Preparation method of two-dimensional high specific surface area porous silicon-carbon negative electrode material and solid-state battery

Abstract

The application provides a preparation method of a two-dimensional high-specific-surface-area porous silicon-carbon negative electrode material and a solid-state battery, and comprises the following steps: 1) iron salt and an organic ligand are added to a solvent, mixed by stirring, heated and continuously stirred to react; then nano silicon powder is added, continuously stirred and mixed uniformly to obtain a mixed solution; 2) the mixed solution is placed in a stainless steel kettle lined with Teflon, and 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 and an intermediate product is obtained; 4) the intermediate product is placed in a quartz boat, and then placed in a tube furnace under a protective gas atmosphere to carry out calcination; after washing, the product is obtained by centrifugation and drying. The method has the advantages of simple synthesis process, mild reaction conditions, high repeatability of the high-specific-surface-area porous silicon-carbon negative electrode preparation method, and the silicon-carbon negative electrode 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 two-dimensional high specific surface area porous silicon-carbon negative electrode material and a solid-state battery. BACKGROUND

[0002] With the deepening of industrialization, 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. As a zero-pollution renewable clean energy, the development of solid-state lithium ion battery is placed in a strategic position of energy development by countries around the world. The positive and negative electrodes and electrolyte in the solid-state battery are important components of the battery. Among them, the electrochemical capacity and stability of the negative electrode play an important role in the energy and life of the battery. Therefore, the research focus of the solid-state battery negative electrode is to develop a negative electrode material with higher specific capacity and higher stability.

[0003] At present, the theoretical specific capacity of Si negative electrode (4200 mAh / g) is much higher than that of commercial graphite negative electrode (372 mAh / g), but due to the serious volume expansion during lithiation, which seriously affects the cycle life and efficiency of the battery, we must modify and optimize the silicon-based negative electrode material. Studies have shown that porous silicon-carbon composite materials not only maintain high capacity, but also improve the cycle stability of the electrode material. Nahyeon (ACSnano, 2018, 12(4):3853-3864) et al. prepared mpSi microparticles with large pore volume by magnesium reduction of zeolite, and the pore size was uniformly distributed in 19-30 nm. Subsequently, the composite material after carbon coating has high specific capacity and cycle stability, but the preparation method is complicated and difficult to mass production. Du (Journal of Materials Chemistry, 2012, 22(23):11636-11641) et al. constructed a new type of ppy-Si-C three-dimensional nanostructure by electropolymerization of polypyrrole and silicon in two steps. The electrode material has excellent electrochemical performance and a reversible capacity of 2800 mAh / g, but the material preparation cost is high, so it is difficult to industrialize. In Chinese patent CN109671928A, carbon-coated nanosilicon material is prepared by water bath stirring of metal salt, organic ligand and nanosilicon, and subsequent calcination. The capacity, initial efficiency and cycle stability of the prepared material in the liquid battery need to be improved. Moreover, during 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

[0004] Therefore, one of the purposes of the present application is to provide a preparation method of two-dimensional high specific surface area porous silicon-carbon negative electrode material. The method uses metal iron salt and organic ligand to form metal organic framework material, and the topological structure of metal iron salt and organic ligand is more inclined to two-dimensional growth, which can prepare flaky structure composite material. And using high-pressure hydrothermal kettle to prepare the precursor, not only makes the material have better dispersity, uniformity and structural stability, but also makes the material have specific size and structure. The method has simple synthesis process, mild reaction condition and high repeatability of high specific surface area porous silicon-carbon negative electrode preparation method. The silicon-carbon negative electrode prepared by the method has high capacity and good cycle stability. In the synthesis process of the present application, no dispersing agent is needed, which is more green, environmentally friendly and healthy.

[0005] The second object of the present application is to provide a solid-state battery comprising the porous silicon-carbon negative electrode material prepared by the above method.

