Porous composite elastomer and silicon-carbon, and preparation methods therefor and use thereof

Abstract

The present application relates to the technical field of negative electrode materials of batteries, and in particular relates to a porous composite elastomer and silicon-carbon, and preparation methods therefor and the use thereof. The present application provides a porous composite elastomer, which is of a porous structure, and comprises a flexible body and a rigid body, which are interpenetrating, wherein the raw material of the flexible body comprises carbon nanotubes, and the rigid body comprises hard carbon. In the present application, a silicon-carbon composite material is prepared by using carbon nanotubes and hard carbon as carbon sources and compounding same with silicon; and compared with a conventional silicon-carbon composite material, the carbon nanotubes, serving as a bridge between the silicon and the hard carbon, can effectively improve the conductivity and the ion conducting energy, thereby improving the rate capability of a negative electrode material.

Description

A porous composite elastomer, silicon carbon and its preparation method and application Technical Field

[0001] The present application relates to the technical field of battery negative electrode materials, and in particular to a porous composite elastomer, silicon carbon, and a preparation method and application thereof. Background Art

[0002] Silicon has an extremely high theoretical lithium insertion capacity and a moderate lithium insertion / extraction potential, so silicon-based negative electrode materials are undoubtedly the next generation of ideal lithium-ion battery negative electrode materials after graphite. However, silicon has very poor electrical conductivity and ion diffusion coefficient, and during the lithium insertion / extraction process, silicon undergoes severe volume expansion (>300%), causing the material to crack and pulverize, and fall off from the current collector, resulting in a rapid decrease in capacity and cycle attenuation. Although existing technologies use carbon materials and silicon composites to alleviate silicon's volume expansion to a certain extent to improve cycle performance, this simple physical composite of silicon and carbon cannot guarantee the ion transport performance of the composite material.

[0003] Patent (CN114420928A) discloses a core-shell silicon-carbon composite material with carbon nanotubes, graphene, and nanosilicon as the core materials and a soft carbon outer layer. Carbon nanotubes and graphene can improve the composite's ion transport capacity, but the grinding of carbon nanotubes, graphene, and silicon cannot guarantee uniformity and, therefore, good bulk ion transport performance. Furthermore, silicon exists in micrometer-sized form, which can lead to severe volume expansion during the delithiation / insertion process, causing a drop in battery cycle performance. Patent (CN115663131A) utilizes CVD vapor deposition to deposit nanosilicon within pelletized carbon nanotubes. Reducing the silicon size alleviates volume expansion, but the pores in the shaped spherical carbon nanotubes are very large, making silicon prone to agglomeration during deposition. Furthermore, the hardness difference between carbon nanotubes and silicon is significant, and the rolling process used to prepare the electrode can cause the material to break. Volume expansion during the delithiation / insertion process can also lead to material pulverization, which can cause a drop in cycle performance. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of this application is to provide a porous composite elastomer, silicon carbon and their preparation method and application.

[0005] To achieve the above-mentioned purpose and other related purposes, the present invention is prepared by including the following technical solutions.

[0006] In a first aspect, the present application provides a porous composite elastomer having a porous structure. The porous composite elastomer comprises a flexible body and a rigid body interpenetrating each other. The raw material of the flexible body comprises carbon nanotubes, and the rigid body is hard carbon.

[0007] In any embodiment of the present application, the porous composite elastomer contains uniformly distributed micropores and / or mesopores.

[0008] In any embodiment of the present application, the mass ratio of the flexible body to the rigid body is (0.01-2): 1. Preferably, the mass ratio of the flexible body to the rigid body is (0.8-1.2):1.

[0009] In any embodiment of the present application, the average pore size of the porous composite elastomer is less than 15 nm, preferably 1.8 to 10 nm.

[0010] In any embodiment of the present application, the total pore volume of the porous composite elastomer is 0.2 to 1.5 cm 3 / g, preferably 0.4 to 1.1 cm 3 / g.

[0011] In any embodiment of the present application, the specific surface area of ​​the porous composite elastomer is greater than 200 m 2 / g, preferably >700m 2 / g.

[0012] In any embodiment of the present application, the D of the porous composite elastomer 50 It is <30 μm, preferably <20 μm.

[0013] In any embodiment of the present application, the tap density of the porous composite elastomer is 0.1 to 1.0 g / cm 3 , preferably 0.2 to 0.7 g / cm 3 .

[0014] In any embodiment of the present application, the resistivity of the porous composite elastomer is less than 5Ω·cm, preferably less than 0.5Ω·cm, and more preferably less than 0.05Ω·cm.

[0015] In any embodiment of the present application, the pore size concentration of the porous composite elastomer is less than 7, preferably 0.5-5.

[0016] A second aspect of the present application provides a method for preparing the aforementioned porous composite elastomer, comprising the following steps:

[0017] S1: Preparation of carbon tube clusters: shaping carbon nanotubes to form carbon tube clusters;

[0018] S2: Preparation of carbon nanotube composite carbon material: adding carbon nanotube clusters into a solution containing a soft template and a polymer, allowing the solution to penetrate into the carbon nanotube clusters, and heat treating to obtain the carbon nanotube composite carbon material;

[0019] S3: Preparation of porous composite elastomer: carbonizing the carbon tube composite carbon material to obtain a porous composite elastomer.

[0020] In any embodiment of the present application, in step S1, the shaping is performed using a shaping machine. Preferably, the main machine frequency of the shaping machine is 5-60 Hz, the auxiliary machine frequency is 20-90 Hz, the fan frequency is 8-30 Hz, and the operating time is 2-100 min.

[0021] In any embodiment of the present application, in step S1, the carbon nanotubes have a length of 0.1 to 50 μm and a diameter of 2 to 20 nm.

[0022] In any embodiment of the present application, in step S1, the D of the carbon tube cluster 50 1~100μm.

[0023] In any embodiment of the present application, in step S1, the carbon tube cluster is a yarn-like structure. Preferably, the shaped carbon tube cluster is spherical or quasi-spherical, and the sphericity of the carbon tube cluster is Sh10% ≥ 0.70, Sh50% ≥ 0.80, and Sh90% ≥ 0.85.

[0024] In any embodiment of the present application, an intermediate modification treatment is further included between step S1 and step S2: adding the carbon tube clusters into an acidic solution and stirring, filtering to obtain a solid, washing to neutrality, and drying to obtain a modified carbon tube cluster.

[0025] In any embodiment of the present application, the mass ratio of the carbon tube clusters to the acidic solution is (0.1-100):1.

[0026] In any embodiment of the present application, the acidic solution is selected from one or more of nitric acid, sulfuric acid, and hydrochloric acid.

[0027] In any embodiment of the present application, the stirring reaction temperature is 30 to 100° C., and the stirring reaction time is 2 to 12 hours.

[0028] In any embodiment of the present application, washing is performed with pure water and drying is performed in a drying oven at a temperature of 60 to 100° C. and a drying time of 2 to 48 hours.

