Conductive metal oxide-coated silicon-carbon materials, their preparation and use in lithium-ion batteries

Abstract

The application discloses a kind of electrically conductive metal oxide coated silicon-carbon material and its preparation method in lithium ion battery application, belong to lithium ion battery material technical field.The electrically conductive metal oxide coated silicon-carbon material is obtained after metal hydroxide coated silicon-carbon material is annealed calcination dehydration under protective atmosphere;The precursor of the metal oxide synthesized in situ on the surface of silicon-carbon material is prepared by stirring at room temperature, ultrasonic treatment, hydrothermal reaction or reflux, suction filtration washing and drying from silicon-carbon material and inorganic solution containing metal ions.The electrically conductive metal oxide coated silicon-carbon material can be used as lithium ion battery negative material, applied in high-power, high-energy density field such as power battery, with high specific capacity, high initial efficiency, excellent long cycle.

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 metal oxide-coated silicon-carbon material and a preparation method and application thereof, wherein the application is mainly as a negative electrode material for lithium-ion batteries. Background Art

[0002] Lithium-ion batteries have been used in all aspects of life due to their excellent properties such as high energy density, lightweight, long life and zero memory. However, with the vigorous development of new energy vehicles, traditional lithium-ion batteries can no longer meet the public's growing demand for power batteries. Therefore, further improving the energy density, fast charging and discharging performance and cycle stability of commercial lithium-ion batteries is urgent. Silicon is considered to be the most promising negative electrode material for the next generation of lithium-ion batteries due to its abundant reserves and ultra-high specific capacity (4200mAh·g-1). However, its disadvantages are also obvious. As a common semiconductor, silicon itself has poor conductivity and the volume expansion of the material is severe (~400%) during the cycle, which leads to material shattering and repeated generation of solid electrolyte membranes, and ultimately irreversible capacity decay.

[0003] The most common method is to reduce the particle size of silicon to buffer the volume change of the material during lithium insertion and extraction, or to wrap a carbon shell in the outer layer of the silicon particles, while slowing down the volume change of the internal silicon particles, further improving the conductivity of the material. For example, Fan et al. (Z.Fan, S.Zheng, S.He, Y.Ye, J.Liang, A.Shi, Z.Wang, Z.Zheng, Preparation of micron Si@C anodes for lithium ion battery by recycling thelamellar submicron silicon in the kerf slurry waste from photovoltaicindustry, Diamond&Related Materials, 107 (2020) 107898.) a silicon-carbon material with a core-shell structure of about 1 μm in diameter is prepared by a hydrothermal method, ample space is provided for the expansion of silicon material, and at the same time, carbon material enhances the conductivity of the composite material, and the capacity retention rate of the composite material is significantly improved after coating. At a current density of 0.1C, after 200 cycles, the capacity of the pure silicon wafer material has dropped to below 100mA h g-1, while the capacity of the composite material can reach 1788.9mA h g-1. In the rate performance test, the capacity of the composite material can reach 1446.8mA h g-1 at a current density of 1C, which is a significant improvement. However, the testing conditions for the materials obtained by this technology are relatively mild, with a low current density (0.1C) and a short test cycle (100 cycles), which is not conducive to reflecting the application of the material in actual scenarios; and the hydrothermal temperature in this technical route reaches 190°C, and the corresponding pressure in the container reaches more than 1MPa. These factors are not conducive to the commercial application of this material.

[0004] Metal oxides are also considered to be applicable to lithium-ion batteries due to their high specific capacity. Among them, tin oxide (SnO2) has received strong attention from scientific researchers. Antimony-doped tin oxide (ATO) is widely welcomed in the fields of advanced functional materials such as photovoltaics, catalysis, and energy storage devices due to its high optical transparency, good conductivity, high cycle stability, and low cost. For example, Zhang et al. (Q. Zhang, Q. Gao, W. Qian, H. Zhang, W. Tian, ​​Z. Li, A C-coated and Sb-doped SnO2 nanocompsite with high surface area and low charge transfer resistance as ultrahigh capacity lithium ion battery anode, Materials Today Energy, Materials Today Energy, 13 (2019) 93-99.) prepared ATO powder by a hydrothermal method, and then coated glucose by a hydrothermal method and carbonized at high temperature to obtain ATO / C composite material (carbon-coated ATO). At a current density of 0.1C, its initial discharge capacity reached 2634.9 mA h g⁻¹. After 1000 cycles at a current density of 1C, it maintained a discharge capacity of 1008.5 mA h g⁻¹. Furthermore, the composite material maintained a reversible capacity of 370 mA h g⁻¹ at a high current density of 10C. This effect is likely due to the reduced charge transfer resistance of the composite material due to antimony doping and carbon coating. However, this technology relies on expensive ATO as the primary source of negative electrode material capacity. Furthermore, the hydrothermal reaction used to synthesize ATO powder involves high temperatures and pressures, placing high demands on the container's high-pressure resistance.

[0005] Chinese invention patent application CN116632223A discloses a metal-doped amorphous carbon-coated silicon-carbon material, its preparation method, and application. The material comprises a core structure and a shell structure coated on the core structure. The core structure comprises porous carbon particles and nano-silicon grains deposited within the porous carbon by silane cracking, while the shell structure comprises metal and amorphous carbon generated by cracking an organometallic compound. Preparation steps: Step S1: placing the porous carbon in a vapor deposition furnace, passing a silane mixture into the furnace for at least one hour, depositing nano-silicon within the porous carbon to obtain a porous carbon deposited with nano-silicon; Step S2: transferring the nano-silicon-deposited porous carbon obtained in Step S1) to a vacuum reactor, passing a vaporized organometallic compound into the vacuum reactor for deposition; Step S3: obtaining the metal-doped amorphous carbon-coated silicon-carbon material. This technology utilizes the reducing properties of carbon to deposit metal on the surface of the silicon-carbon material, improving the electron transport capacity of the composite material and resulting in a significant improvement in both cycling stability and initial coulombic efficiency. However, the organic metal compound deposition process in this technology requires vacuum conditions to prevent oxidation of extremely small metals, increase the cracking reaction rate, and prevent the introduction of impurities. Furthermore, the silane cracking method is flammable and explosive, the process is dangerous, and requires high production equipment. These factors have restricted the commercial application of this technology route. Furthermore, nanometallic materials (such as Cu and Ni) are prone to react with the electrolyte during long-term cycling, leading to electrode failure or performance degradation. Especially at high potentials, some metals are prone to electrochemical corrosion or dissolution, which may trigger electrolyte degradation and lead to electrode failure. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of poor charge transfer performance and complex preparation process of existing silicon-carbon materials, and to provide a conductive metal oxide-coated silicon-carbon material and its preparation method with simple process, low cost, good safety, environmental friendliness, good cycle stability and low capacity loss rate, and the advantage of large-scale production.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A method for preparing a metal oxide-coated silicon-carbon material, characterized by comprising the following steps:

