JP2020087822A - Lithium nickel-containing composite oxide and manufacturing method thereof, and positive electrode active material for lithium ion secondary battery, which is arranged by use of the lithium nickel-containing composite oxide as base material, and manufacturing method thereof - Google Patents

Abstract

To provide a positive electrode active material including a lithium nickel-containing composite oxide coated with a compound containing W and Li, having excellent battery characteristic without marring the crystallinity, where a fine particle and/or coating of the compound containing W and Li is present on a surface of a primary particle.SOLUTION: A method for manufacturing a positive electrode active material for a lithium ion secondary battery comprises the step of preparing a lithium nickel-containing composite oxide by mixing a nickel compound and a lithium compound into a lithium-mixed material and then, increasing the temperature of the lithium-mixed material from a room temperature to a baking temperature equal to or higher than 700°C under an oxidizing atmosphere. In the preparing step, an eluted Li amount of a lithium nickel-containing composite oxide obtained under the condition of the passing time and/or holding time being set to be 45 minutes or a shorter time in a temperature region where the temperature of the lithium-mixed material is 600-650°C, followed by stirring and filtering the resultant mixture is in a range of 0.3 mass% to 0.5 mass%. The lithium nickel-containing composite oxide is used as a base material to form a fine particle and/or coating of a compound containing W and Li on the surface of a primary particle thereof.SELECTED DRAWING: None

Description

The present invention relates to a compound-coated lithium nickel-containing composite oxide containing W and Li used as a positive electrode active material for a lithium ion secondary battery, and more specifically, fine particles of a compound containing W and Li such as lithium tungstate. And/or a lithium nickel-containing composite oxide which is a base material of a positive electrode active material for a lithium-ion secondary battery, which is composed of a compound-coated lithium nickel-containing composite oxide containing W and Li, in which a coating is present on the surface of primary particles, and the same. It relates to a manufacturing method.

Further, the present invention relates to a positive electrode active material for a lithium ion secondary battery using the lithium nickel-containing composite oxide as a base material and a method for producing the same.

In recent years, with the expansion of the use of small information terminals such as smartphones and tablet PCs, the development of small and lightweight secondary batteries having high energy density has been strongly desired. Further, as a battery for a hybrid vehicle or an electric vehicle, development of a high-output large secondary battery is strongly desired.

There is a lithium ion secondary battery as a secondary battery satisfying such requirements. The lithium-ion secondary battery is composed of a negative electrode, a positive electrode, a separator, a nonaqueous electrolyte, and the like, and as an active material forming the negative electrode and the positive electrode, a material capable of desorbing and inserting lithium during charge and discharge is used. It is used. As the non-aqueous electrolyte, a non-aqueous electrolytic solution prepared by dissolving a lithium salt, which is a supporting salt, in an organic solvent, a non-flammable solid electrolyte having ionic conductivity, and the like are used.

Although research and development of lithium ion secondary batteries are still being actively conducted, lithium ion secondary batteries using a lithium transition metal-containing composite oxide having a layered rock salt type or spinel type structure as a positive electrode active material are Since a high voltage of 4 V class can be obtained, it is being put to practical use as a secondary battery having a high energy density.

The lithium-transition metal-containing composite oxides that have been mainly proposed so far include a lithium-cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize, and a lithium-nickel composite oxide that uses nickel that is cheaper 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 using manganese (LiMn ₂ O ₄ ), and these are required. Examples thereof include a lithium transition metal-containing composite oxide to which an additional element is added according to the characteristics.

Of these, the lithium nickel composite oxide has a larger charge/discharge capacity per weight than the lithium cobalt composite oxide, and nickel, which is the main raw material, is cheaper and more stable than cobalt. Since it has the advantage that it is possible, it is expected as a positive electrode active material for the next generation, and its research and development is actively continued.

The lithium-nickel composite oxide is usually produced by mixing and firing a lithium compound and a nickel compound, and is composed of a powder of primary particles monodispersed or a powder of secondary particles which is an aggregate of primary particles. However, each of them has a drawback that thermal stability in a charged state is inferior to that of the lithium cobalt composite oxide.

On the other hand, in order to stabilize the crystal structure in the state where lithium is removed during the charging process and obtain a lithium nickel composite oxide having good thermal stability and charge/discharge cycle characteristics as the positive electrode active material, It is common practice to replace some of the nickel in the oxide with other materials.

However, in the lithium nickel-containing composite oxide in which a part of nickel of the lithium nickel composite oxide is replaced with another substance to reduce the nickel ratio, the thermal stability becomes high, but the battery capacity decreases. On the other hand, if the nickel ratio in the lithium-nickel-containing composite oxide is increased to prevent the decrease in battery capacity, the thermal stability will not be sufficiently improved. Moreover, if the nickel ratio in the lithium-nickel-containing composite oxide is high, there is a problem that cation mixing is likely to occur during firing and synthesis becomes difficult.

On the other hand, for lithium-ion secondary batteries, there is a strong demand for higher output (lower resistance) particularly in battery applications for hybrid vehicles and electric vehicles. In order to improve the output characteristics of the positive electrode active material, a method of adding a tungsten compound to the lithium-nickel-containing composite oxide has been studied from such requirements.

For example, JP-A-2012-079464 discloses the general formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0.10 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0 .97≦z≦1.20, M is composed of primary particles represented by Mn, V, Mg, Mo, Nb, Ti and Al) and primary particles agglomerated. Non-compound lithium-nickel-containing composite oxide containing W and Li, which is composed of a base material of secondary particles and has fine particles of a compound containing W and Li on the surface of primary particles, in particular, fine particles of lithium tungstate. A positive electrode active material for an aqueous electrolyte secondary battery has been proposed.

By allowing fine particles and/or a coating film of a compound containing W and Li such as lithium tungstate to exist on the surface of the primary particles constituting the lithium nickel-containing composite oxide which is a base material, these fine particles or coating film can be converted into lithium. It functions as a protective film that prevents contact between the nickel-containing composite oxide and the electrolytic solution and suppresses the formation of deposits such as phosphate, and these fine particles or coatings have a crystal structure having a Li diffusion path. Therefore, it is considered that the interface resistance can be reduced.

However, in this positive electrode active material, although the output characteristics are improved, the nickel ratio is low, so that it is insufficient in terms of high capacity, and when the nickel ratio is increased, thermal stability is examined. Is also needed. Therefore, fine particles and/or a film of a compound containing W and Li, such as lithium tungstate, which has both high capacity and high output as a positive electrode active material and is excellent in thermal stability are formed on the surface of the primary particles. Studies have been made on existing compound nickel-containing lithium-containing composite oxides containing W and Li.

For example, in JP-A-2015-216105, a lithium mixture in which a nickel compound and a lithium compound are mixed is fired in an oxidizing atmosphere at a temperature range of 700° C. to 780° C. for 1 hour to 6 hours to obtain a compound represented by the general formula: Li _{b Ni 1-x-y Co x} M y O 2 ( where, M represents Mg, Al, Ca, Ti, V, Cr, Mn, Nb, at least one element selected from Zr and Mo, 0 .95≦b≦1.03, 0<x≦0.15, 0<y≦0.07, x+y≦0.16), and is composed of primary particles and secondary particles obtained by aggregating the primary particles. A composite oxide containing is obtained as a base material, and a tungsten compound is added during or after the water-washing treatment of the base material to disperse W on the surface of the primary particles of the base material, and in an oxygen atmosphere or a vacuum atmosphere. It is obtained by heat treatment at a temperature of 100° C. to 600° C., and has fine particles of a compound containing W and Li on the surface of the primary particles of the base material. A positive electrode active material for a non-aqueous electrolyte secondary battery has been proposed in which the length of the lattice constant in the c-axis direction obtained from Rietveld analysis is 14.183Å or more.

Further, in Japanese Patent Laid-Open No. 2017-084513, a tungsten compound is added during or after a water washing treatment of a base material obtained in the same manner as in Japanese Patent Laid-Open No. 2015-216105 to obtain a water content of 6. Obtained by dispersing W on the surface of the primary particles of the base material in a state of being controlled to 5% by mass to 11.5% by mass and heat-treating at a temperature of 100° C. to 600° C. in an oxygen atmosphere or a vacuum atmosphere. , A coating having a thickness of 1 nm to 200 nm containing W and Li on the primary particle surface of the base material, and further a lithium nickel-containing composite oxide of the base material is obtained by Rietveld analysis of X-ray diffraction in the c-axis direction. A positive electrode active material for a non-aqueous electrolyte secondary battery having a lattice constant length of 14.183Å to 14.205Å is proposed.

In these references, in order to remove the water of crystallization from the lithium compound and to uniformly react the lithium compound and the nickel compound in the temperature range where the crystal growth of the lithium nickel-containing composite oxide as the base material proceeds, 400 It is described that it is preferable to perform firing in two stages of a temperature of ℃ to 600 ℃ for 1 hour to 5 hours, followed by a temperature of 700 ℃ to 780 ℃ for 3 hours or more.

JP 2012-079464 A JP, 2015-216105, A JP, 2017-084513, A

In the technologies disclosed in JP-A-2015-216105 and JP-A-2017-084513, W and Li in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface of primary particles. Of the lithium nickel-containing composite oxide, which constitutes the compound-coated lithium nickel-containing composite oxide, and the fine particles of the compound containing W and Li are formed on the surface of the primary particles of the lithium nickel-containing composite oxide. The presence/absence of a coating improves lithium insertion/extraction, reduces reaction resistance, achieves high capacity and high output, and enhances crystallinity, resulting in high thermal performance even when the nickel ratio is high. Achieving stability.

However, in battery applications for hybrid vehicles and electric vehicles, it is required to realize higher capacity and higher output for lithium-ion secondary batteries at a higher level.

In view of the above problems, the present invention relates to a compound-coated lithium-nickel-containing composite oxide containing W and Li, in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface. It is an object of the present invention to improve the battery characteristics of a secondary battery, particularly the discharge capacity and charge/discharge characteristics.

In order to solve the above-mentioned problems, the present inventors have found that fine particles of a compound containing W and Li, such as lithium tungstate, and/or a coating film are present on the surface of primary particles and contain a compound-containing lithium nickel containing W and Li. Focusing on the lithium nickel-containing composite oxide itself, which is the base material of the composite oxide, the lithium nickel-containing composite oxide suitable for allowing fine particles and/or a film of a compound containing W and Li to be present on the surface of the primary particles. The properties of the product and the production conditions for obtaining the lithium-nickel-containing composite oxide having such properties were thoroughly studied.

As a result, in the firing step for producing the lithium-nickel-containing composite oxide, by appropriately controlling the material temperature holding time in a specific temperature range, the surface of the primary particles of the obtained lithium-nickel-containing composite oxide was obtained. It was possible to obtain the knowledge that the amount of the lithium compound that is present and corresponds to the excess Li can be appropriately controlled. In this way, by controlling the amount of surplus Li existing on the surface of the primary particles within a predetermined range, the lithium compound and the tungsten compound are reacted with each other on the surface of the primary particles without extracting Li in the crystal, resulting in battery characteristics. It was found that a lithium nickel-containing composite oxide in which fine particles of a compound containing W and Li such as lithium tungstate and/or a coating film, which are excellent in the presence of the compound, are present on the surface of the primary particles can be obtained.

The present invention has been completed based on these findings.

A first aspect of the present invention is composed of primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles of a compound containing W and Li and/or a coating film on the surface of the primary particles. The present invention relates to a method for producing a lithium-nickel-containing composite oxide, which is a base material of a positive electrode active material for a lithium-ion secondary battery, which is composed of a compound-coated lithium-nickel-containing composite oxide containing W and Li.

The method for producing a lithium nickel-containing composite oxide according to the present invention,
After mixing the nickel compound and the lithium compound to obtain a lithium mixture, the lithium mixture is heated in an oxidizing atmosphere from room temperature to a calcination temperature of 700° C. or higher to obtain primary particles and/or the primary particles. In the step of preparing a lithium-nickel-containing composite oxide composed of secondary particles formed by aggregating particles, a holding time in a temperature range in which the temperature of the lithium mixture is 600°C to 650°C is 45 minutes or less, preferably Is in the range of 10 to 40 minutes.

