3D printing rigid-flexible synergistic three-dimensional porous carbon skeleton, silicon-carbon composite negative electrode material, preparation method of silicon-carbon composite negative electrode material and lithium ion battery

Abstract

The invention provides a 3D printing rigid-flexible synergistic three-dimensional porous carbon skeleton, a silicon-carbon composite negative electrode material, a preparation method of the silicon-carbon composite negative electrode material and a lithium ion battery, and relates to the technical field of lithium ion battery negative electrode materials. The rigid-flexible synergistic three-dimensional porous carbon skeleton for 3D printing provided by the invention comprises a rigid carbon component, a silane coupling agent modified flexible carbon component and a resin carbon binding phase for binding the rigid carbon component and the flexible carbon component into a whole, the rigid carbon component is used for providing rigid support and a stable structure, and the flexible carbon component is used for providing flexible carbon; the flexible carbon component is used for providing flexible buffering and high conductivity. The rigid-flexible synergistic three-dimensional porous carbon skeleton for 3D printing not only can provide sufficient buffer space for silicon expansion, but also has excellent electrical conductivity, thermal conductivity and high mechanical strength; through mutual cooperation of the rigid-flexible synergistic carbon skeleton, the nano silicon particles and the amorphous carbon layer, the silicon-carbon composite negative electrode material has high capacity retention rate and high initial coulombic efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically to a 3D-printed rigid-flexible three-dimensional porous carbon skeleton, silicon-carbon composite anode material, its preparation method, and lithium-ion batteries. Background Technology

[0002] In the field of lithium-ion batteries, high energy density is one of the core directions of current technological development, and the performance of anode materials directly determines the energy density and cycle stability of the battery. Silicon (Si), with its extremely high theoretical specific capacity (4200 mAh / g), is widely recognized as the ideal choice for anode materials in high-energy-density lithium-ion batteries.

[0003] However, silicon undergoes a volume expansion of over 300% during charging and discharging. This issue triggers a series of chain reactions: First, the drastic volume change causes the electrode material to pulverize and crack, compromising the overall structural integrity of the electrode; second, the pulverized silicon particles detach from the conductive network, hindering electron transport and drastically increasing the battery's internal resistance; third, the volume expansion causes the solid electrolyte interface film on the electrode surface to continuously rupture and reconstruct, consuming large amounts of electrolyte and lithium ions, resulting in rapid capacity decay and a significantly shortened cycle life. These problems severely restrict the commercial application of silicon as a negative electrode material.

[0004] To address the challenges posed by silicon's volume expansion, researchers have widely adopted a silicon-carbon composite material approach, with the construction of porous carbon frameworks as silicon carriers being a key strategy. Current technologies often rely on single carbon sources for the preparation of porous carbon frameworks, such as phenolic resins, graphene, carbon nanotubes, expanded graphite, or petroleum coke. However, frameworks constructed from these single carbon sources all exhibit significant defects. Resin-based carbon frameworks: Although porous structures can be formed through template methods, they suffer from poor conductivity and high brittleness, making them prone to fracture under silicon expansion stress and unable to maintain structural stability over long periods. Graphene / carbon nanotube-based carbon frameworks: While possessing excellent conductivity and flexibility, they suffer from high raw material costs and are prone to agglomeration during preparation, making it difficult to achieve uniform silicon particle loading and hindering large-scale production. Single expanded graphite frameworks: Expanded graphite has a worm-like, fluffy structure with excellent conductivity and thermal conductivity, and possesses a certain degree of flexible buffering capacity. However, its mechanical strength is insufficient, and repeated silicon expansion during long-term cycling gradually destroys its worm-like structure, leading to framework collapse. Single petroleum coke-based carbon frameworks: Petroleum coke forms hard carbon after carbonization, exhibiting high mechanical strength and good structural stability. However, its pore structure is singular, and its buffering space is limited, failing to effectively accommodate silicon volume expansion. Furthermore, its conductivity is inferior to that of graphite. Meanwhile, carbon frameworks prepared by traditional powder sintering and template methods have random pore structures and chaotic ion transport pathways, resulting in poor battery rate performance.

[0005] Therefore, developing a silicon-carbon composite anode material that can provide sufficient buffer space for silicon expansion and has excellent electrical conductivity, thermal conductivity and high mechanical strength to obtain high cycle stability is the key to promoting the industrialization of high energy density lithium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a 3D-printed rigid-flexible three-dimensional porous carbon framework, a silicon-carbon composite anode material, its preparation method, and a lithium-ion battery. The 3D-printed rigid-flexible three-dimensional porous carbon framework not only provides sufficient buffer space for silicon expansion but also possesses excellent electrical conductivity, thermal conductivity, and high mechanical strength. The silicon-carbon composite anode material exhibits high capacity retention and high initial coulombic efficiency.

[0007] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a 3D printed rigid-flexible three-dimensional porous carbon skeleton, comprising a rigid carbon component, a silane coupling agent modified flexible carbon component, and a resin carbon bonding phase that bonds the rigid carbon component and the flexible carbon component together. The rigid carbon component is used to provide rigid support and a stable structure, and the flexible carbon component is used to provide flexible buffering and high conductivity.

[0008] In one possible implementation, the flexible carbon component comprises expanded graphite.

[0009] In one possible implementation, the silane coupling agent is selected from one or more of aminosilanes, epoxysilanes, vinylsilanes, methacryloxysilanes, and ureosilanes.

[0010] In one possible implementation, the rigid carbon component includes one or more of coke-based carbon, biomass-based carbon, resin-based carbon, and sugar-based carbon.

[0011] Furthermore, the coke-type carbon is selected from one or more of petroleum coke, needle coke, and pitch coke; the biomass-based carbon is obtained by high-temperature pyrolysis of starch, cellulose, coconut shell, bagasse, or mixtures thereof; the resin-based carbon is obtained by carbonization of phenolic resin and / or epoxy resin; and the sugar-type carbon is obtained by carbonization of glucose, sucrose, maltose, or mixtures thereof.

[0012] In one possible implementation, the resin carbon binder phase is formed by carbonizing phenolic resin, epoxy resin, furan resin, or a mixture thereof.

[0013] In one possible implementation, the mass ratio of the flexible carbon component to the rigid carbon component is (1-9):(1-9).

[0014] In one possible implementation, the three-dimensional porous carbon framework has a hierarchical pore structure designed by a 3D printing program, the hierarchical pore structure including macropores with a diameter >50 nm, mesopores with a diameter of 2-50 nm and micropores with a diameter <2 nm, the macropores being used for rapid transport of ions in the electrolyte, the mesopores being used for wetting the electrolyte, and the micropores being used to provide a high specific surface area.

[0015] Secondly, the present invention provides a silicon-carbon composite anode material, comprising: The above-mentioned 3D printed rigid-flexible three-dimensional porous carbon framework; Nano-silicon particles, selectively loaded onto the flexible carbon component, are used for charge-discharge cycle storage of lithium ions; An amorphous carbon layer is coated on the outer surface of the nano-silicon particles and the three-dimensional porous carbon framework to stabilize the electrode interface of the silicon-carbon anode material and optimize its electrochemical performance.

[0016] In one possible implementation, the mass percentage of the nano-carbon particles in the silicon-carbon composite anode material is 5-40 wt.%.

[0017] Thirdly, the present invention provides a method for preparing the above-mentioned silicon-carbon composite anode material, comprising the following steps: S1. Surface modification: The flexible carbon component is surface modified by using a silane coupling agent to obtain a surface-modified flexible carbon component. S2. Composite: The surface-modified flexible carbon component and the rigid carbon component are mixed evenly to obtain a composite carbon source; S3, 3D printing: Based on the preset three-dimensional model, the composite carbon source and resin binder described in step S2 are 3D printed into a green body with a multi-level pore structure. S4. Curing and Carbonization: The green body described in step S3 is subjected to a step-by-step heat treatment. The step-by-step heat treatment first crosslinks the resin binder through curing, and then converts the resin binder into a resin carbon binder phase through carbonization treatment under an inert atmosphere, thereby obtaining a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon skeleton described in step S4 is placed in a chemical vapor deposition reactor, and a silane gas source is introduced. The silane gas source generates nano-silicon particles through chemical vapor reaction. The nano-silicon particles are selectively deposited on the surface-modified flexible carbon component of the three-dimensional porous carbon skeleton to obtain a three-dimensional porous carbon skeleton loaded with nano-silicon particles. S6. Carbon coating: Replace the silane gas source in step S5 with a hydrocarbon gas source for chemical vapor deposition. An amorphous carbon layer is formed on the surface of the three-dimensional porous carbon skeleton with loaded silicon nanoparticles obtained in step S5, thus obtaining a silicon-carbon composite anode material.

[0018] In one possible implementation, the mass ratio of the silane coupling agent to the flexible carbon component in step S1 is (1-5):100, the surface modification treatment is carried out in a mixed solution of ethanol and water at 60-80 °C, and the surface modification treatment time is 2-4 h.

