JP2017117700A - Method for producing positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a positive electrode active material capable of easily producing a positive electrode active material for a non-aqueous electrolyte secondary battery capable of achieving both high capacity and high output when used as a positive electrode material. To do. SOLUTION: A nickel composite hydroxide in a wet state obtained by neutralization crystallization and a tungsten compound are mixed and then heat-treated at 100 to 750° C. to obtain a tungsten mixture, and the tungsten mixture and further a lithium compound. Are mixed and fired in an oxidizing atmosphere in a temperature range of 700 to 900° C. to obtain a lithium nickel composite oxide composed of primary particles and secondary particles formed by aggregating the primary particles. [Selection diagram] None

Description

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

In recent years, with the rapid expansion of small electronic devices such as mobile phones and laptop computers, the demand for non-aqueous electrolyte secondary batteries as a chargeable / dischargeable power source has increased rapidly. As the positive electrode active material of this non-aqueous electrolyte secondary battery, lithium nickel composite oxide represented by lithium nickelate (LiNiO ₂ ), lithium nickel composite oxide represented by lithium cobaltate (LiCoO ₂ ), manganese Lithium manganese composite oxides typified by lithium acid lithium (LiMnO ₂ ) are widely used.

  By the way, lithium cobaltate has a problem in that it contains cobalt as a main component because it has a small reserve and is expensive, is unstable in supply, and has a large price fluctuation. For this reason, lithium nickel composite oxide or lithium manganese composite oxide containing relatively inexpensive nickel or manganese as a main component has attracted attention from the viewpoint of cost.

  However, although lithium manganate is superior to lithium cobaltate in terms of thermal stability, the charge / discharge capacity is very small compared to other materials, and the charge / discharge cycle characteristics indicating lifetime are also very short. There are many practical problems as a battery. On the other hand, lithium nickelate has a higher charge / discharge capacity than lithium cobaltate, and thus is expected as a positive electrode active material capable of producing a low-cost and high-energy density battery.

This lithium nickelate is usually produced by mixing and firing a lithium compound and a nickel compound such as nickel hydroxide or nickel oxyhydroxide, and the shape thereof is a powder or primary particle of monodispersed primary particles. Although it becomes the powder of the secondary particle with the space | gap which is an aggregate | assembly, all had the fault that the thermal stability in a charge condition was inferior to lithium cobaltate.
That is, pure lithium nickelate has problems in thermal stability, charge / discharge cycle characteristics, etc., and could not be used as a practical battery. This is because the stability of the crystal structure in the charged state is lower than that of lithium cobalt oxide.

Therefore, in order to stabilize the crystal structure in the state where lithium is removed during the charging process, and to obtain a lithium nickel composite oxide having good thermal stability and charge / discharge cycle characteristics as a positive electrode active material, a lithium nickel composite oxide It is common practice to replace part of the nickel with other substances.
For example, Patent Document 1 discloses that Li _{a Mb} Ni _c Co _d O _e (M is a group consisting of Al, Mn, Sn, In, Fe, V, Cu, Mg, Ti, Zn, and Mo as a positive electrode active material. And at least one metal selected from the group consisting of 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2. In the range of 2 and b + c + d = 1) has been proposed.

Further, as a method for improving the thermal stability of the lithium nickel composite oxide, a technique of washing the lithium nickelate after firing with water has been developed.
For example, in Patent Document 2, nickel hydroxide or nickel oxyhydroxide is calcined at a temperature of 600 to 1100 ° C. in an air atmosphere to prepare nickel oxide, and after mixing a lithium compound, oxygen In an atmosphere, the maximum temperature is baked in the range of 650 to 850 ° C., and the obtained baked powder is A ≦ B / 40 in water (where A is the washing time expressed in minutes, B is g / A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery that has been washed with water within a time that satisfies the above condition and that is filtered and dried has been proposed.

However, when a part of nickel in the lithium-nickel composite oxide is replaced with another substance, when a large amount of element substitution (in other words, a state in which the nickel ratio is lowered) is performed, the thermal stability increases, but the battery capacity Decrease. On the other hand, when a small amount of element substitution (in other words, a state in which the nickel ratio is increased) is performed in order to prevent a decrease in battery capacity, the thermal stability is not sufficiently improved. Moreover, if the nickel ratio is high, there is also a problem that cation mixing is likely to occur during firing and synthesis is difficult.
Also, if the lithium nickelate after calcination is washed with water, a positive electrode active material with high capacity and excellent thermal stability and storage characteristics in a high temperature environment can be obtained when it is used in a non-aqueous electrolyte secondary battery. However, a product that sufficiently meets the demand for higher capacity and higher output has not been obtained.

On the other hand, in order to improve output characteristics, a method of adding a tungsten compound to a lithium nickel composite oxide has been studied.
For example, Patent Document 3, the general formula _{Li z Ni 1-xy Co x} M y O 2 ( however, 0.10 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.97 ≦ z ≦ 1 .20, M is lithium composed of primary particles represented by Mn, V, Mg, Mo, Nb, Ti, and Al) and secondary particles formed by aggregation of the primary particles. A positive electrode active material for a non-aqueous electrolyte secondary battery has been proposed in which the primary particle surface of the metal composite oxide powder has a compound containing W and Li.
However, although the positive electrode active material has improved output characteristics, there is a problem that the number of processes increases. Moreover, since the nickel ratio is low, further increase in capacity is desired. In addition, when the nickel ratio is increased, it is necessary to study thermal stability.

  Therefore, although various lithium-nickel composite oxides in which a part of nickel is replaced with other substances have been developed, currently, when used in non-aqueous electrolyte secondary batteries, there is a demand for higher capacity and higher output. However, a positive electrode active material made of a lithium nickel composite oxide that is sufficiently compatible with the above and is easy to manufacture has not been obtained.

Japanese Patent Laid-Open No. 5-242891 JP 2007-273108 A JP 2012-077944 A

  In view of the above problems, the present invention provides a method for producing a positive electrode active material that can easily produce a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high capacity and high output when used as a positive electrode material. The purpose is to provide.

In order to solve the above problems, the present inventors have conducted intensive research on the powder properties of lithium metal composite oxides used as the positive electrode active material for non-aqueous electrolyte secondary batteries and the effect on the positive electrode resistance of the battery. In addition to controlling the crystal structure of the lithium nickel composite oxide with an increased nickel ratio and forming a compound containing W and Li on the primary particle surface constituting the lithium nickel composite oxide, high capacity and high output can be obtained. The knowledge that it was possible to make it compatible was obtained.
Furthermore, as its manufacturing method, after adding a tungsten compound to a wet nickel composite hydroxide and heat-treating it, further adding a lithium compound and firing, a non-aqueous system capable of achieving both high capacity and high output The inventors have found that an electrolyte can be obtained, and have completed the present invention.

That is, the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium nickel composite oxide,
The following steps (A) to (D) are included in the order of steps (A) to (D).
(A) an aqueous solution of a metal compound containing nickel and cobalt and containing at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo as the additive element M; A crystallization step in which a reaction solution containing an aqueous solution containing an ammonium ion supplier is neutralized and crystallized while being kept alkaline, and then solid-liquid separation is performed to obtain a wet nickel composite hydroxide.
(B) A heat treatment step in which a wet nickel composite hydroxide obtained in the crystallization step and a tungsten compound are mixed and then heat treated at 100 to 750 ° C. to obtain a tungsten mixture.
(C) A mixing step in which the tungsten mixture is further mixed with a lithium compound to obtain a lithium mixture.
(D) Firing the lithium mixture in an oxidizing atmosphere at a temperature range of 700 to 900 ° C. to obtain a lithium nickel composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles. Process.

  The water washing step of mixing the calcined powder of the lithium nickel composite oxide obtained in the calcining step with water so as to be 700 g to 2000 g with respect to 1 L of water to form a slurry, and washing the calcined powder with water, It is preferable to further provide.

  The amount of tungsten contained in the tungsten compound mixed with the nickel composite hydroxide is 0.1 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the nickel composite hydroxide. It is preferable to do.

  The wet nickel composite hydroxide preferably has a pH value on a 25 ° C. basis of 8 or more.

  The sulfate content of the nickel composite hydroxide is preferably 0.1 to 0.4% by mass.

