JP2019050099A - Positive electrode active material for non-aqueous electrolyte secondary battery and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for a non-aqueous electrolyte secondary battery, which has excellent output characteristics, excellent charge/discharge cycle characteristics, and excellent paste stability when used as a positive electrode material. SOLUTION: This is represented by the general formula (1): LizNi1-x-yCoxMyO2 (wherein 0.10≤x≤0.35, 0≤y≤0.35, 1.00<z<1.30). A lithium metal composite oxide powder and an ammonium salt of a transition metal oxo anion are contained, and at least a part of the ammonium salt of the transition metal oxo anion is dispersed and present on the surface of the lithium metal composite oxide powder. The transition metal contained in the ammonium salt of an anion is at least one selected from tungsten, molybdenum, and vanadium, and is based on a positive electrode active material for a non-aqueous electrolyte secondary battery. [Selection diagram] Figure 1

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same.

  In recent years, with the spread of mobile electronic devices such as mobile phones and notebook computers, development of a small and lightweight non-aqueous electrolyte secondary battery having a high energy density is strongly desired. Moreover, development of a secondary battery having excellent output characteristics and charge / discharge cycle characteristics is strongly desired as a battery for electric vehicles including hybrid vehicles.

  There is a lithium ion secondary battery as a secondary battery which satisfies such a demand. The lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution and the like, and as the active material of the negative electrode and the positive electrode, a material capable of releasing and inserting lithium is used.

  Such a lithium ion secondary battery is currently under active research and development. Among them, a lithium ion secondary battery using a layered or spinel type lithium metal composite oxide as a positive electrode material is Since a high voltage of 4V class can be obtained, the practical use is advanced as a battery having a high energy density.

Materials mainly proposed until now include lithium cobalt composite oxide (LiCoO ₂ ) which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel which is cheaper than cobalt, lithium nickel Examples include cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), and the like.

  By the way, in order to obtain a lithium ion secondary battery excellent in output characteristics and charge / discharge cycle characteristics, it is necessary that the positive electrode active material be constituted by particles having a small particle diameter and a narrow particle size distribution. This is because particles having a small particle diameter have a large specific surface area, and when used as a positive electrode active material, not only can the reaction area with the electrolytic solution be sufficiently secured, but also the positive electrode is thin and lithium ion This is because the moving distance between the positive electrode and the negative electrode can be shortened, so that the positive electrode resistance can be reduced. In addition, particles having a narrow particle size distribution can equalize the voltage applied to the particles in the electrode, so that it is possible to suppress a decrease in battery capacity due to selective deterioration of the particles.

  In order to further improve the output characteristics and the charge and discharge cycle characteristics, it is effective to make the positive electrode active material into a hollow structure. Such a positive electrode active material can increase the reaction area with the electrolytic solution as compared with a solid structure positive electrode active material having the same particle diameter, so that the positive electrode resistance can be significantly reduced. .

  For example, Patent Documents 1 to 3 clarify the transition metal composite hydroxide particles, which become precursors of the positive electrode active material, in two steps of nucleation step mainly performing nucleation and particle growth step mainly performing particle growth. The method of producing by the crystallization reaction isolate | separated into is disclosed. In these methods, the pH value of the reaction aqueous solution is controlled in the range of 12.0-14.0 in the nucleation step and in the range of 10.5-12.0 in the grain growth step on the basis of a liquid temperature of 25 ° C. doing. The reaction atmosphere is an oxidizing atmosphere at the beginning of the nucleation step and the grain growth step, and is switched to a non-oxidizing atmosphere at a predetermined timing.

  The transition metal composite hydroxide particles obtained by such a method have a small particle diameter and a narrow particle size distribution, and a low density central portion consisting of fine primary particles and a high plate-like or needle-like primary particle It consists of a shell of density. Therefore, when such transition metal composite hydroxide particles are fired, the low density central portion largely shrinks, and a space portion is formed inside. Moreover, as described above, the particle properties of the composite hydroxide particles are taken over to the positive electrode active material. Specifically, the positive electrode active material obtained by the techniques described in these documents has an average particle diameter in the range of 2 μm to 8 μm or 2 μm to 15 μm, and is an index indicating the spread of the particle size distribution [(d90-d10 ) / Average particle diameter] is 0.60 or less, and has a hollow structure.

  Therefore, in the secondary battery using these positive electrode active materials, it is considered that the capacity characteristics, the output characteristics, and the charge and discharge cycle characteristics can be simultaneously improved. Further, in order to further improve charge-discharge cycle characteristics, it is effective to contain lithium in excess of the stoichiometric composition with respect to the metal element such as nickel, cobalt, manganese and the like. However, further improvement of output characteristics and charge / discharge cycle characteristics is required.

  By the way, the positive electrode of the non-aqueous electrolyte secondary battery is prepared by mixing a positive electrode active material and a binder such as PVDF (polyvinylidene fluoride) or NMP (normal methyl-2-pyrrolidone) to form a positive electrode mixture paste, and aluminum foil Etc. It forms by apply | coating to current collectors etc. At this time, in the positive electrode active material containing an excessive amount of lithium, lithium is liberated from the positive electrode active material, and reacts with the water contained in the binder to generate lithium hydroxide. The generated lithium hydroxide and the binder react with each other to cause gelation of the positive electrode mixture paste, resulting in poor operability and deterioration in yield. This tendency is significant when lithium in the positive electrode active material is in excess of the stoichiometric ratio and the proportion of nickel is high.

  As a method of preventing the gelation of the positive electrode mixture paste containing an excessive amount of lithium, for example, in Patent Document 4, a positive electrode active material and particles made of an acidic oxide may be mixed to form a positive electrode composition. Proposed. According to this method, the generated lithium hydroxide is preferentially reacted with the acidic oxide, and the reaction of the generated lithium hydroxide with the binder is suppressed to suppress the gelation of the positive electrode mixture paste. There is. Furthermore, the compound produced by the reaction of the acidic oxide and lithium hydroxide is said to have the effect of reducing the resistance of the positive electrode active material. Therefore, output characteristics, charge / discharge cycle characteristics and paste stability can all be improved.

  As another method for further improving the output characteristics and the charge-discharge cycle characteristics, particles of tungsten oxide are obtained when the positive electrode active material described above in Patent Document 5 is mixed with PVDF and NMP to obtain a positive electrode mixture paste. A method of mixing is proposed.