[0019] In one possible implementation, the 3D printing method in step S3 is direct-write printing. The direct-write printing process includes: mixing the composite carbon source in step S2 with resin binder, solvent and dispersant and grinding them to make printing ink. The resin binder has a mass percentage content of 5-30 wt.% in the printing ink. Then, the printing ink is printed into a green body with a multi-level channel structure according to a preset three-dimensional model.

[0020] In one possible implementation, the 3D printing method in step S3 is binder jet printing. The binder jet printing process includes: jetting resin binder onto the composite carbon source in step S2, and 3D printing a green body with a multi-level pore structure. The resin binder has a mass percentage content of 2-15 wt.% in the green body.

[0021] In one possible implementation, the curing temperature in step S4 is 150-200 °C, and the carbonization temperature is 800-1100 °C.

[0022] In one possible implementation, the temperature of the chemical vapor phase reaction in step S5 is 550-650 °C and the time is 1-4 h. The silane gas source is a mixture of silane and inert gas, and the volume percentage of silane in the mixture is 10%-20%.

[0023] Fourthly, the present invention provides a lithium-ion battery in which the negative electrode material is the aforementioned silicon-carbon composite negative electrode material.

[0024] The positive and progressive effects of this invention are as follows: This invention provides a 3D-printed rigid-flexible three-dimensional porous carbon framework, a silicon-carbon composite anode material, its preparation method, and a lithium-ion battery. The 3D-printed rigid-flexible three-dimensional porous carbon framework, through multi-dimensional synergy of rigid support, flexible buffering, interface anchoring, and structural design, can provide sufficient buffer space for silicon expansion, while also possessing high electrical conductivity, high thermal conductivity, and high mechanical strength. The silicon-carbon composite anode material selectively loads nano-silicon particles onto the aforementioned 3D-printed rigid-flexible three-dimensional porous carbon framework. These nano-silicon particles are chemically bonded to a highly elastic and highly buffered flexible carbon component, reducing the damage to the silicon-carbon anode material caused by nano-silicon particle expansion while significantly improving the retention rate of nano-silicon particles after multiple cycles. This allows the silicon-carbon composite anode material to withstand repeated cycles. Even after 1500 cycles, the silicon-carbon composite anode material retains a high capacity. The synergistic effect of "selective deposition" and "3D printing of a rigid-flexible three-dimensional porous carbon framework" enables the capacity retention rate to exceed 80%. Combined with the coating of amorphous carbon layers, the initial coulombic efficiency and capacity retention rate of the silicon-carbon composite anode material are further improved. The chemical anchoring of the silane coupling agent and the carbon coating together ensure a stable interface, increasing the initial coulombic efficiency of the silicon-carbon composite anode material to over 90%. The multi-level channel system can be actively designed through 3D printing, rather than passively relying on the porosity of the raw materials themselves. Furthermore, the core materials for preparing the 3D-printed rigid-flexible three-dimensional porous carbon framework and silicon-carbon composite anode material are inexpensive, and the 3D printing process is also conducive to continuous and intelligent production.

[0025] To address the shortcomings of existing technologies, this invention provides a 3D-printed rigid-flexible three-dimensional porous carbon framework, a silicon-carbon composite anode material, its preparation method, and a lithium-ion battery. The 3D-printed rigid-flexible three-dimensional porous carbon framework not only provides sufficient buffer space for silicon expansion but also possesses excellent electrical conductivity, thermal conductivity, and high mechanical strength. The silicon-carbon composite anode material exhibits high capacity retention and high initial coulombic efficiency.

[0026] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a 3D printed rigid-flexible three-dimensional porous carbon skeleton, comprising a rigid carbon component, a silane coupling agent modified flexible carbon component, and a resin carbon bonding phase that bonds the rigid carbon component and the flexible carbon component together. The rigid carbon component is used to provide rigid support and a stable structure, and the flexible carbon component is used to provide flexible buffering and high conductivity.

[0027] In one possible implementation, the flexible carbon component comprises expanded graphite.

[0028] In one possible implementation, the silane coupling agent is selected from one or more of aminosilanes, epoxysilanes, vinylsilanes, methacryloxysilanes, and ureosilanes.

[0029] In one possible implementation, the rigid carbon component includes one or more of coke-based carbon, biomass-based carbon, resin-based carbon, and sugar-based carbon.

[0030] Furthermore, the coke-type carbon is selected from one or more of petroleum coke, needle coke, and pitch coke; the biomass-based carbon is obtained by high-temperature pyrolysis of starch, cellulose, coconut shell, bagasse, or mixtures thereof; the resin-based carbon is obtained by carbonization of phenolic resin and / or epoxy resin; and the sugar-type carbon is obtained by carbonization of glucose, sucrose, maltose, or mixtures thereof.

[0031] In one possible implementation, the resin carbon binder phase is formed by carbonizing phenolic resin, epoxy resin, furan resin, or a mixture thereof.

[0032] In one possible implementation, the mass ratio of the flexible carbon component to the rigid carbon component is (1-9):(1-9).

[0033] In one possible implementation, the three-dimensional porous carbon framework has a hierarchical pore structure designed by a 3D printing program, the hierarchical pore structure including macropores with a diameter >50 nm, mesopores with a diameter of 2-50 nm and micropores with a diameter <2 nm, the macropores being used for rapid transport of ions in the electrolyte, the mesopores being used for wetting the electrolyte, and the micropores being used to provide a high specific surface area.

[0034] Secondly, the present invention provides a silicon-carbon composite anode material, comprising: The above-mentioned 3D printed rigid-flexible three-dimensional porous carbon framework; Nano-silicon particles, selectively loaded onto the flexible carbon component, are used for charge-discharge cycle storage of lithium ions; An amorphous carbon layer is coated on the outer surface of the nano-silicon particles and the three-dimensional porous carbon framework to stabilize the electrode interface of the silicon-carbon anode material and optimize its electrochemical performance.

[0035] In one possible implementation, the mass percentage of the nano-carbon particles in the silicon-carbon composite anode material is 5-40 wt.%.

[0036] Thirdly, the present invention provides a method for preparing the above-mentioned silicon-carbon composite anode material, comprising the following steps: S1. Surface modification: The flexible carbon component is surface modified by using a silane coupling agent to obtain a surface-modified flexible carbon component. S2. Composite: The surface-modified flexible carbon component and the rigid carbon component are mixed evenly to obtain a composite carbon source; S3, 3D printing: Based on the preset three-dimensional model, the composite carbon source and resin binder described in step S2 are 3D printed into a green body with a multi-level pore structure. S4. Curing and Carbonization: The green body described in step S3 is subjected to a step-by-step heat treatment. The step-by-step heat treatment first crosslinks the resin binder through curing, and then converts the resin binder into a resin carbon binder phase through carbonization treatment under an inert atmosphere, thereby obtaining a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon skeleton described in step S4 is placed in a chemical vapor deposition reactor, and a silane gas source is introduced. The silane gas source generates nano-silicon particles through chemical vapor reaction. The nano-silicon particles are selectively deposited on the surface-modified flexible carbon component of the three-dimensional porous carbon skeleton to obtain a three-dimensional porous carbon skeleton loaded with nano-silicon particles. S6. Carbon coating: Replace the silane gas source in step S5 with a hydrocarbon gas source for chemical vapor deposition. An amorphous carbon layer is formed on the surface of the three-dimensional porous carbon skeleton with loaded silicon nanoparticles obtained in step S5, thus obtaining a silicon-carbon composite anode material.

[0037] In one possible implementation, the mass ratio of the silane coupling agent to the flexible carbon component in step S1 is (1-5):100, the surface modification treatment is carried out in a mixed solution of ethanol and water at 60-80 °C, and the surface modification treatment time is 2-4 h.

[0038] In one possible implementation, the 3D printing method in step S3 is direct-write printing. The direct-write printing process includes: mixing the composite carbon source in step S2 with resin binder, solvent and dispersant and grinding them to make printing ink. The resin binder has a mass percentage content of 5-30 wt.% in the printing ink. Then, the printing ink is printed into a green body with a multi-level channel structure according to a preset three-dimensional model.

[0039] In one possible implementation, the 3D printing method in step S3 is binder jet printing. The binder jet printing process includes: jetting resin binder onto the composite carbon source in step S2, and 3D printing a green body with a multi-level pore structure. The resin binder has a mass percentage content of 2-15 wt.% in the green body.

[0040] In one possible implementation, the curing temperature in step S4 is 150-200 °C, and the carbonization temperature is 800-1100 °C.

[0041] In one possible implementation, the temperature of the chemical vapor phase reaction in step S5 is 550-650 °C and the time is 1-4 h. The silane gas source is a mixture of silane and inert gas, and the volume percentage of silane in the mixture is 10%-20%.

[0042] Fourthly, the present invention provides a lithium-ion battery in which the negative electrode material is the aforementioned silicon-carbon composite negative electrode material.