  It is preferable that the tungsten compound is at least one selected from the group consisting of tungsten oxide, tungstic acid, ammonium paratungstate, and sodium tungstate, and the lithium compound is lithium hydroxide, oxyhydroxide, It is preferably at least one selected from the group consisting of oxides, carbonates, nitrates and halides.

  In the mixing step, the nickel composite hydroxide and the lithium compound so that the amount of lithium in the lithium compound with respect to the total amount of all metal elements excluding lithium in the mixture is 0.98 to 1.25 in molar ratio. It is preferable to adjust the mixing ratio.

  In the water washing step, it is preferable to adjust the temperature of the slurry during the water washing treatment to 10 to 40 ° C.

The lithium nickel composite oxide is represented by the general formula: Li _a Ni _1-x - in _y Co _x M _y O ₂ (wherein, M represents, Mg, Al, Ca, Ti , V, Cr, Mn, Nb, Zr and It is at least one element selected from Mo. a is 0.95 ≦ a ≦ 1.11, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, and x + y is ≦ 0. The primary particles and the secondary particles are preferably composed of secondary particles formed by agglomeration.

According to the present invention, there is provided a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high capacity and high output when used as a positive electrode material for a non-aqueous electrolyte secondary battery, and is excellent in safety. can get.
Furthermore, the manufacturing method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.

It is a schematic sectional drawing of the coin-type battery 1 used for battery evaluation. It is a schematic explanatory drawing of the measurement example of impedance evaluation, and the equivalent circuit used for analysis.

(1) Method for Producing Positive Electrode Active Material A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as “positive electrode active material”) will be described in detail for each step. .
The method for producing a positive electrode active material of the present invention is a method for producing a positive electrode active material comprising a lithium nickel composite oxide, and includes the following steps (A) to (D).
(A) A crystallization step for obtaining a wet nickel composite hydroxide.
(B) A heat treatment step for obtaining a tungsten mixture.
(C) A mixing step for obtaining a lithium mixture.
(D) A firing step for obtaining a lithium nickel composite oxide.

(A) Crystallization step The crystallization step includes nickel and cobalt, and the additive element M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo. In the step of obtaining a wet nickel composite hydroxide by solid-liquid separation after neutralizing and crystallizing a reaction solution containing an aqueous solution of a metal compound containing an aqueous solution and an aqueous solution containing an ammonium ion supplier is there.

In the crystallization method, nickel composite hydroxide is obtained under various conditions, and the crystallization conditions are not particularly limited, but those obtained under the following conditions are preferred.
Specifically, nickel and cobalt are contained in a reaction vessel heated to 40 to 60 ° C., and the additive element M is Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr, and Mo. An aqueous solution of a metal compound containing at least one selected element and an aqueous solution containing an ammonium ion supplier are dropped, and neutralized and crystallized while being kept alkaline.

The reaction solution is alkaline, preferably, an aqueous solution of an alkali metal hydroxide is dropped as necessary to obtain a nickel composite hydroxide so that the reaction temperature can be maintained at 10 to 14 at a pH value based on a liquid temperature of 25 ° C. .
The additive element M may be co-precipitated with nickel and cobalt, but after obtaining a hydroxide by crystallization, it is coated with a metal compound containing the additive element M, or an aqueous solution containing the metal compound. Nickel composite hydroxide can also be obtained by impregnating with.

The nickel composite hydroxide obtained by the crystallization method becomes a high bulk density powder.
Furthermore, since such a high bulk density composite hydroxide makes it easy to obtain lithium nickel composite oxide particles having a small specific surface area, the lithium nickel composite oxide used as a positive electrode active material for non-aqueous electrolyte secondary batteries can be obtained. The nickel composite hydroxide is suitable as a raw material.

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 is increased in the solution, and only a fine powder is obtained without crystal growth. It may not be possible. On the other hand, if the nickel composite hydroxide is crystallized at a temperature of less than 40 ° C. or a pH of less than 10, there is little generation of nuclei in the liquid, and crystal growth of the particles becomes preferential, and the resulting nickel composite water Coarse particles may be mixed into the oxide. In addition, the residual amount of metal ions in the reaction solution may increase, resulting in a composition shift.
When the nickel composite hydroxide in which such coarse particles are mixed and compositional deviation is used as a raw material, the battery characteristics of the obtained positive electrode active material are deteriorated.
Therefore, when the nickel composite hydroxide used as the nickel compound in the firing step is obtained by crystallization, the reaction solution is maintained at 40 to 60 ° C., and the reaction solution is maintained at a pH value based on the liquid temperature of 25 ° C. It is preferable to crystallize in the state maintained at 10-14.

The nickel composite hydroxide can be used as a nickel oxy composite hydroxide. A method for obtaining nickel oxyhydroxide is not particularly limited, but a nickel oxyhydroxide prepared by oxidizing a nickel composite hydroxide with an oxidizing agent such as sodium hypochlorite or hydrogen peroxide is preferable. The nickel oxy composite hydroxide obtained by this method becomes a high bulk density powder.
Such a high bulk density nickel oxy composite hydroxide makes it easy to obtain lithium nickel composite oxide particles having a small specific surface area. Therefore, a lithium nickel composite oxide used as a positive electrode active material for a non-aqueous electrolyte secondary battery is used. It becomes a nickel oxy composite hydroxide suitable as a raw material.

The nickel composite hydroxide used as the nickel compound preferably has a sulfate radical (SO ₄ ) content of 0.1 to 0.4 mass%, preferably 0.1 to 0.3 mass%. More preferred. This facilitates the control of the crystallinity of the lithium nickel composite oxide in the subsequent firing.

That is, by setting the sulfate radical content to 0.1 to 0.4 mass%, for example, the length of the c-axis can be easily controlled. Moreover, since the shrinkage | contraction of the secondary particle by the growth of the primary particle at the time of baking can be made moderate, the porosity can also be controlled easily.
However, when the sulfate group content is less than 0.1% by mass, the progress of crystallization becomes too fast, and the crystallinity may not be sufficiently controlled. In addition, primary particles grow and secondary particles shrink, and the specific surface area and porosity may become too small. On the other hand, when the content of sulfate radicals exceeds 0.4 mass%, the growth of primary particles is suppressed, so that the specific surface area and the porosity may become too large.

Moreover, the nickel oxy composite hydroxide obtained from the nickel composite hydroxide and the nickel composite oxide obtained in the heat treatment step contain approximately the same amount of sulfate radical as the sulfate radical contained in the nickel composite hydroxide. To do.
Therefore, by setting the content of sulfate radical (SO ₄ ) in the nickel composite hydroxide to 0.1 to 0.4% by mass, the nickel oxy composite hydroxide obtained from the nickel composite hydroxide or the nickel composite The same effect can be obtained when an active material is obtained using an oxide as a raw material.

  The nickel composite hydroxide was obtained by a crystallization method. In this case, a sulfate such as nickel sulfate was used as a raw material, and the sulfate radical was 0.1 to 0.00 by washing thoroughly after crystallization. It is preferable to obtain a nickel composite hydroxide having a content of 4% by mass.

  Further, the washing is preferably performed using an alkaline aqueous solution whose pH is adjusted to 11 to 13 based on a liquid temperature of 25 °. If the pH of the alkaline aqueous solution is less than 11, the sulfate radical content may not be reduced to 0.1 to 0.4 mass%. Even if the pH of the aqueous alkali solution exceeds 13, the effect of reducing sulfate radicals is not improved, and cations in the aqueous alkaline solution may remain as impurities.

  As the alkaline aqueous solution, an alkali metal hydroxide such as sodium hydroxide or an aqueous carbonate solution such as sodium carbonate is preferably used. After washing with an alkaline aqueous solution, washing with water is preferable.

(B) Heat treatment step The heat treatment step is a step in which the wet nickel composite hydroxide obtained in the crystallization step and a tungsten compound are mixed and then heat treated at 100 to 750 ° C to obtain a tungsten mixture.

  The nickel composite hydroxide is obtained by neutralization and crystallization while maintaining alkalinity, and the wet nickel composite hydroxide exhibits alkalinity. For this reason, the tungstate is easily dissolved, and the dissolved tungsten compound is dispersed to the inside of the nickel composite hydroxide particles, that is, the voids inside the nickel composite hydroxide particles and the grain boundaries of the primary particles. Furthermore, even a tungstate that is not sufficiently dissolved at room temperature can be dissolved and dispersed during the temperature increase of the heat treatment.

