Silicon-carbon negative electrode material, preparation method thereof and battery

Abstract

The invention discloses a porous silicon carbon negative electrode material, a preparation method thereof and a battery. A matrix of the porous silicon carbon negative electrode material is porous carbon, a conductive layer is deposited in pores of the porous carbon, a fast ion layer is deposited on the surface of the conductive layer, a silicon nanoparticle layer is deposited on the outer side of the fast ion layer, and carbon coating layers are deposited on the surface of the porous carbon and among silicon nanoparticles. According to the method, the conductive layer is firstly deposited, then the fast ion layer is deposited, and a Li reaction place is changed from point-to-point contact of silicon particles and porous carbon into surface-to-surface contact of the conductive layer and the conductive ion layer, so that a Li < + > desolvation barrier and electronic impedance of a substrate are greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon-carbon negative electrode materials, and particularly relates to a silicon-carbon negative electrode material, a preparation method thereof and a battery. BACKGROUND

[0002] The statements herein merely provide background technology related to the present application, and do not necessarily constitute prior art.

[0003] Continuously improving the energy density of batteries is one of the key directions of lithium-ion battery technology innovation. At present, the actual capacity of mainstream negative electrode graphite materials has approached the theoretical limit, and the space for further improvement is limited. Silicon-based negative electrode materials have become the research focus due to their advantages of abundant resources, ultra-high theoretical capacity and environmental friendliness.

[0004] However, the kinetic performance of silicon-based materials is insufficient, which seriously restricts their large-scale application in the field of electric vehicles.

[0005] In order to solve the above problems, the prior art attempts to prepare a silicon-carbon composite material by compounding porous carbon and silicon particles, that is, depositing silicon nanoparticles in the porous carbon, which can not only improve the energy density of the silicon-carbon composite material, but also ensure the electrical conductivity of the composite material. In addition, this kind of composite material can also alleviate the huge volume expansion and contraction of silicon nanoparticles during the charging and discharging process.

[0006] However, there are many defects (such as vacancies) in the porous carbon, which will reduce the electronic conductivity due to factors such as the destruction of the continuity of the conductive network. In addition, most of the point contacts are formed between the silicon nanoparticles and the porous carbon in the silicon-carbon composite material obtained by depositing silicon nanoparticles in the porous carbon, which seriously affects the transmission efficiency of electrons. In addition, when the pores of the porous carbon are large, the silicon nanoparticles are stacked inside. Since the electronic conductivity and lithium ion transmission performance of the silicon nanoparticles are poor, it is easy to cause a large number of silicon nanoparticles to be difficult to obtain sufficient electrons and lithium ions, thereby leading to low utilization rate of silicon. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the present application is to provide a silicon-carbon negative electrode material, a preparation method thereof and a battery.

[0008] In order to achieve the above-mentioned purpose, the present application is realized by the following technical solutions: In a first aspect, the present application provides a silicon-carbon negative electrode material, the matrix of which is porous carbon, the pores of which are deposited with a conductive layer, the surface of which is deposited with a fast ion layer, the outside of which is deposited with a silicon nanoparticle layer, and the surface of the porous carbon and between the silicon nanoparticles are both deposited with a carbon coating layer.

[0009] In a second aspect, the present application provides a preparation method of the silicon-carbon negative electrode material, comprising the following steps: Choose porous carbon, which has mesopores distributed on it; First, a conductive layer is deposited inside the pores of porous carbon using the ALD method; Then, an ALD method is used to deposit a fast ion layer on the surface of the conductive layer, transforming the mesopores of porous carbon into micropores; Then silicon nanoparticles are deposited inside the pores of porous carbon; Finally, a carbon coating layer is deposited on the porous carbon to obtain the final product.

[0010] Thirdly, the present invention provides a battery in which the negative electrode material is prepared from the silicon-carbon negative electrode material.

[0011] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: Porous carbon materials have many internal defects. The conductive layer is deposited inside the porous carbon, which can repair or fill the internal defects to improve the conductivity of the matrix.

[0012] A fast ion layer is deposited on the surface of the conductive layer, forming a fast lithium ion transport channel. This allows lithium ions to be transported rapidly from the pore opening to the depth of the pore, enabling rapid contact and reaction between lithium ions and silicon nanoparticles, effectively improving the lithium ion transport efficiency.

