KR102337646B1 - Positive electrode active material for nonaqueous electrolyte secondary battery, method for producing the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

An object of the present invention is to provide a positive electrode active material and the like for a non-aqueous electrolyte secondary battery in which high output and high capacity are obtained and the amount of tungsten used is suppressed.
A method comprising: mixing first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate, wherein the first lithium nickel composite oxide particles have a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ A core material including secondary particles in which a plurality of primary particles are aggregated with each other and primary particles positioned on the surface and inside of the first lithium nickel composite oxide particles _{Consisting of} lithium tungstate present on at least a part of the surface, the second lithium nickel composite oxide particles have a composition represented by Li _z2 Ni _{1 -x2- y2} Co _x2 M ² _y2 O ₂ , and a plurality of primary particles are mutually It depends on the manufacturing method etc. of the positive electrode active material for nonaqueous electrolyte secondary batteries comprised from the aggregated secondary particle.

Description

A positive electrode active material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery

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

In recent years, with the spread of portable electronic devices, such as a mobile phone and a notebook computer, development of the small and lightweight secondary battery which has a high energy density is strongly desired. Further, there is a strong demand for the development of high-output secondary batteries as batteries for electric vehicles including hybrid vehicles.

As a secondary battery that satisfies such a requirement, there is a non-aqueous electrolyte secondary battery typified by a lithium ion secondary battery. This lithium ion secondary battery is comprised from a negative electrode, a positive electrode, electrolyte solution, etc., The material which can detach|desorb and insert lithium is used for the active material of a negative electrode and a positive electrode.

Such a non-aqueous electrolyte secondary battery is currently being actively researched and developed, but among them, a lithium ion secondary battery using a layered or spinel lithium-nickel composite oxide as a positive electrode material achieves a high voltage of 4V class. , is being put into practical use as a battery having a high energy density.

As materials that are mainly proposed so far, the synthesis is relatively easy to lithium cobalt oxide (LiCoO ₂₎ or lithium nickel composite oxide with low nickel than cobalt (LiNiO _2), lithium nickel cobalt manganese composite oxide (LiNi _1/3 Co _{1 / 3} Mn _{1 / 3} O ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, and the like. Among them, lithium-nickel composite oxide has good cycle characteristics, has low resistance, and is attracting attention as a material from which high output is obtained.

As a method of realizing the above-mentioned reduction in resistance, addition of a die element is used, and transition metals capable of taking high valences, such as W, Mo, Nb, Ta, and Re, are particularly useful. For example, in Patent Document 1, one or more elements selected from Mo, W, Nb, Ta and Re are contained in an amount of 0.1 to 5 mol% based on the total molar amount of Mn, Ni and Co for a lithium secondary battery positive electrode material. Lithium transition metal-based compound powder has been proposed. In addition, the atomic ratio of the sum of Mo, W, Nb, Ta and Re to the sum of Li and metal elements other than Mo, W, Nb, Ta and Re of the surface portion of the primary particles is the atomic ratio of the total primary particles It is considered that it is preferable to be 5 times or more of According to this proposal, it is possible to achieve both cost reduction and high stability of the lithium transition metal-based compound powder for a positive electrode material for a lithium secondary battery and improvement of high load characteristics and powder handling properties.

However, the lithium transition metal compound powder is obtained by pulverizing a raw material in a liquid medium, spray-drying a slurry in which these are uniformly dispersed, and calcining the obtained spray-dried body. Therefore, there is a problem in that a part of the dual elements such as Mo, W, Nb, Ta and Re are substituted with Ni arranged in a layer, and battery characteristics such as capacity and cycle characteristics of the battery are deteriorated.

In addition, Patent Document 2 discloses at least a positive electrode active material for a non-aqueous electrolyte secondary battery having a lithium transition metal composite oxide having a layered structure, wherein the lithium transition metal composite oxide is a primary particle and a secondary particle that is an aggregate thereof. A positive electrode active material for a non-aqueous electrolyte secondary battery having a compound comprising at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on at least the surface of the particles. According to this proposal, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even under a stricter usage environment can be obtained, and in particular, at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on the surface of the particles. By having the compound having a species, the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics, and output characteristics.

However, the effect of at least one additive element selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine is to improve initial characteristics, that is, initial discharge capacity and initial efficiency, and output characteristics not mentioned Further, according to the manufacturing method disclosed in Patent Document 2, since the additive element is mixed with the hydroxide heat-treated at the same time as the lithium compound and fired, a part of the additive element is substituted with the nickel arranged in a layer, resulting in a decrease in battery characteristics. There is a problem that causes

In addition, 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 combinations thereof The positive electrode active material which coat|covered the intermetallic compound obtained by this and/or the oxide is proposed. Although it is supposed that safety can be ensured by absorbing oxygen gas by such a coating|cover, regarding the output characteristic, it is not disclosed at all. In addition, the disclosed manufacturing method coat|covers using a planetary ball mill, in such a covering method, a physical damage will be given to a positive electrode active material, and a battery characteristic will fall.

Further, Patent Document 4 proposes a positive electrode active material in which a tungstic acid compound is deposited on composite oxide particles mainly composed of lithium nickelate and subjected to heat treatment, and the content of carbonate ions is 0.15 wt% or less. According to this proposal, a tungstic acid compound or a decomposition product of a tungstic acid compound exists on the surface of the positive electrode active material to suppress the oxidation activity on the surface of the composite oxide particle in a charged state, so gas generation due to decomposition of a non-aqueous electrolyte solution or the like is prevented. Although it is supposed that it can be suppressed, the output characteristic is not disclosed at all.

In the manufacturing method disclosed in Patent Document 4, preferably, a sulfuric acid compound, a nitric acid compound, a boric acid compound, or a phosphoric acid compound is deposited with a tungstic acid compound on composite oxide particles heated to a boiling point or higher of a solution in which the adherend component is dissolved. Since a solution dissolved in a solvent is deposited as a component and the solvent is removed in a short time, there is a problem that the tungsten compound is not sufficiently dispersed on the surface of the composite oxide particles, so that it is not uniformly deposited.

Further, improvements are being made in terms of higher output of the lithium-nickel composite oxide. For example, Patent Document 5 discloses a lithium-nickel composite oxide including primary particles and secondary particles constituted by aggregation of the primary particles, and Li ₂ WO ₄ , Li ₄ WO ₅ , Li _{6 on the surface of the lithium-nickel composite oxide.} A positive electrode active material for a non-aqueous electrolyte secondary battery having fine particles containing lithium tungstate represented by any of _{W 2} O _{9 is proposed, and high output is obtained with a high capacity.}

Japanese Patent Laid-Open No. 2009-289726 Japanese Patent Laid-Open No. 2005-251716 Japanese Patent Laid-Open No. 11-16566 Japanese Patent Laid-Open No. 2010-40383 Japanese Patent Laid-Open No. 2013-171785

In Patent Document 5, a high-capacity is maintained while a high-output is achieved, but a further high-capacity is required. Moreover, since tungsten is a rare element and expensive, it is necessary to reduce the usage-amount. 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. It can be mentioned as a task.

In view of these problems, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery in which high output and high capacity are obtained when used in a non-aqueous electrolyte secondary battery as a positive electrode active material, and the amount of tungsten used is suppressed. . Another object of the present invention is to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery that is easy to manufacture, has high productivity, and is suitable for production of various types.

In a first aspect of the present invention, a method for producing a 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 particle not containing lithium tungstate. and mixing, wherein the first lithium nickel composite oxide particles have a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ (provided that 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 core material including secondary particles in which a plurality of primary particles are aggregated with each other; 2 Consists of lithium tungstate present on the surface of the composite oxide particle and at least a part of the surface of the primary particle positioned therein, and the second lithium nickel composite oxide particle has a composition of Li _z2 Ni _{1 -x2- y2} Co _x2 M ² _y2 O ₂ (provided that 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) It is expressed as , and a plurality of primary particles are composed of secondary particles agglomerated with each other.

In addition, the second lithium nickel composite oxide particles may be washed with water before mixing. Moreover, the slurry density|concentration at the time of water washing may be 500 g/L or more and 2500 g/L or less. In addition, in the first lithium nickel composite oxide particle and the second lithium nickel composite oxide particle, the amount of lithium contained in the lithium compound other than lithium tungstate present on the surface of both surfaces and the surface of the primary particles located inside the positive electrode active material 0.05 mass % or less may be sufficient with respect to the whole quantity. The first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles may be mixed so that the content of the first lithium-nickel composite oxide contained in the positive electrode active material is 10 mass % or more with respect to the total amount of the positive electrode active material. In addition, 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 atoms of Ni, Co, and M contained in the positive electrode active material. Mixing the oxide particles and the second lithium-nickel composite oxide particles may be provided.

