A porous carbon skeleton, a porous carbon skeleton silicon-carbon negative electrode and a preparation method

Abstract

This invention proposes a porous carbon framework, a porous carbon framework silicon-carbon anode, and a preparation method thereof. The porous carbon framework silicon-carbon anode comprises a porous carbon framework material, a first solid electrolyte layer, a co-doped nano-silicon layer, an amorphous carbon layer, and a second solid electrolyte protective layer. The method includes the following steps: preparing a porous carbon framework and a first solid electrolyte precursor solution separately; immersing the porous carbon framework in the first solid electrolyte precursor solution to coat the surface of the porous carbon framework with the first solid electrolyte; passing a silicon source and doping gas through the porous carbon framework for vapor phase deposition to form a co-doped nano-silicon layer, followed by acetylene gas deposition for a second vapor phase deposition to obtain a silicon-carbon composite substrate; preparing a second solid electrolyte precursor solution; immersing the silicon-carbon composite substrate in the second solid electrolyte precursor solution; drying and curing under gas protection to obtain the porous carbon framework silicon-carbon anode. The prepared lithium-ion battery exhibits both high specific capacity and long cycle performance, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a porous carbon framework, a porous carbon framework silicon-carbon anode, and a preparation method thereof. Background Technology

[0002] Graphite is the traditional active material for lithium-ion batteries. Based on its intercalation ratio of 6 carbon atoms to 1 lithium atom, graphite has a theoretical specific capacity of 372 mA / g. Silicon has a higher specific capacity than graphite and also possesses better safety characteristics, thus silicon is widely used as an active material in lithium-ion batteries. However, silicon undergoes a volume expansion of approximately 300% during lithium insertion / extraction, leading to electrode pulverization and active material shedding. Simultaneously, silicon reacts with the electrolyte to form an unstable solid electrolyte interphase (SEI) film, resulting in a continuous increase in interfacial impedance and severely impacting the battery's cycle stability.

[0003] To mitigate the volume expansion problem of silicon, researchers often use porous carbon materials as a framework to support silicon nanoparticles, utilizing the buffer space of porous carbon to suppress silicon volume deformation. Chemical vapor deposition (CVD) is a commonly used method for preparing carbon-supported silicon nanoparticles, enabling uniform deposition of silicon nanoparticles on the carbon framework surface. However, the internal interface compatibility between silicon and carbon is poor, exhibiting significant interfacial impedance. Furthermore, side reactions easily occur at the external interface between traditional silicon-carbon anodes and liquid electrolytes, leading to SEI film rupture and regeneration, and cycle performance still needs improvement.

[0004] Therefore, the technology for optimizing the interface of silicon-carbon anode materials still needs further improvement. Summary of the Invention

[0005] In view of this, the present invention proposes a porous carbon framework, a porous carbon framework silicon-carbon anode and a preparation method, which solves the technical problems of SEI film rupture and poor cycle stability caused by poor compatibility of silicon-carbon interface during the charging and discharging process when silicon-carbon is used as an anode material in the prior art.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a porous carbon framework, comprising a porous carbon framework material and a first solid electrolyte layer coated on the pore surface of the porous carbon framework material. The porous carbon framework material is phenolic resin or biomass-based mesoporous carbon, with an average pore size of 2-4 nm and a pore volume of 0.7 cc / g-1.4 cc / g. The proportion of micropores below 2 nm is 30%-85%, the proportion of pore volume between 2 nm and 4 nm is 15%-70%, and the proportion of pore volume above 4 nm is less than 20%. The thickness of the first solid electrolyte layer is 0.5-1.5 nm. After the first solid electrolyte layer is coated on the pore surface of the porous carbon framework material, the average pore size is 1.7 nm-2.3 nm, the pore volume is 0.6 cc / g-1.2 cc / g, the pore volume ratio of micropores below 2 nm is 60-95%, the pore volume ratio of pores above 2 nm is 5%-40%, and the pore volume ratio of pores above 3 nm is less than 5%.

[0007] In a second aspect, the present invention provides a porous carbon framework anode, comprising the porous carbon framework material described in one aspect, a first solid electrolyte layer on the pore surface of the porous carbon framework, a nano-silicon layer deposited on the surface of the porous carbon framework with N, P, B single doping or co-doping of two or more of these elements, an amorphous carbon layer covering the outer layer of the porous carbon framework material, and a second solid electrolyte protective layer.

[0008] Thirdly, the present invention also provides a method for preparing the porous carbon framework silicon-carbon anode described in the second aspect, comprising the following steps: S1, prepare a porous carbon framework and a first solid electrolyte precursor solution respectively. The porous carbon framework includes a porous carbon framework material, and the first solid electrolyte precursor solution includes a first solid electrolyte. Immerse the porous carbon framework in the first solid electrolyte precursor solution, disperse, freeze-dry, and solidify it so that the first solid electrolyte coats the surface of the porous carbon framework. S2, a porous carbon framework is introduced into a silicon source and doping gas for vapor phase deposition to form a co-doped nano-silicon layer, and then acetylene is introduced for secondary vapor phase deposition to obtain a silicon-carbon composite substrate, wherein the doping gas contains at least one of N, P and B. S3, prepare a second solid electrolyte precursor solution, immerse the silicon-carbon composite substrate in the second solid electrolyte precursor solution, dry and cure under gas protection, and form a second solid electrolyte protective layer on the surface of the silicon-carbon composite substrate to obtain a porous carbon framework silicon-carbon anode. The second solid electrolyte precursor solution includes a first solid electrolyte and polymer additives.

