Silicon-carbon anode materials for use in sulfide solid-state batteries and their modification methods

Abstract

This invention relates to a silicon-carbon anode material for use in sulfide solid-state batteries, a modification method thereof, and a sulfide solid-state battery and its preparation method. The modification method includes: providing a porous silicon-carbon material, dispersing it in pure water or anhydrous ethanol to obtain solution A; adding a metal source to pure water, and adding oxalic acid or an alkaline solution dropwise while stirring until homogeneous to obtain solution B; transferring solution A to a water bath for stirring, and slowly adding solution B dropwise until the water evaporates, uniformly coating the surface of the silicon-carbon material with the precursor material to obtain the coated material; drying the coated material, and then heating and holding it under a nitrogen atmosphere to convert the surface metal oxide precursor into metal oxide, thus obtaining the silicon-carbon anode material. This invention avoids the addition of a solid electrolyte by constructing a lithium-ion transport layer in situ on the porous silicon-carbon material, thereby improving the initial discharge capacity and cycle stability of the battery, and achieving high capacity retention.

Description

Technical Field

[0001] This invention relates to the field of sulfide solid-state battery materials technology, and in particular to a silicon-carbon anode material for use in sulfide solid-state batteries and its modification method. Background Technology

[0002] In the fabrication of solid-state lithium batteries, silicon-carbon anodes have broad application prospects due to their high theoretical specific capacity and superior cycle stability compared to pure silicon. However, silicon-carbon anode materials contain pores reserved for the volume expansion and contraction of silicon particles, resulting in poor internal ionic conductivity. When applied to all-solid-state batteries, the solid electrolyte is only encapsulated on the outside of the silicon-carbon material, making the solid-solid contact between the two materials more pronounced. Ultimately, this prevents the high capacity advantage of silicon-carbon anodes from being fully realized, and the poor cycle stability severely restricts their practical application in solid-state batteries.

[0003] Prior art 1 (patent application number: 202110826580.X) discloses a silicon-carbon solid-state battery and its preparation method. This invention discloses a silicon-carbon solid-state battery, comprising a negative electrode and a positive electrode, and a sheet-like solid electrolyte disposed between the positive and negative electrode. The negative electrode comprises silicon-carbon material and a solid electrolyte uniformly mixed with the silicon-carbon material; the positive electrode comprises a positive electrode material and a solid electrolyte uniformly mixed with the positive electrode material; wherein, the solid electrolyte distributed in the positive and negative electrode respectively bonds the positive electrode material and the silicon-carbon material into a whole; the solid electrolyte is a PVDF-based gel solid electrolyte; this invention distributes the gel electrolyte in the active material of both the positive and negative electrode, and the sheet-like gel electrolyte is disposed between the positive and negative electrode, effectively binding the silicon-carbon material and mitigating deformation during cycling.

[0004] Prior art 2 (patent application number: 202410691412.8) discloses a silicon-carbon anode material, its preparation method, and an all-solid-state lithium-ion battery. This invention provides a silicon-carbon anode material, its preparation method, and an all-solid-state lithium battery, comprising a porous carbon framework and multiple composite silicon-based materials dispersed on the porous carbon framework. The composite silicon-based materials include silicon-based particles and a sulfide solid electrolyte layer coating the surface of the silicon-based particles. This invention, by setting a sulfide solid electrolyte layer on the surface of the silicon particles inside the silicon-carbon material, can provide an ion-conducting network for the core silicon-based particles, significantly improving the ionic conductivity of the resulting silicon-carbon anode material, thereby enhancing its rate performance.

[0005] However, existing technology 1 adds a solid electrolyte to the electrode, which reduces the proportion of active material and makes it difficult to take advantage of the high specific capacity of silicon anodes; the specific capacity is not mentioned at all, and in the case of low capacity, high retention rate has little practical significance. Existing technology 2 coats the solid electrolyte onto the surface of silicon-carbon material, but the ionic conductivity of the sulfide solid electrolyte used as the coating material often decreases significantly.

