JP2015191848A - Precursor of positive electrode active material for nonaqueous electrolyte secondary batteries and manufacturing method thereof, and positive electrode active material for nonaqueous electrolyte secondary batteries and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a precursor of a positive electrode active material which makes no contribution to a charge and discharge reaction, and further, enables the obtention of a nonaqueous electrolyte secondary battery superior in battery characteristics and safety by reducing the quantity of impurities which would cause the corrosion of a baking furnace and a surrounding equipment; and a method for manufacturing such a precursor.SOLUTION: A method for manufacturing a precursor of a positive electrode active material for nonaqueous electrolyte secondary batteries which includes nickel complex hydroxide particles having a particular composition ratio and has a hollow or porous structure, comprises: the step of cleaning the nickel complex hydroxide particles each having a cavity structure therein with aqueous carbonate solution of which the carbonate concentration is 0.1 mol/L or more.

Description

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

  In recent years, with the widespread use of portable devices such as mobile phones and notebook computers, development of small and lightweight secondary batteries with high energy density is strongly desired. As such a lithium ion secondary battery using lithium, a lithium alloy, a metal oxide, or carbon as a negative electrode, research and development are actively performed.

A lithium ion secondary battery using a lithium composite oxide, particularly a lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, as a positive electrode material has a high energy density because a high voltage of 4V can be obtained. Is expected to be put to practical use. A battery using a lithium cobalt composite oxide has been developed so far to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

  However, since the lithium cobalt composite oxide uses a rare and expensive cobalt compound as a raw material, it increases the cost of the active material and further the battery. Lowering the cost of active materials and making it possible to manufacture cheaper lithium-ion secondary batteries has significant industrial significance in reducing the weight and size of portable devices that are currently in widespread use, replacing cobalt compounds. A cheaper active material is desired.

New materials for the positive electrode active material for lithium ion secondary batteries include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, and lithium nickel composite oxide (LiNiO ₂ ) using nickel. ).
Lithium-manganese composite oxides are inexpensive materials and have excellent thermal stability, so they can be said to be a powerful alternative to lithium-cobalt composite oxides, but the theoretical capacity is only about half that of LiCoO ₂ , It has the disadvantage that it is difficult to meet the increasing demand for higher capacity lithium ion secondary batteries.

  On the other hand, since lithium nickel composite oxide has a lower electrochemical potential than lithium cobalt composite oxide, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and higher capacity can be expected. Therefore, development is actively conducted. However, the lithium-nickel composite oxide, when a lithium ion secondary battery is manufactured using a material synthesized purely of nickel as a metal other than lithium as the positive electrode active material, is inferior in cycle characteristics compared to the cobalt type, and When used or stored in a high temperature environment, the battery performance is relatively easily lost.

In order to solve such a drawback, a lithium nickel composite oxide in which a part of nickel is substituted with cobalt or the like has also been proposed. For example, Patent Document 1, in order to improve the self-discharge characteristics and cycle characteristics of the lithium ion secondary _{battery, Li x Ni a Co b M} c O 2 (0.8 ≦ x ≦ 1.2,0. 01 ≦ a ≦ 0.99, 0.01 ≦ b ≦ 0.99, 0.01 ≦ c ≦ 0.3, 0.8 ≦ a + b + c ≦ 1.2, M is Al, V, Mn, Fe, Cu and A lithium-containing composite oxide represented by at least one element selected from Zn), and Patent Document 2 discloses a positive electrode capable of maintaining good battery performance during storage and use in a high-temperature environment. As the active material, Li _w Ni _x Co _y B _z O ₂ (0.05 ≦ w ≦ 1.10, 0.5 ≦ x ≦ 0.995, 0.005 ≦ z ≦ 0.20, x + y + z = 1) Lithium-containing composite oxides have been proposed. It is described that these lithium-containing composite oxides have higher charge capacity and discharge capacity than conventional lithium cobalt composite oxides, and the cycle characteristics are also improved.

In order to increase the output of the lithium nickel composite oxide, it has been proposed to increase the specific surface area by controlling the particle structure of the lithium nickel composite oxide particles. For example, Patent Document 3, the general _{formula: Li t Ni 1-x-y} Co x M y O 2 ( wherein, 0.95 ≦ t ≦ 1.15,0 ≦ x ≦ 0.22,0 ≦ y ≦ 0.15, x + y <0.3, M represents at least one element selected from the group consisting of Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Nb, Mo and W ), The average particle diameter is 2 to 8 μm, and the index ((d90-d10) / average particle diameter) indicating the spread of the particle size distribution is 0.65 or less. Thus, a positive electrode active material for a non-aqueous electrolyte secondary battery having [specific surface area × average particle diameter], which is an index indicating the size of the reaction area, is 5.5 or more. And this positive electrode active material for non-aqueous electrolyte secondary battery has a hollow structure, and is composed of lithium nickel composite oxide particles having a small particle size, a uniform particle size, and a large specific surface area. Have a high output.

Japanese Patent Laid-Open No. 8-213015 JP-A-8-045509 International Publication No. 2012/131799

  However, in the lithium nickel composite oxide obtained by the conventional manufacturing method, the discharge capacity is smaller than the charge capacity only in the first charge / discharge, and the so-called irreversible capacity defined by the difference between the two is a cobalt-based composite oxide. There is a problem that it is considerably larger than an oxide and the Coulomb efficiency is low.

One of the causes for the increase in irreversible capacity is that the conventional lithium nickel composite oxide contains impurities that do not contribute to the charge / discharge reaction such as sulfate radicals (SO ₄ ²⁻ ) and chlorine derived from raw materials. Since these impurities do not contribute to the charge / discharge reaction, when the battery is constructed, the negative electrode material must be used in the battery by an amount corresponding to the irreversible capacity of the positive electrode material. The capacity per weight and volume is reduced, and excess lithium is accumulated in the negative electrode as an irreversible capacity, which is a problem in terms of safety.

  Furthermore, residual chlorine as impurities may volatilize during the firing process, corrode the firing furnace and surrounding equipment, and may cause contamination of metal foreign objects to the product leading to a short circuit of the battery. It is done.

  Further, in the positive electrode active material for a non-aqueous electrolyte secondary battery disclosed in Patent Document 3, the discharge capacity is high and the cycle characteristics are improved by controlling the particle size distribution and the specific surface area. , A neutralization crystallization of nickel composite hydroxide including a nucleation step of generating particle nuclei and a particle growth step of growing the generated nuclei is performed, and the particle growth step is relatively low Since crystallization is performed at a pH value, there is a problem that impurities such as sulfate radicals and chlorine easily remain. In addition, since fine particles are crystallized in the nucleation step, high density cannot be obtained even if particle growth is performed in the subsequent particle growth step, and impurities tend to remain inside the particles.

