Preparation method of cobalt hydroxide with large specific surface area

Abstract

The invention discloses a preparation method of cobalt hydroxide with a large specific surface area, which comprises the following steps: carrying out coprecipitation reaction by taking cobalt sulfate and sodium hydroxide as raw materials and VC as a surfactant and an antioxidant, adding cobalt sulfate and VC into a reaction kettle by taking a sodium hydroxide solution as a base solution, and controlling the pH value of a synthesis end point, the synthesis time and the VC content to obtain cobalt hydroxide with a large specific surface area. And washing the synthesized cobalt hydroxide slurry with hot pure water, drying, and crushing with a jet mill to obtain the flaky cobalt hydroxide with BET greater than or equal to 60m < 2 > / g.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery material preparation, and in particular relates to a method for preparing cobalt hydroxide with a large specific surface area for preparing high-voltage positive electrode materials. Background Art

[0002] Lithium cobalt oxide is the earliest commercialized positive electrode material in lithium-ion batteries. It has the advantages of high operating voltage, stable discharge, high specific energy, and good cycle performance. It is mainly used to manufacture lithium-ion battery positive electrode materials for mobile phones, laptops and other portable electronic devices.

[0003] With the development of 3C electronic products, people have higher and higher requirements for battery capacity. Researchers have increased the specific capacity of LCO by increasing the charging cutoff voltage of LCO and allowing more ions to participate in charging and discharging. At present, 4.45V high-voltage LCO is gradually increasing in volume. Positive electrode material manufacturers use the method of adding Al, Mg, Zr, Ti, Ni, Mn and other elements and coating methods in the wet synthesis stage of cobalt tetroxide precursor to produce it, that is, doping cobalt tetroxide and lithium carbonate for solid phase reaction. Because the surface contains excess lithium after the solid phase reaction, it is necessary to coat and sinter the fired lithium cobalt oxide with ultrafine cobalt hydroxide, which can not only effectively reduce the residual amount of lithium, but also form a cobalt-rich concentration gradient layer on the surface of the positive electrode material, thereby improving the cycle performance of the material. However, if the particle size of the cobalt hydroxide coated on the surface of the positive electrode material is too large, the impedance of the positive electrode material will be high, thereby reducing the electrochemical performance.

[0004] The primary particle size of cobalt hydroxide, the currently commercialized lithium cobalt oxide coating agent, is relatively large and has some agglomerates, the coating dispersion is poor, the specific surface area of ​​the coating material cobalt hydroxide is relatively small, the coating effect is limited, and the application of positive electrode materials is restricted. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing cobalt hydroxide with a large specific surface area.

[0006] To this end, the present invention provides the following technical solutions: A method for preparing cobalt hydroxide with a large specific surface area comprises the following steps: (1) Prepare a mixed solution of Co and VC: Prepare a mixed solution using cobalt sulfate and VC as raw materials, with a mass ratio of VC to cobalt sulfate of 1:50-1:10, and a cobalt concentration of 100-120 g / L in the mixed solution; (2) Prepare sodium hydroxide solution: dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100-180 g / L; (3) Synthesis process: 100-180 g / L sodium hydroxide solution is used as the base liquid, the volume of the base liquid is 40-50% of the total volume of the reactor, the temperature is raised to 20-25°C, stirring is turned on, and then the mixed solution of Co and VC in step (1) is added to the reactor to carry out a coprecipitation reaction. During the reaction, the flow rate of the mixed solution of Co and VC, the pH value at the reaction end point, the reaction temperature and the stirring speed are strictly controlled; (4) After the synthesized cobalt hydroxide slurry is aged, it is washed, low-temperature dried, and air flow crushed to finally obtain a cobalt hydroxide product with a large specific surface area.

[0007] Furthermore, in step (3), 100-180 g / L sodium hydroxide solution is used as the base liquid, the volume of the base liquid is 40-50% of the total volume of the reactor, the temperature is raised to 20-25° C., stirring is started, and the Co and VC mixed solution in step (1) is added at the same time, the mass ratio of VC to Co is 1:50-1:10; the amount of Co and VC mixed solution added is controlled so that the pH value of the reaction system at the end point is 10.0-12.0, the reaction temperature is controlled at 20-25° C., the stirring speed of the reactor is 200-400 r / min, and the reaction time is 1-2 h.

[0008] Furthermore, in step (4), the aging time is 1-2 h, the aging temperature is 20-25° C., and the stirring speed during aging is 200-400 r / min.