[0009] Based on this technical solution, and further preferably, step S1 includes: S1.1, the porous carbon framework material is dispersed in an acidic solution, ultrasonically etched for 10-12 min, alkali is added and mixed, activated under gas protection and 700-900℃ for 1-3 h, cooled, washed and dried to obtain a porous carbon framework, the first solid electrolyte and organic solvent are mixed under gas protection, stirred for 5-10 min, and ultrasonically treated for 15-30 min to obtain the first solid electrolyte precursor solution; S1.2, the porous carbon skeleton is immersed in the first solid electrolyte precursor solution, ultrasonically treated for 30-60 min, dried at -100℃ to 80℃ for 6-12 h, heated to 200-300℃, and kept at the temperature for 1-2 h to coat the surface of the porous carbon skeleton with the first solid electrolyte.

[0010] Based on this technical solution, and further preferably, the first solid electrolyte comprises 5-30% by mass of Li6PS5Cl and Li7P3S 11 Li 10 GeP2S 12 Li 5.5 PS 4.5 Cl 1.5 Li 6.8 Si 0.8 As 0.2 S5I.

[0011] Based on this technical solution, and further preferably, step S2 includes: S2.1, The porous carbon framework is placed in a CVD reactor, and silicon source and doping gas are introduced for vapor deposition. The reactor pressure is 1-5 kPa, the heating rate is 3-5℃ / min, the temperature is heated to 500-650℃, and the temperature is held for 1-3 hours to form a co-doped nano-silicon layer. S2.2, acetylene is introduced, and secondary vapor deposition is carried out at a temperature of 500-950℃ for 0.5-12h to obtain silicon-carbon composite substrate.

[0012] More preferably, the silicon source includes silane, the carrier gas includes argon, and the volume ratio of silane to dopant gas is 100:(1-5).

[0013] More preferably, step S3 includes: The first solid electrolyte, polymer additives, and organic solvents are mixed under gas protection, stirred for 9-12 minutes, and ultrasonically treated for 15-30 minutes to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate is immersed in the second solid electrolyte precursor solution, spray-dried under nitrogen protection, and reacted at 200-300℃ for 1-2 hours to obtain a porous carbon framework silicon-carbon anode. The polymer additives include lithium polyacrylate and polyethylene glycol. The second solid electrolyte precursor solution, by mass percentage, includes 8-15% of the first solid electrolyte, 1-5% of the polymer additives, and the balance is organic solvent.

[0014] Finally, the present invention also provides a lithium-ion battery comprising a porous carbon skeleton silicon-carbon negative electrode, a positive electrode, the first solid electrolyte, and a casing.

[0015] The porous carbon framework, porous carbon framework silicon-carbon anode, and preparation method described in this invention have the following advantages over the prior art: The porous carbon skeleton is modified to optimize the pore structure of the carbon skeleton, and the space provided is conducive to the subsequent silicon layer deposition. The solid electrolyte layer formed after the first solid electrolyte coating and solidification has high ionic conductivity, opens up the ion transport channel at the silicon-carbon interface, reduces the impedance of the silicon-carbon interface, and can also suppress the expansion of the silicon layer during the vapor deposition process, thus avoiding the pulverization of the internal structure of the electrode. Furthermore, doping a nano-silicon layer into a porous carbon framework can regulate the electronic structure of silicon-carbon materials, and secondary deposition can form a uniform amorphous carbon layer, thereby enhancing the structural stability of silicon-carbon composite substrates.

[0016] The silicon-carbon composite substrate is then treated with a second solid electrolyte precursor solution to form an outer interface protective layer. The second solid electrolyte solution, by introducing polymer additives, improves the adhesion of the outer interface protective layer, buffers the expansion caused by the charging and discharging process of the co-doped nano-silicon layer, and effectively isolates the direct contact between silicon and electrolyte, inhibits the formation and rupture regeneration of unstable SEI film, and reduces lithium loss caused by interface side reactions. The synergistic effect of inner interface coating, doping modification and outer interface protection enables the silicon-carbon anode to achieve both high specific capacity and long cycle performance, and significantly improves the shortcomings of existing silicon-carbon anodes in terms of insufficient cycle stability caused by interface problems. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a DLDFT pore size distribution diagram of the porous carbon skeleton used in Example 1 of this application.

[0019] Figure 2 This is a scanning electron microscope image of the porous carbon framework silicon-carbon anode of Embodiment 1 of this application. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Silicon, as a negative electrode material for lithium-ion batteries, possesses a theoretical specific capacity far exceeding that of graphite. However, its lithium insertion / extraction process generates a volume expansion of approximately 300%, leading to electrode pulverization and active material shedding. Simultaneously, silicon exhibits poor interfacial compatibility with the carbon framework, resulting in significant interfacial impedance. Furthermore, it is prone to side reactions at the interface with the liquid electrolyte, generating an unstable SEI film that repeatedly ruptures and regenerates, severely impacting battery cycle stability. While current technologies employ porous carbon frameworks to support nano-silicon to mitigate volume expansion, they have not resolved the issues of interfacial compatibility and SEI film stability, leaving cycle performance still requiring improvement.

