Silicon-carbon negative electrode material with high cycling stability and preparation method of silicon-carbon negative electrode material

Abstract

The invention 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, silicon core particles are uniformly dispersed in the carbon matrix, the surface layer of the silicon core particles is a silicon and metal alloy layer, and a silicon carbide layer grows in situ on the surface of the silicon and metal alloy layer. The preparation method comprises the following steps: firstly, taking silicon as an inner core, taking nano-particles of silicon and other metal alloys as a surface layer, then compounding the nano-particles with a resin material, and carrying out vacuum heat treatment to form a composite material in which the nano-particles are homogeneously dispersed in a carbon matrix, so as to form the silicon-carbon negative electrode material. The silicon-carbon composite negative electrode material with excellent cycle stability can be prepared at a low temperature, and the method is simple in process, low in cost, environmentally friendly and easy to industrialize, and is a silicon-carbon negative electrode preparation method with better comprehensive performance compared with an existing route.

Description

Technical Field

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

[0002] Silicon-carbon anode is considered an ideal choice for the next generation of lithium battery anode materials due to its high energy density and excellent electrochemical performance. With the rapid growth of the new energy vehicle market, higher requirements are placed on the energy density, cycle life and safety of batteries. Researchers often improve the cycle life and stability of silicon nanoparticles by reducing the size of silicon nanoparticles, composite granulation with carbon, coating and modifying the surface, or other types of structural design.

[0003] There are two main process routes for mainstream silicon-carbon negative electrode materials in the industry. One is the sand milling method, which nano-scales silicon and then compounds it with carbon materials; the other is the silane method, which deposits gas-phase silicon in a porous carbon matrix. Both technical routes can produce silicon-carbon materials with excellent performance, but they have limitations to a certain extent. The silicon particles and grain sizes of the materials prepared by the former sand milling method are large, resulting in general cycle stability, and a reasonable structure needs to be designed to suppress the volume expansion caused by the cycle; the latter silane method has a high technical threshold, high cost and poor safety, and large-scale application is difficult to achieve in the short term. In particular, both methods need to consider the control of the reaction between silicon and carbon to form silicon carbide. Many studies have shown that silicon carbide, as a high-strength semiconductor material, can be used as a protective layer to inhibit the chemical reaction of the material interface to enhance the stability of the silicon-based negative electrode. Therefore, how to form a dense nano-thickness silicon carbide ceramic layer on the Si surface is particularly important. The formation of silicon carbide requires a higher reaction temperature to overcome the activation energy. Of the two process routes mentioned above, the sand-milling method produces large silicon particles with low surface activity, and requires a higher temperature to form silicon carbide. However, high temperature will cause the silicon crystal size to grow rapidly, which will have a negative impact on the charge and discharge cycle. The silane method produces small silicon particles, usually a few nanometers in size, with a very high surface activity. Even at relatively low temperatures, silicon and carbon are very likely to react to form silicon carbide. After all the original few nanometers of silicon have reacted, the material loses its electrical performance advantage.

[0004] Chinese patent application CN115458715A discloses a silicon-carbon negative electrode material, a preparation method thereof and a lithium-ion battery, wherein the silicon-carbon negative electrode material comprises carbon, composite silicon particles and a conductive agent, and the carbon, composite silicon particles and the conductive agent form a mixture particle, wherein the composite silicon particles comprise a silicon-based core body and a carbon coating layer coating the silicon-based core body, and the carbon coating layer is doped with ceramics. This prior art mixes a second carbon source containing a ceramic precursor with silicon-based particles to form a coating layer, and the method has weak interface bonding force, and the composite particles are granulated with the conductive agent and the carbon source, and the particle sizes of the various phases are greatly different, and the dispersion and density are difficult to ensure, and the structural strength is low. Summary of the invention

[0005] In order to overcome the problems in the prior art, the present invention provides a silicon-carbon negative electrode material with high cycle stability and a preparation method thereof, and prepares a silicon-carbon composite negative electrode material with excellent cycle stability at a lower temperature. The coating layer is integrated with the substrate, and the density and stability are better.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: The present invention provides a silicon-carbon negative electrode material with high cycle stability. The silicon-carbon negative electrode material is based on carbon, silicon core particles are uniformly dispersed in the carbon matrix, the surface layer of the silicon core particles is a silicon and metal alloy layer, and a silicon carbide layer is in-situ grown on the surface of the silicon and metal alloy layer.

[0007] As an optional embodiment, in the silicon-carbon negative electrode 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.