[0029] In any embodiment of the present application, in step S2, the monomer of the polymer is selected from Formula I:

[0030] wherein A1 is selected from X, OH, NH2 or a benzene ring substituted by X, OH or NH2; X is selected from F, Cl, Br and a halide of I; R1, R2 and R3 are independently selected from H, unsubstituted or substituted phenyl, unsubstituted or substituted C1-C 20 Alkyl, unsubstituted or substituted C1-C 20At least one of the alkoxy groups; a substituent group in a substituted phenyl group, a substituted C1-C 20 Substituted groups in alkyl and substituted C1-C 20 The substituent groups in the alkoxy group are independently selected from at least one of halogen, OH or NH2. The polymer is selected from one or more of polyethylene glycol, waterborne polyurethane, polyvinyl alcohol, polyvinylidene fluoride, fluorinated copolymer, polyimide, polyacrylic acid, polyacrylate, polymethyl methacrylate, phenolic resin, epoxy resin, or ionic resin.

[0031] In any embodiment of the present application, in step S2, the soft template is selected from a nonionic surfactant or an ionic surfactant. Preferably, the nonionic surfactant is selected from a polyoxyethylene-polyoxypropylene copolymer; and the ionic surfactant is selected from cetyltrimethylammonium bromide and / or sodium dodecylsulfonate.

[0032] In any embodiment of the present application, in step S2, the mass ratio of the carbon tube clusters to the polymer is (0.1-10): 1. Preferably, the mass ratio of the carbon tube clusters to the polymer is 1:3.

[0033] In any embodiment of the present application, in step S2, the solid content of the polymer in the solution is 20-100%.

[0034] In any embodiment of the present application, in step S2, the solution infiltration into the carbon tube cluster is carried out under negative pressure conditions, wherein the negative pressure condition is -0.9 to -0.01 MPa and the negative pressure duration is 0.5 to 10 hours. After the negative pressure treatment, a positive pressure treatment is also included; the positive pressure condition is 0.15 to 2 MPa and the pressure is maintained for 0.5 to 48 hours.

[0035] In any embodiment of the present application, in step S2, the solvent needs to be evaporated after the heat treatment to obtain a carbon nanotube composite carbon material. The heat treatment temperature is 80-200° C. and the heat treatment time is 0.5-50 h.

[0036] In any embodiment of the present application, in step S3, the carbonization treatment includes subjecting the carbon tube composite carbon material to a high-temperature reaction under a protective gas.

[0037] In any embodiment of the present application, the protective gas in the carbonization treatment is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon, and the flow rate of the protective gas is 1 to 20 L / min.

[0038] In any embodiment of the present application, the temperature of the high-temperature reaction is 500-1000° C., the time of the high-temperature reaction is 1-30 h, and the heating rate is 1-10° C. / min.

[0039] In any embodiment of the present application, the high-temperature reaction further includes a post-processing step: cooling to room temperature.

[0040] The third aspect of the present application provides a silicon carbon, the raw materials of which include the aforementioned porous composite elastomer and nano silicon particles.

[0041] In any embodiment of the present application, the nano-silicon particles are embedded in the porous composite elastomer, and the silicon carbon contains uniformly distributed micropores and / or mesopores.

[0042] In any embodiment of the present application, the specific surface area of ​​the silicon carbon is less than 20m 2 / g.

[0043] In any embodiment of the present application, the D of the silicon carbon 50 The tap density of the silicon carbon is 0.5 to 2 g / cm 3 .

[0044] In any embodiment of the present application, the content of the nano-silicon particles is 30-70% of the total mass of the silicon carbon. The resistivity of the silicon carbon is less than 20Ω·cm.

[0045] In any embodiment of the present application, the specific capacity of the silicon carbon is greater than 1200 mAh / g, the first coulombic efficiency is greater than 89%, the capacity retention rate after 500 cycles is greater than 85%, and the 4C / 1C rate performance is greater than 90%.

[0046] A fourth aspect of the present application provides a method for preparing the aforementioned silicon carbon, comprising: vapor deposition of a porous composite elastomer and a silicon-containing source gas in a high-temperature environment to obtain silicon carbon.

[0047] In any embodiment of the present application, the high temperature environment is a deposition furnace, the high temperature temperature is 300-600°C, and the insulation time is 1-50h; preferably, the pressure in the deposition furnace is maintained at 5-10MPa, and the heating rate is 1-5°C / min.

[0048] In any embodiment of the present application, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; and the carbon source gas is selected from an alkane gas with a cracking temperature below 600°C.

[0049] In any embodiment of the present application, the silicon-containing source gas further includes a carbon source gas.

[0050] In any embodiment of the present application, the vapor deposition time is 1 to 50 hours. Preferably, the vapor deposition time is 10 to 30 hours.

[0051] In any embodiment of the present application, when the silicon-containing source gas is only silicon source gas, the gas flow rate is 1 to 20 L / min.

[0052] In any embodiment of the present application, when the silicon-containing source gas includes silicon source gas and carbon source gas, based on the total volume of the gas, the volume proportion of the silicon source gas is 70 to 99%, and the volume proportion of the carbon source gas is 1 to 30%; the gas flow rate is 5 to 20 L / min.

[0053] In a fifth aspect, the present application provides a carbon-coated silicon-carbon, comprising the aforementioned silicon-carbon and a carbon coating layer coated on the surface of the silicon-carbon.

[0054] In any embodiment of the present application, the carbon coating amount of the carbon-coated silicon-carbon is 0.5-10 wt %. Preferably, the carbon coating amount of the carbon-coated silicon-carbon is 0.5-5 wt %.

[0055] In any embodiment of the present application, the median particle size D of the carbon-coated silicon carbon is 50 It is less than 20μm.

[0056] In any embodiment of the present application, the content of silicon in the carbon-coated silicon carbon is 20-80 wt %.

[0057] In any embodiment of the present application, the specific surface area of ​​the carbon-coated silicon carbon is 0.5 to 20.0 m 2 / g.

[0058] In any embodiment of the present application, the compacted density of the carbon-coated silicon carbon powder is 0.5 to 2 g / cm 3 .

[0059] In a sixth aspect, the present application provides a method for preparing the aforementioned carbon-coated silicon-carbon, comprising introducing a mixed gas comprising a protective gas and a carbon source gas so as to coat the silicon-carbon to form carbon-coated silicon-carbon.

[0060] In any embodiment of the present application, the carbon source gas is selected from an alkane gas having a cracking temperature below 600°C.

[0061] In any embodiment of the present application, the protective gas is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon.

[0062] In any embodiment of the present application, based on the total volume of the mixed gas, the volume proportion of the carbon source gas is 60-80%, the volume proportion of the protective gas is 20-40%, and the gas flow rate of the mixed gas is 0.1-50 L / min, preferably 5-20 L / min.

[0063] In a seventh aspect, the present application provides a silicon-carbon composite negative electrode material, the raw materials of which include the aforementioned porous composite elastomer, the aforementioned silicon-carbon, or the aforementioned carbon-coated silicon-carbon.

[0064] In an eighth aspect, the present application provides the use of the aforementioned porous composite elastomer, the aforementioned silicon-carbon, the aforementioned carbon-coated silicon-carbon, or the aforementioned silicon-carbon composite negative electrode material in the preparation of battery products.

[0065] In a ninth aspect, the present application provides a lithium-ion battery, the raw materials of which include the aforementioned porous composite elastomer, the aforementioned silicon-carbon, the aforementioned carbon-coated silicon-carbon, or the aforementioned silicon-carbon composite negative electrode material.