  On the other hand, as a method of suppressing the gelation of the paste due to the liberation of lithium, a method of removing the liberated lithium by washing the positive electrode active material with water has been proposed. For example, according to Patent Document 6, the positive electrode active material can be industrially washed with water, and it is believed that liberated lithium can be removed.

  Furthermore, as a method of improving the output characteristics of the washed active material, it has been proposed to add, mix and dry an alkaline solution in which a tungsten compound such as lithium tungstate is dissolved. For example, according to Patent Document 7, it is supposed that the output characteristics can be improved by forming fine particles containing W and Li on the entire primary particle surface of the positive electrode active material.

JP 2012-246199 A JP, 2013-147416, A International Publication 2012/131881 JP, 2012-028313, A JP, 2013-084395, A JP 2007-273108 A JP 2012-079464 A

  However, in the methods described in Patent Literatures 4 and 5, the particles of the acidic oxide remain, which may cause damage to the separator and the resultant decrease in safety. Further, the method of Patent Document 6 has a problem that the output characteristics are degraded. Furthermore, the method described in Patent Document 7 requires a water washing step, an addition step, and a drying step, and the number of manufacturing steps is increased, resulting in an increase in manufacturing cost.

  As described above, the method described in the above document can not sufficiently improve all of the output characteristics, the charge / discharge cycle characteristics and the paste stability (suppression of the gelation of the paste) with few steps.

  In view of the above problems, the present invention provides a non-aqueous electrolyte 2 which can be produced in a simple process as well as obtaining excellent output characteristics and excellent charge / discharge cycle characteristics and excellent paste stability when used in a positive electrode material. An object of the present invention is to provide a positive electrode active material for a secondary battery.

  In order to solve the above problems, the present inventors have studied powder characteristics of the lithium metal composite oxide used as a positive electrode active material for non-aqueous electrolyte secondary batteries, the positive electrode resistance and charge / discharge cycle characteristics of the battery, and paste stability. The inventors have intensively studied the influence on the conductivity, and by forming the ammonium salt of the transition metal oxoanion on the particle surface constituting the lithium metal complex oxide powder, the positive electrode resistance of the battery is reduced, and the output characteristics and charge / discharge cycle It has been found that it is possible to improve the slurry stability as well as to improve the properties.

  Furthermore, as a method for producing the same, an aqueous solution of an ammonium salt of transition metal oxoanion is mixed with lithium metal complex oxide powder containing lithium in excess of the stoichiometric composition and dried to obtain fine particles by a simple production method. It has been found that ammonium salts of transition metal oxoanions can be added, and the present invention has been completed.

According to a first aspect of the present invention, the general formula (1): Li _z Ni _1-xy Co _x M _y O ₂ (where 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0. Lithium metal composite oxide powder wherein 35, 1.00 <z <1.30, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W and Al) And an ammonium salt of a transition metal oxo anion, and at least a part of the ammonium salt of the transition metal oxo anion is dispersed on the surface of the lithium metal composite oxide powder, and is contained in the ammonium salt of the transition metal oxo anion The transition metal is at least one selected from tungsten, molybdenum and vanadium, and the positive electrode active material for a non-aqueous electrolyte secondary battery is provided.

  The lithium metal composite oxide powder preferably includes secondary particles formed by aggregating a plurality of primary particles, and a part of the ammonium salt of the transition metal oxo anion is preferably present between the primary particles. Moreover, it is preferable that the pH at 25 ° C. of the supernatant liquid which has been allowed to stand for 10 minutes after dispersing 5 g of the positive electrode active material in 100 ml of pure water is 9.0 or more and 11.8 or less. Preferably, the ammonium salt of the transition metal oxo anion is water soluble. Preferably, the ammonium salt of the transition metal oxo anion comprises ammonium tungstate. Preferably, the ammonium tungstate contains ammonium metatungstate.

According to a second aspect of the present invention, the general formula (1): Li _z Ni _{1 -xy} Co _x M _y O ₂ (where 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0. Lithium metal composite oxide powder wherein 35, 1.00 <z <1.30, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W and Al) , Mixing an aqueous solution of an ammonium salt of at least one transition metal oxoanion selected from tungsten, molybdenum and vanadium with a first step of obtaining a mixture, and a second step of drying the mixture, The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries whose temperature of the said lithium metal complex oxide powder in a process is 10 degreeC or more and 100 degrees C or less is provided.

  In addition, 5 g of the positive electrode active material obtained after the second step is dispersed in 100 ml of pure water, and then the supernatant liquid allowed to stand for 10 minutes has a pH of 9.0 or more and 11.8 or less at 25 ° C. Preferably, the mixing amount of the aqueous solution of the ammonium salt of the transition metal oxoanion in the first step is adjusted. The lithium metal complex oxide powder used in the first step is prepared by dispersing 5 g of the lithium metal complex oxide powder in 100 ml of pure water and then allowing the supernatant liquid to stand for 10 minutes at 25 ° C. It is preferable that it is 11.8 or more. Preferably, the ammonium salt of the transition metal oxo anion is water soluble. Preferably, the ammonium salt of the transition metal oxoanion comprises ammonium tungstate. Preferably, the ammonium tungstate contains ammonium metatungstate.

  According to the present invention, there is provided a positive electrode active material for a non-aqueous electrolyte secondary battery, which can provide excellent output characteristics and excellent charge / discharge cycle characteristics and excellent slurry stability when used as a positive electrode material of a battery. Can. Furthermore, the production method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.

FIG. 1 is a view showing an example of a positive electrode active material according to the embodiment. FIG. 2 is a view showing an example of a method of manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the embodiment. FIG. 3 is a schematic explanatory view of a measurement example of AC impedance evaluation and an equivalent circuit used for analysis. FIG. 4 is a schematic cross-sectional view of a coin-type battery used for battery evaluation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the positive electrode active material is described, and then a method of manufacturing the positive electrode active material and a non-aqueous electrolyte secondary battery using the positive electrode active material are described. Further, in the drawings, in order to make each configuration easy to understand, a part is emphasized or a part is simplified and represented, and an actual structure or a shape, a scale, or the like may be different.

1. Positive Electrode Active Material FIG. 1 is a schematic view showing an example of a positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter, also referred to as “positive electrode active material 10”) of the present embodiment. The positive electrode active material 10 has a general formula: Li _z Ni _1-xy Co _x M _y O ₂ (where, 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0.35, 1.00 <z < 1.30, M is a lithium metal composite oxide powder M represented by Mn, V, Mg, Mo, Nb, Ti, and at least one element selected from W and Al, and ammonium of a transition metal oxoanion And salt A.

