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

Abstract

The invention provides a silicon-carbon negative electrode material, a preparation method and application thereof, and a battery negative electrode, and belongs to the technical field of lithium battery materials. The method comprises the following steps: firstly, uniformly coating porous carbon with a high-conductivity medium so as to improve the conductivity between a porous carbon substrate and silicon crystal grains; performing synchronous vapor deposition on a gaseous silicon source and a nitrogen source in a modified porous carbon pore channel and on the outer surface of the modified porous carbon pore channel to form a local silicon carbide and silicon nitride interface layer so as to inhibit volume expansion of silicon crystal grains; and then liquid resin is used for coating to form a highly-ordered carbon structure coating layer, so that the migration rate of the lithium ion interface is increased. The silicon-carbon negative electrode material prepared by the invention has the characteristics of low cost, low expansion and high rate, and the lithium battery obtained by preparing a battery negative electrode by taking the silicon-carbon negative electrode material as an active component and further assembling has excellent cycling stability, relatively high reversible specific capacity and relatively high initial coulombic efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, and in particular to a silicon-carbon anode material, its preparation method and application, and a battery anode. Background Technology

[0002] Lithium-ion batteries are widely used in 3C digital batteries, power batteries, and energy storage batteries due to their high energy density, high voltage window, wide operating temperature, and long cycle life. The anode material is one of the key materials in lithium-ion batteries, accounting for 10% to 15% of the total cost. It plays a crucial role in energy storage and release, significantly impacting the initial coulombic efficiency, energy density, calendar life, charge / discharge rate, and high / low temperature performance of lithium-ion batteries. Traditional graphite anode materials have low specific capacity and are approaching their energy density development limits, while silicon-based anode materials have a theoretical specific capacity as high as 4200 mAh / g, more than 10 times that of graphite anode materials, and are considered the most likely new anode material for large-scale application in the future.

[0003] However, silicon-based anode materials still face several failure issues that urgently need to be addressed. Silicon grains expand by up to 300% during lithium insertion and extraction, leading to particle breakage and pulverization in the later stages of cycling, as well as continuous SEI (Sediment Layer) fracture and regrowth, resulting in deteriorated lithium battery cycle performance. Furthermore, silicon, being a semiconductor material, has significantly lower conductivity than graphite, making it difficult to improve the fast-charging performance of silicon-based anode materials. To address these issues, current research employs methods such as CVD (Chemical Vapor Deposition), carbon coating, and artificial SEI interface coating. CVD can deposit nano- or amorphous silicon particles within porous carbon channels, effectively mitigating the volume expansion of silicon-carbon materials. Carbon coating can improve the conductivity of silicon-based materials, while artificial SEI interface coating can improve interfacial reactions and stabilize the SEI layer, thereby enhancing the electrochemical performance of silicon-based anodes.

[0004] Patent application CN 111769264 A proposes a method to generate glow discharge by applying a high-voltage current between the anode and cathode of a reactor. This causes the gas inside the furnace to decompose, generating positive carbon and / or nitrogen ions. These positive carbon and / or nitrogen ions bombard the surface of nano-silicon, resulting in carbon and / or nitrogen-doped nano-silicon materials coated with silicon carbide and / or silicon nitride. This method effectively suppresses the volume expansion of silicon materials during charging and discharging. This invention achieves the effect of suppressing the volume expansion of silicon materials by forming a silicon carbide and / or silicon nitride coating layer on the outer surface of nano-silicon particles, and belongs to the field of external interface engineering technology.

[0005] Patent application CN 112028065 A discloses a silicon-carbon composite material comprising a graphite core and SiO₂ layered in situ coated on the surface of the graphite core. x The invention comprises a SiO layer, a SiC layer, and an amorphous carbon layer. The method of this invention utilizes SiO...x SiO is formed on the outer surface of the layer x Layers of SiC and amorphous carbon are used to coat the core SiO to achieve a stable core. x The purpose of the layer still falls under the category of external interface engineering technology.

