JP2018032543A - Positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material by which a secondary battery having an enough charge/discharge capacity and extremely excellent output characteristics can be achieved, a method for manufacturing the positive electrode active material, etc.SOLUTION: A positive electrode active material 10 for a nonaqueous electrolyte secondary battery comprises: a lithium metal composite oxide 3 including secondary particles 2 formed by agglomeration of primary particles 1; a first substance A consisting of a lithium salt of an oxoanion of one or more kinds of transition metal selected from tungsten, molybdenum and vanadium; and a second substance B consisting of conductive fine powder higher than the first substance in electron conductivity. In the positive electrode active material, the first substance A and the second substance B are deposited on at least part of the primary particles 1 which are present at the surface of and inside each secondary particle 2.SELECTED DRAWING: Figure 1

Description

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

  In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, the development of secondary batteries having excellent output characteristics as batteries for electric vehicles such as hybrid vehicles is strongly desired.

  As a secondary battery satisfying such requirements, there is a lithium ion secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as the active material of the negative electrode and the positive electrode. Lithium ion secondary batteries are currently under active research and development. Among them, lithium ion secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are of the 4V class. Since a high voltage can be obtained, practical use is progressing as a battery having a high energy density.

The main cathode materials that have been proposed so far include lithium cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel that is cheaper than cobalt, lithium Examples thereof include nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, and the like.

  Further, the secondary battery is required to improve the output characteristics as described above. In order to obtain a lithium ion secondary battery having excellent output characteristics, the positive electrode active material needs to be composed of particles having a small particle size and a narrow particle size distribution. This is because particles having a small particle size have a large specific surface area, and when used as a positive electrode active material, a sufficient reaction area with the electrolyte can be secured, and the positive electrode is made thin, and a lithium ion positive electrode This is because the positive electrode resistance can be reduced because the moving distance between the negative electrodes can be shortened. In order to further improve the output characteristics, it is effective that the positive electrode active material has a hollow structure. Since such a positive electrode active material can increase the reaction area with the electrolyte compared to a solid positive electrode active material having the same particle size, the positive electrode resistance can be further reduced.

  For example, in Patent Document 1 below, transition metal composite hydroxide particles serving as a precursor of a positive electrode active material are clearly classified into two stages: a nucleation process that mainly performs nucleation and a particle growth process that mainly performs particle growth. A method for producing by a crystallization reaction separated into two is disclosed. In these methods, the pH value of the aqueous reaction solution is in the range of 12.0 to 13.4 or 12.0 to 14.0 in the nucleation step, and 10.5 in the particle growth step, based on a liquid temperature of 25 ° C. It is controlled in the range of ~ 12.0. The reaction atmosphere is an oxidizing atmosphere at the initial stage of the nucleation step and the particle growth step, and is switched to a non-oxidizing atmosphere at a predetermined timing.

  By such a method, the obtained transition metal composite hydroxide particles have a small particle size, a narrow particle size distribution, and a low density center portion composed of fine primary particles and a high density composed of plate-like or needle-like primary particles. Consists of a density outer shell. Therefore, when such transition metal composite hydroxide particles are fired, the low density center portion is greatly contracted, and a space portion is formed inside. Moreover, as described above, the particle properties of the composite hydroxide particles are inherited by 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 size] is 0.60 or less and has a hollow structure.

  On the other hand, as another method for improving the output characteristics, 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, Patent Document 2 and Patent Document 3 describe that 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 2011-119092 A JP 2012-077944 A JP2013-152866A

  In the secondary battery using the positive electrode active material described in Patent Document 1, it is considered that the output characteristics can be improved, but further improvement of the output characteristics is required. Moreover, although the substance containing W and Li represented by lithium tungstate described in Patent Documents 2 and 3 is excellent in lithium ion conductive conductivity, it has poor electronic conductivity. There was a problem that sufficient output could not be obtained due to a decrease in electronic conductivity between the active material particles.

  In view of the above-described problems, the present invention provides a positive electrode active material that has a sufficient battery capacity and can further improve output characteristics when a secondary battery is configured, and a method for manufacturing the same. The purpose is to do. Moreover, an object of this invention is to provide the secondary battery using such a positive electrode active material.

In a first aspect of the present invention, the general _{formula: Li z Ni 1-x-} y Co x M y O 2 ( wherein, x is 0.10 ≦ x ≦ 0.40, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al. A lithium metal composite oxide composed of secondary particles formed by aggregation of a plurality of primary particles, and lithium of an oxoanion of one or more transition metals selected from tungsten, molybdenum and vanadium A first substance made of a salt and a second substance made of a conductive fine powder having higher electron conductivity than the first substance, the surface of the secondary particles and the surface of the primary particles existing inside At least a portion of the first substance and the second substance adhere to each other A positive electrode active material for a non-aqueous electrolyte secondary battery is provided.

Moreover, it is preferable that the positive electrode active material for non-aqueous electrolyte secondary batteries has a specific resistance of the second substance of 5 × 10 ⁻⁴ Ω · cm or less. The second substance is preferably made of fine carbon powder. Moreover, it is preferable that content of carbon fine powder is 10 mass% or less with respect to the said lithium metal complex oxide. The first substance is preferably made of lithium tungstate. Moreover, it is preferable that content of tungsten in lithium tungstate is 5 mass% or less with respect to lithium metal complex oxide.

