Preparation method of three-dimensional composite nano silicon-carbon-based negative electrode material and solid-state battery

Abstract

The application provides a preparation method of a three-dimensional composite nanosilicon-carbon-based negative electrode material and a solid-state battery, and the preparation method comprises the following steps: 1) a cobalt salt and an organic ligand are added into a solvent, stirring and mixing are carried out, heating and continuous stirring reaction are carried out, then nanosilicon powder is added, continuous stirring and mixing are carried out until uniform, and a mixed solution is obtained; 2) the mixed solution is placed in a stainless steel kettle with a Teflon lining, then hydrothermal reaction is carried out at 80-180 DEG C; after the reaction is completed, the mixture is cooled to room temperature and taken out; 3) the mixture is centrifuged, washed, dried after washing, and an intermediate product is obtained; 4) the intermediate product is calcined; after washing, centrifugation is carried out again, then drying is carried out in an oven, and a high specific surface area porous silicon-carbon negative electrode material is obtained. The method has the advantages of simple synthesis process, mild reaction condition, high repeatability of the composite nanosilicon-carbon negative electrode material preparation method, and the silicon-carbon negative electrode material prepared by the method has high capacity and good cycle stability.

Description

TECHNICAL FIELD

[0001] One or more embodiments of the present specification relate to the technical field of lithium battery, and particularly to a preparation method of a three-dimensional composite nano-silicon-carbon-based negative electrode material and a solid-state battery. BACKGROUND

[0002] With the rapid development of economy and the rapid increase of industrial production efficiency, the problems of excessive energy consumption and environmental pollution are becoming increasingly prominent, so finding safe, clean and efficient renewable new energy has become one of the research hotspots. Solar energy, nuclear energy, wind energy, etc. are all good substitutes for traditional coal power generation. However, these clean energy power generation has obvious disadvantages: intermittency, uncontrollability, etc., so before being integrated into the power grid, energy storage devices need to be used to stabilize them. The advent of the era of electric vehicles and the era of 5G has made people's demand for secondary energy reach an unprecedented height. Lithium-ion batteries have become the most widely used secondary batteries in commercial applications due to their high energy density, high voltage, etc.

[0003] The electrolyte in lithium-ion batteries can be divided into liquid-containing liquid electrolyte and liquid-free solid-state electrolyte. Due to the difference between the two, we call it liquid battery and solid-state battery. Compared with liquid batteries, solid-state batteries have higher safety performance, greater energy density, higher power density and better cycle stability. Due to the above advantages of solid-state batteries, solid-state batteries have become a research hotspot at present, and solid-state batteries are also considered to be the most promising development direction of the new generation of high-energy-density lithium batteries.

[0004] The negative electrode, as an important part of ion batteries, has always been a hot research object for researchers. At present, graphite materials are mostly used as negative electrodes in solid-state batteries, but the theoretical capacity of graphite materials is relatively low, which limits the overall energy density of the battery. The theoretical specific capacity of Si negative electrode (4200mAh / g) is much higher than that of graphite negative electrode (372mAh / g), but it has a serious volume expansion phenomenon during lithiation, which seriously affects the cycle life and efficiency of the battery.

[0005] Studies have shown that the structural design of silicon negative electrode materials and the compounding of different materials can improve the cycle stability while maintaining the high capacity of silicon. Cui et al. (Microporous and Mesoporous Materials, 2019, 275:42-49) prepared a titanium dioxide coated nanosilicon electrode material using a dissolution heat method, but this material has general conductivity and large electrochemical impedance, making it difficult to commercialize. Jian (Journal of Power Sources, 2017, 342:529-536) et al. prepared a Si@C@void@C nanocomposite material with a core-shell structure, which not only reduces the interface resistance but also effectively protects the structural stability of Si material, but the preparation method is complex and not suitable for industrial production. In patent CN109671928A, carbon-coated nanosilicon material is prepared by water bath stirring of metal salt, organic ligand and nanosilicon, and calcination in the later stage. The capacity, initial efficiency and cycle stability of the prepared material in the liquid battery need to be improved. Moreover, in the preparation of MOFs material, different metal salts, different proportions of organic ligands, different organic ligands and synthesis conditions all have an impact on the structure, morphology and performance of the material. The patent CN109671928A does not give these preparation details. In addition, the application of the silicon-carbon negative electrode material prepared by this method in the liquid battery and in the solid-state battery has obvious differences in mechanism and performance, and the patent does not mention the application performance in the solid-state battery. SUMMARY

[0006] Therefore, one of the purposes of the present application is to provide a preparation method of a three-dimensional composite nanosilicon-carbon-based negative electrode material. This method uses metal organic framework materials, compared with metal iron salt, the topological structure of metal cobalt salt and organic ligand is more inclined to three-dimensional growth, which can prepare three-dimensional structure composite materials, and the precursor is prepared by using a high-pressure hydrothermal kettle, which not only makes the material have better dispersity, uniformity and structural stability, but also makes the material have a specific size and structure. This method has simple synthesis process, mild reaction conditions and high repeatability. The silicon-carbon negative electrode material prepared by this method has high capacity and good cycle stability when applied in solid-state batteries. The synthesis process of the present application does not need to add dispersant, which is more green, environmentally friendly and healthy.

[0007] The second purpose of the present application is to provide a solid-state battery comprising the three-dimensional composite nanosilicon-carbon-based negative electrode material prepared by the above preparation method.

[0008] Based on the first purpose, the present application provides the following technical solutions :

[0009] A preparation method of a three-dimensional composite nanosilicon-carbon-based negative electrode material, comprising the following steps:

[0010] 1) adding a cobalt salt and an organic ligand into a solvent, stirring and mixing, heating and continuing to stir and react; then adding nano silicon powder, continuing to stir and mix uniformly to obtain a mixed solution;

[0011] The cobalt salt is one or more of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate.

[0012] The organic ligand is any one of terephthalic acid, polybenzene tricarboxylic acid and dimethyl imidazole.

[0013] The solvent is one of N,N-dimethylformamide, anhydrous methanol, anhydrous ethanol and deionized water.

