Silicon-carbon composite material, preparation method thereof and lithium ion battery

Abstract

The invention discloses a silicon-carbon composite material, a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion battery materials. According to the invention, the intermediate material containing a mesoporous or macroporous structure is prepared by adopting a soft template method, so that the full-charge expansion in the charge-discharge process can be reduced, and meanwhile, the electronic conductivity and specific capacity of the material are improved by doping black phosphorus into porous carbon; the intermediate material is subjected to double activation treatment through an alkali activator and water vapor, so that the pore size distribution of the porous carbon can be more accurately regulated and controlled, the expansion is further reduced, and the cycle performance is improved; the surface of the silicon-carbon material is coated with the coating liquid containing the organic acid, the nitrogen-containing organic compound and the organic lithium salt, and sintering treatment is performed, so that defects are reduced, the ionic conductivity of the silicon-carbon composite material is improved, and the expansion of the core silicon-carbon material is further reduced. The method can be used for solving the problems that the pore structure of the silicon-carbon material is uncontrollable, the expansion of the silicon-carbon material is difficult to reduce, and the specific capacity, the first efficiency and the power performance are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, and particularly relates to a silicon-carbon composite material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] The novel silicon-carbon material is generally composed of porous carbon, nano-silicon deposited in the pores of the porous carbon, and amorphous carbon coated on the surface of the porous carbon. However, due to the uncontrollability of the pore structure of the porous carbon material (such as the uncontrollability of the size of the pores and the large number of nano-micropores), the porous carbon material has a low capacity for accommodating nano-silicon, and is prone to introducing significant volume expansion during lithiation / delithiation. At the same time, the impedance of the porous carbon itself is large, and the specific capacity is low (≤300 mAh / g), which further restricts the overall electrochemical performance of the silicon-carbon material.

[0003] Although some researches have tried to improve the electronic / ion conduction capacity of the material by means of material doping or outer coating, these methods have limited improvement on the conductivity, and cannot effectively inhibit the volume expansion of the silicon-carbon material and improve the cycle stability, so that the specific capacity, the initial efficiency and the power performance of the silicon-carbon material are still difficult to meet the actual application requirements. SUMMARY

[0004] The main purpose of the present application is to provide a silicon-carbon composite material, a preparation method thereof and a lithium ion battery, which aims to solve the problem that the existing silicon-carbon material cannot effectively reduce the volume expansion of the silicon-carbon material while improving the initial efficiency, the specific capacity and the power performance.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of a silicon-carbon composite material, which comprises the following steps: S10, mixing a soft template agent, a crosslinking agent, a black phosphorus nanodispersion and a high molecular polymer solution to form a mixture, heating the mixture to make the crosslinking agent and the high molecular polymer perform a crosslinking reaction to form a three-dimensional network structure embedding black phosphorus, so as to obtain an intermediate material; S20, mixing the intermediate material, an alkali activator and pitch, briquetting, then performing carbonization treatment on the briquetted material, and then introducing water vapor to activate and form pores to obtain porous carbon; S30, introducing a mixed gas containing silane gas and inert gas into the porous carbon to perform gas deposition, and then introducing air to perform passivation to obtain a silicon-carbon material; S40, mixing the silicon-carbon material and a coating liquid to perform sintering treatment to obtain the silicon-carbon composite material; The coating liquid comprises an organic acid, a nitrogen-containing organic compound and an organic lithium salt.

[0006] In an embodiment, in step S10: The soft template agent comprises at least one of a triblock polymer, polyacrylamide; and / or, The solute in the high-molecular polymer solution comprises at least one of an epoxy resin, a melamine resin, a polyester resin, a polyurethane, a phenolic resin, a urea-formaldehyde resin, a furan resin, and has a molecular weight of 100,000-1,000,000; the mass concentration of the solute in the high-molecular polymer solution is 1-10 wt%; and / or, The solvent of the high-molecular polymer solution comprises at least one of chloroform, toluene, n-hexane, ethyl acetate, cyclohexanone; and / or, The crosslinking agent comprises at least one of diphenylimidazoline, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole; and / or, The black phosphorus nanodispersion liquid comprises a mixture of black phosphorus quantum dots and polyethylene glycol; wherein the particle size of the black phosphorus quantum dots is 1-10 nm; and / or, The concentration of black phosphorus in the black phosphorus nanodispersion liquid is 0.5-1.5 wt%.

[0007] In an embodiment, in step S10: The mass ratio of the soft template agent, the crosslinking agent, the black phosphorus nanodispersion liquid, and the high-molecular polymer solution is (1-5):(1-5):(100-500):1000; and / or, The temperature of the crosslinking reaction is 50-100℃, and the time of the crosslinking reaction is 1-6 h.

[0008] In an embodiment, in step S20: The alkali activator comprises at least one of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate; and / or, The softening point of the pitch is 80-150℃.

[0009] In an embodiment, in step S20: The mass ratio of the intermediate material, the alkali activator, and the pitch is 100:(100-300):(5-15); and / or, The temperature of the carbonization treatment is 700-1000℃, and the time of the carbonization treatment is 1-6 h; and / or, When water vapor is introduced for activation and pore formation, the flow rate of the water vapor is 100-500 mL / min, the temperature of the activation and pore formation is 900-1300℃, and the time of the activation and pore formation is 30-300 min.

[0010] In an embodiment, in step S30: The silane gas in the mixed gas of the silane gas and the inert gas includes at least one of monosilane, disilane, dichlorodisilane, trichlorosilane, tetrachlorosilane, and silicon tetrafluoride; and / or, The volume ratio of the silane gas to the inert gas is (1-5):10; and / or, When performing the vapor deposition, the flow rate of the mixed gas is 100-500 mL / min, the temperature of the vapor deposition is 450-550℃, and the time of the vapor deposition is 60-300 min; and / or, When passing the air to perform the passivation, the flow rate of the air is 10-50 mL / min, the passivation temperature is 20-30℃, and the passivation time is 60-300 min.

[0011] In an embodiment, in step S40: The organic acid in the coating liquid includes at least one of citric acid, malic acid, tartaric acid, fumaric acid, and lactic acid; and / or, The nitrogen-containing organic compound in the coating liquid includes at least one of methylamine, aniline, naphthylamine, pyridine, pyrrole, and imidazole; and / or, The organic lithium salt in the coating liquid includes at least one of lithium acetate, lithium oxalate, lithium trifluoride, lithium pyruvate, and lithium lactate; and / or, The solvent in the coating liquid includes at least one of dimethyl carbonate, diethyl carbonate, and ethylene carbonate; and / or, The sintering treatment is performed at a temperature of 500-800℃ for 1-6 h.

