Composite material, and preparation method and application thereof

Abstract

The invention discloses a composite material and a preparation method and application thereof, the composite material comprises a first material and hard carbon, the first material comprises an inner core and a coating layer coating the inner core, the material of the inner core comprises porous carbon, and the material of the coating layer comprises carbon, the first material has a proper number of active sites and a good metal storage characteristic, and the first material and the hard carbon are compounded, so that the anti-pressure ability of the coating layer is improved, and the phenomenon that the coating layer is damaged by external force can be improved, thereby reducing the loss rate of the first effect and the capacity of the composite material subjected to external pressure treatment, and prolonging the service life of the composite material. The composite material can be used for preparing an electrode of a battery and is beneficial to improving the performance of the battery.

Description

Technical Field

[0001] This application relates to the field of electrode material technology, specifically to a composite material, a method for preparing the composite material, and its application. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and energy systems, batteries, as the core device for energy conversion, are constantly being updated and iterated. Batteries are now widely used in consumer electronics, advanced robotics, grid-scale energy storage, electric vehicles, and other technological fields.

[0003] In related technologies, porous carbon is one of the common electrode materials. Porous carbon has a high specific surface area, thus providing abundant ion storage sites and endowing it with high specific capacity. Furthermore, the pore structure of porous carbon can act as a "volume buffer space," absorbing the expansion stress generated by ion intercalation, thereby improving electrode breakage and pulverization, and ultimately enhancing battery cycle life. However, during battery operation, the abundance of active sites in porous carbon increases the probability of side reactions. For example, during charge-discharge cycles, the electrolyte forms a solid electrolyte interface film on the surface of the porous carbon. This process irreversibly consumes metal ions (such as lithium or sodium ions) provided by the positive electrode, leading to a decline in battery performance.

[0004] Therefore, how to provide a porous carbon-based material that can be used to prepare battery electrodes and fully utilize the advantages of porous carbon is of great significance to the development of batteries. Summary of the Invention

[0005] In view of the shortcomings of the prior art, this application provides a composite material, a method for preparing the composite material, and its application.

[0006] In a first aspect, this application provides a composite material comprising a first material and hard carbon, wherein the first material comprises a core and a coating layer covering the core, the core being made of porous carbon, and the coating layer being made of carbon.

[0007] Secondly, this application provides a method for preparing a composite material, comprising the steps of: providing a first material and hard carbon respectively, mixing the first material and the hard carbon to obtain the composite material; Wherein, the first material is the first material in the composite material as described in the first aspect, and the hard carbon is the hard carbon in the composite material as described in the first aspect.

[0008] Thirdly, this application provides the application of composite materials as described in the first aspect, or composite materials prepared by the method described in the second aspect, in the preparation of electrodes.

[0009] Fourthly, this application provides a battery comprising a positive electrode and a negative electrode, wherein the material of the negative electrode comprises a composite material as described in the first aspect, or a composite material prepared by the method for preparing the composite material as described in the second aspect; Optionally, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the material of the negative electrode active material layer includes the composite material as described in the first aspect, or the composite material prepared by the method described in the second aspect.

[0010] This application provides a composite material, a method for preparing the composite material, and its application, which has the following technical effects: In the composite material of this application embodiment, the first material is carbon-coated porous carbon. The first material has a suitable number of active sites and good metal storage properties. By compounding the first material with hard carbon, the compressive strength of the coating layer is improved, which can mitigate the phenomenon of external force damaging the coating layer, thereby reducing the initial efficiency and capacity loss rate of the composite material after external pressure treatment. The composite material has good electrochemical properties and can be used to prepare battery electrodes, which is beneficial to improving battery performance. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0012] Figure 1 The image shows the microstructure of the composite material in Example 1, which was not subjected to cold pressing.

[0013] Figure 2 The image shows the microstructure of the composite material in Comparative Example 1, which was not subjected to cold pressing.

[0014] Figure 3 This is a microscopic morphology diagram of the composite material in Material Example 1 after cold pressing.

[0015] Figure 4 The image shows the microstructure of the composite material in Comparative Example 1 after cold pressing. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art, and the materials or reagents used in the embodiments of this application are commercially available. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this application. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0018] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Each embodiment of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0019] In the description of this application, the term "comprising" means "including but not limited to".

[0020] The terms “multiple,” “multiple times,” or similar expressions refer to two or more times, such as two, three, four, five, six, etc.

[0021] The term "and / or" encompasses any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" includes three parallel options: A, B, and A+B.

[0022] The term "inert gas" refers to a class of gases that have stable chemical properties and do not readily react with other substances at room temperature and pressure. These include one or more of nitrogen, helium, neon, argon, krypton, and xenon.

[0023] The term "DV50 particle size" refers to the particle size that accounts for 50% of the total volume of a particle group, also known as the "volume median diameter." In other words, when particles are sorted from smallest to largest, the particle size at which the total volume of all particles not larger than a certain size accounts for 50% of the total volume of all particles is the DV50 particle size. The DV50 particle size of materials is determined according to the method described in GB-T-19077-2024 standard, using a laser particle size analyzer.

[0024] The term "DV00 particle size" refers to the smallest particle size in a particle group. It represents the minimum particle size of all particles in the group, meaning that there are no particles smaller than this value within the group. In this application, the DV00 particle size of the first material refers to the smallest particle size of the first material.

[0025] The term "DV100 particle size" refers to the particle size within a particle group where all particle sizes are no larger than a certain value; this value is considered the DV100 particle size. In other words, the DV100 particle size represents the upper limit or maximum particle size of the particle group. The method for determining the DV100 particle size of materials follows the method described in GB-T-19077-2024 standard, and the testing instrument is a laser particle size analyzer.

[0026] In this application, the method for testing the specific surface area, pore volume, and pore size distribution of the material includes the following steps: degassing the material sample to be tested in a vacuum environment (pressure -0.1 MPa) at 200 °C for 10 h; then, obtaining the nitrogen adsorption-desorption isotherm of the sample at 77 K using a MicromeritcsTristar 3030 instrument; next, calculating the specific surface area using the Brunauer-Emmett-Teller method and adsorption curve branch data in the relative pressure P / P0 range of 0.005~1, and analyzing the pore volume and pore size distribution from the adsorption curve. The model for analyzing the pore volume and pore size distribution is the DensityFunctionTheory model.

