Preparation method and application of catalytic nanoscale quantum dot composite positive electrode

Abstract

The application provides a preparation method of a catalytic nanoscale quantum dot composite positive electrode, and the method comprises the following steps: preparing Co9S8 quantum dots, modifying a solid-state electrolyte, preparing a sulfur / carbon composite S / C / Co9S8@SE composite positive electrode material precursor, and preparing the catalytic nanoscale quantum dot composite positive electrode. The application also provides an application, and the catalytic nanoscale quantum dot composite positive electrode is used for preparing a solid-state lithium-sulfur battery. The catalytic nanoscale quantum dot composite positive electrode of the application introduces catalytic quantum dots as nanobridges and solid-state reaction catalysts into a sulfur / carbon / solid-state electrolyte ternary composite system by designing a functional interface at an atomic / nanoscale, so as to significantly improve solid-solid reaction kinetics and interface stability.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to a method for preparing and applying a catalytic nanoscale quantum dot composite cathode. Background Technology

[0002] Lithium-sulfur batteries have attracted much attention due to their high energy density. However, traditional liquid lithium-sulfur batteries suffer from polysulfide shuttle effects and safety hazards. Constructing all-solid-state lithium-sulfur batteries (ASSLSBs) using solid-state electrolytes (SSEs) is considered the ultimate solution to eliminate the shuttle effect and improve safety.

[0003] However, combining sulfur cathodes with solid electrolytes presents more severe challenges than with liquid systems: (1) Slow solid-solid reaction kinetics: In the solid system, sulfur, the discharge end product Li2S / Li2S2, and the solid electrolyte are all solids, and there is a solid-solid interface between the active material and the electrolyte. The high energy barrier for electron and ion transport at the solid-solid interface leads to extremely slow redox reaction kinetics of sulfur, resulting in large battery polarization and low capacity utilization.

[0004] (2) Poor and unstable interfacial contact: During charging and discharging, sulfur and Li2S undergo about 80% volume change, which can easily lead to failure of rigid solid-solid interface contact and breakage of ion transport channels. At the same time, there may be chemical / electrochemical instability between the sulfur cathode and the solid electrolyte (especially sulfide electrolyte), resulting in increased interfacial impedance.

[0005] (3) Insufficient ionic conductivity inside the positive electrode: Sulfur and Li2S are electron and ion insulators. In solid positive electrodes, relying solely on solid electrolytes as ion transport media often results in an imperfect permeation network, leading to limited ion transport inside the positive electrode and low utilization of active materials.

[0006] Existing technical improvement solutions include: (1) Preparation of sulfur-carbon composite materials: Improves electronic conductivity, but cannot effectively solve the problems of ion transport and reaction kinetics at the solid-solid interface.

[0007] (2) Introducing solid electrolyte particles into the positive electrode: Constructing a "ternary composite positive electrode" to expand the ion transport channels. However, simple physical mixing is difficult to form a continuous and efficient ion conduction network, and its catalytic effect on sulfur conversion is limited.

[0008] (3) Introducing a small amount of liquid / gel electrolyte wetting interface: This goes against the original intention of all solid state and may reintroduce shuttle risks and safety hazards.

