JP2020196643A - Method for producing nickel composite hydroxide - Google Patents

Abstract

To provide a method for producing a nickel composite hydroxide having a large particle size and having the spread of particle size distribution suppressed.SOLUTION: There is provided a method for producing a nickel complex hydroxide comprising a crystallization step of supplying a mixed aqueous solution containing a nickel salt and an alkali aqueous solution to a reaction tank and obtaining a nickel complex hydroxide by a continuous crystallization method, in which the following formula (1) is satisfied when a concentration of metal in the mixed aqueous solution is C (mol/L) and a supply flow rate of the mixed aqueous solution to be supplied to the reaction tank is Q (L/min): 0.8≤Q×C2≤1.2 (1).SELECTED DRAWING: Figure 1

Description

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

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook personal computers, the development of small and lightweight secondary batteries having a high energy density has been required. In addition, the development of high-output secondary batteries is also required as batteries for electric vehicles such as hybrid vehicles. As a non-aqueous electrolyte secondary battery satisfying such a requirement, there is a lithium ion secondary battery.

The lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as the active material of the negative electrode and the positive electrode.

A lithium ion secondary battery using a lithium composite oxide, particularly a lithium cobalt composite oxide that is relatively easy to synthesize, as a positive electrode material is expected to have a high energy density because a high voltage of 4V class can be obtained. Practical use is progressing. Batteries using lithium cobalt composite oxides have been developed in many ways to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

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

As a new material for the active material for a lithium ion secondary battery, a lithium nickel composite oxide using nickel, which is cheaper than cobalt, can be mentioned. Since this lithium nickel composite oxide exhibits a lower electrochemical potential than the lithium cobalt composite oxide, decomposition due to oxidation of the electrolyte is less likely to be a problem, higher capacity can be expected, and a high battery voltage similar to that of cobalt oxide can be expected. As shown, development is being actively carried out.

However, when a lithium ion secondary battery is manufactured using a lithium nickel composite oxide synthesized purely from nickel as a positive electrode material, the cycle characteristics are inferior to those of a cobalt type battery, and due to use and storage in a high temperature environment, It has the disadvantage that the battery performance is relatively easily impaired. For this reason, a lithium nickel composite oxide in which a part of nickel is replaced with cobalt or aluminum is generally known.

As a method for producing a lithium nickel composite oxide or the like, for example, in Patent Document 1, an alkaline solution is added to a mixed aqueous solution of a Ni salt and an M salt to co-precipitate a hydroxide of Ni and M, and the obtained precipitate is obtained. 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 a lithium compound were mixed, and the molar ratio of Li to the total of Ni and M: Li / (Ni + M) was 1.00 to 1.15. The mixture is further mixed at a temperature of 700 ° C. or higher and 1000 ° C. or lower to obtain the lithium nickel composite oxide.
Disclosed is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which comprises a water washing step of washing the obtained lithium nickel composite oxide with water.

Japanese Unexamined Patent Publication No. 2012-119093

By the way, in recent years, there has been a demand for higher capacity and improved cycle characteristics of lithium ion secondary batteries, and in order to meet these demands, the above-mentioned lithium nickel composite oxide and nickel composite water as a precursor thereof are required. For oxides, it is required to increase the particle size and suppress the spread of the particle size distribution.

Therefore, in view of the above-mentioned problems of the prior art, one aspect of the present invention is to provide a method for producing a nickel composite hydroxide having a large particle size and suppressing the spread of the particle size distribution.

According to one aspect of the present invention in order to solve the above problems.
It has a crystallization step of supplying a mixed aqueous solution containing a nickel salt and an alkaline aqueous solution to a reaction vessel to obtain a nickel composite hydroxide by a continuous crystallization method.
The concentration of the metal in the mixed aqueous solution is C (mol / L),
Provided is a method for producing a nickel composite hydroxide satisfying the following formula (1), where Q (L / min) is the supply flow rate of the mixed aqueous solution supplied to the reaction vessel.

0.8 ≤ Q x 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 having a large particle size and suppressing 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, embodiments for carrying out the present invention will be described, but the present invention is not limited to the following embodiments, and various modifications and variations to the following embodiments are made without departing from the scope of the present invention. Substitutions can be added.
[Manufacturing method of nickel composite hydroxide]
The method for producing a 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 vessel to obtain a nickel composite hydroxide by a continuous crystallization method. Can be done.

