Composite material and preparation method thereof, electrode and battery

Abstract

The invention discloses a composite material and a preparation method thereof, an electrode and a battery, and relates to the technical field of new energy. The composite material comprises a graphite matrix, a first coating carbon layer coating the graphite matrix, and a second coating carbon layer coating the first coating carbon layer, wherein the material of the first carbon coating layer comprises carbon nanotubes, and the material of the second carbon coating layer comprises biomass carbon source derived carbon, zeolite imidazate framework material derived carbon and resin derived carbon. The composite material provided by the embodiment of the invention has relatively high conductivity.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a composite material and a preparation method thereof, an electrode and a battery. Background Art

[0002] Graphite is an allotrope of carbon with low hardness, stable chemical properties, and is not easily reactive with acids, alkalis, and other agents. It has physical and chemical properties such as high temperature resistance, corrosion resistance, thermal shock resistance, radiation resistance, high strength, good toughness, and high electrical and thermal conductivity. It is widely used in metallurgy, machinery, electronics, military industry, national defense, aerospace, and other fields.

[0003] In related technologies, the electrical conductivity of graphite materials still needs to be further improved. Summary of the Invention

[0004] In view of this, the present application provides a composite material and a preparation method thereof, an electrode and a battery.

[0005] The embodiments of the present application are implemented as follows: In a first aspect, the embodiments of the present application provide a composite material, comprising a graphite substrate, a first coating carbon layer coating the graphite substrate, and a second coating carbon layer coating the first coating carbon layer;

[0006] The material of the first carbon coating layer includes carbon nanotubes, and the material of the second carbon coating layer includes biomass carbon source derived carbon, zeolite imidazolate skeleton material derived carbon and resin derived carbon.

[0007] Optionally, in some embodiments of the present application, the carbon nanotubes are selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes, and a plurality of the carbon nanotubes are stacked to form a three-dimensional skeleton structure.

[0008] The biomass carbon source-derived carbon is mainly prepared from a biomass carbon source, and the biomass carbon source is selected from one or more of polysaccharide compounds and nitrogen-containing biological molecules.

[0009] The zeolite imidazolate framework material-derived carbon is mainly prepared from a zeolite imidazolate framework material, and the zeolite imidazolate framework material is selected from one or more of a zinc-based zeolite imidazolate framework material and a cobalt-based zeolite imidazolate framework material.

[0010] The resin-derived carbon is mainly prepared from resin, and the resin is selected from one or more of phenolic resin, furan resin, epoxy resin, and urea-formaldehyde resin.

[0011] The biomass carbon source-derived carbon, the zeolite imidazolate framework material-derived carbon, and the resin-derived carbon have a three-dimensional porous network structure.

[0012] The mass ratio of the biomass carbon source derived carbon, the zeolite imidazolate framework material derived carbon and the resin derived carbon is (1.5-3): (2-4): (5-8).

[0013] Optionally, in some embodiments of the present application, the average length of the single-walled carbon nanotubes is 1 μm to 5 μm; the average diameter of the single-walled carbon nanotubes is 1 nm to 2 nm.

[0014] The average length of the multi-walled carbon nanotubes is 1 μm to 5 μm; the average diameter of the single-walled carbon nanotubes is 1 nm to 2 nm.

[0015] The polysaccharide compound is selected from one or more of lignin, cellulose and starch.

[0016] The nitrogen-containing biomolecules are selected from one or more of proteins and amino acids.

[0017] The zinc-based zeolite imidazolate framework material is selected from one or more of ZIF-8 and ZIF-67.

[0018] The cobalt-based zeolite imidazolate framework material is selected from ZIF-11.

[0019] The phenolic resin is selected from one or more of phenol formaldehyde phenolic resin, sulfonated phenolic resin, and terpene phenolic resin.

[0020] The furan resin is selected from one or more of furfural phenol resin, furfural acetone resin and furfuryl alcohol resin.

[0021] The epoxy resin is selected from one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, alicyclic epoxy resins, and epoxidized olefin epoxy resins.

[0022] The urea-formaldehyde resin is selected from one or more of methyl etherified urea-formaldehyde resin and n-butanol etherified urea-formaldehyde resin.

[0023] Optionally, in some embodiments of the present application, the material of the first coating carbon layer further comprises graphitized tar; the graphitized tar is located between the plurality of carbon nanotubes. In the first coating carbon layer, the mass ratio of the carbon nanotubes to the graphitized tar is (1-3):(8-10).

[0024] The average thickness of the first coating carbon layer is 2 nm to 6 nm.

[0025] The average thickness of the second coating carbon layer is 15 nm to 35 nm.

[0026] The mass ratio of the graphite substrate, the first coating carbon layer, and the second coating carbon layer is: 100: (7-10): (5.5-12.5).

[0027] In a second aspect, the present invention also provides a method for preparing a composite material, comprising the following steps:

[0028] Providing raw coke and a modifier, wherein the modifier includes carbon nanotubes, and mixing the raw coke and the modifier to obtain a modified raw coke precursor;

[0029] Graphitizing the modified raw coke precursor to obtain an intermediate product, wherein the intermediate product includes a graphite matrix and a first coating carbon layer coating the graphite matrix, wherein the material of the first coating carbon layer includes the modifier;

[0030] A biomass carbon source, a zeolite imidazolate skeleton material and a resin are provided, mixed with the intermediate product, and carbonized to obtain a second coating carbon layer covering the first coating carbon layer, wherein the material of the second coating carbon layer includes biomass carbon source-derived carbon, zeolite imidazolate skeleton material-derived carbon and resin-derived carbon to obtain a composite material.

[0031] Optionally, in some embodiments of the present application, the raw coke includes one or more of oil-based coke and coal-based coke; the oil-based coke is selected from one or more of petroleum coke and oil-based needle coke, and the coal-based coke is selected from one or more of coal-based needle coke and asphalt coke.

[0032] The carbon nanotubes are selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0033] The modifier further includes tar; in the modifier, the mass ratio of the carbon nanotubes to the tar is (1-3): (8-10).

[0034] The biomass carbon source is selected from one or more of polysaccharide compounds and nitrogen-containing biological molecules.

[0035] The zeolite imidazolate framework material is selected from one or more of a zinc-based zeolite imidazolate framework material and a cobalt-based zeolite imidazolate framework material.

[0036] The resin is selected from one or more of phenolic resin, furan resin, epoxy resin and urea-formaldehyde resin.

[0037] Optionally, in some embodiments of the present application, the mixing of the raw coke and the modifier includes: providing raw coke, performing preheating treatment and crushing treatment to obtain raw coke particles; and mixing the raw coke particles and the modifier.

[0038] The temperature of the preheating treatment is 500° C. to 700° C., and the time of the preheating treatment is 4 hours to 8 hours.

[0039] The average particle size D50 of the raw coke particles is 7 μm to 10 μm.

[0040] The mass ratio of the raw coke particles to the modifier is 100:(7-10).