In a second aspect of the present invention, the general _{formula: Li z Ni 1-x-} y Co x M y O 2 ( in the formula, x is 0.10 ≦ x ≦ 0.40, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al An aqueous solution containing a lithium metal composite oxide composed of secondary particles formed by aggregation of a plurality of primary particles, and one or more oxoanions selected from tungsten, molybdenum and vanadium, Alternatively, preparing a mixture containing a compound and a conductive fine powder, and reacting an oxoanion and lithium ion present in the mixture, the primary particles present on the surface and inside of the secondary particles At least part of the surface of the oxoanion A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery is provided that includes heat treatment to form a lithium salt.

  In addition, the mixture preferably includes an aqueous solution containing the oxoanion, and the heat treatment is preferably performed at a temperature at which at least a part of moisture in the mixture is removed. The aqueous solution containing an oxoanion preferably contains a lithium salt of the oxoanion. The aqueous solution containing an oxoanion preferably contains an ammonium salt of the oxoanion. The mixture preferably contains a compound containing the oxoanion, and the heat treatment is preferably performed at a temperature at which at least a part of the compound can be thermally decomposed. Moreover, it is preferable that a compound consists of 1 or more types of oxo acids selected from tungsten, molybdenum, and vanadium. The conductive fine powder is preferably made of carbon fine powder.

  According to a third aspect of the present invention, there is provided a positive electrode mixture paste for a non-aqueous electrolyte secondary battery including the positive electrode active material for a non-aqueous electrolyte secondary battery.

  In a fourth aspect of the present invention, a non-aqueous electrolyte secondary battery having a positive electrode containing a positive electrode active material for a non-aqueous electrolyte secondary battery is provided.

  ADVANTAGE OF THE INVENTION According to this invention, when used for the positive electrode material of a battery, the positive electrode active material for nonaqueous electrolyte secondary batteries with which the outstanding output characteristic is acquired can be provided. Furthermore, the manufacturing method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.

FIG. 1 is a schematic diagram illustrating an example of the positive electrode active material of the present embodiment. FIG. 2 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment. FIG. 3 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment. FIG. 4 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment. FIG. 5 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment. FIG. 6 is a schematic cross-sectional view of a coin-type battery used for evaluation of battery characteristics. FIG. 7 is a diagram illustrating an example of a Nyquist plot and an equivalent circuit used for impedance evaluation.

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

1. Cathode Active Material FIG. 1A is a schematic diagram showing an example of a cathode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter sometimes simply referred to as “cathode active material”) 10. FIG. 1B is a schematic diagram illustrating an example in which a part of the positive electrode active material 10 is enlarged. The positive electrode active material 10 includes a lithium metal composite oxide 3 composed of secondary particles 2 formed by agglomerating primary particles 1, a first material A composed of an oxoanion lithium salt of a specific transition metal, A second substance B having a higher electron conductivity than the first substance A (hereinafter referred to as “second substance B”). As shown in FIG. 1B, the first substance A and the second substance B are attached to at least a part of the surface of the secondary particle 2 and the surface of the primary particle 1 existing inside. Yes.

  In general, when the surface of the positive electrode active material is coated with a different compound, the movement (intercalation) of lithium ions is greatly limited, and as a result, the output characteristics of the positive electrode active material may deteriorate. However, the positive electrode active material 10 of the present embodiment is obtained by attaching the first substance A and the second substance B to at least a part of the surface of the primary particles 1 of the lithium metal composite oxide 3. The battery capacity (initial discharge capacity) of the secondary battery can be improved and the output characteristics can be improved.

  The reason why the output characteristics are improved is not particularly limited, but the addition of the first substance A containing lithium increases the conductive path of lithium ions, mainly improves the lithium ion conductivity, and improves the positive electrode active. It is considered that the electron conductivity is mainly improved by reducing the reaction resistance of the substance 10 and adding the second substance B. Further, the positive electrode active material 10 combines both the first substance A and the second substance B, so that the positive electrode resistance of the obtained secondary battery is further reduced and output compared to the case where each is attached alone. A synergistic effect that the characteristics can be remarkably improved can be achieved. Hereinafter, each structure of the positive electrode active material 10 will be described.

(1) lithium-metal composite oxide of lithium metal composite oxide 3, the general formula _{Li z Ni 1-x-y} Co x M y O 2 ( in the formula, x is at 0.10 ≦ x ≦ 0.40 Yes, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al. At least one element. The positive electrode active material 10 can obtain excellent output characteristics and excellent charge / discharge cycle characteristics by using the lithium metal composite oxide 3 having the above composition as a base material. Note that the subscript 2 of oxygen (O) in the general formula does not have to be exactly 2, and can take a number other than 2 due to the synthesis conditions and the influence of the additive element.

  In the above formula, z indicating the lithium content is 1.00 <z <1.30. The lithium metal composite oxide 3 can provide a secondary battery having low reaction resistance and high charge / discharge cycle characteristics by containing lithium in excess of the stoichiometric composition with respect to other metals. For example, when z is 1.00 <z <1.25, the battery capacity and output characteristics of the obtained secondary battery are more excellent.

  In addition, as shown in FIG. 1A, the lithium metal composite oxide 3 includes a space 4 between the primary particles 1 inside the secondary particles 2 and a grain boundary where the electrolyte solution can permeate. It is preferable to have. When such a gap 4 is provided, the contact area with the electrolytic solution can be increased, and the output characteristics can be further improved. For example, the lithium metal composite oxide 3 may have a hollow structure from the viewpoint of further improving the output characteristics. Here, a hollow structure means the structure which has a hollow part inside the secondary particle 2 as described in patent document 1, for example.