  The tungstate may be any compound that dissolves in alkaline water when mixed with nickel composite hydroxide and heat-treated, but is selected from the group consisting of tungsten oxide, tungstic acid, ammonium paratungstate, and sodium tungstate. It is preferable that there is at least one. Since no impurities remain, tungsten oxide, tungstic acid, and ammonium paratungstate are more preferable.

  Since tungsten oxide and tungstic acid are readily soluble in alkaline water, the wet nickel composite hydroxide preferably has a pH value of 8 or more on a 25 ° C. basis. By setting the pH value to a wet state of 8 or more, the tungstate can be more easily dissolved by the temperature increase during heating and the increase of the pH value due to evaporation of moisture. Tungsten dissolves during the temperature rise in the heat treatment, but in order to dissolve and further uniformly disperse the tungsten, hold it at a temperature at which it can be dissolved, for example, 60 to 80 ° C. while suppressing an increase in moisture. Is preferred.

  In the heat treatment step, the tungsten compound is dispersed in the nickel composite hydroxide particles and then dried, but the temperature can be further increased to convert the nickel composite hydroxide into a nickel composite oxide. By converting to an oxide, the composition of the obtained lithium nickel composite oxide can be stabilized, and the composition during firing can be made uniform.

In the heat treatment step, the composition of the lithium nickel composite oxide is further stabilized by heating at 500 to 750 ° C. or higher and oxidizing and roasting so that the conversion to an oxide such as nickel composite hydroxide is sufficient. Can do.
If nickel composite hydroxide or the like remains in the nickel composite oxide after oxidative roasting, water vapor is generated during firing, the reaction between the lithium compound and the nickel composite oxide is inhibited, and the crystallinity is lowered. Therefore, it is preferable to sufficiently convert to an oxide.

When the heat treatment temperature is less than 100 ° C., a long time is required for drying, the productivity is lowered, and the composition of the obtained lithium nickel composite oxide is not stable due to residual moisture. On the other hand, if the heat treatment temperature exceeds 750 ° C., the crystallinity of the obtained nickel composite oxide becomes high, and the reactivity of the lithium compound and nickel composite oxide in the subsequent firing is reduced. The crystallinity of the nickel composite oxide decreases. Moreover, the porosity of lithium nickel complex oxide falls.
In addition, the nickel composite oxide undergoes rapid grain growth and coarse nickel composite oxide particles are formed, and the average particle diameter of the lithium nickel composite oxide obtained by mixing and firing the lithium compound increases. It may be too much.

  Therefore, when nickel composite hydroxide or nickel oxy composite hydroxide is heat-treated in an oxidizing atmosphere to obtain nickel composite oxide, preferably 500 to 750 ° C, more preferably 550 to 700 ° C. Heat treatment is preferably performed at a temperature.

Further, the holding time at the heat treatment temperature is preferably 1 to 10 hours, and more preferably 2 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 become too high.
The oxidizing roasting atmosphere may be an oxidizing atmosphere, but it is preferably an air atmosphere in consideration of handling properties and cost.

In mixing with the tungsten compound, the amount of tungsten to be added is 0.1 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the nickel composite hydroxide obtained above. It is preferable that Thereby, the high charge / discharge capacity and output characteristics of the positive electrode active material can be compatible.
If the amount of tungsten is less than 0.1 atomic%, the effect of improving the output characteristics may not be sufficiently obtained. If the amount of tungsten exceeds 3.0 atomic%, the amount of the above-mentioned compound formed becomes too large, and lithium nickel Lithium conduction between the composite oxide particles and the electrolytic solution may be inhibited, and the charge / discharge capacity may be reduced.

(C) Mixing step The mixing step is a step of mixing the tungsten mixture and a lithium compound to obtain a lithium mixture.

The lithium compound to be mixed is not particularly limited, but it is preferable to use at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide.
When such a lithium compound is used, there is an advantage that no impurities remain after firing. It is more preferable to use a lithium hydroxide having good reactivity with the nickel compound. From the viewpoint of suppressing impurities, it is more preferable to use at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, and carbonate.

  The mixing ratio of the nickel compound and the lithium compound is not particularly limited, but the composition of the metal element other than lithium and lithium in the lithium nickel composite oxide after firing is in the mixture obtained by mixing the nickel compound and the lithium compound. Is substantially maintained.

  Therefore, it is preferable to adjust so that the amount of lithium in the lithium compound is 0.98 to 1.25 in terms of molar ratio with respect to the total amount of nickel and other metal elements in the nickel compound.

When the molar ratio is less than 0.98, the crystallinity of the obtained fired powder may be very poor. Further, the lithium content in the obtained fired powder may be less than 0.98.
On the other hand, when the molar ratio exceeds 1.25, firing is likely to proceed and over-firing tends to occur, and the lithium content of the obtained fired powder may also exceed 1.25.

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

(D) Firing step The lithium mixture is fired in an oxidizing atmosphere in a temperature range of 700 to 900 ° C, preferably in a temperature range of 730 to 760 ° C.

  If it is baked at a temperature exceeding 500 ° C., a lithium nickel composite oxide is produced, but if it is less than 700 ° C., its crystal is undeveloped and structurally unstable. When such a lithium nickel composite oxide is used as a positive electrode active material, the crystal structure of the positive electrode active material is easily destroyed due to a phase transition due to charge and discharge. In addition, primary particle growth is insufficient, and the specific surface area and porosity may be too large.

  On the other hand, if firing at a temperature exceeding 900 ° C., cation mixing tends to occur as the nickel content increases, and the layered structure in the crystal of the lithium-nickel composite oxide collapses, and lithium ions are inserted and removed. Separation may be difficult. Therefore, it is preferable to appropriately control the firing temperature depending on the nickel content.

  Water of crystallization in the lithium compound can be removed, and further, in order to cause a uniform reaction in the temperature range in which the crystal growth of the lithium nickel composite oxide proceeds, the temperature is set to 400 to 600 ° C. for 1 to 5 hours, followed by 700 to It is particularly preferable to perform the baking at a temperature of 780 ° C. in two stages of 3 hours or more.

  During firing, the tungsten compound dispersed in the heat treatment step reacts with the lithium compound, and a compound containing tungsten and lithium is formed on the primary particle surface of the lithium nickel composite oxide. In addition, the reaction between tungsten and lithium can suppress the generation of a lithium compound (hereinafter sometimes referred to as “excess lithium”) as an impurity present on the surface of the primary particles after firing. In particular, since the compound is formed up to the surface of the primary particles inside the secondary particles of the lithium nickel composite oxide, both high charge / discharge capacity and output characteristics can be achieved.

This firing can synthesize lithium-nickel composite oxides in an oxidizing atmosphere, but is preferably a mixed gas atmosphere of 18 to 100% by volume of oxygen and an inert gas, with an oxygen concentration of 90% by volume or more. The mixed gas atmosphere is more preferable.
If the baking is performed in an atmosphere having an oxygen concentration of 18% by volume or more, that is, an oxygen content higher than that in the air atmosphere, the reactivity between the lithium compound and the nickel compound can be increased.
In order to further increase the reactivity and obtain a lithium nickel composite oxide having excellent crystallinity, it is more preferable to use a mixed gas atmosphere having an oxygen concentration of 90% by volume or more, and an oxygen atmosphere (oxygen concentration 100%). Is more preferable.

  There are no particular limitations on the apparatus and method for firing the lithium mixture. For example, it is possible to use a firing furnace such as an electric furnace, a kiln, a tubular furnace, a pusher furnace that can be adjusted to a gas atmosphere having an oxygen concentration of 18% by volume or more, such as an oxygen atmosphere, a dehumidified carbon dioxide-treated dry air atmosphere, or the like. it can.

As described above, the general _{formula: Li a Ni 1-x -} y Co x M y O 2 ( where, M is, Mg, Al, Ca, Ti , V, Cr, Mn, Nb, from Zr and Mo A is 0.98 ≦ a ≦ 1.11, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, and x + y is ≦ 0.16. And a lithium nickel composite oxide composed of secondary particles composed of aggregated primary particles and primary particles.

