A tin-silicon-carbon composite material, its preparation method, applications, and batteries.

Abstract

This invention provides a tin-silicon-carbon composite material, its preparation method, application, and battery. The preparation method includes the following steps: (1) under heating, a mixture of oxygen-containing gas and inert gas is introduced into porous carbon deposited with elemental tin for oxidation treatment, thereby oxidizing the tin surface to obtain a tin-carbon composite material; (2) the tin-carbon composite material is subjected to silicon deposition to obtain the tin-silicon-carbon composite material. The tin-silicon-carbon composite material prepared by this invention can significantly improve the rate performance of the electrode and improve cycle stability, overcoming the defects of traditional porous carbon / silicon anodes such as weak interface bonding, easy flash explosion, significant volume effect, and poor conductivity. Moreover, the preparation process is simple, the cost is low, and it is easy to industrialize.

Description

Technical Field

[0001] This invention specifically relates to a tin-silicon-carbon composite material, its preparation method, applications, and batteries. Background Technology

[0002] Lithium-ion batteries, as one of the highest energy density rechargeable batteries currently available, are widely used in portable electronic devices, electric vehicles, and energy storage systems. With the rapid development of the new energy industry, the market is placing higher demands on the energy density, cycle stability, and safety of lithium-ion batteries. The anode material, as a core component determining battery performance, directly affects the overall performance of the battery. Currently, commercially available anode materials are mainly graphite, but its theoretical specific capacity is only 372 mAh / g, which is insufficient to meet the needs of high-energy-density batteries. Therefore, the development of novel high-capacity anode materials has become a research hotspot.

[0003] Silicon (Si) is considered one of the most promising next-generation graphite anode materials due to its extremely high theoretical specific capacity (4200 mAh / g), abundant reserves, and environmental friendliness. However, silicon experiences volume expansion of up to 300% during charge and discharge, leading to electrode structure rupture, active material shedding, and repeated rupture and reconstruction of the solid electrolyte interphase (SEI) film, significantly reducing battery cycle stability. To address this issue, researchers have proposed combining silicon with carbon materials, utilizing the conductivity and structural stability of carbon to mitigate silicon volume expansion. Porous carbon, with its large specific surface area, abundant pore structure, and good conductivity, has become an ideal carrier for silicon. Its pores can accommodate the volume expansion of silicon while providing channels for lithium-ion diffusion. However, traditional porous carbon / silicon composite anodes still have significant drawbacks: the interfacial bonding between silicon and porous carbon is weak, making them prone to interfacial separation during long-term cycling; silicon's intrinsic conductivity is poor, resulting in poor electrode rate performance; furthermore, silicon particles can still agglomerate during cycling, further exacerbating the volume effect. These issues limit the practical application of porous carbon / silicon composite anodes.

[0004] More importantly, in the preparation of traditional silicon-based composite materials, when silicon is directly deposited on the surface of porous carbon using silane, the silane and the carbon in the porous carbon are prone to react at high temperatures to form silicon carbide. This reaction is a strongly exothermic reaction, and the large amount of heat released can cause a sudden rise in local temperature, triggering a violent reaction of silane gas or even a flash explosion, which poses a serious safety hazard. At the same time, the silicon carbide formed is an inert phase and cannot participate in lithium storage reactions, which will reduce the actual specific capacity of the composite material and further restrict the material performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a tin-silicon-carbon composite material, its preparation method, applications, and a battery. The tin-silicon-carbon composite material prepared by this invention significantly improves electrode rate performance and cycle stability, overcoming the defects of traditional porous carbon / silicon anodes such as weak interfacial bonding, susceptibility to flashover, significant volume effects, and poor conductivity. Furthermore, the preparation process is simple, low-cost, and easily industrialized.

