Method for producing nickel compound or nickel hydroxide

Abstract

Provided is a method for producing a nickel compound, the method including: a step for preparing raw material metal compounds which include a first metal including at least nickel and a second metal including at least one component selected from the group consisting of magnesium, calcium, iron, silicon, zinc, copper, aluminum, and chromium; a step for mixing the raw material metal compounds with an aqueous acid solution for acid leaching to produce a first solution containing ions of the first metal and the second metal; a first production step for neutralizing the first solution with a first alkali to produce a solid matter containing the second metal and a second solution containing at least ions of the first metal; a step for subjecting the second solution and the solid matter to solid / liquid separation; a second production step for mixing the second solution with a second alkali including at least ammonia to produce a nickel compound containing at least nickel as the first metal and a third solution; and a step for subjecting the nickel compound and the third solution to solid / liquid separation.

Description

Method for producing nickel compounds or nickel hydroxides CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-059308, filed on April 2, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a method for producing nickel compounds or nickel hydroxides.

[0003] Patent Document 1 describes a process for producing a crude nickel hydroxide starting material, which contains cobalt and nickel and, as impurities other than the cobalt and nickel, one or more of magnesium, calcium, iron, silicon, manganese, zinc, copper, aluminum, and chromium, and in which the nickel content is greater than the cobalt content, by adding water to the starting material, stirring and mixing the material to form a slurry, filtering the resulting precipitate, washing the precipitate with water, and removing the impurities of magnesium and calcium from the precipitate to obtain a crude hydroxide after washing with water; and leaching the crude hydroxide after washing with acid to obtain a crude hydroxide containing cobalt and nickel and the impurities of manganese, magnesium, iron, silicon, calcium, and the like. The paper proposes a "method for producing a cobalt- and nickel-containing solution comprising: a leaching step of obtaining a leaching solution containing one or more of iron, silicon, aluminum, copper and chromium; a neutralization step of adding a pH adjuster to the leaching solution to neutralize it, then subjecting it to solid-liquid separation to remove a neutralization residue containing one or more of the impurities iron, silicon, aluminum and chromium to obtain a neutralized solution; and an extraction step of subjecting the obtained neutralized solution to solvent extraction with an extractant to extract and remove one or more of the impurities manganese, magnesium, calcium, zinc and copper to obtain an extracted solution containing cobalt and nickel simultaneously and with reduced impurities.

[0004] Patent Document 2 proposes "a method for producing high-purity nickel sulfate, the method comprising, in a manufacturing process for producing high-purity nickel sulfate from a solution containing nickel, subjecting the solution containing nickel in the manufacturing process to an impurity element removal treatment process shown in the following (1) to (3)."

[0005] (1) A hydroxide step in which an alkali is added to a part of the solution containing nickel in the manufacturing process to form a hydroxide slurry consisting of a precipitate in which the nickel contained in the solution is converted into nickel hydroxide and a post-hydration liquid other than the precipitate, and nickel components are recovered from the solution containing nickel in the manufacturing process.

[0006] (2) A solid-liquid separation step in which the hydroxide slurry obtained in the hydroxide step (1) is separated into nickel hydroxide as a precipitate and a post-hydration liquid.

[0007] (3) A neutralization step is proposed in which the post-hydroxylation liquid separated in the solid-liquid separation step (2) is neutralized to produce a neutralized precipitate containing impurity elements, and the impurity elements contained in the solution in the manufacturing process are recovered.

[0008] International Publication No. 2020 / 196046 Japanese Patent Application Laid-Open No. 2013-151717

[0009] Both Patent Documents 1 and 2 include a solid-liquid separation process. However, the efficiency of solid-liquid separation depends greatly on the particle size of the solid content. The larger the particle size, the easier the solid-liquid separation becomes.