[0006] Patent application CN 117613233 A discloses a silicon-carbon anode material, comprising a porous carbon substrate, nano-silicon particles deposited within and on the surface of the porous carbon substrate, and a carbon coating layer. The method involves introducing a mixture of silicon source gas and carbon source gas into a reactor containing the porous carbon substrate, followed by vapor deposition to obtain a porous carbon substrate coated with a silicon carbide interface layer. This invention suppresses the volume expansion of silicon grains by simultaneously vapor-depositing silicon and carbon source gas onto the surface of the porous carbon substrate to form a silicon carbide coating layer. A second vapor-phase deposition of silicon and subsequent carbon coating are then performed. The silicon source gas is selected from silane, disilane, dichlorosilane, and trichlorosilane. The silicon source gas material is expensive, and the two vapor-phase deposition processes reduce the utilization rate of the silicon source gas, further increasing the manufacturing cost.

[0007] Currently, the method of preparing silicon-carbon anode materials using porous carbon as a substrate and CVD vapor deposition technology is more suitable for large-scale production. However, in silicon-carbon anode materials prepared by existing methods, the silicon grain expansion stress is large, resulting in severe silicon-carbon particle pulverization and deterioration of lithium battery cycle performance. At the same time, since silicon is a semiconductor material with poor conductivity, the rate performance of silicon-carbon anode materials is poor, affecting fast charging performance. Summary of the Invention

[0008] The purpose of this invention is to provide a silicon-carbon anode material, its preparation method and application, and a battery anode. It utilizes a low-cost silicon source to reduce the cost of silicon-carbon materials and employs a dual-gas-source one-step CVD deposition method to form local silicon carbide and silicon nitride during the deposition process, thereby reducing the volume expansion of silicon grains. Furthermore, it utilizes a highly conductive medium to modify the porous carbon substrate and combines high-quality hard carbon coating to replace the traditional inferior carbon source carbon coating technology, thereby improving the fast-charging performance of silicon-carbon materials.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0011] A highly conductive medium is spray-dried onto porous carbon to obtain modified porous carbon.

[0012] In a protective atmosphere, a gaseous silicon source and a nitrogen source are simultaneously deposited on the modified porous carbon in the first vapor phase, and then a gaseous carbon source is introduced to perform a second vapor phase deposition to obtain a silicon-carbon intermediate; the silicon-carbon intermediate is deposited with a silicon carbide interface layer and a silicon nitride interface layer.

[0013] After the liquid resin is subjected to a second spray drying on the silicon-carbon intermediate, it is carbonized to obtain a silicon-carbon anode material.

[0014] The highly conductive medium includes one or more of titanates, transition metal oxides, polymer-based high dielectric constant composite materials, ionic liquid gels, and perovskite quantum dots.

[0015] Preferably, the porous carbon has a D min The diameter is 0.1–2 μm, D max The value is 10–50 μm, (D max -D min ) / D 50 Its specific surface area is 300–2200 m², ranging from 0.5 to 1.2. 2 / g, with an average pore size of 1–100 nm.

[0016] Preferably, during the first spray drying, the solid content of the high conductivity medium slurry is 1-60 wt%; the mass of the high conductivity medium is 0.1-5% of the mass of the porous carbon.

[0017] The inlet temperature of the first spray dryer is 20-150℃, and the outlet temperature is 100-300℃.

[0018] Preferably, the gaseous silicon source includes one or more of the following: monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, silicon suboxide particles, and silicon dioxide particles.

[0019] The nitrogen source includes one or more of nitrogen, ammonia, nitric oxide, and nitrogen dioxide;

[0020] The total flow rate of the gaseous silicon source and nitrogen source is 0.1 to 100 L / min, and the volume ratio of the gaseous silicon source to the nitrogen source is 0.1 to 100:1.

[0021] Preferably, the gaseous carbon source comprises an alkane gas with a pyrolysis temperature of 400–800°C; the flow rate of the gaseous carbon source is 0.1–50 L / min.

[0022] The temperature of the first vapor deposition is 500–1000℃, and the time is 0.5–48 h; the temperature of the second vapor deposition is 500–1000℃, and the time is 0.1–6 h.

[0023] The thickness of the silicon carbide interface layer is 0.1–5 nm, and the silicon carbide content is 0.1–5 wt%.

[0024] The thickness of the silicon nitride interface layer is 0.1–5 nm, and the silicon nitride content is 0.1–5 wt%.

[0025] Preferably, the liquid resin includes one or more of phenolic resin, epoxy resin, polyimide resin, furfural resin, and polybenzoxazine;

[0026] The inlet temperature of the second spray dryer is 20-150℃, and the outlet temperature is 100-300℃;

[0027] The carbonization treatment is carried out at a temperature of 700–1200°C for a time of 0.5–24 hours.

