Silicon-carbon negative electrode material with high cycle stability and preparation method thereof

Abstract

The application discloses a silicon-carbon negative electrode material with high cycle stability and a preparation method thereof. The silicon-carbon negative electrode material takes carbon as a matrix, and silicon core particles are uniformly dispersed in the carbon matrix. A silicon and metal alloy layer is arranged on the surface of the silicon core particles, and a silicon carbide layer is in-situ grown on the surface of the silicon and metal alloy layer. In the preparation, silicon is taken as the core, and the surface layer is formed by nano particles of silicon and other metal alloys. Then, the nano particles are compounded with resin materials, vacuum heat treatment is conducted, and a composite material in which the nano particles are uniformly dispersed in the carbon matrix is formed to obtain the silicon-carbon negative electrode material. In the application, the silicon-carbon composite negative electrode material with excellent cycle stability can be prepared at a lower temperature. The method is simple in process, low in cost, environment-friendly, and easy to industrialize, and is a silicon-carbon negative electrode preparation method with more excellent comprehensive performance than existing methods.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, and particularly relates to a silicon-carbon anode material with high cycle stability and its preparation method. Background Technology

[0002] Silicon-carbon anodes are considered ideal for next-generation lithium-ion battery anode materials due to their high energy density and excellent electrochemical performance. With the rapid growth of the new energy vehicle market, higher demands are being placed on battery energy density, cycle life, and safety. Researchers often employ methods such as reducing the size of silicon nanoparticles, composite granulation with carbon, surface coating modification, or other structural designs to improve their cycle life and stability.

[0003] There are two main process routes for mainstream silicon-carbon anode materials in the industry: one is the sand milling method, which nanoscales silicon and then combines it with carbon materials; the other is the silane method, which deposits fumed silicon into a porous carbon matrix. Both techniques can produce high-performance silicon-carbon materials, but each has limitations. The sand milling method produces materials with larger silicon particles and grain sizes, resulting in generally lower cycle stability, requiring a well-designed structure to suppress volume expansion caused by cycling. The silane method has a high technical threshold, with high cost and poor safety, making large-scale application difficult in the short term. In particular, both methods require consideration of controlling the reaction between silicon and carbon to form silicon carbide. Many studies have shown that silicon carbide, as a high-strength semiconductor material, can serve as a protective layer to suppress interfacial chemical reactions and enhance the stability of silicon-based anodes. Therefore, forming a dense, nanoscale-thick silicon carbide ceramic layer on the Si surface is particularly important. The formation of silicon carbide requires a high reaction temperature to overcome the activation energy. Of the two process routes mentioned above, the silicon particles produced by the sand milling method are large and have low surface activity. The formation of silicon carbide requires a high temperature, but the high temperature will cause the silicon crystal size to grow rapidly, which will have a negative impact on the charge and discharge cycle. The silicon particles produced by the silane method are small, usually a few nanometers in size, and have very high surface activity. Even at a low temperature, silicon and carbon are very likely to react to form silicon carbide. After all the silicon particles that were originally a few nanometers in size have reacted, the material loses its electrical performance advantages.

[0004] Chinese patent application CN115458715A discloses a silicon-carbon anode material, its preparation method, and a lithium-ion battery. The silicon-carbon anode material includes carbon, composite silicon particles, and a conductive agent, with the carbon, composite silicon particles, and conductive agent forming a mixture of particles. The composite silicon particles include a silicon-based core and a carbon coating layer covering the silicon-based core, with the carbon coating layer doped with ceramics. This prior art involves mixing a second carbon source containing a ceramic precursor with silicon-based particles to form the coating layer. This method suffers from weak interfacial bonding, and the granulation of the composite particles with the conductive agent and carbon source results in large particle size differences between the phases, making it difficult to guarantee dispersibility and density, and leading to low structural strength. Summary of the Invention

[0005] To overcome the problems in the prior art, the present invention provides a silicon-carbon anode material with high cycle stability and its preparation method. The silicon-carbon composite anode material with excellent cycle stability is prepared at a lower temperature, and the coating layer is integrated with the matrix, resulting in better density and stability.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] The present invention provides a silicon-carbon anode material with high cycle stability. The silicon-carbon anode material uses carbon as a matrix, in which silicon core particles are uniformly dispersed. The surface of the silicon core particles is a silicon and metal alloy layer, and a silicon carbide layer is grown in situ on the surface of the silicon and metal alloy layer.

