WO2016067960A1 - Nickel composite hydroxide and method for preparing same - Google Patents

Abstract

Provided is nickel composite hydroxide containing reduced amounts of sulfate radical and chlorine as impurities. This method comprises a crystallization step for crystallizing in a reaction solution obtained by adding an alkali solution to an aqueous solution including: a mixed aqueous solution including nickel and cobalt; an ammonium ion donor; and an aluminum source, the alkali solution being a mixed aqueous solution of alkali metal hydroxide and carbonate. The ratio of the carbonate to the alkali metal hydroxide in the mixed aqueous solution, i.e. [CO₃ ^2-]/[OH^-], is controlled to be 0.002-0.050 inclusive, to thereby obtain nickel composite hydroxide which: is expressed by Ni_1-x-yCo_xAl_y(OH)_2+α (0.05≤x≤0.35, 0.01≤y≤0.2, x+y<0.4, 0≤α≤0.5); is in the form of spherical secondary particles formed by the aggregation of a plurality of plate-like primary particles, the secondary particles having an average particle diameter of 3-20 µm; and contains 1.0 mass% or less of sulfate radical, 0.5 mass% or less of chlorine, and 1.0-2.5 mass% of carbonate radical.

Description

Nickel composite hydroxide and production method thereof

The present invention relates to a nickel composite hydroxide serving as a precursor of a positive electrode active material used as a positive electrode material in a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and a method for producing the same. This application includes Japanese Patent Application No. 2014-221859 filed on October 30, 2014 in Japan and Japanese Patent Application No. 2015-2015 filed on June 23, 2015 in Japan. The priority is claimed on the basis of 125811, which is incorporated herein by reference.

In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high output secondary battery is strongly desired as a battery for electric vehicles including hybrid vehicles. As a secondary battery satisfying such requirements, there is a lithium ion secondary battery. A lithium ion secondary battery includes a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of detaching and inserting lithium is used as an active material for the negative electrode and the positive electrode.

Research and development of lithium ion secondary batteries are currently being actively conducted. Among them, lithium ion secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material have a high voltage of 4V. Therefore, practical use is progressing as a battery having a high energy density.

A battery using a lithium cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize as a positive electrode material of a lithium ion secondary battery has been developed so far to obtain excellent initial capacity characteristics and cycle characteristics. Have already achieved various results. However, since the lithium cobalt composite oxide uses a rare and expensive cobalt compound as a raw material, it causes an increase in the cost of the active material and the battery, and an alternative to the active material is desired.

Therefore, lithium nickel composite oxide (LiNiO ₂ ), which can be expected to have a higher capacity using nickel cheaper than cobalt, has attracted attention. Lithium-nickel composite oxide not only has a low cost but also has a lower electrochemical potential than lithium-cobalt composite oxide. Therefore, decomposition due to oxidation of the electrolyte is less problematic, and higher capacity can be expected. Since it shows a high battery voltage as well as the system, it has been actively developed.

However, the lithium-nickel composite oxide, when a lithium ion secondary battery is produced using a material synthesized purely of nickel alone as a positive electrode active material, is inferior in cycle characteristics compared to cobalt-based materials, and also in a high temperature environment. When used or stored, there is a drawback that the battery performance is relatively easily lost.

To solve such drawbacks, 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 Zn) have been proposed.

In Patent Document 2, LiNi _x M _1-x O ₂ (M is Co, Mn, Cr, Fe, V, Al) as a positive electrode active material that provides a non-aqueous electrolyte secondary battery with high capacity and excellent cycle characteristics. Lithium-containing composite oxides, etc., which are one or more selected from the above and represented by x: 1> x ≧ 0.5) have been proposed.

Japanese Patent Laid-Open No. 08-213015 JP 09-129230 A

However, the lithium nickel composite oxide obtained by the manufacturing methods as described in Patent Documents 1 and 2 has higher charge capacity and discharge capacity than the lithium cobalt composite oxide and improved cycle characteristics. Only in the second charge / discharge, there is a problem that the discharge capacity is smaller than the charge capacity, and the so-called irreversible capacity defined by the difference between the two is large.

The lithium nickel composite oxide is usually manufactured from a step of mixing a nickel composite hydroxide with a lithium compound and baking. The nickel composite hydroxide contains impurities such as sulfate radicals derived from raw materials in the manufacturing process of the nickel composite hydroxide. These impurities often inhibit the reaction with lithium in the step of mixing and baking the lithium compound, and lower the crystallinity of the lithium nickel composite oxide having a layered structure.

The lithium-nickel composite oxide having low crystallinity has a problem in that when a battery is formed as a positive electrode material, the Li diffusion in the solid phase is inhibited and the capacity is reduced. Furthermore, the impurities contained in the nickel composite hydroxide remain in the lithium nickel composite oxide even after mixing with the lithium compound and firing. Since these do not contribute to the charge / discharge reaction, when the battery is configured, the negative electrode material must be used in the battery by an amount corresponding to the irreversible capacity of the positive electrode material. As a result, the capacity per weight and volume of the battery as a whole is reduced, and excess lithium accumulated in the negative electrode as an irreversible capacity becomes a problem from the viewpoint of safety.

Therefore, a lithium nickel composite oxide with a lower impurity content is required, but for that purpose, a nickel composite hydroxide with a lower impurity content is required.

Accordingly, the present invention provides a precursor of a positive electrode active material that can obtain a high-capacity non-aqueous electrolyte secondary battery by inhibiting the reaction with lithium and further reducing the amount of impurities that do not contribute to the charge / discharge reaction. A nickel composite hydroxide and a method for producing the same are provided.

As a result of intensive studies, the present inventors have found that, in the step of producing a nickel composite hydroxide by a crystallization reaction, an alkaline solution is a mixed solution of an alkali metal hydroxide and a carbonate, so that the sulfate group which is an impurity is used. The present invention has been completed with the knowledge that the above can be reduced.

Nickel composite hydroxide according to the present invention for achieving the above object, the general formula _{Ni 1-x-y Co x} Al y (OH) 2 + α (0.05 ≦ x ≦ 0.35,0.01 ≦ y ≦ 0.2, x + y <0.4, 0 ≦ α ≦ 0.5), and are spherical secondary particles formed by aggregation of a plurality of plate-like primary particles, and the secondary particles have an average The particle size is 3 μm to 20 μm, the sulfate radical content is 1.0 mass% or less, the chlorine content is 0.5 mass% or less, and the carbonate radical content is 1.0 mass% to 2.5 mass%. It is characterized by mass%.

The method for producing a nickel composite hydroxide according to the present invention that achieves the above-described object is a method for producing a nickel composite hydroxide by producing a nickel composite hydroxide by a crystallization reaction. A crystallization step of crystallization by adding an alkaline solution to a reaction solution containing a mixed aqueous solution, an ammonium ion supplier, and an aluminum source, wherein the alkaline solution is a mixed aqueous solution of an alkali metal hydroxide and a carbonate The ratio [CO ₃ ²⁻ ] / [OH ⁻ ] of the carbonate to the alkali metal hydroxide in the mixed aqueous solution is 0.002 or more and 0.050 or less.

The present invention provides a nickel composite hydroxide with a low content of impurities that makes it possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having a small irreversible capacity. Further, in the present invention, such a nickel composite hydroxide can be easily manufactured, has high productivity, and extremely high industrial value.

Hereinafter, a nickel composite hydroxide to which the present invention is applied and a method for producing the same will be described in detail. Note that the present invention is not limited to the following detailed description unless otherwise specified. The embodiment according to the present invention will be described in the following order.

