Porous silicon-based composite material, preparation method thereof and lithium ion battery

Abstract

The application provides a porous silicon-based composite material and a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion battery negative materials.The porous silicon-based composite material has a honeycomb structure and is composed of porous silicon blocks, metal skeletons and carbon-based films.The porous silicon blocks are primary particles, the secondary particles are constructed by the metal skeletons, and the carbon-based films are coated on the surfaces of the porous silicon blocks and the metal skeletons.The porous silicon-based composite material can be denoted as Si / M@C.The metal skeleton M has strong rigidity and is used for supporting the porous silicon blocks, also serving as a conductive network and playing a limiting role.The carbon-based film C has elastic properties and is used as an artificial SEI film and for eliminating internal stress generated by volume expansion during charging, thereby protecting the main material.The porous silicon-based composite material has strong mechanical binding and limiting effects, stable interface properties and an optimized conductive network and ion transmission path.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion battery anode materials, and in particular to a porous silicon-based composite material and its preparation method, and a lithium-ion battery. Background Technology

[0002] Silicon possesses extremely high theoretical specific capacity and is considered the most promising anode material for next-generation high-energy-density lithium-ion batteries. However, silicon exhibits severe volume expansion (>300%) during charge and discharge, leading to electrode pulverization, continuous growth of the solid electrolyte interface film, and failure of the electrical contact between the active material and the current collector, thereby causing bottleneck problems such as rapid capacity decay and extremely short cycle life.

[0003] To address these issues, current mainstream technologies focus on nanoscale and porous designs. Porous silicon materials can effectively buffer volume expansion and shorten lithium-ion diffusion paths. Traditional porous silicon preparation methods (such as electrochemical anodic etching and magnesothermic reduction) generally suffer from complex processes, high costs, and limited production capacity, making it difficult to meet the demands of large-scale production. Pure porous silicon has low intrinsic electronic conductivity and surface instability in electrolytes, which restricts the full realization of its electrochemical performance.

[0004] Using aluminum-silicon alloys as raw materials, porous silicon can be prepared by selectively dissolving ("dealloying") the aluminum phase with acid (such as hydrochloric acid). This method offers significant cost advantages and scalability potential. The process is simple, the raw materials are readily available, and the resulting porous silicon framework inherits the morphology of the primary silicon phase in the alloy, typically exhibiting a three-dimensional interconnected macroporous or mesoporous structure, which is beneficial for electrolyte wetting and volume expansion. However, this technology still suffers from structural collapse risks, insufficient conductivity, poor interface stability, and low initial coulombic efficiency.

[0005] Existing technologies attempt to modify porous silicon with carbon coating (such as coating graphite carbon or amorphous carbon through chemical vapor deposition (CVD) or pyrolysis of polymer precursors), but the bonding force between conventional carbon coating layers and silicon substrates is often insufficient, and they are easily peeled off when there are drastic volume changes. At the same time, high-temperature treatment is often required during the coating process, which may lead to sintering of porous structures and growth of silicon grains, thereby weakening their buffering effect.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One of the objectives of this invention is to provide a porous silicon-based composite material with strong mechanical confinement and territorial effects, stable interfacial properties, and optimized conductive network and ion transport pathway.

[0008] The second objective of this invention is to provide a method for preparing porous silicon-based composite materials, using aluminum-silicon alloy as a precursor, and obtaining porous silicon-based composite materials through selective etching and structural modification, which is suitable for industrial-scale production.

[0009] The third objective of this invention is to provide a lithium-ion battery with excellent overall electrochemical performance.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, a porous silicon-based composite material having a honeycomb structure; The porous silicon-based composite material includes a porous silicon block, a metal framework, and a carbon-based membrane; The porous silicon block is a primary particle, and secondary particles are constructed by a metal frame. The carbon-based film is coated on the surface of the porous silicon block and the metal skeleton.

[0011] Furthermore, in X-ray diffraction testing, the porous silicon-based composite material exhibits a first characteristic peak I at 28.3°~28.8°. (111) A second characteristic peak I appears at 47.1°~47.5°. (220) A third characteristic peak I appears at 55.8°~56.4°. (311) ; First characteristic peak I (111) Second characteristic peak I (220) and the third characteristic peak I (311) The peak intensity satisfies 0.30≤I (220) / I (111) ≤0.55, 0.15≤I (311) / I (111) ≤0.30, 0.4≤I (311) / I (220) ≤0.54; Preferably, the microcrystal size D of the porous silicon-based composite material on the (111) crystal plane satisfies 20nm≤D≤100nm.

