JP7371354B2 - Method for producing nickel composite hydroxide - Google Patents

Description

The present invention relates to a method for producing nickel composite hydroxide.

In recent years, with the spread of portable electronic devices such as mobile phones and notebook personal computers, there has been a demand for the development of small and lightweight secondary batteries with high energy density. There is also a demand for the development of high-output secondary batteries for use in electric vehicles such as hybrid vehicles. A lithium ion secondary battery is a non-aqueous electrolyte secondary battery that meets these requirements.

A lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and the active material of the negative electrode and the positive electrode uses a material that can desorb and insert lithium.

Lithium ion secondary batteries that use lithium composite oxide, especially lithium cobalt composite oxide, which is relatively easy to synthesize, as the positive electrode material are expected to be batteries with high energy density because they can obtain high voltages of the 4V class. Practical implementation is progressing. Batteries using lithium cobalt composite oxides have undergone numerous developments to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

However, since lithium cobalt composite oxide uses an expensive cobalt compound as a raw material, the unit price per capacity of a battery using this lithium cobalt composite oxide is significantly higher than that of a nickel metal hydride battery, and the applicable applications are quite limited. Limited.

As a new active material for lithium ion secondary batteries, a lithium-nickel composite oxide using nickel, which is cheaper than cobalt, can be mentioned. This lithium-nickel composite oxide exhibits a lower electrochemical potential than the lithium-cobalt composite oxide, so decomposition due to electrolyte oxidation is less likely to be a problem, and higher capacity can be expected, as well as higher battery voltages like cobalt-based oxides. As shown, development is actively underway.

However, when a lithium-ion secondary battery is manufactured using a lithium-nickel composite oxide synthesized purely from nickel as a positive electrode material, its cycle characteristics are inferior to that of a cobalt-based battery, and when used and stored in high-temperature environments, It has the disadvantage that it is relatively easy to impair battery performance. For this reason, lithium-nickel composite oxides in which part of nickel is replaced with cobalt or aluminum are generally known.

For example, Patent Document 1 describes a method for producing lithium-nickel composite oxide, etc., in which an alkaline solution is added to a mixed aqueous solution of Ni salt and M salt to co-precipitate the hydroxides of Ni and M, and the resulting precipitate is A crystallization step of filtering, washing with water, and drying to obtain nickel composite hydroxide: Ni _x M _1-x (OH) ₂ ;
The obtained nickel composite hydroxide: Ni _x M _1-x (OH) ₂ and the lithium compound were mixed so that the molar ratio of Li to the sum of Ni and M: Li/(Ni+M) was 1.00 to 1.15. a firing step of obtaining the lithium-nickel composite oxide by mixing the mixture so that the mixture becomes 700°C or higher and 1000°C or lower;
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery is disclosed, which includes a washing step of washing the obtained lithium-nickel composite oxide with water.

Japanese Patent Application Publication No. 2012-119093

Incidentally, in recent years, there has been a demand for higher capacity and improved cycle characteristics for lithium ion secondary batteries, and in order to meet this demand, the above-mentioned lithium-nickel composite oxide and its precursor, nickel composite water, have been developed. Regarding oxides, it is required to increase the particle size and suppress the broadening of the particle size distribution.

Therefore, in view of the problems of the above-mentioned conventional techniques, one aspect of the present invention aims to provide a method for producing a nickel composite hydroxide that has a large particle size and suppresses the spread of the particle size distribution.

According to one aspect of the present invention to solve the above problems,
A crystallization step of supplying a mixed aqueous solution containing a nickel salt, an alkaline aqueous solution, and a complexing agent to a reaction tank to form a reaction aqueous solution and obtaining a nickel composite hydroxide by a continuous crystallization method,
In the crystallization step, the pH value of the reaction aqueous solution is controlled to be 10 or more and 13 or less, and the ammonia concentration is 3 g / L or more and 25 g / L or less based on 25 ° C.,
The concentration of metal in the mixed aqueous solution is C (mol/L),
Provided is a method for producing a nickel composite hydroxide that satisfies the following formula (1), where the flow rate of the mixed aqueous solution supplied to the reaction tank is Q (L/min).