[0009] Therefore, developing a novel cathode structure that can simultaneously provide efficient electron / ion conduction, strongly catalyze solid-solid conversion reactions, and maintain a stable interface to adapt to volume changes is a key technology for promoting the development of all-solid-state lithium-sulfur batteries. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for preparing a catalytic nanoscale quantum dot composite cathode, which addresses the shortcomings of the prior art. In this method, the catalytic nanoscale quantum dot composite cathode is designed with functional interfaces at the atomic / nanoscale, and the catalytic quantum dots are uniformly introduced into the sulfur / carbon / solid electrolyte ternary composite system as "nanobridges" and "solid reaction catalysts", thereby significantly improving the solid-solid reaction kinetics and interface stability.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing and applying a catalytic nanoscale quantum dot composite cathode, the method being as follows: S1. Preparation of Co9S8 quantum dots: Cobalt salt and sulfur source were dissolved in a solvent, and then a surfactant was added. After magnetic stirring, a hydrothermal reaction was carried out at a temperature of 120℃~180℃ for 4h~12h. After natural cooling to room temperature, the precipitate was collected by centrifugation, washed, and dispersed in anhydrous ethanol. After ultrasonic treatment, a Co9S8 quantum dot colloidal solution was obtained. S2, Modified solid electrolyte: S201, Secondary hydrothermal reaction: While stirring, the Co9S8 quantum dot colloidal solution obtained in S1 was added dropwise to the solid electrolyte precursor solution. After ultrasonic mixing, ammonia was added dropwise to the system until the pH value reached 10. Then, a hydrothermal reaction was carried out at a temperature of 140℃~180℃ for 8h~16h. After naturally cooling to room temperature, the precipitate was collected by centrifugation, washed, and dried to obtain the composite powder modified with solid electrolyte. S202, Annealing: Under an argon atmosphere, the composite powder of modified solid electrolyte obtained in S201 was heated from room temperature to 400℃~600℃ at a heating rate of 2℃ / min, held at that temperature for 2h~4h, and then naturally cooled to room temperature to obtain Co9S8@SE composite quantum dot powder with core-shell structure. S3. Preparation of sulfur / carbon composite S / C / Co9S8@SE composite cathode material precursor: S301. Preparation of C / Co9S8@SE composite host material: The porous carbon material and the Co9S8@SE composite quantum dot powder with a core-shell structure obtained from S202 were added to anhydrous ethanol, ultrasonically dispersed, and then the solvent was evaporated by stirring at 80℃ to obtain the C / Co9S8@SE composite host material. S302, Preparation of S / C / Co9S8@SE composite cathode material precursor: Using a melt diffusion method, sulfur powder was loaded into the porous structure of the C / Co9S8@SE composite host material obtained in S301, and then naturally cooled to room temperature to obtain the S / C / Co9S8@SE composite cathode material precursor. S4. Preparation of catalytic nanoscale quantum dot composite cathode: S401. Dissolve the binder in N-methylpyrrolidone to obtain an N-methylpyrrolidone solution of the binder, then add the conductive agent and the S / C / Co9S8@SE composite cathode material precursor obtained in S302, stir and mix to obtain a slurry; S402. The slurry obtained in S401 is coated onto the current collector, and after drying, pressing and cutting, a catalytic nanoscale quantum dot composite cathode is obtained.

[0012] The catalytic nanoscale quantum dot composite cathode of this invention is a three-dimensional interconnected composite system composed of a sulfur / carbon composite, solid electrolyte particles, and catalytic quantum dots. The sulfur / carbon composite is composed of elemental sulfur uniformly loaded in a porous conductive carbon matrix, serving as the active material and electron conduction framework. The solid electrolyte particles are dispersed around and within the pores of the sulfur / carbon composite, forming an ion conduction framework. Catalytic quantum dots refer to nanocrystalline materials with sizes within the quantum confinement effect range (typically <10 nm) and catalytic activity. It is a nanostructured material that combines the "size effect of quantum dots" with the "active center function of catalysts," with a size of 1-10 nm. Through chemical bonding and physical anchoring, it selectively and uniformly modifies the surface of the solid electrolyte particles and partially exists at the interface between the sulfur / carbon composite and the solid electrolyte. The catalytic quantum dots, acting as an "interfacial catalyst" and "ion / electron modulation layer," effectively reduce the interfacial energy barrier between sulfur species and the solid electrolyte, catalyzing solid-solid conversion reactions and improving interfacial ion transport.