[0012] Furthermore, the mean L1 of the maximum and minimum lengths of the primary particles passing through the midpoint in the two-dimensional plane satisfies L1≤3μm, and the average gap distance L2 between the primary particles satisfies L2≤3μm; The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane satisfies 3μm<L3≤50μm.

[0013] Furthermore, the metal framework includes at least one of Al, Sn, Ni, Cu, Zn, Ag, Fe, and Bi; Preferably, the carbon-based film includes at least one of polyimide film, acetylene-based hard carbon film, oxygen-nitrogen carbon film, aromatic carbon film, and standard nitrogen-doped carbon film.

[0014] Furthermore, in infrared spectroscopy testing, the porous silicon-based composite material showed a value of 750 cm⁻¹. -1 ~850cm -1 The characteristic peak T1 of Si-O bond appears at 1100 cm⁻¹. -1 ~1200cm -1 The characteristic peak T2 of the Si-O bond appears at this location; The transmittance of the characteristic peaks T1 and T2 of the Si-O bond satisfies 0.3≤T1 / T2≤1.

[0015] Furthermore, the silicon crystal phase content N1 in the porous silicon-based composite material satisfies 60% ≤ N1 < 100%; Preferably, the content of the metallic crystalline phase N2 in the porous silicon-based composite material satisfies 0% < N2 ≤ 40%; Preferably, the mass percentage W1 of the carbon-based membrane in the porous silicon-based composite material satisfies 0.1% ≤ W1 ≤ 5%.

[0016] Furthermore, the specific surface area of ​​the porous silicon-based composite material is 5 m². 2 / g~60m 2 / g, the true density of helium is 1g / cm³ 3 ~3g / cm 3 .

[0017] Secondly, a method for preparing a porous silicon-based composite material according to any one of the above claims includes the following steps: The aluminum-silicon alloy is etched to give the silicon block channels, while retaining and / or transforming the metal framework to obtain a porous silicon block. The porous silicon block is coated with a carbon-based film to obtain the porous silicon-based composite material.

[0018] Furthermore, the etching solution for the aluminum-silicon alloy includes an acid solution; Preferably, the concentration of the acid solution is 1 mol / L to 5 mol / L, and the etching time is 2 h to 48 h; Preferably, the method of converting the metal framework includes a metal displacement reaction; Preferably, the metal replacement reaction takes 2 hours to 24 hours; Preferably, the carbon-based film coating temperature is 200℃~600℃.

[0019] Thirdly, a lithium-ion battery, wherein the negative electrode of the lithium-ion battery uses an active material comprising the porous silicon-based composite material described in any of the preceding claims.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: The porous silicon-based composite material provided by this invention has a honeycomb structure, denoted as Si / M@C. M, as a metallic skeleton, possesses rigidity and strength, supporting the porous silicon block and also acting as a conductive network and confinement layer. C, as a carbon-based film coating layer, possesses elastic properties, acting as an artificial SEI film and eliminating internal stress generated by volume expansion during charging, thereby protecting the main material. The porous silicon-based composite material of this invention exhibits strong mechanical confinement and ion transport effects, stable interface characteristics, and optimized conductive network and ion transport pathways.

[0021] The method for preparing porous silicon-based composite materials provided by this invention uses aluminum-silicon alloy as a precursor and obtains porous silicon-based composite materials through selective etching and structural modification, which is suitable for industrial-scale production.

[0022] The lithium-ion battery provided by this invention has excellent overall electrochemical performance. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the structure of a porous silicon-based composite material provided in one embodiment of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] According to a first aspect of the present invention, a porous silicon-based composite material is provided, see Figure 1 The porous silicon-based composite material has a honeycomb structure; The porous silicon-based composite material comprises a porous silicon block, a metal framework, and a carbon-based membrane; Porous silicon blocks are formed when the surface or internal metal of a silicon block is etched away, and they are primary particles. Secondary particles are constructed by the remaining metal framework. A carbon-based film is coated on the surface of a porous silicon block and a metal framework.

