High-rate compacting negative electrode material and preparation method thereof

Abstract

The application belongs to the field of negative electrode material preparation, and provides a high-rate compaction negative electrode material and a preparation method thereof. First, ZIF-67 is synthesized by taking cobalt nitrate and 2-methyl imidazole as precursors, and is modified by introducing tetraethoxysilane and tetrabutyl titanate through a sol-gel method to obtain a precursor powder, then the precursor is heated in stages in a tube furnace, and high-temperature carbonization is carried out in a mixed gas atmosphere to prepare a MOF-derived material; second, partially reduced graphene oxide is prepared by reacting a graphene oxide dispersion liquid with ascorbic acid under a nitrogen atmosphere; then the partially reduced graphene oxide is mixed with a molybdenum disulfide dispersion liquid, and dopamine, 3,4-ethylenedioxythiophene and silver nitrate are introduced at the same time to obtain a graphene-polymer derivative; the base material, the MOF-derived material, carbon black and the graphene-polymer derivative are uniformly mixed to prepare a negative electrode slurry, and after gradient rolling and argon protection heat treatment, a high-rate compaction negative electrode material is prepared.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of negative electrode material preparation and relates to a high-rate compaction negative electrode material and a preparation method thereof. BACKGROUND

[0002] In the field of electrochemical energy storage, lithium-ion batteries have been widely used in consumer electronics, electric vehicles and renewable energy storage, as a high-efficiency, reliable and rechargeable energy storage technology. With the rapid growth of these application demands, especially the increasing performance requirements of lithium-ion batteries for electric vehicles and high-power devices, the research and development of battery materials are facing many challenges. Among these challenges, high-rate performance, high volumetric energy density and long-term cycle stability are one of the core goals of negative electrode material design. High-rate performance requires the electrode material to quickly and stably complete the storage and release of lithium ions under high charge and discharge rates, while high volumetric energy density requires the material to achieve higher energy storage capacity in a limited volume.

[0003] The performance of the negative electrode material directly determines the rate performance, energy density and cycle life of the lithium-ion battery. Traditional commercial negative electrode materials (such as graphite) are difficult to meet the needs of high-rate applications due to their low theoretical specific capacity and slow lithium ion diffusion dynamics. In the high-rate charge and discharge process, the lithium ion intercalation reaction kinetics of graphite is limited, and its layered structure may cause a mismatch between electron-ion transport rates under high-rate conditions, thereby significantly increasing the polarization phenomenon of the battery and reducing the electrochemical performance. Therefore, it is necessary to develop new high-rate negative electrode materials to solve these problems. On the other hand, the compaction density of the negative electrode material has an important influence on the volumetric energy density of the lithium-ion battery. Increasing the compaction density of the negative electrode material can store more energy in a limited volume, but high compaction density often reduces the porosity of the material, thereby affecting the transport path of lithium ions. Therefore, it has a good application prospect to study a high-rate compaction negative electrode material. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a high-rate compaction negative electrode material and a preparation method thereof. By synthesizing a MOF-derived material, partially reducing graphene oxide and compounding molybdenum disulfide and a conductive polymer, and optimizing the matrix material and multiple components in cooperation, a negative electrode material with high conductivity, high ion migration efficiency, high compaction density and excellent cycle stability is finally prepared by adjusting the gradient rolling and heat treatment process, thereby meeting the needs of actual production.

[0005] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a preparation method of a high-rate compaction negative electrode material, which comprises:

[0007] S1, mixing the cobalt nitrate solution with the 2-methylimidazole solution, then microwave heating to obtain ZIF-67, dispersing tetraethoxysilane and tetrabutyl titanate in anhydrous ethanol, adjusting the pH to 2 to obtain a sol-gel precursor, then dispersing ZIF-67 in an ethanol aqueous solution and adding to the sol-gel precursor to obtain a precursor powder;

[0008] S2, transferring the precursor powder into a tube furnace, passing in a mixed gas, heating and holding to obtain a MOF-derived material;

[0009] S3, adding ascorbic acid to a graphene oxide dispersion solution, reacting to obtain partially reduced graphene oxide, then mixing the partially reduced graphene oxide dispersion solution with a molybdenum disulfide dispersion solution to obtain a mixed solution A, dispersing dopamine, 3,4-ethylenedioxythiophene, silver nitrate, copper sulfate and ammonium persulfate in an ethanol aqueous solution to obtain a mixed solution B, adding the mixed solution B to the mixed solution A and adding sodium borohydride, holding in an argon atmosphere to obtain a graphene-polymer derivative;

[0010] S4, mixing the matrix material, the MOF-derived material and carbon black, adding N-methylpyrrolidone, then adding the graphene-polymer derivative, PVDF and carboxymethyl cellulose to obtain a negative electrode slurry, then coating the negative electrode slurry on a copper foil current collector, drying, then performing gradient rolling and holding in an argon atmosphere to obtain a high-rate compaction negative electrode material.

[0011] Specifically includes:

[0012] S1, mixing the cobalt nitrate solution with the 2-methylimidazole solution, then adjusting the temperature to a first temperature and microwave heating, washing and filtering to obtain ZIF-67, dispersing tetraethoxysilane and tetrabutyl titanate in anhydrous ethanol, using hydrochloric acid to adjust the pH to 2 to obtain a sol-gel precursor, then dispersing ZIF-67 in an ethanol aqueous solution and adding to the sol-gel precursor, stirring at room temperature, and filtering and drying to obtain a precursor powder;

[0013] S2, transferring the precursor powder into a tube furnace, passing in a mixed gas, adjusting the temperature to a second temperature and holding, then adjusting the temperature to a third temperature and holding, finally adjusting the temperature to a fourth temperature and holding, cooling to room temperature and grinding to obtain a MOF-derived material;

[0014] S3, ascorbic acid is added to the graphene oxide dispersion liquid, the temperature is adjusted to the first temperature under nitrogen atmosphere, after the reaction, the partially reduced graphene oxide is obtained by filtering and drying, then the partially reduced graphene oxide dispersion liquid is mixed with the molybdenum disulfide dispersion liquid to obtain a mixed liquid A, dopamine, 3,4-ethylenedioxythiophene, silver nitrate, copper sulfate and ammonium persulfate are dispersed in an ethanol aqueous solution to obtain a mixed liquid B, the mixed liquid B is added dropwise to the mixed liquid A under stirring, and sodium borohydride is added, the product is freeze-dried, then placed in a tube furnace, the temperature is adjusted to the fifth temperature under argon atmosphere, and the product is obtained by grinding after cooling to room temperature;

[0015] S4, the base material, the MOF derived material and the carbon black are mixed and added to N-methyl pyrrolidone, then the graphene-polymer derivative, PVDF and carboxymethyl cellulose are added, the mixture is uniformly mixed, vacuum degassing is performed to obtain a negative electrode slurry, the negative electrode slurry is coated on a copper foil current collector, dried, gradient rolled, and placed in an argon atmosphere for heat preservation, and a high-rate compacted negative electrode material is obtained after cooling to room temperature.