In addition, before mixing, the composition is Li _z3 Ni _{1 -x3- y3} Co _x3 M ¹ _y3 O ₂ (provided that 0.03≤x3≤0.35, 0.01≤y3≤0.35, 0.95≤z3≤1.20, M ¹ is Mn, V, At least one element selected from Mg, Mo, Nb, Ti, and Al), and a base material including secondary particles formed by aggregation of a plurality of primary particles, 2% by mass or more of water based on the total amount of the base material, and tungsten preparing a tungsten mixture containing a compound or a tungsten compound and a lithium compound not containing tungsten, 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 therein; Obtaining lithium nickel composite oxide particles, wherein the tungsten mixture may have a molar ratio of water and a tungsten compound or moisture, a tungsten compound, and a total amount of lithium contained in the lithium compound to the total amount of tungsten contained in the tungsten mixture of 5 or less. In addition, the amount of lithium contained in the lithium compound other than lithium tungstate existing on the surface of the first lithium-nickel composite oxide particle and the surface of the primary particle therein is 0.05% by mass or less with respect to the first lithium-nickel composite oxide particle may be Moreover, before heat processing, you may provide the thing of mixing a base material and water to form a slurry, washing a base material with water, and solid-liquid separation of the washed base material. Moreover, the density|concentration of the water washing slurry of a base material may be 500 g/L or more and 2500 g/L or less. When the water-washed base material is solid-liquid-separated, the moisture content of the washing|cleaning cake obtained may be controlled to 3.0 mass % or more and 15.0 mass % or less. The tungsten compound may contain 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 .} Moreover, the temperature of the heat processing in heat processing may be 100 degreeC or more and 600 degrees C or less. Moreover, the amount of tungsten contained in a tungsten compound may be 0.05-3.0 atomic% with respect to the sum total of the number of atoms of Ni, Co, and M contained in a base material.

In the second aspect of the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery includes first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate, The first lithium nickel composite oxide particles have a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ (provided that 0≤x1≤0.35, 0≤y1≤0.35, 0.95≤z1≤1.15, M ¹ is At least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a core material including secondary particles in which a plurality of primary particles are aggregated with each other, and a surface of the second composite oxide particles and lithium tungstate present on at least a portion of the surface of the primary particles positioned therein, and the second lithium nickel composite oxide particles have a composition of Li _z2 Ni _{1 -x2- y2} Co _x2 M ² _y2 O ₂ (provided that , 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 a plurality of Primary particles are composed of secondary particles agglomerated with each other.

In addition, the amount of lithium contained in the lithium compound other than lithium tungstate present on the surface of the first lithium nickel composite oxide particle and the second lithium nickel composite oxide particle and on the surface of the primary particle positioned therein is the total amount of the positive electrode active material It may be 0.05 mass % or less with respect to it. 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 with respect to the total amount of the positive electrode active material. Moreover, 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 sum total of the number of atoms of Ni, Co, and M contained in a positive electrode active material. Moreover, the amount of tungsten contained in lithium tungstate may be 0.05 atomic% or more and 3.0 atomic% or less with respect to the sum total of the number of atoms of Ni, Co, and M contained in a tungsten-coated composite oxide particle. Further, lithium tungstate may be present on the surface of the first lithium-nickel composite oxide particle and the surface of the inner primary particle 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 particle and the surface of the inner primary particle as a film having a film thickness of 1 nm or more and 200 nm or less. In addition, lithium tungstate exists on the surface of the first lithium-nickel composite oxide particle and on the surface of the inner primary particle in both the form 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. You can do it.

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

ADVANTAGE OF THE INVENTION According to this invention, when used for the positive electrode material of a secondary battery, high output is obtained with high capacity|capacitance, and the positive electrode active material for non-aqueous electrolyte secondary batteries by which the usage-amount of tungsten was suppressed is obtained. In addition, the manufacturing method thereof is easy and high in productivity, suitable for production on an industrial scale, and its industrial value is very large.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram (A) which shows an example of the positive electrode active material which concerns on embodiment, and (B) which shows an example of its manufacturing method.
2 is a schematic diagram showing an example of a first lithium-nickel composite oxide.
3 is a cross-sectional SEM photograph (observational magnification of 10000 times) showing an example of the first lithium-nickel composite oxide (circled portions indicate lithium tungstate).
4 is a view showing an example of a method for manufacturing a first lithium-nickel composite oxide.
5 is a view showing an example of a method for producing a tungsten mixture.
6 is a schematic explanatory diagram of an equivalent circuit used for a measurement example and analysis of impedance evaluation.
7 is a schematic cross-sectional view of a coin-type battery used for battery evaluation.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings. In addition, in the drawings, in order to make each structure easy to understand, a part is emphasized or a part is simplified and shown, and the actual structure, shape, scale, etc. may differ. Hereinafter, this embodiment is demonstrated.

1. Positive electrode active material for non-aqueous electrolyte secondary battery and manufacturing method thereof

1A is a schematic diagram showing an example of a positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter, simply referred to as “positive electrode active material”) 10 of this embodiment, and FIG. 1B is this It is a figure which shows an example of the manufacturing method of the positive electrode active material 10 of embodiment. Hereinafter, first, the positive electrode active material 10 will be described, and then the manufacturing method of the positive electrode active material 10 and the non-aqueous electrolyte secondary battery using the positive electrode active material 10 (hereinafter, simply referred to as "secondary battery" in some cases) about it.

(1) Positive electrode active material for non-aqueous electrolyte secondary battery

As shown in FIG. 1A , the positive electrode active material 10 includes first lithium nickel composite oxide particles (hereinafter, sometimes referred to as “first composite oxide particles”) 1 containing lithium tungstate; , and second lithium nickel composite oxide particles 2 (hereinafter, sometimes referred to as “second composite oxide particles”) that do not contain lithium tungstate.

The first composite oxide particles 1 include a core material 5 including secondary particles 4 in which a plurality of primary particles 3 are aggregated with each other, and a surface of the first composite oxide particles 1 (core material). and lithium tungstate 6 (6a and 6b) present on at least a part of the surface of the primary particles (3) (3a and 3b) positioned therein. The first composite oxide particles 1 have lithium tungstate 6 on the surface of the primary particles 3, so that when the positive electrode active material 10 is used in a secondary battery, high output is obtained and high charging and discharging. The capacity (hereinafter, sometimes referred to as "battery capacity") can be improved.

In general, when the surface of the lithium-nickel composite oxide particle is completely covered with a heterogeneous compound, the movement (intercalation) of lithium ions is greatly restricted, and as a result, the advantage of high capacity of the lithium-nickel composite oxide disappears. have.

On the other hand, the first composite oxide particle 1 used in the present embodiment has lithium tungstate (hereinafter referred to as "LWO compound" for lithium tungstate) on its surface and on the surface of internal primary particles 3 (3a and 3b). In some cases, it has (6). This LWO compound (6) has high lithium ion conductivity and has an effect of accelerating the movement of lithium ions. For this reason, 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) and the electrolytic solution, by forming a conduction path of Li, the reaction resistance of the positive electrode (hereinafter, sometimes referred to as “positive electrode resistance”) can be reduced. 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, when the voltage applied to the load side increases, lithium insertion and removal from the positive electrode are sufficiently performed, so that the battery capacity can be improved.

In addition, as in the prior art, when only the surface of the secondary particle of the lithium nickel composite oxide particle is coated with a layered material, the specific surface area decreases regardless of the coating thickness, so for example, the coating has high lithium ion conductivity. Even if it does, the contact area with electrolyte solution becomes small. In addition, when the layered material is formed only on the surface of the secondary particle, it tends to result in that the formation of the compound (layered product) is concentrated on the surface of the specific secondary particle. Therefore, when the layered material as a coating has high lithium ion conductivity, effects such as improvement of charge/discharge capacity and reduction of reaction resistance are acquired, but the effects are 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 electrolyte occurs on the surface of the primary particles 3 . Here, the surface of the primary particle 3 refers to the surface portion of the primary particle 3 that can be contacted by the electrolyte, for example, the primary particle exposed from the outer surface of the secondary particle (eg, the primary particle 3a). It includes the surface of the primary particle (eg, the primary particle 3b) that is exposed to the voids inside and near the surface of the secondary particle through which the electrolyte can permeate through the surface or the outside of the secondary particle 4 . In addition, the surface of the primary particles 3 includes, for example, the grain boundaries between the primary particles in which the primary particles are incompletely bonded and the electrolyte is in a permeable state.

When the positive electrode active material 10 is used in a secondary battery as described above, the contact between the first composite oxide particle 1 and the electrolyte solution is not only the outer surface of the secondary particle 4 formed by the aggregation of the primary particle 3 but also the secondary particle It also occurs in voids near and inside the surface of , or 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. The first composite oxide particle (1) is not only on the surface of the primary particle (3a) positioned on the surface of the secondary particle (4), but also on the surface of the primary particle (3b) positioned inside the secondary particle (4), LWO compound ( 6), the reaction resistance of the lithium-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 showing an example of the first composite oxide particle 1 (observation magnification 10000 times). If the LWO compound (6) contained in the first composite oxide particles (1) exists on the surface of the primary particles (3) (3a, 3b), the form thereof is not particularly limited. The LWO compound (6) is, for example, in the form of fine particles (6a, 6b) having a particle diameter of 1 nm or more and 500 nm or less, as shown in FIG. 2(A), on the surface of the primary particles (3) (3a, 3b). may exist in In the case of such a form, since the contact area with electrolyte solution is made sufficient and lithium ion conduction can be improved effectively, while improving charge/discharge capacity, positive electrode resistance can be reduced more effectively.