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery that has a reduced amount of impurities, a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance in view of the above-mentioned problems of the prior art. An object of the present invention is to provide a precursor for a positive electrode active material, a method for producing the same, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a method for producing the same.

  As a result of deepening research on the reduction of the amount of impurities in order to solve the above problems, the present inventor washed nickel composite hydroxide having a specific composition and structure with a carbonate aqueous solution, thereby reducing the amount of impurities in the nickel composite. A hydroxide can be obtained, and by using a lithium nickel composite oxide produced from the nickel composite hydroxide as a positive electrode material, excellent battery characteristics are exhibited while avoiding problems such as a decrease in coulomb efficiency. The present inventors have found that a non-aqueous electrolyte secondary battery can be obtained and have completed the present invention.

That is, the method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention comprises nickel composite hydroxide particles represented by the following general formula (1), and has a hollow structure or a porous structure. A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the nickel composite hydroxide particles having a void structure inside the particles are mixed with a carbonate having a carbonate concentration of 0.1 mol / L or more. It is characterized by washing with an aqueous solution.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)

  The nickel composite hydroxide particles preferably have a porosity measured in cross-sectional observation of 15% or more.

The carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate, sodium carbonate, potassium hydrogen carbonate and sodium hydrogen carbonate, and the pH of the carbonate aqueous solution is preferably 11.2 or more.
The washing is preferably performed at a liquid temperature of 10 to 50 ° C.

  The nickel composite hydroxide particles are supplied in a heated reaction tank with a mixed aqueous solution of nickel and cobalt, and optionally a metal compound containing the element M, and an aqueous solution containing an ammonium ion supplier, In that case, the reaction solution is obtained by appropriately supplying a sufficient amount of an aqueous solution of alkali metal hydroxide to maintain alkalinity, and neutralized crystallization. In the neutralized crystallization, the reaction solution It is preferable to separate the nucleation step for generating nuclei and the particle growth step for growing the generated nuclei by controlling the pH value of the nucleation step. It is controlled to be 11.5 to 13.2 on the basis of 25 ° C., and the pH value in the particle growth step is 9.5 to 12.0 on the basis of the liquid temperature 25 ° C., and the pH value in the nucleation step Low value and It is preferably controlled to so that.

  The mixed aqueous solution preferably contains at least one chloride of nickel and cobalt.

The precursor of the positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention is a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery having a hollow structure or a porous structure, and is represented by the following general formula (1): It is represented by nickel composite hydroxide particles having a void structure inside the particles, and has a sulfate group content of 0.5% by mass or less and a sodium content of 0.020% by mass or less.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)
Moreover, it is preferable that the chlorine content of the said precursor is 0.1 mass% or less.

The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is represented by the following general formula (2), and is a non-aqueous electrolyte secondary battery comprising a lithium nickel composite oxide having a hollow structure or a porous structure. A method for producing a positive electrode active material for a non-aqueous electrolyte, comprising: mixing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery with a lithium compound to obtain a lithium mixture; And firing in a range of 850 ° C. to obtain a lithium nickel composite oxide.
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05, 0. <X ≦ 0.20 and 0 <y ≦ 0.07.)

  The method further comprises a roasting step in which the precursor is oxidized and roasted at 400 to 800 ° C. in an oxidizing atmosphere to obtain a nickel composite oxide. In the mixing step, the nickel composite oxide is mixed with a lithium compound to form a lithium mixture. It is preferable to obtain

  After the firing step, the lithium nickel composite oxide is 0.10% by mass with respect to the total amount of lithium compound present at a temperature of 10 to 40 ° C. and on the surface of the lithium nickel composite oxide. It is preferable to include a water washing step of filtering and drying after washing with water at a slurry concentration sufficient to become the following.

  The lithium compound is preferably at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate, and halide.

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is represented by the following general formula (2), is composed of a lithium nickel composite oxide having a hollow structure or a porous structure, and has a sulfate group content of 0.25. It is characterized in that it is not more than mass% and the Na content is not more than 0.02 mass%.
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05, 0. <X ≦ 0.20 and 0 <y ≦ 0.07.)
The chlorine content of the positive electrode active material is preferably 0.05% by mass or less.

According to the present invention, a precursor capable of obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery having a small amount of residual impurities, a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance, and a method for producing the same Is provided. In addition, the manufacturing method of the present invention is easy and high in productivity, and can reduce damage to the manufacturing equipment because the amount of impurities that corrode the firing furnace and peripheral equipment is small.
Furthermore, the method for producing a positive electrode active material using the precursor of the present invention easily obtains a positive electrode active material for a non-aqueous electrolyte secondary battery that has a high capacity, a small irreversible capacity, and excellent coulomb efficiency and reaction resistance. And its industrial value is extremely high.

FIG. 1 is a cross-sectional view of a coin battery used for battery evaluation.

  Hereinafter, a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, a manufacturing method thereof, a positive electrode active material for a nonaqueous electrolyte secondary battery using the precursor, and a manufacturing method thereof will be described in detail. The embodiments described below are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiments.

1. Method for producing precursor of positive electrode active material for nonaqueous electrolyte secondary battery (1) Composition of nickel composite hydroxide particles Precursor of positive electrode active material for nonaqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as “precursor”) The nickel composite hydroxide represented by the following general formula (1) and having a void structure inside the particles, whereby a positive electrode active material having a hollow structure or a porous structure can be obtained. The particles are washed with a carbonate aqueous solution having a carbonate concentration of 0.1 mol / L or more.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)

  X indicating the content of cobalt in the nickel composite hydroxide particles is 0 <x ≦ 0.20, preferably 0.03 ≦ x ≦ 0.20, more preferably 0.10 ≦ x ≦ 0. 20. By using nickel composite hydroxide particles having a cobalt content in the above range as a precursor of the positive electrode active material, a secondary battery having excellent discharge capacity, cycle characteristics, and thermal stability can be obtained.

  The y indicating the content of at least one element M selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W in the nickel composite hydroxide particles is 0 <y ≦ 0.07, and preferably 0.01 ≦ y ≦ 0.05. By using nickel composite hydroxide particles having an M content in the above range as a positive electrode active material precursor, a secondary battery having excellent cycle characteristics and thermal stability can be obtained.

  The composition ratio of nickel, cobalt, and element M in the nickel composite hydroxide particles (precursor) is also maintained in lithium nickel composite hydroxide particles (positive electrode active material) described later.