[0016] Cobalt nitrate hexahydrate, when dissolved in water, releases cobalt ions. 2-Methylimidazole is a nitrogen-containing compound with a molecular structure that includes an imidazole ring. The two nitrogen atoms in the imidazole ring have strong coordination abilities, one being aromatic nitrogen and the other being amino nitrogen. Both nitrogen atoms can simultaneously form coordination bonds with divalent cobalt ions. In aqueous solution, cobalt ions undergo coordination reactions with 2-methylimidazole, forming stable coordination compounds through self-assembly processes. Further coordination allows cobalt ions to bridge with multiple 2-methylimidazole ligands, constructing the crystal structure of ZIF-67. ZIF-67 is a zeolite-like metal-organic framework material with structural characteristics similar to natural zeolites, composed of cobalt ions as metal nodes and 2-methylimidazole as ligands. Specifically, the crystal structure of ZIF-67 is formed by bridging cobalt ions and 2-methylimidazole to form tetrahedral units. These tetrahedral units are connected periodically to form a three-dimensional network with highly ordered pore structures. This unique crystal structure of ZIF-67 not only has high porosity but also exhibits excellent chemical stability. High porosity provides a large specific surface area, which is crucial during the subsequent carbonization process, as it significantly improves the uniformity of thermal decomposition and carbonization reactions, ensuring that the final material has good performance. During the preparation of the sol-gel precursor, tetraethoxysilane is used as a silicon source and undergoes acid-catalyzed hydrolysis to generate silanol molecules. These silanol molecules further connect with each other through condensation reactions to form a three-dimensional silica network structure. Meanwhile, tetrabutyl titanate, as a titanium source, also undergoes hydrolysis in an acidic environment to generate titanium alcohol molecules. Titanium alcohol molecules form a network structure of titanium dioxide through similar condensation reactions. In the reaction system, the hydrolysis and condensation reactions of tetraethoxysilane and tetrabutyl titanate occur simultaneously, ultimately generating a silicon-titanium oxide composite network. As these condensation reactions continue, the sol gradually transforms into a viscous gel-like material, and the resulting sol-gel precursor has excellent dispersibility and uniformity, making it a stable and reliable matrix material for subsequent reactions. Due to the high surface energy of ZIF-67, which has a rich pore structure and polar functional groups on its surface, ZIF-67 can interact with the components in the sol-gel system during the dispersion process. This interaction can be either physical adsorption or chemical bonding. During the compounding of ZIF-67 and the sol-gel precursor, ZIF-67 particles are uniformly embedded in the silicon-titanium oxide gel network, forming a composite material. In addition, some active sites on the surface of ZIF-67, such as cobalt ions or imidazole groups, may interact with hydroxyl groups in the silicon-titanium oxide network through hydrogen bonding or weak chemical bonding, further enhancing the structural stability of the composite material.

[0017] During the calcination of the precursor powder, at the stage of 300-350℃, the 2-methylimidazole ligand in ZIF-67 begins to decompose, and the framework structure of ZIF-67 is composed of cobalt ions and 2-methylimidazole through coordination. When the temperature rises to 300-350℃, the chemical bonds of 2-methylimidazole begin to break, releasing small volatile molecules, including ammonia, carbon dioxide, and other small molecule organic compounds. In this process, the framework structure of ZIF-67 partially collapses, leaving incomplete carbonized organic residues, providing a basis for subsequent carbonization and structural reorganization. At the same time, ammonia decomposes under heating conditions to produce nitrogen and hydrogen. In a high-temperature environment, the active hydrogen and nitrogen atoms produced by the decomposition of ammonia can react with the residual carbon materials and metallic cobalt in the precursor. The decomposition of ammonia not only provides conditions for nitrogen doping of carbon materials, but also partially promotes the transition of cobalt ions to metallic cobalt through the reduction effect of hydrogen. This nitrogen doping process introduces active nitrogen atoms into the carbon skeleton, forming nitrogen-doped carbon materials. Nitrogen doping can significantly improve the electrical conductivity of carbon materials and introduce more electrochemically active sites into the carbon skeleton, thereby enhancing the electrochemical performance of the material. In addition, acetylene molecules may be adsorbed on the surface of ZIF-67 due to their high chemical activity. These acetylene molecules interact with the metal cobalt or carbon species in the framework through surface adsorption, laying the foundation for the subsequent carbonization process. As the heating temperature rises to 500-550℃, hydrogen, ammonia, and acetylene in the mixed gas begin to participate in the reaction in depth, further promoting carbonization, cobalt phase transition, and deepening of nitrogen doping. In this stage, the residues of the ligand begin to further dehydrogenate, converting into a more dense carbon skeleton. Acetylene begins to decompose at this temperature range, generating active carbon atoms that deposit on the surface of the carbon skeleton under the catalytic action of cobalt particles, increasing the carbon content of the material. At the same time, cobalt particles can catalyze the recombination of carbon atoms generated during the decomposition of acetylene, forming low-order graphitized carbon materials. Hydrogen can effectively inhibit the occurrence of excessive cross-linking in the carbon skeleton, making the carbon skeleton more uniform and avoiding structural defects caused by excessive carbonization. At the same time, cobalt ions are further reduced to metallic cobalt particles under the action of hydrogen. At this time, cobalt particles may be uniformly dispersed in the carbon skeleton material in the form of metal, or may react with carbon to form cobalt-based carbides. Cobalt-based carbides are an intermediate phase with excellent electrical conductivity and catalytic activity, which will further participate in the reorganization process of carbon materials in the subsequent high-temperature stage. Ammonia continues to decompose at this stage, and the active nitrogen atoms produced by the decomposition can react with the carbon skeleton, allowing nitrogen atoms to be embedded in the carbon structure in the form of chemical bonds. Nitrogen atoms can exist in various forms, including pyridine nitrogen, pyrrole nitrogen, and graphite nitrogen. These forms of nitrogen doping not only improve the electrical conductivity of carbon materials but also introduce more electrochemically active sites, thereby providing a chemical basis for improving the lithium or sodium storage performance of the material.When the temperature is further increased to 700-750℃, acetylene and hydrogen in the mixed gas begin to play a key role under high temperature conditions, further promoting the graphitization of carbon materials, while cobalt particles play an important catalytic role in this process. In a high temperature environment, amorphous carbon or low-order carbon in carbon materials gradually reorganizes and converts into a graphite structure with higher crystallinity. Acetylene decomposes at this stage, and the generated carbon atoms are integrated into the carbon skeleton, thereby further improving the graphitization degree of the carbon material. Cobalt particles play a catalytic role in this process, effectively catalyzing the reorganization of carbon atoms to form regular hexagonal graphite lattices. This cobalt particle-induced catalytic graphitization process not only improves the electrical conductivity of carbon materials but also optimizes their structural stability, making the materials more dense and uniform.

