A three-dimensional silicon anode material, its preparation method and application

Abstract

This invention provides a three-dimensional silicon anode material, its preparation method, and its application. The three-dimensional silicon anode material comprises a porous silicon material, wherein the pore wall surface and the outer surface of the particles are coated with an oxide layer, a carbon coating layer, and a solid electrolyte layer; the outer surface of the particles of the porous silicon material is also coated with a conductive polymer layer. The three-dimensional silicon anode material of this invention, by coating the pore wall surface and the outer surface of the particles with an oxide layer, a carbon layer, and a solid electrolyte layer, ensures the structural stability of the material and establishes electron transport pathways and ion transport channels. Simultaneously, the outer surface of the particles is coated with a conductive polymer layer, ensuring the structural integrity of the three-dimensional silicon anode material during cycling.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a three-dimensional silicon anode material, its preparation method, and its application. Background Technology

[0002] All-solid-state batteries have garnered significant attention in recent years due to their use of solid-state electrolytes instead of flammable organic electrolytes, which greatly enhances the intrinsic safety of lithium-ion batteries. Solid-state electrolytes, as the core component of all-solid-state batteries, are crucial to their development. Solid-state electrolytes are mainly classified into four categories: polymers, oxides, sulfides, and halides. Furthermore, selecting suitable anode materials is also key to improving the performance of all-solid-state batteries.

[0003] Silicon anode materials have a high specific capacity (theoretical capacity can reach 4200 mAh·g). -1 With its advantages of high capacity and low cost, silicon anode material is a preferred material for high-energy-density all-solid-state batteries. However, high-capacity silicon anode materials have large volume expansion, which can easily lead to poor interfacial contact when used in conjunction with the aforementioned main solid-state electrolytes. That is, when high-capacity silicon anode materials are used in high-energy-density all-solid-state batteries, the large lithium insertion / extraction volume effect of high-capacity silicon anode materials causes poor interfacial contact, resulting in the loss of electron and ion transport pathways in the active material. As a result, the impedance of the all-solid-state battery increases rapidly with cycling, ultimately leading to a rapid deterioration of cell performance.

[0004] Based on the above research, there is a need to provide a three-dimensional silicon anode material that can buffer lithium intercalation expansion, has electron transport pathways and fast ion transport channels, and has strong structural stability. Summary of the Invention

[0005] The purpose of this invention is to provide a three-dimensional silicon anode material, its preparation method and application. The three-dimensional silicon anode material ensures the structural stability of the material by coating the pore wall surface and the particle surface with an oxide layer, a carbon layer and a solid electrolyte layer, and also constructs an electron transport path and an ion transport channel. At the same time, the outer surface of the particle is also coated with a conductive polymer layer to ensure the structural integrity of the three-dimensional silicon anode material during cycling.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a three-dimensional silicon anode material, wherein the porous silicon material has an oxide layer, a carbon coating layer and a solid electrolyte layer sequentially coated on the pore wall surface;

[0008] The outer surface of the porous silicon material particles is sequentially coated with an oxide layer, a carbon coating layer, a solid electrolyte layer, and a conductive polymer layer.

[0009] This invention uses porous silicon material as the core framework material, reserving sufficient space to buffer the expansion caused by lithium intercalation. Both the pore wall surface and the outer surface of the particles are coated with an oxide layer, a carbon coating layer, and a solid electrolyte layer. The oxide layer enhances the structural strength of the porous silicon material and forms a lithium silicate reinforcement layer after lithium intercalation to maintain structural stability. The carbon coating layer further stabilizes the porous silicon material and ensures its electron transport pathway. The solid electrolyte layer establishes a rapid ion transport channel within the porous silicon material. Therefore, the multiple coating layers on the pore wall surface and the outer surface of the particles collectively ensure the material's structural stability, electron transport pathway, and ion transport pathway, improving the rate and cycle performance of the three-dimensional silicon anode material. Furthermore, the outer surface of the porous silicon particles in this invention is also coated with a conductive polymer layer. This conductive polymer layer is elastic and high-strength, maintaining the integrity of the particles during operation and further enhancing the rate and cycle performance of the three-dimensional silicon anode material.