[0008] As an optional implementation, in the silicon-carbon anode material provided by the present invention, the metal in the metal alloy layer is selected from one or more of copper, magnesium, aluminum, tin, silver, and gold.

[0009] As an optional implementation, in the silicon-carbon anode material provided by the present invention, the outer surface of the silicon-carbon anode material has an inorganic coating layer, the inorganic coating layer being an inorganic aluminum-containing compound; the thickness of the inorganic coating layer is 5~30nm.

[0010] As an optional implementation, in the silicon-carbon anode material provided by the present invention, the thickness of the silicon and metal alloy layer is 10~20nm, and the thickness of the silicon carbide layer is 5~10nm.

[0011] Based on the same technical concept, the present invention also provides a method for preparing a silicon-carbon anode material with high cycle stability, comprising the following steps:

[0012] S1. After uniformly mixing nano-silicon and nano-metal powder, surface alloying treatment is performed to obtain Si / metal Si alloy nanoparticles.

[0013] S2. The nanoparticles obtained in step S1 are mixed evenly with resin materials, and then heat-treated in a vacuum furnace at 600~850℃ and 0.01~5Pa to obtain silicon-carbon intermediate powder.

[0014] S3. The silicon-carbon intermediate powder obtained in step S2 is sieved to obtain a silicon-carbon anode material with high cycle stability.

[0015] This invention first uses silicon as the core and silicon and other metal alloy nanoparticles as the surface layer. These nanoparticles are then composited with resin materials and subjected to vacuum heat treatment to form a composite material in which the nanoparticles are homogeneously dispersed in a carbon matrix. Finally, an inorganic coating is applied to the surface of the material to form a silicon-carbon anode material. Because the surface of the nano-silicon is alloyed, the melting point of the Si particles is lowered, the bond length between surface Si-Si atoms is lengthened, and the bonding strength of the Si-Si bonds is weakened, making the Si atoms more reactive and further increasing the attraction of Si to surrounding C atoms. This makes it easier for Si to react with the polymer (resin) pyrolysis carbon to form SiC, thus allowing for a lower heat treatment temperature. The silicon crystal size can be controlled at 600-850℃, and a nanoscale SiC layer can be grown in situ on the surface of the silicon particles. The anode material prepared by this method has high structural strength, small silicon crystal size, and excellent conductivity and ion conduction properties. It can significantly suppress volume expansion during lithium intercalation and exhibits good cycle stability.

[0016] In this invention, heat treatment is performed in a vacuum furnace at 600-850°C and a vacuum degree of 0.01-5 Pa. Under a sufficiently low vacuum, the polymer undergoes pyrolysis, resulting in a higher internal gas partial pressure, which facilitates the reaction with silicon. This process involves the decomposition and carbonization of the resin polymer, and the reaction of silicon with CO or pyrolytic carbon in the pyrolysis atmosphere to generate SiC. The relevant equations are as follows:

[0017] Si+C= SiC, Si+2CO=SiC+CO2↑.

[0018] As an optional implementation, in the preparation method provided by the present invention, in step S1, the median particle size of the single particle of the nano-silicon is 20~500nm, preferably 50~150nm; the median particle size of the nano-metal powder is 10nm~1μm, preferably 30~100nm; and the weight ratio of the nano-silicon to the nano-metal powder is 20:1~200:1, preferably 50:1~100:1.

[0019] In this invention, controlling the particle size of nano-silicon and nano-metal powder is beneficial for further controlling the particle size of Si / metal Si alloy nanoparticles, and controlling the weight ratio of nano-silicon to nano-metal powder is beneficial for controlling the surface alloying depth.

[0020] As an optional implementation, in the preparation method provided by the present invention, in step S1, the nano-silicon and nano-metal powders are surface alloyed in a plasma ball mill, wherein the discharge frequency of the plasma ball mill is 7~15kHz and the rotation speed is 500~1500rpm.