[0018] The catalytic effect of cobalt particles is also reflected in the process of acetylene decomposition to generate carbon atoms and assemble them into a carbon skeleton, while catalyzing the formation of higher-order graphitized carbon structures in carbon materials. The dispersity of cobalt particles is crucial for the uniformity of the graphitization process. Uniformly dispersed cobalt particles can effectively avoid local carbonization unevenness and remain stable in the final material, forming a cobalt-carbon composite structure with graphitized carbon materials. In addition, ammonia and hydrogen in the mixed gas continue to regulate the microstructure of carbon materials at this stage. The role of ammonia prevents the carbon material from being over-graphitized at high temperatures, thereby maintaining the pore structure of the material. The reducing effect of hydrogen can further remove residual oxide impurities on the carbon surface, improving the purity and electrical conductivity of the carbon material. Under high temperature conditions of 700-750℃, nitrogen doping is further stabilized, with nitrogen atoms mainly embedded in the carbon material in the form of graphite nitrogen, giving the material higher electrochemical stability and electrical conductivity. The reducing effect of hydrogen removes possible oxide impurities on the carbon surface, making the carbon skeleton more pure and further enhancing the overall performance of the material.

[0019] The graphene oxide is rich in various oxygen-containing functional groups on its surface, such as hydroxyl, carboxyl and epoxy groups, which significantly enhance the dispersibility and chemical reactivity of graphene oxide in aqueous solution, making it an excellent precursor of functionalized materials. However, the introduction of these oxygen-containing functional groups also destroys the original pi electron conjugation network of graphene, resulting in a decrease in its electrical conductivity. Therefore, in order to restore the electrical conductivity of graphene while retaining its certain dispersibility and chemical reactivity, the present application selects ascorbic acid as a mild reducing agent for the partial reduction of graphene oxide. Ascorbic acid acts as an electron donor through the hydroxyl group in its molecule to gradually reduce the hydroxyl and epoxy groups on the surface of graphene oxide in aqueous solution. In this process, the hydroxyl and epoxy groups are partially converted to carbon-carbon double bonds, while water molecules are released. Due to the weak reducing ability of ascorbic acid, part of the oxygen-containing functional groups in graphene oxide are retained, thereby generating partially reduced graphene oxide. This partially reduced graphene oxide, on the one hand, improves the electrical conductivity of the material, and on the other hand, the retained oxygen-containing functional groups such as carboxyl and hydroxyl provide necessary chemical reaction sites for subsequent modification and functionalization, while maintaining the dispersibility of the material in polar solvents. On the basis of partially reduced graphene oxide, the present application further enhances the functionality of the composite material by introducing dopamine molecules. Dopamine is a small molecule compound with both catechol groups and amino groups. In weak alkaline solution, dopamine forms a polydopamine coating through oxidation-polymerization reaction. The catechol groups in dopamine molecules are first oxidized to o-quinone structure, which is a highly reactive intermediate product, and is connected through intermolecular covalent bonds to form a polymer chain. At the same time, the amino groups in dopamine molecules also participate in crosslinking reaction, thereby generating a polydopamine polymer with a highly crosslinked structure. Polydopamine has high chemical stability and functionality, and can form a dense and uniform coating on the surface of various substrates. In the present application, dopamine molecules form a polydopamine coating on the surface of partially reduced graphene oxide through self-polymerization. The introduction of polydopamine not only significantly enhances the chemical stability of the composite material, but also provides abundant active sites for the adsorption and loading of metal nanoparticles in the subsequent step, including the amino and phenolic hydroxyl groups on the surface of polydopamine. In addition, polydopamine itself has a certain electrical conductivity, which can further optimize the electrochemical performance of the composite material. In terms of mechanical properties, the presence of the polydopamine coating also provides additional mechanical stability to the composite material, allowing it to maintain high structural integrity during subsequent processing and application.

[0020] On the basis of dopamine modification, further by introducing 3,4-ethylenedioxythiophene monomer, using chemical oxidation polymerization method prepared conductive excellent poly(3,4-ethylenedioxythiophene) coating. 3,4-ethylenedioxythiophene is a commonly used conductive polymer monomer, its polymerization product poly(3,4-ethylenedioxythiophene) has been widely used due to its high conductivity and mechanical flexibility. In the present application, 3,4-ethylenedioxythiophene is subjected to radical polymerization by oxidation of ammonium persulfate, ammonium persulfate as a strong oxidizing agent, can oxidize the carbon-carbon double bond in 3,4-ethylenedioxythiophene molecule to generate cationic radicals, these radicals as reactive centers, through step-by-step addition reaction to form long-chain polymers. The polymerization reaction is carried out on the surface of the partially reduced graphene oxide and polydopamine composite material, so that poly(3,4-ethylenedioxythiophene) is uniformly deposited on the material surface. The main chain structure of poly(3,4-ethylenedioxythiophene) provides excellent conductivity due to the intramolecular conjugation effect, its introduction not only significantly enhances the conductivity of the composite material, but also further improves the mechanical flexibility of the material. The flexible dioxo ring structure of poly(3,4-ethylenedioxythiophene) enables the composite material to maintain structural integrity when subjected to mechanical stress. In addition, the interfacial interaction between poly(3,4-ethylenedioxythiophene) and partially reduced graphene oxide, polydopamine further enhances the physical and chemical stability of the composite material, providing the possibility for the application of the material in various electrochemical fields.