[0041] The temperature for mixing the raw coke particles and the modifier is 20° C. to 30° C., and the time for mixing the raw coke particles and the modifier is 0.5 h to 1 h.

[0042] Optionally, in some embodiments of the present application, before the modified raw coke precursor is graphitized, the modified raw coke precursor is also granulated to obtain modified raw coke precursor particles; the granulation includes gradient heating, and the gradient heating includes heating the modified raw coke precursor to a first temperature, keeping it warm for a first time period, and then heating it to a second temperature, and keeping it warm for a second time period.

[0043] The heating rate of heating to the first temperature is 1°C / min to 3°C / min.

[0044] The first temperature is 250°C to 300°C.

[0045] The first time period is 40 minutes to 60 minutes.

[0046] The heating rate of heating to the second temperature is 5°C / min to 8°C / min.

[0047] The second temperature is 600°C to 650°C.

[0048] The second time period is 4 hours to 6 hours.

[0049] The average particle size D50 of the modified raw coke precursor particles is 11 μm to 15 μm.

[0050] Optionally, in some embodiments of the present application, the mixing of the biomass carbon source, the zeolite imidazolate skeleton material, the resin and the intermediate product includes: adding the biomass carbon source, the zeolite imidazolate skeleton material and the resin in sequence, and mixing with the intermediate product; or, adding the zeolite imidazolate skeleton material, the biomass carbon source and the resin in sequence, and mixing with the intermediate product.

[0051] The mass ratio of the intermediate product to the biomass carbon source, the zeolite imidazolate framework material, and the resin is 100:(1.5-3):(2-4):(5-8).

[0052] The temperature for mixing the biomass carbon source and the intermediate product is 20° C. to 30° C., and the time for mixing the biomass carbon source and the intermediate product is 30 min to 40 min.

[0053] The temperature for mixing the zeolite imidazolate framework material and the intermediate product is 20° C. to 30° C., and the time for mixing the zeolite imidazolate framework material and the intermediate product is 5 h to 9 h.

[0054] The temperature for mixing the resin and the intermediate product is 90° C. to 100° C., and the time for mixing the resin and the intermediate product is 6 hours to 8 hours.

[0055] Optionally, in some embodiments of the present application, the temperature of the graphitization treatment is 3000° C. to 3200° C., and the time of the graphitization treatment is 70 h to 85 h.

[0056] The carbonization treatment includes a first carbonization treatment and a second carbonization treatment performed sequentially, the temperature of the second carbonization treatment is greater than the temperature of the first carbonization treatment; the temperature of the first carbonization treatment is 270°C to 650°C, and the time of the first carbonization treatment is 8h to 10h; the temperature of the second carbonization treatment is 650°C to 1050°C, and the time of the second carbonization treatment is 15h to 20h.

[0057] Optionally, in some embodiments of the present application, after the carbonization treatment, the method further comprises: screening and demagnetization to obtain composite particles, wherein the composite particles include the composite material.

[0058] The average particle size D50 of the intermediate product is 9.5 μm to 13.5 μm.

[0059] The average particle size D50 of the composite particles is 17.5 μm to 21.5 μm.

[0060] In a third aspect, an embodiment of the present application further provides an electrode, wherein the material of the electrode includes the above-mentioned composite material, or includes the composite material prepared by the above-mentioned preparation method.

[0061] In a fourth aspect, an embodiment of the present application further provides a battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the material of the negative electrode comprises the above-mentioned composite material, or comprises a composite material prepared by the above-mentioned preparation method, or the negative electrode comprises the above-mentioned electrode.

[0062] In the composite material provided by the present application, a first coating carbon layer and a second coating carbon layer are used to sequentially coat a graphite matrix. The carbon nanotubes in the first coating carbon layer have a one-dimensional nanostructure, which is easy to build an effective conductive network, and its cavity structure can increase the path of ion transmission, fully improve the conductivity of the graphite matrix, and also improve the mechanical properties of the first coating carbon layer; the first coating carbon layer acts as a bridge to connect the graphite matrix and the second coating carbon layer, and the high conductivity bridge can further accelerate electron conduction; the biomass carbon source itself has a natural multi-level structure, and is highly cross-linked during the carbonization process to form a glassy carbon structure. When affected by stress, the stress can be dispersed by rotating and bending the bonds, so that the biomass carbon source-derived carbon in the second coating carbon layer can improve the flexibility and mechanical properties of the composite material, and the zeolite imidazole ester skeleton material retains the dodecahedral morphology of the original structure after carbonization. An interconnected 3D carbon network is formed, and nitrogen atoms are embedded in the carbon skeleton in the form of pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen, etc. During the electrochemical cycle of the battery, the polysulfides adsorbed on the nitrogen active sites can be electrochemically reduced, thereby repairing the original microcracks. Therefore, the zeolite imidazolate skeleton material-derived carbon can provide porous channels and has self-repairing functions, which can realize the destruction of the second coated carbon layer during the self-repair cycle and enhance its electrical conductivity; the resin-derived carbon has a three-dimensional porous network structure, which can promote the transmission of ions; the various materials in the second coated carbon layer work synergistically with each other to jointly improve the mechanical properties of the composite material such as flexibility, and promote the improvement of electrical conductivity; the first coated carbon layer and the second coated carbon layer provided in the present application increase the ion transmission rate and pathway, and when applied to the negative electrode of the battery, they can also adapt to fast charging and discharging and long cycles, thereby fully improving the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0064] Figure 1 This is a flow chart of a method for preparing a composite material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0066] In this application, unless otherwise indicated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of a device in actual use or operation, specifically in the drawing directions of the accompanying drawings; whereas "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "including" means "including but not limited to." Terms such as first, second, and third are used merely as designations and do not impose numerical requirements or establish a sequential order.

[0067] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0068] In this application, "at least one" means one or more, and "plurality" means two or more. "One or several", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0069] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0070] Graphite is currently the most commonly used anode material in lithium-ion batteries. Its layered crystal structure provides ideal insertion and deinsertion channels for lithium ions. Graphite anodes offer the following advantages: 1) a high theoretical specific capacity and a platform voltage close to that of lithium metal, resulting in high safety; 2) excellent conductivity and structural stability, resulting in a long cycle life; and 3) abundant resources and low cost. However, traditional graphite anode technology is no longer sufficient to meet future demands for fast charging, or even ultra-fast charging and ultra-long cycling. Graphite materials in related technologies still require further advancements to enhance battery rate and cycling performance.

[0071] The technical solution of this application is as follows:

[0072] In a first aspect, an embodiment of the present application provides a composite material, comprising a graphite matrix, a first coating carbon layer coating the graphite matrix, and a second coating carbon layer coating the first coating carbon layer; wherein the material of the first coating carbon layer comprises carbon nanotubes, and the material of the second coating carbon layer comprises biomass carbon source-derived carbon, zeolite imidazolate skeleton material-derived carbon, and resin-derived carbon.

[0073] It can be understood that the material of the graphite matrix includes graphite.