[0013] If a fast ion layer is deposited first, followed by a conductive layer, the lithium ions transported by the fast ion layer must pass through the conductive layer before reacting with silicon, significantly reducing the lithium ion transport rate. Furthermore, the conductive layer struggles to repair defects in porous carbon, hindering the improvement of the composite material's conductivity. Conversely, depositing the conductive layer first, followed by the fast ion layer, changes the Li-oxidation reaction site from point-to-point contact between silicon particles and porous carbon to surface-to-surface contact between the conductive and ion-conducting layers, greatly reducing the Li-oxidation rate. + The barriers to desolvation and the electronic impedance of the matrix.

[0014] By first depositing a conductive layer inside porous carbon and then depositing a fast ion layer, the pores of the porous carbon are transformed from mesopores to micropores. When silicon nanoparticles are deposited, most of the silicon nanoparticles can come into contact with the fast ion layer and thus participate in the lithiation reaction quickly, effectively improving the utilization rate of silicon.

[0015] The carbon coating layer, as a coating layer, can limit the volume expansion during silicon lithium intercalation to a certain extent, reducing the breakage rate of silicon nanoparticles. The carbon coating layer can protect the silicon nanoparticles, preventing them from directly contacting the electrolyte and causing side reactions, and can also prevent the silicon nanoparticles from being oxidized.

[0016] In addition, the carbon coating can improve the electrical conductivity between silicon nanoparticles, thereby ensuring the conductivity of the composite material, improving reaction efficiency and silicon utilization. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the structure of the silicon-carbon anode material according to an embodiment of the present invention; Figure 2 This is a comparison diagram of the phase properties of silicon-carbon anode materials prepared in the embodiments and comparative examples of the present invention.

[0019] In the figure, 1-porous carbon; 2-mesopore; 3-fast ion layer; 4-conductive layer; 5-micropore. Detailed Implementation

[0020] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] In a first aspect, the present invention provides a silicon-carbon anode material, the matrix of which is porous carbon, a conductive layer is deposited inside the pores of the porous carbon, a fast ion layer is deposited on the surface of the conductive layer, a silicon nanoparticle layer is deposited on the outside of the conductive layer, and a carbon coating layer is deposited on the surface of the porous carbon and between the silicon nanoparticles.

[0022] Porous carbon serves as the framework and supporting structure of the entire composite material. Its porosity (especially its mesoporous structure) provides a large specific surface area and internal space to accommodate subsequently deposited conductive layers, fast ion layers, silicon nanoparticles, and carbon coatings. It also provides a buffer against the volume expansion of silicon. However, natural or synthetic porous carbon may contain structural defects that significantly hinder electron transport within the matrix, reducing overall conductivity.

[0023] The conductive layer is deposited directly on the inner walls of the pores and defects of the porous carbon matrix, connecting the originally discontinuous conductive paths and significantly reducing the electron transport impedance inside the matrix. This is the foundation for the improved conductivity of the entire structure. Furthermore, the conductive layer forms a continuous conductive film on the inner walls of the pores, providing an efficient electron transport channel for the subsequently deposited fast ion layer and silicon nanoparticle layer, ensuring that the electrons required for the lithiation / delithiation reaction can quickly reach the reaction interface.

[0024] A fast ion layer, composed of a material with high ionic conductivity, is deposited on the surface of the conductive layer. It forms a continuous thin film on the conductive layer surface, facilitating the rapid migration of lithium ions. This allows lithium ions to diffuse efficiently from the pore openings into the depths of the pores, overcoming the problem of slow ion transport at deeper pore depths in conventional materials. It provides a low-resistance ion transport path, reducing energy loss (especially the desolvation barrier) of lithium ions during their journey to the silicon particle reaction interface.

[0025] The fast ion layer is deposited above the conductive layer and below the silicon nanoparticles. This order allows it to directly face the silicon nanoparticles, enabling lithium ions to react immediately with silicon after passing through the fast ion layer. If the order is reversed (fast ions first, then conductive), lithium ions must pass through the conductive layer to reach the silicon, severely hindering the transport rate.

[0026] Silicon nanoparticles are deposited on the outside of the fast ion layer. Silicon is the core lithium-ion storage material, providing a theoretical specific capacity far exceeding that of graphite.

[0027] Silicon nanoparticles can shorten the lithium-ion diffusion path and improve reaction kinetics; alleviate volume expansion stress to some extent; and provide a larger specific surface area. Deposited on a fast-ion layer, silicon particles can directly contact the fast-ion layer, maximizing the use of the fast ion channels it provides.