(2) First Substance The first substance A is made of a lithium salt of one or more oxoanions selected from tungsten, molybdenum, and vanadium. The positive electrode active material 10 adheres the first substance A to at least a part of the surface of the primary particles 1 of the lithium metal composite oxide 3. As a result, when a secondary battery is manufactured, the lithium ion conduction path is increased at the interface between the electrolytic solution and the positive electrode active material 10, and the reaction resistance of the positive electrode active material 10 is reduced to improve the output characteristics. It is done.

Examples of the first substance A include lithium tungstate, lithium molybdate, lithium vanadate, or a mixture thereof. The 1st substance A may be used individually by 1 type, and may be used in combination of 2 or more type. When the first substance A is, for example, lithium tungstate, the obtained secondary battery has a sufficient battery capacity and excellent output characteristics. As the lithium tungstate, not particularly limited, for _{example, Li 2 WO 4, Li 4} WO 5, Li 6 WO 6, Li 2 W 4 O 13, Li 2 W 2 O 7, Li 6 W 2 O 9, Li ₂ W ₂ O ₇ , Li ₂ W ₅ O ₁₆ , Li ₉ W ₁₉ O ₅₅ , Li ₃ W ₁₀ O ₃₀ , Li ₁₈ W ₅ O ₁₅ or a hydrate thereof, or a mixture thereof. In the case of such lithium tungstate, the lithium ion conductivity is further increased, and the effect of reducing the reaction resistance is further increased.

  The content of the first substance A is such that, for example, the amount of transition metals (W, Mo and V) contained is a total of metal elements (Ni, Co and M) other than Li in the lithium metal composite oxide. 0.01 mol% or more and 3 mol% or less, preferably 0.05 mol% or more and 1.5 mol% or less, more preferably 0.1 mol% or more and 0.8 mol% or less. When the content of the first substance A is in the above range, the obtained secondary battery is more excellent in the balance between the battery capacity and the output characteristics.

  When the first substance A is lithium tungstate, the amount of tungsten contained can be, for example, 0.1% by mass or more and 10% by mass or less with respect to the lithium composite hydroxide. The mass is preferably from 5% by mass to 5% by mass, more preferably from 0.1% by mass to 1% by mass, and still more preferably from 0.1% by mass to 0.5% by mass. When the content of the first substance A is within the above range, the balance between the discharge capacity and the output characteristics of the secondary battery obtained using the positive electrode active material is excellent.

  Moreover, it is preferable that the 1st substance A has adhered directly to the surface of the primary particle 1, as shown in FIG.1 (B). In this case, the movement of lithium ions can be further promoted. As will be described later, the first substance A can be fixed to the surface of the primary particles 1 by forming it by reacting with an aqueous solution or compound containing an oxoanion and lithium derived from the lithium metal composite oxide 3. . Moreover, the shape of the 1st substance A is not specifically limited, For example, you may adhere as a fine particle on the primary particle surface, and may adhere in a layer form. Further, the first substance A may be attached so as to be scattered on a part of the surface of the plurality of primary particles 1, and the entire surface of the plurality of primary particles 1 (however, the second substance B is the primary particle). And may be attached to the surface. Also in this case, the above-described movement of lithium ions can be promoted. For example, in the case of fine particles, the first substance A can have a particle diameter of 1 nm to 200 nm, and in the case of a thin film (layered), the film thickness can be 1 nm to 200 nm.

(3) Second substance The second substance B is composed of conductive fine powder having higher electron conductivity than the oxoanion lithium salt (first substance A). The positive electrode active material 10 increases the electron conduction path between the lithium metal composite oxide powders in the positive electrode of the secondary battery obtained by adhering the second substance B to the surface of the primary particles 1. It is thought that the output resistance is further improved by further reducing the reaction resistance of the positive electrode active material.

As the second substance B, a substance having higher electron conductivity than the first substance A can be used. The electron conductivity can be evaluated by a specific resistance, and the second substance B preferably has a specific resistance of 5 × 10 ⁻⁴ Ω · cm or less. When the specific resistance is in the above range, sufficient electron conductivity can be exhibited. Although the minimum of specific resistance is not specifically limited, For example, it is about 1 * 10 < ^-8 > ohm * cm or more. Note that the specific resistance here is a value obtained by measuring the second substance in a bulk state. As will be described later, the second substance B can be a known conductive fine powder, and the specific resistance measured in the powder state can be, for example, 1 Ω · cm or less.

  As the second substance B, for example, conductive fine powders such as metals (gold, platinum, etc.), metal alloys, and carbon can be used. Among these, it is preferable to use carbon fine powder from the viewpoints of stability, weight, cost, and the like. As carbon fine powder, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black, ketjen black, carbon nanotubes, carbon nanofibers, etc. can be used. From the viewpoint of properties and the like, a carbon black material is preferable.

  Content of the 2nd substance B can be 0.1 mass% or more and 10 mass% or less with respect to lithium composite hydroxide, for example. When the content of the second substance B is in the above range, the positive electrode resistance can be further reduced corresponding to the content of the second substance B. In addition, the content of the second substance B is preferably 0.5% by mass or more and 5% by mass or less from the viewpoint of the balance between the discharge capacity and the output characteristics of the obtained secondary battery. More preferably, it is at least 3% by mass.

  Further, when the first substance A is lithium tungstate, the content of tungsten with respect to the content of the second substance B from the viewpoint of further improving the battery capacity (initial discharge capacity) of the obtained secondary battery. However, it is preferable to set it as 10 to 50 mass%.