[0022] This invention provides a method for preparing a porous carbon framework silicon-carbon anode, comprising the following steps: S1, prepare a porous carbon framework and a first solid electrolyte precursor solution respectively. The modified porous carbon framework includes a porous carbon framework material, and the first solid electrolyte precursor solution includes a first solid electrolyte. Immerse the porous carbon framework in the first solid electrolyte precursor solution, disperse, freeze-dry, and solidify it to coat the surface of the porous carbon framework with the first solid electrolyte. Specifically, step S1 includes: S1.1, the porous carbon framework material is dispersed in an acidic solution, ultrasonically etched for 10-12 min, alkali is added and mixed, activated under gas protection and 700-900℃ for 1-3 h, cooled, washed and dried to obtain a porous carbon framework, the first solid electrolyte and organic solvent are mixed under gas protection, stirred for 5-10 min, and ultrasonically treated for 15-30 min to obtain the first solid electrolyte precursor solution; Phenolic resin or biomass-based mesoporous carbon can be used as porous carbon framework materials because they have the characteristics of uniform pore size distribution and sufficient pore volume, which can provide stable support for the deposition of nano-silicon. At the same time, their porous structure can buffer the volume expansion of silicon. Compared with other carbon materials, phenolic resin-based carbon framework has good formability, and biomass-based mesoporous carbon has the advantages of being both environmentally friendly and low-cost.

[0023] The acidic solution used is a dilute solution of sulfuric acid or nitric acid. Ultrasonic etching removes impurities and defects from the carbon skeleton surface, increases surface-active groups, and provides binding sites for subsequent solid electrolyte coating. This ensures surface cleanliness without damaging the overall structure of the carbon skeleton. The alkali used is potassium hydroxide or sodium hydroxide. The alkali mixes with the etched carbon skeleton to activate it, further regulating the pore structure. The average pore size of the porous carbon skeleton is 2nm-4nm, with a pore volume of 0.7cc / g-1.3cc / g. Micropores smaller than 2nm account for 30-85% of the pore volume, pores between 2nm and 4nm account for 15%-70%, and pores larger than 4nm account for less than 20%. This pore structure ensures efficient ion transport while providing sufficient space for silicon volume expansion. The activation temperature is 700-900℃. Too low a temperature results in insufficient activation and an unsatisfactory pore structure, while too high a temperature can cause the carbon skeleton to collapse.

[0024] S1.2, the porous carbon skeleton is immersed in the first solid electrolyte precursor solution, ultrasonically treated for 30-60 min, dried at -100℃ to 80℃ for 6-12 h, heated to 200-300℃, and kept at the temperature for 1-2 h to coat the surface of the porous carbon skeleton with the first solid electrolyte.

[0025] The first solid electrolyte includes Li6PS5Cl and Li7P3S 11 Li 10 GeP2S 12 Li 5.5 PS 4.5 Cl 1.5 Li 6.8 Si 0.8 As 0.2 One or more of S5I are used because sulfide solid electrolytes have high ionic conductivity, which can open up ion transport channels at the silicon-carbon interface and reduce interfacial impedance. Simultaneously, sulfide solid electrolytes exhibit excellent chemical stability, which can inhibit excessive growth and aggregation of the silicon layer during vapor deposition, preventing pulverization of the internal electrode structure. Anhydrous ethanol, acetone, or N-methylpyrrolidone (NMP) are selected as organic solvents, as they have good solubility in solid electrolytes and are easily volatile with no residue. Argon or nitrogen is used for gas protection to prevent oxidation of components during preparation and ensure the stability of the bond between the sulfide solid electrolyte and the porous carbon framework.

[0026] S2, a porous carbon framework is subjected to vapor deposition with a silicon source and a doping gas to form a co-doped nano-silicon layer, followed by secondary vapor deposition with acetylene to obtain a silicon-carbon composite substrate, wherein the doping gas contains at least one of N, P, and B; specifically, step S2 includes: S2.1, The porous carbon framework is placed in a CVD reactor, and silicon source and doping gas are introduced for vapor deposition. The reactor pressure is 1-5 kPa, the heating rate is 3-5℃ / min, the temperature is heated to 500-650℃, and the temperature is held for 1-3 hours to form a co-doped nano-silicon layer. The silicon source selected is silane, which has high reactivity and can achieve uniform deposition of nano-silicon at relatively low temperatures. Compared with other silicon sources such as silicon tetrachloride, the decomposition products of silane are non-corrosive and will not contaminate equipment or damage the carbon skeleton structure. Argon is selected as the carrier gas. Argon is an inert gas that can dilute silane and dopant gas, avoiding excessive local concentration that could lead to silicon particle agglomeration. The dopant gas contains at least one of N, P, and B. N and P atoms can be substituted into the silicon lattice to regulate the electronic structure and improve conductivity. B atoms are acceptor dopants that can form hole carriers, further optimizing electron transport efficiency. The volume ratio of silane to dopant gas is controlled at 100:(1-5). If the doping amount is too low, the modification effect will be insignificant; if it is too high, it will damage the silicon crystal structure and reduce the specific capacity.

[0027] S2.2, acetylene is introduced, and secondary vapor deposition is performed at 500-950℃ for 0.5-12 hours to obtain a silicon-carbon composite substrate. The secondary deposition forms a uniform amorphous carbon layer, which enhances the structural stability of the silicon-carbon composite substrate.

[0028] S3, preparing a second solid electrolyte precursor solution: The silicon-carbon composite substrate is immersed in the second solid electrolyte precursor solution, dried and cured under gas protection to obtain a porous carbon framework silicon-carbon anode material. The second solid electrolyte precursor solution includes a first solid electrolyte and polymer additives. Specifically, step S3 includes: The first solid electrolyte, polymer additives, and organic solvents are mixed under gas protection, stirred for 9-12 minutes, and ultrasonically treated for 15-30 minutes to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate is immersed in the second solid electrolyte precursor solution, spray-dried under nitrogen protection, and reacted at 200-300℃ for 1-2 hours to obtain a porous carbon framework silicon-carbon anode. The polymer additives include lithium polyacrylate and polyethylene glycol. The second solid electrolyte precursor solution, by mass percentage, includes 8-15% of the first solid electrolyte, 1-5% of the polymer additives, and the balance is organic solvent.