[0028] The carbon coating is applied to the outer surface of the porous carbon matrix, the surface of silicon nanoparticles, and between silicon nanoparticles. The carbon coating surrounding the silicon nanoparticles provides mechanical constraint during silicon lithium intercalation expansion, absorbs some stress, reduces particle breakage and pulverization, and improves structural stability.

[0029] The carbon coating isolates silicon particles from the electrolyte, preventing direct contact and significantly reducing irreversible capacity loss and unstable SEI film growth caused by side reactions (such as continuous electrolyte decomposition and silicon oxidation). This improves coulombic efficiency and cycle life. The carbon coating also forms a continuous electron transport network between silicon particles and between silicon particles and the porous carbon matrix / conductive layer, enhancing the overall conductivity and reaction efficiency of the composite material. Furthermore, the carbon coating helps maintain the structural integrity of the pores during cycling, preventing pore collapse and blockage of ion transport pathways. Through these effects, more silicon nanoparticles can effectively participate in the reversible lithium storage reaction, improving silicon utilization.

[0030] The synergistic effect between the layers is analyzed as follows: The fast ion layer is deposited on the surface of the conductive layer, forming a tight interface between the electronic conductive layer and the fast ion layer. This surface-to-surface contact greatly reduces the desolvation energy barrier for lithium ions to enter the active material interface from the electrolyte and the impedance for electrons to cross the interface. This ensures that the electrons and lithium ions required for the lithiation / delithiation reaction can reach the reaction interface of silicon nanoparticles efficiently and with low resistance, significantly improving rate performance and reaction kinetics, which is far superior to the traditional point contact form between silicon nanoparticles and carbon matrix.

[0031] Silicon nanoparticles are directly deposited on the fast ion layer, allowing lithium ions transported at high speed through the fast ion layer to react immediately with the silicon nanoparticles without needing to pass through any barrier layer. This maximizes the efficient ion transport capability of the fast ion layer, significantly improving the rate and efficiency of the lithium ion-silicon nanoparticle contact reaction, and enhancing the utilization rate and rate performance of the silicon nanoparticles.

[0032] The sequential deposition of a conductive layer and a fast ion layer within porous carbon channels reduces the original mesopore size, creating more micropores. When silicon nanoparticles are deposited in this smaller microporous environment, they tend to adhere more tightly to the pore walls (i.e., the fast ion layer). This allows the vast majority of silicon nanoparticles to directly contact the fast ion layer, rather than accumulating in the middle of the pores. This ensures that the high-speed ion channels constructed by the fast ion layer can be fully utilized by the silicon nanoparticles, significantly improving silicon utilization and reaction uniformity.

[0033] The carbon coating directly constrains the volume expansion of silicon nanoparticles, protecting their integrity; simultaneously, it coats the outer surface of the substrate, maintaining overall structural stability. The carbon coating isolates the electrolyte, protecting silicon and its internal structure from corrosion and side reactions, thus stabilizing the SEI film. Furthermore, the carbon coating connects isolated silicon nanoparticles to the substrate / conductive layer, compensating for the poor conductivity of the silicon nanoparticles themselves and ensuring the electron network remains unobstructed during cycling.

[0034] The carbon coating is key to improving cycle stability, coulombic efficiency, and lifespan. Together with the conductive layer, it forms a dual electron protection network throughout the composite material (the conductive layer repairs and reinforces the matrix interior, while the carbon coating connects the particles and surfaces). Simultaneously, it works synergistically with the fast ion layer to maintain a highly efficient ion-electron transport interface.

[0035] In summary, the deposition of silicon nanoparticles effectively improves the capacity of the anode material; the synergy of the conductive layer (fast conductivity), the fast ion layer (fast lithium ion transport), the silicon nanoparticles (short lithium ion diffusion path), and the carbon coating layer (good conductivity) can improve the fast charge and discharge performance of the battery.

[0036] The carbon coating inhibits the expansion of silicon nanoparticles and protects the interface, while the conductive layer and carbon coating maintain the conductive network. The porous carbon matrix provides a buffer space, and the fast ion layer stabilizes the interface reaction. The synergistic effect of these structures can effectively improve the long cycle life of the battery.

[0037] The fast ion layer directly contacts silicon, and the optimized pore structure allows silicon nanoparticles to directly contact the fast ion layer. The carbon coating layer prevents silicon nanoparticles from failing, and the good conductivity and ion conductivity ensure that silicon nanoparticles can fully react. The above synergistic effect effectively improves the utilization rate of silicon.