[0010] One aspect of the present disclosure relates to a method for producing a nickel compound, the method comprising: a step of preparing a raw metal compound containing a first metal including at least nickel and a second metal including at least one selected from the group consisting of magnesium, calcium, iron, silicon, zinc, copper, aluminum, and chromium (preparation step); a step of mixing the raw metal compound with an acid aqueous solution and obtaining a first solution containing ions of the first metal and the second metal by acid leaching (leaching step); a first production step of neutralizing the first solution with a first alkali to produce a solid content including the second metal and a second solution containing at least ions of the first metal; a step of performing solid-liquid separation between the second solution and the solid content (first solid-liquid separation step); a second production step of mixing the second solution with a second alkali including at least ammonia to produce a nickel compound containing at least nickel as the first metal and a third solution; and a step of performing solid-liquid separation between the nickel compound and the third solution (second solid-liquid separation step).

[0011] According to the present disclosure, it is possible to produce nickel compounds with particle sizes suitable for solid-liquid separation. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0012] Hereinafter, embodiments of the present disclosure will be described using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that known components may be applied to components other than those characteristic of the present disclosure. In this specification, when a "range from numerical value A to numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0013] In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of them may be selected and used alone, or two or more may be used in combination, unless otherwise specified.

[0014] The present disclosure also encompasses combinations of two or more features arbitrarily selected from the appended claims, i.e., two or more features arbitrarily selected from the appended claims can be combined unless a technical contradiction arises.

[0015] <Preparation Step> In a method for producing a nickel compound according to one embodiment of the present disclosure (hereinafter also referred to as "production method (M)"), a raw metal compound containing a first metal including at least nickel and a second metal including at least one selected from the group consisting of magnesium, calcium, iron, silicon, zinc, copper, aluminum, and chromium is used as a starting material. The first metal is a metal to be purified, and the second metal is considered an impurity. In addition to nickel, the first metal may further include at least one selected from the group consisting of cobalt and manganese. The first metal may also include three metals: nickel, cobalt, and manganese.

[0016] Typically, the raw metal compound may be an intermediate raw material used in the production of metallic nickel, nickel oxide, nickel sulfate, etc. The intermediate raw material may be a crude metal hydroxide (Metal Hydroxide Precipitate (MHP)), nickel matte, etc. MHP is an unpurified hydroxide, a compound containing nickel hydroxide as a main component and further containing cobalt, manganese, and other metal elements. Of all the metal elements contained in such a raw metal compound, nickel atoms have the highest molar fraction. Therefore, the compound to be produced by production method (M) is a nickel compound, and of all the metal elements contained in the nickel compound, nickel atoms have the highest molar fraction.

[0017] In a typical raw metal compound, the content of the second metal is, for example, about 5 mass% of all metal elements contained in the raw metal compound, the content of magnesium atoms is about 3 mass%, and the content of zinc atoms is about 1 mass%.

[0018] Oxides containing a first metal, i.e., nickel, and possibly cobalt and manganese, are in high demand as raw materials for positive electrode active materials in nonaqueous electrolyte secondary batteries. Nonaqueous electrolyte secondary batteries include lithium ion secondary batteries, lithium metal secondary batteries, and all-solid-state secondary batteries. Such oxides are typically produced using, for example, nickel sulfate as a primary raw material. However, the process of producing nickel sulfate from intermediate raw materials containing many impurities consumes a large amount of energy, and therefore, simplification of the process is desired.

[0019] The present disclosure relates to a process for obtaining a nickel compound having an increased purity of a first metal, which is an active ingredient, from a raw metal compound containing impurities.The present disclosure can be said to be a method for producing a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery.

[0020] <Leaching Step> The manufacturing method (M) includes a step of mixing a raw metal compound with an acid aqueous solution and obtaining a first solution containing ions of a first metal and a second metal by acid leaching. For example, by mixing the raw metal compound with an aqueous sulfuric acid solution, the first metal and the second metal contained in the raw metal compound are eluted as ions into the aqueous sulfuric acid solution.

[0021] The concentration of the aqueous acid solution is not particularly limited, but may be, for example, 0.1 mol / L to 5 mol / L. In addition to sulfuric acid, nitric acid, hydrochloric acid, organic acids, etc. may be used as the acid. The temperature of the aqueous acid solution is not particularly limited, but may be, for example, 0°C to 60°C (typically room temperature). The pH of the first solution containing various metal ions obtained by acid leaching may be controlled to, for example, pH 4.0 or less, and preferably pH 3.0 or less or 2.0 or less. The total ion concentration of the first metal and the second metal in the first solution may be controlled to, for example, 0.1 mol / L to 3 mol / L.