[0006] Based on the first purpose, the present application provides the following technical solutions :

[0007] A method for preparing a high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0008] 1) adding an iron salt and an organic ligand into a solvent, stirring and mixing, heating and continuing to stir the reaction; then adding nano silicon powder, continuing to stir and mix uniformly to obtain a mixed solution;

[0009] 2) placing the mixed solution in a stainless steel kettle lined with Teflon, and then performing a hydrothermal reaction under the conditions of 80-180 DEG C and 0.3-0.5 MPa; after the reaction is completed, cooling to room temperature, and taking out the mixture;

[0010] 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;

[0011] 4) placing the intermediate product into a quartz boat, and then placing it in a tube furnace under a protective gas atmosphere for calcination; after calcination, the solid powder is washed with hydrochloric acid and deionized water, then centrifuged, and then the solid sample is collected and dried in an oven to obtain a high specific surface area porous silicon-carbon negative electrode material.

[0012] The present application uses metal organic framework materials (MOFs) 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 an iron salt), and the nano silicon is a silicon source. The high specific surface area porous silicon-carbon material is prepared by calcining the precursor and then performing multiple washing and centrifuging treatments. The diameter of the nano silicon-carbon material is about 100-200 nm.

[0013] As an embodiment, in step 1), the iron salt is one or more of ferric chloride hexahydrate, ferric nitrate, and ferric sulfate.

[0014] As an embodiment, in step 1), the organic ligand is any one of terephthalic acid, polybenzene tricarboxylic acid, and dimethyl imidazole.

[0015] As an embodiment, in step 1), the solvent is one of N,N-dimethylformamide, anhydrous methanol, anhydrous ethanol, and deionized water.

[0016] As an embodiment, in step 1), the average particle size of the silicon powder is less than 50 nm.

[0017] As an implementation form, in step 1), the molar ratio of the iron salt to the organic ligand is 2:1-2.

[0018] As an implementation form, in step 1), the stirring time of the mixed solution is 10-30 min; and the stirring rate is 80-150 r / min.

[0019] As an implementation form, in step 1), the stirring temperature of the reaction is 50-80℃; and the stirring time is 20-40 min.

[0020] As an implementation form, in step 1), the molar ratio of the iron salt to the nano-silicon powder is 7:140-250.

[0021] As an implementation form, in step 2), the filling volume of the mixed solution in the stainless steel kettle is 50-70 v%.

[0022] As an implementation form, in step 2), the hydrothermal reaction time is 8-16 h.

[0023] As an implementation form, in step 3), the drying temperature in the vacuum drying oven is 80-100℃; and the drying time is 8-14 h.

[0024] As an implementation form, in step 3), the washing times are 2-4 times.

[0025] As an implementation form, in step 4), the heating rate in the tube furnace is 3-10℃ / min, the calcination temperature is 600-900℃, and the calcination time is 2.5-3.5 h.

[0026] As an implementation form, in step 4), the drying temperature in the oven is 50-80℃, and the drying time is 8-12 h.

[0027] As an implementation form, in step 4), the protective gas atmosphere is nitrogen, argon or nitrogen-argon mixed gas.

[0028] Based on the second purpose, the present application provides the following technical solutions :

[0029] A solid-state battery comprising the porous silicon-carbon negative electrode material prepared by the preparation method.

[0030] Any range recited in the present disclosure includes the end values and any numerical value between the end values and any sub-range consisting of any such numerical values.

[0031] Unless otherwise specified, each raw material in the present disclosure can be obtained by commercial purchase, and the equipment used in the present disclosure can adopt the conventional equipment in the field or refer to the prior art in the field.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. The raw materials are simple and low in cost, the reaction conditions are mild, the preparation process is simple and feasible, and the repeatability is high; no dispersing agent needs to be added in the synthesis process, which is more green, environmentally friendly and healthy.

[0034] 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 retention of metal vacancies after calcination of the precursor ensures that the high specific surface area silicon-carbon material has a porous structure.

[0035] 3. The high specific surface area porous silicon-carbon material has a greatly improved conductivity compared with pure silicon material, which reduces the impedance of the material and greatly improves the electrochemical performance of the battery.

[0036] 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.

[0037] 5. The production steps are relatively simple, the raw material price is relatively low, and large-scale production is expected to be realized. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Impedance diagram of the porous silicon-carbon negative electrode material prepared in Example 1 of the present application;

[0039] Figure 2 Structural schematic diagram of the porous silicon-carbon negative electrode material prepared in the present application;

[0040] Figure 3 Transmission electron microscope diagram of the porous silicon-carbon negative electrode material prepared in Example 1 of the present application; DETAILED DESCRIPTION

[0041] 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.