[0012] In an embodiment, in the coating liquid, the total mass of the organic acid, the nitrogen-containing organic compound, and the organic lithium salt is 5%-20% of the solvent, and the mass ratio of the organic acid, the nitrogen-containing organic compound, the organic lithium salt, and the silicon-carbon material is (1-5):(1-5):(1-5):100.

[0013] The present application provides a silicon-carbon composite material prepared by the method.

[0014] The present application also provides a lithium ion battery comprising the silicon-carbon composite material.

[0015] In the technical solution of the present application, firstly, the soft template agent, the crosslinking agent, the black phosphorus nanodispersion and the high polymer polymer solution are subjected to crosslinking reaction to form an intermediate material, wherein the high polymer polymer solution serves as a precursor of a carbon source and a structural framework, a three-dimensional network structure is formed through crosslinking reaction between the crosslinking agent and the high polymer polymer solution, and the soft template agent forms an ordered mesoporous or macroporous structure in the crosslinking and drying process, which can reduce the expansion of the nanosilicon in the charging and discharging process. Meanwhile, the black phosphorus nanodispersion serves as a dopant, is integrated into the crosslinking network through physical and chemical action between the crosslinking agent / high polymer, and can improve the electronic conductivity of the material and the power performance and specific capacity of the porous carbon by virtue of the characteristics of high electronic conductivity and high specific capacity of the black phosphorus itself. Subsequently, the intermediate material, an alkali activator and pitch are mixed and subjected to carbonization treatment and water vapor activation pore forming treatment in sequence, so that the porous carbon material is obtained, wherein the pitch serves as an additional carbon source and a binder for adjusting the graphitization degree and microstructure of the carbon material and binding the intermediate material, the alkali activator and the pitch, and through the synergistic action of the alkali activator and water vapor, the pore size distribution of the porous carbon can be more accurately controlled. Subsequently, nanosilicon is deposited in the interior and surface of the porous carbon material through a gas phase deposition process, and water is used as a passivation agent to perform surface passivation, so that the silicon-carbon material is obtained. Finally, a coating liquid containing organic acid, nitrogen-containing organic compound and organic lithium salt is coated on the surface of the silicon-carbon material and subjected to sintering treatment, so that an amorphous carbon coating layer containing lithium is formed on the surface of the material, defects are reduced, the ion conductivity of the silicon-carbon composite material is improved, and the expansion of the core silicon-carbon material is further reduced. Therefore, through the preparation method of the silicon-carbon composite material provided by the present application, the pore size distribution of the porous carbon can be controlled, the expansion of the core silicon-carbon material in the prepared silicon-carbon composite material can be effectively reduced, and the electronic / ionic conduction capacity of the silicon-carbon composite material can be improved. When the prepared silicon-carbon composite material is applied to a lithium ion battery negative electrode material, the first efficiency, specific capacity and rate performance of the battery can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of the drawings shown.

[0017] Figure 1 SEM image of the silicon-carbon composite material prepared in Example 1 of the present application.

[0018] The implementation, functional features and advantages of the present application will be further described with reference to the drawings. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0020] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0021] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B simultaneously satisfy the scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application.

[0022] The novel silicon-carbon material is composed of porous carbon, nano-silicon deposited in the pores of the porous carbon, and amorphous carbon coated on the surface of the porous carbon. However, due to the uncontrollable size of the pores of the porous carbon material and the large number of nano-micropores, the amount of nano-silicon contained in the porous carbon material is low and the expansion is large, and the impedance of the core porous carbon itself is large, and the specific capacity is low (≤300 mAh / g), thereby reducing the power performance and specific capacity of the silicon-carbon material.

[0023] Currently, some researchers improve the electronic and ionic conductivity of the material by means of internal doping or outer coating, but there are still problems such as limited improvement range, and unimproved material expansion and cycle.

[0024] In view of this, the present application provides a preparation method of a silicon-carbon composite material, comprising the following steps: S10, mixing a soft template agent, a crosslinking agent, a black phosphorus nanodispersion liquid and a high polymer polymer solution to form a mixture, heating the mixture, and allowing the crosslinking agent and the high polymer to perform a crosslinking reaction to form a three-dimensional network structure embedding the black phosphorus, to obtain an intermediate material; S20, mixing the intermediate material, an alkali activator and pitch, briquetting, and then performing carbonization treatment on the briquetted material, and then introducing water vapor to activate and form pores, to obtain porous carbon; S30, introducing a mixed gas containing silane gas and inert gas into the porous carbon, performing gas phase deposition, and then introducing air to perform passivation, to obtain a silicon-carbon material; S40, mixing the silicon-carbon material and a coating liquid, and performing sintering treatment, to obtain the silicon-carbon composite material; The coating liquid comprises an organic acid, a nitrogen-containing organic compound and an organic lithium salt.

[0025] The technical scheme of the present application first performs a cross-linking reaction on a soft template agent, a cross-linking agent, a black phosphorus nanodispersion liquid and a high polymer solution to form an intermediate material, wherein the high polymer solution acts as a precursor of a carbon source and a structural framework, a three-dimensional network structure is formed through the cross-linking reaction between the cross-linking agent and the high polymer solution, and the soft template agent forms an ordered mesoporous or macroporous structure in the cross-linking and drying process. The mesoporous or macroporous structure can reduce the expansion of nanosilicon in the charging and discharging process. The black phosphorus nanodispersion liquid acts as a dopant and is integrated into the cross-linking network through physical and chemical action between the cross-linking agent and the high polymer. The high electronic conductivity and high specific capacity of black phosphorus can improve the electronic conductivity of the material and thus improve the power performance and specific capacity of the porous carbon. Subsequently, the intermediate material, an alkali activator and pitch are mixed and sequentially subjected to carbonization treatment and water vapor activation pore forming treatment, so as to obtain a porous carbon material. The pitch acts as an additional carbon source and a binder for adjusting the graphitization degree and microstructure of the carbon material and bonding the intermediate material, the alkali activator and the pitch. The double-activation synergistic effect of water vapor and the alkali activator can more accurately control the pore size distribution of the porous carbon. Subsequently, nanosilicon is deposited in the interior and on the surface of the porous carbon material through a gas phase deposition process, and water is used as a passivation agent for surface passivation, so as to obtain a silicon-carbon material. Finally, a coating liquid containing an organic acid, a nitrogen-containing organic compound and an organic lithium salt is coated on the surface of the silicon-carbon material and subjected to sintering treatment, so as to form an amorphous carbon coating layer containing lithium on the surface of the material, reduce defects, improve the ionic conductivity of the silicon-carbon composite material and further reduce the expansion of the core silicon-carbon. Therefore, the preparation method of the silicon-carbon composite material provided by the present application can control the pore size distribution of the porous carbon, effectively reduce the expansion of the core silicon-carbon in the prepared silicon-carbon composite material and improve the electronic / ionic conductivity of the silicon-carbon composite material. When the silicon-carbon composite material is applied to a lithium ion battery negative electrode material, the first efficiency, specific capacity and rate performance of the battery can be improved.

