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

Abstract

The invention relates to the technical field of lithium ion battery negative electrode materials, and discloses a silicon carbon material and a preparation method thereof, and a lithium ion battery and application thereof, the silicon carbon material comprises nanometer silicon, silicon carbide and a carbon coating layer coating or partially coating the nanometer silicon, and the carbon coating layer comprises amorphous carbon; the mass ratio of the nano silicon to the carbon coating layer is (1.2-30): 1; and the resistivity of the silicon carbon material is less than or equal to 200 omega.cm. The silicon-carbon material is high in charge and discharge capacity, and meanwhile, nano silicon and carbon are stably combined, so that the cycling stability is good; according to the preparation method, SiO2 and a carbon precursor can be tightly combined, so that the structure and the uniformity of the material in the aluminothermic reaction process of silicon dioxide are effectively controlled; when the composite material is applied to the lithium ion battery, the first lithium intercalation capacity, the first coulombic efficiency and the cycle capacity retention ratio of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials for lithium-ion batteries, and in particular to a silicon-carbon material and a preparation method thereof, a lithium-ion battery and applications thereof. Background Art

[0002] The theoretical specific capacity of graphite negative electrode materials for lithium-ion batteries, which are widely used in the current market, is only 372mA h / g. It is difficult to make breakthrough progress in improving battery performance by improving battery preparation processes, which limits the improvement of lithium-ion battery energy density. Due to its high capacity (4200mAh / g) and high safety, silicon (Si) has become the preferred material for the negative electrode of the next generation of lithium-ion batteries. However, the lithium-silicon alloy phase generated by silicon materials during the process of lithium insertion and extraction is accompanied by a large volume change (about 300%), which causes it to break and pulverize during the charge and discharge process of the electrode, and further separates from the current collector, causing the electrode to fail and the cycle performance to drop sharply.

[0003] To overcome these defects, the solutions that are currently being studied mainly include two types: one is to alleviate the volume change of Si during the charge and discharge process by combining carbon materials with Si materials. Electrochemically active silicon materials are embedded or loaded into carbon materials. On the one hand, carbon materials can improve the conductivity of silicon materials. On the other hand, carbon materials can act as a "buffer medium" to alleviate the internal stress of silicon materials due to volume changes during the charge and discharge process, thereby improving the cycle stability of the composite material. However, during the charge and discharge process of silicon-carbon composite materials, silicon materials must be effectively combined with carbon materials to exert the high charge and discharge capacity of silicon materials. If the silicon material is separated from the carbon material due to multiple expansion and contraction during the electrochemical cycle, the silicon material and the carbon material lose contact and cannot exert the charge and discharge capacity.

[0004] Therefore, there is an urgent need to develop a negative electrode material that can effectively combine silicon materials and carbon materials, has high charge and discharge capacity, and has strong cycle stability. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that in silicon-carbon materials, carbon and silicon in high silicon-carbon ratio materials cannot be effectively combined, resulting in low battery specific capacity and poor cycle stability. A silicon-carbon material and a preparation method thereof, a lithium ion battery and an application thereof are provided. The silicon-carbon material has high charge and discharge capacity, and at the same time, the combination between nano-silicon and carbon is stable, and the cycle stability is good; the preparation method can make SiO2 and carbon precursors tightly combined, so that the structure and uniformity of the material during the silicon dioxide aluminothermic reaction can be effectively controlled; applying it to lithium ion batteries can improve the first lithium insertion capacity, the first coulomb efficiency and the capacity retention rate after 100 cycles of the lithium ion battery.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a silicon-carbon material, wherein the silicon-carbon material comprises nano-silicon and silicon carbide, and a carbon coating layer covering or partially covering the nano-silicon, wherein the carbon coating layer comprises amorphous carbon;

[0007] The mass ratio of the nano-silicon to the carbon coating layer is 1.2-30:1;

[0008] The resistivity of the silicon-carbon material is less than or equal to 200Ω·cm.

[0009] A second aspect of the present invention provides a method for preparing a silicon-carbon material, wherein the preparation method comprises:

[0010] (1) adding silicon dioxide, an amorphous carbon precursor and optionally crystalline carbon into a solvent, stirring uniformly to obtain a colloidal mixture, wherein the colloidal mixture is dried, carbonized at high temperature, and crushed into a composite A;

[0011] (2) Compound A and aluminum powder are uniformly mixed and molded to obtain Compound B;

[0012] (3) Under an atmosphere of protective gas, the composite B undergoes a thermite reaction;

[0013] Based on the total mass of silicon dioxide, amorphous carbon precursor and crystalline carbon, the mass percentage of silicon dioxide is 50wt%-95wt%, the mass percentage of the amorphous carbon precursor is 5wt%-40wt%, and the mass percentage of the crystalline carbon is 0-10wt%.

[0014] A third aspect of the present invention provides a silicon-carbon material obtained by the above-mentioned preparation method.

[0015] A fourth aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, and the negative electrode comprises the above-mentioned silicon-carbon material.

[0016] A fifth aspect of the present invention provides an electronic device, an electric tool, an electric vehicle or a power storage system comprising the lithium-ion battery.

[0017] Through the above technical scheme, the silicon-carbon material and the preparation method thereof, the lithium-ion battery and the application thereof provided by the present invention have the following beneficial effects:

[0018] The silicon-carbon material of the present invention has a high silicon-carbon ratio, so that the silicon-carbon material has excellent charge and discharge performance, that is, it has a high first lithium insertion capacity and coulomb efficiency; further, amorphous carbon is coated or partially coated on nano-silicon, so that the nano-silicon and matrix carbon in the silicon-carbon material can be better combined and are not easily separated during the charge and discharge process, thereby making the silicon-carbon material have better cycle stability; it can meet the requirements of lithium-ion batteries for negative electrode materials.

