Conductive skin silicon carbon material and preparation method and application thereof

Abstract

The invention discloses a conductive skin silicon-carbon material as well as a preparation method and application thereof. A conductive skin silicon-carbon material serves as a core and a core-shell structure of a conductive skin coating layer coating the surface of the core, the core is a silicon-carbon-graphite composite intermediate, graphite with D50 being 4-8 microns serves as a conductive framework, graphene oxide serves as a two-dimensional conductive sheet layer to be coated on the surfaces of the graphite and nano silicon powder, cryptocrystalline graphite serves as interface conductive filler, and the silicon-carbon-graphite composite intermediate is a silicon-carbon-graphite composite intermediate. Under the bonding action of amorphous carbon formed by pyrolysis of a carbon source with the softening point or melting point of 60-200 DEG C, a continuous and intercommunicated conductive network is formed; the first coulombic efficiency of a battery prepared from the material can reach 91.11%, the 3C multiplying power capacity retention rate reaches 90.59%, after 900 cycles under the current density of 0.5 C charging and 1C discharging, 2025.2 mAh capacity remains, the capacity retention rate exceeds 80%, and a good solution is provided for a high-energy-density power battery.

Description

Technical Field

[0001] This invention relates to a silicon-carbon material, specifically a conductive silicon-carbon skin material and its preparation method and application; it belongs to the technical field of lithium-ion battery anode materials. Background Technology

[0002] With the rapid development of consumer electronics, electric vehicles, and large-scale energy storage markets, the market is placing increasingly stringent demands on the energy density, power density, and cycle life of lithium-ion batteries. Traditional lithium-ion batteries generally use graphite-based anode materials, but their theoretical specific capacity is relatively low (approximately 372 mAh / g), which has become a key bottleneck restricting further improvements in battery energy density.

[0003] Against this backdrop, silicon-based anode materials are considered ideal next-generation anode materials due to their extremely high theoretical specific capacity (approximately 4200 mAh / g). Silicon-carbon anodes, formed by combining silicon with graphite, which offers better conductivity and stability, can balance high capacity and relative stability to a certain extent, and are currently the main direction for industrialization. However, the commercial application of silicon-carbon anodes still faces two major challenges: First, silicon materials undergo volume expansion and contraction of over 300% during lithium insertion / extraction. This drastic volume change easily leads to the breakage and shedding of active material particles, resulting in loss of electrical contact with the current collector. Furthermore, it continuously damages the fragile solid electrolyte interphase (SEI) film on the electrode surface, continuously consuming electrolyte and lithium source, thus leading to low initial coulombic efficiency and rapid capacity decay during cycles. Second, to ensure the energy density of the cell, high-nickel cathodes and other high-voltage materials are typically required, which places higher demands on the interface stability and ion and electron conduction efficiency of the electrodes, especially the anode plates. Therefore, the successful application of silicon-carbon anodes to high-performance cylindrical batteries is a systematic engineering project that spans materials, electrodes and cell assembly, and the field still faces many collaborative challenges.

[0004] Chinese invention patent application CN119812244A discloses a multi-stage granulated silicon-carbon material with a self-assembled conductive structure, its preparation method, and its application. The method involves first-stage granulation of a carbon source with a softening point of 150-200℃ and nano-silicon powder to obtain primary granulated silicon-carbon precursor microspheres. These microspheres are then combined with a carbon raiser, graphene oxide, cryptocrystalline graphite, and graphite with a D50 of 9-12 μm through secondary granulation, followed by tertiary granulation or modification with surface polymer surfactants to prepare a multi-stage granulated silicon-carbon material with a self-assembled conductive structure. This technology utilizes a multi-component carbon source to achieve connections between graphene cross-linked networks, constructing a conductive structure with cryptocrystalline graphite intercalation and graphene oxide encapsulation, consisting of a layered structure of conductive carbon black, single-walled carbon nanotubes and graphene oxide, cryptocrystalline graphite, graphite, and a carbon coating layer of silicon-carbon material. This accelerates electron transport and alleviates the problem of silicon material pulverization. However, this technology uses graphite with a D50 of 9~12μm, which has a large size difference from nano-silicon powder. During self-assembly, component segregation is prone to occur, forming microscopically heterogeneous "silicon-rich regions" and "graphite-rich regions," failing to form a continuous three-dimensional conductive pathway. Furthermore, the surface modification process only adds polymeric surfactants to alleviate the hydrophobicity of pitch carbon, but the polymeric surfactants themselves are insulating, and their coating layer can hinder electron transport between particles to some extent, increasing interfacial contact resistance and reducing the conductivity of silicon-carbon material powder. Therefore, the capacity decay is quite significant in high-rate performance tests. Excessively large graphite is too rigid and lacks flexibility, making it more prone to separation from the silicon interface when dealing with silicon expansion. With long-term cycling tests, the capacity decay intensifies. In addition, this technology uses a multiple granulation method, which is relatively complex and not conducive to the industrial application of this material. Summary of the Invention

[0005] To overcome the performance problems of existing silicon-carbon materials, such as low initial coulombic efficiency and rapid decay over long cycles, as well as the production problems such as cumbersome mass production steps and high process costs, the present invention aims to provide an efficient and low-cost industrialization path for a conductive silicon-carbon skin material with high initial coulombic efficiency, good rate performance, slow decay over long cycles, and controllable expansion, as well as its preparation method.

[0006] Another objective of this invention is to provide the application of the conductive silicon-carbon skin material in the preparation of double-layer conductive elastomer coated electrodes, and the application of the double-layer conductive elastomer coated electrodes in the preparation of cylindrical lithium-ion batteries.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A conductive silicon-carbon material with a core-shell structure comprising a core and a conductive skin coating layer covering the surface of the core. The core is a silicon-carbon-graphite composite intermediate, which uses graphite with a D50 of 4~8μm as a conductive framework, graphene oxide as a two-dimensional conductive sheet coating the surface of graphite and nano-silicon powder, and cryptocrystalline graphite as an interfacial conductive filler. Together, they form a continuous and interconnected conductive network under the bonding effect of amorphous carbon formed by the pyrolysis of a carbon source with a softening point or melting point of 60~200℃. The conductive skin coating layer is obtained by spraying a composite powder slurry formed by polymer, conductive agent and deionized water onto the silicon-carbon-graphite composite intermediate.

[0009] The method for preparing the conductive silicon-carbon skin material includes the following steps:

[0010] 1) Use carbon sources with softening or melting points between 60 and 200°C, such as graphene oxide, cryptocrystalline graphite, and D... v 50=4~8μm graphite and nano-silicon powder are ball-milled and mixed uniformly; the carbon source, graphene oxide, cryptocrystalline graphite, and D with softening or melting points of 60~200℃ are mentioned. v The mass ratio of 4~8μm graphite to nano-silicon powder is (1-3):(1-3):(1-3):(1-3):10;

[0011] 2) The obtained material is put into a high-temperature coating machine. Under an inert atmosphere, the temperature is raised to 180℃ and held for 1-2 hours, then raised to 400℃ and held for 1-2 hours, and then raised to 900℃ and held for 2-4 hours to obtain a silicon-carbon-graphite composite intermediate. The oxygen content is controlled at 1-5 ppm throughout the high-temperature coating process.

[0012] 3) Mix the polymer, conductive agent and deionized water evenly to obtain a composite powder slurry;

[0013] 4) The composite powder slurry is uniformly sprayed onto the surface of the silicon-carbon-graphite composite intermediate and dried in situ to obtain a conductive silicon-carbon skin material.

[0014] To further achieve the purpose of this invention, preferably, the carbon source with a softening point or melting point of 60~200℃ is one or more of asphalt, phenolic resin and glucose;

[0015] The polymer is one or more of polyethylene glycol, polyvinylpyrrolidone, polyoxyethylene fatty acid ester, sodium carboxymethyl cellulose, and polyoxyethylene fatty acid ester;

[0016] The conductive agent is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, decomposed carbon nanotubes, reduced graphene oxide, graphene oxide, MXene, and carbon fiber.

[0017] Preferably, the time to raise the temperature to 180°C is 1-2 hours; the time to raise the temperature to 400°C is 0.5-1 hour; and the time to raise the temperature to 900°C is 1-2 hours.

[0018] The mass ratio of the silicon-carbon-graphite composite intermediate, the polymer, and the conductive agent is (2~3):(0.04~0.06):(0.004~0.012).

[0019] Preferably, the ball-to-material mass ratio of the ball mill is (2~10):1, the rotation speed is 10~50 rpm / min, and the time is 1~5 h;

[0020] The inert atmosphere is either Ar or N2.

[0021] The application of the conductive silicon-carbon skin material in the preparation of double-layer conductive elastomer coated electrodes includes the following steps:

[0022] 1) A negative electrode active material, an inner layer conductive agent and a binder are made into a negative electrode inner layer slurry. The negative electrode inner layer slurry is coated on both sides of the negative electrode current collector and dried to obtain an inner layer electrode sheet. The negative electrode active material is composed of conductive skin silicon carbide material and graphite.

[0023] 2) The outer conductive agent and polymer elastomer are made into a conductive elastomer slurry. The conductive elastomer slurry is then coated on both sides of the inner electrode to form a conductive elastomer coating. After drying, a double-layer conductive elastomer coated electrode is obtained.

[0024] Preferably, the negative electrode current collector is a copper foil with a thickness of 5-10 μm;

[0025] The inner conductive agent is one or more of the following: conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, reduced graphene oxide, graphene oxide, and MXene.

[0026] The adhesive is one or more of polyacrylic acid, styrene-butadiene rubber, and sodium carboxymethyl cellulose;

[0027] The outer conductive agent is one or more of the following: conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, reduced graphene oxide, graphene oxide, and MXene.

