Silicon-carbon negative electrode material and preparation method thereof

Abstract

The application discloses a kind of silicon-carbon negative electrode material and preparation method thereof, belong to negative electrode material technical field.The silicon-carbon negative electrode material includes: N-doped porous carbon, using polyimide-polyurethane-phenolic resin copolymer is obtained by carbonization;Nano silicon particles are loaded in the pore and / or surface of N-doped porous carbon;Amorphous carbon coating is coated on the surface of N-doped porous carbon and / or silicon nanoparticles.The application uses polyimide-polyurethane-phenolic resin by copolymerization strategy, polyimide segment, polyurethane segment and phenolic resin segment are copolymerized into molecular main chain, realize the uniform distribution of rigid segment (phenolic, polyimide) and flexible segment (polyurethane) at molecular level, and the introduction of polyurethane can solve the phase separation problem of phenolic, polyimide in prior art, ensure that the N-doped porous carbon pore obtained after carbonization is uniform, and the mechanical properties of carbon skeleton are consistent.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, specifically relating to a silicon-carbon anode material and its preparation method. Background Technology

[0002] Silicon-carbon anode materials have attracted much attention due to silicon's extremely high theoretical specific capacity (approximately 4200 mAh / g), and are considered one of the key anode materials for next-generation high-energy-density lithium-ion batteries. However, the huge volume expansion effect of silicon during charge and discharge (exceeding 300%), as well as the weak interfacial bonding between silicon and the carbon matrix and poor cycle stability, severely restricts its commercialization. To alleviate volume expansion, existing technologies generally employ a strategy of loading silicon nanoparticles onto a porous carbon matrix and combining it with amorphous carbon coating. The internal pores of the porous carbon accommodate the volume changes of silicon, while the outer carbon coating layer isolates the electrolyte and stabilizes the solid electrolyte interphase (SEI) film.

[0003] In the selection of carbon matrix materials, phenolic resin is widely used as a precursor for porous carbon due to its advantages such as high residual carbon content after carbonization, tunable pore structure, and low cost. However, the carbon skeleton formed after carbonization of pure phenolic resin has limited mechanical strength and insufficient conductivity, and lacks effective heteroatom doping sites, making it difficult to meet the requirements of silicon-carbon anode materials for carbon matrix structural stability and electrochemical activity.

[0004] To overcome the aforementioned shortcomings of phenolic resins, researchers have attempted to composite them with high-performance polymers such as polyimide. Polyimide possesses excellent mechanical properties, thermal stability, and nitrogen-rich characteristics; after carbonization, it can form a high-strength carbon skeleton and provide in-situ nitrogen doping. However, the shrinkage behaviors of phenolic resin and polyimide during carbonization differ significantly. Direct physical mixing of the two components leads to shrinkage mismatch, inducing microcracks during carbonization and subsequent cycling, thus disrupting the structural integrity of the carbon matrix. Simultaneously, due to phase separation, a uniform and continuous conductive network cannot be formed, severely limiting the material's conductivity and electrochemical performance. To address these issues, patent publication JP2017165823A discloses a method for chemically bridging phenolic resin and a polyimide precursor (polyamic acid) using an external crosslinking agent to form a crosslinked modified resin. This technology enhances the bonding force between the two components to some extent, but it still has significant shortcomings: First, the introduction of an external crosslinking agent may lead to uneven crosslinking density in the resin system, with local over-crosslinking or under-crosslinking, which in turn affects the uniformity of the channels and the mechanical stability of the carbon skeleton after carbonization. Second, the crosslinking reaction often occurs between specific functional groups, making it difficult to achieve a uniform distribution of phenolic and polyimide segments at the molecular level, and the fundamental issue of phase separation remains unresolved. Third, the system contains only two rigid segments, phenolic and polyimide, and lacks flexible stress buffer units. The carbon skeleton is rigid but lacks toughness, and there is still a risk of structural fatigue failure when subjected to the periodic stress generated by the volume expansion of silicon. Summary of the Invention

[0005] To address the above problems, the purpose of this invention is to provide a silicon-carbon anode material and its preparation method.

[0006] In a first aspect, the present invention provides a silicon-carbon anode material, comprising: Nitrogen-doped porous carbon is obtained by carbonization of a copolymer of polyimide-polyurethane-phenolic resin. Nano-silicon particles, loaded within the pores and / or on the surface of N-doped porous carbon; An amorphous carbon coating layer is applied to the surface of N-doped porous carbon and / or silicon nanoparticles.

[0007] Preferably, the silicon content in the silicon-carbon anode material is 5-90 wt%, more preferably 30-70 wt%.

[0008] Preferably, the specific surface area of ​​the silicon-carbon anode material is 0.1~55m². 2 / g, preferably 0.5~10m 2 / g.

[0009] Preferably, the pore volume of the silicon-carbon anode material is 0.001~0.15 cm. 3 / g, preferably 0.001~0.05cm 3 / g.

[0010] Preferably, the thickness of the amorphous carbon coating layer is 2~100nm.

[0011] Preferably, the copolymer of polyimide-polyurethane-phenolic resin is copolymerized from phenolic resin segment A, polyimide segment B, and polyurethane segment C; wherein: the mass percentage of phenolic resin segment A is 30-70%, the mass percentage of polyimide segment B is 10-50%, the mass percentage of polyurethane segment C is 5-20%, and the sum of the mass percentages of the three is 100%.

[0012] More preferably, the N-doped porous carbon further comprises at least one heteroatom selected from P and B; the P and / or B doping is achieved by introducing phosphorus-containing and / or boron-containing polymeric monomers to achieve in-situ doping.

[0013] Preferably, the method for preparing the copolymer of polyimide-polyurethane-phenolic resin includes the following steps: S1. Preparation of phenolic segment A: Phenol and formaldehyde are polycondensed under acid or alkali catalysis to obtain phenolic resin; S2, Preparation of polyimide segment B: After prepolymerization of dianhydride monomer and diamine monomer, acetic anhydride and pyridine are added for imidization to obtain polyimide with anhydride end groups; S3. Preparation of polyurethane segment C: Diisocyanate is polymerized with polyether polyol or polyester polyol under the action of a catalyst to obtain polyurethane with isocyanate end groups. S4. Copolymerization: Phenolic resin, polyimide with anhydride end group, polyurethane with isocyanate end group and catalyst are mixed and then a solvent is added to carry out a copolymerization reaction to obtain a copolymer of polyimide-polyurethane-phenolic resin.

[0014] Preferably, in step S1, the molar ratio of phenol to formaldehyde is 1:(1.1~1.5), the acid is hydrochloric acid or oxalic acid, and the base is sodium hydroxide solution or ammonia.

[0015] Preferably, in step S1, the polycondensation temperature is 80~90℃ and the polycondensation time is 2~4h.