[0019] Furthermore, the silicon carbide in the present invention has the characteristics of high hardness, which can enhance the bonding force between nano-silicon and carbon materials, and reduce the volume change of nano-silicon materials during the lithium insertion and extraction process of silicon-carbon materials, so that the silicon-carbon material not only has a high first lithium insertion capacity and coulombic efficiency, but also has good cycle stability.

[0020] The present invention adopts a specific amount of silicon dioxide, an amorphous carbon precursor and optionally crystalline carbon, mixes and then carbonizes at high temperature to obtain a compound A containing silicon dioxide and a carbon compound, which can ensure a close bond between SiO2 and the matrix carbon. The obtained silicon-carbon material has low resistivity, high first lithium insertion capacity and coulombic efficiency, and also has good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the silicon-carbon material prepared in Example 1 using petroleum asphalt as an amorphous carbon precursor, carbon nanotubes as crystalline carbon and silicon dioxide as raw materials.

[0022] Figure 2 This is the high-resolution XPS spectrum of silicon in the silicon-carbon material obtained in Example 1.

[0023] Figure 3 This is the XRD spectrum of the silicon-carbon material obtained in Example 1.

[0024] Figure 4 This is a scanning electron microscope (SEM) image of the silicon-carbon material obtained in Example 6. DETAILED DESCRIPTION

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] A first aspect of the present invention provides a silicon-carbon material, wherein the silicon-carbon material comprises nano-silicon and silicon carbide, and a carbon coating layer covering or partially covering the nano-silicon, wherein the carbon coating layer comprises amorphous carbon;

[0027] The mass ratio of the nano-silicon to the carbon coating layer is 1.2-30:1;

[0028] The resistivity of the silicon-carbon material is less than or equal to 200Ω·cm.

[0029] The silicon-carbon material of the present invention has a high silicon-carbon ratio, so that the silicon-carbon material has excellent charge and discharge performance, that is, it has a high first lithium insertion capacity and coulomb efficiency; further, amorphous carbon is coated or partially coated on nano-silicon, so that the nano-silicon and matrix carbon in the silicon-carbon material can be better combined and are not easily separated during the charge and discharge process, thereby making the silicon-carbon material have better cycle stability; it can meet the requirements of lithium-ion batteries for negative electrode materials.

[0030] Furthermore, the silicon carbide in the present invention has the characteristics of high hardness, which can enhance the bonding force between nano-silicon and carbon materials, and reduce the volume change of nano-silicon materials during the lithium insertion and extraction process of silicon-carbon materials, so that the silicon-carbon material not only has a high first lithium insertion capacity and coulombic efficiency, but also has good cycle stability.

[0031] Furthermore, the mass ratio of the nano-silicon to the carbon coating layer is 1.5-20:1.

[0032] Furthermore, the resistivity of the silicon-carbon material is 0.001-100Ω·cm.

[0033] In the present invention, when the resistivity of the silicon-carbon material meets the above range, the transmission and diffusion distance of lithium ions is effectively reduced, and the mechanical stress caused by volume expansion during the charging and discharging process of the silicon-carbon material is reduced, so that the silicon-carbon material has a higher first lithium insertion capacity and first coulomb efficiency, and at the same time, its cycle stability is good.

[0034] Furthermore, the resistivity of the silicon-carbon material is 0.01-90Ω·cm.

[0035] According to a preferred embodiment of the present invention, the resistivity of the silicon-carbon material is 0.1-20Ω·cm.

[0036] According to the present invention, the carbon coating layer further comprises crystalline carbon.

[0037] In the present invention, when the carbon coating layer includes crystalline carbon, the electrical conductivity and mechanical strength of the silicon-carbon material are improved, while the nano-silicon in the carbon material is not easily separated from the matrix carbon, and the silicon-carbon material is not easily broken or pulverized during the cycle, thereby making the silicon-carbon material have better cycle stability.

[0038] According to the present invention, the mass ratio of amorphous carbon to crystalline carbon is 1-10:1.

[0039] In the present invention, when the mass ratio of amorphous carbon to crystalline carbon meets the above range, since the amorphous carbon and crystalline carbon are mixed and evenly coated on the surface of the silicon-based material, the carbon coating layer can not only buffer the volume expansion of silicon when lithium is embedded, but also enhance the mechanical strength and conductivity of the silicon-carbon material, thereby making the silicon-carbon material have better cycle stability.

[0040] Furthermore, the mass ratio of the amorphous carbon to the crystalline carbon is 2-8:1.

[0041] Furthermore, the mass ratio of the amorphous carbon to the crystalline carbon is 3-8:1.

[0042] According to the present invention, the silicon-carbon material also includes silicon oxide.

[0043] In the present invention, silicon oxide can inhibit the volume change of nano-silicon materials during the process of lithium insertion and extraction, thereby improving the cycle stability of silicon-carbon materials.

[0044] According to the present invention, based on the total weight of the silicon-carbon material, the content of nano-silicon is 60wt%-95wt%, the content of the carbon coating is 5wt%-40wt%, the content of silicon carbide is 0.1wt%-3wt%, and the content of silicon oxide is 0wt%-5wt%.

[0045] In the present invention, based on the total weight of the silicon-carbon material, the sum of the content of the nano-silicon, the carbon coating layer, the silicon carbide and the silicon oxide is 100wt%. When the content of each component in the silicon-carbon material meets the above requirements, it has excellent comprehensive performance, that is, it has high first lithium insertion capacity and coulomb efficiency, and at the same time has low resistivity and good cycle stability.

[0046] Furthermore, based on the total weight of the silicon-carbon material, the content of the nano-silicon is 65wt%-85wt%, the content of the carbon coating is 5wt%-30wt%, the content of the silicon carbide is 0.3wt%-2.5wt%, and the content of the silicon oxide is 1.5wt%-4wt%.