[0074] It should be noted that the biomass carbon source-derived carbon refers to the product of carbonization of a biomass carbon source. In other words, the biomass carbon source-derived carbon is mainly obtained by carbonization of a biomass carbon source. The biomass carbon source refers to carbon-containing organic matter derived from an organism.

[0075] The zeolitic imidazolate framework-derived carbon refers to the product of carbonization of the zeolitic imidazolate framework. In other words, the zeolitic imidazolate framework-derived carbon is primarily obtained by carbonization of the zeolitic imidazolate framework. The zeolitic imidazolate framework (ZIF) is a type of MOFs porous crystalline material with a zeolite framework structure, which has high stability, high porosity, and organic functionality.

[0076] The resin-derived carbon is a product of resin carbonization. In other words, the resin-derived carbon is primarily obtained by carbonizing resin. The resin is an organic polymer that softens or melts when heated and tends to flow under external force when softened.

[0077] In the composite material provided by the present application, a first coating carbon layer and a second coating carbon layer are used to sequentially coat a graphite matrix. The carbon nanotubes in the first coating carbon layer have a one-dimensional nanostructure, which is easy to build an effective conductive network, and its cavity structure can increase the path of ion transmission, fully improve the conductivity of the graphite matrix, and also improve the mechanical properties of the first coating carbon layer; the first coating carbon layer acts as a bridge to connect the graphite matrix and the second coating carbon layer, and the high conductivity bridge can further accelerate electron conduction; the biomass carbon source itself has a natural multi-level structure, and is highly cross-linked during the carbonization process to form a glassy carbon structure. When affected by stress, the stress can be dispersed by rotating and bending the bonds, so that the biomass carbon source-derived carbon in the second coating carbon layer can improve the flexibility and mechanical properties of the composite material, and the zeolite imidazole ester skeleton material retains the dodecahedral morphology of the original structure after carbonization. An interconnected 3D carbon network is formed, and nitrogen atoms are embedded in the carbon skeleton in the form of pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen, etc. During the electrochemical cycle of the battery, the polysulfides adsorbed on the nitrogen active sites can be electrochemically reduced, thereby repairing the original microcracks. Therefore, the zeolite imidazolate skeleton material-derived carbon can provide porous channels and has self-repairing functions, which can realize the destruction of the second coated carbon layer during the self-repair cycle and enhance its electrical conductivity; the resin-derived carbon has a three-dimensional porous network structure, which can promote the transmission of ions; the various materials in the second coated carbon layer work synergistically with each other to jointly improve the mechanical properties of the composite material such as flexibility, and promote the improvement of electrical conductivity; the first coated carbon layer and the second coated carbon layer provided in the present application increase the ion transmission rate and pathway, and when applied to the negative electrode of the battery, they can also adapt to fast charging and discharging and long cycles, thereby fully improving the performance of the battery.

[0078] In some embodiments, the average thickness of the first coating carbon layer is 2 nm to 6 nm, for example, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, or a range between any two of the foregoing values. Within the range of the average thickness of the first coating carbon layer, the first coating carbon layer can effectively improve the electrical conductivity of the graphite substrate.

[0079] In some embodiments, the carbon nanotubes are selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0080] Furthermore, the average length of the single-walled carbon nanotubes is 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a range between any two of the above values; the average tube diameter of the single-walled carbon nanotubes is 1 nm to 2 nm, for example, 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm or a range between any two of the above values.

[0081] The average length of the multi-walled carbon nanotubes is 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a range between any two of the above values; the average tube diameter of the single-walled carbon nanotubes is 1 nm to 2 nm, for example, 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm or a range between any two of the above values.

[0082] It should be noted that the diameters of the single-walled carbon nanotubes and the multi-walled carbon nanotubes refer to the outer diameters of the carbon nanotubes.

[0083] The carbon nanotubes can enhance electrical conductivity and provide a three-dimensional skeleton to support the first coating carbon layer, making it more homogeneous. It should be noted that a plurality of the carbon nanotubes are stacked to form a three-dimensional skeleton structure.

[0084] In some embodiments, the material of the first carbon coating layer further comprises graphitized tar. It should be noted that the tar can act as a liquid coating agent to promote the coating of the graphite substrate by the carbon nanotubes, and then graphitize in a subsequent graphitization process to form graphitized tar. The graphitized tar can effectively improve the wettability of the composite material with the electrolyte, thereby improving the cycling performance of the graphite substrate.

[0085] Furthermore, the graphitized tar is located between the plurality of carbon nanotubes.

[0086] In some embodiments, the mass ratio of the carbon nanotubes to the graphitized tar in the first coating carbon layer is (1-3):(8-10), for example, 1:8, 1:9, 1:10, 2:8, 2:9, 2:10, 3:8, 3:9, 3:10, or a range between any two of the above ratios. Within this mass ratio range, the carbon nanotubes and the graphitized tar can jointly improve the electrical conductivity and mechanical properties of the composite material.

[0087] In some embodiments, the average thickness of the second coating carbon layer is 15 nm to 35 nm, for example, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, or a range between any two of the foregoing values. Within the range of the average thickness of the second coating carbon layer, the second coating carbon layer can effectively improve the electrical conductivity of the graphite substrate.

[0088] In some embodiments, the biomass carbon source-derived carbon is mainly prepared from a biomass carbon source, and the biomass carbon source is selected from one or more of polysaccharide compounds and nitrogen-containing biomolecules.

[0089] Furthermore, the polysaccharide compound is selected from one or more of lignin, cellulose, and starch. The nitrogen-containing biomolecule is selected from one or more of protein and amino acid.

[0090] The derived carbon from the carbonized biomass carbon source can significantly enhance the toughness of the composite material. It should be noted that nitrogen from nitrogen-containing biomolecules, such as proteins and amino acids, can remain in the second coating carbon layer, improving the electrical conductivity of the composite material. It should also be noted that some oxygen from the biomass carbon source can also remain in the second coating carbon layer.

[0091] In some embodiments, the zeolite imidazolate framework material-derived carbon is mainly prepared from a zeolite imidazolate framework material, and the zeolite imidazolate framework material is selected from one or more of a zinc-based zeolite imidazolate framework material and a cobalt-based zeolite imidazolate framework material.

[0092] Furthermore, the zinc-based zeolite imidazolate framework material is selected from one or more of ZIF-8 (2-methylimidazole zinc salt, CAS: 59061-53-9) and ZIF-67 (dimethylimidazole cobalt, CAS: 46201-07-4). The cobalt-based zeolite imidazolate framework material is selected from ZIF-11 (CAS: 24304-54-9).

[0093] In some embodiments, the zeolitic imidazolate framework-derived carbon has a three-dimensional porous network structure.