[0028] The polymeric elastomer is one or more of polyvinyl alcohol, styrene-butadiene rubber, polyacrylic acid, and polyimide;

[0029] The graphite mentioned is artificial graphite and / or natural graphite.

[0030] Preferably, the mass percentages of the negative electrode active material, the inner layer binder, and the inner layer conductive agent are (93.5%~96.5%): (2.5%~4.5%): (1.0%~2.0%).

[0031] The mass percentage of the outer conductive agent to the polymer elastomer is 1:(8~12);

[0032] The mass ratio of the conductive silicon carbide skin material to graphite is 1:(9~99).

[0033] The application of the conductive silicon-carbon skin material in the fabrication of cylindrical lithium-ion batteries includes the following steps:

[0034] 1) The positive electrode active material, positive electrode binder, and positive electrode conductive agent are made into a positive electrode slurry;

[0035] 2) The positive electrode slurry is coated on both sides of the positive electrode current collector to obtain the positive electrode sheet;

[0036] 3) Rolling, cutting, riveting and winding the positive electrode sheet and the double-layer conductive elastomer coated electrode sheet made of silicon carbide electro-skin material to obtain a semi-finished battery cell;

[0037] 4) The semi-finished cells are put into the casing, dried, injected with liquid, sealed, and then pre-formed, activated at high temperature, formed, aged at room temperature and capacity tested to obtain cylindrical lithium-ion batteries.

[0038] Preferably, in step 1), the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide; the positive electrode binder is polyvinylidene fluoride; the positive electrode conductive agent is one or more of conductive carbon black Super P, acetylene black, and carbon nanotubes; and the mass ratio of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent is (96~98):(1:2):(0.5~2).

[0039] In step 2), the positive current collector is an aluminum foil with a thickness of 10~16μm;

[0040] In step 3), the riveting is to weld the tabs to the electrode sheets; the winding is to wind the positive and negative electrode sheets together with the separator into a cylindrical battery cell.

[0041] In step 4), the drying process involves transferring the semi-finished battery cell into a vacuum oven to remove moisture, controlling the moisture content to ≤100ppm; the pre-formation process involves charging the battery cell with a small current to increase the voltage from near 0V to a safe voltage of 2~3V; the high-temperature activation process involves placing the battery cell at a high temperature of 45±5℃ to promote electrode interface stability; the formation process involves charging the battery cell to form a stable SEI film; the room temperature aging process involves placing the battery cell at a room temperature of 25±5℃ to stabilize the battery cell performance; and the capacity grading process involves screening and classifying the battery cells according to their capacity.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] 1) The conductive silicon-carbon skin material of this invention uses graphite with a D50 of 4~8μm as the core conductive framework, providing rapid conductivity in the inner layer and acting as internal support to improve the problem of easy pulverization of isolated silicon-based materials. Graphene oxide, as a two-dimensional conductive sheet, is wrapped around the surface of graphite and nano-silicon powder. Cryptocrystalline graphite, as an interfacial conductive intercalation layer, together with nano-silicon powder and amorphous carbon under the bonding effect of a carbon source with a softening point or melting point of 60~200℃, forms a continuous and interconnected conductive structure. The continuous carbon layer coating also alleviates the expansion stress of silicon material. The outer polymer elastomer and conductive agent coating layer improve the hydrophobicity of amorphous carbon and, together with the inner silicon-carbon graphite composite structure, form a three-dimensional conductive network, alleviating the problem of poor conductivity of a single polymer coating layer, improving the material's conductivity and stability, achieving 10A g in button battery applications. -1 At high current density, the remaining capacity is 634.2 mAh g. -1 ,4A g -1 After 1000 cycles at the current density, 813.6 mAh g remains. -1 It has reversible capacity, excellent rate performance, and long cycle life.

[0044] 2) The present invention is based on a double-layer conductive elastomer electrode made of conductive silicon carbon material. The inner layer realizes the energy storage function, while the outer conductive elastomer provides rapid electron conduction and stress buffering. The combined use of multi-dimensional conductive agents, such as dotted conductive carbon black Super P, linear SWCNT, MWCNT, and layered MXene and graphene, forms a combination of dots, lines and surfaces in the electrode, which increases the conductive contact sites. Furthermore, the combination of soft two-dimensional graphene and hard two-dimensional material MXene constructs a conductive system that combines high conductivity and high strength.

[0045] 3) This invention is based on a cylindrical lithium-ion battery made of a double-layer conductive elastomer electrode sheet. The initial coulombic efficiency can reach 91.11%, the 3C rate capacity retention rate can reach 90.59%, and after 900 cycles at a current density of 0.5C charging and 1C discharging, there is still 2025.2mAh capacity remaining, with a capacity retention rate of over 80%. The initial coulombic efficiency, rate performance and long-term cycle stability are significantly improved, meeting the core performance requirements of silicon-carbon anode materials for high-energy-density lithium-ion batteries.

[0046] 4) The process of this invention is simple. The equipment used, such as the ball mill, high-temperature coating machine, and VC mixer, are all conventional equipment that can be directly purchased in industry. Large-scale production can be achieved without major equipment modifications. Attached Figure Description

[0047] Figure 1 The images show the XRD patterns of the conductive silicon-carbon skin material prepared in Example 1 and the small-particle self-assembled silicon-carbon composite material prepared in Comparative Example 1.

[0048] Figure 2 The images show SEM and TEM images of the conductive silicon-carbon skin material prepared in Example 1.

[0049] Figure 3 The image shows a SEM image of the small-particle self-assembled silicon-carbon composite material prepared in Comparative Example 1.

[0050] Figure 4 The image shows a SEM image of the multi-granulated silicon-carbon material with a self-assembled conductive structure prepared in Comparative Example 3.

[0051] Figure 5 The infrared spectrum of the conductive silicon-carbon skin material prepared in Example 1 is shown.

[0052] Figure 6 The image shows the Raman spectrum of the conductive silicon-carbon skin material prepared in Example 1.

[0053] Figure 7 The image shows the XPS full spectrum of the conductive silicon-carbon skin material prepared in Example 1.

[0054] Figure 8 The image shows the high-resolution XPS spectrum of Si 2p of the conductive silicon-carbon skin material prepared in Example 1.

[0055] Figure 9 The XPS high-resolution spectra of the conductive silicon-carbon skin material prepared in Example 1 and C 1s are shown.

[0056] Figure 10 The graph shows a comparison of the powder conductivity and pressure of the conductive silicon-carbon material with a conductive skin prepared in Example 1 and the multi-granulated silicon-carbon material with a self-assembled conductive structure prepared in Comparative Example 3.

[0057] Figure 11 The performance of the conductive silicon-carbon material button cell prepared in Example 1 was tested at 25°C and 0.2 A g. -1 The charge-discharge specific capacity curves for the first three cycles under the current density.

[0058] Figure 12 The performance of the conductive silicon-carbon material button cell prepared in Example 1 was tested at 2A g. -1 The long-cycle performance curve at the current density is shown in the figure.

[0059] Figure 13 The first charge-discharge curve of the cylindrical lithium-ion battery prepared in Example 8 at a current density of 0.2C is shown.

[0060] Figure 14 The graph shows the long-cycle performance of the cylindrical lithium-ion battery prepared in Example 8 at a current density of 0.5C charging and 1C discharging. Detailed Implementation

[0061] The present invention will be further described below with reference to embodiments, comparative examples, and accompanying drawings, but the implementation of the present invention is not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0062] Addressing the performance issues of existing silicon-carbon materials, such as low initial coulombic efficiency and rapid decay over long cycles, as well as production problems like cumbersome mass production steps and high process costs; particularly the multi-stage granulation of silicon-carbon materials with self-assembled conductive structures using D50=9~12μm graphite, combined with primary granulated silicon-carbon precursor microspheres, carbon raisers, graphene oxide, and cryptocrystalline graphite for secondary granulation, this invention, through the significant size difference between D50=9~12μm graphite and nano-silicon powder, easily leads to component segregation during self-assembly, forming microscopically heterogeneous "silicon-rich regions" and "graphite-rich regions," failing to form a continuous three-dimensional conductive pathway, resulting in low initial coulombic efficiency and rapid decay over long cycles. This invention discovers that using D50=4~8μm graphite, combined with a carbon source, graphene oxide, cryptocrystalline graphite, and nano-silicon powder, along with a conductive skin coating layer, can effectively solve the problems of existing technologies. This invention presents a core-shell structure with a conductive silicon-carbon material as the core and a conductive skin coating layer covering the core surface. The core is a silicon-carbon-graphite composite intermediate, consisting of graphite with a D50 of 4-8 μm as the conductive framework, graphene oxide as a two-dimensional conductive sheet coating the graphite and nano-silicon powder surface, and cryptocrystalline graphite as the interfacial conductive filler. These elements, bonded by amorphous carbon formed by the pyrolysis of a carbon source with a softening or melting point of 60-200℃, collectively form a continuous and interconnected conductive network. The conductive skin coating layer is obtained by spraying a composite powder slurry formed from a polymer, conductive agent, and deionized water onto the silicon-carbon-graphite composite intermediate. This conductive silicon-carbon material exhibits significantly improved lithium-ion transport kinetics, excellent long-cycle stability, and superior rate performance, making it particularly suitable for new energy vehicle power batteries with stringent requirements for energy density and power characteristics. It also shows significant advantages in consumer battery applications.