[0047] According to the present invention, the silicon oxide is a compound represented by formula I, SiO x Formula I, wherein 0 <x≤2。

[0048] According to the present invention, the average particle size of the silicon-carbon material is 10 nm-50 μm.

[0049] In the present invention, when the average particle size of the silicon-carbon material meets the above range, the high specific surface area of ​​the silicon-carbon material can buffer the volume expansion of the silicon-based negative electrode, improve the cycle stability of the composite material, and meet the requirements of lithium-ion batteries for negative electrode materials.

[0050] Furthermore, the average particle size of the silicon-carbon material is 100 nm-20 μm.

[0051] According to the present invention, the porosity of the silicon-carbon material is 25-65%.

[0052] In the present invention, when the porosity of the silicon-carbon material meets the above range, it indicates that the silicon-carbon material has abundant voids, which provides expansion space for silicon nanoparticles, shortens the diffusion length of lithium ions in micro-nano spherical particles, improves the ion and electron transmission efficiency, and the prepared lithium-ion battery has good cycle stability.

[0053] Furthermore, the porosity of the silicon-carbon material is 30-55%.

[0054] Furthermore, the porosity of the silicon-carbon material is 38-43%.

[0055] According to the present invention, the density of the silicon-carbon material is 1.9-2.45 g / cm 3 .

[0056] In the present invention, when the density of the silicon-carbon material meets the above range, the silicon-carbon material can meet the requirements of commercial applications for energy density applications.

[0057] Furthermore, the density of the silicon-carbon material is 2-2.3 g / cm 3 .

[0058] A second aspect of the present invention provides a method for preparing a silicon-carbon material, wherein the preparation method comprises:

[0059] (1) adding silicon dioxide, an amorphous carbon precursor and optionally crystalline carbon into a solvent, stirring uniformly to obtain a colloidal mixture, wherein the colloidal mixture is dried, carbonized at high temperature, and crushed into a composite A;

[0060] (2) Compound A and aluminum powder are uniformly mixed and molded to obtain Compound B;

[0061] (3) Under an atmosphere of protective gas, the composite B undergoes an aluminothermic reaction;

[0062] Based on the total mass of silicon dioxide, amorphous carbon precursor and crystalline carbon, the mass percentage of silicon dioxide is 50wt%-95wt%, the mass percentage of the amorphous carbon precursor is 5wt%-40wt%, and the mass percentage of the crystalline carbon is 0-10wt%.

[0063] The present invention adopts a specific amount of silicon dioxide, an amorphous carbon precursor and optionally crystalline carbon, mixes and then carbonizes at high temperature to obtain a compound A containing silicon dioxide and a carbon compound, which can ensure a close bond between SiO2 and the matrix carbon. The obtained silicon-carbon material has low resistivity, high first lithium insertion capacity and coulombic efficiency, and also has good cycle stability.

[0064] In the present invention, in step (1), the solvent is selected from at least one of distilled water, anhydrous ethanol, ethylene glycol and propanol. Preferably, the mass ratio of the silicon dioxide to the solvent is 1:0.6-5.

[0065] In the present invention, the sum of the mass percentages of the silicon dioxide, the amorphous carbon precursor and the crystalline carbon is 100wt%.

[0066] Furthermore, based on the total mass of silicon dioxide, amorphous carbon precursor and crystalline carbon, the mass percentage of silicon dioxide is 60wt%-92wt%, the mass percentage of the amorphous carbon precursor is 8wt%-35wt%, and the mass percentage of the crystalline carbon is 0.1wt%-5wt%.

[0067] In the present invention, when the mass percentage of each component meets the above range, in the obtained silicon-carbon material, the amorphous carbon, the crystalline carbon and nano-silicon are intermixed with each other, and the formed porous structure provides a buffer space for the volume expansion of the silicon-based material, while enhancing the mechanical strength and conductivity of the silicon-carbon material, thereby making the silicon-carbon material have better cycle stability.

[0068] According to the present invention, the mass ratio of silicon dioxide to aluminum powder is 1:0.5-1.5.

[0069] Furthermore, the mass ratio of the silicon dioxide to the aluminum powder is 1:0.6-1.2.

[0070] According to the present invention, the average particle size of the silicon dioxide is 10 nm-50 μm.

[0071] In the present invention, when the average particle size of silica meets the above range, silica, amorphous carbon precursor, crystalline carbon and silicon reducing agent aluminum powder can be evenly distributed in the porous block, so that the block maintains a high porosity, which is conducive to the entry of molten salt and makes the thermite reaction proceed more quickly and efficiently.

[0072] Furthermore, the average particle size of the silicon dioxide is 100 nm-30 μm.

[0073] According to the present invention, the amorphous carbon precursor is selected from at least one of petroleum asphalt, petroleum coke, coal tar, resin materials, citric acid, sugars and rubber.

[0074] In the present invention, when the above-mentioned amorphous carbon precursor is used, after high-temperature carbonization, the amorphous carbon layer formed contains a rich pore structure, so that the volume expansion of the silicon-based material has a certain buffer space, thereby achieving a high charge and discharge specific capacity of the silicon-carbon material and improving the cycle stability of the silicon-carbon material.

[0075] In the present invention, the resin material can be at least one of phenolic resin, polyvinylidene fluoride resin (PVDF), polyethylene (PE), polyvinyl chloride (PVC) and polystyrene (PS); the rubber can be at least one of styrene-butadiene rubber, nitrile rubber and butadiene rubber; and the sugar is glucose.

[0076] Furthermore, the amorphous carbon precursor is selected from at least one of petroleum asphalt, petroleum coke, coal tar and sugars.

[0077] According to the present invention, the crystalline carbon is selected from at least one of graphite, graphene (such as graphene oxide), carbon nanotubes, graphite microplatelets, carbon fibers and graphite microspheres.

