Production method of spherical cobaltosic oxide with multilayer structure

Abstract

The invention relates to a production method of spherical cobaltosic oxide with a multilayer structure, and belongs to the technical field of battery production and manufacturing. According to the method disclosed by the invention, by virtue of a combined innovative process of doping strengthening, gradient pore design and carbon compounding, the problem that cobaltosic oxide with a multi-layer spherical hollow structure is easy to collapse in high-temperature calcination and battery charge-discharge cycle processes is effectively solved; the prepared spherical cobaltosic oxide with the multilayer structure has high specific surface area and high stability, and the charge-discharge efficiency and the cycle service life of the lithium ion battery can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery production and manufacturing, and relates to a production method of spherical cobalt tetroxide with a multilayer structure. Background Art

[0002] As the lithium-ion battery industry is developing rapidly, the performance of cathode materials has become a key factor in determining the overall performance of batteries. As a highly potential precursor of lithium-ion battery cathode materials, cobalt tetroxide has attracted much attention, and the impact of specific surface area on the performance of cobalt tetroxide is particularly critical.

[0003] The specific surface area is directly related to the electrochemical activity of the material. Cobalt tetroxide with a large specific surface area can open up more active sites for electrochemical reactions, thereby playing a significant role in improving the battery's charge and discharge performance and cycle stability. During the battery's charge and discharge process, cobalt tetroxide with a high specific surface area can help lithium ions embed and detach more smoothly, effectively speeding up the reaction rate, improving the charge and discharge efficiency, while reducing electrode polarization, greatly extending the battery's cycle life.

[0004] Therefore, developing a production method to increase the specific surface area of ​​cobalt tetroxide has important practical significance and market demand. Summary of the invention

[0005] The object of the present invention is to provide a method for producing a multi-layer spherical cobalt oxide. The prepared multi-layer spherical cobalt oxide has both high specific surface area and high stability.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for producing spherical cobalt oxide with a multilayer structure comprises the following steps:

[0008] S1, adding a soluble cobalt salt and a precipitant into deionized water, stirring, and obtaining a mixed solution 1;

[0009] S2, adding a morphology directing agent to the mixed solution 1, stirring, and ultrasonically treating to obtain a mixed solution 2;

[0010] S3, placing the mixed solution 2 in a reactor, adjusting the pH of the mixed solution 2 to 9-11 in stages, reacting at 60-80° C. for 3-5 hours to generate a hollow spherical precursor, and after the reaction, washing, centrifuging, and drying the precursor;

[0011] S4, calcining the treated precursor in stages, heating the temperature to 300-400°C at a heating rate of 2-5°C / min and keeping it warm for 1-2 hours in the first stage, and heating the temperature to 500-600°C at a heating rate of 5-8°C / min and keeping it warm for 2-3 hours in the second stage to form spherical cobalt trioxide with a multilayer structure.

[0012] Furthermore, in step S2, a dopant is added to the mixed solution 1, wherein the dopant is manganese nitrate, and the doping amount of the manganese nitrate is 0.5-5% of the molar amount of the cobalt salt.

[0013] Preferably, the morphology directing agent comprises citric acid and sodium dodecyl sulfate, the molar ratio of the citric acid to the cobalt salt is 1:(1-2), and the mass ratio of the citric acid to sodium dodecyl sulfate is 1:(0.1-0.5).

[0014] Furthermore, in step S3, the pH value of the mixed solution 2 is adjusted in stages:

[0015] a. In the first stage, the pH of the mixed solution 2 is adjusted to 8-9, and the mixture is reacted in a reactor at 60-70°C for 1-2 hours to form a dense core layer;

[0016] b. In the second stage, the pH of the mixed solution 2 is adjusted to 10-11, and the mixture is reacted in a reactor at 70-80° C. for 2-3 hours to generate a porous shell layer, thereby forming a core-shell gradient pore structure.

[0017] Preferably, during the calcination process of step S4, a mixed gas of nitrogen and air is introduced, and the volume of the nitrogen accounts for 10-30% of the volume of the mixed gas.

[0018] Furthermore, the step S4 further comprises, after calcination:

[0019] Carbon source composite treatment: The calcined product is mixed with a carbon source and calcined at 700-800°C for 1-2 hours to form a carbon coating layer.

