Method for reducing the content of nickel and iron in high-purity cobalt plates prepared by electrowinning

Abstract

This invention provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrodeposition. The method includes the following steps: mixing an acidic aqueous solution of cobalt salt and a complexing agent uniformly, adjusting the pH to obtain an initial electrolysis solution; placing a cathode plate and an anode plate in the initial electrolysis solution for electrodeposition to obtain a high-purity cobalt plate. This invention utilizes the addition of a complexing agent during electrodeposition. The complexing strength of the complexing agent for nickel and iron ions is greater than that for cobalt ions; that is, the corresponding complexation stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, nickel and iron ions are preferentially complexed, allowing cobalt ions to exist in a free state, limiting the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the goal of simultaneously reducing their content in the high-purity cobalt plate. The method provided by this invention eliminates the complex separation steps of trace nickel and iron elements in the raw cobalt solution, i.e., it does not require complex processes and harsh reaction conditions, balancing the efficiency and cost of high-purity cobalt plate preparation.

Description

Technical Field

[0001] This invention relates to the field of low-impurity high-purity cobalt plate preparation technology, and in particular to a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. Background Technology

[0002] High-purity metals play a pivotal role in the field of integrated circuits, serving as key basic materials that support the miniaturization and high performance of chip processes. Among them, high-purity cobalt, with its excellent conductivity, magnetic properties, and thin film formation characteristics, is widely used in the preparation of sputtering targets and is a core raw material for key structures such as chip interconnects, gates, and barrier layers.

[0003] Currently, the conventional industrial preparation process for high-purity cobalt still mainly relies on electrowinning. This process requires extremely high purity of the raw cobalt solution, therefore, the effectiveness of deep purification and impurity removal of the cobalt solution at the front end determines the quality of the final cobalt product. Existing separation technologies mainly include solvent extraction, ion exchange, and extraction chromatography. However, because cobalt has similar properties to impurity elements such as nickel, iron, and copper, and their separation coefficients are small, the resulting cobalt product contains excessive impurities, failing to meet the impurity content requirements for 5N high-purity cobalt. Furthermore, traditional separation technologies primarily use various types of specialized resins to separate trace amounts of Ni, Fe, and Cu from the cobalt salt solution through ion exchange. Typically, due to the high cobalt concentration, a significant amount of cobalt is lost after resin purification, and the resin has a limited cycle life, resulting in high operating costs. For example, CN115627499A uses sulfuric acid or electric current to dissolve cobalt plates to prepare a cobalt sulfate solution, then uses resin to remove impurities from the cobalt sulfate solution, and finally uses electrowinning to prepare high-purity cobalt. This method involves complex raw material preparation, difficulty in controlling pH and cobalt concentration during the dissolution step, a long dissolution time, and increased production costs due to the use of resin. Even if resin is replaced and ion exchange is used in conjunction with other impurity removal processes, only the removal / reduction of a single impurity element can be achieved. It is impossible to simultaneously reduce the impurity elements in high-purity cobalt. For example, CN103966627A uses electrowinning for impurity removal and iron removal by masking iron ions. Although this simplifies the high-purity cobalt preparation process and avoids the use of ion exchange and hydrolysis precipitation methods, which have high metal loss and are complex to operate, thus reducing the production cost of high-purity cobalt, this process can only remove iron and cannot remove nickel at the same time. To remove nickel, an additional nickel removal process must be added, making the whole process complex and cumbersome.