[0028] The present invention provides a silicon-carbon anode material prepared by the preparation method described in the above technical solution.

[0029] This invention provides the application of the silicon-carbon anode material described in the above technical solution in lithium batteries.

[0030] This invention provides a battery negative electrode, comprising a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector;

[0031] The negative electrode active material layer includes the silicon-carbon negative electrode material described in the above technical solution.

[0032] This invention provides a silicon-carbon anode material. First, a high-dielectric-constant material is coated onto the inner and outer surfaces of porous carbon channels to improve the conductivity between the porous carbon substrate and silicon grains. Then, a gaseous silicon source and a nitrogen source are simultaneously vapor-deposited onto the inner and outer surfaces of the modified porous carbon channels to form a localized silicon carbide and silicon nitride interface layer, suppressing silicon grain volume expansion. Finally, liquid resin coating and carbonization are used to form a highly ordered carbon structure coating layer, enhancing the lithium-ion interface migration rate. The silicon-carbon anode material prepared by this invention combines low cost, low expansion, and high rate capability (fast-charging). Using it as the active component to prepare battery anodes, and further assembling them, results in lithium batteries with low cell expansion and excellent cycle stability, as well as high reversible specific capacity and high initial coulombic efficiency.

[0033] Furthermore, compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Uniformly coating the porous carbon channels with a highly conductive dielectric material can fill the mesopores and macropores within the porous carbon, as well as the defect sites on the outer surface, with highly conductive material. This reduces the average pore size and specific surface area, which is beneficial for improving the first coulombic efficiency of silicon-carbon materials. Secondly, the high-conductivity dielectric covering ultramicropores with pore sizes less than 0.7 nm reduces the proportion of macropores, mesopores, and ultramicropores, thus increasing the proportion of micropores. Furthermore, the highly conductive dielectric coating within the micropores increases the active sites for silicon deposition, promoting the uniform distribution of silicon grains during CVD vapor deposition. In addition, the highly conductive dielectric coating layer formed within and on the outer surface of the porous carbon channels acts as an intermediary connecting the porous carbon substrate and silicon grains, improving the electronic conductivity between them and enhancing the fast-charging performance of the silicon-carbon anode.

[0035] 2. This invention uses inexpensive and widely available monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, silicon suboxide particles, and silicon dioxide particles as raw materials, and obtains gaseous silicon sources through high-temperature vaporization, which greatly reduces the cost of silicon source materials and thus significantly reduces the manufacturing cost of silicon-carbon materials.

[0036] 3. CVD deposition was performed using gaseous silicon and gaseous nitrogen sources as dual gas sources. At a high temperature of 500–1000℃ (more preferably 800–1000℃), a small amount of silicon carbide was formed locally between the gaseous silicon source and the porous carbon substrate. At the same time, a small amount of silicon nitride was formed between the gaseous silicon source and the gaseous nitrogen source. The thickness of the silicon carbide and silicon nitride interface layer could be optimized by adjusting the deposition process parameters. The results showed that the silicon carbide and silicon nitride interface layer could not only enhance the bonding force between silicon grains and the porous carbon substrate, but also suppress the migration and diffusion process of lithium ions between the silicon grains and the porous carbon substrate, so as to suppress the volume expansion of the silicon-carbon anode material.

[0037] 4. By coating the outer surface of the silicon-carbon intermediate with liquid resin and then carbonizing it, a high-quality carbon coating layer can be formed on the surface of the silicon-carbon material particles. Traditional carbon coating processes use organic carbon sources, resulting in amorphous carbon coating layers, which are detrimental to the transport and migration of lithium ions between the carbon coating layer and the silicon grains within the porous carbon channels. This method, however, produces a highly ordered carbon structure coating layer, effectively reducing lithium-ion transport kinetics and thus improving the fast-charging performance of the silicon-carbon anode material.

[0038] This invention uses the prepared silicon-carbon anode material as the active material to prepare the battery anode and assembles it into a lithium-ion battery. This lithium battery has excellent cycle performance and low volume expansion performance, while also having high reversible specific capacity and high initial coulombic efficiency. Detailed Implementation

[0039] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0040] This invention provides a method for preparing a silicon-carbon anode material, comprising the following steps:

[0041] A highly conductive medium is spray-dried onto porous carbon to obtain modified porous carbon.