[0043] The positive and progressive effects of this invention are as follows: This invention provides a 3D-printed rigid-flexible three-dimensional porous carbon framework, a silicon-carbon composite anode material, its preparation method, and a lithium-ion battery. The 3D-printed rigid-flexible three-dimensional porous carbon framework, through multi-dimensional synergy of rigid support, flexible buffering, interface anchoring, and structural design, can provide sufficient buffer space for silicon expansion, while also possessing high electrical conductivity, high thermal conductivity, and high mechanical strength. The silicon-carbon composite anode material selectively loads nano-silicon particles onto the aforementioned 3D-printed rigid-flexible three-dimensional porous carbon framework. These nano-silicon particles are chemically bonded to a highly elastic and highly buffered flexible carbon component, reducing the damage to the silicon-carbon anode material caused by nano-silicon particle expansion while significantly improving the retention rate of nano-silicon particles after multiple cycles. This allows the silicon-carbon composite anode material to withstand repeated cycles. Even after 1500 cycles, the silicon-carbon composite anode material retains a high capacity. The synergistic effect of "selective deposition" and "3D printing of a rigid-flexible three-dimensional porous carbon framework" enables the capacity retention rate to exceed 80%. Combined with the coating of amorphous carbon layers, the initial coulombic efficiency and capacity retention rate of the silicon-carbon composite anode material are further improved. The chemical anchoring of the silane coupling agent and the carbon coating together ensure a stable interface, increasing the initial coulombic efficiency of the silicon-carbon composite anode material to over 90%. The multi-level channel system can be actively designed through 3D printing, rather than passively relying on the porosity of the raw materials themselves. Furthermore, the core materials for preparing the 3D-printed rigid-flexible three-dimensional porous carbon framework and silicon-carbon composite anode material are inexpensive, and the 3D printing process is also conducive to continuous and intelligent production. Detailed Implementation

[0044] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0045] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0046] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0047] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a 3D printed rigid-flexible three-dimensional porous carbon skeleton, comprising a rigid carbon component, a silane coupling agent modified flexible carbon component, and a resin carbon bonding phase that bonds the rigid carbon component and the flexible carbon component together. The rigid carbon component is used to provide rigid support and a stable structure, and the flexible carbon component is used to provide flexible buffering and high conductivity.

[0048] This invention provides a 3D printed rigid-flexible three-dimensional porous carbon skeleton that, through the multi-dimensional synergy of rigid support, flexible buffering, interface anchoring, and structural design, can provide sufficient buffer space for silicon expansion while taking into account high electrical conductivity, high thermal conductivity, and high mechanical strength.

[0049] The rigid carbon component possesses high strength and low ductility, forming a three-dimensional continuous rigid framework through a resin-carbon binder phase. This framework serves as the load-bearing structure of the entire material, limiting excessive deformation of the flexible carbon component during silicon expansion and preventing overall structural collapse. Furthermore, its stable rigid structure allows for the division of independent expansion units, confining the volume expansion of silicon to localized areas and preventing overall cracking caused by the diffusion of expansion stress. Simultaneously, the high structural stability of the rigid carbon component ensures that the three-dimensional porous carbon skeleton maintains its macroscopic morphology integrity during long-term cycles of repeated silicon expansion and contraction, providing boundary protection for the buffer space.

[0050] The flexible carbon component modified with a silane coupling agent exhibits excellent flexibility and compressibility, absorbing stress generated by silicon expansion through its own deformation. When nano-silicon undergoes volume expansion exceeding 300% during charging and discharging, the flexible carbon component can increase in size along with the silicon expansion, undergoing controllable deformation under the constraint of a rigid framework. This converts the expansion stress into its own elastic potential energy, preventing material pulverization caused by stress concentration. The resin-carbon binder phase tightly connects the rigid and flexible carbon components, forming a rigid-flexible interlocking structure. The general molecular formula of the silane coupling agent is YR-Si(OR')3, where Y is an organic functional group, such as amino or vinyl, and -OR' is a siloxane alkyl group. In the silane coupling agent-modified flexible carbon component, the silane coupling agent bonds with the flexible carbon component through organic functional groups, resulting in a large number of siloxane alkyl groups modifying the surface of the flexible carbon component. These siloxane groups can serve as active sites for silicon nucleation, allowing silicon to be selectively loaded onto the flexible carbon component.

[0051] The precision of 3D printing ensures a uniform distribution of porous structures on a macroscopic scale, avoiding localized stress concentrations caused by random pore distribution in traditional fabrication methods. When silicon expands in volume, stress is evenly dispersed through the uniform pore structure, with each buffer unit bearing similar expansion pressure, significantly reducing the probability of local structural damage. Furthermore, the high conductivity of the flexible carbon component ensures efficient electron transport within the three-dimensional porous carbon framework during expansion / contraction. The rigid carbon component acts as a framework support, reducing the breakage of the conductive network caused by excessive deformation of the flexible carbon; the resin carbon binder, after high-temperature carbonization, possesses a certain degree of conductivity, filling the conductive gaps between the rigid and flexible components, forming a three-dimensional conductive network of "flexible carbon as the main component, rigid carbon as a supplement, and resin carbon as a complete component," ensuring high conductivity of the carbon framework. The flexible carbon component has excellent thermal conductivity, rapidly transferring heat generated during charging and discharging to the rigid framework; the rigid carbon component acts as a "dispersion channel" for heat conduction, evenly dissipating heat and preventing localized overheating; the interconnected channels of 3D printing allow electrolyte flow, further optimizing thermal conductivity through convection-assisted heat dissipation. In summary, the rigid carbon component in the silicon-carbon composite anode material determines the structure and maintains strength, while the flexible carbon component absorbs stress and conducts electrical / thermal energy. The resin-carbon bonding phase strengthens the interface and fills the pathways, and the nano-silicon selectively loads and controls the stress source. 3D printing precisely constructs a complex three-dimensional porous carbon framework. This multi-dimensional synergy not only provides multi-level buffering for silicon expansion but also, through matching component properties with structural design, balances electrical conductivity, thermal conductivity, and mechanical strength, solving the problem of expansion suppression and performance balance in traditional silicon-carbon materials.

[0052] In one possible implementation, the flexible carbon component includes expanded graphite. The abundant micropores and mesopores within expanded graphite serve as buffer cavities for silicon expansion, expanding synchronously with the increase in silicon particle volume, reducing compression on the macroscopic structure of the carbon framework. The interlayer van der Waals forces of expanded graphite give it excellent elastic recovery capabilities, allowing it to repeatedly deform without easily undergoing plastic fracture during the expansion and contraction of silicon particles during charge-discharge cycles, maintaining its buffering function over a long period; after 1500 cycles, the deformation recovery rate can still reach over 80%. Expanded graphite, prepared from natural graphite through intercalation and high-temperature expansion, has advantages over flexible carbon materials such as carbon nanotubes and graphene in terms of low raw material cost and simple preparation process, significantly reducing the large-scale production cost of silicon-carbon composite anode materials.

[0053] In one possible implementation, the silane coupling agent is selected from one or more of aminosilanes, epoxysilanes, vinylsilanes, methacryloxysilanes, and ureosilanes. All of the above silane coupling agents possess hydrolyzable siloxane groups -Si(OR')3 and specific organic functional groups, enabling them to form stable chemical bonds with active sites (such as hydroxyl and carboxyl groups) on the surface of flexible carbon components. The amino group of aminosilane can undergo acid-base neutralization or condensation reactions with the carboxyl groups on the surface of expanded graphite to form stable amide bonds (-CONH-). The epoxy group of epoxysilane can undergo ring-opening reactions with the hydroxyl or amino groups (if introduced through pretreatment) on the surface of expanded graphite to form ether bonds or CN bonds. The reaction conditions are mild, and the reaction can be carried out efficiently at 60-80 °C, with excellent product stability. The unsaturated double bonds of vinylsilane and methacryloxysilane can combine with the unsaturated bonds on the surface of flexible carbon components (such as carbon-carbon double bonds at the edge of expanded graphite) through free radical polymerization or thermally initiated reactions. This is especially suitable for systems that require subsequent high-temperature treatment (such as carbonization), and the bond strength becomes more stable with increasing temperature. The urea group (-NH-CO-NH-) of ureosilane has strong polarity and can form multiple interactions with the hydroxyl groups on the surface of flexible carbon components through hydrogen bonds. At the same time, the high reactivity of the urea group allows for uniform modification at low dosages, avoiding the deterioration of the performance of flexible carbon components due to excessive coupling agent.

[0054] In one possible implementation, the rigid carbon component includes one or more of coke-based carbon, biomass-based carbon, resin-based carbon, and sugar-based carbon. Coke-based carbon has a high tendency to graphitize, forming an ordered layered structure after carbonization. It has high mechanical strength and excellent electrical conductivity, and can serve as the load-bearing core of a rigid framework to resist the stress generated by silicon expansion and prevent the overall structure from collapsing. Biomass-based carbon (such as lignin and straw-derived carbon) has a naturally rich three-dimensional porous structure. After carbonization, it retains a large number of interconnected channels, which can provide additional macroscopic buffer space for silicon expansion. At the same time, its irregular carbon framework can disperse stress through multi-directional support, compensating for the high brittleness of coke-based carbon. Resin-based carbon forms an amorphous carbon network after carbonization, with strong interfacial bonding with the flexible carbon component, improving the overall fatigue resistance of the framework. Sugar-based carbon easily forms a microporous-mesoporous composite structure during carbonization, with a high specific surface area. It can help stabilize the SEI film through surface adsorption. At the same time, its low crystallinity can reduce the difference in expansion coefficient with flexible carbon, reducing interfacial stress.

