A porous carbon carrier and a preparation method thereof, a silicon-carbon negative electrode material and a lithium ion battery

Abstract

The application provides a kind of porous carbon carrier and its preparation method, silicon-carbon negative electrode material and lithium ion battery, it is related to battery material technical field, the calcium carbonate and titanium dioxide in polymer-based waste are coexisting in polymer-based waste as filler component;The polymer-based waste is sulfonated crosslinking treatment, and the pre-stabilization precursor is obtained;The pre-stabilization precursor is mixed with additional carbon source and activator, and the mixture material is obtained;The mixture material is subjected to segmented carbonization treatment, and the carbonization product is obtained;The carbonization product is selectively pickled with acid liquor to remove at least part of calcium-based sacrificial template formed by calcium carbonate and its reaction conversion product, and the titanium dioxide is retained.The application utilizes endogenous component synergistic control, constructs hierarchical pore buffer and interface anchoring double structure, effectively relieves silicon negative electrode volume expansion, and improves cycle stability.

Description

Technical Field

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

[0002] White waste plastics mainly include white polyethylene film, white polypropylene packaging parts, polystyrene foam products, white appliance casing scraps, white masterbatch waste, white packaging drums, white pipes, white sheets, and white plastic scraps from daily chemical and electronic products. This type of waste plastic has a wide range of sources and is generated in large quantities, continuously appearing in packaging, logistics, appliance manufacturing, and daily necessities processing. Due to its distinctive color, complex filler composition, and susceptibility to oil contamination, aging, and additive migration during use, it is difficult to reintegrate into high-grade plastic product systems after recycling. It is typically only suitable for low-value reuse, incineration, or landfill disposal, resulting in resource waste and a significant environmental burden.

[0003] From a recycling perspective, while white waste plastics have a relatively uniform color, their actual origins are quite complex. They are typically a mixture of polyolefins, styrene-based plastics, polyesters, polycarbonates, polyamides, and polyurethanes of different grades, processing histories, and inorganic filler contents. These raw materials are prone to problems such as fluctuating rheological properties, decreased compatibility, deterioration of mechanical properties, and irreversible color changes during melt reprocessing. This limits traditional mechanical recycling methods to areas such as recycled boards, low-end reusable products, or modified filler materials.

[0004] While existing methods for preparing carbon materials from waste plastics are considered an important direction for high-value utilization, polyolefins such as polyethylene and polypropylene are prone to chain breakage and generate a large number of volatile small molecules during direct pyrolysis or carbonization, resulting in a generally low carbonization rate. Relying solely on the carbonization of waste plastics not only leads to insufficient carbon framework retention but also affects subsequent activation, pore formation, and particle stability. On the other hand, silicon materials have high theoretical capacity and are an important development direction for high-energy-density lithium-ion battery anodes. However, silicon suffers from significant volume expansion, pulverization, conductive network damage, and repeated rupture of the solid electrolyte interface film during lithium insertion / extraction. Porous carbon itself is not suitable as the sole active anode material in high-performance silicon anode systems, but it can serve as a conductive carrier and buffer framework for silicon phase deposition, insertion, and dispersion. Porous carbon with a synergistic structure of micropores, mesopores, and macropores can provide dispersion space and volume buffer space for the silicon phase and improve electron / ion transport, which is beneficial for enhancing the cycle stability of silicon-carbon composite anodes. Polyolefin plastics, especially polyethylene and polypropylene, have molecular chains mainly composed of saturated C-C bonds and CH bonds, lacking aromatic rings, oxygen-containing functional groups, or structural units that are easily cyclized and cross-linked. During heating in an inert atmosphere, these polymers typically soften and melt, subsequently undergoing reactions such as free radical chain scission, β-cracking, and hydrogen transfer to generate low-molecular-weight hydrocarbons, waxes, and oil and gas products, making it difficult to form a stable and continuous solid carbon skeleton in situ. Therefore, without pre-stabilization treatment, direct carbonization of waste plastics usually suffers from problems such as low solid char yield, difficulty in maintaining particle morphology, insufficient continuity of the carbon skeleton, uncontrollable pore structure, and low efficiency in subsequent activation and pore-forming processes. Summary of the Invention

[0005] To address the problems of low carbonization rate, reliance on external templates for pore structure control, and poor interface stability after silicon loading in existing technologies, this application achieves in-situ dual-function control of endogenous components in polymer-based waste and stable reconstruction of the carbon skeleton through a porous carbon carrier and its preparation method, silicon-carbon anode material, and lithium-ion battery. This results in a high-performance silicon-carbon anode carrier that combines hierarchical pore buffer space and a stable anchoring interface.

[0006] In a first aspect, the present invention provides a method for preparing a porous carbon support, comprising the following steps: S1. Provide white waste plastic as polymer-based waste, wherein the polymer-based waste contains inorganic white filler; S2. Sort, clean, dry and crush polymer-based waste materials; S3. The crushed polymer-based waste is subjected to sulfonation and crosslinking treatment to obtain a pre-stabilized precursor. S4. Mix the prestabilized precursor with a high-carbon auxiliary carbon source and an activator to obtain a mixture. S5. Perform segmented heat treatment on the mixture to obtain carbonized products; S6. The carbonization product is selectively acid-washed with acid to remove the calcium-based sacrificial phase derived from calcium carbonate and retain titanium dioxide. Then, it is washed with water until neutral and dried to obtain the porous carbon support. The calcium-based sacrificial phase is used to form the pore structure, and the retained titanium dioxide is used to form interface anchoring points.

[0007] Preferably, the inorganic white filler includes one or more of TiO2, CaCO3, talc, barium sulfate, zinc oxide, wollastonite, and mica powder, wherein the TiO2 content is 0.1-20 wt% and the CaCO3 content is 0.5-40 wt%.

[0008] Preferably, CaCO3 can be partially converted into calcium sulfate, acid calcium sulfate and / or its hydrate during the sulfonation crosslinking process, and participate in pore formation as a removable calcium-based sacrificial phase during the subsequent acid washing process.

[0009] Preferably, the polymer-based waste includes at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, and polyurethane.

[0010] Preferably, the sulfonating agent used in the sulfonation crosslinking treatment includes at least one of sulfuric acid, fuming sulfuric acid, or chlorosulfonic acid.