[0027] The porous silicon-based composite material of the present invention has a honeycomb structure, which can be denoted as Si / M@C. M, as a metal skeleton, has rigidity and strength, which is used to support the porous silicon block, and also acts as a conductive network and plays a confinement role. C, as a carbon-based film coating layer, has elastic properties, which is used to act as an artificial SEI film and eliminate the internal stress generated by the volume expansion during the charging process, thereby protecting the main material.

[0028] The porous silicon-based composite material of the present invention can be spherical, regular or irregular in shape, and has strong mechanical confinement and territorial effects, stable interface properties and optimized conductive network and ion transport path.

[0029] In X-ray diffraction tests, the porous silicon-based composite material exhibits its first characteristic peak I at 28.3°–28.8°. (111) A second characteristic peak I appears at 47.1°~47.5°. (220) A third characteristic peak I appears at 55.8°~56.4°. (311) .

[0030] I represents the peak intensity of the characteristic peak, the first characteristic peak I (111) Second characteristic peak I (220) and the third characteristic peak I (311) The peak intensity can satisfy 0.30≤I (220) / I (111) ≤0.55, 0.15≤I (311) / I (111) ≤0.30, 0.4≤I (311) / I (220) ≤0.54.

[0031] In a preferred embodiment, the microcrystal size D of the porous silicon-based composite material on the (111) crystal plane can satisfy 20nm≤D≤100nm.

[0032] In a preferred embodiment, the mean L1 of the maximum and minimum lengths of the primary particles passing through the midpoint in the two-dimensional plane satisfies L1≤3μm, and the average gap distance L2 between the primary particles satisfies L2≤3μm.

[0033] If L1 > 3 μm, it indicates that the etching effect is too low, the silicon content is less than 60%, and the capacity and first-time efficiency are low. If L2 > 3 μm, it indicates that the etching effect is too high, the entire honeycomb structure collapses, the specific surface area increases, resulting in excessive electrolyte consumption, unrestricted silicon expansion, and decreased cycle performance. Only when L1 ≤ 3 μm and L2 ≤ 3 μm are satisfied at the same time can the morphology and composition of the secondary particles be the desired honeycomb porous structure, which has high capacity, high first-time efficiency, and good cycle performance.

[0034] In a preferred embodiment, the average value L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane satisfies 3μm < L3 ≤ 50μm. Porous silicon within this range is more suitable as a battery anode material. If L3 is too small, there is a safety hazard; if L3 is too large, the rate performance is poor.

[0035] In a preferred embodiment, the metal framework includes, but is not limited to, at least one of Al, Sn, Ni, Cu, Zn, Ag, Fe, and Bi.

[0036] In a preferred embodiment, the carbon-based film includes, but is not limited to, at least one of polyimide film, acetylene-based hard carbon film, oxygen-containing nitrogen carbon film, aromatic carbon film, and standard nitrogen-doped carbon film.

[0037] In infrared spectroscopy testing, the porous silicon-based composite material showed a wavelength of 750 cm⁻¹. -1 ~850cm -1 The characteristic peak T1 of Si-O bond appears at 1100 cm⁻¹. -1 ~1200cm -1 The characteristic peak T2 of the Si-O bond appears at this location.

[0038] T represents transmittance. The transmittance of the characteristic peaks T1 and T2 of the Si-O bond can satisfy 0.3 ≤ T1 / T2 ≤ 1.

[0039] In a preferred embodiment, the silicon crystal phase content N1 in the porous silicon-based composite material can satisfy 60% ≤ N1 < 100%; the metal crystal phase content N2 in the porous silicon-based composite material can satisfy 0% < N2 ≤ 40%.

[0040] In a preferred embodiment, the mass percentage W1 of the carbon-based membrane in the porous silicon-based composite material can satisfy 0.1% ≤ W1 ≤ 5%.

[0041] In this invention, the specific surface area of ​​the porous silicon-based composite material can be 5 m². 2 / g~60m 2 / g, the true density of helium gas can be 1g / cm³ 3 ~3g / cm 3 .

[0042] According to a second aspect of the present invention, a method for preparing the porous silicon-based composite material according to any one of the above claims is provided, comprising the following steps: The aluminum-silicon alloy is etched to give the silicon block channels, while retaining and / or transforming the metal framework to obtain a porous silicon block. The porous silicon block was coated with a carbon-based film to obtain a porous silicon-based composite material.

[0043] The method of this invention uses aluminum-silicon alloy as a precursor and obtains porous silicon-based composite materials through selective etching and structural modification, which is suitable for industrial-scale production.