[0013] The present invention's cathode incorporates catalytic quantum dots as "nano-bridgers" and "solid-state reaction catalysts" by designing functional interfaces at the atomic scale of the Co9S8 quantum dot surface atomic layer and core-shell interface, and at the nanoscale of the Co9S8 quantum dots, solid electrolyte shell, and porous carbon framework. This allows the catalytic quantum dots to be uniformly introduced into the sulfur / carbon / solid electrolyte ternary composite system, thereby significantly improving solid-solid reaction kinetics and interface stability.

[0014] Preferably, the solvent in S1 is a 20% (v / v) aqueous solution of ethylene glycol; the cobalt salt is cobalt nitrate, cobalt chloride, or cobalt acetate; the sulfur source is thiourea, thioacetamide, or sodium sulfide; the surfactant is polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, or polyethylene glycol; the ratio of cobalt salt, sulfur source, solvent, and surfactant is 2.0 mmol: 6.0 mmol: 50 mL: 0.5 g; and the concentration of the Co9S8 quantum dot colloidal solution is 5 mg / mL.

[0015] Preferably, the magnetic stirring conditions in S1 are: 2000 rpm, 120 min; the centrifugation conditions are: 10000 rpm, 10 min; the washing method is: first wash with deionized water 3 times, then wash with anhydrous ethanol 3 times; the ultrasonic treatment conditions are: 1000 W, 60 min.

[0016] Preferably, the solid electrolyte precursor solution in S201 is prepared by dissolving LiNO3, La(NO3)3·6H2O and ZrOCl2·8H2O in deionized water to obtain the solid electrolyte precursor solution; the ratio of the amount of LiNO3, La(NO3)3·6H2O, ZrOCl2·8H2O and deionized water is 3.0 mmol: 0.5 mmol: 1.0 mmol: 25 mL.

[0017] Preferably, the ammonia water in S201 is an ammonia water solution with a mass fraction of 25% to 28%; the centrifugation conditions in S201 are 2000 rpm for 120 min; the washing method is ethanol washing; and the drying conditions are 80°C for 12 h.

[0018] Preferably, the porous carbon material in S301 is a multi-walled carbon nanotube, mesoporous carbon, or graphene; the ratio of the porous carbon material, the core-shell structured Co9S8@LLZO composite quantum dot powder, and anhydrous ethanol is (0.5-2) g: 0.1 g: 50 mL; the ultrasonic dispersion conditions are: 1000 W, 2 h.

[0019] Preferably, the melt diffusion method described in S302 is as follows: the sulfur powder and the C / Co9S8@SE composite host material are physically ground and mixed, and then heat-treated at a temperature of 155℃~160℃ for 6h~12h under argon protection; the mass ratio of the sulfur powder to the C / Co9S8@SE composite host material is 55:45.

[0020] Preferably, the binder in S401 is polyvinylidene fluoride, and the conductive agent is conductive carbon black; the mass ratio of the binder, conductive agent and S / C / Co9S8@SE composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:(1~2):(7~8); the stirring conditions are: 2000 rpm, 6h.

[0021] Preferably, the current collector in S402 is carbon-coated aluminum foil or nickel foam; the areal density of the slurry coating is 2.0 mg / cm³ based on sulfur mass. 2 ~2.5mg / cm 2 The drying conditions are as follows: first, dry by forced air at 80℃ for 2 hours, then vacuum dry at 50℃~80℃ for 12 hours~24 hours; the pressing conditions are as follows: Rolling; the catalytic nanoscale quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0022] This invention also provides the application of the catalytic nanoscale quantum dot composite cathode prepared by the above preparation method, wherein the catalytic nanoscale quantum dot composite cathode is used to prepare solid-state lithium-sulfur batteries.

[0023] This catalytic nanoscale quantum dot composite cathode can be directly used to assemble all-solid-state lithium-sulfur batteries. Using this cathode as the working electrode and metallic lithium or lithium alloy as the counter electrode, a solid electrolyte membrane (the same type of solid electrolyte used in the cathode) is placed between the two. The batteries are then integrated by applying pressure or thermo-pressing to assemble an all-solid-state lithium-sulfur battery.