[0011] Preferably, the sulfonation crosslinking treatment is carried out at a temperature of 40–160°C for a time of 0.2–8 h.

[0012] Preferably, the sulfonating agent is sulfuric acid with a mass fraction of 60–98 wt%.

[0013] Preferably, the solid-liquid ratio of polymer-based waste to sulfonating agent is 1:(1-12).

[0014] Preferably, after sulfonation and crosslinking treatment, the product after sulfonation and crosslinking treatment is washed until the pH of the filtrate is 1-6, and then dried at 50-120°C for 4-24 hours to obtain a pre-stabilized precursor.

[0015] Preferably, the high-carbon auxiliary carbon source includes one or at least two of the following: waste tire pyrolysis carbon, waste rubber carbon powder, biochar, pitch coke, petroleum coke, waste phenolic resin carbon, waste epoxy resin carbon, and coal-based pitch carbon.

[0016] Preferably, the activator includes at least one of an alkali metal carbonate or an alkali metal hydroxide.

[0017] Preferably, the mixture also includes nitrogen-containing additives, including one or at least two of urea, melamine, dicyandiamine, amino acids, and polyvinylpyrrolidone.

[0018] Preferably, the mass ratio of high-carbon auxiliary carbon source to prestabilized precursor is (0.05-2.0):1, the mass ratio of activator to prestabilized precursor is (0.1-5.0):1, and the mass ratio of nitrogen-containing auxiliary agent to prestabilized precursor is (0.01-1.5):1.

[0019] Preferably, the acid is an inorganic acid that does not dissolve titanium dioxide, including hydrochloric acid or nitric acid.

[0020] Preferably, the concentration of the acid solution is 0.1–6 mol / L, the selective pickling temperature is 20–95 °C, and the time is 0.2–8 h.

[0021] Preferably, the selective acid washing is used to remove calcium-based sacrificial phases derived from CaCO3, the calcium-based sacrificial phases including one or more of CaCO3, CaSO4, Ca(HSO4)2 and their hydrates.

[0022] Preferably, after selective acid washing, the residual calcium content in the porous carbon support is less than 0.1 wt%, the residual potassium content is less than 0.2 wt%, the residual sodium content is less than 0.1 wt%, and the residual iron content is less than 0.2 wt%.

[0023] Preferably, the segmented heat treatment includes: first heating to 200-450°C and holding at that temperature for 0.2-4 hours, then heating to 600-1100°C and holding at that temperature for 0.2-5 hours.

[0024] Preferably, the initial heating rate is 0.5–10 °C / min, and the subsequent heating rate is 1–15 °C / min.

[0025] Preferably, the preparation method further includes: combining a porous carbon support with a silicon source, so that the silicon phase is deposited, embedded or loaded on the pores and surface of the porous carbon support to obtain a silicon-carbon anode material.

[0026] Preferably, the silicon source includes at least one of nano-silicon powder, silane, trichlorosilane, silicon tetrachloride, siloxane, or gaseous silicon source; the mass ratio of silicon in the silicon source to the porous carbon support is (0.1-4):1.

[0027] Secondly, the present invention also provides a porous carbon support having a synergistic distribution structure of micropores, mesopores and macropores, the synergistic distribution structure being used to provide a conductive network and buffer space; The porous carbon support has titanium dioxide lattice anchor points embedded on the carbon skeleton surface and pore walls. These titanium dioxide lattice anchor points are derived from the titanium dioxide filler contained in the polymer-based waste and are used to enhance the interfacial bonding stability.

[0028] Thirdly, the present invention also provides a silicon-carbon anode material, comprising a porous carbon support and a silicon phase supported on the pores and / or surface of the porous carbon support. The mass fraction of silicon in silicon-carbon anode materials is 10–80 wt%. The specific surface area of ​​silicon-carbon anode materials is 5–300 m². 2 / g, tap density is 0.6~1.4g / cm³ 3 The electrical conductivity of the powder is 0.05–2.0 S / cm.

[0029] Fourthly, the present invention also provides a lithium-ion battery, comprising a negative electrode sheet made of silicon-carbon negative electrode material; The negative electrode sheet comprises the following components by weight: 80 to 96 parts of the silicon-carbon negative electrode material, 1 to 10 parts of conductive agent and 1 to 10 parts of binder.

[0030] The beneficial effects of this invention are: 1. This invention utilizes calcium carbonate and titanium dioxide, which are originally considered impurities in polymer-based waste, as endogenous functional components. Through selective acid washing, a one-step synergistic control of sacrificial template pore creation and interface anchor point retention is achieved. Porous carbon carriers with hierarchical pore structure and stable anchoring interface can be constructed without the addition of external template agents, which significantly reduces production costs and simplifies the process.

[0031] 2. By employing a synergistic carbon supplementation strategy of sulfonation crosslinking prestabilization treatment and an external carbon source with high fixed carbon content, the inherent defects of low carbonization rate and easy skeleton collapse during direct carbonization of waste plastics such as polyolefins are effectively overcome. A regenerated carbon skeleton with continuous structure, high mechanical strength and excellent conductivity is obtained, providing a solid material basis for the stable loading of silicon phase.

[0032] 3. The titanium dioxide lattice anchoring points in the porous carbon support of this invention, derived from the internal filler, enhance the interfacial bonding force between the silicon phase and the carbon skeleton at the microscale. Combined with the volume buffer space provided by the hierarchical pore structure, it effectively alleviates the volume expansion stress and interfacial instability problems of silicon anodes during long-term cycling, and significantly improves the cycle life and rate performance of silicon-carbon anode materials.