1. Nickel composite hydroxide 2. Manufacturing method of nickel composite hydroxide 3. Positive electrode active material for non-aqueous electrolyte secondary battery 4. Manufacturing method of positive electrode active material for non-aqueous electrolyte secondary battery Nonaqueous electrolyte secondary battery

<1. Nickel composite hydroxide>
Nickel composite hydroxide of the present invention have the general formula _{Ni 1-x-y Co x} Al y (OH) 2 + α (0.05 ≦ x ≦ 0.35,0.01 ≦ y ≦ 0.2, x + y <0 .4, 0 ≦ α ≦ 0.5), and spherical secondary particles formed by aggregation of a plurality of plate-like primary particles, and the secondary particles have an average particle size of 3 to 20 μm. The sulfate radical content is 1.0 mass% or less, the chlorine content is 0.5 mass% or less, and the carbonate radical content is 1.0 mass% to 2.5 mass%. It is a feature. Hereinafter, the characteristics of each element will be described in detail.

[Particle composition]
Nickel composite hydroxide is particulate, the composition has the general formula _{Ni 1-x-y Co x} Al y (OH) 2 + α (0.05 ≦ x ≦ 0.35,0.01 ≦ y ≦ 0 .2, x + y <0.4, 0 ≦ α ≦ 0.5).

In the above general formula, x indicating the cobalt content is 0.05 ≦ x ≦ 0.35. By appropriately adding cobalt, it is possible to reduce the cycle characteristics of the obtained positive electrode active material and the expansion and contraction behavior of the crystal lattice due to Li deinsertion associated with charge and discharge. If the cobalt content is too small and x is less than 0.05, the expected effect cannot be obtained, which is not preferable. On the other hand, if the cobalt content is too large and x exceeds 0.35, the initial discharge capacity of the positive electrode active material is greatly reduced, and there is a problem in that it is disadvantageous in terms of cost. Therefore, x indicating the cobalt content is 0.05 ≦ x ≦ 0.35, and considering the battery characteristics and cost of the positive electrode active material, 0.07 ≦ x ≦ 0.25 is preferable. More preferably, 0.10 ≦ x ≦ 0.20.

Next, y indicating the aluminum content is 0.01 ≦ y ≦ 0.2, preferably 0.01 ≦ y ≦ 0.1. When aluminum is added in this range, when the obtained positive electrode active material is used as the positive electrode active material of the battery, the durability characteristics and safety of the battery can be improved. In particular, if the aluminum is adjusted so as to be uniformly distributed inside the particles, the above effect can be obtained with the whole particles, and a larger effect can be obtained with the same addition amount, and a decrease in capacity can be suppressed. There is. Since the effect expected when y is less than 0.01 because the amount of aluminum added is too small, it is not preferable. On the other hand, if the amount of aluminum added is too large and exceeds 0.2, the metal element contributing to the Redox reaction decreases, and the battery capacity of the positive electrode active material decreases, which is not preferable. Furthermore, the total atomic ratio of cobalt and aluminum is x + y <0.4. When the atomic ratio of the total of cobalt and aluminum exceeds 0.4, the capacity of the obtained positive electrode active material is excessively reduced.

The composition analysis method is not particularly limited, but can be determined from chemical analysis by ICP emission spectroscopy.

[Particle structure]
The nickel composite hydroxide is composed of spherical secondary particles formed by aggregation of a plurality of primary particles. As the shape of the primary particles constituting the secondary particles, various forms such as a plate shape, a needle shape, a rectangular parallelepiped shape, an elliptical shape, and a rhombohedral shape can be adopted. Also, the aggregated state of a plurality of primary particles can be applied to the present invention not only in the case of aggregation in a random direction but also in the case of aggregation in the major axis direction of the primary particles radially from the center.

As the agglomerated state, it is preferable that plate-like and / or needle-like primary particles are aggregated in random directions to form secondary particles. In such a structure, voids are formed almost uniformly between the primary particles, and when mixed with the lithium compound and fired, the molten lithium compound reaches the secondary particles, and the lithium is sufficiently diffused. Because it is.

In addition, the shape observation method of the primary particles and the secondary particles is not particularly limited, but can be measured by observing the cross section of the nickel composite hydroxide using a scanning electron microscope.

[Average particle size]
The average particle diameter of the nickel composite hydroxide is adjusted to 3 to 20 μm. An average particle size of less than 3 μm is not preferable because when the positive electrode is formed, the packing density of the particles decreases and the battery capacity per positive electrode volume decreases. On the other hand, if the average particle size exceeds 20 μm, the specific surface area of the positive electrode active material is decreased and the interface with the battery electrolyte is decreased, whereby the resistance of the positive electrode is increased and the output characteristics of the battery are decreased. . Therefore, if the nickel composite hydroxide has an average particle diameter of 3 to 20 μm, preferably adjusted to 3 to 15 μm, more preferably 4 to 12 μm, this positive electrode active material was used for the positive electrode. In the battery, the battery capacity per volume can be increased, the safety is high, and the cycle characteristics are good.

The measuring method of the average particle diameter is not particularly limited, but can be determined from, for example, a volume integrated value measured by a laser light diffraction / scattering particle size analyzer.

[Impurity content]
The nickel composite hydroxide contains sulfate radicals and chlorine as impurities. Sulfate radicals and chlorine are derived from the raw materials used in the crystallization process described later. The nickel composite hydroxide has a sulfate radical content of 1.0 mass% or less, preferably 0.6 mass% or less, and a chlorine content of 0.5 mass% or less, preferably 0.3 mass% or less. It is.

When the sulfate group content in the nickel composite hydroxide exceeds 1.0% by mass, the reaction with lithium is inhibited in the step of mixing with the lithium compound and firing, and the crystallinity of the lithium nickel composite oxide having a layered structure Reduce. Lithium nickel composite oxide having low crystallinity has a problem in that when a battery is formed as a positive electrode material, Li diffusion in the solid phase is inhibited and the capacity is reduced. Furthermore, the impurities contained in the nickel composite hydroxide remain in the lithium nickel composite oxide even after being mixed with the lithium compound and baked. Since these impurities do not contribute to the charge / discharge reaction, when the battery is configured, the negative electrode material has to be used in the battery by an amount corresponding to the irreversible capacity of the positive electrode material. As a result, the capacity per weight and volume of the battery as a whole is reduced, and excess lithium accumulated in the negative electrode as an irreversible capacity becomes a problem from the viewpoint of safety.

On the other hand, when the chlorine content exceeds 0.5% by mass, there is a problem of battery capacity reduction and safety as in the case of sulfate radicals. Further, chlorine remains in the lithium nickel composite oxide mainly in the form of LiCl or NaCl. Since these have high hygroscopicity, they cause moisture to be brought into the battery and cause deterioration of the battery.

[Carbonate content]
The nickel composite hydroxide has a carbonate radical content of 1.0% by mass to 2.5% by mass. Here, the carbonate radical contained in the nickel composite hydroxide is derived from the carbonate used in the crystallization step described later. The carbonate radical is volatilized in the step of mixing and firing the nickel composite hydroxide and the lithium compound, and therefore does not remain in the lithium nickel composite oxide as the positive electrode material. If the carbonate radical content in the nickel composite hydroxide is in the range of 1.0% to 2.5% by weight, it is contained in the nickel composite hydroxide when mixed with the lithium compound and fired. As the carbonate radicals volatilize, pores are formed in the particles and can be brought into appropriate contact with the molten lithium compound, and the crystal growth of the lithium nickel composite oxide proceeds appropriately. The carbonate group content can be determined, for example, by measuring the total carbon element content of the nickel composite hydroxide and converting the measured total carbon element amount into CO ₃ .