[0009] 1) dispersing the silicon-carbon material, the reactive surface regulator, and the pH regulator in water by ultrasonication to obtain a reaction solution;

[0010] 2) dissolving a metal ion compound and a ligand in an alcohol solvent to form a coating solution; adding the coating solution to the reaction solution, heating to 70-95° C. and maintaining the temperature for 2-6 hours to obtain a precursor slurry; the ligand is one or more of citric acid, tartaric acid, and thioglycolic acid; and the metal ion compound is tin tetrachloride pentahydrate, antimony trichloride, or indium nitrate;

[0011] 3) After the precursor slurry is cooled, it is filtered under reduced pressure, dried, and washed;

[0012] 4) calcining the washed precursor in two stages to obtain a metal oxide-coated silicon-carbon material; the first stage of the two-stage calcination is annealing and calcining at 180-250° C. in an air atmosphere, and the second stage of the calcination is annealing and calcining at 400-550° C. in an inert atmosphere for 1.5-3 hours.

[0013] To further achieve the purpose of the present invention, preferably, the reactive surface conditioner is one or more of oleyl alcohol, hexadecyltrimethylammonium bromide, sodium oleate and polyvinylpyrrolidone; the pH adjuster is one or more of urea, tetramethylammonium hydroxide and ammonium bicarbonate; the molar ratio of the pH adjuster to the metal ion compound is 3 to 8:1; and the mass ratio of the silicon-carbon material to the reactive surface conditioner is 10 to 30:1.

[0014] Preferably, the alcohol solvent is one or more of ethanol, isopropanol, propylene glycol, methanol and butanol; the mass ratio of the metal ion compound to the ligand is 10 to 50:1; and the mass ratio of the alcohol solvent to the metal ion compound is 10 to 60:1.

[0015] Preferably, the first calcination period is 50 to 90 minutes; the second calcination period is 1.5 to 3 hours; and the heating rates of the first and second calcinations are both 3 to 8° C. / min.

[0016] Preferably, the ultrasonic dispersion time is 30 to 60 minutes, and the ultrasonic frequency is 20 to 90 kHz; the coating liquid is added to the reaction liquid under the action of a peristaltic pump; and the flow rate of the peristaltic pump is set to 0.5 to 3 ml / min.

[0017] Preferably, the silicon-carbon material is a core-shell structure in which a carbon shell encapsulates silicon particles, wherein the mass proportion of silicon particles is 40-90 wt.%; the mass proportion of the carbon shell is 10-60 wt.%;

[0018] The washing detergents are deionized water and ethanol; the drying temperature is 40 to 80° C., and the drying time is 12 to 24 hours.

[0019] A metal oxide-coated silicon-carbon material is prepared by the above-mentioned preparation method.

[0020] The invention discloses an application of a metal oxide-coated silicon-carbon material as a negative electrode material for a lithium-ion battery.

[0021] Preferably, the application process is: mixing the metal oxide-coated silicon-carbon material, carbon black and carboxymethyl cellulose or polyacrylic acid to prepare a slurry, and coating the slurry on a copper foil to obtain a negative electrode sheet for a lithium-ion battery.

[0022] Preferably, the mass ratio of the metal oxide-coated silicon-carbon material, carbon black and carboxymethyl cellulose or polyacrylic acid is (6-8):(1-2):(1-2).

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1) The conductive metal oxide-coated silicon-carbon material of the present invention attaches the conductive metal oxide to the surface of the silicon-carbon material by hydrolysis of alcohol salts. The combination of the two significantly reduces the surface resistance of the silicon-carbon material, promotes electron transport, weakens the polarization phenomenon of the material during the cycle, and improves the electrochemical properties of the silicon-carbon material.

[0025] 2) The present invention uses a two-stage calcination method. The first stage of air calcination causes most of the antimony element in the conductive metal oxide ATO to exist in a pentavalent form, thereby providing more free electrons and holes and improving the conductive properties of the composite material.

[0026] 3) The present invention utilizes the strong conductivity of conductive metal oxides to form a highly conductive coating on the surface of the silicon-carbon material, thereby improving the electron transmission capacity of the silicon-carbon material and fully utilizing the lithium storage capacity of the composite material. When the conductive metal oxide-coated silicon-carbon material synthesized by the present invention is applied to the negative electrode of a lithium-ion battery, when the silicon content is 85%, the electrochemical test results show that compared with the control sample without manganese oxide particles, the material performs excellently: at 25°C and a current density of 2A·g-1, it can maintain a capacity of 1053.53mAh·g-1 after 500 cycles; and it can maintain a capacity of 842.23mAh·g-1 after 500 cycles at a current density of 4A·g-1. This shows that the material obtained by the present invention has excellent resistance to large current interference and lithium ion transmission capabilities, providing a good reference for the development of the field of fast charging and fast discharging of lithium-ion batteries.

[0027] 4) The conductive metal oxide-coated silicon-carbon material of the present invention exhibits a two-dimensional sheet stacking structure, with the surface uniformly coated with nano-scale conductive metal oxides. There are chemical bonds between the internal silicon sheet and the carbon shell to maintain the structural stability of the material.