[0016] Preferably, in step S2, the dianhydride monomer is selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, benzophenone dianhydride, and hexafluoroisopropylidene phthalic anhydride; the diamine monomer is selected from p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, bis(4-aminophenyl)phenylphosphine oxide, 4,4'-diphenyl ether, and 2,2-diphenyl ether. One or more of aminotriphenylphosphine and 4,4'-diaminophenylboronic acid, preferably one or more of bis(4-aminophenyl)phenylphosphine oxide, 4,4'-diaminotriphenylphosphine, 4,4'-diaminophenylboronic acid, and 3,4-diaminophenylboronic acid pinacol ester; the molar ratio of dianhydride monomer to diamine monomer is (1.05~1.1):1, the molar ratio of acetic anhydride to diamine monomer is 1:(2~3); the molar ratio of pyridine to diamine monomer is 1:(2~3).

[0017] Preferably, in step S2, the prepolymerization temperature is 20~30℃ and the prepolymerization time is 10~14h; the imidization temperature is 50~70℃ and the imidization time is 3~5h.

[0018] Preferably, in step S3, the polyether polyol is selected from one or two of polypropylene glycol (PPG) and polytetrahydrofuran ether glycol (PTMEG), and the polyester polyol is selected from one or two of polycaprolactone diol (PCL) and polycarbonate diol (PCDL); the number average molecular weight of the polyether polyol or polyester polyol is less than 3000; the diisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the catalyst is dibutyltin dilaurate; the molar ratio of polyether polyol or polyester polyol to diisocyanate is 1:(1.8~2.2), and the mass of the catalyst is 0.02~0.05% of the mass of diisocyanate.

[0019] Preferably, in step S3, the polymerization temperature is 50~70℃ and the polymerization time is 2~4h.

[0020] Preferably, in step S4, the catalyst is dibutyltin dilaurate catalyst, and the amount of catalyst added is 0.05~0.2% of the total mass of phenolic resin, polyimide with an acid anhydride end group, and polyurethane with an isocyanate end group.

[0021] Preferably, in step S4, the copolymerization temperature is 70~90℃ and the copolymerization time is 3~5h.

[0022] Secondly, the present invention provides a method for preparing a silicon-carbon anode material, comprising the following steps: (1) The copolymer of polyimide-polyurethane-phenolic resin was carbonized in an inert atmosphere and then activated to obtain N-doped porous carbon. (2) Place the N-doped porous carbon in a chemical vapor deposition apparatus, introduce silicon-containing gas, and perform the first stage of vapor deposition. After the deposition is completed, change the carbon source gas and perform the second stage of vapor deposition to obtain silicon-carbon anode material.

[0023] Preferably, in step (1), the inert atmosphere is a nitrogen atmosphere or an argon atmosphere, the carbonization temperature is 600-1200℃, and the carbonization time is 1-10h.

[0024] Preferably, in step (1), one or more of water vapor, carbon dioxide and alkaline substances are used as activators, and activation treatment is carried out at 800~1000℃ for 0.5~1.5h to adjust the average pore size of N-doped porous carbon to 1~5nm.

[0025] Preferably, in step (1), before carbonization, the copolymer of polyimide-polyurethane-phenolic resin is pre-oxidized, wherein the temperature of the pre-oxidation treatment is 200~400℃ and the time of the pre-oxidation treatment is 1~5h.

[0026] Preferably, in step (2), the silicon-containing gas is selected from one or more of silane (SiH4), dichlorosilane (SiH2Cl2), and silicon tetrachloride (SiCl4).

[0027] Preferably, in step (2), the temperature of the first stage of vapor deposition is 600~700℃ and the time of the first stage of vapor deposition is 2~4h.

[0028] Preferably, in step (2), the carbon source gas is selected from one or more of methane, ethylene, acetylene and propylene; or, the carbon source gas is selected from the pyrolysis gas of one or more organic precursors selected from glucose, sucrose, citric acid and polyacrylonitrile.

[0029] Preferably, in step (2), the temperature of the second stage of vapor deposition is 500~800℃, preferably 550~700℃; the time of the second stage of vapor deposition is 0.5~5h, preferably 0.5~3h.

[0030] Thirdly, the present invention provides a lithium-ion battery negative electrode sheet, comprising the aforementioned silicon-carbon negative electrode material.

[0031] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) This invention uses a copolymer of polyimide-polyurethane-phenolic resin. A uniform copolymer is formed through copolymerization between polyimide segments, polyurethane segments and phenolic resin, avoiding the problem of local over-crosslinking or under-crosslinking caused by the addition of crosslinking agents. The polyurethane segments, as flexible stress buffer units, endow the material with excellent elasticity and toughness; the polyimide segments provide high thermal stability and mechanical strength. The three work together to construct a porous carbon skeleton that is both strong and elastic. During cycling, it can effectively buffer the periodic stress generated by the volume expansion of silicon, inhibit structural collapse, and significantly improve the cycling stability and fatigue resistance of the material.

[0032] (2) In this invention, polyimide-polyurethane-phenolic resin is copolymerized to integrate polyimide segments, polyurethane segments and phenolic resin segments into the molecular backbone. At the molecular level, the rigid segments (phenolic, polyimide) and flexible segments (polyurethane) are uniformly distributed. The introduction of polyurethane can solve the phase separation problem of phenolic and polyimide in the prior art, and ensure that the pores of the N-doped porous carbon obtained after carbonization are uniform and the mechanical properties of the carbon skeleton are consistent. Attached Figure Description

[0033] Figure 1 The image shows a SEM image of the silicon-carbon anode material described in Example 1.

[0034] Figure 2 The image shows the infrared spectrum of the polyimide-polyurethane-phenolic resin copolymer prepared in Example 1.

[0035] Figure 3 The image shows the infrared spectrum of the phenolic resin prepared in Comparative Example 1.

[0036] Figure 4 The image shows the infrared spectrum of the anhydride-terminated polyimide prepared in Comparative Example 2.

[0037] Figure 5 The image shows the infrared spectrum of the isocyanate-terminated polyurethane prepared in Comparative Example 3. Detailed Implementation

[0038] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0039] As described above, the present invention provides a silicon-carbon anode material, comprising: Nitrogen-doped porous carbon is obtained by carbonization of a copolymer of polyimide-polyurethane-phenolic resin. Nano-silicon particles, loaded within the pores and / or on the surface of N-doped porous carbon; An amorphous carbon coating layer is applied to the surface of N-doped porous carbon and / or silicon particles.

[0040] This invention constructs a uniform, mechanically superior N-doped porous carbon framework by carbonizing a copolymer of polyimide-polyurethane-phenolic resin. Combined with nano-silicon confinement loading and amorphous carbon coating, it synergistically solves the technical problems of poor structural stability, low initial coulombic efficiency, and short cycle life in the prior art, and has significant electrochemical performance and industrial application prospects.

[0041] The carbonization of the copolymer of polyimide-polyurethane-phenolic resin in this invention can ensure the uniformity of N doping, which helps to improve the conductivity of the carbon matrix and increase the number of active sites.

