Preparation method of porous silicon carbon negative electrode material suitable for vapor deposition

Abstract

The invention discloses a preparation method of a gas-phase porous silicon carbon negative electrode material. The preparation method comprises the following steps: (1) depositing silane gas and carbon source gas in porous carbon through a fluidized bed / rotary kiln equipment vapor deposition process to form a CVD (Chemical Vapor Deposition) porous silicon carbon material; (2) carrying out low-temperature ozone pretreatment on the obtained CVD silicon carbon material; and (3) carrying out ALD atomic layer deposition on the CVD silicon-carbon material subjected to ozone pretreatment to form a nano-scale metal oxide coating layer on the surface of the material. Wherein the ozone treatment process method and the ALD technology are suitable for optimizing artificial coating layers of various CVD gas-phase silicon carbon materials with various initial surface carbon layers, can realize a batch, uniform and stable modification effect, and have stable and positive effects in the aspects of initial capacity, first effect and volume expansion inhibition of the materials. The method has a remarkable CVD silicon carbon secondary coating effect, is suitable for batch preparation of materials, can achieve a remarkable material electrochemical performance optimization effect, and is simple, convenient and efficient.

Description

Technical Field

[0001] This invention relates to the field of battery materials, specifically to the field of lithium-ion battery silicon-carbon anode material preparation and processing, and particularly to an atomic layer deposition coating technology for gas-phase porous silicon-carbon anode materials. Background Technology

[0002] Silicon-carbon anode materials for lithium-ion batteries are key materials for improving battery capacity. However, silicon undergoes significant volume changes during electrochemical lithium insertion and extraction, which can easily lead to mechanical breakage and electrical contact failure. Furthermore, silicon itself is a semiconductor material; its conductivity decreases as its size increases, resulting in increased polarization.

[0003] CVD (Chemical Vapor Deposition) porous silicon-carbon anodes are a novel type of silicon-carbon anode material developed in recent years. They are prepared using porous carbon, silane gas, and carbon source gas. By controlling key process parameters such as reaction temperature, gas pressure, and gas flow rate, silane gas is deposited and adsorbed into the pores of a porous carbon substrate to form nano-silicon. Then, carbon source gas is deposited through gas-phase pyrolysis to form a carbon coating on the surface. Ultimately, this method meets the required particle size, specific surface area, powder resistivity, and other performance indicators, achieving high initial coulombic efficiency and high specific capacity in batteries.

[0004] The carbon coating on the surface of CVD silicon-carbon materials can maintain the chemical stability of silicon to a certain extent, improve conductivity, and suppress electrolyte side reactions. However, CVD porous silicon-carbon materials themselves cannot fully suppress the volume change of silicon. With charge-discharge cycles, the structural strength of the surface-coated carbon layer is insufficient, and it will still crack and fail. At the same time, the density of the deposited carbon layer is limited, making it difficult to prevent side reactions between anions and silicon in the electrolyte, resulting in a gradual capacity decay.

[0005] A crucial aspect of CVD processes is that the carbon source gas used in vapor deposition, if not properly controlled with specific raw materials and processes, is prone to incomplete decomposition during deposition, leading to the formation of tar byproducts that coat the surface of the silicon-carbon material. These byproducts themselves have poor electrical conductivity, resulting in increased powder resistance.

[0006] ALD (Atomic Layer Deposition) technology has been widely developed in the semiconductor field and has been applied in the lithium battery field in recent years. It involves alternately introducing different reaction precursors into the reaction chamber in the form of gas pulses. Compared with traditional deposition processes, ALD has significant advantages in terms of film uniformity, step coverage, and thickness control.

[0007] Further surface coating of silicon-carbon materials with metal oxides using ALD technology helps to construct a uniform, dense, high-strength, thin artificial protective film, thereby significantly suppressing volume expansion during lithium intercalation of silicon materials and reducing side reactions caused by electrolyte penetration. Patent CN118763171A utilizes atomic layer deposition (ALD) titanium dioxide nanofilms coated on the surface of MOF-derived nitrogen-doped microporous carbon to construct an artificial SEI. However, this method only focuses on the role of the liquid-phase synthesized silicon-carbon composite material and the titanium dioxide coating layer, without exploring the role of different raw materials / metal oxide components in the ALD branch technology, nor does it investigate the applicability of ALD technology to CVD vapor deposition of silicon-carbon materials.