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

0.8 ≤ Q x C ² ≤ 1.2 ... (1)
As described above, in recent years, there has been a demand for further increasing the capacity and improving the cycle characteristics of lithium ion secondary batteries. Then, the capacity of the lithium nickel composite oxide used as the positive electrode material of the lithium ion secondary battery can be increased by increasing the particle size. In addition, the cycle characteristics can be improved by suppressing the spread of the particle size distribution. This is because when particles with a relatively small particle size are mixed, a load may be applied to the particles having a relatively small particle size and the charge / discharge capacity may decrease, but the spread of the particle size distribution is suppressed. This is because it is possible to suppress the occurrence of such a phenomenon.

Since the lithium nickel composite oxide is affected by the powder characteristics of the nickel composite hydroxide as a precursor, the lithium nickel composite oxide and the nickel composite hydroxide which is the precursor thereof have a large particle size. In addition, it was required to suppress the spread of the particle size distribution.

Therefore, the inventor of the present invention has diligently studied a method for producing a nickel composite hydroxide having a large particle size and capable of suppressing the spread of the particle size distribution.

In the method for producing a nickel composite hydroxide, from the viewpoint of increasing productivity, a mixed aqueous solution containing a nickel salt as a raw material and an alkaline aqueous solution are continuously supplied to the reaction vessel, and particles precipitated by overflow are recovered. , It is preferable to use the continuous crystallization method for producing. When the nickel composite hydroxide is produced by the continuous crystallization method, particles having a large particle size can be easily obtained as compared with the batch type crystallization method, but there is a problem that the particle size distribution is easily expanded.

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

When the particles are grown by crystallization, the longer they stay in the reaction vessel, the larger the particles grow. In the case of the continuous crystallization method, since the particles are taken out by overflow, how much the particles stay in the tank can be stochastically calculated as a residence time distribution. Then, 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 existing in the reaction vessel, is a nuclear generation that depends on the local supersaturation degree in the vessel of the mixed aqueous solution containing a nickel salt that supplies the metal component of the nickel composite hydroxide. It is determined by the product of the rate R (pieces / min) and the average residence time T (min). The nuclear generation rate R means the number of nuclear weapons generated per unit time. It has been experimentally confirmed that the nuclear generation 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 of existing particles N satisfies the relationship of the following formula (A).

N∝RT∝Q ² C ² T ... (A)
Further, the average residence time T is inversely proportional to the supply flow rate Q of the mixed aqueous solution. That is, the relationship of 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)
Then, by keeping the number of existing particles N, which is the number of particles in the reaction vessel, within a predetermined range, the residence time distribution of the particles in the reaction vessel is suppressed, and the particle size distribution of the obtained nickel composite hydroxide can be obtained. It can be suppressed. Therefore, in the crystallization step of the method for producing a nickel composite hydroxide of the present embodiment, the concentration C (mol / L) of the metal in the mixed aqueous solution is maintained so as to keep the QC ² of the above formula (C) within a predetermined range. ), And the supply flow rate Q (L / min) of the mixed aqueous solution to be supplied to the reaction vessel can be set.

According to the study of the inventor of the present invention, by setting the QC ² to 0.8 or more, the fluctuation of the number of particles in the reaction vessel can be suppressed, and the spread of the residence time distribution of the particles in the reaction vessel can be suppressed. .. Therefore, it is possible to suppress the spread of the particle size distribution of the obtained nickel composite hydroxide. Further, by setting the QC ² to 1.2 or less, it is possible to suppress the excessive increase in the number of particles in the reaction vessel and promote the growth of the particles in the reaction vessel. Therefore, a nickel composite hydroxide having a large particle size grown to a sufficient size can be obtained.

As described 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 the reaction vessel, and a nickel composite hydroxide can be obtained by a continuous crystallization method.

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

First, water is put into the reaction vessel to control the atmosphere and temperature. During the crystallization step, the atmosphere in the reaction vessel is not particularly limited, but an inert atmosphere such as a nitrogen atmosphere can be used. Further, in addition to the inert gas, a gas containing oxygen such as air can be supplied together to adjust the dissolved oxygen concentration of the solution in the reaction vessel. In addition to water, an alkaline aqueous solution described later or a complexing agent may be further added to prepare an initial aqueous solution in the reaction vessel.