[0029] The polymer additives selected are lithium polyacrylate (LiPAA) or polyethylene glycol (PEG). LiPAA molecules contain carboxyl and lithium salt groups, possessing both adhesive and ion-conducting properties, which enhances the bonding force between the protective layer and the silicon-carbon composite substrate. PEG exhibits good flexibility, buffering the volume expansion of silicon during charging and discharging, preventing the protective layer from cracking. The two additives, used alone or in combination, significantly improve the overall performance of the external interface protective layer. In the second solid electrolyte precursor solution, the sulfide solid electrolyte provides ion conduction channels, while the polymer additives help optimize mechanical properties.

[0030] The preparation of the second solid electrolyte precursor solution under gas protection can avoid polymer oxidation and solid electrolyte hydrolysis. After the silicon-carbon composite substrate is immersed, spray drying under nitrogen protection can achieve uniform coating of the precursor. Then, it is kept at 200-300℃ for 1-2 hours to solidify the coating layer and form a dense outer interface protective layer. This protective layer, together with the inner interface coating layer, can effectively isolate the direct contact between silicon and electrolyte and inhibit the formation, rupture and regeneration of unstable SEI film.

[0031] The present invention also provides a lithium-ion battery, comprising the above-mentioned porous carbon skeleton silicon-carbon anode, cathode, first solid electrolyte and shell, wherein the cathode is selected from lithium cobalt oxide, ternary material or lithium iron phosphate, the shell is a conventional lithium-ion battery shell, and the assembly process adopts existing mature technology.

[0032] Example 1 Phenolic resin-based mesoporous carbon was dispersed in an 8% hydrochloric acid solution and ultrasonically etched for 11 min. Potassium hydroxide powder was added, mixed thoroughly, and then placed in an argon-protected tube furnace for activation at 750℃ for 2 h. After cooling to room temperature, it was washed with deionized water until neutral and vacuum dried for 12 h to obtain a porous carbon framework. 30% Li6PS5Cl was added to anhydrous ethanol, stirred for 8 min under argon protection, and ultrasonically treated for 20 min to obtain a first solid electrolyte precursor solution. The porous carbon framework was immersed in this precursor solution, ultrasonically treated for 45 min, freeze-dried at -90℃ for 8 h, and then heated to 250℃ and held for 1.5 h to obtain a solid electrolyte-coated porous carbon framework.

[0033] The obtained porous carbon framework was subjected to particle size distribution testing, such as... Figure 1 As shown, the horizontal axis represents particle size, the red curve represents differential volume distribution (dV / dD), and the blue curve represents cumulative volume distribution. The particle size of the porous carbon framework material is mainly concentrated around 2 nm, and the cumulative volume is basically saturated at D=3 nm. This indicates that its particle size distribution is concentrated and there are no large particle agglomerates. It also shows that after acid etching-alkali activation modification and sulfide electrolyte coating, a uniform pore size structure is obtained, which can provide stable sites for subsequent silicon nanoparticle deposition and avoid local volume expansion differences.

[0034] The porous carbon framework was placed in a CVD reactor, and silane and ammonia were introduced. The volume ratio of silane to ammonia was 100:3. The reactor pressure was 4.5 kPa, the heating rate was 5 °C / min, and the temperature was raised to 650 °C and held for 3 h to form a nitrogen-doped nano-silicon layer. Then acetylene was introduced, and secondary vapor deposition was carried out at 750 °C for 6 h to obtain a silicon-carbon composite substrate.

[0035] Li6PS5Cl (30% by mass) was added to anhydrous ethanol, stirred for 10 min under argon protection, and ultrasonically treated for 25 min to obtain a second solid electrolyte precursor solution. A silicon-carbon composite substrate was immersed in this precursor solution, spray-dried under nitrogen protection, and then kept at 250℃ for 1.5 h to obtain a porous carbon framework silicon-carbon anode. Figure 2 As shown, Figure 2 This is a scanning electron microscope image of the porous carbon framework silicon-carbon anode of this embodiment.

[0036] A porous carbon-framework silicon-carbon anode, Li6PS5Cl, conductive agent SuperP, and binder polyisobutylene were mixed in a mass ratio of 70:15:5:10. Toluene was added as solvent, and the mixture was stirred in a vacuum mixer for 4 hours to obtain an anode slurry. The anode slurry was coated onto a copper foil current collector, dried at 80°C, cold-pressed at 10 MPa, cut into sheets, slit, and vacuum-dried at 100°C for 18 hours to obtain a porous carbon-framework silicon-carbon anode sheet. The above anode sheet was assembled with an NCM811 cathode, Li6PS5Cl solid electrolyte, and a battery casing to obtain a lithium-ion battery. X-ray photoelectron spectroscopy (XPS) detected an N-type anode with a binding energy of 398 eV. 1s Characteristic peak; detected at 560 cm⁻¹ by Fourier transform infrared spectroscopy (FT-IR). -1 The stretching vibration peak of PS appears at 490 cm⁻¹. -1 A stretching vibration peak of P-Cl appears at this location.

[0037] Example 2 Phenolic resin-based mesoporous carbon was dispersed in an 8% hydrochloric acid solution and ultrasonically etched for 11 min. Potassium hydroxide powder was added, mixed thoroughly, and then placed in an argon-protected tube furnace for activation at 750℃ for 2 h. After cooling to room temperature, it was washed with deionized water until neutral and vacuum dried for 12 h to obtain a porous carbon framework. 30% Li6PS5Cl was added to anhydrous ethanol, stirred for 8 min under argon protection, and ultrasonically treated for 20 min to obtain a first solid electrolyte precursor solution. The porous carbon framework was immersed in this precursor solution, ultrasonically treated for 45 min, freeze-dried at -90℃ for 8 h, and then heated to 250℃ and held for 1.5 h to obtain a solid electrolyte-coated porous carbon framework.