[0021] The plasma ball mill used in this invention is a high-energy ball milling technology that combines mechanical pulverization with a plasma electric field. Compared with traditional ball mills, it utilizes the energy surge characteristic of discharge plasma to subject the sample to high-speed impact, friction, and abrasion, thereby achieving ultrafine pulverization and mechanical alloying of the material. Furthermore, by adjusting the plasma ball milling speed and discharge frequency, the degree of surface alloying can be controlled within an optimal range.

[0022] As an optional implementation, in the preparation method provided by the present invention, in step S2, the resin material is selected from one or more of phenolic resin, epoxy resin, and acrylic resin, and the resin material is added at a mass ratio of nanoparticle powder to resin material of 1:1 to 1:5.

[0023] As an optional implementation, in the preparation method provided by the present invention, in step S2, the mixing equipment is a double planetary mixer with a rotation speed of 1000~2000 rpm and a time of 2~4 h.

[0024] As an optional implementation method, in the preparation method provided by the present invention, in step S2, the nanoparticles obtained in step S1 are mixed evenly with resin materials and dried and crushed. The drying temperature is 100~200℃ and the drying time is 24~48h. The median particle size after crushing is 5~20 μm.

[0025] In this invention, the drying equipment in step S2 is selected from one of a vacuum dryer, a double cone dryer, or a rake dryer, and the drying process is the process of solvent evaporation, polymer crosslinking, and curing.

[0026] As an optional implementation, in the preparation method provided by the present invention, in step S2, the pulverizing equipment is an air jet mill.

[0027] As an optional implementation, in the preparation method provided by the present invention, the silicon-carbon intermediate powder obtained in step S2 is mixed evenly with a metal salt and then sintered to obtain a sintered material. The sintered material is then crushed and sieved to obtain a silicon-carbon anode material with high cycle stability.

[0028] As an optional implementation, in the preparation method provided by the present invention, the metal salt is an aluminum salt, which is selected from one or more of aluminum nitrate, aluminum acetate, or aluminum phosphate; the aluminum salt is added at a weight ratio of silicon-carbon intermediate powder to aluminum salt of 50:1 to 200:1.

[0029] In this invention, inorganic coating is selected because, compared to carbon coating, inorganic coating requires a lower coating temperature, thus preventing further growth of silicon crystals.

[0030] As an optional implementation, in the preparation method provided by the present invention, the sintering equipment is a tube furnace or a box furnace, the sintering temperature is 400~600℃, the heating rate is 1~20℃ / min, the holding time is 2~10h, and the sintering atmosphere is selected from N2, Ar or a reducing gas.

[0031] As an optional implementation, in the preparation method provided by the present invention, the silicon-carbon intermediate powder is mixed with a metal salt by a liquid phase mixing method, and then vacuum dried. The drying equipment is a vacuum oven, and the drying temperature is 70~150℃.

[0032] In this invention, a liquid-phase mixing method is used, resulting in a more uniform surface coating after dissolution.

[0033] As an optional implementation, in the preparation method provided by the present invention, in step S4, the depolymerization equipment is a conventional depolymerization machine, the sieving equipment is a vibrating screen with a 500-mesh screen, and the median particle size of the material is controlled to be 6~15μm, preferably 6~10μm.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) In this invention, surface alloying is used to catalyze the silicon carbide generation reaction and polymer pyrolysis reaction, and combined with surface inorganic coating, a composite material in which nano-silicon particles with silicon carbide layer are dispersed in carbon matrix is ​​obtained under low temperature heat treatment conditions. The nano-silicon maintains a low silicon crystal size and, combined with the silicon carbide layer grown in situ on the surface, maintains a stable structure during cycling. In addition, the hard carbon formed by the polymer provides a good buffer for the expansion caused by silicon lithium intercalation.

[0036] (2) The outermost inorganic coating of the present invention further suppresses the expansion of the material and modifies the pores formed by pyrolysis. It also acts as a free ion conductor, similar to an artificial SEI film, to prevent the reduction and decomposition of the electrolyte, reduce lithium consumption, and improve the coulombic efficiency in charge-discharge cycles.

[0037] (3) The preparation method of the present invention involves alloying, which can improve the conductivity and reversible capacity of the material; by first alloying and then growing in situ on the surface, the coating layer is integrated with the substrate, which effectively improves the density and stability; the silicon-carbon anode material prepared is a homogeneous structure with strong density and high structural strength. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The XRD results are for the materials prepared in Example 1, Comparative Example 1, and Comparative Example 3 of this invention.