[0008] The combination of ALD technology and CVD silicon-carbon has recently attracted attention. Patent CN119954159A utilizes ALD atomic layer deposition to grow a first metal oxide on the surface of a carbon substrate, which is then reduced to metal-containing nanodots. These nanodots are used to assist in the deposition of fumed silanes, and a carbon layer is then coated onto the surface of silicon nanowires based on a CVD pyrolysis process. However, this method focuses on the modification and control of the carbon substrate by ALD, and the surface coating layer of the material still consists of a carbon layer, which suffers from the aforementioned limitations.

[0009] In fact, due to the tar byproduct problem in the CVD silicon-carbon preparation process, the active gas source material of ALD and the tar undergo localized reactions and consumption, resulting in an insufficiently uniform and dense ALD coating layer. Therefore, ALD, as an important emerging technology for surface coating modification through atomic layer deposition, cannot yet be effectively combined with the rapidly developing CVD porous silicon-carbon materials in the industry. Summary of the Invention

[0010] To achieve efficient interfacial coating of CVD silicon-carbon materials using ALD technology, it is necessary to analyze and modify the surface composition and structure of CVD silicon-carbon materials to improve the uniformity of ALD coating. Furthermore, based on the conductivity and volume change characteristics of lithium-ion battery silicon-carbon anode materials, a rational design of the ALD deposition coating layer should be developed.

[0011] Analysis of CVD silicon-carbon materials revealed that incomplete carbon gas pyrolysis and adsorption can lead to the accumulation of local tar byproducts on the CVD silicon-carbon surface. Therefore, it is necessary to first treat the material to remove impurities and modify the surface groups to promote uniform deposition of ALD.

[0012] Therefore, this disclosure proposes to pretreat CVD silicon carbide with ozone. In particular, this pretreatment process is different from the ozone self-limiting atomic reaction cyclic deposition process in ALD. The high activity of ozone can effectively react and remove locally accumulated tar byproducts and achieve surface group modification of the material.

[0013] Furthermore, this disclosure also explores in depth the applicability of the ALD process on CVD silicon-carbon, and derives ALD process parameters that are suitable for the comprehensive requirements of electrochemical performance and mechanical strength of lithium battery anode materials.

[0014] Compared with existing technologies, the CVD silicon-carbon pretreatment and ALD deposition material parameter control method implemented in this invention combines ALD technology and CVD silicon-carbon in a more general way, making it more versatile.

[0015] It should be understood that the foregoing general description and the following detailed description are merely illustrative and not intended to limit the invention.

[0016] This invention document provides an overview of various implementations or examples of the techniques described herein, and is not a complete disclosure of the full scope or all features of the disclosed techniques.

[0017] Various embodiments are given in general by way of example rather than limitation, and are used together with the specification and claims to illustrate the disclosed embodiments.

[0018] According to one aspect of the present invention, an object of the present invention is to provide a method for preparing a gas-phase porous silicon-carbon anode material, comprising the following steps: (1) CVD porous silicon-carbon materials are formed by depositing silane gas and carbon source gas in porous carbon through a fluidized bed / rotary kiln vapor deposition process; (2) The obtained CVD silicon-carbon material is subjected to low-temperature ozone pretreatment; (3) The ozone-pretreated CVD silicon-carbon material is subjected to ALD atomic layer deposition to form a nanoscale metal oxide coating layer on the material surface.

[0019] In step (1), the silicon deposition and carbon coating step of the rotary kiln equipment generally includes placing porous carbon, purging with nitrogen at room temperature, heating to 420 degrees and purging with silane gas for nano-silicon deposition, and purging with acetylene gas at 500 degrees for preliminary carbon coating on the surface. The silicon deposition and carbon coating step of the fluidized bed equipment generally includes placing porous carbon, purging with nitrogen at room temperature for half an hour, heating to 420 degrees and purging with nitrogen for 2 hours, then purging with silane gas at 420 degrees for 2 hours, then continuing to purge with nitrogen and heating to 500 degrees, and purging with acetylene gas for 4 hours for preliminary carbon coating on the surface.

[0020] In step (1), the porous carbon substrate includes a biomass substrate, a resin-based substrate, or an asphalt-based porous carbon substrate.

