JP6724361B2 - Positive electrode active material for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery - Google Patents

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 spread of portable electronic devices such as mobile phones and notebook computers, development of small and lightweight secondary batteries having high energy density has been strongly desired. Further, development of a high output secondary battery as a battery for an electric vehicle such as a hybrid vehicle is strongly desired.

As a secondary battery that meets such requirements, there is a non-aqueous electrolyte secondary battery typified by a lithium ion secondary battery. This lithium-ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution and the like, and a material capable of desorbing and inserting lithium is used as an active material of the negative electrode and the positive electrode.

Such non-aqueous electrolyte secondary batteries are currently under active research and development, but among them, lithium ion secondary batteries using a layered or spinel type lithium nickel composite oxide as a positive electrode material are Since a high voltage of 4 V class can be obtained, it is being put to practical use as a battery having a high energy density.

So far, mainly proposed materials 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, and lithium nickel. Examples thereof 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. Among them, the lithium nickel composite oxide has been attracting attention as a material that has good cycle characteristics, low resistance, and high output, and in recent years, low resistance required for high output has been emphasized.

Addition of a different element is used as a method for realizing the above-mentioned low resistance, and in particular, transition metals, such as W, Mo, Nb, Ta and Re, which can be expensive, are considered to be useful. For example, in Patent Document 1, 0.1 to 5 mol% of one or more elements selected from Mo, W, Nb, Ta and Re is contained with respect to the total molar amount of Mn, Ni and Co. A lithium transition metal-based compound powder for a positive electrode material of a lithium secondary battery has been proposed. Further, the atomic ratio of the total of Mo, W, Nb, Ta and Re to the total of metal elements other than Li and Mo, W, Nb, Ta and Re on the surface of the primary particles is the atomic ratio of the entire primary particles. It is said that it is preferably 5 times or more. According to this proposal, it is said that it is possible to achieve both low cost and high safety of the lithium transition metal compound powder for the positive electrode material of the lithium secondary battery, high load characteristics, and improvement of powder handling property. ..

However, the lithium transition metal-based compound powder is obtained by pulverizing raw materials in a liquid medium, spray-drying a slurry in which these are uniformly dispersed, and firing the resulting spray-dried body. Therefore, there is a problem in that some of the different elements such as Mo, W, Nb, Ta, and Re are replaced with Ni arranged in layers, and the battery characteristics such as battery capacity and cycle characteristics deteriorate. It was

Further, Patent Document 2 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide, the lithium transition metal composite oxide being primary particles and aggregates thereof. A non-aqueous electrolyte that exists in the form of particles composed of one or both of some secondary particles, and has at least the surface of the particles, a compound containing at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine. A positive electrode active material for a secondary battery has been proposed. According to this proposal, it is said that a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even under a more severe usage environment can be obtained, and in particular, molybdenum, vanadium, tungsten, boron, and fluorine are formed on the surface of particles. It is stated that by having a compound having at least one selected from the group consisting of the following, the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics and output characteristics.

However, the effect of the at least one additive element selected from the group consisting of molybdenum, vanadium, tungsten, boron, and fluorine is said to be in the improvement of initial characteristics, that is, initial discharge capacity and initial efficiency, and the output characteristics are mentioned. Not a thing. Further, according to the production method disclosed in Patent Document 2, since the additive element is mixed with the lithium compound and the heat-treated hydroxide at the same time and fired, a part of the additive element is arranged in layers. There is a problem that the battery is replaced and the battery characteristics are deteriorated.

Furthermore, in Patent Document 3, a metal containing at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo around the positive electrode active material, and/or a plurality of these metals are included. A positive electrode active material coated with an intermetallic compound and/or an oxide obtained by combination has been proposed. Although it is stated that such a coating makes it possible to absorb oxygen gas and ensure safety, there is no disclosure regarding output characteristics. In addition, the disclosed manufacturing method is a method of coating using a planetary ball mill, and such a coating method causes physical damage to the positive electrode active material, resulting in deterioration of battery characteristics.

Further, in Patent Document 4, a composite oxide particle mainly composed of lithium nickelate is coated with a tungstic acid compound and heat-treated, and the content of carbonate ion is 0.15% by weight or less. Positive electrode active materials have been proposed. According to this proposal, a tungstic acid compound or a decomposed product of a tungstic acid compound is present on the surface of the positive electrode active material, and in order to suppress the oxidation activity of the complex oxide particle surface in a charged state, the decomposition of the nonaqueous electrolytic solution or the like is performed. Although it is said that the generation of gas can be suppressed, there is no disclosure regarding output characteristics.

Further, in the production method disclosed in Patent Document 4, preferably, a complex oxide particle heated to a temperature equal to or higher than a boiling point of a solution in which an adhered component is dissolved is added to a tungstic acid compound, a sulfuric acid compound, a nitric acid compound, a boric acid compound or phosphorus. It is for depositing a solution of an acid compound as a deposition component dissolved in a solvent, and because the solvent is removed in a short time, the tungsten compound is not sufficiently dispersed on the surface of the composite oxide particles and is not deposited uniformly. There is a problem.

In addition, improvements have been made on increasing the output of lithium nickel composite oxides. For example, Patent Document 5 discloses a lithium-nickel composite oxide composed of primary particles and secondary particles formed by aggregating the primary particles, wherein Li ₂ WO ₄ , A positive electrode active material for a non-aqueous electrolyte secondary battery, which has fine particles containing lithium tungstate represented by either Li ₄ WO ₅ or Li ₆ W ₂ O ₉ has been proposed, and it is said that a high capacity and a high output can be obtained. ing.

JP, 2009-289726, A JP-A-2005-251716 JP-A-11-16566 JP, 2010-40383, A JP, 2013-171785, A

In Patent Document 5, although a high capacity is maintained and a high output is achieved, a further higher capacity is required. In addition, since tungsten is a rare element and expensive, it is necessary to reduce the amount used. In addition, since tungsten is added in the middle of the manufacturing process, after the addition of the tungsten compound, the manufacturing line is contaminated with tungsten.Therefore, it is necessary to perform line cleaning when manufacturing multiple types, increasing man-hours and operation. Decline is cited as an issue.

In view of the above problems, the present invention provides a high output with a high capacity when used in a non-aqueous electrolyte secondary battery as a positive electrode active material, and for a non-aqueous electrolyte secondary battery in which the amount of tungsten used is suppressed. It is intended to provide a positive electrode active material. Further, it is an object of the present invention to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which is easy to produce, has high productivity, and is suitable for production of many kinds.

1st aspect of this invention WHEREIN: The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries WHEREIN: The 1st lithium nickel composite oxide particle containing lithium tungstate and the 2nd lithium which does not contain lithium tungstate. Mixing nickel composite oxide particles, and the composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦ 0.35, 0≦y1≦0.35, 0.95≦z1≦1.15, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al). , from a core material consisting of secondary particle child plurality of primary particles are aggregated to each other, and lithium tungstate present in at least part of the surface of the primary particles located on the surface and inside of the second composite oxide particles, The composition of the second lithium-nickel composite oxide particles is Li _z2 Ni _1-x2-y2 Co _x2 M ² _y2 O ₂ (where 0≦x2≦0.35, 0≦y2≦0.35, 0.95≦z2≦1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and secondary particles obtained by aggregating a plurality of primary particles with each other. Composed of.

Further, the second lithium-nickel composite oxide particles may be washed with water before being mixed. The slurry concentration at the time of washing with water may be 500 g/L or more and 2500 g/L or less. Further, the first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles are contained in a lithium compound other than lithium tungstate present on the surfaces of the primary particles located on both surfaces and inside thereof. The amount of lithium may be 0.05% by mass or less based on the total amount of the positive electrode active material. In addition, the content of the first lithium-nickel composite oxide contained in the positive electrode active material is 10% by mass or more with respect to the total amount of the positive electrode active material, and the first lithium-nickel composite oxide particles and the second lithium nickel composite oxide particles are contained. You may mix with a lithium nickel composite oxide particle. The amount of tungsten contained in the first lithium nickel composite oxide particles is 0.03 atomic% or more and 2.5 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material. So that the first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles are mixed.

In addition, before mixing, the composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (where 0.03≦x3≦0.35, 0.01≦y3≦0.35, 0.95 ≦z3≦1.20, M ¹ is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and is a secondary particle formed by aggregating a plurality of primary particles. And a tungsten mixture containing 2% by mass or more of water with respect to the total amount of the base material, a tungsten compound, or a tungsten compound and a lithium compound containing no tungsten, were obtained. Heat-treating the tungsten mixture to form lithium tungstate on the surface of the base material and the surface of the primary particles inside to obtain the first lithium nickel composite oxide particles, and the tungsten mixture is contained. The molar ratio of the total amount of lithium contained in the water and the tungsten compound or the water, the tungsten compound and the lithium compound to the total amount of tungsten may be 5 or less. Further, the first lithium nickel composite oxide particles, the amount of lithium contained in the lithium compound other than lithium tungstate present on the surface and the surface of the primary particles inside the first lithium nickel composite oxide particles. May be 0.05 mass% or less. In addition, before the heat treatment, the base material and water may be mixed to form a slurry, and the base material may be washed with water, and the washed base material may be solid-liquid separated. Further, the slurry concentration of the base material washed with water may be 500 g/L or more and 2500 g/L or less. When the base material washed with water is subjected to solid-liquid separation, the water content of the obtained wash cake may be controlled to 3.0% by mass or more and 15.0% by mass or less. Tungsten compound is tungsten oxide _(WO 3), tungstic acid _{(WO 3 · H 2 O)} , Li 2 WO 4, Li 4 may include at least any one of WO ₅ and _Li 6 _W 2 _{O 9.} The temperature of the heat treatment in Netsusho management may also be 100 ° C. or higher 600 ° C. or less. The amount of tungsten contained in the tungsten compound may be 0.05 to 3.0 atom% with respect to the total number of Ni, Co and M atoms contained in the base material.