On the other hand, when the carbonate radical content is less than 1.0% by mass, the contact with the molten lithium compound becomes insufficient when mixed with the lithium compound and fired. Therefore, the crystallinity of the obtained lithium nickel composite oxide is lowered, and when a battery is constructed as the positive electrode material, there arises a problem that the capacity is reduced by inhibiting Li diffusion in the solid phase. When the carbonate group content exceeds 2.5% by mass, in the step of mixing with a lithium compound and baking to obtain a lithium nickel composite oxide, the generated carbon dioxide gas inhibits the reaction, and the lithium nickel composite oxide Crystallinity decreases.

[Particle size distribution]
The nickel composite hydroxide is preferably adjusted so that [(d90-d10) / average particle size], which is an index indicating the spread of the particle size distribution of the particles, is 0.55 or less.

When the particle size distribution is wide and [(d90−d10) / average particle size], which is an index indicating the spread of the particle size distribution, exceeds 0.55, the particle size is very small with respect to the average particle size. There are many fine particles and particles having a very large particle size (large particles) with respect to the average particle size. When a positive electrode is formed using a positive electrode active material in which a large amount of fine particles are present, heat may be generated due to a local reaction of the fine particles, safety is reduced, and fine particles having a large specific surface area are selectively used. Since it deteriorates, the cycle characteristics deteriorate, which is not preferable. On the other hand, when a positive electrode is formed using a positive electrode active material having a large number of large-diameter particles, the reaction area between the electrolytic solution and the positive electrode active material cannot be sufficiently obtained, and the battery output is decreased due to an increase in reaction resistance. Absent.

Therefore, if the particle size distribution of the positive electrode active material is adjusted so that the index [(d90-d10) / average particle size] indicating the spread of the particle size distribution of the particles is 0.55 or less, the fine particles and large particles Therefore, a battery using this positive electrode active material for the positive electrode is excellent in safety, and good cycle characteristics and battery output can be obtained.

In the index [(d90−d10) / average particle size] indicating the spread of the particle size distribution, d10 is the cumulative volume of all particles when the number of particles in each particle size is accumulated from the smallest particle size. It means the particle size which becomes 10% of the total volume. Further, d90 means a particle size in which the cumulative volume becomes 90% of the total volume of all particles when the number of particles in each particle size is accumulated from the smallest particle size.

The method for obtaining the average particle diameter and d90 and d10 is not particularly limited, but for example, it can be obtained from the volume integrated value measured with a laser light diffraction / scattering particle size analyzer.

[Specific surface area]
The nickel composite hydroxide is preferably adjusted to have a specific surface area of 15 m ² / g to 60 m ² / g. This is because when the specific surface area is in the range of 15 m ² / g to 60 m ² / g, a particle surface area that can contact the molten lithium compound can be sufficiently obtained when mixed with the lithium compound and fired. On the other hand, when the specific surface area is less than 15 m ² / g, the contact with the molten lithium compound is insufficient when mixed and fired with the lithium compound, the crystallinity of the resulting lithium nickel composite oxide is lowered, and the positive electrode material When the battery is configured, there is a problem that the capacity is reduced by inhibiting Li diffusion in the solid phase. When the specific surface area exceeds 60 m ² / g, when mixed with a lithium compound and baked, crystal growth proceeds too much, and cation mixing in which nickel is mixed into the lithium layer of the lithium transition metal composite oxide, which is a layered compound, occurs. This is not preferable because the charge / discharge capacity decreases.

<2. Method for producing nickel composite hydroxide>
The manufacturing method of nickel composite hydroxide manufactures the above-mentioned nickel composite hydroxide by crystallization reaction. The method for producing a nickel composite hydroxide has a pH value of 12.0 to 13.4 measured on a mixed aqueous solution containing nickel and cobalt, an aqueous solution containing an ammonium ion supplier and an aluminum source with a liquid temperature of 25 ° C. as a reference. A nucleation step for nucleation in a reaction solution (hereinafter also referred to as an aqueous solution for nucleation) obtained by adding an alkaline solution so as to become a reaction solution containing nuclei formed in the nucleation step (Hereinafter also referred to as an aqueous solution for particle growth) is a particle growth step of growing nuclei by adding an alkaline solution so that the pH value measured with a liquid temperature of 25 ° C. as a reference is 10.5 to 12.0. Have The alkali solution used is a mixed aqueous solution of alkali metal hydroxide and carbonate, and [CO ₃ ²⁻ ] / [OH ⁻ ] representing the mixing ratio of the alkali metal hydroxide and carbonate in the mixed aqueous solution is 0.002. It is 0.050 or less.

In the conventional continuous crystallization method, since the nucleation reaction and the particle growth reaction proceed simultaneously in the same reaction tank, the particle size distribution of the obtained nickel composite hydroxide becomes wide. On the other hand, in the method for producing a nickel composite hydroxide to which the present invention is applied, the time when the nucleation reaction mainly occurs (nucleation process) and the time when the particle growth reaction mainly occurs (particle growth process) are clearly defined. Even if both steps are carried out in the same reaction vessel, the separation is characterized in that a composite hydroxide having a narrow particle size distribution can be obtained.

Hereinafter, the characteristics of each process will be described in detail.
[Nucleation process]
In the nucleation step, an alkaline aqueous solution containing nickel and cobalt, an aqueous solution containing an ammonium ion supplier and an aluminum source is adjusted so that the pH value measured on the basis of a liquid temperature of 25 ° C. is 12.0 to 13.4. The solution is added, and the nickel composite hydroxide is nucleated in the resulting reaction solution (nucleation solution).

In the nucleation step, a sodium aluminate aqueous solution is preferably contained as an aluminum source. At that time, the molar ratio of sodium to aluminum (Na / Al) in the aqueous sodium aluminate solution is preferably 1.5 to 3.0. The ammonium concentration of the reaction solution is preferably adjusted within the range of 3 to 25 g / L.

In the nucleation step, a mixed aqueous solution containing nickel and cobalt, an ammonium ion supplier, and an aluminum source are placed in a reaction vessel, and an alkali solution is placed therein to adjust the pH, causing a crystallization reaction to produce nuclei. To do. In the nucleation step, the order in which the mixed aqueous solution, the ammonium ion supplier, the aluminum source, and the alkaline solution are put into the reaction tank is not particularly limited, and nucleation may be performed by putting them together.

In the nucleation step, the pH value of the reaction aqueous solution and the concentration of ammonium ions change with the nucleation. Therefore, the alkaline aqueous solution and the aqueous ammonia solution are supplied to the reaction aqueous solution together with the nickel cobalt mixed aqueous solution, and the pH of the reaction aqueous solution The alkali solution and the ammonium ion supplier are appropriately added to the reaction vessel and controlled so that the value and the ammonium concentration are maintained at predetermined values.

In the nucleation step, when a mixed aqueous solution containing nickel and cobalt, an aqueous alkaline solution, an ammonium ion supplier and an aluminum source are continuously supplied to the reaction aqueous solution, new nuclei are continuously generated in the reaction aqueous solution. Will continue. In the nucleation step, when a predetermined amount of nuclei is generated in the reaction solution, the nucleation reaction is terminated. In the nucleation step, whether or not a predetermined amount of nuclei has been generated in the reaction solution can be determined by the amount of metal salt added to the reaction solution.