[0008] As an optional embodiment, in the silicon-carbon negative electrode material provided by the present invention, the outer surface of the silicon-carbon negative electrode material has an inorganic coating layer, and the inorganic coating layer is an inorganic aluminum-containing compound; the thickness of the inorganic coating layer is 5~30nm.

[0009] As an optional embodiment, in the silicon-carbon negative electrode material provided by the present invention, 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.

[0010] Based on the same technical concept, the present invention also provides a method for preparing a silicon-carbon negative electrode material with high cycle stability, comprising the following steps: S1, mixing nano-silicon and nano-metal powders uniformly and performing surface alloying treatment to obtain Si / metal Si alloy nanoparticles; S2, mixing the nanoparticles obtained in step S1 with the resin material, and then heat treating them in a vacuum furnace at 600-850° C. and a vacuum degree of 0.01-5 Pa to obtain a silicon-carbon intermediate powder; S3. The silicon-carbon intermediate powder obtained in step S2 is sieved to obtain a silicon-carbon negative electrode material with high cycle stability.

[0011] In the present invention, silicon is first used as the core, and the surface layer is nanoparticles of silicon and other metal alloys. Then, the nanoparticles are compounded with resin materials, and vacuum heat treatment is performed to form a composite material in which nanoparticles are uniformly dispersed in a carbon matrix; finally, inorganic coating is performed on the surface of the material to form a silicon-carbon negative electrode material. Since the surface of nano-silicon is alloyed, the melting point of Si particles is reduced, the bond length between the surface Si-Si is lengthened, the bonding strength of the Si-Si bond is weakened, the Si atoms are more active, and the attraction of Si to the surrounding C atoms is further increased, so that Si is more likely to react with polymer (resin) pyrolysis carbon to generate SiC, so the heat treatment temperature can be reduced, the silicon crystal size is controlled at a temperature of 600-850°C, and the surface of the silicon particles is in situ grown into a nanometer-thick SiC layer. The negative electrode material prepared by this method has high structural strength, small silicon crystal size, and excellent electrical and ion conductivity. It can greatly inhibit the volume expansion during the lithium insertion process and has good cycle stability.

[0012] In the present invention, heat treatment is performed in a vacuum furnace at 600-850°C and a vacuum degree of 0.01-5Pa. Under a sufficiently low vacuum degree, the polymer is pyrolyzed to form an internal gas with a higher partial pressure, which is more likely to react with silicon. This process is a process in which the resin polymer is decomposed and carbonized, and silicon reacts with CO or pyrolytic carbon in the pyrolysis atmosphere to generate SiC; the equation involved is as follows: Si+C= SiC, Si+2CO=SiC+CO2↑.

[0013] As an optional embodiment, in the preparation method provided by the present invention, in step S1, the median particle size of a 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.

[0014] In the present invention, controlling the particle size of nano-silicon and nano-metal powder is beneficial to further controlling the particle size of Si / metal Si alloy nano-particles, and controlling the weight ratio of nano-silicon to nano-metal powder is beneficial to controlling the surface alloying depth.

[0015] As an optional embodiment, 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, and the discharge frequency of the plasma ball mill is 7~15kHz and the rotation speed is 500~1500rpm.

[0016] The plasma ball mill used in the present invention is a high-energy ball milling technology that combines mechanical pulverization with plasma electric field. Compared with traditional ball mills, it uses the characteristics of the surge in energy of discharge plasma to subject the sample to high-speed impact, friction and wear, thereby achieving ultra-fine pulverization and mechanical alloying of the material. Further, by adjusting the plasma ball milling speed and discharge frequency, the surface alloying degree can be controlled to be within the optimal range.

[0017] As an optional embodiment, 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 according to a mass ratio of nanoparticle powder to resin material of 1:1 to 1:5.

[0018] As an optional embodiment, in the preparation method provided by the present invention, in step S2, the mixing equipment is a double planetary mixer, the rotation speed is 1000~2000rpm, and the time is 2~4h.

[0019] As an optional embodiment, in the preparation method provided by the present invention, in step S2, the nanoparticles obtained in step S1 are mixed evenly with a resin material and dried and crushed, the drying temperature is 100~200°C, and the drying time is 24~48h; the median particle size after crushing is 5~20 μm.

[0020] In the present invention, the drying equipment in step S2 is selected from a vacuum dryer, a double cone dryer or a rake dryer, and the drying process is a process of solvent volatilization, polymer cross-linking and curing.

[0021] As an optional embodiment, in the preparation method provided by the present invention, in step S2, the pulverizing equipment is a jet mill.