[0063] The present invention provides a method for preparing conductive silicon-carbon skin material: a carbon source with a softening or melting point of 60-200℃, graphene oxide, cryptocrystalline graphite, and D... v 50=4~8μm graphite and nano-silicon powder are ball-milled and mixed uniformly. The resulting material is then fed into a high-temperature coating machine, heated to 180℃ and held for 1~2 hours under an inert atmosphere, then heated to 400℃ and held for 1~2 hours, and finally heated to 900℃ and held for 2~4 hours to obtain a silicon-carbon graphite composite intermediate. The oxygen content is controlled at 1~5ppm throughout the high-temperature coating process. A polymer, conductive agent, and deionized water are then mixed uniformly to obtain a composite powder slurry, which is uniformly sprayed onto the surface of the silicon-carbon graphite composite intermediate and dried in situ to obtain a conductive silicon-carbon skin material. Carbon sources, graphene oxide, cryptocrystalline graphite, and D are used, with softening points or melting points controlled at 60~200℃. v The mass ratio of 50=4~8μm graphite to nano-silicon powder is (1-3):(1-3):(1-3):(1-3):10.

[0064] The carbon source of this invention requires a softening point or melting point of 60-200°C, preferably one or more of asphalt, phenolic resin, and glucose; the polymer and conductive agent of this invention have similar applications in this field, and the polymer of this invention is preferably one or more of polyethylene glycol, polyvinylpyrrolidone, polyoxyethylene fatty acid ester, sodium carboxymethyl cellulose, and polyoxyethylene fatty acid ester; the conductive agent is preferably one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, decomposed carbon nanotubes, reduced graphene oxide, graphene oxide, MXene, and carbon fiber.

[0065] The phased temperature control of the present invention has preferred requirements for the heating time. Preferably, the heating time to 180°C is 1-2 hours; the heating time to 400°C is 0.5-1 hours; and the heating time to 900°C is 1-2 hours.

[0066] The preferred mass ratio of silicon-carbon-graphite composite intermediate, polymer, and conductive agent is (2~3):(0.04~0.06):(0.004~0.012). The preferred ball-to-material mass ratio in the ball milling process is (2~10):1, the preferred rotation speed is 10~50 rpm / min, and the preferred time is 1~5 h. Based on cost requirements, the preferred inert atmosphere in this invention is Ar or N2.

[0067] This invention applies conductive silicon-carbon skin material to the preparation of double-layer elastomer electrodes. The conductive pathway of the material, the multi-dimensional conductive agent in the inner layer of the electrode, and the outer conductive elastomer coating are combined in the preparation of cylindrical lithium-ion batteries to form a conductive channel and interface protection system that complements the inner and outer layers, thereby ultimately producing a battery cell with high energy density, high initial efficiency, and excellent cycle performance.

[0068] The application of conductive silicon-carbon skin materials in the preparation of double-layer conductive elastomer coated electrodes includes the following steps:

[0069] 1) A negative electrode active material, an inner layer conductive agent and a binder are made into a negative electrode inner layer slurry. The negative electrode inner layer slurry is coated on both sides of the negative electrode current collector and dried to obtain an inner layer electrode sheet. The negative electrode active material is composed of conductive skin silicon carbide material and graphite.

[0070] 2) The outer conductive agent and polymer elastomer are made into a conductive elastomer slurry. The conductive elastomer slurry is then coated on both sides of the inner electrode to form a conductive elastomer coating. After drying, a double-layer conductive elastomer coated electrode is obtained.

[0071] The application of conductive silicon-carbon coating materials in the fabrication of cylindrical lithium-ion batteries includes the following steps:

[0072] 1) The positive electrode active material, positive electrode binder, and positive electrode conductive agent are made into a positive electrode slurry;

[0073] 2) The positive electrode slurry is coated on both sides of the positive electrode current collector to obtain the positive electrode sheet;

[0074] 3) Rolling, cutting, riveting and winding the positive electrode sheet and the double-layer conductive elastomer coated electrode sheet made of silicon carbide electro-skin material to obtain a semi-finished battery cell;

[0075] 4) The semi-finished cells are put into the casing, dried, injected with liquid, sealed, and then pre-formed, activated at high temperature, formed, aged at room temperature and capacity tested to obtain cylindrical lithium-ion batteries.

[0076] The positive electrode active material is preferably one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide; the positive electrode binder is preferably polyvinylidene fluoride; the positive electrode conductive agent is one or more of conductive carbon black Super P, acetylene black, and carbon nanotubes; the mass ratio of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent is (96~98):(1:2):(0.5~2);

[0077] The positive electrode current collector is preferably made of aluminum foil with a thickness of 10~16μm;

[0078] The rolling process applies pressure to the electrode sheets to increase their compaction density; the cutting process cuts the electrode sheets to ensure consistent specifications; the riveting process connects the tabs to the electrode sheets by welding to establish a conductive path; and the winding process winds the positive and negative electrode sheets together with the separator into a cylindrical battery cell to obtain a semi-finished battery cell.

[0079] Drying involves transferring the semi-finished battery cells into a vacuum oven to remove moisture, controlling the moisture content to ≤100ppm; pre-formation involves charging the battery cells with a small current to increase the voltage from near 0V to a safe voltage of 2~3V; high-temperature activation involves placing the battery cells at a high temperature of 45±5℃ to promote electrode interface stability; formation involves charging the battery cells to form a stable SEI film; room temperature aging involves placing the battery cells at a room temperature of 25±5℃ to stabilize the battery cell performance; capacity grading involves screening and classifying the battery cells according to their capacity.

[0080] Example 1

[0081] A method for preparing a conductive silicon-carbon skin material includes the following steps:

[0082] High-temperature coating: Take 200g of asphalt, 100g of graphene oxide, 200g of cryptocrystalline graphite, and D... v200g of 50=7μm graphite and 1000g of nano-silicon powder were placed in a horizontal ball mill and ball-milled for 180min. The mixture was then fed into a high-temperature coating and modification machine for coating. The heating program was as follows: 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 40min, 400℃~900℃ for 100min, 900℃ for 120min. The protective atmosphere was argon, and the oxygen content was controlled at 1~5ppm throughout the process. The mixture was then cooled and discharged to obtain a silicon-carbon-graphite composite intermediate.

[0083] Surface modification: 1000g of silicon-carbon-graphite composite intermediate was placed in a VC mixer preheated to 100℃ and stirred at 200rpm. 20g of polyethylene glycol (molecular weight 2000) and 2g of single-walled carbon nanotubes were added to a mixing tank along with 198g of deionized water and stirred for 1 hour to prepare a homogeneous slurry with a solid content of 10%. The slurry was then uniformly sprayed onto the surface of the intermediate through a nozzle at a flow rate of 0.05L / min, maintaining the mixing and internal temperature at 95~105℃ during the spraying process. After spraying, the mixture was dried at 80℃ and then sieved to obtain a conductive silicon-carbon skin material.

[0084] Weigh 0.08g of conductive silicon carbide skin material, 0.01g of conductive carbon black Super P, and 0.01g of sodium carboxymethyl cellulose binder. Add 2.5ml of deionized water and stir magnetically for 1 hour. Coat the material onto a copper foil (14mm in diameter) with a loading of 0.6mg / cm². -2 The electrodes are dried, pressed into sheets, and then assembled into CR 2016 button batteries using lithium metal sheets as counter electrodes in a glove box.

[0085] Figure 1 The XRD patterns are of the conductive silicon-carbon skin material prepared in Example 1 and the small particle self-assembled silicon-carbon composite material in Comparative Example 1. The XRD pattern of Example 1 shows a sharp diffraction peak at about 26°, corresponding to the graphite (002) crystal plane, while the graphite-free silicon-carbon material of Comparative Example 1 does not have this characteristic peak, proving the successful incorporation of graphite.

[0086] Figure 2 The images show SEM and TEM images of the conductive silicon-carbon skin material prepared in Example 1. Image a) shows the SEM image of the conductive silicon-carbon skin material, which has a core of graphite with a D50 of 4~8 μm, surrounded by silicon wafers, graphene oxide, cryptocrystalline graphite, and molten pitch, forming an irregular structure. Figure 1 The XRD pattern of approximately 26° graphite (002) crystal plane corroborates this. Figure 2Figures b), c), and d) are TEM images of the conductive silicon-carbon skin material. In b), the graphite layered structure in the middle of the material can be observed to be conductive intercalated cryptocrystalline graphite in the silicon-carbon material. The tubular SWCNTs on the surface form an interwoven network structure covering the outside of the silicon-carbon composite particles, echoing the edge-curled and stacked graphene structure. Figure c) shows that thin-layered graphene acts as a bridging pathway between different particles, with single-walled carbon nanotubes interspersed between the layers. Figure d) shows that the inner layer is a magnified cryptocrystalline graphite layered structure, and the outer layer of about 10 nm carbon coating is molten bitumen, forming a continuous carbon layer coating. Figure 2 The conductive skin material can be observed to have a core conductive framework of graphite with a D50 of 4~8μm, with graphene oxide as a two-dimensional conductive sheet wrapped around the surface of graphite and nano-silicon powder, and cryptocrystalline graphite as an interfacial conductive intercalation layer. Together with nano-silicon powder, under the bonding effect of carbon sources with softening or melting points of 60~200℃ and amorphous carbon bonding effect, they form a continuous and interconnected conductive structure, and together with the outer SWCNT layer, they form a three-dimensional conductive network.

[0087] Figure 5 The image shows the infrared spectrum of the conductive silicon-carbon material with a skin prepared in Example 1. The Si-OC bond is beneficial to the structural stability of the silicon-carbon material. By introducing this covalent bond during the sintering process of the silicon-carbon material with oxygen-containing conductive agents such as graphene oxide, a more stable chemical structure can be formed, which helps to improve the overall stability of the anode material and thus improve the electrochemical performance.