[0004] Therefore, how to provide a method that can simultaneously reduce the nickel and iron content in high-purity cobalt plates prepared by electrowinning, effectively reduce the nickel and iron content in high-purity cobalt plates while ensuring high cobalt recovery rate, and also take into account efficiency and cost, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrodeposition. This invention utilizes a complexing agent added during electrodeposition. The complexing agent has a stronger complexing strength for nickel and iron ions than for cobalt ions; that is, the corresponding complexation stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, it preferentially complexes nickel and iron ions, allowing cobalt ions to exist in a free state, thus limiting the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the goal of simultaneously reducing their content in the high-purity cobalt plate. The method provided by this invention eliminates the complex separation steps of trace nickel and iron elements in the raw cobalt solution, requiring no complex processes or harsh reaction conditions. It balances the efficiency and cost of high-purity cobalt plate preparation, and can be widely applied to the production processes of high-purity cobalt plates in various factories, reducing factory renovation costs.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning, the method comprising the following steps:

[0008] The acidic aqueous solution of cobalt salt and the complexing agent are mixed evenly, and the pH is adjusted to obtain the initial electrolysis solution. The cathode plate and the anode plate are placed in the initial electrolysis solution and electrodeposited to obtain a high-purity cobalt plate.

[0009] It should be noted that the high-purity cobalt plate in this invention refers to a high-purity cobalt plate with a purity of 5N.

[0010] This invention utilizes a complexing agent added during electrodeposition. The complexing agent has a stronger complexing strength for nickel and iron ions than for cobalt ions; that is, the corresponding complexation stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, it preferentially complexes nickel and iron ions, allowing cobalt ions to exist in a free state, thus limiting the simultaneous reduction and deposition of nickel and iron elements. This achieves the goal of simultaneously reducing the content of both in high-purity cobalt plates. The method provided by this invention eliminates the complex separation steps of trace nickel and iron elements in the raw cobalt solution, requiring no complex processes or harsh reaction conditions. It balances the efficiency and cost of high-purity cobalt plate preparation and can be widely applied to the production processes of high-purity cobalt plates in various factories, reducing plant renovation costs.

[0011] As a preferred embodiment of the present invention, the cobalt concentration in the acidic aqueous solution of the cobalt salt is 40 g / L-120 g / L, for example, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, or 120 g / L.

[0012] Preferably, the nickel content in the acidic aqueous solution of the cobalt salt is 0.5ppm-2ppm, such as 0.5ppm, 0.8ppm, 1ppm, 1.2ppm, 1.5ppm, 1.8ppm or 2ppm.

[0013] Preferably, the iron content in the acidic aqueous solution of the cobalt salt is 0.5ppm-2ppm, such as 0.5ppm, 0.8ppm, 1ppm, 1.2ppm, 1.5ppm, 1.8ppm or 2ppm.

[0014] Preferably, the acidic aqueous solution of the cobalt salt includes at least one of the following: a de-oiled cobalt wire P507 back-extraction solution, a battery-grade cobalt sulfate crystal solution, or a 3N8 cobalt plate acid leaching solution.

[0015] The Cu element content of the P507 back-extraction solution after degreasing in this invention is less than 0.1 ppm.

[0016] As a preferred embodiment of the present invention, the complexing agent includes at least one of EDTA, NaCN, oxalic acid, or oxalate.

[0017] The complexing agent of the present invention has a greater complexing strength for nickel and iron ions than for cobalt ions. That is, the complexing stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, nickel and iron ions can be preferentially complexed, limiting the simultaneous reduction and deposition of nickel and iron elements.

[0018] Preferably, the oxalate includes at least one of sodium oxalate, potassium oxalate, or ammonium oxalate.

[0019] As a preferred technical solution of the present invention, the amount of complexing agent added is 100 to 2000 times the total nickel and iron content in the acidic aqueous solution of the cobalt salt, for example, 100 times, 300 times, 500 times, 800 times, 1000 times, 1200 times, 1500 times, 1800 times or 2000 times.

[0020] In this invention, the amount of complexing agent added is controlled to be 100-2000 times the total nickel and iron content in the acidic aqueous solution of cobalt salt. This maximizes the complexation of nickel and iron elements, effectively reducing the nickel and iron content in the high-purity cobalt plate while maintaining cobalt recovery rate. If the amount of complexing agent added is too small, the complexation effect on impurities is insufficient, failing to maximize the complexation of nickel and iron ions, thus failing to effectively reduce the nickel and iron content in the resulting high-purity cobalt plate, easily exceeding the standard. If the amount of complexing agent added is too large, in addition to complexing nickel and iron ions, it will also complex a large amount of cobalt ions, resulting in a significant loss of cobalt and a substantial decrease in cobalt recovery rate. Furthermore, a large amount of complexing agent decomposes, easily contaminating the cathode.