[0020] Preferably, the carbon source is one of glucose, polyvinyl pyrrolidone or graphene, and the mass ratio of the carbon source to the calcined product is (0.1-0.3):1.

[0021] Preferably, the precipitant in step S1 is one of sodium hydroxide, sodium carbonate or ammonia water, and the molar ratio of the precipitant to the cobalt salt is (2-4):1.

[0022] Beneficial effects of the present invention:

[0023] (1) The multi-layer spherical hollow structure of cobalt tetroxide produced by the present invention effectively solves the specific surface area problem mentioned in the background technology. The hollow spherical structure of cobalt tetroxide forms a larger space inside, and the multi-layer structure increases the surface level of the material. The combination of the two significantly increases the specific surface area of ​​cobalt tetroxide. The larger specific surface area provides more active sites for electrochemical reactions, which helps lithium ions to embed and detach more smoothly, thereby improving the charge and discharge performance and cycle stability of the battery.

[0024] (2) Through the coordinated efforts of doping reinforcement, gradient pore design and carbon composite process, the problem of easy collapse of cobalt tetroxide in multi-layer spherical hollow structure during high temperature calcination and battery charge and discharge cycle is effectively solved. First, in the early stage of structure formation, step S3 forms a dense core layer in the first stage by adjusting the pH value in stages. This core layer, as the basis of the entire structure, provides a solid support for cobalt tetroxide and greatly enhances the ability of the structure to resist deformation. Secondly, add a dopant. In step S2, the dopant (manganese nitrate) will be evenly dispersed in the core layer and shell layer. The ions in the dopant enter the lattice of cobalt tetroxide, optimize the overall crystal structure, enhance the interaction between atoms, and comprehensively improve the intrinsic stability of cobalt tetroxide. Finally, the carbon source composite treatment in step S4 puts a layer of "armor" on the material, and the formed carbon coating layer is wrapped in the outermost layer of the cobalt tetroxide particles. It not only improves the conductivity of the material, but also gives the structure a certain flexibility and mechanical strength. When stress is generated during high-temperature calcination or battery charge and discharge cycles, the carbon coating can effectively buffer the impact of external stress on the internal structure and protect the internal core-shell structure. During the entire preparation process, each process link cooperates with each other to enhance the structural stability of the material from different levels. From the dense core layer inside, to the uniformly doped and reinforced overall structure, to the external carbon coating, the three work together from the inside out to build a solid defense line for the multi-layer spherical hollow structure of cobalt oxide, giving it stronger structural stability.

[0025] (3) The high specific surface area and stable structure make the transmission of lithium ions during the battery charging and discharging process more efficient, accelerate the reaction rate, and improve the charging and discharging efficiency. At the same time, the stable structure effectively reduces the electrode polarization phenomenon and greatly extends the cycle life of the battery. DETAILED DESCRIPTION

[0026] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0027] Example 1

[0028] A method for producing spherical cobalt oxide with a multilayer structure comprises the following steps:

[0029] S1: Preparation of mixed solution 1

[0030] In a 500 mL three-necked flask, add 200 mL of deionized water, then take 200 mL of 1 mol / L cobalt nitrate solution (Co(NO3)2·6H2O, 1 mol / L) and add it to the deionized water in the three-necked flask, then add 5.6 mol / L ammonia water (precipitant) dropwise into the three-necked flask according to the molar ratio of cobalt salt to precipitant being 1:2, and at the same time, turn on the mechanical stirrer and stir at 300 rpm for 30 minutes to obtain a mixed solution 1.

[0031] S2: Preparation of mixed solution 2

[0032] A morphology directing agent and a dopant are added to the mixed solution 1. Specifically, the morphology directing agent includes citric acid and sodium dodecyl sulfate. Citric acid is added to the mixed solution 1 at a molar ratio of cobalt salt: citric acid = 1.5:1; sodium dodecyl sulfate is added to the mixed solution 1 at a mass ratio of citric acid to sodium dodecyl sulfate of 1:0.1; manganese nitrate, a dopant, is weighed according to 0.5% of the molar amount of cobalt salt and added to the mixed solution 1; then the mixture is stirred evenly to fully mix the substances, and then the mixed solution is transferred to an ultrasonic device and ultrasonically treated at a frequency of 40 kHz for 30 minutes to obtain a mixed solution 2.