[0038] The porous carbon framework was placed in a CVD reactor, and silane, borane and phosphine were introduced. The volume ratio of silane, borane and phosphine was 100:2:2. The reactor pressure was 4 kPa, the heating rate was 5 °C / min, and the temperature was raised to 650 °C and held for 3 h to form a boron and phosphorus co-doped nano-silicon layer. Then acetylene was introduced, and secondary vapor deposition was carried out at 750 °C for 6 h to obtain a silicon-carbon composite substrate.

[0039] Take 30% by mass of Li6PS5Cl, add anhydrous ethanol, stir for 10 min under argon protection, and sonicate for 25 min to obtain a second solid electrolyte precursor solution; immerse the silicon-carbon composite substrate in the precursor solution, spray dry under nitrogen protection, and then keep it at 250℃ for 1.5 h to obtain a porous carbon framework silicon-carbon anode.

[0040] A porous carbon-framework silicon-carbon anode, Li6PS5Cl, SuperP, and polyisobutylene were mixed in a mass ratio of 70:15:5:10, and cyclohexane was added as a solvent. The mixture was stirred in a vacuum mixer for 4 hours to obtain an anode slurry. The anode slurry was coated onto a copper foil current collector, dried at 80°C, cold-pressed at 10MPa, cut into sheets, slit, and vacuum-dried at 100°C for 18 hours to obtain a porous carbon-framework silicon-carbon anode sheet. The above anode sheet was assembled with an NCM811 cathode, Li6PS5Cl solid electrolyte, and a battery casing to obtain a lithium-ion battery. XPS detected a P binding energy of 133eV. 2p Characteristic peaks and binding energy at 190 eV for B 1s Characteristic peak; detected by FT-IR at 560 cm⁻¹ -1 The stretching vibration peak of PS appears at 490 cm⁻¹. -1 A stretching vibration peak of P-Cl appears at this location.

[0041] Example 3 Phenolic resin-based mesoporous carbon was dispersed in an 8% hydrochloric acid solution and ultrasonically etched for 11 min. Potassium hydroxide powder was added, mixed thoroughly, and then placed in an argon-protected tube furnace for activation at 750℃ for 2 h. After cooling to room temperature, it was washed with deionized water until neutral and vacuum dried for 12 h to obtain a porous carbon framework. 30% Li7P3S was then used... 11 Anhydrous ethanol was added, and the mixture was stirred for 8 minutes under argon protection and then sonicated for 20 minutes to obtain the first solid electrolyte precursor solution. The porous carbon skeleton was immersed in the precursor solution, sonicated for 45 minutes, freeze-dried at -90℃ for 8 hours, and then heated to 250℃ and held for 1.5 hours to obtain a porous carbon skeleton coated with solid electrolyte.

[0042] The porous carbon framework was placed in a CVD reactor, and silane, borane and phosphine were introduced. The volume ratio of silane, borane and phosphine was 100:2:2. The reactor pressure was 4 kPa, the heating rate was 5 °C / min, and the temperature was raised to 650 °C and held for 3 h to form a boron and phosphorus co-doped nano-silicon layer. Then acetylene was introduced, and secondary vapor deposition was carried out at 750 °C for 6 h to obtain a silicon-carbon composite substrate.

[0043] Take 10% by mass of Li7P3S 11 Anhydrous ethanol was added, and the mixture was stirred for 10 min under argon protection and ultrasonically treated for 25 min to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate was immersed in the precursor solution, spray-dried under nitrogen protection, and then kept at 280℃ for 1 h to obtain a porous carbon framework silicon-carbon anode.

[0044] Porous carbon framework silicon-carbon anode, Li7P3S 11 SuperP and sodium carboxymethyl cellulose were mixed in a mass ratio of 70:15:5:10, and toluene was added as solvent. The mixture was stirred in a vacuum mixer for 4 hours to obtain a negative electrode slurry. The negative electrode slurry was coated onto a copper foil current collector, dried at 80°C, cold-pressed at 10 MPa, cut into sheets, slit, and vacuum-dried at 100°C for 18 hours to obtain a porous carbon-framework silicon-carbon negative electrode sheet. The above negative electrode sheet was then combined with an NCM811 positive electrode and Li7P3S... 11 A lithium-ion battery is obtained by assembling a solid electrolyte and a battery casing. XPS can detect a P-type electrode with a binding energy of 133 eV. 2p Characteristic peaks and binding energy at 190 eV for B 1s Characteristic peak; detected by FT-IR at 457 cm⁻¹ -1 A characteristic absorption peak of the PSP bridging bond appears at 828 cm⁻¹. -1 A characteristic absorption peak of the P=S double bond appears at this location.

[0045] Example 4 Phenolic resin-based mesoporous carbon was dispersed in an 8% hydrochloric acid solution and ultrasonically etched for 11 min. Potassium hydroxide powder was added, mixed thoroughly, and then placed in an argon-protected tube furnace for activation at 750℃ for 2 h. After cooling to room temperature, it was washed with deionized water until neutral and vacuum dried for 12 h to obtain a porous carbon framework. 20% Li (by mass) was then used... 10 GeP2S 12 Anhydrous ethanol was added, and the mixture was stirred for 8 minutes under argon protection and then sonicated for 20 minutes to obtain the first solid electrolyte precursor solution. The porous carbon skeleton was immersed in the precursor solution, sonicated for 45 minutes, freeze-dried at -90℃ for 8 hours, and then heated to 250℃ and held for 1.5 hours to obtain a porous carbon skeleton coated with solid electrolyte.