The nickel compound contains Ni, Co, and at least one additive element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W, and is obtained as lithium. The nickel-containing composite oxide is
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
It is preferable to have a composition consisting of

The firing temperature is controlled in the temperature range of 700° C. to 780° C., and the length of the lattice constant in the c-axis direction in the crystal of the lithium nickel-containing composite oxide obtained from Rietveld analysis of X-ray diffraction is 14 It is preferable to be in the range of .183Å to 14.205Å.

A second aspect of the present invention is composed of primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles and/or a film of a compound containing W and Li are formed on the surface of the primary particles. The present invention relates to a lithium nickel-containing composite oxide, which is a base material of a positive electrode active material for a lithium ion secondary battery, which is composed of a compound-coated lithium nickel-containing composite oxide containing W and Li.

The lithium-nickel-containing composite oxide of the present invention is obtained by immersing 10 g of the lithium-nickel-containing composite oxide in 100 ml of pure water, stirring for 1 minute, and allowing it to stand for 3 minutes. ), the amount of eluted Li is 0.3 mass% to 0.5 mass% with respect to the entire lithium nickel-containing composite oxide, preferably 0.35 mass %. To 0.45% by mass,
The lithium nickel-containing composite oxide,
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
It is preferable to have a composition consisting of

The length of the lattice constant in the c-axis direction in the crystal of the lithium nickel-containing composite oxide obtained from Rietveld analysis of X-ray diffraction is preferably in the range of 14.183Å to 14.205Å.

The volume-based average particle size MV of the lithium nickel-containing composite oxide is preferably in the range of 5 μm to 30 μm.

A third aspect of the present invention is composed of a positive electrode active material for a lithium ion secondary battery, that is, primary particles and/or secondary particles formed by aggregating the primary particles, and W is formed on the surface of the primary particles. The present invention relates to a method for producing a compound-coated lithium-nickel-containing composite oxide containing W and Li, in which fine particles and/or a film of a compound containing Li and Li are present.

The method for producing a positive electrode active material for a lithium ion secondary battery of the present invention,
Using the lithium nickel-containing composite oxide obtained in the first aspect of the present invention, that is, the lithium nickel-containing composite oxide in the second aspect of the present invention, the amount of the lithium nickel-containing composite oxide is water. A slurry is formed so as to be 700 g to 2000 g per 1 L, and the lithium nickel-containing composite oxide is washed with water.
During the water washing treatment or after the water washing treatment, a tungsten compound is added to the lithium nickel-containing composite oxide to disperse W on the surface of the primary particles of the lithium nickel-containing composite oxide, and
The lithium nickel-containing composite oxide in which W is dispersed on the surface of the primary particles is heat-treated to form fine particles and/or a film of a compound containing W and Li on the surface of the primary particles of the lithium nickel-containing composite oxide. To do
It is characterized by

The positive electrode active material for the lithium ion secondary battery,
General _{formula: Li a Ni 1-x-} y Co x M y W z O 2 + α ··· (2)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. 0.95≦a≦1.10, 0 <x≦0.15, 0<y≦0.07, x+y≦0.16, 0.001≦z≦0.03, 0≦α≦0.2.)
It is preferable that the compound-coated lithium-nickel-containing composite oxide containing W and Li has a composition of

The amount of W dispersed on the surface of the primary particles of the lithium-nickel-containing composite oxide is 0.1 atom% to 3 with respect to the total number of Ni, Co and M atoms contained in the lithium-nickel-containing composite oxide. It is preferably in the range of 0.0 atomic %.

The heat treatment is preferably performed at a temperature in the range of 100° C. to 600° C. in an oxygen atmosphere or a vacuum atmosphere.

A fourth aspect of the present invention is composed of a positive electrode active material for a lithium ion secondary battery, that is, primary particles and/or secondary particles formed by aggregating the primary particles, and W is formed on the surface of the primary particles. And a compound-coated lithium nickel-containing composite oxide containing W and Li, in which fine particles and/or a film of a compound containing Li are present.

The positive electrode active material for a lithium ion secondary battery of the present invention is the lithium nickel-containing composite oxide of the second aspect of the present invention, that is, 10 g of the lithium nickel containing composite oxide is immersed in 100 ml of pure water and stirred for 1 minute. Then, the amount of eluted Li determined by neutralization titration of the supernatant after standing for 3 minutes with 1 mol/L hydrochloric acid (HCl) was 0. Range of 3 mass% to 0.5 mass% Preferably, the range of 0.35 mass% to 0.45 mass% is used as a base material of the lithium nickel-containing composite oxide, and W and Li are formed on the surface of the primary particles. The present invention is characterized in that fine particles and/or a film of a compound containing is present.

The positive electrode active material for the lithium ion secondary battery,
General _{formula: Li a Ni 1-x-} y Co x M y W z O 2 + α ··· (2)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. 0.95≦a≦1.10, 0 <x≦0.15, 0<y≦0.07, x+y≦0.16, 0.001≦z≦0.03, 0≦α≦0.2.)
It is preferable that the compound-coated lithium-nickel-containing composite oxide containing W and Li has a composition of

The length of the lattice constant in the c-axis direction in the crystal of the compound-coated lithium nickel-containing composite oxide containing W and Li obtained from Rietveld analysis of X-ray diffraction is in the range of 14.183Å to 14.205Å. Preferably.

The volume-based average particle size MV of the compound-coated lithium-nickel-containing composite oxide containing W and Li is preferably in the range of 5 μm to 30 μm.

According to the present invention, lithium, which is a base material of a compound-coated lithium-nickel-containing composite oxide containing W and Li, in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface of primary particles. In the nickel-containing composite oxide, the amount of unreacted lithium compound existing on the surface of the primary particles, that is, the amount of surplus lithium compound, can be appropriately controlled. Therefore, when the fine particles and/or the coating film of the compound containing W and Li are formed on the surface of the primary particles of the lithium nickel-containing composite oxide, the extraction of Li from the crystal is prevented. Therefore, it is possible to provide a positive electrode active material for a lithium ion secondary battery, which has excellent battery characteristics without impairing crystallinity.

FIG. 1 is a perspective view and a cross-sectional view showing a 2032 type coin battery used for battery evaluation. FIG. 2 is a schematic explanatory diagram of an equivalent circuit used for impedance measurement and analysis in battery evaluation.

As described above, the inventors of the present invention have demonstrated that a compound-coated lithium nickel-containing composite oxide containing W and Li, in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface of primary particles. Focusing on the lithium nickel-containing composite oxide itself, which is the base material of the positive electrode active material for a lithium ion secondary battery, and is suitable for allowing fine particles and/or a film of a compound containing W and Li to be present on the surface of the primary particles. Further, the inventors have earnestly studied the properties of the lithium-nickel-containing composite oxide and the production conditions for obtaining the lithium-nickel-containing composite oxide having such properties. As a result, in the firing step for producing the lithium-nickel-containing composite oxide, by appropriately controlling the material temperature holding time in a specific temperature range, the surface of the primary particles of the obtained lithium-nickel-containing composite oxide was obtained. It is possible to appropriately control the amount of the lithium compound that is present and corresponds to excess Li, thereby forming fine particles and/or a film of the compound containing W and Li on the surface of the primary particles of the lithium-nickel-containing composite oxide. In doing so, it was found that it is possible to prevent the extraction of Li from the crystal and obtain a positive electrode active material for a lithium ion secondary battery having excellent battery characteristics. The present invention has been completed based on such findings.

Hereinafter, the present invention will be described in detail for each mode.

1. Method for Producing Lithium Nickel-Containing Composite Oxide The first aspect of the present invention is a compound containing W and Li in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface of primary particles. The present invention relates to a method for producing a lithium-nickel-containing composite oxide, which is a base material of a positive electrode active material for a lithium-ion secondary battery, which comprises a coated lithium-nickel-containing composite oxide.

The method for producing a lithium nickel-containing composite oxide according to the present invention,
After mixing the nickel compound and the lithium compound to obtain a lithium mixture, the lithium mixture is heated in an oxidizing atmosphere from room temperature to a calcination temperature of 700° C. or higher to obtain primary particles and/or the primary particles. In the step of preparing a lithium-nickel-containing composite oxide composed of secondary particles formed by aggregating particles, the passage time and/or the holding time in a temperature range in which the temperature of the lithium mixture is 600° C. to 650° C. 45 minutes or less, preferably 10 to 40 minutes.

[Nickel compound]
The nickel compound used in the firing step contains Ni and Co, and at least one selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W as the additional element M. A compound containing an element.

As the nickel compound, for example, nickel composite hydroxide, nickel oxy composite hydroxide obtained by oxidizing the nickel composite hydroxide with an oxidizing agent, the nickel composite hydroxide and/or the nickel oxy composite hydroxide. It is possible to use any of the nickel composite oxides obtained by oxidative roasting at a temperature in the range of 500°C to 750°C.

The nickel composite hydroxide may be, but not limited to, a nickel composite hydroxide obtained by a crystallization method such as a coprecipitation method or a uniform precipitation method.

In the crystallization method, nickel composite hydroxide can be obtained under various conditions, and the crystallization conditions are not particularly limited, but those obtained under the following conditions are preferable.

Specifically, in a reaction tank heated to a temperature in the range of 40° C. to 60° C., Ni and Co are contained, and Mg, Al, Ca, Ti, V, Cr, Mn as an additional element M are added. A nickel composite hydroxide obtained by dropping an aqueous solution of a metal compound containing at least one element selected from Nb, Zr, Mo and W and an aqueous solution containing an ammonium ion donor is preferable.

During the crystallization, it is preferable to add an aqueous solution of an alkali metal hydroxide, if necessary, so that the reaction solution can be kept alkaline, preferably in the range of 10 to 14 at a pH value based on a liquid temperature of 25°C. ..

Further, by coprecipitating the additional element M with Ni and Co, or after obtaining a nickel composite hydroxide by crystallization, the nickel compound hydroxide is coated with a metal compound containing the additional element M, or A nickel composite hydroxide containing Ni and Co and containing the additional element M can also be obtained by impregnating an aqueous solution containing the metal compound of the additional element M with the nickel composite hydroxide.

The nickel composite hydroxide obtained by such a crystallization method is composed of powder having a high bulk density. Such a high bulk density composite hydroxide is a lithium nickel-containing composite composed of primary particles and/or secondary particles formed by aggregating primary particles having a small specific surface area after washing with water after the firing step. Since it becomes easy to obtain an oxide, it becomes a nickel composite hydroxide suitable as a raw material of a positive electrode active material for a lithium ion secondary battery.

When nickel hydroxide is crystallized in a state where the temperature of the reaction solution exceeds 60°C or the pH exceeds 14, the priority of nucleation in the liquid increases and only fine particles are obtained without crystal growth. Sometimes I can't On the other hand, when the nickel composite hydroxide is crystallized when the temperature of the reaction solution is lower than 40° C. or the pH is lower than 10, the generation of nuclei in the liquid is small and the crystal growth of the particles becomes preferential. Coarse particles may be mixed in the nickel composite hydroxide that is obtained. In addition, the amount of metal ions remaining in the reaction solution increases, which may cause compositional deviation. When a nickel composite hydroxide having such a mixture of coarse particles or a composition shift is used as a raw material, the battery characteristics of the obtained positive electrode active material are deteriorated.

Therefore, when the nickel compound hydroxide obtained by the crystallization method is used as the nickel compound, the reaction solution is maintained at a temperature in the range of 40°C to 60°C, and the reaction solution is kept at a liquid temperature of 25°C. It is preferable to crystallize the nickel composite hydroxide with the pH value maintained at 10 to 14.

When nickel oxy composite hydroxide is used as the nickel compound, the method for producing it is not particularly limited. However, when nickel composite hydroxide is prepared by oxidizing it with an oxidizing agent such as sodium hypochlorite and hydrogen peroxide water, particles of high bulk density can be obtained, so nickel oxy composite water obtained by this method is obtained. It is preferable to use an oxide.

When a nickel composite oxide is used as the nickel compound, the manufacturing method thereof is not particularly limited. However, it is preferable to obtain the nickel composite hydroxide and/or the nickel oxy composite hydroxide by oxidizing and roasting at a temperature in the range of 500° C. to 750° C. in an oxidizing atmosphere. More preferably, the temperature is in the range of 550°C to 700°C.