[0006] Therefore, existing technologies need to be improved. Summary of the Invention

[0007] In the prior art, silicon-carbon anodes cannot fully utilize their high-capacity advantage in solid-state batteries and have poor cycle stability, which severely restricts their practical application in solid-state batteries. Therefore, this application provides a silicon-carbon anode material for use in sulfide solid-state batteries and its modification method to solve the above problems.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for modifying silicon-carbon anode materials for use in sulfide solid-state batteries, comprising the following steps:

[0009] S11. Provide a porous silicon-carbon material and disperse it in pure water or anhydrous ethanol to obtain solution A;

[0010] S12. Add the metal source to pure water, add oxalic acid or alkaline solution dropwise and stir until homogeneous to obtain solution B;

[0011] S13. Transfer the solution A to a water bath and stir. Slowly add the solution B dropwise until the water evaporates. The precursor material is uniformly coated on the surface of the silicon-carbon material to obtain the coated material.

[0012] S14. After drying the coated material, heat and keep it warm under a nitrogen atmosphere to convert the surface metal oxide precursor into metal oxide, thereby obtaining the silicon-carbon anode material.

[0013] In S12, the metal source is any one or a combination of aluminum nitrate, aluminum isopropoxide, aluminum sulfate, aluminum acetate, titanium tetrachloride, tetrabutyl titanate, isopropyl titanate, titanium isopropoxide, titanium sulfate, titanium oxysulfate, titanium trichloride, magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium phosphate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc phosphate, ammonium vanadate, sodium vanadate, and potassium vanadate, and the mass fraction of the metal source is 0.5~5 wt.% of the porous silicon carbon material.

[0014] In one implementation, in S11, the metal oxide after coating accounts for 1% to 20% of the mass fraction of the silicon-carbon anode material.

[0015] In one implementation, a dispersant may be added in S11, wherein the dispersant is sodium dodecylbenzenesulfonate or polyvinylpyrrolidone.

[0016] In one implementation, in S12, the alkaline solution includes any one of sodium hydroxide, potassium hydroxide, lithium hydride aqueous solution, and ammonia solution, with a concentration range of 0.1~5 g / ml.

[0017] In one implementation, in S13, the temperature of the water bath is 50~100℃.

[0018] In one implementation, in S14, the heating temperature is 300~600℃, and the holding time is 2~5h.

[0019] Secondly, the present invention also provides a silicon-carbon anode material for use in sulfide solid-state batteries, which is prepared by the modification method of silicon-carbon anode material for use in sulfide solid-state batteries described in any one of the above-mentioned methods.

[0020] Thirdly, the present invention also provides a sulfide solid-state battery, which includes a negative electrode, said negative electrode including the silicon-carbon negative electrode material described above for use in sulfide solid-state batteries.

[0021] In one implementation, the negative electrode further includes conductive carbon black, binder, sulfide solid electrolyte, lithium sheet and indium sheet, wherein the mass fraction ratio of the silicon-carbon negative electrode material, conductive carbon black and binder is (50%~80%): (10%~20%): (5%~10%).

[0022] Fourthly, the present invention also provides a method for preparing a sulfide solid-state battery, characterized in that the method for preparing the sulfide solid-state battery according to any one of claims 1 to 9 specifically includes:

[0023] S21. Weigh out the negative electrode material, conductive carbon black and binder according to the proportion, add deionized water and mix into a uniform slurry.

[0024] S22. Use a homogenizer to mix the materials thoroughly and evenly; after sieving the slurry, coat it evenly on copper foil and dry it in a vacuum drying oven at 90℃.

[0025] S23. After drying, the electrode sheets are rolled and cut into electrode sheets;

[0026] S24. Cold press the sulfide solid electrolyte into shape;

[0027] S25. The electrode sheet is attached to one side of the sulfide solid electrolyte, and cold-pressed to make the electrode sheet and the sulfide solid electrolyte tightly bonded.

[0028] S26. Attach the lithium sheet and indium sheet to the other side of the sulfide solid electrolyte, add a current collector, and cold press to make the lithium sheet and indium sheet tightly bonded and in close contact with the sulfide solid electrolyte to obtain the negative electrode;

[0029] S27. Provide a sulfide solid electrolyte and a positive electrode, and assemble them with the negative electrode to obtain the sulfide solid battery;

[0030] The positive electrode is lithium iron phosphate (LiFePO4) or nickel cobalt manganese oxide (NCM).