[0042] In some embodiments, the silicon content in the silicon-carbon anode material is 5-90 wt%, including but not limited to: 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%; preferably 30-70 wt%.

[0043] In some embodiments, the specific surface area of ​​the silicon-carbon anode material is 0.1~55m². 2 / g, including but not limited to: 0.1m 2 / g, 1m 2 / g, 10m 2 / g、20m 2 / g、30m 2 / g、40m 2 / g、55m 2 / g, etc.; preferably 0.5~10m 2 / g.

[0044] In some embodiments, the pore volume of the silicon-carbon anode material is 0.001~0.15 cm. 3 / g, including but not limited to: 0.001cm 3 / g, 0.005cm 3 / g, 0.01cm 3 / g, 0.05cm 3 / g, 0.1cm 3 / g, 0.12cm 3 / g, 0.15cm 3 / g, etc.; preferably 0.001~0.05cm 3 / g.

[0045] In some embodiments, the thickness of the amorphous carbon coating layer is 2~100nm, including but not limited to: 2nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

[0046] In some embodiments, the copolymer of polyimide-polyurethane-phenolic resin is copolymerized from phenolic resin segment A, polyimide segment B, and polyurethane segment C; wherein: the mass percentage of phenolic resin segment A is 30-70%, including but not limited to: 30%, 40%, 50%, 60%, 70%, etc.; the mass percentage of polyimide segment B is 10-50%, including but not limited to: 10%, 20%, 30%, 40%, 50%, etc.; the mass percentage of polyurethane segment C is 5-20%, including but not limited to: 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.; the sum of the mass percentages of the three is 100%.

[0047] In this invention, by controlling the mass ratio of the three segments in the copolymer, the overall performance of the N-doped porous carbon matrix can be guaranteed. In particular, the amount of polyurethane segment added is crucial; too little polyurethane segment does not significantly improve the performance of the N-doped porous carbon, while too much polyurethane segment leads to insufficient strength of the N-doped porous carbon, resulting in performance degradation.

[0048] In some embodiments, the N-doped porous carbon further contains at least one doping element selected from P and B; the P and / or B doping is achieved by introducing phosphorus-containing and / or boron-containing polymeric monomers to achieve in-situ doping.

[0049] This invention introduces P- and / or B-containing monomers into copolymers of polyimide-polyurethane-phenolic resins, and introduces P- and / or B doping into N-doped porous carbon, which can significantly improve the electronic conductivity of the carbon matrix and provide abundant active sites, thereby enhancing the adsorption and transport capabilities of lithium ions.

[0050] In some embodiments, the method for preparing the copolymer of polyimide-polyurethane-phenolic resin includes the following steps: S1. Preparation of phenolic segment A: Phenol and formaldehyde are polycondensed under acid or alkali catalysis to obtain phenolic resin; S2, Preparation of polyimide segment B: After prepolymerization of dianhydride monomer and diamine monomer, acetic anhydride and pyridine are added for imidization to obtain polyimide with anhydride end groups; S3. Preparation of polyurethane segment C: Diisocyanate is polymerized with polyether polyol or polyester polyol under the action of a catalyst to obtain polyurethane with isocyanate end groups. S4. Copolymerization: Phenolic resin, polyimide with anhydride end group, polyurethane with isocyanate end group and catalyst are mixed and then a solvent is added to carry out a copolymerization reaction to obtain a copolymer of polyimide-polyurethane-phenolic resin.

[0051] This invention achieves ternary copolymerization by separately synthesizing anhydride-terminated polyimide prepolymer, isocyanate-terminated polyurethane prepolymer, and phenolic resin containing phenolic hydroxyl groups. The reaction of the -NCO groups of the polyurethane with both the anhydride and phenolic hydroxyl groups under catalytic conditions is then utilized. This "stepwise prepolymerization, one-pot copolymerization" strategy allows three polymers with vastly different properties to be orderly linked through polyurethane molecular chains, forming a well-defined and proportionally adjustable ternary copolymer. This provides an ideal integrated carbon precursor for the subsequent carbonization preparation of high-performance silicon-carbon anode materials.

[0052] In some embodiments, in step S1, the molar ratio of phenol to formaldehyde is 1:(1.1~1.5), including but not limited to: 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.; the acid is hydrochloric acid or oxalic acid; the base is sodium hydroxide solution or ammonia water.

[0053] In some embodiments, in step S1, the polycondensation temperature is 80~90℃, including but not limited to: 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, etc.; the polycondensation time is 2~4h, including but not limited to: 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0054] In some embodiments, in step S2, the dianhydride monomer is selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, benzophenone dianhydride, and hexafluoroisopropylidene phthalic anhydride; the diamine monomer is selected from p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, bis(4-aminophenyl)phenylphosphine oxide, 4,4'- One or more of 1,4'-diaminotriphenylphosphine and 4,4'-diaminophenylboronic acid, preferably one or more of bis(4-aminophenyl)phenylphosphine oxide, 4,4'-diaminotriphenylphosphine, 4,4'-diaminophenylboronic acid, and 3,4-diaminophenylboronic acid pinacol ester; the molar ratio of dianhydride monomer to diamine monomer is (1.05~1.1):1; the molar ratio of acetic anhydride to diamine monomer is 1:(2~3); the molar ratio of pyridine to diamine monomer is 1:(2~3).

[0055] In some embodiments, in step S2, the polymerization temperature is 20~30℃, including but not limited to: 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc.; the polymerization time is 10~14h, including but not limited to: 10h, 11h, 12h, 13h, 14h, etc.

[0056] In some embodiments, in step S3, the polyether polyol is selected from one or two of polypropylene glycol and polytetrahydrofuran ether glycol, and the polyester polyol is selected from one or two of polycaprolactone diol and polycarbonate diol; the number average molecular weight of the polyether polyol or polyester polyol is less than 3000; the diisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the catalyst is dibutyltin dilaurate; the molar ratio of the polyether polyol or polyester polyol to the diisocyanate is 1:(1.8~2.2), including but not limited to: 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, etc.; the mass of the catalyst is 0.02~0.05% of the mass of the diisocyanate, including but not limited to: 0.02%, 0.03%, 0.04%, 0.05%, etc.

[0057] In some embodiments, in step S3, the prepolymerization temperature is 50~70℃, including but not limited to: 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, etc.; the prepolymerization time is 2~4h, including but not limited to: 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0058] In some embodiments, in step S4, the catalyst is a dibutyltin dilaurate catalyst, and the amount of catalyst added is 0.05~0.2% of the total mass of phenolic resin, polyimide with an acid anhydride end group, and polyurethane with an isocyanate end group, including but not limited to: 0.05%, 0.1%, 0.15%, 0.2%, etc.