[0033] 4. This invention realizes the high-value transformation of waste plastics into key materials for high-value lithium-ion batteries. It not only provides a new technical path to solve the problem of white pollution, but also provides a sustainable alternative to alleviate the dependence of the new energy industry on resources such as natural graphite, and has significant environmental and economic benefits. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the preparation process of a white waste plastic porous carbon carrier in Example 1 of the present invention. Figure 2This is a SEM image of the porous carbon support prepared in Example 1 of the present invention; Figure 3 The first charge-discharge curve of the silicon-carbon anode battery prepared using the porous carbon support prepared in Example 1 and Comparative Example 2 of the present invention. Figure 4 The graph shows the capacity retention rate of a battery composed of a silicon-carbon anode obtained from the porous carbon support prepared in Example 1 and Comparative Example 2 of this invention after 100 cycles. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] A method for preparing a porous carbon support, such as Figure 1 This includes the following steps: S1. Provide white waste plastic as polymer-based waste, wherein the polymer-based waste contains inorganic white filler; S2. Sort, clean, dry and crush polymer-based waste materials; S3. The crushed polymer-based waste is subjected to sulfonation and crosslinking treatment to obtain a pre-stabilized precursor. S4. Mix the prestabilized precursor with a high-carbon auxiliary carbon source and an activator to obtain a mixture. S5. Perform segmented heat treatment on the mixture to obtain carbonized products; S6. The carbonization product is selectively acid-washed with acid to remove the calcium-based sacrificial phase derived from calcium carbonate and retain titanium dioxide. Then, it is washed with water until neutral and dried to obtain the porous carbon support. The calcium-based sacrificial phase is used to form the pore structure, and the retained titanium dioxide is used to form interface anchoring points.

[0037] By employing the above technical solutions, sulfonation crosslinking treatment can induce a pre-stabilization reaction in polymer molecular chains. Since general-purpose plastics such as polyolefins are prone to chain scission and cracking at high temperatures, generating a large number of volatile small molecules, direct carbonization results in extremely low carbonization rates and framework collapse. Through the action of sulfonating agents, sulfonic acid groups are introduced into the polymer chains, promoting intermolecular dehydration and crosslinking, forming a macromolecular structure with high thermal stability. This pre-stabilized precursor can effectively suppress excessive volatilization during subsequent heating, maintaining the integrity of the solid morphology and laying the material foundation for the final formation of a continuous carbon framework with high mechanical strength. It should be understood that the degree of sulfonation crosslinking needs to be moderate, ensuring sufficient thermal stability while avoiding excessive reaction that could lead to precursor embrittlement or excessive impurity residue.

[0038] Although sulfonation crosslinking enhances the carbonization potential of waste plastics, a high-carbon auxiliary carbon source with high fixed carbon content is introduced as a supplementary skeleton material to further improve the conductivity and structural strength of the carbon framework. The external carbon source is added after sulfonation crosslinking. This avoids its ineffective consumption or destruction in the strongly acidic sulfonation environment and allows it to form a complementary enhancement effect with the pre-stabilized precursor at the microscale. Simultaneously, the addition of an activator aims to etch the carbon layer through a high-temperature redox reaction, working synergistically with the endogenous calcium carbonate template to construct a well-developed porous structure.

[0039] The carbonized product is then obtained through segmented heat treatment. In the lower temperature range, the main processes include further solidification of the pre-stabilized precursor, improvement of the cross-linked network, and initial carbonization, preventing internal stress concentration or structural cracking due to excessively rapid heating. In the higher temperature range, the main processes include graphitization rearrangement of the carbon skeleton, pore-forming reaction of the activator, and stabilization of the endogenous calcium carbonate template. By precisely controlling the heating rate and holding conditions at each stage, a dynamic balance between carbon skeleton densification and pore development can be achieved, resulting in a carbonized intermediate with a complete structure and abundant pores.

[0040] Finally, a porous carbon support is obtained through selective acid washing. Selective acid washing refers to the differential removal of calcium-based sacrificial phases derived from CaCO3 and TiO2 in a specific acid solution, utilizing the difference in chemical stability in the same acid washing system. Specifically, CaCO3 in white waste plastics can undergo an acid-base reaction with sulfuric acid during sulfonation crosslinking, at least partially transforming into calcium-containing intermediate phases such as CaSO4, Ca(HSO4)2, and / or their hydrates. In subsequent staged heat treatment, these calcium-based components can still be distributed as solid site-occupying phases within the carbon skeleton. After selective acid washing with hydrochloric acid or nitric acid, the CaCO3 and its transformed calcium-containing intermediate phases are removed, leaving in-situ interconnected channels formed by the calcium-based sacrificial phase. At the same time, the acid solution is essentially insoluble or has very low solubility for TiO2, allowing the TiO2 particles originally dispersed in the matrix to be stably retained on the surface of the carbon skeleton and inside the pore walls, forming uniformly distributed lattice anchoring points.

[0041] In some embodiments, the inorganic white filler includes one or more of TiO2, CaCO3, talc, barium sulfate, zinc oxide, wollastonite, and mica powder, wherein the TiO2 content is 0.1-20 wt% and the CaCO3 content is 0.5-40 wt%.

[0042] During the sulfonation crosslinking process, CaCO3 can be partially converted into calcium sulfate, acid calcium sulfate and / or its hydrates, and participate in pore formation as a removable calcium-based sacrificial phase in the subsequent acid washing process.

[0043] By adopting the above technical solution, TiO2 and CaCO3 are the intrinsic components of white waste plastics. During the subsequent carbonization process, they can perform dual functions in situ: CaCO3 acts as a sacrificial template to reserve pore channels, while TiO2 acts as an interface anchor point to enhance bonding. This utilization method based on intrinsically coexisting components avoids the uneven dispersion problem caused by poor compatibility in the external template method, while also simplifying the process and reducing raw material costs.

[0044] In some embodiments, polymer-based waste includes at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, and polyurethane.

[0045] In some embodiments, the sulfonating agent used in the sulfonation crosslinking treatment includes at least one of concentrated sulfuric acid, fuming sulfuric acid, or chlorosulfonic acid.

[0046] The sulfonation crosslinking treatment is carried out at a temperature of 40–160℃ for 0.2–8 hours.

[0047] The sulfonating agent is sulfuric acid with a mass fraction of 60–98 wt%.

[0048] The solid-liquid ratio of polymer-based waste to sulfonating agent is 1:(1-12).

[0049] After sulfonation and crosslinking treatment, the product is washed until the pH of the filtrate is 1-6, and then dried at 50-120°C for 4-24 hours to obtain a pre-stabilized precursor.

[0050] By adopting the above technical solutions, the sulfonation treatment with the above parameter combination can efficiently induce the pre-stabilization of polyolefin segments under mild conditions, forming a sufficient cross-linked network.

[0051] In some embodiments, the high-carbon auxiliary carbon source includes one or at least two of the following: waste tire pyrolysis carbon, waste rubber carbon powder, biochar, pitch coke, petroleum coke, waste phenolic resin carbon, waste epoxy resin carbon, and coal-based pitch carbon.