[0031] Beneficial Effects: In this application, an oxide is coated onto the surface of a porous silicon-carbon material using a solution method and a water bath, followed by heat treatment to convert it into a metal oxide. The carbon framework in the porous silicon-carbon material enhances its conductivity and accommodates the volume expansion of silicon, while the nano-silicon particles exhibit good cycle stability. Coating the porous silicon-carbon material with an electronically insulating and ionically conductive metal oxide reduces dendrite formation and direct contact between the electrolyte and silicon, limiting silicon expansion during charging. This invention, by constructing a lithium-ion transport layer in situ on the porous silicon-carbon material, avoids the addition of a solid electrolyte, improving the battery's initial discharge capacity and cycle stability, and exhibiting high capacity retention. Attached Figure Description

[0032] Figure 1 This is a flowchart of the steps of the method for modifying silicon-carbon anode materials for sulfide solid-state batteries provided by the present invention.

[0033] Figure 2 This is a flowchart of the steps in the preparation method of the sulfide solid-state battery provided by the present invention;

[0034] Figure 3 This is a comparison chart of the 0.33C cycle performance of sulfide solid-state batteries provided in some embodiments of the present invention;

[0035] Figure 4 This is a rate performance diagram of a sulfide solid-state battery provided in some embodiments of the present invention;

[0036] Figure 5 This is a transmission electron microscope (TEM) image of a sulfide solid-state battery provided in some embodiments of the present invention.

[0037] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the technical features involved in the various embodiments of the invention can be combined with each other as long as they do not conflict with each other.

[0039] For details, please refer to [link / reference]. Figure 1 , Figure 1 This is a flowchart illustrating the steps of a method for modifying silicon-carbon anode materials for sulfide solid-state batteries, as provided by this invention. This invention provides a method for modifying silicon-carbon anode materials for sulfide solid-state batteries, comprising the following steps:

[0040] S11. Provide a porous silicon-carbon material and disperse it in pure water or anhydrous ethanol to obtain solution A;

[0041] S12. Add the metal source to pure water, add oxalic acid or alkaline solution dropwise and stir until homogeneous to obtain solution B;

[0042] S13. Transfer the solution A to a water bath and stir. Slowly add the solution B dropwise until the water evaporates. The precursor material is uniformly coated on the surface of the silicon-carbon material to obtain the coated material.

[0043] S14. After drying the coated material, heat and keep it warm under a nitrogen atmosphere to convert the surface metal oxide precursor into metal oxide, thereby obtaining the silicon-carbon anode material.

[0044] In S12, the metal source is any one or a combination of aluminum nitrate, aluminum isopropoxide, aluminum sulfate, aluminum acetate, titanium tetrachloride, tetrabutyl titanate, isopropyl titanate, titanium isopropoxide, titanium sulfate, titanium oxysulfate, titanium trichloride, magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium phosphate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc phosphate, ammonium vanadate, sodium vanadate, and potassium vanadate, and the mass fraction of the metal source is 0.5~5 wt.% of the porous silicon carbon material.

[0045] This application provides porous silicon-carbon materials, which can increase the specific surface area of ​​the material, thereby improving the energy density and cycle stability of the battery. By adding a metal source to form metal oxides on the surface, the conductivity, stability, and interfacial compatibility with sulfide solid electrolytes of the electrode material can be improved. Uniformly coating the surface of the silicon-carbon material with metal oxides helps to improve the electrochemical performance of the battery, reduce silicon expansion problems, and improve cycle life.

[0046] Specifically, in step S11, the metal oxide accounts for 1% to 20% of the mass fraction of the silicon-carbon anode material after coating. A dispersant, such as sodium dodecylbenzenesulfonate or polyvinylpyrrolidone, can also be added in step S11. Adding this dispersant improves the dispersibility of the silicon-carbon material in the solution, ensuring that the metal source adheres uniformly to the surface of the silicon-carbon material, preventing agglomeration or precipitation, and facilitating subsequent coating processes and uniform coating of the electrode material, further enhancing battery performance.

[0047] Specifically, in S12, the alkaline solution includes any one of sodium hydroxide, potassium hydroxide, lithium hydride aqueous solution, and ammonia solution, with a concentration range of 0.1~5 g / ml. This alkaline solution, as a solvent, can adjust the reaction conditions, promote the reaction between the metal source and the silicon-carbon material, and help form a metal oxide coating layer. Using alkaline solutions such as sodium hydroxide and potassium hydroxide helps regulate the reaction rate and reaction pathway, thereby controlling the structure and thickness of the metal oxide coating layer. The oxalic acid has a strong chelating effect, forming stable chelates or complexes with metal ions, which helps maintain the stability of metal ions in solution, thus avoiding premature precipitation or undesirable reactions with other components. Oxalic acid can optimize the deposition conditions of the metal precursor and promote the uniform coating of metal oxides on the surface of the silicon-carbon material.