[0024] Compared with the prior art, the present invention has the following advantages: 1. This invention significantly catalyzes solid-solid conversion reactions: Catalytic quantum dots significantly reduce the activation energy barrier for the conversion of sulfur (S8) to Li2S and the decomposition of Li2S, accelerating reaction kinetics, thereby reducing battery polarization and improving capacity and rate performance.

[0025] 2. This invention optimizes ion transport at the solid-solid interface: Quantum dots modified on the surface of a solid electrolyte can act as intermediate stations for "ion hopping," reducing Li... + Migration resistance at the sulfur / electrolyte interface. Some quantum dots (such as the solid electrolyte shell LLZO) may themselves possess high ionic conductivity, further promoting interfacial ion transport.

[0026] 3. This invention has a stable interface and suppresses side reactions: The quantum dot layer forms a physical barrier between the sulfur-active material and the sensitive sulfide solid electrolyte, which can reduce direct contact and side reactions between the two and improve the chemical stability of the interface.

[0027] 4. This invention can maintain interfacial contact: Nanoscale quantum dots can better adapt to volume changes during charging and discharging, and maintain effective solid-solid contact through their high specific surface area, preventing interfacial delamination.

[0028] 5. This invention is a precise interface engineering strategy: Compared with the traditional method of simply mixing the catalyst into the positive electrode, the "modification before composite" strategy of this invention ensures that the catalyst is precisely positioned at the most critical solid-solid interface (solid electrolyte surface), thereby maximizing catalyst utilization and interface efficiency.

[0029] 6. When the catalytic nanoscale quantum dot composite cathode prepared by this invention is used in an all-solid-state lithium-sulfur battery, the initial discharge specific capacity can exceed 1200 mAh / g under 0.1C rate and 60°C conditions; after 100 cycles at 0.2C rate, the capacity retention rate can reach more than 85%; and it can also achieve effective charge and discharge at room temperature, showing significantly better performance than traditional ternary composite cathodes.

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a graph showing the catalytic nanoscale quantum dot composite cathode prepared in Example 1 of this invention undergoing a long-cycle constant current charge-discharge test at room temperature (25°C) and a 0.1 C rate.

[0032] Figure 2 This is the EIS image of the catalytic nanoscale quantum dot composite cathode prepared in Example 1 of this invention.

[0033] Figure 3 This is a rate performance graph of the catalytic nanoscale quantum dot composite cathode prepared in Example 1 of the present invention at different rates (0.1C, 0.2C).

[0034] Figure 4 These are test graphs showing the long-cycle performance of the composite cathodes prepared in Embodiment 1 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0035] Example 1