[0094] The zeolite imidazolate framework material is a type of metal-organic framework material composed of transition metal ions and imidazole ligands. It has a pore structure and topology similar to that of zeolites, and has advantages such as high specific surface area, high porosity, high thermal stability, high chemical stability, adjustable pore size, and functionalized pore walls. The carbonized derivative carbon can fully enhance the stability and self-healing ability of the second coating carbon layer. It should be noted that the zeolite imidazolate framework material contains imidazole groups, and the nitrogen of the imidazole groups can remain in the second coating carbon layer, improving the conductivity of the composite material.

[0095] In some embodiments, the resin-derived carbon is mainly prepared from resin, and the resin is selected from one or more of phenolic resin, furan resin, epoxy resin, and urea-formaldehyde resin.

[0096] Furthermore, the phenolic resin is selected from one or more of phenol-formaldehyde phenolic resin, sulfonated phenolic resin, and terpene phenolic resin. It should be noted that phenol-formaldehyde resin refers to a resin synthesized from phenols and formaldehyde, wherein the phenols include but are not limited to phenol, catechol, resorcinol, and hydroquinone.

[0097] The furan resin is selected from one or more of furfural phenol resin, furfural acetone resin and furfuryl alcohol resin.

[0098] The epoxy resin is selected from one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, alicyclic epoxy resins, and epoxidized olefin epoxy resins.

[0099] The urea-formaldehyde resin is selected from one or more of methyl etherified urea-formaldehyde resin and n-butanol etherified urea-formaldehyde resin.

[0100] In some embodiments, the resin-derived carbon has a three-dimensional porous network structure.

[0101] The resin can play a bonding role, and is fully mixed with the biomass carbon source and the zeolite imidazolate skeleton material to coat the first coating carbon layer. It can also provide a certain supporting rigidity, and together with the biomass carbon source derived carbon and the zeolite imidazolate skeleton material derived carbon, the second coating carbon layer has suitable toughness.

[0102] In some embodiments, the mass ratio of the biomass carbon source-derived carbon, the zeolite imidazolate framework-derived carbon, and the resin-derived carbon is (1.5-3):(2-4):(5-8), for example, 1.5:2:5, 2:4:4, 3:2:6, 3:2.5:7, 2:3.5:8, 2.5:1.5:5, or a range between any two of the above ratios. Within this mass ratio range, the derived carbons are facilitated to cooperate with each other, thereby enhancing the effect of the second coating carbon layer on the graphite substrate.

[0103] In some embodiments, the mass ratio of the graphite substrate, the first coating carbon layer, and the second coating carbon layer is 100:(7-10):(5.5-12.5), for example, 100:7:5.5, 100:8:12.5, 100:9:10, 100:10:6, 100:7.5:11, 100:8.5:12, or a range between any two of the above ratios. Within the above mass ratio range, the composite material has high electrical conductivity, mechanical properties, etc.

[0104] Second, see Figure 1 The present invention also provides a method for preparing a composite material, comprising the following steps:

[0105] Step S11: providing raw coke and a modifier, wherein the modifier includes carbon nanotubes, and mixing the raw coke and the modifier to obtain a modified raw coke precursor;

[0106] Step S12: graphitizing the modified raw coke precursor to obtain an intermediate product, wherein the intermediate product includes a graphite matrix and a first coating carbon layer coating the graphite matrix, and the material of the first coating carbon layer includes the modifier;

[0107] Step S13: provide a biomass carbon source, a zeolite imidazolate skeleton material and a resin, mix them with the intermediate product, and perform carbonization treatment to obtain a second coated carbon layer coated with the first coated carbon layer, wherein the material of the second coated carbon layer includes biomass carbon source-derived carbon, zeolite imidazolate skeleton material-derived carbon and resin-derived carbon to obtain a composite material.

[0108] In the step S11:

[0109] In some embodiments, the raw coke comprises one or more of oil-based coke and coal-based coke. Further, the oil-based coke is selected from one or more of petroleum coke and oil-based needle coke, and the coal-based coke is selected from one or more of coal-based needle coke and pitch coke.

[0110] In some embodiments, the modifier further comprises tar, which can promote the carbon nanotubes to coat the raw coke.

[0111] Furthermore, in the modifier, the mass ratio of the carbon nanotubes to the tar is (1-3):(8-10), for example, 1:8, 1:9, 1:10, 2:8, 2:9, 2:10, 3:8, 3:9, 3:10, or a range between any two of the above ratios. Within the above mass ratio range, the carbon nanotubes and the tar are conducive to jointly modifying and coating the raw coke.

[0112] In some embodiments, mixing the raw coke and the modifier comprises: providing raw coke, preheating and pulverizing the raw coke to obtain raw coke particles; and mixing the raw coke particles with the modifier. It is understood that the raw coke is first preheated and then pulverized.

[0113] Furthermore, the preheating temperature is 500°C to 700°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, or a range between any two of the above values; the preheating time is 4 hours to 8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or a range between any two of the above values. Thus, under the preheating conditions, it is beneficial to deash the raw coke, increase the energy density, reduce the rebound of the subsequently produced negative electrode sheet, and retain the original good properties of the raw coke.

[0114] It should be noted that the preheating treatment can be performed under the protection of a nitrogen atmosphere.

[0115] The pulverization process can reduce the particle size of the raw coke, facilitating subsequent modification and processing. Furthermore, the average particle size D50 of the raw coke particles is between 7 μm and 10 μm, for example, 7 μm, 8 μm, 9 μm, 10 μm, or a range between any two of these values. Within this average particle size D50 range, the raw coke particles have an appropriate specific surface area, facilitating subsequent modification and coating.

[0116] In some embodiments, the mass ratio of the raw coke particles to the modifier is 100:(7-10), for example, 100:7, 100:8, 100:9, 100:10, or a range between any two of the foregoing values. Within this mass ratio range, the modifier is advantageously used to modify and coat the raw coke particles.

[0117] It should be noted that the mixing of the raw coke particles and the modifier includes putting the raw coke particles and the modifier into a fusion machine for fusion.

[0118] In some embodiments, the temperature for mixing the raw coke particles and the modifier is room temperature, such as 20°C to 30°C, and further can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, or a range between any two of the above values; the time for mixing the raw coke particles and the modifier is 0.5h to 1h, such as 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, or a range between any two of the above values. In this way, under the aforementioned mixing conditions, the modifier is conducive to pre-coating the raw coke particles at room temperature, thereby improving the electrical conductivity and other properties of the raw coke particles.

[0119] In some embodiments, before graphitizing the modified raw coke precursor, the modified raw coke precursor is further granulated to obtain modified raw coke precursor particles.

[0120] In some embodiments, the granulation includes gradient temperature increase, and the gradient temperature increase includes heating the modified raw coke precursor to a first temperature, keeping the temperature for a first time period, and then heating it to a second temperature, and keeping the temperature for a second time period.

[0121] Furthermore, the heating rate to the first temperature is 1°C / min to 3°C / min, for example, 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min or a range between any two of the above values.

[0122] The first temperature is 250°C to 300°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C or a range between any two of the above values.

[0123] The first time period is 40 minutes to 60 minutes, for example, it can be 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or a range between any two of the above values.