The positive electrode active material 10 of the present embodiment has a general formula: Li _z Ni _1-xy Co _x M _y O ₂ (where, 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0.35) as a base material. , 1.00 <z <1.30, M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W and Al) lithium metal complex oxide powder M By including, it is possible to obtain excellent output characteristics and excellent charge / discharge cycle characteristics.

  For example, as shown in FIG. 1, the lithium metal composite oxide powder M is made of at least one of a primary particle 1 and a secondary particle 2 formed by aggregating a plurality of primary particles 1. That is, lithium metal complex oxide powder M includes any of the aspect of only primary particle 1, the aspect of only secondary particle 2, and the aspect in which primary particle 1 and secondary particle 2 were mixed. The lithium metal composite oxide powder M may also contain mainly secondary particles 2 and a small amount of primary particles 1.

  The ammonium salt A of the transition metal oxo anion is dispersed and present on the surface of the lithium metal composite oxide powder M, as shown in FIG. In the present specification, the surface of the lithium metal composite oxide powder M refers to a surface that can be in contact with the electrolytic solution in the positive electrode of the secondary battery. That is, the surface of the lithium metal composite oxide powder M means, for example, the surface of the primary particle 1 exposed at the outer surface of the secondary particle 2 and the two that allow the electrolyte solution to penetrate through the secondary particle 2 outside. It includes the surface of primary particle 1 exposed to void 3 in the vicinity and inside of secondary particle 2 surface, and even if it is the grain boundary between primary particles 1, the bonding of primary particle 1 is incomplete and the electrolyte penetrates It is included if possible.

  The ammonium salt A of the transition metal oxo anion is an ammonium salt containing the transition metal oxo anion, preferably an ammonium salt of at least one oxo anion selected from tungsten, molybdenum and vanadium, more preferably tungstic acid It is ammonium, more preferably ammonium metatungstate. The ammonium salt A of the transition metal oxo anion can be reacted with lithium hydroxide in the positive electrode paste to form a lithium salt of the oxo anion, as described later.

  The positive electrode active material 10 forms an ammonium salt A of a transition metal oxoanion on the surface of the lithium metal composite oxide powder M, thereby maintaining the battery capacity of the secondary battery using the positive electrode active material 10 while maintaining the battery capacity. The characteristics and charge / discharge cycle characteristics can be further improved, and the stability of the positive electrode paste including the positive electrode active material 10 can be improved.

  In general, when the surface of the positive electrode active material is completely covered with the foreign compound, the movement (intercalation) of lithium ions is greatly restricted, and as a result, the output characteristics of the positive electrode active material deteriorate. I will. On the other hand, when the positive electrode active material 10 of this embodiment is used for the positive electrode of a secondary battery, output specification can be further improved. The reason for this is not particularly limited, but can be considered, for example, as follows.

  When manufacturing the positive electrode which is a structural member of a battery, the positive electrode paste which mixes a positive electrode active material, a conductive support agent, a binder, and a solvent is produced. In the step of producing the positive electrode paste, lithium hydroxide is generated by the reaction between lithium released from the positive electrode active material 10 and the water contained in the binder. The fine particles of the ammonium salt A of the transition metal oxoanion present on the surface of the lithium metal composite oxide powder M react with the lithium hydroxide thus produced to form a transition metal oxoanion on the surface of the lithium metal composite oxide powder M. Can be formed in the form of islands or very thin layers.

  Lithium salts of transition metal oxo anions have high lithium ion conductivity, and have the effect of promoting lithium ion migration. Therefore, in the positive electrode of the secondary battery, the lithium salt of the transition metal oxoanion formed on the surface of the lithium metal composite oxide powder M secures a conduction path of lithium ions at the interface between the positive electrode active material 10 and the electrolyte. Thus, it is considered that the output resistance can be improved by reducing the reaction resistance of the positive electrode active material 10.

  In general, as in the lithium metal complex oxide powder M according to the present embodiment, in the positive electrode active material in which lithium in the composition is contained in excess of the stoichiometric composition with respect to the transition metal, the positive electrode active material Lithium is liberated from the powder of the above, and reacts with water contained in the binder to easily form lithium hydroxide. Then, as a result of the reaction between the formed lithium hydroxide and the binder, the positive electrode mixture paste may be gelated, which may cause poor operability and deterioration in yield. This tendency is significant when lithium in the positive electrode active material is in excess of the stoichiometric ratio and the proportion of nickel is high.

  In contrast, in the positive electrode active material 10 of the present embodiment, since the ammonium salt A of the acidic transition metal oxo anion is formed on the surface of the lithium metal complex oxide powder M, it is generated in the process of manufacturing the positive electrode paste. The alkaline lithium hydroxide can be neutralized by the ammonium salt A of the transition metal oxo anion. Therefore, the positive electrode active material 10 of the present embodiment can also prevent the gelation of the positive electrode paste.

  The amount of ammonium salt A of the transition metal oxoanion present on the surface of lithium metal complex oxide powder M in positive electrode active material 10 is also influenced by the particle size, specific surface area, etc. of lithium metal complex oxide powder M. However, it is preferable that the amount be within the range of pH measured by the following method.

  That is, after dispersing 5 g of the positive electrode active material 10 in 100 ml of pure water, adjust the pH of the supernatant liquid left to stand for 10 minutes to be in the range of 9.0 to 11.8. It is preferable to adjust so that pH may become 9.0 or more and less than 11.5. Since the ammonium salt A of the transition metal oxo anion is acidic, it means that the lower the pH of the supernatant liquid is, the larger the amount of ammonium salt A of the transition metal oxo anion eluted from the positive electrode active material 10 is.

  When the above pH is less than 9.0, the charge / discharge capacity is lowered due to the addition amount of the ammonium salt A of the transition metal oxo anion being too large, and between the lithium metal complex oxide powder M and the electrolyte solution Lithium conduction is inhibited, reaction resistance is increased, and output characteristics may be degraded. From the viewpoint of obtaining higher battery capacity and output characteristics, the lower limit of the pH is preferably 10.0 or more, and more preferably 11.0 or more. On the other hand, when the above pH is more than 11.8, lithium hydroxide generated in the production process of the positive electrode paste can not be sufficiently neutralized, and as a result, the positive electrode mixture paste is gelated, and the operability is poor. It may lead to the deterioration of the yield.