[0028] 5) The conductive metal oxide-coated silicon-carbon material of the present invention is used as a high-performance lithium-ion battery negative electrode material, with excellent electron transfer rate, long cycle stability, slow capacity decay at high current density and high specific capacity, and has great application potential in the field of power batteries such as new energy vehicles.

[0029] 6) The technical route and method adopted by the present invention are simple, the process is simple, efficient, and low-cost, and the reagents used are safe and environmentally friendly, and have practical prospects for commercialization and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is the SEM image of the silicon powder used in Example 1.

[0032] Figure 2 This is the SEM image of the silicon-carbon material obtained in Example 1.

[0033] Figure 3 This is the SEM image of the ATO-coated silicon-carbon material prepared in Example 1.

[0034] Figure 4 This is the TEM image of the ATO-coated silicon-carbon material prepared in Example 1.

[0035] Figure 5 These are XRD results of the ATO-coated silicon-carbon materials and silicon-carbon materials prepared in Examples 1, 5, 7 and the comparative example.

[0036] Figure 6 This is the full XPS spectrum of the ATO-coated silicon-carbon material prepared in Example 1.

[0037] Figure 7 This is the XPS high-resolution spectrum of Si 2p of the ATO-coated silicon-carbon material prepared in Example 1.

[0038] Figure 8 This is the XPS high-resolution spectrum of Sn 3d of the ATO-coated silicon-carbon material prepared in Example 1.

[0039] Figure 9 This is the XPS high-resolution spectrum of C1s of the ATO-coated silicon-carbon material prepared in Example 1.

[0040] Figure 10 This is the CV diagram of the ATO-coated silicon-carbon material prepared in Example 1.

[0041] Figure 11 The ATO-coated silicon-carbon material prepared in Example 1 was heated to 2A g -1 Long cycle performance diagram at different current densities.

[0042] Figure 12 The ATO-coated silicon-carbon material prepared in Example 1 was heated to 4A g -1 Long cycle performance diagram at different current densities.

[0043] Figure 13 The ATO-coated silicon-carbon material prepared in Example 1 is 0.5-8.0A g -1 Rate performance diagram at different current densities.

[0044] Figure 14 This is a comparison chart of the EIS impedance after the first cycle of the ATO-coated silicon-carbon material obtained in Example 1 and the silicon-carbon material obtained in Comparative Example 1.

[0045] Figure 15 The resistivity data obtained by testing the resistivity of the ATO-coated silicon-carbon material obtained in Example 1 and the silicon-carbon material obtained in Comparative Example 1 by the four-probe method are compared.

[0046] Figure 16 This is the XRD result of the ATO-coated silicon-carbon material obtained in Comparative Example 3.

[0047] Figure 17 This is the TEM image of the ATO-coated silicon-carbon material obtained in Comparative Example 4. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The present invention will be further explained by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0049] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms "a," "the," and "the" used in this disclosure are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0050] Unless otherwise specified, the raw materials used in the present invention are products that can be directly purchased on the market or synthesized by existing methods.

[0051] The submicron silicon-carbon material of the present invention is a core-shell structure in which a carbon shell wraps silicon particles, wherein the mass of the silicon particles accounts for 40-90wt.%; the mass of the carbon shell accounts for 10-60wt.%; the diameter of the silicon particles of the submicron silicon-carbon material is 100-800nm, and the thickness of the carbon shell is 8-12nm.

[0052] Synthesis of Si@C-1 material: See Chinese invention patent CN113644252B, in which a core-shell structured Si@C material is obtained by ball milling silicon powder with asphalt, spray drying, and sintering in a coating machine.

[0053] Synthesis of Si@C-2 material: See Chinese invention patent CN110931725B. A core-shell structured Si@C material was obtained by hydrothermally mixing phenol, formaldehyde and amino-modified silicon nanoparticles, and then calcining at high temperature after filtration.

[0054] Synthesis of Si@C-3 material: See Chinese invention patent application CN113328096A. Glucose, silicon powder and surfactant are placed in a reactor for hydrothermal reaction. After the reaction is completed, the precursor is filtered and dried to obtain a precursor, and the precursor is calcined at high temperature to obtain a core-shell structure Si@C composite material.

[0055] The metal oxide-coated silicon-carbon material of the present invention is prepared by calcining a metal oxide precursor synthesized in situ on the surface of the silicon-carbon material through two stages; the precursor for the metal oxide synthesized in situ on the surface of the silicon-carbon material is prepared by dripping an organic mixed solution containing a metal inorganic salt into a mixed solution containing the silicon-carbon material that has been stirred at room temperature and ultrasonically treated, followed by hydrothermal reaction, filtration and washing; specifically, the preparation method of the metal oxide-coated silicon-carbon material of the present invention comprises the following steps:

[0056] 1) dispersing the silicon-carbon material, the reactive surface regulator, and the pH regulator in water by ultrasonication to obtain a reaction solution;

[0057] 2) dissolving a metal ion compound and a ligand in an alcohol solvent to form a coating solution; adding the coating solution to the reaction solution, heating to 70-95° C. and maintaining the temperature for 2-6 hours to obtain a precursor slurry; the ligand is one or more of citric acid, tartaric acid, and thioglycolic acid; and the metal ion compound is tin tetrachloride pentahydrate, antimony trichloride, or indium nitrate;

[0058] 3) After the precursor slurry is cooled, it is filtered under reduced pressure, dried, and washed;

[0059] 4) calcining the washed precursor in two stages to obtain a metal oxide-coated silicon-carbon material; the first stage of the two-stage calcination is annealing and calcining at 180-250° C. in an air atmosphere, and the second stage of the calcination is annealing and calcining at 400-550° C. in an inert atmosphere for 1.5-3 hours.

