Method for electrodeposition of cobalt in cobalt sulfate system and application

Abstract

The invention relates to a method for electrodeposition of cobalt in a cobaltous sulfate system and application, the method comprises the following steps: S1, preparing an electrolyte containing cobaltous sulfate, and depositing a cobaltosic oxide film on the surface of a working electrode by adopting a cyclic voltammetry method; s2, stripping the cobaltosic oxide film from the working electrode and drying to obtain cobaltosic oxide powder; and S3, the cobaltosic oxide powder is subjected to ball milling at the temperature of 200-300 DEG C, and a cobaltosic oxide finished product is obtained. The deposition process is regulated and controlled through a cyclic voltammetry oxidation-reduction method, cobaltosic oxide is prepared through electro-deposition in a cobaltous sulfate system, lattice defects and the specific surface area of cobaltosic oxide are precisely regulated and controlled, and efficient deposition of cobaltosic oxide is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical material preparation, and particularly relates to a method for electrolytically depositing cobalt in a cobalt sulfate system and its application. Background Art

[0002] Cobalt tetroxide, a black powder or gray-black crystalline chemical with the chemical formula Co₃O₄, is insoluble in water. It has a wide range of industrial applications, including electronics, new energy vehicles, and energy storage devices. With the development of new energy and new materials, higher performance requirements are being placed on cobalt tetroxide.

[0003] Currently, the synthesis methods of cobalt tetroxide include hydrothermal method, sol-gel method and high-temperature calcination method, but these methods generally have the problems of complex process, high energy consumption, poor controllability of product morphology or insufficient product purity. Electrochemical deposition has the advantages of mild reaction conditions and strong controllability, but the existing technology mostly adopts constant current or constant potential deposition, and the product has low crystallinity and serious particle agglomeration, resulting in insufficient cycle stability of lithium-ion batteries, or insufficient regulation of material morphology and electrochemical properties. In addition, traditional electrodeposition products often require high-temperature post-treatment to achieve lithium battery performance optimization. Therefore, it is of great practical significance to develop an efficient, low-cost and high-purity method for preparing cobalt tetroxide. Summary of the Invention

[0004] The present invention aims to provide a method for electrodeposition of cobalt in a cobalt sulfate system, wherein cobalt tetroxide is obtained by electrodeposition on a working electrode through a cyclic voltammetric redox method, and has the advantages of high purity, uniform particle size, and good crystallinity. The method is applied to the field of lithium batteries, significantly improving the performance of lithium batteries and having broad application prospects.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for electrowinning cobalt in a cobalt sulfate system comprises the following steps: S1: Prepare an electrolyte containing cobalt sulfate and use cyclic voltammetry to deposit a cobalt oxide film on the surface of the working electrode; S2: peeling the cobalt oxide film from the working electrode and drying it to obtain cobalt oxide powder; S3: ball-milling the cobalt trioxide powder at 200-300° C. to obtain a finished cobalt trioxide product.

[0006] This technical solution uses cyclic voltammetry to prepare cobalt tetroxide, which helps induce the cobalt tetroxide to form a porous nanosheet structure. When the cobalt tetroxide is used as an electrode material for lithium batteries, it helps to increase the diffusion rate of lithium ions. In step S3, the main purpose of subjecting the cobalt tetroxide powder to ball milling at 200-300°C is to address the problem of particle morphology changes or localized agglomeration caused by the exfoliation process. Through heating and ball milling, particle agglomeration is reduced, particle morphology is optimized, lattice reconstruction is promoted, and the tap density, conductivity, and cyclic stability of the cobalt tetroxide material are improved.

[0007] Preferably, the specific steps of preparing the electrolyte are: using cobalt sulfate as a cobalt source, dissolving it in deionized water, preparing a cobalt solution with a concentration of 0.1-0.5 mol / L, and adjusting the pH of the electrolyte to 8.5-11 to promote arrive Transformation and guarantee Stable existence and promotion of oxidation reaction.

[0008] Preferably, the temperature of the electrolyte is 25-50° C. to avoid damage to the deposited layer structure caused by high temperature.

[0009] Preferably, the electrolyte further contains at least one of a dispersant, an oxidant, a complexing agent, a surfactant, and a binder. Specifically, the dispersant is sodium lauryl sulfate; the concentration of the dispersant in the electrolyte is 0.01-0.05 mol / L. The oxidant is ammonium persulfate or hydrogen peroxide, with a concentration of 0.01-0.05 mol / L, which is used to provide additional oxidizing capacity and enhance arrive The complexing agent is sodium citrate, ammonia or ammonium bicarbonate, with a concentration of 0.1-0.3 mol / L, used to adjust the pH of the electrolyte and stabilize The surfactant is preferably polyethylene glycol with a molecular weight of 4000-6000, which is used to control the product morphology. The binder is polyvinyl pyrrolidone.