[0052] The activator includes at least one of alkali metal carbonates or alkali metal hydroxides.

[0053] The mixture also includes nitrogen-containing additives, including one or at least two of urea, melamine, dicyandiamine, amino acids, and polyvinylpyrrolidone.

[0054] The mass ratio of high-carbon auxiliary carbon source to prestabilized precursor is (0.05-2.0):1, the mass ratio of activator to prestabilized precursor is (0.1-5.0):1, and the mass ratio of nitrogen-containing auxiliary agent to prestabilized precursor is (0.01-1.5):1.

[0055] By adopting the above technical solution, the high-carbon auxiliary carbon source must be added to the mixing system only after the sulfonation crosslinking treatment is completed and the mixture is washed and dried. If added before sulfonation, the high-carbon material will consume a large amount of sulfonation reagent, increasing costs and reducing the modification efficiency of the polymer. However, adding it after sulfonation can maximize its carbon-supplementing function in skeleton reinforcement and conductive network construction. The activator can be one or at least two of K2CO3, KHCO3, Na2CO3, NaHCO3, KOH, and NaOH. The CO2 and metal elements generated by the activator decompose at high temperatures can effectively etch the carbon layer and work together with the endogenous CaCO3 template to construct a well-developed porous structure. The ammonia gas released by the nitrogen-containing additive during heat treatment can be used as a nitrogen source for in-situ doping into the carbon skeleton, which not only improves the surface polarity and electrolyte wettability of the material, but also introduces additional pseudocapacitive lithium storage sites. The optimized range of the proportions of each component ensures a balance between carbon supplementation, pore formation, and doping effects, avoiding pore structure collapse or impurity residue caused by excessive additives.

[0056] In some embodiments, the acid is an inorganic acid that does not dissolve titanium dioxide, including hydrochloric acid or nitric acid.

[0057] The concentration of the acid solution is 0.1–6 mol / L, the selective pickling temperature is 20–95℃, and the time is 0.2–8 h.

[0058] Selective acid washing is used to remove calcium-based sacrificial phases derived from CaCO3, including one or more of CaCO3, CaSO4, Ca(HSO4)2 and their hydrates.

[0059] After selective acid washing, the residual calcium content in the porous carbon support is less than 0.1 wt%, the residual potassium content is less than 0.2 wt%, the residual sodium content is less than 0.1 wt%, and the residual iron content is less than 0.2 wt%.

[0060] By adopting the above technical solutions, the selectivity and purity of the acid washing system are strictly limited, ensuring that the titanium dioxide anchoring points are fully preserved while efficiently removing the calcium carbonate template and activation byproducts. The extremely low residual impurities guarantee the electrochemical stability of the porous carbon support as a battery anode material, avoiding self-discharge or electrolyte decomposition side reactions caused by metal impurities. Specifically, a residual calcium content of less than 0.1 wt% directly proves that the endogenous calcium carbonate template has been efficiently removed, and a continuous hierarchical pore structure has formed inside the carbon framework, providing ample space for subsequent silicon phase loading. If the residual calcium content is too high, it indicates that the pores are blocked, limiting the silicon loading and resulting in insufficient volume buffering capacity.

[0061] In some embodiments, the segmented heat treatment includes: first heating to 200–450°C and holding at that temperature for 0.2–4 hours, then heating to 600–1100°C and holding at that temperature for 0.2–5 hours.

[0062] The initial heating rate is 0.5–10 °C / min, and the subsequent heating rate is 1–15 °C / min.

[0063] By adopting the above technical solutions, the sulfonic acid groups introduced in the first-stage sulfonation further promote intermolecular dehydration condensation, transforming linear or branched polymer chains into trapezoidal or network structures with higher thermal stability. Simultaneously, it avoids the rapid escape of internal small-molecule gases due to excessively rapid heating, which could cause framework rupture or the formation of closed pores. In the second stage, the activator undergoes a redox reaction to etch the carbon layer, forming abundant pores. Simultaneously, amorphous carbon transforms into a microcrystalline graphite structure to improve conductivity. The endogenous calcium carbonate particles also maintain a thermally stable morphology at this temperature, reserving precise template space for subsequent acid washing.

[0064] In some embodiments, the preparation method further includes combining a porous carbon support with a silicon source to deposit, embed, or load a silicon phase onto the pores and surface of the porous carbon support, thereby obtaining a silicon-carbon anode material.

[0065] The silicon source includes at least one of nano-silicon powder, silane, trichlorosilane, silicon tetrachloride, siloxane, or gaseous silicon source; the mass ratio of silicon in the silicon source to the porous carbon support is (0.1-4):1.

[0066] By adopting the above technical solutions, porous carbon supports possess a hierarchical pore system, providing multi-dimensional storage space for the silicon phase. Macropores act as macroscopic buffer chambers to alleviate volume expansion, while mesopores and micropores provide highly dispersed sites and short-range ion transport channels. The composite method can be flexibly selected according to the performance requirements of the target product, including but not limited to physical-mechanical mixing, solution impregnation, and chemical vapor deposition.

[0067] A porous carbon support having a synergistic distribution structure of micropores, mesopores and macropores, the synergistic distribution structure being used to provide a conductive network and buffer space; The porous carbon support has titanium dioxide lattice anchor points embedded on the carbon skeleton surface and pore walls. These titanium dioxide lattice anchor points are derived from the titanium dioxide filler contained in the polymer-based waste and are used to enhance the interfacial bonding stability.

[0068] By adopting the above technical solutions, when used as a silicon-carbon anode support, these in-situ titanium dioxide lattices can form strong interactions with the silicon phase, significantly enhancing the bonding force at the silicon / carbon interface and effectively suppressing the shedding of silicon active materials and the occurrence of interfacial side reactions during cycling. In contrast, if exogenously added titanium dioxide is used for post-modification, it is often difficult to achieve the same level of interfacial stability due to poor interfacial wettability and weak bonding force.

[0069] A silicon-carbon anode material includes a porous carbon support and a silicon phase supported on the pores and / or surface of the porous carbon support. The mass fraction of silicon in silicon-carbon anode materials is 10–80 wt%. The specific surface area of ​​silicon-carbon anode materials is 5–300 m². 2 / g, tap density is 0.6~1.4g / cm³ 3 The electrical conductivity of the powder is 0.05–2.0 S / cm.