[0010] It is understood that the sequential coating involves first coating an oxide layer on the pore wall surface and the outer surface of the particles of the porous silicon material, then coating a carbon coating layer on the surface of the oxide layer, and finally coating a solid electrolyte layer on the surface of the carbon coating layer; the solid electrolyte layer on the outer surface of the particles is also coated with a conductive polymer layer.

[0011] The porous silicon material of the present invention has an oxide layer, a carbon coating layer and a solid electrolyte layer sequentially coated on the pore wall surface and the outer surface of the particles. The advantage of this coating order is that it can simultaneously take into account the material's structural stability and ion-electron transport capability. If the solid electrolyte layer is coated first and then the carbon coating layer is coated, the electron transport pathway of the silicon material will be blocked, resulting in a deterioration of the electrochemical performance.

[0012] Furthermore, the solid electrolyte layer described in this invention is located on the outermost side of the particle's outer surface, which allows it to leverage its elasticity and high strength to enhance particle stability.

[0013] Preferably, the thickness of the oxide layer is 5nm-10nm, for example, it can be 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the carbon coating content in the three-dimensional silicon anode material is 1wt%-3wt%, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the content of the solid electrolyte layer in the three-dimensional silicon anode material is 2wt%-5wt%, for example, it can be 2wt%, 3wt%, 4wt% or 5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the content of the conductive polymer layer in the three-dimensional silicon anode material is 3wt%-5wt%, for example, it can be 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] The present invention preferably allows each layer to achieve its optimal effect within a specific thickness or content range. If the thickness of each layer is too thin or the content is too low, the effect of each layer will be affected. If the thickness of each layer is too thick or the content is too high, the performance of the material will also be affected. For example, if the oxide layer is too thick, it will reduce the initial efficiency and capacity. If the carbon coating layer content is too high, it will affect ion transport. If the solid electrolyte layer content is too high, it will affect electron transport. If the conductive polymer layer content is too high, the ion and electron conductivity of the material will deteriorate.

[0018] Preferably, the particle size D50 of the porous silicon material is 2μm-4μm, for example, it can be 2μm, 2.5μm, 3μm, 3.5μm or 4μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the pore volume of the porous silicon material accounts for 60%-80% of the total volume of the porous silicon material, for example, it can be 60%, 65%, 70%, 75% or 80%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0020] Preferably, the average pore size in the porous silicon material is 0.2μm-0.4μm, for example, it can be 0.2μm, 0.25μm, 0.3μm, 0.35μm or 0.4μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the porous silicon material comprises silicon and / or silicon alloys.

[0022] Preferably, the silicon alloy comprises a silicon-copper alloy and / or a silicon-iron alloy.

[0023] Preferably, in the silicon alloy, the mass percentage of the alloying element is 1wt%-3wt%, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the oxide layer is made of silicon dioxide.

[0025] Preferably, the solid electrolyte layer comprises a sulfide solid electrolyte material.

[0026] The solid electrolyte material in the solid electrolyte layer of this invention is preferably a sulfide solid electrolyte material, which has higher ionic conductivity and can provide better ion transport capability compared to other types of solid electrolyte materials.

[0027] Preferably, the sulfide solid electrolyte material includes Li (6-x) PS (5-x) M (1+x) And / or yLi₂S·(1-y)P₂S₅, wherein M comprises any one or at least a combination of two of Cl, Br, or I, 0 ≤ x ≤ 0.6, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6, 0.2 ≤ y ≤ 0.8, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and the Li (6-x) PS (5-x) M (1+x) And / or yLi2S·(1-y)P2S5 may also contain doping elements.

[0028] Preferably, the conductive polymer layer comprises a conductive polymer electrolyte material.

[0029] Preferably, the conductive polymer electrolyte material in the conductive polymer layer has a content of 75wt%-95wt%, for example, it can be 75wt%, 80wt%, 85wt%, 90wt% or 95wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the conductive polymer electrolyte material comprises polyethylene oxide and / or polysiloxane.