[0033] S3: Generation of hollow spherical precursors and post-processing

[0034] a. The first stage: the mixed solution 2 is transferred to a reactor, and the pH of the mixed solution 2 is adjusted to 8, and the reaction is carried out at 60° C. for 2 hours to generate a hollow spherical precursor;

[0035] b. In the second stage, the pH is adjusted to 10, the reactor is heated to 70°C, and the reaction is continued for 3 hours to generate a porous shell layer, thereby forming a core-shell gradient pore structure;

[0036] c. After the adjustment reaction is completed, transfer the product in the reactor to a centrifuge tube, centrifuge at an appropriate speed, and then wash the precipitate with deionized water. Repeat the centrifugal washing operation 3 times. Place the washed precipitate in a vacuum drying oven and vacuum dry it at 80°C for 12 hours.

[0037] S4: Calcination and carbon source composite treatment

[0038] The treated precursor is calcined in stages:

[0039] The first stage of calcination: the precursor is placed in a high-temperature calcination furnace, a mixture of nitrogen and air is introduced (nitrogen accounts for 10% by volume, that is, the volume ratio of nitrogen to air is 1:9), the furnace temperature is raised to 300°C at a heating rate of 2°C / min, and kept at this temperature for 2 hours;

[0040] Second stage calcination: After the first stage calcination, the furnace temperature was raised to 500°C at a heating rate of 5°C / min and kept at this temperature for 3 hours to form a multilayer spherical cobalt oxide;

[0041] Finally, carbon source composite treatment: according to the mass ratio of calcined product: carbon source = 1:0.1, the carbon source is glucose. The calcined product and glucose are placed in a ball mill and ball milled for 40 minutes. The mixed sample is placed in a high-temperature calcining furnace and calcined at 700°C for 2 hours under an argon atmosphere to form a carbon coating layer.

[0042] Example 2

[0043] A method for producing spherical cobalt oxide with a multilayer structure comprises the following steps:

[0044] S1: Preparation of mixed solution 1

[0045] In a 500 mL three-necked flask, add 200 mL of deionized water, then take 200 mL of 1 mol / L cobalt nitrate solution (Co(NO3)2·6H2O, 1 mol / L) and add it to the deionized water in the three-necked flask, then add 8.1 mol / L ammonia water (precipitant) dropwise into the three-necked flask according to the molar ratio of cobalt salt to precipitant being 1:3, and at the same time, turn on the mechanical stirrer and stir at 300 rpm for 30 minutes to obtain a mixed solution 1.

[0046] S2: Preparation of mixed solution 2

[0047] A morphology directing agent and a dopant are added to the mixed solution 1. Specifically, the morphology directing agent includes citric acid and sodium dodecyl sulfate. Citric acid is added to the mixed solution 1 at a molar ratio of cobalt salt: citric acid = 1.5:1; sodium dodecyl sulfate is added to the mixed solution 1 at a mass ratio of citric acid to sodium dodecyl sulfate of 1:0.3; manganese nitrate, a dopant, is weighed according to 3% of the molar amount of cobalt salt and added to the mixed solution 1; then the mixture is stirred evenly to fully mix the substances, and then the mixed solution is transferred to an ultrasonic device and ultrasonically treated at a frequency of 40 kHz for 30 minutes to obtain a mixed solution 2.

[0048] S3: Generation of hollow spherical precursors and post-processing

[0049] a. The first stage: the mixed solution 2 was transferred to a reactor, and the pH of the mixed solution 2 was adjusted to 8.5, and the reaction was carried out at 65°C for 1.5 hours to generate a hollow spherical precursor;

[0050] b. In the second stage, the pH was adjusted to 10.5, the reactor temperature was raised to 75°C, and the reaction was continued for 2.5 hours to generate a porous shell layer, thereby forming a core-shell gradient pore structure;

[0051] c. After the adjustment reaction is completed, transfer the product in the reactor to a centrifuge tube, centrifuge at an appropriate speed, and then wash the precipitate with deionized water. Repeat the centrifugal washing operation 3 times. Place the washed precipitate in a vacuum drying oven and vacuum dry it at 80°C for 12 hours.