[0014] 2) placing the mixed solution in a stainless steel kettle with a Teflon lining, then performing hydrothermal reaction under the conditions of 80-180℃ and 0.3-0.5MPa; after the reaction is completed, cooling to room temperature and taking out the mixture;

[0015] 3) centrifuging the mixture, washing the sample with methanol and deionized water, drying the solid sample in a vacuum drying box after washing to obtain an intermediate product;

[0016] 4) placing the intermediate product into a quartz boat, then placing it in a tube furnace under a protective gas atmosphere to perform calcination; after calcination, washing the solid powder with hydrochloric acid and deionized water, then centrifuging, and collecting the solid sample to dry in an oven to obtain a high specific surface area porous silicon-carbon negative electrode material.

[0017] The present application uses metal organic framework material and nano silicon as precursors, wherein the metal organic framework material is a carbon source (the ligand in the metal organic framework material is an organic ligand, and the metal salt is a cobalt salt), and the nano silicon is a silicon source; after calcination of the precursors, multiple washing and centrifugal separation are performed to obtain a three-dimensional composite nano silicon-carbon composite material (referred to as a composite nano silicon-carbon material), and the nano silicon-carbon composite material has a particle diameter of about 100-200nm.

[0018] As an embodiment, in step 1), the average particle size of the nano silicon powder is less than 50nm.

[0019] As an embodiment, in step 1), the molar ratio of the cobalt salt to the organic ligand is 2:1-2.

[0020] As an embodiment, in step 1), the stirring and mixing time is 10-30min; and the rate is 80-150r / min.

[0021] As an embodiment, in step 1), the stirring reaction temperature is 50-80℃; the stirring time is 20-40min; and the continued stirring time is 20-40min.

[0022] As an implementation form, in step 1), the molar ratio of the cobalt salt to the nano-silicon powder is 1:10-40.

[0023] As an implementation form, in step 2), the filling amount of the mixed solution in the stainless steel kettle is 50-70v%.

[0024] As an implementation form, in step 2), the hydrothermal reaction time is 8-16h.

[0025] As an implementation form, in step 3), the drying temperature in the vacuum drying oven is 80-100℃; the drying time is 8-14h.

[0026] As an implementation form, in step 3), the washing times are 2-4 times.

[0027] As an implementation form, in step 4), the temperature rising rate in the tube furnace is 3-10℃ / min, the calcination temperature is 400-600℃, and the calcination time is 2.5-3.5h.

[0028] As an implementation form, in step 4), the drying temperature in the oven is 50-80℃, and the drying time is 8-12h.

[0029] As an implementation form, in step 4), the protective gas atmosphere is nitrogen, argon or nitrogen-argon mixed gas.

[0030] Based on the second purpose, the present application provides the following technical solutions :

[0031] A solid-state battery comprising the three-dimensional composite nano-silicon-carbon-based negative electrode material prepared by the preparation method.

[0032] Any range recited in the present disclosure includes the end values and any numerical value between the end values and any sub-range comprised of any numerical value between the end values.

[0033] Unless otherwise specified, each raw material in the present application can be obtained by commercial purchase, and the equipment used in the present application can adopt conventional equipment in the field or refer to the existing technology in the field.

[0034] Compared with the prior art, the present application has the following beneficial effects :

[0035] 1. The raw materials are simple and easy to obtain, the cost is low, the reaction conditions are mild, the preparation process is simple and feasible, and the repeatability is high. In the synthesis process of the present application, no dispersing agent is added, which is more green, environmentally friendly and healthy.

[0036] 2. The porous metal organic framework material is used as a precursor to coat the nano-silicon material, which ensures uniform dispersion of the nano-silicon in the carbon material, and the emergence of metal vacancies in the precursor after calcination ensures that the composite nano-silicon-carbon material has a porous structure.

[0037] 3. The prepared composite nano-silicon-carbon material has a greatly improved conductivity compared to the silicon-carbon material, which reduces the impedance of the material and greatly improves the electrochemical performance of the battery.

[0038] 4. The uniform dispersion of the nano-silicon material in the amorphous carbon helps to improve the volume expansion problem of the silicon material in the electrochemical cycle, and significantly improves the cycle performance of the battery.

[0039] 5. The production steps are relatively simple, and large-scale production is expected to be realized.5. The production steps are relatively simple, and the raw material price is relatively low, and large-scale production is expected to be realized. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a scanning electron microscope picture of the precursor obtained in step 1) of Example 1;

[0041] Figure 2 is a transmission electron microscope picture of the three-dimensional composite nano-silicon-carbon-based negative electrode material obtained in Example 2;

[0042] Figure 3 is a scanning electron microscope picture of the three-dimensional composite nano-silicon-carbon-based negative electrode material obtained in Example 3;

[0043] Figure 4 is a structural schematic diagram of the three-dimensional composite nano-silicon-carbon-based negative electrode material obtained in Example 2. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present disclosure clearer and more apparent, the present disclosure is further described in detail below in combination with specific embodiments.

[0045] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present disclosure should be understood as the usual meaning understood by those skilled in the art to which the present disclosure belongs. The terms "first", "second" and the like used in one or more embodiments of the present disclosure do not represent any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and the like mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects.

[0046] Solid-state battery negative electrode material is an important part of solid-state battery. At present, silicon is used as the negative electrode material of solid-state battery due to its high specific capacity. However, the poor conductivity of silicon material is not conducive to the release of battery capacity, and the alloying reaction in the process of charge and discharge cycle will cause large volume expansion of silicon material, resulting in problems such as powdering and cracking of the negative electrode, which affects the performance of the battery. The main way to solve the above problems at present is to prepare carbon-silicon composite materials with core-shell structure, sandwich structure and complete carbon coating, which not only improves the conductivity of silicon negative electrode, but also improves the volume expansion problem of silicon. However, for the silicon negative electrode of solid-state battery, the complete coating structure will limit the contact between silicon and solid-state electrolyte, thereby affecting the ionic conductivity of the electrode material, which is not conducive to the electrochemical performance of the silicon negative electrode. Therefore, it is an urgent problem to design a silicon-carbon composite structure suitable for the silicon negative electrode of solid-state battery.