[0031] Preferably, the weight-average molecular weight of the conductive polymer electrolyte material is 800,000 to 1,500,000, for example, it can be 800,000, 1,000,000, 1,100,000, 1,300,000 or 1,500,000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the conductive polymer layer further includes a lithium salt.

[0033] Preferably, the lithium salt content in the conductive polymer layer is 1wt%-20wt%, for example, it can be 1wt%, 5wt%, 10wt%, 15wt% or 20wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the lithium salt comprises lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethanesulfonyl)imide.

[0035] Preferably, the conductive polymer layer further includes a conductive agent.

[0036] Preferably, the conductive agent content in the conductive polymer layer is 1wt%-5wt%, for example, it can be 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] Preferably, the conductive agent comprises any one or a combination of at least two of carbon nanotubes, carbon black, carbon nanofibers, Ketjen black, or graphene.

[0038] Secondly, the present invention provides a method for preparing a three-dimensional silicon anode material as described in the first aspect, the method comprising the following steps:

[0039] An oxide layer, a carbon coating layer, and a solid electrolyte layer are prepared on the pore wall surface and the outer surface of particles of porous silicon materials.

[0040] A conductive polymer layer is prepared on the outer surface of porous silicon material particles to obtain the three-dimensional silicon anode material.

[0041] Preferably, the method for preparing the oxide layer includes oxidizing a porous silicon material.

[0042] Preferably, the method for preparing the carbon coating layer includes chemical vapor deposition.

[0043] Preferably, the method for preparing the solid electrolyte layer includes an in-situ coating method.

[0044] Preferably, the method for preparing the conductive polymer layer includes a liquid phase coating method.

[0045] Preferably, the preparation method includes the following steps:

[0046] (1) The porous silicon material is oxidized to achieve oxide coating, and then carbon deposition is performed to achieve carbon coating, so as to obtain a porous silicon material containing oxide layer and carbon coating.

[0047] (2) Spray the raw material solution containing the oxide layer and carbon coating layer of the porous silicon material described in step (1) with the solid electrolyte layer, and then perform heat treatment;

[0048] (3) The conductive polymer layer solution is mixed with the material obtained by heat treatment in step (2) and dried to obtain the three-dimensional silicon anode material.

[0049] Preferably, the oxidation treatment in step (1) is carried out at a temperature of 100℃-150℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, for a time of 2h-6h, for example, 2h, 3h, 4h, 5h or 6h, and is carried out in an oxygen atmosphere.

[0050] Preferably, the carbon deposition temperature in step (1) is 400℃-500℃, for example, it can be 400℃, 425℃, 450℃, 475℃ or 500℃, and it is carried out in a fluidized bed furnace.

[0051] Preferably, the carbon deposition includes chemical vapor deposition, and the gaseous carbon source used includes any one or a combination of at least two of methane, ethylene, or acetylene.

[0052] Preferably, the temperature of the heat treatment in step (2) is 400℃-500℃, for example, 400℃, 425℃, 450℃, 475℃ or 500℃, and the time is 4h-12h, for example, 4h, 6h, 8h, 10h or 12h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, the raw material solution of the solid electrolyte layer in step (2) includes the raw materials for preparing sulfide electrolyte materials and a first solvent, wherein the first solvent includes any one or a combination of at least two of water, ethanol, acetonitrile or tetrahydrofuran.

[0054] Preferably, when spraying the raw material solution for the solid electrolyte layer, the solid electrolyte layer solution is sprayed onto the surface of the carbon coating layer through a fluidized bed.

[0055] Preferably, the conductive polymer layer solution is obtained by mixing a conductive polymer electrolyte material with a second solvent, and lithium salt and a conductive agent may also be added. The second solvent includes any one or a combination of at least two of acetonitrile, tetrahydrofuran, anisole, chloroform, dichloroethane or dimethylformamide.

[0056] Thirdly, the present invention provides a battery comprising a three-dimensional silicon anode material as described in the first aspect.

[0057] Preferably, the battery comprises an all-solid-state battery.