0.8≦Q×C ² < 1.2...(1)

According to one aspect of the present invention, it is possible to provide a method for producing a nickel composite hydroxide that has a large particle size and suppresses the spread of the particle size distribution.

It is a particle size distribution of the nickel composite hydroxide obtained in Examples 1 and 2 and Comparative Examples 1 and 2.

Hereinafter, modes for carrying out the present invention will be described. However, the present invention is not limited to the following embodiments, and various modifications and variations may be made to the following embodiments without departing from the scope of the present invention. Substitutions can be added.
[Method for producing nickel composite hydroxide]
The method for producing nickel composite hydroxide of the present embodiment includes a crystallization step of supplying a mixed aqueous solution containing a nickel salt and an alkaline aqueous solution to a reaction tank and obtaining a nickel composite hydroxide by a continuous crystallization method. I can do it.

When the concentration of metal in the mixed aqueous solution is C (mol/L) and the supply flow rate of the mixed aqueous solution to the reaction tank is Q (L/min), the following equation (1) can be satisfied. preferable.

0.8≦Q×C ² ≦1.2...(1)
As mentioned above, in recent years, lithium ion secondary batteries are required to have even higher capacity and improved cycle characteristics. By increasing the particle size of the lithium-nickel composite oxide used as a positive electrode material for lithium ion secondary batteries, it is possible to increase the capacity. Moreover, by suppressing the spread of particle size distribution, cycle characteristics can be improved. This is because if particles with a relatively small particle size are mixed, there is a risk that the load will be applied to the small particles during repeated charging and discharging and the charge/discharge capacity will decrease, but this suppresses the spread of the particle size distribution. This is because it is possible to suppress the occurrence of such a phenomenon.

Since lithium-nickel composite oxide is affected by the powder characteristics of the nickel composite hydroxide that is its precursor, it is important to note that lithium-nickel composite oxide and its precursor, nickel composite hydroxide, have large particle diameters. There was a need to suppress the broadening of the particle size distribution.

Therefore, the inventors of the present invention conducted extensive studies on a method for producing a nickel composite hydroxide that has a large particle size and can suppress the spread of the particle size distribution.

In order to increase productivity, the manufacturing method for nickel composite hydroxide involves continuously supplying a mixed aqueous solution containing a raw material nickel salt and an alkaline aqueous solution to a reaction tank, and collecting particles precipitated by overflow. , it is preferable to use a continuous crystallization method for producing. When nickel composite hydroxide is produced by a continuous crystallization method, it is easier to obtain particles with a larger particle size than by a batch crystallization method, but there is a problem in that the particle size distribution tends to expand.

Therefore, we investigated how to suppress the particle size distribution while maintaining the large particle size of the obtained nickel composite hydroxide.

When growing particles by crystallization, the longer the particles stay in the reaction tank, the larger the particles grow. In the case of continuous crystallization, particles are taken out by overflow, so how long the particles stay in the tank can be calculated probabilistically as a residence time distribution. By suppressing the spread of the residence time distribution, it is possible to suppress the spread of the particle size distribution of the obtained nickel composite hydroxide.

The number of existing particles N, which is the number of particles present in the reaction tank, is a nucleation that depends on the local supersaturation degree in the tank of the mixed aqueous solution containing nickel salt that supplies the metal component of the nickel composite hydroxide. It is determined by the product of the rate R (numbers/min) and the average residence time T (min). Note that the nucleus generation rate R means the number of nuclei generated per unit time. It has been experimentally confirmed that the nucleation rate R is proportional to the product of the square of the supply flow rate Q (L/min) and the square of the metal concentration C (mol/L) in the mixed aqueous solution. From this, the number N of existing particles satisfies the relationship of equation (A) below.