[0009] Furthermore, in step (4), the slurry is washed with a centrifuge, and the washing water is deionized water at a temperature of 60° C., and the Na content in the cobalt hydroxide after washing is ≤ 0.02%.

[0010] Furthermore, in step (4), the drying equipment is a vacuum drying oven, the drying temperature is 60-80°C, and the moisture content of the material after drying is less than 1.0%.

[0011] Furthermore, in step (4), the crushing equipment is a jet mill, and the crushing pressure is 0.4-0.8 MPa.

[0012] Furthermore, in step (4), the index of the prepared cobalt hydroxide is: D 50 ≤1.0μm, Na%≤0.02%, BET≥60m 2 / g, the microscopic morphology is flaky.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The key to the preparation of nano-scale cobalt hydroxide is to prevent oxidation and particle agglomeration during the synthesis process. This process uses low temperature (40~60℃), high pH value (10.0~12.0), and VC as both a surfactant and an antioxidant, which plays a dual role and can prepare cobalt hydroxide with a large specific surface area. In addition, the subsequent washing step is easy to operate at low pH. This process provides a large specific surface area nano-scale cobalt hydroxide preparation process for the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the microscopic morphology of cobalt hydroxide prepared in Example 1.

[0015] Figure 2 This is the microscopic morphology of cobalt hydroxide prepared in Example 2.

[0016] Figure 3 This is the microscopic morphology of cobalt hydroxide prepared in Example 3. DETAILED DESCRIPTION

[0017] The process and effects of the present invention are described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Example 1 1. Use cobalt sulfate solution and VC as raw materials to prepare a Co and VC mixed solution with a cobalt concentration of 100 g / L and a mass ratio of VC to Co of 1:50.

[0019] 2. Synthesis reaction in 1m 3 The reaction was carried out in a reactor. With 100g / L sodium hydroxide solution as the base liquid, the volume was 50% of the total volume of the reactor, and the Co and VC mixed solution was added into the reactor for synthesis. During the synthesis process, the flow rate of the Co and VC mixed solution was controlled to be 370L / h, the pH value of the reaction system end point was controlled to be 10.0-12.0, the reaction temperature was controlled to be 25°C, the stirring speed of the reactor was 200min, and the reaction time was 1.0h.

[0020] 3. After the synthesis is completed, the feeding is stopped and aging begins. The aging time is 1.0 h, the aging temperature is 25°C, and the stirring speed during aging is 200 r / min.

[0021] 4. After aging, the slurry is put into a centrifuge and washing is started. The washing water is deionized water at a temperature of 60°C. After washing, the product is dehydrated and dried, and then subjected to air flow crushing to obtain a non-agglomerated nano-scale cobalt hydroxide product.

[0022] 5. The cobalt hydroxide slurry prepared in this example is pink, and the specific surface area of ​​the final product cobalt hydroxide is 64.98 m 2 / g, particle size 0.280μm, other information see Table 1, microscopic morphology of prepared cobalt hydroxide see Appendix Figure 1 .

[0023] Example 2 1. Use cobalt sulfate solution and VC as raw materials to prepare a mixed solution of Co and VC, with a cobalt concentration of 110g / L and a mass ratio of VC to Co of 1:25.

[0024] 2. Synthesis reaction at 5m 3 The reaction was carried out in a reactor. With 150g / L sodium hydroxide solution as the base liquid, the volume was 40% of the total volume of the reactor, and the Co and VC mixed solution was added into the reactor for synthesis. During the synthesis process, the flow rate of the Co and VC mixed solution was controlled to be 2000L / h, the pH value of the reaction system end point was controlled to be 10.0~12.0, the reaction temperature was controlled to be 25℃, the stirring speed of the reactor was 300min, and the reaction time was 1.0h.

[0025] 3. After the synthesis is completed, the feeding is stopped and aging begins. The aging time is 1.0 h, the aging temperature is 25°C, and the stirring speed during aging is 300 r / min.

[0026] 4. After aging, the slurry is put into a centrifuge and washing is started. The washing water is deionized water at a temperature of 60°C. After washing, the product is dehydrated and dried, and then subjected to air flow crushing to obtain a non-agglomerated nano-scale cobalt hydroxide product.

[0027] 5. The cobalt hydroxide slurry prepared in this example is pink, and the specific surface area of ​​the final product cobalt hydroxide is 69.54 m 2 / g, particle size 0.399μm, other information see Table 1, microscopic morphology of prepared cobalt hydroxide see Appendix Figure 2 .