[0124] The heating rate for heating to the second temperature is 5°C / min to 8°C / min, for example, 5°C / min, 6°C / min, 7°C / min, 8°C / min or a range between any two of the above values.

[0125] The second temperature is 600° C. to 650° C., for example, 600° C., 610° C., 620° C., 630° C., 640° C., 650° C., or a range between any two of the above values.

[0126] The second time period is 4 hours to 6 hours, for example, it can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or a range between any two of the above values.

[0127] In this way, under the above-mentioned granulation conditions, it is beneficial to obtain modified raw coke precursor particles with suitable particle size.

[0128] Furthermore, the average particle size D50 of the modified raw coke precursor particles is 11 μm to 15 μm, for example, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range between any two of the above values. Within the above average particle size D50 range, subsequent graphitization treatment is facilitated.

[0129] In some embodiments, the graphitization treatment temperature is 3000° C. to 3200° C., for example, 3000° C., 3050° C., 3100° C., 3150° C., 3200° C., or a range between any two of the above values; and the treatment time is 70 h to 85 h, for example, 70 h, 72 h, 75 h, 78 h, 80 h, 82 h, 85 h, or a range between any two of the above values. Thus, under the graphitization treatment conditions, the raw coke is facilitated to be fully graphitized, ensuring the formation of a graphite matrix.

[0130] It should be noted that the graphitization treatment can graphitize the raw coke particles to form a graphene matrix. Due to the change in the form of carbon and the high temperature conditions of graphitization, the average particle size D50 of the intermediate product will decrease, thereby enhancing the coating of the graphite matrix by the first coating carbon layer.

[0131] Furthermore, the average particle size D50 of the intermediate product is 9.5 μm to 13.5 μm, for example, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 13.5 μm or a range between any two of the above values.

[0132] It should also be noted that after graphitization, the carbon nanotubes can be fixed in the amorphous carbon layer of the graphitized tar, thereby enhancing the bonding force and strength of the first coating carbon layer.

[0133] In the step S13:

[0134] The biomass carbon source, zeolite imidazole framework material and resin are mentioned above and will not be described in detail here.

[0135] It should be noted that when mixing with the intermediate product, the biomass carbon source can be added first for fusion, and then the zeolite imidazole framework material and the resin are added in sequence, or the zeolite imidazole framework material can be added first for fusion, and then the biomass carbon source and the resin are added in sequence.

[0136] In some embodiments, the mass ratio of the intermediate product to the biomass carbon source, the zeolite imidazolate framework material, and the resin is 100:(1.5-3):(2-4):(5-8), for example, 100:1.5:4:5, 100:2:3:6, 100:3:2:7, 100:2.5:2.5:8, 100:2:3:6, or a range between any two of the above ratios. Within the mass ratio range, the biomass carbon source, the zeolite imidazolate framework material, and the resin are conducive to copolymerization and coating the intermediate product to form a second coating carbon layer.

[0137] In some embodiments, the temperature for mixing the biomass carbon source and the intermediate product is room temperature, such as 20°C to 30°C, and can further be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C or a range between any two of the above values; the time for mixing the biomass carbon source and the intermediate product is 30min to 40min, for example, it can be 30min, 32min, 35min, 38min, 40min or a range between any two of the above values.

[0138] In some embodiments, the temperature for mixing the zeolite imidazolate framework material and the intermediate product is room temperature, such as 20°C to 30°C, and can further be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C or a range between any two of the above values; the time for mixing the zeolite imidazolate framework material and the intermediate product is 5h to 9h, for example, it can be 5h, 6h, 7h, 8h, 9h or a range between any two of the above values.

[0139] In some embodiments, the temperature for mixing the resin and the intermediate product is 90°C to 100°C, for example, it can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C or a range between any two of the above values; the time for mixing the resin and the intermediate product is 6h to 8h, for example, it can be 6h, 6.5h, 7h, 7.5h, 8h or a range between any two of the above values.

[0140] It should be noted that the resin can be added directly, or raw materials of the resin can be added to ensure uniform synthesis and uniform distribution with the biomass carbon source and the zeolite imidazolate framework material.

[0141] Illustratively, providing the phenolic resin includes providing a phenolic compound and an aldehyde compound, adding a base, and polymerizing the phenolic compound and the aldehyde compound to form the phenolic resin. The phenolic compound may be one or more of resorcinol, phenol, and hydroquinone, and the aldehyde compound may be one or more of formaldehyde and glutaraldehyde.

[0142] In some embodiments, the carbonization process includes a first carbonization process and a second carbonization process performed sequentially, wherein the temperature of the second carbonization process is higher than the temperature of the first carbonization process.

[0143] Furthermore, the temperature of the first carbonization treatment is 270°C to 650°C, for example, it can be 270°C, 300°C, 400°C, 500°C, 550°C, 600°C, 650°C or a range between any two of the above values; the time of the first carbonization treatment is 8h to 10h, for example, it can be 8h, 8.5h, 9h, 9.5h, 10h or a range between any two of the above values.

[0144] The temperature of the second carbonization treatment is 650°C to 1050°C, for example, it can be 650°C, 700°C, 800°C, 900°C, 1000°C, 1050°C or a range between any two of the above values; the time of the second carbonization treatment is 15h to 20h, for example, it can be 15h, 16h, 17h, 18h, 19h, 20h or a range between any two of the above values.

[0145] In this way, under the above-mentioned carbonization treatment conditions, it is beneficial for the biomass carbon source, the zeolite imidazolate skeleton material and the resin to undergo staged coating and copolymerization carbonization to obtain a second carbon coating layer formed by biomass carbon source-derived carbon, zeolite imidazolate skeleton material-derived carbon and resin-derived carbon.

[0146] In some embodiments, after the carbonization treatment, the process further includes screening and demagnetization to obtain composite particles. Screening can remove large particles, agglomerates, or impurities, ensuring consistent particle size and enhancing uniformity. Magnetic separation can effectively remove ferromagnetic impurities, such as metal elements like iron and nickel, to prevent adverse effects on battery performance, such as capacity decay and shortened cycle life.

[0147] In some embodiments, the average particle size D50 of the composite particles is between 17.5 μm and 21.5 μm, for example, 17.5 μm, 18 μm, 19 μm, 20 μm, 21 μm, 21.5 μm, or a range between any two of the foregoing values. Within the aforementioned average particle size D50 range, the conductivity and other properties of the composite particles are improved, thereby improving battery performance.

[0148] It should be noted that the composite particles include the composite material. The composite particles may be a collection of multiple composite materials. It should be noted that the first coating carbon layer and the second coating carbon layer can serve to bond multiple graphite matrices. In the composite particles, multiple graphite matrices are connected by the first coating carbon layer and the second coating carbon layer, thereby improving the tightness of the connection.