[0042] 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 a person 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.

[0043] Silicon-based materials are widely used in solid-state batteries due to their high specific capacity. However, due to the unique alloying charge-discharge mechanism, silicon-based materials will experience significant volume expansion during the charge-discharge cycle, which will lead to the pulverization of the silicon negative electrode and significantly affect its charge-discharge performance and cycle stability.

[0044] Based on this, referring to Figure 1 As an aspect of the present application, a method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material includes the following steps:

[0045] 1) Add an iron salt and an organic ligand to 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;

[0046] 2) Place the mixed solution in a stainless steel kettle lined with Teflon, then perform a hydrothermal reaction at 80-180°C and 0.3-0.5 MPa; after the reaction is complete, cool to room temperature and remove the mixture;

[0047] 3) Centrifuge the mixture, wash the sample with methanol and deionized water, and dry the solid sample in a vacuum drying oven after washing to obtain an intermediate product;

[0048] 4) Place the intermediate product in 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 and collect the solid sample for drying in an oven to obtain a high specific surface area porous silicon-carbon negative electrode material.

[0049] The present application provides a method for preparing 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, significantly improving its charge-discharge capacity; uniform pores can provide more channels for electrons and ions, significantly improving the electrochemical performance of the battery; a good two-dimensional carbon skeleton structure can effectively solve the volume expansion problem of solid silicon negative electrode materials, and increase the conductivity of silicon-based materials, thereby making the composite material have better electrochemical performance. Existing silicon-carbon composite negative electrode materials are mostly coated structures, layered structures or simple composites. For solid-state battery negative electrodes, these structures will limit the ionic conductivity of the material, and the present technology uniformly embeds silicon material in the carbon layer, which is extremely beneficial for improving the ionic conductivity of the electrode material.

[0050] According to certain embodiments of the present application, in step 1), the iron salt is one or more of ferric chloride hexahydrate, ferric nitrate, and ferric sulfate.

[0051] According to some embodiments of the present application, in step 1), the organic ligand is any one of terephthalic acid, polybenzene tricarboxylic acid, and dimethyl imidazole.

[0052] According to some embodiments of the present application, in step 1), the solvent is one of N,N-dimethylformamide, anhydrous methanol, anhydrous ethanol, and deionized water.

[0053] According to some embodiments of the present application, in step 1), the average particle size of the silicon powder is less than 50 nm.

[0054] According to some embodiments of the present application, in step 1), the molar ratio of the iron salt to the organic ligand is 2:1-2.

[0055] According to some embodiments of the present application, in step 1), the mixing time is 10-30 min, and the stirring rate is 80-150 r / min.

[0056] According to some embodiments of the present application, in step 1), the stirring temperature is 50-80°C, for example, 50, 55, 60, 65, 70, 75, or 80°C; and the stirring time is 20-40 min, for example, 20, 25, 30, 35, or 40 min.

[0057] According to some embodiments of the present application, in step 1), the molar ratio of the iron salt to the nano-silicon powder is 7:140-250; or 7:150-250, 7:160-250, 7:170-250, 7:180-250, 7:190-250, 7:200-250, 7:210-250, 7:220-250, 7:230-250, 7:240-250, 7:150-240, 7:150-230, 7:150-220, 7:150-210, 7:150-200, 7:150-190, 7:150-180, 7:150-170, or 7:150-160.

[0058] According to some embodiments of the present application, in step 2), the filling amount of the mixed solution in the stainless steel kettle is 50-70 v%.

[0059] According to some embodiments of the present application, in step 2), the hydrothermal reaction time is 8-16 h.

[0060] According to some embodiments of the present application, in step 3), the drying temperature in the vacuum drying oven is 80-100°C, for example, 80, 85, 90, 95, or 100°C; and the drying time is 8-14 h, for example, 8, 9, 10, 11, 12, 13, or 14 h.

[0061] According to some embodiments of the present application, in step 3), the number of washing times is 2-4 times.

[0062] According to some embodiments of the present application, in step 4), the temperature rising rate 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℃; the calcination time is 2.5-3.5h.

[0063] 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℃; the drying time is 8-12h, for example, 8, 9, 10, 11, or 12h.

[0064] According to some embodiments of the present application, in step 4), the protective gas atmosphere is nitrogen, argon or nitrogen-argon mixture.