(2) Internal structure of nickel composite hydroxide particles The nickel composite hydroxide particles used in the present invention (hereinafter also simply referred to as “composite hydroxide particles”) are hollow by having a void structure inside the particles. Lithium nickel composite oxide particles having a structure or a porous structure (hereinafter also simply referred to as “composite oxide particles”) can be obtained. A positive electrode active material composed of composite oxide particles having a hollow structure or a porous structure is excellent in output characteristics because the contact area with the electrolytic solution is increased.

Here, the “composite hydroxide particle having a void structure inside the particle” means a particle having a structure including a large amount of voids between primary particles constituting the secondary particle. The composite hydroxide particle which can obtain the positive electrode active material which has a porous structure is said. For example, as disclosed in Patent Document 3, a composite hydroxide having a structure in which the center part of a particle is composed of a low density part including many fine voids and the outer shell part is composed of a dense part denser than the center part And particles. In addition, a plurality of low density portions including many spaces or fine voids may exist in the particles, and the entire composite hydroxide particle may have a structure including many voids between primary particles. On the other hand, the “hollow structure or porous structure” of the positive electrode active material is a structure composed of a hollow part consisting of a space at the center of the particle and an outer shell part on the outside, or voids in the particle are dispersed throughout the particle Refers to the structure.
The void structure, hollow structure or porous structure is confirmed by cross-sectional observation of the composite hydroxide particles / composite oxide particles using a scanning electron microscope.

Further, the composite hydroxide particles / composite oxide particles having the above-mentioned void structure, hollow structure or porous structure have a porosity measured in cross-sectional observation of the particles of 5% or more and 15% or more. Is preferable, and it is more preferable that it is 15 to 85%. Thereby, the contact area with the electrolyte solution of a positive electrode active material can be made sufficient, without reducing the bulk density of the positive electrode active material obtained too much.
Here, the porosity can be measured by observing an arbitrary cross section of the composite hydroxide particles / composite oxide particles using a scanning electron microscope and analyzing the image. For example, after embedding a plurality of composite hydroxide particles / composite oxide particles in a resin or the like and making the section of the particles observable by cross-section polisher processing or the like, image analysis software: WinRoof 6.1.1 or the like To measure the voids in the secondary particles (hollow part of the hollow structure or voids of the porous structure) as black, and dense parts (outer shell part of the hollow structure or void structure / porous) in the secondary particle outline Measure the void ratio by measuring the area of [black part / (black part + white part)] for any 20 or more particles, measuring the cross section of the primary particle forming the texture structure as white. Can do.

(3) Method for Producing Nickel Composite Hydroxide Particles As a method for producing nickel composite hydroxide particles used in the present invention, composite hydroxide particles satisfying the above formula (1) and having a void structure are obtained. The method is not particularly limited, and a conventionally known method can be used.

  For example, at least one element M selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W as nickel and cobalt and, if necessary, element M in a heated reaction vessel A mixed aqueous solution of a metal compound containing, and if necessary, an aqueous solution containing an ammonium ion supplier, and at that time, an aqueous solution of an alkali metal hydroxide in an amount sufficient to keep the reaction solution alkaline. A method of appropriately supplying and neutralizing crystallization may be mentioned. The element M may be added by adhering a compound of the element M to the surface of the nickel composite hydroxide particles obtained by neutralization crystallization.

Moreover, when carrying out neutralization crystallization, it is preferable to perform the separation separately into a nucleation step for generating nuclei and a particle growth step for growing the generated nuclei by controlling the pH value of the reaction solution. Thereby, the nickel cobalt manganese composite hydroxide particle which consists of the secondary particle which the primary particle aggregated and has a void structure is obtained.
Here, the separation of the nucleation step and the particle growth step means that the nucleation reaction and the particle growth reaction do not proceed simultaneously in the same layer as in the conventional continuous crystallization method. The time when the nucleation reaction (nucleation process) mainly occurs and the time when the particle growth reaction (particle growth process) mainly occurs are clearly separated.

  The pH value in the nucleation step is controlled to be 11.5 to 13.2 on the basis of the liquid temperature 25 ° C., and the pH value in the particle growth step is 9.5 to 12.2. It is preferable from the viewpoint of particle size uniformity, stability, etc. that the pH is controlled to be 0 and lower than the pH value of the nucleation step, and the pH value in the particle growth step is 0 from the pH value of the nucleation step. It is more preferable to control the value to be lower by 5 or more.

  The atmosphere in the nucleation step and the particle growth step is preferably an atmosphere having an oxygen concentration lower than that in the air atmosphere at least in the nucleation step in order to stably generate nuclei.

Furthermore, the particle structure of the positive electrode active material obtained can be controlled by adjusting the ammonium ion concentration in the reaction solution.
For example, by setting the ammonium ion concentration to 0.1 g / L or less in the nucleation step, a nucleus (center portion) made of fine primary particles and including many fine voids is formed, and then the pH is lower than in the nucleation step. In the particle growth step, a particle structure having an outer shell portion made of plate-like primary particles larger than the fine primary particles can be formed outside the center portion. The composite hydroxide particles having such a particle structure are lithium nickel composite oxide particles having a hollow structure in which fine primary particles at the center are absorbed by the outer shell in the firing step when obtaining the positive electrode active material ( Cathode active material).
Moreover, the primary particle formed in the nucleation process grows by supplying an aqueous solution containing an ammonium ion supplier as necessary, and adjusting the ammonium ion concentration to 3 to 25 g / in the nucleation process and the particle growth process. Thus, composite hydroxide particles having voids between primary particles can be obtained, and in the firing step when obtaining the positive electrode active material, lithium nickel composite oxide particles (positive electrode active material) having a porous structure are obtained.

  The metal compound containing nickel and cobalt is not particularly limited, and a known compound can be used. For example, sulfide, nitrate, chloride, and the like can be used. Among these, it is preferable to use sulfides and chlorides from the viewpoint of ease of wastewater treatment and environmental load. In particular, from the viewpoint of environmental load, it is preferable to use at least one chloride of nickel and cobalt.

  The metal compound containing at least one element M selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W is not particularly limited, and a known compound can be used. , Magnesium sulfate, calcium sulfate, sodium aluminate, aluminum sulfate, titanium sulfate, ammonium peroxotitanate, potassium titanium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, manganese sulfate, zirconium sulfate, zirconium nitrate, Niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, or the like can be used.

  Moreover, it does not specifically limit as an alkali metal hydroxide, A well-known substance can be used, For example, sodium hydroxide, potassium hydroxide, etc. can be used.