[0060] The main features of the metal oxide-coated silicon-carbon material and its preparation method of the present invention are a two-stage calcination process with a selected metal ion compound and the in-situ growth of conductive metal oxide nanoparticles on the surface of the silicon-carbon material. The present invention achieves in-situ growth of conductive metal oxide nanoparticles on the surface of the silicon-carbon material through an alkoxide hydrolysis method. This method first dissolves the metal salt in an alcohol solvent to form a metal alkoxide coating solution, then introduces the coating solution into the reaction solution, and adds a ligand (also a complexing agent) to cooperate with hydrolysis to complete the reaction process. During the hydrolysis process, the metal complex is an intermediate product of the reaction. The addition of the complexing agent (i.e., the ligand) controls the reaction rate, avoids the uneven precipitation caused by local excessive alkalinity due to the addition of an alkaline precipitant, and achieves uniform mixing at the atomic level, ultimately resulting in uniform coating of the metal oxide on the surface of the silicon-carbon material. The present invention then undergoes a two-step annealing and calcination process, based on the carbon layer in the non-oxidized silicon-carbon material, and incorporates a high-valent metal into the lattice of another metal oxide, successfully constructing a conductive metal oxide-coated silicon-carbon material with free electrons and oxygen vacancies. The above two measures significantly reduce the resistivity and interface resistance of the metal oxide-coated silicon-carbon material of the present invention, improve the charge transfer capacity of the metal oxide-coated silicon-carbon material, promote the utilization of the capacity of the composite material under higher current density, alleviate the interface polarization phenomenon, and thus improve the cyclic stability of the material. In addition to the above two process measures, the selection of metal-containing inorganic salts, tetravalent tin salts, trivalent antimony salts (or trivalent indium salts) and ligands are important measures in the above two aspects. As for the alcohol solvent, silicon-carbon material, reactive surface modifier, pH modifier and its dosage, they can be selected in combination with the existing technology under the purpose of the present invention, and other process conditions can also be obtained through experiments in combination with the existing technology under the purpose of the present invention. Among them, the preferred reactive surface modifier is one or more of oleyl alcohol, hexadecyltrimethylammonium bromide, sodium oleate and polyvinylpyrrolidone. The silicon-carbon material is a core-shell structure of silicon particles wrapped in a carbon shell, which is a material already available in the prior art, wherein the mass proportion of silicon particles is 40-90wt.%; the mass proportion of carbon shell is 10-60wt.%.

[0061] It should be noted that ATO, as a conductive metal oxide, has been commercially applied in conductive glass and other fields, and researchers have made some attempts to coat ATO with silicon. Lee et al. (J. Lee, E. Lee, J. Park, S. Park, S. Lee, Ultrahigh-Energy-Density Lithium-ion Batteries Based on a High-Capacity Anode and a High-Voltage Cathode with an Electroconductive Nanoparticle Shell, (2014) 8) stirred, filtered, and calcined Si and a purchased finished ATO colloid to obtain a Si@ATO composite material, which greatly improved its electron transport capacity and effectively utilized the capacity of the silicon material. However, due to the lack of carbon material coating, its cycle retention rate is poor; and the use of finished ATO coating can also cause problems of uneven coating and high cost. In addition, the ATO material itself has the problem of low initial coulombic efficiency during the lithium storage process, all of which restrict its application.

[0062] The conductive metal oxide-coated silicon-carbon material of the present invention uses in-situ generated nano-scale conductive metal oxide powder to coat the surface of the silicon-carbon material to form a conductive network, which more effectively improves the electron transmission capability and greatly enhances the capacity of the composite material under high current density. By coating a small amount of ATO material on the surface and in the pores of the carbon material, the first coulombic efficiency of the target material does not decrease significantly. In particular, the precursor synthesis stage of the present invention is carried out at normal pressure and below 100°C, which has low requirements for instruments and equipment and low cost, and is very conducive to the low-cost large-scale production of silicon-carbon materials.

[0063] The present invention performs characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and four-probe resistance measurement on the materials prepared in the examples and comparative examples to analyze information such as the material morphology, component content, and chemical bond type.

[0064] Example 1

[0065] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0066] 1) Synthesis of silicon-carbon material: Referring to the method of Chinese invention patent CN113644252B, 1 kg of silicon powder and 200 g of asphalt were mechanically ball-milled for 4 h, and then added to a coating machine and calcined at 900°C for 2 h to obtain a core-shell silicon-carbon material. The obtained silicon-carbon material was named Si@C-1; Figure 1This is an SEM image of the silicon powder used in Example 1, showing the submicron-scale two-dimensional silicon wafers obtained by sand grinding; Figure 2 This is the SEM image of the silicon-carbon material obtained in Example 1. After carbon coating, a silicon-carbon material with a submicron size is obtained. It can be observed that the carbon layer is evenly coated on the surface of the silicon material. Figure 5 Shows the XRD results of the silicon-carbon material Si@C-1 of this embodiment.

[0067] 2) Take a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, 0.04 g of tartaric acid, and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0068] 3) Take a 1L beaker, add 10g of silicon-carbon material, 0.5g of hexadecyltrimethylammonium bromide, 1.25g of urea, and 400ml of water to the beaker, and mix them by ultrasonication for 30min to obtain a reaction solution;

[0069] 4) The reaction solution obtained in step (3) was heated to 90° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0070] 5) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-1.

[0071] Figure 3 This is a SEM image of the ATO-coated silicon-carbon material prepared in Example 1. The scanning electron microscope image shows that the final target material presents a two-dimensional submicron flaky structure.

[0072] Figure 4 This is a TEM image of the ATO-coated silicon-carbon material prepared in Example 1. In the image, Si-C-ATO layers arranged from the inside to the outside can be observed, which proves that the ATO-coated silicon-carbon material is obtained by hydrolysis of alcohol salts. The 3-5 nm ATO nanoparticles in the composite material are coated on the surface of the silicon-carbon material. The extremely small size of the nanoparticles also reduces the possibility of breakage of the ATO material during the cycle, constructs a unique and stable conductive network, and greatly contributes to the electron transmission of the composite material. At the same time, the small gaps left between the nanoparticles form abundant lithium ion diffusion paths, which accelerate the electrolyte penetration process and allow the electrolyte to fully infiltrate the interior of the material.