[0040] Figure 2 This is a schematic diagram of the structure of the silicon-carbon anode material prepared in Example 1 of this invention;

[0041] Legend: 1. Si core; 2. Cu3Si alloy layer; 3. SiC layer; 4. Carbon matrix; 5. Al2O3 coating layer. Detailed Implementation

[0042] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0043] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0044] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0045] Example 1

[0046] A method for preparing a silicon-carbon anode material with high cycle stability includes the following steps:

[0047] 100g of silicon powder with a median particle size of 120nm and 1g of copper powder with a median particle size of 100nm were weighed, mixed, and added to a plasma ball mill. The mixture was ball-milled for 5 hours at a speed of 1200rpm and a discharge frequency of 10kHz to obtain surface alloyed powder. The surface alloyed powder was mixed evenly with 250g of phenolic resin and dried in a double cone at 150℃. The dried material was then air-jet pulverized to 10μm and heat-treated in a vacuum furnace at 750℃ for 5 hours. Subsequently, the powder was evenly dispersed with 2g of aluminum nitrate in an aqueous solution and vacuum-dried at 110℃. The dried material was sintered at 500℃ for 2 hours under a N2 atmosphere. Finally, the sintered material was depolymerized and sieved to obtain the silicon-carbon anode material of this embodiment.

[0048] Figure 2This is a schematic diagram of the silicon-carbon anode material prepared in Example 1, which includes a Si core 1, a Cu3Si alloy layer 2, a SiC layer 3, a carbon matrix 4, and an Al2O3 coating layer 5. The silicon-carbon anode material has a silicon core and a silicon-copper alloy layer 2 with a thickness of 10-20 nm, denoted as Si@Cu3Si. A silicon carbide layer 3 with a thickness of 5-10 nm is grown in situ on the surface of the silicon-copper alloy layer, denoted as Si@Cu3Si@SiC. The silicon core particles containing the silicon carbide layer are uniformly dispersed in the carbon matrix 4, denoted as Si@Cu3Si@SiC / C particles, and the outer surface of the silicon-carbon anode material is an Al2O3 coating layer 5 with a thickness of 5-30 nm.

[0049] Example 2

[0050] A method for preparing a silicon-carbon anode material with high cycle stability includes the following steps:

[0051] 150g of silicon powder with a median particle size of 80nm and 1.2g of magnesium powder with a median particle size of 80nm were weighed, mixed, and added to a plasma ball mill. The mixture was ball-milled for 4 hours at 1100rpm and 8kHz to obtain surface-alloyed powder. The surface-alloyed powder was then mixed evenly with 300g of epoxy resin and dried using a double-cone drying process at 160℃. The dried material was then air-jet pulverized to 8μm and heat-treated in a vacuum furnace at 680℃ for 6 hours. Subsequently, the powder was evenly dispersed with 3g of aluminum acetate in an aqueous solution and vacuum-dried at 100℃. The dried material was sintered at 550℃ for 2 hours under a N2 atmosphere. Finally, the sintered material was depolymerized and sieved to obtain the silicon-carbon anode material. The structure of the silicon-carbon anode material prepared in this embodiment is the same as that in Example 1.

[0052] Example 3

[0053] A method for preparing a silicon-carbon anode material with high cycle stability includes the following steps:

[0054] 120g of silicon powder with a median particle size of 160nm and 3g of copper powder with a median particle size of 200nm were weighed, mixed, and added to a plasma ball mill. The mixture was ball-milled for 5 hours at 900rpm and 7kHz to obtain a surface-alloyed powder. The surface-alloyed powder was then mixed evenly with 200g of phenolic resin and dried using a double-cone drying process at 100℃. The dried material was then air-jet pulverized to 12μm and heat-treated in a vacuum furnace at 800℃ for 5 hours. Subsequently, the powder was evenly dispersed with 2g of aluminum phosphate in an aqueous solution and vacuum-dried at 110℃. The dried material was sintered at 700℃ for 2 hours under a N2 atmosphere. Finally, the sintered material was depolymerized and sieved to obtain a silicon-carbon anode material. The structure of the silicon-carbon anode material prepared in this embodiment is the same as that in Example 1.