[0048] Specifically, in S13, the temperature of the water bath is 50~100℃. By setting the water bath temperature at 50~100℃, the evaporation rate of the solution can be effectively controlled, avoiding damage to the material or uneven formation of metal oxides at excessively high temperatures. Furthermore, it also helps to uniformly coat the precursor material, ensuring that the metal oxides adhere evenly to the silicon-carbon surface.

[0049] Specifically, in S14, the heating temperature is 300~600℃, and the holding time is 2~5 hours. This high-temperature treatment not only promotes the formation of metal oxides but also enhances the mechanical stability of silicon-carbon materials, thereby improving the battery's durability and cycle performance.

[0050] The modification method for silicon-carbon anode materials used in sulfide solid-state batteries provided by this invention simplifies the process, making it suitable for large-scale production and reducing costs. The direct metal oxide coating provides good chemical stability and mechanical strength, optimizing ion conduction pathways. Furthermore, it can adapt to specific electrolyte environments, reducing unnecessary side reactions.

[0051] For details, please refer to [link / reference]. Figure 2 , Figure 2 This is a flowchart illustrating the steps of the preparation method of the sulfide solid-state battery provided by this invention. This invention also provides a sulfide solid-state battery, comprising a negative electrode, wherein the negative electrode comprises the silicon-carbon negative electrode material provided by this invention for use in sulfide solid-state batteries. The negative electrode further comprises conductive carbon black, a binder, a sulfide solid electrolyte, a lithium sheet, and an indium sheet, wherein the mass fraction ratio of the silicon-carbon negative electrode material, conductive carbon black, and binder is (50%~80%):(10%~20%):(5%~10%). By adding conductive carbon black, binder, and other materials to the negative electrode, the conductivity and adhesion of the negative electrode can be improved, ensuring the high efficiency performance of the battery.

[0052] The method for preparing a sulfide solid-state battery provided by this invention specifically includes:

[0053] S21. Weigh out the negative electrode material, conductive carbon black and binder according to the proportion, add deionized water and mix into a uniform slurry.

[0054] S22. Use a homogenizer to mix the materials thoroughly and evenly; after sieving the slurry, coat it evenly on copper foil and dry it in a vacuum drying oven at 90℃.

[0055] S23. After drying, the electrode sheets are rolled and cut into electrode sheets;

[0056] S24. Cold press the sulfide solid electrolyte into shape;

[0057] S25. The electrode sheet is attached to one side of the sulfide solid electrolyte, and cold-pressed to make the electrode sheet and the sulfide solid electrolyte tightly bonded.

[0058] S26. Attach the lithium sheet and indium sheet to the other side of the sulfide solid electrolyte, add a current collector, and cold press to make the lithium sheet and indium sheet tightly bonded and in close contact with the sulfide solid electrolyte to obtain the negative electrode;

[0059] S27. Provide a sulfide solid electrolyte and a positive electrode, and assemble them with the negative electrode to obtain the sulfide solid battery;

[0060] The positive electrode is lithium iron phosphate (LiFePO4) or nickel cobalt manganese oxide (NCM).

[0061] Preferably, the sulfide solid electrolyte includes Li6PS5Cl, Li6PS5I (silver sulfide germanium electrolyte), and Li 10 GeP2S 12 Any one of them.

[0062] Example 1

[0063] S11. Disperse 10g of porous silicon carbon in 300ml of ultrapure water, then add 0.1g of sodium dodecylbenzenesulfonate and continue stirring for 2 hours to prepare solution A.

[0064] S12. Add 0.1g of aluminum nitrate and 2g of oxalic acid to 50ml of ultrapure water and stir for 15min to obtain a fully mixed solution B.

[0065] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0066] S14. The dried material is heated to 500℃ and held for 3 hours in a nitrogen atmosphere to convert the surface metal oxide precursor into aluminum oxide, thus obtaining silicon-carbon anode material coated with aluminum oxide.

[0067] Example 2

[0068] S11. Disperse 10g of porous silicon carbon in 300ml of anhydrous ethanol to prepare solution A;

[0069] S12. Provide 10 ml of 3 wt.% tetrabutyl titanate as solution B, wherein the tetrabutyl titanate accounts for 3% of the mass of the silicon-carbon material;

[0070] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0071] S14. The coated material is heated to 700℃ and held for 3 hours under a nitrogen atmosphere to convert the surface metal oxide precursor into titanium dioxide, thus obtaining a titanium dioxide-coated silicon-carbon anode material.