[0088] Figure 6 The image shows the Raman spectrum of the conductive silicon-carbon skin material prepared in Example 1. D / I G The value of 0.81 > 0.8 indicates that there are many defects in the carbon layer. This may be due to the amorphous carbon (low graphitization degree) generated by pitch carbonization and the partial reduction of graphene oxide (GO) to reduced graphene oxide (rGO) during the high-temperature carbonization process, but some oxygen-containing groups and structural defects are still retained.

[0089] Figure 7 The image shows the XPS full spectrum of the conductive silicon-carbon skin material prepared in Example 1. Figure 8 The image shows the high-resolution XPS spectrum of the conductive silicon-carbon material Si 2p prepared in Example 1. Figure 9 The XPS high-resolution spectrum of the conductive silicon-carbon skin material C1s prepared in Example 1 is shown below. Figure 7-9 The detected composite material surface layer contains multiple bond bridges between the carbon layer and silicon, which ensures the stability of the silicon-carbon interface structure. This is also related to... Figure 5 The infrared spectra corroborate each other.

[0090] Example 2

[0091] A method for preparing a conductive silicon-carbon skin material includes the following steps:

[0092] High-temperature coating: Take 300g of asphalt, 100g of graphene oxide, 300g of cryptocrystalline graphite, and D... v 100g of 50=7μm graphite and 1000g of nano-silicon powder were placed in a horizontal ball mill and ball-milled for 180min. The mixture was then fed into a high-temperature coating and modification machine for coating tests. The heating program was as follows: 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 400℃ for 60min, 400℃~900℃ for 100min, and 900℃ for 120min. The protective atmosphere was argon, and the oxygen content was controlled at 1~5ppm throughout the process. The mixture was cooled and discharged to obtain a silicon-carbon-graphite composite intermediate.

[0093] Surface modification: 1000g of silicon-carbon-graphite composite intermediate was placed in a VC mixer preheated to 100℃ and stirred at 200rpm. 20g of polyethylene glycol (molecular weight 2000) and 2g of single-walled carbon nanotubes were added to a mixing tank along with 198g of deionized water and stirred for 1 hour to prepare a homogeneous slurry with a solid content of 10%. The slurry was uniformly sprayed onto the surface of the intermediate through a nozzle at a flow rate of 0.05L / min, maintaining the mixing and internal temperature at 95~105℃ during the spraying process. After spraying, the mixture was dried at 80℃ and then sieved to obtain a conductive silicon-carbon skin material.

[0094] The preparation steps for the CR 2016 button cell are the same as in Example 1.

[0095] Example 3

[0096] A method for preparing a conductive silicon-carbon skin material includes the following steps:

[0097] High-temperature coating: Take 100g of asphalt, 200g of graphene oxide, 100g of cryptocrystalline graphite, and D... v 100g of 50=8μm graphite and 1000g of nano-silicon powder were placed in a horizontal ball mill and ball-milled for 180min. The mixture was then fed into a high-temperature coating and modification machine for coating tests. The heating program was as follows: 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 400℃ for 60min, 400℃~900℃ for 100min, 900℃ for 120min. The protective atmosphere was argon, and the oxygen content was controlled at 1~5ppm throughout the process. The mixture was cooled and discharged to obtain a silicon-carbon-graphite composite intermediate.

[0098] Surface modification: 1000g of silicon-carbon-graphite composite intermediate was placed in a VC mixer preheated to 100℃ and stirred at 200rpm. 20g of polyethylene glycol (molecular weight 2000) and 2g of single-walled carbon nanotubes were added to a mixing tank along with 198g of deionized water and stirred for 1 hour to prepare a homogeneous slurry with a solid content of 10%. The slurry was then uniformly sprayed onto the surface of the intermediate through a nozzle at a flow rate of 0.05L / min, maintaining the mixing and internal temperature at 95~105℃ during the spraying process. After spraying, the mixture was dried at 80℃ and then sieved to obtain a conductive silicon-carbon skin material.

[0099] The preparation steps for the CR 2016 button cell are the same as in Example 1.

[0100] Example 4

[0101] A method for preparing a conductive silicon-carbon skin material includes the following steps:

[0102] High-temperature coating: Take 100g of asphalt, 100g of graphene oxide, 100g of cryptocrystalline graphite, and D... v 300g of 50=4μm graphite and 1000g of nano-silicon powder were placed in a horizontal ball mill and ball-milled for 180min. The mixture was then fed into a high-temperature coating and modification machine for coating tests. The heating program was as follows: 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 400℃ for 60min, 400℃~900℃ for 100min, 900℃ for 120min. The protective atmosphere was argon, and the oxygen content was controlled at 1~5ppm throughout the process. The mixture was cooled and discharged to obtain a silicon-carbon-graphite composite intermediate.

[0103] Surface modification: 1000g of silicon-carbon-graphite composite intermediate was placed in a VC mixer preheated to 100℃ and stirred at 200rpm. 20g of polyethylene glycol (molecular weight 2000) and 2g of single-walled carbon nanotubes were added to a mixing tank along with 198g of deionized water and stirred for 1 hour to prepare a homogeneous slurry with a solid content of 10%. The slurry was then uniformly sprayed onto the surface of the intermediate through a nozzle at a flow rate of 0.05L / min, maintaining the mixing and internal temperature at 95~105℃ during the spraying process. After spraying, the mixture was dried at 80℃ and then sieved to obtain a conductive silicon-carbon skin material.

[0104] The preparation steps for the CR 2016 button cell are the same as in Example 1.

[0105] Comparative Example 1

[0106] A method for preparing a small-particle self-assembled silicon-carbon composite material includes the following steps:

[0107] High-temperature coating: Take 200g of asphalt, 100g of graphene oxide, 200g of cryptocrystalline graphite and 1000g of nano-silicon powder, put them in a horizontal ball mill and ball mill for 180min. Put them into a high-temperature coating and modification machine for coating test. The heating program is 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 400℃ for 60min, 400℃~900℃ for 100min, 900℃ for 120min. The protective atmosphere is argon. The oxygen content is controlled at 1~5ppm throughout the process. Cool and discharge to obtain self-assembled silicon-carbon material intermediate.

[0108] Surface modification: 1000g of the self-assembled silicon-carbon composite intermediate was placed in a VC mixer preheated to 100℃ and stirred at 200rpm. 20g of polyethylene glycol (molecular weight 2000) and 2g of single-walled carbon nanotubes were added to a mixing tank, along with deionized water, and stirred for 1 hour to prepare a homogeneous slurry. The slurry was then uniformly sprayed onto the surface of the intermediate through a nozzle at a flow rate of 0.05L / min. During spraying, the mixing and internal temperature were maintained at 95~105℃. After spraying, the mixture was dried at 80℃ and then sieved to obtain the small-particle self-assembled silicon-carbon composite material of Comparative Example 1.

[0109] The preparation steps of the CR 2016 button cell are the same as those in Example 1, except that the small-particle self-assembled silicon-carbon composite material used in Comparative Example 1 is used.

[0110] Figure 3 The image shows a SEM image of the small-particle self-assembled silicon-carbon composite material prepared in Comparative Example 1. It does not have graphite as a core and the particles are relatively small. It is an irregular structure formed by silicon wafers, graphene oxide, and cryptocrystalline graphite under the bonding effect of molten asphalt.

[0111] Comparative Example 2

[0112] The preparation method is the same as in Example 1, but without surface modification, and includes the following steps:

[0113] High-temperature coating: Take 200g of asphalt, 100g of graphene oxide, 200g of cryptocrystalline graphite and 1000g of nano-silicon powder, put them in a horizontal ball mill and ball mill for 180min. Put them into a high-temperature coating and modification machine for coating test. The heating program is 25~180℃ for 60min, 180℃ for 120min, 180℃~400℃ for 44min, 400℃ for 60min, 400℃~900℃ for 100min, 900℃ for 120min. The protective atmosphere is argon, and the oxygen content is controlled at 1~5ppm throughout the process. Cool and discharge to obtain the unmodified material of Comparative Example 2.

[0114] The preparation steps of the CR 2016 button battery were the same as those in Example 1, except that the unmodified material obtained in Comparative Example 2 was used.

[0115] Comparative Example 3

[0116] The method for preparing a multi-granulated silicon-carbon material with a self-assembled conductive structure, as disclosed in Chinese invention patent application CN119812244A, includes the following steps:

[0117] Precursor preparation by one-time granulation: Take 1275g of nano-silicon powder and 225g of asphalt, add them to a high-speed mixer and stir to disperse; after discharge, add the powder to a coating machine for one-time granulation, control the stirring speed of the coating machine to 20r / min, introduce argon gas through a high-pressure gas cylinder, wait for the oxygen content to drop to 1~5ppm and then start heating; during the heating process, heat from 0~180℃ for 60min, hold at 180℃ for 2h, heat from 180~300℃ for 60min, heat from 300℃~500℃ for 40min, hold at 500℃ for 2h, and obtain one-time granulated silicon-carbon precursor microspheres.

[0118] Secondary granulation: Take 1000g of the obtained primary granulated silicon-carbon precursor microspheres, 100g of pitch, 100g of graphene oxide, 200g of cryptocrystalline graphite, and D... v 400g of 10μm graphite (50) was mixed uniformly and added to a high-temperature coating machine for secondary granulation. The heating program was as follows: 0~180℃ for 60min, 180℃ for 2h, 180~400℃ for 44min, 400℃ for 1h, 400℃~900℃ for 100min, and 900℃ for 2h. The protective atmosphere during the high-temperature carbonization process was argon, and the oxygen content was <5ppm throughout the process. The discharged material was a secondary granulated silicon-carbon composite material.