When the particle diameter of the LWO compound (fine particles) 6a, 6b is less than 1 nm, the fine particles 6a, 6b may not have sufficient lithium ion conductivity. In addition, when the particle diameter of the LWO compound (fine particle) (6a, 6b) exceeds 500 nm, the formation of the fine particle (LWO compound (6)) on the surface of the primary particle (3) (3a, 3b) is non-uniform. , and the effect of reducing the reaction resistance may not be sufficiently obtained. The particle size of the LWO compound (fine particles) (6a, 6b) is preferably from the viewpoint of obtaining a higher effect by uniformly distributing the fine particles of the LWO compound (6) on the surface of the primary particles (3) (3a, 3b). is 1 nm or more and 300 nm or less, and more preferably 5 nm or more and 200 nm or less.

In addition, the LWO compound (6) does not need to be completely formed on the entire surface of the primary particle surface, and may be in a dotted state. Even in a state in which the LWO compound (6) is dotted, if LWO is formed on the surface of the primary particle exposed inside and the outer surface of the lithium nickel composite oxide particle, the effect of reducing the reaction resistance is obtained. In addition, it is not necessary that all of the LWO compounds (fine particles) (6a, 6b) exist as fine particles with a particle diameter of 1 nm or more and 500 nm or less, and preferably the LWO compound (fine particles) (6a, 6b) formed on the surface of the primary particle. When 50% or more by number is formed in the particle diameter range of 1 nm or more and 500 nm or less, a high effect will be acquired.

The LWO compound (6) is present in a form in which the surface of the primary particles (3a, 3b) is coated with a thin film (film) (6c, 6d) formed of the LWO compound, for example, as shown in FIG. 2(B). You can do it. When such films 6c and 6d are formed, a conduction path of Li can be formed at the interface with the electrolyte while suppressing a decrease in specific surface area, and the effect of higher charge/discharge capacity improvement and reduction of reaction resistance is obtained

When the primary particle surface is covered with the coating films 6c and 6d, it is preferable to exist on the primary particle surface of the lithium metal composite oxide as a coating film having a thickness of 1 nm or more and 200 nm or less. In order to acquire the said higher effect, 1 nm or more and 150 nm or less are more preferable, and, as for a film thickness, 1 nm or more and 100 nm or less are still more preferable. When the film thickness of the thin films 6c and 6d is less than 1 nm, the 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, lithium ion conductivity may fall, and the effect higher than the reaction resistance reduction effect may not be acquired.

In addition, the films 6c and 6d may be formed on at least a part of the primary particles 3a and 3b, for example, may be partially formed on the surfaces of the primary particles 3a and 3b. In addition, the film thickness range of all the films 6c and 6d does not need to be 1 nm or more and 200 nm or less. For example, when the films 6c and 6d are formed on at least a part of the primary particle surface with the films 6c and 6d having a film thickness in the above range, a high effect can be obtained.

The LWO compound (6), for example, as shown in Fig. 2 (C), the form of the fine particles (6a, 6b) and the film of the film (6c, 6d) both forms coexist, even if present on the surface of the primary particles do. Also in this case, a high effect on battery characteristics can be obtained.

The properties of the primary particle surfaces 3 ( 3a , 3b ) of the first composite oxide particles 1 can be judged by observation with, for example, 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 has been confirmed that lithium tungstate is formed on the surface of the primary particles of the first composite oxide particles 1 .

The LWO compound (6) is not limited to those in which W and Li are in the form of lithium tungstate, and includes compounds containing W and Li. 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 , 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 at least one type selected from hydrates thereof is preferable. In the case of such lithium tungstate, lithium ion conductivity is further increased, and the effect of reducing the reaction resistance becomes larger.

The amount of tungsten contained in the LWO compound (6) is preferably 0.05 atomic % or more and 3.0 atomic % or less, based on the total number of atoms of Ni, Co, and M contained in the first composite oxide particle (1), 0.05 atomic % or more, and 0.05 atomic % or less % or more and 2.0 atomic% or less, more preferably 0.08 atomic% or more and 1.0 atomic% or less. When the amount of tungsten is within the above range, higher charge/discharge capacity and output characteristics can be made compatible. The amount of tungsten can be measured by IPC emission spectroscopy (ICP method).

When the amount of tungsten is less than 0.05 atomic%, 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 compound formed is excessively large, the lithium conduction between the lithium-nickel composite oxide and the electrolyte is inhibited, and the charge/discharge capacity may decrease.

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 (provided that 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) Consists of particles (8) and does not contain lithium tungstate. 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 as shown in FIG. 1B . When the first composite oxide particles (1) and the second composite oxide particles (2) are mixed, when the positive electrode active material 10 is used for the positive electrode of a secondary battery, high output is obtained and battery capacity can be improved have.

In general, when there is a non-uniformity in battery characteristics among the composite oxide particles constituting the positive electrode active material, a load is applied to a specific particle, which tends to cause deterioration of cycle characteristics and an increase in reaction resistance. In addition, it is considered that the content of the lithium-nickel composite oxide particles containing tungsten as in the first composite oxide particles 1 decreases is disadvantageous in improving the battery characteristics.

However, as a result of investigation by the present inventor, 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 containing tungsten Compared with the case of using (1) alone as a positive electrode active material, there is no decrease in battery characteristics such as output characteristics or battery capacity, or a very slight decrease even if there is a decrease, 2) having no LWO compound on the surface of the primary particles (7) It became clear that it was possible to improve battery characteristics compared with the case where the 2nd composite oxide particle 2 was independent.

Such improvement of battery characteristics is possible by mixing the first composite oxide particles 1, but in order to make this effect more sufficient, the amount of the first composite oxide particles 1 mixed in the positive electrode active material 10 is It is preferable that it is 10 mass % or more with respect to the positive electrode active material 10, and, as for a minimum, it is more preferable that it is 20 mass % or more.

On the other hand, the upper limit of the amount of the first composite oxide particles 1 is preferably 70 mass % or less, more preferably 60 mass % or less, and 50 mass % with respect to the positive electrode active material 10 from the viewpoint of suppressing the amount of tungsten used. It is more preferable that it is the following. When the content of the first composite oxide particles 1 in the positive electrode active material 10 increases, the battery characteristics become close to those in the case where the first composite oxide particles 1 are used alone, but from the viewpoint of suppressing the amount of tungsten, the first It is preferable that the quantity of the composite oxide particle 1 is small in the range from which the improvement of battery characteristics is obtained.

The amount of tungsten contained in the first composite oxide particle 1 (lithium tungstate) is preferably 0.03 atomic % or more and 2.5 atomic % or less with respect to the total number of atoms of Ni, Co and M contained in the positive electrode active material 10, It is more preferable that they are 0.05 atomic% or more and 1.5 atomic% or less, and it is still more preferable that they are 0.05 atomic% or more and 1.0 atomic% or less. The amount of tungsten is an indicator of the amount of lithium tungstate 6 present in that the positive electrode active material 10 has improved battery characteristics with lithium tungstate 6 . When the positive electrode active material 10 is used for a battery because the amount of tungsten is within the above range, sufficient battery characteristics can be obtained.

In the positive electrode active material 10, the amount of lithium contained in lithium compounds other than lithium tungstate existing on the surface of the primary particles of the first composite oxide particles 1 and the second composite oxide particles 2 (hereinafter, “excess lithium Amount") with respect to the whole amount of the positive electrode active material 10, Preferably it is 0.05 mass % or less, More preferably, it is 0.03 mass % or less. By limiting the amount of excess lithium to 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 existing on the surface of the primary particles 3 and 7 . As a lithium compound, lithium hydroxide, lithium carbonate, etc. are mentioned, for example. These lithium compounds have poor lithium conductivity and may inhibit movement of lithium ions from the lithium-nickel composite oxide material (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 increased, and the load on the lithium-nickel composite oxide during charging and discharging is reduced to further improve the output characteristics. Together with this, cycle characteristics can be further improved. In addition, by controlling the amount of excess 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 particles 1 and the second composite oxide particles 2 ). The mobility is also made uniform, the load applied to a specific lithium nickel composite oxide particle is suppressed, and the said effect can be heightened.

Moreover, although the lower limit of the amount of excess lithium is not specifically limited, From a viewpoint of suppressing the fall of battery characteristic, it is preferable that it is 0.01 mass % or more. An excessively small amount of excess lithium indicates that lithium is drawn out excessively from the crystals of the lithium-nickel composite oxide particles, and the battery characteristics are liable to decrease. In addition, the amount of excess lithium can be calculated by adding pure water to the positive electrode active material, stirring for a certain period of time, and analyzing the compound state of lithium eluted from the neutralization point that appears by adding hydrochloric acid while measuring the pH of the filtered filtrate. .