  When the positive electrode active material obtained from this fired product is used for the positive electrode of a battery, thermal stability and the like can be maintained, and further, lithium ion can be easily inserted and removed, thereby increasing capacity and output. Can be realized.

Here, when a indicating the lithium content of the calcined powder is less than 0.98, the crystallinity of the calcined powder is lowered, and in the case of a water washing step, the mole of lithium and a metal other than lithium in the lithium nickel composite oxide The ratio becomes less than 0.95, which may cause a large decrease in battery capacity during the charge / discharge cycle.
On the other hand, if a exceeds 1.25, a large amount of excess lithium is present on the surface of the baked powder, and not only a large amount of gas is generated during charging of the battery, but also a powder exhibiting a high pH. It reacts with materials such as the organic solvent to be used, causing the slurry to gel and causing problems. Moreover, it becomes difficult to remove this by washing with water.

(E) Water-washing process A water-washing process is a process of carrying out the water-washing process of the baking powder of the lithium nickel composite oxide obtained by the baking process, and can be equipped after a baking process.
Specifically, a slurry is formed so that the calcined powder becomes 700 g to 2000 g with respect to 1 L of water, washed with water, filtered and dried to obtain a lithium nickel composite oxide powder (washed powder).

In the washing step, the washing temperature during the washing treatment is preferably adjusted to 10 to 40 ° C, more preferably 10 to 30 ° C.
By adjusting the temperature in this way, impurities present on the surface of the sintered powder of the lithium nickel composite oxide are removed, and the amount of residual lithium such as lithium carbonate and lithium hydroxide present on the surface is reduced with respect to the entire powder. And 0.10% by mass or less.
Thereby, when the obtained positive electrode active material is used for the positive electrode of a battery, gas generation at the time of high temperature maintenance can be suppressed, and high capacity | capacitance, high output, and high safety can be made compatible.

On the other hand, when the washing temperature is less than 10 ° C., the fired powder cannot be sufficiently washed, and many impurities adhering to the surface of the fired powder may remain without being removed. When the impurities remain on the surface of the fired powder in this way, the resistance of the surface of the obtained positive electrode active material increases, so that when used for the positive electrode of the battery, the resistance value of the positive electrode increases. In addition, the specific surface area of the positive electrode active material becomes too small, the reactivity with the electrolytic solution decreases, and when used for the positive electrode of a battery, it is difficult to achieve high capacity and high output.
Furthermore, the amount of surplus lithium present on the surface of the composite oxide exceeds 0.10% by mass, and gas is easily generated during high-temperature storage when used as a battery.

  On the other hand, when the washing temperature exceeds 40 ° C., the amount of lithium eluted from the calcined powder increases, and nickel oxide (NiO) from which Li is removed from the surface layer or nickel oxyhydroxide (NiOOH) in which Li and H are substituted is obtained. May be generated. Since nickel oxide (NiO) and nickel oxyhydroxide (NiOOH) both have high electrical resistance, the resistance of the surface of the composite oxide particles increases, and the Li of the lithium nickel composite oxide decreases and the capacity decreases. .

  In the water washing, water and the fired powder are mixed to form a slurry, and the fired powder is washed by stirring the slurry. In that case, the quantity (g) of the baked powder with respect to 1L of water contained in a slurry is adjusted so that it may become 700-2000g, Preferably 700-1500g.

That is, as the slurry concentration increases, the amount of the fired powder in the slurry increases. However, if the slurry concentration exceeds 2000 g / L, the viscosity of the slurry increases and stirring becomes difficult. In addition, since the alkali concentration in the slurry liquid is high, the dissolution rate of the deposits adhering to the fired powder is slow due to the equilibrium relationship, and even if the deposits are peeled off from the powder, they are reattached. It becomes difficult to remove impurities.
On the other hand, if the slurry concentration is less than 700 g / L, it is too dilute, so that the amount of lithium eluted into the slurry from the individual particle surface increases. In particular, the higher the nickel ratio, the more lithium is eluted and the lower the amount of lithium on the surface. For this reason, desorption of lithium from the crystal lattice of the lithium nickel composite oxide also occurs, and the crystal is easily broken.
Therefore, when the obtained positive electrode active material is used for the positive electrode of the battery, the battery capacity decreases.

The time for washing the fired powder with water is not particularly limited, but is preferably about 5 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 increased, the cleaning effect is not improved and the productivity is lowered.

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

The drying after the water washing treatment is preferably performed as follows.
The temperature and method for drying the lithium nickel composite oxide fired powder after washing with water are not particularly limited, but the drying temperature is preferably 80 to 500 ° C, more preferably 120 to 250 ° C.
By setting the temperature to 80 ° C. or higher, the fired powder after washing with water is dried in a short time, and a lithium concentration gradient is prevented from occurring between the surface and the inside of the composite oxide particles, thereby improving battery characteristics. be able to.
On the other hand, in the vicinity of the surface of the fired powder after washing with water, it is expected that it is very close to the stoichiometric ratio or is in a state close to a charged state with some lithium being desorbed. For this reason, when the temperature exceeds 500 ° C., the crystal structure of the powder close to the charged state is lost, and there is a risk of deteriorating electrical characteristics.

  Therefore, in order to reduce the concern about the physical properties and properties of the lithium nickel composite oxide fired powder after washing with water, 80 to 500 ° C. is preferable, and 120 to 250 ° C. is more preferable in consideration of productivity and thermal energy cost. .

  In addition, the drying method of the lithium nickel composite oxide fired powder is performed at a predetermined temperature using a dryer that can control the powder after filtration in a gas atmosphere or a vacuum atmosphere not containing a compound component containing carbon and sulfur. It is preferable.

(2) Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for non-aqueous electrolyte secondary battery obtained by the present invention (hereinafter simply referred to as “positive electrode active material”) is, for example, a lithium nickel composite oxide. A positive electrode active material comprising primary particles and secondary particles formed by aggregation of the primary particles, and a compound containing tungsten (W) and lithium (Li) on the surface of the primary particles (hereinafter referred to as “LW compound”) It may be said that). Lithium nickel composite oxide is represented by the general _{formula: Li b Ni 1-x -} y Co x M y O 2 ( where, M is, Mg, Al, Ca, Ti , V, Cr, Mn, Nb, Zr and Mo A is 0.95 ≦ b ≦ 1.11, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, and x + y is ≦ 0.16. It is preferably a numerical value satisfying
Here, the lithium nickel composite oxide is a base material for forming a LiW compound on the surface of the primary particles, and the composite oxide particles described below include primary particles having a LiW compound on the surface, and the primary particles aggregate. It means a combination of secondary particles constructed as described above.

[composition]
The positive electrode active material of the present invention is composed of a lithium nickel composite oxide that is a hexagonal layered compound, and in the above general formula (1), (1-xy) indicating the content of nickel (Ni) is It is preferably 0.84 or more and less than 1.
In the positive electrode active material of the present invention, the higher the nickel content, the higher the capacity when used as the positive electrode active material. However, if the nickel content is too high, sufficient thermal stability cannot be obtained. , Cation mixing tends to occur during firing. On the other hand, when the nickel content is reduced, the capacity is lowered, and there is a problem that the capacity per battery volume cannot be sufficiently obtained even when the filling property of the positive electrode is increased.

  Therefore, the nickel content of the lithium nickel composite oxide in the positive electrode active material of the present invention is more preferably 0.84 or more and 0.98 or less, further preferably 0.845 or more and 0.950 or less, and 0.85. Above 0.95 is particularly preferable.

X indicating the content of cobalt (Co) is preferably 0 <x ≦ 0.15, more preferably 0.02 ≦ x ≦ 0.15, and further preferably 0.03 ≦ x ≦ 0.13. is there.
When the cobalt content is within the above range, excellent cycle characteristics and thermal stability can be obtained. Although the cycle characteristics of the positive electrode active material can be improved by increasing the cobalt content, the cobalt content is preferably 0.15 or less in order to increase the capacity of the positive electrode active material.