  In addition, when the lithium metal composite oxide powder M contains lithium in excess of the stoichiometric composition with respect to the transition metal (that is, when 1.00 <z in the above general formula is satisfied), the lithium metal composite oxide is oxidized. By forming the ammonium salt A of the transition metal oxo anion on the surface of the metal powder M, the positive electrode active material 10 can improve the output characteristics and the cycle characteristics without impairing the stability of the positive electrode slurry. The powder characteristics such as particle diameter and tap density as the positive electrode active material 10 may be within the range of a positive electrode active material which is usually used.

  For example, the average particle diameter of the positive electrode active material 10 is preferably in the range of 3 μm to 15 μm. Thereby, the filling property can be enhanced, and the battery capacity per volume of the secondary battery can be made higher. Further, the applied voltage between the lithium metal composite oxide powder can be made uniform, the load among the powders can be made uniform, and the cycle characteristics can be enhanced. In addition, as an average particle diameter of the positive electrode active material 10, it is calculated | required from the volume integration value measured by the laser beam diffraction scattering type | formula particle size analyzer using d50.

  The form of ammonium salt A of the transition metal oxoanion dispersed and present on the surface of lithium metal complex oxide powder M covers the surface in layers even if it is in the state of being attached to the surface in the form of islands. Or both of these states may be included. The transition metal oxoammonium salt A can be formed by precipitating as crystals on the surface of the lithium metal composite oxide powder M using the method for producing the positive electrode active material 10 described later.

  The ammonium salt A of the transition metal oxo anion may be dispersed on the surface of the primary particle 1 and / or the surface of the secondary particle 2 which can be in contact with the electrolyte. In addition, the ammonium salt of the transition metal oxo anion may be present at the grain boundary between the primary particles 1 in which the bonding between the primary particles 1 is incomplete and the electrolyte can penetrate.

  In the production process of the positive electrode active material 10, when mixing (adhering and permeating) an aqueous solution of an ammonium salt of a transition metal oxoanion to the lithium metal composite oxide powder M, secondary in addition to the surface of the secondary particle 2 The aqueous solution of the ammonium salt of the transition metal oxo anion also penetrates between the primary particles 1 constituting the particles 2. Thereafter, the water in the aqueous solution of the ammonium salt of the transition metal oxoanion which has permeated is volatilized by the drying step, and the ammonium salt A of the transition metal oxoanion is also present between the primary particles 1 constituting the secondary particles 2 it can.

2. Method of Manufacturing Positive Electrode Active Material Hereinafter, a method of manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, also referred to as “a method of manufacturing a positive electrode active material”) will be described with reference to FIGS. Each step will be described in detail. The method for producing a positive electrode active material of the present embodiment can easily produce the above-described positive electrode active material 10 on an industrial scale.

[First step]
First, as shown in FIG. 2, a lithium metal composite oxide powder M and an aqueous solution of an ammonium salt of a transition metal oxo anion are mixed (first step: step S1). Thereby, the ammonium salt of the transition metal oxo anion can be dispersed on the surface of the lithium metal composite oxide powder M in the presence of water.

  Here, the surface of the lithium metal composite oxide powder M refers to a surface that can be in contact with the electrolytic solution in the positive electrode of the secondary battery. The surface of the lithium metal composite oxide powder M refers to, for example, the surface of the primary particle 1 exposed on the outer surface of the secondary particle 2 and the secondary particle to which the electrolyte can permeate through the secondary particle 2 outside. 2 includes the surface of the primary particle 1 exposed in the void 3 in the vicinity of the surface and in the inside, and even in the grain boundary between the primary particles 1, the bonding of the primary particle 1 is incomplete and the electrolyte can penetrate If it is in the state, it is included. Hereinafter, details of each material and mixing method used in this process will be described.

(1) Lithium Metal Complex Oxide Powder A lithium metal complex oxide powder M used as a raw material has a general formula: Li _z Ni _1-x-y Co _x M _y O ₂ (where, 0.10 ≦ x ≦ 0. 35, 0 ≦ y ≦ 0.35, 1.00 <z <1.30, M is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W and Al) Ru. In the above general formula, z representing the lithium content is more than 1 and less than 1.30. When lithium is contained in excess of the stoichiometric composition with respect to the transition metal (that is, when z exceeds 1 in the above general formula), a secondary battery using the obtained positive electrode active material for the positive electrode is more It can have low reaction resistance and high charge / discharge cycle characteristics. On the other hand, when z indicating the content ratio of lithium is 1.30 or more, the battery capacity decreases and the pH increases.

  The lithium metal composite oxide powder M is composed of at least one of a single primary particle 1 and a secondary particle 2 formed by aggregation of a plurality of primary particles 1. The lithium metal composite oxide powder M preferably includes secondary particles 2 having voids and grain boundaries between the primary particles 1 which can be permeated by the electrolytic solution. When the secondary particles 2 have voids and grain boundaries between the primary particles 1 to which the electrolyte can permeate, the contact area between the positive electrode active material 10 and the electrolyte increases in the positive electrode of the secondary battery, and the output characteristics are improved. It is advantageous to

  When mixing lithium metal complex oxide powder M and an aqueous solution of ammonium salt of transition metal oxoanion, an aqueous solution of ammonium salt of transition metal oxoanion is contained in voids and grain boundaries between primary particles 1 that can be contacted with the electrolyte Can also penetrate, and after drying (step S2) to be described later, the ammonium salt A of the transition metal oxoanion is dispersed and present on the surface including voids and grain boundaries between such primary particles 1 it can.

  500 degrees C or less is preferable, and, as for the temperature of lithium metal complex oxide powder M used as a raw material in a 1st process (step S1), 200 degrees C or less is more preferable. When the temperature of the lithium metal composite oxide powder M is in the above range, an aqueous solution of an ammonium salt of a transition metal oxo anion can be dispersed more uniformly on the surface of the lithium metal composite oxide powder M. On the other hand, when the temperature of the lithium metal composite oxide powder M exceeds 500 ° C., the ammonium salt of the transition metal oxo anion decomposes, so the effect of the present invention is reduced. The lower limit of the temperature of the lithium metal composite oxide powder is not particularly limited, but if it is 10 ° C. or higher, the ammonium salt of the transition metal oxoanion after drying will be in a sufficiently dispersed state. More preferably, the lower limit of the temperature of the lithium metal composite oxide powder is 30 ° C. or higher, and more preferably 50 ° C. or higher.