The positive electrode active material 10 has a sulfate radical (sulfuric acid group) content of preferably 0.05 mass% or less, more preferably 0.025 mass% or less, still more preferably 0.020 mass% or less. When the content of sulfuric acid groups in the positive electrode active material 10 exceeds 0.05% by mass, when constructing a battery, the negative electrode material has to be further used in the battery by an amount corresponding to the irreversible capacity of the positive electrode active material, and as a result, the weight of the battery as a whole In addition to a decrease in the capacity of sugar and per volume, excess lithium accumulated in the negative electrode as an irreversible capacity poses a problem also in terms of safety, which is not preferable. In addition, although the minimum of the sulfate radical content in the positive electrode active material 10 is although it does not specifically limit, For example, it is 0.001 mass % or more. Sulfate radical content can be calculated|required by converting the amount of S (element sulfur) measured by IPC emission spectroscopy (ICP method) into the amount of sulfate radicals (SO _{4 ).}

In addition, the amount of lithium in the positive electrode active material 10 as a whole (including the first composite oxide particles 1 and the second composite oxide particles 2) is the sum of the number of atoms of Ni, Co and M in the positive electrode active material (Me) and It is preferable that it is the range of 0.95 or more and 1.20 or less, and, as for ratio (Li/Me) of the number of atoms of Li, it is more preferable that it is the range of 0.97 or more and 1.15 or less. Since the reaction resistance of the positive electrode in the nonaqueous electrolyte secondary battery using the obtained positive electrode active material as Li/Me is less than 0.95 becomes large, the output of a battery will become low. Moreover, when Li/Me exceeds 1.20, while the initial stage discharge capacity of a positive electrode active material will fall, the reaction resistance of a positive electrode will also increase. 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 (provided that 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). As for Li/Me in the core material 5, it is more preferable that they are 0.95 or more and 1.15 or less, It is more preferable that they are 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. In addition, as a positive electrode active material, powder characteristics, such as a particle diameter and a tap density, just need to exist in the range of the positive electrode active material normally used.

In addition, the effect of providing lithium tungstate on the primary particle surface of the lithium nickel composite oxide particles is, for example, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel cobalt manganese composite oxide, etc. powder; In addition, it can be applied not only to the positive electrode active material disclosed in the present invention, but also to a generally used positive electrode active material for a lithium secondary battery.

(2) Manufacturing method of positive electrode active material for non-aqueous electrolyte secondary battery

As shown in FIG. 1B , the method for manufacturing the positive electrode active material 10 includes first lithium nickel composite oxide particles (first composite oxide particles) including lithium tungstate (LWO compound) 6 (1) and mixing the second lithium nickel composite oxide particles (second composite oxide particles) (2) not containing the LWO compound (6). 4 is a view showing an example of a method for manufacturing the first composite oxide particles 1 , and FIG. 5 is appropriately referred to when describing the method for manufacturing the first composite oxide particles 1 . In addition, the following description is an example of a manufacturing method, and does not limit a manufacturing method.

The first composite oxide particle 1 has a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ (provided that 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 core material 5 including secondary particles in which a plurality of primary particles are aggregated with each other, and a first composite It is composed of the LWO compound (6) present on the surface of the oxide particle 1 (core material) and at least a part of the surface of the primary particle 3 positioned therein. The manufacturing method of the 1st composite oxide particle 1 should just be what makes lithium tungstate exist on the surface, and a conventionally well-known manufacturing method can be used. Hereinafter, an example of a manufacturing method of the first composite oxide particle 1 will be described with reference to FIGS. 4 and 5 .

In the preparation of the first composite oxide particles 1, as shown in FIG. 4A, first, the composition is Li _z3 Ni _{1 -x3- y3} Co _x3 M ¹ _y3 O ₂ (provided that 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 plurality of primary particles are aggregated to form A tungsten-coated base material containing secondary particles (hereinafter, simply referred to as "base material"), a tungsten mixture containing 2 mass % or more of water and a tungsten compound with respect to the total amount of the base material is adjusted. From the viewpoints of high capacity and high safety, it is preferable to set 0.01≤x3≤0.10, 0.01≤y3≤0.05, and 0.97≤z3≤1.05.

The tungsten mixture contains 2 mass % or more of water with respect to the total amount of the base material. Thereby, tungsten in the tungsten compound with moisture penetrates into the voids between the primary particles communicating with the outside of the secondary particles (base material) or in the grain boundaries between incomplete primary particles, so that a sufficient amount of tungsten can be dispersed on the surface of the primary particles. . Although the upper limit of the quantity of water is not specifically limited, For example, it is 20 mass % or less. When the moisture content is excessively large, the heat treatment efficiency of the subsequent process decreases or the elution of lithium from the lithium metal composite oxide particles (base material) increases, so that the molar ratio of eluted Li in the tungsten mixture becomes excessively high Battery characteristics may deteriorate when used for the positive electrode of

The amount of moisture relative to the total amount of the base material is preferably 2 mass% or more and 20 mass% or less, more preferably 3 mass% or more and 15 mass% or less, and still more preferably 3 mass% or more and 10 mass% or less. When the amount of moisture is within the above range, the pH increases due to the lithium content eluted in the moisture, thereby exhibiting the effect of suppressing the elution of excess lithium. In addition, the amount of moisture in the tungsten mixture can be easily controlled within the above range by washing the base material with water and separating the solid-liquid as will be described later. In addition, the molar ratio of Ni, Co, and M ^{1 in} the base material powder is maintained until the first composite oxide particles 1 (core material 5).

The tungsten compound is a compound containing tungsten (W), and preferably has water solubility enough to dissolve in water contained in the tungsten mixture. When the tungsten compound is water-soluble, tungsten (W) can sufficiently penetrate to the surface of the primary particle inside the secondary particle (base material). The state of a solid may be sufficient as a tungsten compound, for example, and the state of aqueous solution may be sufficient as it. When the tungsten compound is in the state of an aqueous solution, the tungsten compound (aqueous solution) may be in an amount capable of penetrating to the surface of the primary particles inside the secondary particles (base material), and a part of the aqueous solution may contain a solid state. Moreover, even if it is difficult to dissolve a tungsten compound in water at normal temperature, what is necessary is just a compound which melt|dissolves in water by the heating at the time of heat processing. Moreover, since the water|moisture content in a tungsten mixture becomes alkaline with lithium contained in a base material, a tungsten compound may be a compound soluble in alkalinity.

Although it will not specifically limit as long as it is a compound soluble in water as a tungsten compound, For example, tungsten oxide, tungstic acid, lithium tungstate, ammonium tungstate, sodium tungstate, etc. are mentioned. Among these, tungsten oxide, tungstic acid, lithium tungstate, and ammonium tungstate are more preferable from the viewpoint of low possibility of impurity mixing, and tungsten oxide (WO ₃ ), tungstic acid (WO ₃ •H ₂ O), tungsten Lithium acid (Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ W ₂ O ₉ ) is more preferred. A tungsten compound may be used 1 type, and may be used in combination of 2 or more type.

The upper limit of the molar ratio (hereinafter referred to as "Li molar ratio") of the total amount of lithium (Li) contained in moisture and tungsten compound, or moisture and tungsten compound and lithium compound to the amount of tungsten (W) contained in the tungsten mixture is, Preferably it is 5.0 or less, More preferably, it is less than 4.5, More preferably, it is 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 output characteristics, and improve 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 still more preferably 1.5 or more. Lithium, calculated as the Li molar ratio in the tungsten mixture, forms tungsten (W) derived from a tungsten compound and lithium tungstate during subsequent heat treatment. At least a part of lithium can be made into lithium derived from a 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, lithium extracted from the base material to form lithium tungstate increases too much, and the battery characteristics of the first composite oxide particles may be deteriorated.

The amount of tungsten contained in the tungsten mixture is preferably 0.05 atomic % or more and 3.0 atomic % or less, more preferably 0.05 atomic % or more and 2.0 atomic % or less, with respect to the total number of atoms of Ni, Co and M contained in the base material. Preferably it is 0.08 atomic% or more and 1.0 atomic% or less. When the amount of tungsten is within the above range, the amount of tungsten contained in lithium tungstate in the first composite oxide particles 1 can be made into a preferable range, and when the positive electrode active material 1 is used for a secondary battery, high charge and discharge Capacitance and output characteristics can be reconciled at a higher level.

In addition, when adjusting the above tungsten mixture, moisture may be supplied and mixed with the tungsten compound so that the moisture of the tungsten mixture is 2% by mass or more, or an aqueous solution of the tungsten compound or the tungsten compound and water may be supplied separately.

In addition, 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 excess lithium). lithium derived from it. Further, as shown in Fig. 4B, the tungsten mixture may contain a lithium compound containing no tungsten in addition to the base material, moisture, and the tungsten compound. This lithium compound can be used as a lithium source for forming lithium tungstate. As a lithium compound which does not contain tungsten, water-soluble compounds, such as lithium hydroxide, are mentioned.

5 is a view showing an example of a method for adjusting the tungsten mixture obtained in the manufacturing process of the first composite oxide particles 1 . As shown in FIG. 5 , the lithium-nickel composite oxide particles serving as the base material may be washed with water before the tungsten mixture is prepared. Water washing can be performed by mixing the base material with water and forming a slurry. When the base material is washed with water, it is possible to remove impurity elements such as unreacted lithium compounds and sulfate radicals that are excessively present 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. In general, an unreacted lithium compound is present on the surface of secondary particles or primary particles in a metal composite hydroxide or a lithium metal composite oxide obtained by calcining a metal composite oxide and a lithium compound. Lithium (Li) derived from an unreacted lithium compound contained in the base material is eluted in the added moisture when the tungsten mixture is prepared. When the amount of lithium eluted in water is excessively large, it may be difficult to control the upper limit of the Li molar ratio within the above range.

In addition, in order to adjust the water content, the water-washed base material may solid-liquid-separate after water washing. When the base material is separated into solid and liquid, the amount of moisture contained in the tungsten mixture can be easily adjusted.

Conditions for washing with water by slurrying the base material are not particularly limited as long as unreacted lithium compounds 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. In addition, the amount of unreacted lithium compound contained in a base material can be measured by the method similar to the amount of excess lithium in the positive electrode active material (1).

