Negative electrode sheet for sulfide all-solid lithium battery, method for manufacturing same, and solid battery

Abstract

The application discloses a kind of sulfide full solid lithium battery negative plate and its preparation method, solid battery, it is related to lithium ion battery technical field, comprising the following steps: S1: preparation microporous carbon fiber membrane;S2: preparation MoS2-carbon fiber membrane composite layer;S3: preparation benzoquinone-MoS2-carbon fiber membrane composite negative plate;Specific, at room temperature, benzoquinone and lithium perchlorate are dispersed in anhydrous acetonitrile according to the ratio of 30-45 parts:5-10 parts, third mixed solution is obtained, MoS2-carbon fiber membrane composite layer obtained in step S2 is used as working electrode, platinum sheet is used as counter electrode, third mixed solution is used as electrolyte, anodic current is applied, after deposition, benzoquinone-MoS2-carbon fiber membrane composite negative plate is obtained.The application is prepared by a new type of high capacity low expansion molybdenum disulfide MoS2 composite negative plate, the interface contact between negative plate and sulfide solid electrolyte is optimized, the negative influence caused by large volume expansion on the performance of solid battery is avoided, and the capacity, rate and cycle life of solid battery are significantly improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a negative electrode sheet for a sulfide all-solid-state lithium battery and its preparation method, as well as a solid-state battery. Background Technology

[0002] In critical fields such as portable electronic devices, renewable energy, and electric vehicles, lithium-ion batteries using liquid electrolytes are prone to catastrophic battery failures, including fires and explosions. This is primarily due to the susceptibility of liquid electrolytes to leakage and combustion, as well as side reactions between the liquid electrolyte and the electrodes, leading to irreversible performance degradation and significantly reduced battery lifespan. Since solid electrolytes are non-flammable, using them instead of liquid electrolytes minimizes the probability of these problems. Furthermore, the dissolution and migration of side reaction products in solid-state batteries are limited, leading to increasing interest in all-solid-state batteries. However, solid-state batteries still have some drawbacks, such as the low lithium-ion conductivity of solid electrolytes, poor contact between the solid electrolyte and the negative electrode, and the occurrence of side reactions. These can impair battery capacity, cycle life, and power performance, limiting their practical applications. Therefore, solid-state batteries with high capacity, high ionic conductivity and good interfacial contact have become a research hotspot. For example, Chinese patent application number CN202110517996.3 discloses "a lithium-sulfur battery anode with a high specific surface area mesoporous protective film and its preparation and application". The anode includes a matrix of metallic lithium or lithium alloy material and a protective layer formed by copper powder and polar composite on the surface of the matrix. The porous structure inside the anode effectively alleviates the volume expansion effect of the anode. However, the anode prepared in this application has problems such as low battery performance when used in applications. Summary of the Invention

[0003] In response to the technical deficiencies of existing technologies, this application proposes a sulfide-based all-solid-state lithium battery negative electrode sheet and its preparation method, as well as a solid-state battery. By preparing a novel high-capacity, low-expansion molybdenum disulfide (MoS2) composite negative electrode sheet, the interfacial contact between the negative electrode sheet and the sulfide solid electrolyte is optimized, avoiding the negative impact of large volume expansion on the performance of the solid-state battery, and significantly improving the capacity, rate capability, and cycle life of the solid-state battery.

[0004] Specifically, in order to achieve the above technical solution, firstly, this application provides a method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery, comprising the following steps:

[0005] Microporous carbon fiber membranes were prepared by adding methyltriethoxysilane and polyacrylonitrile to DMF solvent in a ratio of 45-65 parts: 25-45 parts and stirring until homogeneous to obtain a first mixed solution; the first mixed solution was used to prepare a first fiber membrane; the first fiber membrane was subjected to heat treatment, transferred to an inert atmosphere high-temperature environment for sintering, and cooled to room temperature to obtain a second fiber membrane; hydrofluoric acid was added to the second fiber membrane to obtain a microporous carbon fiber membrane with a microporous structure.