[0036] The preparation method of the catalytic nanoscale quantum dot composite cathode in this embodiment is as follows: S1. Preparation of Co9S8 quantum dots: 2.0 mmol of cobalt salt (cobalt nitrate, Co(NO3)2·6H2O) and 6.0 mmol of sulfur source (thiourea, CH4N2S) were dissolved in 50 mL of solvent (20% ethylene glycol aqueous solution). Then, 0.5 g of surfactant (polyvinylpyrrolidone, PVP, Mw≈40000) was added. The mixture was magnetically stirred at 2000 rpm for 120 min and then subjected to hydrothermal reaction at 160 °C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min to collect the precipitate. The precipitate was then washed three times with deionized water and three times with anhydrous ethanol. The washed precipitate was dispersed in anhydrous ethanol and sonicated at 1000 W for 60 min to obtain a Co9S8 quantum dot colloidal solution with a concentration of 5 mg / mL. This embodiment can significantly catalyze solid-solid conversion reactions. The catalytic quantum dots greatly reduce the activation energy barrier for the conversion of sulfur (S8) to Li2S and the decomposition of Li2S, accelerating the reaction kinetics, thereby reducing battery polarization and improving capacity and rate performance. S2, Modified solid electrolyte: S201, Secondary hydrothermal reaction: While stirring, the Co9S8 quantum dot colloidal solution obtained in S1 was added dropwise to the solid electrolyte precursor solution. After ultrasonic mixing for 30 min at a power of 1000 W, a 28% ammonia solution was added dropwise to the system until the pH value reached 10. The mixture was then transferred to a new 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 180 °C for 12 h. After naturally cooling to room temperature, the mixture was centrifuged at 2000 rpm for 120 min, and the precipitate was collected. After washing with ethanol and drying at 80 °C for 12 h, the composite powder modified with solid electrolyte was obtained. The solid electrolyte precursor solution is prepared by dissolving 3.0 mmol LiNO3, 0.5 mmol La(NO3)3·6H2O and 1.0 mmol ZrOCl2·8H2O in 25 mL of deionized water to obtain the solid electrolyte precursor solution. S202, Annealing: Under an argon atmosphere, the composite powder of modified solid electrolyte obtained in S201 was heated from room temperature to 550℃ at a heating rate of 2℃ / min, held at that temperature for 3h, and then naturally cooled to room temperature to obtain Co9S8@LLZO composite quantum dot powder with a core-shell structure. This embodiment optimizes ion transport at the solid-solid interface: quantum dots modified on the surface of the solid electrolyte can act as intermediate stations for "ion hopping," reducing Li... +Migration resistance at the sulfur / electrolyte interface; some quantum dots (such as the solid electrolyte shell LLZO) may themselves have high ionic conductivity, which further promotes interfacial ion transport; S3. Preparation of sulfur / carbon composite S / C / Co9S8@LLZO composite cathode material precursor: S301, Preparation of C / Co9S8@LLZO composite host material: 0.9 g of porous carbon material (commercial multi-walled carbon nanotubes MWCNTs) and 0.1 g of Co9S8@LLZO composite quantum dot powder with a core-shell structure obtained from S202 were added to 50 mL of anhydrous ethanol. After ultrasonic dispersion at 1000 W for 2 h, the solvent was evaporated by stirring at 80 °C to obtain C / Co9S8@LLZO composite host material. S302, Preparation of S / C / Co9S8@LLZO composite cathode material precursor: A melt diffusion method was used to load sulfur powder into the porous structure of the C / Co9S8@LLZO composite host material obtained in S301, and then naturally cooled to room temperature to obtain the S / C / Co9S8@LLZO composite cathode material precursor. The melt diffusion method was as follows: the sulfur powder and the C / Co9S8@LLZO composite host material were physically ground and mixed, and then heat-treated at 155°C for 10 hours under argon protection. The mass ratio of the sulfur powder to the C / Co9S8@LLZO composite host material was 55:45. In this embodiment, the quantum dot layer serving as a physical barrier is the Co9S8 quantum dot core (located in the innermost layer of the core-shell structure). Its function is to isolate the sulfur-active material from the inner wall of the solid electrolyte shell, stabilize the interface, and suppress side reactions. The quantum dot layer forms a physical barrier between the sulfur-active material and the sensitive sulfide solid electrolyte, which can reduce direct contact and side reactions between the two, and improve the chemical stability of the interface. S4. Preparation of catalytic nanoscale quantum dot composite cathode: S401. Dissolve the binder (polyvinylidene fluoride, PVDF) in N-methylpyrrolidone (NMP) to obtain an N-methylpyrrolidone solution of the binder. Then add the conductive agent (conductive carbon black, Super P) and the S / C / Co9S8@LLZO composite cathode material precursor obtained in S302. Stir and mix in a planetary mixer at 2000 rpm for 6 hours to obtain a slurry. The mass ratio of the binder, conductive agent and S / C / Co9S8@LLZO composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:2:7. S402. The slurry obtained in S401 is coated onto a current collector (carbon-coated aluminum foil), and after drying, pressing, and cutting, a catalytic nanoscale quantum dot composite cathode is obtained; the areal density of the slurry coating is 2.0 mg / cm³ based on the mass of sulfur. 2 The drying conditions are as follows: first, dry by blowing air at a temperature of 80℃ for 2 hours, and then dry by vacuum at a temperature of 60℃ for 12 hours; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0037] This embodiment can maintain interfacial contact: Nanoscale quantum dots can better adapt to volume changes during charging and discharging, and maintain effective solid-solid contact through their high specific surface area, preventing interfacial delamination.