Water washing by slurrying is performed, for example by mixing and stirring the base material powder and water. 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 deterioration due to the elution of lithium from the base material.

Water washing time can be made into about 5 minutes or more and 60 minutes or less, for example. When water washing time is this range, the amount of unreacted lithium compound contained in a base material can fully be reduced. Water washing temperature can be made into the range of 10 degreeC or more and 40 degrees C or less. When water washing temperature is this range, the amount of unreacted lithium compound contained in a base material can fully be reduced.

When washing the base material with water, if the tungsten mixture as described above is obtained, the procedure for adding the tungsten compound is not particularly limited. For example, as shown in FIG. 5A , the tungsten mixture (including the base material) may be washed with water after the tungsten mixture is prepared by mixing the base material and the tungsten compound. In this case, since the tungsten compound is washed away by water washing, the amount of tungsten in the tungsten mixture may become insufficient. For this reason, for example, as shown in FIGS. 5(B) and (C), it is preferable to add a tungsten compound during the process of washing the base material with water or in at least one process after the solid-liquid separation process to obtain a tungsten mixture. do.

When the tungsten compound is added in the water washing step, the tungsten compound may be added to the water mixed with the base material (powder) in advance to make an aqueous solution or suspension, or after mixing the base material and water to form a slurry, the tungsten compound may be added to the slurry do.

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 does not contain lithium or a compound that is completely soluble in the slurry at the time of washing the tungsten compound. Examples of the tungsten compound dissolved in the slurry and containing lithium include lithium tungstate (Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ W ₂ O ₉ ). , for example _{, tungsten oxide (WO 3} ), tungstic acid (WO ₃ ·H ₂ O). By using these tungsten compounds, the amount of lithium contained in the solid tungsten compound in the tungsten mixture is not affected, and the amount of lithium in the tungsten mixture can be easily controlled.

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

When adding a tungsten compound during a water washing process, either the state of an aqueous solution or a powder state may be sufficient as a tungsten compound. A uniform mixture is obtained by adding a tungsten compound to the slurry and stirring.

In addition, when an aqueous solution or a water-soluble compound is used for the tungsten compound to be used, most of the tungsten compound dissolved in the slurry in the solid-liquid separation step after washing with water is removed together with the liquid component of the slurry. However, the amount of tungsten in the tungsten mixture can be made sufficient by the tungsten dissolved in the moisture in the tungsten mixture. Since the amount of tungsten in the tungsten mixture becomes stable along with the water content under the conditions of washing with water and solid-liquid separation, these conditions can be determined together with the type and amount of tungsten compound added by a preliminary test. The total amount of lithium contained in the water and the tungsten compound in the tungsten mixture (hereinafter referred to as the total lithium amount) can also be determined by a preliminary test similarly to the amount of tungsten.

In addition, the amount of tungsten in the mixture when a tungsten compound is added in a water washing process can be calculated|required by ICP emission spectroscopy. In addition, the amount of lithium contained in the water|moisture content which comprises a mixture can be calculated|required from the analysis value of lithium by ICP emission spectroscopy in the liquid component separated into solid-liquid after water washing, and the water content.

In addition, the amount of lithium contained in the solid tungsten compound constituting the tungsten mixture is determined by adding the tungsten compound to an aqueous lithium hydroxide solution having the same concentration as the liquid component after washing with water and stirring under the same conditions as when washing with water. The ratio of the remaining tungsten compound By calculating the amount remaining as a solid in the tungsten mixture, it can be obtained from the remaining tungsten compound as a solid.

In addition, the amount of tungsten in the mixture when a tungsten compound is added after a solid-liquid separation process can be calculated|required from the amount of tungsten compounds added.

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

When adding the tungsten compound as an aqueous solution after the solid-liquid separation step, the water content preferably does not exceed 20% by mass as described above, so it is necessary to adjust the aqueous solution, and the tungsten concentration is 0.05 mol/L or more and 2 mol/ It is preferable to set it as L or less. When the tungsten concentration is within the above range, a required amount of tungsten can be added while suppressing moisture in the tungsten mixture. When the moisture content exceeds 20% by mass, the moisture may be again subjected to solid-liquid separation to adjust the moisture.

In order to make the water content contained in a tungsten mixture 2 mass % or more, it is preferable to perform mixing after solid-liquid separation at the temperature of 50 degrees C or less. When the temperature exceeds 50°C, the moisture content may be less than 2% by mass due to drying during mixing.

Mixing with the tungsten compound is not limited as long as it is an apparatus capable of uniformly mixing, and a general mixer can be used. For example, by using a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, or the like, the tungsten compound may be sufficiently mixed with the tungsten compound so as not to destroy the shape of the lithium metal composite oxide particles.

The component composition of the first composite oxide particles 1 is composed of composite oxide particles used as a base material, tungsten to be added and increased in the adjustment step, and lithium powder added as necessary. For this reason, the base material has a composition of the general formula Li _z Ni _{1 -x- y} Co _x M _y O ₂ (provided that 0 <x≤0.35, 0≤y≤0.35, 0.95≤z in terms of high capacity and low reaction resistance) ?

On the other hand, when washing the base material with water, Li/Me (corresponding to z in the general formula) in the base material decreases due to lithium elution at the time of washing. A base material adjusted with Li/Me can be used. The reduction of Li/Me due to general water washing conditions is about 0.03 to 0.08. In addition, even when moisture is supplied in the mixing process, lithium is eluted in a small amount. Therefore, when washing with water, it is preferable that z representing Li/Me of the base material before washing with water is 0.95≤z≤1.20, and more preferably 0.97≤z≤1.15.

In addition, since increasing the contact area with the electrolyte is advantageous in improving the output characteristics, it is composed of primary particles and secondary particles formed by aggregation of primary particles, and lithium metal composite having pores and grain boundaries through which the electrolyte can penetrate the secondary particles It is preferred to use an oxide powder.

In addition, 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, using a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, an air blender, etc., it is sufficient to mix enough so that the mold of the tungsten-coated base material is not destroyed. In addition, since excess Li contained in the base material adsorbs carbon dioxide to form lithium carbonate and causes gas generation, the mixed atmosphere is preferably performed at a carbon dioxide concentration of 0 to 100 ppm.

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

The heat treatment conditions are 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 a reaction with moisture or carbonic acid in the atmosphere, an oxidizing atmosphere such as an oxygen atmosphere, or vacuum This can be done in an atmosphere.

Moreover, as heat processing temperature, it is preferable to heat-process at the temperature of 100 degreeC or more and 600 degrees C or less from a viewpoint of preventing deterioration of the electrical characteristic when the positive electrode active material 10 is used for a secondary battery. When the heat treatment temperature is less than 100° C., evaporation of moisture is not sufficient, and the LWO compound (6) may not be sufficiently formed. On the other hand, when the heat treatment temperature exceeds 600 ° C, the primary particles of the lithium metal composite oxide cause sintering and some tungsten is dissolved in the layered structure of the lithium metal composite oxide, so when the charge/discharge capacity of the battery decreases there is

On the other hand, when the tungsten compound contained in the tungsten mixture is not dissolved in water and remains as a solid, especially when the tungsten compound is added as a powder after the solid-liquid separation step, while the solid is sufficiently dissolved, for example For example, it is preferable to set the temperature increase rate to 0.8 to 1.2°C/min until it exceeds 90°C. Even in the process of adjusting the tungsten mixture, the powder of the tungsten compound is dissolved in the water contained in the mixture, but by setting the temperature at such a rate of temperature increase, the solid tungsten compound is sufficiently dissolved during the temperature increase to penetrate to the surface of the primary particles inside the secondary particles. can In addition, in the case of dissolving the solid tungsten compound, it is preferable to heat treatment in a sealed container so that moisture does not volatilize while the dissolution is sufficiently performed.

The heat treatment time is not particularly limited, but from the viewpoint of sufficiently evaporating the moisture in the tungsten mixture to form the LWO compound (6), it is preferably set to 3 hours or more and 20 hours or less, and more preferably 5 hours or more and 15 hours or less. do.

The heat treatment is performed by reacting a lithium compound and a tungsten compound present on the surface of the primary particle of the base material to dissolve the tungsten compound, and performing a first heat treatment to disperse tungsten on the surface of the primary particle, and after the first heat treatment, the temperature of the first heat treatment It is preferable to include performing a second heat treatment to form a lithium tungstate compound on the surface of the primary particles of the lithium nickel composite oxide particles by heat treatment at a higher temperature.

In the first heat treatment, by heating the tungsten mixture containing the tungsten compound, not only the 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 and dissolves. Thereby, excess lithium in the obtained tungsten-coated composite oxide particle can be significantly reduced, and battery characteristics can be improved. Furthermore, it also has the effect of drawing out lithium that is excessively present in the base material, and the drawn lithium reacts with the tungsten compound to contribute to the improvement of crystallinity when it becomes tungsten-coated composite oxide particles, and to make the battery characteristics higher can By the first heat treatment, tungsten is sufficiently dissolved in the moisture in the tungsten mixture, penetrates to the voids between the primary particles inside the secondary particles of the base material or to incomplete grain boundaries, so that tungsten can be dispersed on the surface of the primary particles.