[0006] In the preparation of tin-silicon-carbon composite materials, this invention first introduces a mixture of oxygen-containing gas and inert gas into porous carbon deposited with elemental tin for oxidation treatment, thereby generating an ultrathin SnO oxide layer on the tin surface. x (x = 0.5% - 5%); finally, in SnO x Using a 3D network structure as a base, through SnO x The interface modulation of the layers organically combines the high conductivity of tin, the high capacity of silicon, and the structural stability of carbon to form a multi-level buffered composite structure. This invention introduces tin and precisely modulates the SnO layer... x The transition layer utilizes a tin-based oxide layer as a "buffer interface layer" to block direct contact between silane and carbon, thereby inhibiting the formation of silicon carbide at its source. This avoids the risk of flash explosion, ensuring the safety of the preparation process, and also induces silane to form on an ultra-thin SnO layer with low internal resistance. x The surface-oriented uniform deposition fully leverages the high capacity characteristics of silicon, while utilizing the superior conductivity and low expansion properties of tin to achieve synergistic optimization of high capacity, high rate capability, and high stability, providing a key anode material for the development of high-performance lithium-ion batteries.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions: This invention provides a method for preparing a tin-silicon-carbon composite material, which includes the following steps: (1) Under heating, a mixture of oxygen-containing gas and inert gas is introduced into porous carbon deposited with elemental tin to carry out oxidation treatment, thereby oxidizing the tin surface and obtaining tin-carbon composite material. (2) Silicon deposition is performed on the tin-carbon composite material to obtain the tin-silicon-carbon composite material.

[0008] In step (1), the heating temperature can be 300-700℃, for example 400℃, 500℃, 550℃, 600℃, or 650℃. The heating is generally carried out in a tube furnace, that is, the oxidation treatment is carried out in a tube furnace. According to the conventions of the art, the temperature is generally raised to the heating temperature first, and then the mixture of oxygen-containing gas and inert gas is introduced. The phrase "in a heated state, the mixture of oxygen-containing gas and inert gas is introduced into porous carbon deposited with elemental tin for oxidation treatment" usually refers to first placing the porous carbon deposited with elemental tin into a reaction device (e.g., a tube furnace), then raising the temperature to the heating temperature, and then introducing the mixture of oxygen-containing gas and inert gas for oxidation treatment.

[0009] In step (1), the oxygen-containing gas generally refers to a gas containing oxygen, preferably one or more of water vapor, oxygen, methanol, and ethanol. The inert gas can be conventional in the art, such as nitrogen or argon. The oxygen-containing gas preferably accounts for 3-10% of the total volume of the mixture of oxygen-containing gas and inert gas, for example, 5% or 8%. The total flow rate of the mixture of oxygen-containing gas and inert gas can be 50-120 sccm, for example, 60 sccm, 80 sccm, or 100 sccm. The oxidation treatment time can be 5-30 min, for example, 10 min or 20 min, where the oxidation treatment time refers to the time the mixture of oxygen-containing gas and inert gas is introduced. After the oxidation treatment, the tin surface is oxidized, and the average composition of the entire tin and the surface oxide layer is SnO. x Where x = 1%-5%, for example 1.5%, 2.3%, 2.8%, and x refers to the molar ratio of oxygen atoms to tin atoms.

[0010] In step (1), the mass ratio of tin to carbon in the porous carbon deposited with elemental tin can be (0.5-10):45, for example 1.5:45, 1.6:45, 1.8:45, 1.9:45, 2:45, 4:45 or 6:45.

[0011] In step (1), the method for preparing porous carbon with elemental tin deposited preferably includes the following steps: depositing a tin source into porous carbon under heating conditions.

[0012] The heat treatment is generally carried out in a tube furnace. The temperature of the heat treatment can be 300-700℃, for example 400℃, 500℃, 550℃, 600℃ or 650℃.

[0013] The tin source may be one or more of tin dichloride, tin tetrachloride, tetramethyltin, tetrabutyltin, and tin bromide.

[0014] If the tin source is a solid tin source (e.g., tin dichloride), the tin source can be vaporized using a heated evaporation boat and then carried into the reaction zone by an inert gas. The temperature of the heated evaporation boat can be set at 180-250°C, for example, 200°C, 220°C, or 240°C. The inert gas can be conventional in the art, such as nitrogen or argon; the inert gas flow rate can be 30-100 sccm, for example, 40 sccm, 50 sccm, or 60 sccm. When the tin source is a solid tin source, the deposition pressure can be 30-100 Pa, for example, 40 Pa, 50 Pa, or 60 Pa, where the deposition pressure refers to the pressure inside the deposition apparatus (e.g., a tube furnace); the deposition time can be 30-90 min, for example, 45 min, 60 min, or 75 min. The mass ratio of the porous carbon to the tin source can be (5-30):1, for example, 5:1, 8:1, 9.8:1, 12:1, 15:1, 20:1 or 25:1.