[0073] Figure 5 The XRD results of the ATO-coated silicon-carbon material Si@C@ATO-1 prepared in Example 1 are also shown. The figure shows the characteristic peak corresponding to SnO2 and no characteristic peak of Sb2O5, which proves the successful coating of ATO and the successful doping of Sb.

[0074] Figure 6 This is the full XPS spectrum of the ATO-coated silicon-carbon material Si@C@ATO-1 prepared in Example 1. The presence of ATO powder can be confirmed in the full spectrum.

[0075] Figure 7 This is the XPS high-resolution spectrum of Si 2p of the ATO-coated silicon-carbon material Si@C@ATO-1 prepared in Example 1. The presence of Si-OC bonds indicates that the Si and C layers are not in simple physical contact, but a more stable coating structure is formed by chemical bonds.

[0076] Figure 8 This is the XPS high-resolution spectrum of Sn 3d of the ATO-coated silicon-carbon material Si@C@ATO-1 prepared in Example 1. 5 / 2 and Sn 3d 3 / 2 The peaks indicate that Sn exists in the form of oxides.

[0077] Figure 9 This is the XPS high-resolution spectrum of C1s of the ATO-coated silicon-carbon material Si@C@ATO-1 prepared in Example 1. The presence of CO bonds and C-Si bonds in the figure further confirms the stable structure of Si-C composed of chemical bonds.

[0078] Figure 10 This is a CV graph of the ATO-coated silicon-carbon material prepared in Example 1. The anodic peaks at 0.35V and 0.51V, and the cathodic peak at 0.2V, are characteristic peaks of the silicon electrode charge and discharge processes. Furthermore, the cathode and anodic peaks intensify with cycling, demonstrating improved electrochemical kinetics during cycling.

[0079] The following examples are related to the raw materials, intermediate products and target products. Figure 1-10 Basically similar, not provided one by one.

[0080] Weigh 0.14g of the prepared ATO-coated silicon-carbon material Si@C@ATO-1, 0.03g of carboxymethyl cellulose binder, and 0.03g of conductive carbon black, grind them thoroughly in a mortar and transfer them to a finger bottle. Add 2ml of distilled water, and after magnetic stirring for 12h, use a glass rod to coat the material on a flat copper foil. After the material is dried, press it into a sheet to make an electrode. Use a metal lithium sheet as the counter electrode and assemble it into a CR2016 button battery in a glove box.

[0081] Example 2

[0082] A method for preparing an ITO-coated silicon-carbon material comprises the following steps:

[0083] 1) In a 100 ml beaker, add 1.055 g of indium nitrate pentahydrate, 0.1262 g of tin tetrachloride pentahydrate, 0.06 g of citric acid, and 40 ml of isopropanol and stir to dissolve to obtain a coating solution;

[0084] 2) Take a 1 L beaker, take 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.8 g of oleyl alcohol, 0.5 g of ammonium bicarbonate, and 400 ml of water, add them to the beaker, and mix them evenly by ultrasonication for 30 min to obtain a reaction solution;

[0085] 3) The reaction solution obtained in step (2) was heated to 95° C. in a water bath, and the coating solution obtained in step (1) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 2 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ITO precursor-coated silicon-carbon material.

[0086] 4) After the powdered ITO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 550°C, kept warm for 2 hours, and cooled to room temperature to obtain the ITO-coated silicon-carbon material Si@C@ITO.

[0087] The process for producing CR2016 button battery is the same as that in Example 1.

[0088] Example 3

[0089] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0090] 1) Synthesis of silicon-carbon materials: Referring to Z. Fan, S. Zheng, S. He, Preparation of micron Si@Canodes for lithium ion battery by recycling the lamellar submicron silicon in the kerf slurry waste from photovoltaic industry, Diamond and Related Materials, 107(2020)107898, 200 g of nano-Si sheets, 300 g of glucose, 5 g of CTAB and 3 L of water were placed in a reactor, reacted at 180 ° C for 5 h, filtered and dried, and calcined at 900 ° C for 2 h under Ar atmosphere to obtain a silicon-carbon material and named Si@C-2.

[0091] 2) In a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, 0.05 g of thioglycolic acid, and 40 ml of methanol and stir to dissolve to obtain a coating solution;

[0092] 3) Take a 1L beaker, add 10g of silicon-carbon material, 0.5g of sodium oleate, 1.0g of tetramethylammonium hydroxide, and 400ml of water to the beaker, and mix them by ultrasonication for 30min to obtain a reaction solution;

[0093] 4) The reaction solution obtained in step (3) was heated to 90° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 2.5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0094] 5) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-2.

[0095] The process for producing CR2016 button battery is the same as that in Example 1.

[0096] Example 4

[0097] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0098] 1) Synthesis of Silicon-Carbon Material: Referring to Chinese invention patent CN109817962A, 600 g of nano-Si sheets, 20 g of CTAB, 260 ml of ammonia, 120 g of resorcinol, 190 ml of formaldehyde, and 20 l of water were added to a reactor and heated to 80°C for 24 h. After the reaction, the mixture was filtered, dried, and calcined at 900°C under an Ar atmosphere for 2 h to obtain a core-shell Si@C composite material named Si@C-3.

[0099] 2) Take a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, 0.04 g of tartaric acid, and 40 ml of butanol and stir to dissolve to obtain a coating solution;

[0100] 3) Take a 1L beaker, add 10g of silicon-carbon material, 0.5g of polyvinyl pyrrolidone, 1.25g of urea, and 400ml of water to the beaker, and mix them by ultrasonication for 30min to obtain a reaction solution;

[0101] 4) The reaction solution obtained in step (3) was heated to 85° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 3 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0102] 5) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-3.

[0103] The process for producing CR2016 button battery is the same as that in Example 1.