[0027] The applicant discovered that a coating layer can be prepared on the surface of porous carbon to form a porous carbon material with a closed-cell structure, thereby appropriately reducing the specific surface area of ​​the porous carbon material. Porous carbon materials with a closed-cell structure exhibit excellent sodium or lithium storage properties; sodium or lithium ions are induced to form pseudometals within the closed pores, achieving ultra-high specific capacity. The coating layer can be made of carbon; however, in practical applications, it has been found that carbon-based coating layers are prone to damage and detachment during rolling, leading to a decrease in the battery's initial coulombic efficiency and capacity.

[0028] Based on this, embodiments of this application provide a composite material comprising a first material and hard carbon, wherein the first material comprises a core and a coating layer covering the core, the core being made of porous carbon, and the coating layer being made of carbon.

[0029] In the composite material of this application embodiment, the first material is carbon-coated porous carbon. The first material has a suitable number of active sites and good metal storage properties. By compounding the first material with hard carbon, the compressive strength of the coating layer is improved, which can mitigate the phenomenon of external force damaging the coating layer, thereby enhancing the structural stability of the first material. The composite material of this application embodiment has good capacity and compaction density, and good electrochemical performance.

[0030] It should be noted that the coating layer can partially or completely cover the kernel. The coverage of the kernel by the coating layer can be 80% to 100%. For example, the coverage can be 80%, 85%, 90%, 95%, 100%, or any two of the aforementioned values. The coverage refers to the percentage of the surface area of ​​the kernel covered by the coating layer to the total surface area of ​​the kernel.

[0031] In some embodiments of this application, the mass ratio of the first material to hard carbon in the composite material is 1:(0.01~0.25), for example, it can be 1:(0.01~0.20), 1:(0.01~0.15), 1:(0.01~0.10), 1:(0.01~0.05), or 1:(0.03~0.06). Under this condition, the composite material has a high capacity and the coating layer has good compressive strength, thereby further reducing the first-time efficiency and capacity loss rate of the composite material after external pressure treatment, and further improving the structural and performance stability of the composite material.

[0032] In some embodiments of this application, the particle size of the first material is not less than 2 μm for DV00, not less than 7 μm for DV50, and not greater than 25 μm for DV100, and the particle size distribution curve of the first material is normally distributed. Under these conditions, the particle size of the first material is more suitable, thereby ensuring good compressive strength of the coating layer while reducing the amount of hard carbon added, and further improving the capacity of the composite material.

[0033] To further improve the capacity of the composite material, in some embodiments of this application, the DV50 particle size of the first material is 7 μm to 9 μm, for example, it can be 7 μm, 8 μm, 9 μm or any two of the aforementioned values.

[0034] In some embodiments of this application, the specific surface area of ​​the first material is 6 m². 2 / g~10 m 2 / g, for example, could be 6m 2 / g、7 m 2 / g、8 m 2 / g、9 m 2 / g、10 m 2 / g or any two of the aforementioned values, under these conditions, is beneficial for further improving the electrochemical performance of the composite material.

[0035] It should be noted that, due to the relatively small amount of hard carbon added, the difference between the specific surface area of ​​the composite material and the specific surface area of ​​the first material is small, and the difference between the particle size of the composite material and the particle size of the first material is also small. In some embodiments of this application, the specific surface area of ​​the composite material is 6 m². 2 / g~10 m 2 / g, for example, could be 6 m 2 / g、7 m 2 / g、8 m 2 / g、9 m 2 / g、10 m 2 / g or the range between any two of the aforementioned values; the DV50 particle size of the composite material is 7 μm to 10 μm, the DV00 particle size of the composite material is not less than 2 μm, and the DV100 particle size of the composite material is not greater than 26 μm.

[0036] To further improve the electrochemical performance of the composite material, in some embodiments of this application, the DV50 particle size of the porous carbon is 6 μm to 8 μm, for example, it can be 6 μm, 7 μm, 8 μm, or any two of the aforementioned values. The specific surface area of ​​the porous carbon is 500 m². 2 / g~3500 m 2 / g, for example, could be 500 m 2 / g、800 m 2 / g, 1500 m 2 / g、1800 m 2 / g、2000 m 2 / g、2300 m 2 / g、2800 m 2 / g or any two of the aforementioned values. The pore volume of porous carbon is 0.05 cm³. 3 / g~1.8 cm 3 / g, for example, could be 0.05 cm 3 / g, 1 cm 3 / g, 1 cm 3 / g, 1.2 cm 3 / g, 1.5 cm 3 / g, 1.8cm 3 / g or the range between any two of the aforementioned values.

[0037] It should be noted that porous carbon can be commercially available or prepared at home. The raw materials used to prepare porous carbon include one or more of biomass, pitch, resin and coal tar.

[0038] In some embodiments of this application, the carbon in the coating layer includes one or more of amorphous carbon and heterostructured carbon.

[0039] In some embodiments of this application, the mass ratio of porous carbon to carbon in the coating layer in the first material is 1:(0.3~0.5), for example, it can be 1:0.3, 1:0.4, 1:0.5, or any two of the aforementioned values. Under this condition, the number of active sites in the first material is within a more suitable range, further improving the capacity of the composite material while further reducing the probability of side reactions occurring in the first material. It is understood that for batteries with electrodes comprising composite materials, a more suitable range of active sites in the first material can further improve the phenomenon of excessive electrolyte decomposition, thereby further improving the initial coulombic efficiency of the battery.

[0040] In some embodiments of this application, the DV50 particle size of the hard carbon is 30% to 60% of the DV50 particle size of the first material, for example, it can be 30% to 55%, 30% to 50%, 30% to 45%, 30% to 40%, or 40% to 50%, and the particle size distribution curve of the hard carbon is normally distributed. Under these conditions, the particle size of the hard carbon is within a more suitable range, thereby providing good protection for the coating layer while reducing the amount of hard carbon added, further improving the capacity of the composite material.