When the nickel composite oxide thus obtained is used, when a lithium nickel-containing composite oxide is obtained by firing a lithium mixture obtained by mixing with a lithium compound, the lithium nickel-containing composite oxide is obtained. It becomes possible to stabilize the composition ratio of Li and the metal other than Li in the inside. As a result, when a positive electrode active material containing a lithium-nickel-containing composite oxide as a base material is used in a lithium ion secondary battery, it is possible to obtain an advantage that high capacity and high output can be achieved.

When the oxidation roasting temperature of the nickel composite hydroxide and/or the nickel oxy composite hydroxide is less than 500° C., the conversion to the oxide may be incomplete. When a nickel composite oxide whose conversion to such an oxide is incomplete is used, it is difficult to stabilize the composition of the obtained lithium nickel-containing composite oxide, and the composition is likely to be nonuniform during firing. .. Further, nickel composite hydroxide and/or nickel oxy composite hydroxide remains in the nickel composite oxide after oxidative roasting, and steam is generated during firing, so that the reaction between the lithium compound and the nickel composite oxide This may cause a problem that it is hindered and the crystallinity is lowered.

On the other hand, when the oxidation roasting temperature exceeds 750° C., the crystallinity of the obtained nickel composite oxide becomes high, and the reactivity of the lithium compound and the nickel composite oxide in the firing in the subsequent step decreases, so that the final product is obtained. The crystallinity of the obtained lithium-nickel-containing composite oxide may decrease. Alternatively, the nickel composite oxide may undergo rapid grain growth to form a nickel composite oxide composed of coarse particles, and the average particle size of the finally obtained lithium nickel-containing composite oxide may become too large. ..

The holding time at the oxidation roasting temperature is preferably set in the range of 1 hour to 10 hours, more preferably 2 hours to 6 hours. If it is less than 1 hour, the conversion to the oxide may be incomplete, and if it exceeds 10 hours, the crystallinity of the nickel composite oxide may be too high.

The oxidizing and roasting atmosphere may be an oxidizing atmosphere, but in consideration of handleability and cost, an atmospheric atmosphere is preferable.

The content of sulfate (SO ₄ ) in the nickel composite hydroxide used as the nickel compound is preferably in the range of 0.1% by mass to 0.4% by mass, and 0.1% by mass to 0. It is more preferably in the range of 3% by mass. This makes it easy to control the crystallinity of the lithium-nickel-containing composite oxide in the firing in the subsequent step.

When a nickel composite hydroxide is obtained by a crystallization method and a sulfate such as nickel sulfate is used as a raw material, an alkaline aqueous solution whose pH is adjusted to 11 to 13 at a liquid temperature of 25° is used. By sufficiently washing, the content of the sulfate group can be regulated within the range of 0.1% by mass to 0.4% by mass.

The nickel compound is obtained by containing Ni, Co, and at least one additive element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. The lithium nickel-containing composite oxide is
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
It is preferable to have a composition consisting of

The composition will be described in detail later, but the method for producing a lithium-nickel-containing composite oxide of the present invention is preferably applied when obtaining a lithium-nickel-containing composite oxide with a high nickel ratio.

[Mixing with lithium compound]
The lithium compound mixed with the nickel compound is not particularly limited, but at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide should be used. Is preferred. By using these, the advantage that impurities do not remain after firing is obtained. Among these, it is more preferable to use lithium hydroxide, which has good reactivity with nickel compounds.

The mixing ratio of the nickel compound and the lithium compound is not particularly limited, but the composition of Li and the metal element other than Li in the lithium nickel-containing composite oxide after firing is a mixture obtained by mixing the nickel compound and the lithium compound. Almost maintained in medium composition. Therefore, it is preferable to adjust the amount of Li in the lithium compound to a molar ratio of 0.98 to 1.11 with respect to the total amount of Ni and Co in the nickel compound and the additional element M. If this molar ratio is less than 0.98, the crystallinity of the obtained fired powder may be extremely deteriorated. Further, the lithium content in the obtained fired powder may be less than 0.98. On the other hand, if this molar ratio exceeds 1.11, the firing tends to proceed and over-firing tends to occur, and the Li content of the obtained fired powder may also exceed 1.11.

The device and method for mixing the nickel compound and the lithium compound are not particularly limited as long as they can uniformly mix both. For example, a dry mixer such as a V blender, a mixing granulator, or the like can be used.

[Firing]
The lithium mixture obtained by mixing the nickel compound and the lithium compound will be fired at a firing temperature of 700° C. or higher in an oxidizing atmosphere.

If it is baked at a temperature higher than 500°C, a lithium-nickel-containing composite oxide is produced, but if it is lower than 700°C, its crystal is undeveloped and structurally unstable. When such a lithium-nickel-containing composite oxide is used as the base material of the positive electrode active material, the crystal structure of the positive electrode active material is destroyed due to phase transition due to charge/discharge, or the growth of primary particles becomes insufficient. There is.

In the present invention, the firing temperature is preferably set to 780°C or lower. If the firing temperature exceeds 780° C., cation mixing tends to occur, the layered structure in the crystal of the lithium-nickel-containing composite oxide may be broken, and insertion and desorption of lithium ions may become difficult. Further, as will be described later, the length of the lattice constant in the c-axis direction in the crystal of the lithium nickel-containing composite oxide obtained from Rietveld analysis of X-ray diffraction may be in the range of 14.183Å to 14.205Å. Although preferable, if the firing temperature exceeds 780° C., the length of the lattice constant in the c-axis direction will not be 14.183Å or more. Furthermore, the crystal of the lithium-nickel-containing composite oxide may be decomposed, and nickel oxide or the like may be generated. In addition, the particles forming the lithium-nickel-containing composite oxide may sinter with each other to form coarse particles, and the average particle diameter of the lithium-nickel-containing composite oxide may become too large.

From the above viewpoint, the firing temperature is preferably set in the range of 730°C to 760°C.

The holding time at such a firing temperature is preferably set in the range of 1 hour to 6 hours, and more preferably set in the range of 2 hours to 4 hours. If the holding time is less than 1 hour, crystallization may be insufficient, and if it exceeds 6 hours, calcination may proceed excessively and cation mixing may occur.

In addition, in order to uniformly react the lithium compound and the nickel compound in the temperature range where the crystal water of the lithium compound is removed and the crystal growth of the lithium-nickel-containing composite oxide proceeds, the temperature range of 400° C. to 600° C. It is preferable to perform the two-stage firing in which the passage time and/or the holding time in 1) is set to 1 hour to 5 hours, and then the holding time at the temperature of 700°C to 780°C is set to 3 hours or more.

In the present invention, in addition to these conditions, in the process of raising the temperature of the lithium mixture from room temperature to 700° C. or higher in an oxidizing atmosphere, the temperature range in which the temperature of the lithium mixture is 600° C. to 650° C. The passage time and/or the holding time in (4) are 45 minutes or less, preferably 10 minutes to 40 minutes.

As described above, in the baking step of baking a lithium mixture to obtain a lithium-nickel-containing composite oxide, the baking temperature of the lithium mixture, that is, the maximum temperature at which the lithium mixture is held and the holding time thereof have been studied. ing. Further, from the viewpoint of causing a uniform reaction between the lithium compound and the nickel compound, the passage time and/or the holding time in the temperature range of 400° C. to 600° C. have also been studied.

On the other hand, the inventors of the present invention, when forming fine particles and/or a film of a compound containing W and Li on the surface of the primary particles of the lithium-nickel-containing composite oxide, Li of the lithium-nickel-containing composite oxide. Attention was paid to the reaction between the tungsten compound and W. From this point of view, the amount of surplus Li in the lithium-nickel-containing composite oxide as the base material and the firing conditions of this lithium-nickel-containing composite oxide were earnestly studied. As a result, in the process of raising the temperature of the lithium mixture from room temperature to a calcination temperature of 700° C. or higher, the inventors of the present invention passed through the lithium nickel-containing composite oxide in the temperature range of 600° C. to 650° C. And/or holding time, and the correlation between the amount of excess Li existing on the surface of the primary particles of the finally obtained lithium nickel-containing composite oxide, and by appropriately controlling the amount of excess Li In the reaction between Li of the lithium nickel-containing composite oxide and W of the tungsten compound, Li existing inside the primary particles of the lithium nickel-containing composite oxide is not extracted and appropriate fine particles of a compound containing W and Li are obtained. It was found that it is possible to form a film and/or a film.

Conventionally, in this temperature range, from the viewpoint of improving the crystallinity of the obtained lithium-nickel-containing composite oxide, the rate of temperature increase is set to about 1° C./minute or less, and the temperature of the lithium mixture from 600° C. to 650° C. The transit time in the area was over 45 minutes, for example over 50 minutes. However, when the passage time in the temperature range of 600° C. to 650° C. exceeds 45 minutes, Li sufficiently enters into the crystal of the primary particles in the process of forming the lithium-nickel-containing composite oxide, and the crystallinity is improved. Therefore, the amount of surplus Li existing on the surface of the primary particles becomes insufficient. Therefore, when Li of the lithium-nickel-containing composite oxide reacts with W of the tungsten compound, Li existing inside the primary particles of the lithium-nickel-containing composite oxide is extracted, and the primary of the obtained positive electrode active material is obtained. There is a possibility that the amount of Li in the particles will be insufficient and the battery characteristics will deteriorate.

The shorter the passage time of the lithium mixture in the temperature range of 600° C. to 650° C., the more excess Li that can react with W in the lithium-nickel-containing composite oxide tends to increase. Therefore, the passage time in the temperature range of 600° C. to 650° C. is preferably 40 minutes or less, more preferably 35 minutes or less, and further preferably 20 minutes or less. However, by shortening the time for passing the lithium compound in this temperature range, the excess Li amount becomes excessive, and the energy and equipment cost required for passing this time in a shorter time are reduced. From the viewpoint of increase, it is preferable that the passage time in the temperature range of 600° C. to 650° C. is 10 minutes or more.

In the present invention, the temperature range is not regulated by the temperature of the firing furnace or the like, but is regulated by the material temperature, which is an important temperature region in which the production of the lithium-nickel-containing composite oxide proceeds. In addition, since the range and the transit time are short in the temperature range, it is preferable to regulate by the temperature of the lithium mixture itself. Any equipment that can measure the temperature of the lithium mixture itself in the firing furnace can be used to measure the material temperature, but a non-contact thermometer such as a thermocouple or a radiation thermometer should be used. Is possible.

Further, since the temperature range is usually in the temperature rising process, the passage time in the temperature range of 600° C. to 650° C. is 45 by increasing the temperature rising rate at a rate of 1.11° C./minute or more. It can be less than a minute. However, if the holding time in this temperature region is 45 minutes or less, the amount of surplus Li existing on the surface of the primary particles can be appropriately regulated. Therefore, not only when the temperature is passed through the temperature range at a constant temperature rising rate, but also when the temperature is raised stepwise or the temperature is maintained at an arbitrary temperature within the temperature range for a certain period of time, the present invention is also applicable. Within the range of.

2. Lithium nickel-containing composite oxide The second aspect of the present invention is a compound-coated lithium nickel containing W and Li, in which fine particles and/or a film of a compound containing W and Li such as lithium tungstate are present on the surface of primary particles. The present invention relates to a lithium nickel-containing composite oxide that is a base material of the containing composite oxide.

The lithium nickel-containing composite oxide of the present invention comprises primary particles and secondary particles formed by aggregating the primary particles, and 10 g of the lithium nickel-containing composite oxide is immersed in 100 ml of pure water and stirred for 1 minute. The amount of eluted Li determined by neutralization titration of the supernatant after standing for 3 minutes with 1 mol/L hydrochloric acid (HCl) was 0.3 based on the whole lithium nickel-containing composite oxide. Mass% to 0.5 mass% range Preferably, it is 0.35 mass% to 0.45 mass%.