  The temperature of the lithium metal composite oxide powder M used as the raw material is more preferably 100 ° C. or less. When the temperature of the lithium metal composite oxide powder M is 100 ° C. or lower, consumption of ammonium ions in the aqueous solution is suppressed, and after drying (step S2), a transition metal oxoanion is formed on the surface of the lithium metal composite oxide powder M. More ammonium salt A can be left. In addition, an aqueous solution of an ammonium salt of a transition metal oxoanion can be sufficiently diffused and permeated to the surface of the lithium metal composite oxide powder M (including the grain boundary between primary particles 1) while suppressing the evaporation of water. Thus, the dispersibility of the ammonium salt A of the transition metal oxo anion can be further improved.

  The temperature of the lithium metal composite oxide powder M can be adjusted to the above range by a method such as heating with electromagnetic waves or hot air.

  The lithium metal complex oxide powder M used as a raw material has a pH of 11 of the supernatant liquid obtained by dispersing 5 g of the lithium metal complex oxide powder M in 100 ml of pure water and then allowing it to stand for 10 minutes. Preferably, it is not less than .8. The upper limit of pH is not particularly limited, but is usually about pH 12.5 or less.

(2) Aqueous solution of ammonium salt of transition metal oxoanion The aqueous solution of ammonium salt of transition metal oxoanion refers to an aqueous solution in which ammonium salt A of the transition metal oxoanion described above is dissolved. The ammonium salt of the transition metal oxoanion contained in the aqueous solution is an ammonium salt containing an oxoanion of the transition metal, preferably an ammonium salt of at least one oxoanion selected from tungsten or molybdenum or vanadium.

  The ammonium salt of the transition metal oxo anion is preferably an ammonium salt of a transition metal oxo anion which is readily soluble in water, more preferably ammonium tungstate which is readily soluble, and further more preferably ammonium metatungstate. It can be manufactured at low cost by using an ammonium salt of a transition metal oxoanion which is easily soluble in water.

  The concentration of the transition metal oxoanion ammonium salt in the aqueous solution of the transition metal oxoanion ammonium salt is preferably 100 g / l or more and 2000 g / l or less as the concentration of transition metal contained. When the concentration is less than 100 g / l, the concentration of the ammonium salt of transition metal oxoanion in the aqueous solution is low, and water as a solvent is added to lithium metal composite oxide powder M in a large amount, lithium metal composite oxide Lithium contained in the crystal structure of the powder M may be eluted, which may lead to a decrease in battery characteristics of a secondary battery using the obtained positive electrode active material 10 or a decrease in positive electrode slurry stability. On the other hand, when the concentration of ammonium salt of transition metal oxoanion exceeds 2000 g / l, there is too little water as solvent, and ammonium salt A of transition metal oxoanion is uniformly dispersed on the surface of lithium metal complex oxide powder M There is something I can not do.

  The amount of mixing the aqueous solution of ammonium salt of transition metal oxoanion can be appropriately adjusted according to the physical properties of the lithium metal composite oxide powder M to be mixed, and 5 g of the obtained positive electrode active material 10 was dispersed in 100 ml of pure water After that, it is preferable to adjust the pH of the supernatant liquid that has been allowed to stand for 10 minutes to be 9.0 or more and 11.8 or less, more preferably 10.0 or more and 11.8 or less. It is more preferably adjusted to an amount of 11.0 or more and 11.8 or less.

  When the above pH of the obtained positive electrode active material 10 is less than 9.0, the charge / discharge capacity is lowered due to the addition amount of the ammonium salt of the transition metal oxo anion being too large, and the lithium metal composite oxide and the electrolyte Lithium conduction is inhibited, and the output characteristics may be degraded by the increase in reaction resistance. In addition, when the pH of the obtained positive electrode active material 10 exceeds 11.8, lithium hydroxide produced in the step of producing the positive electrode can not be sufficiently neutralized, and as a result, the slurry for the positive electrode causes gelation. , Poor operability, and poor yield.

  The mixing amount of the transition metal oxoanion ammonium salt aqueous solution is influenced by the particle size of the lithium metal complex oxide powder, the specific surface area, etc. and the concentration of the transition metal oxoanion ammonium salt in the aqueous solution. After confirming lithium metal complex oxide powder which formed the ammonium salt of the transition metal oxo anion after drying by a test by the above-mentioned evaluation so that pH might become in the range of 9.0 or more and 11.8 or less, It is preferable to determine the mixing amount.

(3) Mixing The mixing method in the first step (step S1) is not particularly limited as long as the lithium metal composite oxide powder M and the aqueous solution of ammonium salt of transition metal oxoanion can be uniformly mixed. For example, after adding a predetermined amount of an aqueous solution of an ammonium salt of a transition metal oxo anion to a lithium metal composite oxide powder M, the mixture can be sufficiently mixed using a known mixer to obtain a mixture.

  For example, while stirring lithium metal complex oxide powder M (powder), an aqueous solution of ammonium salt of transition metal oxoanion is sprayed or transition is caused while flowing lithium metal complex oxide powder M (powder) The mixture can be obtained by mixing or the like by spraying an aqueous solution of an ammonium salt of a metal oxo anion. When the aqueous solution of ammonium salt of transition metal oxoanion is sprayed and added, the aqueous solution of ammonium salt of transition metal oxoanion can be easily and uniformly dispersed in the lithium metal complex oxide powder M.

  When dispersing the aqueous solution of ammonium salt of transition metal oxoanion by mixing, a common mixer can be used. As a mixer, a shaker mixer, a Loedige mixer, a Julia mixer, a V blender etc. can be used, for example. Moreover, as a mixer, a fluid bed coating apparatus can also be used.

[Second step]
The second step (step S2) is a step of drying the mixture. Drying is performed under conditions such that the water in the mixture is sufficiently volatilized, and the ammonium salt of the transition metal oxo anion remains undegraded. In the second step, in the mixture, at least a part of the water derived from the aqueous solution of the ammonium salt of transition metal oxoanion volatilizes. By evaporation of water, ammonium salt A of transition metal oxoanion precipitates as crystals on the surface of lithium metal complex oxide powder M, the interface between primary particles 1 constituting the powder of secondary particles 2 and the like. Do.