[0026] By adopting the above technical scheme, the prepared carbon-silicon composite material includes a core and a coating layer. The core includes a black phosphorus-doped porous carbon matrix and nanosilicon deposited in the pores of the black phosphorus-doped porous carbon matrix. The coating layer includes a lithium compound coating layer and an amorphous carbon coating layer (i.e., an amorphous carbon coating layer containing lithium).

[0027] It should be noted that, compared with phosphorus-doped porous carbon directly doped with black phosphorus, the black phosphorus in the form of nanodispersion is selected, and the black phosphorus nanodispersion is added in the step of preparing the intermediate, which can be loaded in the porous carbon precursor through liquid phase, has good dispersity and uniformity, and is beneficial to the preparation of the porous carbon material with uniform performance. Meanwhile, the black phosphorus can be integrated into the crosslinked network through the physical and chemical action between the black phosphorus and the crosslinking agent / polymer, the agglomeration problem of the black phosphorus is improved, and a continuous electron transmission channel is constructed, so that the electron conductivity of the material is improved.

[0028] In addition, the inventors have found that, compared with the coating liquid containing organic acid, nitrogen-containing organic compound and organic lithium salt at the same time, the lack of any one of the organic acid, the nitrogen-containing organic compound and the organic lithium salt in the coating liquid will make the test results of the full charge expansion, the first specific discharge capacity and the first efficiency worse.

[0029] In the embodiment of the present application, the step S10 comprises: The soft template agent, the crosslinking agent, the black phosphorus nanodispersion and the high polymer polymer solution are mixed to form a mixture, and the mixture is heated to make the crosslinking agent and the high polymer polymer perform a crosslinking reaction, so as to form a three-dimensional network structure embedding the black phosphorus, and a crosslinking reaction product is obtained. The solid material is separated from the crosslinking reaction product, and is subjected to washing and drying treatment, so as to obtain an intermediate material.

[0030] In the embodiment of the present application, in the step S10, the soft template agent comprises at least one of a triblock polymer and polyacrylamide. The triblock polymer comprises at least one of F127 template agent and P123 template agent. Although the expansion of nanosilicon can be reduced by using inorganic templates, the inorganic template agent will introduce impurities and reduce the specific capacity, so that the expansion is reduced and the power is improved, and at the same time, the specific capacity and the first efficiency of the material are also improved. In the technical solution of the present application, the soft template method is used to prepare the porous carbon, and in the subsequent vacuum drying or carbonization process, the soft template agent is removed and the pores corresponding to the shape and size of the template agent micelles are left in the carbon material, so that the pore structure can be controlled, and the problem of introducing impurities and reducing the specific capacity by the template agent can be reduced. In addition, the triblock polymer and polyacrylamide are selected as the template agent, so that the pore structure parameters can be easily controlled, and the mesoporous structure with uniform size and ordered pores (pore size is between 2-50 nm) can be obtained.

[0031] In the embodiment of the present application, in the step S10, the solute in the high polymer polymer solution comprises at least one of epoxy resin, melamine resin, polyester resin, polyurethane, phenolic resin, urea-formaldehyde resin and furan resin, and the molecular weight is 100,000-1,000,000; the mass concentration of the solute in the high polymer polymer solution is 1-10 wt%.

[0032] As a precursor of carbon source and structural framework, the high molecular polymer solution pyrolyzes and carbonizes to form a carbon framework in a subsequent high-temperature carbonization process. If the molecular weight of the high molecular polymer is too high, the activation is difficult and it is not easy to form a porous structure; if the molecular weight is too low, the strength is low and the porous structure is easy to collapse. In the technical scheme of the present application, at least one of epoxy resin, melamine resin, polyester resin, polyurethane, phenolic resin, urea-formaldehyde resin and furan resin is selected as the high molecular polymer, and the molecular weight of the high molecular polymer is set to 100,000-1,000,000. These molecular weights are relatively high, the mechanical strength is high, and at the same time, it is easy to disperse uniformly in the raw material system to form a porous structure with high stability.

[0033] In the embodiment of the present application, in step S10, the solvent of the high molecular polymer solution includes at least one of chloroform, toluene, n-hexane, ethyl acetate and cyclohexanone.

[0034] In the embodiment of the present application, in step S10, the crosslinking agent includes at least one of diphenylimidazoline, 2-methylimidazole, 2-ethylimidazole and 2-ethyl-4-methylimidazole. The use of the above substances as crosslinking agents can form a crosslinked structure by using the nitrogen free radicals of the crosslinking agents and other compounds, and the crosslinking effect is good.

[0035] In the embodiment of the present application, in step S10, the black phosphorus nanodispersion liquid includes a mixture of black phosphorus quantum dots and polyethylene glycol; wherein the particle size of the black phosphorus quantum dots is 1-10 nm.

[0036] In the embodiment of the present application, in step S10, the concentration of black phosphorus in the black phosphorus nanodispersion liquid is 0.5-1.5 wt%.

[0037] It should be noted that the black phosphorus nanodispersion liquid can be directly purchased or obtained by dispersing black phosphorus quantum dots in polyethylene glycol. The technical scheme of the present application selects a nanodispersion liquid containing black phosphorus quantum dots, which has good dispersion uniformity and is easy to purchase. In addition, the use of black phosphorus nanodispersion liquid with the above concentration range is beneficial to improving the dispersion performance of the material and preventing agglomeration. If the concentration is too high, it is difficult to disperse uniformly; if the concentration is too low, it affects the efficiency in actual application.