[0119] Surface modification: Take 10 kg of secondary granulated silicon-carbon composite material and 200 g of polyethylene glycol with a molecular weight of 2000, add them to a stirring vessel, add distilled water and stir for 1 hour, add the liquid to a dryer to evaporate to dryness, and after discharge, sieve to obtain a multi-granulated silicon-carbon material with a self-assembled conductive structure.

[0120] Figure 4 The image shows a SEM image of the multi-granulated silicon-carbon material with a self-assembled conductive structure prepared in Comparative Example 3. Using large-particle graphite as the core, an irregular structure is formed by the bonding of outer silicon wafers, graphene oxide, and cryptocrystalline graphite under the action of molten pitch. This structural design is beneficial for improving the material's rate performance and long-cycle stability. However, this structure uses multiple granulation processes, resulting in large particles, and the enrichment of silicon nanosheets can be observed on the particle surface. This leads to the shedding of silicon particles during the volume change of lithium-ion insertion and extraction, affecting the material's electrochemical performance.

[0121] The preparation steps of the CR 2016 button cell are the same as those in Example 1, except that the self-assembled conductive structure of the multi-granulated silicon-carbon material obtained in Comparative Example 3 is used.

[0122] Characterization and performance testing:

[0123] The materials prepared through the above-described embodiments and comparative steps were characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) to analyze their morphology, component content, and chemical bond types.

[0124] X-ray diffraction was performed using a German D8 Advance X-ray diffractometer, with a Cu target as the radiation source and a wavelength of λ. CuKα =0.15406nm, the test angle is 5°≤2θ≤90°, the test voltage is 40kV, and the current is 40mA. Fourier transform infrared spectroscopy was performed using a Bruker Tensor (Germany), with a sampling range of 0~3000cm. -1 Specific surface area analysis was performed using a Beijing Bestech 3H-200PSI microscope with N2 as the adsorbed gas. X-ray photoelectron spectroscopy was performed using a Kratos Axis UltraDLD. Scanning electron microscopy (SEM) was performed using a German LEO 1530VP cold field SEM to analyze the microstructure of the material. Transmission electron microscopy (TEM) was performed using a Japanese JEM-2100HR to observe the internal structural features of the material.

[0125] The materials prepared through the above embodiments and comparative steps were studied through constant current charge-discharge, rate performance testing, impedance and long-cycle testing to investigate the surface resistance, long-cycle stability, resistance to high current interference and lithium storage mechanism of the materials.

[0126] After being left to rest for 24 hours, the batteries prepared in the above embodiments were subjected to constant current charge-discharge (discharge cutoff voltage 0.01 V, charging cutoff voltage 2 V) using a battery tester (Shenzhen Xinwei) and BTS8.0.0 software at a test temperature of 25°C to test their long-term cycle performance. The electrochemical performance of the examples and comparative samples is detailed in Table 1. Table 1 includes four examples and three comparative examples related to the preparation of conductive silicon-carbon skin materials.

[0127] Table 1

[0128]

[0129] As shown in Table 1, Examples 1-4 differ from existing materials in that they possess the characteristic of D.v A conductive silicon-carbon material with a graphite core of 4~8μm (50=4~8μm) as the skin achieves an initial coulombic efficiency of over 87.24% at 10A g. -1 Even at high current density, the remaining capacity is still a minimum of 552.3 mAh g. -1 In 4A g -1 At a current density, after 1000 cycles, the lowest remaining capacity is 659.9 mAh g. -1 The above-mentioned specific charge capacity is 10A g for silicon-carbon materials in Examples 1-4, which use a multi-gradient thermal coating and surface modification composite process with added graphite. -1 Remaining capacity at high current density (552.3 mAh g) -1 ~671.2mAh g -1 Both were higher than those of the comparative example 1 small particle self-assembled silicon-carbon composite material (179.6 mAh g). -1 Comparative Example 2: Unmodified silicon-carbon material (528.5 mAh g) -1 ) and Comparative Example 3, a multi-granulated silicon-carbon material with a self-assembled conductive structure (511.5 mAh g) -1 Meanwhile, the reversible capacity after cycling of the conductive silicon-carbon skin material prepared in Examples 1-4 is 659.9 mAh g. -1 ~813.6mAh g -1 Both were significantly higher than those of the self-assembled silicon-carbon composite material of small particles in Comparative Example 1 (346.8 mAh g). -1 Comparative Example 2: Unmodified silicon-carbon material (537.5 mAh g) -1 ) and Comparative Example 3, a multi-granulated silicon-carbon material with a self-assembled conductive structure (466.1 mAh g) -1 ).

[0130] The small-particle self-assembled silicon-carbon composite material prepared in Comparative Example 1, without the addition of graphite as a core, was made solely from nano-silicon powder, graphene oxide, and cryptocrystalline graphite bonded together under the action of pitch, followed by surface modification. Figure 3 SEM images of small-particle self-assembled silicon-carbon composites reveal that the composites lack a graphite core, have small particles, and do not form an effective three-dimensional conductive network or mechanical support. This leads to the material's susceptibility to breakage and disintegration during cycling at high current densities, resulting in poor performance at high rates (10 A g). -1 At current density, only 179.6 mAh g remains of capacity. -1 Furthermore, the excessively large specific surface area makes electrolyte wetting difficult during the manufacturing process. This invention uses graphite as the core to provide mechanical support, and graphite, along with multiple carbon sources such as graphene oxide, cryptocrystalline graphite, and single-walled carbon nanotubes, synergistically constructs a three-dimensional conductive network, alleviating the problems of low intrinsic conductivity and easy pulverization of silicon-based materials.

[0131] The unmodified silicon-carbon material prepared in Comparative Example 2, 10A g -1 Remaining capacity at higher speeds: 528.5 mAh / g -1 The remaining capacity appears to be 552.3 mAh g, similar to that of Example 2. -1 Similar, 4A g -1 After 1000 cycles, the remaining capacity is 537.5 mAh g. -1 The difference from Example 3 is not significant, but the overall performance of the product obtained in Comparative Example 3 is considerably different from that of the present invention, even in the worst-case scenario. More importantly, the process in this example did not involve surface modification, resulting in hydrophobicity of the outer layer of molten asphalt carbon, leading to poor dispersibility and uneven slurry coating. This severely affects the consistency of battery assembly and poses a risk to high yield and consistency control in industrial production. The present invention employs polymer and conductive agent for surface modification, and the simple process alleviates the hydrophobicity problem of molten asphalt carbon, laying the foundation for industrial applications.

[0132] Comparative Example 3 uses a multi-granulation process disclosed in Chinese invention patent application CN119812244A to prepare a multi-granulated silicon-carbon material with a self-assembled conductive structure. This material has a conductivity of 10 A g. -1 The specific capacity under high charging rate is 511.5mAh g. -1 Compared to Comparative Example 1, which uses graphite-free self-assembled silicon-carbon composite material (10A g), -1 179.6mAh g -1 It has excellent performance in terms of structure, which can resist large current impact. Figure 10 This graph compares the electrical conductivity of Example 1 and Comparative Example 3. It clearly shows that the electrical conductivity of Comparative Example 3 is significantly lower than that of Example 1 under different pressures. This may be because the multi-granulation material prepared in Comparative Example 3 uses D... v Using 10μm graphite as the core, there is a large size difference between it and the nano-silicon powder. During the self-assembly process, it is easy to form microscopically uneven "silicon-rich regions" and "graphite-rich regions", without forming a continuous three-dimensional conductive path. Figure 4 The image shows a SEM image of the multi-granulated silicon-carbon material with a self-assembled conductive structure prepared in Comparative Example 3. The image reveals a relatively large particle size of approximately 30 μm, and numerous interconnected sheet-like structures are observed on the surface, exhibiting morphological characteristics consistent with typical silicon nanosheets. This indicates localized enrichment of silicon in this region, suggesting that the multi-granulation process may cause component segregation during self-assembly. Furthermore, the surface modification in this technique only involves adding a polymeric surfactant to alleviate the hydrophobicity of the pitch carbon. The polymeric surfactant itself is insulating, and its coating layer, to some extent, hinders electron transport between particles, increasing interfacial contact resistance and resulting in poor powder conductivity, thus affecting the conductivity at 10 A g. -1The capacity decay was quite noticeable in the high-rate performance test, resulting in a capacity degradation of 10A g. -1 The performance at lower rates is still significantly different from that of Example 2, which showed poor performance in this invention. More importantly, this material at 4A g -1 After 1000 cycles, only 466.1 mAh g of capacity remained. -1 This is far inferior to Example 3 (659.9 mAh g), which performed poorly in long-cycle testing. -1 This is because the large-particle graphite used in the multi-granulation material prepared in Comparative Example 3 has high rigidity, making it difficult to effectively adapt to the inherent volume expansion effect of the silicon component during long-term charge-discharge cycles. The graphite-silicon interface is more prone to separation, resulting in poor long-cycle performance. In this invention, D is selected... v Smaller graphite particles (50 = 4~8μm) reduce the size difference with nano-silicon powder. Furthermore, conductive agents are added during the modification of the outer surface to alleviate the problem of poor conductivity of the polymer surfactant coating layer. In particular, the segmented temperature-controlled calcination process used in this invention only requires one calcination, which is simpler and cheaper than multiple calcination processes, and has significant advantages in the process of large-scale production.

[0133] Figure 11 The conductive silicon-carbon material button cell prepared in Example 1 was subjected to a process at 25°C and 0.2 A g. -1 The graph shows the charge-discharge specific capacity curves for the first three cycles at a given current density. As can be seen from the graph, within the voltage window of 0.01-2V, the material exhibits an initial coulombic efficiency greater than 89% and a charge specific capacity of 2262.2 mAh g⁻¹. -1 .