In the first heat treatment, the heat treatment temperature is preferably 60 to 80°C. When the heat treatment temperature is within this range, the reaction proceeds sufficiently, and moisture may remain until tungsten penetrates, and the lithium compound and the tungsten compound are reacted to sufficiently disperse tungsten on the surface of the primary particles. When the first heat treatment temperature is less than 60° C., the reaction between the lithium compound and the tungsten compound present 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., since the evaporation of moisture is too fast, the reaction between the lithium compound and the tungsten compound present on the surface of the primary particles and the penetration of tungsten may not proceed sufficiently.

Although the heating time in the 1st heat treatment is not specifically limited, In order that a lithium compound and a tungsten compound may react and tungsten may fully permeate, it is preferable to set it as 0.5 to 2 hours.

In the second heat treatment, the heat treatment is performed at a temperature higher than the heat treatment temperature of the first heat treatment to sufficiently evaporate moisture in the mixture to form a lithium tungstate compound on the surface of the primary particles of the lithium nickel composite oxide particles.

It is preferable that the heat processing temperature of 2nd heat processing shall be 100 degreeC or more and 200 degrees C or less. When the second heat treatment temperature is less than 100°C, the evaporation of moisture is not sufficient, and the lithium tungstate compound may not be sufficiently formed. On the other hand, when the second heat treatment temperature exceeds 200 ° C., the lithium nickel composite oxide particles form necking with each other via lithium tungstate, or the specific surface area of the lithium nickel composite oxide particles is greatly reduced. there is

Although the heat treatment time of the second heat treatment is not particularly limited, in order to sufficiently evaporate moisture to form a lithium tungstate compound, it is preferably set to 1 to 15 hours, and is preferably set to 5 to 12 hours.

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

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 particles 2 obtained by the above method. The method for producing the second composite oxide particles 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 water washing of the base material of the first composite oxide particles 1 described above can be used. When the second composite oxide particles are washed with water, unreacted lithium compounds such as excess lithium hydroxide and lithium carbonate, sulfate radicals, and other impurity elements that deteriorate battery characteristics can be removed.

The mixing ratio of the first composite oxide particles (1) and the second composite oxide particles (2) is such 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 oxide particles (2). In addition, the first composite oxide particles ( It is preferable to mix 1) with the second composite oxide particles (2). Thereby, higher charge/discharge capacity and output characteristics can be made compatible.

When mixing the first composite oxide particles 1 and the second composite oxide particles 2, a general mixer can be used. For example, using a shaker mixer, a Loedige mixer, a Julia mixer, a V blender, an air blender, etc., it is sufficient to mix enough so that the mold of the tungsten-coated base material is not destroyed.

2. Non-aqueous electrolyte secondary battery

The non-aqueous electrolyte secondary battery of this embodiment contains a positive electrode, a negative electrode, a non-aqueous electrolyte, etc., and is comprised by the same component as a general non-aqueous electrolyte secondary battery. In addition, the embodiment described below is merely an illustration, and the non-aqueous electrolyte secondary battery of the present invention is implemented in an embodiment in which various changes and improvements are implemented based on the knowledge of those skilled in the art based on the embodiment described in this specification can do. In addition, 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 nonaqueous electrolyte secondary batteries demonstrated previously, for example, as follows, the positive electrode of a nonaqueous electrolyte secondary battery is produced.

First, a powdery positive electrode active material, a conductive material, and a binder are mixed, and, if necessary, activated carbon and a solvent for purposes such as viscosity adjustment are added, and the mixture is kneaded to prepare a positive electrode mixture paste.

Each mixing ratio in the positive electrode mixture paste also becomes an important factor in determining the performance of the non-aqueous electrolyte secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, similarly to the positive electrode of a general non-aqueous electrolyte secondary battery, the content of the positive electrode active material is 60 to 95 parts by mass, and the content of the conductive material is 1 to 20 parts by mass. And it is preferable to make content of a binder into 1-20 mass parts.

The obtained positive electrode mixture paste is apply|coated to the surface of the electrical power collector made from an aluminum foil, for example, and it is dried, and the solvent is dispersed. If necessary, in order to increase the electrode density, pressurization may be performed by roll press or the like. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut to an appropriate size depending on the intended battery, and used for production of the battery. However, the manufacturing method of a positive electrode is not limited to the thing of an illustration, Another method may be used.

In the production of the positive electrode, as the conductive agent, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), acetylene black, carbon black-based materials such as Ketjen Black (registered trademark), etc. can be used.

The binder serves to connect the active material particles, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylenepropylenediene rubber, styrene-butadiene, cellulose-based resin, polyacrylic acid etc. can be used.

Further, if necessary, the positive electrode active material, the conductive material, and the activated carbon are dispersed, and a solvent for dissolving 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. In addition, 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 obtained by mixing metallic lithium or lithium alloy, or a negative electrode active material capable of occluding and deintercalating 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 such as copper. It is applied, dried, and compressed to increase the electrode density if necessary.

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

(c) separator

A separator is sandwiched between the positive electrode and the negative electrode.

The separator separates the positive electrode and the negative electrode, holds the electrolyte, and is a thin film such as polyethylene or polypropylene, and a film having many micropores can be used.

(d) non-aqueous electrolyte

The non-aqueous electrolyte solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.

Examples of the organic solvent to be used include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; furthermore, diethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate. Chain carbonates such as carbonate and dipropyl carbonate, ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, triethyl phosphate , and a phosphorus compound such as trioctyl phosphate may be used alone or in mixture of two or more.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN(CF ₃ SO ₂ ) _{2 ,} etc. and their complex salts can be used.

Moreover, the non-aqueous electrolyte solution may contain the radical scavenger, surfactant, a flame retardant, etc.

(e) shape and configuration of the 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 described above can be various, such as a cylindrical shape and a stacked type.

In any shape, 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 electrolyte solution, and between the positive electrode current collector and the external positive electrode terminal and the negative electrode current collector A non-aqueous electrolyte secondary battery is completed by connecting a negative electrode terminal that communicates with the outside using a current collector lead or the like, and sealing it in a battery case.

(f) characteristics

The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention has a 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 preferred form, for example, when used for the positive electrode of a 2032 type coin battery, has a high initial discharge capacity of 165 mAh/g or more and a low positive electrode resistance. obtained, with a higher capacity and higher output. Moreover, it can be said that thermal stability is high and it is excellent also in safety|security.

In addition, if the measuring method of the positive electrode resistance in this invention is illustrated, it becomes as follows.

As an electrochemical evaluation method, when the frequency dependence of the battery reaction is measured by a general AC impedance method, a Nyquist diagram based on solution resistance, negative electrode resistance and negative electrode capacity, and positive electrode resistance and positive electrode capacity is obtained as shown in FIG. .

The battery reaction in the electrode includes a resistance component accompanying charge transfer and a capacitance component due to an electric double layer, and when these are expressed as an electric circuit, a parallel circuit of resistance and capacity is obtained. It is expressed as an equivalent circuit in which circuits are connected in series.

Each resistance component and capacitance component can be estimated by performing a fitting calculation with respect to the Nyquist diagram measured using this equivalent circuit.

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, the positive electrode resistance can be estimated by performing AC impedance measurement on the produced positive electrode, and performing fitting calculation with an equivalent circuit with respect to the obtained Nyquist diagram.

[Example]

Hereinafter, although it demonstrates concretely using the Example of this invention, this invention is not limited at all by these Examples.

About the secondary battery which has a positive electrode using the positive electrode active material obtained by this invention, the performance (initial discharge capacity, positive electrode resistance, cycling characteristics) was measured.

Hereinafter, although it demonstrates concretely using the Example of this invention, this invention is not limited by these Examples at all.

(Manufacturing and evaluation of batteries)

For evaluation of the positive electrode active material, a 2032-type coin battery (CBA) (hereinafter referred to as a coin-type battery) shown in FIG. 7 was used. As shown in FIG. 7, the coin-type battery CBA is comprised by the electrode EL and the case CA which accommodates this electrode EL inside. The electrode EL includes a positive electrode PE, a separator SE1, and a negative electrode NE, and is stacked so as to be arranged in this order, and the positive electrode PE is in contact with the inner surface of the positive electrode can PC, and the negative electrode NE is accommodated in the case CA so as to contact the inner surface of the negative electrode can NC.

The case CA has a hollow positive electrode can PC having an open one end, and a negative electrode can NC disposed in an opening of the positive electrode can PC, and the negative electrode can NC is connected to the positive electrode can PC. ), a space for accommodating the electrode EL is formed between the negative electrode can NC and the positive electrode can PC. The case CA is provided with the gasket GA, and the relative movement is fixed by this gasket GA so that the non-contact state between the positive electrode can PC and the negative electrode can NC may be maintained. In addition, the gasket GA also has a function of sealing the gap between the positive electrode can PC and the negative electrode can NC to seal the airtight and liquid-tight barrier between the inside and the outside of the case CA.

The coin-type battery (CBA) was produced 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) are mixed, and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa, the positive electrode ( PE) was produced. The produced positive electrode (PE) was dried at 120 degreeC in a vacuum dryer for 12 hours. Using this positive electrode (PE), negative electrode (NE), separator (SE1), and electrolyte solution, a coin-type battery (CBA) was produced in a glove box in an Ar atmosphere in which the dew point was controlled at -80°C.