[0058] Preferably, the cathode material of the all-solid-state battery includes any one or a combination of at least two of ternary materials, lithium-rich materials, or lithium nickel manganese oxide materials.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] This invention uses porous silicon material as the core framework material, reserving sufficient space to buffer the expansion caused by lithium intercalation. Both the pore wall surface and the outer surface of the particles are coated with an oxide layer, a carbon coating layer, and a solid electrolyte layer. The oxide layer enhances the structural strength of the porous silicon material and forms a lithium silicate reinforcement layer after lithium intercalation to maintain structural stability. The carbon coating layer further stabilizes the porous silicon material and ensures its electron transport pathway. The solid electrolyte layer establishes a rapid ion transport channel within the porous silicon material. Therefore, the multiple coating layers on the pore wall surface and the outer surface of the particles collectively ensure the material's structural stability, electron transport pathway, and ion transport pathway, improving the rate and cycle performance of the three-dimensional silicon anode material. Furthermore, the outer surface of the porous silicon particles in this invention is also coated with a conductive polymer layer. This conductive polymer layer is elastic and high-strength, maintaining the integrity of the particles during operation and further enhancing the rate and cycle performance of the three-dimensional silicon anode material. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] Example 1

[0063] This embodiment provides a three-dimensional silicon anode material, which includes a porous silicon material. The porous silicon material has an oxide layer, a carbon coating layer, and a solid electrolyte layer sequentially coated on the pore wall surface and the outer surface of the particles. The outer surface of the porous silicon material particles is also coated with a conductive polymer layer, which is located on the surface of the solid electrolyte layer on the outer surface of the particles.

[0064] In the three-dimensional silicon anode material, the oxide layer has a thickness of 6 nm, the carbon coating layer has a content of 2 wt%, the solid electrolyte layer has a content of 3 wt%, and the conductive polymer layer has a content of 4 wt%.

[0065] The porous silicon material comprises silicon, the particle size D50 of the porous silicon material is 3 μm, the pore volume accounts for 67% of the total volume of the porous silicon material, and the average pore size is 0.3 μm;

[0066] The oxide layer is made of silicon dioxide, the solid electrolyte layer is made of Li6PS5Cl, and the conductive polymer layer comprises 83wt% polyethylene oxide, 15wt% lithium bis(fluorosulfonyl)imide salt and 2wt% carbon nanotubes.

[0067] The preparation method of the three-dimensional silicon anode material includes the following steps:

[0068] (1) The porous silicon material is oxidized at 100°C for 4 hours in an oxygen atmosphere to form an oxide layer on the pore wall surface and the outer surface of the particles.

[0069] (2) The material obtained in step (1) is subjected to high-temperature treatment with methane gas in a fluidized bed furnace at 450°C to form a carbon coating layer;

[0070] (3) Lithium sulfide, phosphorus pentasulfide and lithium chloride are dissolved in tetrahydrofuran according to the formula to obtain a sulfide electrolyte solution. The sulfide electrolyte solution is sprayed onto the surface of the carbon coating layer through a fluidized bed and then heat-treated at 450°C for 6 hours to obtain a solid electrolyte layer.

[0071] (4) After mixing polyethylene oxide with a weight-average molecular weight of 1 million with acetonitrile, lithium bis(fluorosulfonyl)imide salt and carbon nanotubes are added to obtain a conductive polymer layer solution.

[0072] (5) Disperse the material obtained in step (3) into the above conductive polymer layer solution and spray dry to form the final three-dimensional silicon anode material.

[0073] Example 2

[0074] This embodiment provides a three-dimensional silicon anode material, which includes a porous silicon material. The porous silicon material has an oxide layer, a carbon coating layer, and a solid electrolyte layer sequentially coated on the pore wall surface and the outer surface of the particles. The outer surface of the porous silicon material particles is also coated with a conductive polymer layer, which is located on the surface of the solid electrolyte layer on the outer surface of the particles.

[0075] In the aforementioned three-dimensional silicon anode material, the oxide layer has a thickness of 10 nm, the carbon coating layer has a content of 1 wt%, the solid electrolyte layer has a content of 5 wt%, and the conductive polymer layer has a content of 3 wt%.