[0059] In some embodiments, in step S4, the copolymerization temperature is 70~90℃, including but not limited to: 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃, 90℃, etc.; the copolymerization time is 3~5h, including but not limited to: 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0060] Secondly, the present invention provides a method for preparing a silicon-carbon anode material, comprising the following steps: (1) The copolymer of polyimide-polyurethane-phenolic resin was carbonized in an inert atmosphere and then activated to obtain N-doped porous carbon. (2) Place the N-doped porous carbon in a chemical vapor deposition apparatus, introduce silicon-containing gas, and perform the first stage of vapor deposition. After the deposition is completed, change the carbon source gas and perform the second stage of vapor deposition to obtain silicon-carbon anode material.

[0061] In some embodiments, in step (1), the inert atmosphere is a nitrogen atmosphere or an argon atmosphere, the carbonization temperature is 600 to 1200°C, including but not limited to: 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.; the carbonization time is 1 to 10 hours, including but not limited to: 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.

[0062] In some embodiments, in step (1), one or more of water vapor, carbon dioxide and alkaline substances are used as activators, and activation treatment is carried out at 800~1000℃ for 0.5~1.5h to adjust the average pore size of N-doped porous carbon to 1~5nm.

[0063] In some embodiments, in step (1), before carbonization, the copolymer of polyimide-polyurethane-phenolic resin is pre-oxidized, wherein: the temperature of the pre-oxidation treatment is 200~400℃, including but not limited to: 200℃, 250℃, 300℃, 350℃, 400℃, etc.; the time of the pre-oxidation treatment is 1~5h, including but not limited to: 1h, 2h, 3h, 4h, 5h, etc.

[0064] In some embodiments, in step (2), the silicon-containing gas is selected from one or more of silane, dichlorosilane and silicon tetrachloride.

[0065] In some embodiments, in step (2), the temperature of the first stage of vapor deposition is 600~700℃, including but not limited to: 600℃, 620℃, 650℃, 680℃, 700℃, etc.; the time of the first stage of vapor deposition is 2~4h, including but not limited to: 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0066] In some embodiments, in step (2), the carbon source gas is selected from one or more of methane, ethylene, acetylene and propylene; or, the carbon source gas is selected from the pyrolysis gas of one or more organic precursors selected from glucose, sucrose, citric acid and polyacrylonitrile.

[0067] In some embodiments, in step (2), the temperature of the second stage of vapor deposition is 500~800℃, including but not limited to: 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, etc.; preferably 550~700℃; the time of the second stage of vapor deposition is 0.5~5h, including but not limited to: 0.5h, 1h, 2h, 3h, 4h, 5h, etc.; preferably 0.5~3h.

[0068] Example 1 In this embodiment, the silicon-carbon anode material includes N-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N-doped porous carbon and the silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.5 wt%, the thickness of the amorphous carbon coating layer is 50 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.8 m². 2 / g, pore volume is 0.007cm 3 / g. The specific preparation method is as follows: S1, Synthetic prepolymer: S1-1 Preparation of phenolic segments: Phenol and formaldehyde were added to the reactor at a molar ratio of 1:1.5. 30wt% ammonia water was used as a catalyst, and the amount of catalyst was 0.5% of the mass of phenol. The temperature was then raised to 85℃ and the reaction was maintained for 3 hours. Water and unreacted monomers were removed by vacuum distillation to obtain phenolic resin.

[0069] S1-2, Preparation of polyimide segments: Under nitrogen protection, 0.11 mol of pyromellitic dianhydride (PMDA), 0.1 mol of 4,4'-diaminodiphenyl ether, and N-methylpyrrolidone (NMP) solvent were added to a 500 mL three-necked flask equipped with a stirrer and a condenser. The mixture was then reacted at room temperature for 12 h. After the reaction was complete, 0.25 mol of acetic anhydride and 0.25 mol of pyridine were added, and imidization was performed at 60 °C for 4 h. Then, methanol, a poor solvent, was added, and the mixture was filtered to obtain anhydride-terminated polyimide.

[0070] S1-3. Preparation of polyurethane segments: 0.05 mol of polytetrahydrofuran ether diol (PTMEG, Mn=1000) was added to a 500 mL three-necked flask equipped with a stirrer and a condenser. After vacuum dehydration at 120 °C for 2 h, the temperature was lowered to 60 °C. Then, 0.1 mol of isophorone diisocyanate (IPDI) and 0.15 g of dibutyltin dilaurate catalyst were added, and the polymerization reaction was carried out for 3 h to obtain isocyanate-terminated polyurethane.

[0071] S2. Preparation of polyimide-polyurethane-phenolic resin copolymer: Anhydride-terminated polyimide, phenolic resin, isocyanate-terminated polyurethane, and dibutyltin dilaurate catalyst were mixed and added to a reaction apparatus. The mass ratio of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane was 30:50:20, and the amount of catalyst was 0.1% of the total mass of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane. Then, NMP was added to the reaction apparatus to adjust the total solid content of the reaction solution to 25 wt%. The reaction was then carried out under nitrogen protection and stirred at 80°C for 4 h. After copolymerization, the product was precipitated with water, filtered, washed, and dried to obtain the polyimide-polyurethane-phenolic resin copolymer.

[0072] S3, a copolymer of polyimide-polyurethane-phenolic resin, was placed in a tube furnace and heated to 900°C at a heating rate of 5°C / min under an argon atmosphere. The mixture was held at this temperature for 2 hours for carbonization. After carbonization, the gas was switched to a mixed gas consisting of 10 vol% water vapor and 90 vol% argon. The mixture was then activated at 900°C for 1 hour to adjust the average pore size of the matrix to approximately 2.8 nm, thus obtaining an N-doped porous carbon matrix.

[0073] S4. The N-doped porous carbon matrix is ​​loaded into a fluidized bed reactor, and argon gas is introduced as the fluidizing gas. The reactor is heated to 550°C. After the temperature stabilizes, silane gas (SiH4) is introduced, and the vapor deposition time is 2 hours. The silicon source gas is then stopped, and the residual gas is purged with argon gas. The temperature is then raised to 650°C, and acetylene gas is introduced. Argon gas is used as the carrier gas, and vapor deposition continues for 1 hour. After deposition, the material is naturally cooled to room temperature under an argon atmosphere to obtain the silicon-carbon anode material.

[0074] The SEM image of the silicon-carbon anode material prepared in this embodiment is shown below. Figure 1 As shown, the polyimide-polyurethane-phenolic resin copolymer-based silicon-carbon anode material consists of irregular blocky particles of 5-15 μm with a rough surface and no obvious agglomeration. This copolymer system combines the rigid framework of phenolic resin, the high heat resistance and nitrogen doping properties of polyimide, and the flexible buffer structure of polyurethane. It can synergistically construct a hierarchical porous carbon matrix, effectively confining silicon while improving conductivity and interfacial stability, significantly optimizing the cycle performance and rate performance of the silicon-carbon anode.

[0075] Comparative Example 1 This is basically the same as Example 1, except that step S1 is different; the specific preparation method is as follows: S1. Prepare phenolic resin according to the method in step S1-1.