  The drying temperature may be set to such a range that the water in the mixture is sufficiently volatilized and the ammonium salt of the transition metal oxoanion is not decomposed and remains, for example, 500 ° C. or less, preferably 400 ° C. C. or less, more preferably 300.degree. C. or less, still more preferably 200.degree. C. or less. When the drying temperature exceeds 500 ° C., decomposition of the ammonium salt of the transition metal oxo anion may proceed, and the effect of the present invention may be reduced. The lower limit of this temperature is not particularly limited, but is preferably 25 ° C. or more. If it is less than 25 ° C., the drying time until the water is volatilized will be long, and the productivity will be reduced.

  The drying time is, for example, 6 hours or less, preferably 4 hours or less, more preferably 2 hours or less, still more preferably 1 hour or less. When the drying time exceeds 6 hours, decomposition of the ammonium salt of the transition metal oxoanion may proceed even when the drying temperature is 500 ° C. or less, and the effect of the present invention may be reduced. The lower limit of the drying time is not particularly limited, but is preferably 10 minutes or more. If the drying time is less than 10 minutes, the water may not evaporate.

  The atmosphere for drying is preferably an oxidizing atmosphere such as an oxygen atmosphere or a reduced pressure atmosphere to avoid reaction with moisture and carbonic acid in the atmosphere.

  The lithium metal composite oxide obtained after drying may be used as it is as the positive electrode active material 10, or after further performing other steps such as a crushing step for adjusting the particle size distribution, the positive electrode active material 10 It may be used as

3. Nonaqueous Electrolyte Secondary Battery The nonaqueous electrolyte secondary battery of the present embodiment includes a positive electrode, a negative electrode, and a nonaqueous electrolytic solution. The non-aqueous electrolyte secondary battery of the present embodiment may be configured by, for example, the same components as general non-aqueous electrolyte secondary batteries. Note that the embodiments described below are merely examples, and the non-aqueous electrolyte secondary battery of the present invention has various modifications based on the knowledge of those skilled in the art based on the embodiments described herein. It can implement in the form which gave improvement. Moreover, the non-aqueous electrolyte secondary battery of this invention does not specifically limit the use.

(A) Positive Electrode A positive electrode of a non-aqueous electrolyte secondary battery is manufactured, for example, as follows, using the above-described positive electrode active material for non-aqueous electrolyte secondary battery.

First, a powdery positive electrode active material, a conductive material, and a binder are mixed, and if necessary, activated carbon and a solvent for adjusting viscosity etc. are added, and the mixture is kneaded to prepare a positive electrode mixture paste.
The mixing ratio of each in the positive electrode mixture paste is also an important factor in determining the performance of the non-aqueous electrolyte secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 to 95 parts by mass as in the positive electrode of a general non-aqueous electrolyte secondary battery. It is desirable that the content of the binder be 1 to 20 parts by mass, and the content of the binder be 1 to 20 parts by mass.

  The obtained positive electrode mixture paste is applied, for example, on the surface of a current collector made of aluminum foil, and dried to disperse the solvent. If necessary, pressure may be applied by a roll press or the like to increase the electrode density. Thus, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery, and can be used for battery production. However, the method of producing the positive electrode is not limited to the illustrated one, and may be another method.

  In the preparation of the positive electrode, for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), carbon black-based materials such as acetylene black and ketjen black can be used as the conductive agent.

  The binding agent plays a role of holding the active material particles, and for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose resin, polyacrylic An acid etc. can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. In addition, activated carbon can be added to the positive electrode mixture in order to increase the capacity of the electric double layer.

(B) Negative electrode In the negative electrode, metal lithium, lithium alloy, etc. or a negative electrode active material capable of absorbing and desorbing lithium ions, a binder is mixed, and an appropriate solvent is added to make a negative electrode composite material Is applied to the surface of a metal foil current collector such as copper, dried, and compressed if necessary to increase the electrode density.

  As the negative electrode active material, it is possible to use, for example, a calcined product of an organic compound such as natural graphite, artificial graphite, or a phenol resin, or a powder of a carbon material such as coke. In this case, as the negative electrode binder, a fluorine-containing resin such as PVDF can be used as in the positive electrode, and as a solvent for dispersing the active material and the binder, N-methyl-2-pyrrolidone and the like can be used. Organic solvents can be used.

(C) Separator A separator is interposed and arrange | positioned between a positive electrode and a negative electrode. The separator separates the positive electrode and the negative electrode and holds the electrolyte, and may be a thin film of polyethylene, polypropylene or the like and a film having a large number of minute holes.

(D) Nonaqueous Electrolyte The nonaqueous electrolyte is a lithium salt as a supporting salt dissolved in an organic solvent.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, linear carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and dipropyl carbonate, and further tetrahydrofuran, 2- Ethers such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate alone or in combination of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) _{2 and the} like, and complex salts thereof can be used. Furthermore, the non-aqueous electrolytic solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(E) Shape and Configuration of Battery The shape of the non-aqueous electrolyte secondary battery of the present invention, which is composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte described above, is variously cylindrical, laminated, etc. It can be

  In any of the shapes, the positive electrode and the negative electrode are stacked via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolytic solution and passed to the positive electrode current collector and the outside. Connection with the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside are connected using a current collection lead or the like, and sealed in a battery case to complete a non-aqueous electrolyte secondary battery. .

(F) Characteristics The nonaqueous electrolyte secondary battery using the positive electrode active material of the present embodiment has high capacity and high output. A non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention obtained in a particularly preferred form is, for example, a high initial discharge capacity of 145 mAh / g or more and a low positive electrode when used for the positive electrode of a 2032 type coin battery Resistance is obtained.

  The following is an example of a method of measuring the positive electrode resistance. When the frequency dependence of the cell reaction is measured by the general alternating current impedance method as an electrochemical evaluation method, the Nyquist diagram based on the solution resistance, the negative electrode resistance and the negative electrode capacity, and the positive electrode resistance and the positive electrode capacity is shown in FIG. As obtained.

  The cell reaction at the electrode is composed of a resistance component associated with charge transfer and a capacity component by the electric double layer, and when these are represented by an electric circuit, it becomes a parallel circuit of resistance and capacity. It is represented by an equivalent circuit in which circuits are connected in series. Fitting calculations can be performed on the Nyquist diagram measured using this equivalent circuit to estimate each resistance component and capacitance component. The positive electrode resistance is equal to the diameter of the low frequency side semicircle of the obtained Nyquist diagram.

  From the above, it is possible to estimate the positive electrode resistance by performing alternating current impedance measurement on the manufactured positive electrode and performing fitting calculation on the obtained Nyquist diagram using an equivalent circuit.