[0104] Example 5

[0105] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0106] 1) Take a 100 ml beaker, add 2.5 g of tin tetrachloride pentahydrate, 0.20 g of antimony trichloride, 0.12 g of tartaric acid, and 40 ml of propylene glycol and stir to dissolve to obtain a coating solution;

[0107] 2) Take a 1 L beaker, take 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 2.5 g of urea, and 400 ml of water, add them to the beaker, and mix them evenly by ultrasonication for 30 min to obtain a reaction solution;

[0108] 3) The reaction solution obtained in step (2) was heated to 80° C. in a water bath, and the coating solution obtained in step (1) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 3.5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0109] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-4. Figure 5 Also shown are the XRD results for the ATO-coated silicon-carbon material Si@C@ATO-4, prepared in Example 1. The characteristic peaks in the figure are consistent with those on the standard card, while the intensity of the characteristic peak corresponding to SnO2 is higher than that of Si@C@ATO-1, demonstrating the increased ATO coating content.

[0110] The process for producing CR2016 button battery is the same as that in Example 1.

[0111] Example 6

[0112] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0113] 1) Take a 100 ml beaker, add 3.75 g of tin tetrachloride pentahydrate, 0.30 g of antimony trichloride, 0.12 g of tartaric acid, and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0114] 2) Take a 1 L beaker, take 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 3.75 g of urea, and 400 ml of water, add them to the beaker, and ultrasonicate for 30 min to mix them evenly to obtain a reaction solution;

[0115] 3) The reaction solution obtained in step (2) was heated to 75° C. in a water bath, and the coating solution obtained in step (1) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 4 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0116] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-5.

[0117] The process for producing CR2016 button battery is the same as that in Example 1.

[0118] Example 7

[0119] A method for preparing an ATO-coated silicon-carbon material comprises the following steps:

[0120] 1) Take a 100 ml beaker, add 0.625 g of tin tetrachloride pentahydrate, 0.05 g of antimony trichloride, 0.02 g of tartaric acid, and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0121] 2) Take a 1 L beaker, take 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 0.625 g of urea, and 400 ml of water, add them to the beaker, and ultrasonicate for 30 min to mix them evenly to obtain a reaction solution;

[0122] 3) The reaction solution obtained in step (2) was heated to 70° C. in a water bath, and the coating solution obtained in step (1) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 4.5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0123] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-6. Figure 5 Also shown are the XRD results for the ATO-coated silicon-carbon material Si@C@ATO-6, prepared in Example 1. The characteristic peaks in the figure are consistent with those on the standard card, while the intensity of the characteristic peak corresponding to SnO2 is lower than that of Si@C@ATO-1, demonstrating a decrease in the ATO coating amount.

[0124] The process for producing CR2016 button battery is the same as that in Example 1.

[0125] Comparative Example 1 (Silicon-carbon material without metal oxide coating)

[0126] Synthesis of silicon-carbon materials: Referring to the method described in Chinese invention patent CN113644252A, 1 kg of silicon powder and 200 g of asphalt were mechanically ball-milled for 4 hours, then placed in a coating machine and calcined at 900°C for 2 hours to obtain a core-shell silicon-carbon material. The silicon-carbon material obtained by this step is named Si@C@1.

[0127] The process for producing CR2016 button battery is the same as that in Example 1.

[0128] Comparative Example 2 (Effect of Air Calcination)

[0129] 1) Take a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, 0.04 g of tartaric acid, and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0130] 2) Take a beaker with a capacity of 1 liter, add 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 1.25 g of urea, and 400 ml of water into the beaker, and mix them uniformly by ultrasonication for 30 minutes to obtain a reaction solution;

[0131] 3) The reaction solution obtained in step (3) was heated to 90° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0132] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-7.

[0133] The process for producing CR2016 button battery is the same as that in Example 1.

[0134] Comparative Example 3 (composition alloy coating)

[0135] 1) Take a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, 0.04 g of tartaric acid, and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0136] 2) Take a beaker with a capacity of 1 liter, add 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 1.25 g of urea, and 400 ml of water into the beaker, and mix them uniformly by ultrasonication for 30 minutes to obtain a reaction solution;

[0137] 3) The reaction solution obtained in step (3) was heated to 90° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0138] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 750°C, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-8.

[0139] The process for producing CR2016 button battery is the same as that in Example 1.

[0140] Comparative Example 4 (changing the reaction steps and using coprecipitation method)

[0141] 1) Take a beaker with a capacity of 1 liter, add 10g of the silicon-carbon material obtained in step (1) of Example 1, 0.5g of hexadecyltrimethylammonium bromide, and 400ml of water into the beaker, and mix them uniformly by ultrasonication for 30 minutes to obtain a reaction solution;

[0142] 2) Add 1.25 g of tin tetrachloride pentahydrate, 0.10 g of antimony trichloride, and 0.04 g of tartaric acid to the reaction solution;

[0143] 3) Use a peristaltic pump (flow rate set at 2 ml / min) to drop 10 ml of ammonia water (25%) into the resulting reaction solution (stirring continuously during the addition process). After the addition is complete, heat to 90°C and keep warm for 2 hours. After the reaction is complete, cool to room temperature and filter, wash three times with deionized water and anhydrous ethanol respectively, and place in an oven at 60°C for 24 hours to obtain a powdered ATO precursor-coated silicon-carbon material.

[0144] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 500 degrees Celsius, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-9.

[0145] The process for producing CR2016 button battery is the same as that in Example 1.

[0146] Comparative Example 5 (no Sb doping)

[0147] 1) Take a 100 ml beaker, add 1.25 g of tin tetrachloride pentahydrate and 40 ml of ethanol and stir to dissolve to obtain a coating solution;

[0148] 2) Take a beaker with a capacity of 1 liter, add 10 g of the silicon-carbon material obtained in step (1) of Example 1, 0.5 g of hexadecyltrimethylammonium bromide, 1.25 g of urea, and 400 ml of water into the beaker, and mix them uniformly by ultrasonication for 30 minutes to obtain a reaction solution;

[0149] 3) The reaction solution obtained in step (3) was heated to 90° C. in a water bath, and the coating solution obtained in step (2) was slowly dripped into the reaction solution using a peristaltic pump (flow rate set at 2 ml / min). After the addition was completed, the solution was kept warm and refluxed for 5 h. After the reaction was completed, the solution was cooled to room temperature and filtered, washed three times with deionized water and anhydrous ethanol, respectively, and dried in an oven at 60° C. for 24 h to obtain a powdered ATO precursor-coated silicon-carbon material.