[0021] In step (1), the carbon source gas is selected from one or more different carbon-containing gases selected from methane, ethylene, acetylene, propylene, and toluene.

[0022] In step (2), the ozone treatment method for CVD silicon carbide materials is to put the material into an ALD device and directly or pulsely introduce ozone gas with nitrogen as the carrier gas. In step (2), the ozone pretreatment temperature for CVD silicon carbide materials is below 200 degrees Celsius. In step (2), the ozone pretreatment time for CVD silicon carbide materials is 10s-30min; In step (3), ALD atomic layer deposition is performed on the pretreated CVD silicon-carbon, and the coating layer includes one or more of aluminum oxide, titanium oxide, zinc oxide, cerium oxide or zirconium oxide.

[0023] In step (3), ALD atomic layer deposition is performed on the pretreated CVD silicon-carbon. The raw material for the metal oxide deposition coating layer is an organometallic vapor containing the corresponding metal element, and the oxygen source is water vapor or ozone.

[0024] In step (3), the ALD deposition process is pulse deposition, and the pulse time of the reaction gas source is 0.01s-3s; In step (3), the ALD deposition process is pulse deposition, and the pulse temperature of the reaction gas source is 50 degrees to 500 degrees. In step (3), the ALD deposition process is pulse deposition, and the number of pulse cycles is 5 to 500.

[0025] According to another aspect of the present invention, another object of the present invention is to provide a vapor-phase porous silicon-carbon anode material, said material being prepared by the above-described preparation method, wherein the vapor-phase porous silicon-carbon anode material, after battery testing, has a first-charge specific capacity of not less than 1600 mAh / g, a first-charge coulombic efficiency of not less than 88%, and an electrode full-charge expansion rate of not more than 60%.

[0026] Beneficial effects The ozone treatment process and ALD technology of this invention are applicable to the optimization of artificial coatings on various CVD fumed silicon-carbon materials with different initial surface carbon layers. They can achieve uniform and stable modification effects in batches, and have a stable and positive effect on the initial capacity, first-efficiency performance, and suppression of volume expansion. The method of this invention has a significant effect on the secondary coating of CVD silicon-carbon and is suitable for batch preparation of materials, achieving significant optimization of the material's electrochemical performance. The method is simple and efficient. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is the process route for ALD deposition and coating of CVD silicon-carbon according to the present invention; Figure 2 This is a TEM image of CVD silicon-carbon coated with ALD deposition after ozone pretreatment in Example 1; Figure 3 This is a TEM image of the raw CVD silicon-carbon in Comparative Example 1 without ALD treatment; Figure 4 This is a TEM image of CVD silicon-carbon coated with ALD deposition without ozone pretreatment in Comparative Example 2. Figure 5 This is an infrared image of the original CVD silicon-carbon without ALD treatment in Example 1; Figure 6 This is an infrared image of CVD silicon-carbon treated with ALD in Comparative Example 1. Detailed Implementation

[0029] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0030] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0031] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0032] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0033] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0034] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0035] Example 1 In a fluidized bed reactor, resin-based porous carbon is used as the substrate. Silane gas is introduced for nano-silicon adsorption and deposition. Then, acetylene is introduced for cracking, producing an amorphous carbon layer that coats the porous silicon-carbon surface, forming the initial CVD silicon-carbon material. The fluidized bed model is a Sepfit GTLHC-15010 fluidized bed. The process parameters are as follows: porous carbon is placed in the fluidized bed, nitrogen is introduced at room temperature for half an hour, the temperature is initially raised to 420 degrees Celsius and nitrogen is continuously introduced for 2 hours, then silane gas is introduced at 420 degrees Celsius for 2 hours, followed by nitrogen introduction and heating to 500 degrees Celsius, then acetylene gas is introduced for 4 hours, then nitrogen is introduced and the temperature is lowered to room temperature before discharge. The CVD silicon-carbon material is placed in a 100-gram-scale rolling powder atomic layer deposition apparatus. Ozone is introduced for 20 seconds at room temperature using nitrogen as the carrier gas, then the temperature is raised to 160 degrees Celsius, and water and trimethylaluminum are introduced alternately in pulses, with each pulse lasting 0.3 seconds. After completing 10 pulse deposition cycles, the material was cooled to obtain silicon-carbon material coated with alumina. A battery was then assembled using this silicon-carbon material for testing.