[0038] Compared with the traditional method of simply mixing the catalyst into the positive electrode, the "modification before composite" strategy of this invention ensures that the catalyst is precisely positioned at the most critical solid-solid interface (solid electrolyte surface), thereby maximizing catalyst utilization and interface efficiency.

[0039] This embodiment also provides the application of the prepared catalytic nanoscale quantum dot composite cathode, which is used to prepare solid-state lithium-sulfur batteries.

[0040] This catalytic nanoscale quantum dot composite cathode can be directly used to assemble all-solid-state lithium-sulfur batteries. Using this cathode as the working electrode and metallic lithium or lithium alloy as the counter electrode, a solid electrolyte membrane (the same type of solid electrolyte used in the cathode) is placed between the two. The batteries are then integrated by applying pressure or thermo-pressing to assemble an all-solid-state lithium-sulfur battery.

[0041] To evaluate the electrochemical performance and cycle stability of the catalytic nanoscale quantum dot composite cathode in this embodiment under low-rate conditions at room temperature, it was assembled into an all-solid-state lithium-sulfur battery. Constant-current charge-discharge long-cycle tests were conducted at room temperature (25°C) and a rate of 0.1C. The test results are as follows: Figure 1 As shown.

[0042] from Figure 1 As can be seen, this composite cathode exhibits excellent initial capacity and cycle stability at room temperature (0.1 C).

[0043] The initial discharge specific capacity reached 1270 mAh / g, exceeding 1200 mAh / g, indicating that under normal temperature conditions, this composite cathode can achieve efficient utilization of sulfur active materials and fully leverage its high specific capacity characteristics. After 200 charge-discharge cycles, the discharge specific capacity remained at 1090 mAh / g, with a capacity retention rate as high as 86%. Throughout the cycle, the capacity curve showed a gentle downward trend without obvious "cliff-like" decay, and the average capacity decay rate per cycle was only 0.07%, exhibiting an extremely low capacity decay rate.

[0044] This superior performance stems from the structural design advantages of the composite cathode of this invention: high capacity utilization at room temperature: the strong catalytic effect of Co9S8 quantum dots can effectively reduce the energy barrier of polysulfide conversion reaction, and can efficiently promote the redox reaction of sulfur species even at room temperature (25 ℃), avoiding the problems of poor kinetics and limited capacity utilization of traditional all-solid-state lithium-sulfur batteries at room temperature, and achieving a high initial capacity of more than 1200mAh / g. Excellent room temperature cycling stability: The LLZO modification layer constructs a stable ion transport channel, while physically confining and chemically anchoring Co9S8 quantum dots to prevent them from agglomerating, dissolving or deactivating during cycling; the carbon matrix ensures the overall conductivity of the electrode and alleviates volume stress changes. The three work together to suppress the polysulfide shuttle effect and interface degradation, enabling the battery to maintain more than 86% capacity retention after 200 room temperature cycles. Electrochemical impedance spectroscopy (EIS) was used to test the all-solid-state lithium-sulfur battery assembled with the catalytic nanoscale quantum dot composite cathode prepared in this example, in order to analyze the interfacial charge transport characteristics and ion diffusion kinetics of the electrode. The tests were performed at room temperature, with a frequency scan range of 10... -2 Hz~10 5 Hz, AC disturbance amplitude is 5mV, the Nyquist curve of the test results is as follows Figure 2 As shown.

[0045] EIS test results show that the catalytic nanoscale quantum dot composite cathode prepared in this embodiment exhibits low ohmic impedance, low charge transfer impedance, and rapid ion diffusion kinetics. The catalytic effect and interface regulation of the core-shell Co9S8@LLZO composite quantum dots significantly optimize the interfacial contact and reaction kinetics of the electrode, effectively reducing polarization and providing direct electrochemical kinetic basis for the excellent rate performance and long-cycle stability of the battery.