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] 1. This application uses carbon nanotubes and hard carbon as carbon sources to compound with silicon to prepare silicon-carbon composite materials. Compared with conventional silicon-carbon composite materials, carbon nanotubes serve as a bridge between silicon and hard carbon, effectively improving the electrical conductivity and ion conduction energy, thereby improving the rate performance of the negative electrode material.

[0068] 2. This application utilizes yarn-like carbon tubes to form a macroporous material to accommodate ordered micro-mesoporous carbon of moderate hardness, and then uses the micro-mesoporous material to accommodate the extremely hard elemental nano-silicon. On the one hand, the high-strength ordered micro-mesoporous carbon is a hard carbon, which gives the composite material high strength, greatly reducing the risk of the negative electrode material being crushed during the roller pressing process, thereby improving the safety of the electrode preparation. On the other hand, the flexible carbon tubes give the composite material a certain degree of elasticity and ductility, preventing the composite material from falling off the electrode due to volume expansion during the charge and discharge process, thereby preventing the battery from experiencing cycling problems.

[0069] 3. This application uses a soft template method to create pores, and achieves pore creation through a simple heating process. Compared with the existing activation pore creation technology, it greatly simplifies the preparation process of porous carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] FIG1 is a schematic diagram of the preparation process of silicon carbon in this application.

[0071] FIG2 is a SEM image of the CNT clusters of the present application.

[0072] FIG3 is a SEM image of the CNT composite carbon material of the present application.

[0073] FIG4 is a SEM image of the porous composite elastomer of the present application.

[0074] FIG5 is a SEM image of silicon carbon of the present application. DETAILED DESCRIPTION

[0075] In order to make the invention purpose, technical scheme and beneficial effects of this application clearer, the present application is further described below with reference to the examples. It should be understood that the examples are only used to explain this application and are not used to limit the scope of the application. Unless otherwise specified, the test methods used in the following examples are all conventional methods. People familiar with this technology can easily understand other advantages and effects of this application from the content disclosed in this description.

[0076] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0077] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0078] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0079] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the examples, any prior art methods, devices, and materials similar or equivalent to those in the examples may be used to implement the present invention, based on the knowledge of the prior art by those skilled in the art and the disclosure of this invention.

[0080] After extensive exploration and research, the inventors of this application have discovered a high-cycle and high-rate silicon-carbon composite negative electrode material and its preparation method. This application first winds carbon nanotubes into a microsphere or microsphere-like structure of an ultra-large-pore wool ball. The carbon tubes are interconnected, which can guarantee the ion conductivity and electrical conductivity to the greatest extent; then, a polymer carbon source material mixed with a soft template is used to fill the loose large pores of the wool ball, and a CNT ordered micro / mesoporous carbon skeleton is formed through low-temperature curing and high-temperature carbonization to form pores, and then CVD vapor-phase silicon deposition is performed on this base skeleton to prepare a silicon-carbon composite negative electrode material. The material contains abundant carbon nanotubes, so it has good ion and electron transport properties; the material is filled with disordered carbon material on the basis of flexible carbon nanotubes so that the strength of the composite structure is guaranteed to a certain extent, and the disordered carbon is templated and pore-formed by high-temperature carbonization to obtain a CNT ordered porous carbon composite material. CVD vapor-phase silicon deposition is performed on the basis of this ordered porous material to ensure the uniform compounding of elemental silicon.

[0081] The first aspect of the present application provides a porous composite elastomer, which is a porous structure, and the porous composite elastomer includes a flexible body and a rigid body interpenetrating each other, the raw material of the flexible body includes carbon nanotubes, and the rigid body includes hard carbon. Wherein, the mass ratio of the flexible body to the rigid body is (0.01-2):1. Specifically, it can be (0.01-0.5):1, (0.5-1.0):1, (1.0-1.5):1 or (1.5-2.0):1, etc. Preferably, the mass ratio of the flexible body to the rigid body is (0.8-1.2):1. In a specific embodiment of the present application, the length of the carbon nanotube is 0.1-50 μm, specifically 0.1-1 μm, 1-10 μm, 10-20 μm, 20-30 μm, 30-40 μm, or 40-50 μm, etc. The diameter of the carbon tube cluster is 2-20 nm, specifically 2-10 nm, 10-15 nm, or 15-20 nm. 50 The thickness is 1 to 100 μm, specifically 1 to 10 μm, 10 to 50 μm, or 50 to 100 μm.

[0082] The porous composite elastomer provided in the present application contains uniformly distributed micropores and / or mesopores. The average pore size of the porous composite elastomer is less than 15 nm, preferably 1.8 to 10 nm. The total pore volume is 0.2 to 1.5 cm3 / g, preferably 0.4 to 1.1 cm 3 / g. Specific surface area of ​​porous composite elastomer>200m 2 / g, preferably >700m 2 / g; more preferably, 600 to 1200 m 2 / g. D of porous composite elastomer 50 The tap density of the porous composite elastomer is 0.1 to 1.0 g / cm 3 , preferably 0.2 to 0.7 g / cm 3 The resistivity of the porous composite elastomer is less than 5Ω·cm, preferably less than 0.5Ω·cm, and more preferably less than 0.05Ω·cm. The pore size concentration of the porous composite elastomer is less than 7, preferably 0.5 to 5, and the pore size concentration = (V 90 -V 10 ) / V 50 , where V 10 Refers to the pore diameter corresponding to the pore volume distribution percentage reaching 10%, V 50 Refers to the pore diameter corresponding to the pore volume distribution percentage reaching 50%, V 90 It refers to the pore diameter corresponding to when the pore volume distribution percentage reaches 90%.

[0083] A second aspect of the present application provides a method for preparing the aforementioned porous composite elastomer, comprising the following steps:

[0084] S1: Preparation of carbon tube clusters: shaping carbon nanotubes to form carbon tube clusters;

[0085] S2: Preparation of carbon nanotube composite carbon material: adding carbon nanotube clusters into a solution containing a soft template and a polymer, allowing the solution to penetrate into the carbon nanotube clusters, and heat treating to obtain the carbon nanotube composite carbon material;

[0086] S3: Preparation of porous composite elastomer: carbonizing the carbon tube composite carbon material to obtain a porous composite elastomer.

[0087] In any embodiment of the present application, step S1 refers to the preparation of carbon tube clusters: shaping carbon nanotubes to form carbon tube clusters.

[0088] In the preparation method provided herein, in step S1, the shaping is performed using a shaping machine. Preferably, the main machine frequency of the shaping machine is 5-60 Hz, specifically 5-10 Hz, 10-20 Hz, or 20-60 Hz; the auxiliary machine frequency is 20-90 Hz, specifically 20-30 Hz, 30-50 Hz, or 50-90 Hz. The fan frequency is 8-30 Hz, specifically 8-10 Hz, 10-20 Hz, or 20-30 Hz. The operating time is 2-100 min, specifically 2-10 min, 10-50 min, or 50-100 min.