[0149] The embodiment of the present application uses biomass carbon source, zeolite imidazolate skeleton material and resin as composite coating agents to achieve step-by-step coating copolymerization. The biomass carbon source can enhance the flexibility and bonding strength of the second coating carbon layer. The unique nitrogen-doped three-dimensional carbon skeleton of the zeolite imidazolate skeleton material can provide good structural support for the second coating carbon layer and can achieve self-repair to ensure the cycle performance of the battery. The resin can be cross-copolymerized with the biomass carbon source and zeolite imidazolate skeleton material to achieve uniform coating and complementary performance. While improving the density of the second coating carbon layer, it further improves the conductivity and structural stability of the second coating carbon layer, thereby improving the rate and cycle performance of the battery.

[0150] In a third aspect, an embodiment of the present application further provides an electrode, wherein the material of the electrode includes the above-mentioned composite material, or includes the composite material prepared by the above-mentioned preparation method.

[0151] In a fourth aspect, an embodiment of the present application further provides a battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the material of the negative electrode comprises the above-mentioned composite material, or comprises a composite material prepared by the above-mentioned preparation method.

[0152] The positive electrode, separator, and electrolyte can be made of conventional materials in this field.

[0153] The embodiments of the present application improve the graphite negative electrode, and the composite material can adapt to fast charging and discharging and long cycles, meet the performance requirements of fast charging and long cycles, and enable the battery to exhibit excellent performance of high rate and long cycle.

[0154] The present application will be described in detail below through specific examples. The following examples are only some examples of the present application and are not limitations of the present application.

[0155] Composite material example 1

[0156] This composite material embodiment provides a composite material, and a preparation method of the composite material includes the following steps:

[0157] Step S21: providing raw coke (petroleum coke and pitch coke), heating the raw coke to 200° C. at a rate of 8° C. / min, then to 500° C. at a rate of 5° C. / min, and heating the raw coke for 4 hours under a nitrogen atmosphere for preheating treatment; and using a pulverizer to obtain raw coke particles having an average particle size D50 of 9 μm.

[0158] Step S22, mixing tar and single-walled carbon nanotubes (average length of 3 μm, average tube diameter of 2 nm) in a mass ratio of 8:2 to obtain a modifier; adding the raw coke particles and the modifier in a mass ratio of 100:8 into a fusion machine, controlling the fusion speed at 15 Hz, the fusion temperature at room temperature, and the fusion time at 1 hour to obtain a modified raw coke precursor;

[0159] Step S23, placing the modified raw coke precursor into a vertical reactor, rotating at 35 Hz, slowly heating from room temperature to 280° C. at a heating rate of 2° C. / min, holding the temperature for 50 min, rotating at 35 Hz, then heating to 650° C. at a heating rate of 6° C. / min, and holding the temperature for 5 h, then cooling to room temperature to obtain modified raw coke precursor particles with an average particle size D50 of 12.5 μm, which are sent to a graphitization furnace for graphitization, heated at 3200° C. for 8 h, to obtain an intermediate product with an average particle size D50 of 11.8 μm, the intermediate product comprising a graphite matrix and a first coating carbon layer, the material of the first coating carbon layer comprising single-walled carbon nanotubes and graphitized tar;

[0160] Step S24, the intermediate product is dispersed in hexadecyltrimethylammonium bromide and put into a fusion machine, and inert gas protection is applied throughout the process; first, biomass carbon source lignin is added (the mass ratio of intermediate product: lignin is 100:2), and fusion is carried out at room temperature for 35 minutes; then, zeolite imidazole ester framework material ZIF-8 is added (the mass ratio of intermediate product: ZIF-8 is 100:2), and fusion is carried out at room temperature for 8 hours; finally, resorcinol and formaldehyde are added, and phenolic resin is synthesized under the catalysis of sodium citrate (the mass ratio of intermediate product: phenolic resin is 100:6), and 95°C The mixture was fused for 8 hours; then it was sent to a microwave carbonization furnace with inert gas protection throughout the process, with a carbonization heating rate of 50°C / min, heated to 500°C, kept warm for 9 hours, and a rotation speed of 20Hz. Then it was heated to 1000°C, with a rotation speed of 15Hz, and kept warm for 18 hours. After screening and demagnetization, composite particles with an average particle size D50 of 19.5μm were obtained. The composite particles included composite materials. Compared with the intermediate product, the composite material also included a second coating carbon layer coating the first coating carbon layer. The materials of the second coating carbon layer included lignin-derived carbon, ZIF-8-derived carbon and phenolic resin-derived carbon.

[0161] Composite material example 2

[0162] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that the single-walled carbon nanotubes in step S22 are replaced with multi-walled carbon nanotubes (average length 3 μm, average tube diameter 2 nm) in this composite material embodiment.

[0163] Composite material example 3

[0164] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that, in step S22 of this composite material embodiment, the mass ratio of raw coke particles to modifier is 100:7.

[0165] Composite material embodiment 4

[0166] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that, in step S22 of this composite material embodiment, the mass ratio of raw coke particles to modifier is 100:10.

[0167] Composite material example 5

[0168] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that, in this composite material embodiment, the biomass carbon source lignin in step S24 is replaced with amino acids.

[0169] Composite material example 6

[0170] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the lignin is 100:1.5.

[0171] Composite material embodiment 7

[0172] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the lignin is 100:3.

[0173] Composite material embodiment 8

[0174] This composite material embodiment is substantially the same as the composite material embodiment 1, with the only difference being that, in this composite material embodiment, the zeolite imidazolate framework material ZIF-8 in step S24 is replaced by ZIF-67.

[0175] Composite material embodiment 9

[0176] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the zeolite imidazolate framework material ZIF-8 is 100:2.

[0177] Composite material example 10

[0178] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the zeolite imidazolate framework material ZIF-8 is 100:4.

[0179] Composite Material Example 11

[0180] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that, in step S24 of this composite material embodiment, formaldehyde is replaced by furfural to synthesize furfural resin.

[0181] Composite material example 12

[0182] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the phenolic resin is 100:5.

[0183] Composite Material Example 13

[0184] This composite material embodiment is substantially the same as composite material embodiment 1, with the only difference being that in step S24 of this composite material embodiment, the mass ratio of the intermediate product to the phenolic resin is 100:8.

[0185] Composite material comparative example 1

[0186] The composite material comparative example is substantially the same as the composite material embodiment 1, with the only difference being that in the composite material comparative example, only the raw coke particles are graphitized to obtain single-particle artificial graphite.

[0187] Composite material comparative example 2

[0188] The composite material comparative example is substantially the same as the composite material embodiment 1, with the only difference being that step S22 is not performed in the composite material comparative example, that is, the composite material does not contain the first coating carbon layer.

[0189] Composite material comparative example 3

[0190] The composite material comparative example is substantially the same as the composite material embodiment 1, with the only difference being that step S24 is not performed in the composite material comparative example, that is, the composite material does not contain the second coating carbon layer.

[0191] The C, O, and N element contents, the thickness of the first coating carbon layer, the thickness of the second coating carbon layer, and the electrical conductivity and internal resistance R of the composite materials of Examples 1 to 13 and Comparative Examples 1 to 3 were tested. The test results are shown in Table 1.