[0041] In some embodiments of this application, the DV50 particle size of the hard carbon is 2.8 µm to 4.5 µm, for example, it can be 2.8 µm, 3.0 µm, 4.0 µm, 4.5 µm, or any range between two of the aforementioned values. The specific surface area of ​​the hard carbon is 2 m². 2 / g~7 m 2 / g, for example, could be 2 m 2 / g、3 m 2 / g、4 m 2 / g、5 m 2 / g、6 m 2 / g、7 m 2 / g or any two of the aforementioned values. The pore volume of hard carbon is 0.01 cm³. 3 / g~0.1 cm 3 / g, for example, could be 0.01 cm 3 / g, 0.012 cm3 / g, 0.03 cm 3 / g, 0.05 cm 3 / g, 0.08 cm 3 / g, 0.1 cm 3 / g or the range between any two of the aforementioned values.

[0042] In some embodiments of this application, the hard carbon is selected from one or more of biomass hard carbon, resin-based hard carbon, pitch-based hard carbon, and coal tar hard carbon. Hard carbon can be commercially available or prepared in-house.

[0043] Taking resin-based hard carbon as an example, the preparation method of resin-based hard carbon includes the following steps: First, take an appropriate amount of phenolic resin and cure it at 110 ℃~150 ℃ for 10 h~15 h to obtain a cured product; then, crush the cured product to obtain a precursor; next, under the protection of an inert gas atmosphere, heat the precursor to a first temperature of 500 ℃~600 ℃ and keep it at the first temperature for 1 h~5 h to obtain a first carbonized product; next, sieve the first carbonized product, and then, under the protection of an inert gas atmosphere, heat the sieved first carbonized product to a second temperature of 1200 ℃~1500 ℃ and keep it at the second temperature for 1 h~5 h to obtain a second carbonized product; finally, sieve the second carbonized product to obtain the target hard carbon.

[0044] This application also provides a method for preparing a composite material, which can be used to prepare any of the composite materials described above. The method for preparing the composite material includes the steps of: providing a first material and hard carbon respectively, mixing the first material and hard carbon to obtain the composite material. The first material and hard carbon are as described above. The method for preparing the composite material has the advantages of simple process, low cost, and suitability for industrialization.

[0045] In the method for preparing the composite material according to the embodiments of this application, the method for preparing the first material includes the steps of: providing porous carbon and forming a coating layer on the surface of the porous carbon, wherein the material of the coating layer includes carbon. The method for forming the coating layer can be one or more of solid-phase coating, liquid-phase coating, gas-phase coating, and plasma coating. When forming the coating layer using the gas-phase coating method, the carbon source includes one or more of gas-phase coating agents such as methane, acetylene, and ethylene; when forming the coating layer using the liquid-phase coating method, the carbon source includes one or more of tar and liquid resin; when forming the coating layer using the solid-phase coating method, the carbon source includes one or more of pitch and solid resin.

[0046] In some embodiments of this application, the mixing method of the first material and hard carbon includes one or more of ball milling and stirring. In the step of mixing the first material and hard carbon, the mass ratio between the first material and hard carbon is 1:(0.01~0.25), for example, it can be 1:(0.01~0.20), 1:(0.01~0.15), 1:(0.01~0.10), 1:(0.01~0.05), or 1:(0.03~0.06). Under these conditions, the resulting composite material has high capacity and good compressive strength of the coating layer, thereby further reducing the initial efficiency and capacity loss rate of the composite material after external pressure treatment, and further improving the structural and performance stability of the composite material. In some embodiments of this application, the preparation method of the first material includes the steps of: providing porous carbon, using porous carbon as a deposition matrix, introducing a gas containing a carbon source, and having the carbon source decompose to form carbon atoms that are deposited on the surface of the porous carbon.

[0047] In some embodiments of this application, the carbon source includes one or more of methane, ethane, propane, butane, ethylene, propylene, acetylene, and propyne.

[0048] In some embodiments of this application, the step of providing porous carbon, using porous carbon as a deposition matrix, introducing a gas containing a carbon source, and having the carbon source decompose to form carbon atoms that are deposited on the porous carbon includes: heating the porous carbon in an inert gas atmosphere to a third temperature; then, while maintaining the third temperature, introducing a gas containing a carbon source. The third temperature is not less than the temperature at which the carbon source gas is cracked to form carbon atoms. In some embodiments of this application, the third temperature is 900 ℃ to 1000 ℃, for example, it can be 900 ℃, 930 ℃, 950 ℃, 980 ℃, 1000 ℃ or any two of the aforementioned values.

[0049] In order to make the thickness of the coating layer within a more suitable range, thereby further improving the electrochemical performance of the prepared composite material, in some embodiments of this application, the flow rate of the introduced gas is 10 L / min to 20 L / min, for example, it can be 10 L / min, 12 L / min, 14 L / min, 16 L / min, 18 L / min, 20 L / min or any two of the aforementioned values; the total duration of the gas introduction is 1 h to 15 h, for example, it can be 1 h, 3 h, 5 h, 10 h, 15 h or any two of the aforementioned values.

[0050] To further improve the uniformity of the coating layer on porous carbon, in some embodiments of this application, the gas also includes an inert gas, and the volume of the carbon source accounts for 10% to 70% of the total volume of the gas, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70% or any two of the aforementioned values.

[0051] This application also provides an application of the composite material as described above, or the composite material prepared by the method described above, in the preparation of electrodes.

[0052] This application provides a battery comprising a positive electrode and a negative electrode. The negative electrode is made of a composite material as described above, or a composite material prepared by the method described above. The battery has good performance.