In the second aspect of the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery comprises a first lithium nickel composite oxide particle containing lithium tungstate and a second lithium nickel composite oxide containing no lithium tungstate. And a first lithium nickel composite oxide particle having a composition of Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦0.35, 0≦y1≦ 0.35, 0.95≦z1≦1.15, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a plurality of primary particles are aggregated with each other. a core material made of the secondary particle child, lithium tungstate present in at least part of the surface of the primary particles located on the surface and inside of the second composite oxide particles are composed of a second lithium nickel The composite oxide particles have a composition of Li _z2 Ni _1-x2-y2 Co _x2 M ² _y2 O ₂ (where 0≦x2≦0.35, 0≦y2≦0.35, 0.95≦z2≦1. 15, M ² is represented by Mn, V, Mg, Mo, Nb, Ti and at least one element selected from Al), and is composed of secondary particles in which a plurality of primary particles are aggregated with each other.

Further, the amount of lithium contained in the lithium compound other than lithium tungstate, which is present on the surfaces of the primary particles located on the surfaces and inside of the first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles. However, the amount may be 0.05% by mass or less based on the total amount of the positive electrode active material. Further, the amount of the first lithium nickel composite oxide particles contained in the positive electrode active material may be 10% by mass or more based on the total amount of the positive electrode active material. Further, the amount of tungsten contained in lithium tungstate may be 0.03 atomic% or more and 2.5 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material. Further, even if the amount of tungsten contained in the lithium tungstate is 0.05 atom% or more and 3.0 atom% or less with respect to the total number of Ni, Co and M atoms contained in the tungsten-coated composite oxide particles. Good. Further, lithium tungstate may be present on the surface of the first lithium-nickel composite oxide particles and the surface of the primary particles inside thereof as fine particles having a particle diameter of 1 nm or more and 500 nm or less. Further, lithium tungstate may be present on the surface of the first lithium-nickel composite oxide particles and the surface of the primary particles inside thereof as a film having a film thickness of 1 nm or more and 200 nm or less. In addition, lithium tungstate is present on the surface of the first lithium-nickel composite oxide particles and the surface of the primary particles inside thereof as both forms of fine particles having a particle diameter of 1 nm or more and 500 nm or less and a film having a film thickness of 1 nm or more and 200 nm or less. Good.

In a third aspect of the present invention, a non-aqueous electrolyte secondary battery has a positive electrode containing a positive electrode active material for a non-aqueous electrolyte secondary battery.

According to the present invention, when used as a positive electrode material for a secondary battery, a high capacity and high output are obtained, and a positive electrode active material for a non-aqueous electrolyte secondary battery in which the amount of tungsten used is suppressed can be obtained. Furthermore, the production method is easy and highly productive, suitable for production on an industrial scale, and its industrial value is extremely large.

FIG. 1 is a schematic diagram (A) showing an example of the positive electrode active material according to the embodiment and a diagram (B) showing an example of a manufacturing method thereof. FIG. 2 is a schematic diagram showing an example of the first lithium-nickel composite oxide. FIG. 3 is a cross-sectional SEM photograph (observation magnification: 10,000 times) showing an example of the first lithium-nickel composite oxide. (The circled portion shows lithium tungstate.) FIG. 4 is a diagram showing an example of a method for producing the first lithium-nickel composite oxide. FIG. 5: is a figure which shows an example of the manufacturing method of a tungsten mixture. FIG. 6 is a schematic explanatory view of an equivalent circuit used for measurement examples and analysis of impedance evaluation. FIG. 7 is a schematic sectional view of a coin-type battery used for battery evaluation.

Embodiments of the present invention will be described below with reference to the drawings. In addition, in the drawings, in order to make each configuration easy to understand, a part thereof is emphasized or a part thereof is simplified, and an actual structure or shape, a reduced scale, or the like may be different. The present embodiment will be described below.

1. Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery and Manufacturing Method Thereof FIG. 1A shows a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter, may be simply referred to as “positive electrode active material”). 10 is a schematic diagram showing an example of FIG. 1, and FIG. 1B is a diagram showing an example of a method for manufacturing the positive electrode active material 10 of the present embodiment. Hereinafter, first, the positive electrode active material 10 will be described, and then a method for manufacturing the positive electrode active material 10 and a non-aqueous electrolyte secondary battery (hereinafter, simply referred to as “secondary battery”) using the positive electrode active material 10. explain.

(1) Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery As shown in FIG. 1(A), the positive electrode active material 10 includes first lithium nickel composite oxide particles containing lithium tungstate (hereinafter, referred to as “first composite”). 1) and second lithium nickel composite oxide particles 2 that do not contain lithium tungstate (hereinafter, may be referred to as “second composite oxide particles”). ..

The first composite oxide particle 1 comprises a core 5 consisting of a plurality of primary particles 3 aggregated together secondary particle slave 4, primary particles located on the surface and inside of the first mixed oxide particle 1 (core material) 3 (3a and 3b) on at least a part of the surface of lithium tungstate 6 (6a and 6b). Since the first composite oxide particles 1 have the lithium tungstate 6 on the surface of the primary particles 3, when the positive electrode active material 10 is used in a secondary battery, a high output is obtained and a high charge/discharge capacity ( Hereinafter, it may be referred to as “battery capacity”.) can be improved.

Generally, when the surface of lithium nickel composite oxide particles is completely covered with a different kind of compound, the movement (intercalation) of lithium ions is largely restricted, resulting in the high capacity of the lithium nickel composite oxide. The advantages may be lost.

On the other hand, in the first composite oxide particle 1 used in the present embodiment, lithium tungstate (hereinafter, lithium tungstate is referred to as “LWO compound” is referred to as “LWO compound”) on the surface and the surface of the primary particles 3 (3a and 3b) inside. Yes, I have 6. The LWO compound 6 has high lithium ion conductivity and has an effect of promoting migration of lithium ions. Therefore, when the positive electrode active material 10 is used in a secondary battery, by having the LWO compound 6 on the surface of the primary particles 3 (3a and 3b) of the first composite oxide particles 1, the primary particles 3 (3a and 3b) are obtained. It is possible to reduce the reaction resistance of the positive electrode (hereinafter sometimes referred to as “positive electrode resistance”) by forming a Li conduction path at the interface between the electrolyte solution and the electrolyte solution. By reducing the positive electrode resistance, the voltage lost in the battery is reduced, and the voltage actually applied to the load side is relatively high, so that a high output can be obtained. In addition, since the voltage applied to the load side is increased, lithium is sufficiently inserted into and extracted from the positive electrode, so that the battery capacity can be improved.

Further, as in the prior art, when only the secondary particle surface of the lithium nickel composite oxide particles is coated with the layered material, the specific surface area is reduced regardless of the coating thickness, and thus the coating material is high. Even if it has lithium ion conductivity, the contact area with the electrolytic solution becomes small. Further, when the layered material is formed only on the surface of the secondary particles, the formation of the compound (layered material) tends to be concentrated on the surface of the specific secondary particle. Therefore, although the layered material as the coating has a high lithium ion conductivity, the effects of improving the charge/discharge capacity and reducing the reaction resistance can be obtained, but the effect is not sufficient and there is room for improvement.

On the other hand, when the positive electrode active material 10 is used in a secondary battery, the contact between the first composite oxide particles 1 and the electrolytic solution occurs on the surface of the primary particles 3. Here, the surface of the primary particle 3 refers to a surface portion of the primary particle 3 that can be contacted with the electrolytic solution, and for example, the surface of the primary particle (for example, the primary particle 3a) exposed on the outer surface of the secondary particle, Secondary particles 4 includes surfaces of primary particles (for example, primary particles 3b) exposed to the vicinity of the surfaces of the secondary particles that can penetrate into the outside of the secondary particles 4 and to the inside and voids inside. Further, the surface of the primary particles 3 includes, for example, grain boundaries between the primary particles in which the binding of the primary particles is incomplete and the electrolytic solution can penetrate.

As described above, when the positive electrode active material 10 is used in a secondary battery, the first composite oxide particles 1 are in contact with the electrolytic solution only on the outer surface of the secondary particles 4 formed by aggregating the primary particles 3. Not only that, it also occurs in the vicinity of the surface of the secondary particles and in the voids and incomplete grain boundaries. Therefore, by forming the LWO compound 6 also on the surface of the primary particles 3 (3a, 3b), the movement of lithium ions can be further promoted. Since the first composite oxide particle 1 has the LWO compound 6 not only on the surface of the primary particle 3a located on the surface of the secondary particle 4, but also on the surface of the primary particle 3b located inside the secondary particle 4, lithium The reaction resistance of the nickel composite oxide particles can be further reduced.

FIG. 2 is a schematic diagram showing an example of the first composite oxide particle 1, and FIG. 3 is a cross-sectional SEM photograph (observation magnification: 10,000 times) showing an example of the first composite oxide particle 1. The form of the LWO compound 6 contained in the first composite oxide particles 1 is not particularly limited as long as it exists on the surface of the primary particles 3 (3a, 3b). The LWO compound 6 may be present on the surface of the primary particles 3 (3a, 3b) in the form of fine particles 6a, 6b having a particle diameter of 1 nm or more and 500 nm or less, for example, as shown in FIG. 2(a). In the case of such a form, the contact area with the electrolytic solution is sufficient, and lithium ion conduction can be effectively improved, so that the charge/discharge capacity can be improved and the positive electrode resistance can be more effectively reduced. ..

When the particle size of the LWO compounds (fine particles) 6a, 6b is less than 1 nm, the fine particles 6a, 6b may not have sufficient lithium ion conductivity. When the particle size of the LWO compounds (fine particles) 6a, 6b exceeds 500 nm, the formation of the fine particles (LWO compound 6) on the surface of the primary particles 3 (3a, 3b) becomes uneven, and the effect of reducing reaction resistance is reduced. You may not get enough. The particle size of the LWO compound (fine particles) 6a, 6b is preferably 1 nm or more and 300 nm or less from the viewpoint that the particles of the LWO compound 6 are evenly distributed on the surface of the primary particles 3 (3a, 3b) to obtain a higher effect. And more preferably 5 nm or more and 200 nm or less.