[0076] S2 is basically the same as step S3, except that phenolic resin is used instead of the copolymer of polyimide-polyurethane-phenolic resin.

[0077] S3, same as step S4.

[0078] Comparative Example 2 This is basically the same as Example 1, except that step S1 is different; the specific preparation method is as follows: S1. Prepare anhydride-terminated polyimide according to the method in steps S1-2.

[0079] S2 is basically the same as step S3, except that an anhydride-terminated polyimide is used instead of a copolymer of polyimide-polyurethane-phenolic resin.

[0080] S3, same as step S4.

[0081] Comparative Example 3 This is basically the same as Example 1, except that step S1 is different; the specific preparation method is as follows: S1. Prepare isocyanate-terminated polyurethane according to steps S1-3.

[0082] S2 is basically the same as step S3, except that isocyanate-terminated polyurethane is used instead of the copolymer of polyimide-polyurethane-phenolic resin.

[0083] S3, same as step S4.

[0084] The infrared spectra of the polyimide-polyurethane-phenolic resin copolymer prepared in Example 1, the phenolic resin prepared in Comparative Example 1, the anhydride-terminated polyimide prepared in Comparative Example 2, and the isocyanate-terminated polyurethane prepared in Comparative Example 3 are shown below. Figures 2-5 As shown; from Figures 2-5 The comparison shows that Figure 2 3340cm -1 The broad, strong peak at 2925 cm⁻¹ is attributed to the stretching vibrations of the phenolic hydroxyl group (-OH) and the amino group (-NH₃). -1 2855cm -1 The stretching vibration of the methylene CH segment in the polyurethane soft segment; 1730 cm⁻¹ -1 The strong absorption peak is the result of the superposition of carbonyl vibrations, and the peak broadening proves the cross-linking between components; 1378 cm⁻¹ -1 The stretching vibration of the polyimide imide ring CN confirmed its successful integration; 1120cm -1 The broad absorption band is attributed to the stretching vibration of the ether bond and CO; furthermore, the copolymer spectrum in Example 1 does not contain a 2270 cm⁻¹ band. -1 The isocyanate peak indicates that the isocyanate reaction was complete; in summary, this confirms that the terpolymer in Example 1 was successfully prepared.

[0085] Comparative Example 4 This method is basically the same as Example 1, except that step S2 is different. The specific preparation method is as follows: S1, the same as step S1 in Example 1.

[0086] S2. The phenolic resin prepared in step S1-1, the anhydride-terminated polyimide prepared in step S1-2, and the isocyanate-terminated polyurethane prepared in step S1-3 are blended in a mass ratio of 50:30:20 to obtain a mixture.

[0087] S3 is basically the same as step S3 in Example 1, except that the copolymer of polyimide-polyurethane-phenolic resin is replaced by a mixture.

[0088] S4, same as step S4 in Example 1.

[0089] Comparative Example 5 This method is basically the same as Example 1, except that steps S1 and S2 are different. The specific preparation method is as follows: S1. Preparation of prepolymer: S1-1, same as step S1-1 in Example 1.

[0090] S1-2, same as step S1-2 in Example 1.

[0091] S2. Anhydride-terminated polyimide, phenolic resin, and dibutyltin dilaurate catalyst are mixed and added to a reaction apparatus, wherein the mass ratio of anhydride-terminated polyimide to phenolic resin is 37.5:62.5, and the amount of catalyst is 0.1% of the total mass of anhydride-terminated polyimide and phenolic resin; then NMP is added to the reaction apparatus to adjust the total solid content of the reaction solution to 25wt%; then, under nitrogen protection, the reaction is stirred at 80°C for 4 hours. After copolymerization, the product is precipitated with water, filtered, washed, and dried to obtain a copolymer of polyimide-phenolic resin.

[0092] S3: Basically the same as step S3 in Example 1, except that the copolymer of polyimide-phenolic resin is used instead of the copolymer of polyimide-polyurethane-phenolic resin.

[0093] S4: Same as step S4 in Example 1.

[0094] Comparative Example 6 This method is basically the same as Example 1, except that steps S1 and S2 are different. The specific preparation method is as follows: S1. Preparation of prepolymer: S1-1, same as step S1-1 in Example 1.

[0095] S1-2, Same as step S1-3 in Example 1.

[0096] S2. Phenolic resin, isocyanate-terminated polyurethane, and dibutyltin dilaurate catalyst are mixed and added to a reaction apparatus, wherein the mass ratio of phenolic resin to isocyanate-terminated polyurethane is 71.43:28.57, and the amount of catalyst is 0.1% of the total mass of phenolic resin and isocyanate-terminated polyurethane; then NMP is added to the reaction apparatus to adjust the total solid content of the reaction solution to 25wt%; then the reaction is stirred at 80°C for 4 hours under nitrogen protection. After copolymerization, the product is precipitated with water, filtered, washed, and dried to obtain a polyurethane-phenolic resin copolymer.

[0097] S3 is the same as step S3 in Example 1, except that the copolymer of polyurethane-phenolic resin is used instead of the copolymer of polyimide-polyurethane-phenolic resin.

[0098] S4, same as step S4 in Example 1.

[0099] Comparative Example 7 This method is basically the same as Example 1, except that steps S1 and S2 are different. The specific preparation method is as follows: S1. Preparation of prepolymer: S1-1, same as step S1-2 in Example 1.

[0100] S1-2, Same as step S1-3 in Example 1.

[0101] S2. Anhydride-terminated polyimide, isocyanate-terminated polyurethane, and dibutyltin dilaurate catalyst are mixed and added to a reaction apparatus. The mass ratio of anhydride-terminated polyimide to isocyanate-terminated polyurethane is 60:40, and the amount of catalyst is 0.1% of the total mass of anhydride-terminated polyimide and isocyanate-terminated polyurethane. Then, NMP is added to the reaction apparatus to adjust the total solid content of the reaction solution to 25wt%. The reaction is then carried out under nitrogen protection and stirred at 80°C for 4 hours. After copolymerization, the product is precipitated with water, filtered, washed, and dried to obtain a polyimide-polyurethane copolymer.

[0102] S3 is the same as step S3 in Example 1, except that the copolymer of polyimide-polyurethane is used instead of the copolymer of polyimide-polyurethane-phenolic resin.

[0103] S4, same as step S4 in Example 1.

[0104] Example 2 In this embodiment, the silicon-carbon anode material includes N-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N-doped porous carbon and the silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.6 wt%, the thickness of the amorphous carbon coating layer is 49 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.6 m². 2 / g, pore volume is 0.009cm 3 / g.

[0105] The preparation method is basically the same as in Example 1, except that in step S2, the mass ratio of anhydride-terminated polyimide, phenolic resin and isocyanate-terminated polyurethane is 35.6:59.4:5.