  The performance of the pH of the positive electrode active material obtained by the present invention, the positive electrode mixture paste, and the secondary battery having the positive electrode using this positive electrode active material (initial discharge capacity, positive electrode resistance, after 60 ° C. 500 charge / discharge cycles Discharge capacity maintenance rate) was measured. In the present example, Wako Pure Chemical Industries, Ltd. reagent special grade samples were used for producing the composite hydroxide, the positive electrode active material, and the secondary battery. Hereinafter, the present invention will be specifically described using examples of the present invention, but the present invention is not limited to these examples.

(Battery manufacture and evaluation)
For the evaluation of the positive electrode active material, a 2032 type coin battery CBA (hereinafter referred to as a coin type battery CBA) shown in FIG. 4 was used.

  As shown in FIG. 4, the coin-type battery CBA is composed of a case CA and an electrode 3 housed in the case CA.

  The case CA has a hollow positive electrode can PC open at one end and a negative electrode can NC disposed at the opening of the positive electrode can PC. When the negative electrode can NC is disposed at the opening of the positive electrode can PC A space for accommodating the electrode EL is formed between the negative electrode can NC and the positive electrode can PC. The electrode EL is composed of a positive electrode PE, a separator SE, and a negative electrode NE, and is stacked in this order, the positive electrode PE contacts the inner surface of the positive electrode can PC, and the negative electrode NE contacts the inner surface of the negative electrode can NC. Is housed in case CA.

  The case CA is provided with a gasket GA, and the relative movement is fixed by the gasket GA so as to maintain a non-contact state between the positive electrode can PC and the negative electrode NC. In addition, the gasket GA also has a function of sealing the gap between the positive electrode can PC and the negative electrode NC to shut off the inside and the outside of the case CA from airtight liquid tightness.

The coin-type battery CBA shown in FIG. 4 described above was manufactured as follows.
First, 52.5 mg of a positive electrode active material for a non-aqueous electrolyte secondary battery, 15 mg of acetylene black, and 7.5 mg of a polytetrafluoroethylene resin (PTFE) are mixed to prepare a positive electrode mixture paste, and a diameter of 11 mm is obtained at a pressure of 100 MPa. It press-molded to 100 micrometers in thickness, and produced positive electrode PE. The produced positive electrode PE was dried in a vacuum dryer at 120 ° C. for 12 hours.

Using the positive electrode PE, the negative electrode NE, the separator SE, and the electrolytic solution, the above-described coin-type battery CBA was produced in a glove box under an Ar atmosphere with a dew point controlled to -80.degree.
In addition, as the negative electrode NE, a negative electrode sheet in which a graphite powder having an average particle diameter of about 20 μm punched into a disk shape having a diameter of 14 mm and polyvinylidene fluoride were coated on a copper foil was used.

A polyethylene porous film with a film thickness of 25 μm was used as the separator SE. As an electrolyte solution, an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (made by Toyama Pharmaceutical Co., Ltd.) using 1 M LiClO ₄ as a supporting electrolyte was used.

  The initial discharge capacity and positive electrode resistance which show the performance of the manufactured coin-type battery CBA were evaluated as follows.

(Initial discharge capacity)
The initial discharge capacity is left for about 24 hours after manufacturing the coin-type battery CBA, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density to the positive electrode is set to 0.1 mA / cm 2 and the cutoff voltage 4. The capacity at the time of charging to 3 V and discharging to a cutoff voltage of 3.0 V after one hour of rest was taken as the initial discharge capacity.

(Positive electrode resistance)
The positive electrode resistance is measured by an alternating current impedance method using a frequency response analyzer and a potentio galvanostat (manufactured by Solartron, 1255B) after charging the coin-type battery CBA at a charging potential of 4.1 V, the Nyquist plot shown in FIG. can get. Since this Nyquist plot is expressed as the sum of solution resistance, negative electrode resistance and its capacity, and positive electrode resistance and characteristic curve showing its capacity, fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and positive electrode resistance is calculated. The value of was calculated.

(Discharge capacity maintenance rate)
Evaluation of the discharge capacity retention rate after the charge and discharge cycle at 60 ° C for 500 ° C is maintained at 60 ° C and paused for 10 minutes after the measurement of initial discharge capacity, and the charge and discharge cycle is measured in the same manner as the initial discharge capacity measurement. 500 cycles (charge and discharge) were repeated. The discharge capacity at the 500th cycle was measured, and the percentage of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle (initial discharge capacity) was determined as the volume retention (%).

Example 1
A lithium metal composite represented by Li _1.20 Ni _0.35 Co _0.35 Mn _0.30 O ₂ obtained by a known technique in which a nickel-based oxide powder and lithium hydroxide are mixed and fired Oxide powder M was used as a base material.

  Ammonium metatungstate aqueous solution 0 having a tungsten concentration of 150 g / l in ammonium metatungstate aqueous solution (MW-2, manufactured by Japan Inorganic Chemical Industry Co., Ltd.) in 50 g of lithium metal composite oxide powder which is a base material adjusted to 50 ° C. After adding .31 ml, they were mixed and dried at 190 ° C for 5 hours to obtain a mixture of lithium metal composite oxide powder in which ammonium metatungstate was dispersed. The presence of ammonium metatungstate was confirmed by XRD diffraction.

[PH measurement]
After dispersing 5 g of the obtained active material in 100 ml of pure water, the pH at 25 ° C. of the supernatant liquid in which it was allowed to stand for 10 minutes was measured.

[Evaluation of positive electrode mixture paste]
During the preparation of the positive electrode mixture paste, the occurrence of gelation was evaluated. The case where it did not gelatinize was made into "(circle)" and the case where it gelatinized was made into "x".

[Battery evaluation]
The battery characteristics of a coin-type battery CBA having a positive electrode manufactured using the obtained positive electrode active material were evaluated. Table 1 shows evaluation values of pH measurement, positive electrode mixture paste, and battery characteristics (initial discharge capacity, positive electrode resistance, discharge capacity retention ratio after 60 ° C. 500 charge / discharge cycles).

Example 2
In the same manner as in Example 1 except that the ammonium metatungstate solution used was changed to 0.62 ml, a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained, and evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
[Example 3]
In the same manner as in Example 1 except that the ammonium metatungstate solution used was changed to 1.24 ml, a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained, and the pH, the positive electrode mixture paste, and the battery characteristics were evaluated. The results are shown in Table 1.
Example 4
In the same manner as in Example 1 except that the used ammonium metatungstate solution was changed to 2.48 ml, a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained, and the pH, the positive electrode mixture paste, and the battery characteristics were evaluated. The results are shown in Table 1.
[Example 5]
In the same manner as in Example 1 except that the ammonium metatungstate solution used was changed to 4.96 ml, a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained, and evaluation of pH, positive electrode mixture paste, and battery characteristics The results are shown in Table 1.