[0134] Figure 12 This is a graph showing the long-cycle performance of a button cell made of conductive silicon-carbon material with a silicon-carbon skin, as described in Example 1. The material exhibits performance at 4Ag... -1 After 1000 cycles at a current density, it still has 813.6 mAh g. -1 It has a high specific charging capacity and excellent long-cycle stability.

[0135] Data from the examples and comparative examples show that, with small particle D vConductive silicon-carbon materials with a 4~8μm graphite core, which are constructed by surface modification, have significant advantages over multi-granulated silicon-carbon materials with self-assembled conductive structures in terms of powder conductivity, rate performance and cycle stability. The conductive skin material uses graphite with a D50 of 4~8μm as the core conductive framework, providing rapid conductivity in the inner layer and acting as internal support to improve the problem of pulverization of isolated silicon-based materials. Graphene oxide, as a two-dimensional conductive sheet, is wrapped around the surface of graphite and nano-silicon powder. Cryptocrystalline graphite acts as an interfacial conductive intercalation layer. Together with nano-silicon powder and amorphous carbon, they form a continuous and interconnected conductive structure under the bonding effect of carbon sources with softening or melting points of 60~200℃. The continuous carbon layer also alleviates the expansion stress of silicon materials. The outer layer of polymer elastomer and conductive agent coating improves the hydrophobicity of amorphous carbon and works synergistically with the inner silicon-carbon-graphite composite structure to form a three-dimensional conductive network, improving the material's conductivity and stability. In practical applications, this can improve the cell's energy density, rate performance, and long cycle life, and is suitable for industrialized and consistent production. In consumer battery applications such as e-cigarettes and emergency power supplies that require high-rate instantaneous discharge, this structural design can protect the negative electrode of the material.

[0136] Example 5

[0137] A method for preparing a double-layer conductive elastomer coated electrode includes the following steps:

[0138] Inner electrode: 58.6g of conductive silicon-carbon skin material obtained in Example 1 and 1895.2g of artificial graphite (D50=12μm) were used as active materials. 25.1g of CMC powder, 2.0g of MXene, and 8.2g of conductive carbon black Super-P were added to a planetary mixer, and the slurry was prepared in the following order: 1. Turn on the mixer and mix the dry powder at a revolution speed of 10 rpm for 30 min; 2. Add 750g of deionized water, 39.1g of NMP, and 125.1g of PAA slurry, and premix at a revolution speed of 10 rpm and a dispersion disc speed of 200 rpm for 10 min; 3. After confirming the dispersion state of the slurry, scrape the slurry and continue mixing at a revolution speed of 15 rpm and a dispersion disc speed of 200 rpm for 80 min; 4. 1. Add 1160g of deionized water, 411.9g of SWCNT slurry, 160.2g of MWCNT slurry, and 131.5g of rGO slurry. Mix and stir for 90 minutes in a strong dispersion mode with a revolution speed of 25 rpm and a dispersion disc speed of 1800 rpm. 2. After the viscosity reaches the range of 5000-8000 cp, add 93.8g of SBR and mix for 60 minutes in a mode with a revolution speed of 20 rpm and a dispersion disc speed of 800 rpm. 3. Stop the dispersion function and stir at a low speed of only 10 rpm for 60 minutes to complete defoaming, obtaining the final slurry. Transfer the obtained slurry to a coating equipment, select 8μm copper foil as the current collector, and use a double-sided coating method to form the inner electrode sheet.

[0139] Outer electrode layer: Polyvinyl alcohol slurry and styrene-butadiene rubber latex are mixed evenly at a solid mass ratio of 2:1 to form a polymer elastomer slurry. SWCNT slurry is used as the outer conductive agent. An aqueous slurry is prepared at a polymer elastomer:SWCNT (based on solids) mass ratio of 10:1. This slurry is then applied to both sides of the inner electrode layer. After drying, a 15μm conductive elastomer coating is obtained on the outer layer. The electrode layer is then rolled under a pressure of 1000 PSI, controlling the compaction density to be 1.45 g / cm³. 3 A double-layer conductive elastomer coated electrode was obtained.

[0140] Example 6

[0141] A method for preparing a double-layer conductive elastomer coated electrode includes the following steps:

[0142] Inner electrode: 58.6g of conductive silicon-carbon skin material obtained in Example 1 and 1895.2g of artificial graphite (D50=12μm) were used as active materials. 26.6g of CMC powder, 3.1g of MXene, and 16.4g of conductive carbon black Super-P were added to a planetary mixer, and the slurry was prepared in the following order: 1. Turn on the mixer and mix the dry powder at a revolution speed of 10 rpm for 30 min; 2. Add 675g of deionized water, 39.1g of NMP, and 125.1g of PAA slurry, and premix at a revolution speed of 10 rpm and a dispersion disc speed of 200 rpm for 10 min; 3. After confirming the dispersion state of the slurry, scrape the slurry and continue mixing at a revolution speed of 15 rpm and a dispersion disc speed of 200 rpm for 80 min; 4. 1. Add 1489g of deionized water, 155.9g of SWCNT slurry, 180.2g of MWCNTs slurry, and 181.5g of rGO slurry. Mix and stir for 90 minutes in a strong dispersion mode with a revolution speed of 25 rpm and a dispersion disc speed of 1800 rpm. 2. After the viscosity reaches the range of 5000-8000 cp, add 93.8g of SBR and mix for 60 minutes in a mode with a revolution speed of 20 rpm and a dispersion disc speed of 800 rpm. 3. Stop the dispersion function and stir at a low speed of 10 rpm for 60 minutes to complete defoaming, obtaining the final slurry. Transfer the obtained slurry to a coating device, select 6μm copper foil as the current collector, and use a double-sided coating method to form the inner electrode sheet.

[0143] Outer electrode layer: Polyvinyl alcohol slurry and styrene-butadiene rubber latex are mixed evenly at a solid mass ratio of 2:1 to form a polymer elastomer slurry. MWCNT slurry and MXene are used as the outer conductive agent. An aqueous slurry is prepared at a mass ratio of polymer elastomer:MWCNT (based on solids):MXene = 12:1:0.5. This slurry is then applied to both sides of the inner electrode layer. After drying, a 15μm conductive elastomer coating is obtained on the outer layer. The electrode layer is then rolled under a pressure of 1000 PSI to control the compaction density at 1.45 g / cm³. 3 A double-layer conductive elastomer coated electrode was obtained.

[0144] Example 7

[0145] A method for preparing a double-layer conductive elastomer coated electrode includes the following steps:

[0146] Inner electrode: 58.6g of conductive silicon-carbon skin material obtained in Example 1 and 1895.2g of artificial graphite (D50=14μm) were used as active materials. 23.5g of CMC powder, 1.0g of MXene, and 16.4g of conductive carbon black Super-P were added to a planetary mixer, and the slurry was prepared in the following order: 1. Turn on the mixer and mix the dry powder at a revolution speed of 10 rpm for 30 min; 2. Add 750g of deionized water, 39.1g of NMP, and 125.1g of PAA slurry, and premix at a revolution speed of 10 rpm and a dispersion disc speed of 200 rpm for 10 min; 3. After confirming the dispersion state of the slurry, scrape the slurry and continue mixing at a revolution speed of 15 rpm and a dispersion disc speed of 200 rpm for 80 min; 4. 1. Add 1360g of deionized water, 467.8g of SWCNT slurry, and 331.5g of rGO slurry. Mix and stir for 90 minutes in a strong dispersion mode with a revolution radius of 25 rpm and a dispersion disc of 1800 rpm. 2. After the viscosity reaches the range of 5000-8000 cp, add 93.8g of SBR and mix for 60 minutes in a mode with a revolution radius of 20 rpm and a dispersion disc of 800 rpm. 3. Stop the dispersion function and stir at a low speed of 10 rpm for 60 minutes to complete defoaming, obtaining the final slurry. Transfer the obtained slurry to a coating device, select 9μm copper foil as the current collector, and use a double-sided coating method to form the inner electrode sheet.

[0147] Outer electrode: Same as in Example 5.

[0148] Comparative Example 4

[0149] Except for the following differences, all other conditions are the same as in Example 5:

[0150] The active material is a bilayer electrode of a small particle self-assembled silicon-carbon composite material, as described in Comparative Example 1.

[0151] Comparative Example 5

[0152] Except for the following differences, all other conditions are the same as in Example 5:

[0153] The active material used in Comparative Example 3 is a bilayer electrode of silicon-carbon material with a self-assembled conductive structure obtained by multiple granulation of silicon-carbon material using the preparation method disclosed in Chinese Invention Patent Application CN119812244A.

[0154] This invention applies conductive silicon-carbon skin material to an electrode with a double-layer composite structure. An ultrathin conductive elastomer coating is prepared using a casting method on top of a conventional inner electrode, forming an interface protective layer that combines flexibility and high conductivity. This allows the conductive network of the conductive silicon-carbon skin itself to synergize with the multi-dimensional conductive agent and the conductive elastomer coating in the electrode, thereby improving overall performance. Examples 5-7 and Comparative Examples 4 and 5 all used the four-probe method to test the electrode conductivity; the test structures are shown in Table 2.

[0155] Examples 5-7 demonstrate the application of conductive silicon-carbon skin materials in electrode sheets with a double-layer composite structure design. Comparative Example 4 shows a double-layer electrode sheet in which the active material is a small-particle self-assembled silicon-carbon composite material as described in Comparative Example 1. Comparative Example 5 shows a double-layer electrode sheet in which the active material is a multi-granulated silicon-carbon material with a self-assembled conductive structure as described in Comparative Example 3.