[0070] By adopting the above technical solutions, the key physicochemical indicators of the final silicon-carbon anode material were defined, ensuring that the material has high capacity, a suitable specific surface area to balance the first-efficiency and electrolyte consumption, good tap density to improve volumetric energy density, and sufficient electronic conductivity to support high-rate charge and discharge.

[0071] A lithium-ion battery, comprising a negative electrode sheet made of silicon-carbon negative electrode material; The negative electrode sheet comprises the following components by weight: 80 to 96 parts of the silicon-carbon negative electrode material, 1 to 10 parts of conductive agent and 1 to 10 parts of binder.

[0072] Example Example 1: A silicon-carbon anode material was prepared by the following method: Weigh 100g of a cleaned and dried white PE / PP film mixture, containing 7.5wt% TiO2 and 20.0wt% CaCO3, and crush it to approximately 1-3mm. Add it to 400mL of 92% sulfuric acid and stir in an oil bath at 85℃ for 2 hours. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12 hours to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor and mix it with 30g of waste tire pyrolysis char, 80g of K2CO3, and 20g of urea, and ball mill for 30min. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, raise the temperature to 320℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 800℃ at 5℃ / min and hold for 2 hours. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-1. WPRPC-1 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-1.

[0073] Example 2: A silicon-carbon anode material was prepared by the following method: 100g of cleaned and dried white PS foam lunch box, containing 7.5wt% TiO2 and 20.0wt% CaCO3, was weighed and crushed to approximately 1-3mm. It was added to 400mL of 90% sulfuric acid and stirred in an oil bath at 80℃ for 1.5h. The mixture was filtered and washed until the pH of the filtrate reached 3, then vacuum dried at 80℃ for 12h to obtain a pre-stabilized precursor. 100g of the pre-stabilized precursor was mixed with 30g of waste tire pyrolysis char, 60g of K2CO3, and 20g of urea, and ball-milled for 30min. The resulting mixture was placed in a tube furnace and purged with high-purity N2. The temperature was first increased to 320℃ at 3℃ / min and held for 1h, then increased to 780℃ at 5℃ / min and held for 2h. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-2. WPRPC-2 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-2.

[0074] Example 3: A silicon-carbon anode material was prepared by the following method: Weigh 100g of cleaned and dried white PE / PP masterbatch scraps, containing 7.5wt% TiO2 and 20.0wt% CaCO3, and crush them to approximately 1-3mm. Add the scraps to 400mL of 95% sulfuric acid and stir in an oil bath at 90℃ for 1.5h. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12h to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor and mix it with 30g of waste tire pyrolysis char, 100g of K2CO3, and 20g of urea, and ball mill for 30min. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, raise the temperature to 320℃ at 3℃ / min and hold for 1h, then raise the temperature to 820℃ at 5℃ / min and hold for 2h. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-3. WPRPC-3 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-3.

[0075] Example 4: A silicon-carbon anode material was prepared by the following method: 100g of cleaned and dried white PET packaging sheet, containing 7.5wt% TiO2 and 20.0wt% CaCO3, was weighed and crushed to approximately 1-3mm. It was added to 400mL of 88% sulfuric acid and stirred in an oil bath at 100℃ for 1h. The mixture was filtered and washed until the pH of the filtrate reached 3, then vacuum dried at 80℃ for 12h to obtain a pre-stabilized precursor. 100g of the pre-stabilized precursor was mixed with 30g of waste tire pyrolysis char, 90g of K2CO3, and 20g of urea, and ball-milled for 30min. The resulting mixture was placed in a tube furnace and purged with high-purity N2. The temperature was first increased to 320℃ at 3℃ / min and held for 1h, then increased to 840℃ at 5℃ / min and held for 2h. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-4. WPRPC-4 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-4.

[0076] Example 5: A silicon-carbon anode material was prepared by the following method: Weigh 100g of cleaned and dried white ABS appliance casing scraps, containing 7.5wt% TiO2 and 20.0wt% CaCO3, and crush them to approximately 1-3mm. Add the scraps to 400mL of 85% sulfuric acid and stir in an oil bath at 95℃ for 2 hours. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12 hours to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor and mix it with 25g of petroleum coke, 90g of K2CO3, and 20g of urea, and ball mill for 30 minutes. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, raise the temperature to 320℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 800℃ at 5℃ / min and hold for 2 hours. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-5. WPRPC-5 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-5.

[0077] Example 6: A silicon-carbon anode material was prepared by the following method: Weigh 100g of cleaned and dried white PC / ABS mixed scrap, containing 7.5wt% TiO2 and 20.0wt% CaCO3, and crush it to approximately 1-3mm. Add it to 400mL of 80% sulfuric acid and stir in an oil bath at 110℃ for 1h. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12h to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor and mix it with 40g of waste tire pyrolysis char, 120g of K2CO3, and 20g of urea, and ball mill for 30min. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, raise the temperature to 320℃ at 3℃ / min and hold for 1h, then raise the temperature to 860℃ at 5℃ / min and hold for 2h. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support, WPRPC-6. WPRPC-6 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment, so that the nano-silicon was embedded and loaded into the pores and surface of the porous carbon three-dimensional network to obtain the silicon-carbon anode material Si / WPRPC-6.

[0078] Example 7: A silicon-carbon anode material was prepared by the following method: Weigh 100g of cleaned and dried white PU / PA composite scrap, containing 7.5wt% TiO2 and 20.0wt% CaCO3, and crush it to approximately 1-3mm. Add it to 400mL of 90% sulfuric acid and stir in an oil bath at 75℃ for 3h. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12h to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor and mix it with 30g of biochar, 100g of K2CO3 and Na2CO3, and 20g of urea, and ball mill for 30min. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, heat to 320℃ at 3℃ / min and hold for 1h, then heat to 780℃ at 5℃ / min and hold for 2h. The obtained carbonization product was acid-washed with 1 mol / L hydrochloric acid at 60 °C for 1.5 h, washed with water until neutral, and dried to obtain a hierarchical porous carbon support WPRPC-7. WPRPC-7 was mixed with nano-silicon powder at a mass ratio of 1:1.5 and subjected to gas-phase carbon coating treatment to embed and load nano-silicon into the pores and surface of the porous carbon three-dimensional network, thus obtaining the silicon-carbon anode material Si / WPRPC-7.