[0022] Next, as an optional process, a reduction treatment of the trivalent metal may be performed. For example, by adding an appropriate amount of a reducing agent to a mixture of the raw metal compound and the aqueous sulfuric acid solution, the trivalent metal (e.g., nickel) is reduced to a divalent metal, thereby improving the elution rate of the first metal ion. As the reducing agent, a weakly acidic reducing agent is preferable, such as NaHSO. ３ Examples of suitable solutions include ascorbic acid, citric acid, oxalic acid, and hydrogen peroxide. For example, trivalent nickel can be reduced to divalent nickel by the following reaction: Other metals react in a similar manner.

[0023] Ni ２ O ３ +NaHSO ３ +2H ２ O → 2Ni ２＋ +SO ４ ２－ +Na ＋ +5H＋

[0024] <First Generation Step> Next, the first generation step is performed, in which the first solution is neutralized with a first alkali to generate a solid content containing a second metal and a second solution containing ions of at least the first metal. In the first generation step, a solid content containing at least one second metal selected from the group consisting of calcium, iron, silicon, zinc, copper, aluminum, and chromium is generated. Most of the ions of the second metal precipitate at a pH of 7.0 or less (e.g., pH = 4.5 to 6.0). For example, the following reaction proceeds:

[0025] H ２ SO4 + CaCO ３ →CaSO ４ +H ２ O+CO ２ FeSO4 + 2H ２ O→Fe(OH)2+H ２ SO4 Fe(OH)2+O2→+Fe ２ O3 + H ２ O

[0026] The first alkali for neutralization may be, for example, lime, calcium carbonate, calcium oxide, or a metal hydroxide such as sodium hydroxide or calcium hydroxide. An aqueous solution of the first alkali dissolved in water may also be used. The concentration of the first aqueous alkali solution may be, for example, 1 mol / L to 10 mol / L.

[0027] Alternatively, divalent metal ions may be oxidized to trivalent ions by bubbling oxygen into the first solution, and then precipitated. For example, Fe ２＋ ions as Fe ２ O ３ It can be precipitated as

[0028] <First Solid-Liquid Separation Step> Next, a step of solid-liquid separation into the second solution and the solid content is performed. Solid-liquid separation can be performed using a vacuum dehydrator, centrifugal concentration dehydrator, multiple-disk dehydrator, filter press, belt press, screw press, rotary drum screen, belt screen, vibrating screen, multiple-disk wave filter, suction filtration, or other methods. The second solution contains dissolved ions of the first metal and may also contain ions of some second metals, such as magnesium. The concentration of the first metal ions in the second solution is, for example, 0.5 mol / L to 2.5 mol / L.

[0029] <Second Generation Step> Next, a second generation step is performed in which the separated second solution is mixed with a second alkali containing at least ammonia to generate a nickel compound containing at least nickel as the first metal and a third solution (residue solution).

[0030] The second solution contains at least nickel and may contain at least one selected from the group consisting of cobalt, manganese, and magnesium. By adding a second alkali to the second solution and controlling the pH to 7.5 to 9.5 (e.g., pH = 8.8 to 9.2), the first metals, nickel, cobalt, and manganese, form precipitates. This allows, for example, a nickel compound containing at least nickel with a sufficiently reduced impurity content. Furthermore, when the first metal contains nickel, cobalt, and manganese, a nickel-cobalt-manganese composite compound can be obtained. Such compounds are suitable for use as raw materials for positive electrode active materials in lithium-ion secondary batteries, lithium metal secondary batteries, and the like.

[0031] The second alkali may be, for example, a metal hydroxide such as sodium hydroxide or potassium hydroxide, or ammonia. An aqueous solution of the second alkali dissolved in water may also be used. The concentration of the aqueous solution of the second alkali is, for example, 0.5N (normal) to 10N, or may be 0.5N to 2N, or may be 0.5N to 1.5N. The concentration of the aqueous solution of the second alkali other than ammonia may be, for example, 0.5N (normal) to 10N, or may be 0.5N to 2N, or may be 0.5N to 1.5N.