[0089] In the preparation method provided in the present application, in step S1, the length of the carbon nanotubes is 0.1 to 50 μm, specifically 0.1 to 1 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, or 40 to 50 μm. The diameter of the carbon nanotubes is 2 to 20 nm, specifically 2 to 10 nm, 10 to 15 nm, or 15 to 20 nm. The median particle size D of the carbon nanotube clusters is 0.1 to 50 μm, specifically 0.1 to 1 μm, 1 to 10 μm, 10 to 20 μm, 20 to 30 μm, 30 to 40 μm, or 40 to 50 μm. 50 The carbon tube clusters after shaping are 1 to 100 μm, specifically 1 to 10 μm, 10 to 50 μm, or 50 to 100 μm. The carbon tube clusters after shaping are wool-like structures. Preferably, the carbon tube clusters after shaping are spherical or quasi-spherical, and the sphericity Sh10% of the carbon tube clusters is ≥0.70, the sphericity Sh50% is ≥0.80, and the sphericity Sh90% is ≥0.85, wherein the sphericity Sh10% refers to the sphericity corresponding to the particle size distribution percentage reaching 10%, the sphericity Sh50% refers to the sphericity corresponding to the particle size distribution percentage reaching 50%, and the sphericity Sh90% refers to the sphericity corresponding to the particle size distribution percentage reaching 90%.

[0090] The preparation method provided herein includes an intermediate modification step between step S1 and step S2: adding the carbon tube clusters to an acidic solution, reflux stirring, filtering to obtain a solid, washing to neutrality, and drying to obtain the modified carbon tube clusters. The mass ratio of the carbon tube clusters to the acidic solution is (0.1-100):1; specifically, it can be (0.1-10):1, (10-50):1, or (50-100:1).

[0091] In the preparation method provided in this application, the acidic solution is selected from a combination of one or more of nitric acid, sulfuric acid, and hydrochloric acid. The stirring reaction temperature is 30-100°C, specifically 30-40°C, 40-50°C, or 50-100°C; the stirring reaction time is 2-12 hours, specifically 2-4 hours, 4-8 hours, or 8-12 hours. Washing is carried out with pure water; drying is carried out in a drying oven. The drying temperature is 60-100°C, specifically 60-70°C, 70-80°C, or 80-100°C; the drying time is 2-48 hours, specifically 2-12 hours, 12-24 hours, or 24-48 hours. The purpose of the intermediate modification treatment is to modify the carbon tube clusters. The modified carbon tube clusters will produce groups such as carboxyl groups and amino groups. When modified to carboxyl groups, they can load -NH2 or -OH in the polymer, and the loading is carried out through chemical bonding or physical bonding.

[0092] In the preparation method provided in the present application, step S2 refers to the preparation of carbon tube composite carbon material: adding carbon tube clusters into a solution containing a soft template and a polymer, allowing the solution to penetrate into the carbon tube clusters, and heat treating to obtain the carbon tube composite carbon material.

[0093] The preparation method provided herein uses a polymer with a specific group, and requires the carbon tube pellets to undergo an intermediate modification process so that the polymer fills the pores of the carbon tube pellets through chemical bonding or hydrogen bonding. The polymer monomer used when the intermediate modification process is required is selected from Formula I:

[0094] wherein A1 is selected from X, OH, NH2 or a benzene ring substituted by X, OH or NH2; X is selected from F, Cl, Br and a halide of I; R1, R2 and R3 are independently selected from H, unsubstituted or substituted phenyl, unsubstituted or substituted C1-C 20 Alkyl, unsubstituted or substituted C1-C 20 At least one of the alkoxy groups; a substituent group in a substituted phenyl group, a substituted C1-C 20 Substituted groups in alkyl and substituted C1-C 20 The substituent groups in the alkoxy group are independently selected from at least one of halogen, OH, or NH2. The polymer is selected from one or more of polyethylene glycol, waterborne polyurethane, polyvinyl alcohol, polyvinylidene fluoride, fluorinated copolymer, polyimide, polyacrylic acid, polyacrylate, polymethyl methacrylate, phenolic resin, epoxy resin, or ionic resin; preferably, the fluorinated copolymer is selected from a copolymer of vinylidene fluoride and hexafluoroethylene.

[0095] In the preparation method provided in the present application, in step S2, when the polymer is selected as one or more of phenolic resin, epoxy resin or ionic resin, it can be selected from carbon tube clusters that have undergone intermediate modification or carbon tube clusters that have not undergone modification. The polymer here can be filled in the pores of the carbon tube clusters through curing.

[0096] In the preparation method provided in the present application, in step S2, the soft template is selected from a non-ionic surfactant or an ionic surfactant; preferably, the non-ionic surfactant is selected from a polyoxyethylene-polyoxypropylene copolymer; the ionic surfactant is selected from hexadecyltrimethylammonium bromide and / or sodium dodecylsulfonate; more preferably, the non-ionic surfactant is selected from F108, F127, F68, or Pluronic reagents.

[0097] In the preparation method provided herein, in step S2, the mass ratio of the carbon tube clusters to the polymer is (0.1-10):1, specifically (0.1-1):1, (1-5):1, or (5-10):1. In a preferred embodiment of the present invention, the mass ratio of the carbon tube clusters to the polymer is 1:3.

[0098] In the preparation method provided in the present application, in step S2, the solid content of the polymer in the solution is 20-100%, specifically 20-30%, 30-50%, or 50-100%.

[0099] In the preparation method provided in the present application, in step S2, the solution infiltrates into the carbon tube clusters under negative pressure conditions, which are -0.9 to -0.01 MPa, specifically -0.9 to -0.1 MPa, -0.1 to -0.05 MPa, or -0.05 to -0.01 MPa; the negative pressure duration is 0.5 to 10 hours, specifically 0.5 to 1 hour, 1 to 2 hours, or 2 to 10 hours. After the negative pressure treatment, positive pressure treatment is also included; the positive pressure condition is 0.15 to 2 MPa, and the pressure holding time is 0.5 to 48 hours. Preferably, the positive pressure condition is 0.6 to 1 MPa, and the pressure holding time is 2 to 12 hours.

[0100] In the preparation method provided in the present application, in step S2, the heat treatment temperature is 80-200°C, specifically 80-100°C, 100-150°C, or 150-200°C, etc.; the heat treatment time is 0.5-50h, specifically 0.5-1h, 1-5h, or 5-50h, etc.

[0101] In the preparation method provided in the present application, step S3 refers to the preparation of a porous composite elastomer: carbonizing the carbon tube composite carbon material to obtain a porous composite elastomer.

[0102] Among them, the carbonization treatment includes subjecting the carbon nanotube composite carbon material to a high-temperature reaction under a protective gas to carbonize and form pores. The protective gas in the carbonization treatment is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon, and the flow rate of the protective gas is 1 to 20 L / min, specifically 1 to 10 L / min, 10 to 15 L / min, or 15 to 20 L / min. The temperature for carbonization and pore formation is 500 to 1000°C, specifically 500 to 700°C, 700 to 800°C, or 800 to 1000°C. The time for carbonization and pore formation is 1 to 30 hours, specifically 1 to 10 hours, 10 to 15 hours, or 15 to 30 hours. The heating rate is 1 to 10°C / min, specifically 1 to 3°C / min, 3 to 5°C / min, or 5 to 10°C / min. After the high-temperature reaction, a post-treatment step is also included: cooling to room temperature.