[0044] The etched silicon block has abundant channels. By controlling the etching degree to retain and / or transform the metal framework, the composite material can be endowed with both rigidity and flexibility, possessing both high mechanical strength and high ductility. Carbon-based film coating further enhances the overall structural stability of the material.

[0045] A typical preparation method for a porous silicon-based composite material includes the following steps: Step S1: The commercial aluminum-silicon alloy is mixed with an acid solution for etching. After continuous stirring, it is filtered and washed, and then dried in a vacuum oven to obtain a porous silicon precursor. Step S2: If substitution is required, disperse the porous silicon precursor in a polar proton inert solvent, add a metal salt to carry out the substitution reaction, filter and wash, and dry in a vacuum oven to obtain the porous silicon composite precursor. Step S3: Using chemical vapor deposition, the porous silicon composite precursor is placed in a coating atmosphere to coat it with a carbon-based film, thereby obtaining a porous silicon-based composite material.

[0046] In a preferred embodiment, the concentration of the acid solution can be from 1 mol / L to 5 mol / L, with typical but non-limiting concentrations such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, and 5 mol / L. The etching time can be from 2 h to 48 h, with typical but non-limiting times such as 2 h, 4 h, 6 h, 8 h, 10 h, 15 h, 20 h, 30 h, 40 h, and 48 h.

[0047] The acid solution may be selected from at least one of hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, oxalic acid, and acetic acid.

[0048] In a preferred embodiment, the metal substitution reaction can be carried out over a period of 2 hours to 24 hours, with typical but non-limiting times being 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, and 24 hours.

[0049] The metal displacing agent can be selected from soluble salts of copper, tin, nickel, iron, zinc, silver and / or bismuth, such as chlorides, sulfates and nitrates.

[0050] In this invention, the polar protonic inert solvent may be selected from at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphoric triamine, and 1,3-dimethyl-2-imidazolinone.

[0051] In a preferred embodiment, the coating temperature of the carbon-based film can be 200°C to 600°C, with typical but non-limiting temperatures such as 200°C, 300°C, 400°C, 500°C, and 600°C being more conducive to improving the coating effect of the carbon-based film.

[0052] The gas source used for carbon-based membrane coating can be selected from at least one of methane, ethane, propylene, ammonia, acetylene, benzene, dianhydride monomers, diamine monomers, carbon dioxide, nitrogen oxides, nitrogen, and argon.

[0053] In summary, this invention addresses both conductivity and mechanical strength issues from within the material itself by controlling the degree of hydrochloric acid etching of the aluminum-silicon alloy, thus intentionally retaining a portion of the aluminum as an internal conductive network and mechanical support framework. This approach, rather than relying solely on external coating, constructs a robust "metal-silicon" composite conductive framework. Furthermore, it coats the porous silicon structure with a high elastic modulus and high toughness, acting not only as a continuous conductive coating but also, crucially, as an "elastic constraint shell." This restricts excessive expansion of silicon during lithium insertion / extraction, guiding it towards internal pores while simultaneously isolating the electrolyte from direct contact with silicon, forming a stable SEI film. Additionally, the combination of partially retained / replaced internal metal framework and the external tough carbon encapsulation layer creates a "rigid-flexible" secondary protection mechanism. The metal framework provides rigid support and a high-speed electron pathway, while the carbon encapsulation layer provides elastic constraint and a stable interface. This synergistic effect ensures high structural integrity during long-term cycling, significantly enhancing the material's overall electrochemical performance.

[0054] According to a third aspect of the present invention, a lithium-ion battery is provided, wherein the negative electrode of the lithium-ion battery uses an active material comprising the porous silicon-based composite material described in any of the preceding claims.

[0055] The lithium-ion battery of this invention has excellent overall electrochemical performance.

[0056] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0057] Example 1 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 1M hydrochloric acid solution and stirred for 24 hours. After filtration, washing and drying, a porous silicon precursor was obtained. Then, the porous silicon precursor was dispersed in N-methyl-2-pyrrolidone, anhydrous zinc chloride was added, the mixture was stirred and reacted for 18 hours, filtered, washed, and dried to obtain the porous silicon composite precursor. Finally, using chemical vapor deposition, the porous silicon composite precursor was reacted at 200°C for 7 hours in a mixed atmosphere of acetylene / nitrogen to obtain a porous silicon-based composite material containing an acetylene-based hard carbon film. The Si crystal phase content was 65%, the zinc crystal phase content was 35%, and the carbon-based film accounted for 1% of the mass. The obtained porous silicon-based composite material has a specific surface area of ​​20.8 m². 2 / g, the true density of helium is 1.97g / cm³. 3 .