[0032] At a pH of 9.5 or less, magnesium does not precipitate and remains as ions in the third solution. That is, by controlling the pH of the third solution to 9.5 or less (preferably 9.0 or less), a nickel compound containing no magnesium can be produced. The pH may be controlled to 9.0 or more or 9.5 or more to co-precipitate magnesium with the first metal.

[0033] Here, it is important to mix ammonia as part of the second alkali into the second solution. In the coexistence of ammonia and an alkali other than ammonia, the rate of precipitation of nickel compounds is slow, and the particle size of the precipitate grows large. The particle size can be controlled by appropriately adjusting the amount of ammonia used.

[0034] Ammonia may be bubbled into the second solution, or an aqueous ammonia solution prepared by dissolving ammonia in water may be used. The concentration of the aqueous ammonia solution is, for example, 0.01N to 2N, and may be 0.5N to 1.5N.

[0035] In one preferred mixing method, the second solution and an aqueous solution of a second alkali other than ammonia are simultaneously added to an aqueous ammonia solution and mixed. Alternatively, the aqueous solution of a second alkali other than ammonia is mixed with a mixed solution obtained by mixing an aqueous ammonia solution and the second solution. When mixed in this manner, the reaction between the first metal ions and the second alkali does not proceed excessively quickly, making it easy to grow the particle size of the nickel compound large.

[0036] <Second solid-liquid separation step> Next, a step of solid-liquid separation into the third solution and the solid content is performed. Solid-liquid separation can be performed by a method such as a vacuum dehydrator, a centrifugal concentration dehydrator, a multiple disk dehydrator, a filter press, a belt press, a screw press, a rotary drum screen, a belt screen, a vibrating screen, a multiple disk wave filter, or suction filtration.

[0037] The median diameter at 50% cumulative volume in the volume-based particle size distribution of the nickel compound (hereinafter referred to as "D50") preferably exceeds 0.5 μm. In this case, solid-liquid separation can be performed quickly and efficiently, dramatically improving the productivity of the nickel compound. The D50 of the nickel compound may be controlled to 1 μm or more and 20 μm or less, 2 μm or more and 15 μm or less, or 4 μm or more and 10 μm or less.

[0038] If ammonia were not used in the second production step, the D50 of the nickel compound would be very small, and solid-liquid separation would take a long time.

[0039] <Nickel Compound> The nickel compound obtained by solid-liquid separation contains hydroxide and may usually contain sulfate. That is, the nickel compound is obtained as a mixture of hydroxide sulfate, hydroxide, and sulfate. The content of sulfate in the nickel compound is, for example, 20 mol% or less.

[0040] At least a portion of the nickel compound obtained by the above process is represented by the formula (1): (Ni ａ Co ｂ Mn ｃ )(OH)x(SO ４ ) ｙ In this case, the following conditions may be satisfied: a ≥ 0.5, b ≤ 0.2, c ≤ 0.5 (preferably c ≤ 0.3), a + b + c = 1, 1.5 ≤ x + 2y ≤ 2.5, y ≤ 0.2. The nickel compound may also contain about 0.1 to 1 atomic % of magnesium or zinc as a second metal as an impurity.

[0041] <Crystallization Step> The nickel compound or the mixture of hydroxysulfate, hydroxide, and sulfate may be further dissolved in an aqueous sulfuric acid solution to adjust the composition and particle size. Nickel hydroxide containing at least nickel as the first metal may be crystallized from the resulting nickel sulfate aqueous solution. For example, high-purity nickel hydroxide can be obtained by dissolving an alkali in the nickel sulfate aqueous solution. Through crystallization, the value of y in formula (1), which represents the composition of the nickel compound, can be reduced to, for example, y≦0.05. The resulting hydroxide can be suitably used as a raw material for positive electrode active materials in lithium-ion secondary batteries, lithium metal secondary batteries, and the like.