[0038] In the embodiment of the present application, in step S10, the mass ratio of the soft template agent, the crosslinking agent, the black phosphorus nanodispersion liquid and the high molecular polymer solution is (1-5):(1-5):(100-500):1000. The use of the soft template agent, the crosslinking agent, the black phosphorus nanodispersion liquid and the high molecular polymer solution in the above range is beneficial to obtaining a porous carbon material with high specific surface area, fast mass transfer, excellent electrical conductivity and high specific capacity.

[0039] In the embodiment of the present application, in step S10, the temperature of the cross-linking reaction is 50-100°C, and the time of the cross-linking reaction is 1-6h. Illustratively, the temperature of the cross-linking reaction can be 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, and the time of the cross-linking reaction can be 1h, 2h, 3h, 4h, 5h or 6h. Controlling the process parameters of the cross-linking reaction in the above range can maximize the reduction of the oxidation loss of black phosphorus while meeting the reaction efficiency, and obtain a porous carbon intermediate material with high specific surface area, ordered pore structure, good mechanical strength and retained functional characteristics of black phosphorus.

[0040] In the embodiment of the present application, in step S20, the alkali activator includes at least one of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate. The alkali activator is used to chemically react with carbon at high temperature, etch the carbon skeleton, create a large number of micropores and mesopores, and significantly increase the specific surface area. The technical solution of the present application selects commonly used alkali activator materials, has good activation effect, and is easy to control cost.

[0041] In the embodiment of the present application, in step S20, the softening point of the pitch is 80-150°C. On the one hand, as an additional carbon source, the pitch with a softening point of 80-150°C usually has moderate molecular weight and aromatic content, good flowability, is conducive to mixing and molding, and forms a carbon structure with high order degree in the carbonization process, thereby being conducive to improving the electrical conductivity and mechanical properties of the material. On the other hand, as a binder, the pitch ensures the briquetting. The pitch with a softening point of 80-150°C is easy to mix uniformly with the powder. When pressure is applied, it can plastically deform to fill the gaps between the particles, thereby playing a good “bonding” role, so as to form a block with complete structure and moderate strength.

[0042] In the embodiment of the present application, in step S20, the mass ratio of the intermediate material, the alkali activator and the pitch is 100:(100-300):(5-15). Using a high proportion of alkali activator to deeply activate the resin material is conducive to obtaining high specific surface area and developed pores; at the same time, using a small amount of pitch can meet the demand for binder while ensuring that the intermediate material still serves as the functional core and structural basis, avoiding dilution or blockage.

[0043] In the embodiment of the present application, in step S20, the carbonization treatment temperature is 700-1000℃, and the carbonization treatment time is 1-6h. For example, the carbonization treatment temperature can be 700℃, 750℃, 800℃, 900℃ or 1000℃, and the carbonization treatment time can be 1h, 2h, 3h, 4h, 5h or 6h. By setting the process parameters of carbonization treatment in the above range, uniform pores can be formed, and moisture and volatile matter in the material can be fully discharged, thereby improving the anisotropy of carbon and reducing the impedance.

[0044] In the embodiment of the present application, in step S20, when water vapor is introduced for activation and pore formation, the flow rate of the water vapor is 100-500mL / min, the activation and pore formation temperature is 900-1300℃, and the activation and pore formation time is 30-300min. For example, the flow rate of the water vapor can be 100mL / min, 200mL / min, 300mL / min, 400mL / min or 500mL / min, the activation and pore formation temperature can be 900℃, 1000℃, 1100℃, 1200℃ or 1300℃, and the activation and pore formation time can be 30min, 60min, 120min, 180min, 240min or 300min. By setting the process parameters of water vapor introduction in the above range, it is ensured that the activation reaction can be carried out efficiently and quickly, and more mesopores and macropores are formed, which is beneficial to obtain porous carbon with extremely high specific surface area and pore volume.

[0045] In step S30, in the specific operation, the porous carbon can be transferred to a fluidized bed, inert gas is first introduced to discharge the air in the pipe, then heated and introduced into a silane mixed gas, and nanosilicon is vapor deposited on the surface or inside of the porous carbon, and then cooled to room temperature and introduced into air for passivation. Among them, the air (mainly oxygen and water vapor) is discharged to prevent the porous carbon from being oxidized at high temperature, and to create an oxygen-free environment for subsequent reactions.

[0046] In the embodiment of the present application, in step S30, in the mixed gas of silane gas and inert gas, the silane gas includes at least one of monosilane, disilane, dichlorodihydrogen silane, trichlorosilane, tetrachlorosilane and silicon tetrafluoride. In the present application, the inert gas includes nitrogen (N2) or argon (Ar). In the present application, the silane gas refers to gaseous silane, which is broken down at high temperature to precipitate solid silicon atoms and deposit on the inner and outer surfaces of the porous carbon. The above-mentioned silane is used for vapor deposition in the technical solution of the present application, and the obtained nanosilicon can be gasified and decomposed and more uniformly incorporated into the porous carbon material.

[0047] In the embodiment of the present application, in step S30, the volume ratio of the silane gas and the inert gas is (1-5):10. For example, the volume ratio of the silane gas and the inert gas can be 1:10, 2:10, 3:10, 4:10 or 5:10.

[0048] In the embodiment of the present application, in step S30, when the vapor deposition is performed, the flow rate of the mixed gas is 100-500 mL / min, the temperature of the vapor deposition is 450-550 ℃, and the time of the vapor deposition is 60-300 min. For example, the flow rate of the mixed gas can be 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min or 500 mL / min, the temperature of the vapor deposition can be 450 ℃, 480 ℃, 500 ℃, 525 ℃ or 550 ℃, and the time of the vapor deposition can be 60 min, 120 min, 180 min, 240 min or 300 min.

[0049] By setting the flow rate of the mixed gas in the above range, slow and gentle deposition can be achieved, which is beneficial to obtaining a uniform thin layer. By setting the temperature and time of the vapor deposition in the above range, sufficient reaction rate can be ensured, and the deposition reaction can be fully performed, so that the silane gas is fully decomposed to generate nanosilicon, and the generation of SiC without specific capacity is avoided, and crystal nanosilicon is obtained, the pores of the porous carbon are filled, and the impedance is reduced.