The LWO compound 6 does not need to be completely formed on the entire surface of the primary particles, and may be scattered. Even in the state where the LWO compound 6 is scattered, if LWO is formed on the outer surface and the inner surface of the primary particle exposed to the inside of the lithium nickel composite oxide particles, the effect of reducing the reaction resistance can be obtained. Further, the LWO compounds (fine particles) 6a and 6b do not all need to exist as fine particles having a particle diameter of 1 nm or more and 500 nm or less, and preferably, the number of the LWO compounds (fine particles) 6a and 6b formed on the surface of the primary particles is 50. A high effect can be obtained if at least 100% is formed in the particle size range of 1 nm or more and 500 nm or less.

The LWO compound 6 may be present in a form in which the surfaces of the primary particles 3a and 3b are covered with thin films (coatings) 6c and 6d formed of the LWO compound, as shown in FIG. 2B, for example. When such coatings 6c and 6d are formed, the conduction path of Li can be formed at the interface with the electrolytic solution while suppressing the decrease of the specific surface area, and thus the higher charge/discharge capacity and the lower reaction resistance can be achieved. The effect is obtained.

When the surfaces of the primary particles are coated with the coatings 6c and 6d, it is preferable that the coatings having a thickness of 1 nm or more and 200 nm or less are present on the surfaces of the primary particles of the lithium metal composite oxide. In order to obtain the higher effect, the film thickness is more preferably 1 nm or more and 150 nm or less, further preferably 1 nm or more and 100 nm or less. When the film thickness of the thin films 6c and 6d is less than 1 nm, the coating film may not have sufficient lithium ion conductivity. On the other hand, when the film thickness of the thin films 6c and 6d exceeds 200 nm, the lithium ion conductivity decreases, and a higher effect than the reaction resistance reducing effect may not be obtained.

The coatings 6c and 6d may be formed on at least a part of the primary particles 3a and 3b, and may be partially formed on the surfaces of the primary particles 3a and 3b, for example. Further, the film thickness range of all the films 6c and 6d may not be 1 nm or more and 200 nm or less. For example, the coatings 6c and 6d are highly effective if the coatings 6c and 6d having a thickness within the above range are formed on at least a part of the surface of the primary particles.

For example, as shown in FIG. 2(C), the LWO compound 6 may be present on the surface of the primary particles in a mixture of the forms of the fine particles 6a and 6b and the forms of the coating films 6c and 6d. Also in this case, a high effect on the battery characteristics can be obtained.

The properties of the primary particle surfaces 3 (3a, 3b) of the first composite oxide particles 1 can be determined by, for example, observing with a field emission scanning electron microscope or a transmission electron microscope. In the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, for example, as shown in FIG. 3, it was confirmed that lithium tungstate was formed on the surface of primary particles of the first composite oxide particles 1. There is.

The LWO compound 6 is not limited to one in which W and Li are in the form of lithium tungstate, but refers to one containing a compound containing W and Li. The LWO compound 6 is, 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 , or It is preferably at least one form selected from 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 hydrates thereof. In the case of using such lithium tungstate, the lithium ion conductivity is further enhanced and the effect of reducing the reaction resistance is further enhanced.

The amount of tungsten contained in the LWO compound 6 may be 0.05 atom% or more and 3.0 atom% or less with respect to the total number of Ni, Co and M atoms contained in the first composite oxide particles 1. It is more preferably from 0.05 atomic% to 2.0 atomic %, still more preferably from 0.08 atomic% to 1.0 atomic %. When the amount of tungsten is in the above range, higher charge/discharge capacity and output characteristics can both be achieved. The amount of tungsten can be measured by IPC emission spectroscopy (ICP method).

When the amount of tungsten is less than 0.05 atom %, the effect of improving the output characteristics may not be sufficiently obtained. On the other hand, when the amount of tungsten exceeds 3.0 atomic %, the amount of the above-mentioned compound formed becomes too much, which hinders the lithium conduction between the lithium-nickel composite oxide and the electrolytic solution, which may reduce the charge/discharge capacity.

As shown in FIG. 1A, the composition of the second composite oxide particles 2 is Li _z2 Ni _1-x2-y2 Co _x2 M ² _y2 O ₂ (where 0≦x2≦0.35, 0≦ y2≦0.35, 0.95≦z2≦1.15, M ² is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a plurality of primary particles 7 Are composed of secondary particles 8 aggregated with each other and do not contain lithium tungstate. As shown in FIG. 1B, the positive electrode active material 10 can be obtained, for example, by mixing the first composite oxide particles 1 and the second composite oxide particles 2. When the first composite oxide particles 1 and the second composite oxide particles 2 are mixed, a high output is obtained and the battery capacity is improved when the positive electrode active material 10 is used for the positive electrode of the secondary battery. be able to.

It is generally said that if the composite oxide particles forming the positive electrode active material have non-uniform battery characteristics, a load is applied to specific particles, which tends to deteriorate cycle characteristics and increase reaction resistance. Further, it is considered that the reduction of the content of the lithium nickel composite oxide particles containing tungsten such as the first composite oxide particles 1 is disadvantageous in improving the battery characteristics.

However, as a result of examination by the present inventors, when the first composite oxide particles 1 containing the LWO compound and the composite oxide 2 not containing the LWO compound are mixed, 1) the first composite oxide particles 1 containing tungsten are obtained. Compared to the case of using it alone as a positive electrode active material, there is no deterioration in the battery characteristics such as output characteristics and battery capacity, or even if it decreases, it is negligible. 2) No LWO compound on the surface of the primary particles 7. It was clarified that the battery characteristics can be improved as compared with the case of using the two-composite oxide particles 2 alone.

Such improvement of the battery characteristics can be achieved by mixing the first composite oxide particles 1, but in order to make this effect more sufficient, the first composite oxide mixed in the positive electrode active material 10 is used. The lower limit of the amount of the material particles 1 is preferably 10% by mass or more, and more preferably 20% by mass or more with respect to the positive electrode active material 10.

On the other hand, the upper limit of the amount of the first composite oxide particles 1 is preferably 70% by mass or less and more preferably 60% by mass or less with respect to the positive electrode active material 10 from the viewpoint of suppressing the amount of tungsten used. It is more preferably 50% by mass or less. When the content of the first composite oxide particles 1 in the positive electrode active material 10 increases, the battery characteristics become closer to those when the first composite oxide particles 1 are used alone, but from the viewpoint of suppressing the amount of tungsten used, The amount of the one composite oxide particle 1 is preferably as small as possible in the range in which the battery characteristics are improved.

The amount of tungsten contained in the first composite oxide particles 1 (lithium tungstate) is 0.03 atomic% or more and 2.5 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material 10. Is more preferable, it is more preferably 0.05 atom% or more and 1.5 atom% or less, and further preferably 0.05 atom% or more and 1.0 atom% or less. The above-mentioned amount of tungsten is an index of the amount of lithium tungstate 6 present, since the positive electrode active material 10 improves the battery characteristics by the lithium tungstate 6. When the amount of tungsten is in the above range, sufficient battery characteristics can be obtained when the positive electrode active material 10 is used in a battery.

In the positive electrode active material 10, the amount of lithium contained in the lithium compound other than lithium tungstate present on the primary particle surfaces of the first composite oxide particles 1 and the second composite oxide particles 2 (hereinafter, “excess lithium amount”). Is preferably 0.05% by mass or less, and more preferably 0.03% by mass or less, based on the total amount of the positive electrode active material 10. By limiting the amount of surplus lithium within the above range, it is possible to obtain higher charge/discharge capacity and output characteristics and improve cycle characteristics.

The lithium compound is a compound containing lithium other than lithium tungstate present on the surfaces of the primary particles 3 and 7. Examples of the lithium compound include lithium hydroxide and lithium carbonate. These lithium compounds have poor lithium conductivity and may inhibit the movement of lithium ions from the lithium-nickel composite oxide substance (including the first composite oxide particles 1 and the second composite oxide particles 2). The amount of lithium contained in these lithium compounds can be expressed as an excess amount of lithium.

By reducing the amount of excess lithium in the positive electrode active material 10, the effect of promoting the movement of lithium ions by the lithium tungstate 6 is enhanced, the load on the lithium nickel composite oxide at the time of charging and discharging is reduced, and the output characteristics are further improved. In addition, the cycle characteristics can be further improved. In addition, by controlling the excess amount of lithium in the positive electrode active material 10 within the above range, lithium ions between the lithium nickel composite oxide particles (including the first composite oxide particle 1 and the second composite oxide particle 2) can be obtained. Are also made uniform, and it is possible to suppress the load on the specific lithium-nickel composite oxide particles and to enhance the above-mentioned effect.

The lower limit of the amount of excess lithium is not particularly limited, but is preferably 0.01% by mass or more from the viewpoint of suppressing deterioration of battery characteristics. When the amount of excess lithium is too small, it indicates that lithium is excessively extracted from the crystals of the lithium-nickel composite oxide particles, and the battery characteristics are likely to deteriorate. The amount of excess lithium is the compound state of lithium that elutes from the neutralization point that appears when hydrochloric acid is added while measuring the pH of the filtered filtrate after adding pure water to the positive electrode active material and stirring for a certain period of time. Can be calculated by analyzing

The positive electrode active material 10 has a sulfate group (sulfate group) content of preferably 0.05% by mass or less, more preferably 0.025% by mass or less, and further preferably 0.020% by mass or less. When the sulfate group content in the positive electrode active material 10 exceeds 0.05% by mass, the negative electrode material has to be additionally used in the battery in an amount corresponding to the irreversible capacity of the positive electrode active material when configuring the battery. As a result, the capacity per weight and volume of the battery as a whole is reduced, and the extra lithium accumulated in the negative electrode as an irreversible capacity is also unfavorable from the viewpoint of safety. The lower limit of the sulfate content in the positive electrode active material 10 is not particularly limited, but is, for example, 0.001% by mass or more. The sulfate group content can be obtained by converting the measured S (sulfur element) amount into a sulfate group (SO ₄ ) amount by IPC emission spectroscopy (ICP method).