[0042] In a protective atmosphere, a gaseous silicon source and a nitrogen source are simultaneously deposited on the modified porous carbon in the first vapor phase, and then a gaseous carbon source is introduced to perform a second vapor phase deposition to obtain a silicon-carbon intermediate; the silicon-carbon intermediate is deposited with a silicon carbide interface layer and a silicon nitride interface layer.

[0043] After the liquid resin is subjected to a second spray drying on the silicon-carbon intermediate, it is carbonized to obtain a silicon-carbon anode material.

[0044] The highly conductive medium includes one or more of titanates, transition metal oxides, polymer-based high dielectric constant composite materials, ionic liquid gels, and perovskite quantum dots.

[0045] The present invention involves spray drying a highly conductive medium onto porous carbon to obtain modified porous carbon.

[0046] In this invention, the D of the porous carbon min The thickness is 0.1–2 μm, more preferably 0.5–1.8 μm, D max The value is 10–50 μm, more preferably 16–30 μm, (D max -D min ) / D 50 The specific surface area is 0.5–1.2, more preferably 0.8–1.0, and the specific surface area is 300–2200 m². 2 / g, more preferably 500-1800m 2 / g, with an average pore size of 1-100nm, more preferably 2-60nm, and even more preferably 20-30nm.

[0047] The present invention does not have any special limitation on the source of the porous carbon; porous carbon that meets the above conditions can be prepared or obtained in a manner known in the art.

[0048] In this invention, the high conductivity medium includes one or more of titanates, transition metal oxides, polymer-based high dielectric constant composite materials, ionic liquid gels, and perovskite quantum dots. When the high conductivity medium is two or more of the above, this invention does not have a special limitation on the ratio of different types of high conductivity media, and can be adjusted according to needs.

[0049] In this invention, the titanate is preferably BaTiO3, SrTiO3, or BaSrTiO3; the transition metal oxide is preferably HfO2, ZrO2, or TiO2; the polymer-based high dielectric constant composite material is preferably PVDF / BaTiO3 composite material, P(VDF-TrFE) / graphene composite material, or epoxy resin / CNT composite material; the ionic liquid gel is preferably EMIM / polymer PEO gel; and the perovskite quantum dots are preferably -CsPbBr3.

[0050] The present invention does not impose any particular limitations on the specific preparation and source of the polymer-based high dielectric constant composite material, ionic liquid gel and perovskite quantum dots, and any material with the above composition prepared in a manner known in the art can be used.

[0051] In this invention, the mass of the highly conductive medium is preferably 0.1 to 5% of the mass of the porous carbon, more preferably 0.5 to 4%, and even more preferably 1 to 2%.

[0052] In this invention, during the first spray drying, the solid content of the high-conductivity medium slurry is preferably 1-60 wt%, more preferably 10-50 wt%, and even more preferably 10-30 wt%. This invention does not impose any special limitation on the type of dispersant used in the high-conductivity medium slurry; any conventional solvent or reagent known in the art that can disperse the above-mentioned high-conductivity medium is acceptable.

[0053] In this invention, the inlet temperature of the first spray dryer is 20-150°C, more preferably 60-120°C, and the outlet temperature is 100-300°C, more preferably 150-200°C.

[0054] This invention employs a spray drying method to uniformly coat a highly conductive medium (with a high dielectric constant) onto the inner and outer surfaces of porous carbon channels.

[0055] After obtaining the modified porous carbon, the present invention performs a first vapor deposition on the modified porous carbon simultaneously with a gaseous silicon source and a nitrogen source in a protective atmosphere, and then introduces a gaseous carbon source to perform a second vapor deposition to obtain a silicon-carbon intermediate.

[0056] In this invention, the protective atmosphere preferably includes nitriding or argon.

[0057] In this invention, the silicon source in the gaseous silicon source preferably includes one or more of monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, silicon suboxide particles, and silicon dioxide particles; this invention does not have any special limitations on the source of the silicon source and its gasification process, and it can be obtained in a manner well known in the art.

[0058] In this invention, the nitrogen source includes one or more of nitrogen, ammonia, nitric oxide and nitrogen dioxide, more preferably nitrogen.

[0059] When the gaseous silicon source or nitrogen source is one or more of the above-mentioned types, the present invention does not have a special limitation on the ratio of different types of gaseous silicon sources or nitrogen sources, and can be adjusted according to the requirements.