[0022] As an optional embodiment, in the preparation method provided by the present invention, the silicon-carbon intermediate powder obtained in step S2 is evenly mixed with the metal salt and then sintered to obtain a sintered material, and then the sintered material is crushed and sieved to obtain a silicon-carbon negative electrode material with high cycle stability.

[0023] As an optional embodiment, in the preparation method provided by the present invention, 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 according to a weight ratio of silicon-carbon intermediate powder to aluminum salt of 50:1 to 200:1.

[0024] In the present invention, inorganic coating is selected. Compared with carbon coating, the coating temperature of inorganic coating is lower, thereby avoiding further growth of silicon crystals.

[0025] As an optional embodiment, in the preparation method provided by the present invention, the equipment used for sintering is a tube furnace or a box furnace, the sintering temperature is 400~600℃, the heating rate is 1~20℃ / min, the insulation time is 2~10h, and the sintering atmosphere is selected from one of N2, Ar or reducing gas.

[0026] As an optional embodiment, in the preparation method provided by the present invention, the silicon-carbon intermediate powder is mixed with the metal salt by a liquid phase mixing method, and then vacuum dried after mixing, the drying equipment is a vacuum oven, and the drying temperature is 70~150°C.

[0027] In the present invention, a liquid phase mixing method is adopted, and the surface coating is more uniform after dissolution.

[0028] As an optional embodiment, in the preparation method provided by the present invention, in step S4, the depolymerization equipment is a conventional depolymerization machine, the screening equipment is a vibrating screen with a 500-mesh screen, and the median particle size of the material is controlled to be 6 to 15 μm, preferably 6 to 10 μm.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) In the present invention, the silicon carbide formation reaction and the polymer pyrolysis reaction are catalyzed by surface alloying, and combined with surface inorganic coating, a composite material of nano-silicon particles dispersed in a carbon matrix is ​​obtained under low-temperature heat treatment conditions; the nano-silicon maintains a relatively low silicon crystal size and cooperates with the silicon carbide layer grown in situ on the surface to maintain a stable structure during the cycle process, and the hard carbon formed by the polymer also provides a good buffer for the expansion caused by lithium embedding in silicon.

[0030] (2) The outermost inorganic coating of the present invention further inhibits the expansion of the material and modifies the pores formed by thermal decomposition. It also acts as a free ion conductor, analogous to an artificial SEI membrane to prevent the reduction and decomposition of the electrolyte, thereby reducing lithium consumption and improving the coulombic efficiency during the charge and discharge cycle.

[0031] (3) The preparation method of the present invention performs alloying treatment to improve the conductivity and reversible capacity of the material; by first alloying and then in-situ growth on the surface, the coating layer and the substrate are integrated, effectively improving the density and stability; the prepared silicon-carbon negative electrode material has a homogeneous structure, strong density and high structural strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 The XRD results of the materials prepared in Example 1, Comparative Example 1 and Comparative Example 3 of the present invention are shown; Figure 2 Schematic diagram of the structure of the silicon-carbon negative electrode material prepared in Example 1 of the present invention; Legend: 1. Si core; 2. Cu3Si alloy layer; 3. SiC layer; 4. Carbon matrix; 5. Al2O3 coating layer. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0037] Example 1 A method for preparing a silicon-carbon negative electrode material with high cycle stability comprises the following steps: 100 g of silicon powder with a median particle size of 120 nm and 1 g of copper powder with a median particle size of 100 nm were weighed, mixed and added into a plasma ball mill, and surface alloyed powder was obtained after ball milling at a rotation speed of 1200 rpm and a discharge frequency of 10 kHz for 5 h; the surface alloyed powder was mixed evenly with 250 g of phenolic resin, and double-cone dried at 150°C; the dried material was air-flow crushed into 10 μm; heat-treated at 750°C in a vacuum furnace for 5 h; the powder was then evenly dispersed in an aqueous solution with 2 g of aluminum nitrate, and vacuum-dried at 110°C; the dried material was sintered at 500°C for 2 h under a N2 atmosphere; finally, the sintered material was depolymerized and sieved to obtain the silicon-carbon negative electrode material of this embodiment.