[0106] Example 3 In this embodiment, the silicon-carbon anode material includes N-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N-doped porous carbon and the silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.4 wt%, the thickness of the amorphous carbon coating layer is 48 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.9 m². 2 / g, pore volume is 0.008cm³ 3 / g.

[0107] The preparation method is basically the same as in Example 1, except that in step S2, the mass ratio of anhydride-terminated polyimide, phenolic resin and isocyanate-terminated polyurethane is 31.9:53.1:15.

[0108] Example 4 In this embodiment, the silicon-carbon anode material includes N / P co-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N / P-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N / P-doped porous carbon and silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.7 wt%, the thickness of the amorphous carbon coating layer is 51 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.6 m². 2 / g, pore volume is 0.010cm³ 3 / g.

[0109] The preparation method is basically the same as in Example 1, except that 4,4'-diaminodiphenyl ether in steps S1-2 is replaced by 4,4'-diaminotriphenylphosphine.

[0110] Example 5 In this embodiment, the silicon-carbon anode material includes N / B co-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N / B-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N / B-doped porous carbon and silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.5 wt%, the thickness of the amorphous carbon coating layer is 49 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.7 m². 2 / g, pore volume is 0.008cm³ 3 / g.

[0111] The preparation method is basically the same as in Example 1, except that the 4,4'-diaminodiphenyl ether in steps S1-2 is replaced by 3,4-diaminophenylboronic acid pinacol ester.

[0112] Example 6 In this embodiment, the silicon-carbon anode material includes N / P / B co-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N / P / B doped porous carbon, and an amorphous carbon coating layer covering the N / P / B doped porous carbon and the surface of the silicon particles. Specifically, the content of nano-silicon particles in the silicon-carbon anode material is 49.8 wt%, the thickness of the amorphous carbon coating layer is 51 nm, and the specific surface area of ​​the silicon-carbon anode material is 2.8 m². 2 / g, pore volume is 0.010cm³ 3 / g.

[0113] The preparation method is basically the same as in Example 1, except that the 4,4'-diaminodiphenyl ether in steps S1-2 is replaced by 4,4'-diaminotriphenylphosphine and 3,4-diaminophenylboronic acid pinacol ester in a molar ratio of 1:1.

[0114] Example 7 In this embodiment, the silicon-carbon anode material includes N-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N-doped porous carbon, and an amorphous carbon coating layer covering the N-doped porous carbon and the surface of the silicon particles. Specifically, the content of the nano-silicon particles in the silicon-carbon anode material is 35 wt%, the thickness of the amorphous carbon coating layer is 60 nm, and the specific surface area of ​​the silicon-carbon anode material is 8.2 m². 2 / g, pore volume 0.05cm 3 / g. The specific preparation method is as follows: S1, Synthetic prepolymer: S1-1 Preparation of phenolic resin segments: Phenol and formaldehyde were added to a reaction vessel at a molar ratio of 1:1.1, with 30wt% ammonia water as a catalyst. The amount of catalyst was 0.4% of the mass of phenol. The temperature was then raised to 90℃ and the reaction was maintained for 2 hours. Water and unreacted monomers were removed by vacuum distillation to obtain phenolic resin.

[0115] S1-2, Preparation of polyimide segments: Under nitrogen protection, 0.105 mol of pyromellitic dianhydride, 0.1 mol of 4,4'-diaminodiphenyl ether, and N-methylpyrrolidone solvent were added to a 500 mL three-necked flask equipped with a stirrer and a condenser. The mixture was then reacted at room temperature for 12 h. After the reaction was complete, 0.2 mol of acetic anhydride and 0.2 mol of pyridine were added, and imidization was performed at 50 °C for 5 h. Then, methanol, a poor solvent, was added, and the mixture was filtered to obtain anhydride-terminated polyimide.

[0116] S1-3, Preparation of polyurethane segments: 0.05 mol of polycaprolactone diol (PCL, Mn=800) was added to a 500 mL three-necked flask equipped with a stirrer and a condenser. After vacuum dehydration at 120 °C for 2 h, the temperature was lowered to 60 °C, and then 0.1 mol of diphenylmethane diisocyanate and 0.15 g of dibutyltin dilaurate catalyst were added. The polymerization reaction was carried out for 3 h to obtain isocyanate-terminated polyurethane.

[0117] S2. Preparation of polyimide-polyurethane-phenolic resin copolymer: Anhydride-terminated polyimide, phenolic resin, isocyanate-terminated polyurethane, and dibutyltin dilaurate catalyst were mixed and added to a reaction apparatus. The mass ratio of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane was 20:70:10, and the amount of catalyst was 0.2% of the total mass of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane. Then, NMP was added to the reaction apparatus to adjust the total solid content of the reaction solution to 25 wt%. The reaction was then carried out under nitrogen protection at 90°C with stirring for 3 hours. After copolymerization, the product was precipitated with water, filtered, washed, and dried to obtain the polyimide-polyurethane-phenolic resin copolymer.

[0118] S3, a copolymer of polyimide-polyurethane-phenolic resin, was placed in a tube furnace and heated to 1200°C at a heating rate of 5°C / min under an argon atmosphere. The mixture was held at this temperature for 1 hour for carbonization. After carbonization, the gas was switched to a mixture of 10 vol% water vapor and 90 vol% argon, and activated at 1000°C for 0.5 hours. The average pore size of the matrix was adjusted to approximately 3.5 nm to obtain an N-doped porous carbon matrix.

[0119] S4. The N-doped porous carbon matrix is ​​loaded into a fluidized bed reactor, and argon gas is introduced as the fluidizing gas. The reactor is heated to 600°C. After the temperature stabilizes, silicon tetrachloride is introduced, and the vapor deposition time is 2 hours. The silicon source gas is then stopped, and the residual gas is purged with argon gas. The temperature is then raised to 700°C, and acetylene gas is introduced. Argon gas is used as the carrier gas, and vapor deposition continues for 2 hours. After deposition, the material is naturally cooled to room temperature under an argon atmosphere to obtain the silicon-carbon anode material.

[0120] Example 8 In this embodiment, the silicon-carbon anode material includes N-doped porous carbon, nano-silicon particles loaded within the pores and / or on the surface of the N-doped porous carbon, and an amorphous carbon coating layer covering the surface of the N-doped porous carbon and the silicon particles. Specifically, the content of the nano-silicon particles in the silicon-carbon anode material is 60.2 wt%, the thickness of the amorphous carbon coating layer is 20 nm, and the specific surface area of ​​the silicon-carbon anode material is 0.9 m². 2 / g, pore volume is 0.002cm 3 / g. The specific preparation method is as follows: S1, Synthetic prepolymer: S1-1 Preparation of phenolic resin segments: Phenol and formaldehyde were added to the reactor at a molar ratio of 1:1.3, with 30wt% ammonia water as the catalyst. The amount of catalyst was 0.2% of the mass of phenol. The temperature was then raised to 80℃ and the reaction was maintained for 4 hours. Water and unreacted monomers were removed by vacuum distillation to obtain phenolic resin.