[0047] Based on this, referring to Figure 1 As an aspect of the present application, a preparation method of a three-dimensional composite nano-silicon-carbon-based negative electrode material is provided, comprising the following steps:

[0048] 1) Add cobalt salt and organic ligand into a solvent, stir and mix, heat and continue to stir and react; then add nano-silicon powder, continue to stir and mix uniformly to obtain a mixed solution;

[0049] The cobalt salt is one or more of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate;

[0050] The organic ligand is any one of terephthalic acid, polybenzene tricarboxylic acid and dimethyl imidazole;

[0051] The solvent is one of N,N-dimethylformamide, anhydrous methanol, anhydrous ethanol and deionized water;

[0052] 2) Put the mixed solution into a stainless steel kettle lined with Teflon, then perform hydrothermal reaction under the conditions of 80-180℃ and 0.3-0.5MPa; after the reaction is completed, cool to room temperature and take out the mixture;

[0053] 3) Centrifuge the mixture, wash the sample with methanol and deionized water, dry the solid sample in a vacuum drying box after washing to obtain an intermediate product;

[0054] 4) Put the intermediate product into a quartz boat, then place it in a tube furnace under a protective gas atmosphere for calcination; after calcination, wash the solid powder with hydrochloric acid and deionized water, then centrifuge, collect the solid sample and dry it in an oven to obtain a high specific surface area porous silicon-carbon negative electrode material.

[0055] The application provides a preparation method of a high specific surface area porous silicon-carbon negative electrode. The high specific surface area can provide more lithium storage sites and electrochemical reaction sites for the electrode material, so that the charge and discharge capacity of the electrode material is obviously improved. The uniform pores can provide more channels for electrons and ions, so that the electrochemical performance of the battery is significantly improved. The good two-dimensional carbon skeleton structure can effectively solve the volume expansion problem of the solid silicon negative electrode material, and increase the conductivity of the silicon-based material, so that the composite material has better electrochemical performance. The existing silicon-carbon composite negative electrode material is mostly in a coating structure, a layered structure or a simple composite. For the solid battery negative electrode, these structures limit the ionic conductivity of the material. The technology uniformly embeds the silicon material in the carbon layer, which is extremely beneficial to improving the ionic conductivity of the electrode material.

[0056] According to some embodiments of the application, in step 1), the average particle size of the silicon powder is less than 50 nm.

[0057] According to some embodiments of the application, in step 1), the molar ratio of the cobalt salt to the organic ligand is 2:1-2.

[0058] According to some embodiments of the application, in step 1), the stirring mixing time is 10-30 min, and the stirring rate is 80-150 r / min.

[0059] According to some embodiments of the application, in step 1), the stirring reaction temperature is 50-80℃, for example, 50, 55, 60, 65, 70, 75 or 80℃; and the stirring time is 20-40 min, for example, 20, 25, 30, 35 or 40 min.

[0060] According to some embodiments of the application, in step 1), the molar ratio of the cobalt salt to the nano-silicon powder is 1:10-40, or 1:10-35, or 1:10-30, or 1:10-25, or 1:10-20, or 1:10-15, or 1:15-40, or 1:15-35, or 1:15-30, or 1:15-25, or 1:15-20, or 1:20-40, or 1:20-35, or 1:20-30, or 1:20-25, or 1:25-40, or 1:25-35, or 1:25-30, or 1:30-40.

[0061] According to some embodiments of the application, in step 2), the filling amount of the mixed solution in the stainless steel kettle is 50-70 v%.

[0062] According to some embodiments of the application, in step 2), the hydrothermal reaction time is 8-16 h.

[0063] According to some embodiments of the present application, in step 3), the temperature for drying in the vacuum drying oven is 80-100℃, such as 80, 85, 90, 95, 100℃; and the time is 8-14h, such as 8, 9, 10, 11, 12, 13, or 14h.

[0064] According to some embodiments of the present application, in step 3), the number of washing is 2-4 times.

[0065] According to some embodiments of the present application, in step 4), the heating rate for calcination in the tube furnace is 3-10℃ / min, or 4-10℃ / min, or 5-10℃ / min, or 6-10℃ / min, or 7-10℃ / min, or 8-10℃ / min, or 9-10℃ / min, or 5-9℃ / min, or 6-8℃ / min; the calcination temperature is 600-900℃, or 620-900℃, or 640-900℃, or 660-900℃, or 680-900℃, or 700-900℃, or 720-900℃, or 740-900℃, or 760-900℃, or 780-900℃, or 800-900℃, or 820-900℃, or 840-900℃, or 860-900℃, or 650-850℃, or 700-800℃, or 750-800℃, and the calcination time is 2.5-3.5h.

[0066] According to some embodiments of the present application, in step 4), the temperature for drying in the oven is 50-80℃, or 55-80℃, or 60-80℃, or 65-80℃, or 70-80℃, or 75-80℃, or 50-70℃, or 50-60℃; and the drying time is 8-12h, such as 8, 9, 10, 11, or 12h.

[0067] According to some embodiments of the present application, in step 4), the protective gas atmosphere is nitrogen, argon, or nitrogen-argon mixture.

[0068] As another aspect of the present application, the present application provides a solid-state battery comprising the porous silicon-carbon negative electrode material prepared by the above method.

[0069] In practical application, the high specific surface area porous silicon-carbon material can be used together with electrolyte, or used alone. Further, the high specific surface area porous silicon-carbon material can be directly coated or sprayed onto the electrode sheet, or transferred to the surface of the electrode sheet by other methods.