[0036] Example 2 In a fluidized bed reactor, resin-based porous carbon was used as a substrate. Silane gas was introduced for nano-silicon adsorption deposition, followed by acetylene cracking to produce an amorphous carbon layer that coated the porous silicon-carbon surface, forming the initial CVD silicon-carbon material. The fluidized bed model and process parameters were the same as in Example 1. The CVD silicon-carbon material was placed in a powder atomic layer deposition apparatus, and ozone was introduced at room temperature using nitrogen as a carrier gas for 20 seconds. The temperature was then raised to 180 degrees Celsius, and water and trimethylaluminum were alternately pulsed for 0.15 seconds per pulse. After 20 pulse deposition cycles, the material was cooled to obtain alumina-coated silicon-carbon material. This silicon-carbon material was used to assemble and test batteries.

[0037] Example 3 In a rotary kiln, biomass-based porous carbon was used as a substrate. Silane gas was introduced for nano-silicon adsorption deposition, followed by ethylene cracking to generate an amorphous carbon layer that coated the porous silicon-carbon surface, forming the initial CVD silicon-carbon material. The rotary kiln used was a DM3060 model from Dongmu Kiln, with the same process parameters as in Example 1. The CVD silicon-carbon material was placed in a powder atomic layer deposition apparatus, and ozone was introduced for 30 seconds at room temperature using nitrogen as the carrier gas. The temperature was then raised to 200 degrees Celsius, and ozone and titanium tetrachloride were alternately pulsed for 0.3 seconds each. After 15 pulse deposition cycles, the material was cooled to obtain titanium oxide-coated silicon-carbon material. This silicon-carbon material was used to assemble and test batteries.

[0038] Comparative Example 1 In a fluidized bed reactor, resin-based porous carbon is used as a substrate. Silane gas is introduced to perform nano-silicon adsorption and deposition. Then, acetylene is introduced for cracking, producing an amorphous carbon layer that coats the porous silicon-carbon surface, forming a CVD silicon-carbon material. This silicon-carbon material is then used to assemble and test batteries.

[0039] Comparative Example 2 In a fluidized bed reactor, resin-based porous carbon was used as a substrate. Silane gas was introduced to perform nano-silicon adsorption deposition, followed by acetylene cracking to produce an amorphous carbon layer that coated the porous silicon-carbon surface, forming the initial CVD silicon-carbon material. The CVD silicon-carbon material was then placed in a powder atomic layer deposition (PAL) apparatus. Unlike Example 1, ozone pretreatment was not performed; the temperature was directly raised to 160 degrees Celsius, and water and trimethylaluminum were alternately pulsed for 0.3 seconds per pulse. After 10 pulse deposition cycles, the material was cooled to obtain alumina-coated silicon-carbon material. This silicon-carbon material was used to assemble and test batteries.

[0040] Comparative Example 3 In a fluidized bed reactor, resin-based porous carbon was used as a substrate. Silane gas was introduced for nano-silicon adsorption deposition, followed by acetylene cracking to produce an amorphous carbon layer that coated the porous silicon-carbon surface, forming the initial CVD silicon-carbon material. The CVD silicon-carbon material was placed in a powder atomic layer deposition apparatus, and ozone was introduced at room temperature using nitrogen as a carrier gas for 30 seconds. The temperature was then raised to 160 degrees Celsius, and water and trimethylaluminum were alternately pulsed for 0.3 seconds per pulse. Unlike Example 1, after 150 pulse deposition cycles, the material was cooled to obtain alumina-coated silicon-carbon material. This silicon-carbon material was used to assemble and test batteries.

[0041] Test Example 1: Performance Testing (1) Physical property testing The materials prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to particle size analysis using a laser particle size analyzer. The laser particle size analysis method involved adding the material to the dispersion to prepare the test sample. The test results are shown in Table 1.

[0042] Table 1

[0043] Analysis: The similar particle size across the various embodiments and comparative examples indicates that the atomic layer deposition characteristics of the ALD process allow for effective control of the coating thickness at the nanometer level, thus limiting the impact of different ALD processes on particle size. However, the significantly higher particle size distribution in Comparative Example 3 compared to the other embodiments and comparative examples demonstrates that excessive deposition cycles can still lead to over-coating.