Further, y indicating the content of at least one element M selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo is preferably 0 <y ≦ 0.07, More preferably, 0.01 ≦ y ≦ 0.05. When the content of M is in the above range, excellent cycle characteristics and thermal stability can be obtained.
If y exceeds 0.07, it may be difficult to increase the capacity of the positive electrode active material. When no additive element is added, the effect of improving battery characteristics cannot be obtained. Therefore, in order to sufficiently obtain the effect of improving battery characteristics, y is preferably set to 0.01 or more.

B indicating the content of lithium (Li) is preferably 0.95 ≦ b ≦ 1.11.
When b is less than 0.95, a metal element such as Ni is mixed in the lithium layer in the layered compound and Li insertion / removability is reduced, so that the battery capacity is reduced and the output characteristics are deteriorated. On the other hand, when b exceeds 1.03, Li is mixed in the metal layer in the layered compound, and thus the battery capacity is lowered.
Therefore, the lithium content of the lithium nickel composite oxide in the positive electrode active material in the present invention is 0.95 ≦ b ≦ 1.03 in order to improve battery capacity and output characteristics, and More preferably, 95 ≦ b ≦ 1.01.

[Length of c-axis]
Here, in the positive electrode active material obtained in the present invention, in a preferred embodiment of the lithium nickel composite oxide, the nickel content is 0.84 or more, preferably 0.98 or less, and the nickel content is very high. have.
When the content of nickel increases, problems such as a decrease in thermal stability occur. Therefore, the content of nickel is generally lower than 0.84, and generally about 0.80 to 0.83. To be adjusted.

However, in the positive electrode active material of the present invention, by appropriately controlling the length of the c-axis obtained by performing the Rietveld analysis of the X-ray diffraction of the crystal of the lithium nickel composite oxide, the high nickel content Is possible.
That is, in the positive electrode active material of the present invention, the c-axis length (hereinafter simply referred to as the c-axis length) obtained by performing the Rietveld analysis of the X-ray diffraction of the crystal is 14.183 angstroms or more. Preferably, the nickel content is high by making it 14.185 angstroms or more.

In the case of a hexagonal lithium-nickel composite oxide such as the positive electrode active material of the present invention, the c-axis length affects the insertion / extraction of lithium (Li) from the crystal.
In general, since the interlayer distance of the lithium layer increases as the c-axis length increases, the insertion / extraction of Li from the crystal is improved, and when such a lithium nickel composite oxide is used as a positive electrode active material. It becomes a positive electrode active material with high capacity and high output.
On the other hand, when the c-axis length is shortened, the ability to insert and extract Li from the crystal is lowered. Therefore, when used as a positive electrode active material, the capacity of the lithium nickel composite oxide is lowered and the output is also lowered. Further, since the crystallinity is lowered due to cation mixing, the cycle characteristics and thermal stability are also deteriorated.
For example, when the length of the c-axis is less than 14.183 angstroms, the ability to insert and remove Li from the crystal is lowered, resulting in a decrease in battery capacity and output characteristics.

Since the positive electrode active material of the present invention has a c-axis length of 14.183 angstroms or more, it is excellent in the ability to insert and extract Li from the crystal, and becomes a positive electrode active material with high capacity and high output. .
That is, in the positive electrode active material of the present invention, by increasing the c-axis length to 14.183 angstroms or more, the capacity increases as the nickel content increases, and the c-axis length increases by increasing the c-axis length. Achieves higher capacity and higher output.

The upper limit of the c-axis length is not particularly limited, but the upper limit is about 14.205 angstroms. In the positive electrode active material of the present invention, the c-axis length is 14.183 angstroms or more and 14.205 angstroms or less. It is preferable that
If the length of the c-axis is 14.185 angstroms or more and 14.200 angstroms or less, it is more preferable in terms of higher capacity and improved thermal stability due to higher crystallinity.

[Compound containing W and Li]
Generally, if the surface of the positive electrode active material is unevenly coated with a different compound, the lithium ion conductivity of the uncoated portion is lowered, resulting in the high capacity of the lithium nickel composite oxide. The advantages are erased.
In contrast, in the present invention, a compound containing tungsten (W) and lithium (Li) is uniformly formed on the surface of the primary particles of the lithium nickel composite oxide, but this LW compound has high lithium ion conductivity, It has the effect of promoting the movement of lithium ions. Therefore, by forming the compound on the surface of the primary particles, a Li conduction path is formed at the interface with the electrolytic solution, thereby reducing the reaction resistance of the active material and improving the output characteristics. .

  Here, when the surface of the composite oxide particles is coated with a layered material, the specific surface area decreases regardless of the coating thickness, so even if the coating has high lithium ion conductivity, The contact area with the electrolytic solution is reduced, which tends to cause a decrease in charge / discharge capacity and an increase in reaction resistance.

However, by forming the LW compound according to the present invention, it is possible to effectively improve lithium ion conduction with a sufficient contact area with the electrolytic solution, thereby suppressing reduction in charge / discharge capacity and reducing reaction resistance. be able to.
Such an LW compound preferably has a thickness of 1 to 100 nm.
If the thickness is less than 1 nm, fine particles may not have sufficient lithium ion conductivity. Further, if the thickness exceeds 100 nm, the formation of the coating with the LW compound becomes non-uniform, and the effect of reducing the reaction resistance may not be sufficiently obtained.

Furthermore, since the contact with the electrolytic solution occurs on the surface of the primary particles, it is important that the LW compound is formed on the surface of the primary particles.
Here, the primary particle surface in the present invention refers to the primary particle surface exposed on the outer surface of the secondary particle and the void in the vicinity of the inner surface of the secondary particle through which the electrolyte solution can penetrate through the outer surface of the secondary particle. It includes exposed primary particle surfaces. Furthermore, even a grain boundary between primary particles is included as long as the primary particles are not completely bonded and the electrolyte solution can penetrate.

Therefore, by forming the LW compound on the entire primary particle surface, it becomes possible to further promote the movement of lithium ions and further reduce the reaction resistance of the composite oxide particles.
In addition, the LW compound does not need to be completely formed on the entire surface of the primary particles, and may be in a scattered state. Even in the scattered state, the outer surface and internal voids of the composite oxide particle If a compound is formed on the surface of the primary particles exposed to, reaction resistance can be reduced.

  The surface properties of such primary particles can be determined by observing with a field emission scanning electron microscope, for example. The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is made of a lithium nickel composite oxide. It has been confirmed that a compound containing W and Li is formed on the surface of the primary particles.

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

This compound in the present invention may be any compound containing W and Li, but W and Li are preferably in the form of lithium tungstate, and Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ WO ₆ , Li ₂ W ₄ O ₁₃ , Li ₂ W ₂ O ₇ , Li ₆ W ₂ O ₉ , Li ₂ W ₂ O ₇ , Li ₂ W ₅ O ₁₆ , Li ₉ W ₁₉ O ₅₅ , Li ₃ W ₁₀ O ₃₀ , Li ₁₈ W ₅ O _15, or at least one form selected from these hydrates is preferred. By forming this lithium tungstate, the lithium ion conductivity is further increased, and the effect of reducing the reaction resistance is further increased.

  The amount of tungsten contained in the LW compound is preferably 0.1 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the composite oxide particles. Thereby, it is possible to achieve both high charge / discharge capacity and output characteristics.

  If the amount of tungsten is less than 0.1 atomic%, the effect of improving the output characteristics may not be sufficiently obtained. If the amount of tungsten exceeds 3.0 atomic%, too much LW compound is formed and lithium nickel is formed. Lithium conduction between the composite oxide particles and the electrolytic solution may be inhibited, and the charge / discharge capacity may be reduced.

  In addition, the amount of lithium contained in the LW compound is not particularly limited, and if lithium is contained in the LW compound, an effect of improving lithium ion conductivity can be obtained, but an amount sufficient to form lithium tungstate. It is preferable that

When the amount of tungsten and 0.1 to 3.0 atomic%, the composite oxide particles, the general _{formula: Li b Ni 1 - x -} y Co x M y W Z O 2+ α ( wherein, M is It is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo. b is 0.95 <b ≦ 1.10, x is 0 <x ≦ 0. 15, y is 0 <y ≦ 0.07, x + y is ≦ 0.16, z is a numerical value satisfying 0.001 ≦ z ≦ 0.03, and α is 0 ≦ α ≦ 0.2. It is preferable.

