CVD silicon carbon structure and preparation process
By coating a sub-nanometer barrier layer, a buffer layer and a conductive layer on the CVD silicon-carbon substrate, the problems of poor bonding and volume expansion of silicon-carbon materials are solved, and the cycle stability and first-cycle coulombic efficiency of the battery are improved.
Patent Information
- Application Number
- CN202510853117.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-24
- Publication Date
- 2025-09-26
AI Technical Summary
The existing CVD silicon-carbon materials have poor bonding between silicon and porous carbon during the cycle process, resulting in the shedding of active nano-silicon particles. In addition, the edges and corners of the biomass porous carbon break during the compaction process, making it impossible to block electrolyte erosion, leading to severe battery degradation.
A sub-nanometer barrier layer, a sub-nanometer buffer layer, and a sub-nanometer conductive layer are coated on a CVD silicon-carbon substrate, and a lithium aluminum phosphate film is deposited by atomic layer deposition to form a three-layer structure with a thickness controlled within 1 nm, thereby enhancing the bonding force and alleviating volume expansion.
The compaction performance and cycle stability of the material are improved, the capacity loss is reduced, the electron channel and ion channel are expanded, and the first-cycle coulombic efficiency is improved.
Smart Images
Figure CN120709319A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a structure and a preparation process of CVD silicon carbon, belonging to the technical field of CVD silicon carbon preparation. Background Art
[0002] Silicon-carbon composite anodes prepared by chemical vapor deposition (CVD) have attracted widespread attention due to their advantages such as high charge and discharge efficiency, good cycle stability, low equipment requirements, and suitability for industrial production.
[0003] At present, the porous carbon substrates of CVD silicon-carbon materials are mainly divided into two categories: resin-based and biomass-based. Both types of porous carbon substrates can provide a large internal surface for depositing silicon, and at the same time have a certain structural strength. Among them, resin-based porous carbon has the unique advantages of extremely high sphericity, large specific surface area, and high pore volume. Its high sphericity brings greater pressure resistance to the CVD silicon-carbon prepared by this substrate, which is conducive to its application in batteries with higher volume density. However, this route faces a wide variety of resins and it is extremely difficult to find a suitable resin substrate. In terms of process, it also faces the difficulty of balling process, especially the difficulty of controlling particle size, which leads to high costs.
[0004] Biomass porous carbon has the advantages of wide sources, large reserves, mature preparation technology, etc., which also brings about low prices.
[0005] However, biomass, especially coconut shells, will form sharp edges during the processing of porous carbon microparticles. Compaction will cause the edges to break, which cannot prevent the electrolyte from eroding the internal active silicon, resulting in severe battery degradation and poor overall performance.
[0006] In addition, the bonding force between the porous carbon substrate and silicon is poor. When silicon undergoes huge volume changes during charging and discharging, the active nano-silicon particles easily fall off from the electronic conductive network constructed by the porous carbon substrate, lose their electrochemical activity, and ultimately lead to capacity loss of the negative electrode material.
[0007] At present, how to strengthen the bonding between silicon and porous carbon, alleviate the expansion of silicon-carbon materials during cycling, and improve the electrochemical performance of silicon-carbon negative electrodes are technical problems that technicians in this field urgently need to solve. Summary of the Invention
[0008] The main purpose of the present invention is to provide a CVD silicon carbon structure and preparation process.
[0009] The purpose of the present invention can be achieved by adopting the following technical solutions:
[0010] A CVD silicon-carbon structure comprises a CVD silicon-carbon material substrate, and a sub-nanometer barrier layer coated on the surface of the CVD silicon-carbon substrate;
[0011] The sub-nanometer buffer layer is coated on the sub-nanometer barrier layer;
[0012] The sub-nanometer conductive layer is coated on the sub-nanometer buffer layer.
[0013] Preferably, the sub-nanometer barrier layer comprises silicon carbide, aluminum phosphide, aluminum nitride, aluminum oxide, lithium phosphate, aluminum phosphate, or lithium aluminum phosphate;
[0014] The sub-nanometer conductive layer includes silicon carbide, aluminum phosphide, aluminum nitride, aluminum oxide, lithium phosphate, aluminum phosphate, and lithium aluminum phosphate.