[0103] The shape of the porous composite elastomer is sponge-like and its pore distribution is uniform. Step S3 can form holes because, after high-temperature carbonization treatment, the polymer in the carbon tube composite carbon material undergoes thermal decomposition to form hard carbon, which fills the gaps in the carbon tube clusters to form a composite elastomer in which hard carbon and carbon tubes are interspersed with each other. And during the high-temperature carbonization process, the polymer thermally decomposes to produce gas, thereby forming pores inside and on the surface of the composite elastomer, obtaining a composite elastomer with a porous structure. The uniform pore distribution of this step is determined by temperature and heating rate. This technology uses a soft template method to form pores, and pore formation is achieved through a simple heating process. Compared with the existing activation pore-forming technology, the preparation process of porous carbon is greatly simplified.

[0104] The third aspect of the present application provides a silicon carbon, the raw materials of which include the aforementioned porous composite elastomer and nano silicon particles.

[0105] In the silicon carbon provided in the present application, nano silicon particles are embedded in the porous composite elastomer, and the silicon carbon contains uniformly distributed micropores and / or mesopores. The specific surface area of ​​the silicon carbon is less than 20m 2 / g. The total pore volume of silicon carbon is less than 0.05m 2 / g. The silicon carbon D 50 <20 μm; preferably, 100 nm to 12 μm. The tap density of the silicon carbon is 0.5 to 2 g / cm 3 .

[0106] The silicon-carbon provided in this application contains nano-silicon particles at a content of 30-70% of the total mass of the silicon-carbon. The silicon-carbon has a specific capacity greater than 1200 mAh / g, an initial coulombic efficiency greater than 89%, a capacity retention rate greater than 85% after 500 cycles, and a 4C / 1C rate performance greater than 90%. C represents the battery's charge and discharge capacity. 1C represents the current intensity when the battery is fully discharged in one hour. 4C represents the current intensity when the battery is fully discharged in four hours.

[0107] The fourth aspect of the present application provides the aforementioned method for preparing silicon carbon, comprising: vapor deposition of a porous composite elastomer and a silicon-containing source gas in a high-temperature environment to obtain silicon carbon. Wherein, the high-temperature environment is a deposition furnace, the high-temperature temperature is 300-600°C, specifically 300-400°C, 400-500°C, or 500-600°C, etc.; the holding time is 1-50h; specifically 1-10h, 10-20h, or 20-50h, etc.; preferably, the pressure in the deposition furnace is maintained at 5-10MPa, and the heating rate is 1-5°C / min. The silicon-containing source gas is cracked at high temperature, atoms such as H and Cl are volatilized, silicon forms nano-silicon particles, and is deposited in the pores of the porous composite elastomer.

[0108] In the silicon-carbon preparation method provided in the present application, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; the carbon source gas is selected from an alkane gas with a cracking temperature below 600°C, preferably, the carbon source gas is selected from acetylene and / or ethylene.

[0109] In the silicon-carbon preparation method provided in the present application, when the silicon-containing source gas is only silicon source gas, the gas flow rate is 1 to 20 L / min, specifically 1 to 10 L / min, 10 to 15 L / min, or 15 to 20 L / min, etc.; preferably, 2 to 10 L / min. The silicon-containing source gas also includes a carbon source gas. When the silicon-containing source gas includes silicon source gas and carbon source gas, based on the total volume of the gas, the volume proportion of the silicon source gas is 70 to 99%, and the volume proportion of the carbon source gas is 1 to 30%. The total gas flow rate is 5 to 20 L / min; specifically, it can be 5 to 10 L / min, 10 to 15 L / min, or 15 to 20 L / min, etc. When the silicon-containing source gas includes carbon source gas and silicon source gas, the carbon source gas limits the silicon source gas to prevent all silicon from falling into the same hole.

[0110] In a fifth aspect, the present application provides a carbon-coated silicon-carbon, comprising the aforementioned silicon-carbon and a carbon coating layer coated on the surface of the silicon-carbon.

[0111] In the carbon-coated silicon-carbon provided in the present application, the carbon coating amount in the carbon-coated silicon-carbon composite negative electrode material is 0.5 to 10 wt %; preferably, 0.5 to 5 wt %. The median particle size D of the carbon-coated silicon-carbon composite negative electrode material is 50 The silicon content is 20-80 wt%, specifically 20-30 wt%, 30-40 wt%, 40-50 wt%, 50-60 wt%, 60-70 wt% or 70-80 wt%, etc.; the specific surface area is 0.5-20.0 m 2 / g, specifically 0.5 to 10.0 m2 / g, 10.0~15.0m 2 / g, or 15.0~20.0m 2 / g, etc.; pore volume <0.1cm 3 g -1 , the powder compaction density is 0.5~2g / cm 3 , specifically 0.5 to 0.7 g / cm 3 , 0.7~0.9g / cm 3 , 0.9~1.2g / cm 3 1.2~1.5g / cm 3 or 1.5-2 g / cm 3 wait.

[0112] In a sixth aspect, the present application provides a method for preparing the aforementioned carbon-coated silicon-carbon, comprising introducing a mixed gas comprising a protective gas and a carbon source gas so as to coat the silicon-carbon to form carbon-coated silicon-carbon.

[0113] In the preparation method provided in the present application, the carbon source gas is selected from an alkane gas with a cracking temperature of 600°C or less. Preferably, the carbon source gas is selected from acetylene and / or ethylene. The protective gas is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon. Based on the total volume of the mixed gas, the volume proportion of the carbon source gas is 60-80%, and the volume proportion of the protective gas is 20-40%; the gas flow rate of the mixed gas is 0.1-50 L / min, specifically 0.1-10 L / min, 10-20 L / min, or 20-50 L / min, etc.; preferably, it is 5-20 L / min. The role of the mixed gas is to coat another layer of carbon protective layer.

[0114] The seventh aspect of the present application provides a silicon-carbon composite negative electrode material, the raw materials of which include the aforementioned porous composite elastomer, the aforementioned silicon-carbon, or the aforementioned carbon-coated silicon-carbon. This technology uses carbon nanotubes and hard carbon as carbon sources to composite with silicon to prepare silicon-carbon composite materials. Compared with conventional silicon-carbon composite materials, carbon nanotubes act as a bridge between silicon and hard carbon, effectively improving the electrical conductivity and ion conduction energy, thereby improving the rate performance of the negative electrode material. The present application uses wool-like carbon tubes to form a macroporous material to accommodate ordered micro-mesoporous carbon with moderate hardness, and then uses micro-mesoporous materials to accommodate single nano-silicon with excessive hardness. On the one hand, the ordered micro-mesoporous carbon with higher strength belongs to hard carbon, which makes the composite material have higher strength, which can greatly reduce the risk of the negative electrode material being crushed during the rolling process of the electrode sheet, and improve the safety performance of the electrode sheet preparation; on the other hand, the flexible carbon tubes give the composite material a certain elasticity and ductility, which can prevent the composite material from falling off from the electrode sheet due to volume expansion during the charge and discharge process, thereby avoiding the problem of battery cycle diving.

[0115] In an eighth aspect, the present application provides the use of the aforementioned porous composite elastomer, the aforementioned silicon-carbon, the aforementioned carbon-coated silicon-carbon, or the aforementioned silicon-carbon composite negative electrode material in the preparation of battery products.

[0116] In a ninth aspect, the present application provides a lithium-ion battery, the raw materials of which include the aforementioned porous composite elastomer, the aforementioned silicon-carbon, the aforementioned carbon-coated silicon-carbon, or the aforementioned silicon-carbon composite negative electrode material.