[0076] The porous silicon material comprises silicon, the particle size D50 of the porous silicon material is 2 μm, the pore volume accounts for 80% of the total volume of the porous silicon material, and the average pore size is 0.2 μm;

[0077] The oxide layer is made of silicon dioxide, the solid electrolyte layer is made of Li6PS5Cl, and the conductive polymer layer comprises 75wt% polysiloxane, 20wt% lithium bis(trifluoromethanesulfonylimide) and 5wt% carbon black.

[0078] The preparation method of the three-dimensional silicon anode material includes the following steps:

[0079] (1) The porous silicon material is oxidized at 150°C for 6 hours in an oxygen atmosphere to form an oxide layer on the pore wall surface and the outer surface of the particles.

[0080] (2) The material obtained in step (1) is subjected to high-temperature treatment with methane gas in a fluidized bed furnace at 400°C to form a carbon coating layer;

[0081] (3) Lithium sulfide, phosphorus pentasulfide and lithium chloride are dissolved in ethanol according to the formula to obtain a sulfide electrolyte solution. The sulfide electrolyte solution is sprayed onto the surface of the carbon coating layer through a fluidized bed and then heat-treated at 500°C for 4 hours to obtain a solid electrolyte layer.

[0082] (4) After mixing polysiloxane with a weight average molecular weight of 1.5 million with tetrahydrofuran, lithium bis(trifluoromethanesulfonylimide) and carbon black are added to obtain a conductive polymer layer solution.

[0083] (5) Disperse the material obtained in step (3) into the above conductive polymer layer solution and spray dry to form the final three-dimensional silicon anode material.

[0084] Example 3

[0085] This embodiment provides a three-dimensional silicon anode material, which includes a porous silicon material. The porous silicon material has an oxide layer, a carbon coating layer, and a solid electrolyte layer sequentially coated on the pore wall surface and the outer surface of the particles. The outer surface of the porous silicon material particles is also coated with a conductive polymer layer, which is located on the surface of the solid electrolyte layer on the outer surface of the particles.

[0086] In the three-dimensional silicon anode material, the oxide layer has a thickness of 5 nm, the carbon coating layer has a content of 3 wt%, the solid electrolyte layer has a content of 2 wt%, and the conductive polymer layer has a content of 5 wt%.

[0087] The porous silicon material comprises silicon, the particle size D50 of the porous silicon material is 4 μm, the pore volume accounts for 60% of the total volume of the porous silicon material, and the average pore size is 0.4 μm;

[0088] The oxide layer is made of silicon dioxide, the solid electrolyte layer is made of Li6PS5Cl, and the conductive polymer layer comprises 95wt% polyethylene oxide, 4wt% lithium bis(fluorosulfonyl)imide salt and 1wt% carbon nanotubes.

[0089] The preparation method of the three-dimensional silicon anode material includes the following steps:

[0090] (1) The porous silicon material is oxidized at 100°C for 2 hours in an oxygen atmosphere to form an oxide layer on the pore wall surface and the outer surface of the particles.

[0091] (2) The material obtained in step (1) is subjected to high-temperature treatment with methane gas in a fluidized bed furnace at 500°C to form a carbon coating layer;

[0092] (3) Lithium sulfide, phosphorus pentasulfide and lithium chloride are dissolved in tetrahydrofuran according to the formula to obtain a sulfide electrolyte solution. The sulfide electrolyte solution is sprayed onto the surface of the carbon coating layer through a fluidized bed and then heat-treated at 400°C for 12 hours to obtain a solid electrolyte layer.

[0093] (4) After mixing polyethylene oxide with a weight-average molecular weight of 800,000 with acetonitrile, lithium bis(fluorosulfonyl)imide salt and carbon nanotubes are added to obtain a conductive polymer layer solution.

[0094] (5) Disperse the material obtained in step (3) into the above conductive polymer layer solution and spray dry to form the final three-dimensional silicon anode material.

[0095] Example 4

[0096] This embodiment provides a three-dimensional silicon anode material, which is the same as that in Embodiment 1 except that the positions of the carbon coating layer and the solid electrolyte layer are interchanged.

[0097] In the preparation method of the three-dimensional silicon anode material described in this embodiment, except for the interchange of the coating order of steps (2) and (3), the rest are the same as in embodiment 1.