[0058] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-1.8 μm, and the average gap distance L2 between primary particles is 0-0.78 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-25 μm.

[0059] Example 2 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 3M hydrochloric acid solution and stirred for 18 hours. The solution was then filtered, washed and dried to obtain a porous silicon precursor. Then, the porous silicon precursor was dispersed in N-methyl-2-pyrrolidone, anhydrous zinc chloride was added, the mixture was stirred for 12 hours, filtered, washed, and dried to obtain the porous silicon composite precursor. Finally, using chemical vapor deposition, the porous silicon composite precursor was reacted at 200°C for 7 hours in a mixed atmosphere of acetylene / nitrogen to obtain a porous silicon-based composite material containing an acetylene-based hard carbon film. The Si crystal phase content was 75%, the zinc crystal phase content was 25%, and the carbon-based film accounted for 1% of the mass. The specific surface area of ​​the obtained porous silicon-based composite material is 30.4 m². 2 / g, the true density of helium is 1.78g / cm³. 3 .

[0060] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-1.5 μm, and the average gap distance L2 between primary particles is 0-1.1 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-23 μm.

[0061] Example 3 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 3M hydrochloric acid solution and stirred for 14 hours. After filtration, washing and drying, a porous silicon precursor was obtained. Then, the porous silicon precursor was dispersed in N-methyl-2-pyrrolidone, anhydrous copper chloride was added, the mixture was stirred for 12 hours, filtered, washed, and dried to obtain the porous silicon composite precursor. Finally, using chemical vapor deposition, the porous silicon composite precursor was reacted at 500°C for 2 hours in a mixed atmosphere of acetylene / nitrogen to obtain a porous silicon-based composite material containing an acetylene-based hard carbon film. The Si crystal phase content was 65%, the copper crystal phase content was 35%, and the carbon-based film accounted for 1% of the mass. The obtained porous silicon-based composite material has a specific surface area of ​​21.3 m². 2 / g, the true density of helium is 2.04 g / cm³. 3 .

[0062] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-1.8 μm, and the average gap distance L2 between primary particles is 0-0.78 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-25 μm.

[0063] Example 4 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 3M hydrochloric acid solution and stirred for 18 hours. The solution was then filtered, washed and dried to obtain a porous silicon precursor. Then, the porous silicon precursor was dispersed in N-methyl-2-pyrrolidone, anhydrous copper chloride was added, the mixture was stirred for 12 hours, filtered, washed, and dried to obtain the porous silicon composite precursor. Finally, using chemical vapor deposition, the porous silicon composite precursor was reacted at 200°C for 0.1 hours in a mixed atmosphere of pyromellitic dianhydride / 4,4'-diaminodiphenyl ether / nitrogen to obtain a porous silicon-based composite material containing a polyimide film. The Si crystal phase content was 75%, the copper crystal phase content was 25%, and the carbon-based film accounted for 0.3% by mass. The specific surface area of ​​the obtained porous silicon-based composite material is 32.5 m². 2 / g, the true density of helium is 1.82g / cm³. 3 .

[0064] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-1.5 μm, and the average gap distance L2 between primary particles is 0-1.1 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-23 μm.

[0065] Example 5 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 3M hydrochloric acid solution and stirred for 14 hours. After filtration, washing and drying, a porous silicon precursor was obtained. Finally, using chemical vapor deposition, the porous silicon precursor was reacted at 500°C for 2 hours in a mixed atmosphere of acetylene / nitrogen to obtain a porous silicon-based composite material containing an acetylene-based hard carbon film. The Si crystal phase content was 75%, the aluminum crystal phase content was 25%, and the carbon-based film accounted for 1% of the mass. The obtained porous silicon-based composite material has a specific surface area of ​​38.7 m². 2 / g, the true density of helium is 1.76g / cm³. 3 .

[0066] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-1.5 μm, and the average gap distance L2 between primary particles is 0-1.1 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-23 μm.