[0021] As a preferred technical solution of the present invention, the pH of the initial electrolytic solution is 1-4, such as 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8 or 4.

[0022] As a preferred embodiment of the present invention, the current density of the electrodeposition is 10 A / m. 2 -500A / m 2 For example, 10A / m 2 30A / m 2 50A / m 2 80A / m 2 100A / m 2 120A / m 2 150A / m 2 180A / m 2 200A / m 2 220A / m 2 250A / m 2 280A / m 2 300A / m 2 320A / m 2 350A / m 2 380A / m 2 400A / m 2 420A / m 2 450A / m 2 480A / m 2 Or 500A / m 2 wait.

[0023] In this invention, the current density for electrodeposition is controlled to be 10 A / m. 2 -500A / m 2 This approach can balance the production volume and quality of high-purity cobalt plates. However, if the electrodeposition current density is too high, the complexing agent decomposes too quickly, and impurities are more easily electrodeposited, increasing the proportion of impurity ions deposited.

[0024] Preferably, the electrodeposition temperature is 40℃-80℃, such as 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃ or 80℃.

[0025] Preferably, the electrodeposition time is 48h-96h, such as 48h, 60h, 72h, 84h or 96h.

[0026] As a preferred embodiment of the present invention, the cathode plate includes a titanium plate or a cobalt plate.

[0027] Preferably, the anode plate comprises a titanium-coated noble metal oxide plate or a titanium plate.

[0028] As a preferred embodiment of the present invention, after the electrodeposition is completed, the process further includes the steps of stripping, polishing, acid washing and drying.

[0029] Preferably, the concentration of the acid solution used for pickling is 2M-4M, such as 2M, 2.5M, 3M, 3.5M or 4M.

[0030] Preferably, the acid used in the pickling includes hydrochloric acid.

[0031] Preferably, the method of uniform mixing includes stirring and dissolving.

[0032] As a preferred embodiment of the present invention, the nickel content in the high-purity cobalt plate is <0.5ppm, for example 0.49ppm, 0.45ppm, 0.4ppm, 0.35ppm, 0.3ppm, 0.25ppm, 0.2ppm, 0.15ppm, 0.1ppm, 0.05ppm or 0.01ppm, etc., preferably <0.3ppm.

[0033] As a preferred embodiment of the present invention, the iron content in the high-purity cobalt plate is <0.5ppm, for example 0.49ppm, 0.45ppm, 0.4ppm, 0.35ppm, 0.3ppm, 0.25ppm, 0.2ppm, 0.15ppm, 0.1ppm, 0.05ppm or 0.01ppm, etc., preferably <0.35ppm.

[0034] It should be noted that in this invention, ppm refers to mass content.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] 1) This invention adds a complexing agent during electrodeposition. The complexing strength of the complexing agent for nickel and iron ions is greater than that for cobalt ions. That is, the complexing stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, nickel and iron ions will be preferentially complexed, so that cobalt ions exist in a free state, which restricts the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the purpose of simultaneously reducing the content of both in high-purity cobalt plates.

[0037] 2) The method for reducing the nickel and iron content in high-purity cobalt plates prepared by the electrodeposition method provided by this invention eliminates the complicated separation steps of trace nickel and iron elements in the raw cobalt solution. That is, it does not require complicated processes and harsh reaction conditions, and takes into account the preparation efficiency and cost of high-purity cobalt plates. It can be widely applied to the production process of high-purity cobalt plates in various factories, and reduces the cost of factory renovation. Detailed Implementation

[0038] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0039] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0040] The degreased cobalt wire P507 back-extraction solution used in the specific embodiments of this invention is obtained through the following steps:

[0041] The cobalt intermediate was reduced and acid-leached, then pre-extracted with P204 to remove impurities, yielding a P204 raffinate. This raffinate was then countercurrently mixed with saponified P507 to obtain a cobalt-loaded P507 organic phase. The organic phase was washed with 0.5 mol / L dilute hydrochloric acid to remove trace amounts of Ni entrained in the organic phase. 2+ A high-purity cobalt-supported organic phase was obtained, and back-extracted with 1.5 mol / L HCl to obtain cobalt wire P507 back-extracting solution. The organic phase residue was adsorbed by resin and diluted with deionized water to obtain oil-free cobalt wire P507 back-extracting solution (the cobalt concentration was adjusted to 40 g / L-120 g / L, the nickel content to 0.5 ppm-2 ppm, and the iron content to 0.5 ppm-2 ppm by adjusting the amount of deionized water added).

[0042] Example 1

[0043] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning, the method comprising the following steps:

[0044] The deoiled cobalt wire P507 back-extraction solution (cobalt concentration 40 g / L, nickel content 0.5 ppm, iron content 0.5 ppm) and EDTA and NaCN (mass ratio 1:1) were mixed and stirred to dissolve. The amount of EDTA and NaCN added was 1000 times the total nickel and iron content in the deoiled cobalt wire P507 back-extraction solution. The pH was adjusted to 1 to obtain the initial electrolysis solution.

[0045] A titanium plate (cathode plate) and a titanium-coated ruthenium-iridium plate (RuO2-IrO2 / Ti, anode plate) were placed in the initial electrolysis solution at a current density of 10 A / m. 2 The electrodeposition temperature was 40℃, and the electrodeposition time was 72h. Then, the obtained cobalt plate was peeled off from the surface of the titanium plate. The surface of the cobalt plate in contact with the titanium plate was polished, and then washed with 3M hydrochloric acid and dried to obtain a high-purity cobalt plate.

[0046] Example 2

[0047] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning, the method comprising the following steps:

[0048] The degreased cobalt wire P507 back-extraction solution (with cobalt concentration adjusted to 80 g / L, nickel content to 1 ppm, and iron content to 1 ppm) was mixed with oxalic acid and sodium oxalate (mass ratio of 1:1) and stirred to dissolve. The amount of oxalic acid and sodium oxalate added was 100 times the total nickel and iron content in the degreased cobalt wire P507 back-extraction solution. The pH was adjusted to 2 to obtain the initial electrolysis solution.

[0049] A titanium plate (cathode plate) and a titanium-coated ruthenium-iridium plate (RuO2-IrO2 / Ti, anode plate) were placed in the initial electrolysis solution at a current density of 200 A / m. 2 The electrodeposition temperature was 60℃, and the electrodeposition time was 72h. Then, the obtained cobalt plate was peeled off from the surface of the titanium plate. The surface of the cobalt plate in contact with the titanium plate was polished, and then washed with 3M hydrochloric acid and dried to obtain a high-purity cobalt plate.

[0050] Example 3

[0051] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning, the method comprising the following steps:

[0052] The deoiled cobalt wire P507 back-extraction solution (with cobalt concentration adjusted to 120 g / L, nickel content to 2 ppm, and iron content to 2 ppm) was mixed with EDTA and oxalic acid (mass ratio 1:1) and stirred to dissolve. The amount of EDTA and oxalic acid added was 2000 times the total nickel and iron content in the deoiled cobalt wire P507 back-extraction solution. The pH was adjusted to 4 to obtain the initial electrolysis solution.

[0053] A titanium plate (cathode plate) and a titanium-coated ruthenium-iridium plate (RuO2-IrO2 / Ti, anode plate) were placed in the initial electrolysis solution at a current density of 500 A / m. 2 The electrodeposition temperature was 80℃, and the electrodeposition time was 72h. Then, the obtained cobalt plate was peeled off from the surface of the titanium plate. The surface of the cobalt plate in contact with the titanium plate was polished, and then washed with 3M hydrochloric acid and dried to obtain a high-purity cobalt plate.