[0150] 4) After the powdered ATO precursor-coated silicon-carbon material is evenly spread in a porcelain boat, it is heated to 250 degrees Celsius in an air atmosphere in a tube furnace and kept warm for 1.5 hours. Subsequently, the tube furnace is ventilated under an argon atmosphere for 30 minutes, and then heated to 650°C, kept warm for 2 hours, and cooled to room temperature to obtain the ATO-coated silicon-carbon material Si@C@ATO-10.

[0151] The process for producing CR2016 button battery is the same as that in Example 1.

[0152] Performance test: The present invention tests the surface resistance, long cycle stability, resistance to large current interference and lithium storage performance of the material through constant current charge and discharge, rate performance test, impedance and long cycle test. After the batteries prepared in the embodiment of the present invention were left for 24 hours, they were all tested using a battery tester (Shenzhen Xinwei) and BTS 8.0.0 software at a temperature of 25°C and a current density of 0.2-8A g -1 , various types of batteries are charged and discharged at constant current (discharge cut-off voltage is 0.01V, charge cut-off voltage is 2V) to test the long-term cycle performance of the battery.

[0153] Table 1 shows the electrochemical performance test results of the conductive metal oxide-coated silicon-carbon materials prepared in Examples 1-7 at 25°C.

[0154] Table 1

[0155]

[0156] Figure 11 The ATO-coated silicon-carbon material prepared in Example 1 was heated to 2A g -1 Long cycle performance diagram at different current densities. Figure 12 The ATO-coated silicon-carbon material prepared in Example 1 was heated to 4A g -1 Long cycle performance diagram under current density.

[0157]

[0158] The material showed good electrochemical performance, especially at high current density (4A g -1 ) under the condition of high temperature, high humidity and low humidity, the long cycle curve of the composite material electrode is smooth, showing a higher specific capacity and the capacity retention rate has made great progress compared with the control example.

[0159] Figure 13 The ATO-coated silicon-carbon material prepared in Example 1 is 0.5-8.0A g -1 The rate performance test diagram under current density is 8.0A g -1 A high charge capacity of 1034.21 can still be achieved at high current density, showing excellent rate performance. The rate performance is closely related to the electron transport capacity of the electrode, which proves that the electron transport capacity of the composite material has made great progress through coating.

[0160] Figure 14 This is a comparison chart of the EIS impedance after the first cycle of the ATO-coated silicon-carbon material obtained in Example 1 and the silicon-carbon material obtained in Comparative Example 1. In the figure, the semicircle diameters corresponding to the electron transfer impedance and SEI film impedance of Example 1 are smaller than those of Comparative Example 1, proving that the electron transfer impedance and SEI film impedance of the composite material are greatly reduced through ATO coating, which helps to improve the rate performance and cycle life of the battery and enhance the electrochemical reaction activity of the material.

[0161] Figure 15 The resistivity data of the ATO-coated silicon-carbon material obtained in Example 1 and the silicon-carbon material obtained in Comparative Example 1 were compared by four-probe method. The average resistivity of the sample obtained in Example 1 was 2522 Ωcm. -1 The resistivity of the sample obtained in comparative example 1 is 6655Ωcm -1 The measured data further show that after ATO coating, the resistivity and electron transfer impedance of the composite material are greatly reduced. Figure 14 The eis impedance test results confirm each other.

[0162] Comparative Example 1 is a silicon-carbon material without ATO coating. Due to the high resistivity of the silicon-carbon material and the side reactions and polarization problems during the cycle, it performs poorly in long-cycle and rate performance tests.

[0163] Comparative Example 2 is a sample that did not undergo two-stage calcination. The lack of two-stage calcination makes it difficult for Sb to be doped into SnO2 in the pentavalent form, and ultimately makes it impossible to successfully construct the highly conductive ATO coating of the silicon-carbon material. The resistivity of the composite material is difficult to significantly reduce, so that although the first coulombic efficiency of the composite material is improved compared to before coating, the capacity retention rate is poor during long cycles.

[0164] In Comparative Example 3, the calcination temperature was increased, which caused the tin-antimony oxide in the designed ATO coating layer to be reduced by the carbon layer, generating a tin-antimony alloy and constructing a tin-antimony-tin metal coating structure. Figure 16 In the XRD result diagram of Comparative Example 3, the peaks of tin-antimony alloy and tin appear, while the peak of SnO2 does not appear, which can confirm the metal coating. In such a coating layer, the alloy material may melt during the calcination process due to its low melting point, and cannot form a dispersed conductive network to reduce the resistivity of the composite material; the metal may also undergo electrochemical dissolution during long cycles; at the same time, tin oxide is prone to volume expansion and breakage during the cycle, all of which lead to the inability to form an effective conductive coating layer, resulting in a lower cycle retention rate and first coulomb efficiency.

[0165] Comparative Example 4 uses a coprecipitation method as a coating method. This coating method easily causes ATO to form floccules, which have poor crystallinity, and the particles are too small and cannot form a uniformly coated conductive network. Figure 17 This is a TEM image of the composite material of Comparative Example 4. In the image, it can be seen that the formed ATO particles are extremely small, less than 1 nm, with poor crystallinity and uneven coating. Such characterization results are consistent with the electrochemical performance.

[0166] Comparative Example 5 did not add antimony doping, and constructed a structure with oxide SnO2 as the coating layer. Compared with the examples, it was found that its first coulombic efficiency and capacity retention rate were both low, which may be due to the poor conductivity of SnO2 and its easy volume expansion and breakage during the cycle.