[0021] To further enhance the electrochemical performance of the composite material, the present application loads metal nanoparticles by chemical reduction method, silver nitrate and copper sulfate are used as the source of silver ions and copper ions respectively, by introducing sodium borohydride as a strong reducing agent, the silver ions and copper ions are reduced to metal elements in aqueous solution, and the nanoparticles are deposited on the surface of the composite material. The strong reducing ability of sodium borohydride ensures the efficient reduction of metal ions, and the reaction rate can effectively control the size and distribution of nanoparticles. During the reduction process, the metal nanoparticles are fixed on the surface of the polydopamine coating through electrostatic interaction or chemical bond interaction, the amino and phenolic hydroxyl groups on the surface of polydopamine provide ideal active sites for the adsorption and reduction of metal ions, thereby ensuring the uniform distribution of metal nanoparticles. These loaded metal nanoparticles significantly improve the overall conductivity of the composite material, and at the same time provide more active sites for electrochemical reactions. In the last stage of the preparation of the composite material, heat treatment at 200-250 DEG C is adopted to optimize the material, the main effects of heat treatment include removing residual solvents and unreacted precursors, improving the purity of the material; promote the interface combination between partially reduced graphene oxide, polydopamine, poly(3,4-ethylenedioxythiophene) and metal nanoparticles, enhance the structural stability of the material; further remove part of the residual oxygen-containing functional groups in the partially reduced graphene oxide, thereby improving the conductivity; and promote the recrystallization of metal nanoparticles, make its distribution more uniform, at the same time improve the porous structure of the material. Finally, a multifunctional composite material is obtained, which takes partially reduced graphene oxide as the substrate, forms a chemical active coating through the self-polymerization of dopamine, and combines 3,4-ethylenedioxythiophene polymerization and metal nanoparticle loading. The material has high conductivity, excellent mechanical stability and rich electrochemical active sites, which makes it have broad application prospects in energy storage devices, electrocatalysis and other electrochemical fields.

[0022] In the process of preparing the negative electrode slurry, the matrix material is composed of graphite, hard carbon and titanium carbide. The hard carbon is an amorphous carbon material with high specific surface area and micro-nano pore structure, which can provide more active sites for lithium ion storage. The amorphous nature of hard carbon enables it to have excellent rate performance, especially at high rate charge and discharge, which can maintain a high capacity. Titanium carbide is a conductive ceramic material with metallic properties. Its high conductivity and chemical stability enable it to act as a bridge for electron conduction in the negative electrode material, while enhancing the mechanical strength and durability of the material. In addition, the surface of titanium carbide can provide additional lithium storage sites, and its high hardness can also improve the compaction density of the negative electrode material. The MOF material after pyrolysis is usually composed of conductive carbon skeleton and dispersed metal or metal compound particles. Cobalt-based MOF derived material can contain metallic cobalt or cobalt-based carbide. These species not only have high conductivity, but also can provide catalytic activity in electrochemical reactions, promoting the kinetics of lithium ion intercalation / deintercalation reaction. In addition, the porous structure of the MOF derived material further improves the specific surface area of the negative electrode material, providing more paths and sites for lithium ion storage. PVDF is a non-polar polymer material that can tightly bind the active material, conductive additive and current collector through intermolecular forces. The chemical stability and high temperature resistance of PVDF enable it to maintain the bonding effect in the electrolyte environment for a long time, avoiding material shedding. Carboxymethyl cellulose is a water-soluble polymer, and its carboxyl group can weakly chemisorb on the surface of metal oxides and carbon materials in the slurry, thereby promoting the dispersibility of the material. CMC can form a flexible network structure after drying, further enhancing the mechanical stability and compaction density of the negative electrode material. After coating and drying of the negative electrode slurry on the copper foil, gradient rolling and argon protection heat treatment are carried out. Gradient rolling promotes the closer contact between negative electrode material particles by gradually increasing the pressure, thereby improving the compaction density of the material. In a high pressure environment, the physical combination between graphite, hard carbon, MOF derived material and carbon black particles is more closely, while the possible residual micropores and bubbles in the slurry are excluded, reducing the porosity of the material. In the high temperature environment under argon protection, the solvent and binder remaining on the surface of the material may decompose or volatilize in small amounts, releasing low molecular weight impurities, thereby improving the purity of the material. And heat treatment promotes the interface fusion between PVDF and active material, conductive material, improving the overall structural stability of the material.

[0023] In the present application, the preparation of high-rate negative electrode material involves the synergistic effect of multiple components, including the following aspects: (1) conductive network, graphite as a layered structure material provides good intrinsic conductivity, and its two-dimensional sheet structure helps to build a macroscopic electron conduction path, and the graphene in the graphene-polymer derivative further optimizes the conductive network. Graphene has extremely high conductivity and two-dimensional sheet characteristics, not only can form an electron conduction bridge between the graphite layers, but also can be in close contact with the matrix material and other components, reducing the interface resistance. The MOF-derived material not only has conductivity, but also can physically contact with graphene and carbon black to form a multi-level electron conduction bridge. These bridges further reduce the length of the electron transport path in the porous carbon skeleton, thereby improving the electron conduction efficiency; (2) ion transport path, the amorphous nature of hard carbon and the porous structure of the MOF-derived material provide abundant active sites for lithium ion storage and form continuous ion migration channels between particles. The MOF-derived material retains part of the original MOF's porous properties after high-temperature carbonization. These porous structures can reduce the diffusion resistance of lithium ion transport. The polymer and residual oxygen-containing functional groups in the graphene-polymer derivative can improve the interface wettability of the negative electrode material, promote the infiltration of the electrolyte, and thus reduce the ion transport resistance; (3) compaction density and mechanical stability, the gradient rolling gradually increases the compaction density of the negative electrode material, making the particles more closely contact each other and reducing the porosity of the material. The flexible sheet structure of graphene and the bonding effect of PVDF during the rolling process buffer the stress concentration between particles. High-temperature heat treatment promotes the surface recombination of the MOF-derived material and the hard carbon particles, making the interface between the particles more firm.

[0024] As a preferred technical solution of the present application, in step S1, the mass fraction of the cobalt nitrate solution is 5.7wt.%, and the solute is cobalt nitrate hexahydrate.

[0025] In some optional embodiments, the mass fraction of the 2-methylimidazole solution is 10.7wt.%.

[0026] In some optional embodiments, the mass ratio of the cobalt nitrate hexahydrate to 2-methylimidazole is 1:2.

[0027] In some optional embodiments, the first temperature is 80-90℃, for example, it can be 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃ or 90℃, but not limited to the listed temperatures. Other unlisted temperatures in this temperature range are also applicable.

[0028] In some optional embodiments, the volume ratio of tetraethoxysilane to tetrabutyl titanate is 5:3.

[0029] In some alternative embodiments, the volume ratio of the tetraethoxysilane to the anhydrous ethanol is 5:40.

[0030] In some alternative embodiments, the concentration of the hydrochloric acid is 1M.

[0031] In some alternative embodiments, the mass volume ratio of the ZIF-67 to the aqueous ethanol solution is 1g:10mL, and the mass fraction of the aqueous ethanol solution is 60wt.%.

[0032] In some alternative embodiments, the volume mass ratio of the tetraethoxysilane to the ZIF-67 is 1mL:1g.