[0042] (Additional Notes) The above description discloses the following technology: (Technology 1) A method for producing a nickel compound, comprising: a step of preparing a raw metal compound containing a first metal including at least nickel and a second metal including at least one selected from the group consisting of magnesium, calcium, iron, silicon, zinc, copper, aluminum, and chromium; a step of mixing the raw metal compound with an acid aqueous solution and obtaining a first solution containing ions of the first metal and the second metal by acid leaching; a first production step of neutralizing the first solution with a first alkali to produce a solid content including the second metal and a second solution containing at least ions of the first metal; a step of performing solid-liquid separation of the second solution and the solid content; a second production step of mixing the second solution with a second alkali including at least ammonia to produce a nickel compound containing at least nickel as the first metal and a third solution; and a step of performing solid-liquid separation of the nickel compound and the third solution. (Technology 2) The method for producing a nickel compound according to Technology 1, wherein the first metal further comprises at least one selected from the group consisting of cobalt and manganese. (Technology 3) The method for producing a nickel compound according to Technology 1 or 2, wherein the mole fraction of nickel atoms is the highest among all metal elements contained in the nickel compound. (Technology 4) The method for producing a nickel compound according to any one of Technology 1 to 3, wherein the nickel compound comprises a hydroxysulfate, a hydroxide, and a sulfate, and the content of the sulfate is 20 mol% or less. (Technology 5) The method for producing a nickel compound according to Technology 1, wherein the nickel compound is a hydroxysulfate, a hydroxide, and a sulfate, and the content of the sulfate is 20 mol% or less. ａ Co ｂ Mn ｃ )(OH)x(SO ４ ) ｙWhen expressed as above, the following conditions are satisfied: a≧0.5, b≦0.2, c≦0.5 (preferably c≦0.3), a+b+c=1, 1.5≦x+2y≦2.5, y≦0.2. (Technology 6) The method for producing a nickel compound according to any one of Technologies 1 to 5, wherein the pH of the second solution is 7.0 or less. (Technology 7) The method for producing a nickel compound according to any one of Technologies 1 to 6, wherein the pH of the third solution is 9.5 or less. (Technology 8) The method for producing a nickel compound according to any one of Technologies 1 to 7, wherein the second production step produces the nickel compound having a median diameter at 50% cumulative volume in a volume-based particle size distribution of more than 0.5 μm. (Technology 9) The method for producing a nickel compound according to any one of Technologies 1 to 8, wherein the concentration of ions of the first metal in the second solution is 0.5 mol / L to 2.5 mol / L, the second alkali is mixed with the second solution as an aqueous alkali solution of 0.5 N to 10 N, and the ammonia is mixed with the second solution as an aqueous ammonia solution of 0.01 N to 2 N. (Technology 10) A method for producing a nickel hydroxide, further comprising the steps of: dissolving the nickel compound obtained by the method according to any one of Technologies 1 to 9 in an aqueous sulfuric acid solution to obtain a nickel sulfate aqueous solution; and crystallizing nickel hydroxide containing at least nickel as the first metal from the nickel sulfate aqueous solution.

[0043] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0044] Example 1 Preparation Step MHP (a crude nickel compound containing nickel, cobalt, and manganese and containing a second metal as an impurity) was prepared as a raw metal compound.

[0045] <Leaching step> 100 g of MHP was dispersed in 500 ml of water, and mixed with 125 ml of a 6.5 mol / L (13 N) aqueous sulfuric acid solution to adjust the overall sulfuric acid concentration to 0.8 mol / L (1.6 N). Acid leaching was performed at 25°C to obtain a first solution (pH = 1.9).

[0046] <First Forming Step> Calcium carbonate was added as a first alkali to the first solution, and the pH was controlled to 4.5 to 6 to form a solid material containing a second metal and a second solution.

[0047] <First solid-liquid separation step> The solid matter containing the second metal was filtered under suction to separate the second solution. Note that although the solid matter contained calcium sulfate, it did not take long to separate the calcium sulfate.

[0048] <Second Generation Step> The second solution (the ion concentration of the first metal was 1.0 mol / L) was mixed with a 1.0 mol / L aqueous NaOH solution and a 1 mol / L aqueous ammonia solution as the second alkali solution. Specifically, 500 mL of the second solution and 1000 mL of the aqueous NaOH solution were added to 250 mL of the aqueous ammonia solution in a beaker using a double jet method, and the three were simultaneously mixed. This produced a nickel compound A1 containing nickel, cobalt, and manganese, and a third solution. The pH of the third solution was controlled to 9.0, and magnesium ions were allowed to remain in the third solution.