  B which shows content of lithium (Li) is 0.95 <= b <= 1.10. When b exceeds 1.10, lithium is consumed by the compound formed on the surface of the primary particles, but the lithium content in the lithium nickel composite oxide is excessive, and Li is mixed into the metal layer in the layered compound. Sometimes. On the other hand, when b is 0.95 or less, lithium is consumed by the compound, and as a result, a metal element such as Ni may be easily mixed into the lithium layer in the layered compound. Therefore, in order to improve battery capacity and output characteristics, 0.95 <b ≦ 1.08 is more preferable.

[Average particle size]
The positive electrode active material of the present invention comprises the lithium nickel composite oxide particles shown so far, and the composite oxide particles preferably have an average particle size of 8 to 20 μm.

When the average particle size is less than 8 μm, the filling property of the positive electrode when used as the positive electrode active material of the battery is lowered, and the battery capacity per volume may be lowered. On the other hand, when the average particle size exceeds 20 μm, the contact area between the positive electrode active material and the battery electrolyte may decrease, resulting in a decrease in battery capacity and output characteristics.
Therefore, the positive electrode active material of the present invention preferably has an average particle size of the composite oxide particles of 8 to 20 μm, and 8 to 17 μm in order to increase the filling property in the positive electrode while maintaining the battery capacity and output characteristics. More preferably.

The positive electrode active material of the present invention is composed of primary particles and secondary particles formed by aggregating primary particles. By adopting such a particle structure, the contact with the electrolytic solution is not limited to the outer surface of the secondary particles formed by agglomeration of the primary particles, but also the vicinity of the surface of the secondary particles and the internal voids, and further It will occur even at perfect grain boundaries.
In order to make contact with such an electrolytic solution, the average particle diameter of the composite oxide particles according to the present invention is 8 to 20 μm. In the range of this average particle diameter, it is possible to achieve both contact with the electrolyte and filling properties.

In addition, the specific surface area by BET method measurement of the positive electrode active material is preferably in the range of 0.4~1.2m ² / g, more preferably 0.4~1.0m 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 improved. However, when the specific surface area is less than 0.4 m ² / g, the contact with the electrolytic solution may be too small, and when the specific surface area exceeds 1.2 m ² / g, the contact with the electrolytic solution becomes too much, Stability may be reduced.

Furthermore, the porosity measured in the cross-sectional observation of the secondary particles is preferably 0.5 to 4%, and more preferably 0.7 to 3.5%.
As a result, the electrolyte can be sufficiently penetrated into the secondary particles, and the battery capacity and output characteristics can be further enhanced. On the other hand, if the porosity exceeds 4%, the crystallinity becomes insufficient and the reaction resistance may increase.

Here, the porosity can be measured by observing an arbitrary cross section of the secondary particles using a scanning electron microscope and analyzing the image.
For example, after embedding a plurality of secondary particles in a resin or the like and making it possible to observe the cross section of the particles by cross-section polisher processing or the like, image analysis software: WinRoof 6.1.1 etc. For the secondary particles, the total area of all the particles was measured with the voids in the secondary particles as black and the dense part in the secondary particle outline as white, and [black part / (black part + white part)] The porosity can be obtained by calculating the area ratio.

(3) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention is a positive electrode active material composed of the lithium-nickel composite oxide shown above, in particular, the lithium-nickel composite oxide obtained by the above production method. As a positive electrode active material, a positive electrode was produced, and produced using this positive electrode, which has high capacity, high output and high safety.

Hereinafter, the structure of the non-aqueous electrolyte secondary battery of the present invention will be described.
The non-aqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as a secondary battery) uses the positive electrode active material for non-aqueous electrolyte secondary batteries of the present invention (hereinafter simply referred to as a positive electrode active material) as the positive electrode material. Has a structure substantially equivalent to a general non-aqueous electrolyte secondary battery.

Specifically, the secondary battery of the present invention has a structure including a case, and a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator accommodated in the case.
More specifically, a positive electrode and a negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and a positive electrode current collector of the positive electrode and a positive electrode terminal connected to the outside are provided. And the negative electrode current collector of the negative electrode and the negative electrode terminal communicating with the outside using a current collecting lead or the like, and sealed in a case, the secondary battery of the present invention is formed. Yes.

  In addition, it cannot be overemphasized that the structure of the secondary battery of this invention is not limited to the said example, Moreover, the external shape can employ | adopt various shapes, such as a cylinder shape and a laminated form.

(Positive electrode)
First, the positive electrode that is a feature of the secondary battery of the present invention will be described.
The positive electrode is a sheet-like member, and the positive electrode mixture containing the positive electrode active material of the present invention can be formed by, for example, coating and drying on the surface of a current collector made of aluminum foil. The method is not particularly limited. For example, it is possible to produce a positive electrode by supporting a positive electrode mixture containing positive electrode active material particles and a binder on a belt-like positive electrode core material (positive electrode current collector).

  In addition, a positive electrode is suitably processed according to the battery to be used. For example, a cutting process for forming an appropriate size according to a target battery, a pressure compression process using a roll press or the like to increase the electrode density, and the like are performed.

(Positive electrode mixture)
The positive electrode mixture can be formed by adding a solvent to the positive electrode agent formed by mixing the positive electrode active material of the present invention in a powder form, a conductive material and a binder, and kneading them. .
Hereinafter, materials constituting the positive electrode mixture other than the positive electrode active material will be described.

[Binder]
As the binder of the positive electrode mixture, either a thermoplastic resin or a thermosetting resin may be used, but a thermoplastic resin is preferable.

Examples of the thermoplastic resin used include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotri Fluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECT E), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, Examples include ethylene-methyl acrylate copolymer and ethylene-methyl methacrylate copolymer.
The said resin may be used independently and may be used in combination of 2 or more type. These may be cross-linked products of Na ⁺ ions and the like.

[Conductive material]
The conductive material of the positive electrode mixture is not particularly limited as long as it is an electron conductive material that is chemically stable in the battery. For example, graphite such as natural graphite (flaky graphite, etc.), artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and conductive such as carbon fiber, metal fiber, etc. Use 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, carbon fluoride, etc. Can do. These may be used alone or in combination of two or more.

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

[solvent]
The solvent dissolves the binder and disperses the positive electrode active material, the conductive material, and the like in the binder. The solvent is not particularly limited, and for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.

[Positive electrode core material]
The positive electrode core material (positive electrode current 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, conductive resin, or the like can be used, and among these, aluminum foil, aluminum alloy foil, and the like are more preferable.

Here, a carbon or titanium layer or an oxide layer can be formed on the surface of the foil or sheet. Further, irregularities can be imparted to the surface of the foil or sheet, and nets, punching sheets, lath bodies, porous bodies, foams, fiber group molded bodies, and the like can also be used.
The thickness of the positive electrode core material is not particularly limited, but is preferably 1 to 500 μm, for example.

[Components other than positive electrode]
Next, components other than the positive electrode among the components of the nonaqueous electrolyte secondary battery of the present invention will be described.
The nonaqueous electrolyte secondary battery of the present invention is characterized in that the positive electrode active material is used, and other components can be appropriately selected according to the use and required performance. It is not limited to what will be described later.

The negative electrode is not particularly limited as long as it can charge and discharge lithium.
For example, a material in which a negative electrode mixture containing a negative electrode active material and a binder and containing a conductive material and a thickener as optional components is supported on a negative electrode core material can be used. Such a negative electrode can be produced in the same manner as the positive electrode.

The negative electrode active material may be any material that can electrochemically charge and discharge lithium. For example, graphites, non-graphitizable carbon materials, lithium alloys and the like can be used.
The lithium alloy is not particularly limited, but an alloy containing at least one element selected from the group consisting of silicon, tin, aluminum, zinc and magnesium is preferable.
Moreover, the average particle diameter of a negative electrode active material is not specifically limited, For example, 1-30 micrometers is preferable.

[Binder]
As the binder of the negative electrode mixture, either a thermoplastic resin or a thermosetting resin may be used, but a thermoplastic resin is preferable.