  Although it does not specifically limit as an ammonium ion supplier, For example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride etc. can be used.

(4) Washing with aqueous carbonate solution In the method for producing a precursor of the present invention, the concentration of nickel composite hydroxide particles is 0.10 mol / L or more, preferably 0.10 to 2.00 mol / L, more preferably 0.8. It is characterized by washing with 10 to 1.50 mol / L carbonate aqueous solution.
By washing with a carbonate aqueous solution having a concentration of 0.10 mol / L or more, impurities in the nickel composite hydroxide particles, particularly sulfate radicals and chlorine, are ion-exchanged with carbonic acid in the carbonate aqueous solution. It can be removed efficiently. In particular, in the case of nickel composite hydroxide particles having the above-described void structure, it is difficult to remove impurities inside the particles by washing with an aqueous alkali metal solution such as water or sodium hydroxide, which has been conventionally used. Washing with an aqueous salt solution is effective.

  When washing, the pH is preferably 11.2 or more, more preferably 11.5 or more, on a 25 ° C. basis. By adjusting the pH to 11.2 or higher, sulfate radicals and chlorine that form acids can be more efficiently removed. Although the upper limit of pH is not specifically limited, since carbonate aqueous solution is used, about 12.5 becomes an upper limit by pH of 25 degreeC reference | standard.

The carbonate aqueous solution is preferably at least one aqueous solution selected from potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), potassium hydrogen carbonate and sodium hydrogen carbonate. Since lithium carbonate, calcium carbonate, and barium carbonate have low solubility in water, an aqueous solution in which a sufficient amount is dissolved may not be obtained.

  For example, when sodium carbonate is used as the carbonate, the aqueous solution concentration is preferably 0.2 mol / L or more, and more preferably 0.25 to 0.60 mol / L. Since sodium carbonate has high solubility in water, impurities such as sulfate radicals and chlorine can be more efficiently removed by setting the concentration of the aqueous solution to 0.2 mol / L or more.

  The water temperature of the carbonate aqueous solution is preferably 10 ° C to 50 ° C. When the water temperature is in the above range, the ion exchange reaction becomes active and the impurity removal proceeds efficiently.

  As the amount of carbonate aqueous solution used for washing, the sulfate content of the nickel composite hydroxide particles is 0.5% by mass or less, and the sodium content is 0.020% by mass or less, if it can be sufficiently washed, Although it does not specifically limit, 1000 mL or more is preferable with respect to 1000 g of nickel composite hydroxide, and, as for the liquid volume in the case of using sodium carbonate aqueous solution, for example, 2000-5000 mL is more preferable. If it is 1000 mL or less, the impurity ions and carbonate ions may not be sufficiently substituted, and the cleaning effect may not be sufficiently obtained.

  The washing time with the carbonate aqueous solution is not particularly limited as long as it can be sufficiently washed so that the sulfate content of the composite hydroxide particles is 0.5% by mass or less and the sodium content is 0.020% by mass or less. Usually, 0.5 to 2 hours.

  As a cleaning method, nickel composite hydroxide particles are added to an aqueous carbonate solution, and the slurry is washed and then filtered, or a normal cleaning method in which filtration is performed, or nickel composite hydroxide generated by neutralization crystallization. The slurry containing the particles can be supplied to a filter such as a filter press, and can be performed by water flow washing in which an aqueous carbonate solution is passed. Washing with water is preferable because it has high impurity removal efficiency, and filtration and washing can be performed continuously in the same facility and productivity is high.

  After washing with an aqueous carbonate solution, washing with pure water is preferably performed as necessary. By washing with pure water, cation impurities such as sodium can be removed.

  For cleaning with pure water, a method that is usually performed can be used. However, when water carbonate cleaning is performed, water cleaning with pure water is continuously performed after water carbonate cleaning with a carbonate aqueous solution. preferable.

2. Precursor of positive electrode active material for nonaqueous electrolyte secondary battery The precursor of the positive electrode active material for nonaqueous electrolyte secondary battery of the present invention is represented by the following general formula (1), and is a nickel composite hydroxide having a void structure It consists of particle | grains, A sulfate radical content is 0.5 mass% or less, Sodium content is 0.020 mass% or less, It is characterized by the above-mentioned.
General formula: Ni _1-xy Co _y Mn _z M _t (OH) ₂ (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)

  The content of sulfate radicals in the precursor does not decrease even in the firing step performed when the positive electrode active material is manufactured, and remains in the positive electrode active material. Therefore, it is necessary to sufficiently reduce the content of the precursor. By making the sulfate radical content 0.5 mass% or less, preferably 0.4 mass% or less, more preferably 0.3 mass% or less, the sulfate radical content of the positive electrode active material obtained is also 0.4 mass. % Or less, preferably 0.3% by mass or less.

  The content of sodium in the precursor does not decrease even in the firing step performed when the positive electrode active material is manufactured, but may increase due to the lithium salt as a mixed raw material. On the other hand, it is removed to some extent when washed with water after firing, but in order to sufficiently reduce the sodium content of the positive electrode active material, it is 0.020% by mass or less, preferably 0.017% by mass or less, more preferably 0.015% by mass. It is necessary to sufficiently reduce the sodium content in the precursor so as to be not more than%.

  Furthermore, the chlorine content in the precursor is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.02% by mass or less. Chlorine is easy to decrease in the firing process and has less influence on the positive electrode active material compared to the sulfate radical, but the remaining chlorine has an adverse effect on the firing furnace during the production of the positive electrode active material, so it is sufficient in the precursor. It is preferable to reduce it.

  The contents of sulfate radical, sodium and chlorine in the precursor are adjusted appropriately by adjusting the concentration of the carbonate aqueous solution, the amount of carbonate aqueous solution, the temperature, etc. when washing the nickel composite hydroxide particles with the carbonate aqueous solution, It can be set as the said range.

3. Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery The method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention comprises a mixing step (b) of mixing the precursor with a lithium compound to obtain a lithium mixture. ) And the lithium mixture in an oxygen atmosphere in the range of 650 to 850 ° C., and the lithium nickel composite oxide particles represented by the following general formula (2) (hereinafter simply referred to as “lithium composite oxide particles”) A firing step (c).
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05, 0. <X ≦ 0.20 and 0 <y ≦ 0.07.)
Moreover, before the mixing step (b), it is preferable to include a roasting step (a) in which the precursor is oxidized and roasted at 400 to 800 ° C. in an oxidizing atmosphere to obtain a nickel composite oxide. After c), it is preferable to include a water washing step (d) in which the lithium nickel composite oxide is filtered and dried after being washed with water.
Hereinafter, each step will be described.