[0038] In some embodiments, the porous carbon has a mesoporous porosity of 80-90%, a D50 of 5-10 μm, and a pore size of 2-50 nm.

[0039] In some embodiments, the thickness of the conductive layer is 0.5-25 nm, preferably 1-20 nm. For example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm.

[0040] Preferably, the conductive layer is made of at least one of Cu, Al, Ag, Pt, Au, tungsten carbide, chromium carbide, tantalum carbide, or titanium carbide, with Cu, Ag, Au, and other metals with good conductivity being preferred.

[0041] In some embodiments, the thickness of the fast ion layer is 0.5-25 nm, preferably 1-25 nm, more preferably 2-20 nm, and even more preferably 2-10 nm. For example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm.

[0042] Preferably, the material of the fast ion layer is selected from at least one of LiF, solid electrolyte, lithium titanate or alumina. More preferably, the material of the fast ion layer is an oxide electrolyte (such as LLZO, Li3PO4, etc.).

[0043] When silicon particles are deposited on the ion layer, the bonding force between the silicon particles and the substrate is also enhanced.

[0044] In some embodiments, silicon nanoparticles account for 20-60% of the mass of the silicon-carbon composite material.

[0045] In some embodiments, the carbon coating layer accounts for 1-5% of the mass of the silicon nanoparticles.

[0046] In a second aspect, the present invention provides a method for preparing the silicon-carbon anode material, comprising the following steps: selecting porous carbon, wherein mesopores are distributed on the porous carbon; First, a conductive layer is deposited inside the pores of porous carbon using the ALD method; Then, an ALD method is used to deposit a fast ion layer on the surface of the conductive layer, transforming the mesopores of porous carbon into micropores; Then silicon nanoparticles are deposited inside the pores of porous carbon; Finally, a carbon coating layer is deposited on the porous carbon to obtain the final product.

[0047] Atomic layer deposition (ALD) is a thin film deposition method based on self-limiting surface chemical reactions. Its core principle is to achieve precise and uniform growth of materials at the atomic layer level on the substrate surface by alternating pulses of different precursor gases and thoroughly purging with inert gas between each pulse.

[0048] Thirdly, the present invention provides a battery in which the negative electrode material is prepared from the silicon-carbon negative electrode material.

[0049] The present invention will be further described below with reference to the embodiments.

[0050] Example 1 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 30 nm, and a porosity of 80%. A copper layer with a thickness of 20 nm was deposited in the pores of porous carbon using the ALD method: copper acetylacetone source pulse time 1.5 s, carrier gas Ar, purging 20 s, reducing gas H2, pulse time 2.5 s, purging 20 s, cycle 200 times. LiF with a thickness of 8.2 nm was deposited in the pores of porous carbon using the ALD method: lithium tert-butoxide as the lithium source with a pulse time of 0.5 s and Ar / N2 as the carrier gas, followed by a 20 s purge; and TiF4 as the fluorine source with a pulse time of 0.5 s and Ar / N2 as the carrier gas, followed by a 20 s purge, for a total of 40 cycles. A 50% silicon nanoparticle layer was deposited in the pores of porous carbon using CVD: a mixed gas of silane, hydrogen, and Ar, with silane volume fraction of 15% and hydrogen volume fraction of 40%; the deposition temperature of the nano-silicon was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0051] The above materials were mixed with CMC, SBR, and SP in a ratio of 96:1:2:1 to form a slurry. The slurry was then coated onto copper foil at a coating weight of 80 g / m². 2After the electrode is dried, it is prepared into a sheet and assembled into a coin cell. The corresponding electrode is a lithium sheet, the electrolyte is 1 MLiPF6, and the solvent is a mixture of EC, DEC and DMC in a volume ratio of 1:1:1.

[0052] Example 2 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 10 nm, and a porosity of 80%. A copper layer with a thickness of 4.1 nm was deposited in porous carbon pores using the ALD method: copper acetylacetone source pulse time 1.5 s, carrier gas Ar, purging 20 s, reducing gas H2, pulse time 2.5 s, purging 20 s, cycle 40 times. LiF with a thickness of 4.1 nm was deposited in porous carbon using the ALD method: lithium tert-butoxide as the lithium source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging; and TiF4 as the fluorine source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging, for a total of 20 cycles. A 50% silicon nanoparticle layer was deposited in the pores using CVD: a mixed gas of silane, hydrogen, and Ar, with silane volume fraction of 15% and hydrogen volume fraction of 40%; the deposition temperature of the nano-silicon was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0053] The above materials were mixed with CMC, SBR, and SP in a ratio of 96:1:2:1 to form a slurry. The slurry was then coated onto copper foil at a coating weight of 80 g / m². 2 After the electrode sheets are dried, the sheet fabrication and battery assembly are carried out, as in Example 1.