The thermoplastic resin is not particularly limited. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer (FEP). , Tetrafluoroethylene-perfluoroalkyl 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 Polymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer Examples thereof include a copolymer, an ethylene-methyl acrylate copolymer, and an ethylene-methyl methacrylate copolymer.
These may be used alone or in combination of two or more. Moreover, these may be a crosslinked body by Na + ions or the like.

[Conductive material]
The conductive material of the negative electrode mixture is not particularly limited as long as it is an electron conductive material that is chemically stable in the battery. For example, graphite such as natural graphite (flaky graphite, etc.), graphite such as artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and conductive such as carbon fiber, metal fiber, etc. For example, conductive fibers, metal powders such as copper and nickel, organic conductive materials such as polyphenylene derivatives, and the like can be used. These may be used alone or in combination of two or more.
Although the addition amount of this electrically conductive material is not specifically limited, 1-30 mass% is preferable with respect to the negative electrode active material particle contained in a negative mix, and 1-10 mass% is more preferable.

[Negative electrode core]
The negative electrode core material (negative electrode current 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 stainless steel, nickel, copper, titanium, carbon, conductive resin or the like can be used, and copper and a copper alloy are preferable.

On the surface of the foil or sheet, a layer of carbon, titanium, nickel or the like can be provided, or an oxide layer can be formed. Further, irregularities can be imparted to the surface of the foil or sheet, and nets, punching sheets, lath bodies, porous bodies, foams, fiber group molded bodies, and the like can also be used.
The thickness of the negative electrode core material is not particularly limited, but is preferably 1 to 500 μm, for example.

[Non-aqueous electrolyte]
As the non-aqueous electrolyte, a non-aqueous solvent in which a lithium salt is dissolved is preferable.
The non-aqueous solvent used is not particularly limited, but cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate ( DMC), chain carbonates such as diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and 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), ethoxymethoxyethane (EME), tetrahydrofuran, 2-methyltetrahydrofuran Cyclic ethers such as dimethylsulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl Sulfolane, 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.
In particular, it is preferable to use a mixed solvent of a cyclic carbonate and a chain carbonate, or a mixed solvent of a cyclic carbonate, a chain carbonate, and an aliphatic carboxylic acid ester.

[Lithium salt]
Examples of the lithium salt dissolved in the non-aqueous electrolyte include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , and Li (CF ₃ SO ₂ ). ₂ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, lithium imide salt, etc. . 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 0.2 to 2 mol / L, more preferably 0.5 to 1.5 mol / L.

[Other additives]
In order to improve the charge / discharge characteristics of the battery, various additives other than the lithium salt may be added to the non-aqueous electrolyte.
Although the additive is not particularly limited, for example, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric acid triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl An ether etc. can be mentioned.

[Separator]
Further, a fine separator is interposed between the positive electrode and the negative electrode.
The separator is not particularly limited, but a microporous thin film having a large ion permeability, a predetermined mechanical strength, and insulating properties is preferable. In particular, the microporous thin film preferably has a function of closing the pores at a certain temperature or higher and increasing the resistance.

The material of the microporous thin film is not particularly limited. For example, polyolefin such as polypropylene and polyethylene having excellent organic solvent resistance and hydrophobicity can be used. Moreover, the sheet | seat produced from glass fiber etc., a nonwoven fabric, a woven fabric etc. can also be used.
When the separator is a microporous thin film, the hole diameter of the holes formed in the separator is not particularly limited, but is preferably 0.01 to 1 μm, for example. The porosity of the separator is not particularly limited, but generally 30 to 80% is preferable. The thickness of the separator is not particularly limited, but generally 10 to 300 μm is preferable.

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

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.
In Examples and Comparative Examples, the following methods were used for the metal analysis method and the c-axis length of the lithium nickel composite oxide.
(1) Metal analysis: ICP emission analysis was performed.
(2) c-axis length measurement: XRD diffractometer (manufactured by Panalical: X'Pert PRO)
[Method for producing secondary battery for battery performance evaluation]
For the evaluation of the battery performance of the nonaqueous electrolyte secondary battery employing the lithium nickel composite oxide of the present invention as the positive electrode active material, a 2032 type coin type battery (hereinafter referred to as coin type battery 1) shown in FIG. 1 was used. .

As shown in FIG. 1, the coin-type battery 1 is composed of a case 2 and an electrode 3 accommodated in the case 2.
The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.

The electrode 3 includes a positive electrode (evaluation electrode) 3a, a separator 3c, and a negative electrode (lithium metal negative electrode) 3b, which are stacked in this order, and the positive electrode 3a is in contact with the inner surface of the positive electrode can 2a. 3b is accommodated in the case 2 so as to contact the inner surface of the negative electrode can 2b.
The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.

Said coin type battery 1 was produced with the following manufacturing method.
First, 90 parts by weight of the positive electrode active material powder was mixed with 5 parts by weight of acetylene black and 5 parts by weight of polyvinylidene fluoride, and n-methylpyrrolidone was added to make a paste.
This prepared paste was applied to an aluminum foil having a thickness of 20 μm. The paste was applied so that the weight of the positive electrode active material after drying was 0.05 g / cm ² .
Thereafter, the aluminum foil coated with the paste was vacuum-dried at 120 ° C., and then punched out into a disk shape having a diameter of 1 cm to form a positive electrode 3a.

Using the positive electrode 3a, the negative electrode 3b, the separator 3c, and the electrolytic solution, the coin-type battery 1 was produced in a glove box under an Ar atmosphere with a dew point controlled at −80 ° C.
For the negative electrode 3b, lithium metal punched into a disk shape having a diameter of 15 mm was used.
For the separator 3c, a polyethylene porous film having a thickness of 20 μm was used.
As an electrolytic solution, an equivalent mixed solution (manufactured by Ube Industries) of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt was used.

Battery characteristics were evaluated using the produced coin-type battery.
As battery characteristics, initial discharge capacity and positive electrode reaction resistance were measured.
The initial discharge capacity was measured by the following method.
First, after producing the coin-type battery 1, it is left for about 24 hours.
After the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is set to 0.1 mA / cm ² , charged to a cut-off voltage of 4.3 V, and after a pause of 1 hour, to a cut-off voltage of 3.0 V Discharge. And the capacity | capacitance when discharged to the cut-off voltage 3.0V was made into the initial stage discharge capacity.

Next, the positive electrode reaction resistance was calculated by the following method.
First, the coin-type battery of each example is charged at a charging potential of 4.1 V, and the electrical resistance is measured by an AC impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B). If the relationship between the measured mechanism and frequency is graphed, the Nyquist plot shown in FIG. 2 is obtained.
Since this Nyquist plot is represented as the sum of the characteristic curves indicating the solution resistance, negative electrode resistance and its capacity, and positive resistance and its capacity, fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and the positive reaction The resistance value was calculated.

Example 1
First, the temperature in the reaction vessel was set to 49.5 ° C., and the reaction solution in the reaction vessel was maintained at pH 13.0 based on a liquid temperature of 25 ° C. with a 20 mass% sodium hydroxide solution. A mixed aqueous solution of sodium sulfate and cobalt sulfate, an aqueous sodium aluminate solution, and 25% by mass ammonia water were added and recovered by overflow. Furthermore, after washing with a 45 g / L aqueous sodium hydroxide solution having a pH of 12.5 based on a liquid temperature of 25 ° C., it was washed with water and dried to obtain a nickel composite hydroxide (neutralization crystallization method).

When this nickel composite hydroxide was analyzed by the ICP method, it was confirmed that the nickel composite hydroxide had a molar ratio of Ni: Co: Al of 94: 3: 3. To this nickel composite hydroxide, sodium tungstate powder was added and mixed, and heat-treated for 24 hours in an air dryer at 120 ° C. and dried.
When the composition of the obtained nickel composite hydroxide was analyzed by the ICP method, it was confirmed that the tungsten content was a composition of 0.35 atomic% with respect to the total number of Ni, Co and Al atoms.
The volume-based average particle diameter MV of this nickel composite hydroxide measured by laser diffraction scattering method was 13 μm.
In addition, when sulfur was quantitatively analyzed by ICP emission spectrometry, and the sulfur was oxidized to give sulfate radicals (SO ₄ ) and multiplied by a coefficient, the sulfate radical content was 0.28% by mass. It was. Table 1 shows the sulfate group content of the nickel composite hydroxide.