  As with the first substance A described above, the second substance B is preferably directly attached to the surface of the primary particles 1. The second substance B is fixed to the surface of the primary particle 1 by mixing with the lithium metal composite oxide 3 before forming the first substance on the surface of the primary particle 1 by the heat treatment (step S20) described later. be able to. Further, the shape of the second substance B is not particularly limited, but it is preferable that the second substance B is exposed to the outside of the first substance A. In this case, the movement of electrons between the lithium metal composite oxide 3 in the positive electrode active material 10 can be further promoted. For example, when the second substance B is a carbon black material, the carbon black material forms an aggregate (aggregate) in which primary particles of several tens of nm are aggregated. When it is larger than the particle diameter or film thickness of the substance A, it can be exposed on the surface of the positive electrode active material 10. In the carbon black-based material, the size of primary particles (single) or aggregates (aggregates) can be, for example, about 10 nm to 1000 nm.

  In addition, the site | part of the surface of the primary particle 1 to which the 1st substance A and the 2nd substance B adhere is preferable the surface of the primary particle which can contact with electrolyte solution when producing a secondary battery. The surface of the primary particle 1 includes the surface of the primary particle exposed at the outer surface of the secondary particle 2, and the vicinity of the surface of the secondary particle 2 through which the electrolyte solution can permeate through the outside of the secondary particle 2 and the void 4 inside. The surface of the primary particle 1 exposed to the surface is included. Further, the surface of the primary particle 1 is included even if it is a grain boundary between the primary particles 1 as long as the primary particles 1 are not completely bonded and the electrolyte solution can penetrate. By using the method for producing a positive electrode active material described later, the first substance A and the second substance B are efficiently and simply attached to the surface of the primary particles that can be in contact with the electrolytic solution. Can do.

  The positive electrode active material 10 includes the lithium metal composite oxide 3 mainly composed of the secondary particles 2 formed by aggregating a plurality of primary particles 1. For example, the positive electrode active material 10 agglomerates as the secondary particles 2. A small amount of primary particles 1 such as primary particles 1 that have not been present or primary particles 1 that have fallen from secondary particles 2 after aggregation may be included. Further, the positive electrode active material 10 may include a lithium metal composite oxide other than the lithium metal composite oxide 3 described above.

2. 2. Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery FIG. 2 shows an example of a method for producing the positive electrode active material for nonaqueous electrolyte secondary battery (hereinafter also referred to as “positive electrode active material”) of this embodiment. FIG. By using the manufacturing method of the present embodiment, the positive electrode active material 10 can be easily and efficiently manufactured on an industrial scale. Hereinafter, the manufacturing method of this embodiment is demonstrated with reference to FIG.

  As shown in FIG. 2, the method for producing a positive electrode active material according to this embodiment is a lithium metal composite oxide and one or more oxo anions (hereinafter referred to as “oxo anions”) selected from tungsten, molybdenum, and vanadium. ) Containing an aqueous solution or compound and a conductive fine powder (Step S10), and reacting oxoanions and lithium ions present in the mixture with secondary particles. And heat-treating at least a part of the surface of the primary particle surface and the surface of the primary particle so as to form a lithium salt of an oxoanion (step S20).

  As a method for forming the lithium salt of the oxoanion on the surface of the primary particle of the lithium metal composite oxide, a known method can be used. For example, the methods described in Patent Documents 2 and 3 can be appropriately used. it can. In the production method of the present embodiment, a lithium salt of an oxoanion is formed on the surface of the primary particles in the presence of the conductive fine powder by preparing a mixture containing the conductive fine powder and performing a heat treatment. Thereby, both the oxoanion lithium salt and the conductive fine powder can be fixed to the surface of the primary particles with an appropriate strength, and an attached lithium metal composite oxide powder can be obtained. Hereinafter, each material contained in said mixture is demonstrated.

[Lithium metal composite oxide]
The lithium metal composite oxide has a general formula: Li _z Ni _1-xy Co _x M _y O ₂ (wherein x is 0.10 ≦ x ≦, similar to the lithium metal composite oxide 3 described above. 0.40, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is Mn, V, Mg, Mo, Nb, Ti, W And at least one element selected from Al.), And secondary particles formed by aggregating a plurality of primary particles.

  The manufacturing method of lithium metal complex oxide is not specifically limited, A conventionally well-known manufacturing method can be used. Moreover, from the viewpoint of obtaining higher output characteristics, the nickel composite hydroxide as a precursor clearly separated the nucleation step and the particle growth step as described in Patent Document 1, for example. It is preferable to include a two-stage crystallization process. When nickel composite hydroxide obtained by a method including such a two-stage crystallization process is used as a precursor, a lithium metal composite oxide having a high porosity and a uniform particle size is obtained. Can do.

[Aqueous solution or compound containing oxoanion]
The mixture can include an aqueous solution or compound containing one or more oxoanions selected from tungsten, molybdenum and vanadium. The aqueous solution or the oxoanion contained in the compound is subjected to a heat treatment described later, and then reacts with the lithium ion contained in the mixture to form lithium ions of the oxoanion on the surface of the primary particles of the lithium metal composite oxide. A salt can be formed.

  The aqueous solution containing an oxoanion is not particularly limited, and known ones can be used. For example, a lithium salt of an oxoanion, an ammonium salt of an oxoanion, or the like can be used. The aqueous solution containing an oxoanion may be prepared by dissolving a compound containing an oxoanion in water or an alkaline solution in advance, or a compound (powder) containing an oxoanion and water directly. An aqueous solution containing an oxoanion may be prepared on the surface of the lithium metal composite oxide by mixing with the lithium metal composite oxide.