[0006] To prepare a MoS2-carbon fiber membrane composite layer, thiourea and Na2MoO4 were dissolved in a mixed solvent of anhydrous ethanol and deionized water at a ratio of 20-40 parts: 35-45 parts to obtain a second mixed solution. The microporous carbon fiber membrane was completely immersed in the second mixed solution and subjected to specific treatment to obtain the MoS2-carbon fiber membrane composite layer.

[0007] A benzoquinone-MoS2-carbon fiber membrane composite negative electrode was prepared. Benzoquinone and lithium perchlorate were dispersed in anhydrous acetonitrile at a ratio of 30-45 parts: 5-10 parts at room temperature to obtain a third mixed solution. The MoS2-carbon fiber membrane composite layer was used as the working electrode, a platinum sheet was used as the counter electrode, and the third mixed solution was used as the electrolyte. An anolyte current was applied, and after deposition, the benzoquinone-MoS2-carbon fiber membrane composite negative electrode was obtained. The total thickness of the benzoquinone-MoS2-carbon fiber membrane composite negative electrode was 50-300 μm.

[0008] Preferably, the mass fraction of DMF in the first mixed solution is 70-85%.

[0009] Preferably, the specific steps for preparing the first mixed solution into a first fiber membrane are as follows: the first mixed solution is subjected to electrospinning technology to obtain a large-area first fiber membrane. The specific parameters for electrospinning are: receiving distance of 15-20 cm, spinning voltage of 15-25 kV, solution flow rate of 1.5-2.5 ml / h, temperature of 30-40℃, injection pump specification of 20-30 ml, and the average pore size of the prepared first fiber membrane is 300-600 nm.

[0010] Preferably, the heat treatment is performed in air at 150-250°C for 1-2 hours, and the sintering in an inert atmosphere high-temperature environment is performed in an inert gas environment at 1000-1300°C for 1-2 hours with a heating rate of 1-3°C / min, the concentration of hydrofluoric acid is 30-40%, and the inert gas is one of nitrogen, argon, or helium.

[0011] Preferably, the volume ratio of anhydrous ethanol to deionized water in the second mixed solution is 1-1.5:1-1.5, and the total mass fraction of thiourea and Na2MoO4 is 4.5-6.5%.

[0012] Preferably, the second mixed solution is stirred at 60-100 rpm for 30-45 minutes at room temperature. The specific treatment is carried out in a high-pressure reactor at 200-250°C for 24-36 hours to generate MoS2 nanoparticles on the surface of the fiber membrane. The carbon fiber membrane is then removed and vacuum dried at 90-110°C for 3-5 hours, followed by sintering at 800-900°C in an inert atmosphere for 30-60 minutes.

[0013] Preferably, the total mass fraction of benzoquinone and lithium perchlorate in the third mixed solution is 30-45%, and the applied anolyte current is 2.5-3.5 mA / cm. 2 The deposition time is 1-5 minutes.

[0014] Preferably, the benzoquinone-MoS2-carbon fiber membrane composite negative electrode consists of a benzoquinone layer and a MoS2-carbon fiber membrane. The thickness of the benzoquinone layer is 50-150 nanometers, and the benzoquinone is replaced by one of anthraquinone, phenanthrenequinone, or benzoquinone polycarbonylquinone derivatives.

[0015] Secondly, this application provides a composite negative electrode sheet for a sulfide all-solid-state lithium battery, which is prepared by a method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery provided in any embodiment of this application.

[0016] Thirdly, this application provides a solid-state battery, which includes a solid electrolyte. A positive electrode and a negative electrode are disposed on both sides of the solid electrolyte. The positive electrode includes a positive active material, a carbon-based conductive agent, and an inorganic salt. The positive active material, carbon-based conductive agent, and inorganic salt of the positive electrode are in a ratio of 70-80:50-70:5-10. The thickness of the positive electrode is 100-300 μm. The solid electrolyte is a sulfide. The negative electrode is a sulfide-based composite negative electrode for an all-solid-state lithium battery according to any embodiment of this application.

