Cobalt-based bimetallic core-shell microspheres and cobalt-based bimetallic oxide core-shell microspheres, and preparation methods and applications thereof

Abstract

The invention generally relates to the technical field of lithium electronics, in particular to a cobalt-based bimetal core-shell microsphere and a cobalt-based bimetal oxide core-shell microsphere as well as a preparation method and application of the cobalt-based bimetal core-shell microsphere and the cobalt-based bimetal oxide core-shell microsphere, and the cobalt-based bimetal core-shell microsphere comprises cobalt and iron or cobalt and nickel; cobalt and iron or cobalt and nickel are uniformly distributed in the core-shell microspheres, the molar percentage content of cobalt is 50%-60%, and the molar percentage content of iron or nickel is 40%-50%; the particle size of the cobalt-based bimetallic core-shell microsphere is 1.2-1.8 [mu] m, the particle size of the core is 0.8-1.6 [mu] m, the thickness of the shell is 50-300 nm, and the preparation method of the cobalt-based bimetallic core-shell microsphere is a solvothermal reaction. And calcining the cobalt-based bimetallic core-shell microspheres to obtain the cobalt-based bimetallic oxide core-shell microspheres. The product can be used as a catalyst of a lithium supplement agent of a lithium battery.

Description

Technical Field

[0001] This invention relates generally to the field of lithium battery technology, and specifically to a cobalt-based bimetallic core-shell microsphere and a cobalt-based bimetallic oxide core-shell microsphere, as well as their preparation methods and applications. Background Technology

[0002] Currently, commercially available lithium batteries commonly use non-aqueous liquid electrolytes, typically composed of lithium salts and organic solvents such as carbonic acid. The insoluble products generated from the reaction of the organic solvents or lithium salts deposit on the electrode surface, forming an electronically insulating / ionicly conductive solid electrolyte interphase (SEI) film. The thickness of this SEI film ranges from several to tens or even hundreds of Å (1 Å = 1 × 10⁻⁶). -10 The formation of the SEI film can effectively prevent excessive electrolyte decomposition caused by direct contact between the electrode and the electrolyte. Therefore, the SEI film on the electrode surface plays a crucial role in the cycle life of the battery.

[0003] However, the formation of the SEI film irreversibly consumes the active lithium stored in the positive electrode material within the battery, reducing the active lithium content and thus lowering the battery's energy density. Simultaneously, lithium loss keeps the positive electrode in a "lithium-deficient state" for extended periods, leading to a reduction in battery cycle life. Graphite anodes typically experience approximately 10% irreversible capacity loss during the first charge cycle, a problem even more pronounced in alloy-type anodes. Therefore, there is an urgent need to develop effective and practical pre-lithiation technologies to address the active lithium loss issue, improve battery energy density and cycle life, and provide necessary technological reserves for the development of next-generation high-energy-density lithium-ion batteries.

[0004] Cathode pre-lithiation refers to the introduction of additional active lithium into the cathode system to compensate for the irreversible capacity loss in the battery, so that the amount of active lithium in the battery can still be maintained at a high level after formation.

[0005] The most commonly used cathode pre-lithiation technology is lithium-rich additives, which usually have the following four key characteristics: (1) the energy density of the additive should be much higher than that of the commonly used cathode materials; (2) the delithiation process of the additive within the voltage range of the cathode material is irreversible; (3) the additive is compatible with the current battery manufacturing process; (4) the additive has no negative effect on the battery system before and after playing the role of lithium replenishment.

[0006] Currently, lithium-rich additives are mainly divided into two categories: binary lithium-rich additives based on Li3N, Li2O, and Li2S, and ternary lithium-rich additives based on Li2CO3, Li2C2O4, and Li5FeO4. The main problems hindering the large-scale application of lithium-rich additives are their excessively high decomposition voltage and poor conductivity. The introduction of catalysts can effectively improve these problems, and therefore has attracted widespread attention.