[0060] In this invention, the total flow rate of the gaseous silicon source and the nitrogen source is preferably 0.1 to 100 L / min, more preferably 10 to 80 L / min, and even more preferably 30 to 50 L / min. The volume ratio of the gaseous silicon source to the nitrogen source is preferably 0.1 to 100:1, more preferably 1 to 80:1, and even more preferably 10 to 50:1.

[0061] In this invention, the gaseous carbon source preferably includes an alkane gas with a pyrolysis temperature of 400-800°C; the alkane gas is preferably methane, ethane, or propane; the flow rate of the gaseous carbon source is preferably 0.1-50 L / min, more preferably 1-30 L / min, and even more preferably 10-20 L / min.

[0062] In this invention, the temperature of the first vapor deposition is preferably 500-1000°C, more preferably 550-850°C, and even more preferably 600-800°C, and the time is preferably 0.5-48h, more preferably 4-36h, and even more preferably 8-24h.

[0063] In this invention, the temperature of the second vapor deposition is preferably 500-1000°C, more preferably 550-850°C, and even more preferably 650-800°C; the time is preferably 0.1-6h, more preferably 0.5-5h, and even more preferably 2-4h.

[0064] This invention employs a vapor deposition method to simultaneously deposit gaseous silicon and nitrogen sources onto the inner and outer surfaces of modified porous carbon channels. Then, a gaseous carbon source is introduced to form a carbon coating layer on the outer surface of the modified porous carbon. After pulverization and classification, a silicon-carbon intermediate is obtained.

[0065] In this invention, the silicon-carbon intermediate is deposited with a silicon carbide interface layer and a silicon nitride interface layer; the thickness of the silicon carbide interface layer is preferably 0.1-5 nm, more preferably 0.1-2 nm, and the silicon carbide content is preferably 0.1-5 wt%, more preferably 0.5-2 wt%; the thickness of the silicon nitride interface layer is preferably 0.1-5 nm, and the silicon nitride content is preferably 0.1-5 wt%, more preferably 0.5-2 wt%.

[0066] After obtaining the silicon-carbon intermediate, the present invention performs a second spray drying of liquid resin on the silicon-carbon intermediate, followed by carbonization treatment to obtain a silicon-carbon anode material.

[0067] In this invention, the liquid resin preferably includes one or more of phenolic resin, epoxy resin, polyimide-based resin, furfural resin, and polybenzoxazine; the polyimide-based resin is preferably polyimide; when the liquid resin is two or more of the above, this invention does not have a special limitation on the ratio of different types of liquid resins, and can be adjusted according to actual needs.

[0068] In this invention, the mass of the liquid resin is preferably 0.1 to 5% of the mass of the silicon-carbon intermediate, more preferably 0.5 to 4%, and even more preferably 1 to 2%.

[0069] In this invention, the inlet temperature of the second spray dryer is preferably 20-150°C, more preferably 60-100°C, and the outlet temperature is preferably 100-300°C, more preferably 120-150°C.

[0070] This invention uses a spray drying method to coat the outer surface of a silicon-carbon intermediate with liquid resin.

[0071] In this invention, the carbonization treatment temperature is preferably 700-1200℃, more preferably 800-900℃, and the time is preferably 0.5-24h, more preferably 2-12h, and even more preferably 5-6h.

[0072] The present invention provides a silicon-carbon anode material prepared by the preparation method described in the above technical solution.

[0073] This invention provides the application of the silicon-carbon anode material described in the above technical solution in lithium batteries.

[0074] This invention provides a battery negative electrode, comprising a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector;

[0075] The negative electrode active material layer includes the silicon-carbon negative electrode material described in the above technical solution.

[0076] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0077] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0078] Example 1

[0079] 1) The porous carbon D used minIt is 1.8μm, D max It is 16μm, (D max -D min ) / D 50 Its strength is 1.0, and its specific surface area is 1800 m². 2 / g, with an average pore size of 2nm;

[0080] A 10% BaTiO3 aqueous dispersion slurry was coated onto porous carbon using spray drying. The mass of BaTiO3 was controlled to be 2% of the mass of the porous carbon. The inlet temperature of the spray drying was 60°C and the outlet temperature was 150°C, resulting in modified porous carbon.