[0017] This application has the following beneficial effects: The highly crystalline MoS2 material deposited on the surface of a porous carbon fiber membrane using a hydrothermal method has a particle size in the nanometer range, which significantly improves the conductivity. The numerous pores inside the carbon fiber membrane provide more channels for lithium-ion transport and increase the flexibility of the fiber membrane, making it easier to release the mechanical stress generated by the negative electrode during charging and discharging. At the same time, it maintains close contact with the solid electrolyte even when there are volume changes between the electrode and the solid electrolyte, which can significantly reduce the internal resistance of the solid battery. By preparing a novel high-capacity, low-expansion molybdenum disulfide MoS2 composite negative electrode, the interfacial contact between the negative electrode and the sulfide solid electrolyte is optimized, avoiding the negative impact of large volume expansion on the performance of the solid battery, and significantly improving the capacity, rate capability, and cycle life of the solid battery. Moreover, the preparation method provided in this application is controllable. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart illustrating a method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to an embodiment of this application. Detailed Implementation

[0021] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] In the description of this application, it should be noted that the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] The Chinese meanings of the English abbreviations appearing in this application

[0024] PAN: Polyacrylonitrile; DMF: N,N-dimethylformamide; HF: Hydrofluoric acid.

[0025] Please see Figure 1 In a preferred embodiment, this application provides a method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery, comprising the following steps:

[0026] S1: Preparation of microporous carbon fiber membranes; First, methyltriethoxysilane and polyacrylonitrile are added to N,N-dimethylformamide (DMF) solvent at a mass ratio of 45-65:25-45. The mixture is stirred at 80-140 rpm for 1-2 hours at room temperature until completely dissolved, with the mass fraction of DMF in the solution being 70-85%. Then, the homogeneously mixed solution is electrospinned to obtain a large-area white methyltriethoxysilane-PAN fiber membrane. Specific electrospinning parameters are: receiving distance 15-20 cm, spinning voltage 15-25 kV, solution flow rate 1.5-2.5 mL / h, temperature 30-40℃, and syringe pump specification 20-30 mL. The prepared triethylsilane-PAN fiber membrane has an average pore size of 300-600 nm. By increasing the volume of the mixed solution, large-area fiber membranes can be prepared. The obtained methyltriethoxysilane-PAN fiber membrane was then heat-treated in air at 150-250℃ for 1-2 hours to remove residual solvent. It was then sintered at 1000-1300℃ for 1-2 hours under an inert atmosphere with a heating rate of 1-3℃ / min, converting the methyltriethoxysilane in the fiber membrane into silica nanoparticles. After cooling to room temperature, 30-40% hydrofluoric acid (HF) was added to remove the silica from the fiber membrane, yielding a carbon fiber membrane with a large number of microporous structures.

[0027] S2: Preparation of MoS2-carbon fiber membrane composite layer; Thiourea and Na2MoO4 are dissolved in a mixed solvent composed of anhydrous ethanol and deionized water at a mass ratio of 20-40:35-45, the volume ratio of anhydrous ethanol to deionized water is 1-1.5:1-1.5, and the total mass fraction of thiourea and Na2MoO4 is 4.5-6.5%. The mixture is stirred at 60-100 rpm for 30-45 minutes at room temperature and then transferred to a high-pressure reactor. The microporous carbon fiber membrane obtained in step S1 is then completely immersed in the above solution and subjected to hydrothermal reaction at 200-250℃ for 24-36 hours to generate MoS2 nanoparticles on the surface of the fiber membrane. The carbon fiber membrane is then removed and vacuum dried at 90-110℃ for 3-5 hours. Subsequently, it is sintered at 800-900℃ under an inert atmosphere for 30-60 minutes to improve the crystallinity of MoS2 nanoparticles and improve the lithium-ion transport performance of MoS2 nanoparticles, thus obtaining the MoS2-carbon fiber membrane composite layer.