[0098] Example 5

[0099] This embodiment provides a three-dimensional silicon anode material, which is the same as that in Embodiment 1 except that the thickness of the oxide layer is 2 nm.

[0100] In the preparation method of the three-dimensional silicon anode material described in this embodiment, except for the change in the thickness of the oxide layer due to the change in the temperature and / or time of oxidation in step (1), the rest are the same as in Example 1.

[0101] Example 6

[0102] This embodiment provides a three-dimensional silicon anode material, which is the same as that in Embodiment 1 except that the thickness of the oxide layer is 20 nm.

[0103] In the preparation method of the three-dimensional silicon anode material described in this embodiment, except for the change in the thickness of the oxide layer due to the change in the temperature and / or time of oxidation in step (1), the rest are the same as in Example 1.

[0104] Comparative Example 1

[0105] This comparative example provides a negative electrode material, which is the porous silicon material described in Example 1.

[0106] Comparative Example 2

[0107] This comparative example provides a negative electrode material, which is the same as that in Example 1 except that it does not include an oxide layer;

[0108] In the preparation method of the negative electrode material described in this comparative example, except that step (1) is not performed, the rest is the same as in Example 1.

[0109] Comparative Example 3

[0110] This comparative example provides a negative electrode material, which is the same as that in Example 1 except that it does not include a carbon coating layer;

[0111] In the preparation method of the negative electrode material described in this comparative example, except that step (2) is not performed, the rest is the same as in Example 1.

[0112] Comparative Example 4

[0113] This comparative example provides a negative electrode material, which is the same as that in Example 1 except that it does not include a solid electrolyte layer;

[0114] In the preparation method of the negative electrode material described in this comparative example, except that step (3) is not performed, the rest is the same as in Example 1.

[0115] Comparative Example 5

[0116] This comparative example provides a negative electrode material, which is the same as that in Example 1 except that it does not include a conductive polymer layer;

[0117] In the preparation method of the negative electrode material described in this comparative example, except that steps (4) and (5) are not performed, the rest are the same as in Example 1.

[0118] Li6PS5Cl with a particle size of 3μm was placed in a mold battery and a 1mm electrolyte sheet was formed under a pressure of 30MPa. NCM811 and 1μm Li6PS5Cl with a particle size of 1μm were mixed evenly at a mass ratio of 9:1 and placed on one side of the electrolyte sheet. The negative electrode material obtained in the above examples and comparative examples was mixed with Li6PS5Cl at a mass ratio of 9:1 and placed on the other side of the electrolyte sheet to prepare the battery cell.

[0119] The specific capacity and first efficiency of the battery cell are tested by charging and discharging at a rate of 0.1C. The specific capacity at 0.1C discharge is the specific capacity of the material, and the first efficiency is the first discharge capacity divided by the first charge capacity.

[0120] Test the rate retention rate of the battery cell: charge at 0.1C, discharge at 0.1C and 1C respectively, and divide the 1C discharge capacity by the 0.1C discharge capacity to get the rate retention rate.

[0121] Test cell cycle life: the number of cycles of charging at 1C and discharging at 1C until the capacity decays to 80%.

[0122] The test results are shown in Table 1:

[0123] Table 1

[0124]

[0125] As can be seen from Table 1:

[0126] As shown in Examples 1-3 and Comparative Example 1, the porous silicon material co-coated with an oxide layer, a carbon coating layer, a solid electrolyte layer, and a conductive polymer layer of the present invention can significantly improve the cycle performance of the porous silicon material and also improve its rate capability and other properties. As shown in Examples 1 and Comparative Examples 2-5, the oxide coating of the present invention improves structural stability, the carbon coating layer ensures electron transport pathways, the solid electrolyte layer ensures ion pathways, and the conductive polymer layer ensures the overall structural stability of the particles. The absence of any coating layer will cause a decrease in the performance of the material. As shown in Examples 1 and 4, the present invention preferably has an oxide layer, a carbon coating layer, and a solid electrolyte layer sequentially coated on the pore wall surface and the outer surface of the particles of the porous silicon material, which can further promote the function of each layer and further improve the performance of the material. As shown in Examples 1 and 5-6, the present invention preferably has an oxide layer within a specific thickness range, which can not only further ensure the effective function of the oxide layer, but also avoid affecting the introduction of other layers, thereby enabling the optimal performance of the three-dimensional silicon anode material.