[0117] The present application is further described below by way of examples, but the scope of the present application is not limited thereby.

[0118] Example 1

[0119] (1) CNT clusters: Carbon nanotubes with a length of 10 μm and a diameter of 5 nm were shaped by a shaping machine with a main machine frequency of 30 Hz, a secondary machine frequency of 60 Hz, a fan frequency of 10 Hz, and an operating time of 60 min to form a spherical yarn ball structure material; the median particle size D of the CNT clusters 50 The sphericity Sh10% is 0.75, the sphericity Sh50% is 0.85, and the sphericity Sh90% is 0.88; the average pore diameter is 38.5 nm, and the pore volume is 1.69 cm 3 / g, specific surface area is 175.8m 2 / g, tap density <0.15g / cm 3 , resistivity <0.005Ω·cm;

[0120] (2) Modified CNT clusters: Add the wool-like carbon nanotubes to a 65% nitric acid solution at a mass ratio of 1:1, and reflux and stir at 100°C for 6 h; separate and filter to obtain a solid, then wash with pure water until neutral, and then dry in an oven at 80°C for 10 h to obtain a modified carbon nanotube cluster;

[0121] (3) CNT composite carbon material: CTAB is added to a polyethylene glycol aqueous solution with a solid content of 50%, and then the modified carbon tube clusters are added according to a mass ratio of polyethylene glycol: modified carbon tube clusters = 1:1, and stirred and mixed. Then, the polyethylene glycol aqueous solution is uniformly infiltrated into the yarn ball under -0.50MPa. After the pressure is maintained for 2 hours, the solution is completely infiltrated and slowly heated at 100°C for 5 hours to slowly evaporate the solvent. The polymer is filled in the pores of the modified carbon tube clusters through bonding to obtain a CNT composite carbon material;

[0122] (4) CNT porous carbon: The CNT composite carbon material is placed in a high-temperature furnace, argon gas is introduced at a flow rate of 10 L / min, and the temperature is raised to 800 °C at 2 °C / min for high-temperature carbonization and pore formation treatment. After carbonization for 10 h, the furnace is naturally cooled to room temperature while maintaining a protective atmosphere to obtain a sponge-like CNT porous carbon with uniform pore distribution, i.e., a porous elastic composite. The median particle size D of the porous elastic composite is 2. 50 The average pore size is 6.5 μm, the average pore size is 2.62 nm, and the pore volume is 0.98 cm 3 / g, with a specific surface area of ​​876.7m 2 / g, pore concentration is 2.5, and tap density is 0.33g / cm 3 , the resistivity is 0.04Ω·cm;

[0123] (5) Preparation of silicon-carbon negative electrode material: The composite material obtained in step (4) is placed in a deposition furnace. After the temperature is raised to 500°C, a mixture of silicon source gas and carbon source gas (70% monosilane, 30% acetylene) is introduced into the deposition furnace at a flow rate of 10 L / min. The tail pipe air pressure valve is adjusted and the gas is continuously ventilated for vapor deposition for 5 hours to obtain silicon carbon. The silicon carbon at this time can be directly used as a silicon-carbon composite negative electrode material.

[0124] The preparation process is shown in Figure 1, and the SEM images of each stage are shown in Figures 2 to 5. The material performance data of each stage of preparation are shown in Table 1:

[0125] Table 1 Material performance data for each stage

[0126] Example 2

[0127] The difference from Example 1 is that: the polymer is phenolic resin;

[0128] (3) Carbon tube composite elastomer: CTAB was added to a phenolic resin-ethanol solution with a solid content of 50%, and then the modified carbon tube pellets were added at a mass ratio of phenolic resin: modified carbon tube pellets = 1:1. The mixture was stirred and mixed. The phenolic resin-ethanol solution was then uniformly infiltrated into the yarn ball under -0.50 MPa. After maintaining the pressure for 2 hours, the solution was completely infiltrated and slowly heated at 120°C for 5 hours to slowly evaporate the solvent. The phenolic resin was filled in the pores of the modified carbon tube pellets through curing and bonding, thereby obtaining a carbon tube composite elastomer.

[0129] Example 3

[0130] The difference from Example 1 is that: the polymer is polyimide;

[0131] (3) Carbon nanotube composite elastomer: CTAB was added to a phenolic resin-NMP solution with a solid content of 50%. The modified carbon nanotube pellets were then added at a mass ratio of polyimide to modified carbon nanotube pellets = 1:1. The mixture was stirred and mixed. The polyimide-NMP solution was then uniformly infiltrated into the yarn ball under -0.50 MPa. After maintaining the pressure for 2 hours, the solution was completely infiltrated and slowly heated at 120°C for 5 hours to evaporate the solvent. The polyimide was filled in the pores of the modified carbon nanotube pellets through hydrogen bonding, resulting in a CNT composite carbon material.

[0132] Example 4

[0133] The difference from Example 1 is that: the polymer is epoxy resin;

[0134] (3) Carbon nanotube composite elastomer: CTAB was added to an epoxy resin-toluene solution with a solid content of 50%. Subsequently, carbon nanotubes were added at a mass ratio of epoxy resin: carbon nanotubes = 1:1. The mixture was stirred and mixed. The epoxy resin-toluene solution was then uniformly infiltrated into the yarn at 120°C and -0.50 MPa. After maintaining the pressure for 2 hours, the solution was completely infiltrated and slowly cooled to room temperature. The epoxy resin was cured to fill the pores of the modified carbon nanotubes, resulting in a CNT composite carbon material.

[0135] Comparative Example 1

[0136] The difference from Example 1 is that step (3) is not performed and the polymer is not compounded.

[0137] Comparative Example 2

[0138] The difference from Example 1 is that step (4) is not performed and pore creation is not performed.

[0139] Comparative Example 3

[0140] The difference from Example 1 is that steps (1) to (3) are not performed, and the carbon source of the porous carbon is replaced by a polymer instead of a carbon tube composite elastomer.

[0141] Batteries were assembled using the negative electrode materials prepared in each embodiment and each comparative example.

[0142] (1) Preparation of positive electrode sheets: The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), the conductive agent Super P, carbon nanotubes, and the binder polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97:1:0.5:1.5 to prepare a positive electrode slurry (solid content of 70 wt%), which was then coated on both sides of the current collector aluminum foil, dried at 100°C, and cold pressed at 4 MPa at room temperature. The positive electrode sheets were then trimmed, cut, and striped, and the tabs were welded to form the positive electrode sheets.

[0143] (2) Preparation of negative electrode sheet: Under nitrogen protection atmosphere, the solvent N-methylpyrrolidone and the binder PVDF were stirred and mixed, and then the conductive agent Super P was added and stirred and mixed, and then the negative electrode active material was added and stirred and mixed thoroughly to prepare a negative electrode slurry (solid content of 50wt%).

[0144] The negative electrode active material is obtained by fully and uniformly mixing the silicon-carbon composite negative electrode materials prepared in the above embodiment and comparative example with graphite so that the gram capacity of the negative electrode material is 450 mAh / g.

[0145] The negative electrode slurry is coated on both sides of the current collector copper foil, dried at 100°C, cold pressed at 4 MPa at room temperature, and then trimmed, cut, and striped, and the tabs are welded to make negative electrode sheets.