[0015] A CVD silicon-carbon preparation process comprises the following steps:
[0016] S11: providing a CVD silicon-carbon material substrate;
[0017] S12: introducing a vapor precursor to deposit a lithium aluminum phosphate thin film on the surface of the CVD silicon-carbon material by atomic layer deposition at a flow rate of 5 to 200 sccm;
[0018] S13: performing multilayer deposition, repeating the process cycle of step S12 on the lithium aluminum phosphate thin film material obtained by the double-layer atomic layer deposition, thereby stacking another lithium aluminum phosphate thin film on the lithium aluminum phosphate thin film material, while controlling the total thickness of the lithium aluminum phosphate film to not more than 2 nm;
[0019] S14: The material obtained in S13 is used in subsequent steps to prepare the CVD silicon-carbon material of the structure.
[0020] Preferably, the S12 specifically includes the following steps:
[0021] S121: Laying out base materials: tert-butyl lithium is laid out in the tert-butyl lithium tank, trimethyl phosphate is laid out in the trimethyl phosphate cylinder, trimethyl aluminum is laid out in the trimethyl aluminum cylinder, and a porous carbon substrate is laid out in the reaction chamber;
[0022] S122: Heating the equipment, heating the initial temperature of tert-butyl lithium to 120°C and the initial temperature of trimethyl phosphate to 45°C; heating the initial temperature of the reaction chamber to 100-500°C, heating the initial temperature of the transport pipeline and the ALD pulse valve to 180°C, and evacuating the reaction chamber and the transport pipeline to a pressure of 5-500 Pa;
[0023] S123: After applying a lithium source and the ALD system is evenly heated, the ALD pulse valve at the tert-butyl lithium tank is opened for 300 to 3000 ms to allow the tert-butyl lithium to enter the reaction chamber, undergo self-saturation adsorption and exchange reaction with the surface of the substrate to be plated, and generate a lithium-substituted substrate;
[0024] S124: Cleaning the remaining material, introducing an inert gas pulse into the reaction chamber to clean the unreacted tert-butyl lithium and the by-products generated by the reaction;
[0025] S125: Reduction reaction: Open the ALD pulse valve at the trimethyl phosphate cylinder for 20 to 1000 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the lithium-substituted base material, and form a lithium phosphate thin film blank;
[0026] S126: Cleaning the film, introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction, thereby forming a single-layer atomic layer deposited lithium phosphate film through self-saturation;
[0027] S127: Open the ALD pulse valve at the trimethyl aluminum cylinder for 20 to 1000 ms to allow the trimethyl aluminum to enter the reaction chamber in the gas phase and chemically adsorb and react with the surface of the lithium phosphate film to generate an aluminum-based replacement base material;
[0028] S128: Cleaning the membrane: introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction;
[0029] S129: Reduction reaction: Open the ALD pulse valve at the trimethyl phosphate cylinder for 20 to 1000 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the aluminum-substituted base material, and form a lithium aluminum phosphate thin film blank;
[0030] S1210: Cleaning and film formation: Introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction, and then generating a double-layer atomic layer deposited lithium aluminum phosphate film through self-saturation.
[0031] Preferably, steps S121 to S1210 use nitrogen as the carrier gas;
[0032] In S13, the total thickness of the lithium aluminum phosphate film is controlled to be no more than 1 nm;
[0033] In step S122, the initial temperature of the reaction chamber is heated to 150-300°C, and the reaction chamber and the transport pipeline are evacuated to a pressure of 10-200 Pa;
[0034] In step S123, the ALD pulse valve at the tert-butyl lithium tank is opened for 500 to 2000 ms;
[0035] In step S125, the ALD pulse valve at the trimethyl phosphate cylinder is opened for 50 to 500 ms;
[0036] In step S127, the ALD pulse valve at the trimethyl aluminum cylinder is opened for 50 to 500 ms;
[0037] In step S129, the ALD pulse valve at the trimethyl phosphate cylinder is opened for 50 to 500 ms.