[Particle growth process]
In the particle growth step, the pH value of the reaction solution (particle growth aqueous solution) containing nuclei formed in the nucleation step is 10.5 to 12.2. The particle growth reaction is carried out by adjusting to be in the range of 0 to obtain nickel composite hydroxide particles. More specifically, the pH value of the reaction aqueous solution is controlled by adding an inorganic acid of the same type as the acid constituting the metal compound, for example, sulfuric acid or the like, or adjusting the supply amount of the alkaline aqueous solution.

In the particle growth step, when the pH value of the aqueous solution for particle growth becomes 12.0 or less, nuclei in the aqueous solution for particle growth grow to form a nickel composite hydroxide having a predetermined particle diameter. In the particle growth process, the pH value of the aqueous solution for particle growth is in the range of 10.5 to 12.0, and the nucleus growth reaction takes precedence over the nucleus generation reaction. Nuclei are hardly generated.

In the particle growth step, when a predetermined amount of nickel composite hydroxide having a predetermined particle size is generated in the aqueous solution for particle growth, the particle growth reaction is terminated. In the particle growth step, the amount of nickel composite hydroxide having a predetermined particle size is determined by the amount of metal salt added to the reaction aqueous solution.

The materials and conditions used in the nucleation process and the particle growth process are described below.

(Mixed aqueous solution containing nickel and cobalt)
The salt such as nickel salt and cobalt salt used in the mixed aqueous solution containing nickel and cobalt is not particularly limited as long as it is a water-soluble compound, but sulfate, nitrate, chloride, etc. may be used. it can. For example, nickel sulfate and cobalt sulfate are preferable.

The concentration of the mixed aqueous solution is preferably 1 mol / L to 2.6 mol / L, more preferably 1 mol / L to 2.2 mol / L in total of the metal salts. If the concentration is less than 1 mol / L, the resulting hydroxide slurry concentration is low and the productivity is poor. On the other hand, if it exceeds 2.6 mol / L, crystal precipitation and freezing occur at −5 ° C. or less, which may clog the piping of the equipment, and it is necessary to keep the piping warm or warm, which is expensive.

Further, the amount of the mixed aqueous solution supplied to the reaction tank is such that the concentration of the crystallized product at the time when the crystallization reaction is completed is approximately 30 g / L to 250 g / L, preferably 80 g / L to 150 g / L. It is preferable to do. When the crystallized substance concentration is less than 30 g / L, aggregation of primary particles may be insufficient, and when it exceeds 250 g / L, diffusion of the mixed aqueous solution to be added in the reaction vessel is sufficient. This is because the grain growth may be biased.

(Ammonia ion supplier)
The ammonium ion supplier is not particularly limited as long as it is a water-soluble compound, but ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, and the like can be used. For example, ammonia and ammonium sulfate are preferably used. It is done.

The ammonium ion supplier is such that the ammonia concentration in the reaction solution is preferably 3 g / L to 25 g / L, more preferably 5 g / L to 20 g / L, and even more preferably 5 g / L to 15 g / L. To supply. Due to the presence of ammonium ions in the reaction solution, metal ions, particularly Ni ions, form ammine complexes, the solubility of the metal ions increases, the growth of primary particles is promoted, and the dense nickel composite hydroxide particles are formed. It is easy to obtain. Furthermore, since the solubility of metal ions is stable, nickel composite hydroxide particles having a uniform shape and particle size are easily obtained. In particular, by setting the ammonia concentration in the reaction solution to 3 g / L to 25 g / L, it is easy to obtain nickel composite hydroxide particles having a more precise shape and particle size.

If the ammonia concentration in the reaction solution is less than 3 g / L, the solubility of metal ions may become unstable, primary particles having a uniform shape and particle size are not formed, and gel-like nuclei are formed. The particle size distribution may be broadened. On the other hand, when the ammonia concentration exceeds 25 g / L, the solubility of metal ions becomes too high, the amount of metal ions remaining in the reaction aqueous solution increases, and the composition may shift. The concentration of ammonium ions can be measured with a general ion meter.

(Alkaline solution)
The alkaline solution is a mixed aqueous solution of alkali metal hydroxide and carbonate. The ratio of carbonate to alkali metal hydroxide ([CO ₃ ²⁻ ] / [OH ⁻ ]) representing the mixing ratio of alkali metal hydroxide and carbonate is 0.002 or more and 0.050 or less, 0 0.005 or more and 0.030 or less is preferable, and 0.010 or more and 0.025 or less is more preferable.

By making the alkaline solution a mixed aqueous solution of alkali metal hydroxide and carbonate, anions such as sulfate radicals and chlorine remaining as impurities in the nickel composite hydroxide obtained in the crystallization step are converted to carbonate radicals and ions. Can be exchanged. The carbonate radical is volatilized in the step of mixing and firing the nickel composite hydroxide and the lithium compound, and therefore does not remain in the lithium nickel composite oxide as the positive electrode material. Therefore, by exchanging sulfate radicals and chlorine with carbonate radicals, it is possible to reduce the number of impurities such as sulfate radicals and chlorine remaining in the nickel composite acid.

When the ratio of carbonate to alkali metal hydroxide ([CO ₃ ²⁻ ] / [OH ⁻ ]) is less than 0.002, in the crystallization process, sulfate radicals or chlorine and carbonate ions, which are impurities derived from the raw material, are used. Substitution becomes insufficient, and these impurities are easily incorporated into the nickel composite hydroxide. On the other hand, even if [CO ₃ ²⁻ ] / [OH ⁻ ] exceeds 0.050, the reduction of sulfate radicals and chlorine, which are impurities derived from the raw materials, remains the same, and the excessively added carbonate increases the cost. .

The alkali metal hydroxide is preferably at least one selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide, and a compound that is easily dissolved in water is preferable because the amount added can be easily controlled.

The carbonate is preferably at least one selected from sodium carbonate, potassium carbonate, and ammonium carbonate, and a compound that is easily soluble in water is preferable because the amount added can be easily controlled.

Further, the method for adding the alkaline solution to the reaction vessel is not particularly limited, and the pH value of the reaction solution is maintained within a predetermined range described later with a pump capable of flow rate control such as a metering pump. , May be added.

(Aluminum source)
The aluminum source used in the crystallization step is preferably an aqueous sodium aluminate solution. When other compounds such as aluminum sulfate are used, aluminum hydroxide precipitates at a lower pH than nickel hydroxide or cobalt hydroxide, so that aluminum hydroxide is likely to precipitate alone and has a narrow particle size distribution. Nickel composite hydroxide cannot be obtained.

The sodium aluminate aqueous solution can be obtained, for example, by dissolving a predetermined amount of sodium aluminate in water to form an aqueous solution and adding a predetermined amount of sodium hydroxide. At this time, the sodium in the sodium aluminate aqueous solution is more preferably in a molar ratio of 1.5 to 3.0 with respect to aluminum. When the amount of sodium, that is, the amount of sodium hydroxide is out of the range of 1.5 to 3.0 in terms of molar ratio, the stability of the aqueous sodium aluminate solution decreases, and immediately after being added to the reaction vessel or before being added. It is easy to precipitate as aluminum hydroxide fine particles, and the coprecipitation reaction with nickel hydroxide and cobalt hydroxide does not occur easily, and particles with a wide particle size distribution are generated, and the aluminum concentration inside the particles is not distributed. This is not preferable because a problem of uniformity occurs.