N∝RT∝Q ² C ² T...(A)
Moreover, the average residence time T is inversely proportional to the supply flow rate Q of the mixed aqueous solution. That is, the following equation (B) is satisfied.

Q∝1/T...(B)
From the above formulas (A) and (B), the following formula (C) is derived.

N∝QC ² ...(C)
By keeping the number N of existing particles, which is the number of particles in the reaction tank, within a predetermined range, the residence time distribution of particles in the reaction tank is suppressed, and the particle size distribution of the obtained nickel composite hydroxide is Can be suppressed. Therefore ^, in the crystallization step of the method for producing a nickel composite hydroxide of the present embodiment, the metal concentration C (mol/L ), and the supply flow rate Q (L/min) of the mixed aqueous solution supplied to the reaction tank can be set.

According to studies by the inventors of the present invention, by setting ^QC2 to 0.8 or more, it is possible to suppress fluctuations in the number of particles in the reaction tank and to suppress the spread of the residence time distribution of particles in the reaction tank. . Therefore, broadening of the particle size distribution of the obtained nickel composite hydroxide can be suppressed. Further, by setting QC ² to 1.2 or less, it is possible to suppress the number of particles in the reaction tank from increasing excessively and promote the growth of particles in the reaction tank. Therefore, it is possible to obtain a large particle size nickel composite hydroxide that has grown to a sufficient size.

As mentioned above, the QC ² is preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less, and preferably 0.95 or more and 1.05 or less. More preferred.

In the crystallization step, as described above, a mixed aqueous solution containing a nickel salt and an alkaline aqueous solution are supplied to a reaction tank, and a nickel composite hydroxide can be obtained by a continuous crystallization method.

Specifically, it is preferable to carry out the following procedure, for example.

First, water is poured into a reaction tank and the atmosphere and temperature are controlled to a predetermined level. Note that during the crystallization step, the atmosphere in the reaction tank is not particularly limited, but may be an inert atmosphere such as a nitrogen atmosphere. Further, in addition to the inert gas, a gas containing oxygen such as air can also be supplied to adjust the dissolved oxygen concentration of the solution in the reaction tank. In addition to water, an alkali aqueous solution or a complexing agent, which will be described later, may be further added to the reaction tank to form an initial aqueous solution.

Next, the mixed aqueous solution and the alkaline aqueous solution are added to the reaction tank to form a reaction aqueous solution. Then, by stirring the reaction aqueous solution at a constant speed and controlling the pH, particles of nickel composite hydroxide can be co-precipitated and crystallized in the reaction tank.The mixed aqueous solution contains nickel salt and nickel composite hydroxide. A salt of a metal other than nickel may be added to the hydroxide. For example, when producing a nickel cobalt aluminum composite hydroxide as the nickel composite hydroxide, the mixed aqueous solution can contain a nickel salt, a cobalt salt, and an aluminum salt. Further, when producing a nickel cobalt manganese composite hydroxide as the nickel composite hydroxide, the mixed aqueous solution can contain a nickel salt, a cobalt salt, and a manganese salt. In any case, if any additional element is further included, the mixed aqueous solution may further include a salt of the additional element.

Even if all of the metal element salts contained in the nickel composite hydroxide to be manufactured are not added to one mixed aqueous solution, a mixed aqueous solution containing some metal salts and an aqueous solution containing the remaining metal salts are supplied. good. Alternatively, aqueous solutions of each metal salt may be prepared separately, and the aqueous solutions containing each metal salt may be supplied to the reaction tank. When the metal salt is divided into a plurality of solutions and supplied to the reaction tank in this way, the concentration of the metal in the whole of the plurality of solutions can be set to the concentration C of the metal in the mixed aqueous solution described above.

The mixed aqueous solution can be prepared by adding salts of each metal to water as a solvent. The type of salt is not particularly limited, and for example, one or more types of salts selected from sulfates, nitrates, chlorides, etc. can be used. Although the types of salts for each metal may be different, it is preferable to use the same type of salt from the viewpoint of preventing contamination with impurities.