[0038] Beneficial technical effects of the present invention:
[0039] The present invention provides a CVD silicon-carbon structure and preparation process. By adding three sub-nanometer layers with controllable thickness to a CVD silicon-carbon substrate, the thickness of the sub-nanometer layers can be controlled to no more than 1 nm, expanding more electron and ion channels, while having minimal impact on the first-cycle Coulombic efficiency of the negative electrode and causing no significant capacity loss. Furthermore, the buffer layer and outermost conductive layer provided by the present invention improve the material's compaction performance and reduce volume expansion during cycling, thereby improving the material's cyclic stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Figure 1 This is a diagram showing the steps for preparing a sub-nanometer barrier layer and a sub-nanometer conductive layer according to a preferred embodiment 1 of a CVD silicon carbon structure and preparation process of the present invention;
[0041] Figure 2 A diagram showing the steps for preparing a silicon-carbon negative electrode structure according to a preferred embodiment of a CVD silicon-carbon structure and preparation process of the present invention;
[0042] Figure 3 SEM images of samples of Comparative Example (a) and Example 1 (b), Example 2 (c) and Example 3 (d) according to a preferred embodiment of the structure and preparation process of CVD silicon carbon of the present invention;
[0043] Figure 4 Figure 1 is a graph showing the electrochemical expansion performance test of a lithium battery according to a preferred embodiment of the structure and preparation process of CVD silicon carbon of the present invention (Comparative Example (a), Example 3 (b), Example 1 (c));
[0044] Figure 5 Graph showing electrochemical cycle capacity retention rates of a comparative example and Example 1 according to a preferred embodiment of the structure and preparation process of CVD silicon-carbon of the present invention;
[0045] Figure 6 This is a diagram of the barrier layer-buffer layer-conductive layer structure of the present invention according to a preferred embodiment of the structure and preparation process of CVD silicon carbon of the present invention. DETAILED DESCRIPTION
[0046] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is further described in detail below with reference to embodiments and drawings, but the embodiments of the present invention are not limited thereto.
[0047] The process steps of the CVD silicon carbon substrate provided in the present invention are as follows:
[0048] Silicon was deposited on the porous carbon substrate by vapor deposition. Specifically, the fluidized bed equipment (FB-CVD-20) was heated to 480°C, and silane (SiH4) and nitrogen were introduced. Nitrogen was used as a carrier gas, the silane flow rate was 3 L / min, and the nitrogen flow rate was 15 L / min. After 200 minutes of deposition, the silane flow was turned off and the substrate was allowed to cool naturally.
[0049] Example 1: A structure and preparation process of CVD silicon carbon;
[0050] The sub-nanometer barrier / conductive layer used was lithium aluminum phosphate. Atomic layer deposition (ALD) was used (using a Yunlong-LAY-500G ALD system) to deposit a lithium aluminum phosphate thin film on a CVD silicon-carbon substrate. A carbon layer was then deposited on the sub-nanometer barrier layer using chemical vapor deposition. Finally, a lithium aluminum phosphate thin film was deposited on the carbon layer using atomic layer deposition.
[0051] (The CVD silicon-carbon substrate is made of porous carbon MRP16 produced by Changzhou Chuangming Super Electric Material Technology Co., Ltd. and deposited with a certain amount of silicon. The silicon content is the same in the embodiment and the comparative example, both set to 50%.)
[0052] Step (1): depositing a lithium aluminum phosphate thin film on a CVD silicon carbon substrate, specifically comprising the following steps:
[0053] Step S121: placing a lithium source in a tert-butyl lithium tank, placing trimethyl phosphate in a trimethyl phosphate cylinder, placing trimethyl aluminum in a trimethyl aluminum cylinder, and placing a porous carbon substrate in a reaction chamber;
[0054] Step S122: The equipment is heated to an initial temperature of tert-butyl lithium to 120°C and an initial temperature of trimethyl phosphate to 45°C. The reaction chamber is also heated to an initial temperature of 200°C, and the transport pipeline and ALD pulse valve are heated to an initial temperature of 180°C. The reaction chamber and transport pipeline are then evacuated to a pressure of 1000 Pa.
[0055] Step S123: After the ALD system is evenly heated, the ALD pulse valve at the tert-butyl lithium tank is opened for 800 ms to allow tert-butyl lithium to enter the reaction chamber, undergo self-saturated adsorption and exchange reaction with the surface of the substrate to be plated, and generate a lithium-substituted substrate;
[0056] Step S124: introducing an inert gas pulse into the reaction chamber to clean the unreacted tert-butyl lithium and the by-products generated by the reaction;
[0057] Step S125: opening the ALD pulse valve at the trimethyl phosphate cylinder for 200 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the lithium-substituted base material, and form a lithium phosphate thin film blank;
[0058] Step S126: introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the byproducts generated by the reaction, thereby forming a single-layer atomic layer deposition lithium phosphate film through self-saturation;
[0059] Step S127: opening the ALD pulse valve at the trimethyl aluminum cylinder for 200 ms to allow the trimethyl aluminum to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the lithium phosphate film, and generate an aluminum-based replacement base material;
[0060] Step S128: introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction;
[0061] Step S129: opening the ALD pulse valve at the trimethyl phosphate cylinder for 200 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the aluminum-substituted base material, and form a lithium aluminum phosphate thin film blank;
[0062] Step S1210: introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the byproducts generated by the reaction, thereby forming a double-layer atomic layer deposition lithium aluminum phosphate film through self-saturation;
[0063] Step (2): The material obtained in step (1) is subjected to carbon coating treatment, specifically, in a rotary kiln, the equipment is heated to 580°C, acetylene is introduced, the acetylene flow rate is 3L / min, the nitrogen flow rate remains unchanged, and after deposition for 93 minutes, it is naturally cooled.