[0028] S3: Preparation of benzoquinone-MoS2-carbon fiber membrane composite negative electrode; specifically, benzoquinone and lithium perchlorate are dispersed in anhydrous acetonitrile at a molar ratio of 30-45:5-10 at room temperature, wherein the total mass fraction of benzoquinone and lithium perchlorate is 30-45%, which is used as the electrolyte. A two-electrode system is formed with the MoS2-carbon fiber membrane composite layer as the working electrode and a platinum sheet as the counter electrode, and an application of 2.5-3.5 mA / cm² is applied. 2The anolyte current was adjusted, and the deposition time was 1-5 minutes to deposit benzoquinone on the surface of the MoS2-carbon fiber film composite layer. The thickness of benzoquinone was controlled by adjusting the anolyte current density and the deposition time. In this step, the benzoquinone deposition thickness was 50-150 nm. Too thin a thickness would not be conducive to suppressing the volume change of MoS2 during the charge and discharge process, while too thick a thickness would increase the internal resistance of the battery. Finally, a benzoquinone-MoS2-carbon fiber film composite negative electrode was obtained, with a total thickness of 50-300 μm.

[0029] As an alternative implementation, methyltriethoxysilane can be replaced by one of tetraethyl orthosilicate or methyl orthosilicate; PAN can be replaced by one of acrylonitrile cellulose or other PAN derivatives (brominated, sulfonated, etc.).

[0030] As another alternative implementation, benzoquinone can be replaced by one of anthraquinone (AQ), phenanthrenequinone (PQ), and benzoquinone polycarbonylquinone derivatives (including 14-pentaphenyltetraone, nonanoxaquinone, pyrene-4,5,9,10-tetraone, 5-quinone, etc.). The above materials have strong π-π intermolecular forces due to their highly delocalized π system, which can effectively improve electronic and ion conduction and improve rate performance. In addition, benzoquinone materials can maintain a stable particle structure during charge and discharge, effectively suppressing the volume change of MoS2 and extending the cycle life of solid-state batteries.

[0031] Example 1

[0032] Preparation of molybdenum disulfide composite negative electrode:

[0033] a. First, methyltriethoxysilane and polyacrylonitrile (PAN) were added to N,N-dimethylformamide (DMF) solvent at a mass ratio of 55:30. The mixture was stirred at 120 rpm for 1.5 hours at room temperature until completely dissolved, resulting in a DMF mass fraction of 75% in the solution. Then, the homogeneous solution was electrospinned to obtain a large-area white methyltriethoxysilane-PAN fiber membrane. The specific electrospinning parameters were: receiving distance of 18 cm, spinning voltage of 18 kV, solution flow rate of 2.0 mL / h, temperature of 35 °C, and a 25 mL syringe pump. The prepared tetraethylsilane-PAN fiber membrane had an average pore size of approximately 450 nm. The resulting methyltriethoxysilane-PAN fiber membrane was then heat-treated in air at 220 °C for 1.5 hours to remove residual solvent. Finally, it was sintered at 1100 °C for 1.5 hours under an inert atmosphere with a heating rate of 2 °C / min, converting the methyltriethoxysilane in the fiber membrane into silica nanoparticles. After cooling to room temperature, 38% hydrofluoric acid (HF) was added to remove silica from the fiber membrane, resulting in a carbon fiber membrane with a large number of micropores.

[0034] b. Thiourea and Na2MoO4 were dissolved in a mixed solvent of anhydrous ethanol and deionized water at a mass ratio of 35:35, with a volume ratio of 1:1. The total mass fraction of thiourea and Na2MoO4 was 5%. The mixture was stirred at 90 rpm for 35 minutes at room temperature and then transferred to a high-pressure reactor. The microporous carbon fiber membrane obtained in step a was then completely immersed in the above solution and subjected to hydrothermal reaction at 220°C for 30 hours. MoS2 nanoparticles were generated on the surface of the fiber membrane. The carbon fiber membrane was then removed and vacuum dried at 100°C for 4 hours. Subsequently, it was sintered at 850°C under an inert atmosphere for 45 minutes to improve the crystallinity of the MoS2 nanoparticles and enhance their lithium-ion transport performance, thus obtaining a MoS2-carbon fiber membrane composite layer.