[0079] Comparative Example Comparative Example 1, a silicon-carbon anode material Si / CP-1, differs from Example 1 only in that the pre-sulfonation crosslinking step is omitted. Instead, the white PE / PP film mixture after cleaning, drying and crushing is directly mixed with waste tire pyrolysis carbon, K2CO3 and urea, and then subjected to segmented heat treatment, acid washing and silicon composite.

[0080] Comparative Example 2, a silicon-carbon anode material Si / CP-2, differs from Example 1 only in that a transparent PE / PP mixture without TiO2 and CaCO3 replaces the white PE / PP waste plastic.

[0081] Comparative Example 3, a silicon-carbon anode material Si / CP-3, differs from Example 1 only in that it does not contain a high-carbon auxiliary carbon source.

[0082] Comparative Example 4: A silicon-carbon anode material, Si / CP-4, was prepared by the following method: Weigh 100g of the cleaned and dried transparent PE / PP film mixture and crush it to approximately 1-3mm. Add it to 400mL of 92% sulfuric acid and stir for 2 hours in an oil bath at 85℃. Filter and wash until the pH of the filtrate reaches 3, then vacuum dry at 80℃ for 12 hours to obtain a pre-stabilized precursor. Take 100g of the pre-stabilized precursor, add 7.5g of TiO2 and 20g of CaCO3, and mix with 30g of waste tire pyrolysis carbon, 80g of K2CO3, and 20g of urea. Ball mill for 30min. Place the resulting mixture in a tube furnace and introduce high-purity N2. First, raise the temperature to 320℃ at 3℃ / min and hold for 1 hour, then raise the temperature to 800℃ at 5℃ / min and hold for 2 hours. The resulting carbonized product is acid-washed with 1mol / L hydrochloric acid at 60℃ for 1.5 hours, washed with water until neutral, and dried to obtain a hierarchical porous carbon support CP-4. Hierarchical porous carbon support and nano-silicon powder are mixed at a mass ratio of 1:1.5 and then subjected to gas phase carbon coating treatment, so that nano-silicon is embedded and loaded into the pores and surface of the porous carbon three-dimensional network, thus obtaining silicon-carbon anode material Si / CP-4.

[0083] Comparative Example 5, a silicon-carbon anode material Si / CP-5, differs from Comparative Example 4 only in that it does not contain 7.5g of TiO2.

[0084] Performance testing (1) Pore structure and specific surface area test: The porous carbon support or silicon-carbon anode material to be tested was placed under vacuum and degassed at 120℃ for 6 hours to remove adsorbed water and volatile impurities from the material surface and pores. Subsequently, nitrogen adsorption-desorption tests were performed at 77K using a specific surface area and pore size analyzer. The specific surface area of ​​the material was calculated using the BET method, the pore volume and pore size distribution were analyzed using the DFT method or BJH method, the micropore volume was calculated using the t-plot method or DFT model, and the microporosity was calculated as the proportion of micropore volume to total pore volume.

[0085] (2) Powder conductivity test: The dried silicon-carbon anode material powder was added into the powder conductivity test mold and compacted under a set pressure to form a powder sheet. The resistivity was measured using a four-probe powder resistivity tester and the powder conductivity was calculated. Each sample was tested in parallel at least 3 times, and the average value was taken as the final result.

[0086] (3) Tap density test: Weigh a certain mass of dry silicon-carbon anode material powder, place it in a clean and dry graduated cylinder, and use a tap density meter to perform a tap test until the sample volume basically no longer changes. Calculate the tap density based on the sample mass and the volume after tapping. The calculation formula is: Tap density = Sample mass / Volume after tapping.

[0087] (4) Morphological observation: The microstructure of the porous carbon support and silicon-carbon anode material was observed using a scanning electron microscope (SEM), with a focus on the pore structure, particle morphology, and dispersion of the silicon phase in the carbon framework. Before testing, the sample was uniformly dispersed on conductive adhesive and sputtered with gold or platinum as needed.

[0088] (5) Preparation of negative electrode sheet: The silicon-carbon negative electrode materials prepared in Examples 1-7 and Comparative Examples 1-5 were used as negative electrode active materials, and were prepared according to a mass ratio of negative electrode active material, conductive agent and binder of 80:10:10. Among them, the conductive agent was conductive carbon black Super P, and the binder was composed of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), with a mass ratio of CMC to SBR of 1:1. Specifically, the silicon-carbon negative electrode material, Super P and CMC were added to an appropriate amount of deionized water and stirred and dispersed for 2 hours to fully wet and uniformly disperse the active material and conductive agent; then the SBR emulsion was added and stirred for another 4 hours to obtain a uniform and stable negative electrode slurry. The obtained slurry was uniformly coated on the surface of the copper foil current collector using a scraper. The coated electrode sheet was first dried at 80°C for 2 hours to remove most of the moisture; then it was rolled to improve the electrode compaction density and interfacial contact performance. The rolled negative electrode sheet was cut into circular electrode sheets with a diameter of 12 mm and dried in a vacuum drying oven at 100℃ for 12 hours to thoroughly remove residual moisture. The dried negative electrode sheets were then transferred to an argon-filled glove box for later use. The active material loading in the resulting negative electrode sheet was controlled to be 1.0–1.5 mg / cm³. 2 .

[0089] (6) Button cell assembly: The electrochemical performance of the silicon-carbon anode materials obtained in Examples 1-7 and Comparative Examples 1-5 was evaluated using CR2032 button cells. Battery assembly was carried out in a glove box filled with high-purity argon gas, with water and oxygen content controlled below 0.1 ppm. The silicon-carbon anode sheet prepared above was used as the working electrode, lithium metal sheet as the counter electrode and reference electrode, and polypropylene microporous membrane as the separator. A 1 mol / L LiPF6 solution was used as the electrolyte, with the solvent being a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a volume ratio of 1:1:1, and 5 wt% fluoroethylene carbonate (FEC) was added as a film-forming additive to improve the stability of the SEI film on the silicon-based anode surface. During assembly, the anode shell, spring sheet, gasket, lithium metal sheet, separator, appropriate amount of electrolyte, and silicon-carbon anode sheet were placed sequentially, and then the positive electrode shell was added and sealed. After encapsulation, the coin cells were left to stand at room temperature for 12 hours to allow the electrolyte to fully wet the electrodes and separator, and then a constant current charge-discharge test was performed.