[0007] Core-shell structured materials exhibit more regular morphology than metal particle catalysts. They demonstrate strong morphological stability under external stimuli such as voltage and stress, and are less prone to breakage due to excessive volume changes. Furthermore, existing methods for preparing core-shell materials often employ multi-step processes, which are complex and have poor repeatability, hindering practical applications. Summary of the Invention

[0008] To address the shortcomings and deficiencies of existing technologies, this invention provides cobalt-based bimetallic core-shell microspheres and cobalt-based bimetallic oxide core-shell microspheres, their preparation methods, and applications. The cobalt-based bimetallic core-shell microspheres have uniform composition, size, and morphology, and possess a double-layer core-shell structure, with cobalt and another metal evenly distributed throughout the overall structure. The preparation method of this application is simple, involving calcining the cobalt-based bimetallic core-shell microspheres to obtain cobalt-based bimetallic oxide core-shell microspheres. Both can be used as catalysts for lithium battery lithium replenishment agents, solving the problems existing in the prior art of lithium replenishment agent catalysts.

[0009] The technical solution of this application is that, on one hand, the present invention provides a cobalt-based bimetallic core-shell microsphere, comprising cobalt and iron, or cobalt and nickel; the cobalt and iron or cobalt and nickel are uniformly distributed in the cobalt-based bimetallic core-shell microsphere, wherein the molar percentage of cobalt is 50%-60%, and the molar percentage of iron or nickel is 40%-50%; the particle size of the cobalt-based bimetallic core-shell microsphere is 1.2μm~1.8μm, wherein the particle size of the core is 0.8μm-1.6μm, and the thickness of the shell is 50-300nm.

[0010] A second aspect of the present invention provides a method for preparing cobalt-based bimetallic core-shell microspheres according to the first aspect of the present invention, comprising the following steps: Step 1: Take one of nickel nitrate or ferric nitrate, cobalt nitrate and citric acid, disperse them in a mixed solution of deionized water and ethanol, stir thoroughly to dissolve, then pour the solution into the inner liner of a high-temperature reaction vessel, add a high-temperature stirring rotor and transfer it to a stainless steel hydrothermal reactor for a solvothermal reaction under stirring conditions to obtain a reaction solution. Step 2: The reaction solution is centrifuged and washed with a mixture of deionized water and ethanol, and then dried to obtain the cobalt-based bimetallic shell microspheres.

[0011] Furthermore, in step one above: the molar ratio of one of nickel nitrate or ferric nitrate, cobalt nitrate and citric acid is 1: (1.5~4): (1~3); in the mixed solution of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:2~1:4.

[0012] Furthermore, in step one above: the stirring speed in the solvothermal reaction under stirring conditions is 100~400 rpm; the temperature of the solvothermal reaction is 170~220℃, and the time is 16 h~32 h; in step two, drying is carried out under vacuum at 60-80℃.

[0013] A third aspect of the present invention provides the application of the above-described cobalt-based bimetallic core-shell microspheres as a catalyst for lithium battery lithium replenishment.

[0014] A fourth aspect of the present invention provides a cobalt-based bimetallic oxide core-shell microsphere, which is obtained by calcining the cobalt-based bimetallic core-shell microsphere of the first aspect of the present invention; the cobalt-based bimetallic oxide core-shell microsphere contains uniformly distributed cobalt oxide and iron oxide or cobalt oxide and nickel oxide, wherein the mass percentage of cobalt oxide is 50%-60%, and the mass percentage of iron oxide or nickel oxide is 40%-50%; the particle size of the cobalt-based bimetallic oxide core-shell microsphere is 1.2μm~1.8μm; wherein the thickness of the core is 0.8μm-1.6μm, and the thickness of the shell is 50-300nm.

[0015] Furthermore, the above-mentioned calcination involves placing the cobalt-based bimetallic core-shell microspheres in a ceramic boat and calcining them in a tube furnace under a nitrogen atmosphere. The temperature control mechanism for calcination is as follows: the temperature is increased from room temperature to 700℃-800℃ at a heating rate of 5℃ / min, and then held at that temperature for 2h-4h.

[0016] The fifth aspect of the present invention provides the application of the cobalt-based bimetallic oxide core-shell microspheres of the fourth aspect of the present invention as a catalyst for lithium battery lithium replenishment agents.