[0167] Comparing Examples 1-7 with Comparative Examples 1-5 reveals improved initial coulombic efficiencies in the Examples compared to the Comparative Examples. This is due to the ATO coating, which reduces the resistivity of the composite material and the presence of a thin film of ATO on the surface, which also reduces side reactions during the initial charge and discharge process. The electrochemical performance test results in Table 1 show that this reduction in resistivity, enhanced electron transport performance, and reduced polarization effects ultimately lead to increases in the long-term cycle retention of the Example materials from approximately 70% to 76-81% at a current density of 2A g⁻¹, and from approximately 60-65% to 70-75% at a current density of 4A g⁻¹. Furthermore, in rate performance testing, the charge capacity of the Examples increased by 150-300 mAh g⁻¹ at a high current density of 8A g⁻¹. The combined test results, shown in the various figures, demonstrate the successful coating of the conductive metal oxide, the enhanced electron transport capacity, and the reduced SEI impedance. This ultimately leads to significant improvements in cycling stability and rate performance.

[0168] The present invention adopts an alkoxide hydrolysis method as a synthesis method and applies a two-step calcination method to in-situ coat the conductive metal oxide ATO (ITO) on the surface of a silicon-carbon material to form a composite material. The coating of the conductive metal oxide significantly reduces the resistivity of the composite material, reduces the interface resistance of the silicon-carbon material, improves the charge transfer capability of the composite material, promotes the performance of the composite material capacity at a higher current density, alleviates the interface polarization phenomenon, and thus improves the cycle stability of the material.

[0169] The alcohol salt hydrolysis method adopted by the present invention does not require a high-temperature, high-pressure or vacuum reaction process and does not use a vapor deposition method. It is safe and efficient, and can uniformly coat a conductive metal oxide precursor on the surface of a silicon-carbon material. Assisted by two-step annealing and calcination, a high-valent metal is incorporated into another metal oxide lattice on the basis of a carbon layer in the non-oxidized silicon-carbon material, thereby successfully constructing a conductive metal oxide-coated silicon-carbon material with free electrons and oxygen vacancies. The raw materials and chemical reagents used are all common medicines and have environmentally friendly characteristics. In summary, the present invention has the potential for commercial large-scale production.

Claims

1. A method for preparing a metal oxide-coated silicon-carbon material, characterized in that The steps include: 1) dispersing a silicon-carbon material, a reactive surface conditioner, and a pH adjuster in water by ultrasonication to obtain a reaction solution; the reactive surface conditioner is one or more of oleyl alcohol, hexadecyltrimethylammonium bromide, sodium oleate, and polyvinylpyrrolidone; 2) dissolving the metal ion compound and the ligand in an alcohol solvent to form a coating solution; The coating liquid is added to the reaction solution, heated to 70-95° C. and kept warm for 2-6 hours to obtain a precursor slurry; the ligand is one or more of citric acid, tartaric acid, and thioglycolic acid; the metal ion compound is tin tetrachloride pentahydrate and antimony trichloride; or the metal ion compound is tin tetrachloride pentahydrate and indium nitrate; 3) After the precursor slurry is cooled, it is filtered under reduced pressure, dried, and washed; 4) calcining the washed precursor in two stages to obtain a metal oxide-coated silicon-carbon material; The first stage of the two-stage calcination is annealing and calcining at 180-250° C. in an air atmosphere, and the second stage of the calcination is annealing and calcining at 400-550° C. in an inert atmosphere for 1.5-3 h.

2. The method for preparing a metal oxide-coated silicon-carbon material according to claim 1, wherein: The pH regulator is one or more of urea, tetramethylammonium hydroxide and ammonium bicarbonate; the molar ratio of the pH regulator to the metal ion compound is 3 to 8:1; and the mass ratio of the silicon-carbon material to the reactive surface regulator is 10 to 30:

1.

3. The method for preparing a metal oxide-coated silicon-carbon material according to claim 1, wherein: The alcohol solvent is one or more of ethanol, isopropanol, propylene glycol, methanol and butanol; the mass ratio of the metal ion compound to the ligand is 10-50:1; and the mass ratio of the alcohol solvent to the metal ion compound is 10-60:

1.

4. The method for preparing a metal oxide-coated silicon-carbon material according to claim 1, wherein: The time of the first calcination stage is 50-90 min; the heating rates of the first calcination stage and the second calcination stage are both 3-8° C. / min.

5. The method for preparing a metal oxide-coated silicon-carbon material according to claim 1, wherein: The ultrasonic dispersion time is 30-60 minutes, and the ultrasonic frequency is 20-90 kHz. The coating liquid is added to the reaction liquid under the action of a peristaltic pump. The flow rate of the peristaltic pump is set to 0.5-3 ml / min.

6. The method for preparing a metal oxide-coated silicon-carbon material according to claim 1, wherein: The silicon-carbon material is a core-shell structure in which a carbon shell encapsulates silicon particles, wherein the mass of the silicon particles accounts for 40-90 wt.%; the mass of the carbon shell accounts for 10-60 wt.%; The detergents used for washing are deionized water and ethanol; the drying temperature is 40-80° C., and the drying time is 12-24 hours.

7. A metal oxide-coated silicon-carbon material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the metal oxide-coated silicon-carbon material according to claim 7 as a negative electrode material for a lithium-ion battery.

9. Use of the metal oxide-coated silicon-carbon material according to claim 8 as a negative electrode material for lithium-ion batteries, characterized in that The application process is as follows: the metal oxide-coated silicon-carbon material, carbon black and carboxymethyl cellulose or polyacrylic acid are mixed and then pulped, and the pulp is coated on copper foil to obtain a negative electrode sheet for a lithium-ion battery.

10. Use of the metal oxide-coated silicon-carbon material according to claim 9 as a negative electrode material for lithium-ion batteries, characterized in that: The mass ratio of the metal oxide-coated silicon-carbon material, carbon black and carboxymethyl cellulose or polyacrylic acid is (6-8): (1-2): (1-2).

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