In this case, it is more preferable to include DEC in an amount of 15% by volume to 80% by volume with respect to the total volume of the mixed solvent. This is because such a mixed solvent can enhance the stability of the solvent during high-voltage charging while maintaining the low temperature characteristics and charge / discharge cycle characteristics of the battery high.

As the electrolyte salt related to the non-aqueous electrolyte, a salt of a fluorine-containing compound such as lithium perchlorate, lithium organic boron, trifluoromethanesulfonate, imide salt, or the like is preferably used. Specific examples of the electrolyte salt, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C 2 F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) 3, LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (Rf ₃ OSO ₂ ) ₂ [where Rf Represents a fluoroalkyl group. These may be used alone or in combination of two or more thereof. Among these, LiPF ₆ and LiBF ₄ are more preferable because of good charge / discharge characteristics. This is because these fluorine-containing organic lithium salts have a large anionic property and are easily ion-separated, so that they are easily dissolved in the solvent. The concentration of the electrolyte salt in the solvent is not particularly limited, but is usually 0.5 to 1.7 mol / L.

  In addition, for the purpose of improving the safety, charge / discharge cycleability, and high-temperature storage properties of the nonaqueous electrolyte, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, Additives such as t-butylbenzene can be added as appropriate. When the lithium-containing composite oxide contains Mn or when an active material containing Mn is used for the composite particles, the surface activity can be stabilized, and therefore an additive containing sulfur element can be added. Particularly preferred.

  The nonaqueous secondary battery of the present invention includes, for example, an electrode laminate in which the electrode of the present invention and the negative electrode are laminated via the separator, and an electrode wound body in which the electrode laminate is wound in a spiral shape. The electrode body and the non-aqueous electrolyte are manufactured and sealed in an exterior body according to a conventional method. As the form of the battery, similarly to the conventionally known non-aqueous secondary battery, a cylindrical battery using a cylindrical (cylindrical or rectangular) outer can, or a flat (circular in plan view) A flat battery using a rectangular flat-shaped outer can, a soft package battery using a metal-deposited laminated film as an outer package, and the like. The outer can can be made of steel or aluminum.

  The non-aqueous secondary battery of the present invention is used for power supplies of various electronic devices such as portable electronic devices such as mobile phones and notebook computers, and is used for power tools, automobiles, bicycles, power storage, etc. where safety is important. It can also be applied to other uses.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Synthesis of lithium-containing composite oxide>
Aqueous ammonia whose pH was adjusted to about 12 by adding sodium hydroxide was placed in a reaction vessel, and while vigorously stirring, nickel sulfate, manganese sulfate, and cobalt sulfate were each added to 3.76 mol / dm ^3. , 0.21 mol ^/ dm 3, a mixed aqueous solution containing a concentration of 0.21 mol / dm ^3, and aqueous ammonia 25% strength by weight, respectively, 23cm ³ / min at a rate of 6.6 cm ³ / min, The mixture was added dropwise using a metering pump to synthesize a coprecipitation compound of Ni, Mn, and Co (spherical coprecipitation compound). At this time, the temperature of the reaction solution is kept at 50 ° C., and a sodium hydroxide aqueous solution having a concentration of 6.4 mol / dm ³ is dropped at the same time so that the pH of the reaction solution is maintained around 12. Further, nitrogen gas was bubbled at a flow rate of 1 dm ³ / min for reaction in an inert atmosphere.

The coprecipitated compound was washed with water, filtered and dried to obtain a hydroxide containing Ni, Mn and Co in a molar ratio of 90: 5: 5. 0.196 mol of this hydroxide, 0.204 mol of LiOH.H ₂ O and 0.001 mol of TiO ₂ were dispersed in ethanol to form a slurry, and then mixed for 40 minutes with a planetary ball mill. And dried to obtain a mixture. Next, the mixture is put into an alumina crucible, heated to 600 ° C. in a dry air flow of 2 dm ³ / min, held at that temperature for 2 hours for preheating, further heated to 800 ° C. and heated to 12 ° C. Lithium-containing composite oxide was synthesized by firing for a period of time. The obtained lithium-containing composite oxide was pulverized into a powder in a mortar and then stored in a desiccator.