[0070] Example 1

[0071] A method for preparing a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0072] 1) 10 mmol of cobalt chloride and 5 mmol of terephthalic acid were respectively placed in 4 ml of methanol and stirred for 10 min, then the two were mixed and stirred at 50°C for 20 min; then 250 mmol of nano-silicon powder was added to the mixed solution and stirred for 20 min;

[0073] 2) The mixed solution of step 1) was placed in a stainless steel kettle lined with Teflon, filled to 50% of the filling capacity, and the reaction kettle was sealed and placed in a muffle furnace for hydrothermal reaction at 80°C and 0.3 MPa for 8 h. After the reaction kettle was naturally cooled to room temperature, the mixture was taken out;

[0074] 3) The product of step 2) was collected by centrifugation, and the sample was washed with methanol and deionized water three times respectively, and then placed in a vacuum drying oven at 80°C for 8 h to obtain an intermediate product;

[0075] 4) The intermediate product of step 3) was taken out and placed in a quartz boat, which was placed in a tube furnace under a nitrogen atmosphere, and the temperature was raised to 400°C at a rate of 3°C / min and maintained for 3 h to calcine the material, and then the product was washed with hydrochloric acid and deionized water and centrifuged, and then the sample was collected and dried in a vacuum oven at 50°C for 8 h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0076] 5) The composite nano-silicon-carbon material was uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 using a homogenizer for 30 min, then the mixed slurry was coated on a copper foil, dried at 100°C for 3 h, and punched into a 9 mm diameter sheet; finally, a solid-state battery was assembled and its electrochemical performance was tested, as shown in Table 1 below.

[0077] Figure 1 is a scanning electron microscope image of the precursor obtained in step 1) of Example 1.

[0078] Example 2

[0079] A method for preparing a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0080] 1) 10 mmol of cobalt chloride and 5 mmol of terephthalic acid were respectively placed in 4 ml of methanol and stirred for 10 min, then the two were mixed and stirred at 50°C for 20 min; then 250 mmol of nano-silicon powder was added to the mixed solution and stirred for 20 min;

[0081] 2) The mixed solution of step 1) was placed in a stainless steel kettle lined with Teflon, filled to 50% of the filling capacity, and the reaction kettle was sealed and placed in a muffle furnace for hydrothermal reaction at 80°C and 0.4 MPa for 8 h. After the reaction kettle was naturally cooled to room temperature, the mixture was taken out;

[0082] 3) centrifugal collection of the product of step 2), three centrifugal washings of the sample with methanol and deionized water, respectively, drying of the sample in a vacuum drying oven at 80°C for 8h, to obtain an intermediate product;

[0083] 4) taking the intermediate product of step 3) into a quartz boat, placing it in a tube furnace under a nitrogen atmosphere, heating at 3°C / min to 400°C for 3h to calcine the material, obtaining a product, washing and centrifuging the product with hydrochloric acid and deionized water, and then collecting the sample and drying it in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0084] 5) using a homogenizer to uniformly mix the composite nano-silicon-carbon material with a sulfide electrolyte and a conductive agent at a ratio of 50:50:3 for 30min, then coating the mixed slurry on a copper foil, drying at 100°C for 3h, punching out a thin sheet with a diameter of 9mm, and finally assembling a solid-state battery therefrom and testing its electrochemical performance, as shown in Table 1 below.

[0085] Example 3

[0086] A method for preparing a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0087] 1) placing 10mmol of cobalt chloride and 5mmol of terephthalic acid in 4ml of methanol, respectively, and stirring for 10min, then mixing the two and stirring at 50°C for 20min, and then adding 250mmol of nano-silicon powder to the mixed solution and stirring for 20min;

[0088] 2) placing the mixed solution of step 1) in a stainless steel kettle lined with Teflon, filling to a filling amount of 50%, sealing the reaction kettle, and then carrying out hydrothermal reaction in a muffle furnace at 80°C and 0.5MPa for 8h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0089] 3) centrifugal collection of the product of step 2), three centrifugal washings of the sample with methanol and deionized water, respectively, drying of the sample in a vacuum drying oven at 80°C for 8h, to obtain an intermediate product;

[0090] 4) taking the intermediate product of step 3) into a quartz boat, placing it in a tube furnace under a nitrogen atmosphere, heating at 3°C / min to 400°C for 3h to calcine the material, obtaining a product, washing and centrifuging the product with hydrochloric acid and deionized water, and then collecting the sample and drying it in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0091] 5) Using a homogenizer, the composite nanosilicon-carbon material was mixed with the sulfide electrolyte and conductive agent at a ratio of 50:50:3 for 30 min. Then the mixed slurry was coated on a copper foil, dried at 100°C for 3 h, and punched into a 9 mm diameter sheet. Finally, the solid-state battery was assembled and its electrochemical performance was tested, as shown in Table 1 below.

[0092] Example 4

[0093] A method for preparing a composite nanosilicon-carbon-based negative electrode material, comprising the following steps:

[0094] 1) 10 mmol of cobalt nitrate and 10 mmol of polybenzene tricarboxylic acid were dissolved in 5 ml of ethanol and stirred in a room temperature water bath for 20 min. Then the two were mixed and stirred at 70°C for 30 min. Then 260 mmol of nanosilicon powder was added to the mixed solution and stirred for 30 min;

[0095] 2) The mixed solution of step 1) was placed in a stainless steel kettle lined with Teflon, filled to 60% of the filling capacity, and the reaction kettle was sealed. The sealed reaction kettle was placed in a muffle furnace and hydrothermally reacted at 120°C and 0.3 MPa for 10 h. After the reaction kettle was naturally cooled to room temperature, the mixture was removed;

[0096] 3) The product of step 2) was collected by centrifugation, and the sample was washed with methanol and deionized water four times by centrifugation. The sample was placed in a vacuum drying oven and dried at 90°C for 10 h to obtain an intermediate product;

[0097] 4) The intermediate product of step 3) was placed in a quartz boat and placed in a tube furnace under an argon protective gas atmosphere. The temperature was raised to 500°C at a rate of 5°C / min and held for 3 h to calcine the material. The product was washed and centrifuged with hydrochloric acid and deionized water, and then the sample was collected and dried in a vacuum oven at 60°C for 10 h to obtain a composite nanosilicon-carbon-based negative electrode material;

[0098] 5) Using a homogenizer, the composite nanosilicon-carbon material was mixed with the sulfide electrolyte and conductive agent at a ratio of 50:50:3 for 40 min. Then the mixed slurry was coated on a copper foil, dried at 90°C for 3 h, and punched into a 9 mm diameter sheet. Finally, the solid-state battery was assembled and its electrochemical performance was tested, as shown in Table 1 below.