[Amount of eluted Li]
Usually, in the finally obtained positive electrode active material for a lithium ion secondary battery, the excess Li amount, that is, the Li amount eluted in water, is, for example, 0.2% by mass or less based on the whole lithium nickel-containing composite oxide It has been reduced. However, as described above, the inventors have found that fine particles of a compound containing W and Li and/or fine particles of a compound containing W and Li are formed on the surface of primary particles of a lithium nickel-containing composite oxide as a base material of a positive electrode active material for a lithium ion secondary battery. Focusing on the reaction between Li of the lithium nickel-containing composite oxide and W of the tungsten compound when forming the coating film, by appropriately controlling the excess Li amount in the lithium nickel-containing composite oxide that is the base material, In the reaction between Li of the lithium nickel-containing composite oxide and W of the tungsten compound, Li existing inside the primary particles of the lithium nickel-containing composite oxide is not extracted, and appropriate fine particles of the compound containing W and Li and We have found that it is possible to form a film.

In the present invention, with respect to the excess Li amount in the lithium nickel-containing composite oxide that is the base material of the positive electrode active material for a lithium ion secondary battery, 10 g of the lithium nickel-containing composite oxide is immersed in 100 ml of pure water and stirred for 1 minute. It is possible to measure the amount of eluted Li, which is obtained by neutralization titration of the supernatant after standing for 3 minutes with 1 mol/L hydrochloric acid (HCl).

When the amount of eluted Li is less than 0.3% by mass with respect to the entire lithium nickel-containing composite oxide, the excess Li existing on the surface of the primary particles of the lithium nickel-containing composite oxide is insufficient, so the lithium nickel-containing composite oxide During the reaction between the oxide Li and the tungsten compound W, Li is extracted from the crystal.

When the amount of eluted Li is 0.3% by mass or more with respect to the entire lithium nickel-containing composite oxide, a lithium ion secondary battery using the finally obtained positive electrode active material for a lithium ion secondary battery is sufficient. Discharge capacity and charging/discharging efficiency are achieved.

On the other hand, when the eluted Li amount exceeds 0.5 mass% with respect to the entire lithium nickel-containing composite oxide, the excess Li amount present on the surface of the primary particles of the lithium nickel containing composite oxide becomes excessive, and finally In the obtained positive electrode active material for a lithium ion secondary battery, the Li seat occupancy rate decreases, its crystallinity deteriorates, and the battery characteristics deteriorate.

In the present invention, until the elution Li amount reaches 0.5% by mass with respect to the entire lithium nickel-containing composite oxide, the battery characteristics of the finally obtained positive electrode active material for a lithium ion secondary battery tend to be improved. Can be seen. From this viewpoint, it is preferable that the amount of Li eluted in water be in the range of 0.35% by mass to 0.45% by mass.

More specifically, the elution Li amount is obtained by taking 10 g of the obtained lithium nickel-containing composite oxide and pouring it into room temperature, for example, 100 ml of pure water so that it becomes 25 composite oxide, and immersing it in 1 It can be obtained by performing neutralization titration with 1 mol/L hydrochloric acid (HCl), which is obtained by stirring for 1 minute and then leaving still for 3 minutes.

The lithium nickel-containing composite oxide of the present invention is used for forming fine particles and/or a film of a compound containing W and Li on the surface of a base material of a positive electrode active material for a lithium ion secondary battery, that is, the primary particles thereof. Such a particle property that is a base material and is composed of primary particles and/or secondary particles formed by aggregating primary particles can be obtained by the production method described in the first aspect of the present invention.

[composition]
The lithium nickel-containing composite oxide of the present invention,
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
It is preferable to have a composition consisting of

The lithium-nickel-containing composite oxide of the present invention is a hexagonal layered compound, and in the above general formula, (1-xy) indicating the Ni content is 0.84 or more and less than 1.

In the lithium-nickel-containing composite oxide of the present invention, the higher the Ni content, the higher the capacity when the finally obtained positive electrode active material is used, but when the Ni content is too high, the heat Stability cannot be sufficiently obtained, and cation mixing easily occurs during firing. On the other hand, when the Ni content decreases, the capacity decreases, and there is a problem that the capacity per battery volume cannot be sufficiently obtained even if the filling property of the positive electrode is increased.

Therefore, the Ni content of the lithium-nickel-containing composite oxide is preferably 0.84 or more and 0.98 or less, more preferably 0.845 or more and 0.950 or less, and even more preferably 0.85 or more and 0.95 or less. preferable.

X showing the Co content is 0<x≦0.15, preferably 0.02≦x≦0.15, and more preferably 0.03≦x≦0.13.

When the Co content is in the above range, excellent cycle characteristics and thermal stability can be obtained in the finally obtained positive electrode active material. By increasing the Co content, the cycle characteristics of the positive electrode active material can be improved, but when the Co content exceeds 0.15, it becomes difficult to increase the capacity of the positive electrode active material.

Y indicating the content of at least one element M selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W is 0<y≦0.07, and preferably y , 0.01≦y≦0.05. When the content of M is within the above range, excellent cycle characteristics and thermal stability can be obtained.

When y exceeds 0.07, it becomes difficult to increase the capacity of the positive electrode active material. If the additional element M is not added, the effect of improving the battery characteristics cannot be obtained. Therefore, in order to sufficiently obtain the effect of improving the battery characteristics, y is preferably 0.01 or more.

In addition, as M, at least Al is contained, and in the finally obtained lithium-nickel-containing composite oxide, y indicating the content of Al is preferably 0.03 to 0.07.

The value a indicating the Li content is 0.95≦a≦1.03. When a is less than 0.95, a metal element such as Ni is mixed in the Li layer in the layered compound to lower the Li insertion/removal property, so that the battery capacity decreases as the Li seat occupancy decreases, and the output power increases. The characteristics deteriorate. On the other hand, when a exceeds 1.03, Li is mixed in the metal layer in the layered compound, so that the battery capacity decreases.

Therefore, the Li content in the lithium-nickel-containing composite oxide is 0.95≦a≦1.03 and 0.95≦a≦1.01 in order to improve the battery capacity and output characteristics. Is more preferable.

[Length of lattice constant in c-axis direction]
Here, the Ni content in the lithium-nickel-containing composite oxide of the present invention is 0.84 or more, preferably 0.98 or less, which is a very high Ni content. When the Ni content becomes high, problems such as a decrease in thermal stability occur. Therefore, the Ni content is usually adjusted to be lower than 0.84, and generally 0.80 to 0.83. It

However, in the present invention, the crystal of the lithium-nickel-containing composite oxide has a lattice constant length in the c-axis direction obtained by Rietveld analysis of X-ray diffraction (hereinafter, referred to as “length of c-axis”). ) Is appropriately controlled to enable a high nickel content.

That is, by setting the length of the c-axis of the crystal of the lithium nickel-containing composite oxide to 14.183Å or more, preferably 14.185Å or more, a high nickel ratio is possible.

Further, in the case of the hexagonal lithium nickel-containing composite oxide of the present invention, the length of the c-axis affects the insertion/extraction of Li from the crystal. Generally, as the length of the c-axis increases, the interlayer distance of the lithium layer increases, so that the insertion/extraction of Li from the crystal is improved, and such a lithium-nickel-containing composite oxide is used as a base material. By doing so, a high capacity and high output positive electrode active material can be obtained.

On the other hand, when the length of the c-axis is shortened to less than 14.183Å, the ability to insert and extract Li from the crystal deteriorates, so that the capacity and the output of the finally obtained positive electrode active material decrease. Further, since the crystallinity is lowered due to the cation mixing, the cycle characteristics and the thermal stability are also deteriorated.

The upper limit of the length of the c-axis is not particularly limited, but the upper limit is about 14.205Å, and in the present invention, the length of the c-axis is preferably in the range of 14.183Å to 14.205Å.

[Average particle size]
The volume-based average particle size MV of the particles (primary particles and/or secondary particles) constituting the lithium nickel-containing composite oxide of the present invention is preferably in the range of 5 μm to 30 μm, and in the range of 5 μm to 25 μm. More preferably, it is more preferably in the range of 8 μm to 20 μm, and further preferably in the range of 8 μm to 17 μm.

If the volume-based average particle size MV is less than 5 μm, the filling property in the positive electrode when used as the positive electrode active material of the battery may be reduced, and the battery capacity per volume may be reduced. On the other hand, if the volume-based average particle size MV exceeds 30 μm, the contact area between the positive electrode active material and the battery electrolyte may decrease, and the battery capacity and output characteristics may deteriorate.

Therefore, by controlling the volume-based average particle size MV within the above range, it is possible to further improve the filling property in the positive electrode while maintaining the battery capacity and output characteristics in the finally obtained positive electrode active material. Further, the finally obtained positive electrode active material is composed of primary particles and/or secondary particles, and due to such a particle structure, contact with the electrolytic solution is not limited to the outer surface of the secondary particles, but the secondary particles. Near the surface of and inside the voids, as well as incomplete grain boundaries. From the viewpoint of sufficiently causing such contact with the electrolytic solution, it is preferable that the volume-based average particle size MV be within the above range.

The specific surface area by BET method measurement of the lithium nickel-containing complex oxide of the present invention ^is preferably in the range of ^{0.20m 2 /g~0.50m 2 / g, 0.25m} 2 / g~0. More preferably, it is in the range of 45 m ² /g.

By having such a specific surface area, the contact with the electrolytic solution is in an appropriate range, and the battery capacity and output characteristics can be further enhanced. If the BET specific surface area is less than 0.20 m ² /g, the excess Li existing on the surface of the primary particles of the lithium nickel-containing composite oxide is insufficient, so that Li of the lithium nickel-containing composite oxide and W of the tungsten compound are not present. In the reaction of, Li will be extracted from the crystal. On the other hand, when the BET specific surface area exceeds 0.50 m ² /g, the amount of excess Li existing on the surface of the primary particles of the lithium nickel-containing composite oxide becomes excessive, that is, in the synthesis of the lithium nickel-containing composite oxide, nickel This means that the reaction between the compound and the lithium compound did not proceed sufficiently. Therefore, in the finally obtained positive electrode active material for a lithium ion secondary battery, the Li seat occupancy rate decreases, its crystallinity deteriorates, and the battery characteristics deteriorate.

3. Method for producing positive electrode active material for lithium-ion secondary battery The third aspect of the present invention is a positive electrode active material for a lithium-ion secondary battery, that is, fine particles of a compound containing W and Li and/or a film surface of primary particles. And a compound coating lithium-nickel-containing composite oxide containing W and Li, which is present in.

The method for producing a positive electrode active material for a lithium ion secondary battery of the present invention,
Using the lithium nickel-containing composite oxide obtained in the first aspect of the present invention, that is, the lithium nickel-containing composite oxide in the second aspect of the present invention, the amount of the lithium nickel-containing composite oxide is water. A slurry is formed so as to be 700 g to 2000 g per 1 L, and the lithium nickel-containing composite oxide is washed with water.
During the water washing treatment or after the water washing treatment, a tungsten compound is added to the lithium nickel-containing composite oxide to disperse W on the surface of the primary particles of the lithium nickel-containing composite oxide, and
The lithium nickel-containing composite oxide in which W is dispersed on the surface of the primary particles is heat-treated to form fine particles and/or a film of a compound containing W and Li on the surface of the primary particles of the lithium nickel-containing composite oxide. To do
It is characterized by

[Washing process]
The water washing step is a step of subjecting the fired powder of the lithium-nickel-containing composite oxide obtained in the firing step to water washing. Specifically, a slurry is formed so that the calcined powder is 700 g to 2000 g per 1 L of water, washed with water, filtered, and dried to obtain a lithium nickel-containing composite oxide powder (washed powder).

In the rinsing step, the rinsing temperature during the rinsing treatment is preferably adjusted to be in the range of 10°C to 40°C, more preferably 10°C to 30°C. This removes impurities existing on the surface of the fired powder of the lithium-nickel-containing composite oxide. By the water washing treatment, excess Li such as lithium carbonate and lithium hydroxide existing on the surface is removed together with the impurities. However, by performing the water washing under the above water washing treatment conditions, the excess Li amount is lithium nickel after the water washing. The content is more than 0.10% by mass, preferably 0.15% by mass or more, and more preferably 0.20% by mass or more, based on the entire contained complex oxide.

Thereby, when forming fine particles and/or a film of a compound containing W and Li on the surface of the primary particles of the lithium-nickel-containing composite oxide, enough Li to react with W of the tungsten compound is contained in the primary particles. Since it exists on the surface, Li is not extracted from the inside by the reaction with W. On the other hand, due to proper regulation of the excess Li amount, excess Li does not exist on the surface of the finally obtained positive electrode active material. Therefore, when this positive electrode active material is used for the positive electrode of a lithium ion secondary battery, It is possible to suppress the generation of gas when kept at a high temperature, and it is possible to achieve both high capacity and high output and high safety.