When the composition of the lithium-containing composite oxide powder was measured with an atomic absorption spectrometer, a composition represented by Li _1.02 Ni _0.895 Co _0.05 Mn _0.05 Ti _0.005 O ₂ [ In the general composition formula (1), x = 0.02, a = 89.5 mol%, b = 5 mol%, c = 5 mol%, d = 0 mol%, e = 0 mol%, f = 0.5 mol%, b + c + d + e + f = 10.5 mol%].

In addition, in order to analyze the state of the lithium-containing composite oxide, X-ray absorption spectroscopy of Mn (using a BL4 beam port of a superconducting small radiation source “Aurora” (manufactured by Sumitomo Electric Industries) of Ritsumeikan University SR Center ( XAS). The analysis of the obtained data can be found in the literature [Journal
of the Electrochemical Society, 146, p2799-2809 (1999)], using the analysis software “REX” manufactured by Rigaku Electric Co., Ltd.

First, in order to determine the average valence of Ni of the lithium-containing composite oxide, NiO and LiNi _0.5 Mn _1.5 O ₄ (both containing Ni having an average valence of 2) are used as standard samples. Compound standard sample), and LiNi _0.82 Co _0.15 Al _0.03 O ₂ (standard sample of compound containing Ni having an average valence of 3), the same state as lithium-containing composite oxide Analysis was performed, and a regression line representing the relationship between the Ni K absorption edge position and the Ni valence of each standard sample was created. When the above state analysis was performed on the lithium-containing composite oxide, it was found that the average valence of Ni was 2.85.

Moreover, in order to determine the average valence of Mn, as a standard sample, MnO ₂ and LiNi _0.5 Mn _1.5 O ₄ (both are standard samples of a compound containing Mn having an average valence of 4), LiMn ₂ O ₄ (standard sample of a compound containing Mn having an average valence of 3.5), LiMnO ₂ and Mn ₂ O ₃ (both are standard samples of a compound containing Mn having an average valence of 3) , And MnO (standard sample of a compound containing Mn having an average valence of 2), the same state analysis as that of the lithium-containing composite oxide was performed. A regression line representing the relationship with numbers was created. When the above state analysis was performed on the lithium-containing composite oxide, it was found that the average valence of Mn was 4.0.

Further, regarding the average valence of Co, CoO (standard sample of a compound containing Co having an average valence of 2), Co ₃ O ₄ (standard of a compound containing Co having an average valence of 2.67) Sample) and LiCoO ₂ (standard sample of a compound containing Co having an average valence of 3) were obtained in the same manner as the average valence of Ni and found to be 2.9. .

The lithium-containing composite oxide powder has a BET specific surface area of 0.25 m ² / g, and when the particle size distribution is measured after pulverizing the powder to primary particles, particles having a particle size of 1 μm or less The ratio of was 21% by volume.

<Preparation of positive electrode>
100 parts by mass of the lithium-containing composite oxide, 20 parts by mass of an N-methyl-2-pyrrolidone (NMP) solution containing PVDF as a binder at a concentration of 10% by mass, and 1 mass of artificial graphite as a conductive aid Part and 1 part by mass of ketjen black were kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste.

  The positive electrode mixture-containing paste is applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, and then vacuum-dried at 120 ° C. for 12 hours to form a positive electrode mixture layer on both sides of the aluminum foil. Formed. Thereafter, press treatment was performed to adjust the thickness and density of the positive electrode mixture layer, and a nickel lead body was welded to the exposed portion of the aluminum foil to produce a belt-like positive electrode having a length of 375 mm and a width of 43 mm. In addition, the positive electrode mixture layer in the obtained positive electrode had a thickness of 55 μm on one side.

<Production of negative electrode>
To 97.5 parts by mass of natural graphite having a number average particle size of 10 μm as a negative electrode active material, 1.5 parts by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose as a thickener, Were added and mixed to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste was applied to both sides of a copper foil having a thickness of 8 μm, and then vacuum-dried at 120 ° C. for 12 hours to form negative electrode mixture layers on both sides of the copper foil. Thereafter, press treatment was performed to adjust the thickness and density of the negative electrode mixture layer, and a nickel lead body was welded to the exposed portion of the copper foil to produce a strip-shaped negative electrode having a length of 380 mm and a width of 44 mm. The negative electrode mixture layer in the obtained negative electrode had a thickness of 65 μm on one side.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent of EC, MEC, and DEC in a volume ratio of 2: 3: 1.