[0055] Furthermore, the coke-type carbon is selected from one or more of petroleum coke, needle coke, and pitch coke; the biomass-based carbon is obtained by high-temperature pyrolysis of starch, cellulose, coconut shell, bagasse, or mixtures thereof; the resin-based carbon is obtained by carbonization of phenolic resin and / or epoxy resin; and the sugar-type carbon is obtained by carbonization of glucose, sucrose, maltose, or mixtures thereof. Petroleum coke, as a byproduct of petroleum refining, has extremely low raw material costs and high mechanical strength, making it suitable as a basic load-bearing unit for rigid frames and widely adaptable to scenarios with different silicon loading. Needle coke has a highly oriented fibrous structure with a higher degree of graphitization (graphitization degree >80%) and a thermal conductivity of 50-80 W / (m·K), which can quickly dissipate the heat generated by silicon reactions during charging and discharging, avoiding local overheating, and is especially suitable for high-rate battery scenarios. Pitch coke is made by carbonizing coal pitch or petroleum pitch. The powder particles have regular morphology and good flowability. When mixed with flexible carbon components, it is easy to form a uniform system, which can improve the density uniformity of 3D printed green bodies and reduce porosity defects in the carbonized frame. Petroleum coke, needle coke, and pitch coke can be used alone or in combination, balancing cost and strength while allowing for flexible adjustment of electrical and thermal conductivity to meet customized development needs for different performance requirements. Starch, cellulose, coconut shells, and bagasse are all agricultural / forestry wastes or bulk agricultural products that can be directly pyrolyzed without complex pretreatment. The production process produces no highly toxic byproducts, and the raw material cost is only 1 / 2 to 1 / 3 of that of petroleum coke, significantly reducing industrialization costs. Furthermore, biomass-based carbon surfaces are rich in polar groups such as hydroxyl and carboxyl groups, resulting in strong interfacial bonding with resin carbon adhesive phases, reducing the risk of interfacial delamination between rigid skeletons and flexible carbon components. Phenolic resins and epoxy resins form dense amorphous carbon networks during carbonization, and their bonding with flexible carbon is a molecular-level carbon-carbon bond, which helps improve the flexural strength of the skeleton. Sugar carbon obtained from the carbonization of glucose, sucrose, and malt is rich in active groups such as hydroxyl and aldehyde groups, which can form hydrogen bonds with silane coupling agent-modified flexible carbon components and simultaneously adsorb Li in the electrolyte. + It helps stabilize the SEI film and reduces side reactions between silicon particles and electrolyte.

[0056] In one possible embodiment, the resin-carbon binder phase is formed by carbonizing phenolic resin, epoxy resin, furan resin, or a mixture thereof. Phenolic resin, epoxy resin, and furan resin are all polar organic compounds that can tightly bond with the surfaces of rigid and flexible carbon through van der Waals forces or hydrogen bonds, and are easily and uniformly dispersed during powdering or extrusion. After carbonization, phenolic resin generates a carbon network rich in cross-linked structures, forming C-C covalent bonds with the carbon skeleton of rigid / flexible carbon, significantly improving the interfacial shear strength, which is far higher than that of traditionally physically mixed carbon materials. After carbonization, epoxy resin retains some ether bonds (-O-), which can form hydrogen bonds with the hydroxyl groups (-OH) on the surface of flexible carbon to assist in bonding, enhancing the connection stability between flexible carbon and the rigid framework. After carbonization, furan resin forms a dense carbon layer with a high residual carbon content, which can fill the micron-level gaps between rigid and flexible carbon, reducing interfacial porosity and improving the overall structural density.

[0057] In one possible implementation, the mass ratio of the flexible carbon component to the rigid carbon component is (1-9):(1-9). The core function of the flexible carbon component is to buffer silicon expansion, while the core function of the rigid carbon component is to provide structural support. Limiting the mass ratio of the flexible carbon component to the rigid carbon component to (1-9):(1-9) adapts to different application scenarios. A high flexibility ratio is suitable for high silicon load scenarios: when the silicon load is 25-40 wt.%, the volume change of silicon caused by charge-discharge cycles is drastic, requiring more flexible carbon component to absorb expansion / contraction stress. The buffer space of the high-component flexible carbon can accommodate the volume change of silicon in high-silicon load scenarios, while the rigid carbon can still form a continuous framework, preventing structural collapse caused by excessive deformation of the flexible carbon. A medium-component flexible carbon ratio is suitable for medium silicon load balance scenarios: when the silicon load is 15-25 wt.%, the flexible carbon can buffer the volume change of silicon in high-silicon load scenarios. When the mass ratio of flexible carbon component to rigid carbon component is (4-6):(4-6), the flexible carbon can buffer silicon expansion through local deformation, while the rigid carbon can avoid overall deformation through framework constraint. The two work together to enable the material to have both high capacity and high capacity retention rate, while the mechanical strength and conductivity are both at an excellent level. The low proportion of flexible carbon is suitable for low silicon load and high stability scenarios: when the silicon load is 5-15 wt.%, a large amount of flexible carbon is not required for buffering, and the high rigidity ratio can further improve the structural stability and mechanical strength of the material.

[0058] In one possible implementation, the three-dimensional porous carbon framework has a hierarchical pore structure designed by a 3D printing program. This hierarchical pore structure includes macropores with a diameter >50 nm, mesopores with a diameter of 2-50 nm, and micropores with a diameter <2 nm. The macropores are used for rapid transport of ions in the electrolyte, the mesopores are used for wetting the electrolyte, and the micropores are used to provide a high specific surface area. The macropores with a diameter >50 nm are mostly interconnected channels distributed within the framework gaps of the rigid carbon components. These macropores can serve as high-speed channels for lithium ions inside the electrode, significantly shortening the ion transport distance and reducing ion diffusion resistance. The pore size of the mesopores (2-50 nm) is adapted to the size of the electrolyte molecules, enabling sufficient filling and rapid penetration of the electrolyte, ensuring that each silicon particle is encapsulated by the electrolyte. The high specific surface area of ​​the micropores can temporarily store some lithium ions through physical adsorption, gradually releasing them during discharge, thus supplementing capacity. Simultaneously, the adsorption of lithium ions by the micropores can reduce the free lithium ions in the electrolyte. i+ This reduces consumption and further improves cycle stability.

[0059] Secondly, the present invention provides a silicon-carbon composite anode material, comprising: The above-mentioned 3D printed rigid-flexible three-dimensional porous carbon framework; Nano-silicon particles, selectively loaded onto the flexible carbon component, are used for charge-discharge cycle storage of lithium ions; An amorphous carbon layer is coated on the outer surface of the nano-silicon particles and the three-dimensional porous carbon framework to stabilize the electrode interface of the silicon-carbon anode material and optimize its electrochemical performance.

[0060] The silicon-carbon composite anode material provided by this invention selectively loads nano-silicon particles onto the aforementioned rigid-flexible synergistic carbon skeleton. This allows the nano-silicon particles to be primarily loaded onto a highly elastic and buffered flexible carbon component, concentrating the expansion stress of the nano-silicon particles in the buffered flexible region. This reduces the adhesion of nano-silicon particles to the relatively brittle rigid region (rigid carbon component + resin carbon binder phase). The deformation capability of the flexible carbon component can "actively adapt" to the volume changes of the nano-silicon particles, preventing the rigid component from directly bearing the expansion stress. This reduces the damage to the silicon-carbon anode material caused by the expansion of nano-silicon particles while ensuring the long-term cycling stability of the overall structure. Furthermore, the chemical bonds formed by the silane coupling agent on the surface of the flexible carbon component firmly anchor the nano-silicon particles, preventing particle detachment or separation from the carbon skeleton even during drastic silicon volume changes. This significantly improves the retention rate of nano-silicon particles after multiple cycles, enabling the silicon-carbon composite anode material to maintain a high capacity even after repeated cycles. Nano-silicon has extremely high surface activity, making it prone to side reactions with the electrolyte to form an unstable SEI film. This consumes a large amount of lithium ions and electrolyte, resulting in low initial coulombic efficiency and rapid capacity decay in silicon-carbon composite anode materials. An amorphous carbon layer can completely cover the active sites on the silicon surface, preventing direct contact between silicon and the electrolyte and reducing the rate of side reactions. Simultaneously, the carbon layer itself reacts with the electrolyte to form a more stable and denser SEI film, which is less prone to cracking due to silicon expansion. The flexibility of the amorphous carbon layer allows it to deform synchronously with the expansion / contraction of silicon, preventing cracks in the SEI film due to silicon volume changes. Coating with an amorphous carbon layer further improves the initial coulombic efficiency and capacity retention of silicon-carbon anode materials. The synergistic effect of the rigid-flexible carbon framework, nano-silicon particles, and amorphous carbon layer enables silicon-carbon composite anode materials to possess high capacity retention and high initial coulombic efficiency.