[0054] Example 3 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 20 nm, and a porosity of 80%. A copper layer with a thickness of 12.2 nm was deposited in porous carbon pores using the ALD method: copper acetylacetone source pulse time 1.5 s, carrier gas Ar, purging 20 s, reducing gas H2, pulse time 2.5 s, purging 20 s, cycle 120 times. LiF with a thickness of 6.0 nm was deposited in porous carbon using the ALD method: lithium tert-butoxide as the lithium source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging; and TiF4 as the fluorine source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging, for a total of 30 cycles. 50% silicon nanoparticles were deposited in the pores using CVD. The silicon nanoparticle layer consisted of a mixed gas of silane, hydrogen, and Ar, with silane comprising 15% by volume and hydrogen comprising 40% by volume. The deposition temperature of the silicon nanoparticles was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0055] The above materials were mixed with CMC, SBR, and SP in a ratio of 96:1:2:1 to form a slurry. The slurry was then coated onto copper foil at a coating weight of 80 g / m². 2 After the electrode sheets are dried, the sheet fabrication and battery assembly are carried out, as in Example 1.

[0056] Example 4 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 20 nm, and a porosity of 80%. An Ag layer with a thickness of 12.5 nm was deposited in porous carbon pores using the ALD method: silver source trimethylphosphine silver pulse time 1.5 s, carrier gas Ar, purging 20 s, reducing gas H2, pulse time 5 s, purging 20 s, cycle 125 times. Lithium titanate with a thickness of 6.5 nm was deposited in porous carbon using the ALD method: titanium source tetraisopropyl titanate pulse 1s, H2O pulse 1s, purge 20s, cycle 60 times; lithium source tert-butoxide pulse 1.5s, H2O pulse 1s, purge 20s, cycle 50 times, annealed at 300℃. 50% silicon nanoparticles were deposited in the pores using CVD. The silicon nanoparticle layer consisted of a mixed gas of silane, hydrogen, and Ar, with silane comprising 15% by volume and hydrogen comprising 40% by volume. The deposition temperature of the silicon nanoparticles was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0057] Example 5 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 30 nm, and a porosity of 85%. A 13.6 nm thick tungsten carbide layer was deposited in porous carbon pores using the ALD method: tungsten source (tungsten hexacarbonyl) pulse for 1.5 s, carrier gas was Ar, purging for 20 s, C2H4 pulse for 1.5 s, H2 plasma was introduced for 5 s, purging for 20 s, and the cycle was repeated 120 times. Alumina with a thickness of 7.8 nm was deposited in porous carbon using the ALD method: aluminum source trimethylaluminum pulse 0.1 s, purge 20 s, H2O pulse 0.1 s, purge 20 s, cycle 80 times; 50% silicon nanoparticles were deposited in the pores using CVD. The silicon nanoparticle layer consisted of a mixed gas of silane, hydrogen, and Ar, with silane comprising 15% by volume and hydrogen comprising 40% by volume. The deposition temperature of the silicon nanoparticles was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0058] Comparative Example 1 Compared with Example 2, the difference is that the conductive layer and fast ion layer are omitted, while everything else is the same as Example 2.

[0059] Specifically as follows: A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 10 nm, and a porosity of 80%. A 50% silicon nanoparticle layer was deposited in the pores using CVD: a mixed gas of silane, hydrogen, and Ar, with silane volume fraction of 15% and hydrogen volume fraction of 40%; the deposition temperature of the nano-silicon was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0060] The above materials are mixed with CMC, SBR, and SP in a ratio of 96:1:2:1 to form a slurry. The slurry is then coated onto copper foil. After the electrode sheets are dried, the sheets are fabricated and the batteries are assembled.

[0061] Comparative Example 2 A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, a micropore diameter of 1.8 nm, and a porosity of 80%. A silicon nanoparticle layer with a content of 50% was deposited in the pores by CVD, followed by carbon deposition with a content of 1% of the silicon deposition amount, as in Example 2. The above materials were mixed with CMC, SBR, and SP in a ratio of 96:1:2:1 to form a slurry. The slurry was then coated onto copper foil at a coating weight of 80 g / m². 2 After the electrode sheets are dried, the sheet fabrication and battery assembly are carried out.