[0038] Figure 2Schematic diagram of the structure of the silicon-carbon negative electrode 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 negative electrode material has silicon as the core, and the surface layer is a silicon-copper alloy layer 2 with a thickness of 10~20nm, which is recorded as Si@Cu3Si; a silicon carbide layer 3 with a thickness of 5~10nm is in situ grown on the surface of the silicon-copper alloy layer, which is recorded as Si@Cu3Si@SiC; silicon core particles containing the silicon carbide layer are uniformly dispersed in the carbon matrix 4, which is recorded as Si@Cu3Si@SiC / C particles, and the outer surface of the silicon-carbon negative electrode material is an Al2O3 coating layer 5 with a thickness of 5~30nm.

[0039] Example 2 A method for preparing a silicon-carbon negative electrode material with high cycle stability comprises the following steps: Weigh 150g of silicon powder with a median particle size of 80nm and 1.2g of magnesium powder with a median particle size of 80nm, mix and add to a plasma ball mill, and ball mill for 4h at a speed of 1100rpm and a discharge frequency of 8kHz to obtain a surface alloyed powder; mix the surface alloyed powder with 300g of epoxy resin, and dry it at 160℃ double cone; air flow crush the dried material into 8μm; heat treat it at 680℃ in a vacuum furnace for 6h; then disperse the powder and 3g of aluminum acetate in an aqueous solution, vacuum dry it at 100℃; sinter the dried material at 550℃ under N2 atmosphere for 2h; finally, depolymerize and sieve the sintered material to obtain a silicon-carbon negative electrode material. The structure of the silicon-carbon negative electrode material prepared in this embodiment is the same as that in Example 1.

[0040] Example 3 A method for preparing a silicon-carbon negative electrode material with high cycle stability comprises the following steps: 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 and mixed and added to a plasma ball mill. After ball milling for 5h at a speed of 900rpm and a discharge frequency of 7kHz, a surface alloyed powder was obtained; the surface alloyed powder was mixed evenly with 200g of phenolic resin and dried at 100℃ double cone; the dried material was air flow crushed into 12μm; heat treated at 800℃ in a vacuum furnace for 5h; then 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℃ in a N2 atmosphere for 2h; finally, the sintered material was depolymerized and sieved to obtain a silicon-carbon negative electrode material. The structure of the silicon-carbon negative electrode material prepared in this embodiment is the same as that in Example 1.

[0041] Comparative Example 1 A method for preparing a silicon-carbon negative electrode material comprises the following steps: Weigh 100g of silicon powder with a median particle size of 120nm and mix it evenly with 250g of phenolic resin, and dry it at 150℃ double cone; crush the dried material into 10μm by air flow; heat treat it at 750℃ in a vacuum furnace for 5h; then disperse the powder and 2g of aluminum nitrate in an aqueous solution evenly, and vacuum dry it at 110℃; sinter the dried material at 500℃ for 2h in a N2 atmosphere; finally, depolymerize and sieve the sintered material to obtain a silicon-carbon negative electrode material.

[0042] Comparative Example 2 A method for preparing a silicon-carbon negative electrode material comprises the following steps: Weigh 150g of silicon powder with a median particle size of 80nm and 1.2g of magnesium powder with a median particle size of 80nm, mix them and add them into a plasma ball mill, and ball mill them at a rotation speed of 1100rpm and a discharge frequency of 8kHz for 4h to obtain surface alloyed powder; mix the surface alloyed powder with 300g of epoxy resin evenly, and double-cone dry at 160℃; air flow pulverize the dried material into 8μm; heat treat it at 680℃ in a vacuum furnace for 6h; depolymerize and sieve the heat-treated material to obtain a silicon-carbon negative electrode material.

[0043] Comparative Example 3 A method for preparing a silicon-carbon negative electrode material comprises the following steps: Weigh 100g of silicon powder with a median particle size of 150nm and mix it evenly with 200g of phenolic resin, and dry it at 120℃ double cone; crush the dried material into 7μm by air flow; heat treat it at 1250℃ in an atmosphere furnace for 5h; then mix the powder with 8g of asphalt; sinter it at 1100℃ for 2h in N2 atmosphere; finally, depolymerize and sieve the sintered material to obtain a silicon-carbon negative electrode material.

[0044] Performance Testing 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 a slurry, which was then coated on copper foil and vacuum dried and rolled as the negative electrode; the ternary electrode sheet was used as the positive electrode, and the CR2430 button battery was assembled in the order of positive electrode shell, positive electrode, electrolyte, diaphragm, electrolyte, negative electrode, nickel foam, and negative electrode shell. After standing for 24 hours, the battery was charged and discharged at a constant current of 0.2C or 1C, and the voltage was limited to 0~1.5V for testing.