[0053] Specifically, firstly, the first material in the composite material is carbon-coated porous carbon. This first material has an appropriate number of active sites and good metal storage properties, thereby improving the battery capacity. Furthermore, because the porous carbon is coated with carbon, it reduces the probability of side reactions at the negative electrode and mitigates excessive electrolyte decomposition, which is beneficial for improving the battery's initial coulombic efficiency and cycle performance. Secondly, by compounding the first material with hard carbon, the compressive strength of the coating layer is improved. The composite material has good compaction density, which can mitigate damage and detachment of the coating layer during rolling, thereby reducing the initial efficiency and capacity loss rate of the composite material after rolling treatment, which is beneficial for further improving the battery's initial coulombic efficiency and capacity. Based on its geometric shape, the battery in this application embodiment can be a square battery, a cylindrical battery, a button battery, or an irregularly shaped battery. Based on its packaging form, the battery in this application embodiment can be a pouch battery or a hard-case battery. Based on its assembly form, the battery in this application embodiment can be a battery cell, a battery module, or a battery pack. Based on its operating nature and storage method, the battery in this application embodiment can be a primary battery, a secondary battery, or an activated battery. Based on the type of current-carrying ions in the battery, the battery in this application embodiment can be a lithium-ion battery or a sodium-ion battery.

[0054] In some embodiments of this application, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the material of the negative electrode active material layer includes a composite material prepared by the composite material preparation method described above, or a composite material as described above.

[0055] The negative electrode current collector includes a first surface and a second surface disposed opposite to each other along its own thickness direction, and at least one of the first surface and the second surface is provided with a negative electrode active material layer. The material of the negative electrode current collector includes copper foil, composite copper foil, or copper mesh.

[0056] In some embodiments of this application, the negative electrode active material layer further includes a negative electrode binder and a negative electrode conductive agent. The negative electrode binder and negative electrode conductive agent can be materials commonly found in the art. Specifically, the negative electrode binder includes one or more of lithium polyacrylate, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, sodium alginate, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. The negative electrode conductive agent includes one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0057] The preparation method of the negative electrode may include the following steps: mixing and dispersing the negative electrode active material, negative electrode conductive agent, and negative electrode binder in a first dispersion medium to form a negative electrode slurry; then, coating the negative electrode slurry onto a negative electrode current collector, followed by a drying process and a rolling process to obtain the negative electrode. It should be noted that the negative electrode slurry can also be cast on a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the first surface and / or the second surface of the negative electrode current collector. The first dispersion medium includes one or more of N-methylpyrrolidone, acetone, and water.

[0058] In the battery of this application embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. It is understood that the positive electrode current collector includes a third surface and a fourth surface disposed opposite to each other along its own thickness direction, and at least one of the third surface and the fourth surface is provided with a positive electrode active material layer.

[0059] The positive electrode current collector is made of a metal foil or a composite current collector. The metal foil includes aluminum foil, platinum foil, or palladium foil. The composite current collector includes a substrate and a metal layer. The substrate includes a third surface and a fourth surface disposed opposite each other along its thickness direction. At least one of the third surface and the fourth surface has a metal layer. The substrate is made of one or more of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene. The metal layer is made of one or more of aluminum, platinum, palladium, nickel, titanium, and silver.

[0060] The positive electrode active material layer comprises a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The positive electrode active material, positive electrode binder, and positive electrode conductive agent can be conventional materials in the art. When the battery is a lithium-ion battery, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium permanganate, lithium iron phosphate, lithium nickel oxide, lithium manganese phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. When the battery is a sodium-ion battery, the positive electrode active material includes one or more of metal oxides, Prussian compounds, and polyanionic compounds, wherein the chemical formula of the metal oxide is Na. x MO2, where M is a transition metal element, including one or more of Mn, Ni, Cr, Fe, Ti, and V. Suitable examples include Na(Li). 1 / 3 Ti 1 / 6 Mn 1 / 2 O2, NaFeO2 and Na 2 / 3 Ni 1 / 3 Mn 1 / 2 Ti 1 / 6 One or more of O2; the chemical formula of Prussian compounds is Na. x M a (M b (CN)6), M a Including one or more of Fe, Mn, and Ni, M b Suitable examples of Prussian compounds include one or more of Fe and Mn, including Na. x Mn(Fe(CN)6); the chemical formula of the polyanionic compound is Na x A y ((XO m ) n ) z A is a metallic element with a variable valence state, including one or more of Fe and V, X is one or more of P and S, and suitable examples of polyanionic compounds include one or more of Na3V2(PO4)3, NaFePO4, Na2Fe2(SO4)3 and Na4Mn(SO4)2.

[0061] It is understandable that the compounds listed above as positive electrode active materials may have a coating layer on their surface, and the coating layer material may include carbon materials.

[0062] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0063] Positive conductive agents include one or more of carbon black, graphite, graphene, carbon nanotubes, carbon fibers, superconducting carbon, and acetylene black.

[0064] The preparation method of the positive electrode may include the following steps: mixing and dispersing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in a second dispersion medium to form a positive electrode slurry; then, coating the positive electrode slurry onto a positive electrode current collector, followed by a drying process and a rolling process to obtain the positive electrode. It should be noted that the positive electrode slurry can also be cast on a separate carrier to form a film layer, then the film layer is separated from the carrier, and then the film layer is stacked on the third and / or fourth surfaces of the positive electrode current collector. The first dispersion medium includes one or more of N-methylpyrrolidone, acetone, and water.

[0065] It should be noted that the battery in this embodiment may also include other conventional structures. For example, the battery in this embodiment may also include a separator disposed between the positive and negative electrodes. The separator may be a single-layer thin film or a composite membrane with a multi-layer structure. When the separator is a composite membrane, the material of each layer in the composite membrane may be the same or different. The material of the separator includes one or more of glass fiber, non-woven fabric, polyester, Teflon, polyethylene, polypropylene, and polytetrafluoroethylene.

[0066] The electrolyte can be a conventional electrolyte in the art, comprising metal salts and organic solvents. The organic solvents include one or more of the following: ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, 1,4-butyrolactone, ethylene carbonate, propylene carbonate, propylene sulfite, propyl acetate, propyl propionate, methyl butyrate, butyl acetate, ethyl propionate, ethyl butyrate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0067] When the battery is a lithium-ion battery, the metal salt includes lithium salts, including LiPF6, LiClO4, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiODFB, LiTFSI, LiFSI, LiCl, LiI, and LiN(C x F 2x+1 SO2)(C y F 2y+1 One or more of SO2, wherein x and y are integers from 1 to 20, and the mass of lithium salt accounts for 10% to 15% of the total mass of the electrolyte.