[0065] 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.

[0066] 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 on the electrode sheet, or transferred to the surface of the electrode sheet by other methods.

[0067] Example 1

[0068] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0069] 1) 10mmol of ferric chloride hexahydrate and 5mmol of terephthalic acid were respectively placed in 4ml of methanol and stirred for 10min, then the two were mixed and stirred at 50℃ for 20min. Then 250mmol of nano-silicon powder was added to the mixed solution and stirred for 20min.

[0070] 2) Put the mixed solution of step 1) into a stainless steel kettle with Teflon inner liner, fill it to 50% of the capacity, seal the reactor, and then hydrothermally react in a muffle furnace at 80°C and 0.3 MPa for 8 h. After the reactor is naturally cooled to room temperature, the mixture is taken out.

[0071] 3) Centrifuge the product of step 2), wash the sample with methanol and deionized water three times respectively, and then dry the sample in a vacuum drying oven at 80°C for 8 h to obtain the intermediate product.

[0072] 4) Take the product of step 3) and put it into a quartz boat, place it in a tube furnace under a nitrogen atmosphere, heat it to 600°C at a rate of 3°C / min and keep it at this temperature for 3 h to calcine the material, then wash and centrifuge it with hydrochloric acid and deionized water, and then collect the sample and dry it in a vacuum oven at 50°C for 8 h to obtain the target product.

[0073] 5) Use a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material 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 it at 100°C for 3 h, punch a 9 mm diameter sheet, and finally assemble a solid-state battery and test its electrochemical performance, as shown in Table 1 below.

[0074] Figure 1 Impedance diagram of the porous silicon-carbon negative electrode material prepared in Example 1 of the present application;

[0075] Figure 2 Structural schematic diagram of the porous silicon-carbon negative electrode material prepared in Example 2 of the present application;

[0076] Figure 3 Transmission electron microscope image of the porous silicon-carbon negative electrode material prepared in Example 1 of the present application.

[0077] Example 2

[0078] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0079] 1) Dissolve 10 mmol of iron chloride hexahydrate and 10 mmol of polybenzene tricarboxylic acid in 5 ml of ethanol respectively and stir them in a room temperature water bath for 20 min; then mix them and stir at 70°C for 30 min; then add 260 mmol of nano-silicon powder to the mixed solution and stir them together for 30 min;

[0080] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill it to 60% of its capacity, seal the reaction kettle, and then hydrothermally react in a muffle furnace at 120°C and 0.4 MPa for 10 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0081] 3) Centrifugally collect the product of step 2), wash the sample with methanol and deionized water four times respectively, and then place the sample in a vacuum drying oven at 90°C for 10 h to obtain an intermediate product;

[0082] 4) Take the product of step 3) and place it in a quartz boat, which is placed in a tube furnace under an argon protective gas atmosphere, and then heated at a rate of 5°C / min to 700°C and kept for 3 h to calcine the material. The target product is obtained after multiple washing and centrifugation of the collected sample with hydrochloric acid and deionized water, followed by drying the sample in a vacuum oven at 60°C for 10 h;

[0083] 5) Use a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 40 min, and then coat the mixed slurry on a copper foil, dry it at 120°C for 3 h, and punch out a 9 mm diameter wafer. Finally, the wafer is assembled into a solid-state battery and its electrochemical performance is tested, as shown in Table 1 below.

[0084] Example 3

[0085] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0086] 1) Dissolve 10 mmol of iron chloride hexahydrate and 10 mmol of polybenzene tricarboxylic acid in 5 ml of ethanol respectively and stir them in a room temperature water bath for 20 min. Then mix the two solutions and stir them at 70°C for 30 min. Then add 260 mmol of nano-silicon powder to the mixed solution and stir them together for 30 min;

[0087] 2) Put the mixed solution of step 1) into a stainless steel kettle lined with Teflon, fill it to 60% of its capacity, seal the reaction kettle, and then hydrothermally react in a muffle furnace at 120°C and 0.5 MPa for 10 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0088] 3) Centrifugally collect the product of step 2), wash the sample with methanol and deionized water four times respectively, and then place the sample in a vacuum drying oven at 90°C for 10 h to obtain an intermediate product;