[0061] In one possible implementation, the mass percentage of the nano-carbon particles in the silicon-carbon composite anode material is 5-40 wt.%. The mass percentage of nano-silicon particles directly determines the specific capacity of the silicon-carbon composite anode, and the range of 5-40 wt.% can flexibly adapt to the needs of different application scenarios. Within the low silicon content range of 5-15 wt.%, the buffer space of the flexible carbon component and the constraint of the rigid carbon skeleton can easily accommodate expansion, significantly extending the cycle life of the material and making it suitable for scenarios requiring high cycle stability. Within the medium silicon content range of 15-25 wt.%, the specific capacity contributed by silicon and the capacity of the carbon skeleton, when combined, result in a total specific capacity of 1100-1700 mAh / g. At the same time, the volume expansion of silicon can be completely suppressed by the synergistic buffering of multi-level channels and flexible carbon, making it suitable for scenarios requiring a balance between capacity and cycle life. Within the high silicon content range of 25-40 wt.%, the specific capacity contributed by silicon accounts for more than 60%, and the total specific capacity of the material can reach 1700-2500 mAh / g, which can significantly improve the battery energy density and is suitable for scenarios with extreme energy density requirements.

[0062] Thirdly, the present invention provides a method for preparing the above-mentioned silicon-carbon composite anode material, comprising the following steps: S1. Surface modification: The flexible carbon component is surface modified by using a silane coupling agent to obtain a surface-modified flexible carbon component. In step S1, the silane coupling agent forms a chemical bond on the surface of the flexible carbon component, that is, the Y group in YR-Si (OR')3 reacts with the hydroxyl group on the carbon surface, introducing active sites for the nucleation of nano-silicon, and realizing the differentiated modification of the flexible carbon component. Compared with the unmodified rigid carbon component, the modified flexible carbon surface can significantly reduce the nucleation energy barrier of nano-silicon. S2. Composite: The surface-modified flexible carbon component and the rigid carbon component are mixed evenly to obtain a composite carbon source; In step S2, the modified flexible carbon and rigid carbon components are mixed evenly to form a composite carbon source. The rigid carbon component is used to provide rigid support and a stable structure, while the flexible carbon component is used to provide flexible buffering and high conductivity. S3, 3D printing: Based on the preset three-dimensional model, the composite carbon source and resin binder described in step S2 are 3D printed into a green body with a multi-level pore structure. In step S3, a three-dimensional model is preset through the 3D printing program according to the battery performance requirements, which can precisely control the pore structure of the printed blank. S4. Curing and Carbonization: The green body described in step S3 is subjected to a step-by-step heat treatment. The step-by-step heat treatment first crosslinks the resin binder through curing, and then converts the resin binder into a resin carbon binder phase through carbonization treatment under an inert atmosphere, thereby obtaining a 3D printed rigid-flexible three-dimensional porous carbon skeleton. In step S4, a step-by-step heat treatment process is adopted. First, the resin binder is cross-linked through curing, providing a complete structural basis for subsequent carbonization. Then, carbonization is carried out under argon or nitrogen protection, which can completely transform the resin binder into an amorphous resin carbon binder phase, allowing it to form molecular-level carbon-carbon bonds with the rigid and flexible carbon components. S5. In-situ selective deposition: The three-dimensional porous carbon skeleton described in step S4 is placed in a chemical vapor deposition reactor, and a silane gas source is introduced. The silane gas source generates nano-silicon particles through chemical vapor reaction. The nano-silicon particles are selectively deposited on the surface-modified flexible carbon component of the three-dimensional porous carbon skeleton to obtain a three-dimensional porous carbon skeleton loaded with nano-silicon particles. In step S5, the active sites of the silane coupling agent on the modified flexible carbon surface can guide the preferential deposition of nano-silicon particles generated by the decomposition of silane gas source, so that the volume expansion of silicon is concentrated in the buffer space of the flexible carbon component. The nano-silicon particles are tightly bound to the flexible carbon through the Si-O-Si chemical bonds of the silane coupling agent, reducing the silicon particle shedding rate. S6. Carbon coating: Replace the silane gas source in step S5 with a hydrocarbon gas source for chemical vapor deposition. An amorphous carbon layer is formed on the surface of the three-dimensional porous carbon skeleton with loaded nano-silicon particles obtained in step S5, and a 3D printed rigid-flexible silicon-carbon composite anode material is obtained. In step S6, by replacing the gas source of the chemical vapor phase reaction with hydrocarbons, a dense amorphous carbon layer can be formed on the surface of the three-dimensional porous carbon framework loaded with nano-silicon particles, which can stabilize the electrode interface of the silicon-carbon anode material and optimize its electrochemical performance.

[0063] The above preparation method, through the process design of "interface modification-composite-3D printing-curing carbonization-in-situ deposition-carbon coating", deeply binds the functional requirements of the material with the process characteristics, which not only realizes the precise construction of rigid-flexible synergistic structure and selective loading of nano-silicon, but also ensures the stability of material performance and industrialization feasibility.

[0064] In one possible implementation, the mass ratio of the silane coupling agent to the flexible carbon component in step S1 is (1-5):100. The surface modification treatment is carried out in a mixed solution of ethanol and water at 60-80 °C for 2-4 h. Limiting the mass ratio of the silane coupling agent to the flexible carbon component to (1-5):100 ensures sufficient active sites are formed on the surface of the flexible carbon component, guiding the preferential deposition of nano-silicon particles onto the flexible carbon surface. Simultaneously, it controls the cost of the coupling agent, balancing performance and economy, which is beneficial for large-scale production. The silane coupling agent must first undergo hydrolysis via the -Si(OR')3 group to generate silanol groups (-SiOH) before it can undergo a condensation reaction with the hydroxyl groups on the flexible carbon surface. In a pure water environment, the hydrolysis rate of the coupling agent is too fast, easily forming siloxane oligomer agglomerates; in a pure ethanol environment, the hydrolysis rate is too slow, significantly prolonging the reaction cycle. The ethanol / water mixture solution allows for precise control of the hydrolysis rate by adjusting the ratio, ensuring that the coupling agent molecules are uniformly dispersed in the solution in a monomolecular hydrolyzed state, preventing aggregation and ensuring that the surface of each flexible carbon particle can contact the coupling agent, resulting in high modification uniformity. At a temperature of 60-80 ℃, the activation energy of the hydrolysis reaction of the silane coupling agent is fully excited, resulting in a high hydrolysis rate of the coupling agent, which can complete the bonding with the surface of the flexible carbon within 2-4 h.

[0065] In one possible implementation, the 3D printing method in step S3 is direct-write printing. The direct-write printing process includes: mixing the composite carbon source from step S2 with a resin binder, solvent, and dispersant, and then grinding the mixture to prepare printing ink. The resin binder has a mass percentage content of 5-30 wt.% in the printing ink. The printing ink is then printed into a green body with a multi-level pore structure according to a preset three-dimensional model. Mixing and grinding the composite carbon source with the resin binder, solvent, and dispersant to prepare a printing ink suitable for 3D printing, the printing ink contains solid particles such as rigid carbon and flexible carbon. Direct-write printing is compatible with high solid content systems, reducing volume shrinkage during subsequent curing and carbonization processes, preventing green body cracking or pore collapse, and ensuring the integrity of the carbon skeleton structure. Limiting the mass percentage content of the resin binder to 5-30 wt.% allows the binder to form a continuous bonding network between solid particles, resulting in high flexural strength in the green body. This allows it to withstand mechanical stress during transfer and stacking, and maintains pore structure stability before curing, which helps improve the green body yield.

[0066] In one possible implementation, the 3D printing method in step S3 is binder jet printing. The binder jet printing process includes: jetting resin binder onto the composite carbon source described in step S2, and 3D printing a green body with a multi-level pore structure. The resin binder content in the green body is 2-15 wt.%. Binder jet printing, through an additive manufacturing method of "powder spreading-selective binder jetting," allows for precise control of the pore structure through on-demand jetting and is compatible with the dry powder characteristics of composite carbon sources formed by mixing rigid and flexible carbon. Its advantages lie in the controllability of the pores and material compatibility. The content of the resin binder directly determines the quality of the green body and the performance of the carbon skeleton after carbonization. When the resin binder content is in the range of 2-15 wt.%, the binder can form point-like bonds at the particle contact points, giving the green body sufficient strength to withstand the mechanical stress of powder cleaning and stacking transfer, while maintaining the preset pore structure, resulting in a high green body yield.