[0078] In the present invention, when the above-mentioned crystalline carbon is used, the crystalline carbon has its own high electrical conductivity, which improves the electrical conductivity and mechanical strength of the silicon-carbon material, making it difficult for the nano-silicon and the matrix carbon in the silicon-carbon material to separate, and the silicon-carbon material is not easy to break or pulverize during the cycle, thereby making the silicon-carbon material have better cycle stability.

[0079] Furthermore, the crystalline carbon is selected from at least one of graphene, carbon nanotubes and carbon fibers.

[0080] According to the present invention, the average particle sizes of the amorphous carbon precursor and the crystalline carbon are independently 10 nm to 30 μm.

[0081] In the present invention, when the average particle size of the amorphous carbon precursor or the crystalline carbon meets the above range, in the obtained silicon-carbon material, the amorphous carbon and the crystalline carbon can be mixed and evenly coated on the surface of the silicon-based material, thereby alleviating the volume expansion / electrode pulverization problem of nano-silicon, reducing the volume change during the lithium insertion and deinsertion process, shortening the lithium ion diffusion path, and enhancing the effect of electrochemical reaction activity; so that the silicon-carbon material not only has a high first lithium insertion capacity and coulombic efficiency, but also has good cycle stability.

[0082] Furthermore, the average particle sizes of the amorphous carbon precursor and the crystalline carbon are independently 50 nm to 20 μm.

[0083] According to the present invention, in step (1), the stirring conditions include: stirring temperature of 40-100° C., and stirring time of 0.5-6 h.

[0084] In the present invention, when the above stirring conditions are met, the silicon dioxide, amorphous carbon precursor and crystalline carbon can be better dispersed, the raw materials are evenly distributed, and a uniform carbon layer can be formed on the surface of the silicon dioxide after carbonization.

[0085] According to the present invention, the drying conditions include: drying temperature of 70-150° C., and drying time of 1-24 hours.

[0086] In the present invention, when the above drying conditions are met, the deposition and stratification of the colloidal mixture can be avoided, so that the silicon dioxide, amorphous carbon precursor and crystalline carbon are dispersed more evenly.

[0087] Furthermore, the drying conditions include: drying temperature of 70-130° C. and drying time of 4-24 h.

[0088] According to the present invention, the conditions for high temperature carbonization include: a high temperature carbonization temperature of 600-1300° C. and a high temperature carbonization time of 0.5-5 h.

[0089] In the present invention, when the above-mentioned high-temperature carbonization conditions are met, it is beneficial for amorphous carbon to generate a microcrystalline structure, enhance the lithium storage performance and structural stability of the silicon-carbon material, and thus enable the lithium-ion battery to obtain a higher initial lithium insertion capacity and capacity retention rate.

[0090] Furthermore, the high temperature carbonization conditions include: the high temperature carbonization temperature is 700-1200° C., and the high temperature carbonization time is 1-3 hours.

[0091] In the present invention, the protective atmosphere for high temperature carbonization is selected from at least one of argon atmosphere, nitrogen atmosphere and helium atmosphere.

[0092] According to the present invention, in step (2), the molding conditions include: molding temperature of 10-38° C., molding time of 10-100 s, and molding pressure of 8-40 MPa.

[0093] In the present invention, when the above molding conditions are met, the silicon dioxide, amorphous carbon precursor and crystalline carbon can be tightly bonded, and the composite B can have a porous structure, so that the silicon-carbon material after the aluminothermic reaction has a better structure and uniformity.

[0094] Furthermore, in step (2), the molding conditions include: a molding temperature of 20-35° C., a molding time of 20-80 s, and a molding pressure of 10-30 MPa.

[0095] According to the present invention, the porosity of the composite B is 10-55%.

[0096] In the present invention, when the porosity of the composite B satisfies the above range, the salt melt medium containing AlCl3 can better enter the composite B, thereby improving the aluminothermic reaction rate and material yield.

[0097] Furthermore, the porosity of the composite B is 20-40%.

[0098] Furthermore, the porosity of the composite B is 30-40%.

[0099] According to the present invention, the density of the composite B is 1.8-2.5 g / cm 3 .

[0100] In the present invention, when the density of the composite B meets the above range, it indicates that the composite B has a higher mass energy density, and the prepared silicon-carbon material can meet the energy density requirements of high specific energy batteries.

[0101] Furthermore, the density of the composite B is 1.9-2.4 g / cm 3 .

[0102] According to the present invention, the resistivity of the composite B is less than or equal to 200Ω·cm.

[0103] In the present invention, when the resistivity of the composite B satisfies the above range, it indicates that the composite B has good conductivity, and the prepared silicon-carbon material has good rate performance and cycle stability as a negative electrode material.

[0104] Furthermore, the resistivity of the composite B is 0.001-100Ω·cm.

[0105] Furthermore, the resistivity of the composite B is 0.01-90Ω·cm.

[0106] According to a preferred embodiment of the present invention, the resistivity of the composite B is 0.1-20Ω·cm.

[0107] In the present invention, there is no special requirement for the size and shape of the composite B. For example, the shape of the composite B can be at least one of a disc, a cube and a cuboid.

[0108] According to the present invention, the step (3) comprises: under an atmosphere of protective gas, the compound B undergoes an aluminothermic reaction in a salt melt medium containing AlCl3 to obtain an aluminothermic reduction product, removes the salt melt medium, and obtains a silicon-carbon material after drying, crushing and screening.

[0109] In the present invention, a compound B comprising silicon dioxide and a carbon compound is subjected to an aluminothermic reaction in a salt melt medium containing AlCl3, the silicon dioxide and carbon in the compound are intermixed with each other, and the reduced silicon is separated from each other under the action of the aluminothermic replacement reaction, which can improve the dispersion uniformity of nano-silicon in the silicon-carbon material, improve the degree of bonding with the carbon coating layer, and is beneficial to improving the electrochemical properties and cycle stability of the silicon-carbon material.