  As an aqueous solution containing an oxoanion, an aqueous solution of an ammonium salt of an oxoanion is preferably used. When an aqueous solution of an ammonium salt of an oxoanion is used, positive electrode resistance can be further reduced and output characteristics can be improved. When an ammonium salt of an oxoanion is used, a heat treatment (drying) described later causes a neutralization reaction between the alkaline lithium compound present on the surface of the lithium metal composite oxide powder and the ammonium salt of the oxoanion, and the lithium metal An oxoanion lithium salt can be attached to the surface of the composite oxide powder. Thereby, the lithium metal complex oxide powder to which both the electroconductive fine powder and the oxoanion lithium salt were made to adhere can be obtained.

  As the compound containing an oxoanion, known compounds that are particularly limited can be used, but oxoacid (powder) is preferably used. The oxo acid in the mixture can be thermally decomposed by a heat treatment described later. The oxide produced by thermal decomposition of oxo acid, for example, causes a neutralization reaction with an alkaline lithium compound (excess lithium) present on the surface of the lithium metal composite oxide, and the surface of the primary particles of the lithium metal composite oxide powder. In addition, lithium salts of oxoanions can be formed. Thereby, the lithium metal complex oxide powder to which both the electroconductive fine powder and the oxoanion lithium salt were made to adhere can be obtained.

[Conductive fine powder]
The conductive fine powder is not particularly limited, and a known conductive fine powder can be used. As the conductive fine powder, the same material as the second material B described above can be used.

  FIG. 3 is a diagram showing an example of a method for producing a positive electrode active material by preparing the above mixture using an aqueous solution containing an oxoanion. For example, as shown in FIG. 3, the mixture is prepared by first mixing conductive fine powder with lithium metal composite oxide (S11), and then further mixing an aqueous solution containing an oxoanion (S12). Can do.

  The method of mixing the lithium metal composite oxide powder and the conductive fine powder is not particularly limited as long as both can be mixed uniformly, and a known method can be used, for example, using a ball mill or the like. Can do. Thereby, electroconductive fine powder can be disperse | distributed on the surface of lithium metal complex oxide powder. In addition, said mixing can be performed to such an extent that the form of the secondary particle which comprises lithium metal complex oxide powder is not destroyed.

  Next, the lithium metal composite oxide and an aqueous solution containing an oxoanion are mixed (step S12). The mixing method in this case is not particularly limited, and for example, it can be mixed by a known method using a general mixer (shaker mixer, Laedige mixer, Julia mixer, V blender, etc.). From the viewpoint of more uniformly diffusing the oxoanion on the surface of the primary particles, for example, a lithium metal composite that sprays an aqueous solution containing the oxoanion while stirring the lithium metal composite oxide in which the conductive fine powder is dispersed. A method of spraying an aqueous solution containing an oxoanion while flowing an oxide can be used.

  Next, the oxoanion present in the mixture obtained by the above-described method is reacted with lithium ions, so that at least a part of the surface of the secondary particle and the surface of the primary particle existing inside the oxoanion Heat treatment (drying) is performed so as to form a lithium salt (step S21).

  In the drying (step S21), a mixture obtained by mixing a lithium metal composite oxide, an aqueous solution containing an oxoanion, and a conductive fine powder is dried, and surplus lithium and lithium metal composite dissolved in water in the mixture are dried. Excess lithium in the oxide particles is reacted with tungsten contained in the tungsten oxide to form a lithium salt of an oxoanion on the surface of the primary particles.

  The drying temperature can be performed at a temperature at which at least part of the water contained in the mixture is removed. For example, the drying temperature is preferably 450 ° C. or lower. When it exceeds 450 ° C., lithium may further be liberated from the crystal of the lithium metal composite oxide, and the gelation of the paste may not be sufficiently suppressed. From the viewpoint of drying more sufficiently and preventing the liberation of lithium from the lithium metal composite oxide, the drying temperature is more preferably 100 ° C. or higher and 300 ° C. or lower.

  The atmosphere during drying is preferably decarboxylated air, an inert gas, or a vacuum atmosphere in order to avoid the reaction of moisture or carbonic acid in the atmosphere with lithium on the surface of the lithium metal composite oxide particles. Furthermore, the pressure of the atmosphere during drying is preferably 1 atm or less. When the atmospheric pressure is higher than 1 atm, the water content of the positive electrode active material may not be sufficiently lowered.

  Although the moisture content of the lithium metal composite oxide particles after drying is not particularly limited, it is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less. When the moisture content of the powder exceeds 0.2% by mass, a gas component containing carbon and sulfur in the atmosphere may be absorbed to generate a lithium compound on the surface. In addition, the measured value of the said moisture rate is a measured value at the time of measuring with a Karl Fischer moisture meter on condition of vaporization temperature of 300 degreeC.

  FIG. 4 is a diagram showing another example of a method for producing a positive electrode active material by preparing the above mixture using an aqueous solution containing an oxoanion. For example, as shown in FIG. 4, the mixture may be manufactured by simultaneously mixing conductive fine powder and an aqueous solution containing an oxoanion (step S <b> 13).

  FIG. 5 is a diagram showing an example of a method for producing a positive electrode active material by preparing the above mixture using oxo acid which is a compound containing an oxo anion. In the case of using an oxo acid, it can be mixed by a conventionally known method as in the case of the aqueous solution containing the oxo anion. In FIG. 5, conductive fine powder is mixed with lithium metal composite oxide (step S11), and then oxo acid is mixed (step S14). The oxo acid may be added at the same time and mixed.