[0028] Example 3 1. Use cobalt sulfate solution and VC as raw materials to prepare a mixed solution of Co and VC, with a cobalt concentration of 120g / L and a mass ratio of VC to Co of 1:10.

[0029] 2. Synthesis reaction in 10m 3 The reaction was carried out in a reactor. With 180g / L sodium hydroxide solution as the base liquid, the volume was 40% of the total volume of the reactor, and the Co and VC mixed solution was added into the reactor for synthesis. During the synthesis process, the flow rate of the Co and VC mixed solution was strictly controlled to be about 4400L / h, the pH value of the reaction system end point was controlled to be 10.0-12.0, the reaction temperature was controlled to be 25°C, the stirring speed of the reactor was 200min, and the reaction time was about 1.0h.

[0030] 3. After the synthesis is completed, the feeding is stopped and aging begins. The aging time is 1.0 h, the aging temperature is 25°C, and the stirring speed during aging is 200 r / min.

[0031] 4. After aging, the slurry is put into a centrifuge and washing is started. The washing water is deionized water at a temperature of 60°C. After washing, the product is dehydrated and dried, and then subjected to air flow crushing to obtain a non-agglomerated nano-scale cobalt hydroxide product.

[0032] 5. The cobalt hydroxide slurry prepared in this example is pink, and the specific surface area of ​​the final product cobalt hydroxide is 79.32 m 2 / g, particle size 0.566μm, other information see Table 1, microscopic morphology of prepared cobalt hydroxide see Appendix Figure 3 .

[0033] Table 1 Specific table and particle size data of Examples 1-3 In summary, the present invention provides a method for preparing nano-scale cobalt hydroxide with a large specific surface area. The method of the present invention can be used to prepare cobalt hydroxide with a large specific surface area. Low temperature (40-60° C.) and high pH value (10.0-12.0) are used, and VC is used as a surfactant and an antioxidant at the same time, which plays a dual role. In addition, the subsequent washing step is easy to operate at a low pH.

Claims

1. A method for preparing cobalt hydroxide with a large specific surface area, characterized in that: The following steps are involved: (1) Prepare a mixed solution of Co and VC: Prepare a mixed solution using cobalt sulfate and VC as raw materials, with a mass ratio of VC to cobalt sulfate of 1:50-1:10, and a cobalt concentration of 100-120 g / L in the mixed solution; (2) Prepare sodium hydroxide solution: dilute industrial liquid alkali with water to prepare a sodium hydroxide solution with a concentration of 100-180 g / L; (3) Synthesis process: 100-180 g / L sodium hydroxide solution is used as the base liquid, the volume of the base liquid is 40-50% of the total volume of the reactor, the temperature is raised to 20-25°C, stirring is turned on, and then the mixed solution of Co and VC in step (1) is added to the reactor to carry out a coprecipitation reaction. During the reaction, the flow rate of the mixed solution of Co and VC, the pH value at the reaction end point, the reaction temperature and the stirring speed are strictly controlled; (4) After the synthesized cobalt hydroxide slurry is aged, it is washed, low-temperature dried, and air flow crushed to finally obtain a cobalt hydroxide product with a large specific surface area.

2. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (3), 100-180 g / L sodium hydroxide solution is used as the base liquid, the volume of the base liquid is 40-50% of the total volume of the reactor, the temperature is raised to 20-25° C., stirring is started, and the Co and VC mixed solution in step (1) is added at the same time, the mass ratio of VC to Co is 1:50-1:10; the amount of Co and VC mixed solution added is controlled so that the pH value of the reaction system at the end point is 10.0-12.0, the reaction temperature is controlled at 20-25° C., the stirring speed of the reactor is 200-400 r / min, and the reaction time is 1-2 h.

3. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (4), the aging time is 1-2 h, the aging temperature is 20-25° C., and the stirring speed during aging is 200-400 r / min.

4. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (4), the slurry is washed by a centrifuge, and the washing water is deionized water at a temperature of 60° C. After washing, the Na content in the cobalt hydroxide is ≤ 0.02%.

5. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (4), the drying equipment is a vacuum drying oven, the drying temperature is 60-80°C, and the moisture content of the material after drying is less than 1.0%.

6. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (4), the crushing equipment is a jet mill, and the crushing pressure is 0.4-0.8 MPa.

7. A method for preparing cobalt hydroxide with a large specific surface area as claimed in claim 1, characterized in that: In step (4), the index of the prepared cobalt hydroxide is: D 50 ≤1.0μm, Na%≤0.02%, BET≥60m 2 / g, the microscopic morphology is flaky.

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