[0121] S1-2, Preparation of polyimide segments: Under nitrogen protection, 0.109 mol of pyromellitic dianhydride, 0.1 mol of 4,4'-diaminodiphenyl ether, and N-methylpyrrolidone solvent were added to a 500 mL three-necked flask equipped with a stirrer and a condenser. The mixture was then reacted at room temperature for 12 h. After the reaction was complete, 0.3 mol of acetic anhydride and 0.3 mol of pyridine were added, and imidization was performed at 50 °C for 6 h. Then, methanol, a poor solvent, was added, and the mixture was filtered to obtain anhydride-terminated polyimide.

[0122] S1-3. Preparation of polyurethane segments: 0.05 mol of polycaprolactone diol (PCL, Mn=800) was added to a 500 mL three-necked flask equipped with a stirrer and a condenser. After vacuum dehydration at 120 °C for 2 h, the temperature was lowered to 70 °C. Then, 0.11 mol of toluene diisocyanate and 0.15 g of dibutyltin dilaurate catalyst were added, and the polymerization reaction was carried out for 2 h to obtain isocyanate-terminated polyurethane.

[0123] S2. Preparation of polyimide-polyurethane-phenolic resin copolymer: Anhydride-terminated polyimide, phenolic resin, isocyanate-terminated polyurethane, and dibutyltin dilaurate catalyst were mixed and added to a reaction apparatus. The mass ratio of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane was 40:40:20, and the amount of catalyst was 0.05% of the total mass of anhydride-terminated polyimide, phenolic resin, and isocyanate-terminated polyurethane. Then, NMP was added to the reaction apparatus to adjust the total solid content of the reaction solution to 25 wt%. The reaction was then carried out under nitrogen protection at 70°C for 5 h with stirring. After copolymerization, the product was precipitated with water, filtered, washed, and dried to obtain the polyimide-polyurethane-phenolic resin copolymer.

[0124] S3, a copolymer of polyimide-polyurethane-phenolic resin, was placed in a tube furnace and heated to 600°C at a heating rate of 5°C / min under an argon atmosphere. The mixture was held at this temperature for 10 hours for carbonization. After carbonization, the gas was switched to a mixture of 10 vol% water vapor and 90 vol% argon, and the mixture was activated at 800°C for 1.5 hours. The average pore size of the matrix was adjusted to approximately 5 nm to obtain an N-doped porous carbon matrix.

[0125] S4. The N-doped porous carbon matrix is ​​loaded into a fluidized bed reactor, and argon gas is introduced as the fluidizing gas. The reactor is heated to 700°C. After the temperature stabilizes, silicon tetrachloride is introduced, and the vapor deposition time is 4 hours. The silicon source gas is then stopped, and the residual gas is purged with argon gas. The temperature is then raised to 550°C, and methane gas is introduced. Argon gas is used as the carrier gas, and vapor deposition continues for 0.5 hours. After deposition, the material is naturally cooled to room temperature under an argon atmosphere to obtain the silicon-carbon anode material.

[0126] Preparation of silicon-carbon anode sheet: Silicon-carbon composite material, conductive agent, and binder are mixed evenly at a mass ratio of 85:8:7. An appropriate amount of N-methylpyrrolidone solvent is added, and the mixture is stirred at high speed at room temperature for 5 hours to obtain a uniform anode slurry. The slurry is uniformly coated on the surface of a copper foil current collector, pre-dried at room temperature, and then transferred to a vacuum oven at 100°C for thorough drying to remove the solvent. The compaction density of the anode sheet is then adjusted by roller pressing, and finally cut into a specified size. The anode sheet is then thoroughly dried under vacuum conditions to obtain the silicon-carbon anode sheet.

[0127] Performance testing of silicon-carbon anode materials: 1. Electrochemical performance: A CR2032 coin cell was assembled using a negative electrode as the working electrode, lithium metal as the counter electrode, and 1 mol / L LiPF6 (EC / DMC / EMC+10% FEC) as the electrolyte.

[0128] Initial coulombic efficiency and specific capacity: Charge and discharge at 0.1C, voltage range 0.01~1.5V. The first-cycle discharge specific capacity is the 1.5V specific capacity; initial coulombic efficiency = first-cycle charge capacity / first-cycle discharge capacity × 100%.

[0129] Cyclic stability: Cycle at 1C rate and record the capacity retention rate after a specific number of cycles.

[0130] 1C rate performance: Capacity was measured by constant current charging to 0.01V and 1C discharge to 1.5V.

[0131] 2. Full-charge expansion rate: Assemble the soft-pack half-cell, fully charge it (0.01V), and let it stand. Measure the thickness using a micrometer. Expansion rate = (Fully charged thickness - Initial thickness) / Initial thickness × 100%.

[0132] 3. Compressive strength: Press the powder into a disc with a diameter of 10 mm and a thickness of about 2 mm (pressure 2T), place it in a universal testing machine, apply pressure at a speed of 1 mm / min, record the maximum load when it breaks, and calculate the strength.

[0133] 4. Specific surface area: The N2 adsorption-desorption method (BET) was used. The sample was first degassed in a vacuum at 200℃ for 4 hours, and then measured and calculated at liquid nitrogen temperature.

[0134] The test results are shown in Table 1.

[0135] Table 1 As can be seen from the data in Table 1, the battery assembled with silicon-carbon anode material prepared using polyimide-polyurethane-phenolic resin terpolymer precursor in Example 1 has high specific capacity, first-time efficiency and cycle stability, and high compressive strength.

[0136] Comparative Examples 1-3, using only phenolic resin, polyimide, or polyurethane as a single precursor, showed significantly lower specific capacity, initial efficiency, and cycle stability compared to Example 1, and also exhibited poor compressive strength. This may be because a single component cannot simultaneously provide the flexibility required to buffer volume expansion and the rigidity required to support the structure: pure phenolic resin, after carbonization, has a single pore size and high brittleness; pure polyimide, while possessing high mechanical strength, lacks flexible units and cannot dissipate cyclic stress; and pure polyurethane, after carbonization, has a loose structure and excessively low strength. None of these three components can form a rigid-flexible interpenetrating network, thus their performance is far inferior to that of Example 1.

[0137] In Comparative Example 4, the resin was simply physically blended instead of copolymerized. The electrochemical performance of the battery assembled from the prepared silicon-carbon anode material was improved compared to the single precursor, but it was still significantly worse than that of Example 1. This may be because physical blending cannot achieve a uniform distribution of rigid and flexible segments at the molecular level. The blend is prone to phase separation during carbonization, resulting in uneven pores, local stress concentration, and a compressive strength far lower than that of Example 1, which cannot effectively suppress the volume expansion of silicon.