[0067] In one possible implementation, the curing temperature in step S4 is 150-200 ℃, and the carbonization temperature is 800-1100 ℃. When the curing temperature is 150-200 ℃, the resin crosslinking reaction is mild and controllable, and the volatiles are released slowly, which can avoid the rapid shrinkage of the green body volume caused by the rapid escape of volatiles. When the carbonization temperature is 800-1100 ℃, the resin is completely pyrolyzed, and the generated amorphous resin carbon is tightly combined with rigid carbon and flexible carbon through carbon-carbon bonds. It fills the surface defects of rigid carbon and penetrates into the interlayer gaps of flexible carbon, forming a "rigid-flexible interlocking" skeleton structure. The carbon skeleton has high flexural strength and can withstand the stress generated by silicon expansion without cracking.

[0068] In one possible implementation, the chemical vapor phase reaction in step S5 is carried out at a temperature of 550-650 °C for 1-4 h. The silane gas source is a mixture of silane and an inert gas, with the volume percentage of silane in the mixture being 10%-20%. At 550-650 °C, on the one hand, silane can be efficiently decomposed into silicon free radicals (Si・) and hydrogen, providing sufficient active silicon for the deposition of nano-silicon particles. On the other hand, the growth rate and diffusion rate of silicon atoms at the active sites on the flexible carbon component surface are balanced, resulting in the formation of nano-silicon particles with uniform particle size. The reaction time of 1-4 h can be adjusted by modifying the deposition time to flexibly control the loading of nano-silicon on the flexible carbon surface, matching the needs of different application scenarios.

[0069] Fourthly, the present invention provides a lithium-ion battery in which the negative electrode material is the aforementioned silicon-carbon composite negative electrode material.

[0070] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0071] Example 1

[0072] This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding petroleum coke powder and expanded graphite modified with aminosilane (KH-550) through a resin-carbon binder phase. Petroleum coke powder provides rigid support and structural stability, while expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 1:9. The resin-carbon binder phase is formed by carbonizing phenolic resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 5%.

[0073] The method for preparing silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 10 g of expanded graphite was dispersed in a mixed solution of 200 mL of ethanol and water with a volume ratio of ethanol to water of 9:1. Then, 0.3 g of KH-550 was added, and the mixture was stirred at 75 °C for 3 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2, Composite: The surface-modified expanded graphite obtained in step S1 is added to 90 g of petroleum coke powder (D50=5 μm) and mixed in a high-speed mixer at a speed of 1500 r / min for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D Printing: The composite carbon source obtained in step S2 is added to a ball mill along with 30 g of phenolic resin, 500 mL of ethanol, 1 g of polyethylene glycol, 5 g of hydroxypropyl methylcellulose, and 2 g of glycerol. The ball-to-material ratio is controlled at 5:1, the ball mill speed is 300 r / min, and the milling is carried out for 4 h to produce printing ink. A direct-write 3D printer is used to print the printing ink into a green body with a cross-grid macroporous structure according to the preset cross-grid model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 100 ℃ at a heating rate of 2 ℃ / min and held for 1.5 h to remove the solvent. Then, it is heated to 180 ℃ and held for 3 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 100 mL / min. The temperature is increased to 1000 ℃ at 2 ℃ / min and held for 2 h for carbonization. It is then naturally cooled to room temperature to obtain a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon framework obtained in step S4 is placed in a chemical vapor reactor, and a mixture of silane and argon is introduced. The volume concentration of silane in the mixture is 10%, and the total flow rate of the mixture is set to 50 mL / min. The temperature is raised to 650 °C and held for 1 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After the deposition is completed, the introduction of silane is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon particles is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to acetylene. The acetylene flow rate is 50 mL / min. The temperature is increased to 800 ℃ at a heating rate of 3 ℃ / min and held for 1 h. After the coating is completed, the gas supply is stopped and the material is cooled to room temperature to obtain silicon-carbon composite anode material.

[0074] Example 2

[0075] This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding expanded graphite modified with petroleum coke powder and epoxy silane (KH-560) through a resin-carbon binder phase. Petroleum coke powder provides rigid support and structural stability, while expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 1:4. The resin-carbon binder phase is formed by carbonizing phenolic resin and epoxy resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 10%.

[0076] The method for preparing silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 20 g of expanded graphite was dispersed in a mixed solution of 200 mL of ethanol and water, with a volume ratio of ethanol to water of 8.5:1.5. Then, 0.4 g of KH-560 was added, and the mixture was stirred at 70 °C for 2.5 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2. Composite: The surface-modified expanded graphite obtained in step S1 is added to 80 g of petroleum coke powder (D50=8 μm) and mixed in a high-speed mixer at a speed of 1500 r / min for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D Printing: The composite carbon source obtained in step S2 is added to a ball mill along with 15 g of phenolic resin, 10 g of epoxy resin, 450 mL of ethanol, and 0.8 g of sodium dialkylbenzene sulfonate. The ball-to-material ratio is controlled at 5:1, the ball mill speed is 300 r / min, and the milling is carried out for 4 hours to produce printing ink. A direct-write 3D printer is used to print the printing ink into a green body with a cross-grid macroporous structure according to the preset cross-grid model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 90 ℃ at a heating rate of 1.5 ℃ / min and held for 2 h to remove the solvent. Then, it is heated to 170 ℃ and held for 3.5 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 80 mL / min. The temperature is increased to 950 ℃ at 2 ℃ / min and held for 2.5 h for carbonization. It is then naturally cooled to room temperature to obtain a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon framework prepared in the procedure book is placed in a chemical vapor reactor. A mixture of silane and argon is introduced, with a silane volume concentration of 12% and a total flow rate of 70 mL / min. The temperature is raised to 620 °C and held for 2.5 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After deposition, the silane supply is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon particles is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to methane, with a methane flow rate of 60 mL / min. The temperature is increased to 750 °C at a heating rate of 3 °C / min and held for 1 h. After coating, the gas supply is stopped and the material is cooled to room temperature to obtain silicon-carbon composite anode material.

[0077] Example 3

[0078] This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding resin-based carbon and expanded graphite modified with methacryloyloxysilane (KH-570) through a resin-carbon binder phase. The resin-based carbon provides rigid support and structural stability, while the expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 3:7. The resin-carbon binder phase is formed by carbonizing phenolic resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 40%.

[0079] The method for preparing silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 30 g of expanded graphite was dispersed in a mixed solution of 400 mL of ethanol and water with a volume ratio of ethanol to water of 9.5:0.5. Then, 1.2 g of KH-570 was added, and the mixture was stirred at 80 °C for 4 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2. Composite: The surface-modified expanded graphite obtained in step S1 and the resin-based carbon (D50=3 μm) obtained by carbonizing 70 g of phenolic resin were added to a high-speed mixer and mixed. The speed of the high-speed mixer was 1500 r / min and the mixture was mixed for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D printing: The composite carbon source obtained in step S2 is added to a ball mill along with 35 g of phenolic resin, 550 mL of ethanol and 1.2 g of polyvinylpyrrolidone. The ball-to-material ratio is controlled at 5:1, the ball mill speed is 300 r / min, and the milling is carried out for 4 h to produce printing ink. A direct-write 3D printer is used to print the printing ink into a green body with a cross-grid macroporous structure according to the preset cross-grid model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 110 ℃ at a heating rate of 1.5 ℃ / min and held for 1 h to remove the solvent. Then, it is heated to 190 ℃ and held for 2.5 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 120 mL / min. The temperature is increased to 1050 ℃ at 3 ℃ / min and held for 1.5 h for carbonization. It is then naturally cooled to room temperature to obtain a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon framework prepared in the procedure book is placed in a chemical vapor reactor. A mixture of silane and argon is introduced, with a silane volume concentration of 18% and a total flow rate of 90 mL / min. The temperature is raised to 640 °C and held for 3 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After deposition, the silane supply is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon particles is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to a 1:1 mixture of acetylene and methane. The acetylene flow rate is 70 mL / min. The temperature is increased to 850 °C at a heating rate of 3 °C / min and held for 0.8 h. After coating, the gas supply is stopped and the mixture is cooled to room temperature to obtain the silicon-carbon composite anode material.

[0080] Example 4 This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding saccharide carbon and expanded graphite modified with methacryloylurea silane (KH-602) through a resin-carbon binder phase. The saccharide carbon provides rigid support and structural stability, while the expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 1:5.7. The resin-carbon binder phase is formed by carbonizing epoxy resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 25%.