The amount of lithium in the entire positive electrode active material 10 (including the first composite oxide particles 1 and the second composite oxide particles 2) is the sum (Me) of the atomic numbers of Ni, Co, and M in the positive electrode active material. The ratio (Li/Me) of Li to the number of atoms is preferably 0.95 or more and 1.20 or less, and more preferably 0.97 or more and 1.15 or less. When Li/Me is less than 0.95, the reaction resistance of the positive electrode in the non-aqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the output of the battery decreases. When Li/Me exceeds 1.20, the initial discharge capacity of the positive electrode active material decreases and the reaction resistance of the positive electrode also increases. Li/Me can be measured by IPC emission spectroscopy (ICP method).

The lithium nickel composite oxide particles as the core material 5 of the first composite oxide particles 1 have a composition of Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦0.35, 0 ≦y1≦0.35, 0.95≦z1≦1.15, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al). Li/Me in the core material 5 is more preferably 0.95 or more and 1.15 or less, and further preferably 0.95 or more and 1.10 or less.

The positive electrode active material 10 forms lithium tungstates 6a and 6b on the surfaces of the primary particles 3a and 3b of the first composite oxide particle 1 to improve output characteristics and cycle characteristics. The powder characteristics such as the particle size and tap density of the positive electrode active material may be within the range of the normally used positive electrode active material.

The effect of providing lithium tungstate on the surface of the primary particles of the lithium nickel composite oxide particles is, for example, a lithium cobalt-based composite oxide, a lithium manganese-based composite oxide, a lithium nickel cobalt manganese-based composite oxide, or the like. It can be applied not only to powders, but also to the positive electrode active materials listed in the present invention, as well as the commonly used positive electrode active materials for lithium secondary batteries.

(2) Method for Producing Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery As shown in FIG. 1(B), the method for producing the positive electrode active material 10 is the first lithium nickel containing lithium tungstate (LWO compound) 6. The composite oxide particles (first composite oxide particles) 1 and the second lithium nickel composite oxide particles (second composite oxide particles) 2 that do not contain the LWO compound 6 are mixed. Further, FIG. 4 is a diagram showing an example of a method for producing the first composite oxide particles 1, and when explaining the method for producing the first composite oxide particles 1, FIG. 5 is appropriately referred to. In addition, the following description is an example of a manufacturing method and does not limit the manufacturing method.

The composition of the first composite oxide particles 1 is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦0.35, 0≦y1≦0.35, 0.95≦z1 ≦ 1.15, ^{M 1} is Mn, V, Mg, Mo, Nb, represented by at least one element) selected from Ti and Al, the core material in which a plurality of primary particles composed of secondary particles child aggregated together 5 and the LWO compound 6 present on at least a part of the surface of the first composite oxide particles 1 (core material) and the surfaces of the primary particles 3 located inside. The method for producing the first composite oxide particles 1 may be any one that allows lithium tungstate to be present on the surface, and a conventionally known production method can be used. Hereinafter, an example of a method for producing the first composite oxide particles 1 will be described with reference to FIGS. 4 and 5.

In the production of the first composite oxide particles 1, as shown in FIG. 4(A), first, the composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (where 0.00≦x3≦0. .35, 0.00≦y3≦0.35, 0.95≦z3≦1.20, M ¹ is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) And a tungsten-coated base material composed of secondary particles formed by aggregating a plurality of primary particles (hereinafter, also simply referred to as “base material”), and 2% by mass or more of water with respect to the total amount of the base material, A tungsten mixture containing a tungsten compound is prepared. From the viewpoint of high capacity and high safety, it is preferable that 0.01≦x3≦0.10, 0.01≦y3≦0.05, and 0.97≦z3≦1.05.

The tungsten mixture contains water in an amount of 2% by mass or more based on the total amount of the base material. As a result, the tungsten in the tungsten compound permeates with the moisture into the voids between the primary particles that communicate with the outside of the secondary particles (base material) and the grain boundaries between the incomplete primary particles, and the surface of the primary particles is sufficiently filled. An amount of tungsten can be dispersed. The upper limit of the amount of water is not particularly limited, but is, for example, 20% by mass or less. When the water content is excessively high, the efficiency of the heat treatment in the subsequent step is decreased, or the elution of lithium from the lithium metal composite oxide particles (base material) is increased, and the elution Li molar ratio in the tungsten mixture is increased. When the obtained positive electrode active material is used for the positive electrode of a battery, the battery characteristics may deteriorate.

The amount of water relative to the total amount of the base material is preferably 2% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and further preferably 3% by mass or more and 10% by mass or less. When the amount of water is in the above range, the pH is increased by the lithium content eluted in the water, and the effect of suppressing the elution of excess lithium is exhibited. The amount of water in the tungsten mixture can be easily controlled within the above range by washing the base material with water and subjecting it to solid-liquid separation, as described later. The molar ratio of Ni, Co and M ¹ in the base material powder is maintained up to the first composite oxide particles 1 (core material 5).

The tungsten compound is a compound containing tungsten (W), and preferably has a water solubility enough to dissolve in the water contained in the tungsten mixture. When the tungsten compound is water-soluble, tungsten (W) can be sufficiently permeated to the surface of the primary particles inside the secondary particles (base material). The tungsten compound may be in a solid state or an aqueous solution state, for example. When the tungsten compound is in the state of an aqueous solution, the amount of the tungsten compound (aqueous solution) may be such that it can penetrate to the surface of the primary particles inside the secondary particles (base material), and even if a part of the aqueous solution contains a solid state. Good. Further, the tungsten compound may be a compound which is difficult to dissolve in water at room temperature, but is soluble in water by heating during heat treatment. Further, the tungsten compound may be a compound that can be dissolved in alkalinity, because the water contained in the tungsten mixture becomes alkaline by the lithium contained in the base material.

The tungsten compound is not particularly limited as long as it is a compound soluble in water, but examples thereof include tungsten oxide, tungstic acid, lithium tungstate, ammonium tungstate, and sodium tungstate. Among these, tungsten oxide, tungstic acid, lithium tungstate, and ammonium tungstate are more preferable from the viewpoint of low possibility of mixing impurities, and tungsten oxide (WO ₃ ), tungstic acid (WO ₃ .H ₂ O), lithium tungstate _{(Li 2 WO 4, Li 4} WO 5, Li 6 W 2 O 9) are more preferable. The tungsten compound may be used alone or in combination of two or more kinds.

The molar ratio of the total amount of lithium (Li) contained in the water and the tungsten compound or the water, the tungsten compound and the lithium compound to the amount of tungsten (W) contained in the tungsten mixture (hereinafter, referred to as “Li molar ratio”). The upper limit of () is preferably 5.0 or less, more preferably less than 4.5, and further preferably 4.0 or less. When the upper limit of the Li molar ratio is within the above range, it is possible to suppress the amount of excess lithium in the first composite oxide particles, improve the output characteristics, and improve the cycle characteristics.

On the other hand, the lower limit of the Li molar ratio is preferably 0.5 or more, more preferably 1.0 or more, and further preferably 1.5 or more. Lithium calculated as the Li molar ratio in the tungsten mixture forms lithium tungstate during the subsequent heat treatment with tungsten (W) derived from the tungsten compound. At least a part of lithium can be lithium derived from the base material. When the lower limit of the Li molar ratio is less than 0.5, when the Li molar ratio is less than 0.5, too much lithium is extracted from the base material to form lithium tungstate and the first composite oxide particles Battery characteristics may deteriorate.

The amount of tungsten contained in the tungsten mixture is preferably 0.05 atom% or more and 3.0 atom% or less, more preferably 0. 0% or less with respect to the total number of Ni, Co and M atoms contained in the base material. It is from 05 atomic% to 2.0 atomic %, more preferably from 0.08 atomic% to 1.0 atomic %. When the amount of tungsten is in the above range, the amount of tungsten contained in lithium tungstate in the first composite oxide particles 1 can be set in a preferable range, and when the positive electrode active material 1 is used in a secondary battery, Both high charge and discharge capacity and output characteristics can be achieved at a higher level.

When adjusting the above-mentioned tungsten mixture, water may be supplied and mixed together with the tungsten compound so that the water content of the tungsten mixture is 2% by mass or more. An aqueous solution of the tungsten compound or the tungsten compound and water are separately supplied. You may.

The lithium source forming lithium tungstate is, for example, lithium derived from a tungsten compound such as lithium tungstate, or a base material (Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ or surplus lithium). Lithium derived from. Further, as shown in FIG. 4B, the tungsten mixture may contain a lithium compound containing no tungsten in addition to the base material, the water, and the tungsten compound. The lithium compound can be a lithium source that forms lithium tungstate. Examples of the lithium compound containing no tungsten include water-soluble compounds such as lithium hydroxide.

FIG. 5: is a figure which shows an example of the adjustment method of the tungsten mixture obtained in the manufacturing process of the 1st composite oxide particle 1. As shown in FIG. As shown in FIG. 5, the lithium nickel composite oxide particles as the base material may be washed with water before preparing the tungsten mixture. Washing with water can be performed by mixing the base material and water to form a slurry. When the base material is washed with water, it is possible to remove excess unreacted lithium compounds and impurity elements such as sulfate radicals that deteriorate the battery characteristics. Examples of the unreacted lithium compound include lithium hydroxide and lithium carbonate.

When the base material is washed with water, the amount of lithium present in the water in the tungsten mixture is reduced, and the upper limit of the Li molar ratio can be easily controlled. Usually, a metal composite hydroxide or a lithium metal composite oxide obtained by firing a metal composite oxide and a lithium compound has unreacted lithium compound on the surface of secondary particles or primary particles. .. Lithium (Li) derived from the unreacted lithium compound contained in the base material is eluted in the added water when the tungsten mixture is prepared. When the amount of lithium eluted into water is too large, it may be difficult to control the upper limit of the Li molar ratio to the above range.