  The mixture containing the lithium metal composite oxide, the conductive fine powder, and the oxo acid thermally decomposes the oxo acid by heat treatment (step S22). Thereby, the thermally decomposed oxide (oxo anion) and the lithium ion contained in the lithium metal composite oxide react to form a lithium salt of the oxo anion. In this case, the heat treatment temperature is, for example, about 350 ° C. or more and 550 ° C. or less, and the heat treatment time is 0.5 hour or more and 20 hours or less.

  The lithium metal composite oxide used in the manufacturing method of the present embodiment includes the lithium metal composite oxide 3 mainly composed of secondary particles 2 formed by aggregating a plurality of primary particles 1. However, for example, a small amount of primary particles 1 such as primary particles 1 that have not been aggregated as secondary particles 2 or primary particles 1 that have fallen off secondary particles 2 after aggregation may be included. Moreover, the manufacturing method of this embodiment may contain lithium metal composite oxides other than the lithium metal composite oxide 3 mentioned above in the said mixture.

3. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also referred to as “secondary battery”) includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and is similar to a general lithium ion secondary battery. It can be composed of the following components. Hereinafter, an example of the secondary battery of the present embodiment will be described for each component. The embodiment described below is merely an example, and the secondary battery can be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiment. Further, the use of the secondary battery is not particularly limited.

(Positive electrode)
Using the positive electrode active material 10 described above, a positive electrode of a non-aqueous electrolyte secondary battery is produced. Below, an example of the manufacturing method of a positive electrode is demonstrated. First, the positive electrode active material 10 (powder), a conductive material, and a binder (binder) are mixed, and if necessary, activated carbon or a solvent for adjusting viscosity is added and kneaded. A positive electrode mixture paste is prepared.

  Since the mixing ratio of each material in the positive electrode mixture is an element that determines the performance of the lithium secondary battery, it can be adjusted according to the application. The mixing ratio of the materials can be the same as that of the positive electrode of a known lithium secondary battery. For example, when the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the positive electrode active material is 60%. -95 mass%, 1-20 mass% of electrically conductive materials, and 1-20 mass% of binders can be contained.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil, and dried to disperse the solvent, thereby producing a sheet-like positive electrode. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. The sheet-like positive electrode thus obtained can be cut into an appropriate size according to the target battery and used for battery production. However, the manufacturing method of the positive electrode is not limited to the above-described examples, and may depend on other methods.

  As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, and the like), and carbon black materials such as acetylene black and ketjen black can be used.

  As the binder (binder), it plays the role of holding the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluoro rubber, ethylene propylene diene rubber, styrene butadiene, cellulose series Resins and polyacrylic acid 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. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(Negative electrode)
For the negative electrode, metallic lithium, a lithium alloy, or the like can be used. The negative electrode is prepared by mixing a negative electrode active material capable of occluding and desorbing lithium ions with a binder and adding a suitable solvent to form a paste on the surface of a metal foil current collector such as copper. You may use what was formed by compressing in order to apply | coat, dry and to raise an electrode density as needed.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(Separator)
A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains the electrolyte. For example, a thin film such as polyethylene or polypropylene and a film having many fine holes can be used.

(Non-aqueous electrolyte)
The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, tetrahydrofuran, 2- Use one kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can do.

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

(Battery shape and configuration)
The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte described above can have various shapes such as a cylindrical shape and a laminated shape. In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the nonaqueous electrolyte secondary battery.

[Characteristics of secondary battery]
The nonaqueous electrolyte secondary battery using the positive electrode active material of the present embodiment has a high capacity and a high output. In particular, the non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention obtained in a more preferable form has a high value of 145 mAh / g or more when used for the positive electrode of the 2032 type coin battery used in the examples. An initial discharge capacity and a low positive electrode resistance are obtained.

  An example of the method for measuring the positive electrode resistance is as follows. When the frequency dependence of the battery reaction is measured by a general AC 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. Is obtained as follows.

  The battery reaction at the electrode consists of a resistance component accompanying the charge transfer and a capacity component due to the electric double layer. When these are expressed as 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 calculation is performed on the Nyquist diagram measured using this equivalent circuit, and each resistance component and capacitance component can be estimated. The positive resistance is equal to the diameter of the semicircle on the low frequency side of the Nyquist diagram obtained. From the above, the positive electrode resistance can be estimated by performing AC impedance measurement on the manufactured positive electrode and performing fitting calculation on the obtained Nyquist diagram with an equivalent circuit.

(Battery manufacture and evaluation)
For the evaluation of the positive electrode active material, a 2032 type coin battery BA (hereinafter referred to as a coin type battery) shown in FIG. 6 was used. Coin type battery BA is composed of a case and an electrode accommodated in the case.

  The case has a positive electrode can PC that is hollow and open at one end, and a negative electrode can NC that is disposed in the opening of the positive electrode can PC. When the negative electrode can NC is disposed in the opening of the positive electrode can PC, A space for accommodating the electrode is formed between the negative electrode can NC and the positive electrode can PC.

  The electrode is composed of a positive electrode PE, a separator SE, and a negative electrode NE, which are stacked in this order, so that 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 a case.

  The case includes a gasket GA, and 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 can NC. Further, the gasket GA also has a function of sealing a gap between the positive electrode can PC and the negative electrode can NC to block the inside and outside of the case in an airtight and liquid tight manner.

  Hereinafter, a manufacturing method of the coin-type battery BA will be described.