[0050] In the embodiment of the present application, in step S30, when the air is introduced for passivation, the flow rate of the air is 10-50 mL / min, the passivation temperature is 20-30 ℃, and the passivation time is 60-300 min. For example, the flow rate of the air can be 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min or 50 mL / min, the passivation temperature can be 20 ℃, 22 ℃, 25 ℃, 27 ℃ or 30 ℃, and the passivation time can be 60 min, 120 min, 180 min, 240 min or 300 min.

[0051] The purpose of introducing the air is to perform controllable oxidation on the newly deposited silicon surface with extremely active chemical properties to form a dense silicon dioxide (SiO2) passivation layer. After cooling to room temperature (20-30 ℃), the air is introduced again, which can prevent the silicon from being severely oxidized or even combusted due to the introduction of the air at high temperature. By setting the flow rate of the air and the passivation time in the above range, the air is introduced at a low flow rate for a long time, so that slow and uniform surface oxidation is achieved, severe reaction is avoided, and the chemical stability and cycle stability of the material are improved.

[0052] In step S40, in a specific operation, the organic acid, the nitrogen-containing organic compound, and the organic lithium can be added into the organic solvent, mixed uniformly, and then configured into a coating liquid. Then, the coating liquid is mixed uniformly with the silicon-carbon material, and transferred into a reaction kettle. Subsequently, inert gas is introduced to discharge air, and a heating sintering treatment is performed, so as to obtain the silicon-carbon composite material.

[0053] In the embodiment of the present application, in step S40, the organic acid in the coating liquid includes at least one of citric acid, malic acid, tartaric acid, fumaric acid, and lactic acid. The above-mentioned organic acid is selected, the reaction condition is mild, and the reaction efficiency is high.

[0054] In the embodiment of the present application, in step S40, the nitrogen-containing organic compound in the coating liquid includes at least one of methylamine, aniline, naphthylamine, pyridine, pyrrole, and imidazole. The above-mentioned nitrogen-containing organic compound is selected, the reaction condition is mild, and the reaction efficiency is high.

[0055] In the embodiment of the present application, in step S40, the organic lithium salt in the coating liquid includes at least one of lithium acetate, lithium oxalate, lithium trifluoride, lithium pyruvate, and lithium lactate. The above-mentioned organic lithium salt is selected, the reaction condition is mild, and the reaction efficiency is high.

[0056] In the embodiment of the present application, in step S40, the solvent in the coating liquid includes at least one of dimethyl carbonate, diethyl carbonate, and ethylene carbonate.

[0057] Further, in the embodiment of the present application, in the coating liquid, the total mass of the organic acid, the nitrogen-containing organic compound, and the organic lithium salt is 5% to 20% of the solvent, and the mass ratio of the organic acid, the nitrogen-containing organic compound, the organic lithium salt, and the silicon-carbon material is (1-5):(1-5):(1-5):100. The use of a small amount of coating layer material has little effect on the specific capacity reduction of the overall silicon-carbon material. Controlling the amount of the organic acid, the nitrogen-containing organic compound, the organic lithium salt, and the silicon-carbon material in the above range avoids the problem of excessive alkalinity or acidity of the material system due to excessive amount of a certain organic compound, thereby adversely affecting the stability of the slurry, and is beneficial to improve the processing performance. Furthermore, controlling the amount of the organic acid, the nitrogen-containing organic compound, the organic lithium salt, and the silicon-carbon material in the above range can improve the comprehensive performance of the prepared silicon-carbon composite material.

[0058] In the embodiment of the present application, in step S40, the sintering treatment temperature is 500-800℃, and the sintering treatment time is 1-6h. Exemplarily, the sintering treatment temperature can be 500℃, 600℃, 700℃, or 800℃, and the sintering treatment time can be 1h, 2h, 3h, 4h, 5h, or 6h.

[0059] The application provides a silicon-carbon composite material prepared by the preparation method of the silicon-carbon composite material.

[0060] The application provides a lithium ion battery comprising the silicon-carbon composite material.

[0061] The technical solutions of the application are further described in detail below in combination with specific embodiments. It should be understood that the following embodiments are only used to explain the application and do not limit the application.

[0062] In the following embodiments, the black phosphorus nanodispersion is from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd., black phosphorus nanodispersion, CAS: 7723-14-0, the concentration is 0.5-1.5 wt %, and the solvent is polyethylene glycol; The asphalt is from Shandong Yingbang Asphalt Technology Co., Ltd., the product name is SBS modified asphalt, and the softening temperature is 80-150 DEG C. The epoxy resin is purchased from Shandong Shengquan New Material Co., Ltd., CAS: 61788-97-4. The melamine resin is purchased from Shandong Shengquan New Material Co., Ltd., CAS: 9003-08-1. The polyester resin is purchased from Shandong Shengquan New Material Co., Ltd., CAS: 25135-73-3, the molecular formula is C 22 H 26 O 10 , and the molecular weight is 450.436. The polyacrylamide is purchased from Anhui Jucheng Fine Chemical Co., Ltd., CAS: 9003-05-8. F127 is purchased from Beijing Hayfluda Technology Co., Ltd., CAS 9003-11-6. P123 is purchased from Zhengzhou Aikemu Chemical Co., Ltd., CAS: 106392-12-5.

[0063] Example 1 A preparation method of a silicon-carbon composite material comprises the following steps: (1) 3g P123 (amphoteric triblock polymer), 3g diphenylimidazoline, 300g black phosphorus nanodispersion (1 wt %, polyethylene glycol solution of black phosphorus quantum dots) and 1000g chloroform solution (the concentration of solute is 5 wt %, the epoxy equivalent weight is 210 g / eq) of epoxy resin are mixed, a crosslinking reaction is carried out at 80 DEG C for 3h, a reaction product is obtained, the reaction product is filtered to obtain a solid, and the solid is vacuum dried at 80 DEG C for 24h to obtain an intermediate material; (2) 100 g of the intermediate material, 200 g of potassium hydroxide, and 10 g of pitch were mixed, briquetted, and then subjected to carbonization treatment at 750°C for 3 h, and then activated to form pores by passing water vapor at a flow rate of 300 mL / min for 180 min at a temperature of 1100°C to obtain a porous carbon; (3) The porous carbon obtained in step (2) was transferred to a fluidized bed, argon was first passed to remove air in the tube, and then heated to 500°C, and a mixed gas of disilane and nitrogen (volume ratio of disilane to nitrogen: 3:10) was passed at a flow rate of 300 mL / min for 180 min to perform vapor deposition, and then cooled to room temperature, and air was passed at a flow rate of 30 mL / min for 180 min to perform passivation to obtain a silicon-carbon material; (4) 3 g of citric acid, 3 g of methylamine, 3 g of lithium acetate, and 90 g of dimethyl carbonate were mixed to form a coating solution of 10 wt%, and then the coating solution and 100 g of the silicon-carbon material obtained in step (3) were mixed and transferred to a reaction kettle, and then argon was first passed to remove air in the reaction kettle, and then heated to 650°C for sintering treatment for 3 h to obtain a silicon-carbon composite material.