[0017] Furthermore, the specific method of the above application is to mix the lithium replenishing agent, conductive agent and binder, and then add the cobalt-based bimetallic oxide core-shell microspheres into the mixture and mix them evenly to make a positive electrode, using lithium nickel cobalt manganese oxide as the active material and graphite as the negative electrode to assemble a coin cell.

[0018] Furthermore, the mass ratio of the lithium replenishing agent, conductive agent and binder is 8:1:1, wherein the conductive agent is one or more of SP, Ketjen black, acetylene black and carbon nanotubes, the binder is PVDF, and the amount of cobalt-based bimetallic oxide core-shell microspheres added is 2 to 6 wt% of the lithium replenishing agent.

[0019] Compared with the prior art, the advantages of the present invention are: I. The cobalt-based bimetallic core-shell microspheres of this invention have cobalt and iron or nickel uniformly distributed within the core and shell of the microspheres, unlike existing bimetallic core-shell microspheres which have an uneven distribution with one metal as the core and the other as the shell. This allows both metals to function simultaneously. The cobalt-based bimetallic core-shell microspheres of this invention allow for controllable shell thickness and porosity, increasing the specific surface area of ​​the material, providing more active sites, and the synergistic effect of different components, potentially overcoming the performance limitations of single materials.

[0020] II. This invention uses a one-step method to synthesize cobalt-based bimetallic core-shell microsphere structure materials. No other impurities are generated during the reaction process. The resulting core-shell microspheres have uniform composition and size. The preparation method is simple and easy to operate.

[0021] Third, the cobalt-based bimetallic oxide core-shell microspheres based on the present invention also have a uniform internal and external compositional distribution, unlike the non-uniform distribution of existing bimetallic core-shell oxide microspheres with one metal oxide as the core and the other as the shell, allowing both metals to function simultaneously. Microspheres with identical core and shell compositions allow for control of shell thickness and porosity, increasing the specific surface area of ​​the material, providing more active sites, and the synergistic effect of different components may overcome the performance limitations of single materials.

[0022] IV. The bimetallic core-shell microspheres and bimetallic oxide core-shell microspheres prepared in this invention are added to the positive electrode raw materials of batteries as lithium replenishing agents and used for lithium battery assembly. Through testing, it can be found that the catalyst has a significant effect on reducing the decomposition voltage of lithium replenishing agents and has excellent characteristics such as being green and environmentally friendly and easy to operate. Attached Figure Description

[0023] These and / or other aspects and advantages of the present invention will become clearer and more readily understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a scanning electron microscope image of the nickel-cobalt bimetallic core-shell microspheres of Example 1 of the present invention.

[0024] Figure 2 and Figure 5 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the nickel-cobalt bimetallic oxide core-shell microspheres of Example 1 of the present invention.

[0025] Figure 3 This is a scanning electron microscope image of the iron-cobalt bimetallic core-shell microspheres of Example 5 of the present invention.

[0026] Figure 4 and Figure 6 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the iron-cobalt bimetallic oxide core-shell microspheres of Example 5 of the present invention.

[0027] Figure 7The image shows the XRD pattern of nickel-cobalt bimetallic oxide core-shell microspheres from Example 1.

[0028] Figure 8 The image shows the XRD pattern of the iron-cobalt bimetallic oxide core-shell microspheres from Example 5.

[0029] Figure 9 The image shows the catalytic effect of nickel-cobalt bimetallic core-shell microspheres as a lithium supplement catalyst in Example 1.

[0030] Figure 10 The image shows the catalytic effect of nickel-cobalt bimetallic oxide core-shell microspheres as a lithium supplement catalyst in Example 1.

[0031] Figure 11 The image shows the catalytic effect of iron-cobalt bimetallic core-shell microspheres as a lithium supplement catalyst in Example 5.