[0089] 4) Take out the product of step 3) and place it in a quartz boat, and place it in a tube furnace under an argon protective gas atmosphere, and heat it to 700 DEG C at a rate of 5 DEG C / min and keep it for 3 h to calcine the material, and obtain an intermediate product, which is washed and centrifuged with hydrochloric acid and deionized water multiple times, and then collect the sample and place it in a vacuum oven to dry at 60 DEG C for 10 h to obtain the target product;

[0090] 5) Use a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 40 min, and then coat the mixed slurry on a copper foil, dry it at 120 DEG C for 3 h, punch a 9 mm diameter sheet, and finally assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0091] Example 4

[0092] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0093] 1) Dissolve 10 mmol of iron chloride hexahydrate and 10 mmol of polybenzene tricarboxylic acid in 5 ml of ethanol respectively and stir them in a room temperature water bath for 20 min; then mix them and stir them at 70 DEG C for 30 min; and then add 260 mmol of nano silicon powder to the mixed solution and stir them together for 30 min;

[0094] 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 hydrothermally react it in a muffle furnace at 120 DEG C and 0.3 MPa for 10 h; and then naturally cool the kettle to room temperature and take out the mixture;

[0095] 3) Centrifugally collect the product of step 2), and centrifugally wash the sample with methanol and deionized water four times respectively, and then place the sample in a vacuum drying oven to dry it at 90 DEG C for 10 h to obtain an intermediate product;

[0096] 4) Take out the product of step 3) and place it in a quartz boat, and place it in a tube furnace under an argon protective gas atmosphere, and heat it to 700 DEG C at a rate of 5 DEG C / min and keep it for 3 h to calcine the material, and obtain an intermediate product, which is washed and centrifuged with hydrochloric acid and deionized water multiple times, and then collect the sample and place it in a vacuum oven to dry at 60 DEG C for 10 h to obtain the target product;

[0097] 5) Use a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 40 min, and then coat the mixed slurry on a copper foil, dry it at 120 DEG C for 3 h, punch a 9 mm diameter sheet, and finally assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0098] Example 5

[0099] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0100] 1) 10 mmol of iron chloride hexahydrate and 15 mmol of polybenzene tricarboxylic acid 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 270 mmol of nano silicon powder is added to the mixed solution and stirred for 35 min;

[0101] 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;

[0102] 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;

[0103] 4) The product of step 3) is taken out and placed in a quartz boat, which is placed in a tube furnace under nitrogen and argon protection gas atmosphere, and heated to 800°C at a rate of 7°C / min and kept for 3 h to calcine the material. The intermediate product is washed with hydrochloric acid and deionized water, then the sample is collected and dried in a vacuum oven at 70°C for 10 h to obtain the target product;

[0104] 5) The high specific surface area porous 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 30 min, then the mixed slurry is coated on a copper foil, dried at 110°C for 3 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.

[0105] Example 6

[0106] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0107] 1) 10 mmol of iron chloride hexahydrate and 20 mmol of polybenzene tricarboxylic 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 280 mmol of nano silicon powder is added to the mixed solution and stirred for 40 min;

[0108] 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 and 0.3 MPa for 16 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0109] 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;

[0110] 4) Taking the product of step 3) and placing it in a quartz boat, placing it in a tube furnace under a nitrogen protective gas atmosphere, and then heating it to 900°C at a rate of 10°C / min and keeping it at this temperature for 3 h to calcine the material, multiple washing of the calcined material with hydrochloric acid and deionized water, centrifugal collection of the sample, and then placing the sample in a vacuum oven at 80°C for 12 h to obtain the target product;

[0111] 5) Using a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 30 min, then coating the mixed slurry on a copper foil, drying it at 90°C for 3 h, punching out a 9 mm diameter wafer, and finally assembling a solid-state battery therefrom and testing its electrochemical performance, as shown in Table 1 below.