[0064] Example 2 Compared with Example 1, the difference is that: In step (1), the raw materials were 1 g of polyacrylamide, 1 g of 2-methylimidazole, 100 g of a black phosphorus nanodispersion solution (0.5 wt%, a polyethylene glycol solution of black phosphorus quantum dots), and 1000 g of a toluene solution of melamine resin (the concentration of the solute was 1 wt%); the temperature of the crosslinking reaction was 50°C, and the time of the crosslinking reaction was 6 h; In step (2), the raw materials were 100 g of an intermediate material, 100 g of potassium hydroxide, and 5 g of pitch; the temperature of the carbonization treatment was 700°C, and the time of the carbonization treatment was 6 h; when activated to form pores, the temperature was increased to 900°C, water vapor was passed at a flow rate of 100 mL / min for 300 min; In step (3), the temperature was heated to 450°C; a mixed gas of methylsilane and nitrogen (volume ratio of methylsilane to nitrogen: 1:10) was passed at a flow rate of 100 mL / min for 300 min; when passivated, air was passed at a flow rate of 10 mL / min for 300 min; In step (4), the coating solution was a coating solution (5 wt%) formed by mixing 1 g of malic acid, 1 g of aniline, 1 g of lithium oxalate, and 60 g of diethyl carbonate; the temperature of the sintering treatment was 500°C, and the time of the sintering treatment was 6 h.

[0065] Example 3 Compared with Example 1, the difference is that: In step (1), the raw materials are 5 g of F127 (a triblock copolymer), 5 g of 2-ethylimidazole, 500 g of a black phosphorus nanodispersion (1.5 wt% of a polyethylene glycol solution of black phosphorus quantum dots), and 1000 g of a cyclohexane solution of a polyester resin (10 wt% of solute); the crosslinking reaction temperature is 100°C, and the crosslinking reaction time is 1 h; In step (2), the raw materials are 100 g of an intermediate material, 300 g of potassium carbonate, and 15 g of pitch; the carbonization treatment temperature is 1000°C, and the carbonization treatment time is 1 h; when activating and forming pores, the temperature is raised to 1300°C, the water vapor flow rate is 500 mL / min, and the water vapor flow time is 30 min; In step (3), the temperature is raised to 550°C; a mixed gas of dichlorosilane and nitrogen (a volume ratio of dichlorosilane to nitrogen of 5:10) is introduced at a flow rate of 500 mL / min for 60 min; when passivating, air is introduced at a flow rate of 50 mL / min for 60 min; In step (4), the coating liquid is a coating liquid (20 wt%) formed by mixing 5 g of citric acid, 5 g of pyridine, 5 g of lithium lactate, and 75 g of ethylene carbonate; the sintering treatment temperature is 800°C, and the sintering treatment time is 1 h.

[0066] Example 4 Compared with Example 1, the difference is that in step (1), the amount of the black phosphorus nanodispersion (a polyethylene glycol solution of black phosphorus quantum dots) is 10 g, and the concentration of the black phosphorus quantum dots in the black phosphorus nanodispersion is 0.1 wt%.

[0067] Example 5 Compared with Example 1, the difference is that in step (1), the amount of the black phosphorus nanodispersion (a polyethylene glycol solution of black phosphorus quantum dots) is 1000 g, and the concentration of the black phosphorus quantum dots in the black phosphorus nanodispersion is 3 wt%.

[0068] Example 6 Compared with Example 1, the difference is that in step (4), the amount of citric acid is 0.5 g.

[0069] Example 7 Compared with Example 1, the difference is that in step (4), the amount of citric acid is 10 g.

[0070] Example 8 Compared with Example 1, the difference is that in step (4), the amount of methylamine is 0.5 g.

[0071] Example 9 Compared with Example 1, the difference is that in step (4), the amount of methylamine is 10 g.

[0072] Comparative Example 1 Compared with Example 1, the difference is that black phosphorus nano-dispersion is not added in step (1).

[0073] Comparative Example 2 Compared with Example 1, the difference is that potassium hydroxide is not added in step (2).

[0074] Comparative Example 3 Compared with Example 1, the difference is that step (4) is not performed.

[0075] Comparative Example 4 Compared with Example 1, the difference is that lithium acetate is not added in step (4).

[0076] Comparative Example 5 The difference from Example 1 is that citric acid is not added in step (4).

[0077] Comparative Example 6 The difference from Example 1 is that methylamine is not added in step (4).

[0078] Comparative Example 7 Compared with Example 1, the difference is that black phosphorus nano-dispersion is not added in step (1), but is added in step (2).

[0079] Step (2) The specific steps are as follows: Mix 100g of intermediate material, 200g of potassium hydroxide and 10g of asphalt, press into blocks, and then carbonize at 750℃ for 3h. Then raise the temperature to 1100℃ and pass water vapor at a flow rate of 300mL / min for 180min to activate and create pores, thereby obtaining porous carbon. Then soak the porous carbon material in 300g of black phosphorus nano-dispersion liquid (1wt%, polyethylene glycol solution of black phosphorus) for 6h. After soaking, dry at 80℃.

[0080] Comparative Example 8 Compared with Example 1, an equal amount of black phosphorus micron flake dispersion (1 wt%, polyethylene glycol solution of black phosphorus) was used instead of black phosphorus nano dispersion, wherein the particle size of the micron flake material in the black phosphorus micron flake dispersion was 1~5 µm.

[0081] Performance testing 1. Scanning electron microscopy (SEM) test: SEM images of the silicon-carbon composite material prepared in Example 1 are shown below. Figure 1 As shown. By Figure 1 It can be seen that the material exhibits a spherical structure with slight adhesion, a reasonable size distribution, and a particle size between 3 and 8 µm.

[0082] 2. Button cells and their physicochemical properties testing: The specific surface area of the silicon-based composite material of the above examples and comparative examples was tested according to the national standard GB / T-38823-2020 “Silicon Carbon”. The powder resistance of the silicon-carbon composite material of the examples and comparative examples was tested by a four-probe tester. The test results are shown in Table 1.