On the other hand, when the water washing temperature is lower than 10° C., the washing becomes insufficient, and the impurities adhering to the surface of the fired powder may remain without being removed. The presence of such residual impurities increases the resistance of the surface of the positive electrode active material, and thus increases the resistance value of the positive electrode of the secondary battery. Further, since the specific surface area of the positive electrode active material becomes too small and the reactivity with the electrolytic solution decreases, it becomes difficult to achieve high capacity and high output of the secondary battery.

On the other hand, when the water washing temperature exceeds 40° C., the amount of Li eluted from the calcined powder increases, and nickel oxide (NiO) from which Li has escaped or Li and H are substituted in the surface layer of the lithium nickel-containing composite oxide. Nickel oxyhydroxide (NiOOH) may be produced. Both nickel oxide and nickel oxyhydroxide have a high electric resistance and increase the resistance of the surface of the positive electrode active material, and reduce Li in the positive electrode active material to reduce the capacity of the secondary battery.

The amount of the calcined powder with respect to 1 L of water contained in the slurry is adjusted to be 700 g to 2000 g, preferably 700 g to 1500 g.

That is, when the slurry concentration exceeds 2000 g/L, the viscosity of the slurry becomes high and stirring becomes difficult. Furthermore, since the alkali concentration of the liquid in the slurry becomes high, the dissolution rate of the deposits adhering to the calcined powder will slow down due to the equilibrium relationship, and even if detachment of the deposits from the powder occurs, reattachment will occur. Therefore, it becomes difficult to remove the impurities.

On the other hand, when the slurry concentration is less than 700 g/L, the amount of Li eluted from the surface of each particle into the slurry is large because it is too dilute. In particular, the higher the nickel ratio, the larger the amount of eluted Li, and the smaller the amount of Li on the surface becomes. For this reason, Li is also desorbed from the crystal lattice of the lithium-nickel-containing composite oxide, and the crystal is easily broken. Therefore, the capacity of the secondary battery is reduced.

The time for washing the baked powder with water is not particularly limited, but it is preferably about 5 minutes to 60 minutes. If the washing time is short, impurities on the powder surface may not be sufficiently removed and may remain. On the other hand, even if the washing time is prolonged, the washing effect is not improved and the productivity is lowered.

The water used for forming the slurry is not particularly limited, but in order to prevent deterioration of battery performance due to adhesion of impurities to the positive electrode active material, water having an electric conductivity of less than 10 μS/cm is preferable, and 1 μS/cm is preferable. More preferably, the water is cm or less.

[Drying process]
The temperature and method for drying the lithium nickel-containing composite oxide after washing with water are not particularly limited, but the drying temperature is preferably set in the range of 80°C to 500°C, and set in the range of 120°C to 250°C. More preferably. By setting the temperature to 80° C. or higher, the powder after washing with water is dried in a short time, a gradient of the lithium concentration between the surface and the inside of the particle is suppressed, and the characteristics of the positive electrode active material are further improved. You can

On the other hand, in the vicinity of the surface of the calcined powder after washing with water, it is expected that the stoichiometric ratio will be extremely close to the surface, or Li will be slightly desorbed and the state will be close to the charged state. Therefore, at a temperature higher than 500° C., the crystal structure of the powder close to the charged state may be broken, which may lead to deterioration in electrical characteristics.

From these viewpoints, the drying temperature is preferably in the range of 80°C to 500°C, and more preferably in the range of 120°C to 250°C in consideration of productivity and heat energy cost.

Regarding the drying method, it is preferable that the powder after filtration is dried at a predetermined temperature using a dryer that can be controlled in a gas atmosphere or a vacuum atmosphere that does not contain a compound component containing carbon and sulfur.

[Tungsten addition process]
The tungsten addition step is a step of adding a tungsten compound to the powder during or after the water washing treatment to disperse W on the surface of the primary particles.

That is, W can be added to the slurry during the water washing treatment, to the powder after the water washing treatment before drying, or to the powder dried after the water washing treatment. In any case, by controlling the water content of the powder after dehydration, the uniformity of W dispersion is enhanced and the elution of Li is suppressed, and W and Li are dispersed on the surface of the primary particles of the positive electrode active material. Fine particles and/or coatings of the compounds containing can be formed.

The amount of W dispersed on the surface of the primary particles of the calcined powder is in the range of 0.1 atom% to 3.0 atom% with respect to the total number of Ni, Co and M atoms contained in the calcined powder. Is preferable, and it is more preferable to set it in the range of 0.1 atom% to 1.0 atom %. As a result, fine particles and/or a film of a compound containing W and Li are formed more uniformly on the surface of the primary particles of the positive electrode active material, and when used as the positive electrode of the secondary battery, the fine particles and/or the film are not formed at the interface with the electrolytic solution. By forming a conduction path of Li, the reaction resistance of the positive electrode active material can be reduced, and the output characteristics can be further improved.

Whether the fine particles of the compound containing W and Li or the coating film of the compound containing W and Li are formed on the surface of the primary particles, or both are formed, the powder after dehydration It is determined by the water content of. In the case of addition to the powder after the water washing treatment and before drying, the water content of the powder after dehydration is controlled so as to be in the range of 3.0% by mass to 11.5% by mass. When the water content of the powder is 3.0% by mass or more and less than 6.5% by mass, fine particles of a compound containing W and Li are formed on the surface of the primary particles. By setting the water content of the powder to 6.5% by mass or more, a coating film of a compound containing W and LI tends to be formed on the surface of the primary particles, and the coating film and the fine particles are mixed. By setting the water content of the powder to be 9.0% by mass or more, only the coating film of the compound containing W and Li can be formed on the surface of the primary particles. The water content after the dehydration is calculated from the mass of the water-containing powder after dehydration and the mass of the powder after drying it at 180° C. for 3 hours: “Moisture content=(mass of water-containing powder before drying−after drying) Mass of powder)/(mass of hydrous powder before drying)".

The W may be added to the slurry during the aqueous treatment, to the calcined powder after washing with water and before drying, or to the calcined powder after aqueous treatment and drying.

W may be added either in the form of an alkaline solution in which a tungsten compound is dissolved (hereinafter referred to as “alkali solution (W)”) or in the form of a tungsten compound.

When it is added as an alkaline solution (W), the tungsten compound has only to be soluble in the alkaline solution, and a tungsten compound that is easily soluble in alkali, such as tungsten oxide, lithium tungstate, or ammonium tungstate, is used. Is preferred.

As the alkali used in the alkaline solution (W), a general alkaline solution containing no impurities harmful to the positive electrode active material, such as ammonia or lithium hydroxide, can be used in order to obtain a high charge/discharge capacity. From the viewpoint of making it possible to supply a sufficient amount of Li to form a compound containing W and Li from the excess Li and the alkaline solution (W), and from the viewpoint of not interfering with the intercalation of Li, water It is preferable to use lithium oxide.

On the other hand, when added in the form of a tungsten compound, it is preferable to use a tungsten compound soluble in alkali as the tungsten compound, more preferably a tungsten compound containing lithium, and further preferably lithium tungstate. .. As the lithium tungstate, at least one selected from Li ₂ WO ₄ , Li ₄ WO ₅ , and Li ₆ W ₂ O ₉ can be used.

In any case, the addition of W is a compound containing W and LI such as lithium tungstate formed on the surface of the particles constituting the lithium nickel-containing composite oxide by solid-liquid separation or crushing after heat treatment. It is necessary to select the processing conditions and addition means so that the W content in the fine particles and/or the coating film falls within the range of the present invention. Since these processing conditions and addition means are known, detailed description thereof is omitted here.

[Heat treatment process]
In the heat treatment step, the lithium nickel-containing composite oxide in which W is dispersed on the surface of the primary particles is heat-treated, so that the fine particles and/or the coating film of the compound containing W and Li are removed from the primary particles of the lithium nickel-containing composite oxide. It is a step of forming on the surface. As a result, fine particles and/or a film of a compound containing W and Li are formed from W and Li supplied in the tungsten addition step, and a compound containing W and Li of the compound containing W and Li is formed on the surface of the primary particles of the lithium nickel-containing composite oxide. A positive electrode active material for a lithium ion secondary battery, which comprises a compound-coated lithium nickel-containing composite oxide containing W and Li and has fine particles and/or a coating film, can be obtained. When W is added to the slurry during the water washing treatment or the baked powder after the water washing treatment and before drying, the heat treatment step can replace the drying step.

The heat treatment method is not particularly limited, but in order to prevent deterioration of electrical characteristics when used as a positive electrode active material for a lithium ion secondary battery, it is in an oxygen atmosphere or a vacuum atmosphere, and is in the range of 100°C to 600°C. It is preferable to perform heat treatment at a temperature.

When the heat treatment temperature is lower than 100° C., the evaporation of water is not sufficient, and the fine particles of the compound containing W and Li and/or the film may not be sufficiently formed. On the other hand, when the heat treatment temperature exceeds 600° C., the primary particles of the lithium-nickel-containing composite oxide sinter and a part of W is solid-solved in the layered structure of the lithium-nickel-containing composite oxide. Charge and discharge capacity may decrease. From such a viewpoint, the heat treatment temperature is more preferably 550° C. or lower, and further preferably 500° C. or lower.

The atmosphere during the heat treatment is preferably an oxidizing atmosphere such as an oxygen atmosphere or a vacuum atmosphere in order to avoid reaction with moisture or carbonic acid in the atmosphere.

The heat treatment time is not particularly limited, but is preferably in the range of 5 hours to 15 hours in order to sufficiently evaporate the water in the composite oxide particles to form a coating film.

The moisture content of the dried composite oxide particles is not particularly limited, but is preferably 0.2% by mass or less, more preferably 0.1% by mass or less. When the water content of the powder exceeds 0.2 mass %, gas components containing carbon and sulfur in the atmosphere may be absorbed to form a lithium compound on the surface.

When particles agglomerate after heat treatment, the particles are crushed to the extent that secondary particles are not destroyed, and a positive electrode active material composed of particles having a volume-based average particle size MV in the range of 5 μm to 30 μm is produced. To do.

4. Positive electrode active material for lithium ion secondary battery The fourth aspect of the present invention is a positive electrode active material for a lithium ion secondary battery, that is, fine particles and/or a film of a compound containing W and Li such as lithium tungstate on the surface. The present invention relates to a compound-coated lithium nickel-containing composite oxide containing W and Li.

More specifically, the positive electrode active material for a lithium ion secondary battery of the present invention forms a lithium nickel-containing composite oxide that is a base material, and is formed by the surface of primary particles and/or the aggregation of primary particles. Fine particles of a compound containing W and Li and/or a coating film are formed on the surfaces of the primary particles constituting the secondary particles thus prepared. In particular, in the positive electrode active material for a lithium ion secondary battery of the present invention, the lithium nickel-containing composite oxide is the lithium nickel-containing composite oxide of the second aspect of the present invention, that is, 10 g of the lithium nickel-containing composite oxide. Was immersed in 100 ml of pure water, stirred for 1 minute and allowed to stand for 3 minutes, and the supernatant liquid was neutralized and titrated with 1 mol/L hydrochloric acid (HCl). It is characterized by comprising a lithium nickel-containing composite oxide in a range of 0.3% by mass to 0.5% by mass with respect to the entire nickel-containing composite oxide.

Since the characteristics of the base material are descriptions, redundant description will be omitted, and the fine particles and/or the coating film of the compound containing W and Li will be described below.

[Fine particles and/or coating of compound containing W and Li]
Generally, if the surface of the positive electrode active material is completely covered with a different compound, the migration (intercalation) of lithium ions is greatly limited, resulting in the high capacity of the lithium nickel-containing composite oxide. That advantage is erased.

On the other hand, in the present invention, fine particles of a compound containing W and Li are formed on the surface of the primary particles of the lithium nickel-containing composite oxide, or the surface of the primary particles is made of a compound containing W and Li and has a thickness of Is in the range of 1 nm to 200 nm, preferably in the range of 1 nm to 150 nm, and more preferably in the range of 2 nm to 100 nm.