  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 polytetrafluoroethylene resin (PTFE) are mixed, and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. A positive electrode PE was prepared. The produced positive electrode PE was dried at 120 ° C. for 12 hours in a vacuum dryer.

  As the negative electrode NE, a negative electrode sheet in which graphite powder with an average particle diameter of about 20 μm punched into a disk shape with a diameter of 14 mm and polyvinylidene fluoride were applied to a copper foil was used.

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

  Using the positive electrode PE, the negative electrode NE, the separator SE, and the electrolytic solution (not shown), the coin-type battery BA described above was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.

The initial discharge capacity and the positive electrode resistance showing the performance of the manufactured coin-type battery BA were evaluated as follows. The initial discharge capacity is left for about 24 hours after the coin-type battery BA is manufactured. After the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is set to 0.1 mA / cm ² and the cut-off voltage 4 The capacity when the battery was charged to 3 V, discharged after a pause of 1 hour to a cutoff voltage of 3.0 V was defined as the initial discharge capacity.

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

  In this example, Wako Pure Chemical Industries, Ltd. reagent special grade reagents were used for composite hydroxide production, positive electrode active material and secondary battery production.

Example 1
[Production of lithium metal composite oxide]
(Nucleation process)
First, the temperature in the tank was set to 40 ° C. while stirring by adding half the amount of water in the reaction tank. The inside of the reaction vessel at this time was an oxidizing atmosphere (oxygen concentration: 21% by volume). Appropriate amounts of 25% by mass aqueous sodium hydroxide and 25% by mass ammonia water were added to the water in the reaction tank, and the pH of the reaction liquid in the tank was adjusted to 13.0 based on the liquid temperature of 25 ° C. . Moreover, the ammonia concentration in the aqueous solution before reaction was adjusted to 10 g / L to obtain an aqueous solution before reaction.

  Next, nickel sulfate, manganese sulfate, and cobalt sulfate were dissolved in water to prepare a 2 mol / L mixed aqueous solution. This mixed aqueous solution was adjusted so that the element molar ratio of each metal was Ni: Mn: Co = 35: 30: 35. This mixed aqueous solution was added to the pre-reaction aqueous solution in the reaction tank at a predetermined ratio to obtain a reaction aqueous solution. At the same time, 25% by mass aqueous ammonia and 25% by mass sodium hydroxide aqueous solution are also added to this reaction aqueous solution at a constant rate, and the ammonia concentration in the reaction aqueous solution (nucleation aqueous solution) is maintained at the above value. While controlling the value to 13.0 (nucleation pH value), nucleation was performed by crystallization for a predetermined time.

(Particle growth process)
After the nucleation was completed, only the supply of the 25 mass% sodium hydroxide aqueous solution was temporarily stopped until the pH value of the reaction aqueous solution became 11.6 based on the liquid temperature of 25 ° C. After the pH value of the reaction aqueous solution reached 11.6, the supply of the 25 mass% sodium hydroxide aqueous solution was restarted again to the reaction aqueous solution (particle growth aqueous solution). The crystallization was continued for 10 minutes while controlling to 6, and after the particle growth was performed, the liquid supply was temporarily stopped, and the nitrogen gas was supplied at 5 L / min until the oxygen concentration in the reaction vessel space reached 8-12 vol%. Distributed. Then, liquid supply was restarted and crystallization was performed for 20 minutes. Thereafter, the liquid supply was temporarily stopped, and nitrogen gas was circulated at 5 L / min until the oxygen concentration in the space in the reaction tank became 0.2% by volume or less. Then, the liquid supply was restarted and crystallization was performed for 210 minutes. The product was washed with water, filtered and dried to obtain a composite hydroxide.

(Heat treatment, firing process)
After heat-treating the obtained composite hydroxide at 150 ° C. for 12 hours, commercially available lithium carbonate was added so that the molar ratio of metal to lithium (Li / M ratio) was 1.2, and a shaker mixer apparatus ( The mixture was sufficiently mixed using TURBULA Type T2C manufactured by Willy et Bacofen (WAB) to obtain a mixture. This mixture was calcined at 850 ° C. in an air stream (oxygen: 21% by volume) and further pulverized to obtain a lithium metal composite oxide powder.

[Mixing of conductive fine powder]
1% by weight of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) is added as a conductive fine powder to the obtained lithium metal composite oxide powder, and mixed by a ball mill to form a conductive fine powder (second substance B). Lithium metal composite oxide powder was obtained.

[Mixing of aqueous solution of ammonium tungstate]
The lithium metal composite oxide powder to which the conductive fine powder (second substance B) is attached is mixed with a 20 wt% aqueous solution of ammonium metatungstate with respect to the total amount of lithium metal composite oxide. It sprayed so that it might become 25 wt%.

[Dry]
Thereafter, the lithium metal composite oxide powder was dried at 150 ° C. for 12 hours to obtain a positive electrode active material in which both acetylene black and lithium tungstate were adhered to the surface of the lithium metal composite oxide powder.

  The obtained positive electrode active material was dissolved with an inorganic acid and then subjected to chemical analysis by ICP emission spectroscopy to confirm the composition. The obtained composition is shown in Table 1. Moreover, formation of lithium tungstate in the positive electrode active material was confirmed by an XRD diffraction pattern.

[Battery evaluation]
Using the obtained positive electrode active material, the battery characteristics of the coin-type battery BA having the positive electrode produced by the above method were evaluated. Table 1 shows the evaluation values of the initial discharge capacity and the positive electrode resistance.