[0033] In some alternative embodiments, the stirring time is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0034] In some alternative embodiments, the drying temperature is 70-80℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃, but not limited to the listed temperatures, other unlisted temperatures in this range are also applicable.

[0035] In some alternative embodiments, the drying time is 8-10h, for example, it can be 8.0h, 8.2h, 8.4h, 8.6h, 8.8h, 9.0h, 9.2h, 9.4h, 9.6h, 9.8h or 10.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0036] As a preferred technical solution of the present application, in step S2, the volume fraction ratio of argon, ammonia, acetylene and hydrogen in the mixed gas is 70:15:5:10.

[0037] In some alternative embodiments, the second temperature is 300-350℃, for example, it can be 300℃, 305℃, 310℃, 315℃, 320℃, 325℃, 330℃, 335℃, 340℃, 345℃ or 350℃, but not limited to the listed temperatures, other unlisted temperatures in this range are also applicable.

[0038] In some optional embodiments, the second temperature holding time is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0039] In some optional embodiments, the third temperature is 500-550℃, for example, it can be 500℃, 510℃, 520℃, 530℃, 540℃ or 550℃, but not limited to the listed temperatures, other unlisted temperatures in this range are also applicable.

[0040] In some optional embodiments, the third temperature holding time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0041] In some optional embodiments, the fourth temperature is 700-750℃, for example, it can be 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃, but not limited to the listed temperatures, other unlisted temperatures in this range are also applicable.

[0042] In some optional embodiments, the fourth temperature holding time is 3-4h, for example, it can be 3.0h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h or 4.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0043] As a preferred technical solution of the present application, in step S3, the concentration of the graphene oxide dispersion liquid is 1mg / mL.

[0044] In some optional embodiments, the mass ratio of ascorbic acid to graphene oxide is 3:1.

[0045] In some optional embodiments, the first temperature reaction time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but not limited to the listed times, other unlisted times in this range are also applicable.

[0046] In some optional embodiments, the mass fraction of the partially reduced graphene oxide dispersion is 6 wt.%, and the solvent is deionized water and anhydrous ethanol in a volume ratio of 5:1.

[0047] In some optional embodiments, the mass fraction of the molybdenum disulfide dispersion is 9 wt.%, and the solvent is anhydrous ethanol.

[0048] In some optional embodiments, the mass ratio of dopamine, 3,4-ethylenedioxythiophene, silver nitrate, copper sulfate and ammonium persulfate is 1:2:1:1:1.

[0049] In some optional embodiments, the mass fraction of the ethanol aqueous solution is 33 wt.%.

[0050] In some optional embodiments, the mass volume ratio of the dopamine to the ethanol aqueous solution is 1 g:150 mL.

[0051] In some optional embodiments, the dropping speed is 10 mL / min.

[0052] In some optional embodiments, the mass ratio of silver nitrate to sodium borohydride is 1:0.5.

[0053] In some optional embodiments, the fifth temperature is 200-250°C, for example, it can be 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C or 250°C, but is not limited to the listed temperatures, and other unlisted temperatures within this temperature range are also applicable.

[0054] As a preferred technical solution of the present invention, in step S4, the mass ratio of the matrix material, MOF derivative material, carbon black, graphene-polymer derivative, PVDF and carboxymethyl cellulose is 14:1.2:0.4:1.2:1.6:0.4.

[0055] In some optional embodiments, the matrix material is graphite, hard carbon and titanium carbide, with a mass ratio of 100:10:5.

[0056] In some optional embodiments, the mass volume ratio of the matrix material to N-methylpyrrolidone is 14 g:50 mL.

[0057] In some optional embodiments, the gradient rolling is: 10 MPa bidirectional 2 times, 70 MPa unidirectional 2 times.

[0058] In some alternative embodiments, the temperature for maintaining is 120-140℃, for example, it can be 120℃, 122℃, 124℃, 126℃, 128℃, 130℃, 132℃, 134℃, 136℃, 138℃ or 140℃, but not limited to the listed temperatures, other unlisted temperatures in this temperature range are also applicable.

[0059] In some alternative embodiments, the time for maintaining is 1-2h, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but not limited to the listed times, other unlisted times in this time range are also applicable.

[0060] In the second aspect, the application provides a high-rate compaction negative electrode material prepared by the preparation method of the first aspect.

[0061] Compared with the prior art, the application has the following beneficial effects:

[0062] (1) Compared with the single pore structure of the traditional negative electrode material, the present application retains a high specific surface area to provide more lithium ion storage active sites by preparing the MOF-derived material and the graphene-polymer derivative, and the pore structure improves the lithium ion migration rate of the material, so that the material can still maintain a high specific capacity under high-rate conditions;

[0063] (2) By introducing the functional coating formed by dopamine oxidation polymerization and 3,4-ethylenedioxythiophene polymerization, the present application forms a uniform conductive protective layer on the surface of the material, which can not only effectively alleviate the volume expansion problem of MoS2 during the cycle process and prevent the exfoliation of the sheet, but also inhibit the occurrence of side reactions and reduce the excessive growth of the SEI film, thereby improving the long cycle capacity retention rate of the material;

[0064] (3) The staged heating process is adopted in the heat treatment process to gradually realize the carbonization and structure optimization of the precursor material, which not only improves the mechanical strength and conductivity of the MOF-derived carbon skeleton, but also maximizes the integrity of the pore structure while maintaining a high compaction density, thereby improving the ion transmission efficiency of the material. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 The TEM image of ZIF-67 provided for Example 1 of the application;

[0066] Figure 2 The SEM image of partially reduced graphene oxide provided for Example 1 of the application. DETAILED DESCRIPTION

[0067] The technical solutions of the present application will be described in detail below with reference to specific embodiments and drawings. The embodiments described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; these descriptions are all explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the embodiments described herein, those skilled in the art can also adopt other technical solutions that are obvious based on the content disclosed in the claims and the description of the present application, which include technical solutions that make any obvious replacement and modification to the embodiments described herein.

[0068] The chemical reagents used in the embodiments and comparative examples of the present application are all commercially available products and are not subjected to any further purification treatment.