[0146] (3) Assembly of lithium-ion batteries

[0147] Using a PE porous polymer film as a separator, the prepared positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator positioned between the positive and negative electrodes, and then wound to obtain a bare cell. The bare cell was placed in an aluminum-plastic shell and dried at 100°C under a relative vacuum pressure of -0.95×105Pa until the moisture content reached below 100ppm. An electrolyte consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (EC:EMC:DEC volume ratio = 1:1:1) and LiPF6 (1.0M) was injected into the dried bare cell. The cells were then packaged, allowed to stand, formed (0.02C constant current charging for 2h, 0.1C constant current charging for 2h), shaped, and capacity tested (capacity grading) to produce a soft-pack liquid lithium-ion battery.

[0148] During battery assembly, five batteries were prepared for each test, and a total of five sets of data were tested. The final performance was taken as the average value of the five sets of data.

[0149] The battery cycle performance is tested on Xinwei equipment, specifically:

[0150] First coulombic efficiency test: At 25°C, first discharge at 0.1C to 0.005V, then discharge at 0.08C to 0.001V, discharge at 0.05C to 0.001V, discharge at 0.02C to 0.001V, and let it stand for 10 minutes; then charge at 0.1C to 1.5V, let it stand for 10 minutes, record the charge and discharge capacity after the first cycle, and calculate the first coulombic efficiency;

[0151] Cycle capacity retention rate test: Cycle 500 times as described above, record the charge and discharge capacity after 500 cycles, and calculate the capacity retention rate after 500 cycles;

[0152] Rate performance test: Use 1C charging, then discharge at a discharge current of 4C, and test the discharge capacity and capacity retention rate at a 1C rate.

[0153] Table 2 Performance of different embodiments and comparative examples

[0154] As can be seen from Table 1, in Comparative Example 1, the lithium insertion capacity and the capacity retention rate after 500 cycles of the silicon-carbon negative electrode material are not as good as those of Examples 1 to 4 because the polymer is not composited. In Comparative Example 2, the lithium insertion capacity, the first coulombic efficiency and the capacity retention rate after 500 cycles are not as good as those of Examples 1 to 4 because pores are not formed. In Comparative Example 3, steps (1) to (3) are not performed, and the polymer is directly carbonized to prepare porous carbon. Due to the lack of carbon tubes, the conductivity of the negative electrode material deteriorates, and the performance is significantly reduced.

[0155] In summary, this application utilizes yarn-like carbon tubes to form a macroporous material to accommodate ordered micro-mesoporous carbon of moderate hardness, and then uses the micro-mesoporous structure to accommodate the extremely hard elemental nano-silicon. On the one hand, the high-strength ordered micro-mesoporous carbon is a hard carbon, which gives the composite material high strength, greatly reducing the risk of the negative electrode material being crushed during the roller pressing process, thereby improving the safety performance of the electrode preparation. On the other hand, the flexible carbon tubes give the composite material a certain degree of elasticity and ductility, which can prevent the composite material from falling off the electrode due to volume expansion during the charge and discharge process, thereby preventing the battery from experiencing cycling problems.

[0156] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein shall be covered by the claims of this application.

Claims

1. A porous composite elastomer having a porous structure, wherein the porous composite elastomer comprises a flexible body and a rigid body interpenetrating each other, wherein the raw material of the flexible body comprises carbon nanotubes, and the rigid body is hard carbon.

2. The porous composite elastomer according to claim 1, wherein The porous composite elastomer contains uniformly distributed micropores and / or mesopores; And / or, the mass ratio of the flexible body to the rigid body is (0.01-2):

1.

3. The porous composite elastomer according to claim 2, wherein Include one or more of the following characteristics: a1) the average pore size of the porous composite elastomer is less than 15 nm; a2) The total pore volume of the porous composite elastomer is 0.2 to 1.5 cm 3 / g; a3) The specific surface area of the porous composite elastomer is >200m 2 / g; a4) D of the porous composite elastomer 50 <30 μm; a5) The tap density of the porous composite elastomer is 0.1 to 1.0 g / cm 3 ; a6) the resistivity of the porous composite elastomer is less than 5Ω·cm, preferably less than 0.5Ω·cm; a7) The pore size concentration of the porous composite elastomer is <7.

4. The porous composite elastomer according to claim 3, wherein Include one or more of the following characteristics: a1) the average pore diameter of the porous composite elastomer is 1.8 to 10 nm; a2) The total pore volume of the porous composite elastomer is 0.4 to 1.1 cm 3 / g; a3) The specific surface area of the porous composite elastomer is >700m 2 / g; a4) D of the porous composite elastomer 50 <20 μm; a5) The tap density of the porous composite elastomer is 0.2 to 0.7 g / cm 3 ; a6) the resistivity of the porous composite elastomer is less than 0.05Ω·cm; a7) The pore size concentration of the porous composite elastomer is 0.5 to 5.

5. A method for preparing the porous composite elastomer according to any one of claims 1 to 4, comprising the following steps: S1: Preparation of carbon tube clusters: shaping carbon nanotubes to form carbon tube clusters; S2: Preparation of carbon tube composite elastomer: adding carbon tube clusters into a solution containing a soft template and a polymer, allowing the solution to penetrate into the carbon tube clusters, and heating and curing to obtain the carbon tube composite elastomer; S3: Preparation of porous composite elastomer: subjecting the carbon tube composite elastomer to high-temperature carbonization and activation treatment to obtain a porous composite elastomer.

6. The preparation method according to claim 5, wherein In step S1, the shaping is performed using a shaping machine; And / or, in step S1, the carbon nanotubes have a length of 0.1 to 50 μm and a diameter of 2 to 20 nm; And / or, in step S1, the carbon tube clusters are spherical or quasi-spherical; And / or, in step S1, the sphericity Sh10% of the carbon tube clusters is ≥ 0.70; And / or, in step S1, the sphericity Sh50% of the carbon tube clusters is ≥ 0.80; And / or, in step S1, the sphericity Sh90% of the carbon tube clusters is ≥ 0.85; And / or, in step S1, the D of the carbon tube clusters 50 1~100μm; And / or, in step S1, the carbon tube ball is a wool ball-like structure.

7. The preparation method according to claim 6, wherein The main machine frequency of the shaping machine is 5-60Hz, the auxiliary machine frequency is 20-90Hz, the fan frequency is 8-30Hz, and the operation time is 2-100min.

8. The preparation method according to claim 5, wherein An intermediate modification process is also included between step S1 and step S2: adding the carbon tube clusters into an acidic solution and stirring, filtering to obtain a solid, washing to neutrality, and drying to obtain the modified carbon tube clusters.

9. The preparation method according to claim 8, wherein The mass ratio of the carbon tube clusters to the acidic solution is (0.1-100):1; And / or, the acidic solution is selected from one or more of nitric acid, sulfuric acid, and hydrochloric acid; and / or, the stirring reaction temperature is 30 to 100° C., and the stirring reaction time is 2 to 12 hours; And / or, washing is performed using pure water; drying is performed in a drying oven; And / or, the drying temperature is 60-100° C., and the drying time is 2-48 hours.