(1) Roasting process (a)
The roasting step (a) is a step of roasting the nickel composite hydroxide to obtain the nickel composite oxide. As a result, the ratio of lithium to a metal element other than lithium can be easily controlled. Roasting is performed at a temperature of 400 to 800 ° C., more preferably 500 to 700 ° C. in an oxidizing atmosphere.
By setting the roasting temperature to 400 to 800 ° C., the quality of the lithium nickel composite oxide obtained using this can be stabilized, and the composition at the time of synthesis can be made more uniform. Moreover, the rapid grain growth of the primary particle which comprises particle | grains can be suppressed, and sufficient reaction area by the side of nickel composite oxide can be ensured in the manufacturing process of subsequent lithium nickel composite oxide. As a result, the lithium compound and the nickel composite oxide cannot sufficiently react, and it becomes easy to prevent the problem of specific gravity separation between the nickel compound having a large specific gravity in the lower layer and the lithium compound in the molten state in the upper layer.

(2) Mixing step (b)
The mixing step (b) is a step of obtaining a lithium mixture by mixing the precursor with a lithium compound.
When the mixing ratio of the precursor and the lithium compound does not include the water washing step (d), the molar ratio between lithium (Li) and a metal element (Me) other than lithium (hereinafter referred to as Li / Me) is 0.85. It is preferable to adjust so that it may become -1.05, Preferably it is 0.95-1.04. That is, it mixes so that Li / Me in a lithium mixture may become the same as Li / Me in the positive electrode active material of this invention. This is because Li / Me does not change before and after the firing step (c), and thus Li / Me mixed in the mixing step (b) becomes Li / Me in the positive electrode active material.
When Li / Me of the obtained positive electrode active material is less than 0.85, it causes a large decrease in battery capacity during charge / discharge cycles. On the other hand, when Li / Me exceeds 1.05, a battery is obtained. The internal resistance of the positive electrode will increase.

Moreover, when a water washing process (d) is included, it is preferable that Li / Me is 0.95-1.13 about the mixing ratio of a precursor and a lithium compound.
That is, when Li / Me is less than 0.95, the molar ratio of the fired powder obtained is also less than 0.95, the crystallinity is very poor, and when washed with water, the molar ratio of lithium to a metal other than lithium (Li / Me) may be less than 0.85. On the other hand, if the molar ratio exceeds 1.13, the molar ratio of the calcined powder obtained also exceeds 1.13, and a large amount of excess lithium compound is present on the surface, which is difficult to remove by washing with water. For this reason, when this is used as a positive electrode active material, not only a large amount of gas is generated during charging of the battery, but also a slurry that reacts with a material such as an organic solvent used in electrode preparation because it is a powder exhibiting a high pH. Causes gelation and causes problems. Moreover, the molar ratio (Li / Me) of the positive electrode active material after washing with water may exceed 1.05.

  The lithium compound is not particularly limited, and at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide is preferably used. Lithium hydroxide and / or carbonate is used.

  For mixing the precursor and the lithium compound, a general mixer can be used. For example, a dry mixer such as a V blender or a mixing granulator is used.

(3) Firing step (c)
A baking process (c) is a process of baking the said lithium mixture in the range of 650-850 degreeC in oxygen atmosphere. As a calcination temperature, the range of 650-800 degreeC, Preferably the range of 730-790 degreeC is used. In other words, lithium nickelate is produced if heat treatment is performed at a temperature exceeding 500 ° C., but if the temperature is lower than 650 ° C., the crystal is undeveloped and structurally unstable, and the structure is easily formed by phase transition due to charge / discharge. It will be destroyed. On the other hand, when the temperature exceeds 800 ° C., cation mixing is likely to occur, the layered structure is destroyed, lithium ion insertion or desorption becomes difficult, and nickel oxide or the like is generated by decomposition.
Further, after removing crystal water and the like contained in the lithium compound, calcining is performed at a temperature of 400 to 600 ° C. for 1 hour or more in order to cause a uniform reaction in a temperature range in which crystal growth proceeds, and subsequently 650 to 800. It is particularly preferable to bake at a temperature of 3 ° C. for 3 hours or more.

  For the firing of the lithium mixture, a firing furnace such as an electric furnace, a kiln, a tubular furnace, or a pusher furnace adjusted to a gas atmosphere having an oxygen concentration of 20% by mass or more such as an oxygen atmosphere, a dehumidified and decarbonized dry air atmosphere or the like is used. Used.

(4) Water washing step (d)
The water washing step (d) is a step of filtering and drying the lithium nickel composite oxide obtained in the firing step (c) after washing with water.
The lithium nickel composite oxide after the firing step (c) is used as a positive electrode active material as it is, but by removing excess lithium on the surface of the particles, the surface area that can be contacted with the electrolytic solution is increased and charge / discharge is performed. Since a capacity | capacitance can be improved, it is preferable to perform a water-washing process (d) after baking. Moreover, since the weak part formed in the particle | grain surface is fully removed, a contact with electrolyte solution can increase and charge / discharge capacity can be improved.

When washing with water, the slurry concentration is sufficient so that the lithium amount of the lithium compound existing on the surface of the lithium nickel composite oxide is 0.10% by mass or less with respect to the total amount at a temperature of 10 to 40 ° C. Then, it is preferable to wash with water, and then filter and dry.
In the water washing treatment, by setting the temperature to 10 to 40 ° C., the amount of lithium existing on the surface of the lithium nickel composite oxide powder can be reduced to 0.10% by mass or less, and gas generation at the time of holding at high temperature is suppressed. be able to. In addition, a positive electrode active material capable of achieving high capacity and high output can be obtained, and high safety can be achieved at the same time.

  The amount of lithium present on the surface of the lithium nickel composite oxide was determined by adding ultrapure water to 10 g of lithium nickel composite oxide powder up to 100 ml and stirring, followed by titration with 1 mol / liter hydrochloric acid until the second neutralization point. Measure and obtain as alkali content neutralized with hydrochloric acid.

  Further, the washing time is not particularly limited, but it is necessary that the washing time is sufficient for the lithium amount of the lithium compound present on the surface of the lithium nickel composite oxide to be 0.10% by mass or less based on the total amount. Yes, depending on the washing temperature, it is generally not 20 minutes to 2 hours.