[0035] c. A conductive quinone material was deposited on the surface of a MoS2-carbon fiber membrane composite layer by electrochemical deposition. Specifically, benzoquinone and lithium perchlorate were dispersed in anhydrous acetonitrile at a molar ratio of 35:8 at room temperature, with a total mass fraction of 35% for both benzoquinone and lithium perchlorate. This mixture served as the electrolyte. A two-electrode system was formed using the MoS2-carbon fiber membrane composite layer as the working electrode and a platinum sheet as the counter electrode, and an application of 3.0 mA / cm² was applied. 2 The anolyte current was set at 3 minutes, the deposition time was 3 minutes, and the benzoquinone deposition thickness was 75 nanometers. Finally, a benzoquinone-MoS2-carbon fiber film composite negative electrode was obtained. The benzoquinone-MoS2-carbon fiber film composite negative electrode is the sulfide all-solid lithium battery composite negative electrode prepared in this application, and the total thickness of the negative electrode is 170 μm.

[0036] Preparation of solid-state batteries:

[0037] The positive electrode active material, carbon-based conductive agent, and inorganic salt were added to a high-energy vibratory ball mill at a mass ratio of 75:55:8 and ball-milled for 30 minutes at room temperature. The mixture was then transferred to a mold and pressed into a positive electrode sheet with a thickness of 200 μm under 150 standard atmospheres. The positive electrode active material was lithium iron phosphate (LFP), the carbon-based conductive agent was carbon nanotubes, and the inorganic salt was lithium lanthanum zirconate.

[0038] In an environment where the water and oxygen content are both below 10 ppm, the benzoquinone-MoS2-carbon fiber membrane composite negative electrode prepared in step c is used as the negative electrode, and sulfide Li10GeP2S12 is used as the solid electrolyte. The positive and negative electrode sheets are pressed onto both sides of the solid electrolyte at 80 standard atmospheres to form a coin cell all-solid-state battery.

[0039] Example 2

[0040] Compared with Example 1, the preparation process of the molybdenum disulfide composite negative electrode in Example 2 is as follows:

[0041] First, methyltriethoxysilane and polyacrylonitrile (PAN) were added to N,N-dimethylformamide (DMF) solvent at a mass ratio of 65:25. The mixture was stirred at 140 rpm for 2 hours at room temperature until completely dissolved, resulting in a DMF mass fraction of 85% in the solution. Then, the homogeneous solution was electrospinned to obtain a large-area white methyltriethoxysilane-PAN fiber membrane. The specific electrospinning parameters were: receiving distance of 15 cm, spinning voltage of 15 kV, solution flow rate of 1.5 mL / h, temperature of 30 °C, and a 20 mL syringe pump. The prepared tetraethylsilane-PAN fiber membrane had an average pore size of 300 nm. The resulting methyltriethoxysilane-PAN fiber membrane was then heat-treated in air at 250 °C for 1 hour to remove residual solvent. Finally, it was sintered at 1000 °C for 2 hours under an inert atmosphere with a heating rate of 1 °C / min, converting the methyltriethoxysilane in the fiber membrane into silica nanoparticles. After cooling to room temperature, 40% hydrofluoric acid HF was added to remove silica from the fiber membrane, resulting in a carbon fiber membrane with a large number of micropores. The remaining conditions were the same as in Example 1.