<Battery assembly>
The belt-like positive electrode is stacked on the belt-like negative electrode through a microporous polyethylene separator (porosity: 41%) having a thickness of 16 μm, wound in a spiral shape, and then pressed so as to be flat. An electrode winding body having a flat winding structure was formed, and the electrode winding body was fixed with an insulating tape made of polypropylene. Next, the electrode winding body is inserted into a rectangular battery case made of aluminum alloy having an outer dimension of 4.0 mm in thickness, 34 mm in width, and 50 mm in height to weld the lead body, and a lid made of aluminum alloy The plate was welded to the open end of the battery case. Thereafter, the nonaqueous electrolyte is injected from the inlet provided in the cover plate, and left for 1 hour, and then the inlet is sealed. The nonaqueous secondary battery having the structure shown in FIG. 1 and the appearance shown in FIG. Got. The design electric capacity of the non-aqueous secondary battery was 1000 mAh.

  Here, the battery shown in FIGS. 1 and 2 will be described. FIG. 1A is a plan view, and FIG. 1B is a partial cross-sectional view thereof. As shown in FIG. 2 is spirally wound through the separator 3 and then pressed so as to be flat, and accommodated in a rectangular (rectangular tube) battery case 4 together with a nonaqueous electrolyte as a flat electrode winding body 6. Has been. However, in FIG. 1, in order to avoid complication, a metal foil, a non-aqueous electrolyte, and the like as a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 are not illustrated.

  The battery case 4 is made of an aluminum alloy and constitutes an outer package of the battery. The battery case 4 also serves as a positive electrode terminal. An insulator 5 made of a polyethylene sheet is arranged at the bottom of the battery case 4, and is connected to one end of each of the positive electrode 1 and the negative electrode 2 from the flat electrode winding body 6 made of the positive electrode 1, the negative electrode 2, and the separator 3. The positive electrode lead body 7 and the negative electrode lead body 8 thus drawn are drawn out. A stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the battery case 4 via a polypropylene insulating packing 10, and an insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached.

  And this cover plate 9 is inserted in the opening part of the battery case 4, and the opening part of the battery case 4 is sealed by welding the joint part of both, and the inside of the battery is sealed. Further, in the battery of FIG. 1, a non-aqueous electrolyte inlet 14 is provided in the lid plate 9, and the non-aqueous electrolyte inlet 14 is welded by, for example, laser welding with a sealing member inserted. The battery is sealed to ensure the hermeticity of the battery (therefore, in the battery of FIGS. 1 and 2, the nonaqueous electrolyte inlet 14 is actually a nonaqueous electrolyte inlet and a sealing member. , For ease of explanation, shown as non-aqueous electrolyte inlet 14). Further, the lid plate 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the temperature of the battery rises.

  In the battery of Example 1, the outer can 5 and the cover plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the lid plate 9, and the negative electrode lead body 8 is welded to the lead plate 13. The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the battery case 4, the sign may be reversed. There is also.

  FIG. 2 is a perspective view schematically showing the external appearance of the battery shown in FIG. 1. FIG. 2 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 1, the inner peripheral portion of the electrode body is not cross-sectional.