[0068] When the battery is a sodium-ion battery, the metal salt includes sodium salts, which include one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium 4,5-dicyano-2-trifluoromethylimidazolium, sodium 4,5-dicyano-2-pentafluoromethylimidazolium, and sodium fluorosulfonyl (perfluorobutylsulfonyl)imide.

[0069] It should be noted that the positive electrode, negative electrode, and separator can be formed into a battery cell through a winding or stacking process. The electrolyte wets the positive and negative electrodes, and packaging one or more battery cells yields a single battery cell. The battery cell can be packaged using a rigid shell or a pouch. The rigid shell includes a metal shell or a plastic shell with high hardness, while the pouch material includes one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0070] Battery cells can be assembled to form a battery module. Each battery module includes multiple battery cells arranged sequentially along a first direction and secured with fasteners. The first direction can be the length, width, or height of the battery module. It is understood that the battery module also has a housing for accommodating the multiple battery cells.

[0071] Battery modules can be assembled to form a battery pack, with each battery pack containing multiple battery modules. The battery pack also includes a housing for accommodating the multiple battery modules, which can be arranged sequentially along the length or width of the housing. Understandably, the battery pack also includes some conventional components, including a battery management system, buffers, and cooling devices.

[0072] This application also provides an application of the aforementioned battery in electronic devices, electric vehicles, and energy storage systems. The electronic devices, electric vehicles, and energy storage systems respectively employ the aforementioned battery as a power source and / or energy storage component. The electronic devices include mobile phones, computers, digital cameras, camcorders, video game consoles, smart wearable devices, drones, Bluetooth speakers, wireless headphones, security equipment, medical equipment, and aerospace equipment. The electric vehicles include electric cars, electric motorcycles, electric bicycles, electric scooters, and electric balance scooters. The energy storage systems include home energy storage systems, solar energy storage systems, wind energy storage systems, and grid-connected energy storage power stations.

[0073] The technical solutions and effects of this application will be described in detail below through specific embodiments and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application in any specific way.

[0074] Material Example 1 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio between the first material and hard carbon is 1:0.06.

[0075] The DV50 particle size of hard carbon is 2.8 μm, and the specific surface area of ​​hard carbon is 3 m². 2 / g, and the pore volume of hard carbon is 0.01cm. 3 / g. The preparation method of hard carbon includes the following steps: 1 kg of phenolic resin (purchased from Suzhou Xingye, product model PF1834) is placed in a fluidized bed, nitrogen gas is introduced, and the phenolic resin is carbonized under the nitrogen atmosphere at a temperature of 1400 ℃ for 10 h; after carbonization, the carbonized product is allowed to cool naturally to room temperature, and then crushed, pulverized, and graded sequentially to obtain hard carbon.

[0076] The first material comprises a core and a coating layer covering the core. The core material comprises porous carbon, and the coating layer material comprises carbon. The first material has a DV100 particle size of 24.6 μm, the hard carbon has a DV50 particle size that is 40% of the DV50 particle size of the first material, and the first material has a specific surface area of ​​7 m². 2 / g. The DV50 particle size of the porous carbon is 6.5 μm, and the specific surface area of ​​the porous carbon is 2240 m². 2 / g, the pore volume of porous carbon is 1.0 cm³. 3 / g, and the precursor for the preparation of porous carbon is phenolic resin. In the first material, the mass ratio between porous carbon and carbon in the coating layer is 1:0.4.

[0077] The preparation method of the first material includes the following steps: 1 kg of porous carbon is placed in a fluidized bed, nitrogen gas is introduced, and the porous carbon is heated under the nitrogen atmosphere at a heating rate of 5 ℃ / min to raise the temperature of the porous carbon to 950 ℃; while keeping the temperature constant at 950 ℃, the introduced gas is replaced with a gas composed of acetylene and nitrogen, wherein the volume of acetylene accounts for 10% of the total gas volume, the gas flow rate is 12 L / min, the gas is continuously introduced for 10 h, and then the material is naturally cooled in a nitrogen atmosphere to obtain the first material.

[0078] The composite material has a DV50 particle size of 7.0 μm and a specific surface area of ​​5 m². 2 / g.

[0079] The preparation method of the composite material includes the following steps: mixing the first material and hard carbon at a mass ratio of 1:0.06 to obtain the composite material.

[0080] The microstructure of the composite material in this embodiment was observed using a scanning electron microscope. The microstructure of the composite material in this embodiment is as follows: Figure 1 As shown.

[0081] Material Example 2 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to the hard carbon is 1:0.03. The first material is the same as the first material in Material Example 1, and the hard carbon is the same as the hard carbon in Material Example 1.

[0082] The method for preparing the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.03 to obtain the composite material.

[0083] Material Example 3 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to the hard carbon is 1:0.01. The first material is the same as the first material in Material Example 1, and the hard carbon is the same as the hard carbon in Material Example 1.

[0084] The method for preparing the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.01 to obtain the composite material.

[0085] Material Example 4 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to the hard carbon is 1:0.15. The first material is the same as the first material in Material Example 1, and the hard carbon is the same as the hard carbon in Material Example 1.

[0086] The method for preparing the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.15 to obtain the composite material.

[0087] Material Example 5 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to the hard carbon is 1:0.25. The first material is the same as the first material in Material Example 1, and the hard carbon is the same as the hard carbon in Material Example 1.

[0088] The method for preparing the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.25 to obtain the composite material.

[0089] Material Example 6 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to hard carbon is 1:0.06. The first material is the same as the first material in Material Example 1.

[0090] The DV50 particle size of hard carbon is 3.5 μm, and the specific surface area of ​​hard carbon is 3 m². 2 / g, and the pore volume of hard carbon is 0.01cm. 3 / g. The DV50 particle size of hard carbon is 50% of the DV50 particle size of the first material.

[0091] The preparation method of the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.06 to obtain the composite material.

[0092] Material Example 7 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to hard carbon is 1:0.06. The first material is the same as the first material in Material Example 1.

[0093] The DV50 particle size of hard carbon is 2.1 μm, and the specific surface area of ​​hard carbon is 3 m². 2 / g, and the pore volume of hard carbon is 0.01cm. 3 / g. The DV50 particle size of hard carbon is 30% of the DV50 particle size of the first material.