An alkaline aqueous solution can be prepared by adding an alkaline component to water, which is a solvent. Although the type of alkali component is not particularly limited, for example, one or more types selected from sodium hydroxide, potassium hydroxide, sodium carbonate, etc. can be used.

The composition of the metal elements contained in the mixed aqueous solution and the composition of the metal elements contained in the obtained nickel composite hydroxide are almost the same. Therefore, it is preferable to adjust the composition of the metal elements in the mixed aqueous solution to be the same as the composition of the metal elements in the target nickel composite hydroxide.

In the crystallization step, any component other than the above mixed aqueous solution and alkaline aqueous solution can be added to the mixed aqueous solution.

For example, a complexing agent can be added to the aqueous reaction solution together with the aqueous alkaline solution.

The complexing agent is not particularly limited, and any complexing agent may be used as long as it can bond with nickel ions and other metal ions in an aqueous solution to form a complex. Examples of complexing agents include ammonium ion donors. The ammonium ion donor is not particularly limited, and for example, one or more types selected from ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc. can be used.

The temperature and pH of the aqueous reaction solution in the crystallization step are not particularly limited, but for example, when a complexing agent is not used, the temperature of the aqueous reaction solution is preferably in the range of more than 60 ° C. and less than 80 ° C., and It is preferable that the pH of the aqueous reaction solution at temperature is 10 or more and 12 or less (based on 25° C.).

In the crystallization step, when a complexing agent is not used, by setting the pH of the aqueous reaction solution to 12 or less, it is possible to prevent the particles of the nickel composite hydroxide from becoming fine particles and improve filterability.

Further, by setting the pH of the aqueous reaction solution to 10 or more, the rate of production of nickel composite hydroxide particles can be increased, and it is possible to prevent some components such as Ni from remaining in the filtrate. Therefore, particles of nickel composite hydroxide having the desired composition can be obtained more reliably.

In the crystallization process, when a complexing agent is not used, setting the temperature of the reaction aqueous solution to over 60°C will increase the solubility of Ni, so the amount of Ni precipitated will deviate from the target composition, making it easier to prevent coprecipitation. It can definitely be avoided.

Further, by setting the temperature of the aqueous reaction solution to 80° C. or lower, the amount of water evaporated can be suppressed, and therefore the slurry concentration can be prevented from increasing. By preventing the slurry concentration from increasing, for example, it is possible to suppress unintentional crystals such as sodium sulfate from precipitating in the reaction aqueous solution and increasing the impurity concentration.

On the other hand, when an ammonium ion donor such as ammonia is used as a complexing agent, the solubility of Ni increases, so the pH of the reaction aqueous solution in the crystallization step is preferably 10 or more and 13 or less (25° C. standard). Moreover, in this case, it is preferable that the temperature of the reaction aqueous solution is 30°C or more and 60°C or less.

When adding an ammonium ion donor as a complexing agent to the reaction aqueous solution, the ammonia concentration in the reaction aqueous solution is preferably maintained within a constant range of 3 g/L or more and 25 g/L or less in the reaction tank.

By setting the ammonia concentration in the reaction aqueous solution to 3 g/L or more, the solubility of metal ions can be kept particularly constant, thereby forming primary particles of nickel composite hydroxide with a uniform shape and particle size. be able to.

By setting the ammonia concentration in the reaction aqueous solution to 25 g/L or less, it is possible to prevent the solubility of metal ions from becoming excessively large and to suppress the amount of metal ions remaining in the reaction aqueous solution, thereby ensuring that nickel of the desired composition is produced. Particles of composite hydroxide can be obtained.

Furthermore, if the ammonia concentration fluctuates, the solubility of metal ions will fluctuate and there is a risk that hydroxide with a uniform composition will not be formed, so it is preferable to maintain it within a certain range. For example, during the crystallization step, the ammonia concentration is preferably maintained at a desired concentration with the width between the upper and lower limits being within about 5 g/L.