The base material washed with water may be subjected to solid-liquid separation after being washed with water in order to adjust the water content. When the base material is solid-liquid separated, the amount of water contained in the tungsten mixture can be easily adjusted.

The water washing condition by making the base material into a slurry is not particularly limited as long as the unreacted lithium compound can be sufficiently reduced. The amount of unreacted lithium compound contained in the base material after washing with water is, for example, 0.08 mass% or less, preferably 0.05 mass% or less, based on the total amount of the base material. The amount of unreacted lithium compound contained in the base material can be measured by the same method as the amount of surplus lithium in the positive electrode active material 1.

Washing with water by slurrying is performed, for example, by mixing the base material powder and water and stirring. The concentration of the base material powder contained in the slurry is, for example, 200 g or more and 5000 g or less with respect to 1 L of water. When the concentration of the base material powder is within this range, the unreacted lithium compound can be more sufficiently reduced while suppressing the deterioration due to the elution of lithium from the base material.

The washing time can be, for example, about 5 minutes or more and 60 minutes or less. When the water washing time is in this range, the amount of unreacted lithium compound contained in the base material can be sufficiently reduced. The washing temperature can be in the range of 10°C or higher and 40°C or lower. When the washing temperature is within this range, the amount of unreacted lithium compound contained in the base material can be sufficiently reduced.

When the base material is washed with water, the procedure for adding the tungsten compound is not particularly limited as long as the above-mentioned tungsten mixture is obtained. For example, as shown in FIG. 5A, after the base material and the tungsten compound are mixed and the tungsten mixture is prepared, the tungsten mixture (including the base material) can be washed with water. In this case, since the tungsten compound is washed away by washing with water, the amount of tungsten in the tungsten mixture may be insufficient. Therefore, for example, as shown in FIGS. 5B and 5C, a tungsten compound is added in at least one of the step of washing the base material with water and the step of solid-liquid separation to obtain a tungsten mixture. Is preferred.

When the tungsten compound is added in the water washing step, the tungsten compound may be previously added to water to be mixed with the base material (powder) to form an aqueous solution or suspension, and the base material and water are mixed to form a slurry, and then in the slurry. You may add a tungsten compound to this.

As shown in FIG. 5B, when the tungsten compound is added when the base material is washed with water, it is preferable to use a compound that is completely dissolved in the slurry at the time of washing with water or a compound that does not contain lithium. Examples of the tungsten compound that dissolves in the slurry and contains lithium include lithium tungstate (Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ W ₂ O ₉ ), and examples of the lithium compound that does not contain lithium include: , Tungsten oxide (WO ₃ ), and tungstic acid (WO ₃ .H ₂ O). By using these tungsten compounds, the amount of lithium in the tungsten mixture can be easily controlled without being affected by the amount of lithium contained in the solid tungsten compound in the tungsten mixture.

As shown in FIG. 5C, when the tungsten compound is added after the solid-liquid separation, there is no lithium or tungsten that is removed together with water during the solid-liquid separation, and all the tungsten compound remains in the mixture. It becomes easy to control the molar ratio. In this case, the tungsten compound may be in an aqueous solution state or a powder state.

When the tungsten compound is added during the water washing step, the tungsten compound may be in an aqueous solution state or a powder state. A homogeneous mixture is obtained by adding the tungsten compound to the slurry and stirring.

When the tungsten compound used is an aqueous solution or a water-soluble compound, most of the tungsten compound dissolved in the slurry is removed together with the liquid component of the slurry in the solid-liquid separation step after washing with water. However, the amount of tungsten in the tungsten mixture can be made sufficient due to the tungsten dissolved in the water in the tungsten mixture. The amount of tungsten in the tungsten mixture becomes stable along with the amount of water depending on the washing condition and the solid-liquid separation condition. Therefore, these conditions can be determined together with the type and addition amount of the tungsten compound by a preliminary test. Moisture with respect to tungsten in the tungsten mixture and the total amount of lithium contained in the tungsten compound (hereinafter, referred to as the total amount of lithium) can also be determined by a preliminary test similarly to the amount of tungsten.

The amount of tungsten in the mixture when the tungsten compound is added in the water washing step can be determined by ICP emission spectroscopy. Further, the amount of lithium contained in the water constituting the mixture can be determined from the analysis value of lithium by ICP emission spectroscopy in the liquid component obtained by solid-liquid separation after washing with water and the amount of water.

The amount of lithium contained in the solid tungsten compound that constitutes the tungsten mixture is the same as that of the liquid component after washing with water, and the tungsten compound is added to the aqueous solution of lithium hydroxide and stirred under the same conditions as when washing with water. The amount remaining as a solid content in the tungsten mixture can be calculated from the ratio of the tungsten compound remaining as a solid content, and can be determined from the tungsten compound remaining as a solid content.

Further, the amount of tungsten in the mixture when the tungsten compound is added after the solid-liquid separation step can be obtained from the amount of the added tungsten compound.

On the other hand, the total amount of lithium in the tungsten mixture is the amount of lithium in water determined from the analysis value of lithium by ICP emission spectroscopy and the amount of water in the liquid component that has undergone solid-liquid separation after washing with water, and the amount of the added tungsten compound or tungsten compound. It can be calculated as the sum of the amounts of lithium obtained from the lithium compound.

When the tungsten compound is added as an aqueous solution after the solid-liquid separation step, it is necessary to adjust the aqueous solution so that the water content preferably does not exceed 20 mass% as described above, and the tungsten concentration is set to 0. It is preferably not less than 05 mol/L and not more than 2 mol/L. When the tungsten concentration is in the above range, the required amount of tungsten can be added while suppressing the water content of the tungsten mixture. When the amount of water exceeds 20% by mass, solid-liquid separation may be performed again to adjust the amount of water, but the amount of tungsten and the amount of lithium in the removed liquid component should be determined to confirm the Li molar ratio of the mixture. Is required.

Since the amount of water contained in the tungsten mixture is 2% by mass or more, the mixing after solid-liquid separation is preferably performed at a temperature of 50° C. or less. When the temperature is higher than 50°C, the water content may be less than 2% by mass due to drying during mixing.

The mixing with the tungsten compound is not limited as long as it is a device capable of uniformly mixing, and a general mixer can be used. For example, a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, or the like may be used to sufficiently mix with the tungsten compound to the extent that the skeleton of the lithium metal composite oxide particles is not destroyed.

The component composition of the first composite oxide particles 1 is composed of composite oxide particles as a base material, tungsten that is added and increased in the adjusting step, and a lithium content that is added as necessary. Therefore, the base material is, from the viewpoint of high capacity and low reaction resistance, composition formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0 <x ≦ 0.35,0 ≦ y ≦ 0.35, 0.95 ≤ z ≤ 1.20, M is a lithium metal composite oxide represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al). It is preferable.

On the other hand, when the base material is washed with water, the amount of Li/Me (corresponding to z in the general formula) in the base material decreases due to the lithium elution during the water washing. As the material of the base material, a base material in which Li/Me is adjusted can be used. The reduction amount of Li/Me under general washing conditions is about 0.03 to 0.08. In addition, when water is supplied in the mixing step, lithium is eluted although it is a small amount. Therefore, in the case of washing with water, z indicating Li/Me of the base material before washing with water is preferably 0.95≦z≦1.20, and more preferably 0.97≦z≦1.15. preferable.

Further, since increasing the contact area with the electrolytic solution is advantageous for improving the output characteristics, it is composed of the primary particles and the secondary particles formed by aggregating the primary particles, and the secondary particles have the electrolytic solution. It is preferable to use a lithium metal composite oxide powder having permeable voids and grain boundaries.

Moreover, when mixing a base material and a tungsten compound, or a tungsten compound and a lithium compound, a general mixer can be used. For example, a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, an air blender, or the like may be used to thoroughly mix the tungsten-coated base material without destroying the skeleton of the base material. It should be noted that excess Li contained in the base material becomes lithium carbonate by adsorbing carbon dioxide and causes gas generation. Therefore, the mixed atmosphere is preferably performed at a carbon dioxide concentration of 0 to 100 ppm.

Next, as shown in FIG. 4, the tungsten mixture obtained as described above is heat-treated. By heat treatment, lithium contained in the moisture of the tungsten mixture reacts with tungsten to form lithium tungstate (LWO compound) on the surface of the primary particles of the base material (core material), and the first composite oxide particles 1 Is obtained.

The heat treatment condition is not particularly limited as long as the LWO compound 6 is formed on the surface of the primary particles of the base material (core material). The heat treatment conditions are, for example, from the viewpoint of preventing deterioration of electrical characteristics when the positive electrode active material 10 is used in a secondary battery, avoiding reaction with moisture and carbonic acid in the atmosphere, and oxidizing such as oxygen atmosphere. It can be performed in an atmosphere or a vacuum atmosphere.

Further, the heat treatment temperature is preferably 100° C. or more and 600° C. or less from the viewpoint of preventing deterioration of electrical characteristics when the positive electrode active material 10 is used in a secondary battery. When the heat treatment temperature is lower than 100° C., the evaporation of water is not sufficient and the LWO compound 6 may not be sufficiently formed. On the other hand, if the heat treatment temperature exceeds 600° C., the primary particles of the lithium metal composite oxide will sinter and a part of the tungsten will form a solid solution in the layered structure of the lithium metal composite oxide. The discharge capacity may decrease.