  As the slurry concentration when washing with water, the amount (g) of the calcined powder with respect to 1 L of water contained in the slurry is preferably 500 to 2000 g / L. That is, as the slurry concentration increases, the amount of powder increases. When the slurry concentration exceeds 2000 g / L, the viscosity is very high and stirring becomes difficult. However, it becomes difficult to separate the powder from the powder even when peeling occurs. On the other hand, if the slurry concentration is less than 500 g / L, the amount of lithium elution is large and the amount of lithium on the surface is small because the solution is too dilute, but lithium is desorbed from the crystal lattice of the positive electrode active material. Not only tends to collapse, but the aqueous solution having a high pH absorbs carbon dioxide in the atmosphere and reprecipitates lithium carbonate. In consideration of productivity from an industrial point of view, the slurry concentration is preferably in the above range from the viewpoint of facility capacity and workability.

  The filtration method after washing with water may be a commonly used method, and for example, a suction filter, a filter press, a centrifuge, or the like can be used.

The drying temperature after filtration is not particularly limited and is preferably 80 to 350 ° C. If the temperature is less than 80 ° C., the drying of the positive electrode active material after washing with water becomes slow, so that a gradient of lithium concentration occurs between the particle surface and the inside of the particle, and the battery characteristics may be deteriorated. On the other hand, near the surface of the positive electrode active material, it is expected that it is very close to the stoichiometric ratio, or slightly desorbed lithium and close to the charged state. As a result, the crystal structure close to 1 may be destroyed, and the battery characteristics may be deteriorated.
Although it does not specifically limit as drying time, Preferably it is 2 to 24 hours.

4). Positive electrode active material for nonaqueous electrolyte secondary battery The positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention is represented by the following general formula (2), and is a lithium nickel composite oxide having a hollow structure or a porous structure. The sulfate radical content is 0.25% by mass or less, and the Na content is 0.020% by mass or less.
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05. 0 <x ≦ 0.20 and 0 <y ≦ 0.07.)

  In the positive electrode active material of the present invention, the sulfate group content is 0.25% by mass or less, preferably 0.20% by mass or less, more preferably 0.15% by mass or less. Thereby, an irreversible capacity | capacitance can be made small, ie, coulomb efficiency can be made high, and a high capacity | capacitance is obtained when it uses for the positive electrode active material of a battery. In addition, excess lithium accumulated in the negative electrode can be suppressed, and safety can be improved.

  Sodium content is 0.020 mass% or less, Preferably it is 0.015 mass% or less. Sodium also increases the irreversible capacity in the same manner as the sulfate radical, and by setting the content to 0.020% by mass or less, the irreversible capacity can be reduced and high Coulomb efficiency can be obtained. Moreover, since sodium raises the resistance value of a positive electrode active material, an output characteristic can be improved by making the content into the said range.

  Furthermore, since chlorine also increases the irreversible capacity, the chlorine content is preferably 0.05% by mass or less, and more preferably 0.02% by mass or less.

Since the lithium nickel composite oxide particles have a hollow structure or a porous structure, the contact area with the electrolytic solution can be increased. Thereby, it can be set as the positive electrode active material excellent in output characteristics.
Furthermore, in order to improve output characteristics, the porosity inside the lithium nickel composite oxide particles measured in cross-sectional observation is preferably 15% or more, and more preferably 15 to 85%. The particle structure and porosity can be confirmed and determined by the same method as that for the nickel composite hydroxide particles described above.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The metal analysis method and evaluation method of nickel composite hydroxide / lithium nickel composite oxide used in Examples and Comparative Examples are as follows.

(1) Composition analysis: Measured by ICP emission spectrometry.
(2) Sulfate radical content: Sulfur was quantitatively analyzed by an ICP emission analysis method, and the sulfur content was determined by multiplying a coefficient by assuming that all sulfur was oxidized to become sulfate radicals (SO ₄ ²⁻ ).
(3) Na, Cl content: measured by atomic absorption spectrometry.
(4) Charge / discharge capacity, coulomb efficiency:
The charge / discharge capacity is allowed to stand for about 24 hours after the coin-type battery is produced, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm ² and the cut-off voltage is 4. Charge to 3V, after 1 hour of rest, discharge capacity to 3.0V cut-off voltage, discharge capacity, ratio of discharge capacity to charge capacity (discharge capacity / charge capacity) at this time Coulomb efficiency (%) It was.
(5) Reaction resistance:
For the reaction resistance, a coin-type battery was charged at a charging potential of 4.1 V, an AC impedance method Nyquist plot was created using a frequency response analyzer and a potento-galvanostat (manufactured by Solartron, 1255B), and fitting was performed using an equivalent circuit. The value of the positive electrode resistance was calculated by calculation.

(Example 1)
[Production of cathode active material precursor]
(Nucleation process)
Into the reaction tank (34L), half the amount of water was added and the temperature in the tank was set to 40 ° C. while stirring at 500 rpm using an inclined paddle type stirring blade. An appropriate amount of a 25% by mass aqueous sodium hydroxide solution was added to the water in the reaction tank, and the pH value of the reaction liquid in the tank was adjusted to 12.6 based on the liquid temperature of 25 ° C. to obtain a pre-reaction solution. .
Next, a mixed aqueous solution of 2.0 mol / L obtained by dissolving nickel sulfate, cobalt chloride, sodium aluminate (metal element molar ratio Ni: Co: Al = 82: 15: 3) in water was added to the reaction vessel. Was added at a rate of 88 ml / min to the pre-reaction aqueous solution. At the same time, a 25% by mass aqueous sodium hydroxide solution is also added to the reaction aqueous solution at a constant rate, and the pH value of the reaction aqueous solution (nucleation aqueous solution) is controlled to 12.6 (nucleation pH value) on a 25 ° C. basis. Crystallization (nucleation) was performed for 15 seconds.

(Particle growth process)
After the nucleation was completed, only the supply of the 25 mass% aqueous sodium hydroxide solution was temporarily stopped until the pH value of the reaction aqueous solution reached 10.2 based on the liquid temperature of 25 ° C.
After the pH value of the aqueous reaction solution reached 10.2 on the basis of 25 ° C., the supply of the 25% by mass aqueous sodium hydroxide solution was resumed in the aqueous reaction solution (particle growth aqueous solution), and the pH value was 10.2 ( Particle growth was carried out while controlling the particle growth pH value), and crystallization was carried out for 2 hours from the start of growth.
When the reaction vessel became full, crystallization was stopped and stirring was stopped and the mixture was allowed to stand to promote precipitation of the product. Then, after extracting half amount of the supernatant from the reaction tank, crystallization was resumed, and after crystallization for 2 hours (particle growth: 4 hours in total), crystallization was terminated. The product was washed with water, filtered, and dried to obtain nickel composite hydroxide particles.
In the crystallization, the pH was controlled by adjusting the supply flow rate of the sodium hydroxide aqueous solution with a pH controller, and the fluctuation range was within the range of 0.2 above and below the set value.
The obtained nickel composite hydroxide particles had a void structure and consisted of secondary particles having a spherical average particle diameter of 9.3 μm in which primary particles of 1 μm or less were aggregated, and the porosity was 49%. Moreover, the composition had a molar ratio of nickel, cobalt, and aluminum of 82: 15: 3.