Note that, for the negative electrode NE, a negative electrode sheet in which a graphite powder having an average particle diameter of about 20 μm and polyvinylidene fluoride punched out into a disk shape with a diameter of 14 mm and polyvinylidene fluoride was applied to a copper foil was used. A polyethylene porous film with a film thickness of 25 µm was used for the separator SE1. As the electrolyte solution, an equal amount mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using _{1M LiClO 4 as a supporting electrolyte (manufactured by Tomiyama Yakuhin Kogyo Co., Ltd.) was used.}

The initial discharge capacity and positive electrode resistance which show the performance of the manufactured coin-type battery (CBA) were evaluated as follows. The initial discharge capacity is left for about 24 hours after the coin-type battery (CBA) is manufactured, and after the open circuit voltage (OCV) is stabilized, the current density for the positive electrode is 0.1 mA/cm2 and the cut-off voltage is 4.3V. The capacity at the time of charging and discharging to a cut-off voltage of 3.0 V after a pause of 1 hour was taken as the initial discharge capacity.

When the positive electrode resistance is measured by the AC impedance method using a frequency response analyzer and a potentio galvanostat (manufactured by Solartron, 1255B) by charging a coin-type battery (CBA) to a charging potential of 4.1 V, the age shown in FIG. A quist plot is obtained. Since this Nyquist plot is expressed as the sum of the characteristic curves indicating solution resistance, negative electrode resistance and its capacity, and positive electrode resistance and its capacity, fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and positive electrode The value of the resistance was calculated. In addition, the positive electrode resistance computed the relative value which made Comparative Example 1 "1.00".

In addition, in this Example, each sample of Wako Junyaku Kogyo Co., Ltd. reagent grade was used for manufacture of a composite hydroxide, a positive electrode active material, and a secondary battery.

(Example 1)

[Production of positive electrode active material]

(Preparation of first composite oxide particles)

_{Li 1} obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and calcined _{. 020} Ni _{0 . 91} Co _{0 . 06} Al _{0 .} The powder of lithium-nickel composite oxide particles represented by ₀₃ O _{2 was used as the base material.} After adding 500 mL of 25 degreeC pure water to a 500 g base material, and setting it as a slurry, stirring was performed for 15 minutes, and it washed with water. The slurry after water washing was filtered using a Nutchet, and solid-liquid separation was carried out. The water content of the obtained washing|cleaning cake was 8.5 mass %.

_{3.58 g of tungsten oxide (WO 3} ) was added to the washing cake so that the amount of W was 0.30 atomic % with respect to the total number of atoms of Ni, Co and Al contained in the base material, and a shaker mixer (Willi A. Bacofen (WAB)) A tungsten mixture was obtained by sufficiently mixing using TURBULA Type T2C (manufactured by TURBULA).

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 bag made of aluminum, transferred to a container made of SUS, and left still drying (heat treatment) for 10 hours using a vacuum dryer heated to 190°C, followed by furnace cooling.

Lithium nickel composite oxide particles (first composite oxide particles) having a lithium tungstate compound on the surface of primary particles of a core material (base material) were obtained by pulverizing the obtained dried tungsten mixture through a sieve of 38 μm. It was confirmed that the amount of excess lithium (the amount of Li contained in lithium compounds other than lithium tungstate) of the obtained first composite oxide particles was 0.05 mass % or less.

(Preparation of second composite oxide particles)

_{Li 1} obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and calcined _{. 020} Ni _{0 . 91} Co _{0 . 06} Al _{0 . To} 500 g of powder of lithium nickel composite oxide particles represented by 03 O ₂ , 667 mL of pure water at 25° C. was added to make a slurry, washed with water for 15 minutes, separated from solid and liquid, and dried to obtain second composite oxide particles. It was confirmed that the obtained second composite oxide particles had an excess lithium content of 0.05 mass % or less.

(Mixing of the first composite oxide particles and the 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) not containing a lithium tungstate compound was added, and a shaker mixer (Willi A. Bacofen (WAB)) TURBULA TypeT2C manufactured by the company) 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 atoms of Ni, Co and Al. Moreover, it was confirmed that the sulfate radical content of the obtained positive electrode active material was 0.05 mass % or less.

[Analysis of surplus lithium]

The excess lithium of the obtained positive electrode active material was evaluated by titrating Li eluted from the positive electrode active material. After adding 10 ml of pure water to 1 g of the obtained positive electrode active material, stirring for 1 minute, measuring the pH of the filtered filtrate while adding hydrochloric acid, the compound state of lithium eluted from the neutralization point was analyzed, and the amount of excess lithium was evaluated. The amount of excess 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) which has a positive electrode produced using the obtained positive electrode active material were evaluated. In addition, as for the positive electrode resistance, the relative value which made Comparative Example 1 "1.00" was made into the evaluation value. The initial discharge capacity was 213.1 mAh/g.

Hereinafter, only the substances and conditions changed from Comparative Example 1 are shown for Examples and Comparative Examples. In addition, the evaluation values of the initial discharge capacity and positive electrode resistance of an Example and a comparative example are shown in Table 1 and Table 2 together.

(Example 2)

Example 1 except that 5.37 g of _{tungsten oxide (WO 3} ) was added to the cleaning cake so that the amount of W was 0.45 atomic % with respect to the total number of atoms of Ni, Co and Al contained in the lithium nickel composite oxide (base material) In the same manner as described above, the mixture was sufficiently mixed using a shaker mixer device (TURBULA Type T2C manufactured by Willy A. Barcofen (WAB)) to obtain a tungsten mixture.

The resulting 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, transferred to a container made of SUS, and it left still drying using the vacuum dryer heated to 190 degreeC for 10 hours, and furnace-cooled after that.

The obtained dried tungsten mixture was pulverized by sieving through a sieve having an eye size of 38 µm to obtain a lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the primary particle surface of the core material (base material). To 300 g of the obtained complex oxide (first complex oxide), 600 g of a lithium nickel complex oxide (second complex oxide particles) not containing a lithium tungstate compound obtained in the same manner as in Example 1 was added, followed by a shaker mixer (Willi A. Bacofen ( The mixture was sufficiently mixed using TURBULA Type T2C) manufactured by WAB) 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 atoms of Ni, Co and Al.

(Example 3)

Example 1 except that 8.98 g of _{tungsten oxide (WO 3} ) was added to the cleaning cake so that the amount of W was 0.75 atomic % with respect to the total number of atoms of Ni, Co and Al contained in the lithium nickel composite oxide (base material) In the same manner as described above, the mixture was sufficiently mixed using a shaker mixer device (TURBULA Type T2C manufactured by Willy A. Barcofen (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, transferred to a container made of SUS, and it left still drying using the vacuum dryer heated to 190 degreeC for 10 hours, and furnace-cooled after that.

Lithium-nickel composite oxide (first composite oxide) having a lithium tungstate compound obtained in the same manner as in Example 1 on the surface of primary particles of a core material (base material) by pulverizing the obtained dried tungsten mixture through a sieve 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 particles) not containing a lithium tungstate compound was added, and a shaker mixer (TURBULA TypeT2C manufactured by Willie A. Bacofen (WAB)) was stirred. It used and 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 atoms of Ni, Co and Al.

(Example 4)

667 mL of 25 degreeC pure water was added to a 500-g base material, it was set as the slurry, and water washing for 15 minutes was performed. After washing with water, solid-liquid separation was performed by filtration using a Nutche. The moisture content of the washing cake was 8.5% by mass.

4.04 g of _{lithium tungstate (LWO:Li 2} WO ₄ ) is added to the cleaning cake so that the amount of W is 0.30 atomic % with respect to the total number of atoms of Ni, Co and Al contained in the lithium nickel composite oxide (base material), It thoroughly mixed using a shaker mixer apparatus (TURBULA TypeT2C manufactured by Willy A. Barcofen (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, transferred to a container made of SUS, and it left still drying using the vacuum dryer heated to 190 degreeC for 10 hours, and furnace-cooled after that.

The obtained dried tungsten mixture was pulverized by sieving through a sieve having an eye size of 38 µm to obtain a lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the primary particle surface of the core material (base material).

To 300 g of the obtained complex oxide (first complex oxide), 300 g of a lithium nickel complex oxide (second complex oxide particles) not containing a lithium tungstate compound obtained in the same manner as in Example 1 was added, followed by a shaker mixer (Willi A. Bacofen) (TURBULA Type T2C manufactured by (WAB)) was sufficiently 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 atoms of Ni, Co and Al.

(Example 5)

667 mL of 25 degreeC pure water was added to a 500-g base material, it was set as the slurry, and water washing for 15 minutes was performed. After washing with water, solid-liquid separation was performed by filtration using a Nutche. The moisture content of the washing cake was 8.5% by mass.

6.06 g of _{lithium tungstate (LWO:Li 2} WO ₄ ) is added to the cleaning cake so that the amount of W is 0.45 atomic% based on the total number of atoms of Ni, Co and Al contained in the lithium nickel composite oxide (base material), It thoroughly mixed using a shaker mixer apparatus (TURBULA TypeT2C manufactured by Willy A. Barcofen (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, transferred to a container made of SUS, and it left still drying using the vacuum dryer heated to 190 degreeC for 10 hours, and furnace-cooled after that.

The obtained dried tungsten mixture was pulverized by sieving through a sieve having an eye size of 38 µm to obtain a lithium nickel composite oxide having a lithium tungstate compound (first composite oxide) on the primary particle surface of the core material (base material).