Example 2
Nickel sulfate, cobalt sulfate and aluminum sulfate, ^{respectively, 3.76mol / dm 3, 0.21mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.21 mol / dm ^3, similarly as in Example 1 Thus, a coprecipitation compound was synthesized. A hydroxide containing Ni, Co, and Al at a molar ratio of 89.5: 5: 5 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.195 mol of the oxide, 0.205 mol of LiOH.H ₂ O, and 0.001 mol of TiO ₂ were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 3
Nickel sulfate, cobalt sulfate and magnesium sulfate, ^{respectively, 3.76mol / dm 3, 0.38mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.04 mol / dm ^3, are as in Example 1 A coprecipitated compound was synthesized in the same manner. Then, a hydroxide containing Ni, Co, and Mg in a molar ratio of 89.5: 9: 1 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.202 mol of oxide, 0.198 mol of LiOH.H ₂ O, and 0.001 mol of TiO ₂ were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 4
Nickel sulfate, manganese sulfate and aluminum sulfate, ^{respectively, 3.76mol / dm 3, 0.25mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.17 mol / dm ^3, similarly as in Example 1 Thus, a coprecipitation compound was synthesized. A hydroxide containing Ni, Mn and Al in a molar ratio of 89.5: 6: 4 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol of oxide, 0.200 mol of LiOH.H ₂ O, and 0.001 mol of TiO ₂ were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 5
Nickel sulfate, manganese sulfate and magnesium sulfate, ^{respectively, 3.77mol / dm 3, 0.25mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.16 mol / dm ^3, similarly as in Example 1 Thus, a coprecipitation compound was synthesized. A hydroxide containing Ni, Mn and Mg in a molar ratio of 91.5: 6: 4 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that 0.201 mol of oxide, 0.199 mol of LiOH.H ₂ O, and 0.001 mol of TiO ₂ were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 6
Nickel sulfate, aluminum sulfate and magnesium sulfate, ^{respectively, 3.77mol / dm 3, 0.21mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.21 mol / dm ^3, similarly as in Example 1 Thus, a coprecipitation compound was synthesized. Then, a hydroxide containing Ni, Al, and Mg in a molar ratio of 91.5: 5: 5 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.201 mol of hydroxide, 0.199 mol of LiOH.H ₂ O, and 0.001 mol of TiO ₂ were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 7
Nickel sulfate, cobalt sulfate, manganese sulfate and aluminum sulfate, ^{respectively, 3.78mol / dm 3, 0.21mol /} dm 3, 0.13mol / dm 3, a mixed aqueous solution containing a concentration of 0.08 mol / dm ³ A coprecipitated compound was synthesized in the same manner as in Example 1 except that it was used. Then, a hydroxide containing Ni, Co, Mn, and Al at a molar ratio of 90: 5: 3: 2 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol of this hydroxide and 0.200 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 8
A mixed aqueous solution containing nickel sulfate, cobalt sulfate, manganese sulfate and magnesium sulfate at concentrations of 3.79 mol / dm ³ , 0.21 mol / dm ³ , 0.12 mol / dm ³ and 0.08 mol / dm ³ , respectively. A coprecipitated compound was synthesized in the same manner as in Example 1 except that it was used. Then, a hydroxide containing Ni, Co, Mn, and Mg in a molar ratio of 92: 5: 3: 2 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.202 mol of this hydroxide and 0.198 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 9
A mixed aqueous solution containing nickel sulfate, cobalt sulfate, aluminum sulfate and magnesium sulfate at concentrations of 3.79 mol / dm ³ , 0.21 mol / dm ³ , 0.12 mol / dm ³ and 0.08 mol / dm ³ , respectively. A coprecipitated compound was synthesized in the same manner as in Example 1 except that it was used. Then, a hydroxide containing Ni, Co, Al, and Mg at a molar ratio of 92: 5: 3: 2 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol of this hydroxide and 0.200 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 10
Nickel sulfate, cobalt sulfate, manganese sulfate, aluminum sulfate and magnesium sulfate, ^{respectively, 3.79mol / dm 3, 0.12mol /} dm 3, 0.12mol / dm 3, 0.08mol / dm 3 0.08mol / dm ^A coprecipitated compound was synthesized in the same manner as in Example 1 except that a mixed aqueous solution containing ³ was used. And the hydroxide which contains Ni, Co, Mn, Al, and Mg by the molar ratio of 92: 3: 3: 2: 2 similarly to Example 1 except having used the said coprecipitation compound. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol of this hydroxide and 0.200 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 11
Nickel sulfate, cobalt sulfate, manganese sulfate, aluminum sulfate and magnesium sulfate, ^{respectively, 3.99mol / dm 3, 0.08mol /} dm 3, 0.08mol / dm 3, 0.04mol / dm 3 0.04mol / dm ^A coprecipitated compound was synthesized in the same manner as in Example 1 except that a mixed aqueous solution containing ³ was used. And the hydroxide which contains Ni, Co, Mn, Al, and Mg by the molar ratio of 95: 2: 1: 1: 1 like Example 1 except having used the said coprecipitation compound. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.199 mol of this hydroxide and 0.201 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 12
Nickel sulfate, cobalt sulfate, manganese sulfate, aluminum sulfate and magnesium sulfate, ^{respectively, 3.97mol / dm 3, 0.08mol /} dm 3, 0.08mol / dm 3, 0.04mol / dm 3 0.04mol / dm ^A coprecipitated compound was synthesized in the same manner as in Example 1 except that a mixed aqueous solution containing ³ was used. And the hydroxide which contains Ni, Co, Mn, Al, and Mg by the molar ratio of 95: 2: 1: 1: 1 like Example 1 except having used the said coprecipitation compound. A lithium-containing composite oxide was prepared in the same manner as in Example 1 except that 0.199 mol of this hydroxide, 0.201 mol of LiOH.H ₂ O, and 0.001 mol of ZrO ₂ were used. Synthesized. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 13
Nickel sulfate, cobalt sulfate, mixed aqueous solution of manganese sulfate, and magnesium sulfate, ^{respectively,} to ^{2.69mol / dm 3, 0.84mol / dm} 3, 0.63mol / dm 3, at a concentration of 0.04 mol / dm ³ A coprecipitated compound was synthesized in the same manner as in Example 1 except that was used. Then, a hydroxide containing Ni, Co, Mn, and Mg in a molar ratio of 64: 20: 15: 1 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.2 mol of this hydroxide and 0.2 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Example 14
0.2 mol of hydroxide containing Ni, Co, Mn and Mg in a molar ratio of 64: 20: 15: 1, 0.2 mol of LiOH.H ₂ O and 0.0004 mol of GeO ₂ are used. A lithium-containing composite oxide was synthesized in the same manner as in Example 13 except that. Further, a positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 13 except that this lithium-containing composite oxide was used.