Next, the mixed aqueous solution and the alkaline aqueous solution are added to the reaction vessel to prepare a reaction aqueous solution. Then, by controlling the pH by stirring the reaction aqueous solution at a constant rate, the nickel composite hydroxide particles can be co-precipitated and crystallized in the reaction vessel, and the mixed aqueous solution is a nickel salt and a nickel composite. It can include salts of metals other than nickel added to the hydroxide. For example, when a nickel cobalt-aluminum composite hydroxide is produced as a nickel composite hydroxide, the mixed aqueous solution can contain a nickel salt, a cobalt salt, and an aluminum salt. When a nickel cobalt-manganese composite hydroxide is produced 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 additive element or the like is further contained, the mixed aqueous solution may further contain a salt of the additive element.

Even if all the salts of the metal elements contained in the nickel composite hydroxide to be produced are not added to one mixed aqueous solution, and a mixed aqueous solution containing a part of the metal salt and an aqueous solution containing the remaining metal salt are supplied. good. Alternatively, an aqueous solution of each metal salt may be prepared separately, and an aqueous solution containing each metal salt may be supplied to the reaction vessel. When the metal salt is separately supplied to the reaction vessel by the plurality of solutions in this way, the concentration of the metal in the entire plurality of solutions can be set to the concentration C of the metal in the above-mentioned mixed aqueous solution.

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

The alkaline aqueous solution can be prepared by adding an alkaline component to water as a solvent. The type of the alkaline component is not particularly limited, but for example, one or more selected from sodium hydroxide, potassium hydroxide, sodium carbonate and the like can be used.

The composition of the metal element contained in the mixed aqueous solution and the composition of the metal element contained in the obtained nickel composite hydroxide are almost the same. Therefore, it is preferable to adjust the composition of the metal element in the mixed aqueous solution so as to have the same composition as the metal element of 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 reaction aqueous solution together with the alkaline aqueous solution.

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

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

When a complexing agent is not used in the crystallization step, the pH of the reaction aqueous solution is set to 12 or less to prevent the nickel composite hydroxide particles from becoming fine particles and improve the filterability.

Further, by setting the pH of the reaction aqueous solution to 10 or more, the rate of formation 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, the nickel composite hydroxide particles having the desired composition can be obtained more reliably.

When a complexing agent is not used in the crystallization step, the solubility of Ni increases by setting the temperature of the reaction aqueous solution to more than 60 ° C., so that the amount of Ni precipitated deviates from the target composition and does not coprecipitate. It can be definitely avoided.

Further, by setting the temperature of the reaction aqueous solution to 80 ° C. or lower, the amount of water evaporation can be suppressed, so that the slurry concentration can be prevented from increasing. By preventing the slurry concentration from increasing, it is possible to prevent unintended 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 feeder such as ammonia is used as a complexing agent, the pH of the reaction aqueous solution in the crystallization step is preferably 10 or more and 13 or less (based on 25 ° C.) because the solubility of Ni increases. In this case, the temperature of the reaction aqueous solution is preferably 30 ° C. or higher and 60 ° C. or lower.

When an ammonium ion feeder is added to the reaction aqueous solution as a complexing agent, the ammonia concentration in the reaction aqueous solution is preferably kept within a certain range of 3 g / L or more and 25 g / L or less in the reaction vessel.

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, so that primary particles of nickel composite hydroxide having a uniform shape and particle size are formed. 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 high and suppress the amount of metal ions remaining in the reaction aqueous solution, so that nickel having the desired composition can be more reliably composed. Particles of composite hydroxide can be obtained.

Further, when the ammonia concentration fluctuates, the solubility of metal ions fluctuates, and a hydroxide having a uniform composition may not be formed. Therefore, it is preferable to keep the concentration within a certain range. For example, during the crystallization step, the ammonia concentration is preferably maintained at a desired concentration with the upper and lower limits within about 5 g / L.

Then, a mixed aqueous solution, an alkaline aqueous solution, and in some cases, an aqueous solution containing an ammonium ion feeder is continuously supplied to the reaction vessel, overflowed from the reaction vessel to collect a precipitate, filtered, washed with water, and nickel composite water. Oxides can be obtained.