[0032] Figure 12 The image shows the catalytic effect of iron-cobalt bimetallic oxide core-shell microspheres as a lithium supplement catalyst in Example 5. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0034] Example 1 0.5 g nickel nitrate, 0.75 g cobalt nitrate and 0.33 g citric acid were dissolved in a mixed solution of 15 mL water and 30 mL ethanol. After stirring and mixing evenly, the solution was transferred to a hydrothermal reactor and reacted at 170 °C for 16 h at 100 rpm. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0035] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 700℃ for 2 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0036] Figure 1 The image shows a scanning electron microscope (SEM) image of the nickel-cobalt bimetallic core-shell microspheres of this embodiment. It can be seen from the image that core-shell structured microspheres can be synthesized in large quantities with a size of 1.3 μm-1.7 μm, where the core thickness is 1.0 μm-1.5 μm and the shell thickness is 50-300 nm.

[0037] Figure 2 and Figure 5The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the nickel-cobalt bimetallic oxide core-shell microspheres of this embodiment. The images show the core-shell structure of the oxide microspheres, with a size of 1.3 μm-1.7 μm. The core thickness is 1.0 μm-1.5 μm, and the shell thickness is 50-300 nm.

[0038] Figure 7 This is the XRD pattern of the nickel-cobalt bimetallic oxide core-shell microspheres in this embodiment.

[0039] Example 2 0.5 g nickel nitrate, 1.5 g cobalt nitrate and 0.66 g citric acid were dissolved in a mixed solution of 11 mL water and 33 mL ethanol. After stirring and mixing evenly, the solution was transferred to a hydrothermal reactor and reacted at 190 °C at 300 rpm for 24 h. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0040] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 800℃ for 3 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0041] Example 3 0.5 g nickel nitrate, 2.0 g cobalt nitrate and 0.99 g citric acid were dissolved in a mixed solution of 9 mL water and 36 mL ethanol. After stirring and mixing evenly, the mixture was transferred to a hydrothermal reactor and reacted at 220 °C for 32 h at 400 rpm. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0042] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 700℃ for 3 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0043] Example 4 0.5 g nickel nitrate, 1.0 g cobalt nitrate and 0.66 g citric acid were dissolved in a mixed solution of 11 mL water and 33 mL ethanol. After stirring and mixing evenly, the solution was transferred to a hydrothermal reactor and reacted at 200 °C for 28 h at 100 rpm. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0044] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 700℃ for 4 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0045] Example 5 0.5 g ferric nitrate, 0.9 g cobalt nitrate and 0.63 g citric acid were dissolved in a mixed solution of 15 mL water and 30 mL ethanol. After stirring and mixing evenly, the mixture was transferred to a hydrothermal reactor and reacted at 180 °C for 16 h at 100 rpm. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0046] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 800℃ for 2 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0047] Figure 3 The image shows a scanning electron microscope (SEM) image of the iron-cobalt bimetallic core-shell microspheres in this embodiment. It can be seen from the image that core-shell structured microspheres can be synthesized in large quantities with a size of 1.3 μm-1.8 μm, wherein the core particle size is 0.8 μm-1.6 μm and the shell thickness is 50-300 nm.

[0048] Figure 4 and Figure 6 The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the iron-cobalt bimetallic oxide core-shell microspheres of this embodiment. The images show the core-shell structure of the oxide microspheres, with a size of 1.2 μm-1.8 μm. The core thickness is 0.8 μm-1.6 μm, and the shell thickness is 50-300 nm.

[0049] Figure 8 This is the XRD pattern of the iron-cobalt bimetallic oxide core-shell microspheres in this embodiment.

[0050] Example 6 0.5 g ferric nitrate, 1.2 g cobalt nitrate and 1.26 g citric acid were dissolved in a mixed solution of 11 mL water and 33 mL ethanol. After stirring and mixing evenly, the mixture was transferred to a hydrothermal reactor and reacted at 220 °C for 32 h at 300 rpm. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0051] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 800℃ for 4 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0052] Example 7 0.5 g ferric nitrate, 1.8 g cobalt nitrate and 1.89 g citric acid were dissolved in a mixed solution of 9 mL water and 36 mL ethanol. After stirring and mixing evenly, the mixture was transferred to a hydrothermal reactor and reacted at 170 °C at 250 rpm for 20 h. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0053] The obtained precursor material was placed in a tube furnace and calcined at 800℃ for 2 h (heating rate 5℃ / min) to obtain cobalt-nickel based bimetallic oxide core-shell microspheres.