[0015] If the tin source is a liquid tin source (e.g., tetrabutyltin, tetramethyltin), the tin source can be placed in a constant temperature container, and its vapor pressure can be adjusted by controlling the temperature (which can be 40-100℃, e.g., 50℃, 65℃, 70℃ or 80℃). A dual-channel gas control system is adopted. One channel is an inert carrier gas, which is introduced into the tin source container after the flow rate is controlled by a flow meter (which can be 30-60 sccm, e.g., 40 sccm, 45 sccm, 50 sccm or 55 sccm), carrying the gaseous tin source into the tube furnace for deposition. The other channel is a dilution gas (inert gas, which can be the same type as the carrier gas), which is directly introduced into the tube furnace to adjust the total gas flow rate (which can be 60-100 sccm, e.g., 70 sccm, 75 sccm, 80 sccm, 85 sccm or 90 sccm). When the tin source is a liquid tin source, the vapor pressure of the tin source in the constant temperature container can be 15-100 Pa, for example 20 Pa, 35 Pa, or 50 Pa; the deposition time can be 30-90 min, for example 45 min, 60 min, or 75 min. The mass ratio of the porous carbon to the tin source can be (3-30):1, for example 4:1, 5:1, 5.1:1, 8:1, 9.8:1, 12:1, 15:1, 20:1, or 25:1.

[0016] If the tin source (e.g., tin dichloride) cannot be directly decomposed into metallic tin under heating, hydrogen gas needs to be introduced for reduction during calcination after the deposition reaction. The calcination temperature can be 300-700℃, for example, 400℃, 500℃, 550℃, 600℃, or 650℃. The hydrogen gas is generally introduced after the tin source has been loaded into the tube furnace. The hydrogen flow rate can be 10-40 sccm, for example, 15 sccm, 20 sccm, 25 sccm, or 30 sccm; the hydrogen introduction time can be 10-30 min, for example, 15 min, 20 min, or 25 min.

[0017] Preferably, the porous carbon requires pretreatment before use. The pretreatment process preferably includes the following steps: annealing the porous carbon under an inert gas atmosphere.

[0018] The porous carbon can be commercially available or prepared in-house. The pore size of the porous carbon is preferably 2-80 nm; the specific surface area of ​​the porous carbon is preferably 2000-2500 m² / g; and the pore size of the porous carbon is preferably 0.5-10 nm, for example, 1 nm, 1.5 nm, 1.75 nm, 2 nm, 4 nm, or 5 nm.

[0019] The type of inert gas is as described above. The annealing treatment is generally carried out in a tube furnace; the annealing temperature can be 300-700℃, for example 400℃, 500℃, 550℃, 600℃, or 650℃; the annealing time can be 15-120 min, for example 20 min, 30 min, 45 min, or 60 min. Preferably, a vacuum treatment is performed before the annealing treatment, more preferably to a vacuum level of <5 Pa.

[0020] In step (1), the porous carbon is pretreated, the tin source is deposited onto the porous carbon, hydrogen is introduced for reduction, and a mixture of oxygen-containing gas and inert gas is introduced into the porous carbon deposited with elemental tin for oxidation treatment. These treatment steps can be carried out independently, that is, at their respective treatment temperatures. After each step is completed, the temperature is lowered to room temperature before proceeding to the next step. In addition, in order to improve efficiency and save energy, the process can also be carried out during continuous heating. That is, during the next step, the temperature is directly raised, lowered, or maintained at the initial temperature based on the previous operation temperature. During this process, only the type of gas introduced needs to be changed. It is not necessary to lower the temperature to room temperature after each heating operation and then raise the temperature to the temperature required for the next operation.

[0021] In step (2), the silicon deposition is generally performed by vapor deposition. The silicon source used in the vapor deposition process can be conventional in the art, generally silane, or silicon tetrachloride, trichlorosilane, etc.

[0022] In step (2), the silicon deposition temperature can be 300-700℃, for example 350℃, 400℃, 500℃, 550℃ or 600℃. The silicon deposition time can be 0.5-2h, for example 30min, 1h or 1.5h.