[0156] Table 2

[0157]

[0158] As shown in Table 2, Examples 5-7 differ from existing materials in that their conductivity is ≥0.108 S / mm at 10 MPa pressure and ≥0.514 S / mm at 60 MPa pressure. The conductivity at each different pressure exceeds that of Comparative Example 4, which uses a double-layer electrode made of a small-particle self-assembled silicon-carbon composite material (conductivity of 0.079 S / mm at 10 MPa pressure and 0.387 S / mm at 60 MPa pressure), and Comparative Example 5, which uses a double-layer electrode made of a multi-granulated silicon-carbon material with a self-assembled conductive structure (conductivity of 0.103 S / mm at 10 MPa pressure and 0.427 S / mm at 60 MPa pressure).

[0159] Comparative Example 4 is a bilayer electrode using a small-particle self-assembled silicon-carbon composite material as the active material in Comparative Example 1. As shown in Table 2, the conductivity of Comparative Example 4 under different pressures from 10 MPa to 60 MPa is significantly lower than that of the bilayer conductive elastomer electrode in Example 5. The active material used in Comparative Example 4 is a small-particle self-assembled silicon-carbon composite material without a graphite core for support. This results in the lack of a connected conductive path, and as the pressure increases during conductivity testing, this unsupported material is prone to damage, leading to insufficient stability of the conductive network. Consequently, the increase in conductivity with increasing pressure is limited, resulting in poor conductivity on the electrode.

[0160] Comparative Example 5 is a bilayer electrode using the multi-granulated silicon-carbon material with a self-assembled conductive structure, as described in Comparative Example 3. This electrode exhibits a conductivity of 0.103 S / mm at an initial pressure of 10 MPa, seemingly similar to Example 7. However, the conductivity increases less with increasing pressure, reaching only 0.447 S / mm at 60 MPa, which is significantly lower than the poor performance of Example 7 in this invention. The multi-granulated silicon-carbon material with a self-assembled conductive structure used in Comparative Example 5 has a polymer coating on its surface that hinders electron transport to some extent. Furthermore, the material uses large-particle graphite as its core, resulting in a significant size difference between the material and the nano-silicon powder. During self-assembly, this easily leads to the formation of microscopically heterogeneous "silicon-rich regions" and "graphite-rich regions," failing to create a continuous three-dimensional conductive pathway. Therefore, although a conductive agent and conductive elastomer coating are added to the electrode, the insufficient conductivity of the material itself still limits the overall performance. The conductive silicon-carbon material used in this invention has excellent conductivity due to the small-particle graphite core and the surface modification of the outer conductive agent, which creates a synergistic effect with the electrode. The additional conductive agent added to the electrode, the outer conductive elastomer coating, the conductive skin on the material surface, and the continuous conductive network inside form a "bridging" effect, which reduces the contact resistance and thus improves the conductivity of the electrode.

[0161] Example 8

[0162] A method for preparing a cylindrical lithium-ion battery includes the following steps:

[0163] Electrode fabrication: The negative electrode uses the double-layer conductive elastomer coated electrode from Example 5. The positive electrode uses the high-nickel ternary material LiNi. 0.8 Co 0.1 Mn 0.1 Using O2 as the positive electrode active material, and with a mass ratio of positive electrode active material:PVDF:conductive carbon black:SWCNT=97.6:1.5:0.4:0.5, and NMP as the solvent, the viscosity was adjusted to 5000±500 mPa·s. The positive electrode slurry was then uniformly coated on both sides of a 15μm copper foil current collector, with a coating density of 177.83 g / m. 2 The electrode sheets were rolled under a pressure of 45t to control the compaction density to 3.28g / cm³. 3 .

[0164] Cell assembly: The positive and negative electrode plates are riveted together and formed into 18650 cylindrical cells using an automatic winding machine together with a 16μm thick ceramic separator. The cells are then placed in the casing, welded, and baked in a vacuum oven at 85℃, with the water content inside the cell controlled to be ≤100ppm.

[0165] Electrolyte Injection and Formation: After drying, the battery cells were injected with commercial silicon-carbon electrolyte FH097 in a drying chamber at a volume of 5.6g using a vacuum injection process with a vacuum level of -0.095MPa. Pre-formation was then performed: the cells were charged to 3.0V at a constant current of 100mA. After activation at 45℃ for 5 days, a stepped formation process was followed: constant current charging at 0.05C to 3.75V, followed by a 3-minute rest; constant current charging at 0.1C to 3.85V, followed by a 3-minute rest; and constant current and voltage charging at 0.5C to 3.95V, with a cutoff current of 0.02C. Following formation, the cells were aged at room temperature for 3 days and then capacity-balanced at 0.2C to obtain cylindrical lithium-ion batteries.

[0166] Example 9

[0167] Except for the following differences, all other conditions are the same as in Example 8:

[0168] The negative electrode uses the double-layer conductive elastomer coating electrode of Example 6.

[0169] Comparative Example 6

[0170] Except for the following differences, all other conditions are the same as in Example 8:

[0171] The negative electrode uses a bilayer electrode made of a small-particle self-assembled silicon-carbon composite material, as described in Comparative Example 4.

[0172] Comparative Example 7

[0173] Except for the following differences, all other conditions are the same as in Example 8:

[0174] The negative electrode uses a double-layer electrode made of multi-granulated silicon-carbon material with a self-assembled conductive structure, as described in Comparative Example 5.

[0175] This invention achieves a systematic integration of materials, electrodes, and batteries at the cylindrical lithium-ion battery level. By applying conductive silicon-carbon skin materials and conductive elastomer-coated electrodes to the cylindrical battery system, it improves battery energy density while also ensuring cycle stability. The above embodiments and comparative examples were all tested using a battery tester (Shenzhen Xinwei) and BTS8.0.0 software after capacity testing at 25°C. Charge-discharge tests were performed on various types of batteries. The initial efficiency and rate testing voltage window was 4.2-2.5V, and the long-cycle testing voltage window was 4.2-3.0V. The electrochemical performance of the embodiment and comparative sample samples is detailed in Table 3. Table 3 includes two embodiments and two comparative examples related to the preparation of conductive silicon-carbon skin materials.

[0176] Example 8 applies the conductive silicon-carbon skin material of Example 1 and the double-layer conductive elastomer coated electrode of Example 5 to a cylindrical lithium-ion battery. Example 9 applies the double-layer conductive elastomer coated electrode of Example 6 to a cylindrical lithium-ion battery. Comparative Example 6 is a cylindrical lithium-ion battery prepared using a double-layer electrode of a small-particle self-assembled silicon-carbon composite material as described in Comparative Example 4. Comparative Example 7 is a cylindrical lithium-ion battery prepared using a double-layer electrode of a multi-granulated silicon-carbon material with a self-assembled conductive structure as described in Comparative Example 5.

[0177] Table 3

[0178]

[0179] As shown in Table 3, Examples 8 and 9 differ from existing materials in that the cell with conductive silicon-carbon skin material applied to the double-layer conductive elastomer coated electrode has an initial coulombic efficiency of 91.11%. Figure 13 The discharge capacities at 3C current density were 2560.5mAh and 2558.6mAh, with capacity retention rates of 90.59% and 89.58%, respectively. These figures were higher than those of Comparative Example 6 (2500.8mAh, 84.76% capacity retention rate) and Comparative Example 7 (2478.2mAh, 86.83% capacity retention rate). Example 8 retained 2182.5mAh of capacity after 400 cycles at 1C current density, achieving a capacity retention rate of 87.07%. After 900 cycles, 2025.2mAh of capacity remained, with a post-cycle capacity retention rate exceeding 80%. Figure 14 Example 9, after 400 cycles at a 1C current density, still retained 2190.9 mAh of capacity, achieving a capacity retention rate of 86.46%. In comparison, Comparative Example 6 showed a capacity retention rate of only 73.81% after 400 cycles at the same 1C current density, and Comparative Example 7 showed a capacity retention rate of 83.31%, both inferior to Examples 8 and 9. This data comparison confirms that the present invention successfully integrates conductive silicon-carbon skin material with a double-layer conductive elastomer electrode in a cylindrical lithium-ion battery, providing a complete and reliable technical solution for high-energy-density batteries.

[0180] Comparative Example 6, using the small-particle self-assembled silicon-carbon composite material from Comparative Example 1, produced a cylindrical lithium-ion battery with a discharge capacity of 2500.8 mAh at 3C, compared to 84.76% capacity retention at 0.2C. However, after 400 cycles at 1C, the capacity retention was only 73.81%, significantly lower than the 87.07% capacity retention of Example 8 and 86.46% capacity retention of Example 9 under the same cycling conditions. The small-particle self-assembled silicon-carbon composite material used in Comparative Example 6 lacked graphite, resulting in the absence of an effective three-dimensional conductive network. This led to a low capacity retention at 3C, and the absence of graphite as a core for mechanical support caused the material to easily pulverize during cycling, resulting in poor electrochemical performance. In contrast, Examples 8-9 of this invention used conductive silicon-carbon coating material as the active material. This conductive coating material, with graphite as its core, works synergistically with multiple carbon sources, improving rate performance while mitigating the problem of silicon particle pulverization during cycling, thus producing cylindrical lithium-ion batteries with excellent electrochemical performance.