[0049] <Second solid-liquid separation step> The nickel compound was separated from the third solution by suction filtration. The nickel compound obtained after drying had a D50 of 5.6 μm, and the time required for filtration was about 10 minutes.

[0050] Examples 2 to 4 Nickel compounds A2 to A4 were obtained in the same manner as in Example 1, except that the concentration of the aqueous ammonia solution was changed as shown in Table 1. The D50 of the produced nickel compounds and the time required for filtration are shown in Table 1.

[0051] Comparative Example 1 Nickel compound B1 was obtained by the same procedure as in Example 1, except that the aqueous ammonia solution was not used. The D50 of the produced nickel compound and the time required for filtration are shown in Table 1.

[0052]

[0053] As shown in Table 1, in Examples 1 to 4, the use of ammonia in the second generation step increased the particle size of the nickel compound, allowing for efficient filtration. On the other hand, in Comparative Example 1, the particle size of the nickel compound became so small that filtration took a long time, and furthermore, measurement of D50 was difficult due to aggregation of the nickel compound.

[0054] The method for producing a nickel compound according to the present disclosure is low cost, has a small environmental impact, and is highly economically rational.

[0055] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

Claims

1. A method for producing a nickel compound, comprising: a step of preparing a raw metal compound containing a first metal including at least nickel and a second metal including at least one selected from the group consisting of magnesium, calcium, iron, silicon, zinc, copper, aluminum, and chromium; a step of mixing the raw metal compound with an acid aqueous solution and obtaining a first solution containing ions of the first metal and the second metal by acid leaching; a first production step of neutralizing the first solution with a first alkali to produce a solid component including the second metal and a second solution containing at least ions of the first metal; a step of performing solid-liquid separation of the second solution and the solid component; a second production step of mixing the second solution with a second alkali including at least ammonia to produce a nickel compound containing at least nickel as the first metal and a third solution; and a step of performing solid-liquid separation of the nickel compound and the third solution.

2. The method for producing a nickel compound according to claim 1, wherein the first metal further comprises at least one selected from the group consisting of cobalt and manganese.

3. The method for producing a nickel compound according to claim 1, wherein the mole fraction of nickel atoms is the highest among all metal elements contained in the nickel compound.

4. The method for producing a nickel compound according to claim 1, wherein the nickel compound contains a hydroxysulfate, a hydroxide, and a sulfate, and the content of the sulfate is 20 mol% or less.

5. The nickel compound is reacted with a compound of the formula: (Ni ａ Co ｂ Mn ｃ )(OH)x(SO ４ ) ｙ The method for producing a nickel compound according to claim 1, wherein, when expressed by the formula (I), the following conditions are satisfied: a≧0.5, b≦0.2, c≦0.5, a+b+c=1, 1.5≦x+2y≦2.5, and y≦0.

2.

6. The method for producing a nickel compound according to claim 1, wherein the pH of the second solution is 7.0 or less.

7. The method for producing a nickel compound according to claim 1, wherein the pH of the third solution is 9.5 or less.

8. A method for producing a nickel compound according to claim 1, wherein the second production step produces the nickel compound having a median diameter at 50% cumulative volume in a volume-based particle size distribution of more than 0.5 μm.

9. The method for producing a nickel compound according to claim 1, wherein the concentration of ions of the first metal in the second solution is 0.5 mol / L to 2.5 mol / L, the second alkali is mixed with the second solution as an aqueous alkali solution of 0.5N to 10N, and the ammonia is mixed with the second solution as an aqueous ammonia solution of 0.01N to 2N.

10. A method for producing nickel hydroxide, further comprising the steps of: dissolving the nickel compound obtained by the method according to claim 1 in an aqueous sulfuric acid solution to obtain an aqueous nickel sulfate solution; and crystallizing nickel hydroxide containing at least nickel as the first metal from the aqueous nickel sulfate solution.

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