[0112] Example 7

[0113] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0114] 1) Dissolving 10 mmol of iron sulfate and 20 mmol of polybenzene tricarboxylic acid in 5 ml of deionized water and stirring at room temperature for 35 min; then mixing the two and stirring at 80°C for 40 min; and then adding 290 mmol of nano-silicon powder to the mixed solution and stirring for 40 min;

[0115] 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 and 0.3 MPa for 16 h; After the reaction kettle is naturally cooled to room temperature, the mixture is taken out;

[0116] 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;

[0117] 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 900°C at a rate of 10°C / min, and keep it at this temperature for 3 h to calcine the material, and obtain an intermediate product, which is washed multiple times with hydrochloric acid and deionized water and centrifuged, and then the sample is collected and placed in a vacuum oven and dried at 80°C for 12 h to obtain the target product;

[0118] 5) The high specific surface area porous silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 40 min using a homogenizer, and then the mixed slurry is coated on a copper foil, dried at 120°C for 3 h, and punched into a 9 mm diameter sheet; finally, it is assembled into a solid-state battery and its electrochemical performance is tested, as shown in Table 1 below.

[0119] Example 8

[0120] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0121] 1) 10 mmol of iron chloride and 20 mmol of polybenzene tricarboxylic acid are dissolved in 5 ml of deionized water and stirred at room temperature for 35 min; then the two are mixed and stirred at 80°C for 40 min; then 300 mmol of nano silicon powder is added to the mixed solution and stirred for 40 min;

[0122] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, and filled to 70% of the capacity. After sealing the reaction kettle, hydrothermal reaction is carried out in a muffle furnace at 120°C and 0.3 MPa for 12 h. The reaction kettle is naturally cooled to room temperature, and the mixture is taken out;

[0123] 3) The product of step 2) is collected by centrifugation, and the sample is washed multiple times with methanol and deionized water, and then the sample is placed in a vacuum drying oven and dried at 100°C for 14 h to obtain an intermediate product;

[0124] 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 800°C at a rate of 5°C / min, and keep it at this temperature for 3 h to calcine the material, and obtain an intermediate product, which is washed multiple times with hydrochloric acid and deionized water and centrifuged, and then the sample is collected and placed in a vacuum oven and dried at 80°C for 12 h to obtain the target product;

[0125] 5) The high specific surface area porous silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 20 min using a homogenizer, and 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, it is assembled into a solid-state battery and its electrochemical performance is tested, as shown in Table 1 below.

[0126] Example 9

[0127] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0128] 1) 10 mmol of ferric chloride and 10 mmol of polybenzene tricarboxylic acid are respectively dissolved in 5 ml of deionized water and stirred in a normal temperature water bath for 35 min. Then the two are mixed and stirred at 80°C for 40 min. Then 200 mmol of nano silicon powder is added to the mixed solution and stirred together for 40 min.

[0129] 2) The mixed solution of step 1) is placed in a stainless steel kettle lined with Teflon, filled according to the filling amount of 70%, and the reaction kettle is sealed. After being placed in a muffle furnace, it is hydrothermally reacted at 120°C and 0.3 MPa for 12 h. The reaction kettle is naturally cooled to room temperature, and the mixture is taken out.

[0130] 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 100°C for 14 h to obtain an intermediate product.

[0131] 4) The product of step 3) is taken out and placed in a quartz boat, which is placed in a tube furnace under a nitrogen protective gas atmosphere, and heated to 600°C at a rate of 5°C / min and kept for 3 h to calcine the material. The intermediate product is washed with hydrochloric acid and deionized water and centrifuged, and then the sample is collected and dried in a vacuum oven at 80°C for 12 h to obtain the target product.

[0132] 5) The high specific surface area porous 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, and 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, it is assembled into a solid-state battery and its electrochemical performance is tested, as shown in Table 1 below.

[0133] Example 10

[0134] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0135] 1) 10 mmol of ferric chloride and 10 mmol of polybenzene tricarboxylic acid are respectively dissolved in 5 ml of deionized water and stirred in a normal temperature water bath for 35 min. Then the two are mixed and stirred at 80°C for 40 min. Then 200 mmol of nano silicon powder is added to the mixed solution and stirred together for 40 min.

[0136] 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 120°C and 0.3 MPa for 12 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out.

[0137] 3) Centrifugally collect the product of step 2), wash the sample with methanol and deionized water multiple times, and then place the sample in a vacuum drying oven at 100°C for 14 h to obtain an intermediate product.