[0094] The preparation method of the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.06 to obtain the composite material.

[0095] Material Example 8 This embodiment provides a composite material and its preparation method. The composite material includes a first material and hard carbon, wherein the mass ratio of the first material to hard carbon is 1:0.06. The first material is the same as the first material in Material Example 1.

[0096] The DV50 particle size of hard carbon is 4.2 μm, and the specific surface area of ​​hard carbon is 3 m². 2 / g, and the pore volume of hard carbon is 0.01cm. 3 / g. The DV50 particle size of hard carbon is 60% of the DV50 particle size of the first material.

[0097] The preparation method of the composite material includes the following steps: mixing a first material and hard carbon at a mass ratio of 1:0.06 to obtain the composite material.

[0098] Material Comparison Example 1 This comparative example provides a composite material, which is the first material in Material Example 1. The microstructure of the composite material in this comparative example was observed using a scanning electron microscope, and the microstructure is as follows: Figure 2 As shown.

[0099] Material Comparison Example 2 This comparative example provides a hard carbon, which is the hard carbon in Material Example 1.

[0100] Application Example 1 This embodiment provides a sodium-ion battery and its preparation method. The sodium-ion battery in this embodiment is a CR2032 button cell, wherein a metallic sodium sheet is used as the counter electrode. The separator is a glass fiber membrane (Whatman GF / D). The electrolyte is a 1 mol / L NaPF6 solution, the solvent of which is prepared by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 1:1:1.

[0101] In this embodiment, the working electrode of the sodium-ion battery includes an electrode current collector and an electrode active material layer disposed on the surface of the electrode current collector. The electrode current collector is an aluminum foil (9 μm thick), and the electrode active material layer includes an electrode active substance, an electrode binder, and an electrode conductive agent. The electrode active substance is the composite material in Material Example 1, the electrode binder is styrene-butadiene rubber and carboxymethyl cellulose, and the electrode conductive agent is conductive carbon black Super-P.

[0102] The preparation method of the working electrode includes the following steps: First, according to the mass ratio of the composite material in Material Example 1: styrene-butadiene rubber: sodium carboxymethyl cellulose: conductive carbon black Super-P of 94.5:2.5:1.5:1.5, the above four raw materials are weighed. The above four raw materials are mixed evenly with ultrapure water to form a slurry. Then, the slurry is coated onto the surface of copper foil using a coating machine, and the coating thickness is 140 µm. Next, the copper foil coated with slurry is placed in a vacuum drying oven and vacuum dried at 90 °C for 24 h to obtain the working electrode, wherein the thickness of the electrode active material layer is 90 µm.

[0103] The sodium-ion battery in this embodiment is assembled in a glove box, the gas atmosphere inside the glove box includes argon, and the total content of water and oxygen inside the glove box is less than 0.01 ppm.

[0104] Application Example 2 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 1, which has undergone cold pressing treatment. The cold pressing treatment method includes the following steps: placing the composite material from Material Example 1 in a press, applying a pressure of 5T to the composite material, and removing the pressure after it stabilizes for 1 minute.

[0105] The composite material in Example 1, which underwent cold pressing, was observed using a scanning electron microscope. Figure 1 and Figure 3 The comparison shows that the composite material in Example 1, after cold pressing, still retains a relatively complete morphology, indicating that the cold pressing process did not damage the coating layer of the composite material. This demonstrates that compounding the first material with hard carbon can improve the compressive strength of the coating layer, thereby mitigating the phenomenon of external force damaging the coating layer and improving the structural and performance stability of the first material.

[0106] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0107] Application Example 3 This embodiment provides a sodium-ion battery. The difference between this sodium-ion battery and the one in Application Example 1 is that the electrode active material is the composite material from Material Example 2.

[0108] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0109] Application Example 4 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Application Example 2, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0110] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0111] Application Example 5 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 3.

[0112] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0113] Application Example 6 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Application Example 3, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0114] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0115] Application Example 7 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 4.

[0116] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0117] Application Example 8 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 4, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0118] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0119] Application Example 9 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 5.

[0120] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0121] Application Example 10 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 5, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0122] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0123] Application Example 11 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 6.

[0124] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0125] Application Example 12 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 6, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0126] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0127] Application Example 13 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 7.

[0128] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0129] Application Example 14 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 7, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0130] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0131] Application Example 15 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 8.

[0132] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0133] Application Example 16 This embodiment provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this embodiment is that the electrode active material is the composite material from Material Example 8, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0134] The sodium-ion battery of this embodiment can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0135] Application Example 17 This embodiment provides a lithium-ion battery and its preparation method. The lithium-ion battery in this embodiment is a CR2032 button cell, in which a lithium metal sheet is used as the counter electrode. The separator is a glass fiber membrane (Whatman GF / D). The electrolyte is a 1 mol / L LiPF6 solution, and the solvent of the LiPF6 solution is prepared by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 1:1:1. In this embodiment, the working electrode of the lithium-ion battery includes an electrode current collector and an electrode active material layer disposed on the surface of the electrode current collector. The electrode current collector is an aluminum foil (9 μm thick), and the electrode active material layer includes an electrode active substance, an electrode binder, and an electrode conductive agent. The electrode active substance is the composite material in Material Example 1, the electrode binder is styrene-butadiene rubber and carboxymethyl cellulose, and the electrode conductive agent is conductive carbon black Super-P.

[0136] The working electrode was prepared by referring to the preparation method of the working electrode in Application Example 1.

[0137] The lithium-ion battery in this embodiment is assembled in a glove box, the gas atmosphere inside the glove box includes argon, and the total content of water and oxygen inside the glove box is less than 0.01 ppm.

[0138] Application Example 18 This embodiment provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this embodiment is that the electrode active material is the composite material from Application Example 1, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0139] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0140] Application Example 19 This embodiment provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this embodiment is that the electrode active material is the composite material from Material Example 2.

[0141] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0142] Application Example 20 This embodiment provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this embodiment is that the electrode active material is the composite material from Application Example 2, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0143] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0144] Application Example 21 This embodiment provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this embodiment is that the electrode active material is the composite material from Material Example 6.