(Washing with carbonate)
The obtained composite hydroxide particles were solid-liquid separated by a filter press filter, and 0.28 mol / L sodium carbonate aqueous solution at 25 ° C. and pH 11.5 (25 ° C. standard) was added to 1000 g of the composite hydroxide particles. Then, it was washed by passing through the filter press at a rate of 3000 mL, and pure water was passed through for washing. Table 1 shows the results of the composition, impurity amount, etc. of the nickel composite hydroxide (precursor) after washing.

[Production of positive electrode active material]
The obtained nickel composite hydroxide particles were roasted at 700 ° C. in an air atmosphere using an electric furnace to obtain nickel composite oxide particles (roasting step). Nickel composite hydroxide and water so that the molar ratio of each metal component of the lithium nickel composite oxide particles is Ni: Co: Al: Li = 0.85: 0.12: 0.03: 1.03. Lithium oxide monohydrate (Wako Pure Chemical Industries, Ltd.) was weighed and mixed (mixing step). The obtained mixture was calcined at 500 ° C. for 3 hours in an atmosphere having an oxygen concentration of 30% or more using an electric furnace, and then finally calcined at 750 ° C. for 20 hours (firing step). Then, after cooling in a furnace to room temperature, pulverization was performed to obtain a spherical fired powder in which primary particles were aggregated.
A slurry was prepared by mixing the obtained spherical calcined powder with pure water so that the slurry concentration was 1500 g / L, and the mixture was washed with water at room temperature for 30 minutes using a stirrer and then filtered. After filtration, it is kept at 190 ° C. for 14 hours and cooled to room temperature using a vacuum dryer (water washing step), and lithium nickel composite oxide particles having a volume-based average particle diameter by laser diffraction scattering method of 9.3 μm ( A positive electrode active material) was obtained. Table 2 shows the composition and impurity amount of the obtained positive electrode active material.

[Evaluation of positive electrode active material]
About this positive electrode active material embedded in a resin and subjected to cross section polisher, cross-sectional observation by SEM with a magnification of 5000 times was performed, and an outer shell portion formed by sintering primary particles, It was confirmed that the hollow structure provided with a hollow portion therein. The porosity of the positive electrode active material determined from this observation was 43%. Using this positive electrode active material, a battery was produced by the following method. Table 1 shows the physical property results of the precursor, and Table 2 shows the physical property results of the active material. Table 2 shows the composition and impurity amount of the obtained positive electrode active material.

(Battery preparation method)
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 form a paste. The paste was applied to the active material weight after drying in an aluminum foil of 20μm thickness is 0.05 g / cm ^2, and vacuum dried at 120 ° C., then the positive electrode and punched than this into a disk form having a diameter of 1cm did.
Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt was used as the electrolyte. Further, a 2032 type coin battery was manufactured in a glove box in an Ar gas atmosphere in which a separator made of polyethylene was impregnated with an electrolytic solution and the dew point was controlled at −80 ° C. FIG. 1 shows a schematic structure of a 2032 type coin battery. Here, the coin battery includes a positive electrode (evaluation electrode) 1 in a positive electrode can 5, a lithium metal negative electrode 3 in a negative electrode can 6, an electrolyte-impregnated separator 2, and a gasket 4. Table 2 shows the characteristics (discharge capacity, coulomb efficiency, reaction resistance) of the obtained battery.

(Example 2)
A positive electrode active material lithium-nickel composite oxide was produced and evaluated except that the aqueous sodium carbonate solution was washed with pH 11.8 (25 ° C. standard) changed to 0.47 mol / L and washed. . The evaluation results are shown in Tables 1 and 2.

(Example 3)
A positive electrode active material was produced and evaluated in the same manner as in Example 1 except that the sodium carbonate aqueous solution was washed with a pH of 12.0 (based on 25 ° C.) of 1.12 mol / L. The evaluation results are shown in Tables 1 and 2.

Example 4
The same procedure as in Example 1 was performed except that 25 mass% ammonia water was supplied and the ammonia concentration in the reaction solution was adjusted to 15 g / L in the nucleation step and particle growth step during the production of the precursor. The positive electrode active material was manufactured and evaluated. The evaluation results are shown in Tables 1 and 2.
The obtained composite hydroxide particles had a void structure, consisted of secondary particles having a spherical average particle diameter of 9.8 μm in which primary particles of 1 μm or less were aggregated, and the porosity was 26%. Moreover, the composition had a molar ratio of nickel, cobalt, and aluminum of 82: 15: 3. Further, the positive electrode active material had a porous structure, and the porosity was 19%.

(Example 5)
Using the precursor obtained in Example 1, the positive electrode active material was manufactured in the same manner as in Example 1 except that the water washing step (the spherical fired powder was washed with water and vacuum dried) was not performed after firing. evaluated. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 1)
Performed in the same manner as in Example 1 except that the aqueous sodium carbonate solution was changed to 0.09 mol / L at pH 11.0 (25 ° C.) and washed, and the spherical fired powder was washed with water and not vacuum dried after firing. The positive electrode active material was manufactured and evaluated. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 2)
The sodium carbonate aqueous solution was changed to a 1.60 mol / L aqueous sodium hydroxide solution having a pH of 13.5 (based on 25 ° C.) and washed, and the water washing step (washing the spherical fired powder with water and vacuum drying) was not performed after firing. Was carried out in the same manner as in Example 1, and a positive electrode active material was produced and evaluated. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 3)
The sodium carbonate aqueous solution was changed to a 3.39 mol / L sodium hydroxide aqueous solution having a pH of 14.0 (25 ° C. standard) and washed, and the water washing step (washing the spherical fired powder with water and vacuum drying) was not performed after firing. Was carried out in the same manner as in Example 1, and a positive electrode active material was produced and evaluated. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 4)
Using a reaction tank for continuous crystallization provided with an overflow pipe at the top, while maintaining the pH at 25 ° C. at a constant value of 11.6, a mixed aqueous solution, an aqueous ammonia solution, and an aqueous sodium hydroxide solution as in Example 4 Was continuously added at a constant flow rate, and crystallization was performed by a method of continuously recovering the overflowing slurry with an average residence time in the tank of 10 hours. After the reaction vessel was in an equilibrium state, the slurry was recovered and solid-liquid separated, and the product was washed with water, filtered and dried to obtain nickel composite hydroxide particles, and the washing step was not performed after firing. Except for this, the same procedure as in Example 1 was carried out, and a positive electrode active material lithium nickel composite oxide was produced and evaluated. The evaluation results are shown in Tables 1 and 2.
The obtained composite hydroxide particles were not observed to have a void structure, had a dense particle structure, and consisted of secondary particles having a spherical average particle size of 8.5 μm in which primary particles of 1 μm or less were aggregated. The rate was 3%. Moreover, the composition had a molar ratio of nickel, cobalt, and aluminum of 82: 15: 3. Further, the positive electrode active material had a dense particle structure, and the porosity was 4%.