[0081] The method for preparing silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 15 g of expanded graphite was dispersed in a mixed solution of 200 mL of ethanol and water, with a volume ratio of ethanol to water of 8:2. Then, 0.15 g of KH-602 was added, and the mixture was stirred at 60 °C for 2 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2, Composite: The surface-modified expanded graphite obtained in step S1 and the sugar carbon (D50=10 μm) obtained by carbonizing 85 g of glucose are added to a high-speed mixer and mixed. The speed of the high-speed mixer is 1500 r / min and the mixture is mixed for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D printing: The composite carbon source obtained in step S2 is added to a ball mill along with 20 g of epoxy resin, 400 mL of ethanol and 0.5 g of polyethylene glycol. The ball-to-material ratio is controlled at 5:1, the ball mill speed is 300 r / min, and the milling is carried out for 3 h to produce printing ink. A direct-write 3D printer is used to print the printing ink into a green body with a cross-grid macroporous structure according to the preset cross-grid model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 80 ℃ at a heating rate of 2 ℃ / min and held for 2 h to remove the solvent. Then, it is heated to 150 ℃ and held for 4 h for curing. After curing, the green body is transferred to a tube furnace, nitrogen is introduced, and the nitrogen flow rate is controlled at 80 mL / min. The temperature is increased to 800 ℃ at 1 ℃ / min and held for 3 h for carbonization. It is then naturally cooled to room temperature to obtain a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon framework obtained in step S4 is placed in a chemical vapor reactor, and a mixture of silane and argon is introduced. The volume concentration of silane in the mixture is 10%, and the total flow rate of the mixture is set to 60 mL / min. The temperature is raised to 550 °C and held for 4 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After the deposition is completed, the introduction of silane is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon particles is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to propane. The propane flow rate is 40 mL / min. The temperature is increased to 700 ℃ at a heating rate of 3 ℃ / min and held for 2 h. After the coating is completed, the gas supply is stopped and the material is cooled to room temperature to obtain silicon-carbon composite anode material.

[0082] Example 5 This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding biomass-based carbon with KH-550 and KH-560 modified expanded graphite via a resin-carbon binder. The biomass-based carbon provides rigid support and structural stability, while the expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 1:3. The resin-carbon binder is formed by carbonizing phenolic resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 35%.

[0083] The method for preparing silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 25 g of expanded graphite was dispersed in a mixed solution of 200 mL of ethanol and water with a volume ratio of 9:1. Then, 0.5 g of KH-550 and 0.5 g of KH-560 were added, and the mixture was stirred at 75 °C for 3.5 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2, Composite: The surface-modified expanded graphite obtained in step S1 and the biomass-based carbon (D50=6 μm) obtained by high-temperature pyrolysis of starch (75 g) are added to a high-speed mixer and mixed. The speed of the high-speed mixer is 1500 r / min and the mixture is mixed for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D printing: The composite carbon source obtained in step S2 is added to a ball mill along with 32 g of phenolic resin, 520 mL of ethanol and 1 g of polyethylene glycol. The ball-to-material ratio is controlled at 5:1, the ball mill speed is 300 r / min, and the milling is carried out for 4.5 h to produce printing ink. A direct-write 3D printer is used to print the printing ink into a green body with a cross-grid macroporous structure according to the preset cross-grid model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 100 ℃ at a heating rate of 2 ℃ / min and held for 1.5 h to remove the solvent. Then, it is heated to 180 ℃ and held for 3 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 110 mL / min. The temperature is increased to 980 ℃ at a rate of 2.5 ℃ / min and held for 2 h for carbonization. It is then naturally cooled to room temperature to obtain a 3D printed rigid-flexible three-dimensional porous carbon skeleton. S5. In-situ selective deposition: The three-dimensional porous carbon framework obtained in step S4 is placed in a chemical vapor reactor, and a mixture of silane and argon is introduced. The volume concentration of silane in the mixture is 16%, and the total flow rate of the mixture is set to 85 mL / min. The temperature is raised to 600 ℃ and held for 2.5 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After the deposition is completed, the introduction of silane is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to acetylene. The acetylene flow rate is 50 mL / min. The temperature is increased to 800 ℃ at a heating rate of 3 ℃ / min and held for 1 h. After the coating is completed, the gas supply is stopped and the material is cooled to room temperature to obtain the 3D printed rigid-flexible synergistic silicon-carbon composite anode material.

[0084] Example 6 This embodiment provides a silicon-carbon composite anode material, comprising: The structure consists of an outer carbon coating, nano-silicon particles, and a 3D-printed rigid-flexible three-dimensional porous carbon framework. The framework is formed by bonding petroleum coke powder and KH-570-modified expanded graphite with a resin-carbon binder. The petroleum coke powder provides rigid support and structural stability, while the expanded graphite provides flexible buffering and high conductivity. The mass ratio of expanded graphite to petroleum coke powder is 9:41. The resin-carbon binder is formed by carbonizing furan resin. The three-dimensional porous carbon framework has a hierarchical pore structure, including macropores (>50 nm), mesopores (2-50 nm), and micropores (<2 nm). Macropores facilitate rapid ion transport in the electrolyte, mesopores wet the electrolyte, and micropores provide a high specific surface area. Nano-silicon particles are selectively loaded onto the expanded graphite, with a mass percentage of 32%.

[0085] The method for preparing 3D-printed rigid-flexible silicon-carbon composite anode material provided in this embodiment includes the following steps: S1. Surface modification: 18 g of expanded graphite was dispersed in a mixed solution of 200 mL of ethanol and water, with a volume ratio of ethanol to water of 8.5:1.5. Then, 0.54 g of KH-570 was added, and the mixture was stirred at 72 °C for 2.8 h. After the reaction was completed, the mixture was filtered, washed three times with ethanol, and dried under vacuum at 80 °C for 6 h to obtain surface-modified expanded graphite. S2, Composite: The surface-modified expanded graphite obtained in step S1, 82 g of petroleum coke powder (D50=4 μm) and 1 g of p-toluenesulfonic acid are added to a high-speed mixer and mixed. The speed of the high-speed mixer is 1500 r / min and the mixture is mixed for 1 h to obtain an interface-functionalized composite carbon source. S3, 3D printing: A binder jet printer is used, with an ethanol solution of furan resin as the binder. The mass concentration of furan resin is 30%, and the jetting amount is controlled to 0.03 g of binder per gram of composite carbon source. The green body with a cross-grid macroporous structure is printed according to the preset model. S4. Curing and Carbonization: The green body obtained in step S3 is placed in an oven and heated to 90 ℃ at a heating rate of 2 ℃ / min and held for 2 h to remove the solvent. Then, it is heated to 175 ℃ and held for 3.2 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 90 mL / min. The temperature is increased to 920 ℃ at a rate of 2 ℃ / min and held for 2.2 h for carbonization. It is then naturally cooled to room temperature to obtain a three-dimensional porous carbon framework. S5. In-situ selective deposition: The three-dimensional porous carbon framework obtained in step S4 is placed in a chemical vapor reactor, and a mixture of silane and argon is introduced. The volume concentration of silane in the mixture is 14%, and the total flow rate of the mixture is set to 75 mL / min. The temperature is raised to 610 °C and held for 2.2 h. The chemical vapor reaction generates nano-silicon particles, which are selectively deposited on the surface-modified expanded graphite of the three-dimensional porous carbon framework. After the deposition is completed, the introduction of silane is stopped, and a three-dimensional porous carbon framework loaded with nano-silicon is obtained. S6. Carbon Coating: The gas source in the chemical vapor reactor in step S5 is switched to acetylene. The acetylene flow rate is 55 mL / min, and the temperature is increased to 780 ℃ at a heating rate of 3 ℃ / min and held for 1.1 h. After the coating is completed, the gas supply is stopped and the material is cooled to room temperature to obtain the 3D printed rigid-flexible synergistic silicon-carbon composite anode material.

[0086] Comparative Example 1 This comparative example provides a silicon-carbon composite anode material, the preparation method of which includes the following steps: S1. Add 10 g of modified expanded graphite and 90 g of petroleum coke powder (D50=5 μm) to a high-speed mixer and mix. The speed of the high-speed mixer is 1500 r / min. Mix for 1 h to obtain an interface-functionalized composite carbon source. S2. Preparation of slurry: Add the composite carbon source obtained in step S1, 30 g of phenolic resin, 50 mL of ethanol and 1 g of polyethylene glycol to a ball mill, control the ball-to-material ratio to be 5:1, the ball mill speed to be 300 r / min, and ball mill for 4 h to make a slurry and pour it into a mold of a preset shape. S3. Curing and Carbonization: The mold from step S2 is placed in an oven and heated to 100℃ at a heating rate of 2℃ / min and held for 1.5 h to remove the solvent. Then, it is heated to 180℃ and held for 3 h for curing. After curing, the green body is transferred to a tube furnace, argon gas is introduced, and the argon gas flow rate is controlled at 100 mL / min. The temperature is increased to 1000℃ at a rate of 2℃ / min and held for 2 h for carbonization. The carbon body is then naturally cooled to room temperature to obtain a three-dimensional porous carbon framework. S4. Silicon deposition: The three-dimensional porous carbon framework obtained in step S3 is placed in a chemical vapor reactor, and a mixture of silane and argon is introduced. The volume concentration of silane in the mixture is 15%, and the total flow rate of the mixture is set to 80 mL / min. The temperature is raised to 650 °C and held for 2 h. The chemical vapor reaction generates nano-silicon particles. After the deposition is completed, the introduction of silane is stopped, and argon is continued to be introduced to cool to room temperature, thus obtaining silicon-carbon composite anode material.

[0087] Performance Testing and Result Analysis The silicon-carbon composite anode materials prepared in Examples 1-6 and Comparative Example 1 were subjected to performance tests, and the test methods are as follows: Half-cell assembly: Silicon-carbon anode material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added to make a slurry. The slurry was coated on copper foil and vacuum dried at 80 °C for 12 h. The slurry was then cut into electrodes with a diameter of 12 mm. Using lithium metal as the counter electrode and 1 mol / L LiPF6 / EC+DMC+EMC (volume ratio 1:1:1) as the electrolyte, CR2032 coin cells were assembled in an argon glove box.