[0192] The composite material is microwave digested and then the content of each element is tested and analyzed using an X-ray fluorescence spectrometer (XRF).

[0193] The thickness of the first coating carbon layer and the second coating carbon layer were observed by transmission electron microscopy (TEM).

[0194] Conductivity was measured using the Orion StarT TM The conductivity was measured using an A212 benchtop conductivity meter at room temperature.

[0195] The internal resistance is measured by electrochemical impedance spectroscopy using a blue electric system.

[0196] Table 1

[0197]

[0198]

[0199] From Table 1, we can get:

[0200] It can be seen from composite material examples 1 to 4 and composite material comparative examples 1 to 3 that in this solution, by coating the graphite substrate with a first coating carbon layer and a second coating carbon layer, the one-dimensional nanostructure of the carbon nanotubes in the first coating carbon layer builds an effective conductive network, and its cavity structure increases the path for ion transmission, fully improving the electrical conductivity of the graphite substrate, reducing the internal resistance R, and facilitating accelerated electron conduction;

[0201] It can be seen from composite material embodiments 1, 5 to 13 and composite material comparison examples 1 to 3 that this scheme improves the flexibility and mechanical properties of the composite material by coating the graphite matrix with a first coating carbon layer and a second coating carbon layer. The biomass carbon source-derived carbon in the second coating carbon layer improves the flexibility and mechanical properties of the composite material. The zeolite imidazolate skeleton material-derived carbon provides porous channels, thereby enhancing the electrical conductivity of the composite material. The resin-derived carbon has a three-dimensional porous network structure, which can promote the transmission of ions. The materials in the second coating carbon layer work synergistically with each other to jointly reduce the internal resistance R and promote the improvement of electrical conductivity.

[0202] Battery Example 1

[0203] This battery embodiment provides a battery, and a method for preparing the battery includes the following steps:

[0204] The composite material of composite material example 1 was mixed evenly with conductive agent (SP), binder (CMC, sodium carboxymethyl cellulose), and binder (SBR, styrene-butadiene rubber) at a ratio of 95:1.5:1.5:2. The mixture was applied on copper foil to obtain a compacted density of 1.60 g / cm 3 , vacuum dried and used as the negative electrode, lithium metal as the counter electrode, the electrolyte used was a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) of IMLiPP6 in a mass ratio of 1:1, and the separator was a PE / PPPE composite film to assemble a button battery.

[0205] Battery Examples 2 to 13

[0206] Battery Examples 2 to 13 are substantially the same as Battery Example 1, with the only difference being that the composite material of Composite Material Example 1 is replaced by the composite materials of Composite Material Examples 2 to 13 in Battery Examples 2 to 13, respectively.

[0207] Battery Comparison Examples 1 to 3

[0208] Comparative battery examples 1 to 3 are substantially the same as Example 1, with the only difference being that the composite material of Example 1 is replaced by the composite materials of Comparative battery examples 1 to 3, respectively.

[0209] The charge and discharge performance and cycle performance of the batteries of battery examples 1 to 13 and battery comparison examples 1 to 3 were tested: the rate charge and discharge were carried out at a current density of 0.5C to 10C, the charging voltage was limited to 0.005V to 2V, and the test results of the cycle performance (within 800 cycles) at a rate of 0.5C and the test results of the negative electrode sheet expansion rate after 800 cycles (i.e., expansion rate = thickness of the negative electrode sheet after 800 cycles / thickness of the negative electrode sheet in the first cycle * 100%) were referred to Table 2; the rate performance test of battery example 1 and battery comparison examples 1 to 3 at different rates (a total of 35 times, cycled 5 times at rates of 0.5C (first time), 1C, 3C, 5C, 7C, 10C, and 0.5C (second time) in sequence) were referred to Table 3.

[0210] Table 2

[0211]

[0212]

[0213] From Table 2, we can get:

[0214] As can be seen from battery examples 1 to 4 and battery comparative examples 1 to 3, in the embodiments of the present application, using carbon nanotubes and tar as the materials for the first coating carbon layer can effectively improve the discharge performance and cycle performance of the battery, enhance the mechanical structural stability of the negative electrode material, reduce the expansion rate of the negative electrode, and reduce the volume change of the battery during charge and discharge, thereby ensuring long-term use of the battery.

[0215] It can be seen from battery examples 1, 5 to 13 and battery comparison examples 1 to 3 that the composite material provided in the examples of the present application is applied to the negative electrode of the battery. Under the joint action of the various carbon sources of the second coated carbon layer provided in the examples of the present application, the first discharge specific capacity and the first discharge efficiency of the battery can be improved. After 800 cycles, it still has a high cycle capacity, and the negative electrode plate has a lower expansion rate, so that the battery can adapt to rapid charging and discharging, thereby improving the performance of the battery.

[0216] Table 3

[0217]

[0218] From Table 3 we can get:

[0219] It can be seen from Battery Example 1 and Battery Comparative Examples 1 to 3 that under tests of various rates and the recovery to the initial rate after a high rate, the cycle performance of Battery Example 1 is superior to that of Battery Comparative Examples 1 to 3, especially at a rate of 10C, the capacity retention rate of Battery Example 1 is close to 70%, while that of Battery Comparative Example 1 is only 12.7%; the battery provided in the embodiments of the present application has good cycle performance and can extend the service life of the battery.

[0220] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A composite material, characterized in that The invention comprises a graphite substrate, a first coating carbon layer coating the graphite substrate, and a second coating carbon layer coating the first coating carbon layer; The material of the first carbon coating layer includes carbon nanotubes, and the material of the second carbon coating layer includes biomass carbon source derived carbon, zeolite imidazolate skeleton material derived carbon and resin derived carbon.

2. The composite material according to claim 1, wherein The carbon nanotubes are selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes; a plurality of the carbon nanotubes are stacked to form a three-dimensional skeleton structure; The biomass carbon source-derived carbon is mainly prepared from a biomass carbon source, and the biomass carbon source is selected from one or more of polysaccharide compounds and nitrogen-containing biological molecules; The zeolite imidazolate framework material-derived carbon is mainly prepared from a zeolite imidazolate framework material, and the zeolite imidazolate framework material is selected from one or more of a zinc-based zeolite imidazolate framework material and a cobalt-based zeolite imidazolate framework material; The resin-derived carbon is mainly prepared from resin, and the resin is selected from one or more of phenolic resin, furan resin, epoxy resin, and urea-formaldehyde resin; The biomass carbon source derived carbon, the zeolite imidazolate framework material derived carbon, and the resin derived carbon have a three-dimensional porous network structure; The mass ratio of the biomass carbon source derived carbon, the zeolite imidazolate framework material derived carbon and the resin derived carbon is (1.5-3): (2-4): (5-8).