[0069] Embodiment 1

[0070] The present embodiment provides a preparation method of a high-rate compaction negative electrode material, which specifically comprises the following steps:

[0071] S1, 50 mL of 5.7 wt.% cobalt nitrate solution and 50 mL of 10.7 wt.% 2-methylimidazole solution were mixed, and then the temperature was adjusted to 88℃ for microwave heating, and ZIF-67 was obtained by washing and filtering; 5 mL of tetraethoxysilane and 3 mL of tetrabutyl titanate were dispersed in 40 mL of anhydrous ethanol, and the pH was adjusted to 2 using hydrochloric acid to obtain a sol-gel precursor; then 5 g of ZIF-67 was dispersed in 50 mL of an ethanol aqueous solution and added to the sol-gel precursor, and stirring was performed at room temperature for 3.6 h, and the precursor powder was obtained by filtering and drying at 77℃ for 8.2 h;

[0072] S2, the precursor powder was transferred to a tube furnace, mixed gas was introduced, the temperature was adjusted to 330℃ and kept for 1.2 h, then the temperature was adjusted to 550℃ and kept for 2.1 h, and finally the temperature was adjusted to 720℃ and kept for 3.2 h, and after cooling to room temperature and grinding, a MOF-derived material was obtained;

[0073] S3, 0.3 g ascorbic acid was added into 100 mL, 1 mg / mL graphene oxide dispersion, the temperature was adjusted to 88℃ under nitrogen atmosphere for 2.3 h, after reaction, the partially reduced graphene oxide was obtained by filtration and drying, then 120 mL, 6 wt.% partially reduced graphene oxide dispersion was mixed with 100 mL, 9 wt.% molybdenum disulfide dispersion to obtain mixture A, 1 g dopamine, 2 g 3,4-ethylenedioxythiophene, 1 g silver nitrate, 1 g copper sulfate and 1 g ammonium persulfate were dispersed in 150 mL ethanol aqueous solution to obtain mixture B, mixture B was added dropwise into mixture A at a speed of 10 mL / min under stirring condition and 0.5 g sodium borohydride was added, the product was freeze-dried and placed in a tube furnace, the temperature was adjusted to 200℃ under argon atmosphere for 1.2 h, and the product was ground after cooling to room temperature to obtain graphene-polymer derivative;

[0074] S4, 14 g matrix material, 1.2 g MOF derivative material and 0.4 g carbon black were mixed and added into 50 mL N-methylpyrrolidone to mix uniformly, then 1.2 g graphene-polymer derivative, 1.6 g PVDF and 0.4 g carboxymethyl cellulose were added and mixed uniformly to obtain negative electrode slurry, the negative electrode slurry was coated on a copper foil current collector, dried, gradient-rolled (10 Mpa bidirectional for 2 times, 70 Mpa unidirectional for 2 times), and placed in an argon atmosphere at 122℃ for 1.2 h, and cooled to room temperature to obtain a high-rate compaction negative electrode material.

[0075] Figure 1 A TEM image of ZIF-67 prepared in the example is shown, and the crystal structure of ZIF-67 shows a highly ordered three-dimensional structure. Figure 2 A SEM image of partially reduced graphene oxide provided in the example is shown.

[0076] Example 2

[0077] The example provides a preparation method of a high-rate compaction negative electrode material, which specifically comprises the following steps:

[0078] S1, 50 mL, 5.7 wt.% cobalt nitrate solution and 50 mL, 10.7 wt.% 2-methyl imidazole solution were mixed, and the temperature was adjusted to 81℃ for microwave heating, and ZIF-67 was obtained by washing and filtering, 5 mL tetraethoxysilane and 3 mL tetrabutyl titanate were dispersed in 40 mL anhydrous ethanol, and a sol-gel precursor was obtained by adjusting the pH to 2 using hydrochloric acid, 5 g ZIF-67 was dispersed in 50 mL ethanol aqueous solution and added into the sol-gel precursor, and stirring was performed at room temperature for 3.1 h, and the precursor powder was obtained by filtering and drying at 72℃ for 8.9 h;

[0079] S2, transferring the precursor powder into a tube furnace, introducing mixed gas, adjusting the temperature to 310℃ for 1.8h, then adjusting the temperature to 510℃ for 2.8h, finally adjusting the temperature to 750℃ for 3.9h, cooling to room temperature, grinding to obtain the MOF-derived material;

[0080] S3, adding 0.3g ascorbic acid into 100mL, 1mg / mL graphene oxide dispersion, adjusting the temperature to 81℃ for 2.4h under nitrogen atmosphere, filtering and drying to obtain partially reduced graphene oxide, then mixing 120mL, 6wt.% partially reduced graphene oxide dispersion with 100mL, 9wt.% molybdenum disulfide dispersion to obtain mixed solution A, dispersing 1g dopamine, 2g 3,4-ethylenedioxythiophene, 1g silver nitrate, 1g copper sulfate and 1g ammonium persulfate in 150mL ethanol aqueous solution to obtain mixed solution B, adding mixed solution B into mixed solution A at a speed of 10mL / min under stirring condition and adding 0.5g sodium borohydride, freezing and drying the product and placing it in a tube furnace, adjusting the temperature to 220℃ for 1.6h under argon atmosphere, grinding after cooling to room temperature to obtain graphene-polymer derivative;

[0081] S4, mixing 14g matrix material, 1.2g MOF-derived material and 0.4g carbon black and adding 50mL N-methylpyrrolidone to mix uniformly, then adding 1.2g graphene-polymer derivative, 1.6g PVDF and 0.4g carboxymethyl cellulose, uniformly mixing to obtain negative electrode slurry, then coating the negative electrode slurry on copper foil current collector, drying, gradient rolling, 10Mpa bidirectional 2 times, 70Mpa unidirectional 2 times, placing in argon atmosphere at 140℃ for 1.9h, cooling to room temperature to obtain a high-rate compaction negative electrode material.

[0082] Example 3

[0083] The embodiment provides a preparation method of a high-rate compaction negative electrode material, and specifically includes the following steps:

[0084] S1, mixing 50mL, 5.7wt.% cobalt nitrate solution with 50mL, 10.7wt.% 2-methylimidazole solution, adjusting the temperature to 86℃ for microwave heating, washing and filtering to obtain ZIF-67, dispersing 5mL tetraethoxysilane with 3mL tetrabutyl titanate in 40mL anhydrous ethanol, using hydrochloric acid to adjust the pH to 2 to obtain sol-gel precursor, dispersing 5g ZIF-67 in 50mL ethanol aqueous solution and adding it into the sol-gel precursor, stirring at room temperature for 3.9h, filtering and drying at 79℃ for 9.7h to obtain precursor powder;

[0085] S2, transferring the precursor powder into a tube furnace, introducing mixed gas, adjusting the temperature to 350℃ for 1.6h, then adjusting the temperature to 530℃ for 2.6h, finally adjusting the temperature to 700℃ for 3.4h, cooling to room temperature, grinding to obtain the MOF-derived material;