Then, a mixed aqueous solution, an alkaline aqueous solution, and an aqueous solution containing an ammonium ion donor in some cases are continuously supplied to the reaction tank, and the precipitate is collected by overflowing from the reaction tank, filtered and washed with nickel composite water. Oxide can be obtained.

The composition of the nickel composite hydroxide produced by the method for producing a nickel composite hydroxide of the present embodiment is not particularly limited, and can be selected according to the composition of the positive electrode active material for a lithium ion secondary battery to be produced. For example, the nickel composite hydroxide produced by the method for producing a nickel composite hydroxide of the present embodiment has the general formula: Ni _1-x-y Co _x Al _y (OH) _2+α (0≦x≦0.3, 0.005≦y≦0.15, 0≦α≦0.5) or the general formula: Ni _a Co _b Mn _c M _d (OH) _2+β (a+b+c+d =1, 0.1≦a≦0.7, 0.1≦b≦0.5, 0.1≦c≦0.8, 0≦d≦0.02, 0≦β≦0.5, M can be a nickel cobalt manganese composite hydroxide represented by one or more additive elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W.
[Method for producing positive electrode active material for lithium ion secondary battery]
The nickel composite hydroxide described above can be used as a precursor of a positive electrode active material for a lithium ion secondary battery.

Next, a configuration example of the method for manufacturing a positive electrode active material for a lithium ion secondary battery (hereinafter referred to as "method for manufacturing a positive electrode active material") of the present embodiment will be described.

The method for manufacturing a positive electrode active material of this embodiment can include the following steps.

A mixing step of preparing a raw material mixture by mixing the aforementioned nickel composite hydroxide and a lithium compound.
A firing process in which a raw material mixture is fired in an oxygen-containing atmosphere.

Each step will be explained below.
(Mixing process)
In the mixing step, a raw material mixture can be obtained by mixing the nickel composite hydroxide produced by the method for producing a nickel composite hydroxide described above and a lithium compound.

Since the nickel composite hydroxide has already been explained, its explanation will be omitted here.

The lithium compound is not particularly limited, and for example, one or more types selected from lithium carbonate, lithium hydroxide, etc. can be used. Note that lithium hydroxide may contain hydration water and can be used as is, but it is preferable to roast it in advance to reduce the hydration water.

A general mixer can be used to mix the nickel composite hydroxide and the lithium compound, for example, one or more types selected from a shaker mixer, Loedige mixer, Julia mixer, V blender, etc. be able to. The mixing conditions in the mixing step are not particularly limited, but it is preferable to select the conditions so that the raw ingredients are sufficiently mixed without destroying the particles of the raw material such as nickel composite hydroxide.

It is preferable that the raw material mixture is sufficiently mixed in a mixing step before being subjected to the firing step. If the mixing is insufficient, Li/Me may vary among individual particles, which may cause problems such as insufficient battery characteristics. Note that Li/Me means the ratio of the number of atoms of lithium (Li) and a metal other than lithium (Me) contained in the raw material mixture.

The ratio of each metal contained in the raw material mixture and the lithium-nickel composite oxide obtained after the firing process hardly changes. For this reason, in the mixing step, the content ratio of each metal in the raw material mixture is mixed so that it is the same as the content ratio of each metal aimed at in the positive electrode active material obtained by the method for producing a positive electrode active material of this embodiment. It is preferable.
(Firing process)
In the firing step, the raw material mixture obtained in the mixing step is fired in an oxygen-containing atmosphere to obtain a lithium-nickel composite oxide.

When the raw material mixture is fired in the firing step, lithium in the lithium compound diffuses into the particles of the nickel composite hydroxide, so that a lithium-nickel composite oxide consisting of particles with a polycrystalline structure is formed.