[0138] 4) Take the product of step 3) and place it in a quartz boat, which is placed in a tube furnace under a nitrogen protective gas atmosphere. The material is calcined by heating at 5°C / min to 600°C and maintaining the temperature for 3 h. The intermediate product is washed multiple times with hydrochloric acid and deionized water, and then the sample is collected and dried in a vacuum oven at 80°C for 12 h to obtain the target product.

[0139] 5) The high specific surface area porous silicon-carbon material is uniformly mixed with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 20 min using a homogenizer, and 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.

[0140] Example 11

[0141] A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, comprising the following steps:

[0142] 1) Dissolve 10 mmol of iron chloride and 20 mmol of polybenzene tricarboxylic acid in 5 ml of deionized water and stir in a water bath at room temperature for 35 min. Then mix the two and stir at 80°C for 40 min. Then add 250 mmol of nano-silicon powder to the mixed solution and stir for 40 min.

[0143] 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 110°C and 0.3 MPa for 12 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out.

[0144] 3) Centrifugally collect the product of step (2), wash the sample with methanol and deionized water multiple times, and then place the sample in a vacuum drying oven at 100°C for 14 h to obtain an intermediate product.

[0145] 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 800°C at a rate of 5°C / min, and keep it at this temperature for 3 h to calcine the material, and obtain an intermediate product, and wash and centrifuge it with hydrochloric acid and deionized water multiple times, and then collect the sample and place it in a vacuum oven, and dry it at 80°C for 12 h to obtain the target product.

[0146] 5) Use a homogenizer to uniformly mix the high specific surface area porous silicon-carbon material with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 20 min, and then coat the mixed slurry on a copper foil, dry it at 100°C for 3 h, and punch out a thin piece with a diameter of 9 mm; finally, assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0147] Comparative Example 1

[0148] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0149] 1) Place 0.2 g of the product of the nanosilicon material in a tube furnace, and calcine it under an ethyne atmosphere at a rate of 5°C / min to 700°C for 20 min to obtain a nanocarbon-coated silicon (Si@C) material.

[0150] 2) Use a homogenizer to uniformly mix the nanocarbon-coated silicon with the sulfide electrolyte and the conductive agent at a ratio of 50:50:3 for 30 min, and then coat the mixed slurry on a copper foil, dry it at 100°C for 3 h, and punch out a thin piece with a diameter of 9 mm; finally, assemble a solid-state battery therefrom and test its electrochemical performance, as shown in Table 1 below.

[0151] As can be seen from the above Comparative Example 1, the Si@C material is a non-porous structure, and the carbon is coated on the surface of Si, and Si cannot directly contact the solid-state electrolyte, so the discharge capacity and cycle stability of the Si@C material are not as good as the performance of the high specific surface area and porous silicon-based material in the examples.

[0152] Comparative Example 2

[0153] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0154] 1) Dissolve 5 g of glucose in 10 g of deionized water and stir until dissolved, and then add 2 ml of ethyl silicate and continue stirring for 20 min.

[0155] 2) Place the mixed solution of step (1) in a stainless steel kettle lined with Teflon, and fill it to 70% of its capacity, seal the reaction kettle, and then place it in a muffle furnace and hydrothermally react at 180°C for 10 h. After the reaction kettle is naturally cooled to room temperature, the mixture is taken out.

[0156] 3) Centrifugation to collect the product of step (2), and the sample is washed with methanol and deionized water for multiple times, and then the sample is placed in a vacuum drying oven at 100°C for 14h to obtain an intermediate product A.

[0157] 4) 0.1g of the product of step (3) and 0.1g of magnesium powder are taken out, and the mixture is placed in a tube furnace under an argon-hydrogen gas atmosphere, and the temperature is increased to 600°C at a rate of 10°C / min, and the material is calcined for 3h to obtain an intermediate product, which is washed with hydrochloric acid and deionized water for multiple times, and then the sample is collected and placed in a vacuum oven at 80°C for 12h to obtain a product B.

[0158] 5) The product of step (3) is placed in a tube furnace under an acetylene gas atmosphere, and the temperature is increased to 700°C at a rate of 5°C / min, and the material is calcined for 20min to obtain a silicon coated with carbon (Si@C) material.

[0159] 6) The silicon coated with carbon is uniformly mixed with a sulfide electrolyte and a conductive agent at a ratio of 50:50:3 using a homogenizer for 30min, 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, a solid-state battery is assembled and the electrochemical performance is tested, as shown in Table 1 below.