[0023] In step (2), the silicon deposition is preferably carried out in a mixture of a silicon source and an inert gas. The type of inert gas is as described above. The flow rate of the silicon source is preferably 3-30 sccm, for example, 5 sccm, 10 sccm, or 20 sccm. The flow rate of the inert gas is preferably 50-200 sccm, for example, 20 sccm, 80 sccm, 120 sccm, or 150 sccm. The total pressure of the mixture of the silicon source and the inert gas can be 50-500 Pa, for example, 80 Pa, 100 Pa, or 200 Pa.

[0024] In one specific implementation, during the silicon deposition process, the silane flow rate is 12 sccm, the inert gas flow rate is 88 sccm, the deposition pressure is controlled at 80 Pa, and the deposition time is 60 minutes.

[0025] In this invention, the preparation method of the tin-silicon-carbon composite material preferably includes the following steps: (a) The porous carbon was annealed under an inert gas atmosphere to obtain pretreated porous carbon; (b) Under heating conditions, a tin source is deposited into the pretreated porous carbon to obtain porous carbon with elemental tin deposited on it; (c) Under heating, a mixture of oxygen-containing gas and inert gas is introduced into porous carbon deposited with elemental tin to perform oxidation treatment, thereby oxidizing the tin surface and obtaining a tin-carbon composite material. (d) The tin-carbon composite material is subjected to silicon deposition to obtain the tin-silicon-carbon composite material.

[0026] If the tin source (e.g., tin dichloride) cannot be directly decomposed to generate metallic tin under heating, that is, porous carbon with elemental tin deposited cannot be directly obtained in step (b), but porous carbon with tin source deposited is obtained instead, then an additional operation step (b') needs to be added between step (b) and step (c). Step (b') includes the following: hydrogen gas is introduced for reduction under calcination.

[0027] The parameter restrictions for steps (a)-(d) and step (b') are as described above.

[0028] The present invention also provides a tin-silicon-carbon composite material prepared by the preparation method described above.

[0029] In this invention, the preferred mass ratio of silicon, tin, and carbon in the tin-silicon-carbon composite material is (30-40):(0.5-10):45, for example, 35:1.5:45, 35:1.6:45, 35:1.8:45, 35:1.9:45, or 35:2:45.

[0030] The present invention also provides an application of the tin-silicon-carbon composite material as described above in a battery.

[0031] The present invention also provides a battery comprising the tin-silicon-carbon composite material as described above.

[0032] In this invention, the tin-silicon-carbon composite material is preferably used as a negative electrode material.

[0033] In this invention, the battery may be a lithium battery or a sodium battery.

[0034] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0035] The reagents and raw materials used in this invention are all commercially available.

[0036] The positive and progressive effects of this invention are as follows: The tin-silicon-carbon composite material prepared by this invention can significantly improve the rate performance of the electrode and improve the cycle stability, overcoming the defects of traditional porous carbon / silicon anodes such as weak interface bonding, significant volume effect and poor conductivity. Moreover, the preparation process is simple, the cost is low, and it is easy to industrialize. Attached Figure Description

[0037] Figure 1 The image shows a SEM image of the tin-silicon-carbon anode material prepared in Example 1. Detailed Implementation