[0110] In the present invention, a salt melt medium containing AlCl3 is used to enter the pores inside the composite B in a molten state, so that the aluminum powder in the composite B is dissolved in the reaction medium eutectic salt, and the liquid Al is evenly distributed in the system composed of silicon dioxide, amorphous carbon precursor and crystalline carbon, which can improve the reduction degree of silicon dioxide and make the aluminothermic reaction more uniform and controllable.

[0111] According to the present invention, in step (3), the salt melt medium containing AlCl3 is AlCl3 molten salt or AlCl3 eutectic salt.

[0112] Furthermore, the salt melt medium of AlCl3 is AlCl3 eutectic salt.

[0113] In the present invention, when AlCl3 eutectic salt is used, the melting point of aluminum powder can be lowered, and the aluminum powder melts in the AlCl3 eutectic salt to make the reaction more uniform. At the same time, the reaction conditions are mild, energy consumption is reduced, and costs are saved.

[0114] According to the present invention, the AlCl3 eutectic salt is AlCl3+MX 1 a , wherein M is at least one of Ba, Li, Ca, Cs, Na, K, Mg, Rb, Be, Zn and Sr; X 1 is Cl and / or F, and a is 1 or 2.

[0115] In the present invention, when two or more AlCl3 eutectic salts are selected, the melting temperature can be further reduced, energy consumption can be further saved, costs can be reduced, and the environment is environmentally friendly.

[0116] Furthermore, M is at least one of Ba, Li, Ca and Zn; X 1 is Cl and / or F.

[0117] According to the present invention, based on the total mass of the AlCl3 eutectic salt, AlCl3 is 40wt%-95wt%.

[0118] In the present invention, when the content of AlCl3 satisfies the above range, the molten aluminum powder can be more evenly distributed in the system consisting of silicon dioxide, amorphous carbon precursor and crystalline carbon, the degree of silicon dioxide reduction is improved, and the reaction is more uniform and controllable.

[0119] Furthermore, based on the mass of the AlCl3 eutectic salt, AlCl3 is 45wt%-90wt%.

[0120] According to the present invention, the temperature of the thermite reaction is 180-250° C., and the time of the thermite reaction is 1-12 hours.

[0121] In the present invention, when the temperature of the thermite reaction satisfies the above range, the degree of bonding between the reduced nano-silicon and the amorphous carbon is higher, thereby improving the electrochemical cycle stability of the silicon-carbon material.

[0122] Furthermore, the temperature of the thermite reaction is 190-240° C., and the time of the thermite reaction is 2-10 hours.

[0123] In the present invention, there is no particular limitation on the method for removing the salt melt medium in the aluminothermic reduction product, and the conventional method for removing AlCl3 molten salt and eutectic salt in the art can be used. Preferably, the removal of eutectic salt includes washing with an inorganic acid, water and an organic solvent in sequence to remove the molten salt in the aluminothermic reduction product. Preferably, the inorganic acid is hydrochloric acid; preferably, the concentration of the hydrochloric acid is 1-3 vol%. Preferably, the amount of the hydrochloric acid is 300-500 mL. Preferably, the organic solvent is anhydrous ethanol.

[0124] In the present invention, in step (3), the drying refers to vacuum drying for 6h-48h.

[0125] A third aspect of the present invention provides a silicon-carbon material obtained by the above-mentioned preparation method.

[0126] A fourth aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, and the negative electrode comprises the above-mentioned silicon-carbon material.

[0127] When the silicon-carbon material of the present invention is applied to the negative electrode material of a lithium ion battery, the amorphous carbon and the nano-silicon can be effectively combined and are not easily separated during the charge and discharge process. The lithium ion battery has a higher first lithium insertion capacity, first coulomb efficiency and cycle stability.

[0128] A fifth aspect of the present invention provides an electronic device, an electric tool, an electric vehicle or a power storage system comprising the lithium-ion battery.

[0129] The present invention will be described in detail below through examples.

[0130] In the following examples and comparative examples:

[0131] The porosity of the silicon-carbon material and composite B was measured by mercury intrusion porosimetry.

[0132] The density of the silicon-carbon material and the composite B is measured by a true density meter.

[0133] The resistivity of the silicon-carbon material and the composite B is measured by a conductivity tester.

[0134] The average particle size of the silicon-carbon material is measured by a laser particle size tester.

[0135] The content of carbon coating in silicon-carbon material is measured by thermal gravimetric method.

[0136] The contents of nano-silicon, silicon carbide and silicon oxide in silicon-carbon materials were tested using XRD and calculated through full spectrum refinement.

[0137] Mass ratio of amorphous carbon to crystalline carbon: According to the high-temperature carbonization conditions described in step (1), an amorphous carbon precursor with a mass of M is subjected to high-temperature carbonization, and a residual carbon rate of X% (X is less than 100) is calculated; when the masses of the amorphous carbon precursor and the crystalline carbon in the colloidal mixture are M and m respectively, the mass ratio of amorphous carbon to crystalline carbon in the silicon-carbon material is (M·X%):m.

[0138] In the present invention, due to the low content of crystalline carbon, after a small amount of crystalline carbon undergoes high-temperature carbonization and thermite reaction, the crystalline carbon structure is damaged to varying degrees, and the disorder and defect levels will increase. When the silicon-carbon material contains a small amount of crystalline carbon, for example, when the crystalline carbon content in the silicon-carbon material is less than 5wt%, the typical characteristic peak of crystalline carbon cannot be observed near 26°.

[0139] In the following examples and comparative examples:

[0140] Silica powder A: a commercially available product of Shandong Shida Shenghua Chemical Group Co., Ltd., with a purity of 99.95% and an average particle size of 10 μm.

[0141] Silicon dioxide powder B: a commercial product of Zhejiang Lichen New Material Technology Co., Ltd., with a purity of 99.9% and an average particle size of 6 μm.