On the other hand, when the tungsten compound contained in the tungsten mixture remains as a solid without being dissolved in water, particularly when the tungsten compound is added as a powder after the solid-liquid separation step, the solid is sufficiently dissolved. During the operation, it is preferable to set the rate of temperature rise to 0.8 to 1.2° C./minute until the temperature exceeds 90° C., for example. Even in the step of adjusting the tungsten mixture, the powder of the tungsten compound is dissolved in the water contained in the mixture, but such a temperature increasing rate allows the solid tungsten compound to be sufficiently dissolved during the temperature increase. It is possible to penetrate to the surface of the primary particles inside the secondary particles. When the solid tungsten compound is dissolved, it is preferable that the solid tungsten compound is heat-treated in a closed container so that water does not volatilize while the dissolution is sufficiently performed.

The heat treatment time is not particularly limited, but is preferably 3 hours or more and 20 hours or less, and preferably 5 hours or more and 15 hours or less, from the viewpoint of sufficiently evaporating the water in the tungsten mixture to form the LWO compound 6. Is more preferable.

The heat treatment is performed by reacting a lithium compound existing on the surface of the primary particles of the base material with a tungsten compound to dissolve the tungsten compound, and performing a first heat treatment of dispersing tungsten on the surface of the primary particles; The second heat treatment for forming the lithium tungstate compound on the primary particle surfaces of the lithium-nickel composite oxide particles by performing the heat treatment at a temperature higher than the heat treatment temperature of No. 1 is preferably included.

In the first heat treatment, by heating the tungsten mixture containing the tungsten compound, not only lithium eluted in the mixture but also the lithium compound remaining on the surface of the primary particles of the base material reacts with the tungsten compound. Dissolve. Thereby, surplus lithium in the obtained tungsten-coated composite oxide particles can be significantly reduced and battery characteristics can be improved. Furthermore, it also has an effect of extracting lithium excessively present in the base material, and the extracted lithium reacts with a tungsten compound, which also contributes to improvement of crystallinity when it becomes a tungsten-coated composite oxide particle. The battery characteristics can be improved. By the first heat treatment, tungsten is sufficiently dissolved in water in the tungsten mixture and penetrates into voids between primary particles and incomplete grain boundaries inside the secondary particles of the base material to disperse the tungsten on the surface of the primary particles. Can be made.

The heat treatment temperature in the first heat treatment is preferably 60 to 80°C. If the heat treatment temperature is in this range, the reaction can proceed sufficiently, and moisture can remain until the tungsten penetrates, react with the lithium compound and the tungsten compound, and sufficiently disperse the tungsten on the surface of the primary particles. it can. When the first heat treatment temperature is lower than 60° C., the reaction between the lithium compound and the tungsten compound existing on the surface of the primary particles of the base material does not sufficiently occur, and the required amount of lithium tungstate may not be synthesized. On the other hand, when the first heat treatment temperature is higher than 80° C., the evaporation of water is premature, so that the reaction between the lithium compound and the tungsten compound existing on the surface of the primary particles and the infiltration of tungsten may not proceed sufficiently. ..

The heating time in the first heat treatment is not particularly limited, but is preferably 0.5 to 2 hours because the lithium compound and the tungsten compound react and the tungsten is sufficiently permeated.

The second heat treatment is performed at a temperature higher than the heat treatment temperature of the first heat treatment to sufficiently evaporate the water content in the mixture and form a lithium tungstate compound on the surface of the primary particles of the lithium nickel composite oxide particles. It is a thing.
The heat treatment temperature of the second heat treatment is preferably 100° C. or higher and 200° C. or lower. If the second heat treatment temperature is lower than 100° C., the evaporation of water may not be sufficient and the lithium tungstate compound may not be sufficiently formed. On the other hand, if the second heat treatment temperature exceeds 200° C., the lithium nickel composite oxide particles may form necking via lithium tungstate, or the specific surface area of the lithium nickel composite oxide particles may be significantly reduced. Therefore, the battery characteristics may deteriorate.

The heat treatment time of the second heat treatment is not particularly limited, but is preferably 1 to 15 hours, and preferably 5 to 12 hours in order to sufficiently evaporate the water to form the lithium tungstate compound.

The atmosphere in the heat treatment (including the first heat treatment and the second heat treatment) is decarbonated air, an inert gas, or a vacuum in order to avoid a reaction between moisture and carbonic acid in the atmosphere and lithium on the surface of the lithium nickel composite oxide particles. The atmosphere is preferable.

Next, as shown in FIG. 1B, the positive electrode active material 10 is obtained by mixing the first composite oxide particles 1 and the second composite oxide 2 obtained by the above method. The method for producing the second composite oxide 2 is not particularly limited, and a conventionally known method for producing lithium nickel composite oxide particles can be used.

The second composite oxide particles 2 are preferably washed with water before mixing. As the water washing conditions, the same conditions as the above-mentioned water washing of the base material of the first composite oxide particles 1 can be used. When the second composite oxide particles are washed with water, excess unreacted lithium compounds such as lithium hydroxide and lithium carbonate, sulfate radicals, and other impurity elements that deteriorate the battery characteristics can be removed.

The mixing ratio of the first composite oxide particles 1 and the second composite oxide particles 2 is set so that the amount of the first composite oxide particles 1 is 10% by mass or more with respect to the positive electrode active material 10. It is preferable to mix with the composite oxide particles 2. In addition, the amount of tungsten contained in the first composite oxide particles 1 is 0.03 to 2.5 atom% with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material 10. It is preferable to mix one composite oxide particle 1 and the second composite oxide particle 2. This makes it possible to achieve both higher charge/discharge capacity and output characteristics.

When mixing the first composite oxide particles 1 and the second composite oxide particles 2, a general mixer can be used. For example, a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, an air blender, or the like may be used to thoroughly mix the tungsten-coated base material without destroying the skeleton of the base material.

2. Non-Aqueous Electrolyte Secondary Battery The non-aqueous electrolyte secondary battery of the present embodiment includes a positive electrode, a negative electrode, a non-aqueous electrolyte solution, and the like, and is configured with the same constituent elements as a general non-aqueous electrolyte secondary battery. The embodiments described below are merely examples, and the non-aqueous electrolyte secondary battery of the present invention is based on the embodiments described in the present specification, and various modifications based on the knowledge of those skilled in the art. It can be implemented in a modified form. The use of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited.

(A) Positive Electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery described above, for example, a positive electrode for a non-aqueous electrolyte secondary battery is manufactured as follows.
First, a powdery positive electrode active material, a conductive material, and a binder are mixed and, if necessary, activated carbon, a solvent for the purpose of adjusting viscosity, etc. are added, and this is kneaded to prepare a positive electrode mixture paste.
The respective mixing ratios in the positive electrode mixture paste are also important factors that determine 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, and the conductive material is the same as the positive electrode of a general non-aqueous electrolyte secondary battery. The content of the binder is preferably 1 to 20 parts by mass, and the content of the binder is preferably 1 to 20 parts by mass.

The obtained positive electrode mixture paste is applied to the surface of a current collector made of aluminum foil, for example, and dried to scatter the solvent. If necessary, pressure may be applied by a roll press or the like in order to increase the electrode density. In this way, a sheet-shaped positive electrode can be manufactured. The sheet-shaped positive electrode can be cut into an appropriate size according to the intended battery and used for the production of the battery. However, the method for producing the positive electrode is not limited to the example, and other methods may be used.

In producing the positive electrode, as the conductive agent, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), a carbon black-based material such as acetylene black, Ketjen Black (registered trademark), or the like can be used.

The binder plays a role of binding the active material particles, and examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, and polyacryl. An acid or the like 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. As the solvent, specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used. Activated carbon may be added to the positive electrode mixture to increase the electric double layer capacity.

(B) Negative electrode For the negative electrode, a negative electrode mixture material prepared by mixing metallic lithium, a lithium alloy or the like, or a negative electrode active material capable of occluding and desorbing lithium ions with a binder and adding an appropriate solvent to form a paste. Is applied to the surface of a metal foil current collector made of copper or the like, dried, and compressed to increase the electrode density if necessary.

As the negative electrode active material, for example, a natural graphite, artificial graphite, a fired body of an organic compound such as phenol resin, or a powdery body of a carbon material 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 positive electrode, and a solvent for dispersing the active material and the binder may be N-methyl-2-pyrrolidone or the like. Organic solvents can be used.

(C) Separator A separator is sandwiched between the positive electrode and the negative electrode.
The separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film of polyethylene, polypropylene, or the like, which has a large number of minute holes, can be used.

(D) Non-Aqueous Electrolyte Solution The non-aqueous electrolyte solution is a lithium salt as a supporting salt dissolved in an organic solvent.
The organic solvent used, ethylene carbonate, propylene carbonate, butylene carbonate, cyclic carbonates such as trifluoropropylene carbonate, also, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, chain carbonates such as dipropyl carbonate, further, tetrahydrofuran, A single compound selected from ether compounds such as 2-methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more thereof. Can be used.
As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN(CF ₃ SO ₂ ) ₂ or the like, and a complex salt thereof can be used.
Furthermore, the non-aqueous electrolyte 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 composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte solution described above is various such as cylindrical type and laminated type. can do.
Whichever shape is adopted, the positive electrode and the negative electrode are laminated with a separator interposed therebetween to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolytic solution and communicated with the positive electrode current collector and the outside. The non-aqueous electrolyte secondary battery is completed by connecting between the positive electrode terminal and the negative electrode current collector and the negative electrode terminal communicating with the outside by using a current collecting lead or the like and sealing the battery case. ..

(F) Characteristics The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention has high capacity and 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 initial discharge capacity of 165 mAh/g or more and a low initial discharge capacity when used for the positive electrode of a 2032 type coin battery, for example. Positive electrode resistance is obtained, and the capacity and output are high. Further, it can be said that it has high thermal stability and is excellent in safety.
The method for measuring the positive electrode resistance according to the present invention will be described below.
When the frequency dependence of the battery reaction is measured by a general AC impedance method as an electrochemical evaluation method, a 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.