[0044] The post-materials of Example 1, Comparative Example 1, and Comparative Example 2 were observed by transmission electron microscopy.

[0045] analyze: Figure 2 These are transmission electron microscope (TEM) images of the materials in Example 1, and Figure 3 Comparing the transmission electron microscopy (TEM) images of the materials in Comparative Example 1, it can be seen that the surface layer is more uniform after ALD deposition coating, while the surface coating of the material without ALD coating, prepared solely by CVD pyrolysis, is very uneven. Furthermore, through... Figure 2 Compared with Comparative Example 2, CVD silicon-carbon coated by ALD deposition without ozone pretreatment Figure 4 The comparison shows that the overall thickness of the coating layer prepared by ALD deposition is more uniform after ozone pretreatment. This demonstrates the important role of ozone pretreatment in improving the surface structure of the substrate and enhancing the uniformity of ALD coating.

[0046] Infrared spectral characterization analysis was performed on Example 1 and Comparative Example 1.

[0047] analyze: Figure 5 This is the infrared spectrum of the original CVD silicon-carbon in Example 1 without ALD treatment. Figure 6 The image shows the infrared spectrum of CVD silicon-carbon treated with ALD in Comparative Example 1. The comparison reveals that the surface of the original CVD silicon-carbon material exhibits a significant 2923 cm⁻¹ pattern associated with tar byproducts. -1 The characteristic peak of the nearby CHx group. However, after ALD coating, the original peak at 2923 cm⁻¹... -1 The disappearance of the characteristic peaks of the nearby CHx groups indicates that ALD effectively coats the material.

[0048] (2) Electrical performance test The silicon-carbon finished battery panels prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The general process for preparing lithium battery negative electrode sheets using negative electrode materials is as follows: silicon-carbon negative electrode material: carbon black conductive agent SP: binder PAA = 8:1:1, prepared into a slurry, mechanically stirred at room temperature for 30 min at a stirring speed of 2000 r / min, the prepared slurry is coated onto the current collector, dried in an oven at 50℃ for 30 min, and then dried in a vacuum drying oven at 100℃ for 8 h to obtain the prepared electrode sheet.

[0049] The general procedure for half-cell assembly and testing is as follows: Electrodes are prepared and assembled into lithium-ion coin cells for constant current charge-discharge testing. Using a lithium electrode as the counter electrode, LiPF6 is dissolved at a concentration of 1 mol / L in a mixed solvent of EC / DEC / EMC = 2:3:1 to form a non-aqueous electrolyte. EC is ethylene carbonate, EMC is methyl ethyl carbonate, and DEC is diethyl carbonate. The cells are then assembled in a glove box for electrochemical performance testing. Finally, 5% FEC (fluoroethylene carbonate) is added.

[0050] Capacity and initial coulombic efficiency testing: The half-cell was subjected to the first charge and discharge at 0.1C / 0.1C to test the material specific capacity and initial cycle efficiency.

[0051] Full-charge expansion test: Lithium insertion was performed on the half-cell at 0.1C, with a cutoff voltage of 0.005V. For cells with fully lithium-intercalated electrodes, disassembly was carried out in a glove box, and the thickness change of the electrodes before and after lithium insertion was recorded. The full-charge expansion rate was calculated. The compaction density difference of the coated electrodes should not exceed 0.05 mg / cm³. 3 .

[0052] The formula for calculating the full-charge expansion rate is: Expansion rate = (T1 - T0) / T0 × 100% T1 is the thickness of the silicon-carbon electrode obtained by averaging the thickness measured at five points using a micrometer after the battery electrode has been fully charged and lithium-ion intercalated using the specific capacity testing method, and the electrode has been removed. T0 is the thickness of the silicon-carbon electrode obtained by averaging the thickness measured at five points using a micrometer before the battery is assembled.