[0010] The principle of cyclic voltammetry is: using anodic oxidation to Partial oxidation to , while simultaneously providing electrons through cathode reduction, ultimately depositing Co3O4 directly on the electrode surface. The cyclic voltammetry method employs a three-electrode system, comprising a working electrode, a counter electrode, and a reference electrode. Preferably, the working electrode is at least one of platinum sheet, carbon cloth, titanium sheet, FTO conductive glass, stainless steel, and graphite; pre-cleaning and activating the surface before operation facilitates the reaction. The counter electrode is a platinum sheet or graphite rod, and the reference electrode is a saturated Gangun electrode or Ag / AgCl.

[0011] Preferably, the scanning potential range of the cyclic voltammetry is -0.2~2.0V, the scanning rate is 10-50mV / s, and the number of cycles is 10-30 times.

[0012] Preferably, the anode potential range of the cyclic voltammetry is 1.2 to 2.0 V to ensure Oxidized to ; The cathode potential range is -1.2~0.2V to provide electrons and promote the reduction reaction.

[0013] Preferably, the specific operation steps of step S2 are: immersing the deposited working electrode in deionized water or ethanol solution, using an ultrasonic cleaner to peel off the cobalt tetroxide, and placing it in a vacuum drying oven to dry to obtain cobalt tetroxide powder.

[0014] Specifically, the power of the ultrasonic cleaning machine is 50-150W, and the time is 5-15 minutes.

[0015] Preferably, the drying temperature is 40-60° C. to avoid high-temperature decomposition.

[0016] Preferably, in step S3, the cobalt trioxide powder is ball-milled under an inert atmosphere for 1-4 hours, the rotation speed of the ball mill is 300-500 rpm, and the ball-to-material ratio is 5-10:1.

[0017] A cobalt trioxide is prepared by the above method.

[0018] A lithium battery electrode material comprises the above-mentioned cobalt tetroxide.

[0019] An application of the electrode material as described above in the preparation of a lithium battery, specifically, the cobalt trioxide is a precursor of a positive electrode material in a lithium battery, and is used to prepare a positive electrode material such as lithium cobalt oxide. .

[0020] Beneficial effects of the present invention: (1) The present invention regulates the deposition process by cyclic voltammetric redox method, prepares cobalt tetroxide by electrodeposition in a cobalt sulfate system, accurately controls the lattice defects and specific surface area of cobalt tetroxide, and realizes efficient deposition of cobalt tetroxide.

[0021] (2) The present invention combines the heated ball milling process to promote crystal structure optimization, reduce particle agglomeration, optimize particle morphology, and improve the material's tap density, conductivity, and cycle stability. It significantly improves the electrochemical properties and lithium ion diffusion rate of cobalt tetroxide, meets the needs of high-energy-density lithium-ion batteries, and has significant industrial application value. DETAILED DESCRIPTION

[0022] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0023] Example 1 A cobalt trioxide is prepared by the following method: S11: Use cobalt sulfate as the cobalt source, dissolve it in 30±2℃ deionized water to prepare a cobalt solution with a concentration of 0.3 mol / L, and add ammonia water to adjust the electrolyte pH to 10±0.2; S12: Depositing a cobalt tetroxide thin film on the surface of the working electrode using cyclic voltammetry; specifically, the cyclic voltammetry scan potential range is -1.0 to 1.0 V, the scan rate is 30 mV / s, and the number of cycles is 15; S2: Immerse the deposited working electrode in an ethanol solution, use an ultrasonic cleaner to peel off the cobalt tetroxide, and obtain cobalt tetroxide powder after drying. The power of the ultrasonic cleaner is 100±2W, the time is 10±2min, and the drying temperature is 50±2°C.

[0024] S3: ball-milling the cobalt oxide powder at 250±2° C. to obtain a cobalt oxide product; wherein the ball milling time is 3 hours, the ball mill speed is 400 rpm, and the ball-to-material ratio is 10:1.

[0025] Example 2 The difference between this embodiment and embodiment 1 is that the concentration of the cobalt solution in this embodiment is 0.1 mol / L.

[0026] Example 3 The difference between this embodiment and embodiment 1 is that the concentration of the cobalt solution in this embodiment is 0.5 mol / L.

[0027] Example 4 The difference between this embodiment and embodiment 1 is that, in step S11 of this embodiment, sulfuric acid is added to adjust the pH of the electrolyte to 5±0.2.

[0028] Example 5 The difference between this embodiment and embodiment 1 is that in step S11 of this embodiment, hydrogen peroxide with a concentration of 0.03 mol / L and PEG4000 with a concentration of 0.02 mol / L are added to the electrolyte.

[0029] Example 6 The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the cobalt trioxide powder is ball-milled under an inert atmosphere of nitrogen.

[0030] Comparative Example 1 Compared with Example 1, the difference of this comparative example is that the cobalt trioxide powder obtained in step S2 is directly used as the finished product without performing step S3.

[0031] Comparative Example 2 Compared with Example 1, the difference of this comparative example is that in step S3 of this comparative example, the temperature of ball milling is 400±2°C.

[0032] Comparative Example 3 Compared with Example 1, the difference of this comparative example is that in step S3 of this comparative example, the temperature of ball milling is 100±2°C.