[0038] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions. Example 1

[0039] (1) Pretreatment: 45g of porous carbon (manufacturer: Shengquan, model ZLD-4; BET specific surface area 2200m²) was added. 2 / g, average pore size 1.750 nm) were placed in a vacuum tube furnace (Hefei Kejing OTF-1200-80), first evacuated to 0.5 Pa, then argon was introduced as a protective gas at a flow rate of 120 sccm, and the temperature was raised to 600℃ at a heating rate of 3℃ / min and held for 30 minutes for pretreatment. (2) Deposition of tin compounds: After pretreatment, while maintaining the furnace temperature at 600°C, tin compounds are loaded in porous carbon. The loading process is as follows: 4.6g of tin dichloride powder (purity 99.9%, Aladdin) is placed in an electric heating evaporation boat (tungsten boat). Tin dichloride vapor is introduced into the reaction zone through argon gas. The evaporation temperature is controlled at 220°C, the argon flow rate is 50sccm, the deposition pressure in the tube furnace is maintained at 50Pa, and the deposition time is 60 minutes. (3) Reduction of tin compounds: After deposition, turn off the power supply of the evaporation boat, continue to maintain the furnace temperature at 600℃, switch to 20sccm H2 and continue to purge for 20min to reduce tin dichloride to metallic tin; (4) Oxidation treatment: After the reduction reaction is completed, while maintaining the furnace temperature at 600℃, a mixed gas of 5% H2O and 95% N2 (H2O is introduced quantitatively through a precision injection pump) is introduced at a total flow rate of 80 sccm for 10 minutes to form an oxide layer on the tin surface. Then, it is naturally cooled to room temperature. XPS analysis shows that the oxide layer composition is SnO. x (x=2.8%) (5) Silane deposition: The porous carbon containing oxides prepared in step (4) was heated to 550°C under an argon atmosphere (flow rate 120 sccm), and then the argon was replaced with a mixture of silane (purity 99.999%, purchased from Linde Group, flow rate 12 sccm) and argon (flow rate 88 sccm) (silane volume fraction 12%), with a total flow rate of 100 sccm. The deposition pressure was controlled at 80 Pa, and the deposition time was 60 minutes. x Silicon was deposited on the surface of the layer and in the remaining pores of the porous carbon, ultimately producing a tin-silicon-carbon composite material (porous carbon / Sn / SnO). x Elemental analysis revealed that Si:Sn:C = 35:2:45 (wt%). Example 2

[0040] Compared to Example 1, except that the treatment time of the mixed gas of 5% H2O and 95% N2 in step (4) was adjusted to 5 minutes, all other operations and conditions were the same as in Example 1. XPS analysis showed that the oxide layer composition was SnO. x (x=1.5%). Example 3

[0041] Compared with Example 1, except that the deposition time of tin dichloride in step (2) is adjusted to 40 minutes, all other operations and conditions are the same as in Example 1. Example 4

[0042] Compared with Example 1, except that the deposition time of silane in step (5) is adjusted to 45 minutes, all other operations and conditions are the same as in Example 1. Example 5

[0043] (1) Pretreatment: 45g of porous carbon (manufacturer: Shengquan, model ZLD-4; BET specific surface area 2200m²) was added. 2 / g) is placed in a vacuum tube furnace, first evacuated to 0.5Pa, then argon is introduced as a protective gas at a flow rate of 120sccm, and the temperature is raised to 600℃ at a heating rate of 3℃ / min and held for 30 minutes for pretreatment. (2) Deposition of elemental tin: After pretreatment, while maintaining the furnace temperature at 600℃, 8.8g of tetrabutyltin (purity 98%, Sinopharm Chemical Reagent) was introduced into the furnace cavity by argon gas. The vapor pressure in the container containing the tetrabutyltin was controlled at 35Pa (65℃ constant temperature water bath). The deposition time was 60 minutes. After the tetrabutyltin decomposed, tin particles were loaded in the porous carbon. A dual-channel gas control system was adopted. One channel was argon carrier gas, which was introduced into the container containing tetrabutyltin after the flow rate was controlled at 50sccm by a flow meter, carrying the gaseous tin source into the tube furnace. The other channel was dilution argon gas, which was directly introduced into the tube furnace to adjust the total gas flow rate to 80sccm. (3) Oxidation treatment: After the deposition reaction is completed, the furnace temperature is maintained at 600℃. A mixed gas of 5% H2O and 95% N2 (H2O is introduced quantitatively through a precision injection pump) is switched to be introduced. The total flow rate is 80 sccm and the treatment time is 10 minutes to form an oxide layer on the tin surface. The oxide layer composition is SnO by X-ray diffraction (model D8 Advance, purchased from Bruker GmbH, Germany). x (x=2.3%) (4) Silane deposition: The porous carbon containing oxides prepared in step (3) was heated to 550°C under an argon atmosphere (flow rate 120 sccm), and then the argon was replaced with a mixture of silane (purity 99.999%, purchased from Linde Group) and argon (silane volume fraction 12%), with a total flow rate of 100 sccm, a deposition pressure controlled at 80 Pa, and a deposition time of 60 minutes, in SnO x Silicon is deposited on the surface of the layer and in the remaining pores of the porous carbon, ultimately producing porous carbon / Sn / SnO. xThe Si composite anode material, after elemental analysis, yielded a Si:Sn:C ratio of 35:1.8:45 (wt%).