(Example 2)
A positive electrode active material for a non-aqueous electrolyte secondary battery is obtained and battery characteristics are obtained in the same manner as in Example 1 except that lithium carbonate is added so that the molar ratio of metal to lithium (Li / M ratio) is 1.25. The results are shown in Table 1.

(Example 3)
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the addition amount of acetylene black was 5 wt%. Table 1 shows the results.

Example 4
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the amount of W added by the ammonium metatungstate aqueous solution was 1.0 wt%. It is shown in 1.

(Example 5)
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the lithium tungstate aqueous solution was used. Table 1 shows the results.

(Comparative Example 1)
Except not adding acetylene black and ammonium metatungstate aqueous solution, it carried out similarly to Example 1, obtained the positive electrode active material for nonaqueous electrolyte secondary batteries, evaluated the battery characteristic, and Table 1 shows the result.

(Comparative Example 2)
A positive electrode active material for a nonaqueous electrolyte secondary battery is obtained and battery characteristics are obtained in the same manner as in Example 1 except that lithium carbonate is added so that the molar ratio of metal to lithium (Li / M ratio) is 1.3. The results are shown in Table 1.

(Comparative Example 3)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and battery characteristics were evaluated in the same manner as in Example 1 except that the amount of acetylene black added was 10 wt%. Table 1 shows the results.

(Comparative Example 4)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the amount of W added by the ammonium metatungstate aqueous solution was 5.0 wt%. It is shown in 1.

(Comparative Example 5)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the amount of W added by the ammonium metatungstate aqueous solution was 0 wt% (no addition). Is shown in Table 1.

(Comparative Example 6)
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that the addition amount of acetylene black was 0 wt% (no addition). The results are shown in Table 1. Show.

(Evaluation results)
The secondary battery using the positive electrode active material of the example is a comparative example 1 that does not include a conductive fine powder or a lithium salt of an oxoanion, or a comparative example 2 that includes one of a conductive fine powder or a lithium salt of an oxoanion. Compared with Example 3, the positive electrode resistance was greatly reduced, indicating that the output characteristics were significantly improved. In addition, the secondary batteries of the examples also had an initial discharge capacity that was comparable or slightly higher than that of Comparative Example 1, indicating that the secondary batteries had sufficient battery capacity. In Comparative Example 4 in which the Li content (z) was 1.3, the initial discharge capacity was low and the positive electrode resistance was high.

  Although the embodiments and examples of the present invention have been described in detail as described above, it will be understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. It will be easy to understand. Therefore, all such modifications are included in the scope of the present invention. Further, for example, a term described together with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. The configuration and operation of the positive electrode active material for a non-aqueous electrolyte secondary battery are not limited to those described in the embodiments and examples of the present invention, and various modifications can be made.

DESCRIPTION OF SYMBOLS 10 ... Positive electrode active material 1 ... Primary particle 2 ... Secondary particle 3 ... Lithium metal complex oxide 4 ... Void A ... 1st material B ... 2nd material PE ... Positive electrode (evaluation electrode)
NE ... Negative electrode SE ... Separator GA ... Gasket PC ... Positive electrode can NC ... Negative electrode can

Claims (15)

General formula: Li _z Ni _1-xy Co _x M _y O ₂ (wherein x is 0.10 ≦ x ≦ 0.40, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al. Lithium metal composite oxide comprising secondary particles formed by aggregation of primary particles of
A first substance comprising a lithium salt of an oxoanion of one or more transition metals selected from tungsten, molybdenum and vanadium;
A second substance made of conductive fine powder having higher electron conductivity than the first substance,
The positive electrode active material for a non-aqueous electrolyte secondary battery in which the first substance and the second substance are attached to at least a part of the surface of the secondary particle and the surface of the primary particle present therein. . The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the specific resistance of the second substance is 5 × 10 ⁻⁴ Ω · cm or less.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the second substance is made of fine carbon powder.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 3, wherein a content of the carbon fine powder is 10% by mass or less with respect to the lithium metal composite oxide.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the first substance is made of lithium tungstate.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein a content of tungsten in the lithium tungstate is 5% by mass or less with respect to the lithium metal composite oxide. General formula: Li _z Ni _1-xy Co _x M _y O ₂ (wherein x is 0.10 ≦ x ≦ 0.40, y is 0 ≦ y ≦ 0.35, z is 1.00 <z <1.30, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, W, and Al. Lithium metal composite oxide comprising secondary particles formed by aggregation of primary particles of
An aqueous solution or compound containing one or more oxoanions selected from tungsten, molybdenum and vanadium;
Preparing a mixture comprising conductive fine powder;
The oxoanion and lithium ion present in the mixture are reacted to form a lithium salt of the oxoanion on at least a part of the surface of the secondary particle and the surface of the primary particle present inside. And a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the mixture includes an aqueous solution containing the oxoanion, and the heat treatment is performed at a temperature at which at least a part of moisture in the mixture is removed. Production method.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8, wherein the aqueous solution containing the oxoanion contains a lithium salt of the oxoanion.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8, wherein the aqueous solution containing the oxoanion contains an ammonium salt of the oxoanion.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the mixture includes a compound containing the oxoanion, and the heat treatment is performed at a temperature at which at least a part of the compound can be thermally decomposed. .   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 11, wherein the compound comprises one or more oxo acids selected from tungsten, molybdenum, and vanadium.   The positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 7 to 12, wherein the conductive fine powder is composed of carbon fine powder.   A positive electrode mixture paste for a non-aqueous electrolyte secondary battery, comprising the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6. A non-aqueous electrolyte secondary battery comprising a positive electrode comprising the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.

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