[0054] Example 8 0.5 g ferric nitrate, 2.0 g cobalt nitrate and 1.26 g citric acid were dissolved in a mixed solution of 10 mL water and 35 mL ethanol. After stirring and mixing evenly, the mixture was transferred to a hydrothermal reactor and reacted at 195 °C at 400 rpm for 24 h. After the reaction was completed, the solution was centrifuged and the solid product was washed with deionized water and ethanol to obtain cobalt-based bimetallic core-shell microspheres.

[0055] The obtained cobalt-based bimetallic core-shell microspheres were placed in a tube furnace and calcined at 800℃ for 3 h (heating rate 5℃ / min) to obtain cobalt-nickel-based bimetallic oxide core-shell microspheres.

[0056] The molar ratio of the size of the metal microspheres and oxide microspheres obtained in each embodiment of the present invention to the metal raw materials (nickel nitrate or iron nitrate: cobalt nitrate) is shown in Table 1.

[0057] Table 1. Relationship between the size of metal microspheres and oxide microspheres and the molar ratio of metal raw materials obtained in each embodiment. Lithium-ion battery performance testing methods with added lithium replenishing agents and catalysts The lithium supplement (lithium ferrite), conductive agent, and binder were mixed at a mass ratio of 8:1:1. The conductive agent could be one or more of SP, Ketjen Black, acetylene black, and carbon nanotubes. PVDF was chosen as the binder. Bimetallic core-shell microspheres or oxide core-shell microspheres were added to the positive electrode at 2-6 wt% (relative to the lithium supplement). A coin cell was assembled using lithium nickel cobalt manganese oxide as the positive electrode active material and graphite as the negative electrode for testing and characterization. Testing was conducted at 0.1 C, with constant current and constant voltage charging to 4.4 V to test the catalyst's catalytic decomposition characteristics of the lithium supplement.

[0058] The bimetallic core-shell microspheres or oxide core-shell microspheres obtained in each embodiment were subjected to the above-mentioned performance experiments. The results showed that the bimetallic core-shell microspheres or oxide core-shell microspheres of the present invention can effectively reduce the decomposition voltage of the lithium replenishing agent when used as a lithium replenishing agent catalyst in lithium-ion batteries. The voltage is lower than 4.2 V without the catalyst, which helps to reduce the impact of lithium consumed during the formation of the SEI film during the first charge of the battery on the battery performance.

[0059] The potentials of the bimetallic core-shell microspheres or oxide core-shell microspheres obtained in each embodiment after catalysis are shown in Table 2.

[0060] Table 2. Voltage of bimetallic core-shell microspheres or oxide core-shell microspheres obtained in each example when used as catalysts. Figure 9 The figure shows the catalytic effect of nickel-cobalt bimetallic core-shell microspheres as a lithium replenishing agent catalyst in Example 1. As can be seen from the figure, the decomposition potential of the lithium replenishing agent decreased from 4.2V to 4.05V in the presence of the catalyst, and the battery capacity was significantly improved.

[0061] Figure 10 The figure shows the catalytic effect of nickel-cobalt bimetallic oxide core-shell microspheres as a lithium replenishing agent catalyst in Example 1. As can be seen from the figure, the decomposition potential of the lithium replenishing agent decreased from 4.2V to 3.90V in the presence of the catalyst, and the battery capacity was significantly improved.

[0062] Figure 11 The figure shows the catalytic effect of iron-cobalt bimetallic core-shell microspheres as a lithium replenishing agent catalyst in Example 5. As can be seen from the figure, the decomposition potential of the lithium replenishing agent decreased from 4.2V to 4.1V in the presence of the catalyst, and the battery capacity was significantly improved.

[0063] Figure 12 The figure shows the catalytic effect of iron-cobalt bimetallic oxide core-shell microspheres as a lithium replenishing agent catalyst in Example 5. It can be seen from the figure that in the presence of the catalyst, the decomposition potential of the lithium replenishing agent decreased from 3.95V to 3.9V, and the battery capacity was significantly improved.