Example 15
0.2 mol of hydroxide containing Ni, Co, Mn and Mg in a molar ratio of 64: 20: 15: 1, 0.2 mol of LiOH.H ₂ O, 0.0002 mol of B ₂ O ₃ A lithium-containing composite oxide was synthesized in the same manner as Example 13 except that was used. Further, a positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 13 except that this lithium-containing composite oxide was used.

Example 16
0.2 mol of hydroxide containing Ni, Co, Mn and Mg in a molar ratio of 64: 20: 15: 1, 0.2 mol of LiOH.H ₂ O, 0.0002 mol of Ga ₂ O ₃ A lithium-containing composite oxide was synthesized in the same manner as Example 13 except that was used. Further, a positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 13 except that this lithium-containing composite oxide was used.

Example 17
0.2 mol of hydroxide containing Ni, Co, Mn and Mg in a molar ratio of 64: 20: 15: 1, 0.2 mol of LiOH.H ₂ O and 0.0004 mol of SrCO ₃ are used. A lithium-containing composite oxide was synthesized in the same manner as in Example 13 except that. Further, a positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 13 except that this lithium-containing composite oxide was used.

Example 18
0.2 mol of hydroxide containing Ni, Co, Mn and Mg in a molar ratio of 64: 20: 15: 1, 0.2 mol of LiOH.H ₂ O and 0.0004 mol of Ba (OH) ₂ A lithium-containing composite oxide was synthesized in the same manner as in Example 13, except that and were used. Further, a positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 13 except that this lithium-containing composite oxide was used.

Example 19
After 90 parts by mass of the lithium-containing composite oxide synthesized in Example 1 and 5 parts by mass of lithium cobaltate powder (number average particle diameter 10 μm) were dry-mixed, 10 parts by mass of PVDF as a binder was added here. 20 parts by mass of NMP solution contained at a concentration of% was added and mixed to obtain composite particles.

  A positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 1 except that this composite particle was used in place of the lithium-containing composite oxide.

Example 20
A composite particle was prepared in the same manner as in Example 19 except that lithium manganate powder (number average particle diameter 10 μm) was used instead of lithium cobalt oxide powder. In the same manner as in 19, a positive electrode and a nonaqueous secondary battery were produced.

Comparative Example 1
A positive electrode and a non-aqueous secondary battery were produced in the same manner as in Example 1 except that a commercially available LiNi _0.80 Co _0.15 Al _0.05 O ₂ was used.