The composition of the nickel composite hydroxide produced by the method for producing the 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 the lithium ion secondary battery to be produced. For example, nickel composite hydroxide produced by a production method of the nickel composite hydroxide of the present embodiment, the general _{formula: Ni 1-x-y Co} x Al y (OH) 2 + α (0 ≦ x ≦ 0.3, It is a nickel cobalt-aluminum composite hydroxide represented by 0.005 ≦ y ≦ 0.15, 0 ≦ α ≦ 0.5), or is a 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).
[Manufacturing method of 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.

Therefore, next, a configuration example of the method for producing the positive electrode active material for the lithium ion secondary battery of the present embodiment (hereinafter, referred to as “method for producing the positive electrode active material”) will be described.

The method for producing the positive electrode active material of the present embodiment can have the following steps.

A mixing step of mixing the above-mentioned nickel composite hydroxide and a lithium compound to prepare a raw material mixture.
A firing process in which a raw material mixture is fired in an oxygen-containing atmosphere.

Hereinafter, each step will be described.
(Mixing process)
In the mixing step, the nickel composite hydroxide produced by the method for producing a nickel composite hydroxide described above and the lithium compound can be mixed to obtain a raw material mixture.

Since the nickel composite hydroxide has already been described, the description thereof is omitted here.

The lithium compound is not particularly limited, and for example, one or more selected from lithium carbonate, lithium hydroxide, and the like can be used. Lithium hydroxide may have hydrated water and can be used while having hydrated water, but it is preferable to roast in advance to reduce the hydrated water.

A general mixer can be used for mixing the nickel composite hydroxide and the lithium compound, and for example, one or more selected from a shaker mixer, a Raydige mixer, a Julia mixer, a V blender, and the like are used. 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 material components are sufficiently mixed without destroying the skeletons such as particles of the raw material such as nickel composite hydroxide.

It is preferable that the raw material mixture is sufficiently mixed in the mixing step before being subjected to the firing step. If the mixing is not sufficient, Li / Me may vary among the individual particles, and problems such as insufficient battery characteristics may occur. In addition, Li / Me means the ratio of the number of atoms of lithium (Li) and metal (Me) other than lithium contained in a raw material mixture.

Then, the ratio of each metal contained in the raw material mixture and the lithium nickel composite oxide obtained after the firing step hardly changes. Therefore, in the mixing step, the raw material mixture is mixed so that the content ratio of each metal is the same as the content ratio of each metal of the target positive electrode active material obtained by the method for producing the positive electrode active material of the present embodiment. Is preferable.
(Baking process)
In the firing step, the raw material mixture obtained in the mixing step can be 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 is diffused into the particles of the nickel composite hydroxide, so that a lithium nickel composite oxide composed of particles having a polycrystalline structure is formed.

The firing temperature of the raw material mixture is not particularly limited, but is preferably 650 ° C. or higher and 900 ° C. or lower, and more preferably 650 ° C. or higher and 850 ° C. or lower. By setting the calcination temperature to 650 ° C. or higher, lithium can be sufficiently diffused in the nickel composite hydroxide, and excess lithium and unreacted nickel composite hydroxide can be suppressed from remaining. Further, it is preferable because the crystallinity of the obtained lithium nickel composite oxide can be enhanced.

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

Further, during the firing step, it is preferable to temporarily stop the temperature rise at a temperature near the melting point of the lithium compound and hold it. More preferred. By temporarily stopping and holding the temperature rise at a 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 firing temperature described above is also not particularly limited, but is preferably, for example, 2 hours or more, and more preferably 4 hours or more. By setting the holding time at the calcination temperature to 2 hours or more, lithium can be sufficiently diffused in the nickel composite hydroxide, and excess lithium and unreacted nickel composite hydroxide can be suppressed from remaining. Further, it is preferable because the crystallinity of the obtained lithium nickel composite oxide can be enhanced.

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

The atmosphere at the time of firing is preferably an oxidizing atmosphere, and more preferably an atmosphere having an oxygen concentration of 18% by volume or more and 100% by volume or less. This is because the crystallinity of the obtained lithium nickel composite oxide can be particularly enhanced by setting the oxygen concentration to 18% by volume or more. The balance other than oxygen is not particularly limited, but may be, for example, an inert gas such as nitrogen or a rare gas. In addition, carbon dioxide, water vapor, and the like may be contained in the balance other than the oxygen. It is more preferable that the firing is performed in, for example, the atmosphere or an oxygen stream.