[0142] Petroleum asphalt: a commercial product of Liaoning Xinde Company, with a softening point of 280°C.

[0143] Phenolic resin powder: a commercially available product of Jinan Shengquan Group Co., Ltd., with an average particle size of 8 μm.

[0144] Coal tar granules: a commercial product of Hebei Yaotan Chemical Technology Co., Ltd.

[0145] Polyvinylidene fluoride (PVDF): a commercial product of Sinochem Blue Sky Group Co., Ltd.

[0146] Glucose: a commercial product of Changzhou Yaoshengmei Environmental Protection Technology Co., Ltd.

[0147] Other raw materials used in the examples and comparative examples are all commercially available.

[0148] Example 1

[0149] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 12wt%, and carbon nanotubes are 2wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0150] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0151] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0152] Example 2

[0153] (1) Add silica powder A, glucose powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:1.8). Stir at 40°C for 4 hours to prepare a colloidal mixture (92wt% of silica, 6wt% of glucose powder and 2wt% of carbon nanotubes). Dry the colloidal mixture at 80°C for 24 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 650°C for 5 hours. After crushing, obtain composite A.

[0154] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:0.6). Compound B was obtained by molding at a molding temperature of 35°C, a pressure of 30 MPa, and a time of 70 seconds. The parameters of Compound B are shown in Table 1.

[0155] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and CaCl2 (AlCl3 was 50wt%), the aluminothermic reaction temperature was 240°C, the reaction time was 10h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 350mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 20h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0156] Example 3

[0157] (1) Add silica powder B, petroleum coke powder and carbon fiber into deionized water (mass ratio of silica to solvent is 1:5). Stir at 80°C for 2 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum coke powder is 13wt%, carbon fiber is 1wt%), dry the colloidal mixture at 85°C for 10 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1000°C for 3 hours to obtain a composite A after crushing.

[0158] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.05). Compound B was obtained by molding at a molding temperature of 20°C, a pressure of 10 MPa, and a time of 80 seconds. The parameters of Compound B are shown in Table 1.

[0159] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 190°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 300mL of 3vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 6h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0160] Example 4

[0161] (1) Add silica powder A, petroleum asphalt powder and graphene oxide to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 13wt%, and graphene oxide is 1wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0162] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:0.55). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0163] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 10h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0164] Example 5

[0165] (1) Add silica powder A and petroleum asphalt powder to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 14wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 650°C for 2 hours. After crushing, obtain composite A.

[0166] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.05). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0167] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 10h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0168] Example 6

[0169] (1) Add silica powder A, phenolic resin powder and carbon fiber to ethylene glycol (the mass ratio of silica to solvent is 1:2). Stir at 55°C for 1 hour to prepare a colloidal mixture (silicon dioxide is 86wt%, phenolic resin is 13wt%, and carbon fiber is 1wt%). Dry the colloidal mixture at 100°C by air drying for 8 hours, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1200°C for 2 hours. After crushing, obtain composite A.

[0170] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:0.95). Compound B was obtained by molding at a molding temperature of 20°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0171] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in AlCl3 as a molten salt, the aluminothermic reaction temperature was 200°C, the reaction time was 10 hours, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500 mL of 1 vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 36 hours, and crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0172] Example 7

[0173] (1) Add silica powder B, coal tar pitch particles and polyvinylidene fluoride (PVDF) resin powder into deionized water (mass ratio of silica to solvent is 1:4). Stir at 45°C for 2h to prepare a colloidal mixture (90wt% silica, 10wt% amorphous carbon precursor (7wt% coal tar pitch particles, 3wt% PVDF resin powder)). Dry the colloidal mixture at 100°C for 12h by air drying, crush it mechanically, and then carbonize it at high temperature in a nitrogen atmosphere at a temperature of 1100°C for 2h. After crushing, obtain composite A.

[0174] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0175] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and CaCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 220°C, the reaction time was 12h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 36h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0176] Example 8

[0177] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 12wt%, and carbon nanotubes are 2wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 600°C for 2 hours. After crushing, obtain composite A.

[0178] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0179] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0180] Example 9

[0181] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 12wt%, and carbon nanotubes are 2wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1500°C for 2 hours. After crushing, obtain composite A.

[0182] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0183] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0184] Example 10

[0185] (1) Add silica powder A and petroleum asphalt powder to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 87wt%, petroleum asphalt powder is 13wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0186] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0187] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0188] Embodiment 11

[0189] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 12wt%, and carbon nanotubes are 2wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0190] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.8). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0191] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 20h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. Due to the excessive mass ratio of aluminum powder and the long reaction time, SiOx was completely reduced to silicon. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0192] Example 12

[0193] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 12wt%, and carbon nanotubes are 2wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0194] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0195] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction at a temperature of 800°C for 10 hours to obtain an aluminothermic reduction product. The aluminothermic reduction product was washed with 500 mL of 2 vol% dilute hydrochloric acid, water, and anhydrous ethanol in sequence to remove the salt melt medium, and then vacuum dried for 24 hours, crushed and sieved to obtain an unreduced silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0196] Embodiment 13

[0197] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 86wt%, petroleum asphalt powder is 13wt%, and carbon nanotubes are 1wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0198] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0199] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0200] Embodiment 14

[0201] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (silicon dioxide is 64wt%, petroleum asphalt powder is 19wt%, and carbon nanotubes are 17wt%). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0202] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0203] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0204] Comparative Example 1

[0205] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (30wt% silica, 65wt% petroleum asphalt powder, 5wt% carbon nanotubes), dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours to obtain a composite A after crushing.

[0206] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.05). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0207] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 10h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0208] Comparative Example 2

[0209] (1) Add silica powder A and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60° C. for 3 h to prepare a colloidal mixture (95 wt % of silica and 5 wt % of carbon nanotubes). Dry the colloidal mixture at 100° C. for 12 h by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150° C. for 2 h. After crushing, obtain composite A.