[0090] (7) Initial charge-discharge performance test: A constant current charge-discharge test was conducted using a battery testing system at 25±2℃, with a test voltage range of 0.01~1.5V. The first cycle was performed using a current density of 0.1A / g. The initial discharge specific capacity was calculated based on the capacity of the first lithium insertion process and the mass of the active material. The initial coulombic efficiency was calculated as the ratio of the initial delithiation capacity to the initial lithium insertion capacity. The calculation formula is as follows: Initial coulombic efficiency = initial charge specific capacity / initial discharge specific capacity × 100%.

[0091] (8) Cyclic stability test: After the coin cell battery is activated by the first charge-discharge cycle, a cyclic charge-discharge test is conducted at a current density of 0.5 A / g within the same voltage range, and the reversible capacity after 100 cycles is recorded. The capacity retention rate after 100 cycles is calculated as the ratio of the discharge capacity of the 100th cycle to the initial discharge capacity, and the calculation formula is as follows: Capacity retention rate = Specific capacity at 100th cycle / Initial cycle discharge specific capacity × 100%.

[0092] At least three parallel cells were assembled for each sample group for testing, and the average value was taken as the final electrochemical performance data.

[0093] The test results are listed in Table 1 and Table 2. Table 1 is as follows: Table 1 Physicochemical properties of hierarchical porous carbon supports and silicon-carbon materials

[0094] As shown in Table 1, the micropore volume, microporosity, powder conductivity, tap density, and specific surface area of ​​Example 1 are all at optimal levels, indicating that under the synergistic effect of appropriate amounts of endogenous TiO2 / CaCO3, pre-sulfonation crosslinking, and carbonate activation, the resulting carbon material can form a well-developed pore structure and maintain a good conductive network. Figure 2 As can be seen, the material in Example 1 exhibits a well-developed three-dimensional interconnected porous network structure. The carbon skeleton is cross-linked to form a continuous conductive network channel structure. It is evident that the in-situ porous carbon skeleton left after the removal of the calcium-based sacrificial phase has a certain thickness, indicating that after sulfonation cross-linking pre-stabilization treatment, the polymer precursor was successfully transformed into a structurally continuous solid carbon skeleton, rather than a fragmented or powdery morphology. Examples 2 and 3 show slight differences in material properties due to variations in raw material type, filler content, and final heat treatment temperature, but overall, they still maintain a high specific surface area and high powder conductivity, demonstrating that the method of this invention has good adaptability to white waste plastics from different sources.

[0095] Comparative Example 1, omitting the pre-sulfonation crosslinking step, exhibited lower micropore volume, microporosity, powder conductivity, and specific surface area compared to Example 1. This indicates that polymer segments without pre-stabilization treatment are more prone to decomposition and volatilization during heating, resulting in insufficient carbon skeleton continuity and consequently affecting the activation and pore-forming effect. Comparative Example 2, using a transparent PE / PP mixture instead of white waste plastic, underwent the same pre-sulfonation and activation treatments. However, due to the lack of endogenous CaCO3 sacrificial templates and TiO2 interface anchoring points, its pore structure regulation and interface functionalization effects were weaker than those of Example 1. This demonstrates that the endogenous inorganic components in the white waste plastic are not ineffective impurities in the system of this invention, but rather important structural sources participating in pore formation and interface regulation.

[0096] Table 2 Electrochemical performance of silicon-carbon anode materials

[0097] From Table 2 and Figure 3 It can be seen that the initial discharge specific capacity of the negative electrode material obtained in Example 1 reached 2335.1 mAh / g, and the initial efficiency was 93.2%, indicating that the prepared regenerated TiO2 lattice-anchored hierarchical porous carbon can provide abundant lithium storage sites and form a relatively stable electrode / electrolyte interface in the first cycle. Figure 4 It can be seen that the capacity retention rate of Example 1 reached 96.5% after 100 cycles, indicating that its hierarchical pore structure can buffer the volume change during the lithium insertion and extraction process, the TiO2 lattice anchoring points help to improve interface stability, and the continuous carbon skeleton ensures the stability of the electron transport channel.

[0098] The initial discharge specific capacity of Examples 2 to 7 was 2056.5–2257.1 mAh / g, the initial efficiency was 91.6–93.1%, and the capacity retention rate after 100 cycles was 94.2–96.3%, which is close to that of Example 1, indicating that the method of the present invention has good applicability to white waste plastics from different sources. The differences in their electrochemical performance are basically consistent with the trends of changes in physicochemical properties such as micropore volume, microporosity, specific surface area, and powder conductivity in Table 1, indicating that the degree of pore structure development, the integrity of the conductive network, and the distribution state of endogenous inorganic components jointly affect the lithium storage behavior of the material. After omitting the pre-sulfonation crosslinking step, the initial discharge specific capacity, initial efficiency, and cycle retention rate of Comparative Example 1 were all lower than those of Example 1, indicating that pre-sulfonation crosslinking is beneficial to improving the thermal stability and carbon skeleton retention of the polymer precursor, thereby improving subsequent activation pore formation and cycle stability. Comparative Example 2 used a transparent PE / PP mixture without TiO2 and CaCO3. Although it could still form a certain capacity, its capacity retention rate was significantly lower than that of Example 1 due to the lack of CaCO3 sacrificial template for pore formation and TiO2 interface anchoring. This proves that the endogenous inorganic components in white waste plastics are not ineffective impurities, but rather important functional sources participating in pore formation and interface regulation. Comparative Example 3 did not add a high-carbon auxiliary carbon source, indicating that carbon supplementation also plays an important role in maintaining the conductive framework and improving cycle performance. Comparative Example 4, after adding TiO2 and CaCO3, performed better than Comparative Example 2, but still lower than Example 1. This shows that although the added filler can partially play a role in pore formation and anchoring, its compatibility with polymer-based waste and dispersion uniformity are not as good as those of endogenous fillers. Comparative Example 5 only has the pore-forming effect of CaCO3 and lacks TiO2 anchoring points. Its cycle retention rate was lower than that of Comparative Example 4 and Example 1, indicating that a single pore-forming structure cannot fully replace the synergistic stabilization mechanism of hierarchical pore buffering and TiO2 interface anchoring.