[0042] Example 3

[0043] Compared with Example 1, the preparation process of the composite negative electrode in Example 3 is as follows:

[0044] Thiourea and Na₂MoO₄ were dissolved in a mixed solvent of anhydrous ethanol and deionized water at a mass ratio of 40:35, with a volume ratio of anhydrous ethanol to deionized water of 1.5:1. The total mass fraction of thiourea and Na₂MoO₄ was 4.5%. The solution was stirred at 100 rpm for 30 minutes at room temperature and then transferred to a high-pressure reactor. The microporous carbon fiber membrane obtained in step a was then completely immersed in the solution and subjected to a hydrothermal reaction at 200°C for 24 hours. MoS₂ nanoparticles were generated on the surface of the fiber membrane. The carbon fiber membrane was then removed and vacuum dried at 90°C for 3 hours. Subsequently, it was sintered at 900°C under an inert atmosphere for 30 minutes to improve the crystallinity of the MoS₂ nanoparticles and enhance their lithium-ion transport performance, thus obtaining a MoS₂-carbon fiber membrane composite layer. The remaining conditions were the same as in Example 1.

[0045] Example 4

[0046] Compared to Example 1, the quinone deposition method in Example 4 is as follows:

[0047] Benzoquinone and lithium perchlorate were dispersed in anhydrous acetonitrile at a molar ratio of 30:10 at room temperature, with a total mass fraction of 45% for both benzoquinone and lithium perchlorate. This mixture was used as the electrolyte. A two-electrode system was constructed using a MoS2-carbon fiber membrane composite layer as the working electrode and a platinum sheet as the counter electrode, and an applied current of 3.5 mA / cm² was applied. 2The anolyte current was set at 5 minutes, the deposition time was 5 minutes, and the benzoquinone deposition thickness was 150 nanometers. Finally, a benzoquinone-MoS2-carbon fiber film composite negative electrode was obtained with a total electrode thickness of 300 μm. The other conditions were the same as in Example 1.

[0048] Example 5

[0049] Compared with Example 1, in Example 5, methyltriethoxysilane is replaced by tetraethyl orthosilicate; PAN is replaced by acrylonitrile cellulose; benzoquinone can be replaced by 14-pentaphenyltetraone; the positive electrode active material is lithium cobalt oxide (LCO), the carbon conductive agent is Ketjen black; the inorganic salt is lithium aluminum titanium phosphate; and the remaining conditions are the same as in Example 1.

[0050] Comparative Example 1

[0051] Compared to Example 1, Comparative Example 1 did not add methyltriethoxysilane, and all other conditions were the same as in Example 1.

[0052] Comparative Example 2

[0053] Compared with Example 1, in Comparative Example 2, methyltriethoxysilane and polyacrylonitrile (PAN) were not subjected to electrospinning treatment, and the other conditions were the same as in Example 1.

[0054] Comparative Example 3

[0055] Compared with Example 1, Comparative Example 3 did not contain PAN and was not subjected to HF etching, while the other conditions were the same as in Example 1.

[0056] Comparative Example 4

[0057] Compared with Example 1, the MoS2 nanoparticles in Comparative Example 4 were not sintered in an inert atmosphere at 800-900℃, and the other conditions were the same as in Example 1.

[0058] Comparative Example 5

[0059] Compared with Example 1, no conductive quinone material was added in Comparative Example 5, and the other conditions were the same as in Example 1.

[0060] Comparative Example 6

[0061] Compared to Example 1, the conductive quinone material in Comparative Example 6 had a thickness of 250 nanometers, and the other conditions were the same as in Example 1.

[0062] Comparative Example 7

[0063] Compared with Example 1, Comparative Example 7 used a conventional lithium metal sheet as the negative electrode, and the other conditions were the same as in Example 1.

[0064] Comparative Example 8

[0065] Compared with Example 1, Comparative Example 8 used a conventional MoS2 sheet as the negative electrode, and the other conditions were the same as in Example 1.