The battery reaction at the electrode consists of a resistance component due to charge transfer and a capacitance component due to the electric double layer. When expressed as an electric circuit, it is 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 electrode resistance is equal to the diameter of the semicircle on the low frequency side of the obtained Nyquist diagram. From the above, it is possible to estimate the positive electrode resistance by performing AC impedance measurement on the manufactured positive electrode and performing fitting calculation on the obtained Nyquist diagram with an equivalent circuit.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

The performance (initial discharge capacity, positive electrode resistance, cycle characteristics) of a secondary battery having a positive electrode using the positive electrode active material obtained by the present invention was measured.
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Battery manufacturing and evaluation)
A 2032 type coin battery CBA (hereinafter, referred to as a coin type battery) shown in FIG. 7 was used for evaluation of the positive electrode active material. As shown in FIG. 6, the coin-type battery CBA is composed of an electrode EL and a case CA that houses the electrode EL therein. The electrode EL includes a positive electrode PE, a separator SE1, and a negative electrode NE, which are stacked in this order, and 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. Thus, it is housed in the case CA.

The case CA has a positive electrode can PC which is hollow and one end of which is open, and a negative electrode can NC which is arranged in the opening of the positive electrode can PC. When the negative electrode can NC is arranged in the opening of the positive electrode can PC. A space for housing the electrode EL is formed between the negative electrode can NC and the positive electrode can PC. The case CA includes a gasket GA, and the gasket GA fixes the relative movement of the positive electrode can PC and the negative electrode can NC so as to maintain a non-contact state. Further, the gasket GA also has a function of sealing the gap between the positive electrode can PC and the negative electrode can NC to shut off the inside and outside of the case CA in a gas-tight and liquid-tight manner.

The coin-type battery CBA 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 polytetrafluoroethylene resin (PTFE) were mixed, and press-molded at a pressure of 100 MPa to a diameter of 11 mm and a thickness of 100 μm. A positive electrode PE was produced. 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 SE1, and the electrolytic solution, a coin battery CBA was produced in a glove box in an Ar atmosphere with a dew point controlled at −80° C.
As the negative electrode NE, there was used a negative electrode sheet in which a copper foil was coated with graphite powder having an average particle size of about 20 μm, which was punched into a disk shape with a diameter of 14 mm. A 25-μm-thick polyethylene porous film was used as the separator SE1. As the electrolytic solution, a 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.

The initial discharge capacity and the positive electrode resistance showing the performance of the manufactured coin type battery CBA were evaluated as follows. After the coin-type battery CBA was manufactured, the initial discharge capacity was left for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) became stable, the current density to the positive electrode was set to 0.1 mA/cm ² and the cut-off voltage was 4 The initial discharge capacity was defined as the capacity when the battery was charged to 0.3 V, and after being rested for 1 hour, it was discharged to a cutoff voltage of 3.0 V.

The positive electrode resistance was measured by the AC impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B) by charging a coin-type battery CBA with a charging potential of 4.1V, and the Nyquist plot shown in FIG. 6 was obtained. can get. Since this Nyquist plot is expressed as the sum of the characteristic curves showing the solution resistance, the negative electrode resistance and its capacity, and the positive electrode resistance and its capacity, a fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and the positive electrode resistance is calculated. The value of was calculated. The positive electrode resistance was calculated as a relative value with Comparative Example 1 being “1.00”.

In this example, each sample of the reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. was used for the production of the composite hydroxide, the production of the positive electrode active material and the secondary battery.

(Example 1)
[Manufacture of positive electrode active material]
(Production of first composite oxide particles)
A lithium nickel composite oxide represented by Li _1.020 Ni _0.91 Co _0.06 Al _0.03 O ₂ obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and fired. The powder of material particles was used as the base material. To 500 g of the base material, 500 mL of pure water at 25° C. was added to prepare a slurry, which was then stirred for 15 minutes and washed with water. The slurry after washing with water was filtered using a Nutsche to perform solid-liquid separation. The water content of the obtained washed cake was 8.5% by mass.
3.58 g of tungsten oxide (WO ₃ ) was added to the washed cake so that the W content was 0.30 atomic% with respect to the total number of Ni, Co and Al atoms contained in the base material, and a shaker mixer device was used. (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) was thoroughly mixed to obtain a tungsten mixture.
The obtained tungsten mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and dried by standing still (heat treatment) for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
The obtained tungsten mixture after drying is sieved with a sieve having an opening of 38 μm and crushed to obtain lithium nickel composite oxide particles (first composite oxide) having a lithium tungstate compound on the surface of primary particles of a core material (base material). Object particles) were obtained. It was confirmed that the surplus lithium amount (the amount of Li contained in a lithium compound other than lithium tungstate) in the obtained first composite oxide particles was 0.05% by mass or less.
(Production of second composite oxide particles)
A lithium nickel composite oxide represented by Li _1.020 Ni _0.91 Co _0.06 Al _0.03 O ₂ obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and fired. 667 mL of pure water at 25° C. was added to 500 g of the powder of physical particles to form a slurry, which was washed with water for 15 minutes, solid-liquid separated, and then dried to obtain second composite oxide particles. It was confirmed that the amount of surplus lithium in the obtained second composite oxide particles was 0.05% by mass or less.
(Mixing of first composite oxide particles and second composite oxide particles)
To 300 g of the obtained lithium nickel composite oxide particles (first composite oxide particles), 300 g of lithium nickel composite oxide (second composite oxide particles) containing no lithium tungstate compound was added, and a shaker mixer device (Willy TURBULA Type T2C manufactured by E. Bakofen (WAB) was thoroughly mixed to obtain a positive electrode active material. When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms. In addition, it was confirmed that the sulfate content of the obtained positive electrode active material was 0.05% by mass or less.

[Excessive lithium analysis]
The surplus lithium of the obtained positive electrode active material was evaluated by titrating Li eluted from the positive electrode active material. 10 ml of pure water was added to 1 g of the obtained positive electrode active material, and the mixture was stirred for 1 minute, and the compound state of lithium eluted from the neutralization point that appears when hydrochloric acid is added while measuring the pH of the filtered filtrate is analyzed. Then, the amount of excess lithium was evaluated. The amount of surplus lithium was 0.02 mass% with respect to the total amount of the positive electrode active material.

[Battery evaluation]
The battery characteristics of the coin-type battery CBA having a positive electrode manufactured using the obtained positive electrode active material were evaluated. The positive electrode resistance was evaluated as a relative value with Comparative Example 1 being “1.00”. The initial discharge capacity was 213.1 mAh/g.
In the following, for Examples and Comparative Examples, only the substances and conditions changed from Comparative Example 1 are shown. Tables 1 and 2 also show the evaluation values of the initial discharge capacity and the positive electrode resistance of the examples and comparative examples.

(Example 2)
5. Tungsten oxide (WO ₃ ) was added to the wash cake so that the W content was 0.45 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). Except that 37 g was added, the mixture was thoroughly mixed in the same manner as in Example 1 using a shaker mixer device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) to obtain a tungsten mixture.
The obtained mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and left to stand and dry for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
A lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the surface of primary particles of a core material (matrix) is obtained by crushing the obtained dried tungsten mixture through a sieve having openings of 38 μm. Got To 300 g of the obtained composite oxide (first composite oxide), 600 g of lithium nickel composite oxide (second composite oxide particles) containing no lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer was added. Using a device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)), they were thoroughly mixed to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 3)
7. Tungsten oxide (WO ₃ ) was added to the wash cake so that the W content was 0.75 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). Except having added 98 g, it fully mixed using the shaker mixer apparatus (TURBULA TypeT2C by the Willy e Bakkofen (WAB) company) like Example 1, and the tungsten mixture was obtained.
The obtained tungsten mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and left to stand and dry for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
A lithium nickel composite having the lithium tungstate compound obtained in the same manner as in Example 1 on the primary particle surface of the core material (base material) was obtained by crushing the obtained dried tungsten mixture through a sieve having an opening of 38 μm and crushing. An oxide (first composite oxide) was obtained.
To 300 g of the obtained composite oxide (first composite oxide), 1200 g of lithium nickel composite oxide (second composite oxide particles) containing no lithium tungstate compound was added, and a shaker mixer device (Willie & Bakkofen (WAB ) TURBULA Type T2C manufactured by KK) was sufficiently mixed to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 4)
667 mL of pure water at 25° C. was added to 500 g of the base material to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtering using a Nutsche. The water content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the wash cake so that the W content was 0.30 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and thoroughly mixed using a shaker mixer device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and left to stand and dry for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
A lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the surface of primary particles of a core material (matrix) is obtained by crushing the obtained dried tungsten mixture through a sieve having openings of 38 μm. Got
To 300 g of the obtained composite oxide (first composite oxide), 300 g of lithium nickel composite oxide (second composite oxide particles) containing no lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer was added. A device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) was used for thorough mixing to obtain a mixed positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 5)
667 mL of pure water at 25° C. was added to 500 g of the base material to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtering using a Nutsche. The water content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the wash cake so that the W content was 0.45 atom% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and thoroughly mixed using a shaker mixer device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and left to stand and dry for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
A lithium nickel composite oxide having a lithium tungstate compound (first composite oxide) on the surface of primary particles of a core material (matrix) by crushing the obtained dried tungsten mixture through a sieve having an opening of 38 μm. Got
To 300 g of the obtained composite oxide (first composite oxide), 600 g of lithium nickel composite oxide (second composite oxide) containing no lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer device was added. (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) was thoroughly mixed to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 6)
667 mL of pure water at 25° C. was added to 500 g of the base material to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtering using a Nutsche. The water content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the wash cake so that the W content was 0.75 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and thoroughly mixed using a shaker mixer device (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was placed in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, and left to stand and dry for 10 hours using a vacuum dryer heated to 190° C., and then furnace cooled.
A lithium nickel composite oxide having a lithium tungstate compound (first composite oxide) on the surface of primary particles of a core material (matrix) by crushing the obtained dried tungsten mixture through a sieve having an opening of 38 μm. Got
To 300 g of the obtained composite oxide (first composite oxide), 1200 g of lithium nickel composite oxide (second composite oxide) containing no lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer device was added. (TURBULA Type T2C manufactured by Willy E. Bakkofen (WAB)) was thoroughly mixed to obtain a mixed positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Comparative Example 1)
Except that 500 mL of pure water at 25° C. was added to 500 g of lithium nickel composite oxide particles having the same composition as the above base material to form a slurry, and no tungsten compound was added to the wash cake after solid-liquid separation. In the same manner as in the first composite oxide of Example 1, composite oxide particles (corresponding to the second composite oxide) were obtained and used as the positive electrode active material.