[0081] 2) Under a nitrogen atmosphere, gaseous silicon source (gaseous single-crystal silicon) and nitrogen source (nitrogen) were simultaneously vapor-deposited onto modified porous carbon using a vapor-phase deposition method. The vapor-phase deposition temperature was 550℃ and the time was 4h. Then, a gaseous carbon source (methane) was introduced, and vapor-phase deposition was continued at 550℃ for another 4h. After pulverization and classification, a silicon-carbon intermediate was obtained. The total flow rate of the gaseous silicon source and nitrogen source was 10L / min, and the volume ratio of the gaseous silicon source to the nitrogen source was 10:1. The flow rate of the gaseous carbon source was 1L / min.

[0082] The silicon-carbon intermediate is deposited with a partial silicon carbide and silicon nitride interface layer.

[0083] The silicon carbide interface layer has a thickness of 1 nm and a silicon carbide content of 1 wt%.

[0084] The silicon nitride interface layer has a thickness of 1 nm and a silicon carbide content of 1 wt%.

[0085] 3) Liquid resin (phenolic resin) is coated onto the outer surface of the silicon-carbon intermediate by spray drying. The mass of the liquid resin is 2% of the mass of the silicon-carbon intermediate. The inlet temperature of the spray dryer is 60°C and the outlet temperature of the spray dryer is 150°C. Then, carbonization is performed at a temperature of 800°C for 5 hours to obtain the silicon-carbon anode material.

[0086] Using the silicon-carbon anode material prepared in Example 1 as the anode active material, it was mixed with graphite at a mass ratio of 10% to form an anode, coated on copper foil to form an anode sheet, and assembled into a 21700 type lithium battery.

[0087] The silicon-carbon anode material prepared in Example 1 and the lithium battery were tested respectively. The reversible specific capacity of the silicon-carbon anode material was 1832 mAh / g, the initial coulombic efficiency was 91.3%, the electrode expansion rate after capacity formation in the lithium battery was 23.8%, the charging time from 20% to 80% SOC was 12.7 s, the capacity retention rate after 100 cls of cycling was 96.7%, and the capacity retention rate after 500 cls of cycling was 89.2%.

[0088] Example 2

[0089] The only difference from Example 1 is:

[0090] The porous carbon D min 1μm, D max It is 22μm, (D max -D min ) / D 50 It has a strength of 0.8 and a specific surface area of ​​1500 m². 2 / g, with an average pore size of 20nm;

[0091] The silicon carbide interface layer has a thickness of 2 nm and a silicon carbide content of 2 wt%.

[0092] The silicon nitride interface layer has a thickness of 3 nm and a silicon carbide content of 3 wt%.

[0093] The nitrogen source is ammonia.

[0094] The highly conductive medium is a TiO2 aqueous dispersion with a solid content of 20 wt%.

[0095] The liquid resin is a polyimide liquid resin;

[0096] The inlet temperature for both spray drying processes is 100°C, and the outlet temperature for the spray drying process is 200°C.

[0097] The temperature of the vapor deposition was 900°C;

[0098] The carbonization treatment temperature is 900℃ and the carbonization treatment time is 10h;

[0099] Under the same conditions as in Example 1, a silicon-carbon anode material was obtained.

[0100] Using the silicon-carbon anode material prepared in Example 2 as the anode active material, a 21700 type lithium battery was assembled according to the method in Example 1.

[0101] The silicon-carbon anode material and lithium battery prepared in Example 2 were tested respectively. The reversible specific capacity of the silicon-carbon anode material was 2074 mAh / g, the initial coulombic efficiency was 92.2%, the electrode expansion rate after capacity formation in the lithium battery was 21.6%, the charging time from 20% to 80% SOC was 11.9 s, the capacity retention rate after 100 cls of cycling was 97.1%, and the capacity retention rate after 500 cls of cycling was 90.3%.

[0102] Example 3

[0103] The only difference from Example 1 is:

[0104] The porous carbon D min 2μm, D max It is 50μm, (D max -D min ) / D 50 The specific surface area is 2200 m², with a value of 1.2. 2 / g, with an average pore size of 100nm;

[0105] The silicon-carbon intermediate is deposited with a silicon carbide and silicon nitride interface layer.

[0106] The silicon carbide interface layer has a thickness of 5 nm and a silicon carbide content of 5 wt%.

[0107] The silicon nitride interface layer has a thickness of 4 nm and a silicon carbide content of 4 wt%.

[0108] The gaseous silicon source is gaseous silicon suboxide;

[0109] The highly conductive dielectric slurry is an aqueous dispersion of epoxy resin-CNT mixture, with a mass ratio of epoxy resin to CNT of 7:3 and a solid content of 60wt%.