[0086] S3, adding 0.3g ascorbic acid into 100mL, 1mg / mL graphene oxide dispersion, adjusting the temperature to 87℃ for 2.9h under nitrogen atmosphere, filtering and drying to obtain partially reduced graphene oxide, then mixing 120mL, 6wt.% partially reduced graphene oxide dispersion with 100mL, 9wt.% molybdenum disulfide dispersion to obtain mixed solution A, dispersing 1g dopamine, 2g 3,4-ethylenedioxythiophene, 1g silver nitrate, 1g copper sulfate and 1g ammonium persulfate in 150mL ethanol aqueous solution to obtain mixed solution B, adding mixed solution B into mixed solution A at a speed of 10mL / min under stirring condition and adding 0.5g sodium borohydride, freezing and drying the product and placing it in a tube furnace, adjusting the temperature to 250℃ for 1.9h under argon atmosphere, grinding after cooling to room temperature to obtain graphene-polymer derivative;

[0087] S4, mixing 14g matrix material, 1.2g MOF-derived material and 0.4g carbon black and adding 50mL N-methylpyrrolidone to mix uniformly, then adding 1.2g graphene-polymer derivative, 1.6g PVDF and 0.4g carboxymethyl cellulose, uniformly mixing to obtain negative electrode slurry, then coating the negative electrode slurry on copper foil current collector, drying, gradient rolling, 10Mpa bidirectional 2 times, 70Mpa unidirectional 2 times, placing in argon atmosphere at 135℃ for 1.4h, cooling to room temperature to obtain a high-rate compaction negative electrode material.

[0088] Example 4

[0089] The embodiment provides a preparation method of a high-rate compaction negative electrode material, and specifically includes the following steps:

[0090] S1, mixing 50mL, 5.7wt.% cobalt nitrate solution with 50mL, 10.7wt.% 2-methylimidazole solution, adjusting the temperature to 84℃ for microwave heating, washing and filtering to obtain ZIF-67, dispersing 5mL tetraethoxysilane with 3mL tetrabutyl titanate in 40mL anhydrous ethanol, using hydrochloric acid to adjust the pH to 2 to obtain sol-gel precursor, dispersing 5g ZIF-67 in 50mL ethanol aqueous solution and adding it into the sol-gel precursor, stirring at room temperature for 3.4h, filtering and drying at 76℃ for 9.1h to obtain precursor powder;

[0091] S2, transferring the precursor powder into a tube furnace, introducing mixed gas, adjusting the temperature to 320℃ for 1.9h, then adjusting the temperature to 500℃ for 2.4h, finally adjusting the temperature to 740℃ for 3.6h, cooling to room temperature, grinding to obtain the MOF derived material;

[0092] S3, adding 0.3g ascorbic acid into 100mL, 1mg / mL graphene oxide dispersion, adjusting the temperature to 84℃ for 2.6h under nitrogen atmosphere, filtering and drying to obtain partially reduced graphene oxide after the reaction, then mixing 120mL, 6wt.% partially reduced graphene oxide dispersion with 100mL, 9wt.% molybdenum disulfide dispersion to obtain mixed solution A, dispersing 1g dopamine, 2g 3,4-ethylenedioxythiophene, 1g silver nitrate, 1g copper sulfate and 1g ammonium persulfate in 150mL ethanol aqueous solution to obtain mixed solution B, adding mixed solution B into mixed solution A at a speed of 10mL / min under stirring condition and adding 0.5g sodium borohydride, freezing and drying the product and placing it in a tube furnace, adjusting the temperature to 210℃ for 1.1h under argon atmosphere, grinding after cooling to room temperature to obtain graphene-polymer derivative;

[0093] S4, mixing 14g matrix material, 1.2g MOF derived material and 0.4g carbon black and adding 50mL N-methylpyrrolidone to mix uniformly, then adding 1.2g graphene-polymer derivative, 1.6g PVDF and 0.4g carboxymethyl cellulose, uniformly mixing to obtain negative electrode slurry, then coating the negative electrode slurry on copper foil current collector, drying, gradient rolling, 10Mpa bidirectional 2 times, 70Mpa unidirectional 2 times, placing in argon atmosphere at 129℃ for 1.6h, cooling to room temperature to obtain a high rate compaction negative electrode material.

[0094] Comparative Example 1

[0095] This comparative example provides a preparation method of a high rate compaction negative electrode material, which is different from Example 1 in that the mass of dopamine in S3 is 0.1g, which is 0.9g less than that of Example 1, and other process parameters and operating conditions are exactly the same as those of Example 1.

[0096] Comparative Example 2

[0097] This comparative example provides a preparation method of a high rate compaction negative electrode material, which is different from Example 1 in that the mass of dopamine in S3 is 2g, which is 1g more than that of Example 1, and other process parameters and operating conditions are exactly the same as those of Example 1.

[0098] Comparative Example 3

[0099] The comparative example provides a preparation method of a high-rate compaction negative electrode material, which is different from example 1 in that the mass of 3,4-ethylenedioxythiophene in S3 is 0.5 g, which is reduced by 1.5 g compared with example 1, and other process parameters and operating conditions are completely the same as those of example 1.

[0100] Comparative example 4

[0101] The comparative example provides a preparation method of a high-rate compaction negative electrode material, which is different from example 1 in that the mass of 3,4-ethylenedioxythiophene in S3 is 4 g, which is increased by 2 g compared with example 1, and other process parameters and operating conditions are completely the same as those of example 1.

[0102] Test method: lithium iron phosphate is used as the positive electrode, a 1M LiPF6 carbonate solution is used as the electrolyte to assemble the battery, and after the cyclic charge and discharge, the prepared battery is subjected to charge and discharge test with a cut-off potential window of 2V at a current density of 3C. The true density detection standard is GB / T 24533-2019. The test results are shown in Table 1.

[0103] Table 1 Test results of high-rate compaction negative electrode materials prepared in examples 1-4 and comparative examples 1-4

[0104]

[0105] As shown in Table 1, compared with example 1, the true density of comparative example 1, the capacity retention rate at 3C rate after 200 cycles and the initial charge specific capacity decreased, and the initial discharge specific capacity increased; the true density of comparative example 2 increased, and the initial discharge specific capacity, the initial charge specific capacity and the capacity retention rate at 3C rate after 200 cycles decreased. This is because the dopamine dosage in comparative example 1 is insufficient, and the coating effect of polydopamine is poor, which causes part of rGO and MoS2 to be exposed in the reaction system, which will make the pore structure of the final material retain more open pores, resulting in a decrease in true density; the active sites of part of rGO and MoS2 may be directly exposed to the electrolyte, increasing the number of active sites and improving the initial discharge specific capacity. Due to the lack of interface protection, the formation of SEI film may be more significant, resulting in an increase in irreversible capacity and a decrease in initial charge specific capacity. Insufficient dopamine will lead to insufficient interface protection of the material, and the volume expansion of MoS2 or the peeling of graphene sheets is prone to occur during long-term charge and discharge, resulting in a decrease in cycle performance. In comparative example 2, the generated polydopamine coating in the reaction system will grow excessively and cover the surface of part of the reduced graphene oxide and molybdenum disulfide, and carbonize during the heat treatment process, thereby forming amorphous carbon. Excessive amorphous carbon will fill the pores of the material, resulting in an increase in true density. Although the amorphous carbon layer has good conductivity, its contribution to lithium ion storage is limited, and the initial discharge specific capacity, the initial discharge specific capacity and the cycle performance decrease.