[0045] The method for calculating the size of silicon crystals is to obtain an XRD spectrum by XRD testing the material and take the strongest diffraction peak of Si as <111> The diffraction angle and half-height width were obtained by fitting the diffraction peaks, and then the silicon <111> The grain size of the crystal face.

[0046] The silicon crystal size and electrochemical performance test results of the negative electrode materials prepared in the examples and comparative examples are shown in Tables 1 and Figure 1 shown.

[0047] Table 1: Silicon crystal size and electrochemical performance results of each material in the examples and comparative examples

[0048] Compared with Example 1, Comparative Example 1 did not undergo surface alloying treatment, and silicon carbide could not be formed at low temperatures. Even if the silicon crystal size was small, the performance stability was poor. Comparative Example 2 underwent surface alloying but was not coated with inorganic substances. Although the cycle performance was greatly improved compared to Comparative Example 1, it was still worse than that of Example 2, especially under high rate conditions. Comparative Example 3 was prepared using a conventional process route to form silicon carbide at high temperatures, but due to the large size of the silicon crystals and the difficulty in controlling the silicon carbide reaction, the electrical properties were poor.

[0049] Figure 1 The XRD test results of the materials of comparative example 1, comparative example 3 and embodiment 1 of the present invention are shown in FIG. The material of comparative example 1 has a small silicon peak and no silicon carbide peak, and the material of comparative example 3 has a large silicon peak and a strong silicon carbide peak, and both have poor electrochemical properties; while the material of embodiment 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, and the material performance is significantly better than that of the comparative example.

[0050] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A silicon-carbon negative electrode material with high cycle stability, characterized in that: The silicon-carbon negative electrode material is based on carbon, in which silicon core particles are uniformly dispersed, the surface layer of the silicon core particles is a silicon and metal alloy layer, and a silicon carbide layer is in-situ grown on the surface of the silicon and metal alloy layer.

2. The silicon-carbon negative electrode material with high cycle stability according to claim 1, characterized in that: The metal in the metal alloy layer is selected from one or more of copper, magnesium, aluminum, tin, silver and gold.

3. The silicon-carbon negative electrode material with high cycle stability according to claim 1, characterized in that: The outer surface of the silicon-carbon negative electrode material is provided with an inorganic coating layer, and the inorganic coating layer is an inorganic aluminum-containing compound; the thickness of the inorganic coating layer is 5-30 nm.

4. The silicon-carbon negative electrode material with high cycle stability according to claim 1, characterized in that: 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.

5. A method for preparing a silicon-carbon negative electrode material with high cycle stability as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1, mixing nano-silicon and nano-metal powders uniformly and performing surface alloying treatment to obtain Si / metal Si alloy nanoparticles; S2, mixing the nanoparticles obtained in step S1 with the resin material, and then heat treating them in a vacuum furnace at 600-850° C. and a vacuum degree of 0.01-5 Pa to obtain a silicon-carbon intermediate powder; S3. The silicon-carbon intermediate powder obtained in step S2 is sieved to obtain a silicon-carbon negative electrode material with high cycle stability.

6. The method for preparing a silicon-carbon negative electrode material with high cycle stability according to claim 5, characterized in that: In step S1, the median particle size of a single particle of the nano-silicon is 20-500 nm, the median particle size of the nano-metal powder is 10 nm-1 μm, and the weight ratio of the nano-silicon to the nano-metal powder is 20:1-200:1; the nano-silicon and the nano-metal powder are surface alloyed in a plasma ball mill, and the discharge frequency of the plasma ball mill is 7-15 kHz and the rotation speed is 500-1500 rpm.

7. The method for preparing a silicon-carbon negative electrode material with high cycle stability according to claim 5, characterized in that: 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 according to a mass ratio of nanoparticles to resin material of 1:1 to 1:5; the nanoparticles obtained in step S1 are mixed evenly with the resin material and dried and crushed at a drying temperature of 100 to 200° C. for a drying time of 24 to 48 hours; the median particle size after crushing is 5 to 20 μm.

8. The method for preparing a silicon-carbon negative electrode material with high cycle stability according to claim 5, characterized in that: The silicon-carbon intermediate powder obtained in step S2 is mixed evenly with the metal salt and then sintered to obtain a sintered material, which is then crushed and sieved to obtain a silicon-carbon negative electrode material with high cycle stability.

9. The method for preparing a silicon-carbon negative electrode material with high cycle stability according to claim 8, characterized in that: 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 according to a weight ratio of silicon-carbon intermediate powder to aluminum salt of 50:1 to 200:

1.

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

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