[0044] Comparative Example 1 Compared with Example 1, except that the mixed gas of 5% H2O and 95% N2 by volume is not introduced during step (4), all other operations and conditions are the same as in Example 1.

[0045] Comparative Example 2 Compared with Example 1, except that tin dichloride powder vapor is not introduced during step (2), all other operations and conditions are the same as in Example 1.

[0046] Comparative Example 3 Compared with Example 1, except that a mixture of 5% H2O and 95% N2 by volume is not introduced in step (4) and silane is not introduced in step (5), all other operations and conditions are the same as in Example 1.

[0047] Comparative Example 4 Compared with Example 1, except that silane is not introduced during step (5), all other operations and conditions are the same as in Example 1. Effect Example

[0048] (1) Characterization of material properties Figure 1 The image shows a SEM image of the tin-silicon-carbon composite material prepared in Example 1.

[0049] The tin-silicon-carbon composite materials prepared in Examples 1-5 and the material samples prepared in Comparative Examples 1-4 were subjected to elemental analysis and X-ray photoelectron spectroscopy characterization, respectively.

[0050] Elemental analysis: Accurately weigh 20 mg of the sample to be tested and place it in a polytetrafluoroethylene digestion tube. Add 5 mL of HF (40%, Sinopharm Group), 2 mL of HNO3 (analytical grade, Maclean), and 1 mL of HClO4 (analytical grade, Aladdin). Heat at 80 °C for 30 min on a temperature-controlled heating plate (EH35A, LabTech), then increase the temperature to 150 °C and heat for 2 h until the solution is clear. After cooling, transfer to a 50 mL volumetric flask and dilute to volume with ultrapure water. Perform a blank experiment simultaneously. Inject the test solution into an ICP-MS (7900, Agilent). Plot a standard curve using 1000 mg / L Si and Sn standard solutions (National Nonferrous Metals and Electronic Materials Analysis and Testing Center). Calculate the mass fractions of Si and Sn using the formula ω = (C × V) / (m × 1000) × 100% (C is the concentration to be measured, V is the volume to be diluted, and m is the sample mass). Separately weigh 10 mg of... The sample was placed in a porcelain boat, and 0.2g of tungsten granule combustion aid (99.9%, Sinopharm Group) was added. The sample was then subjected to high-frequency induction combustion (3.5kW) at an oxygen flow rate of 300mL / min for 60s using a carbon-sulfur analyzer (CS-230, LECO) to convert carbon into CO2. The CO2 was then measured by an infrared detector and the C mass fraction was calculated by comparing it with the standard sample (GBW01650, National Institute of Metrology, China).

[0051] X-ray photoelectron spectroscopy (XPS) analysis was performed using a Thermo ESCALAB 250Xi photoelectron spectrometer. The testing conditions were: monochromatic Al Kα rays (1486.6 eV) as the excitation source, and a vacuum level better than 1 × 10⁻⁶. -9 Pa was used to determine the characteristic peak positions of O 1s and Sn 3d using a wide-scan spectrum, and the O 1s (binding energy 530-535 eV) and Sn 3d (binding energy 480-490 eV) regions were narrow-scanned. Peak fitting was performed using XPS Peak 4.1 software, and after background subtraction, the peak areas of O 1s and Sn 3d were calculated. The atomic ratio was then calculated using sensitivity factors (O: 0.711, Sn: 6.83) to obtain the SnO2 content. x The x value (i.e., oxygen content) in the figure.