Fine particles of a compound containing W and Li have high lithium ion conductivity and have an effect of promoting the movement of lithium ions. Therefore, by forming fine particles of a compound containing W and Li on the surface of the primary particles, a conduction path of Li is formed at the interface with the electrolytic solution, so that the reaction resistance of the positive electrode active material (“positive electrode resistance”). It is possible to improve the output characteristics. By controlling the thickness of the coating film of the compound containing W and Li in the range of 1 nm to 200 nm, the same effect as that of the fine particles of the compound containing W and Li can be obtained.

That is, since the positive electrode resistance is reduced, the voltage lost in the secondary battery is reduced, and the voltage actually applied to the load side is relatively high, so that a high output can be obtained. In addition, since the voltage applied to the load side is increased, lithium is sufficiently inserted into and extracted from the positive electrode, so that the battery capacity is also improved. Further, the reduction of the positive electrode resistance also reduces the load of the positive electrode active material at the time of charging and discharging, so that the cycle characteristics can be improved.

Here, when the surface of the primary particles constituting the positive electrode active material is coated with a compound containing W and Li in an excessively large thickness, the specific surface area decreases, so that the compound containing W and Li has a high lithium ion conductivity. Even if it has the property, the contact area with the electrolytic solution becomes small, and accordingly, the charge/discharge capacity and the reaction resistance are likely to decrease. Further, the presence of the compound containing W and Li lowers the reaction resistance, but the compound itself containing W and Li has a low electron conductivity, and therefore the electron conductivity of the electrode is lowered, and the secondary battery is reduced. Lead to deterioration of output characteristics.

In the present invention, a fine particle having a predetermined particle size and made of a compound containing W and Li, or a coating film having a predetermined range of film thickness made of a compound containing W and Li and present on the surface of the primary particle. In this way, lithium ion conduction is effectively improved without excessively reducing the electrode surface or significantly increasing the bulk resistance of the electrode, suppressing the decrease in charge/discharge capacity and reducing the reaction resistance. It is possible to let.

The fine particles of the compound containing W and Li preferably have a particle diameter in the range of 1 nm to 100 nm. If the particle size is less than 1 nm, the fine particles may not have sufficient lithium ion conductivity. On the other hand, if the particle size exceeds 100 nm, the formation of the coating by the fine particles becomes non-uniform, and the effect of reducing the reaction resistance may not be sufficiently obtained. It is not necessary that all of the fine particles have a particle diameter in the range of 1 nm to 100 nm, and preferably 50% or more of the total number of the fine particles formed on the surface of the primary particles are particles in the range of 1 nm to 100 nm. If it has a diameter, a higher effect of improving battery characteristics can be obtained. The maximum particle size of the fine particles in this case is about 200 nm.

The film of the compound containing W and Li preferably has a thickness in the range of 1 nm to 200 nm. If the thickness is less than 1 nm, the coating may not have sufficient lithium ion conductivity. On the other hand, if the thickness exceeds 200 nm, the reaction area may decrease and the bulk resistance of the electrode may increase, and the reaction resistance may not be sufficiently reduced.

Since contact with the electrolytic solution occurs on the surface of the primary particles, it is important that fine particles and/or a film of a compound containing W and Li are formed on the surface of the primary particles. Here, the surface of the primary particle in the present invention is the surface of the primary particle when the lithium-nickel-containing composite oxide is composed of the primary particle. When the lithium nickel-containing composite oxide is composed of secondary particles, the surface of the primary particles exposed on the outer surface of the secondary particles, and the secondary particles through which the electrolytic solution can penetrate through the outside of the secondary particles. Both the vicinity of the surface of the primary particles and the surface of the primary particles exposed in the voids inside are included in the surface of the primary particles. Further, even at the grain boundaries between the primary particles, if the binding of the primary particles is incomplete and the electrolytic solution is permeable, such portions are also included in the surface of the primary particles.

Therefore, by forming fine particles and/or a film of a compound containing W and Li on the entire surface of the primary particles, the movement of lithium ions is further promoted, and the reaction resistance of the particles constituting the positive electrode active material is further reduced. It becomes possible.

The fine particles and/or the coating film of the compound containing W and Li do not have to be formed on the entire surface of the primary particles that can come into contact with the electrolytic solution. The fine particles and/or the coating film of the compound containing W and Li may be scattered, and even in the scattered state, the primary particles forming the positive electrode active material or the secondary particles forming the positive electrode active material. If fine particles and/or a film of a compound containing W and Li are formed on the outer surface of the secondary particles and the surface of the primary particles exposed to the voids inside, the effect of reducing the reaction resistance can be obtained. However, the higher the presence ratio of these on the surface of the primary particles, the more easily the reaction resistance reducing effect is obtained.

On the other hand, among the particles constituting the lithium-nickel-containing composite oxide, if the fine particles are formed non-uniformly, the movement of lithium ions between the particles becomes non-uniform, so a load is applied to specific particles, and the cycle It is easy to cause deterioration of characteristics and increase of reaction resistance. Therefore, it is preferable that the fine particles are uniformly formed among the particles forming the lithium-nickel-containing composite oxide.

Further, even when the fine particles of the compound containing W and Li and the coating film are mixed and formed on the surface of the primary particles, a high effect on the battery characteristics can be obtained. In this case, the fine particles of the compound containing W and Li preferably have a particle diameter in the range of 1 nm to 200 nm in order to obtain a higher effect of improving the battery characteristics. It is not necessary that all of the fine particles have a particle size in the range of 1 nm to 200 nm, and preferably 50% or more of the total number of the fine particles formed on the surface of the primary particles are particles in the range of 1 nm to 200 nm. If it has a diameter, the higher effect of improving the battery characteristics can be obtained by the interaction with the coating.

By adopting such a form, the contact area with the electrolytic solution can be made sufficient and the lithium ion conduction can be effectively improved, so that the charge/discharge capacity can be improved and the reaction resistance can be more effectively reduced. You can

The properties of the surface of such primary particles can be determined by, for example, cross-section observation by a field emission scanning electron microscope, cross-section element mapping by EDX analysis of a scanning transmission electron microscope (STEM), cross-section observation by a transmission ionization microscope, and the like. .. By these means, in the positive electrode active material for a lithium ion secondary battery of the present invention, fine particles and/or a film of a compound containing W and Li are formed on the surface of the primary particles constituting the lithium nickel-containing composite oxide. It is possible to confirm that

In the present invention, it is preferable that the fine particles of the compound containing W and Li and/or the compound containing W and Li constituting the film be lithium tungstate. Lithium _{tungstate, 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 At least one form selected from W ₅ O ₁₆ , Li ₉ W ₁₉ O ₅₅ , Li ₃ W ₁₀ O ₃₀ , Li ₁₈ W ₅ O ₁₅ and hydrates thereof is preferable. By forming such lithium tungstate, the lithium ion conductivity is further enhanced and the effect of reducing the reaction resistance is further enhanced.

The number of W atoms contained in the compound containing W and Li is 0.1 atom% to 3.0 atom% with respect to the total number of Ni, Co and M atoms contained in the particles constituting the positive electrode active material. Is preferably in the range of 0.1 atomic% to 1.0 atomic %, more preferably in the range of 0.1 atomic% to 0.6 atomic %. .. This makes it possible to achieve both high charge/discharge capacity and output characteristics.

If the amount of W is less than 0.1 atomic %, the output characteristics may not be sufficiently improved. When the amount of W exceeds 3.0 atom %, the coating of the surface of the primary particles with the fine particles and/or coating of the compound containing W and Li becomes too thick, the specific surface area decreases, and the bulk resistance of the electrode increases. In some cases, a sufficient reaction resistance reduction effect may not be obtained.

Further, the amount of Li contained in the fine particles of the compound containing W and Li and/or the coating film is not particularly limited, and the effect of improving lithium ion conductivity can be obtained if Li is contained. However, it is preferable that the amount of Li is sufficient to form lithium tungstate.

When the W amount is in the range of 0.1 atom% to 3.0 atom %, the positive electrode active material is
General _{formula: Li a Ni 1-x-} y Co x M y W z O 2 + α ··· (2)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. 0.95≦a≦1.10, 0 <x≦0.15, 0<y≦0.07, x+y≦0.16, 0.001≦z≦0.03, 0≦α≦0.2.)
It is preferable that the lithium nickel-containing composite oxide has a composition of Note that W can be contained inside the lithium-nickel-containing composite oxide as the additional element M. In this case, the amount of W contained as the additional element M is included in the W amount (z in the composition formula). Is not included.

The value a indicating the Li content is 0.95≦a≦1.10. If a exceeds 1.10, the Li content in the lithium-nickel-containing composite oxide becomes too large, and Li may be mixed in the metal layer in the layered compound. On the other hand, when a is 0.95 or less, a metal element such as Ni may be mixed in the lithium layer. Therefore, in order to improve the battery capacity and the output characteristics, it is more preferable that 0.95<a≦1.08. It is preferable that z representing the W content is 0.001≦z≦0.01.

5. Lithium-ion secondary battery A lithium-ion secondary battery obtained by using the positive-electrode active material for a lithium-ion secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, a nonaqueous electrolyte, and the like, like a general lithium-ion battery. Composed. For example, the 2032 type coin battery 1 shown in FIG. 1 (hereinafter referred to as “coin type battery”) includes a case 2 and an electrode 3 housed in the case 2.

The case 2 includes a positive electrode can 2a that is hollow and has one end opened, and a negative electrode can 2b that is arranged in the opening of the positive electrode can 2a. When the negative electrode can 2b is arranged in the opening of the positive electrode can 2a. A space for housing the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.

The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a is housed in the case 2 such that it contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b.

The case 2 is provided with a gasket 2c, and the gasket 2c prevents relative movement between the positive electrode can 2a and the negative electrode can 2b so as to maintain a non-contact state between them. The gasket 2c also has a function of hermetically sealing the gap between the positive electrode can 2a and the negative electrode can 2b and air-tightly and liquid-tightly blocking the inside and the outside of the case 2.

In addition, the embodiment described below is merely an example, and the lithium ion secondary battery of the present invention has various modifications and improvements based on the embodiments described in the present specification based on the knowledge of those skilled in the art. It can be carried out in the applied form. The use of the lithium ion secondary battery of the present invention is not particularly limited.

[Positive electrode]
Using the lithium nickel-containing composite oxide of the present invention as a positive electrode active material forming a positive electrode, for example, the positive electrode of a lithium ion secondary battery can be manufactured as follows.

First, a powdery positive electrode active material, a conductive agent, and a binder are mixed, and further a slurry solvent, and if necessary, activated carbon, a viscosity adjusting additive, etc. are added, and these are kneaded to form a positive electrode mixture paste. To make.

The mixing ratio of each member in the positive electrode mixture paste is also an important factor that determines the performance of the lithium ion secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass to 95 parts by mass as in the positive electrode of a general lithium ion secondary battery, The content of the agent is preferably 1 part by mass to 20 parts by mass, and the content of the binder is preferably 1 part by mass to 20 parts by mass.

The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector and dried to scatter the slurry solvent. If necessary, pressure can be applied by a roll press or the like in order to increase the electrode density. In this way, a sheet-shaped positive electrode is manufactured.

The sheet-shaped positive electrode is cut into a suitable size according to the intended battery and then used for the production of the battery. However, the method for producing the positive electrode is not limited to the exemplified method, and other means can be adopted.

The conductive agent is not particularly limited as long as it is an electron conductive material that is chemically stable in the battery. For example, natural graphite (scaly graphite etc.), graphite such as artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc. Use of conductive fibers, metal powders such as aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, organic conductive materials such as polyphenylene derivatives, and carbon fluoride. You can These may be used alone or in combination of two or more.

The amount of the conductive agent added to the positive electrode mixture is not particularly limited, but is preferably in the range of 0.5% by mass to 50% by mass with respect to the positive electrode active material contained in the positive electrode mixture. It is more preferably in the range of 0.5% by mass to 30% by mass, and further preferably in the range of 0.5% by mass to 15% by mass.

The binder plays a role of binding the active material particles together. Examples of the binder include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-peroxide. Fluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer Combined, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer Examples include coalescing.

The above resins may be used alone or in combination of two or more. Further, these may be cross-linked products with Na ⁺ ions or the like.

As the paste solvent, specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used. Further, activated carbon may be added to the positive electrode mixture in order to increase the electric double layer capacity.