From Tables 1 and 2, it can be seen that in Examples 1 to 5 that satisfy all the requirements of the present invention, the amount of impurities in the particles of the obtained nickel composite hydroxide particles and lithium composite oxide particles is very low. Moreover, the secondary battery using the lithium composite oxide particles having a hollow structure or a porous structure obtained in Examples 1 to 5 as a positive electrode active material has a high capacity, high coulomb efficiency, and low reaction resistance. It has excellent battery characteristics.
On the other hand, in Comparative Examples 1 to 3 that do not satisfy the requirements of the present invention, the amount of impurities in the obtained nickel composite hydroxide particles and lithium composite oxide particles is large, and the obtained lithium composite oxide particles are The secondary battery used as the positive electrode active material has a lower discharge capacity than Examples 1-5. In Comparative Examples 2 and 3, which were washed with sodium hydroxide, the concentration of the sodium hydroxide solution was increased to decrease the sulfate radical (SO ₄ ) amount, but the sodium root remained, resulting in a decrease in discharge capacity. And reaction resistance is high.
On the other hand, in Comparative Example 4, since the composite hydroxide particles having a dense particle structure were sufficiently washed with sodium carbonate, the amount of impurities was smaller than that of the Example, but the obtained positive electrode Since the active material has a structure with few voids, the contact area with the electrolytic solution is reduced, and the battery characteristics are degraded as compared with Example 4 having the same composition ratio.

  The precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery and the positive electrode active material for a non-aqueous electrolyte secondary battery obtained by the present invention have a very low impurity content, and a non-aqueous electrolyte using the same A secondary battery is suitable as a chargeable / dischargeable secondary battery particularly used in the field of small electronic devices because of its high capacity, excellent coulomb efficiency, and reaction resistance, and its industrial applicability is extremely large.

1 Positive electrode (Evaluation electrode)
2 Separator (electrolyte impregnation)
3 Lithium metal negative electrode 4 Gasket 5 Positive electrode can 6 Negative electrode can

Claims (15)

A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a nickel composite hydroxide particle represented by the following general formula (1) and having a hollow structure or a porous structure,
A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the nickel composite hydroxide particles having a void structure inside the particles are washed with a carbonate aqueous solution having a carbonate concentration of 0.1 mol / L or more. Body manufacturing method.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)   2. The method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the nickel composite hydroxide particles have a porosity measured in cross-sectional observation of 15% or more. .   The carbonate aqueous solution is at least one aqueous solution selected from potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate, and the pH of the carbonate aqueous solution is 11.2 or more. A method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to 1 or 2.   The said washing | cleaning is performed in the range of 10-50 degreeC of liquid temperature, The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 1-3 characterized by the above-mentioned. The nickel composite hydroxide particles are supplied in a heated reaction tank with a mixed aqueous solution of nickel and cobalt and, if necessary, the metal compound containing the element M. At that time, the reaction solution is kept alkaline. It is obtained by appropriately supplying a sufficient amount of an aqueous solution of an alkali metal hydroxide to carry out neutralization crystallization,
In the neutralization crystallization, the nucleation step for generating nuclei and the particle growth step for growing the generated nuclei are performed separately by controlling the pH value of the reaction solution. The manufacturing method of the precursor of the positive electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 1-4.   The pH value in the nucleation step is controlled to be 11.5 to 13.2 based on a liquid temperature of 25 ° C., and the pH value in the particle growth step is 9.5 to 12.2. 6. The method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein control is performed so that the pH value is 0 and lower than a pH value in the nucleation step.   The method for producing a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 5 or 6, wherein the mixed aqueous solution contains at least one chloride of nickel and cobalt. A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery having a hollow structure or a porous structure, comprising a nickel composite hydroxide particle represented by the following general formula (1) and having a void structure inside the particle A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the sulfate radical content is 0.5 mass% or less and the sodium content is 0.020 mass% or less.
The general _{formula: Ni 1-x-y Co} x M y (OH) 2 ··· (1)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and 0 <x ≦ 0.20, 0 <y ≦ 0. .07.)   The precursor of the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 8, wherein the chlorine content is 0.1% by mass or less. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery represented by the following general formula (2) and comprising a lithium nickel composite oxide having a hollow structure or a porous structure,
A mixing step of mixing the precursor of the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 8 or 9 with a lithium compound to obtain a lithium mixture;
A firing step of firing the lithium mixture in an oxygen atmosphere in a range of 650 to 850 ° C. to obtain a lithium nickel composite oxide;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries characterized by including this.
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05. 0 <x ≦ 0.20 and 0 <y ≦ 0.07.)   The method further comprises a roasting step in which the precursor is oxidized and roasted at 400 to 800 ° C. in an oxidizing atmosphere to obtain a nickel composite oxide. In the mixing step, the nickel composite oxide is mixed with a lithium compound to form a lithium mixture. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 10 characterized by the above-mentioned.   After the firing step, the lithium nickel composite oxide is 0.10% by mass with respect to the total amount of lithium compound present at a temperature of 10 to 40 ° C. and on the surface of the lithium nickel composite oxide. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 10 or 11, further comprising a water washing step of filtering and drying after washing with water at a slurry concentration sufficient to become: .   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. It is represented by the following general formula (2), and is composed of a lithium nickel composite oxide having a hollow structure or a porous structure. The sulfate radical content is 0.25% by mass or less, and the Na content is 0.020% by mass or less. A positive electrode active material for a non-aqueous electrolyte secondary battery.
General _{formula: Li a Ni 1-x-} y Co x M y O 2 ··· (2)
(In the formula, M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Zr, Mo and W, and a is 0.85 ≦ a ≦ 1.05. 0 <x ≦ 0.20 and 0 <y ≦ 0.07.)   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 14, wherein the chlorine content is 0.05% by mass or less.

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