[0083] The silicon-carbon composite material described in the above examples and comparative examples was assembled into a button cell as a lithium ion battery negative electrode material, and the specific preparation method included the following steps: a binder, a conductive agent and a solvent were added to the silicon-carbon composite material described in the above examples and comparative examples, respectively, and stirring was performed to prepare a slurry, which was coated on a copper foil, and then dried and rolled to obtain a negative electrode sheet; the binder used was PVDF, the conductive agent was conductive carbon black (SP), and the solvent was N-methyl pyrrolidone (NMP); the amount ratio of the negative electrode material, SP, PVDF and NMP was 95g:1g:4g:220mL; LiPF6 was used as the electrolyte in the electrolyte, and the mixture of EC and DEC in a volume ratio of 1:1 was used as the solvent; a lithium metal sheet was used as the counter electrode, and a polypropylene (PP) film was used as the separator. The button cell was assembled in an argon-filled glove box.

[0084] The obtained battery was subjected to electrochemical performance testing, and the electrochemical performance was tested on a Wuhan Lan Electric CT2001A battery tester, with a charge-discharge voltage range of 0.005V~2.0V and a charge-discharge rate of 0.1C. The charge direct current resistance (DCR) of the battery under the conditions of 25℃ and 50% SOC was also tested. The diffusion coefficient of the silicon-carbon composite material of the above examples and comparative examples was tested by GITT. The silicon-carbon composite material of the above examples and comparative examples was placed at a temperature of 45℃ for 48h to test the gas production. The test results are shown in Table 1.

[0085] The test process of full charge expansion was as follows: the thickness D1 of the negative electrode sheet of the button cell sheet after rolling was tested, then the button cell was fully charged to 100% SOC, and the full charge thickness D2 of the negative electrode sheet was dissected, and then the expansion rate of the negative electrode sheet was calculated (expansion rate=(D1-D2) / D1*100%); the test results are shown in Table 1.

[0086] Table 1 Performance test results of the button cells made from examples 1-9 and comparative examples 1-8

[0087] From Table 1, the following conclusions can be drawn: Compared with comparative examples 1-8, the resistivity, direct current resistance (DCR), gas production and full charge expansion test results of the silicon-carbon composite material provided by examples 1-3 are smaller, and the first discharge specific capacity, first efficiency and diffusion coefficient test results are higher.

[0088] According to the test results of Example 1 and Comparative Example 1, it can be seen that, without adding the black phosphorus nanodispersion in the porous carbon material, due to the reduction of phosphorus doping, the test results of the powder resistivity and DCR are both larger, and the test results of the first specific discharge capacity, the first efficiency and the diffusion coefficient are all smaller. The test results of the powder resistivity and DCR of Example 1 are both smaller than those of Comparative Example 7, and the diffusion coefficient is also higher than that of Comparative Example 7. The above results show that the effect of adding the black phosphorus nanodispersion in the step of preparing the intermediate is better, which may be because, in the step of cross-linking reaction of the soft template agent, the cross-linking agent, the black phosphorus nanodispersion and the high polymer solution to form the intermediate material, the black phosphorus quantum dots can be integrated into the cross-linking network through the physical and chemical action between the cross-linking agent / high polymer, while the porous carbon is doped with the black phosphorus nanodispersion, although the black phosphorus nanodispersion is added, the black phosphorus does not participate in the cross-linking network, and the stability and dispersibility are both poor. Compared with the dispersion of the black phosphorus microparticle (Comparative Example 8), the powder resistivity and DCR of Example 1 using the dispersion containing the black phosphorus quantum dots are smaller, and the effect of improving the first specific discharge capacity and the first efficiency is better, which may be because the black phosphorus quantum dots have a large specific surface area and a large number of edge active sites, can form a more close and uniform interface contact with the silicon / carbon matrix, and compared with the black phosphorus nanosheet, are not easy to stack and agglomerate, and are more conducive to building a conductive network. According to the test results of Comparative Example 2 and Example 1, it can be seen that, if the alkali activator is not added when preparing the porous carbon, the test results of the powder resistivity, DCR, gas production and full charge expansion are all larger, and the test results of the first specific discharge capacity, the first efficiency and the diffusion coefficient are all smaller.

[0089] According to the test results of Example 1 and Comparative Example 3, it can be seen that, after forming the porous carbon material, without setting the amorphous coating carbon layer, the test results of the powder resistivity, DCR, gas production and full charge expansion are all larger, and the test results of the first specific discharge capacity, the first efficiency and the diffusion coefficient are all smaller.

[0090] According to the test results of Example 1 and Comparative Examples 4-6, it can be seen that, when the material of the coating solution contains the organic acid, the nitrogen-containing organic compound and the organic lithium salt at the same time, the performance test results are the best, and if one of the organic acid, the nitrogen-containing organic compound and the organic lithium salt is missing, the test results of the powder resistivity, DCR, gas production and full charge expansion are all larger, and the test results of the first specific discharge capacity, the first efficiency and the diffusion coefficient are all smaller.

[0091] The above results show that, by adding the black phosphorus quantum dot nanodispersion in the step of preparing the intermediate, the black phosphorus is doped in the porous carbon, and at the same time, the coating solution containing the organic acid, the nitrogen-containing organic compound and the organic lithium salt is used to coat the lithium amorphous carbon on the surface of the material, the electronic conductivity of the material is improved, the polarization is reduced, the defects are reduced, the specific capacity, the first efficiency and the ion diffusion coefficient of the battery are improved, and the full charge expansion is smaller.

[0092] In addition, according to the test results of Examples 1 and 4-9, it can be seen that the comprehensive performance of Example 1 is better than that of Examples 4-9, indicating that by controlling the concentration and amount of black phosphorus nanodispersion, and by controlling the amount of organic acid and nitrogen-containing organic compound, a silicon-carbon composite material with better initial efficiency and specific capacity can be obtained, thereby improving the overall electrochemical performance of the silicon-carbon material.

[0093] 3. Soft package battery test: The silicon-based composite materials of the above examples and comparative examples were mixed with 95% artificial graphite to prepare negative electrode sheets; ternary material (LiNi 0.8 Co 0.1 Mn 0.1 O2) as the positive electrode material; LiPF6 as the electrolyte, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 as the solvent to form an electrolyte; and Celgard 2400 film as the separator. A 5Ah soft package battery was prepared, and the liquid absorption capacity, electrode sheet surface resistance test, and rate performance test were carried out.