[0064] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. Cobalt-based bimetallic core-shell microspheres, characterized in that, comprising cobalt and iron, or cobalt and nickel; the cobalt and iron, or cobalt and nickel are uniformly distributed in the cobalt-based bimetallic core-shell microspheres, wherein the molar percentage of cobalt is 50%-60%, and the molar percentage of iron or nickel is 40%-50%; the particle size of the cobalt-based bimetallic core-shell microspheres is 1.2 μm-1.8 μm, wherein the particle size of the core is 0.8 μm-1.6 μm, and the thickness of the shell is 50-300 nm.

2. A method for preparing cobalt-based bimetallic core-shell microspheres as described in claim 1, characterized in that, comprising the following steps: Step one, taking one of nickel nitrate or iron nitrate, cobalt nitrate and citric acid, dispersing them in a mixed solution of deionized water and ethanol, stirring to dissolve, then performing a solvothermal reaction under stirring to obtain a reaction solution; Step two, centrifugal washing the reaction solution with a mixed solution of deionized water and ethanol, then drying to obtain the cobalt-based bimetallic core-shell microspheres.

3. The method for preparing cobalt-based bimetallic core-shell microspheres as described in claim 2, characterized in that, In step one: the molar ratio of one of nickel nitrate or iron nitrate, cobalt nitrate and citric acid is 1: (1.5-4): (1-3); in the mixed solution of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:2-1:

4.

4. The preparation method of the cobalt-based bimetallic core-shell microspheres according to claim 2, characterized in that, In step one: the solvothermal reaction is to place the mixture after stirring and dissolving into the inner shell of a high-temperature reaction kettle, add a stirring rotor to the inner shell of the high-temperature reaction kettle, then transfer the inner shell of the high-temperature reaction kettle to a stainless steel hydrothermal kettle; the stirring speed of the stirring rotor is 100-400 rpm; the temperature of the solvothermal reaction is 170-220℃, and the time is 16 h-32 h; In step two, drying is performed under vacuum at 60-80℃.

5. Use of the cobalt-based bimetallic core-shell microspheres according to claim 1, characterized in that, a catalyst for use as a lithium battery lithium supplement agent.

6. A cobalt-based double metal oxide core-shell microsphere, characterized in that, obtained by calcining the cobalt-based bimetallic core-shell microspheres according to claim 1; the cobalt-based bimetallic oxide core-shell microspheres uniformly distribute cobalt oxide and iron oxide, or cobalt oxide and nickel oxide therein, wherein the mass percentage of cobalt oxide is 50%-60%, and the mass percentage of iron oxide or nickel oxide is 40%-50%; the particle size of the cobalt-based bimetallic oxide core-shell microspheres is 1.2 μm-1.8 μm, wherein the thickness of the core is 0.8 μm-1.6 μm, and the thickness of the shell is 50-300 nm.

7. The cobalt-based double metal oxide core-shell microspheres of claim 6, wherein, The calcination is to perform calcination of the cobalt-based bimetallic core-shell microspheres in a tube furnace under a nitrogen atmosphere, and the temperature control mechanism for calcination is to increase the temperature from room temperature to 700℃-800℃ at a rate of 5℃ / min, and to keep the temperature for 2h-4h.

8. Use of the cobalt-based double metal oxide core-shell microspheres according to claim 6, characterized in that a catalyst for use as a lithium battery lithium supplement agent.

9. Use of cobalt-based double metal oxide core-shell microspheres according to claim 8, characterized in that mixing a lithium supplement agent, a conductive agent and a binder, then adding the cobalt-based bimetallic oxide core-shell microspheres to the mixture, and mixing uniformly to make a positive electrode, taking lithium nickel cobalt manganese oxide as an active material, and taking graphite as a negative electrode to assemble a button cell.

10. Use of cobalt-based bimetal oxide core-shell microspheres according to claim 9, characterized in that The mass ratio of the lithium supplement agent, the conductive agent and the binder is 8:1:1, wherein the conductive agent is one or more of SP, Ketjen black, acetylene black and carbon nanotubes, the binder is PVDF, and the addition amount of the cobalt-based bimetallic oxide core-shell microspheres is 2-6 wt% of the lithium supplement agent.

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