[0067] Example 6 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 2M hydrochloric acid solution and stirred for 24 hours. After filtration, washing and drying, a porous silicon precursor was obtained. Finally, using chemical vapor deposition, the porous silicon precursor was reacted at 200°C for 0.1 hours in a mixed atmosphere of pyromellitic dianhydride / 4,4'-diaminodiphenyl ether / nitrogen to obtain a porous silicon-based composite material containing a polyimide film. The Si crystal phase content was 92%, the aluminum crystal phase content was 8%, and the carbon-based film accounted for 0.1% by mass. The obtained porous silicon-based composite material has a specific surface area of ​​53.8 m². 2 / g, the true density of helium is 1.53g / cm³. 3 .

[0068] In this embodiment, the porous silicon-based composite material has a honeycomb structure. The porous silicon block is a primary particle, and secondary particles are constructed by a metal skeleton. A carbon-based film is coated on the surface of the porous silicon block and the metal skeleton. The mean L1 of the maximum and minimum lengths of primary particles passing through the midpoint in the two-dimensional plane is 0-0.98 μm, and the average gap distance L2 between primary particles is 0-1.4 μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane is 1-21 μm.

[0069] Comparative Example 1 A method for preparing a porous silicon-based composite material includes the following steps: First, an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50 and Dmax of 2μm, 10μm and 28μm respectively was added to a 2M hydrochloric acid solution and stirred for 48 hours. After filtration, washing and drying, a porous silicon precursor was obtained. Finally, using chemical vapor deposition, the porous silicon precursor was reacted at 500°C for 2 hours in a mixed atmosphere of acetylene / nitrogen to obtain a porous silicon-based composite material containing an acetylene-based hard carbon film. The Si crystal phase content was 100%, and the mass percentage of the carbon-based film was 1%. The specific surface area of ​​the obtained porous silicon-based composite material is 64.8 m². 2 / g, the true density of helium is 1.18g / cm³. 3 .

[0070] Comparative Example 2 The only difference between this comparative example and Example 1 is that the porous silicon composite precursor was not coated with a carbon-based film. The remaining steps are the same as in Example 1, resulting in a porous silicon-based composite material.

[0071] Comparative Example 3 This comparative example uses an aluminum-silicon alloy with a silicon phase content of 30% and Dmin, Dv50, and Dmax of 2μm, 10μm, and 28μm, respectively, as the anode material.

[0072] Test case The XRD, infrared, charge transfer resistance, electrode expansion rate, and cycle retention rate of the materials obtained in each embodiment and comparative example are shown in Table 1.

[0073] The materials obtained in each embodiment and comparative example are used as negative electrode active materials to prepare negative electrode sheets; Negative electrode composition: 95% active material, 2% SBR binder, 2.8% conductive agent SP, and 0.2% SWCNT; CR2032 coin cells were fabricated using conventional methods with negative electrode sheets, and the electrical performance of the cells was tested. (1) Half-cell assembly: Assemble CR2032 button cells in a glove box, with lithium metal sheet as counter electrode, polypropylene microporous membrane as separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1), wherein the concentration of LiPF6 is 1 mol / L. The battery was charged and discharged using the LAND battery testing system; (2) Charge transfer resistance test: After the CR2032 button battery is left to stand for 6 hours, it is discharged to 0.005V at 0.1C, and then discharged at a constant voltage of 0.005V until the current is 0. After standing for 5 minutes, it is charged at a constant current of 0.1C for 5 hours. After standing for 5 minutes, the charge transfer resistance Rct is tested using an electrochemical workstation. (3) Electrode expansion rate: After the CR2032 type button cell was left to stand for 6 hours, it was discharged to 0.005V at 0.05C, and then discharged to 0.005V at 0.01C; then the button cell was disassembled in the glove box, the electrode was cleaned with DMC and the thickness of the electrode was measured; the expansion rate was calculated as: (thickness of electrode in the first fully charged state - thickness of fresh electrode) / thickness of fresh electrode × 100%; (4) Cyclic test: After the CR2032 button battery is left to stand for 6 hours, it is discharged to 0.005V at 0.1C, then discharged at a constant voltage of 0.005V until the current is 0 and cut off, then charged to 1.5V at 0.5C, and then discharged to 0.05V at 0.5C. This process is repeated 20 times. The test results are shown in Table 1.