In order to uniformly disperse aluminum inside the nickel composite hydroxide particles, a mixed aqueous solution containing nickel and cobalt and a sodium aluminate aqueous solution may be simultaneously added to the reaction vessel. At this time, as shown in the general formula, the metal concentrations of nickel, cobalt, and aluminum and the addition flow rates of the mixed aqueous solution and the sodium aluminate aqueous solution are adjusted so as to meet the target composition ratio.

(PH control)
In the crystallization step, the pH value measured on the basis of 25 ° C. is 12.0 to 13.4 in an aqueous solution containing nickel and cobalt, an ammonium ion supplier, and an aluminum source. A nucleation step in which an alkali solution is added to perform nucleation, and a reaction solution (particle growth aqueous solution) containing nuclei formed in the nucleation step has a pH value of 10 measured based on a liquid temperature of 25 ° C. More preferably, it comprises a particle growth step in which an alkali solution is added so as to be 5 to 12.0 and controlled to grow nuclei. That is, the nucleation reaction and the particle growth reaction do not proceed at the same time in the same tank, but mainly the time when the nucleation reaction (nucleation process) occurs and the time when the particle growth reaction (particle growth process) occurs mainly. It is characterized by clearly separating.

In the nucleation step, the pH value of the reaction aqueous solution is controlled so as to be in the range of 12.0 to 13.4, preferably 12.3 to 13.0 based on the liquid temperature of 25 ° C. When pH value exceeds 13.4, the produced | generated nucleus becomes too fine and there exists a problem which reaction aqueous solution gelatinizes. On the other hand, when the pH value is less than 12.0, a nucleus growth reaction occurs together with nucleation, so that the range of the particle size distribution of the nuclei formed becomes wide and non-uniform. That is, in the nucleation step, by controlling the pH value of the reaction aqueous solution to 12.0 to 13.4, it is possible to suppress the growth of the nuclei and cause only the nucleation, and the formed nuclei are homogeneous and The range of the particle size distribution can be narrow.

On the other hand, in the particle growth step, it is necessary to control the pH value of the aqueous reaction solution to be in the range of 10.5 to 12.0, preferably 11.0 to 12.0 on the basis of the liquid temperature of 25 ° C. When the pH value exceeds 12.0, the number of newly generated nuclei increases and fine secondary particles are generated, so that a nickel composite hydroxide having a good particle size distribution cannot be obtained. On the other hand, when the pH value is less than 10.5, the solubility by ammonium ions is high, and the metal ions remaining in the liquid without being precipitated increase, so that the production efficiency is deteriorated. In other words, by controlling the pH value of the reaction aqueous solution to 10.5 to 12.0 in the particle growth process, only the growth of nuclei generated in the nucleation process is preferentially caused and new nucleation is suppressed. And the resulting nickel composite hydroxide can be homogeneous and have a narrow particle size distribution range.

When the pH value is 12, it is a boundary condition between nucleation and particle growth, and therefore, it can be set as either a nucleation step or a particle growth step depending on the presence or absence of nuclei present in the reaction aqueous solution. . That is, if the pH value in the nucleation step is higher than 12 and a large amount of nuclei are produced, and if the pH value is set to 12 in the particle growth step, a large amount of nuclei are present in the reaction aqueous solution, so the growth of nuclei takes priority. As a result, nickel hydroxide having a narrow particle size distribution and a relatively large particle size can be obtained.

On the other hand, in a state where no nuclei exist in the reaction solution, that is, when the pH value is set to 12 in the nucleation step, since no nuclei grow, nucleation occurs preferentially, and the pH value of the particle growth step is set to 12. By making it smaller, the produced | generated nucleus grows and a favorable nickel composite hydroxide is obtained.

In any case, the pH value of the particle growth process may be controlled to a value lower than the pH value of the nucleation process. To clearly separate nucleation and particle growth, the pH value of the particle growth process is It is preferably 0.5 or more lower than the pH value of the production step, more preferably 1.0 or more.

As described above, the nucleation process and the particle growth process are clearly separated according to the pH value, so that the nucleation process takes precedence in the nucleation process and almost no nucleus growth occurs. Only new nuclei are produced and almost no new nuclei are generated. For this reason, in the nucleation step, homogeneous nuclei with a narrow particle size distribution range can be formed, and in the particle growth step, nuclei can be grown homogeneously. Therefore, in the method for producing nickel composite hydroxide, uniform nickel composite hydroxide particles having a narrow particle size distribution range can be obtained.

(Reaction temperature)
In the reaction vessel, the temperature of the reaction solution (particle growth aqueous solution) is preferably set to 20 to 80 ° C., more preferably 30 to 70 ° C., and further preferably 35 to 60 ° C. When the temperature of the reaction solution is lower than 20 ° C., the solubility of metal ions is low, so that nucleation is likely to occur and control becomes difficult. On the other hand, when the temperature exceeds 80 ° C., volatilization of ammonia is promoted, so that an excess ammonium ion supplier must be added to maintain a predetermined ammonia concentration, resulting in high cost.

(Reaction atmosphere)
The particle size and particle structure of the nickel composite hydroxide are also controlled by the reaction atmosphere in the crystallization process.

When the atmosphere in the reaction vessel during the crystallization process is controlled to a non-oxidizing atmosphere, the growth of primary particles forming the nickel composite hydroxide is promoted, the primary particles are large and dense, and the particle size is appropriately large. Secondary particles are formed. In particular, in the crystallization step, relatively large primary particles can be obtained by setting a non-oxidizing atmosphere having an oxygen concentration of 5.0% by volume or less, preferably 2.5% by volume or less, more preferably 1.0% by volume or less. As a result, the growth of particles is promoted by the aggregation of the primary particles, and secondary particles having an appropriate size can be obtained.

As a means for maintaining the space in the reaction tank in such an atmosphere, it is possible to circulate an inert gas such as nitrogen to the space in the reaction tank, and further to bubble the inert gas in the reaction solution. can give.

In the method for producing a nickel composite hydroxide as described above, when an alkaline solution is added to an aqueous solution containing a mixed aqueous solution containing nickel and cobalt, an ammonium ion supplier, and an aluminum source, the alkali metal in the alkaline solution is added. The ratio of carbonate to hydroxide ([CO ₃ ²⁻ ] / [OH ⁻ ]) is 0.002 or more and 0.050 or less, so that the carbonate radical and the sulfate radical or chlorine of the impurity are ion-exchanged. To reduce residual sulfate radicals and chlorine. Thereby, the sulfate radical content in the obtained nickel composite hydroxide becomes 1.0 mass% or less, and the chlorine content becomes 0.5 mass% or less. Therefore, the positive electrode active material using this nickel composite hydroxide as a precursor has high crystallinity, can increase the battery capacity, and can provide a non-aqueous electrolyte secondary battery having high safety. Further, this nickel composite hydroxide production method can easily produce a nickel composite hydroxide, has high productivity, and has extremely high industrial value.

[3. Cathode active material for non-aqueous electrolyte secondary battery]
A positive electrode active material for a non-aqueous electrolyte secondary battery can be obtained using the nickel composite hydroxide described above as a precursor. The positive electrode active material is made of a lithium-nickel composite oxide composed of a hexagonal lithium-containing composite oxide having a layered structure using nickel composite hydroxide as a raw material. Since the lithium nickel composite oxide has a predetermined composition and average particle size and is adjusted to a predetermined particle size distribution, it has excellent cycle characteristics and safety, small particle size, high particle size uniformity, It is suitable as a material for the positive electrode of an aqueous electrolyte secondary battery.