[0066] The negative electrode sheets from Examples 2-5 and Comparative Examples 1-8 were used to prepare corresponding solid-state batteries. The specific preparation conditions were the same as those provided in the examples. Electrochemical performance tests were performed on the prepared solid-state batteries, specifically including tests on actual capacity, internal resistance, and cycle life. Cycle life tests were conducted at 30°C and 60°C, within a suitable voltage range (the specific voltage depends on the type of positive electrode material), at a charge / discharge rate of 0.1C. The discharge capacity of the first week was marked as the actual battery capacity. When the battery reached 80% of its actual capacity (first week discharge capacity), the cycle life was considered terminated, and the test was stopped.

[0067] The internal resistance of the battery was tested by electrochemical impedance spectroscopy (EIS) at 30℃ and 60℃ and 50% SOC. The applied voltage amplitude was 5mV and the frequency range was 0.1Hz-1000000Hz. The specific results are shown in Table 1.

[0068] Table 1: Performance Test Table of All-Solid-State Batteries under Different Conditions

[0069] Example 1 6.72 89.2 608 Example 2 6.58 89.7 605 Example 3 6.63 89.4 603 Example 4 6.52 90.1 601 Example 5 6.69 89.5 607 Comparative Example 1 6.13 110.6 525 Comparative Example 2 6.38 96.9 558 Comparative Example 3 5.25 123.7 503 Comparative Example 4 6.48 100.8 532 Comparative Example 5 6.59 97.4 541 Comparative Example 6 6.64 99.9 539 Comparative Example 7 5.87 145.6 397 Comparative Example 8 5.32 138.2 502

[0070] As shown in Table 1, and in conjunction with Examples 1-5, it can be observed that the composite anode prepared within the technical requirements of this application exhibits good capacity, internal resistance, and cycle life, with Example 1 showing the best technical effect. Combining Example 1 and Comparative Examples 1-3, carbon fiber provides a flexible substrate. Simultaneously, after HF etching removes silica nanoparticles, numerous pores remain within the carbon fiber, which helps increase the specific surface area and the coverage of MoS2 nanoparticles. This also provides ample lithium-ion transport channels, significantly improving the conductivity of the solid-state battery and enhancing its capacity, internal resistance, and cycle life. Combining Example 1 and Comparative Examples 4-6, high-temperature sintering to increase the crystallinity of MoS2 nanoparticles helps reduce battery internal resistance and improve battery performance. Furthermore, the deposition of conductive quinones suppresses volume changes in MoS2 nanoparticles without increasing battery internal resistance, preventing particle shedding and cracking caused by repeated volume changes during long-term cycling, thus significantly extending the cycle life of the solid-state battery. In conjunction with Example 1 and Comparative Examples 7-8, compared with conventional lithium metal sheets and MoS2 sheets, the MoS2-based composite anode prepared in this application has higher flexibility, higher lithium-ion transport performance and better mechanical stability. It avoids the interfacial reaction between the sulfide solid electrolyte and lithium metal and the formation of lithium dendrites, overcomes the large volume change of conventional MoS2 sheets, and significantly increases the performance and safety of solid-state batteries.

[0071] The above are merely preferred embodiments of this application; however, the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and its improved concept, should be covered within the scope of protection of this application.

Claims

1. A method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery, characterized in that, Includes the following steps: Microporous carbon fiber membranes were prepared by adding methyltriethoxysilane and polyacrylonitrile to DMF solvent in a ratio of 45-65 parts: 25-45 parts and stirring until homogeneous to obtain a first mixed solution; the first mixed solution was used to prepare a first fiber membrane; the first fiber membrane was subjected to heat treatment, transferred to an inert atmosphere high-temperature environment for sintering, and cooled to room temperature to obtain a second fiber membrane; hydrofluoric acid was added to the second fiber membrane to obtain a microporous carbon fiber membrane with a microporous structure. To prepare a MoS2-carbon fiber membrane composite layer, thiourea and Na2MoO4 are dissolved in a mixed solvent composed of anhydrous ethanol and deionized water at a ratio of 20-40 parts: 35-45 parts to obtain a second mixed solution. The microporous carbon fiber membrane is completely immersed in the second mixed solution and subjected to specific treatment to obtain the MoS2-carbon fiber membrane composite layer. A benzoquinone-MoS2-carbon fiber membrane composite negative electrode was prepared. Benzoquinone and lithium perchlorate were dispersed in anhydrous acetonitrile at a ratio of 30-45 parts: 5-10 parts at room temperature to obtain a third mixed solution. The MoS2-carbon fiber membrane composite layer was used as the working electrode, a platinum sheet was used as the counter electrode, and the third mixed solution was used as the electrolyte. An anolyte current was applied, and after deposition, a benzoquinone-MoS2-carbon fiber membrane composite negative electrode was obtained. The total thickness of the benzoquinone-MoS2-carbon fiber membrane composite negative electrode was 50-300 μm.

2. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 1, characterized in that, The mass fraction of DMF in the first mixed solution is 70-85%.

3. A method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 1 or 2, characterized in that, The specific steps for preparing the first mixed solution into a first fiber membrane are as follows: the first mixed solution is subjected to electrospinning technology to obtain a large-area first fiber membrane. The specific electrospinning parameters are: receiving distance of 15-20 cm, spinning voltage of 15-25 kV, solution flow rate of 1.5-2.5 ml / h, temperature of 30-40℃, injection pump specification of 20-30 ml, and the average pore size of the prepared first fiber membrane is 300-600 nm.

4. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 1, characterized in that, The heat treatment is performed in air at 150-250℃ for 1-2 hours. The sintering in the inert atmosphere high-temperature environment is performed in an inert gas environment at 1000-1300℃ for 1-2 hours with a heating rate of 1-3℃ / minute. The concentration of the hydrofluoric acid is 30-40%, and the inert gas is one of nitrogen, argon, and helium.

5. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 4, characterized in that, The volume ratio of anhydrous ethanol to deionized water in the second mixed solution is 1-1.5:1-1.5, and the total mass fraction of thiourea and Na2MoO4 is 4.5-6.5%.

6. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 1, characterized in that, The second mixed solution is stirred at 60-100 rpm for 30-45 minutes at room temperature. The specific treatment is carried out in a high-pressure reactor at 200-250°C for 24-36 hours with hydrothermal reaction to generate MoS2 nanoparticles on the surface of the fiber membrane. The carbon fiber membrane is then removed and vacuum dried at 90-110°C for 3-5 hours, followed by sintering at 800-900°C in an inert atmosphere for 30-60 minutes.

7. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 6, characterized in that, The total mass fraction of benzoquinone and lithium perchlorate in the third mixed solution is 30-45%, and the applied anolyte current is 2.5-3.5 mA / cm. 2 The deposition time is 1-5 minutes.

8. The method for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery according to claim 1, characterized in that, The benzoquinone-MoS2-carbon fiber membrane composite negative electrode consists of a benzoquinone layer and a MoS2-carbon fiber membrane. The thickness of the benzoquinone layer is 50-150 nanometers. The benzoquinone is replaced by one of anthraquinone, phenanthrenequinone, or benzoquinone polycarbonylquinone derivatives.

9. A composite negative electrode sheet for a sulfide-based all-solid-state lithium battery, characterized in that, The negative electrode sheet is prepared by any one of the methods described in claims 1-8 for preparing a composite negative electrode sheet for a sulfide all-solid-state lithium battery.

10. A solid-state battery, characterized in that, The solid-state battery includes a solid electrolyte, with a positive electrode and a negative electrode disposed on both sides of the solid electrolyte. The positive electrode comprises a positive active material, a carbon-based conductive agent, and an inorganic salt. The positive active material, the carbon-based conductive agent, and the inorganic salt are disposed in a ratio of 70-80:50-70:5-10. The thickness of the positive electrode is 100-300 μm. The solid electrolyte is a sulfide. The negative electrode is a composite negative electrode for a sulfide all-solid-state lithium battery as described in claim 9.

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