[0046] The porous carbon framework was placed in a CVD reactor, and silane, borane and phosphine were introduced. The volume ratio of silane, borane and phosphine was 100:2:2. The reactor pressure was 4 kPa, the heating rate was 5 °C / min, and the temperature was raised to 650 °C and held for 3 h to form a boron and phosphorus co-doped nano-silicon layer. Then acetylene was introduced, and secondary vapor deposition was carried out at 750 °C for 6 h to obtain a silicon-carbon composite substrate.

[0047] Take 10% Li by mass 10 GeP2S 12 Anhydrous ethanol was added, and the mixture was stirred for 10 min under argon protection and ultrasonically treated for 25 min to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate was immersed in the precursor solution, spray-dried under nitrogen protection, and then kept at 280℃ for 1 h to obtain a porous carbon framework silicon-carbon anode.

[0048] Porous carbon framework silicon-carbon anode, Li 10 GeP2S 12 Conductive carbon black and styrene-butadiene rubber were mixed in a mass ratio of 70:15:5:10, and DMSO solvent was added. The mixture was stirred in a vacuum mixer for 4 hours to obtain a negative electrode slurry. The negative electrode slurry was coated onto a copper foil current collector, dried at 80°C, cold-pressed at 10MPa, cut into sheets, slit, and vacuum-dried at 100°C for 18 hours to obtain a porous carbon-framework silicon-carbon negative electrode sheet. The above negative electrode sheet was then combined with an NCM811 positive electrode and Li... 10 GeP2S 12 A lithium-ion battery is obtained by assembling a solid electrolyte and a battery casing. XPS can detect a P-type electrode with a binding energy of 133 eV. 2p Characteristic peaks and binding energy at 190 eV for B 1s Characteristic peak; the characteristic absorption peak located at 578 cm⁻¹ can be detected by FT-IR. -1 The Ge-S bond and located at 685cm -1 The PS key.

[0049] Example 5 Phenolic resin-based mesoporous carbon was dispersed in an 8% hydrochloric acid solution and ultrasonically etched for 11 min. Potassium hydroxide powder was added, mixed thoroughly, and then placed in an argon-protected tube furnace for activation at 750℃ for 2 h. After cooling to room temperature, it was washed with deionized water until neutral and vacuum dried for 12 h to obtain a porous carbon framework. 20% Li (by mass) was then used... 10 GeP2S 12 Anhydrous ethanol was added, and the mixture was stirred for 8 minutes under argon protection and then sonicated for 20 minutes to obtain the first solid electrolyte precursor solution. The porous carbon skeleton was immersed in the precursor solution, sonicated for 45 minutes, freeze-dried at -90℃ for 8 hours, and then heated to 250℃ and held for 1.5 hours to obtain a porous carbon skeleton coated with solid electrolyte.

[0050] The porous carbon framework was placed in a CVD reactor, and silane, ammonia, borane and phosphine were introduced. The volume ratio of silane, ammonia, borane and phosphine was 100:2:2:2. The reactor pressure was 4.5 kPa, the heating rate was 5 °C / min, and the temperature was raised to 650 °C and held for 3 h to form a nitrogen, boron and phosphorus co-doped nano-silicon layer. Then acetylene was introduced, and secondary vapor deposition was carried out at 750 °C for 6 h to obtain a silicon-carbon composite substrate.

[0051] Take 10% Li by mass 10 GeP2S 12 Anhydrous ethanol was added, and the mixture was stirred for 10 min under argon protection and ultrasonically treated for 25 min to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate was immersed in the precursor solution, spray-dried under nitrogen protection, and then kept at 280℃ for 1 h to obtain a porous carbon framework silicon-carbon anode.

[0052] Porous carbon framework silicon-carbon anode, Li 10 GeP2S 12 Conductive carbon black and styrene-butadiene rubber were mixed in a mass ratio of 70:15:5:10, and DMSO solvent was added. The mixture was stirred in a vacuum mixer for 4 hours to obtain a negative electrode slurry. The negative electrode slurry was coated onto a copper foil current collector, dried at 80°C, cold-pressed at 10MPa, cut into sheets, slit, and vacuum-dried at 100°C for 18 hours to obtain a porous carbon-framework silicon-carbon negative electrode sheet. The above negative electrode sheet was then combined with an NCM811 positive electrode and Li... 10 GeP2S 12 A lithium-ion battery is obtained by assembling a solid electrolyte and a battery casing. The binding energy of N₂ at 398 eV can be detected using XPS. 1s Characteristic peaks, binding energy of P at 133 eV 2p Characteristic peaks and binding energy at 190 eV for B 1s Characteristic peak; the characteristic absorption peak located at 578 cm⁻¹ can be detected by FT-IR. -1 The Ge-S bond and located at 685cm -1 The PS key.

[0053] Comparative Example 1 Compared with Example 1, the difference is that: in step S1, the first solid electrolyte coating treatment was not performed, and the porous carbon framework was directly used for vapor deposition in step S2.

[0054] Comparative Example 2 The difference compared to Example 1 is that the porous carbon skeleton in step S1 was not modified.

[0055] Comparative Example 3 Compared with Example 1, the difference is that in step S2, no doping gas is introduced, but only a silicon source is introduced for vapor deposition.

[0056] Comparative Example 4 Compared with Example 1, the difference is that no polymer additives were added to the second solid electrolyte precursor solution in step S3.

[0057] Comparative Example 5 The difference from Example 1 is that the secondary vapor deposition in step S2 was not performed.