[0064] (3) Repeat step (1).
[0065] Example 2: A structure and preparation process of CVD silicon carbon.
[0066] Compared with Example 1, step (3) was not performed.
[0067] Example 3: A structure and preparation process of CVD silicon carbon;
[0068] Compared with Example 1, steps (2) and (3) were not performed.
[0069] Comparative Example: The CVD silicon carbon substrate was not treated in any way and served as a blank control sample of the embodiment.
[0070] The CVD silicon carbon of Examples 1 to 3 and the CVD silicon carbon substrate structure of Comparative Example 1 were subjected to BET test, SEM test, electrochemical-mechanical property test and electrochemical test. The results are as follows:
[0071] Table 1 Comparative analysis results of Examples 1.2.3 and Comparative Example 1;
[0072]
[0073]
[0074] Figure 3 SEM images of samples of Comparative Example (a) and Example 1 (b), Example 2 (c) and Example 3 (d).
[0075] exist Figure 3 It can be clearly seen from the SEM photos that Figure 3 The surface of the untreated CVD silicon carbon substrate in a is rough, with very few exposed silicon agglomerates on the surface and sharp edges and corners; after being coated with a layer of aluminum oxide Figure 3 There is no obvious difference between the surface of d and the initial one, which is due to the smaller thickness of the coated lithium aluminum phosphate and the slightly reduced edges and corners.
[0076] After the sample was coated with carbon layer, Figure 3 c, It is clearly visible that the number of miscellaneous particles on the sample surface is significantly less, and except for the edges, the edges and corners of the rest of the sample are almost gone, and it appears thick under the electron microscope background; Figure 3 b is a fully processed CVD silicon carbon sample, which has formed the unique barrier layer-buffer layer-conductive layer structure mentioned in the present invention. A dense lithium aluminum phosphate film is formed on the surface of the sample, with no exposed particles on the surface, a clean surface, and evenly covered edges and corners.
[0077] Figure 4 Lithium battery expansion performance test.
[0078] It is clearly visible that the untreated blank sample expands rapidly during the charging process, with the thickness increasing by about 5μm from 60,000s to 18,000s.
[0079] It is clearly visible that the expansion is relatively slow during the charging process, but the phenomenon of thickness expansion during the charging process can still be seen intuitively. From 60,000s to 18,000s, the thickness increases by about 2μm.
[0080] It is clearly visible that during the charging process, the expansion is more gradual and the thickness remains basically unchanged from 6000s to 15000s, which indicates that the buffer layer designed in the present invention plays a positive role. From 60000s to 18000s, the thickness increases by about 1.6μm.
[0081] Figure 5Electrochemical cycle capacity retention results of the comparative example and Example 1;
[0082] Figure 5 The difference between the two curves is clearly visible. The establishment of the conductive layer and the barrier layer significantly improves the cycle performance of CVD silicon carbon. After 200 cycles, there is no obvious drop.
[0083] Figure 6 The barrier layer-buffer layer-conductive layer structure of the present invention;
[0084] It should be noted that the present invention mainly provides an atomic layer deposition method to introduce the barrier layer and conductive layer structure, and the intermediate buffer layer is introduced by the CVD method. The introduction of the barrier layer, conductive layer and buffer layer may also be achieved by vapor deposition method, solution method, evaporation method, magnetron sputtering and other technologies.
[0085] The above is only a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the scope disclosed by the present invention, which fall within the scope of protection of the present invention.
Claims
1. A CVD silicon-carbon structure, characterized in that: It includes a CVD silicon-carbon material substrate, and a sub-nanometer barrier layer coated on the surface of the CVD silicon-carbon substrate; The sub-nanometer buffer layer is coated on the sub-nanometer barrier layer; The sub-nanometer conductive layer is coated on the sub-nanometer buffer layer.