[0210] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0211] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 10h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0212] Comparative Example 3

[0213] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (mass ratio of silica to solvent is 1:2). Stir at 60° C. for 3 h to prepare a colloidal mixture (silicon dioxide is 86 wt%, petroleum asphalt powder is 12 wt%, carbon nanotubes is 2 wt%), dry the colloidal mixture at 100° C. for 12 h by air drying, and then crush it mechanically to obtain a composite A.

[0214] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0215] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0216] Comparative Example 4

[0217] (1) Add silica powder A, petroleum asphalt powder and carbon nanotubes to deionized water (the mass ratio of silica to solvent is 1:2). Stir at 60°C for 3 hours to prepare a colloidal mixture (98wt% of silica, 1.5wt% of petroleum asphalt powder and 0.5wt% of carbon nanotubes). Dry the colloidal mixture at 100°C for 12 hours by air drying, crush it mechanically, and then carbonize it at high temperature in an argon atmosphere at a temperature of 1150°C for 2 hours. After crushing, obtain composite A.

[0218] (2) Compound A and aluminum powder were mixed evenly (the mass ratio of silicon dioxide to aluminum powder was 1:1.2). Compound B was obtained by molding at a molding temperature of 25°C, a pressure of 15 MPa, and a time of 60 seconds. The parameters of Compound B are shown in Table 1.

[0219] (3) In an argon environment, the composite B was subjected to an aluminothermic reaction in a eutectic salt composed of AlCl3 and ZnCl2 (AlCl3 was 55wt%), the aluminothermic reaction temperature was 210°C, the reaction time was 8h, and an aluminothermic reduction product was obtained. The aluminothermic reduction product was washed with 500mL of 1vol% dilute hydrochloric acid, water, and anhydrous ethanol in turn to remove the salt melt medium, and then vacuum dried for 24h, crushed and sieved to obtain a silicon-carbon material. The content of each component of the silicon-carbon material and other parameters are shown in Table 2.

[0220] Test Case

[0221] The silicon-carbon materials of the embodiment were used to prepare lithium-ion battery electrodes according to the following method: silicon-carbon material was used as active material, carbon black was used as conductive agent, glucose and sodium alginate were used as binders, and mixed evenly in a mass ratio of 9:0.5:0.5, and then stirred evenly with deionized water as solvent to form a slurry, and the slurry was coated on a 10μm thick copper foil and cut into a pole piece with a diameter of 13mm, and then dried at 80℃ for 12h and rolled to the required thickness of the pole piece, and dried at 120℃ under vacuum for 12h for standby use. A button cell was assembled with a metal lithium sheet as the counter electrode, a Celgard 2300 membrane as the diaphragm, and 1mol / L LiPF6 / EC+DEC+DMC (the volume ratio of EC, DEC and DMC was 1:1:1) as the electrolyte. The electrochemical performance of the experimental battery, i.e., the first lithium insertion capacity and the first coulomb efficiency, was tested using the Xinwei battery test system. The charge and discharge voltage range is 0.005-1.5V, the charge and discharge current density is 100mA / g, and the capacity retention rate of the test battery after 100 cycles is C 100 / C1.

[0222] Table 1

[0223]

[0224] Table 2

[0225]

[0226]

[0227] Table 2

[0228]

[0229] Table 3

[0230]

[0231]

[0232] It can be seen from the results in Table 2 that the silicon-carbon material of the present invention has a high silicon content, rich pore structure, uniform material composite, and low resistivity. The prepared lithium-ion battery exhibits excellent first lithium insertion capacity, first coulombic efficiency, and cycle stability.

[0233] Figure 1 This is a scanning electron microscope (SEM) image of the silicon-carbon material prepared using petroleum asphalt as an amorphous carbon precursor, carbon nanotubes as crystalline carbon and silicon dioxide as raw materials in Example 1. It can be seen that the nano-silicon-carbon composite material is a uniformly dispersed sand mold, indicating that the silicon-carbon material has a nano-scale structure after aluminothermic reduction, and silicon and carbon are well combined under high-temperature carbonization.

[0234] Figure 2 This is the high-resolution XPS spectrum of silicon in the silicon-carbon material obtained in Example 1. Peaks of SiC and SiO2 can be seen.

[0235] Figure 3 This is the XRD spectrum of the silicon-carbon material obtained in Example 1. No characteristic peak of graphite material is observed at 26°, indicating that high-temperature carbonization causes the carbon precursor petroleum asphalt to generate amorphous carbon; due to the low crystalline carbon content of crystalline carbon nanotubes in the silicon-carbon material, no characteristic peak of crystalline carbon is observed at 26°. SiC is also observed, indicating the generation of SiC during the reduction process, while retaining a small amount of unreacted SiO2.

[0236] Figure 4 This is a scanning electron microscope (SEM) image of the silicon-carbon material obtained in Example 6. It can be seen that the carbon after high-temperature carbonization of the phenolic resin is in a flocculent shape and is interlaced with the reduced nano-scale silicon material.

[0237] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A silicon-carbon material, characterized in that: The silicon-carbon material includes nano-silicon and silicon carbide, and a carbon coating layer covering or partially covering the nano-silicon, wherein the carbon coating layer includes amorphous carbon; The mass ratio of the nano-silicon to the carbon coating layer is 1.2-30:1; The resistivity of the silicon-carbon material is less than or equal to 200Ω·cm.

2. The silicon-carbon material according to claim 1, wherein The mass ratio of the nano-silicon to the carbon coating layer is 1.5-20:1; Preferably, the resistivity of the silicon-carbon material is 0.001-100Ω·cm, preferably 0.01-90Ω·cm; Preferably, the carbon coating layer further comprises crystalline carbon; Preferably, the mass ratio of the amorphous carbon to the crystalline carbon is 1-10:1, preferably 2-8:

1.