[0058] Performance Testing and Results Analysis The lithium-ion batteries prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests. The test items, methods, and results are as follows: Cyclic stability test: At 25℃, the battery was charged to 4.2V at a rate of 0.1C and discharged to 2.0V at a rate of 0.1C to activate it. Then, it was charged and discharged at a rate of 0.5C for 500 cycles. The specific capacity of the first discharge and the specific capacity of the discharge after 500 cycles were recorded. The capacity retention rate (%) was calculated as (specific capacity of discharge after 500 cycles / specific capacity of the first discharge) × 100%.

[0059] Interfacial impedance testing: The interfacial impedance of the battery was tested using an electrochemical workstation via electrochemical impedance spectroscopy (EIS) in the frequency range of 10mHz-100kHz and the amplitude of 5mV.

[0060] Volume expansion rate test: After the negative electrode is charged and discharged 100 times, the electrode cross section is observed using a scanning electron microscope (SEM), the electrode thickness before and after the cycle is measured, and the volume expansion rate (%) is calculated as (thickness after cycle - thickness before cycle) / thickness before cycle × 100%.

[0061] The test results are shown in the table below: Table 1 Battery Performance Test Combining Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 did not undergo the first solid electrolyte coating treatment and directly used the porous carbon framework for vapor deposition, resulting in a lack of ion transport channels at the silicon-carbon interface, with an interface impedance as high as 126.3Ω, significantly higher than the 38.2Ω of Example 1; at the same time, it could not suppress silicon layer agglomeration and pulverization, with a capacity retention rate of only 68.5% after 500 cycles and a volume expansion rate of 22.8% after 100 cycles, far lower than the 88.6% and 9.5% of Example 1, indicating that the first solid electrolyte coating is the basis for opening up ion transport at the internal interface, suppressing abnormal silicon layer growth, and reducing impedance and expansion rate.

[0062] As shown in the table, Example 4 exhibits an initial discharge specific capacity of 1955 mAh / g, a capacity retention rate of 89.2% after 500 cycles, an interface impedance of 35.6 Ω, and a volume expansion rate of 9.0%. This may be due to the presence of Li... 10GeP2S 12 Its ionic conductivity is significantly higher than that of Li6PS5Cl and Li7P3S 11 It can more efficiently open up ion transport channels and reduce interface impedance; at the same time, Li 10 GeP2S 12 The improved compatibility with the silicon-carbon interface further suppresses interfacial side reactions, enhancing specific capacity and cycle stability. Example 5 outperforms Examples 1-4 because it employs N, B, and P co-doping, which, compared to single-element or dual-element doping, more comprehensively fills silicon lattice defects, improving electronic conductivity and structural rigidity. Simultaneously, Li... 10 GeP2S 12 The solid electrolyte and polymer additive-modified outer interface protective layer maximize the suppression of silicon volume expansion and active material shedding, achieving comprehensive optimization of specific capacity, cycle stability, and impedance characteristics.

[0063] Combining Example 1 and Comparative Example 2, it can be seen that the porous carbon framework of Comparative Example 2 was not modified by acid and alkali activation, and the pore structure was not optimized, resulting in uneven silicon layer deposition and insufficient buffer space for volume expansion. After 500 cycles, the capacity retention rate was only 65.7%, and the volume expansion rate reached 24.5%, both lower than that of Example 1. The interface impedance of 118.6Ω was also higher than that of 38.2Ω in Example 1. This indicates that the modification of the porous carbon framework can optimize the pore structure, provide support for uniform silicon deposition and expansion buffer, and is the key to improving structural stability and interface compatibility.

[0064] Combining Example 1 and Comparative Example 3, it can be seen that Comparative Example 3 did not introduce doping gas, but only introduced silicon source for vapor deposition. The electronic structure of silicon-carbon material was not regulated, the conductivity was insufficient, and the interface impedance reached 95.8Ω, which was higher than 38.2Ω in Example 1. At the same time, the silicon lattice defects were not filled, the structural rigidity was insufficient, and the capacity retention rate after 500 cycles was 72.3% and the volume expansion rate was 18.6%, both of which were worse than 88.6% and 9.5% in Example 1, respectively. This shows that N, P, and B doping can regulate the electronic structure, improve conductivity and structural rigidity, and is the core means to suppress silicon particle volume expansion and reduce interface impedance.

[0065] Based on the results of Example 1 and Comparative Example 4, it can be seen that the second solid electrolyte precursor solution in Comparative Example 4 did not contain any polymer additives. As a result, the adhesion and flexibility of the outer interface protective layer were insufficient, making it prone to breakage during charging and discharging. This resulted in the inability to effectively isolate silicon from the electrolyte, leading to repeated regeneration of the SEI film. The interface impedance of 68.4Ω was higher than that of Example 1 (38.2Ω). The capacity retention rate after 500 cycles was 74.6%, and the volume expansion rate was 16.3%, both lower than those of Example 1. This indicates that polymer additives such as lithium polyacrylate and polyethylene glycol can enhance the overall performance of the outer interface protective layer, buffer the volume expansion of silicon, and stabilize the SEI film, which is the key to improving the stability of the outer interface.