[0062] Comparative Example 3 The difference from Example 2 is that a LiF layer with a thickness of 4.1 nm is deposited first, followed by a copper layer with a thickness of 4.1 nm. All other aspects are the same as in Example 2.

[0063] Comparative Example 4 The difference between Example 2 and Example 3 is that the LiF layer deposition step is placed after the silicon nanoparticle layer deposition, while the rest is the same as Example 2.

[0064] Specifically as follows: A method for preparing a silicon-carbon anode material includes the following steps: Porous carbon was selected, with a D50 of 5 μm, an average mesopore diameter of 10 nm, and a porosity of 80%. A copper layer with a thickness of 4.1 nm was deposited in porous carbon pores using the ALD method: copper acetylacetone source pulse time 1.5 s, carrier gas Ar, purging 20 s, reducing gas H2, pulse time 2.5 s, purging 20 s, cycle 40 times. A 50% silicon nanoparticle layer was deposited in the pores using CVD: a mixed gas of silane, hydrogen, and Ar, with silane volume fraction of 15% and hydrogen volume fraction of 40%; the deposition temperature of the nano-silicon was 500℃, the deposition time was 100 min, and the flow rate of the mixed gas of silane, hydrogen, and Ar was 0.25 L / min. LiF with a thickness of 4.1 nm was deposited in porous carbon using the ALD method: lithium tert-butoxide as the lithium source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging; and TiF4 as the fluorine source with a pulse time of 0.5 s, Ar / N2 as the carrier gas, and 20 s purging, for a total of 20 cycles. Finally, carbon is deposited, with the carbon coating accounting for 1% of the total silicon deposition.

[0065] Comparative Example 5 The difference from Example 2 is that the 4.1 nm thick copper layer is omitted, while everything else is the same as in Example 2.

[0066] Comparative Example 6 The difference from Example 2 is that the 4.1 nm thick LiF layer is omitted; otherwise, they are the same as in Example 2.

[0067] Table 1. Electrochemical impedance spectroscopy (EIS) tests were performed on the assembled coin cells to analyze their performance changes:

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A porous silicon-carbon anode material, characterized in that: Its matrix is ​​porous carbon, with a conductive layer deposited inside the pores of the porous carbon, a fast ion layer deposited on the surface of the conductive layer, a silicon nanoparticle layer deposited on the outside of the fast ion layer, and a carbon coating layer deposited on the surface of the porous carbon and between the silicon nanoparticles.

2. The porous silicon-carbon anode material according to claim 1, characterized in that: The porous carbon has a mesoporous porosity of 80-90%, a D50 of 5-10 μm, and a pore size of 2-50 nm.

3. The porous silicon-carbon anode material according to claim 1, characterized in that: The thickness of the conductive layer is 0.5-25nm, preferably 1-20nm.

4. The porous silicon-carbon anode material according to claim 1, characterized in that: The conductive layer is made of at least one of Cu, Al, Ag, Pt, Au, tungsten carbide, chromium carbide, tantalum carbide or titanium carbide; preferably Cu, Ag or Au.

5. The porous silicon-carbon anode material according to claim 1, characterized in that: The thickness of the fast ion layer is 0.5-25 nm, preferably 1-25 nm, more preferably 2-20 nm, and even more preferably 2-10 nm.

6. The porous silicon-carbon anode material according to claim 1, characterized in that: The fast ion layer is made of at least one of LiF, solid electrolyte, lithium titanate, or alumina. Preferably, the fast ion layer is made of an oxide electrolyte.

7. The porous silicon-carbon anode material according to claim 1, characterized in that: Silicon nanoparticles account for 20-60% of the mass of silicon-carbon composite materials.

8. The porous silicon-carbon anode material according to claim 1, characterized in that: The carbon coating accounts for 1-5% of the mass of silicon nanoparticles.

9. A method for preparing the porous silicon-carbon anode material according to any one of claims 1-8, characterized in that: Includes the following steps: Choose porous carbon, which has mesopores distributed on it; First, a conductive layer is deposited inside the pores of porous carbon using the ALD method; Then, an ALD method is used to deposit a fast ion layer on the surface of the conductive layer, transforming the mesopores of porous carbon into micropores; Then silicon nanoparticles are deposited inside the pores of porous carbon; Finally, a carbon coating layer is deposited on the porous carbon to obtain the final product.

10. A battery, characterized in that: The negative electrode material of the battery is prepared from any of the porous silicon-carbon negative electrode materials described in claims 1-8.

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