[0099] This invention achieves the synergistic utilization of polymer carbon source, CaCO3 sacrificial template, and TiO2 anchoring points in white waste plastics through a process route of pre-sulfonation crosslinking, carbonate activation, and acid washing demolding. Compared with the comparative examples without pre-sulfonation or without white filler, the materials obtained in this embodiment simultaneously possess higher specific surface area, higher microporosity, better powder conductivity, and excellent cycle stability. This indicates that the present invention can effectively solve the problems of low carbonization rate, simple pore structure, insufficient interfacial activity, and poor lithium storage stability of white waste plastics, and is suitable for preparing high-performance recycled porous carbon materials for lithium-ion battery anodes.

[0100] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing a porous carbon support, characterized in that, Includes the following steps: S1. Provide white waste plastic as polymer-based waste, wherein the polymer-based waste contains inorganic white filler; S2. Sort, clean, dry and crush polymer-based waste materials; S3. The crushed polymer-based waste is subjected to sulfonation and crosslinking treatment to obtain a pre-stabilized precursor. S4. Mix the prestabilized precursor with a high-carbon auxiliary carbon source and an activator to obtain a mixture. S5. Perform segmented heat treatment on the mixture to obtain carbonized products; S6. Selectively acid-wash the carbonization product with acid solution to remove the calcium-based sacrificial phase derived from calcium carbonate and retain titanium dioxide. Then wash with water until neutral and dry to obtain the porous carbon support. The calcium-based sacrificial phase is used to form the pore structure, and the retained titanium dioxide is used to form interface anchoring points. The inorganic white filler contains 0.1–20 wt% TiO2 and 0.5–40 wt% CaCO3. During the sulfonation crosslinking process, the CaCO3 can be partially converted into calcium sulfate, acid calcium sulfate and / or its hydrate, and participate in pore formation as a removable calcium-based sacrificial phase in the subsequent acid washing process. The sulfonation crosslinking treatment is performed at a temperature of 40–160°C for a time of 0.2–8 hours.

2. The preparation method according to claim 1, characterized in that, The inorganic white filler also includes one or more of the following: talc, barium sulfate, zinc oxide, wollastonite, and mica powder; The polymer-based waste includes at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, and polyurethane.

3. The method for preparing porous carbon support according to claim 1, characterized in that, The sulfonating reagent used in the sulfonation crosslinking treatment includes at least one of sulfuric acid, fuming sulfuric acid, or chlorosulfonic acid.

4. The method for preparing porous carbon support according to claim 3, characterized in that, The sulfonating agent is sulfuric acid with a mass fraction of 60–98 wt%; The solid-liquid ratio of the polymer-based waste to the sulfonating agent is 1:(1-12). The process after sulfonation and crosslinking treatment further includes washing the sulfonation and crosslinking product until the pH of the filtrate is 1-6, and then drying it at 50-120°C for 4-24 hours to obtain the pre-stabilized precursor.

5. The method for preparing porous carbon support according to claim 1, characterized in that, The high-carbon auxiliary carbon source includes one or at least two of the following: waste tire pyrolysis char, biomass char, pitch coke, petroleum coke, waste phenolic resin char, and waste epoxy resin char. The activator includes at least one of alkali metal carbonates or alkali metal hydroxides; The mixture also includes nitrogen-containing additives, which include one or at least two of urea, melamine, dicyandiamine, amino acids, and polyvinylpyrrolidone. The mass ratio of the high-carbon auxiliary carbon source to the prestabilized precursor is (0.05-2.0):1, the mass ratio of the activator to the prestabilized precursor is (0.1-5.0):1, and the mass ratio of the nitrogen-containing auxiliary agent to the prestabilized precursor is (0.01-1.5):

1.

6. The method for preparing porous carbon support according to claim 1, characterized in that, The acid solution is an inorganic acid that does not dissolve titanium dioxide, including hydrochloric acid or nitric acid; The concentration of the acid solution is 0.1–6 mol / L, and the temperature of the selective acid washing is 20–95°C, and the time is 0.2–8 h. The selective acid elution is used to remove the calcium-based sacrificial phase derived from CaCO3, which includes one or more of CaCO3, CaSO4, Ca(HSO4)2 and their hydrates; The residual calcium content in the porous carbon support is less than 0.1 wt%, the residual potassium content is less than 0.2 wt%, the residual sodium content is less than 0.1 wt%, and the residual iron content is less than 0.2 wt%.

7. The method for preparing porous carbon support according to claim 1, characterized in that, The segmented heat treatment includes first heating to 200–450°C and holding at that temperature for 0.2–4 hours, then heating to 600–1100°C and holding at that temperature for 0.2–5 hours; The initial heating rate is 0.5–10 °C / min, and the subsequent heating rate is 1–15 °C / min. The preparation method further includes: combining the porous carbon support with a silicon source, so that the silicon phase is deposited, embedded or loaded on the pores and surface of the porous carbon support to obtain a silicon-carbon anode material; The silicon source includes at least one of nano-silicon powder, silane, trichlorosilane, silicon tetrachloride, or siloxane; the mass ratio of silicon in the silicon source to the porous carbon support is (0.1-4):

1.

8. A porous carbon support, prepared by any one of the preparation methods of claims 1 to 7, characterized in that, The porous carbon support has a synergistic distribution structure of micropores, mesopores and macropores, which is used to provide a conductive network and buffer space; The porous carbon carrier has titanium dioxide lattice anchor points embedded on the carbon skeleton surface and pore walls. These titanium dioxide lattice anchor points are derived from the titanium dioxide filler contained in the polymer-based waste and are used to enhance the interfacial bonding stability.

9. A silicon-carbon anode material, characterized in that, Includes the porous carbon support as described in claim 8, and a silicon phase supported on the pores and / or surface of the porous carbon support; The silicon mass fraction in the silicon-carbon anode material is 10–80 wt%; The specific surface area of ​​the silicon-carbon anode material is 5–300 m². 2 / g, tap density is 0.6~1.4g / cm³ 3 The electrical conductivity of the powder is 0.05–2.0 S / cm.

10. A lithium-ion battery, characterized in that, Including anode sheets made of the silicon-carbon anode material as described in claim 9; The negative electrode sheet comprises the following components by weight: 80-96 parts of the silicon-carbon negative electrode material, 1-10 parts of conductive agent and 1-10 parts of binder.

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