[0055] Comparative Example 1

[0056] A method for preparing a silicon-carbon anode material includes the following steps:

[0057] 100g of silicon powder with a median particle size of 120nm was weighed and mixed evenly with 250g of phenolic resin, and dried at 150℃ using a double cone dryer. The dried material was then pulverized into 10μm particles by air jet. The material was then heat-treated in a vacuum furnace at 750℃ for 5h. Subsequently, the powder was evenly dispersed with 2g of aluminum nitrate in an aqueous solution and dried under vacuum at 110℃. The dried material was then sintered at 500℃ for 2h under a N2 atmosphere. Finally, the sintered material was depolymerized and sieved to obtain silicon-carbon anode material.

[0058] Comparative Example 2

[0059] A method for preparing a silicon-carbon anode material includes the following steps:

[0060] 150g of silicon powder with a median particle size of 80nm and 1.2g of magnesium powder with a median particle size of 80nm were weighed, mixed, and added to a plasma ball mill. The mixture was ball-milled for 4 hours at a speed of 1100rpm and a discharge frequency of 8kHz to obtain surface alloyed powder. The surface alloyed powder was mixed evenly with 300g of epoxy resin and dried in a double cone at 160℃. The dried material was then air-jet pulverized to 8μm. The material was then heat-treated in a vacuum furnace at 680℃ for 6 hours. The heat-treated material was depolymerized and sieved to obtain silicon-carbon anode material.

[0061] Comparative Example 3

[0062] A method for preparing a silicon-carbon anode material includes the following steps:

[0063] 100g of silicon powder with a median particle size of 150nm was weighed and mixed evenly with 200g of phenolic resin, and dried at 120℃ using a double cone dryer. The dried material was then pulverized into 7μm particles by airflow and heat-treated in an atmosphere furnace at 1250℃ for 5h. Subsequently, the powder was mixed with 8g of asphalt and sintered at 1100℃ for 2h under a N2 atmosphere. Finally, the sintered material was depolymerized and sieved to obtain silicon-carbon anode material.

[0064] Performance testing

[0065] The silicon-carbon composite negative electrode materials prepared in the above experimental examples were mixed with conductive carbon black and LA133 binder in a mass ratio of 7:2:1 to form slurries, which were then coated onto copper foil and vacuum dried and rolled to serve as negative electrodes. Ternary electrodes were used as positive electrodes, and CR2430 coin cells were assembled in the following order: positive electrode shell, positive electrode, electrolyte, separator, electrolyte, negative electrode, nickel foam, and negative electrode shell. After standing for 24 hours, the cells were tested using a constant current charge-discharge of 0.2C or 1C, with the voltage limited to 0~1.5V.

[0066] The method for calculating silicon crystal size involves obtaining the XRD pattern of the material through XRD testing, and then identifying the strongest diffraction peak of Si. <111> The diffraction angle and full width at half maximum (FWHM) are obtained by fitting the diffraction peaks, and then silicon is calculated according to the Scherrer equation. <111> Grain size of the crystal face.

[0067] The silicon crystal size and electrochemical performance test results of the anode materials prepared in the examples and comparative examples are shown in Table 1 and... Figure 1 As shown.

[0068] Table 1: Silicon crystal size and electrochemical performance results of each material in the examples and comparative examples

[0069]

[0070] Compared with Example 1, Comparative Example 1 did not undergo surface alloying treatment, and silicon carbide could not be formed at low temperatures. Even with small silicon crystal size, the performance stability was poor. Comparative Example 2 underwent surface alloying but did not undergo inorganic coating. Although the cycle performance was greatly improved compared with Comparative Example 1, it was still worse than Example 2, especially under high-rate conditions. Comparative Example 3 was prepared using a conventional process route, forming silicon carbide at high temperatures. However, due to the large silicon crystal size and the difficulty in controlling the silicon carbide reaction, the electrical performance was poor.