Comparative Example 2
A coprecipitated compound was synthesized in the same manner as in Example 1 except that a mixed aqueous solution containing nickel sulfate and aluminum sulfate at concentrations of 3.99 mol / dm ³ and 0.21 mol / dm ³ was used. Then, a hydroxide containing Ni and Al at a molar ratio of 95: 5 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol of LiOH.H ₂ O was used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

Comparative Example 3
Nickel sulfate, cobalt sulfate and aluminum sulfate, ^{respectively, 4.12mol / dm 3, 0.04mol /} dm 3, except for using a mixed aqueous solution containing a concentration of 0.04 mol / dm ^3, similarly as in Example 1 Thus, a coprecipitation compound was synthesized. A hydroxide containing Ni, Co, and Al at a molar ratio of 98: 1: 1 was synthesized in the same manner as in Example 1 except that the coprecipitation compound was used. A lithium-containing composite oxide was synthesized in the same manner as in Example 1 except that 0.200 mol and 0.200 mol of LiOH.H ₂ O were used. Furthermore, a positive electrode and a nonaqueous secondary battery were produced in the same manner as in Example 1 except that this lithium-containing composite oxide was used.

  Table 1 shows the compositions of the lithium-containing composite oxides used for the positive electrodes of Examples 1 to 18 and Comparative Examples 1 to 3, and Table 2 shows the lithium used for the positive electrodes of Examples 1 to 18 and Comparative Examples 1 to 3. The average valences of Ni, Co, and Mn of the containing composite oxide are shown respectively.

In Table 3, the ratio of primary particles having a particle diameter of 1 μm or less in all primary particles of the lithium-containing composite oxides used in the positive electrodes of Examples 1 to 20 and Comparative Examples 1 to 3 (in the table, “ The ratio of particles of 1 μm or less ”), BET specific surface area and tap density, and the density of the positive electrode mixture layer of the positive electrodes of Examples 1 to 20 and Comparative Examples 1 to 3 are shown.

  “M ′” in Table 1 represents Ni, Co, Mn, Al, and elements other than Mg and Ti (for example, Zr) among all the constituent elements of M in the general composition formula (1), g represents the total of the ratio (mol%) of elements other than Ni, Co, Mn, Al, Mg, and Ti.

  Further, the following evaluations were performed on the nonaqueous secondary batteries of Examples 1 to 20 and Comparative Examples 1 to 3. The results are shown in Table 4.

<Capacity measurement and evaluation of load characteristics>
After each battery of Examples 1-20 and Comparative Examples 1-3 was stored at 60 ° C. for 7 hours, it was charged at 20 ° C. with a current value of 200 mA for 5 hours, and the battery voltage decreased to 3 V at a current value of 200 mA. The charge / discharge cycle of discharging until the discharge was repeated until the discharge capacity became constant. Next, constant current-constant voltage charging (constant current: 500 mA, constant voltage: 4.2 V, total charging time: 3 hours) is performed, and after a pause of 1 hour, discharging is performed until the battery voltage reaches 3 V at a current value of 200 mA. Standard capacity was determined. The standard capacity was measured for 100 batteries for each battery, and the average value was used as the standard capacity for each example and comparative example.

<Charge / discharge cycle characteristics>
Each of the batteries of Examples 1 to 20 and Comparative Examples 1 to 3 was charged at a constant current-constant voltage under the same conditions as when measuring the standard capacity, and then discharged after a pause of 1 minute until the battery voltage reached 3 V at a current value of 200 mA. The charge / discharge cycle was repeated, the number of cycles until the discharge capacity decreased to 70% of the initial discharge capacity was determined, and the charge cycle characteristics of each battery were evaluated. In addition, the said cycle number in charging / discharging cycling characteristics measured about 10 batteries with respect to each battery, The average value was made into the cycle number of each Example and a comparative example.

<Evaluation of safety>
The batteries of Examples 1 to 20 and Comparative Examples 1 to 3 were charged in a constant temperature-constant voltage charge (constant current: 1 C, constant voltage: 4.25 V, total charge time: 3 hours) and then placed in a thermostatic chamber. After resting for 2 hours, the temperature was raised from 30 ° C. to 170 ° C. at a rate of 5 ° C. per minute and then allowed to stand at 170 ° C. for 3 hours to measure the surface temperature of the battery. At this time, a battery having a maximum temperature of 180 ° C. or lower was evaluated as “◯”, and a battery exceeding 180 ° C. was evaluated as “X”.