The method for producing the positive electrode active material of the present embodiment is not limited to the above steps, and may further include any step.

For example, it is also possible to have an oxidative roasting step of oxidatively roasting the nickel composite hydroxide to be used in the mixing step.

When the oxidative roasting step is carried out, in the mixing step, the nickel composite hydroxide obtained by oxidative roasting and the lithium compound can be mixed to obtain a raw material mixture.
(Oxidation roasting process)
When the oxidative roasting step is carried out, the nickel composite hydroxide can be obtained by firing the nickel composite hydroxide obtained in the crystallization step in an oxygen-containing atmosphere and then cooling to room temperature. In the oxidative roasting step, the nickel composite hydroxide can be calcined to reduce the water content, and at least a part of the nickel composite hydroxide can be obtained as the nickel composite oxide as described above. However, in the oxidative roasting step, it is not necessary to completely convert the nickel composite hydroxide into a nickel composite oxide, and the nickel composite oxide here contains, for example, a nickel composite hydroxide or an intermediate thereof. You may be.

The roasting conditions in the oxidative roasting step are not particularly limited, but it is preferable to bake in an oxygen-containing atmosphere, for example, in an air atmosphere at a temperature of 350 ° C. or higher and 1000 ° C. or lower 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 is possible to prevent the specific surface area of the obtained nickel composite oxide from becoming excessively large. Further, by setting the firing temperature to 1000 ° C. or lower, it is possible to prevent the specific surface area of the nickel composite oxide from becoming excessively small, which is preferable.

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

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

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

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 crystallization device equipped with a reaction tank (stirring tank) having a cylindrical shape inside was prepared.

A stirring blade is installed in the reaction vessel, and the initial aqueous solution or the reaction aqueous solution in the reaction vessel can be stirred by the stirring blade. In addition, the reaction vessel is provided with an overflow port so that the nickel composite hydroxide produced by continuous overflow can be recovered.

First, the temperature in the tank was set to 45 ° C. while adding half the amount of water to the reaction tank (60 L) and stirring the mixture. During the crystallization step, the initial aqueous solution and the reaction aqueous solution will be kept at the same temperature as the temperature in the tank. Also, within the reaction vessel, nitrogen gas _{(N 2)} and air as (Air) to supply the dissolved oxygen concentration in the reaction vessel was equal to or less than 1.5 mg / L or more 2.5mg / L _N 2 / The Air flow rate was adjusted.

An appropriate amount of 25% by mass sodium hydroxide aqueous solution which is an alkaline aqueous solution and 25% by mass ammonia water which is a complexing agent are added to the water in this reaction tank, and the pH value becomes 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 are dissolved in pure water so that the ratio of the amount of substances of nickel, cobalt, and aluminum is 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 vessel at a supply flow rate (supply rate) of 2 L / min to prepare a reaction aqueous solution. At this time, a 25 mass% sodium hydroxide aqueous solution which is an alkaline aqueous solution and a 25 mass% ammonia water which is a complexing agent are also dropped into the initial aqueous solution at a constant rate, and the pH value of the reaction aqueous solution is 11 based on the liquid temperature of 25 ° C. At .6, the ammonia concentration was controlled to be maintained at 12 g / L. By this operation, nickel composite hydroxide particles were crystallized (crystallization step).

Then, the slurry containing the nickel composite hydroxide particles recovered from the overflow port provided in the reaction vessel was filtered, and 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 type particle size distribution measuring device (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.

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

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

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

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

The results are shown in Table 1. The particle size distribution of the obtained nickel composite hydroxide is shown in FIG.
[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 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. 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 and evaluated 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. 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. 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 in which 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 [(). It was confirmed that [D90-D10) / average particle size] was sufficiently low, 1 or less.

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

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

Claims (2)

It has a crystallization step of supplying a mixed aqueous solution containing a nickel salt and an alkaline aqueous solution to a reaction vessel to obtain a nickel composite hydroxide by a continuous crystallization method.
The concentration of the 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 Q (L / min) is the supply flow rate of the mixed aqueous solution supplied to the reaction vessel.
0.8 ≤ Q x C ² ≤ 1.2 ... (1) The nickel composite hydroxide
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) nickel represented by cobalt Is it an 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 represented by 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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