[0138] The electrochemical performance of the silicon-carbon anode materials assembled from the binary copolymers in Comparative Examples 5-7 was further improved compared to Comparative Examples 1-3, but still not as good as Example 1. This may be because the binary system lacks a third component, making it impossible to form a complete ternary synergistic network: the polyimide-phenolic system lacks flexible polyurethane units, resulting in insufficient stress buffering capacity; the polyurethane-phenolic system lacks high-rigidity polyimide, resulting in insufficient mechanical strength; and the polyimide-polyurethane system lacks the rigid framework and crosslinking sites provided by phenol. Only ternary copolymerization can simultaneously achieve the synergistic effect of "rigid support - flexible buffering - uniform pores".

[0139] In Examples 2 and 3, the content of polyurethane segments was adjusted based on Example 1. The electrochemical performance and compressive strength of the prepared silicon-carbon anode materials fluctuated to some extent. Among them, Example 3 showed the best overall performance.

[0140] Examples 4-6 introduced N / P co-doping, N / B co-doping, and N / P / B ternary co-doping, respectively, based on Example 1. The electrochemical performance of the batteries assembled from the corresponding silicon-carbon anode materials was further improved. Among them, Example 6 showed the best specific capacity, first-stage efficiency, and cycle stability, and also exhibited strong compressive strength. This is because heteroatom doping further enhanced the electronic conductivity of the carbon framework and the chemical anchoring effect on silicon particles. The synergistic effect of ternary doping, combined with the original rigid-flexible interpenetrating network, more effectively suppressed the breakage and aggregation of silicon particles.

[0141] In Examples 7 and 8, the carbonization temperature, activation time, silicon and carbon source types, deposition temperature and time, and other process parameters were significantly adjusted. Although the electrochemical performance of the silicon-carbon anode materials prepared accordingly fluctuated to some extent, they all exhibited good performance.

[0142] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A silicon-carbon anode material, characterized in that, include: Nitrogen-doped porous carbon is obtained by carbonization of a copolymer of polyimide-polyurethane-phenolic resin. Nano-silicon particles, loaded within the pores and / or on the surface of N-doped porous carbon; An amorphous carbon coating layer is applied to the surface of N-doped porous carbon and / or silicon particles.

2. The silicon-carbon anode material according to claim 1, characterized in that, The silicon content in the silicon-carbon anode material is 5-90 wt%; And / or: The specific surface area of ​​the silicon-carbon anode material is 0.1~55m². 2 / g; And / or: The pore volume of the silicon-carbon anode material is 0.001~0.15 cm³. 3 / g; And / or: The thickness of the amorphous carbon coating layer is 2~100nm.

3. The silicon-carbon anode material according to claim 1, characterized in that, The copolymer of polyimide-polyurethane-phenolic resin is formed by copolymerizing phenolic resin segment A, polyimide segment B, and polyurethane segment C; wherein: the mass percentage of phenolic resin segment A is 30~70%, the mass percentage of polyimide segment B is 10~50%, the mass percentage of polyurethane segment C is 5~20%, and the sum of the mass percentages of the three is 100%.

4. The silicon-carbon anode material according to claim 1, characterized in that, The N-doped porous carbon also contains at least one doping element selected from P and B.

5. The silicon-carbon anode material according to any one of claims 1 to 4, characterized in that, The copolymer of polyimide-polyurethane-phenolic resin is prepared by the following steps: S1. Preparation of phenolic segment A: Phenol and formaldehyde are polycondensed under acid or alkali catalysis to obtain phenolic resin; S2, Preparation of polyimide segment B: After prepolymerization of dianhydride monomer and diamine monomer, acetic anhydride and pyridine are added for imidization to obtain polyimide with anhydride end groups; S3. Preparation of polyurethane segment C: Diisocyanate is polymerized with polyether polyol or polyester polyol under the action of a catalyst to obtain polyurethane with isocyanate end groups. S4. Copolymerization: Phenolic resin, polyimide with anhydride end group, polyurethane with isocyanate end group and catalyst are mixed and then a solvent is added to carry out a copolymerization reaction to obtain a copolymer of polyimide-polyurethane-phenolic resin.

6. The silicon-carbon anode material according to claim 5, characterized in that, In step S1, the molar ratio of phenol to formaldehyde is 1:(1.1~1.5), the acid is hydrochloric acid or oxalic acid, and the base is sodium hydroxide solution or ammonia water; And / or: In step S1, the polycondensation temperature is 80~90℃ and the polycondensation time is 2~4h; And / or: In step S2, the dianhydride monomer is selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, diphenyl ether tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, and hexafluoroisopropylidene diphthalic anhydride; the diamine monomer is selected from one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-bis(4-aminophenoxy)benzene, bis(4-aminophenyl)phenylphosphine oxide, 4,4'-diaminotriphenylphosphine, and 4,4'-diaminophenylboronic acid; the molar ratio of the dianhydride monomer to the diamine monomer is (1.05~1.1):1, the molar ratio of acetic anhydride to the diamine monomer is 1:(2~3); the molar ratio of pyridine to the diamine monomer is 1:(2~3); And / or: In step S2, the prepolymerization temperature is 20~30℃ and the prepolymerization time is 10~14h; the imidization temperature is 50~70℃ and the imidization time is 3~5h; And / or: In step S3, the polyether polyol is selected from one or two of polypropylene glycol and polytetrahydrofuran ether glycol, and the polyester polyol is selected from one or two of polycaprolactone diol and polycarbonate diol; the number average molecular weight of the polyether polyol or polyester polyol is less than 3000; the diisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; the catalyst is dibutyltin dilaurate; the molar ratio of polyether polyol or polyester polyol to diisocyanate is 1:(1.8~2.2), and the mass of the catalyst is 0.02~0.05% of the mass of diisocyanate; And / or: In step S3, the polymerization temperature is 50~70℃ and the polymerization time is 2~4h.

7. The silicon-carbon anode material according to claim 5, characterized in that, In step S4, the catalyst is dibutyltin dilaurate catalyst, and the amount of catalyst added is 0.05~0.2% of the total mass of phenolic resin, polyimide with anhydride end group, and polyurethane with isocyanate end group; And / or: The copolymerization temperature is 70~90℃, and the copolymerization time is 3~5h.

8. The method for preparing the silicon-carbon anode material according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) The copolymer of polyimide-polyurethane-phenolic resin was carbonized in an inert atmosphere and then activated to obtain N-doped porous carbon. (2) Place the N-doped porous carbon in a chemical vapor deposition apparatus, introduce silicon-containing gas, and perform the first stage of vapor deposition. After the deposition is completed, change the carbon source gas and perform the second stage of vapor deposition to obtain silicon-carbon anode material.

9. The method for preparing the silicon-carbon anode material according to claim 8, characterized in that, In step (1), before carbonization, the copolymer of polyimide-polyurethane-phenolic resin is pre-oxidized.

10. A lithium-ion battery negative electrode sheet, characterized in that, Includes the silicon-carbon anode material according to any one of claims 1 to 7, or the silicon-carbon anode material prepared by the method according to any one of claims 8 to 9.

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