[0127] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A three-dimensional silicon anode material, characterized in that, The three-dimensional silicon anode material includes a porous silicon material, wherein the pore wall surface of the porous silicon material is sequentially coated with an oxide layer, a carbon coating layer and a solid electrolyte layer. The outer surface of the porous silicon material particles is sequentially coated with an oxide layer, a carbon coating layer, a solid electrolyte layer, and a conductive polymer layer. The thickness of the oxide layer is 5nm-10nm; In the three-dimensional silicon anode material, the carbon coating layer contains 1wt%-3wt%, the solid electrolyte layer contains 2wt%-5wt%, and the conductive polymer layer contains 3wt%-5wt%. The oxide layer is made of silicon dioxide; The solid electrolyte layer comprises a sulfide solid electrolyte material, which includes Li (6-x) PS (5-x) M (1+x) And / or yLi2S·(1-y)P2S5, wherein M includes any one or at least two of Cl, Br or I, 0≤x≤0.6, 0.2≤y≤0.8; The conductive polymer layer includes a conductive polymer electrolyte material, a lithium salt, and a conductive agent.

2. The three-dimensional silicon anode material according to claim 1, characterized in that, The particle size D50 of the porous silicon material is 2μm-4μm; And / or, the pore volume of the porous silicon material accounts for 60%-80% of the total volume of the porous silicon material; And / or, in the porous silicon material, the average pore size is 0.2 μm-0.4 μm; And / or, the porous silicon material comprises silicon and / or silicon alloys; The silicon alloy includes silicon-copper alloy and / or silicon-iron alloy; In the silicon alloy, the mass percentage of the alloying elements is 1wt%-3wt%.

3. The three-dimensional silicon anode material according to claim 1 or 2, characterized in that, The conductive polymer layer contains 75wt%-95wt% of conductive polymer electrolyte material. The conductive polymer electrolyte material includes polyethylene oxide and / or polysiloxane; The conductive polymer layer contains 1wt%-20wt% lithium salt. The conductive polymer layer contains 1wt%-5wt% of a conductive agent.

4. A method for preparing a three-dimensional silicon anode material as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: An oxide layer, a carbon coating layer, and a solid electrolyte layer are prepared on the pore wall surface and the outer surface of particles of porous silicon materials. A conductive polymer layer is prepared on the outer surface of porous silicon material particles to obtain the three-dimensional silicon anode material.

5. The preparation method according to claim 4, characterized in that, The method for preparing the oxide layer includes oxidizing a porous silicon material; And / or, the method for preparing the carbon coating includes chemical vapor deposition; And / or, the method for preparing the solid electrolyte layer includes in-situ coating; And / or, the method for preparing the conductive polymer layer includes liquid phase coating; And / or, the preparation method includes the following steps: (1) The porous silicon material is oxidized to achieve oxide coating, and then carbon deposition is performed to achieve carbon coating, so as to obtain a porous silicon material containing oxide layer and carbon coating. (2) Spray the raw material solution containing the oxide layer and carbon coating layer of the porous silicon material described in step (1) with the solid electrolyte layer, and then perform heat treatment; (3) The conductive polymer layer solution is mixed with the material obtained by heat treatment in step (2) and dried to obtain the three-dimensional silicon anode material.

6. The preparation method according to claim 5, characterized in that, The oxidation treatment in step (1) is carried out at a temperature of 100℃-150℃ for 2h-6h, and in an oxygen atmosphere. And / or, the raw material solution of the solid electrolyte layer in step (2) includes the raw materials for preparing sulfide electrolyte materials; And / or, the heat treatment in step (2) is performed at a temperature of 400℃-500℃ for a time of 4h-12h.

7. A battery, characterized in that, The battery comprises a three-dimensional silicon anode material as described in any one of claims 1-3.

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