  Next, this nickel composite hydroxide is oxidized and roasted at a temperature of 600 ° C. in an air atmosphere to form a nickel composite oxide, and then Ni: Co: Al: Li = 0.94: 0 in molar ratio. 0.03: 0.03: 1.025 The nickel composite oxide and lithium hydroxide-hydrate were weighed and mixed to obtain a lithium mixture.

The obtained lithium mixture was calcined for 3 hours at a temperature of 500 ° C. in an oxygen atmosphere using an electric furnace, then held at 745 ° C. for 3 hours, and baked for 20 hours from the start of temperature rise to the end of holding. . Then, it cooled in the furnace to room temperature, the crushing process was performed, and the baked powder was obtained.
When the obtained base material was analyzed by the ICP method, it was confirmed that the molar ratio of Ni: Co: Al: Li was 0.94: 0.03: 0.03: 1.024.

Next, pure water at 20 ° C. is added to the obtained base material to obtain a slurry containing 750 g of the base material with respect to 1 L of water, and this slurry is stirred for 20 minutes, followed by solid-liquid separation with a filter press and further drying. As a result, a positive electrode active material was obtained.
Moreover, the specific surface area by BET method of the obtained positive electrode active material was 0.93 m ² / g.

  When this positive electrode active material was embedded in a resin and subjected to cross section polisher, cross-sectional observation by SEM with a magnification of 5000 times was performed. As a result, primary particles and secondary particles formed by aggregation of primary particles were obtained. It was confirmed from the results of X-ray diffraction analysis that island-shaped or layered lithium tungstate was formed on the primary particle surface. Furthermore, the porosity of the secondary particles determined from this observation was 2.1%.

[Battery evaluation]
The battery characteristics of the obtained positive electrode active material were evaluated. In addition, the positive value resistance made the relative value which set Example 1 1.00 the evaluation value.

  Hereinafter, about Examples 2-7 and Comparative Examples 1-4, only the substance and conditions which changed with the said Example 1 are shown. Table 1 shows the evaluation values of the discharge capacities and positive electrode resistances of Examples 1 to 7 and Comparative Examples 1 to 4.

(Example 2)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the amount of sodium tungstate added was doubled. The results are shown in Table 1.

(Example 3)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the nickel composite hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 91: 6: 3. The results are shown in Table 1.

Example 4
Example 1 except that the nickel composite hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 88: 9: 3 and that the firing temperature was changed from 745 ° C. to 760 ° C. Similarly, a positive electrode active material was obtained and evaluated. The results are shown in Table 1.

(Example 5)
The nickel composite hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 91: 6: 3, and the aqueous solution of sodium hydroxide used for washing after recovery by overflow was a liquid temperature of 25 ° C. A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the pH was changed to a 10 g / L sodium carbonate aqueous solution having a reference pH of 11.0. The results are shown in Table 1.

(Example 6)
The nickel hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 88: 9: 3, and the aqueous sodium hydroxide solution used for washing after recovery by overflow was a liquid temperature of 25 ° C. A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the pH was changed to 65 g / L sodium hydroxide aqueous solution having a reference pH of 13.5. The results are shown in Table 1.

(Example 7)
A positive electrode in the same manner as in Example 1 except that the aqueous sodium hydroxide solution used for washing after recovery by overflow was changed to a 10 g / L aqueous sodium hydroxide solution having a pH of 10.5 based on a liquid temperature of 25 ° C. An active material was obtained and evaluated. The results are shown in Table 1.

(Comparative Example 1)
Except that the nickel composite hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 82: 15: 3, and the oxidation roasting temperature was changed from 600 ° C. to 760 ° C. In the same manner as in Example 1, a positive electrode active material was obtained and evaluated. The results are shown in Table 1.

(Comparative Example 2)
As the nickel composite hydroxide, a positive electrode was formed in the same manner as in Example 1 except that the Ni: Co: Al molar ratio was crystallized to be 91: 6: 3 and no tungsten compound was added. An active material was obtained and evaluated. The results are shown in Table 1.

(Comparative Example 3)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that no tungsten compound was added. The results are shown in Table 1.

(Comparative Example 4)
Example 1 except that the nickel composite hydroxide was crystallized so that the molar ratio of Ni: Co: Al was 88: 9: 3, and the oxidation roasting temperature was changed from 600 ° C. to 790 ° C. Similarly, a positive electrode active material was obtained and evaluated. The results are shown in Table 1.

［評価］
表１から明らかなように、実施例１〜７の正極活物質は、本発明に従って製造されたため、比較例１〜４に比べて放電容量が高く、正極抵抗も低いものとなっており、高容量かつ高出力な非水系電解質二次電池用正極活物質となっている。

[Evaluation]
As is clear from Table 1, since the positive electrode active materials of Examples 1 to 7 were manufactured according to the present invention, the discharge capacity was higher than that of Comparative Examples 1 to 4, and the positive electrode resistance was low. It is a positive electrode active material for non-aqueous electrolyte secondary batteries with high capacity and high output.

  Since the non-aqueous electrolyte secondary battery of the present invention provides a high-capacity and highly safe non-aqueous electrolyte secondary battery, it is particularly suitable for small portable electronic devices (such as notebook personal computers and mobile phone terminals). It is suitable as a rechargeable secondary battery.

DESCRIPTION OF SYMBOLS 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 (10)

A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a lithium nickel composite oxide,
The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries characterized by including the process of following (A)-(D) in order of the process of (A)-(D).
(A) an aqueous solution of a metal compound containing nickel and cobalt and containing at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo as the additive element M; A crystallization step in which a reaction solution containing an aqueous solution containing an ammonium ion supplier is neutralized and crystallized while being kept alkaline, and then solid-liquid separation is performed to obtain a wet nickel composite hydroxide.
(B) A heat treatment step in which a wet nickel composite hydroxide obtained in the crystallization step and a tungsten compound are mixed and then heat treated at 100 to 750 ° C. to obtain a tungsten mixture.
(C) A mixing step in which the tungsten mixture is further mixed with a lithium compound to obtain a lithium mixture.
(D) Firing the lithium mixture in an oxidizing atmosphere at a temperature range of 700 to 900 ° C. to obtain a lithium nickel composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles. Process.   The water washing step of mixing the calcined powder of the lithium nickel composite oxide obtained in the calcining step with water so as to be 700 g to 2000 g with respect to 1 L of water to form a slurry, and washing the calcined powder with water, The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, further comprising:   The amount of tungsten contained in the tungsten compound mixed with the nickel composite hydroxide is 0.1 to 3.0 atomic% with respect to the total number of Ni, Co and M atoms contained in the nickel composite hydroxide. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 1 or 2 characterized by the above-mentioned.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the wet nickel composite hydroxide has a pH value of 25 or more at a reference temperature of 8 or more. .   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the nickel composite hydroxide has a sulfate group content of 0.1 to 0.4 mass%. Manufacturing method.   The non-aqueous electrolyte 2 according to claim 1, wherein the tungsten compound is at least one selected from the group consisting of tungsten oxide, tungstic acid, ammonium paratungstate, and sodium tungstate. A method for producing a positive electrode active material for a secondary battery.   The lithium compound is at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries as described in any one of.   In the mixing step, the nickel composite hydroxide and the lithium compound so that the amount of lithium in the lithium compound with respect to the total amount of all metal elements excluding lithium in the mixture is 0.98 to 1.25 in molar ratio. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 1-7 characterized by adjusting a mixing ratio.   In the said water washing process, the temperature of the slurry at the time of a water washing process is adjusted to 10-40 degreeC, The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries in any one of Claims 2-8 characterized by the above-mentioned. The lithium nickel composite oxide is represented by the general formula: Li _a Ni _1-x - in _y Co _x M _y O ₂ (wherein, M represents, Mg, Al, Ca, Ti , V, Cr, Mn, Nb, Zr and It is at least one element selected from Mo. a is 0.95 ≦ a ≦ 1.11, x is 0 <x ≦ 0.15, y is 0 <y ≦ 0.07, and x + y is ≦ 0. The non-aqueous system according to claim 1, wherein the non-aqueous system is composed of secondary particles composed of primary particles and primary particles aggregated. A method for producing a positive electrode active material for an electrolyte secondary battery.

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