To 300 g of the obtained composite oxide (first composite oxide), 600 g of a lithium nickel composite oxide (second composite oxide) not containing a lithium tungstate compound obtained in the same manner as in Example 1 was added, followed by a shaker mixer (Willi A. Bacofen (WAB) ) manufactured by TURBULA Type T2C) 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 atoms of Ni, Co and Al.

(Example 6)

667 mL of 25 degreeC pure water was added to a 500-g base material, it was set as the slurry, and water washing for 15 minutes was performed. After washing with water, solid-liquid separation was performed by filtration using a Nutche. The moisture content of the washing cake was 8.5% by mass.

10.14 g of _{lithium tungstate (LWO:Li 2} WO ₄ ) is added to the cleaning cake so that the amount of W is 0.75 atomic% with respect to the total number of atoms of Ni, Co and Al contained in the lithium nickel composite oxide (base material), It thoroughly mixed using a shaker mixer apparatus (TURBULA TypeT2C manufactured by Willy A. Barcofen (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, transferred to a container made of SUS, and it left still drying using the vacuum dryer heated to 190 degreeC for 10 hours, and furnace-cooled after that.

The obtained dried tungsten mixture was pulverized by sieving through a sieve having an eye size of 38 µm to obtain a lithium nickel composite oxide having a lithium tungstate compound (first composite oxide) on the primary particle surface of the core material (base material).

To 300 g of the obtained complex oxide (first complex oxide), 1200 g of a lithium nickel complex oxide (second complex oxide) not containing a lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer (Willi A. Bacofen (WAB) ) manufactured by TURBULA Type T2C) was sufficiently 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 atoms of Ni, Co and Al.

(Comparative Example 1)

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

(Comparative Example 2)

The first composite oxide of Example 1, except that 667 mL of 25°C pure water was added to 500 g of lithium nickel composite oxide particles having the same composition as the base material to make a slurry, and no tungsten compound was added to the cleaning cake after solid-liquid separation In the same manner as above, composite oxide particles (corresponding to the second composite oxide) were obtained, and this was used as a positive electrode active material.

(Comparative Example 3)

In the same manner as in the first composite oxide of Example 1, the composite oxide particles (2nd equivalent to a complex oxide). To the obtained composite oxide particles (corresponding to the second composite oxide), _{2.0 g of lithium tungstate (LWO:Li 2} WO ₄ ) powder was added, and using a shaker mixer (TURBULA TypeT2C manufactured by Willy A. Bacofen (WAB)) The mixture 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 atoms of Ni, Co and Al.

[evaluation]

As is clear from Tables 1 and 2, since the positive electrode active materials of Examples were manufactured according to the present invention, they have high initial discharge capacity and low positive electrode resistance, and exhibit superior battery characteristics compared to Comparative Examples 1 and 2 . 3 shows an example of cross-sectional SEM observation results of the positive electrode active material obtained in Examples of the present invention, the obtained positive electrode active material includes primary particles and secondary particles constituted by aggregation of primary particles, and tungstic acid on the surface of the primary particles It was confirmed that lithium was formed. The microparticles|fine-particles containing lithium tungstate are enclosed by the circle in FIG. 3 and are shown.

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. In Comparative Example 3, although there is an effect of reducing the resistance 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 has a low initial discharge capacity.

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

1: first lithium nickel composite oxide
2: Second lithium nickel composite oxide
3, 3a, 3b: primary particles (first lithium nickel composite oxide)
4: secondary particles (first lithium nickel composite oxide)
5: core material
6, 6a, 6b: lithium tungstate
7: Primary particle (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 the second lithium-nickel composite oxide particles not containing lithium tungstate;
The first lithium-nickel composite oxide particles have a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ (provided that 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 core material including secondary particles in which a plurality of primary particles are aggregated with each other, and the first lithium-nickel composite Consisting of lithium tungstate present on the surface of the oxide particle and at least a part of the surface of the primary particle positioned therein,
The second lithium nickel composite oxide particles have a composition of Li _z2 Ni _{1 -x2- y2} Co _x2 M ² _y2 O ₂ (provided that 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.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that. The method of claim 1, wherein the second lithium-nickel composite oxide particles are washed with water before 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 tungstic acid according to any one of claims 1 to 3, wherein the first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles are present on both surfaces of the lithium-nickel composite oxide particles and on the surface of the primary particles located therein. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the amount of lithium contained in a lithium compound other than lithium is 0.05 mass % or less with respect to the total amount of the positive electrode active material. The first lithium nickel according to any one of claims 1 to 3, wherein the content of the first lithium nickel composite oxide particles 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. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising mixing the composite oxide particles and the second lithium nickel composite oxide particles. The amount of tungsten contained in the first lithium-nickel composite oxide particles is 0.03 atoms with respect to the total number of atoms of Ni, Co and M contained in the positive electrode active material according to any one of claims 1 to 3 % or more and 2.5 atomic% or less, comprising mixing the first lithium-nickel composite oxide particles and the second lithium-nickel composite oxide particles. According to any one of claims 1 to 3, before the mixing,
The composition is Li _z3 Ni _{1 -x3- y3} Co _x3 M ¹ _y3 O ₂ (provided that 0.00≤x3≤0.35, 0.00≤y3≤0.35, 0.95≤z3≤1.20, M ¹ is Mn, V, Mg, Mo, Nb , Ti and at least one element selected from Al), and a base material including secondary particles formed by aggregation of a plurality of primary particles;
2% by mass or more of moisture with respect to the total amount of the base material,
A tungsten compound, or a tungsten compound and a lithium compound that does not contain tungsten
Adjusting the tungsten mixture containing
To obtain the first lithium-nickel composite oxide particles by heat-treating the obtained tungsten mixture to form lithium tungstate on the surface of the base material and the surface of the primary particles therein
to provide
In the tungsten mixture, the molar ratio of the moisture and the tungsten compound, or the moisture, the tungsten compound, and the total amount of lithium contained in the lithium compound to the total amount of tungsten contained is 5 or less.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that. The first lithium-nickel composite oxide particle according to claim 7, wherein the amount of lithium contained in the lithium compound other than lithium tungstate existing on the surface of the first lithium-nickel composite oxide particle and the surface of the primary particle therein is the first lithium-nickel composite oxide particle It is 0.05 mass % or less with respect to the manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries characterized by the above-mentioned. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 7, wherein before the heat treatment, the base material and water are mixed to form a slurry, the base material is washed with water, and the washed base material is solid-liquid separated. A method for producing an active material. The method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, wherein the concentration of the washing slurry of the base material is 500 g/L or more and 2500 g/L or less. 10. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, wherein when the washed base material is solid-liquid separated, the water content of the resulting cleaning cake is controlled to be 3.0 mass % or more and 15.0 mass % or less. According to claim 7, wherein the tungsten compound, 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 at least any one A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: The method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein a temperature of the heat treatment in the heat treatment is 100°C or more and 600°C or less. The non-aqueous electrolyte secondary according to claim 7, wherein the amount of tungsten contained in the tungsten compound is 0.05 atomic % or more and 3.0 atomic % or less with respect to the total number of atoms of Ni, Co and M contained in the base material. A method for producing a positive electrode active material for a battery. A first lithium-nickel composite oxide particle containing lithium tungstate and a second lithium-nickel composite oxide particle not containing lithium tungstate,
The first lithium-nickel composite oxide particles have a composition of Li _z1 Ni _{1 -x1- y1} Co _x1 M ¹ _y1 O ₂ (provided that 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 core material including secondary particles in which a plurality of primary particles are aggregated with each other, and the first lithium-nickel composite Consisting of lithium tungstate present on the surface of the oxide particle and at least a part of the surface of the primary particle positioned therein,
The second lithium nickel composite oxide particles have a composition of Li _z2 Ni _{1 -x2- y2} Co _x2 M ² _y2 O ₂ (provided that 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.
A positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that. The amount of lithium contained in the lithium compound other than lithium tungstate according to claim 15, which is present on the surfaces of the first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles and on the surfaces of the primary particles positioned therein. The positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that it is 0.05 mass % or less with respect to the total amount of the positive electrode active material. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 15, wherein the amount of the first lithium-nickel composite oxide particles 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. The non-aqueous electrolyte according to claim 15, wherein the amount of tungsten contained in the lithium tungstate is 0.03 atomic % or more and 2.5 atomic % or less with respect to the total number of atoms of Ni, Co and M contained in the positive electrode active material. A positive electrode active material for secondary batteries. 16. The method according to claim 15, wherein 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 atoms of Ni, Co and M contained in the first lithium nickel composite oxide particles. A positive electrode active material for a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte according to claim 15, wherein the lithium tungstate is present as fine particles with a particle diameter of 1 nm or more and 500 nm or less on the surface of the first lithium-nickel composite oxide particle and on the surface of the inner primary particle. A positive electrode active material for secondary batteries. The non-aqueous electrolyte according to claim 15, wherein the lithium tungstate is present on the surface of the first lithium-nickel composite oxide particle and the surface of the inner primary particle as a film having a film thickness of 1 nm or more and 200 nm or less. A positive electrode active material for secondary batteries. The method according to claim 15, wherein the lithium tungstate is in the form 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 on the surface and inside of the first lithium-nickel composite oxide particles. A positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that it exists on the surface of the primary particles. It has a positive electrode containing the positive electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 15-22, The non-aqueous electrolyte secondary battery characterized by the above-mentioned.

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