[0074] As can be seen from the data in Table 1, compared with the porous silicon material without metal skeleton support in Comparative Example 1 and the porous silicon composite material without carbon-based film coating in Comparative Example 2, the porous silicon-based composite materials of Examples 1-6 of the present invention have strong mechanical confinement and fast electronic conduction through the synergistic effect of metal skeleton and carbon-based film, thereby making the material have excellent charge transport resistance, electrode expansion and cycle stability.

[0075] Table 1

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A porous silicon-based composite material, characterized in that, The porous silicon-based composite material has a honeycomb structure; The porous silicon-based composite material includes a porous silicon block, a metal framework, and a carbon-based membrane; The porous silicon block is a primary particle, and secondary particles are constructed by a metal frame. The carbon-based film is coated on the surface of the porous silicon block and the metal skeleton.

2. The porous silicon-based composite material according to claim 1, characterized in that, In X-ray diffraction testing, the porous silicon-based composite material exhibits a first characteristic peak I at 28.3°~28.8°. (111) A second characteristic peak I appears at 47.1°~47.5°. (220) A third characteristic peak I appears at 55.8°~56.4°. (311) ; First characteristic peak I (111) Second characteristic peak I (220) and the third characteristic peak I (311) The peak intensity satisfies 0.30≤I (220) / I (111) ≤0.55, 0.15≤I (311) / I (111) ≤0.30, 0.4≤I (311) / I (220) ≤0.54; The microcrystal size D of the porous silicon-based composite material on the (111) crystal plane satisfies 20nm≤D≤100nm.

3. The porous silicon-based composite material according to claim 1 or 2, characterized in that, The mean L1 of the maximum and minimum lengths of the primary particles passing through the midpoint in the two-dimensional plane satisfies L1≤3μm, and the average gap distance L2 between the primary particles satisfies L2≤3μm. The mean L3 of the maximum and minimum lengths of the secondary particles passing through the midpoint in the two-dimensional plane satisfies 3μm<L3≤50μm.

4. The porous silicon-based composite material according to claim 3, characterized in that, The metal framework includes at least one of Al, Sn, Ni, Cu, Zn, Ag, Fe, and Bi; The carbon-based film includes at least one of polyimide film, acetylene-based hard carbon film, oxygen-containing nitrogen carbon film, aromatic structure carbon film, and standard nitrogen-doped carbon film.

5. The porous silicon-based composite material according to claim 3, characterized in that, In infrared spectroscopy testing, the porous silicon-based composite material showed up at 750 cm⁻¹. -1 ~850cm -1 The characteristic peak T1 of Si-O bond appears at 1100 cm⁻¹. -1 ~1200cm -1 The characteristic peak T2 of the Si-O bond appears at this location; The transmittance of the characteristic peaks T1 and T2 of the Si-O bond satisfies 0.3≤T1 / T2≤1.

6. The porous silicon-based composite material according to claim 1, characterized in that, The silicon crystal phase content N1 in the porous silicon-based composite material satisfies 60% ≤ N1 < 100%; The content of the metallic crystalline phase N2 in the porous silicon-based composite material satisfies 0% < N2 ≤ 40%; The mass percentage W1 of the carbon-based membrane in the porous silicon-based composite material satisfies 0.1% ≤ W1 ≤ 5%.

7. The porous silicon-based composite material according to claim 1, characterized in that, The specific surface area of ​​the porous silicon-based composite material is 5 m². 2 / g~60m 2 / g, the true density of helium is 1g / cm³ 3 ~3g / cm 3 .

8. A method for preparing a porous silicon-based composite material according to any one of claims 1-7, characterized in that, Includes the following steps: The aluminum-silicon alloy is etched to give the silicon block channels, while retaining and / or transforming the metal framework to obtain a porous silicon block. The porous silicon block is coated with a carbon-based film to obtain the porous silicon-based composite material.

9. The preparation method according to claim 8, characterized in that, The etching solution for the aluminum-silicon alloy includes an acid solution; The concentration of the acid solution is 1 mol / L to 5 mol / L, and the etching time is 2 h to 48 h. The method of converting the metal framework includes metal displacement reactions; The metal replacement reaction takes 2 to 24 hours. The carbon-based film coating temperature is 200℃~600℃.

10. A lithium-ion battery, characterized in that, The active material used in the negative electrode of the lithium-ion battery includes the porous silicon-based composite material as described in any one of claims 1-7.

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