3. The composite material according to claim 2, wherein The average length of the single-walled carbon nanotubes is 1 μm to 5 μm; the average diameter of the single-walled carbon nanotubes is 1 nm to 2 nm; The average length of the multi-walled carbon nanotubes is 1 μm to 5 μm; the average diameter of the single-walled carbon nanotubes is 1 nm to 2 nm; The polysaccharide compound is selected from one or more of lignin, cellulose, and starch; The nitrogen-containing biomolecule is selected from one or more of proteins and amino acids; The zinc-based zeolite imidazolate framework material is selected from one or more of ZIF-8 and ZIF-67; The cobalt-based zeolite imidazolate framework material is selected from ZIF-11; The phenolic resin is selected from one or more of phenol formaldehyde phenolic resin, sulfonated phenolic resin, and terpene phenolic resin; The furan resin is selected from one or more of furfural phenol resin, furfural acetone resin and furfuryl alcohol resin; The epoxy resin is selected from one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, alicyclic epoxy resins, and epoxidized olefin epoxy resins; The urea-formaldehyde resin is selected from one or more of methyl etherified urea-formaldehyde resin and n-butanol etherified urea-formaldehyde resin.

4. The composite material according to claim 1, wherein The material of the first coating carbon layer further comprises graphitized tar; the graphitized tar is located between the plurality of carbon nanotubes; wherein, in the first coating carbon layer, the mass ratio of the carbon nanotubes to the graphitized tar is (1-3):(8-10); The average thickness of the first coating carbon layer is 2nm to 6nm; The average thickness of the second coating carbon layer is 15nm to 35nm; The mass ratio of the graphite substrate, the first coating carbon layer, and the second coating carbon layer is: 100: (7-10): (5.5-12.5).

5. A method for preparing a composite material, characterized in that: The steps include: Providing raw coke and a modifier, wherein the modifier includes carbon nanotubes, and mixing the raw coke and the modifier to obtain a modified raw coke precursor; Graphitizing the modified raw coke precursor to obtain an intermediate product, wherein the intermediate product includes a graphite matrix and a first coating carbon layer coating the graphite matrix, wherein the material of the first coating carbon layer includes the modifier; A biomass carbon source, a zeolite imidazolate skeleton material and a resin are provided, mixed with the intermediate product, and carbonized to obtain a second coating carbon layer covering the first coating carbon layer, wherein the material of the second coating carbon layer includes biomass carbon source-derived carbon, zeolite imidazolate skeleton material-derived carbon and resin-derived carbon to obtain a composite material.

6. The preparation method according to claim 5, wherein The raw coke includes one or more of oil-based coke and coal-based coke; the oil-based coke is selected from one or more of petroleum coke and oil-based needle coke, and the coal-based coke is selected from one or more of coal-based needle coke and pitch coke; The carbon nanotubes are selected from one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes; The modifier further includes tar; in the modifier, the mass ratio of the carbon nanotubes to the tar is (1-3): (8-10); The biomass carbon source is selected from one or more of polysaccharide compounds and nitrogen-containing biological molecules; The zeolite imidazolate framework material is selected from one or more of a zinc-based zeolite imidazolate framework material and a cobalt-based zeolite imidazolate framework material; The resin is selected from one or more of phenolic resin, furan resin, epoxy resin and urea-formaldehyde resin.

7. The preparation method according to claim 5, wherein The mixing of the raw coke and the modifier comprises: providing raw coke, performing preheating and crushing treatment to obtain raw coke particles; mixing the raw coke particles and the modifier; wherein, The temperature of the preheating treatment is 500°C to 700°C, and the time of the preheating treatment is 4h to 8h; The average particle size D50 of the raw coke particles is 7 μm to 10 μm; The mass ratio of the raw coke particles to the modifier is 100:(7-10); The temperature for mixing the raw coke particles and the modifier is 20° C. to 30° C., and the time for mixing the raw coke particles and the modifier is 0.5 h to 1 h.

8. The preparation method according to claim 5, wherein Before the modified raw coke precursor is graphitized, the modified raw coke precursor is granulated to obtain modified raw coke precursor particles; the granulation includes gradient heating, and the gradient heating includes heating the modified raw coke precursor to a first temperature, keeping the temperature for a first time period, and then heating the modified raw coke precursor to a second temperature, keeping the temperature for a second time period; wherein, The heating rate of heating to the first temperature is 1°C / min to 3°C / min; The first temperature is 250° C. to 300° C.; The first time period is 40 minutes to 60 minutes; The heating rate of heating to the second temperature is 5°C / min to 8°C / min; The second temperature is 600° C. to 650° C.; The second time period is 4 hours to 6 hours; The average particle size D50 of the modified raw coke precursor particles is 11 μm to 15 μm.

9. The preparation method according to claim 5, wherein The mixing of the biomass carbon source, the zeolite imidazolate skeleton material, the resin and the intermediate product comprises: sequentially adding the biomass carbon source, the zeolite imidazolate skeleton material and the resin, and mixing them with the intermediate product; or sequentially adding the zeolite imidazolate skeleton material, the biomass carbon source and the resin, and mixing them with the intermediate product; wherein, The mass ratio of the intermediate product to the biomass carbon source, the zeolite imidazolate framework material, and the resin is 100: (1.5-3): (2-4): (5-8); The temperature for mixing the biomass carbon source and the intermediate product is 20° C. to 30° C., and the time for mixing the biomass carbon source and the intermediate product is 30 min to 40 min. The temperature for mixing the zeolite imidazolate framework material and the intermediate product is 20° C. to 30° C., and the time for mixing the zeolite imidazolate framework material and the intermediate product is 5 h to 9 h; The temperature for mixing the resin and the intermediate product is 90° C. to 100° C., and the time for mixing the resin and the intermediate product is 6 hours to 8 hours.

10. The preparation method according to claim 5, characterized in that The temperature of the graphitization treatment is 3000° C. to 3200° C., and the time of the graphitization treatment is 70 hours to 85 hours; The carbonization treatment includes a first carbonization treatment and a second carbonization treatment performed sequentially, the temperature of the second carbonization treatment is greater than the temperature of the first carbonization treatment; the temperature of the first carbonization treatment is 270°C to 650°C, and the time of the first carbonization treatment is 8h to 10h; the temperature of the second carbonization treatment is 650°C to 1050°C, and the time of the second carbonization treatment is 15h to 20h.

11. The preparation method according to claim 5, wherein After the carbonization treatment, the method further includes: screening and demagnetization to obtain composite particles, wherein the composite particles include the composite material; wherein, The average particle size D50 of the intermediate product is 9.5 μm to 13.5 μm; The average particle size D50 of the composite particles is 17.5 μm to 21.5 μm.

12. An electrode, characterized in that: The material of the electrode includes the composite material according to any one of claims 1 to 4, or includes the composite material prepared by the preparation method according to any one of claims 5 to 11.

13. A battery, characterized in that: The battery includes a positive electrode, a negative electrode, a separator and an electrolyte, the material of the negative electrode includes the composite material according to any one of claims 1 to 4, or includes the composite material prepared by the preparation method according to any one of claims 5 to 11, or the negative electrode includes the electrode according to claim 12.

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