[composition]
The positive electrode active material is composed of a lithium nickel cobalt aluminum composite oxide, and the composition thereof is represented by a general formula: Li _t Ni _1-xy Co _x Al _y O ₂ (where 0.97 ≦ t ≦ 1 .20, 0.05 ≦ x ≦ 0.35, 0.01 ≦ y ≦ 0.2, and x + y <0.4.

In the positive electrode active material, the atomic ratio t of lithium is preferably in the above range (0.97 ≦ t ≦ 1.20). When the atomic ratio t of lithium is less than 0.97, the reaction resistance of the positive electrode in the nonaqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the battery output decreases. On the other hand, when the atomic ratio t of lithium is larger than 1.20, the initial discharge capacity of the positive electrode active material is lowered and the reaction resistance of the positive electrode is also increased. Accordingly, the atomic ratio t of lithium is preferably 0.97 ≦ t ≦ 1.20, and more preferably, the atomic ratio t of lithium is 1.05 or more.

Favorable cycle characteristics can be obtained by including cobalt in the positive electrode active material. This is because by replacing a part of nickel in the crystal lattice with cobalt, the expansion and contraction behavior of the crystal lattice due to lithium desorption due to charge / discharge can be reduced. Further, the atomic ratio of cobalt is preferably 0.05 ≦ x ≦ 0.35, and more preferably 0.07 ≦ x ≦ 0.25, and 0.10 ≦ x ≦ 0. More preferably, it is 20.

In the positive electrode active material, the atomic ratio y of aluminum to the atoms of all metals other than lithium is preferably adjusted so that 0.01 ≦ y ≦ 0.2, and 0.01 ≦ y ≦ 0.1. It is more preferable to adjust so that it becomes. The reason is that by adding aluminum in the positive electrode active material, the durability and safety of the battery can be improved when used as the positive electrode active material of the battery. In particular, in the case of the positive electrode active material, if the aluminum is adjusted so as to be uniformly distributed inside the particle, the effect of improving the durability and safety of the battery can be obtained throughout the particle, and the same addition amount is obtained. However, there is an advantage that a greater effect can be obtained and a decrease in capacity can be suppressed.

On the other hand, in the positive electrode active material, when the atomic ratio y of aluminum to the atoms of all metals other than lithium is less than 0.01, cycle characteristics and safety are insufficient, which is not preferable. In addition, when the atomic ratio y of aluminum to atoms of all metals other than lithium in the positive electrode active material exceeds 0.2, the metal element contributing to the Redox reaction is decreased, and the battery capacity is decreased, which is not preferable.

The positive electrode active material has inherited the properties of the above-mentioned nickel composite hydroxide as a precursor, the sulfate radical content is 1.0 mass% or less, preferably 0.6 mass% or less, and the chlorine content. Is 0.5 mass% or less, preferably 0.3 mass% or less, and the carbonate radical content is 1.0 mass% to 2.5 mass%.

Also, the average particle diameter of the positive electrode active material is 3 μm to 25 μm, the battery capacity per volume can be increased, the safety is high, and the cycle characteristics are also good.

The index indicating the spread of the particle size distribution of the positive electrode active material [(D90-D10) / average particle size] is 0.55 or less, and the proportion of particles and large particles is small. The battery used in the above has excellent safety and can obtain good cycle characteristics and battery output.

The method for producing the positive electrode active material is not particularly limited as long as it can be produced from the nickel composite hydroxide described above. However, if the following method for producing the positive electrode active material is employed, the positive electrode active material is more reliably produced. This is preferable because it is possible.

The manufacturing method of the positive electrode active material is such that a nickel compound hydroxide as a raw material of the positive electrode active material is heat-treated and a lithium compound is mixed with the nickel composite hydroxide particles after the heat treatment step to remove moisture. Then, a mixing step for forming a mixture is performed, and a baking step for baking the mixture formed in the mixing step is performed. And in the manufacturing method of a positive electrode active material, a lithium nickel composite oxide, ie, a positive electrode active material, can be obtained by crushing the baked fired material.

In the heat treatment step, it may be heated to a temperature at which the residual moisture of the nickel composite hydroxide is removed, and the heat treatment temperature is not particularly limited, but is preferably 300 ° C to 800 ° C. When the heat treatment temperature is less than 300 ° C., the decomposition of the nickel composite hydroxide does not proceed sufficiently and the significance of performing the heat treatment step is diminished, which is not industrially appropriate. On the other hand, when the heat treatment temperature exceeds 800 ° C., the particles converted into the nickel composite oxide may sinter and aggregate.

In the heat treatment step, the atmosphere in which the heat treatment is performed is not particularly limited, and is preferably performed in an air stream that can be easily performed.

In the mixing step, the lithium-containing material to be mixed with the nickel composite hydroxide particles after the heat treatment is not particularly limited. For example, lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof is available. It is preferable in that it is easy. In particular, in view of ease of handling and quality stability, it is more preferable to use lithium hydroxide in the mixing step.

In the mixing step, a general mixer can be used for the mixing process, and for example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used. When these mixers are used, it is sufficient that the heat-treated particles and the lithium-containing material are sufficiently mixed to such an extent that a complex such as a composite hydroxide is not destroyed.

In the firing step, the lithium mixture is fired at 700 ° C. to 850 ° C., particularly preferably at 720 ° C. to 820 ° C. When the firing temperature of the lithium mixture is less than 700 ° C., the diffusion of lithium into the heat treated particles is not sufficiently performed, surplus lithium and unreacted particles remain, or the crystal structure is not sufficiently arranged, There arises a problem that sufficient battery characteristics cannot be obtained.

In the firing step, the firing time of the lithium mixture is preferably at least 3 hours or more, and more preferably 6 to 24 hours. This is because when the firing time of the lithium mixture is less than 3 hours, the lithium nickel composite oxide may not be sufficiently generated.

In the firing step, the atmosphere at the time of firing the lithium mixture is preferably an oxidizing atmosphere, and more preferably an atmosphere having an oxygen concentration of 18 volume% to 100 volume%.

In the method for producing a positive electrode active material as described above, since the above-described raw material uses the above-described impurity sulfate radical and nickel composite hydroxide having a low chlorine content, when mixed with a lithium compound and fired, lithium Is not inhibited, and a decrease in crystallinity of the lithium nickel composite oxide can be suppressed. Thereby, the positive electrode active material obtained by this positive electrode active material production method has few impurities remaining inside and high crystallinity, so the capacity per unit weight and volume as a whole battery does not decrease, A positive electrode of a non-aqueous electrolyte secondary battery having a higher capacity than before can be obtained.

<5. Non-aqueous electrolyte secondary battery>
The positive electrode active material described above is preferably used as a positive electrode active material for a non-aqueous electrolyte secondary battery. Hereinafter, the embodiment at the time of using for nonaqueous electrolyte secondary batteries is illustrated.

The nonaqueous electrolyte secondary battery employs a positive electrode using the positive electrode active material described above. Since the nonaqueous electrolyte secondary battery has substantially the same structure as a general nonaqueous electrolyte secondary battery except that the positive electrode active material described above is used as the positive electrode material, it will be briefly described.

The non-aqueous electrolyte secondary battery has a structure including a case, a positive electrode, a negative electrode, a non-aqueous electrolyte solution, and a separator housed in the case.

The positive electrode is a sheet-like member. For example, a positive electrode mixture paste obtained by mixing a positive electrode active material, a conductive material, and a binder is applied to the surface of an aluminum foil current collector and dried. Can be formed.

The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste containing a negative electrode active material to the surface of a metal foil current collector such as copper and drying it.