[0054] Example 4

[0055] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Example 1 is that EDTA and NaCN (mass ratio of 1:1) are replaced with EDTA of the same mass, while the rest of the preparation method and parameters remain the same as in Example 1.

[0056] Example 5

[0057] This embodiment provides a method for reducing the nickel and iron content in the preparation of high-purity cobalt by electrowinning. The difference between this method and Example 1 is that the amount of EDTA and NaCN added is 500 times the total nickel and iron content, while the rest of the preparation method and parameters remain the same as in Example 1.

[0058] Example 6

[0059] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Example 1 is that the amount of EDTA and NaCN added is 1500 times the total nickel and iron content, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0060] Example 7

[0061] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Example 1 is that the amount of EDTA and NaCN added is 50 times the total nickel and iron content, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0062] Example 8

[0063] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Example 1 is that the amount of EDTA and NaCN added is 2100 times the total nickel and iron content, while the other preparation methods and parameters remain the same as in Example 1.

[0064] Example 9

[0065] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Embodiment 1 is that the current density is 530 A / m. 2 The remaining preparation methods and parameters are consistent with those in Example 1.

[0066] Example 10

[0067] This embodiment provides a method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrowinning. The difference between this method and Example 1 is that EDTA and NaCN are replaced with ammonia water of the same mass (mass concentration of 10wt%), while the rest of the preparation methods and parameters remain the same as in Example 1.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing high-purity cobalt plates by electrowinning. The difference between this method and Example 1 is that the addition of EDTA and NaCN is omitted to obtain high-purity cobalt plates, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0070] The nickel and iron contents of the high-purity cobalt plates provided in Examples 1-10 and Comparative Example 1 were determined. The specific testing method involved using GD-MS to detect the Fe and Ni contents of the high-purity cobalt plates. The specific test results are shown in Table 1.

[0071] Table 1

[0072]

[0073] The test results show that:

[0074] (1) As can be seen from Examples 1 to 6, the present invention adds a complexing agent during electrodeposition. The complexing strength of the complexing agent for nickel ions and iron ions is greater than that for cobalt ions. That is, the complexing stability of nickel complexes and iron complexes is higher than that of cobalt complexes. Therefore, nickel ions and iron ions will be preferentially complexed, so that cobalt ions exist in a free state, which restricts the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the purpose of simultaneously reducing the content of both in high-purity cobalt plates.

[0075] Specifically, the high-purity cobalt plate contains less than 0.3 ppm of nickel and less than 0.35 ppm of iron.

[0076] (2) As can be seen from Examples 1 and 7-8, by further controlling the amount of complexing agent added to 100-2000 times the total content of nickel and iron in the acidic aqueous solution of cobalt salt, the present invention can achieve the maximum complexation of nickel and iron elements, effectively reduce the content of nickel and iron elements in high-purity cobalt plates, and at the same time take into account the recovery rate of cobalt. If the amount added is too small, the complexation effect of impurities is not enough and it is easy to exceed the standard. If the amount added is too large, in addition to complexing nickel ions and iron ions, a large amount of cobalt ions will be complexed, resulting in a large loss of cobalt elements. Moreover, the additive decomposes too much during the electrowinning process, which can easily cause pollution such as suspended particles in the cathode.

[0077] (3) As can be seen from Examples 1 and 9, the current density for electrodeposition controlled by the present invention is 10 A / m. 2 -500A / m 2 This approach can balance the production volume and quality of high-purity cobalt plates.

[0078] (4) As can be seen from Examples 1 and 10, the present invention selects a complexing agent with a greater complexing strength for nickel and iron ions than for cobalt ions, which can preferentially complex nickel and iron ions, so that cobalt ions exist in a free state, restricting the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the purpose of simultaneously reducing the content of both in the high-purity cobalt plate. However, when ammonia is used as a complexing agent, since its complexing strength for cobalt is greater than that for nickel and iron, it cannot achieve the effect of reducing nickel and iron.