[0094] 1) Liquid absorption capacity test: A 1 mL burette was used to absorb VmL of electrolyte, and a drop of electrolyte was added to the surface of the electrode sheet, and the time was recorded until the electrolyte was completely absorbed. The time t was recorded, and the test results are shown in Table 2.

[0095] 2) Electrode sheet surface resistance test: A membrane resistance tester was used, and the negative electrode sheet (size 100cm 2 ) was tested for resistance under a pressure of 50KN, and the surface resistance of the electrode sheet was calculated. The test results are shown in Table 2.

[0096] 3) Rate performance test: Under the conditions of a charge-discharge voltage range of 2.8~4.2V and a test temperature of 25±3.0℃, the battery was charged at 1.0C, 3.0C, and 5.0C, and discharged at 1.0C, and the constant current ratio of the battery under different charging modes was tested. The test results are shown in Table 2.

[0097] Table 2: Liquid absorption capacity, electrode sheet surface resistance, and rate performance test results of Examples 1-9 and Comparative Examples 1-8

[0098] As can be seen from Table 2, the test results of the liquid absorption speed, the electrode sheet surface resistance and the rate performance of the silicon-carbon composite materials provided by Examples 1-3 are better than those of Comparative Examples 1-8, indicating that the method for preparing the silicon-carbon composite material according to the application can improve the rate performance of the silicon-carbon composite material. Moreover, as can be seen from the test results of Examples 1 and 4-9, controlling the concentration and the amount of the black phosphorus nanodispersion, and the amount of the organic acid and the nitrogen-containing organic compound, is beneficial to obtaining the silicon-carbon composite material with better rate performance.

[0099] The above merely describes exemplary embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural transformation made according to the technical concept of the present application, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A method for preparing a silicon-carbon composite material, characterized in that, Includes the following steps: S10. Mix the soft template agent, crosslinking agent, black phosphorus nano-dispersion liquid and polymer solution to form a mixture, heat the mixture to allow the crosslinking agent and polymer to undergo a crosslinking reaction, forming a three-dimensional network structure embedded with black phosphorus, to obtain an intermediate material. S20. Mix the intermediate material, alkali activator and asphalt, press into blocks, and then carbonize the pressed material before passing water vapor through it to activate and create pores, thus obtaining porous carbon. S30. A mixed gas containing silane gas and inert gas is introduced into the porous carbon to perform vapor phase deposition, followed by passivation by introducing air to obtain silicon-carbon material. S40. The silicon-carbon material and the coating liquid are mixed and sintered to obtain the silicon-carbon composite material. The coating solution includes organic acids, nitrogen-containing organic compounds, and organolithium salts.

2. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S10: The soft template agent comprises at least one of a triblock polymer and polyacrylamide; and / or, The solute in the polymer solution includes at least one selected from epoxy resin, melamine resin, polyester resin, polyurethane, phenolic resin, urea-formaldehyde resin, and furan resin, with a molecular weight of 100,000 to 1,000,000; the mass concentration of the solute in the polymer solution is 1 to 10 wt%; and / or, The solvent for the polymer solution includes at least one of chloroform, toluene, n-hexane, ethyl acetate, and cyclohexanone; and / or, The crosslinking agent includes at least one selected from diphenylimidazoline, 2-methylimidazolium, 2-ethylimidazolium, and 2-ethyl-4-methylimidazolium; and / or, The black phosphorus nano-dispersion comprises a mixture of black phosphorus quantum dots and polyethylene glycol; wherein the particle size of the black phosphorus quantum dots is 1~10 nm; and / or, The concentration of black phosphorus in the black phosphorus nano-dispersion is 0.5~1.5wt%.

3. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S10: The mass ratio of the soft template agent, crosslinking agent, black phosphorus nano-dispersion, and polymer solution is (1~5):(1~5):(100~500):1000; and / or, The cross-linking reaction is carried out at a temperature of 50~100℃ for 1~6 hours.

4. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S20: The alkaline activator includes at least one selected from potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate; and / or, The softening point of the asphalt is 80~150℃.

5. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S20: The mass ratio of the intermediate material, alkali activator, and asphalt is 100:(100~300):(5~15); and / or, The carbonization treatment temperature is 700~1000℃, and the carbonization treatment time is 1~6h; and / or, When water vapor is introduced for activation and pore formation, the flow rate of the water vapor is 100~500mL / min, the activation and pore formation temperature is 900~1300℃, and the activation and pore formation time is 30~300min.

6. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S30: The mixture of silane gas and inert gas includes at least one of the following: methylsilane, diethylsilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and silicon tetrafluoride; and / or, The volume ratio of the silane gas to the inert gas is (1~5):10; and / or, During vapor deposition, the flow rate of the mixed gas is 100-500 mL / min, the vapor deposition temperature is 450-550 °C, and the vapor deposition time is 60-300 min; and / or, When air is introduced for passivation, the air flow rate is 10~50mL / min, the passivation temperature is 20~30℃, and the passivation time is 60~300min.

7. The method for preparing the silicon-carbon composite material as described in claim 1, characterized in that, In step S40: The organic acid in the coating solution includes at least one of citric acid, malic acid, tartaric acid, fumaric acid, and lactic acid; and / or, The nitrogen-containing organic compound in the coating solution includes at least one of methylamine, aniline, naphthylamine, pyridine, pyrrole, and imidazole; and / or, The organic lithium salt in the coating solution includes at least one of lithium acetate, lithium oxalate, lithium trifluoroate, lithium pyruvate, and lithium lactate; and / or, The solvent in the coating solution includes at least one of dimethyl carbonate, diethyl carbonate, and ethylene carbonate; and / or, The sintering temperature is 500~800℃, and the sintering time is 1~6h.

8. The method for preparing the silicon-carbon composite material as described in claim 7, characterized in that, In the coating solution, the total mass of the organic acid, nitrogen-containing organic compound and organolithium salt is 5% to 20% of the solvent, and the mass ratio of the organic acid, nitrogen-containing organic compound and organolithium salt to the silicon-carbon material is (1~5):(1~5):(1~5):

100.

9. A silicon-carbon composite material, characterized in that, The silicon-carbon composite material is prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the silicon-carbon composite material as described in claim 9.

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