[0110] The gaseous carbon source is propane;

[0111] The liquid resin is a polybenzoxazine liquid resin;

[0112] The inlet temperature of the spray dryer is 150°C, and the outlet temperature of the spray dryer is 220°C.

[0113] The temperature of the vapor deposition is 800°C;

[0114] The carbonization treatment temperature is 1000℃ and the carbonization treatment time is 16h;

[0115] Under the same conditions as in Example 1, a silicon-carbon anode material was obtained.

[0116] Using the silicon-carbon anode material prepared in Example 3 as the anode active material, a 21700 type lithium battery was assembled according to the method in Example 1.

[0117] The silicon-carbon anode material and lithium battery prepared in Example 3 were tested respectively. The reversible specific capacity of the silicon-carbon anode material was 1788 mAh / g, the initial coulombic efficiency was 90.6%, the electrode expansion rate after capacity formation in the lithium battery was 24.3%, the charging time from 20% to 80% SOC was 13.4 s, the capacity retention rate after 100 cls of cycling was 95.5%, and the capacity retention rate after 500 cls of cycling was 88.7%.

[0118] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, Includes the following steps: A highly conductive medium is spray-dried onto porous carbon to obtain modified porous carbon. In a protective atmosphere, a gaseous silicon source and a nitrogen source are simultaneously deposited on the modified porous carbon in the first vapor phase, and then a gaseous carbon source is introduced to perform a second vapor phase deposition to obtain a silicon-carbon intermediate; the silicon-carbon intermediate is deposited with a silicon carbide interface layer and a silicon nitride interface layer. After the liquid resin is subjected to a second spray drying on the silicon-carbon intermediate, it is carbonized to obtain a silicon-carbon anode material. The highly conductive medium includes one or more of titanates, transition metal oxides, polymer-based high dielectric constant composite materials, ionic liquid gels, and perovskite quantum dots.

2. The preparation method according to claim 1, characterized in that, The porous carbon D min The diameter is 0.1–2 μm, D max The value is 10–50 μm, (D max -D min ) / D 50 Its specific surface area is 300–2200 m², ranging from 0.5 to 1.

2. 2 / g, with an average pore size of 1–100 nm.

3. The preparation method according to claim 1, characterized in that, In the first spray drying process, the solid content of the high conductivity medium slurry used is 1-60 wt%; the mass of the high conductivity medium is 0.1-5% of the mass of the porous carbon. The inlet temperature of the first spray dryer is 20-150℃, and the outlet temperature is 100-300℃.

4. The preparation method according to claim 1, characterized in that, The gaseous silicon source includes one or more of the following: monocrystalline silicon particles, polycrystalline silicon particles, amorphous silicon particles, sub-silicon oxide particles, and silicon dioxide particles. The nitrogen source includes one or more of nitrogen, ammonia, nitric oxide, and nitrogen dioxide; The total flow rate of the gaseous silicon source and nitrogen source is 0.1 to 100 L / min, and the volume ratio of the gaseous silicon source to the nitrogen source is 0.1 to 100:

1.

5. The preparation method according to claim 1, characterized in that, The gaseous carbon source includes alkane gases with a pyrolysis temperature of 400–800°C; the flow rate of the gaseous carbon source is 0.1–50 L / min. The temperature of the first vapor deposition is 500–1000℃, and the time is 0.5–48 h; the temperature of the second vapor deposition is 500–1000℃, and the time is 0.1–6 h. The thickness of the silicon carbide interface layer is 0.1–5 nm, and the silicon carbide content is 0.1–5 wt%. The thickness of the silicon nitride interface layer is 0.1–5 nm, and the silicon nitride content is 0.1–5 wt%.

6. The preparation method according to claim 1, characterized in that, The liquid resin includes one or more of phenolic resin, epoxy resin, polyimide resin, furfural resin, and polybenzoxazine; the mass of the liquid resin is 0.1% to 5% of the mass of the silicon-carbon intermediate. The inlet temperature of the second spray dryer is 20-150℃, and the outlet temperature is 100-300℃; The carbonization treatment is carried out at a temperature of 700–1200°C for a time of 0.5–24 hours.

7. The silicon-carbon anode material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the silicon-carbon anode material according to claim 7 in lithium batteries.

9. A battery negative electrode, characterized in that, Includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector; The negative electrode active material layer includes the silicon-carbon negative electrode material as described in claim 7.