<Evaluation of high-temperature storage characteristics>
The batteries of Examples 1 to 20 and Comparative Examples 1 to 3 were subjected to constant current-constant voltage charging (constant current: 1 C, constant voltage: 4.25 V, total charging time: 3 hours), and the battery thickness was maximum. After measuring the point which becomes, it put into the thermostat kept at 80 degreeC, and stored for 5 days. After storage, the battery was air-cooled for 2 hours to 24 hours, and then the point at which the battery thickness was maximized was measured again, and the high-temperature storage characteristics were evaluated based on the change in battery thickness before and after storage.

  As is clear from Table 4, the batteries of Examples 1 to 20 were stable while having a high capacity by using a positive electrode comprising a lithium-containing composite oxide having an appropriate composition and an average valence of Ni as an active material. Compared with the batteries of Comparative Examples 1 to 3, the charge / discharge cycle life is long and the safety is excellent. Moreover, since the battery of Examples 1-20 had little gas generation | occurrence | production at the time of high temperature storage, it was able to suppress the thickness change of the battery at the time of high temperature storage compared with the battery of Comparative Examples 1-3.

  In particular, the batteries of Example 12 and Examples 14 to 18 to which an element selected from Ge, Ca, Sr, Ba, B, Zr, and Ga is added have a more remarkable effect of suppressing the change in the thickness of the battery. The battery was more excellent in performance.

1 Positive electrode 2 Negative electrode 3 Separator

Claims (11)

General composition formula Li _{1 + x} MO ₂ [Where -0.3 ≦ x ≦ 0.3, and M represents at least three elements selected from Co, Mn, Al, Mg and Ti, and Ni. 4 represents a group of four or more elements, and in each element constituting M, the ratios (mol%) of Ni, Co, Mn, Al, Mg, and Ti are respectively a, b, c, d, e, and f. And 45 ≦ a ≦ 97, b ≦ 49, c ≦ 49, d ≦ 10, e ≦ 10, f ≦ 10, and 3 ≦ b + c + d + e + f ≦ 55], and the average valence of Ni is 2 A non-aqueous secondary battery electrode comprising an electrode mixture layer using a lithium-containing composite oxide having a valence of 0.5 to 2.9.   The electrode for a non-aqueous secondary battery according to claim 1, wherein an average valence number of Co in the lithium-containing composite oxide is 2.2 to 2.9.   The electrode for nonaqueous secondary batteries according to claim 1 or 2, wherein the average valence of Mn of the lithium-containing composite oxide is 3.5 to 4. The lithium-containing composite oxide is in the form of particles, and in all the primary particles, primary particles having a particle size of 1 μm or less are 30% by volume or less, and a BET specific surface area is 0.3 m ² / g or less. The electrode for nonaqueous secondary batteries in any one of 3. The tap density of a lithium containing complex oxide is 2.3 g / cm < ³ > or more, The electrode for nonaqueous secondary batteries in any one of Claims 1-4. The density of an electrode mixture layer is 3.1 g / cm < ³ > or more, The electrode for nonaqueous secondary batteries in any one of Claims 1-5.   The electrode for a nonaqueous secondary battery according to any one of claims 1 to 6, wherein the electrode mixture layer contains polyvinylidene fluoride, polyhexafluoroethylene, or polytetrafluoroethylene as a binder.   The electrode for a nonaqueous secondary battery according to any one of claims 1 to 7, wherein the electrode mixture layer contains graphite or carbon black as a conductive additive.   The non-water according to claim 1, wherein the element group M in the general composition formula further contains at least one element M ′ selected from Ge, Ca, Sr, Ba, B, Zr and Ga. Secondary battery electrode.   The electrode for a non-aqueous secondary battery according to claim 9, wherein the ratio of the element M ′ in the element group M is 10 mol% or less. A non-aqueous secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The said positive electrode is an electrode for nonaqueous secondary batteries in any one of Claims 1-10, The nonaqueous secondary battery characterized by the above-mentioned.

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