The collector is not particularly limited as long as it is an electron conductor that is chemically stable in the battery. For example, a foil or sheet made of aluminum, stainless steel, nickel, titanium, carbon, a conductive resin or the like can be used, and among these, aluminum foil, aluminum alloy foil and the like are more preferable. On the surface of the foil or sheet, a carbon or titanium layer can be provided or an oxide layer can be formed. In addition, the surface of the foil or sheet can be provided with irregularities, and a net, punching sheet, lath body, porous body, foamed body, fiber group molded body or the like can also be used. The thickness of the current collector is also not particularly limited, but is preferably in the range of 1 μm to 500 μm.

(2) Negative Electrode For the negative electrode, metallic lithium, lithium alloy, or the like can be used. For example, as the negative electrode, a negative electrode mixture prepared by mixing a binder with a negative electrode active material capable of absorbing and desorbing lithium ions and adding a suitable solvent to form a paste is used as a surface of a metal foil current collector such as copper. A sheet-like electrode is used, which is formed by applying it to, drying it, and, if necessary, compressing it to increase the electrode density.

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

(3) Separator A separator is sandwiched and arranged between the positive electrode and the negative electrode. The separator holds the electrolyte while electrically separating the positive electrode and the negative electrode, and serves as a movement path of lithium ions between the positive electrode and the negative electrode. As a general separator, a thin film of polyethylene, polypropylene or the like, which has a large number of fine holes, can be used. It is also possible to use a solid electrolyte.

The separator may be composed of a microporous thin film. In this case, the diameter of the holes formed in the separator is not particularly limited, but is preferably in the range of 0.01 μm to 1 μm, for example. The porosity of the separator is not particularly limited, but is generally about 30% to 80%. The thickness of the separator is also not particularly limited, but is generally about 10 μm to 300 μm.

Further, the separator may be used separately from the positive electrode and the negative electrode, but a non-aqueous electrolytic solution and a polymer electrolyte made of a polymer material holding the non-aqueous electrolytic solution may be integrated with the positive electrode or the negative electrode to be used as the separator. You can also The polymer material is not particularly limited as long as it can hold the non-aqueous electrolyte solution, and is preferably a copolymer of vinylidene fluoride and hexafluoropropylene.

(4) Non-Aqueous Electrolyte As the non-aqueous electrolyte, in addition to a non-aqueous electrolytic solution obtained by dissolving a lithium salt, which is a supporting salt, in an organic solvent, a non-flammable solid electrolyte having ionic conductivity is used.
A non-aqueous electrolyte solution that is widely used as a non-aqueous electrolyte of a lithium ion secondary battery is a solution of a lithium salt as a supporting salt in an organic solvent. As the organic solvent used,
Cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and trifluoropropylene carbonate;
Chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, dipropyl carbonate;
Aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate;
Lactones such as γ-butyrolactone and γ-valerolactone;
Chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME);
Ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane;
Sulfur compounds such as ethyl methyl sulfone and butane sultone;
Phosphorus compounds such as triethyl phosphate and trioctyl phosphate;
Dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3- Dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole, dimethyl sulfoxide, N-methyl-2-pyrrolidone, etc.;
Can be mentioned. These may be used alone or in combination of two or more.

Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN(CF ₃ SO ₂ ) ₂ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li(CF _{3 ).} SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, lithium imide salt and the like. These may be used alone or in combination of two or more. It is preferable to use at least LiPF ₆ .

The lithium salt concentration in the non-aqueous solvent is not particularly limited, but is preferably in the range of 0.2 mol/L to 2 mol/L, more preferably in the range of 0.5 mol/L to 1.5 mol/L. ..

Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

On the other hand, the solid _electrolyte, or the like can be used _{Li 1.3 Al 0.3 Ti 1.7 (PO} 4) 3 and _{Li 2} S-SiS 2.

[Shape and configuration of lithium-ion secondary battery]
The shape of the lithium ion secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte described above can have various shapes such as a cylindrical shape and a laminated shape.

In any of the shapes, for example, when using a non-aqueous electrolyte as the non-aqueous electrolyte, the positive electrode and the negative electrode, the electrode body by laminating the positive electrode and the negative electrode through the separator, the obtained electrode body, non-aqueous electrolysis Use a lead for current collection to connect between the positive electrode current collector and the positive electrode terminal that communicates with the outside, and between the negative electrode current collector and the negative electrode terminal that communicates with the outside by impregnating the liquid, and attach it to the battery case. Seal and complete the lithium-ion secondary battery.

[Characteristics of lithium-ion secondary battery]
A lithium ion secondary battery using the compound-coated lithium nickel-containing composite oxide containing W and Li, in which the fine particles and/or coating film of the compound containing W and Li of the present invention are present on the surface of primary particles, is , High capacity and high output.

In particular, a lithium ion secondary battery using the positive electrode active material for a lithium ion secondary battery of the present invention obtained in a more preferable form has an initial discharge capacity when used, for example, in the positive electrode of the coin battery shown in FIG. Of 200 mAh/g or more, preferably 205 mAh/g or more, and high initial charge/discharge efficiency of 88% or more, and high capacity and high output.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In this example, the nickel compound, the cobalt compound, the compound of the additional element M, the lithium compound, and the materials used for the production of the lithium-nickel-containing composite oxide and the lithium-ion secondary battery were used as the precursor. , A special grade reagent of Wako Pure Chemical Industries, Ltd. was used.

(Example 1)
[Production and evaluation of lithium nickel-containing composite oxide]
The temperature in the reaction tank was set to 49.5° C., and the reaction solution in the reaction tank was kept at pH 13.0 at a liquid temperature of 25° C. with a 20 mass% sodium hydroxide solution, while nickel sulfate and sulfuric acid were added to the reaction solution. A mixed aqueous solution of cobalt, an aqueous solution of sodium aluminate, and 25 mass% aqueous ammonia were added, and the mixture was recovered by overflow. Further, the solution was washed with 45 g/L sodium hydroxide aqueous solution having a pH of 12.5 at a liquid temperature of 25° C., washed with water and dried to obtain a nickel composite hydroxide (neutralization crystallization method).

This nickel composite hydroxide is composed of secondary particles in which primary particles having a particle size of 1 μm or less are aggregated into a spherical shape, and ICP emission spectroscopic analyzer (ICPE-9000, manufactured by Shimadzu Corporation, Shimadzu Corporation) is used. It was confirmed by an optical emission analysis that the nickel composite hydroxide had a Ni:Co:Al molar ratio of 90.5:4.8:4.7.

The volume-based average particle size MV of the nickel composite hydroxide measured using a laser light diffraction/scattering particle size analyzer (Microtrac HRA manufactured by Nikkiso Co., Ltd.) was 12 μm.

Further, the sulfur content was found to be 0.28% by mass when the sulfur was quantitatively analyzed by ICP emission spectrometry and all the sulfur was oxidized to form sulfate radicals (SO ₄ ). It was

Next, this nickel composite hydroxide was oxidized and roasted at a temperature of 600° C. in the air atmosphere to obtain a nickel composite oxide, and then, in a molar ratio, Ni:Co:Al:Li=90.5:4. The nickel composite oxide and the lithium hydroxide-hydrate were weighed so that the ratio was 8:4.7:1.02, and a shaker mixer device (TURBULA Type T2C manufactured by Willie & Bakkofen (WAB)) was used. And mixed to obtain a lithium mixture.

1. The obtained lithium mixture is calcined in an oxygen atmosphere in an electric furnace at a temperature of 500° C. for 3 hours, and then the passage time in a temperature range of 600° C. to 650° C. is 20 minutes. The temperature was raised from 500° C. to 745° C. at a heating rate of 5° C./min, and the temperature was further held at 745° C. for 3 hours. Then, it was cooled to room temperature in the furnace and crushed to obtain a fired powder (hereinafter, referred to as "base material"). In the firing step, a thermocouple was inserted into the lithium mixture and the temperature of the mixture itself was measured.

When the obtained base material was analyzed by the ICP method, it was confirmed that the molar ratio of Ni:Co:Al:Li was 90.5:4.8:4.7:1.02. Further, 10 g of the base material was sampled, put into 100 mL of pure water held at 25° C., immersed, stirred for 1 minute, and then left still for 3 minutes. After that, the supernatant liquid was subjected to neutralization titration with 1 mol/L hydrochloric acid (HCl) to measure the eluted Li amount. The eluted Li amount was 0.37% by mass based on the whole base material. Met.

Next, pure water at 20° C. was added to the obtained base material to form a slurry containing 750 g of the base material in 1 L of water. The slurry was stirred for 20 minutes, then passed through a filter press for dehydration. A base material cake was prepared.

The addition of W to the base material is carried out by passing an alkaline solution (W) containing a tungsten compound through the dehydrated base material cake in a filter press, and then dehydrating again to form W on the surface of the primary particles of the base material. Was dispersed.

Here, the addition amount of the tungsten compound is determined by the tungsten concentration of the alkali solution (W) to be passed and the water content of the base material cake after dehydration. That is, the amount of tungsten contained in the water after dehydration is the added amount.

In this embodiment, an alkali having a tungsten concentration of 0.58 mol/L is prepared by adding 131.8 g of tungsten oxide (WO ₃ ) to an aqueous solution in which 50.6 g of lithium hydroxide (LiOH.H ₂ O) is dissolved in 1 L of pure water. Solution (W) was used. The water content of the base material cake after dehydration was 6.1%.

The obtained lithium nickel-containing composite oxide infiltrated with the alkaline solution (W) was subjected to a treatment of standing and drying for 10 hours using a vacuum dryer heated to 190°C.

Finally, a positive electrode active material having fine particles of a compound containing W and Li and a coating film on the surface of the primary particles was obtained by crushing by sieving with a sieve having an opening of 38 μm.

When the composition of the obtained positive electrode active material was analyzed by ICP emission spectrometry, the molar ratio of Ni:Co:Al:Li was 90.5:4.8:4.7:0.98, and the W content was Ni. It was confirmed that the composition was 0.35 atomic% with respect to the total number of Co, Al and Al atoms. In addition, it was confirmed that the fine particles of the compound containing W and Li and the coating film on the surface of the primary particles were made of lithium tungstate (Li ₂ WO ₄ ).

The specific surface area of the obtained positive electrode active material by the BET method was 0.93 m ² /g.

A cross-section of the positive electrode active material embedded in a resin and subjected to cross-section polisher processing was observed by SEM at a magnification of 5000. As a result, primary particles and secondary particles formed by aggregating the primary particles were observed. Confirmed to consist of. The porosity of the secondary particles obtained from this observation was 2.1%. Moreover, after making this positive electrode active material into a state in which a cross-section can be observed with a scanning transmission electron microscope (STEM: manufactured by Hitachi High-Technologies Corporation, scanning electron microscope S-4700), the vicinity of the surface of the primary particles is observed with STEM. Upon observation, it was confirmed that fine particles having a particle diameter in the range of 10 nm to 200 nm and a coating film having a thickness in the range of 2 nm to 115 nm were formed on the surface of the primary particles. Furthermore, it was confirmed from the results of powder XRD analysis using an X-ray diffraction (XRD) device (X'Pert PRO manufactured by PANalytical Inc.) that these fine particles and the coating were made of lithium tungstate.

[Manufacturing and evaluation of lithium-ion batteries]
The coin-type battery 1 shown in FIG. 1 was manufactured as follows. First, 90 parts by mass of a positive electrode active material for a lithium ion secondary battery, 5 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride were mixed, and n-methylpyrrolidone was added to form a paste. This prepared paste was applied to an aluminum foil having a thickness of 20 μm. The paste was applied such that the mass of the positive electrode active material after drying was 0.05 g/cm ² . Then, the paste-coated aluminum foil was vacuum dried at 120° C. for 12 hours, and then punched into a disk shape having a diameter of 1 cm to obtain a positive electrode 3a.

Using the positive electrode 3a, the negative electrode 3b, the separator 3c, and the nonaqueous electrolytic solution, the coin battery 1 shown in FIG. 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80° C.

For the negative electrode 3b, a lithium metal stamped into a disk shape having a diameter of 15 mm was used.

A polyethylene porous film having a thickness of 20 μm was used for the separator 3c.