[0052] S4: Calcination and carbon source composite treatment

[0053] The treated precursor is calcined in stages:

[0054] The first stage of calcination: the precursor is placed in a high-temperature calcination furnace, a mixture of nitrogen and air is introduced (nitrogen accounts for 20% by volume, that is, the volume ratio of nitrogen to air is 2:8), the furnace temperature is raised to 350°C at a heating rate of 3.5°C / min, and the temperature is kept for 1.5 hours;

[0055] Second stage calcination: After the first stage calcination, the furnace temperature was raised to 550°C at a heating rate of 6.5°C / min and kept at this temperature for 2.5 hours to form a multilayer spherical cobalt oxide.

[0056] Carbon source composite treatment: The mass ratio of calcined product to carbon source is 1:0.2, and the carbon source is glucose. The calcined product and glucose are placed in a ball mill and mixed for 40 minutes. The mixed sample is placed in a high-temperature calcining furnace and calcined at 750°C for 1.5 hours under an argon atmosphere to form a carbon coating layer.

[0057] Example 3

[0058] A method for producing spherical cobalt oxide with a multilayer structure comprises the following steps:

[0059] S1: Preparation of mixed solution 1

[0060] In a 500 mL three-necked flask, add 200 mL of deionized water, then take 200 mL of 1 mol / L cobalt nitrate solution (Co(NO3)2·6H2O, 1 mol / L) and add it to the deionized water in the three-necked flask, then add 10.7 mol / L ammonia water (precipitant) dropwise into the three-necked flask according to the molar ratio of cobalt salt to precipitant being 1:4, and at the same time, turn on the mechanical stirrer and stir at 300 rpm for 30 minutes to obtain a mixed solution 1.

[0061] S2: Preparation of mixed solution 2

[0062] A morphology directing agent and a dopant are added to the mixed solution 1. Specifically, the morphology directing agent includes citric acid and sodium dodecyl sulfate. Citric acid is added to the mixed solution 1 at a molar ratio of cobalt salt: citric acid = 2:1; sodium dodecyl sulfate is added to the mixed solution 1 at a mass ratio of citric acid to sodium dodecyl sulfate of 1:0.5; manganese nitrate, a dopant, is weighed according to 5% of the molar amount of the cobalt salt and added to the mixed solution 1; then the mixture is stirred evenly to fully mix the substances, and then the mixed solution is transferred to an ultrasonic device and ultrasonically treated at a frequency of 40 kHz for 30 minutes to obtain a mixed solution 2.

[0063] S3: Generation of hollow spherical precursors and post-processing

[0064] a. The first stage: the mixed solution 2 is transferred to a reactor, and the pH of the mixed solution 2 is adjusted to 9, and the reaction is carried out at 70°C for 1 hour to generate a hollow spherical precursor;

[0065] b. In the second stage, the pH is adjusted to 11, the reactor is heated to 80°C, and the reaction is continued for 2 hours to generate a porous shell layer, thereby forming a core-shell gradient pore structure;

[0066] c. After the adjustment reaction is completed, transfer the product in the reactor to a centrifuge tube, centrifuge at an appropriate speed, and then wash the precipitate with deionized water. Repeat the centrifugal washing operation 3 times. Place the washed precipitate in a vacuum drying oven and vacuum dry it at 80°C for 12 hours.

[0067] S4: Calcination and carbon source composite treatment

[0068] The treated precursor is calcined in stages:

[0069] The first stage of calcination: the precursor is placed in a high-temperature calcination furnace, a mixture of nitrogen and air is introduced (nitrogen accounts for 30% by volume, that is, the volume ratio of nitrogen to air is 3:7), the furnace temperature is raised to 400°C at a heating rate of 5°C / min, and the temperature is kept for 1 hour;

[0070] Second stage calcination: After the first stage calcination, the furnace temperature was raised to 600°C at a heating rate of 8°C / min and kept at this temperature for 2 hours to form a multilayer spherical cobalt oxide.

[0071] Carbon source composite treatment: According to the mass ratio of calcined product: carbon source = 1:0.3, the carbon source is glucose. The calcined product and glucose are placed in a ball mill and ball milled for 40 minutes. The mixed sample is placed in a high-temperature calcining furnace and calcined at 800°C for 1 hour under an argon atmosphere to form a carbon coating layer.