[0106] From Table 1, compared with Example 1, the true density of Comparative Example 3 increases, the first discharge specific capacity, the first charge specific capacity and the capacity retention rate after 200 cycles at 3C rate decrease; the true density, the first discharge specific capacity, the first charge specific capacity and the capacity retention rate after 200 cycles at 3C rate of Comparative Example 4 decrease. In Comparative Example 3, 3,4-ethylenedioxythiophene is insufficient, the generated poly(3,4-ethylenedioxythiophene) coating will be incomplete or unevenly distributed, the material surface cannot form a continuous conductive network, resulting in partial exposure of the pore structure, the porosity of the material is higher, the true density decreases, the generated poly(3,4-ethylenedioxythiophene) coating is not uniform enough, and an intact conductive network cannot be formed on the surface of the material, and the surface of the uncovered rGO and MoS2 may be exposed to the electrolyte, resulting in excessive generation of SEI film, and the first discharge specific capacity, the first discharge specific capacity and the cycle performance decrease. In Comparative Example 4, 3,4-ethylenedioxythiophene is excessive, which will cause the generated poly(3,4-ethylenedioxythiophene) coating to be excessively coated on the surface of part of the reduced graphene oxide and molybdenum disulfide, the porosity decreases, and the true density increases. The excessive poly(3,4-ethylenedioxythiophene) coating will form a conductive polymer covering layer with a higher thickness on the surface of the material, although such a coating can significantly improve the electronic conductivity, but the diffusion path of lithium ions may be hindered, and the first discharge specific capacity, the first discharge specific capacity and the cycle performance decrease.

[0107] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a high-rate compaction negative electrode material, characterized in that: The preparation method comprises: S1, after mixing a cobalt nitrate solution and a 2-methylimidazole solution, adjusting the temperature to a first temperature and heating in a microwave, washing and filtering to obtain ZIF-67, dispersing tetraethoxysilane and tetrabutyl titanate in anhydrous ethanol, adjusting the pH to 2 with hydrochloric acid to obtain a sol-gel precursor, and then dispersing ZIF-67 in an ethanol aqueous solution and adding the mixture to the sol-gel precursor, stirring at room temperature, and filtering and drying to obtain a precursor powder; S2, transferring the precursor powder to a tube furnace, introducing a mixed gas, adjusting the temperature to a second temperature and holding it, then adjusting the temperature to a third temperature and holding it, and finally adjusting the temperature to a fourth temperature and holding it, cooling to room temperature and grinding to obtain a MOF-derived material; S3, adding ascorbic acid to the graphene oxide dispersion, adjusting the temperature to a first temperature for reaction under a nitrogen atmosphere, filtering and drying after the reaction to obtain partially reduced graphene oxide, then mixing the partially reduced graphene oxide dispersion with a molybdenum disulfide dispersion to obtain a mixed solution A, dispersing dopamine, 3,4-ethylenedioxythiophene, silver nitrate, copper sulfate and ammonium persulfate in an ethanol aqueous solution to obtain a mixed solution B, adding the mixed solution B dropwise to the mixed solution A under stirring, and adding sodium borohydride, freeze-drying the product and placing it in a tube furnace, adjusting the temperature to a fifth temperature for insulation under an argon atmosphere, cooling to room temperature and grinding to obtain a graphene-polymer derivative; S4, mixing the matrix material, MOF derivative material and carbon black and adding N-methylpyrrolidone to mix evenly, then adding graphene-polymer derivative, PVDF and carboxymethyl cellulose, mixing evenly and then vacuum degassing to obtain a negative electrode slurry, then coating the negative electrode slurry on a copper foil current collector, drying, performing gradient roller pressing and keeping warm in an argon atmosphere, and cooling to room temperature to obtain a high-rate compacted negative electrode material; The second temperature is 300-350° C.; The second temperature holding time is 1-2h; The third temperature is 500-550° C.; The third temperature holding time is 2-3h; The fourth temperature is 700-750° C.; The fourth temperature holding time is 3-4h.

2. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S1, The mass fraction of the cobalt nitrate solution is 5.7 wt.%, and the solute is cobalt nitrate hexahydrate; The mass fraction of the 2-methylimidazole solution is 10.7wt.%; The mass ratio of the cobalt nitrate hexahydrate to 2-methylimidazole is 1:

2.

3. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S1, The volume ratio of tetraethoxysilane to tetrabutyl titanate is 5:3; The volume mass ratio of the tetraethoxysilane to ZIF-67 is 1 mL:1 g.

4. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S2, The volume fraction ratio of argon, ammonia, acetylene and hydrogen in the mixed gas is 70:15:5:

10.

5. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S3, The concentration of the graphene oxide dispersion is 1 mg / mL; The mass ratio of ascorbic acid to graphene oxide is 3:

1.

6. The method for preparing a high-rate compaction negative electrode material according to claim 1, characterized in that: In S3, The mass fraction of the partially reduced graphene oxide dispersion is 6 wt.%, and the solvent is deionized water and anhydrous ethanol, with a volume ratio of 5:1; The mass fraction of the molybdenum disulfide dispersion is 9 wt.%, and the solvent is anhydrous ethanol.

7. The method for preparing a high-rate compaction negative electrode material according to claim 1, characterized in that: In S3, The mass ratio of dopamine, 3,4-ethylenedioxythiophene, silver nitrate, copper sulfate and ammonium persulfate is 1:2:1:1:1; The mass ratio of the silver nitrate to the sodium borohydride is 1:0.

5.

8. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S4, The mass ratio of the matrix material, MOF derivative material, carbon black, graphene-polymer derivative, PVDF and carboxymethyl cellulose is 14:1.2:0.4:1.2:1.6:0.

4.

9. The method for preparing a high-rate compaction negative electrode material according to claim 1, wherein: In S4, The matrix material is graphite, hard carbon and titanium carbide, with a mass ratio of 100:10:

5.

10. A high-rate compaction negative electrode material obtained according to the preparation method according to any one of claims 1 to 9.

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