[0033] Comparative Example 4 Compared with Example 1, the difference of this comparative example is that the operation of step S3 of this comparative example is: calcining the cobalt trioxide powder at 250±2° C. for 3 h to obtain a cobalt trioxide finished product.

[0034] The finished cobalt trioxide products obtained in Example 1-6 and Comparative Example 1-4 were numbered, wherein the finished product of Example 1-6 was numbered 1-6, and the finished product of Comparative Example 1-4 was numbered 7-10.

[0035] 1. X-ray diffraction analysis (XRD): After step S3 is completed, the product powder is taken for XRD testing. The following is the measured XRD characteristic peak data.

[0036] Table 1 It can be clearly seen from Table 1 above that the strongest peak is located at 31.3°, which is the crystal diffraction peak of cobalt trioxide, indicating that the main product of the present invention is cobalt trioxide.

[0037] 2. Energy Dispersive X-ray Spectroscopy (EDS): The surface elemental composition of the product was determined by SEM-EDS, and it was found that among various chemical elements, the content of cobalt and oxygen accounted for the highest proportion, and was close to 3:4. It can be seen that the product of the present invention is cobalt tetroxide.

[0038] 3. Lithium battery preparation: The above-numbered cobalt tetroxide products were mixed with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, coated on aluminum foil, and dried to form electrode sheets. Metallic lithium was used as the counter electrode, 1 mol / L LiPF6 (EC / DMC=1:1) was used as the electrolyte, and Celgard2400 polypropylene film was used as the separator to assemble into a CR2032 button lithium battery.

[0039] In lithium-ion batteries, As a precursor of the positive electrode material, during the charging process, Reacts with lithium salts (such as lithium carbonate Li2CO3) at high temperature to convert into lithium-containing compounds lithium cobalt oxide , thus becoming part of the positive electrode. The reaction pathway is as follows: Co3O4+Li2CO3→3LiCoO2+CO2↑ The electrochemical performance tests were performed on the lithium batteries prepared by the above methods.

[0040] (1) Rate performance test: Charge and discharge tests were performed at rates of 0.1C, 0.5C, 1C, 2C, and 5C to obtain the discharge specific capacity at different rates.

[0041] (2) Cycle stability test: Perform 100 cycles at 1C rate and calculate the capacity retention rate. Capacity retention rate = discharge capacity after 100 cycles / initial discharge capacity × 100% The test results are shown in Table 2.

[0042] Table 2 As can be seen from the test results in Table 2, the lithium batteries prepared from the cobalt oxide of Examples 1-6 have higher discharge specific capacities at rates of 0.1C, 0.5C, 1C, 2C, and 5C than the lithium batteries prepared from the cobalt oxide of Comparative Examples 1-4. Moreover, the capacity retention rate of the lithium batteries prepared from the cobalt oxide of Examples 1-6 at a rate of 1C is ≥88.0%, which is significantly higher than the capacity retention rate of Comparative Examples 1-4, indicating that the finished cobalt oxide product prepared by the present invention has better performance.

[0043] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for electrowinning cobalt in a cobalt sulfate system, characterized in that: The following steps are involved: S1: Prepare an electrolyte containing cobalt sulfate and use cyclic voltammetry to deposit a cobalt oxide film on the surface of the working electrode; S2: peeling the cobalt oxide film from the working electrode and drying it to obtain cobalt oxide powder; S3: ball-milling the cobalt trioxide powder at 200-300° C. to obtain a finished cobalt trioxide product.

2. The method according to claim 1, characterized in that In step S1, the specific steps of preparing the electrolyte are: using cobalt sulfate as a cobalt source, dissolving it in deionized water to prepare a cobalt solution with a concentration of 0.1-0.5 mol / L, and adjusting the pH of the electrolyte to 8.5-11.

3. The method according to claim 1, characterized in that The electrolyte further contains at least one of a dispersant, an oxidant, a complexing agent, a surfactant, and a binder.

4. The method according to claim 1, wherein The scanning potential range of the cyclic voltammetry is -1.2-2.0 V, the scanning rate is 10-50 mV / s, and the number of cycles is 10-30 times.

5. The method according to claim 1, wherein The specific operation steps of step S2 are: immersing the deposited working electrode in deionized water or ethanol solution, using an ultrasonic cleaner to peel off the cobalt tetroxide, and obtaining cobalt tetroxide powder after drying.

6. The method according to claim 1, characterized in that In step S1, the temperature of the electrolyte is 25-50°C; in step S2, the drying temperature is 40-60°C.

7. The method according to claim 1, characterized in that In step S3, the cobalt trioxide powder is ball-milled in an inert atmosphere for 1-4 hours, the rotation speed of the ball mill is 300-500 rpm, and the ball-to-material ratio is 5-10:

1.

8. A cobalt trioxide, characterized in that The method according to any one of claims 1 to 7 is used for preparation.

9. An electrode material for a lithium battery, characterized in that: The method comprises the cobalt trioxide as claimed in claim 8.

10. Use of the electrode material according to claim 9 in preparing a lithium battery, characterized in that: The cobalt tetroxide is a precursor of the positive electrode material in lithium batteries.

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