2. A CVD silicon-carbon structure according to claim 1, characterized in that: The sub-nanometer barrier layer includes silicon carbide, aluminum phosphide, aluminum nitride, aluminum oxide, lithium phosphate, aluminum phosphate, and lithium aluminum phosphate; The sub-nanometer conductive layer includes silicon carbide, aluminum phosphide, aluminum nitride, aluminum oxide, lithium phosphate, aluminum phosphate, and lithium aluminum phosphate.
3. A CVD silicon-carbon preparation process, based on the CVD silicon-carbon structure according to any one of claims 1-2, characterized in that: The steps include: S11: providing a CVD silicon-carbon material substrate; S12: introducing a vapor precursor to deposit a lithium aluminum phosphate thin film on the surface of the CVD silicon-carbon material by atomic layer deposition at a flow rate of 5 to 200 sccm; S13: performing multilayer deposition, repeating the process cycle of step S12 on the lithium aluminum phosphate thin film material obtained by the double-layer atomic layer deposition, thereby stacking another lithium aluminum phosphate thin film on the lithium aluminum phosphate thin film material, while controlling the total thickness of the lithium aluminum phosphate film to not more than 2 nm; S14: The material obtained in S13 is used in subsequent steps to prepare the CVD silicon-carbon material of the structure.
4. A CVD silicon-carbon preparation process according to claim 3, characterized in that: The S12 specifically includes the following steps: S121: Laying out base materials: tert-butyl lithium is laid out in the tert-butyl lithium tank, trimethyl phosphate is laid out in the trimethyl phosphate cylinder, trimethyl aluminum is laid out in the trimethyl aluminum cylinder, and a porous carbon substrate is laid out in the reaction chamber; S122: Heating the equipment, heating the initial temperature of tert-butyl lithium to 120°C and the initial temperature of trimethyl phosphate to 45°C; heating the initial temperature of the reaction chamber to 100-500°C, heating the initial temperature of the transport pipeline and the ALD pulse valve to 180°C, and evacuating the reaction chamber and the transport pipeline to a pressure of 5-500 Pa; S123: After applying a lithium source and the ALD system is evenly heated, the ALD pulse valve at the tert-butyl lithium tank is opened for 300 to 3000 ms to allow the tert-butyl lithium to enter the reaction chamber, undergo self-saturation adsorption and exchange reaction with the surface of the substrate to be plated, and generate a lithium-substituted substrate; S124: Cleaning the remaining material, introducing an inert gas pulse into the reaction chamber to clean the unreacted tert-butyl lithium and the by-products generated by the reaction; S125: Reduction reaction: Open the ALD pulse valve at the trimethyl phosphate cylinder for 20 to 1000 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the lithium-substituted base material, and form a lithium phosphate thin film blank; S126: Cleaning the film, introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction, thereby forming a single-layer atomic layer deposited lithium phosphate film through self-saturation; S127: Open the ALD pulse valve at the trimethyl aluminum cylinder for 20 to 1000 ms to allow the trimethyl aluminum to enter the reaction chamber in the gas phase and chemically adsorb and react with the surface of the lithium phosphate film to generate an aluminum-based replacement base material; S128: Cleaning the membrane: introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction; S129: Reduction reaction: Open the ALD pulse valve at the trimethyl phosphate cylinder for 20 to 1000 ms to allow the trimethyl phosphate to enter the reaction chamber in the gas phase, undergo chemical adsorption and reaction with the surface of the aluminum-substituted base material, and form a lithium aluminum phosphate thin film blank; S1210: Cleaning and film formation: Introducing an inert gas pulse into the reaction chamber to clean the unreacted phosphoric acid source and the by-products generated by the reaction, and then generating a double-layer atomic layer deposited lithium aluminum phosphate film through self-saturation.
5. A CVD silicon-carbon preparation process according to claim 4, characterized in that: In steps S121 to S1210, nitrogen is used as the carrier gas; In S13, the total thickness of the lithium aluminum phosphate film is controlled to be no more than 1 nm; In step S122, the initial temperature of the reaction chamber is heated to 150-300°C, and the reaction chamber and the transport pipeline are evacuated to a pressure of 10-200 Pa; In step S123, the ALD pulse valve at the tert-butyl lithium tank is opened for 500 to 2000 ms; In step S125, the ALD pulse valve at the trimethyl phosphate cylinder is opened for 50 to 500 ms; In step S127, the ALD pulse valve at the trimethyl aluminum cylinder is opened for 50 to 500 ms; In step S129, the ALD pulse valve at the trimethyl phosphate cylinder is opened for 50 to 500 ms.