[0072] Comparative Example 1

[0073] The difference from Example 2 is that: in step S3, the staged pH control is cancelled, the pH of the mixed solution 2 is adjusted to 10.5, and then the mixed solution 2 is transferred to a reactor and reacted at 75° C. for 4 hours.

[0074] Comparative Example 2

[0075] The difference from Example 2 is that manganese nitrate is not added in step S2.

[0076] Comparative Example 3

[0077] The difference from Example 2 is that the carbon compounding treatment in step S4 is omitted.

[0078] Test Case

[0079] The finished products of the multilayer spherical cobalt trioxide prepared in Example 2 and Comparative Examples 1-3 were taken as samples and the following tests were carried out:

[0080] (1) Specific surface area test (BET nitrogen adsorption method): Take 50 mg of sample and place it in a Quantachrome Autosorb-iQ instrument, vacuum degassing at 200°C for 6 hours, and perform nitrogen adsorption-desorption test at liquid nitrogen temperature (77K), and calculate the specific surface area using the BET model. The larger the specific surface area, the more electrochemical active sites.

[0081] (2) Tap density test: 5 g of sample was placed in a 25 mL measuring cylinder and vibrated at 250 times per minute using a Hosokawa PT-S tap density tester. The density (g / cm2) was recorded when the sample was tapped to a constant volume. 3 ).

[0082] (3) Cycle retention test (500 cycles):

[0083] Battery assembly: Sample: acetylene black: PVDF were slurried in a ratio of 80:10:10, coated on aluminum foil, and vacuum dried at 120°C for 12 hours. Metallic lithium was used as the counter electrode, 1M LiPF6 / EC:DMC (1:1) was used as the electrolyte, and button cells (CR2032) were assembled in a glove box.

[0084] Test conditions: 0.5C (1C=137mA / g), voltage window 3.0-4.3V, record the 1st and 500th discharge capacities, and calculate the retention rate (%).

[0085] (4) Mechanical strength test: Take 1g of sample and place it in a mold, apply 10MPa pressure for 5 minutes, take it out and pass it through a 325 mesh sieve (45μm), and calculate the mass percentage of unbroken particles. The lower the crushing rate, the higher the mechanical strength of the material and the better the electrode processing performance.

[0086] The test data of the above four test cases are shown in Table 1.

[0087] Table 1:

[0088]

[0089] It can be seen from Table 1 that:

[0090] (1) The specific surface area of ​​Example 2 reaches 82.5 m 2 / g, while the comparative example 1 is only 45.6m 2 / g. Comparative Example 1 cancels the staged pH regulation, which results in the inability to form a core-shell gradient pore structure, greatly affecting the specific surface area. In contrast, the present invention generates a dense core layer and a porous shell layer by adjusting the pH value in stages, and the multi-layer spherical hollow structure formed has a large internal space and rich surface layers, which effectively increases the specific surface area and provides more active sites for electrochemical reactions.

[0091] (2) The tap density of Example 2 is 2.02 g / cm 3 , higher than 1.68g / cm in Comparative Example 1 3 , Comparative Example 2: 1.78 g / cm 3 and 1.95 g / cm2 of Comparative Example 3 3 . Comparative Example 1 lacks staged pH regulation, and cannot form a reasonable core-shell gradient pore structure, resulting in a loose internal structure and low tap density; Comparative Example 2 does not add manganese nitrate for doping and strengthening, and the overall structure is not tight enough; Comparative Example 3 does not undergo carbon composite treatment, and the structural strength and density of the material are slightly inferior. This shows that the dense core layer and gradient pore structure formed by staged pH adjustment, combined with doping and strengthening and carbon composite processes, can effectively improve the tap density of the material and optimize the internal structure of the material.

[0092] (3) The cycle retention rate of Example 2 is 94.7%, which is much higher than 72.1% of Comparative Example 1, 85.2% of Comparative Example 2, and 82.6% of Comparative Example 3. Comparative Example 1 cancels the staged pH control, and the structural stability is poor. The structure is easy to collapse during the charge and discharge cycle, resulting in obstruction of lithium ion transmission and low cycle retention rate; Comparative Example 2 lacks doping strengthening, and the crystal structure is not stable enough, which affects the charge and discharge performance; Comparative Example 3 does not perform carbon composite treatment, and cannot effectively buffer external stress, reducing the cycle life of the battery. This shows that the present invention enhances the structural stability of the material and reduces the electrode polarization phenomenon through the synergy of multiple processes, thereby significantly improving the cycle retention rate of the battery.