The firing temperature of the raw material mixture is not particularly limited, but is preferably, for example, 650°C or higher and 900°C or lower, more preferably 650°C or higher and 850°C or lower. By setting the firing temperature to 650° C. or higher, lithium can be sufficiently diffused into the nickel composite hydroxide, and it can be suppressed that excess lithium and unreacted nickel composite hydroxide remain. It is also preferable because it can improve the crystallinity of the obtained lithium-nickel composite oxide.

Further, by setting the firing temperature to 900° C. or lower, it is possible to suppress violent sintering between particles of the lithium-nickel composite oxide and abnormal particle growth, and to suppress the generation of irregularly shaped coarse particles.

In addition, during the firing process, it is preferable to temporarily stop increasing the temperature and hold it at a temperature near the melting point of the lithium compound. In this case, it is preferable to hold the temperature for 1 hour or more and 5 hours or less, and it is preferable to hold it for 2 hours or more and 5 hours or less. More preferred. By temporarily stopping the temperature increase and maintaining the temperature near the melting point of the lithium compound, the nickel composite hydroxide and the lithium compound can be reacted more uniformly.

The holding time at the above-mentioned firing temperature is also not particularly limited, but is preferably 2 hours or more, and more preferably 4 hours or more, for example. By setting the holding time at the firing temperature to 2 hours or more, lithium can be sufficiently diffused into the nickel composite hydroxide, and excess lithium and unreacted nickel composite hydroxide can be suppressed from remaining. It is also preferable because it can improve the crystallinity of the obtained lithium-nickel composite oxide.

Note that the upper limit of the firing time is not particularly limited, but from the viewpoint of productivity, it is preferably 48 hours or less.

The atmosphere during firing is preferably an oxidizing atmosphere, more preferably an atmosphere in which the oxygen concentration is 18% by volume or more and 100% by volume or less. This is because by setting the oxygen concentration to 18% by volume or more, the crystallinity of the obtained lithium-nickel composite oxide can be particularly improved. Note that the remainder other than oxygen is not particularly limited, and may be, for example, nitrogen or an inert gas such as a rare gas. Further, the remainder other than oxygen may include carbon dioxide, water vapor, and the like. It is more preferable that the firing is carried out, for example, in the atmosphere or in an oxygen stream.

Note that the method for producing a positive electrode active material of this embodiment is not limited to the above steps, and may further include any steps.

For example, it is possible to include an oxidative roasting step in which the nickel composite hydroxide to be subjected to the mixing step is oxidized and roasted.

When carrying out the oxidative roasting process, in the mixing process, the oxidative roasted nickel composite hydroxide and the lithium compound can be mixed to form a raw material mixture.
(Oxidation roasting process)
When performing the oxidation roasting step, the nickel composite hydroxide obtained in the crystallization step is fired in an oxygen-containing atmosphere, and then cooled to room temperature, thereby obtaining the nickel composite oxide. In addition, in the oxidation roasting step, by firing the nickel composite hydroxide, the moisture content can be reduced and at least a part of it can be converted into the nickel composite oxide as described above. However, it is not necessary to completely convert nickel composite hydroxide into nickel composite oxide in the oxidation roasting process, and the nickel composite oxide referred to here does not include, for example, nickel composite hydroxide or its intermediates. You can leave it there.

Although the roasting conditions in the oxidative roasting step are not particularly limited, it is preferable to perform the roasting in an oxygen-containing atmosphere, for example, in an air atmosphere, at a temperature of 350° C. or more and 1000° C. or less for 5 hours or more and 24 hours or less.

This is because it is preferable to set the firing temperature to 350° C. or higher because it can prevent the specific surface area of the obtained nickel composite oxide from becoming excessively large. In addition, it is preferable to set the firing temperature to 1000° C. or lower because it can prevent the specific surface area of the nickel composite oxide from becoming excessively small.

By setting the firing time to 5 hours or more, the temperature inside the firing container can be made particularly uniform, and the reaction can proceed uniformly, which is preferable. Further, even if the sintering is performed for a time longer than 24 hours, no major change is observed in the obtained nickel composite oxide, so from the viewpoint of energy efficiency, the sintering time is preferably 24 hours or less.