[0181] Comparing the cylindrical lithium-ion battery prepared using the bilayer electrode of the self-assembled conductive structure-based multi-granulated silicon-carbon material in Comparative Example 7 with Examples 8 and 9, it was found that although the capacity retention rates at low rates of 0.2C, 0.5C, and 1C were similar, the capacity retention rates at 2C (89.94%) and 3C (86.83%) were significantly lower than those of Example 8 (92.56% at 2C), Example 9 (91.90% at 2C), and Example 8 (90.59%) and Example 9 (89.58%) at 3C. In terms of long-term cycle stability, Comparative Example 9 achieved a capacity retention rate of 83.31% after 400 cycles at 1C, which was also slightly lower than the poorer performance of Example 9 (86.46%) in this invention. The self-assembled conductive structure-based multi-granulated material used in Comparative Example 7 was selected using D... v While using 9-12μm large-particle graphite as a support provides a basic conductive path, its small specific surface area and significant size difference compared to nano-silicon powder lead to the formation of uneven "silicon-rich" and "graphite-rich" regions in the composite. Furthermore, the use of polymeric surfactants for surface modification without the addition of conductive agents means that the insulating properties of the surfactants themselves can affect electron transport between particles, further impacting the rate performance of the battery cell. Additionally, D... vThe 9-12 μm large-particle graphite and nano-silicon components have a mismatch issue in quality control. During long-term cycling, the stress generated by the volume change of silicon particles during repeated lithium-ion insertion / extraction is difficult to alleviate effectively by the large-particle rigid graphite core, leading to particle breakage. Furthermore, the component segregation problem easily caused by repeated granulation accelerates capacity decay during cycling. In contrast, this invention uses small-particle graphite, whose size characteristics are more compatible with nano-silicon powder, enabling more compact filling and more uniform dispersion. This not only significantly improves the tap density and structural consistency of the composite material but also constructs a more tightly packed three-dimensional conductive framework. Combined with subsequent material-level modification with polymeric surfactants and conductive agents, as well as the inner multi-dimensional conductive agent and outer conductive elastomer coating at the electrode level, the prepared battery cell more effectively maintains the stability of electronic conduction and the integrity of the interface structure, thus exhibiting advantages in rate performance and long-cycle performance.

[0182] Figure 13 The figure shows the initial charge-discharge curves of the cylindrical lithium-ion battery prepared in Example 8 at 25°C and a current density of 0.2C. As can be seen from the figure, the voltage window is 4.2-2.5V, the initial coulombic efficiency of the cell is approximately 91.11%, and the initial discharge capacity is approximately 2826.4 mAh g. -1 .

[0183] Figure 14 The graph shows the long-cycle performance of the cylindrical lithium-ion battery prepared in Example 8 at 25°C and a current density of 0.5C charging and 1C discharging. The battery cell retains more than 80% of its capacity after 900 cycles, demonstrating excellent long-cycle stability.

[0184] The above embodiments are only used to explain the present invention and are not intended to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A conductive silicon-carbon coating material, characterized in that: The structure consists of a core and a conductive skin coating layer covering the core surface. The core is a silicon-carbon-graphite composite intermediate, which uses graphite with a D50 of 4~8μm as a conductive framework, graphene oxide as a two-dimensional conductive sheet coating the surface of graphite and nano-silicon powder, and cryptocrystalline graphite as an interfacial conductive filler. Together, they form a continuous and interconnected conductive network under the bonding effect of amorphous carbon formed by the pyrolysis of carbon source with a softening point or melting point of 60~200℃. The conductive skin coating layer is obtained by spraying a composite powder slurry formed by polymer, conductive agent and deionized water onto the silicon-carbon-graphite composite intermediate.

2. The method for preparing the conductive silicon-carbon skin material according to claim 1, characterized in that... Includes the following steps: 1) A carbon source with a softening point or melting point of 60~200℃, graphene oxide, cryptocrystalline graphite, graphite with Dv50=4~8μm, and nano-silicon powder are ball-milled and mixed uniformly; the mass ratio of the carbon source with a softening point or melting point of 60~200℃, graphene oxide, cryptocrystalline graphite, graphite with Dv50=4~8μm, and nano-silicon powder is (1-3):(1-3):(1-3):(1-3):10; 2) The obtained material is put into a high-temperature coating machine. Under an inert atmosphere, the temperature is raised to 180℃ and held for 1-2 hours, then raised to 400℃ and held for 1-2 hours, and then raised to 900℃ and held for 2-4 hours to obtain a silicon-carbon-graphite composite intermediate. The oxygen content is controlled at 1-5 ppm throughout the high-temperature coating process. 3) Mix the polymer, conductive agent and deionized water evenly to obtain a composite powder slurry; 4) The composite powder slurry is uniformly sprayed onto the surface of the silicon-carbon-graphite composite intermediate and dried in situ to obtain a conductive silicon-carbon skin material.

3. The method for preparing the conductive silicon-carbon skin material according to claim 2, characterized in that, The carbon source with a softening point or melting point of 60~200℃ is one or more of pitch, phenolic resin and glucose; The polymer is one or more of polyethylene glycol, polyvinylpyrrolidone, polyoxyethylene fatty acid ester, sodium carboxymethyl cellulose, and polyoxyethylene fatty acid ester; The conductive agent is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, decomposed carbon nanotubes, reduced graphene oxide, graphene oxide, MXene, and carbon fiber.

4. The method for preparing the conductive silicon-carbon skin material according to claim 2, characterized in that, The time to raise the temperature to 180℃ is 1~2 hours; the time to raise the temperature to 400℃ is 0.5~1 hour; the time to raise the temperature to 900℃ is 1~2 hours. The mass ratio of the silicon-carbon-graphite composite intermediate, the polymer, and the conductive agent is (2~3):(0.04~0.06):(0.004~0.012).

5. The method for preparing the conductive silicon-carbon skin material according to claim 2, characterized in that, The ball mill has a ball-to-material mass ratio of (2~10):1, a rotation speed of 10~50 rpm / min, and a time of 1~5 h; The inert atmosphere is either Ar or N2.

6. The application of the conductive silicon-carbon skin material of claim 1 in the preparation of double-layer conductive elastomer coated electrodes, characterized in that... Includes the following steps: 1) A negative electrode active material, an inner layer conductive agent and a binder are made into a negative electrode inner layer slurry. The negative electrode inner layer slurry is coated on both sides of the negative electrode current collector and dried to obtain an inner layer electrode sheet. The negative electrode active material is composed of conductive skin silicon carbide material and graphite. 2) The outer conductive agent and polymer elastomer are made into a conductive elastomer slurry. The conductive elastomer slurry is then coated on both sides of the inner electrode to form a conductive elastomer coating. After drying, a double-layer conductive elastomer coated electrode is obtained.

7. The application of the conductive silicon-carbon skin material according to claim 6 in the preparation of double-layer conductive elastomer coated electrodes, characterized in that, The negative electrode current collector is a 5~10μm copper foil; The inner conductive agent is one or more of the following: conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, reduced graphene oxide, graphene oxide, and MXene. The adhesive is one or more of polyacrylic acid, styrene-butadiene rubber, and sodium carboxymethyl cellulose; The outer conductive agent is one or more of the following: conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, reduced graphene oxide, graphene oxide, and MXene. The polymeric elastomer is one or more of polyvinyl alcohol, styrene-butadiene rubber, polyacrylic acid, and polyimide; The graphite mentioned is artificial graphite and / or natural graphite.

8. The application of the conductive silicon-carbon skin material according to claim 6 in the preparation of double-layer conductive elastomer coated electrodes, characterized in that, The mass percentages of the negative electrode active material, inner layer binder, and inner layer conductive agent are (93.5%~96.5%): (2.5%~4.5%): (1.0%~2.0%). The mass percentage of the outer conductive agent to the polymer elastomer is 1:(8~12); The mass ratio of the conductive silicon carbide skin material to graphite is 1:(9~99).

9. The application of the conductive silicon-carbon skin material of claim 1 in the preparation of cylindrical lithium-ion batteries, characterized in that... Includes the following steps: 1) The positive electrode active material, positive electrode binder, and positive electrode conductive agent are made into a positive electrode slurry; 2) The positive electrode slurry is coated on both sides of the positive electrode current collector to obtain the positive electrode sheet; 3) Rolling, cutting, riveting and winding the positive electrode sheet and the double-layer conductive elastomer coated electrode sheet made of silicon carbon material with electro-coated skin to obtain a semi-finished battery cell; 4) The semi-finished cells are placed into the casing, dried, injected with electrolyte, sealed, and then pre-formed, activated at high temperature, formed, aged at room temperature and capacity tested to obtain cylindrical lithium-ion batteries.

10. The application of the conductive silicon-carbon skin material according to claim 9 in the preparation of cylindrical lithium-ion batteries, characterized in that: In step 1), the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide; the positive electrode binder is polyvinylidene fluoride; the positive electrode conductive agent is one or more of conductive carbon black Super P, acetylene black, and carbon nanotubes; the mass ratio of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent is (96~98):(1:2):(0.5~2). In step 2), the positive current collector is an aluminum foil with a thickness of 10~16μm; In step 3), the riveting is to weld the tabs to the electrode sheets; the winding is to wind the positive and negative electrode sheets together with the separator into a cylindrical battery cell. In step 4), the drying process involves transferring the semi-finished battery cell into a vacuum oven to remove moisture, controlling the moisture content to ≤100ppm; the pre-formation process involves charging the battery cell with a small current to increase the voltage from near 0V to a safe voltage of 2~3V; the high-temperature activation process involves placing the battery cell at a high temperature of 45±5℃ to promote electrode interface stability; the formation process involves charging the battery cell to form a stable SEI film; the room temperature aging process involves placing the battery cell at a room temperature of 25±5℃ to stabilize the battery cell performance; and the capacity grading process involves screening and classifying the battery cells according to their capacity.

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