[0072] Example 3

[0073] S11. Disperse 10g of porous silicon carbon in 300ml of anhydrous ethanol to prepare solution A;

[0074] S12. Provide 10 ml of 3 wt.% magnesium nitrate as solution B, and add dropwise 3 ml of 3% sodium hydroxide aqueous solution (0.1 g / ml), wherein the concentration of sodium hydroxide aqueous solution is 0.1 g / ml, and the magnesium nitrate accounts for 3% of the mass of the silicon carbide material;

[0075] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0076] S14. The coated material is heated to 500℃ and held for 3 hours under a nitrogen atmosphere to convert the surface metal oxide precursor into magnesium oxide, thus obtaining magnesium oxide coated silicon-carbon anode material.

[0077] Example 4

[0078] S11. Disperse 10g of porous silicon carbon in 300ml of anhydrous ethanol to prepare solution A;

[0079] S12. Provide 10 ml of 3 wt.% zinc nitrate as solution B, and add dropwise 3 ml of 3% sodium hydroxide aqueous solution (0.1 g / ml), wherein the concentration of sodium hydroxide aqueous solution is 0.1 g / ml, and the zinc nitrate accounts for 3% of the mass of the silicon carbide material;

[0080] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0081] S14. The coated material is heated to 500℃ and held for 3 hours under a nitrogen atmosphere to convert the surface metal oxide precursor into zinc oxide, thus obtaining a zinc oxide-coated silicon-carbon anode material.

[0082] Example 5

[0083] S11. Disperse 10g of porous silicon carbon in 300ml of anhydrous ethanol to prepare solution A;

[0084] S12. Provide 10 ml of 3 wt.% ammonium vanadate as solution B, and add dropwise 3 ml of 3% sodium hydroxide aqueous solution (0.1 g / ml), wherein the concentration of sodium hydroxide aqueous solution is 0.1 g / ml, and the ammonium vanadate accounts for 3% of the mass of the silicon carbide material;

[0085] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0086] S14. The coated material is heated to 500℃ and held for 3 hours under a nitrogen atmosphere to convert the surface metal oxide precursor into lithium vanadate, thus obtaining a silicon-carbon anode material coated with lithium vanadate.

[0087] Example 6

[0088] S11. Disperse 10g of porous silicon carbon in 300ml of anhydrous ethanol to prepare solution A;

[0089] S12. Provide 10 ml of 3 wt.% tin sulfate as solution B, and add dropwise 3 ml of 3% sodium hydroxide aqueous solution (0.1 g / ml), wherein the concentration of sodium hydroxide aqueous solution is 0.1 g / ml, and the ammonium vanadate accounts for 3% of the mass of the silicon carbide material;

[0090] S13. Transfer solution A to an 80℃ water bath and stir. Add solution B dropwise using a separatory funnel. Allow the two to react fully until the water evaporates completely. Then, perform a drying process.

[0091] S14. The coated material is heated to 500℃ and held for 3 hours under a nitrogen atmosphere to convert the surface metal oxide precursor into tin oxide, thus obtaining tin oxide-coated silicon-carbon anode material.

[0092] Comparative Example 1

[0093] The porous silicon-carbon material in the above embodiments was not coated.

[0094] The silicon-carbon anode material provided above was used to prepare a sulfide solid-state battery, and its electrochemical performance was tested.

[0095] The fabrication of sulfide solid-state batteries specifically includes:

[0096] S21. Provide 70g of silicon-carbon anode material, 15g of conductive carbon black, and 8g of binder CMC, and mix them with deionized water to form a uniform slurry.

[0097] S22. Use a homogenizer to mix the materials thoroughly and evenly; after sieving the slurry, coat it evenly on copper foil and dry it in a vacuum drying oven at 90℃.

[0098] S23. After drying, the electrode sheets are rolled and cut into electrode sheets;

[0099] S24. Cold press the sulfide solid electrolyte into shape;

[0100] S25. The electrode sheet is attached to one side of the sulfide solid electrolyte, and cold-pressed to make the electrode sheet and the sulfide solid electrolyte tightly bonded.

[0101] S26. Attach the lithium sheet and indium sheet to the other side of the sulfide solid electrolyte, add a current collector, and cold press to make the lithium sheet and indium sheet tightly bonded and in close contact with the sulfide solid electrolyte to obtain the negative electrode;

[0102] S27. Provide a sulfide solid electrolyte and a positive electrode lithium iron phosphate, assemble them with the negative electrode to obtain the sulfide solid battery, tighten the screws to ensure the operating external pressure of the solid battery.