10. The preparation method according to claim 5, characterized in that In step S2, the monomer of the polymer is selected from formula I: wherein A1 is selected from X, OH, NH2 or a benzene ring substituted by X, OH or NH2; X is selected from F, Cl, Br and a halide of I; R1, R2 and R3 are independently selected from H, unsubstituted or substituted phenyl, unsubstituted or substituted C1-C 20 Alkyl, unsubstituted or substituted C1-C 20 At least one of the alkoxy groups; a substituent group in a substituted phenyl group, a substituted C1-C 20 Substituted groups in alkyl groups and substituted C1-C 20 The substituents in the alkoxy group are independently selected from at least one of halogen, OH or NH2.

11. The preparation method according to claim 5 or 10, characterized in that: In step S2, the polymer is selected from one or more of polyethylene glycol, waterborne polyurethane, polyvinyl alcohol, polyvinylidene fluoride, fluorinated copolymer, polyimide, polyacrylic acid, polyacrylate, polymethyl methacrylate, phenolic resin, epoxy resin or ionic resin.

12. The preparation method according to claim 5, characterized in that In step S2, the soft template is selected from a nonionic surfactant or an ionic surfactant; And / or, in step S2, the mass ratio of the carbon tube clusters to the polymer is (0.1-10):1; and / or, in step S2, the solid content of the polymer in the solution is 20 to 100%; and / or, in step S2, the solution infiltrating into the carbon tube clusters is performed under negative pressure; and / or, in step S2, the curing temperature is 80 to 200° C., and the curing time is 0.5 to 50 hours; And / or, in step S2, after solidification, the solvent needs to be evaporated to obtain the carbon nanotube composite material.

13. The preparation method according to claim 12, wherein In step S2, the nonionic surfactant is selected from polyoxyethylene-polyoxypropylene copolymer; and / or, the ionic surfactant is selected from cetyltrimethylammonium bromide and / or sodium dodecylsulfonate; And / or, the negative pressure condition is -0.9 to -0.01 MPa, and the negative pressure time is 0.5 to 10 hours; And / or, positive pressure treatment is also included after negative pressure treatment; the positive pressure condition is 0.15-2MPa, and the pressure holding time is 0.5-48h; And / or, the mass ratio of the carbon tube clusters to the polymer is 1:

3.

14. The preparation method according to claim 5, wherein In step S3, the carbonization treatment includes subjecting the carbon nanotube composite carbon material to a high-temperature reaction under a protective gas.

15. The preparation method according to claim 14, wherein The protective gas in the carbonization treatment is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon; And / or, the flow rate of the protective gas is 1 to 20 L / min; And / or, the temperature of the high temperature reaction is 500-1000°C; And / or, the high temperature reaction time is 1 to 30 hours; And / or, the heating rate of the high temperature reaction is 1 to 10°C / min; And / or, the high temperature reaction further includes a post-treatment step: cooling to room temperature.

16. A silicon carbon, wherein the raw material comprises the porous composite elastomer according to any one of claims 1 to 4, and further comprises nano-silicon particles, wherein the nano-silicon particles are embedded in the porous composite elastomer.

17. The silicon carbon according to claim 16, wherein Include one or more of the following characteristics: b1) The specific surface area of the silicon carbon is less than 20m 2 / g; b2) D of the silicon carbon 50 <20 μm; b3) The tap density of the silicon carbon is 0.5 to 2 g / cm 3 ; b4) the content of the nano-silicon particles is 30-70% of the total mass of silicon and carbon; b5) the resistivity of the silicon carbon is less than 20Ω·cm; b6) The silicon carbon has a specific capacity greater than 1200 mAh / g, an initial coulombic efficiency greater than 89%, a capacity retention rate after 500 cycles greater than 85%, and a 4C / 1C rate performance greater than 90%.

18. The method for preparing silicon carbon according to any one of claims 16 to 17, comprising: The porous composite elastomer and silicon-containing source gas are vapor-deposited in a high-temperature environment to obtain silicon carbon.

19. The preparation method according to claim 18, characterized in that The high temperature environment is a deposition furnace, the high temperature temperature is 300 to 600° C., and the holding time is 1 to 50 hours; And / or, the silicon source gas is selected from one or more of monosilane, disilane, dichlorosilane, and trichlorosilane; And / or, the silicon-containing source gas further includes a carbon source gas; And / or, the vapor deposition time is 1 to 50 hours.

20. The preparation method according to claim 19, wherein The pressure inside the deposition furnace is 5-10 MPa, and the heating rate is 1-5°C / min; And / or, the carbon source gas is selected from alkane gases having a cracking temperature below 600°C; and / or, when the silicon-containing source gas is only silicon source gas, the gas flow rate is 1 to 20 L / min; And / or, when the silicon-containing source gas includes a silicon source gas and a carbon source gas, based on the total volume of the gas, the volume proportion of the silicon source gas is 70-99%, and the volume proportion of the carbon source gas is 1-30%; and / or, when the silicon-containing source gas includes a silicon source gas and a carbon source gas, the gas flow rate is 5 to 20 L / min; And / or, the vapor deposition time is 10 to 30 hours.

21. A carbon-coated silicon carbon, comprising the silicon carbon according to any one of claims 16 to 17 and a carbon coating layer coated on the surface of the silicon carbon.

22. The carbon-coated silicon carbon according to claim 21, wherein The carbon coating amount of the carbon-coated silicon carbon is 0.5 to 10 wt %; And / or, the median particle size D of the carbon-coated silicon carbon 50 <20 μm; and / or, the silicon content of the carbon-coated silicon carbon is 20 to 80 wt%; And / or, the specific surface area of the carbon-coated silicon carbon is 0.5 to 20.0 m 2 / g; And / or, the compacted density of the carbon-coated silicon carbon powder is 0.5 to 2 g / cm 3 .

23. The method for preparing carbon-coated silicon-carbon according to any one of claims 21 to 22, comprising introducing a mixed gas comprising a protective gas and a carbon source gas to coat the silicon-carbon to form the carbon-coated silicon-carbon.

24. The preparation method according to claim 23, wherein The carbon source gas is selected from an alkane gas having a cracking temperature below 600°C; and / or, the protective gas is selected from one or more of nitrogen, neon, argon, krypton, xenon, and radon; and / or, the gas flow rate of the mixed gas is 0.1 to 50 L / min; And / or, based on the total volume of the mixed gas, the volume proportion of the carbon source gas is 60-80%, and the volume proportion of the protective gas is 20-40%.

25. A silicon-carbon composite negative electrode material, wherein the raw materials thereof comprise the porous composite elastomer according to any one of claims 1 to 4, the silicon-carbon according to any one of claims 16 to 17, or the carbon-coated silicon-carbon according to any one of claims 21 to 22.

26. Use of the porous composite elastomer according to any one of claims 1 to 4, the silicon-carbon according to any one of claims 16 to 17, the carbon-coated silicon-carbon according to any one of claims 21 to 22, or the silicon-carbon composite negative electrode material according to claim 25 in the preparation of battery products.

27. A lithium-ion battery, the raw materials of which include the porous composite elastomer according to any one of claims 1 to 4, the silicon-carbon according to any one of claims 16 to 17, the carbon-coated silicon-carbon according to any one of claims 21 to 22, or the silicon-carbon composite negative electrode material according to claim 25.

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