[0099] Figure 2 is a transmission electron microscope image of the composite nanosilicon-carbon-based negative electrode material obtained in Example 2.

[0100] Figure 4 is a structural schematic diagram of the composite nanosilicon-carbon-based negative electrode material obtained in Example 2.

[0101] Example 5

[0102] A preparation method of a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0103] 1) 10 mmol of cobalt sulfate and 15 mmol of dimethylimidazole are respectively dissolved in 5 ml of DMF and stirred in a room temperature water bath for 30 min; then the two are mixed and stirred at 60°C for 35 min. Then 280 mmol of nano-silicon powder is added to the mixed solution and stirred for 35 min;

[0104] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, filled to 65% of the filling capacity, and the reaction kettle is sealed. Hydrothermal reaction is carried out in a muffle furnace at 150°C and 0.3 MPa for 14 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0105] 3) The product of step 2) is collected by centrifugation, washed with methanol and deionized water several times, and then placed in a vacuum drying oven at 95°C for 12 h to obtain an intermediate product;

[0106] 4) The intermediate product of step 3) is taken out and placed in a quartz boat, which is placed in a tube furnace under nitrogen and argon protective gas atmosphere, and heated to 600°C at a rate of 7°C / min and kept for 3 h to calcine the material. The product is washed with hydrochloric acid and deionized water several times, then the sample is collected and dried in a vacuum oven at 70°C for 10 h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0107] 5) The composite nano-silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 using a homogenizer for 20 min, then the mixed slurry is coated on a copper foil, dried at 100°C for 2 h, and punched into a 9 mm diameter sheet. Finally, it is assembled into a solid-state battery and its electrochemical performance is tested; see Table 1 below.

[0108] Figure 3 is the scanning electron microscope picture of the composite nano-silicon-carbon-based negative electrode material obtained in Example 3.

[0109] Example 6

[0110] A preparation method of a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0111] 1) 10 mmol of cobalt acetate and 20 mmol of terephthalic acid are respectively dissolved in 5 ml of deionized water and stirred in a room temperature water bath for 35 min; then the two are mixed and stirred at 80°C for 40 min. Then 290 mmol of nano-silicon powder is added to the mixed solution and stirred for 40 min;

[0112] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill to 70% of the capacity, seal the reaction kettle, and then hydrothermally react at 180°C and 0.3 MPa in a muffle furnace for 16 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0113] 3) Centrifugal collection of the product of step 2), multiple washing of the sample with methanol and deionized water, and then placing the sample in a vacuum drying oven at 100°C for 14 h to obtain an intermediate product;

[0114] 4) Take the intermediate product of step 3) and place it in a quartz boat, which is placed in a tube furnace under a nitrogen protective gas atmosphere, and then the material is calcined by heating at 10°C / min to 600°C and maintaining the temperature for 3 h. The product is washed multiple times with hydrochloric acid and deionized water, centrifuged, and then the sample is collected and dried in a vacuum oven at 80°C for 12 h to obtain a composite nano silicon-carbon-based negative electrode material;

[0115] 5) Homogenously mix the silicon-carbon composite material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 using a homogenizer for 30 min, then coat the mixed slurry on a copper foil, dry at 100°C for 3 h, punch a 9 mm diameter wafer, and finally assemble a solid-state battery and test its electrochemical performance, as shown in Table 1 below.

[0116] Example 7

[0117] A method for preparing a composite nano silicon-carbon-based negative electrode material, comprising the following steps:

[0118] 1) Dissolve 10 mmol of cobalt chloride and 20 mmol of dimethylimidazole in 5 ml of deionized water respectively and stir in a normal temperature water bath for 30 min; then mix the two and stir at 80°C for 30 min. Then add 300 mmol of nano silicon powder to the mixed solution and stir for 40 min;

[0119] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill to 70% of the capacity, seal the reaction kettle, and then hydrothermally react at 150°C and 0.3 MPa in a muffle furnace for 12 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0120] 3) Centrifugal collection of the product of step 2), multiple washing of the sample with methanol and deionized water, and then placing the sample in a vacuum drying oven at 80°C for 12 h to obtain an intermediate product;

[0121] 4) Take out the product of step 3) and place it in a quartz boat, and place it in a tube furnace under a nitrogen protective gas atmosphere, and heat it to 450°C at a rate of 5°C / min and keep it for 3h to calcine the material, and obtain the product, and wash it with hydrochloric acid and deionized water multiple times, and then collect the sample and place it in a vacuum oven to dry at 80°C for 12h to obtain the composite nano silicon-carbon-based negative electrode material;

[0122] 5) Use a homogenizer to uniformly mix the silicon-carbon composite material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 20min, and then coat the mixed slurry on a copper foil, dry it at 80°C for 3h, and punch out a thin sheet with a diameter of 9mm; finally, assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0123] Example 8

[0124] A preparation method of a composite nano silicon-carbon-based negative electrode material, comprising the following steps:

[0125] 1) Dissolve 10mmol of cobalt nitrate and 20mmol of dimethyl imidazole in 5ml of deionized water respectively and stir them in a water bath at room temperature for 30min. Then mix them and stir them at 80°C for 30min. Then add 285mmol of nano silicon powder to the mixed solution and stir them together for 30min;

[0126] 2) Place the mixed solution of step 1) in a stainless steel kettle lined with Teflon, fill it to 60% of its capacity, seal the kettle, and then place it in a muffle furnace for hydrothermal reaction at 120°C and 0.3MPa for 10h. Let the kettle cool naturally to room temperature, and take out the mixture;

[0127] 3) Centrifuge the product of step 2), wash the sample multiple times with methanol and deionized water, and then place the sample in a vacuum drying oven to dry at 80°C for 10h to obtain an intermediate product;