[0103] In step S24, the electrolyte is a Li2S-P2S5 electrolyte, which has high ionic conductivity and can be formed into sheets at low temperatures. In step S27, the electrolyte is a Li7P3S11 electrolyte, which has high conductivity and better chemical stability near the lithium metal anode, making it suitable for improving battery safety during long-term use.

[0104] Test parameters: Cyclic tests use a current density of 0.33C, and rate tests use 0.1, 0.2, 0.5, 0.8, 1, and 0.1C.

[0105] The test results are shown in Tables 1 and 2.

[0106] Table 1: Cyclic performance test results of Examples 1-2 and Comparative Example 1.

[0107]

[0108] Table 2: Rate performance test results of Examples 1-2 and Comparative Example 1.

[0109]

[0110] According to Table 1 and Figure 3 ,in, Figure 3 This is a comparison chart of the 0.33C cycle performance of the sulfide solid-state battery provided in some embodiments of the present invention. It can be seen that the titanium dioxide-coated silicon-carbon anode material provided in Embodiment 2 has a first-cycle reversible capacity of 1460 mAh / g and an first-cycle coulombic efficiency of 80.45%. After 100 cycles, the capacity retention rate is 74.5%, which shows superior cycle performance.

[0111] According to Table 2 and Figure 4 ,in, Figure 4 This is a rate performance diagram of a sulfide solid-state battery provided in some embodiments of the present invention. It can be seen that the titanium dioxide-coated silicon-carbon anode material provided in Embodiment 2 has a reversible capacity of 1446 mAh / g at 0.1C in the first cycle and a reversible capacity of 919 mAh / g at 1C current density, with a capacity retention rate of 63.57%, which is ~20% higher than the comparative example, and has a better 1C retention rate.

[0112] pass Figure 5 The transmission electron microscope (TEM) images of the sulfide solid-state battery provided in some embodiments of the present invention show that the oxide was successfully coated on the surface of the silicon-carbon anode, and the coating thickness was about 2 nm.

[0113] In summary, this application involves coating a porous silicon-carbon material with an oxide using a solution method and a water bath, followed by heat treatment to convert it into a metal oxide. The carbon framework in the porous silicon-carbon material enhances conductivity and accommodates the volume expansion of silicon, while the nano-silicon particles exhibit good cycle stability. Coating the porous silicon-carbon material with an electronically insulating and ionically conductive metal oxide reduces dendrite formation and direct contact between the electrolyte and silicon, limiting silicon expansion during charging. This invention, by constructing a lithium-ion transport layer in situ on the porous silicon-carbon material, avoids the addition of a solid electrolyte, improving the battery's initial discharge capacity and cycle stability, and achieving high capacity retention.

[0114] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for modifying silicon-carbon anode materials for use in sulfide solid-state batteries, characterized in that, Includes the following steps: S11. Provide a porous silicon-carbon material and disperse it in pure water to obtain solution A; S12. Add the metal source to pure water, add oxalic acid dropwise and stir until homogeneous to obtain solution B; S13. Transfer the solution A to a water bath and stir. Slowly add the solution B dropwise until the water evaporates. The precursor material is uniformly coated on the surface of the silicon-carbon material to obtain the coated material. S14. After drying the coated material, heat and keep it warm under a nitrogen atmosphere to convert the surface metal oxide precursor into metal oxide, thereby obtaining the silicon-carbon anode material. In S11, solution A also contains a dispersant, which is sodium dodecylbenzenesulfonate and its content is 1 wt.% of the porous silicon-carbon material. In S12, the metal source is aluminum nitrate, the mass fraction of the metal source is 1 wt.% of the porous silicon-carbon material, and the mass fraction of the oxalic acid is 20 wt.% of the porous silicon-carbon material. In S13, the temperature of the water bath is 80°C; In S14, the heating temperature is 500℃ and the holding time is 3h.

2. A silicon-carbon anode material for use in sulfide solid-state batteries, characterized in that, It is prepared by the modification method of silicon-carbon anode material for use in sulfide solid-state batteries as described in claim 1.

3. A sulfide solid-state battery, characterized in that, Includes a negative electrode, wherein the negative electrode comprises the silicon-carbon negative electrode material for use in sulfide solid-state batteries as described in claim 2.

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