[Example 6]
A positive electrode active material for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except that Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ was used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
[Example 7]
A positive electrode active material for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 2 except that Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ was used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
[Example 8]
A positive electrode active material for a non-aqueous electrolyte secondary battery is prepared in the same manner as in Example 3 except that Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ is used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
[Example 9]
A positive electrode active material for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 4 except that Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ was used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
[Example 10]
A positive electrode active material for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 5 except that Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ was used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.

Comparative Example 1
The pH of the lithium metal composite oxide powder represented by Li _1.20 Ni _0.35 Co _0.35 Mn _0.30 O ₂ , the positive electrode mixture paste, and the battery characteristics were evaluated, and the results are shown in Table 1. Show.
Comparative Example 2
The pH of the lithium metal composite oxide powder represented by Li _1.25 Ni _0.35 Co _0.35 Mn _0.30 O ₂ , the positive electrode mixture paste, and the battery characteristics were evaluated, and the results are shown in Table 1. Show.

Comparative Example 3
A positive electrode active material for a non-aqueous electrolyte secondary battery is prepared in the same manner as in Example 2 except that Li _1.00 Ni _0.35 Co _0.35 Mn _0.30 O ₂ is used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.
Comparative Example 4
A positive electrode active material for a non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 2 except that Li _1.30 Ni _0.35 Co _0.35 Mn _0.30 O ₂ was used as a positive electrode active material as a base material. While being obtained, evaluation of pH, positive electrode mixture paste, and battery characteristics was performed. The results are shown in Table 1.

[Evaluation results]
In the positive electrode active material obtained in the example, ammonium metatungstate (ammonium salt A of transition metal oxoanion) was detected by XRD. After dispersing 5 g of the positive electrode active material obtained in the example in 100 ml of pure water, the pH of the supernatant liquid allowed to stand for 10 minutes is in the range of 11.3 to 11.7 at 25 ° C. When the positive electrode paste was produced, it was confirmed that gelation was suppressed.

  On the other hand, gelation of the positive electrode paste was confirmed in the positive electrode active materials obtained in Comparative Examples 1 and 2 which did not contain the ammonium salt of the transition metal oxo anion.

  In addition, secondary batteries using the positive electrode active material obtained in the examples have comparable initial charge and discharge capacities compared to using the positive electrode active material of the positive electrode active material obtained in Comparative Examples 1 and 2. In addition, it was confirmed that the positive electrode resistance and the charge / discharge capacity retention rate were further reduced.

  Furthermore, in Comparative Example 3 in which the content (z) of Li of the lithium metal composite oxide powder used as the base material is 1, the positive electrode resistance and the charge / discharge capacity retention ratio increase, and the content (z) of Li is In the comparative example 4 which is 1.3, it was confirmed that initial stage discharge capacity falls.

M: lithium metal composite oxide powder A: ammonium salt of transition metal oxo anion 1: primary particle 2: secondary particle 3: air gap 10: positive electrode active material CBA: coin-type battery CA: case PC ...... Positive electrode can NC ... Negative electrode can GA ... Gasket EL ... Electrode PE ... Positive electrode NE ... Negative electrode SE ... Separator

Claims (13)

General formula (1): Li _z Ni _1-xy Co _x M _y O ₂ (where, 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0.35, 1.00 <z <1.30) , M, lithium metal composite oxide powder represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W and Al), and an ammonium salt of a transition metal oxoanion ,
At least a portion of the ammonium salt of the transition metal oxo anion is present in a dispersed manner on the surface of the lithium metal composite oxide powder,
The positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the transition metal contained in the ammonium salt of the transition metal oxo anion is at least one selected from tungsten, molybdenum and vanadium.   The lithium metal composite oxide powder includes secondary particles formed by aggregating a plurality of primary particles, and a part of ammonium salt of the transition metal oxoanion exists between the primary particles. The positive electrode active material for non-aqueous electrolyte secondary batteries as described.   After dispersing 5 g of the positive electrode active material in 100 ml of pure water, the supernatant liquid which has been allowed to stand for 10 minutes has a pH at 25 ° C. of 9.0 or more and 11.8 or less. The positive electrode active material for non-aqueous electrolyte secondary batteries as described in-.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the ammonium salt of the transition metal oxoanion is water soluble.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the ammonium salt of the transition metal oxoanion contains ammonium tungstate.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the ammonium tungstate contains ammonium metatungstate. General formula (1): Li _z Ni _1-xy Co _x M _y O ₂ (where, 0.10 ≦ x ≦ 0.35, 0 ≦ y ≦ 0.35, 1.00 <z <1.30) , M is at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb, Ti, W and Al) lithium metal complex oxide powder, and at least one selected from tungsten, molybdenum and vanadium Mixing an aqueous solution of an ammonium salt of one transition metal oxoanion to obtain a mixture;
And d) drying the mixture.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising mixing the lithium metal composite oxide powder at 10 ° C. to 100 ° C. with an aqueous solution of an ammonium salt of the transition metal oxoanion in the first step.   After dispersing 5 g of the positive electrode active material obtained in the second step in 100 ml of pure water, the supernatant liquid allowed to stand for 10 minutes has a pH of 9.0 or more and 11.8 or less at 25 ° C. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of Claim 7 which adjusts the quantity mixed with the aqueous solution of the ammonium salt of the said transition metal oxo anion in the said 1st process.   The lithium metal complex oxide powder used in the first step has a pH of the supernatant liquid at 25 ° C. which is allowed to stand for 10 minutes after dispersing 5 g of the lithium metal complex oxide powder in 100 ml of pure water. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of Claim 8 which is 11.8 or more.   The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries as described in any one of Claims 7-9 whose ammonium salt of the said transition metal oxo anion is water-soluble.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 10, wherein the ammonium salt of the transition metal oxoanion contains ammonium tungstate.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 11, wherein the ammonium tungstate contains ammonium metatungstate. A positive electrode, a negative electrode, and a non-aqueous electrolyte,
The non-aqueous electrolyte secondary battery in which the said positive electrode contains the positive electrode active material for non-aqueous electrolyte secondary batteries as described in any one of Claims 1-6.

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