[0071] Figure 1 The XRD test results are for the materials of Comparative Example 1, Comparative Example 3, and Example 1 of this invention. The material of Comparative Example 1 has a small silicon peak and no silicon carbide peak, while the material of Comparative Example 3 has a large silicon peak and a strong silicon carbide peak. Both of them have poor electrochemical performance. However, the material of Example 1 has a small silicon crystal and a weak silicon carbide peak. The material maintains a small grain size and forms a silicon carbide layer. The material performance is significantly better than that of the comparative examples.

[0072] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-carbon negative electrode material with high cycle stability, characterized in that, The method comprises the following steps: S1, uniformly mixing nano-silicon and nano-metal powder, and then performing surface alloying treatment in a plasma ball mill, wherein the discharge frequency of the plasma ball mill is 7-15 kHz, and the rotating speed is 500-1500 rpm, to obtain Si / metal Si alloy nanoparticles; the weight ratio of the nano-silicon to the nano-metal powder is 20:1-200:1; S2, uniformly mixing the nanoparticles obtained in step S1 with a resin material, and then performing heat treatment in a vacuum furnace under the conditions of 680-800 DEG C and a vacuum degree of 0.01-5 Pa to obtain a silicon-carbon intermediate powder; the resin material is selected from one or more of phenolic resin, epoxy resin and acrylic resin; S3, sieving the silicon-carbon intermediate powder obtained in step S2 to obtain a silicon-carbon negative electrode material with high cycle stability; The silicon-carbon negative electrode material prepared by the above method has a carbon matrix, and silicon core particles are uniformly dispersed in the carbon matrix; a silicon and metal alloy layer is arranged on the surface of the silicon core particles; and a silicon carbide layer is in-situ grown on the surface of the silicon and metal alloy layer; the thickness of the silicon and metal alloy layer is 10-20 nm, and the thickness of the silicon carbide layer is 5-10 nm.

2. The method for preparing the silicon-carbon anode material with high cycle stability according to claim 1, characterized in that, The metal is selected from one or more of copper, magnesium, aluminum, tin, silver and gold.

3. The method of claim 1, wherein the silicon-carbon anode material has a high cycle stability. The silicon-carbon negative electrode material has an inorganic coating layer on the outer surface, and the inorganic coating layer is an inorganic aluminum-containing compound; the thickness of the inorganic coating layer is 5-30 nm.

4. The method of claim 1, wherein the silicon-carbon anode material having high cycle stability is prepared by the steps of: preparing a mixture of a silicon source, a carbon source, and a solvent; and performing a heat treatment on the mixture. In step S1, the median particle size of a single particle of the nano-silicon is 20-500 nm, and the median particle size of the nano-metal powder is 10 nm-1 μm.

5. The method of claim 1, wherein the silicon-carbon anode material having high cycle stability is prepared by the steps of: preparing a mixture of a silicon source, a carbon source, and a solvent; and performing a heat treatment on the mixture. In step S2, the resin material is added in a mass ratio of 1:1-1:5 of the nanoparticles to the resin material; the nanoparticles obtained in step S1 are uniformly mixed with the resin material, dried and crushed, the drying temperature is 100-200 DEG C, and the drying time is 24-48 h; and the median particle size after crushing is 5-20 μm.

6. The method of claim 1, wherein the silicon-carbon anode material has a high cycle stability. The silicon-carbon intermediate powder obtained in step S2 is uniformly mixed with a metal salt, sintered to obtain sintered material, and then crushed and sieved to obtain a silicon-carbon negative electrode material with high cycle stability.

7. The method of claim 6, wherein the silicon-carbon anode material has a high cycle stability. The metal salt is an aluminum salt, and the aluminum salt is selected from one or more of aluminum nitrate, aluminum acetate or aluminum phosphate; the aluminum salt is added in a weight ratio of 50:1-200:1 of the silicon-carbon intermediate powder to the aluminum salt.

8. The method for preparing the silicon-carbon anode material with high cycle stability according to claim 6, characterized in that, The sintering device is a tube furnace or a box furnace, the sintering temperature is 400-600 DEG C, the heating rate is 1-20 DEG C / min, the holding time is 2-10 h, and the sintering atmosphere is selected from one of N2, Ar or a reducing gas; the silicon-carbon intermediate powder and the metal salt are mixed by a liquid phase mixing method, and then vacuum dried, and the drying device is a vacuum oven, and the drying temperature is 70-150 DEG C.

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