As the separator, for example, a thin film such as polyethylene or polypropylene and a film having many fine pores can be used. In addition, if it has a function of a separator, it will not specifically limit.

The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. As the organic solvent, ethylene carbonate, propylene carbonate, or the like can be used. As the electrolyte salt, LiPF ₆ , LiBF ₄ , LiClO ₄ or the like can be used.

Since the non-aqueous electrolyte secondary battery having the above-described configuration has a positive electrode using the positive electrode active material having the nickel composite hydroxide as a precursor, the capacity per unit weight and volume as a whole battery. Has a high capacity, a small irreversible capacity, and a high safety.

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 addition, an Example and a comparative example were evaluated by the measurement result using the following apparatuses and methods.

The nickel composite hydroxides obtained by the crystallization steps described in Examples 1 to 15 and Comparative Examples 1 to 3 were washed, solid-liquid separated, dried and collected as a powder, and then various analyzes were performed by the following methods. .

The composition of the nickel composite hydroxide was measured with a high frequency inductively coupled plasma (ICP) emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation) after dissolving the sample in nitric acid.

The sulfate radical content was determined by dissolving the sample with nitric acid and then measuring the elemental sulfur with an ICP emission spectrophotometer (ICPS-8100, manufactured by Shimadzu Corporation) and converting the measured amount of elemental sulfur to SO ₄ . Was determined by

The chlorine content was measured with an automatic titration apparatus (Hiranuma Sangyo Co., Ltd., COM-1600).

The carbonate radical content was determined by measuring the total carbon element content with a carbon sulfur analyzer (CS-600 manufactured by LECO) and converting the measured total carbon element amount into CO ₃ .

The specific surface area was measured by a BET method using a specific surface area measuring device (manufactured by Yuasa Ionics Co., Ltd., Kantasorb QS-10).

The lithium nickel composite oxide was prepared and evaluated by the following method. The nickel composite hydroxide particles produced in the examples and comparative examples were heat-treated at 700 ° C. for 6 hours in an air (oxygen: 21 vol%) air stream to recover the nickel composite oxide particles. Subsequently, lithium hydroxide was weighed so that Li / Me = 1.025 and mixed with the recovered nickel composite oxide particles to form a mixture. Mixing was performed using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)).

Next, the obtained mixture was calcined at 500 ° C. for 4 hours in an oxygen stream (oxygen: 100% by volume), then calcined at 730 ° C. for 24 hours, cooled and then crushed to obtain lithium nickel composite oxide. I got a thing.

The sulfate group content of the obtained lithium nickel composite oxide was determined by measuring the elemental sulfur using an ICP emission spectroscopic analyzer (ICPS-8100, manufactured by Shimadzu Corporation) after dissolving the sample in nitric acid. the amount of the element was determined by converting the SO _4.

The Li-occupancy ratio indicating the crystallinity of the lithium-nickel composite oxide was calculated by performing a Rietveld analysis from a diffraction pattern obtained using an X-ray diffractometer (manufactured by Panalical, X'Pert PRO).

In Examples and Comparative Examples, a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. was used for each sample for the production of nickel composite hydroxide.

(Example 1)
The nickel composite hydroxide was produced as follows using the method of the present invention.

First, 0.9 L of water was placed in the reaction vessel (5 L) and the temperature inside the vessel was set to 50 ° C. while stirring, and nitrogen gas was passed through the reaction vessel to form a nitrogen atmosphere. At this time, the oxygen concentration in the reaction vessel space was 2.0%.

Appropriate amounts of 25% aqueous sodium hydroxide and 25% aqueous ammonia are added to the water in the reaction tank, and the pH of the reaction solution in the tank is 12.8 as a pH value measured with a liquid temperature of 25 ° C. as a reference. It was adjusted. Further, the ammonia concentration in the reaction solution was adjusted to 10 g / L.

Next, nickel sulfate and cobalt chloride were dissolved in water to form a 2.0 mol / L mixed aqueous solution. In this mixed aqueous solution, the element molar ratio of each metal was adjusted to be Ni: Co = 0.84: 0.16. Separately, a predetermined amount of sodium aluminate was dissolved in water, and a 25% aqueous sodium hydroxide solution was added so that the ratio of sodium to aluminum was 1.7. Further, an alkali solution was prepared by dissolving sodium hydroxide and sodium carbonate in water such that [CO ₃ ²⁻ ] / [OH ⁻ ] was 0.025.

The mixed aqueous solution was added to the reaction solution in the reaction vessel at 12.9 ml / min. At the same time, a sodium aluminate aqueous solution, 25% aqueous ammonia, and an alkaline solution were also added to the reaction solution in the reaction tank at a constant rate, and the pH value was set to 12. with the ammonia concentration in the reaction solution maintained at 10 g / L. While controlling at 8 (nucleation pH value), crystallization was carried out for 2 minutes and 30 seconds to perform nucleation. The addition rate of the sodium aluminate aqueous solution was adjusted so that the molar ratio of metal elements in the slurry was Ni: Co: Al = 81: 16: 3.

Thereafter, 64% sulfuric acid was added until the pH value of the reaction solution reached 11.6 (particle growth pH value) as a pH value measured with a liquid temperature of 25 ° C. as a reference. After the pH value of the reaction solution reached 11.6, the supply of the mixed aqueous solution, aqueous sodium aluminate solution, 25% aqueous ammonia and alkaline solution was resumed as the pH value measured with the liquid temperature of 25 ° C. as the reference value. The nickel composite hydroxide was obtained by continuing the crystallization for 4 hours and controlling the particle growth while controlling the value at 11.6.

(Example 2)
In Example 2, a nickel composite hydroxide is obtained in the same manner as in Example 1 except that when adjusting the alkali solution, [CO ₃ ²⁻ ] / [OH ⁻ ] is 0.003. And evaluated.

(Example 3)
In Example 3, a nickel composite hydroxide is obtained in the same manner as in Example 1, except that when adjusting the alkaline solution, [CO ₃ ²⁻ ] / [OH ⁻ ] is 0.040. And evaluated.

Example 4
In Example 4, when sodium aluminate was dissolved in a predetermined amount of water, the same procedure as in Example 1 was performed except that a 25% sodium hydroxide aqueous solution had a ratio of sodium to aluminum of 1.0. Nickel composite hydroxide was obtained and evaluated.

(Example 5)
In Example 5, when dissolving a predetermined amount of sodium aluminate in water, nickel was added in the same manner as in Example 1 except that a 25% sodium hydroxide aqueous solution had a ratio of sodium to aluminum of 3.5. A composite hydroxide was obtained and evaluated.

(Example 6)
In Example 6, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH of the nucleation step was 13.6.

(Example 7)
In Example 7, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH of the nucleation step was 11.8.

(Example 8)
In Example 8, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH of the particle growth step was 12.3.

Example 9
In Example 9, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the pH of the particle growth step was 10.2.

(Example 10)
In Example 10, the addition rate of the sodium aluminate aqueous solution was the same as in Example 1 except that the molar ratio of metal elements in the slurry was adjusted to be Ni: Co: Al = 78: 15: 7. Nickel composite hydroxide was obtained and evaluated.

(Example 11)
In Example 11, the addition rate of the aqueous sodium aluminate solution was adjusted in the same manner as in Example 1 except that the molar ratio of metal elements in the slurry was adjusted to be Ni: Co: Al = 74: 14: 12. Nickel composite hydroxide was obtained and evaluated.