[0128] 4) Take out the product of step 3) and place it in a quartz boat, and place it in a tube furnace under a nitrogen protective gas atmosphere, and heat it to 600°C at a rate of 3°C / min and keep it for 3h to calcine the material, and obtain the product, and wash it with hydrochloric acid and deionized water multiple times, and then collect the sample and place it in a vacuum oven to dry at 80°C for 12h to obtain the composite nano silicon-carbon-based negative electrode material;

[0129] 5) Use a homogenizer to uniformly mix the silicon-carbon composite material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 30min, and then coat the mixed slurry on a copper foil, dry it at 110°C for 3h, and punch out a thin sheet with a diameter of 9mm; finally, assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0130] Example 9

[0131] A preparation method of a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0132] 1) 10 mmol of cobalt chloride and 10 mmol of terephthalic acid are respectively placed in 4 ml of methanol and stirred for 10 min, then the two are mixed and stirred at 50°C for 20 min; then 230 mmol of nano-silicon powder is added to the mixed solution and stirred for 20 min;

[0133] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, filled according to the filling amount of 50%, and the reaction kettle is sealed, then placed in a muffle furnace according to 80°C, 0.3 MPa hydrothermal reaction for 8 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0134] 3) The product of step 2) is collected by centrifugation, and the sample is washed with methanol and deionized water for three times respectively, and then placed in a vacuum drying oven at 80°C for 8 h to obtain an intermediate product;

[0135] 4) The product of step 3) is taken out and placed in a quartz boat, which is placed in a tube furnace under nitrogen atmosphere, heated to 500°C at a rate of 3°C / min and kept for 3 h to calcine the material, then washed with hydrochloric acid and deionized water, and then the sample is collected and dried in a vacuum oven at 50°C for 8 h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0136] 5) The composite nano-silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent according to the ratio of 50:50:3 using a homogenizer for 30 min, then the mixed slurry is coated on a copper foil, dried at 100°C for 3 h, and punched into a 9 mm diameter sheet; finally, a solid-state battery is assembled and its electrochemical performance is tested, as shown in Table 1 below.

[0137] Example 10

[0138] A preparation method of a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0139] 1) 10 mmol of cobalt chloride and 10 mmol of terephthalic acid are respectively placed in 4 ml of methanol and stirred for 10 min, then the two are mixed and stirred at 50°C for 20 min; then 230 mmol of nano-silicon powder is added to the mixed solution and stirred for 20 min;

[0140] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, filled according to the filling amount of 50%, and the reaction kettle is sealed, then placed in a muffle furnace according to 80°C, 0.3 MPa hydrothermal reaction for 8 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0141] 3) centrifugal collection of the product of step 2), three times of centrifugal washing of the sample with methanol and deionized water respectively, and drying of the sample in a vacuum drying oven at 80°C for 8h to obtain an intermediate product;

[0142] 4) taking the product of step 3) into a quartz boat, placing it in a tube furnace under a nitrogen atmosphere, heating at 3°C / min to 600°C and keeping for 3h to calcine the material, centrifugal washing of the product with hydrochloric acid and deionized water for multiple times, and then collecting the sample and drying it in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0143] 5) using a homogenizer to uniformly mix the composite nano-silicon-carbon material with a sulfide electrolyte and a conductive agent at a ratio of 50:50:3 for 30min, then coating the mixed slurry on a copper foil, drying at 100°C for 3h, punching a thin sheet with a diameter of 9mm, and finally assembling a solid-state battery and testing its electrochemical performance, as shown in Table 1 below.

[0144] Example 11

[0145] A preparation method of a composite nano-silicon-carbon-based negative electrode material, comprising the following steps:

[0146] 1) stirring 10mmol of cobalt chloride and 5mmol of terephthalic acid in 4ml of methanol for 10min, then mixing the two and stirring at 50°C for 20min, and then adding 200mmol of nano-silicon powder into the mixed solution and stirring for 20min;

[0147] 2) placing the mixed solution of step 1) into a stainless steel kettle lined with Teflon, filling according to a filling amount of 50%, sealing the reaction kettle, and then carrying out hydrothermal reaction in a muffle furnace at 80°C and 0.3MPa for 8h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0148] 3) centrifugal collection of the product of step 2), three times of centrifugal washing of the sample with methanol and deionized water respectively, and drying of the sample in a vacuum drying oven at 80°C for 8h to obtain an intermediate product;

[0149] 4) taking the product of step 3) into a quartz boat, placing it in a tube furnace under a nitrogen atmosphere, heating at 3°C / min to 400°C and keeping for 3h to calcine the material, centrifugal washing of the product with hydrochloric acid and deionized water for multiple times, and then collecting the sample and drying it in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0150] 5) The composite nano-silicon-carbon material is mixed with sulfide electrolyte and conductive agent in a ratio of 50:50:3 using a homogenizer for 30 min. Then the mixed slurry is coated on a copper foil, dried at 100°C for 3 h, and punched into a 9 mm diameter sheet. Finally, the solid-state battery is assembled and its electrochemical performance is tested, as shown in Table 1 below.

[0151] Comparative Example 1

[0152] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0153] 1) 10 mmol of cobalt chloride and 5 mmol of terephthalic acid are respectively placed in 4 ml of methanol and stirred for 10 min. Then the two are mixed and stirred at 50°C for 20 min. Then 400 mmol of nano-silicon powder is added to the mixed solution and stirred for 20 min.

[0154] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, filled to 50% of the capacity, and sealed in a muffle furnace for hydrothermal reaction at 80°C for 8 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0155] 3) The product of step 2) is collected by centrifugation, and the sample is washed with methanol and deionized water three times respectively, and then placed in a vacuum drying oven at 80°C for 8 h to obtain an intermediate product;

[0156] 4) The product of step 3) is placed in a quartz boat and placed in a tube furnace under a nitrogen atmosphere, heated to 400°C at a rate of 3°C / min and held for 3 h to calcine the material. The product is washed and centrifuged with hydrochloric acid and deionized water, and then the sample is collected and dried in a vacuum oven at 50°C for 8 h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0157] 5) The composite nano-silicon-carbon material is mixed with sulfide electrolyte and conductive agent in a ratio of 50:50:3 using a homogenizer for 30 min. Then the mixed slurry is coated on a copper foil, dried at 100°C for 3 h, and punched into a 9 mm diameter sheet. Finally, the solid-state battery is assembled and its electrochemical performance is tested, as shown in Table 1 below.