As the electrolytic solution, a mixed solution (manufactured by Ube Industries, Ltd.) of ethylene carbonate (EC) and diethyl carbonate (DEC) in an equal amount using 1 M LiClO ₄ as a supporting electrolyte was used.

The initial discharge capacity, the initial charge/discharge efficiency, and the positive electrode resistance showing the performance of the manufactured coin-type battery 1 were evaluated as follows.

The initial charge capacity and the initial discharge capacity were left to stand for about 24 hours after the coin-type battery 1 was manufactured, and after the open circuit voltage OCV (Open Circuit Voltage) became stable, the current density to the positive electrode was set to 0.1 mA/cm ^2. The capacity when the cutoff voltage was charged to 4.3V was taken as the initial charge capacity, and the capacity when the cutoff voltage was discharged to 3.0V after a 1-hour rest was taken as the initial discharge capacity. [(Initial discharge capacity)/(Initial charge capacity)]×100 was calculated as the initial charge/discharge efficiency.

The positive electrode resistance is measured by charging the coin-type battery 1 at a charging potential of 4.1 V and using a frequency response analyzer and a potentiogalvanostat (Solartron, 1255B) according to the AC impedance method to obtain Nyquist as shown in FIG. A plot is obtained.

Since this Nyquist plot is expressed as the sum of the characteristic curves showing the solution resistance, the negative electrode resistance and its capacity, and the positive electrode resistance and its capacity, a fitting calculation is performed based on this Nyquist plot using an equivalent circuit to determine the positive electrode resistance. The value of was calculated.

The coin-type battery 1 using a positive electrode prepared by using the obtained positive electrode active material for a lithium ion secondary battery has an initial discharge capacity of 205 mAh/g, an initial charge/discharge efficiency of 89.0%, and a positive electrode resistance of 4. It was 8Ω.

Table 1 shows the firing conditions of the lithium-nickel-containing composite oxide, the characteristics of the obtained lithium-nickel-containing composite oxide, and the battery characteristics of the lithium-ion secondary battery. The results for Example 2 and Comparative Examples 1 and 2 below are also shown in Table 1.

(Example 2)
In the same manner as in Example 1 except that the temperature was raised from 500° C. to 745° C. at a temperature rising rate of 1.43° C./min so that the passage time in the temperature range of 600° C. to 650° C. was 35 minutes. Then, a lithium-nickel-containing composite oxide, a positive electrode active material for a lithium-ion secondary battery, and a lithium-ion secondary battery were manufactured, and their respective evaluations were performed. The composition of the obtained lithium nickel-containing composite oxide was the general formula: Li _1.02 Ni _0.905 Co _0.048 Al _0.047 O ₂ . The eluted Li amount was 0.35 mass% with respect to the entire base material. The composition of the obtained positive electrode active material for a lithium ion secondary battery was a general formula: Li _0.99 Ni _0.905 Co _0.048 Al _0.047 W _0.0035 O ₂ . 3. The coin-type battery 1 using a positive electrode prepared by using the obtained positive electrode active material for a lithium ion secondary battery has an initial discharge capacity of 208 mAh/g, an initial charge/discharge efficiency of 90.0%, and a positive electrode resistance of 4. It was 6Ω.

(Comparative Example 1)
In the same manner as in Example 1 except that the temperature was raised from 500° C. to 745° C. at a temperature rising rate of 0.91° C./min so that the passage time in the temperature range of 600° C. to 650° C. was 55 minutes. Then, a lithium-nickel-containing composite oxide, a positive electrode active material for a lithium-ion secondary battery, and a lithium-ion secondary battery were manufactured, and their respective evaluations were performed. The composition of the obtained lithium nickel-containing composite oxide was the general formula: Li _1.02 Ni _0.905 Co _0.048 Al _0.047 O ₂ . The eluted Li amount was 0.28 mass% with respect to the entire base material. The composition of the obtained positive electrode active material for a lithium ion secondary battery was a general formula: Li _0.99 Ni _0.905 Co _0.048 Al _0.047 W _0.0035 O ₂ . The coin-type battery 1 using a positive electrode prepared by using the obtained positive electrode active material for a lithium ion secondary battery has an initial discharge capacity of 198 mAh/g, an initial charge/discharge efficiency of 85.0%, and a positive electrode resistance of 5. It was 7Ω.

(Comparative example 2)
In the same manner as in Example 1 except that the temperature was raised from 500°C to 745°C at a temperature rising rate of 5.0°C/min so that the passage time in the temperature range of 600°C to 650°C was 10 minutes. Then, a lithium-nickel-containing composite oxide, a positive electrode active material for a lithium-ion secondary battery, and a lithium-ion secondary battery were manufactured, and their respective evaluations were performed. The composition of the obtained lithium nickel-containing composite oxide was the general formula: Li _1.02 Ni _0.905 Co _0.048 Al _0.047 O ₂ . The eluted Li amount was 0.55 mass% with respect to the entire base material. The composition of the obtained positive electrode active material for a lithium ion secondary battery was a general formula: Li _0.99 Ni _0.905 Co _0.048 Al _0.047 W _0.0035 O ₂ . The coin-type battery 1 using a positive electrode prepared by using the obtained positive electrode active material for a lithium ion secondary battery has an initial discharge capacity of 197 mAh/g, an initial charge/discharge efficiency of 84.0%, and a positive electrode resistance of 6. It was 0Ω.

Using the lithium-nickel-containing composite oxide of the present invention as a base material, fine particles of a compound containing W and Li and/or a coating film are present on the surface of primary particles to obtain a positive electrode active material for a lithium ion secondary battery, whereby a crystal is obtained. A high-capacity and high-output positive electrode active material is provided without impairing the property. Such a positive electrode active material having high quality and excellent electrical characteristics is suitable as a positive electrode material used in a lithium ion secondary battery for power source applications such as electric vehicles and hybrid vehicles.

1 coin type battery 2 case 2a positive electrode can 2b negative electrode can 2c gasket 3 electrode 3a positive electrode 3b negative electrode 3c separator

Claims (17)

A compound containing W and Li, which comprises primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles and/or a coating film of the compound containing W and Li are present on the surface of the primary particles. A method for producing a lithium-nickel-containing composite oxide, which is a base material of a positive electrode active material for a lithium-ion secondary battery comprising a coated lithium-nickel-containing composite oxide,
After mixing a nickel compound and a lithium compound to obtain a lithium mixture, the lithium mixture is heated in an oxidizing atmosphere from room temperature to a firing temperature of 700° C. or higher to obtain the lithium nickel-containing composite oxide. In the step of preparing, it is characterized in that the passage time and/or the holding time in the temperature range in which the temperature of the lithium mixture is 600° C. to 650° C. is 45 minutes or less.
Method for producing lithium nickel-containing composite oxide. The method for producing a lithium-nickel-containing composite oxide according to claim 1, wherein the passage time and/or the holding time is in the range of 10 minutes to 40 minutes. The nickel compound contains Ni, Co, and an additive element of at least one selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W, and lithium nickel is obtained. The contained complex oxide is
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
Having a composition consisting of,
The method for producing the lithium nickel-containing composite oxide according to claim 1. The firing temperature is controlled in the temperature range of 700° C. to 780° C., and the length of the lattice constant in the c-axis direction in the crystal of the lithium nickel-containing composite oxide obtained from Rietveld analysis of X-ray diffraction is 14 The manufacturing method of the lithium nickel containing complex oxide in any one of Claims 1-3 which makes it the range of 0.183Å~14.205Å. A compound containing W and Li, which comprises primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles and/or a coating film of the compound containing W and Li are present on the surface of the primary particles. A base material of a positive electrode active material for a lithium ion secondary battery comprising a coated lithium nickel-containing composite oxide, which is a lithium nickel-containing composite oxide,
10 g of the lithium nickel-containing composite oxide was immersed in 100 ml of pure water, stirred for 1 minute and allowed to stand for 3 minutes, and the supernatant was obtained by neutralization titration with 1 mol/L hydrochloric acid. The amount of Li is in the range of 0.3 mass% to 0.5 mass% with respect to the entire lithium nickel-containing composite oxide,
Lithium-nickel-containing composite oxide. The lithium nickel-containing composite oxide according to claim 5, wherein the eluted Li amount is in the range of 0.35% by mass to 0.45% by mass. General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (1)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo and W, and 0.98≦a≦1.11, 0 <x≦0.15, 0<y≦0.07, and x+y≦0.16.)
Having a composition consisting of,
The lithium-nickel-containing composite oxide according to claim 5 or 6. The length of the lattice constant in the c-axis direction in the crystal of the lithium nickel-containing composite oxide obtained from Rietveld analysis of X-ray diffraction is in the range of 14.183Å to 14.205Å. The lithium nickel-containing composite oxide according to any one of claims. The lithium-nickel-containing composite oxide according to claim 5, having a volume-based average particle size MV in the range of 5 μm to 30 μm. A compound containing W and Li, which comprises primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles and/or a coating film of the compound containing W and Li are present on the surface of the primary particles. A method for producing a positive electrode active material for a lithium ion secondary battery comprising a coated lithium nickel-containing composite oxide,
A lithium nickel-containing composite oxide obtained by the method for producing a lithium nickel-containing composite oxide according to claim 1 is used as a base material, and the amount of the lithium nickel-containing composite oxide is 1 L of water. To 700 g to 2000 g, a slurry is formed, and the lithium nickel-containing composite oxide is washed with water,
During the water washing treatment or after the water washing treatment, a tungsten compound is added to the lithium nickel-containing composite oxide to disperse W on the surface of the primary particles of the lithium nickel-containing composite oxide, and
The lithium nickel-containing composite oxide in which W is dispersed on the surface of the primary particles is heat-treated to form fine particles and/or a film of a compound containing W and Li on the surface of the primary particles of the lithium nickel-containing composite oxide. To do
Characterized by that
A method for producing a positive electrode active material for a lithium ion secondary battery. The positive electrode active material for the lithium ion secondary battery,
General _{formula: Li a Ni 1-x-} y Co x M y W z O 2 + α ··· (2)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. 0.95≦a≦1.10, 0 <x≦0.15, 0<y≦0.07, x+y≦0.16, 0.001≦z≦0.03, 0≦α≦0.2.)
Which is composed of a compound-coated lithium-nickel-containing composite oxide containing W and Li having a composition of
The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 10. The amount of W dispersed on the surface of the primary particles of the lithium-nickel-containing composite oxide is 0.1 atom% to 3 with respect to the total number of Ni, Co and M atoms contained in the lithium-nickel-containing composite oxide. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 10, wherein the content is in the range of 0.0 atomic %. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 10, wherein the heat treatment is performed in an oxygen atmosphere or a vacuum atmosphere at a temperature in the range of 100° C. to 600° C. 14. A compound containing W and Li, which comprises primary particles and/or secondary particles formed by aggregating the primary particles, and fine particles and/or a coating film of the compound containing W and Li are present on the surface of the primary particles. A positive electrode active material for a lithium ion secondary battery comprising a coated lithium nickel-containing composite oxide,
The compound-coated lithium nickel-containing composite oxide containing W and Li is fine particles of a compound containing W and Li on the surface of the primary particles of the lithium nickel-containing composite oxide according to any one of claims 5 to 9, and/or Characterized by having a coating present,
Positive electrode active material for lithium-ion secondary batteries. The positive electrode active material for the lithium ion secondary battery,
General _{formula: Li a Ni 1-x-} y Co x M y W z O 2 + α ··· (2)
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, Mo, and W. 0.95≦a≦1.10, 0 <x≦0.15, 0<y≦0.07, x+y≦0.16, 0.001≦z≦0.03, 0≦α≦0.2.)
Which is composed of a compound-coated lithium-nickel-containing composite oxide containing W and Li having a composition of
The positive electrode active material for a lithium ion secondary battery according to claim 14. The length of the lattice constant in the c-axis direction in the crystal of the compound-coated lithium nickel-containing composite oxide containing W and Li obtained from Rietveld analysis of X-ray diffraction is in the range of 14.183Å to 14.205Å. The positive electrode active material for a lithium ion secondary battery according to claim 14 or 15. The positive electrode for a lithium ion secondary battery according to claim 14, wherein the volume-based average particle size MV of the compound-coated lithium nickel-containing composite oxide containing W and Li is in the range of 5 μm to 30 μm. Active material.

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