The oxygen concentration in the oxygen-containing atmosphere during the heat treatment is not particularly limited, but it is preferable, for example, that the oxygen concentration is 20% by volume or more. Since an oxygen atmosphere can also be used, the upper limit value of the oxygen concentration of the oxygen-containing atmosphere can be 100% by volume.

In the method for producing a positive electrode active material of the present embodiment described above, a nickel composite hydroxide having a large particle size and suppressing the spread of particle size distribution, which is produced by the method for producing a nickel composite hydroxide described above, is used. It is used as a raw material. Therefore, according to the method for producing a positive electrode active material of the present embodiment, a positive electrode active material having a large particle size and suppressing the spread of the particle size distribution can be obtained. Therefore, when the positive electrode active material is used as a positive electrode material for a lithium ion secondary battery, the lithium ion secondary battery can have excellent charge/discharge capacity and cycle characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.
[Example 1]
A crystallizer equipped with a reaction tank (stirring tank) having a cylindrical shape inside was prepared.

A stirring blade is installed in the reaction tank, and is configured so that the initial aqueous solution or the reaction aqueous solution in the reaction tank can be stirred by the stirring blade. Further, the reaction tank is equipped with an overflow port, and is configured to allow continuous overflow and recovery of the generated nickel composite hydroxide.

First, water was poured into a reaction tank (60 L) to half the volume, and the temperature inside the tank was set at 45° C. while stirring. During the crystallization process, the initial aqueous solution and the reaction aqueous solution will be kept at the same temperature as the temperature inside the tank. In addition, nitrogen gas (N ₂ ) and air are supplied into the reaction tank so that _the dissolved oxygen concentration in the reaction tank liquid is 1.5 mg/L or more and 2.5 mg/L or less. Air flow rate was adjusted.

Appropriate amounts of a 25% by mass aqueous sodium hydroxide solution, which is an alkaline aqueous solution, and a 25% by mass aqueous ammonia, which is a complexing agent, are added to the water in this reaction tank to adjust the pH value to 11.6 based on the liquid temperature of 25°C. An initial aqueous solution was prepared so that the ammonia concentration was 12 g/L.

At the same time, nickel sulfate, cobalt sulfate, and sodium aluminate were dissolved in pure water such that the ratio of the amounts of nickel, cobalt, and aluminum was Ni:Co:Al=80:15:5. A mixed aqueous solution having a metal concentration of 0.71 mol/L was prepared.

This mixed aqueous solution was added dropwise to the initial aqueous solution in the reaction tank at a supply flow rate (feed rate) of 2 L/min to form a reaction aqueous solution. At this time, a 25% by mass aqueous sodium hydroxide solution, which is an alkaline aqueous solution, and a 25% by mass aqueous ammonia solution, which is a complexing agent, are also added dropwise to the initial aqueous solution at a constant rate, so that the pH value of the reaction aqueous solution is 11% based on the liquid temperature of 25°C. 6, the ammonia concentration was controlled to be maintained at 12 g/L. Through this operation, nickel composite hydroxide particles were crystallized (crystallization step).

Thereafter, the slurry containing nickel composite hydroxide particles collected from an overflow port provided in the reaction tank was filtered, water-soluble impurities were washed and removed with ion-exchanged water, and then dried. As a result, a nickel composite hydroxide represented by Ni _0.80 Co _0.15 Al _0.05 (OH) ₂ was obtained.

The particle size distribution of the obtained nickel composite hydroxide was measured using a laser diffraction scattering particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).

Then, from the obtained particle size distribution, the average particle size and the spread of the particle size distribution [(D90-D10)/average particle size] were calculated.

Note that the average particle size means the particle size (D50) at an integrated value of 50% in the particle size distribution determined by laser diffraction/scattering method.

Moreover, D90 means the particle size at 90% of the volume integrated value in the particle size distribution determined by laser diffraction/scattering method.