[0066] Based on the comparison of Example 1 and Comparative Example 5, it can be seen that Comparative Example 5 did not undergo secondary vapor deposition in step S2, and lacked the coating and support of an amorphous carbon layer. The silicon-carbon composite substrate had poor structural stability, and the active material was easily detached during cycling. The capacity retention rate after 500 cycles was only 70.2%, which was significantly lower than 88.6% in Example 1. The volume expansion rate of 20.1% and the interface impedance of 89.5Ω were also inferior to those in Example 1, indicating that the amorphous carbon layer formed by secondary vapor deposition can further buffer the volume expansion of silicon and enhance the structural integrity of the substrate.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A porous carbon framework, characterized in that, It includes a porous carbon framework material and a first solid electrolyte layer coated on the pore surface of the porous carbon framework material; The porous carbon framework material is phenolic resin or biomass-based mesoporous carbon, with an average pore size of 2-4 nm and a pore volume of 0.7 cc / g-1.4 cc / g. The proportion of micropores below 2 nm is 30%-85%, the proportion of pore volume between 2 nm and 4 nm is 15%-70%, and the proportion of pore volume above 4 nm is less than 20%. The thickness of the first solid electrolyte layer is 0.5-1.5 nm. After the first solid electrolyte layer is coated on the pore surface of the porous carbon framework material, the average pore size is 1.7 nm-2.3 nm, the pore volume is 0.6 cc / g-1.2 cc / g, the pore volume ratio of micropores below 2 nm is 60-95%, the pore volume ratio of pores above 2 nm is 5%-40%, and the pore volume ratio of pores above 3 nm is less than 5%.

2. A porous carbon-framework silicon-carbon anode, characterized in that, It includes the porous carbon framework material as described in claim 1, a first solid electrolyte layer on the pore surface of the porous carbon framework, a nano-silicon layer deposited on the surface of the porous carbon framework with N, P, B single doping or co-doping of two or more of these elements, an amorphous carbon layer covering the outer layer of the porous carbon framework material, and a second solid electrolyte protective layer.

3. A method for preparing a porous carbon framework silicon-carbon anode as described in claim 2, characterized in that, Includes the following steps: S1, prepare a porous carbon framework and a first solid electrolyte precursor solution respectively. The porous carbon framework includes a porous carbon framework material, and the first solid electrolyte precursor solution includes a first solid electrolyte. Immerse the porous carbon framework in the first solid electrolyte precursor solution, disperse, freeze-dry, and solidify it so that the first solid electrolyte coats the surface of the porous carbon framework. S2, a porous carbon framework is introduced into a silicon source and doping gas for vapor phase deposition to form a co-doped nano-silicon layer, and then acetylene is introduced for secondary vapor phase deposition to obtain a silicon-carbon composite substrate, wherein the doping gas contains at least one of N, P and B. S3, prepare a second solid electrolyte precursor solution, immerse the silicon-carbon composite substrate in the second solid electrolyte precursor solution, dry and cure under gas protection, and form a second solid electrolyte protective layer on the surface of the silicon-carbon composite substrate to obtain a porous carbon framework silicon-carbon anode. The second solid electrolyte precursor solution includes a first solid electrolyte and polymer additives.

4. The method for preparing a porous carbon framework silicon-carbon anode as described in claim 3, characterized in that, Step S1 includes: S1.1, the porous carbon framework material is dispersed in an acidic solution, ultrasonically etched for 10-12 min, alkali is added and mixed, activated under gas protection and 700-900℃ for 1-3 h, cooled, washed and dried to obtain a porous carbon framework, the first solid electrolyte and organic solvent are mixed under gas protection, stirred for 5-10 min, and ultrasonically treated for 15-30 min to obtain the first solid electrolyte precursor solution; S1.2, the porous carbon skeleton is immersed in the first solid electrolyte precursor solution, ultrasonically treated for 30-60 min, dried at -100℃ to 80℃ for 6-12 h, heated to 200-300℃, and kept at the temperature for 1-2 h to coat the surface of the porous carbon skeleton with the first solid electrolyte.

5. The method for preparing a porous carbon framework silicon-carbon anode as described in claim 4, characterized in that, The first solid electrolyte includes 5-30% by mass of Li6PS5Cl and Li7P3S 11 Li 10 GeP2S 12 Li 5.5 PS 4.5 Cl 1.5 Li 6.8 Si 0.8 As 0.2 S5I porous carbon framework material.

6. The method for preparing a porous carbon framework silicon-carbon anode as described in claim 3, characterized in that, Step S2 includes: S2.1, The porous carbon framework is placed in a CVD reactor, and silicon source and doping gas are introduced for vapor deposition. The reactor pressure is 1-5 kPa, the heating rate is 3-5℃ / min, the temperature is heated to 500-650℃, and the temperature is held for 1-3 hours to form a co-doped nano-silicon layer. S2.2, acetylene is introduced, and secondary vapor deposition is carried out at a temperature of 500-950℃ for 0.5-12h to obtain silicon-carbon composite substrate.

7. The method for preparing a porous carbon framework silicon-carbon anode as described in claim 6, characterized in that, The silicon source includes silane, and the carrier gas includes argon. The volume ratio of silane to doping gas is 100:(1-5).

8. The method for preparing a porous carbon framework silicon-carbon anode as described in claim 3, characterized in that, Step S3 includes: The first solid electrolyte, polymer additives, and organic solvents are mixed under gas protection, stirred for 9-12 minutes, and ultrasonically treated for 15-30 minutes to obtain a second solid electrolyte precursor solution. The silicon-carbon composite substrate is immersed in the second solid electrolyte precursor solution, spray-dried under nitrogen protection, and reacted at 200-300℃ for 1-2 hours to obtain a porous carbon framework silicon-carbon anode. The polymer additives include lithium polyacrylate and polyethylene glycol. The second solid electrolyte precursor solution, by mass percentage, includes 8-15% of the first solid electrolyte, 1-5% of the polymer additives, and the balance is organic solvent.

9. A lithium-ion battery, characterized in that, It includes the porous carbon framework silicon-carbon anode and cathode as described in claim 2, and the first solid electrolyte and shell as described in claim 5.

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