[0052] (2) Electrochemical performance testing The electrochemical testing method was as follows: The tin-silicon-carbon composite materials prepared in Examples 1-5 and the materials prepared in Comparative Examples 1-4 were mixed with conductive carbon black and sodium carboxymethyl cellulose at a mass ratio of 80:10:10. Deionized water was added to form a slurry, which was then coated onto a 10 μm thick copper foil. After vacuum drying at 120°C for 12 hours, the slurry was punched into electrode sheets with a diameter of 12 mm (the areal density of the active material on the electrode sheet was 2.9 mg / cm³). 2The negative electrode was lithium metal, and a 1 mol / L LiPF6 electrolyte was used (solvents were EC, DMC, and FEC, EC:DMC = 1:1 (volume ratio), and FEC accounted for 5% of the total solvent volume). CR2032 button cells were assembled in an argon glove box, and constant current charge / discharge tests were performed on a LAND CT2001A battery testing system, with a test voltage range of 0.01-1.5 V (vs. Li / Li). + The current density was 0.1C (1C = 2000 mA / g), and five charge-discharge cycles were performed at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C, respectively. A cycle test was then conducted at 10C. The test results are shown in Table 1. Table 1

[0053] Based on the above experimental results, the tin-silicon-carbon composite material prepared in this invention exhibits good rate performance and specific capacity. Comparative Example 1, due to the absence of H2O vapor, was unable to form SnO. x The oxide layer results in a weak silicon / tin / carbon bonding interface, making it difficult for Si to bond with SnO. x Directional deposition of the oxide layer results in poor interfacial compatibility between tin and silicon / carbon, easily forming unstable interfacial phases such as the Sn-Si disordered alloy phase, leading to a decline in the cycling performance of the composite electrode. Comparative Example 2, lacking the introduction of Sn, causes silane to easily form silicon carbide during porous carbon deposition, resulting in flash explosions, poor material conductivity, significant silicon expansion and pulverization, and poor specific capacity and rate performance. Comparative Example 3, due to the absence of H₂O and silane, suffers from a significant reduction in specific capacity and rate performance. Comparative Example 4, lacking the introduction of silicon, results in a low specific capacity.

[0054] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing a tin-silicon-carbon composite material, characterized in that, Includes the following steps: (1) Under heating, a mixture of oxygen-containing gas and inert gas is introduced into porous carbon deposited with elemental tin to carry out oxidation treatment, thereby oxidizing the tin surface and obtaining tin-carbon composite material. (2) Silicon deposition is performed on the tin-carbon composite material to obtain the tin-silicon-carbon composite material.

2. The method for preparing the tin-silicon-carbon composite material as described in claim 1, characterized in that, Step (1) satisfies one or more of the following conditions: (1) The heating temperature is 300-700℃, for example 400℃, 500℃, 550℃, 600℃ or 650℃; (2) The oxygen-containing gas refers to a gas containing oxygen, preferably one or more of water vapor, oxygen, methanol and ethanol; (3) The oxygen-containing gas accounts for 3-10% of the total volume of the mixture of oxygen-containing gas and inert gas introduced, for example, 5% or 8%; (4) The total flow rate of the mixture of oxygen-containing gas and inert gas is 50-120 sccm, for example 60 sccm, 80 sccm or 100 sccm; (5) The oxidation treatment time is 5-30 min, for example 10 min or 20 min; (6) In the porous carbon deposited with elemental tin, the mass ratio of tin to carbon is (0.5-10):45, for example 1.5:45, 1.6:45, 1.8:45, 1.9:45, 2:45, 4:45 or 6:45; (7) The method for preparing porous carbon with elemental tin deposited includes the following steps: depositing a tin source into porous carbon under heating conditions; The temperature of the heat treatment is preferably 300-700°C, for example 400°C, 500°C, 550°C, 600°C or 650°C; The tin source is preferably one or more of tin dichloride, tin tetrachloride, tetramethyltin, tetrabutyltin, and tin bromide.

3. The method for preparing the tin-silicon-carbon composite material as described in claim 2, characterized in that, If the tin source is a solid tin source, the tin source is vaporized by a heated evaporation boat and then carried into the reaction zone by an inert gas. The set temperature of the heated evaporation boat is preferably 180-250°C, for example 200°C, 220°C, or 240°C; the flow rate of the inert gas is preferably 30-100 sccm, for example 40 sccm, 50 sccm, or 60 sccm; when the tin source is a solid tin source, the deposition pressure is preferably 30-100 Pa, for example 40 Pa, 50 Pa, or 60 Pa; the deposition time is preferably 30-90 min, for example 45 min, 60 min, or 75 min; the mass ratio of the porous carbon to the tin source is preferably (5-30):1, for example 5:1, 8:1, 9.8:1, 12:1, 15:1, 20:1, or 25:

1. If the tin source is a liquid tin source, it is placed in a thermostatic container, and its vapor pressure is regulated by controlling the temperature. A dual-channel gas control system is used. One channel is an inert carrier gas, whose flow rate is controlled by a flow meter (30-60 sccm, for example, 40 sccm, 45 sccm, 50 sccm, or 55 sccm) before being introduced into the tin source container, carrying the gaseous tin source into the tube furnace for deposition. The other channel is a dilution gas (inert gas), which is directly introduced into the tube furnace to adjust the total gas flow rate (60-100 sccm, for example, 70 sccm, 75 sccm, 80 sccm, 85 sccm, or 90 sccm). The vapor pressure of the tin source in the thermostatic container is preferably 15-100 Pa, for example, 20 Pa, 35 Pa, or 50 Pa. Pa; the deposition time is preferably 30-90 min, for example 45 min, 60 min or 75 min; the mass ratio of the porous carbon to the tin source is preferably (3-30):1, for example 4:1, 5:1, 5.1:1, 8:1, 9.8:1, 12:1, 15:1, 20:1 or 25:

1.

4. The method for preparing the tin-silicon-carbon composite material as described in claim 2, characterized in that, If the tin source cannot be directly decomposed into metallic tin under heating, hydrogen gas needs to be introduced for reduction under calcination after the deposition reaction is completed. The calcination temperature is preferably 300-700℃, such as 400℃, 500℃, 550℃, 600℃ or 650℃. The hydrogen gas is preferably introduced after the tin source has been loaded into the tube furnace. The hydrogen gas flow rate is preferably 10-40 sccm, such as 15 sccm, 20 sccm, 25 sccm or 30 sccm. The hydrogen gas introduction time is preferably 10-30 min, such as 15 min, 20 min or 25 min.

5. The method for preparing the tin-silicon-carbon composite material as described in claim 2, characterized in that, The porous carbon needs to be pretreated before use; the annealing temperature is preferably 300-700℃, such as 400℃, 500℃, 550℃, 600℃ or 650℃; the annealing time is preferably 15-120min, such as 20min, 30min, 45min or 60min. The pretreatment process preferably includes the following steps: annealing the porous carbon under an inert gas atmosphere; And / or, the porous carbon has a pore size of 2-80 nm; And / or, the specific surface area of ​​the porous carbon is 2000-2500 m² / g; And / or, the porous carbon has a pore size of 0.5-10 nm, for example 1 nm, 1.5 nm, 1.75 nm, 2 nm, 4 nm or 5 nm.

6. The method for preparing the tin-silicon-carbon composite material as described in claim 1, characterized in that, In step (2), the silicon deposition is performed by vapor deposition; the silicon source used in the vapor deposition process is preferably silane, silicon tetrachloride or trichlorosilane; And / or, the silicon deposition temperature is 300-700°C, for example 350°C, 400°C, 500°C, 550°C or 600°C; And / or, the silicon deposition time is 0.5-2 hours, for example, 30 minutes, 1 hour or 1.5 hours.

7. The method for preparing the tin-silicon-carbon composite material as described in claim 1, characterized in that, In step (2), the silicon deposition is carried out in a mixture of silicon source and inert gas; The flow rate of the silicon source is preferably 3-30 sccm, for example 5 sccm, 10 sccm or 20 sccm; The flow rate of the inert gas is preferably 50-200 sccm, for example 20 sccm, 80 sccm, 120 sccm or 150 sccm; The total pressure of the mixture of silicon source and inert gas is preferably 50-500 Pa, for example 80 Pa, 100 Pa or 200 Pa.

8. A tin-silicon-carbon composite material prepared by the method described in any one of claims 1-7; Preferably, in the tin-silicon-carbon composite material, the mass ratio of silicon, tin, and carbon is (30-40):(0.5-10):45, for example, 35:1.5:45, 35:1.6:45, 35:1.8:45, 35:1.9:45, or 35:2:

45.

9. The application of the tin-silicon-carbon composite material as described in claim 8 in a battery.

10. A battery, characterized in that, Including the tin-silicon-carbon composite material as described in claim 8.

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