[0145] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0146] Application Example 22 This embodiment provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this embodiment is that the electrode active material is the composite material from Material Example 6, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0147] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0148] Application Comparative Example 1 This comparative example provides a sodium-ion battery. Compared with the sodium-ion battery in Application Example 1, the difference in this comparative example is that the electrode active material is the composite material in Material Comparative Example 1.

[0149] The sodium-ion battery of this comparative example can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0150] Application Comparative Example 2 This comparative example provides a sodium-ion battery. Compared to the sodium-ion battery in Application Example 1, the difference in this comparative example is that the electrode active material is the composite material in Comparative Example 1, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2. The composite material in Comparative Example 1, after cold pressing treatment, was observed using a scanning electron microscope. Figure 2and Figure 4 The comparison shows that, Figure 4 The presence of warping in the coating layer of the composite material indicates that cold pressing has a certain destructive effect on the coating layer.

[0151] The sodium-ion battery of this comparative example can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0152] Application Comparative Example 3 This comparative example provides a sodium-ion battery. Compared with the sodium-ion battery in Application Example 1, the difference in this comparative example is that the electrode active material is hard carbon, as in Material Comparative Example 2.

[0153] The sodium-ion battery of this comparative example can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0154] Application Comparative Example 4 This comparative example provides a sodium-ion battery. The difference between this sodium-ion battery and the one in Application Example 1 is that the electrode active material is hard carbon, as in Comparative Example 2, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0155] The sodium-ion battery of this comparative example can be prepared by referring to the preparation method of the sodium-ion battery in Application Example 1.

[0156] Application Comparative Example 5 This comparative example provides a lithium-ion battery. Compared with the lithium-ion battery in Application Example 17, the difference in this comparative example is that the electrode active material is the composite material in Material Comparative Example 1.

[0157] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0158] Application Comparative Example 6 This comparative example provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this comparative example is that the electrode active material is the composite material in Comparative Example 1, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0159] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0160] Application Comparative Example 7 This comparative example provides a lithium-ion battery. Compared with the lithium-ion battery in Application Example 17, the difference in this comparative example is that the electrode active material is the composite material in Material Comparative Example 2.

[0161] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0162] Application Comparative Example 8 This comparative example provides a lithium-ion battery. Compared to the lithium-ion battery in Application Example 17, the difference in this comparative example is that the electrode active material is the composite material in Comparative Example 2, which has undergone cold pressing treatment. The cold pressing treatment method is the same as that in Application Example 2.

[0163] The lithium-ion battery of this embodiment can be prepared by referring to the preparation method of the lithium-ion battery in Application Example 17.

[0164] Performance Test 1 The compaction density of the composite materials in Material Examples 1 to 8 and Material Comparative Example 1, and the compaction density of the hard carbon in Material Comparative Example 2 were tested respectively.

[0165] The test method for compaction density shall be in accordance with GB / T 44330-2024.

[0166] The test results are shown in Table 1 below: Table 1

[0167] As shown in Table 1, the composite materials in Material Examples 1 to 8 have high compaction densities. Specifically, the compaction densities of the composite materials in Material Examples 1 to 8 are 0.81 g / cm³. 3 ~0.92 g / cm 3 .

[0168] This demonstrates that combining the first material with hard carbon can improve the compressive strength of the coating layer, thereby mitigating the phenomenon of external force damaging the coating layer and improving the structural and performance stability of the first material.

[0169] Performance Test 2 The performance of the sodium-ion batteries in Application Examples 1 to 16 and Application Comparative Examples 1 to 4 was tested respectively.

[0170] The test method for the first coulombic efficiency and specific capacity includes the following steps: Under a constant temperature environment of 25 ℃, each sodium-ion battery is tested using a Blue Electric tester. The battery is charged and discharged twice at 0.01C within a voltage range of 0.01 V to 2.00 V. The specific capacity of the first charge cycle, the specific capacity of the first discharge cycle, and the specific capacity of the second discharge cycle are recorded. The specific capacity of the second discharge cycle is the specific capacity. The first coulombic efficiency is calculated as follows: First coulombic efficiency (ICE, %) = Specific capacity of the first discharge cycle / Specific capacity of the first charge cycle × 100%.

[0171] The test results are shown in Table 2 below: Table 2

[0172] As shown in Table 2, the sodium-ion batteries in Application Examples 1, 3, 5, 7, 9, 11, 13, and 15 used composite materials with untreated electrode active materials, exhibiting an ICE (Inductively Coupled Electrode) of 91%–93% and a specific capacity of 432 mAh / g–461 mAh / g. The sodium-ion batteries in Application Examples 2, 4, 6, 8, 10, 12, 14, and 16 used composite materials with treated electrode active materials, exhibiting an ICE of 88.00%–92.35% and a specific capacity of 424.58 mAh / g–443.49 mAh / g. For the sodium-ion batteries in Application Examples 1 to 16, compared to the sodium-ion batteries with untreated composite materials, the sodium-ion batteries with treated composite materials showed smaller differences in ICE and specific capacity, with an ICE decrease rate of 0.7%–3.3% and a specific capacity decrease rate of 0.4%–7.5%.

[0173] Compared to the sodium-ion battery in Comparative Example 1, the performance of the sodium-ion battery in Comparative Example 2 was significantly reduced, with an ICE reduction rate of 9.7% and a specific capacity reduction rate of 8.9%. This is because the coating layer in the composite material was damaged to some extent during the cold pressing process.

[0174] The performance difference between the sodium-ion battery in Application Comparative Example 3 and the sodium-ion battery in Application Comparative Example 4 is small, but the ICE and specific capacity of both sodium-ion batteries in Application Comparative Example 3 and Application Comparative Example 4 are low.