[0158] As can be seen from the above Comparative Example 1, the Si@C composite material prepared has a porous structure, but the Si loading is too high and the mixture is not uniform, and the pores in the material are all filled. Therefore, the discharge capacity and cycle stability of the material are not as good as the high specific surface area porous silicon-carbon negative electrode material obtained in the examples.

[0159] Comparative Example 2

[0160] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0161] 1) Dissolve 5 g of glucose in 10 g of deionized water and stir until dissolved, then add 2 ml of ethyl silicate and continue stirring for 20 min;

[0162] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill to 70% of the capacity, seal the reaction kettle, and then hydrothermally react in a muffle furnace at 180°C for 10 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0163] 3) Centrifuge the product of step 2), wash the sample with methanol and deionized water several times, and then place the sample in a vacuum drying oven at 100°C for 14 h to obtain product A;

[0164] 4) Take out the product of step 3), weigh 0.1 g of A and 0.1 g of magnesium powder, place them in a tube furnace under an argon-hydrogen gas atmosphere, heat to 600°C at 10°C / min and maintain for 3 h to calcine the material, and then wash with hydrochloric acid and deionized water, centrifuge, and then collect the sample and dry in a vacuum oven at 80°C for 12 h to obtain product B;

[0165] 5) Place the product of step 3) in a tube furnace under an ethyne gas atmosphere, heat to 700°C at 5°C / min, and calcine for 20 min to obtain a nano-carbon coated silicon (Si@C) material.

[0166] 6) Use a homogenizer to uniformly mix the nano-carbon coated silicon with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 30 min, then coat the mixed slurry on a copper foil, dry at 100°C for 3 h, punch out a 9 mm diameter sheet, and finally assemble a solid-state battery and test its electrochemical performance, as shown in Table 1 below.

[0167] As can be seen from the above Comparative Example 2, the Si@C composite material prepared has a porous structure, but the silicon-carbon material and magnesium powder are mixed by dry method, which is not uniform, causing the pore size in the material to be uneven. In addition, the surface is uniformly coated with a layer of carbon material, which blocks the contact between Si and the solid-state electrolyte, so the discharge capacity and cycle stability of the material are not as good as the high specific surface area porous silicon-carbon negative electrode material obtained in the examples.

[0168] Comparative Example 3

[0169] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0170] 1) Dissolve 10 mmol of cobalt chloride and 5 mmol of terephthalic acid in 4 ml of methanol and stir for 10 min, then mix the two and stir at 50°C for 20 min; then add 80 mmol of nano-silicon powder to the mixed solution and stir for 20 min;

[0171] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill it to 50% of its capacity, seal the reaction kettle, and then perform hydrothermal reaction at 80°C in a muffle furnace for 8h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0172] 3) Centrifugal collection of the product of step 2), three times of centrifugal washing of the sample with methanol and deionized water respectively, and then placing the sample in a vacuum drying oven at 80°C for 8h to obtain an intermediate product;

[0173] 4) Take out the product of step 3) and place it in a quartz boat, which is placed in a tube furnace under a nitrogen atmosphere, and then the material is calcined by heating at a rate of 3°C / min to 400°C and maintaining the temperature for 3h. The product is washed with hydrochloric acid and deionized water, and then the sample is collected and dried in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0174] 5) The composite nano-silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 30min using a homogenizer, and then the mixed slurry is coated on a copper foil, dried at 100°C for 3h, and punched into a 9mm diameter sheet. Finally, it is assembled into a solid-state battery and its electrochemical performance is tested, as shown in Table 1 below.

[0175] As can be seen from the above Comparative Example 3, the Si@C composite material prepared has a porous structure, but the Si loading is too low and the mixing is not uniform, and the pore size in the material is not uniform. In addition, the surface is uniformly coated with a layer of carbon material, which blocks the contact between Si and the solid-state electrolyte, so the discharge capacity and cycle stability of the material are not as high as the high specific surface area porous silicon-carbon negative electrode material obtained in the examples.

[0176] Comparative Example 4

[0177] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0178] 1) 20mmol of cobalt chloride and 5mmol of terephthalic acid are respectively placed in 4ml of methanol and stirred for 10min, and then the two are mixed and stirred at 50°C for 20min; then 40mmol of nano-silicon powder is added to the mixed solution and stirred for 20min;

[0179] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill it to 50% of its capacity, seal the reaction kettle, and then perform hydrothermal reaction at 80°C in a muffle furnace for 8h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0180] 3) centrifugal collection of the product of step 2) and washing the sample with methanol and deionized water for three times respectively, and then drying the sample in a vacuum drying oven at 80°C for 8h to obtain an intermediate product;

[0181] 4) taking the product of step 3) into a quartz boat, and then placing it in a tube furnace under nitrogen atmosphere, and heating it to 400°C at a rate of 3°C / min and keeping it at 400°C for 3h to calcine the material, and then washing and centrifuging the product with hydrochloric acid and deionized water, and then collecting the sample and drying it in a vacuum oven at 50°C for 8h to obtain a composite nano-silicon-carbon-based negative electrode material;

[0182] 5) using a homogenizer to uniformly mix the composite nano-silicon-carbon material with a sulfide electrolyte and a conductive agent at a ratio of 50:50:3 for 30min, and then coating the mixed slurry on a copper foil, drying it at 100°C for 3h, and punching a thin sheet with a diameter of 9mm; and finally assembling a solid-state battery therefrom and testing its electrochemical performance, as shown in Table 1 below.

[0183] As can be seen from the above Comparative Example 4, the Si@C composite material prepared therefrom has a porous structure, but the low Si loading and high metal salt content result in uneven pore size in the material. In addition, the surface is uniformly coated with a layer of carbon material, which blocks the contact between Si and the solid-state electrolyte, and thus the discharge capacity and cycle stability of the material are not as good as those of the high specific surface area porous silicon-carbon negative electrode material obtained in the examples.