[0093] (4) The crushing rate of Example 2 is 5.2%, which is significantly lower than 18.7% of Comparative Example 1, 12.3% of Comparative Example 2, and 15.9% of Comparative Example 3. Comparative Example 1 has no reasonable gradient pore structure, so the material has low mechanical strength and is easy to break; Comparative Example 2 is not doped and has insufficient structural strength; Comparative Example 3 lacks the protection of the carbon coating layer and is more likely to break when subjected to pressure. This reflects that the gradient pore structure formed by staged pH regulation, doping enhancement, and carbon composite process greatly enhance the mechanical strength of the material and improve the stability of the material during processing and use.

[0094] In summary, through detailed analysis of Example 2 and the comparative data, it can be seen that the multilayer structure spherical cobalt oxide production method of the present invention, by adjusting the pH value in stages, doping strengthening and carbon composite process, is significantly better than the comparative samples in performance indicators such as specific surface area, tap density, cycle retention rate and mechanical strength. It not only increases the specific surface area and provides more active sites for electrochemical reactions, but also enhances the structural stability and ensures the performance of the material in high temperature calcination and charge and discharge cycles, thereby comprehensively improving the charge and discharge performance and cycle life of the battery, showing the advancement and superiority of the production method.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. 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 producing spherical cobalt oxide with a multilayer structure, characterized in that: The following steps are involved: S1, adding a soluble cobalt salt and a precipitant into deionized water, stirring, and obtaining a mixed solution 1; S2, adding a morphology directing agent to the mixed solution 1, stirring, and ultrasonically treating to obtain a mixed solution 2; S3, placing the mixed solution 2 in a reactor, adjusting the pH of the mixed solution 2 to 9-11 in stages, reacting at 60-80° C. for 3-5 hours to generate a hollow spherical precursor, and after the reaction, washing, centrifuging, and drying the precursor; S4, calcining the treated precursor in stages, heating the temperature to 300-400°C at a heating rate of 2-5°C / min and keeping it warm for 1-2 hours in the first stage, and heating the temperature to 500-600°C at a heating rate of 5-8°C / min and keeping it warm for 2-3 hours in the second stage to form spherical cobalt trioxide with a multilayer structure.

2. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: In step S2, a dopant is further added to the mixed solution 1, wherein the dopant is manganese nitrate, and the doping amount of the manganese nitrate is 0.5-5% of the molar amount of the cobalt salt.

3. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: The morphology directing agent includes citric acid and sodium dodecyl sulfate, the molar ratio of the citric acid to the cobalt salt is 1:(1-2), and the mass ratio of the citric acid to the sodium dodecyl sulfate is 1:(0.1-0.5).

4. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: In step S3, the pH value of the mixed solution 2 is adjusted in stages: a. In the first stage, the pH of the mixed solution 2 is adjusted to 8-9, and the mixture is reacted in a reactor at 60-70°C for 1-2 hours to form a dense core layer; b. In the second stage, the pH of the mixed solution 2 is adjusted to 10-11, and the mixture is reacted in a reactor at 70-80° C. for 2-3 hours to generate a porous shell layer, thereby forming a core-shell gradient pore structure.

5. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: During the calcination process in step S4, a mixed gas of nitrogen and air is introduced, and the volume of the nitrogen accounts for 10-30% of the volume of the mixed gas.

6. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: After the calcination, the step S4 further comprises: Carbon source composite treatment: The calcined product is mixed with a carbon source and calcined at 700-800°C for 1-2 hours to form a carbon coating layer.

7. The method for producing multilayer spherical cobalt oxide according to claim 6, characterized in that: The carbon source is one of glucose, polyvinyl pyrrolidone or graphene, and the mass ratio of the carbon source to the calcined product is (0.1-0.3):

1.

8. The method for producing multilayer spherical cobalt oxide according to claim 1, characterized in that: The precipitant in step S1 is one of sodium hydroxide, sodium carbonate or ammonia water, and the molar ratio of the precipitant to the cobalt salt is (2-4):1.

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