(Comparative example 2)
Except that 667 mL of pure water at 25° C. was added to lithium nickel composite oxide particles having the same composition as the base material of 500 g to form a slurry, and no tungsten compound was added to the wash cake after solid-liquid separation. A composite oxide particle (corresponding to the second composite oxide) was obtained in the same manner as the first composite oxide of Example 1, and was used as the positive electrode active material.

(Comparative example 3)
The first composite oxide of Example 1 except that 667 mL of pure water at 25° C. was added to 500 g of the base material to form a slurry, and the tungsten compound was not added to the wash cake after solid-liquid separation. In the same manner, composite oxide particles (corresponding to the second composite oxide) were obtained. 2.0 g of lithium tungstate (LWO:Li ₂ WO ₄ ) powder was added to the obtained composite oxide particles (corresponding to the second composite oxide), and a shaker mixer device (Willie & Bakkofen (WAB) Co., Ltd.) was used. (TURBULA Type T2C manufactured by TURBULA) was thoroughly mixed to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

[Evaluation]
As is clear from Tables 1 and 2, the positive electrode active materials of the examples have high initial discharge capacities and low positive electrode resistances, since they are manufactured according to the present invention, and thus are more positive than those of Comparative Examples 1 and 2. It exhibits excellent battery characteristics. Further, FIG. 3 shows an example of a cross-sectional SEM observation result of the positive electrode active material obtained in the example of the present invention. The positive electrode active material obtained is a secondary particle formed by aggregating primary particles and primary particles. It was confirmed that lithium tungstate was formed on the surface of the primary particles composed of particles. The fine particles containing lithium tungstate are circled in FIG.

On the other hand, in Comparative Examples 1 and 2, since fine particles containing lithium tungstate are not formed on the surface of the primary particles, the positive electrode resistance is significantly high, and it is difficult to meet the demand for higher output. Further, in Comparative Example 3, although the resistance reducing effect is obtained by adding lithium tungstate, since the lithium tungstate compound is not formed on the surface of the primary particles of the lithium nickel composite oxide, the battery having a low initial discharge capacity is obtained. Is becoming

The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is suitable for use as a power source for small portable electronic devices (notebook personal computers, mobile phone terminals, etc.) that always require high capacity, and has high output. It can also be suitably used for a required battery for an electric vehicle. In addition, the non-aqueous electrolyte secondary battery of the present invention has excellent safety, can be downsized, and has high output, and thus can be suitably used as a power source for an electric vehicle that is restricted in mounting space. it can. The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is not only a power source for an electric vehicle driven purely by electric energy but also a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. It can also be used as a power source.

DESCRIPTION OF SYMBOLS 1... 1st lithium nickel composite oxide 2... 2nd lithium nickel composite oxide 3, 3a, 3b... Primary particle (1st lithium nickel composite oxide)
4... Secondary particles (first lithium-nickel composite oxide)
5... Core material 6, 6a, 6b... Lithium tungstate 7... Primary particles (second lithium nickel composite oxide)
8... Secondary particles (second lithium nickel composite oxide)
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 SE1... Separator

Claims (23)

Mixing the first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate,
The composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦0.35, 0≦y1≦0.35, 0. 95 ≦ z1 ≦ 1.15, ^{M 1} is Mn, V, Mg, Mo, Nb, represented by at least one element) selected from Ti and Al, the secondary particle child plurality of primary particles are aggregated to each other Consisting of a core material and a lithium tungstate present on at least a part of the surface of the primary particles located inside and on the surface of the first lithium nickel composite oxide particles,
The composition of the second lithium nickel composite oxide particles is Li _z2 Ni _1-x2-y2 Co _x2 M ² _y2 O ₂ (where 0≦x2≦0.35, 0≦y2≦0.35, 0. 95≦z2≦1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and is composed of secondary particles in which a plurality of primary particles are aggregated with each other. Will be
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the second lithium nickel composite oxide particles are washed with water before the mixing. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein the slurry concentration at the time of washing with water is 500 g/L or more and 2500 g/L or less. The first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles are contained in a lithium compound other than lithium tungstate present on the surfaces of the primary particles located on both surfaces and inside thereof. The amount of lithium is 0.05% by mass or less based on the total amount of the positive electrode active material, and the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein Production method. The content of the first lithium nickel composite oxide particles contained in the positive electrode active material is 10 mass% or more with respect to the total amount of the positive electrode active material, and the first lithium nickel composite oxide particles. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the second lithium nickel composite oxide particles are mixed. The amount of tungsten contained in the first lithium nickel composite oxide particles is 0.03 atomic% or more and 2.5 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material. It mixes with the said 1st composite oxide particle and the said 2nd lithium nickel composite oxide particle so that it may become, It is provided, The any one of Claims 1-5 characterized by the above-mentioned. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. Before the mixing,
The composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (however, 0.00≦x3≦0.35, 0.00≦y3≦0.35, 0.95≦z3≦1.20, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a base material composed of secondary particles formed by aggregating a plurality of primary particles,
2% by mass or more of water with respect to the total amount of the base material,
A tungsten compound, or a lithium compound containing no tungsten compound and tungsten,
Adjusting the tungsten mixture containing, and heat-treating the obtained tungsten mixture to form lithium tungstate on the surface of the base material and the surface of the primary particles inside, and the first lithium nickel composite oxide To obtain object particles,
In the tungsten mixture, the molar ratio of the total amount of lithium contained in the water and the tungsten compound, or the water, the tungsten compound and the lithium compound, to the total amount of contained tungsten is 5 or less.
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5. The first lithium nickel composite oxide particles, the amount of lithium contained in the lithium compound other than lithium tungstate present on the surface and the surface of the internal primary particles, the first lithium nickel composite oxide particles. It is 0.05 mass% or less with respect to the above, The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of Claim 7 characterized by the above-mentioned. Prior to the heat treatment, the base material and water are mixed to form a slurry, and the base material is washed with water, and the washed base material is subjected to solid-liquid separation. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7 or 8. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, wherein a slurry concentration of the base material washed with water is 500 g/L or more and 2500 g/L or less. When the base material washed with water is subjected to solid-liquid separation, the water content of the wash cake obtained is controlled to 3.0% by mass or more and 15.0% by mass or less. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The tungsten compound contains at least one of tungsten oxide (WO ₃ ), tungstic acid (WO ₃ .H ₂ O), Li ₂ WO ₄ , Li ₄ WO ₅ and Li ₆ W ₂ O _9. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 7 to 11. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 7-12, wherein the temperature of the heat treatment in the heat treatment is at 100 ° C. or higher 600 ° C. or less. The amount of tungsten contained in the tungsten compound is 0.05 atom% or more and 3.0 atom% or less with respect to the total number of atoms of Ni, Co and M contained in the base material. Item 14. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Items 7 to 13. Includes first lithium nickel composite oxide particles containing lithium tungstate, and second lithium nickel composite oxide particles not containing lithium tungstate,
The composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0≦x1≦0.35, 0≦y1≦0.35, 0. 95 ≦ z1 ≦ 1.15, ^{M 1} is Mn, V, Mg, Mo, Nb, represented by at least one element) selected from Ti and Al, the secondary particle child plurality of primary particles are aggregated to each other Consisting of a core material and a lithium tungstate present on at least a part of the surface of the primary particles located inside and on the surface of the first lithium nickel composite oxide particles,
The composition of the second lithium nickel composite oxide particles is Li _z2 Ni _1-x2-y2 Co _x2 M ² _y2 O ₂ (where 0≦x2≦0.35, 0≦y2≦0.35, 0. 95≦z2≦1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and is composed of secondary particles in which a plurality of primary particles are aggregated with each other. Will be
A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: The amount of lithium contained in a lithium compound other than lithium tungstate, which is present on the surfaces of the primary particles located on the surfaces and insides of the first lithium nickel composite oxide particles and the second composite oxide particles, The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 15, wherein the content of the positive electrode active material is 0.05% by mass or less based on the total amount of the positive electrode active material. The amount of the said 1st lithium nickel composite oxide particle contained in a positive electrode active material is 10 mass% or more with respect to the total amount of the said positive electrode active material, The non-aqueous system of Claim 15 or 16 characterized by the above-mentioned. Positive electrode active material for electrolyte secondary batteries. The amount of tungsten contained in the lithium tungstate is 0.03 atom% or more and 2.5 atom% or less with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material. Item 18. A positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Items 15 to 17. The amount of tungsten contained in the lithium tungstate is 0.05 atomic% or more and 3.0 atomic% or less with respect to the total number of Ni, Co and M atoms contained in the first composite oxide particles. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 15 to 18. 20. The lithium tungstate is present on the surface of the first lithium-nickel composite oxide particles and the surface of primary particles inside thereof as fine particles having a particle diameter of 1 nm or more and 500 nm or less. Item 1. A positive electrode active material for a non-aqueous electrolyte secondary battery according to item 1. The lithium data tungsten acid, any of claim 15 to 19, characterized in that present on the surface and the surface of the interior of the primary particles of the first lithium nickel complex oxide particles as 200nm or less of the film than the film thickness 1nm 2. A positive electrode active material for a non-aqueous electrolyte secondary battery according to item 1. The lithium tungstate is present on the surface of the first lithium-nickel composite oxide particles and the surface of the primary particles inside thereof as both forms of fine particles having a particle diameter of 1 nm or more and 500 nm or less and a film having a film thickness of 1 nm or more and 200 nm or less. 20. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 15 to 19. A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 15 to 22.