[0184] Table 1 below lists the product performance data of different examples and comparative examples.

[0185] Table 1: Comparison of initial charge and discharge capacities of different nano-silicon-carbon solid-state negative electrodes

[0186]

[0187]

[0188] As can be seen from the above Table 1, Example 1 has higher first cycle charge capacity and first cycle discharge capacity, and Example 2 has the highest capacity retention rate after 200 cycles. The Si@C composite material prepared therefrom has a porous structure, and the Si is uniformly dispersed, and the pore size of the material is uniform. Therefore, the discharge capacity and cycle stability of the material are relatively good.

[0189] The above describes specific embodiments of the present specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different than the order in the embodiments and still achieve desirable results. In addition, the processes depicted in the specification do not necessarily require the particular order shown or sequential order to achieve the desired results. In certain implementations, multitasking and parallel processing can be advantageous or possible.

[0190] It should be understood by those of ordinary skill in the art that the discussion of any embodiment is merely exemplary and is not intended to be limiting of the scope of the disclosure, including the claims, which are intended to be accorded their full breadth of scope. The technical features of the above embodiments or among different embodiments can also be combined, steps can be implemented in any order, and there are many other changes, as described above, of different aspects of one or more embodiments of the specification, which are not provided in detail for the sake of brevity.

[0191] In addition, for simplicity and clarity of illustration, where considered appropriate, reference numbers can be re-used in several drawings and / or in several instances to refer to the same or similar elements. In general, the same reference numbers in different drawings indicate the same or similar elements or steps.

[0192] Although the present disclosure has been described in connection with certain specific embodiments thereof, many modifications, changes, variations and substitutions will be apparent to those of ordinary skill in the art.

[0193] It is intended that one or more embodiments of the specification encompass all such substitutions, modifications, and variations as fall within the scope of the appended claims. Accordingly, any one or more of the above-described embodiments can be combined, steps can be implemented in any order, and there are many alternatives to the embodiments described above, which will be apparent to those of ordinary skill in the art upon reading this specification.

Claims

1. A method for preparing a three-dimensional composite nano-silicon-carbon-based negative electrode material, characterized in that, It comprises the following steps: 1) adding a cobalt salt and an organic ligand into a solvent, stirring and mixing, heating and continuing stirring reaction; then adding nano silicon powder, continuing stirring and mixing uniformly to obtain a mixed solution; The cobalt salt is one or more of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate; The organic ligand is any one of terephthalic acid, polyphenyltricarboxylic acid and dimethyl imidazole; The solvent is one of N, N-dimethylformamide, anhydrous methanol, anhydrous ethanol and deionized water; 2) placing the mixed solution in a stainless steel kettle with Teflon lining, then performing hydrothermal reaction under the conditions of 80-180℃ and 0.3-0.5MPa; after the reaction is completed, cooling to room temperature and taking out the mixture; 3) centrifuging the mixture, washing the sample with methanol and deionized water, drying the solid sample in a vacuum drying box after washing to obtain an intermediate product; 4) placing the intermediate product into a quartz boat, then placing it in a tube furnace under a protective gas atmosphere to perform calcination; after calcination, washing the solid powder with hydrochloric acid and deionized water, then centrifuging and collecting the solid sample to dry in an oven to obtain a high specific surface area porous silicon-carbon negative electrode material; In step 1), the molar ratio of the cobalt salt to the nano silicon powder is 1:10-40.

2. The method for preparing the composite nano-silicon-carbon based anode material according to claim 1, characterized in that: In step 1), the average particle size of the nano silicon powder is less than 50nm.

3. The method of claim 1, wherein the method further comprises: mixing the silicon nanoparticles and the carbon-based material to form a mixture; and heating the mixture to form the composite nano-silicon-carbon-based anode material. In step 1), the molar ratio of the cobalt salt to the organic ligand is 2:1-2.

4. The method of claim 1, wherein the method further comprises: In step 1), the stirring and mixing time is 10-30min; the rate is 80-150r / min.

5. The method of claim 1, wherein the method further comprises: In step 1), the stirring reaction temperature is 50-80℃; the stirring time is 20-40min; and the continued stirring time is 20-40min.

6. The method of claim 1, wherein the method further comprises: In step 2), the filling amount of the mixed solution in the stainless steel kettle is 50-70v%.

7. The method of claim 1, wherein the method further comprises: mixing the silicon nanoparticles and the carbon-based material to form a mixture; and heating the mixture to form the composite nano-silicon-carbon-based anode material. In step 2), the hydrothermal reaction time is 8-16h.

8. The method of claim 1, wherein the method further comprises: mixing the silicon nanoparticles with the carbon-based material to form a mixture; and heating the mixture to form the composite nano-silicon-carbon-based anode material. In step 3), the drying temperature in the vacuum drying box is 80-100℃; and the time is 8-14h.

9. The method of claim 1, wherein the method further comprises: mixing the silicon nanoparticles with the carbon-based material to form a mixture; and heating the mixture to form the composite nano-silicon-carbon-based anode material. In step 3), the washing frequency is 2-4 times.

10. The method of claim 1, wherein the method further comprises: In step 4), the heating rate for calcination in the tube furnace is 3-10℃ / min, the calcination temperature is 400-600℃, and the calcination time is 2.5-3.5h. ​ 11. The method of claim 1, wherein the method further comprises: In step 4), the drying temperature in the oven is 50-80℃, and the drying time is 8-12h.

12. The method of claim 1, wherein the method further comprises: mixing the silicon nanoparticles with the carbon-based material to form a mixture; and heating the mixture to form the composite nano-silicon-carbon-based anode material. In step 4), the protective gas atmosphere is nitrogen, argon or nitrogen-argon mixed gas.

13. A solid state battery, characterized by It comprises the composite nano silicon-carbon-based negative electrode material prepared by the preparation method in any one of claims 1-12.

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