Example 12
In Example 12, the addition rate of the sodium aluminate aqueous solution was adjusted in the same manner as in Example 1 except that the molar ratio of metal elements in the slurry was adjusted to be Ni: Co: Al = 69: 13: 18. Nickel composite hydroxide was obtained and evaluated.

(Example 13)
In Example 13, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the alkali metal hydroxide in preparing the alkaline solution was potassium hydroxide and the carbonate was potassium carbonate. .

(Example 14)
In Example 14, nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that sodium carbonate was changed to ammonium carbonate and the ammonia concentration was adjusted to 20 g / L.

(Example 15)
In Example 15, a nickel composite hydroxide was obtained and evaluated in the same manner as in Example 1 except that the bath temperature was set to 35 ° C.

(Comparative Example 1)
In Comparative Example 1, a nickel composite hydroxide was obtained in the same manner as in Example 1 except that the alkali solution was only sodium hydroxide and [CO ₃ ²⁻ ] / [OH ⁻ ] was 0. evaluated.

(Comparative Example 2)
In Comparative Example 2, a nickel composite hydroxide is obtained in the same manner as in Example 1 except that when adjusting the alkaline solution, [CO ₃ ²⁻ ] / [OH ⁻ ] is 0.001. And evaluated.

(Comparative Example 3)
In Comparative Example 3, a nickel composite hydroxide is obtained in the same manner as in Example 1 except that when adjusting the alkaline solution, [CO ₃ ²⁻ ] / [OH ⁻ ] is 0.055. And evaluated.

(Evaluation)
Table 1 shows the production conditions of the nickel composite hydroxides of Examples 1 to 15 and Comparative Examples 1 to 3. Furthermore, the evaluation result of the obtained nickel composite hydroxide is shown in Table 2, and the evaluation result of the lithium nickel composite oxide is shown in Table 3.

As shown in Table 2, in Examples 1 to 15, the obtained nickel composite hydroxide had an average particle size of 3 to 20 μm or less, a sulfate radical content of 1.0 mass% or less, and a chlorine content. The amount is 0.5% by mass or less, and the carbonate content is 1.0% by mass to 2.5% by mass. As shown in Table 3, in Examples 1 to 15, the lithium site occupancy ratio indicating the crystallinity in the case of the lithium nickel composite oxide exceeds 99.0%, and the lithium nickel excellent in crystallinity It turns out that complex oxide is obtained and it is useful as a positive electrode active material.

On the other hand, in Comparative Examples 1 and 2, as shown in Tables 1 and 2, [CO ₃ ²⁻ ] / [OH ⁻ ] representing the mixing ratio of the alkali metal hydroxide and carbonate in the alkaline solution was 0.002 Therefore, the sulfate radical and chlorine content became high. And as shown in Table 3, the Li seat occupation rate which shows crystallinity at the time of setting it as lithium nickel composite oxide is less than 99.0%, and is inferior compared with Example 1 which has the same composition ratio etc. It was.

In Comparative Example 3, [CO ₃ ²⁻ ] / [OH ⁻ ] representing the mixing ratio of the alkali metal hydroxide and carbonate in the alkaline solution exceeds 0.050, so that the carbonate group content is high and the lithium nickel composite The Li seat occupancy ratio indicating the crystallinity in the case of an oxide was lower than 99.0%, which was inferior to that of Example 1 having the same composition ratio.

Among the examples, Na / Al in sodium aluminate is in the range of 1.5 to 3.0, the pH of the nucleation step is in the range of 12.0 to 13.4, and the pH of the particle growth step is Examples 1 to 3 and 10 to 15 in the range of 10.5 to 12.0 have a narrower particle size distribution and appropriate specific surface area than Examples 4 to 9 which do not satisfy any of these. became.

From the above results, if nickel composite hydroxide particles are produced using the method for producing nickel composite hydroxide to which the present invention is applied, a lithium nickel composite oxide with high crystallinity is obtained, and a high capacity non-capacitance is obtained. It turns out that it is useful as a positive electrode material of an aqueous electrolyte secondary battery.

The nickel composite hydroxide of the present invention can be used not only for electric vehicles driven purely by electric energy but also as a precursor for battery materials for so-called hybrid vehicles used in combination with combustion engines such as gasoline engines and diesel engines. it can. The power source for the electric vehicle includes not only a purely electric vehicle driven by electric energy but also a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. A non-aqueous electrolyte secondary battery including a positive electrode active material obtained using a product as a precursor can be suitably used as a power source for these hybrid vehicles.

Claims (10)

1. Formula _{Ni 1-x-y Co x} Al y (OH) 2 + α (0.05 ≦ x ≦ 0.35,0.01 ≦ y ≦ 0.2, x + y <0.4,0 ≦ α ≦ 0.5 )
   Spherical secondary particles formed by agglomerating a plurality of plate-like primary particles, and the secondary particles have an average particle size of 3 μm to 20 μm and a sulfate group content of 1.0 mass% or less, A nickel composite hydroxide characterized by having a chlorine content of 0.5% by mass or less and a carbonate radical content of 1.0% by mass to 2.5% by mass.
2. 2. The nickel composite hydroxide according to claim 1, wherein [(d90−d10) / average particle diameter], which is an index indicating the spread of the particle size distribution of the nickel composite hydroxide, is 0.55 or less. .
3. 3. The nickel composite hydroxide according to claim 1, wherein the specific surface area is 15 m ² / g to 60 m ² / g.
4. A method for producing a nickel composite hydroxide by producing a nickel composite hydroxide by a crystallization reaction,
   A crystallization step of crystallization in a reaction solution obtained by adding an alkaline solution to an aqueous solution containing a mixed aqueous solution containing nickel and cobalt, an ammonium ion supplier, and an aluminum source;
   The alkali solution is a mixed aqueous solution of an alkali metal hydroxide and a carbonate, and a ratio [CO ₃ ²⁻ ] / [OH ⁻ ] of the carbonate to the alkali metal hydroxide in the mixed aqueous solution is 0.002. The manufacturing method of the nickel composite hydroxide characterized by being above 0.050 or less.
5. In the crystallization step, a sodium aluminate aqueous solution is used as the aluminum source,
   The method for producing a nickel composite hydroxide according to claim 4, wherein a molar ratio of sodium to aluminum (Na / Al) in the aqueous sodium aluminate solution is 1.5 to 3.0.
6. The crystallization step includes a nucleation step and a particle growth step,
   In the nucleation step, an alkali solution is added to the aqueous solution so that the pH value measured with a liquid temperature of 25 ° C. as a reference is 12.0 to 13.4, and nucleation is performed in the reaction solution,
   In the particle growth step, an alkaline solution is added so that the reaction solution containing the nuclei formed in the nucleation step has a pH value of 10.5 to 12.0 measured based on a liquid temperature of 25 ° C. The method for producing a nickel composite hydroxide according to claim 4 or 5, wherein:
7. The nickel composite water according to any one of claims 4 to 6, wherein the alkali metal hydroxide is at least one selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide. Production method of oxide.
8. The method for producing a nickel composite hydroxide according to any one of claims 4 to 7, wherein the carbonate is one or more selected from sodium carbonate, potassium carbonate, and ammonium carbonate.
9. The nickel composite hydroxide according to any one of claims 4 to 8, wherein in the crystallization step, the ammonia concentration of the reaction solution is maintained within a range of 3 g / L to 25 g / L. Manufacturing method.
10. The method for producing a nickel composite hydroxide according to any one of claims 4 to 9, wherein in the crystallization step, a reaction temperature is maintained within a range of 20 ° C to 80 ° C.