3. The silicon-carbon material according to claim 1 or 2, wherein: The silicon-carbon material also includes silicon oxide; Preferably, based on the total weight of the silicon-carbon material, the content of the nano-silicon is 60wt%-95wt%, the content of the carbon coating layer is 5wt%-40wt%, the content of the silicon carbide is 0.1wt%-3wt%, and the content of the silicon oxide is 0wt%-5wt%; More preferably, based on the total weight of the silicon-carbon material, the content of the nano-silicon is 65wt%-85wt%, the content of the carbon coating layer is 5wt%-30wt%, the content of the silicon carbide is 0.3wt%-2.5wt%, and the content of the silicon oxide is 1.5wt%-4wt%; Preferably, the silicon oxide is a compound represented by formula I, SiO x Formula I Among them, 0 <x≤2。 4. The silicon-carbon material according to any one of claims 1 to 3, wherein: The average particle size of the silicon-carbon material is 10nm-50μm, preferably 100nm-20μm; Preferably, the porosity of the silicon-carbon material is 25-65%, preferably 30-55%; Preferably, the density of the silicon-carbon material is 1.9-2.45 g / cm 3 , preferably 2-2.3 g / cm 3 .

5. A method for preparing a silicon-carbon material, characterized in that: The preparation method comprises: (1) adding silicon dioxide, an amorphous carbon precursor and optionally crystalline carbon into a solvent, stirring uniformly to obtain a colloidal mixture, wherein the colloidal mixture is dried, carbonized at high temperature, and crushed into a composite A; (2) Compound A and aluminum powder are uniformly mixed and molded to obtain Compound B; (3) Under an atmosphere of protective gas, the composite B undergoes an aluminothermic reaction; Based on the total mass of silicon dioxide, amorphous carbon precursor and crystalline carbon, the mass percentage of silicon dioxide is 50wt%-95wt%, the mass percentage of the amorphous carbon precursor is 5wt%-40wt%, and the mass percentage of the crystalline carbon is 0-10wt%.

6. The preparation method according to claim 5, wherein: Based on the total mass of silicon dioxide, amorphous carbon precursor and crystalline carbon, the mass percentage of silicon dioxide is 60wt%-92wt%, the mass percentage of the amorphous carbon precursor is 8wt%-35wt%, and the mass percentage of the crystalline carbon is 0.1wt%-5wt%; Preferably, the mass ratio of silicon dioxide to aluminum powder is 1:0.5-1.5, preferably 1:0.6-1.

2.

7. The preparation method according to claim 5 or 6, wherein: The average particle size of the silicon dioxide is 10nm-50μm, preferably 100nm-30μm; Preferably, the amorphous carbon precursor is selected from at least one of petroleum asphalt, petroleum coke, coal tar, resin materials, citric acid, sugars and rubber, preferably at least one of petroleum asphalt, petroleum coke, coal tar and sugars; Preferably, the crystalline carbon is selected from at least one of graphite, graphene, carbon nanotubes, graphite microplatelets, carbon fibers and graphite microspheres, preferably at least one of graphene, carbon nanotubes and carbon fibers; Preferably, the average particle sizes of the amorphous carbon precursor and the crystalline carbon are independently 10 nm to 30 μm.

8. The preparation method according to any one of claims 5 to 7, wherein: In step (1), the stirring conditions include: stirring temperature of 40-100° C., stirring time of 0.5-6 h; Preferably, the drying conditions include: drying temperature of 70-150°C, drying time of 1-24h; Preferably, the high temperature carbonization conditions include: the high temperature carbonization temperature is 600-1300° C., preferably 700-1200° C.; the high temperature carbonization time is 0.5-5 h, preferably 1-3 h.

9. The preparation method according to any one of claims 4 to 8, wherein: In step (2), the molding conditions include: molding temperature of 10-38° C., preferably 20-35° C.; molding time of 10-100 s, preferably 20-80 s; molding pressure of 8-40 MPa, preferably 10-30 MPa; Preferably, the porosity of the composite B is 10-55%, preferably 20-40%; Preferably, the density of the composite B is 1.8-2.5 g / cm 3 , preferably 1.9-2.4 g / cm 3 ; Preferably, the resistivity of the composite B is less than or equal to 200 Ω·cm, preferably 0.001-100 Ω·cm, and more preferably 0.01-90 Ω·cm.

10. The preparation method according to any one of claims 5 to 9, wherein: The step (3) comprises: in an atmosphere of protective gas, the composite B is subjected to an aluminothermic reaction in a salt melt medium containing AlCl3 to obtain an aluminothermic reduction product, and the salt melt medium is removed, and the product is dried, crushed and sieved to obtain a silicon-carbon material; Preferably, the AlCl3-containing salt melt medium is an AlCl3 molten salt or an AlCl3 eutectic salt, preferably an AlCl3 eutectic salt; Preferably, the AlCl3 eutectic salt is AlCl3+MX 1 a , wherein M is at least one of Ba, Li, Ca, Cs, Na, K, Mg, Rb, Be, Zn and Sr; X 1 is Cl and / or F, and a is 1 or 2. Preferably, based on the total mass of the AlCl3 eutectic salt, AlCl3 is 40wt%-95wt%, preferably 45wt%-90wt%; Preferably, the temperature of the thermite reaction is 180-250°C, preferably 190-240°C; the time of the thermite reaction is 1-12h, preferably 2-10h.

11. A silicon-carbon material obtained by the preparation method according to any one of claims 5 to 10.

12. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the negative electrode comprises the silicon-carbon material according to any one of claims 1 to 4 and 11.

13. Use of the lithium-ion battery according to claim 12 in an electronic device, an electric tool, an electric vehicle or a power storage system.

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