D10 means the particle size at 10% volume integrated value in the particle size distribution determined by laser diffraction/scattering method.

The smaller the spread of the particle size distribution [(D90-D10)/average particle diameter], the smaller the spread of the particle size distribution.

The results are shown in Table 1. Moreover, the particle size distribution of the obtained nickel composite hydroxide is shown in FIG.
[Example 2]
In the crystallization step, nickel composite hydroxide was prepared in the same manner as in Example 1, except that the metal concentration of the mixed aqueous solution was 0.5 mol/L, and the supply flow rate of the mixed aqueous solution was 4 L/min. went. The results are shown in Table 1. Moreover, the particle size distribution of the obtained nickel composite hydroxide is shown in FIG.
[Comparative example 1]
In the crystallization step, a nickel composite hydroxide was prepared in the same manner as in Example 1, except that the metal concentration of the mixed aqueous solution was 0.71 mol/L, and the supply flow rate of the mixed aqueous solution was 1 L/min. went. The results are shown in Table 1. Moreover, the particle size distribution of the obtained nickel composite hydroxide is shown in FIG.
[Comparative example 2]
In the crystallization step, a nickel composite hydroxide was prepared and evaluated in the same manner as in Example 1, except that the metal concentration of the mixed aqueous solution was 1 mol/L, and the supply flow rate of the mixed aqueous solution was 2 L/min. . The results are shown in Table 1. Moreover, the particle size distribution of the obtained nickel composite hydroxide is shown in FIG.

表１に示した結果によるとＱ×Ｃ^２が０．８以上１．２以下の範囲にある実施例１、２においては、得られたニッケル複合水酸化物の粒度分布の拡がりである［（Ｄ９０－Ｄ１０）／平均粒径］が１以下と十分に低くなることを確認できた。

According to the results shown in Table 1, in Examples 1 and 2 where Q×C ² is in the range of 0.8 or more and 1.2 or less, the particle size distribution of the obtained nickel composite hydroxide is expanded [( D90-D10)/average particle size] was confirmed to be sufficiently low at 1 or less.

In Comparative Example 1, it was confirmed that the spread of the particle size distribution [(D90-D10)/average particle size] exceeded 1 and the variation in the particle size distribution became large.

On the other hand, in Comparative Example 2, although the spread of the particle size distribution [(D90-D10)/average particle size] is 1 or less, the peak position of the particle size distribution is 6.97 μm, and Examples 1 and 2, Comparative Example It was confirmed that the size was significantly smaller than that of 1.

Claims (2)

A crystallization step of supplying a mixed aqueous solution containing a nickel salt, an alkaline aqueous solution, and a complexing agent to a reaction tank to form a reaction aqueous solution and obtaining a nickel composite hydroxide by a continuous crystallization method,
In the crystallization step, the pH value of the reaction aqueous solution is controlled to be 10 or more and 13 or less, and the ammonia concentration is 3 g / L or more and 25 g / L or less based on 25 ° C.,
The concentration of metal in the mixed aqueous solution is C (mol/L),
A method for producing a nickel composite hydroxide that satisfies the following formula (1), where the flow rate of the mixed aqueous solution supplied to the reaction tank is Q (L/min).
0.8≦Q×C ² <1.2...(1) The nickel composite hydroxide is
Nickel cobalt represented by the general formula: Ni _1-x-y Co _x Al _y (OH) _2+α (0≦x≦0.3, 0.005≦y≦0.15, 0≦α≦0.5) Is it aluminum composite hydroxide?
General formula: Ni _a Co _b Mn _c M _d (OH) _2+β (a+b+c+d=1, 0.1≦a≦0.7, 0.1≦b≦0.5, 0.1≦c≦0.8, 0≦d≦0.02, 0≦β≦0.5, M is one or more additive elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) The method for producing a nickel composite hydroxide according to claim 1, which is a nickel cobalt manganese composite hydroxide.

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