[0175] In summary, using a composite material containing a first material and hard carbon as the electrode material for sodium-ion batteries is beneficial to improving the overall performance of sodium-ion batteries, especially their stress resistance. This is because: the first material is porous carbon coated with carbon, which has an appropriate number of active sites and good metal storage properties, thereby increasing the battery capacity. Furthermore, since the porous carbon is coated with carbon, the probability of side reactions in the electrode can be reduced, and the phenomenon of excessive electrolyte decomposition can be improved, which is beneficial to improving the initial coulombic efficiency and cycle performance of the battery. In addition, by combining the first material and hard carbon, the stress resistance of the coating layer is improved, and the initial efficiency and capacity loss rate of the composite material after cold pressing are reduced.

[0176] Performance Test 3 The performance of the lithium-ion batteries in Application Examples 17 to 22 and Application Comparative Examples 5 to 8 were tested respectively.

[0177] The initial coulombic efficiency and specific capacity tests were conducted using the corresponding test methods described in Performance Testing 2.

[0178] The test results are shown in Table 3 below: Table 3

[0179] As shown in Table 3, the lithium-ion batteries in Application Examples 17, 19, and 21 used composite materials with untreated electrode active materials, exhibiting an ICE (Inductively Coupled Electrode) of 85%–87% and a specific capacity of 353 mAh / g–360 mAh / g. The lithium-ion batteries in Application Examples 18, 20, and 22 used composite materials with treated electrode active materials, exhibiting an ICE of 83.81%–85.96% and a specific capacity of 347.00 mAh / g–354.60 mAh / g. The comparison shows that the lithium-ion batteries using composite materials with treated electrode active materials exhibit smaller differences in ICE and specific capacity compared to those using untreated composite materials, with an ICE decrease rate of 1.2%–1.6% and a specific capacity decrease rate of 1.3%–1.7%.

[0180] Compared to the lithium-ion battery in Comparative Example 5, the performance of the lithium-ion battery in Comparative Example 6 was significantly reduced, with an ICE reduction rate of 9.4% and a specific capacity reduction rate of 7.3%. This is because the coating layer in the composite material was damaged to some extent during the cold pressing process.

[0181] The performance difference between the lithium-ion battery in Application Comparative Example 7 and the lithium-ion battery in Application Comparative Example 8 is small, but the ICE and specific capacity of the lithium-ion batteries in Application Comparative Example 7 and Application Comparative Example 8 are both low.

[0182] In conclusion, using a composite material containing the first material and hard carbon as the electrode material for lithium-ion batteries is beneficial to improving the overall performance of lithium-ion batteries, especially their stress resistance.

[0183] The foregoing has provided a detailed description of a composite material, a method for preparing the composite material, and its applications, as provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in each of the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A composite material, characterized in that, The composite material includes a first material and hard carbon, wherein the first material includes a core and a coating layer covering the core, the core being made of porous carbon, and the coating layer being made of carbon.

2. The composite material according to claim 1, characterized in that, In the composite material, the mass ratio between the first material and the hard carbon is 1:(0.01~0.25); Optionally, the mass ratio between the first material and the hard carbon is 1:(0.03~0.06).

3. The composite material according to claim 1, characterized in that, The first material has a DV00 particle size of not less than 2 μm, a DV50 particle size of not less than 7 μm, and a DV100 particle size of not more than 25 μm, and the particle size distribution curve of the first material is normally distributed; optionally, the DV50 particle size of the first material is 7 μm to 9 μm. The specific surface area of ​​the first material is 6 m² 2 / g~10 m 2 / g.

4. The composite material according to claim 1, characterized in that, The porous carbon has a DV50 particle size of 6 μm to 8 μm and a specific surface area of ​​500 m². 2 / g~3500 m 2 / g, and the pore volume of the porous carbon is 0.05 cm³. 3 / g~1.8cm 3 / g; The carbon in the coating layer includes one or more of amorphous carbon and heterostructured carbon. In the first material, the mass ratio between the porous carbon and the carbon in the coating layer is 1:(0.3~0.5).

5. The composite material according to claim 1, characterized in that, The DV50 particle size of the hard carbon is 30% to 60% of the DV50 particle size of the first material, and the particle size distribution curve of the hard carbon is normally distributed. Optionally, the DV50 particle size of the hard carbon is 40% to 50% of the DV50 particle size of the first material; the DV50 particle size of the hard carbon is 2.8 µm to 4.5 µm, and the specific surface area of ​​the hard carbon is 2 m². 2 / g~7 m 2 / g, and the pore volume of the hard carbon is 0.01cm. 3 / g~0.1 cm 3 / g.

6. A method for preparing a composite material, characterized in that, The steps include: providing a first material and hard carbon respectively, mixing the first material and the hard carbon to obtain the composite material; Wherein, the first material is the first material in the composite material as described in any one of claims 1 to 5, and the hard carbon is the hard carbon in the composite material as described in any one of claims 1 to 5.

7. The method for preparing the composite material according to claim 6, characterized in that, The method for preparing the first material includes the steps of: providing the porous carbon in the composite material as described in any one of claims 1 to 5, using the porous carbon as a deposition matrix, introducing a gas containing a carbon source, wherein the carbon source is decomposed to form carbon atoms that are deposited on the surface of the porous carbon; Optionally, the carbon source includes one or more of methane, ethane, propane, butane, ethylene, propylene, acetylene, and propyne; the gas also includes an inert gas, and the volume of the carbon source accounts for 10% to 70% of the total volume of the gas.

8. The method for preparing the composite material according to claim 6, characterized in that, The method of mixing the first material and the hard carbon includes one or more of ball milling and stirring. In the step of mixing the first material and the hard carbon, the mass ratio between the first material and the hard carbon is 1:(0.01~0.25); optionally, the mass ratio between the first material and the hard carbon is 1:(0.03~0.06).

9. The use of the composite material according to any one of claims 1 to 5, or the composite material prepared by the method of preparing the composite material according to any one of claims 6 to 8, in the preparation of electrodes.

10. A battery, characterized in that, The battery includes a positive electrode and a negative electrode, wherein the material of the negative electrode includes the composite material as described in any one of claims 1 to 5, or the composite material prepared by the method of preparing the composite material as described in any one of claims 6 to 8; Optionally, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the material of the negative electrode active material layer includes the composite material as described in any one of claims 1 to 5, or the composite material prepared by the method of preparing the composite material as described in any one of claims 6 to 8.

Images