[0079] (5) As can be seen from Example 1 and Comparative Example 1, the present invention adds a complexing agent during electrodeposition. The complexing strength of the complexing agent for nickel ions and iron ions is greater than that for cobalt ions. That is, the complexing stability of nickel complexes and iron complexes is higher than that of cobalt complexes. Therefore, nickel ions and iron ions will be preferentially complexed, so that cobalt ions exist in a free state, which restricts the simultaneous reduction and deposition of nickel and iron elements, thereby achieving the purpose of reducing the content of both in the high-purity cobalt plate. If the addition of the complexing agent is omitted, the nickel and iron content in the obtained high-purity cobalt plate will seriously exceed the standard, and it is impossible to reduce their content in the high-purity cobalt plate.

[0080] In summary, this invention utilizes a complexing agent added during electrodeposition. The complexing agent has a stronger complexing strength for nickel and iron ions than for cobalt ions; that is, the corresponding complexation stability of nickel and iron complexes is higher than that of cobalt complexes. Therefore, it preferentially complexes nickel and iron ions, allowing cobalt ions to exist in a free state, thus limiting the simultaneous reduction and deposition of nickel and iron elements. This achieves the goal of simultaneously reducing the content of both in high-purity cobalt plates. The method provided by this invention eliminates the complex separation steps of trace nickel and iron elements in the raw cobalt solution, requiring no complex processes or harsh reaction conditions. It balances the efficiency and cost of high-purity cobalt plate preparation and can be widely applied to the production processes of high-purity cobalt plates in various factories, reducing factory renovation costs.

[0081] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for reducing the nickel and iron content in high-purity cobalt plates prepared by electrodeposition, characterized in that, The method includes the following steps: The acidic aqueous solution of cobalt salt and the complexing agent are mixed evenly, and the pH is adjusted to obtain the initial electrolysis solution. The cathode plate and the anode plate are placed in the initial electrolysis solution and electrodeposited to obtain a high-purity cobalt plate.

2. The method according to claim 1, characterized in that, The cobalt concentration in the acidic aqueous solution of the cobalt salt is 40 g / L-120 g / L; Preferably, the nickel content in the acidic aqueous solution of the cobalt salt is 0.5 ppm to 2 ppm; Preferably, the iron content in the acidic aqueous solution of the cobalt salt is 0.5 ppm to 2 ppm; Preferably, the acidic aqueous solution of the cobalt salt includes at least one of the following: a de-oiled cobalt wire P507 back-extraction solution, a battery-grade cobalt sulfate crystal solution, or a 3N8 cobalt plate acid leaching solution.

3. The method according to claim 1 or 2, characterized in that, The complexing agent includes at least one of EDTA, NaCN, oxalic acid, or oxalate. Preferably, the oxalate includes at least one of sodium oxalate, potassium oxalate, or ammonium oxalate.

4. The method according to any one of claims 1-3, characterized in that, The amount of complexing agent added is 100 to 2000 times the total nickel and iron content in the acidic aqueous solution of the cobalt salt.

5. The method according to any one of claims 1-4, characterized in that, The initial solution for electrolysis has a pH of 1-4.

6. The method according to any one of claims 1-5, characterized in that, The current density of the electrodeposition is 10 A / m 2 -500A / m 2 ; Preferably, the electrodeposition temperature is 40℃-80℃; Preferably, the electrodeposition time is 48h-96h.

7. The method according to any one of claims 1-6, characterized in that, The cathode plate may be a titanium plate or a cobalt plate; Preferably, the anode plate comprises a titanium-coated noble metal oxide plate or a titanium plate.

8. The method according to any one of claims 1-7, characterized in that, After the electrodeposition is completed, the process also includes peeling, polishing, acid washing and drying steps; Preferably, the concentration of the acid solution used in the pickling is 2M-4M; Preferably, the acid used in the pickling includes hydrochloric acid.

9. The method according to any one of claims 1-8, characterized in that, The nickel content in the high-purity cobalt plate is <0.5ppm, preferably <0.3ppm.

10. The method according to any one of claims 1-9, characterized in that, The high-purity cobalt plate has an iron content of <0.5ppm, preferably <0.35ppm.

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