[0160] 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 is mixed with magnesium powder by dry method, 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.

[0161] Comparative Example 3

[0162] A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

[0163] 1) 0.2g of a nanosilicon material and 0.5g of glucose are placed in an autoclave, and the temperature is increased to 120°C and kept constant for 3h to obtain a silicon coated with carbon (Si@C) material.

[0164] 2) The silicon coated with carbon is uniformly mixed with a sulfide electrolyte and a conductive agent at a ratio of 50:50:3 using a homogenizer for 30min, 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, a solid-state battery is assembled and the electrochemical performance is tested, as shown in Table 1 below.

[0165] It can be seen from the above Comparative Example 3 that the Si@C material is a non-porous structure, and the carbon is coated on the surface of Si, and Si cannot directly contact the solid-state electrolyte, so the discharge capacity and cycle stability of the Si@C material are not as good as the performance of the high specific surface area and porous silicon-based material in the examples.

[0166] The product performance data of different examples and comparative examples are listed in the following Table 1.

[0167] Table 1: Comparison of initial charge and discharge capacities of different nano-silicon-carbon solid-state negative electrodes

[0168]

[0169] The above describes specific embodiments of the present disclosure. 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 a different order and still accomplish desirable results. Additionally, the processes depicted in the specification are not necessarily involved in every embodiment. In certain embodiments, multitasking and parallel processing can be advantageous.

[0170] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary in nature and is not intended to imply that the disclosure, including the claims, is limited to these examples; the technical features between the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present disclosure as described above, which are not provided in detail for the sake of brevity.

[0171] In addition, for the sake of simplicity and discussion, where specific details are set forth in order to describe an exemplary embodiment of the present disclosure, it will be apparent to those skilled in the art that the present disclosure can be practiced without these specific details or with variations on these specific details. Therefore, these descriptions should be considered as illustrative and not restrictive.

[0172] Although the present disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations will be apparent to those skilled in the art from the foregoing description.

[0173] One or more embodiments of the present disclosure are intended to cover all such alternatives, modifications and variations as falling within the broad scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made in the spirit and principle of one or more embodiments of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a two-dimensional high specific surface area porous silicon-carbon negative electrode material, characterized in that, The method comprises the following steps: 1) adding an iron 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; 2) placing the mixed solution into a stainless steel kettle lined with Teflon, and then performing hydrothermal reaction under the conditions of 80-180℃ and 0.3-0.5 MPa; 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, and then placing it into 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.

2. The method of claim 1, wherein: In step 1), the iron salt is one or more of ferric chloride hexahydrate, ferric nitrate, and ferric sulfate; In step 1), the organic ligand is any one of terephthalic acid, polybenzene tricarboxylic acid, and dimethyl imidazole; In step 1), the solvent is one of N,N-dimethylformamide, anhydrous methanol, anhydrous ethanol, and deionized water; In step 1), the average particle size of the silicon powder is less than 50 nm.

3. The method of claim 1, wherein: In step 1), the molar ratio of the iron salt to the organic ligand is 2:1-2; In step 1), the stirring and mixing time is 10-30 min; the rate is 80-150 r / min; In step 1), the stirring reaction temperature is 50-80℃; the stirring time is 20-40 min; In step 1), the molar ratio of the iron salt to the nano silicon powder is 7:140-250.

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

5. The method of claim 1, wherein: In step 2), the hydrothermal reaction time is 8-16 h.

6. The method of claim 1, wherein: In step 3), the drying temperature in the vacuum drying box is 80-100℃; the time is 8-14 h.

7. The method of claim 1, wherein: In step 3), the washing frequency is 2-4 times.

8. The method of claim 1, wherein: In step 4), the temperature rising rate in the tube furnace for calcination is 3-10℃ / min, the calcination temperature is 600-900℃, and the calcination time is 2.5-3.5 h.

9. The method of claim 1, wherein: In step 4), the drying temperature in the oven is 50-80℃, and the drying time is 8-12 h; In step 4), the protective gas atmosphere is nitrogen, argon, or a mixture of nitrogen and argon.

10. A solid-state battery, characterized by, The porous silicon-carbon negative electrode material is prepared by the method according to any one of claims 1-9.

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