[0053] The test results of the battery capacity initial efficiency and full-charge expansion rate of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2 below: Table 2

[0054] Analysis: As shown in Table 2, in Examples 1-3, the CVD silicon-carbon materials treated with ozone and coated with metal oxides via ALD deposition using suitable process parameters showed a significant improvement in initial coulombic efficiency compared to the original CVD silicon-carbon material in Comparative Example 1, while maintaining a high reversible specific capacity. Simultaneously, the charge expansion rate decreased significantly, thanks to the effective suppression of volume expansion during the electrochemical reaction process of the silicon-carbon material by the dense nano-metal oxide layer. In Comparative Example 2, the CVD silicon-carbon material directly coated with ALD without ozone treatment exhibited uneven surface coating due to side reactions between surface CHx groups and the ALD active material. Therefore, although performance was improved, the improvement was not significant. On the other hand, for the material in Comparative Example 3 with unsuitable process parameters and excessive ALD deposition coating, the excessively thick surface coating layer caused difficulties in ion transport, resulting in a significant decrease in both capacity and initial efficiency.

[0055] In summary, by analyzing the surface structure and composition characteristics of CVD silicon-carbon materials and combining them with ALD (Alternating Current Deposition) technology for surface coating modification, and by proposing targeted pretreatment methods for the materials, CVD silicon-carbon materials can be better compatible with the ALD deposition process. The finally prepared ALD-modified CVD silicon-carbon materials exhibit good capacity utilization, high first-time coulombic efficiency, and significantly reduced electrode full-charge expansion rate.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a vapor-phase porous silicon-carbon anode material, comprising the following steps: (1) CVD porous silicon-carbon materials are formed by depositing silane gas and carbon source gas in porous carbon through a fluidized bed / rotary kiln vapor deposition process; (2) The obtained CVD silicon-carbon material is subjected to low-temperature ozone pretreatment; (3) The ozone-pretreated CVD silicon-carbon material is subjected to ALD atomic layer deposition to form a nanoscale metal oxide coating layer on the material surface.

2. The preparation method according to claim 1, characterized in that, Preferably, in step (1), the silicon deposition and carbon coating step of the rotary kiln equipment generally includes placing porous carbon, purging with nitrogen at room temperature, heating to 420 degrees and purging with silane gas for nano-silicon deposition, and heating to 500 degrees and purging with acetylene gas for preliminary carbon coating on the surface; the silicon deposition and carbon coating step of the fluidized bed equipment generally includes placing porous carbon, purging with nitrogen at room temperature for half an hour, heating to 420 degrees and continuously purging with nitrogen for 2 hours, then purging with silane gas at 420 degrees for 2 hours, then continuing to purge with nitrogen and heating to 500 degrees, and purging with acetylene gas for 4 hours for preliminary carbon coating on the surface; Preferably, in step (1), the porous carbon substrate includes a biomass substrate, a resin-based substrate, or an asphalt-based porous carbon substrate; Preferably, in step (1), the carbon source gas is selected from one or more different carbon-containing gases selected from methane, ethylene, acetylene, propylene, and toluene.

3. The preparation method according to claim 1, characterized in that, Preferably, in step (2), the ozone treatment method for CVD silicon carbide materials is to place the material into an ALD device and directly or pulse-feed ozone gas with nitrogen as the carrier gas. Preferably, in step (2), the ozone pretreatment temperature for CVD silicon carbide materials is below 200 degrees Celsius; Preferably, in step (2), the ozone pretreatment time for CVD silicon carbide materials is 10s-30min.

4. The preparation method according to claim 1, characterized in that, Preferably, in step (3), ALD atomic layer deposition is performed on the pretreated CVD silicon-carbon, and the coating layer includes one or more of aluminum oxide, titanium oxide, zinc oxide, cerium oxide or zirconium oxide; Preferably, in step (3), ALD atomic layer deposition is performed on the pretreated CVD silicon-carbon, and the raw material for the metal oxide deposition coating layer is an organometallic vapor containing the corresponding metal element, and the oxygen source is water vapor or ozone. Preferably, in step (3), the ALD deposition process is pulse deposition, and the pulse time of the reaction gas source is 0.01s-3s; Preferably, in step (3), the ALD deposition process is pulse deposition, and the pulse temperature of the reaction gas source is 50 degrees to 500 degrees. Preferably, in step (3), the ALD deposition process is pulse deposition, and the number of pulse cycles is 5 to 500.

5. A vapor-phase porous silicon-carbon anode material, wherein the material is prepared by the preparation method according to any one of claims 1 to 4, and the vapor-phase porous silicon-carbon anode material, after battery testing, has a first-charge specific capacity of not less than 1600 mAh / g, a first-charge coulombic efficiency of not less than 88%, and an electrode full-charge expansion rate of not more than 60%.

Images