[0088] Electrochemical performance testing: The Blue Battery testing system was used to test the initial charge-discharge capacity and initial coulombic efficiency at a rate of 0.1C within the voltage range of 0.01-1.5 V, and the capacity retention rate after 1500 cycles was tested at a rate of 0.5C. Rate performance was tested at different rates (0.1C, 0.2C, 0.5C, 1C, 2C) (with the 0.1C capacity as 100%, the capacity retention rate at each rate was calculated). The test results are shown in Table 1.

[0089] Table 1. Electrochemical performance of silicon-carbon composite anode materials prepared in Examples 1-6 and Comparative Example 1

[0090] The test results show that: The silicon-carbon composite anode materials in Examples 1-6 all exhibited excellent electrochemical performance, with initial discharge capacity of 2310-2680 mAh / g, initial coulombic efficiency of 90.2-93.1%, capacity retention of 80.1-83.2% after 1500 cycles, and 1C rate capacity retention of 85.5%-89.2%, fully demonstrating the advantages of 3D-printed rigid-flexible synergistic silicon-carbon composite anode materials. In contrast, the silicon-carbon composite anode material prepared by the traditional powder sintering method in Comparative Example 1, due to the random pore structure of the carbon framework, impaired ion transport pathways, and uneven distribution of rigid and flexible units, could not effectively suppress silicon volume expansion, resulting in performance far lower than that of Examples 1-6. This demonstrates the importance of 3D printing technology for the precise construction of macroscopic structures. In Comparative Example 1, although a flexible structure was introduced, the deposition of nano-silicon particles between the flexible and rigid structures of its carbon framework was random. During charge-discharge cycles, the large number of nano-silicon particles deposited between the rigid structures would disrupt the carbon framework due to drastic volume changes, causing a rapid decline in capacity retention. In addition, due to the lack of strong chemical bonds between the nano-silicon particles and the carbon skeleton, the nano-silicon particles are easy to detach from their carbon skeleton, resulting in performance far lower than that of Examples 1-6, demonstrating the important role of silane coupling agents in selective deposition and chemical anchoring.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 3D printed rigid-flexible synergistic three-dimensional porous carbon skeleton, characterized in that, comprise a rigid carbon component, a flexible carbon component modified by a silane coupling agent, and a resin carbon bonding phase bonding the rigid carbon component and the flexible carbon component into one body, the rigid carbon component being used to provide a rigid support and stable structure, and the flexible carbon component being used to provide flexible cushioning and high electrical conductivity.

2. The 3D printed rigid-flexible synergic three-dimensional porous carbon skeleton according to claim 1, wherein, The flexible carbon component comprises expanded graphite.

3. The 3D printed rigid-flexible synergic three-dimensional porous carbon skeleton according to claim 1, wherein, The silane coupling agent is selected from one or more of an amino silane, an epoxy silane, a vinyl silane, a methacryloxy silane, and a ureido silane.

4. The 3D printed rigid-flexible synergistic three-dimensional porous carbon skeleton of claim 1, wherein, The rigid carbon component comprises one or more of a coke-based carbon, a biomass-based carbon, a resin-based carbon, and a saccharide-based carbon.

5. The 3D printed rigid-flexible synergic three-dimensional porous carbon skeleton according to claim 4, wherein, The coke-based carbon is selected from one or more of petroleum coke, needle coke, and pitch coke, the biomass-based carbon is prepared by high-temperature pyrolysis of starch, cellulose, coconut shell, sugar cane residue, or a mixture thereof, the resin-based carbon is prepared by carbonization of phenol-formaldehyde resin and / or epoxy resin, and the saccharide-based carbon is prepared by carbonization of glucose, sucrose, maltose, or a mixture thereof.

6. The 3D printed three-dimensional porous carbon skeleton with rigid-flexible synergy of claim 1, wherein, The resin carbon bonding phase is formed by carbonization of phenol-formaldehyde resin, epoxy resin, furan resin, or a mixture thereof.

7. The 3D printed three-dimensional porous carbon skeleton with rigid-flexible synergy of claim 1, wherein, The mass ratio of the flexible carbon component to the rigid carbon component is (1-9):(1-9).

8. The 3D printed three-dimensional porous carbon skeleton with rigid-flexible synergy of claim 1, wherein, The three-dimensional porous carbon framework has a multi-level pore structure designed by a 3D printing program, the multi-level pore structure comprising macropores with a pore size >50 nm, mesopores with a pore size of 2-50 nm, and micropores with a pore size <2 nm, the macropores being used for rapid transmission of ions in an electrolyte, the mesopores being used for imbibition of the electrolyte, and the micropores being used for providing a high specific surface area.

9. A silicon-carbon composite negative electrode material, characterized by, comprise: the 3D printed rigid-flexible synergistic three-dimensional porous carbon framework of any one of claims 1-8; nanosilicon particles selectively loaded on the flexible carbon component for storing lithium ions in charge and discharge cycles; an amorphous carbon layer coated on the nanosilicon particles and the outer surface of the three-dimensional porous carbon framework for stabilizing the electrode interface of the silicon-carbon negative electrode material and optimizing the electrochemical performance thereof.

10. The silicon-carbon composite negative electrode material according to claim 9, characterized in that In the silicon-carbon composite negative electrode material, the mass percentage of the nanosilicon particles is 5-40 wt.%.

11. A method for preparing the silicon-carbon composite negative electrode material according to claim 9 or 10, characterized in that, comprise the following steps: S1, surface modification: surface modification treatment of the flexible carbon component by a silane coupling agent to obtain a surface-modified flexible carbon component; S2, compounding: uniform mixing of the surface-modified flexible carbon component and a rigid carbon component to obtain a composite carbon source; S3, 3D printing: 3D printing of the composite carbon source and a resin binder into a green body having a multi-level pore structure according to a predetermined three-dimensional model; S4, curing and carbonization: stepwise heat treatment of the green body, the stepwise heat treatment first cross-linking the resin binder and then converting the resin binder into a resin carbon bonding phase by carbonization treatment in an inert atmosphere to obtain the 3D printed rigid-flexible synergistic three-dimensional porous carbon framework: S5, in-situ selective deposition: placing the three-dimensional porous carbon framework in step S4 into a chemical vapor deposition reactor, and introducing a silane gas source, wherein the silane gas source generates nano-silicon particles by chemical vapor reaction, and the nano-silicon particles are selectively deposited on the surface-modified flexible carbon component of the three-dimensional porous carbon framework, to obtain a three-dimensional porous carbon framework loaded with nano-silicon particles; S6, carbon coating: replacing the silane gas source in step S5 with a hydrocarbon gas source for chemical vapor deposition, and forming an amorphous carbon layer on the surface of the three-dimensional porous carbon framework loaded with nano-silicon particles prepared in step S5, to obtain a silicon-carbon composite negative electrode material.

12. The method of claim 11, wherein the silicon-carbon composite negative electrode material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon composite negative electrode material. The mass ratio of the silane coupling agent to the flexible carbon component in step S1 is (1-5): 100, and the surface modification treatment is carried out in a mixed solution of ethanol and water at 60-80 ℃, and the surface modification treatment time is 2-4 h.

13. The method of claim 11, wherein the silicon-carbon composite negative electrode material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon composite negative electrode material. In step S3, the 3D printing method is direct writing forming printing, and the process of the direct writing forming printing includes: grinding the composite carbon source in step S2 after mixing with a resin binder, a solvent and a dispersant to prepare a printing ink, the mass percentage content of the resin binder in the printing ink is 5-30 wt.%, and then printing the printing ink into a green body with a hierarchical pore structure according to a preset three-dimensional model.

14. The method of claim 11, wherein the silicon-carbon composite negative electrode material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture at a temperature of 800-1,200°C for 1-10 hours in an inert atmosphere. In step S3, the 3D printing method is binder jetting printing, and the process of the binder jetting printing includes: spraying a resin binder on the composite carbon source in step S2, and 3D printing into a green body with a hierarchical pore structure, and the mass percentage content of the resin binder in the green body is 2-15 wt.%.

15. The method of claim 11, wherein the silicon-carbon composite negative electrode material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon composite negative electrode material. In step S4, the curing temperature is 150-200 ℃, and the carbonization treatment temperature is 800-1100 ℃.

16. The method of claim 11, wherein the silicon-carbon composite negative electrode material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon composite negative electrode material. In step S5, the temperature of the chemical vapor reaction is 550-650 ℃, and the time is 1-4 h, the silane gas source is a mixed gas of silane and inert gas, and the volume ratio of silane in the mixed gas is 10%-20%.

17. A lithium-ion battery, characterized by, The negative electrode material is the silicon-carbon composite negative electrode material of claim 9 or 10. The negative electrode material is the silicon-carbon composite negative electrode material of claim 9 or 10.

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