[0046] The electrode of Example 1 was tested for performance at different rate ranges, such as... Figure 3As shown: Under 0.1C and 60℃ conditions, the battery's initial discharge specific capacity can reach 1220mAh / g, exceeding 1200mAh / g, and still maintains 1010mAh / g after 200 cycles, demonstrating excellent capacity performance and cycle stability under high-temperature conditions; at 0.2C rate, the battery's initial discharge specific capacity is 1120mAh / g, the capacity retention rate exceeds 85% after 100 cycles, and it can still reach 890mAh / g after 200 cycles, with an average capacity decay rate of only 0.1% per cycle, proving that it still has stable reaction kinetics and structural integrity at medium rate. The above results fully demonstrate that the composite strategy of the core-shell structure Co9S8@LLZO composite quantum dots and carbon matrix designed in this invention solves the core problems of polysulfide shuttle, catalytic center deactivation and limited ion transport in traditional lithium-sulfur batteries through multi-dimensional synergy of catalysis, confinement and ion transport. It exhibits significantly better electrochemical performance than traditional ternary composite cathodes under high rate and wide temperature conditions, providing an effective path for the development of high-performance all-solid-state lithium-sulfur batteries.

[0047] Comparative Example 1 The preparation method of the S / C / LLZO composite cathode material in this comparative example is as follows: S1, Modified solid electrolyte: S101. Dissolve 3.0 mmol LiNO3, 0.5 mmol La(NO3)3·6H2O and 1.0 mmol ZrOCl2·8H2O in 25 mL of deionized water to obtain a solid electrolyte precursor solution. After ultrasonically mixing the solid electrolyte precursor solution at 1000 W for 30 min, add 28% ammonia solution dropwise to the system until the pH value is 10. Transfer the solution to a new 100 mL hydrothermal reactor and carry out a hydrothermal reaction at 180 °C for 12 h. After naturally cooling to room temperature, centrifuge at 2000 rpm for 120 min, collect the precipitate, wash with ethanol, and dry at 80 °C for 12 h to obtain the modified solid electrolyte powder. S102, Annealing: Under an argon atmosphere, the modified solid electrolyte powder obtained in S101 was heated from room temperature to 550℃ at a heating rate of 2℃ / min, held at that temperature for 3h, and then naturally cooled to room temperature to obtain LLZO powder. S2. Preparation of sulfur / carbon composite S / C@LLZO composite cathode material precursor: S201. Preparation of C@LLZO composite host material: 0.9 g of porous carbon material (commercial multi-walled carbon nanotubes MWCNTs) and 0.1 g of LLZO powder obtained from S102 were added to 50 mL of anhydrous ethanol. After ultrasonic dispersion at 1000 W for 2 h, the solvent was evaporated by stirring at 80 °C to obtain C@LLZO composite host material. S202, Preparation of S / C@LLZO composite cathode material precursor: A melt diffusion method was used to load sulfur powder onto the C@LLZO composite host material obtained in S201, and then naturally cooled to room temperature to obtain an S / C@LLZO composite cathode material precursor. The melt diffusion method involved physically grinding and mixing the sulfur powder and the C@LLZO composite host material, followed by heat treatment at 155°C for 10 hours under argon protection. The mass ratio of the sulfur powder to the C@LLZO composite host material was 55:45. S3. Preparation of S / C / LLZO composite cathode material: S301. Dissolve the binder (polyvinylidene fluoride, PVDF) in N-methylpyrrolidone (NMP) to obtain an N-methylpyrrolidone solution of the binder. Then add the conductive agent (conductive carbon black, Super P) and the S / C@LLZO composite cathode material precursor obtained in S202. Stir and mix in a planetary mixer at 2000 rpm for 6 hours to obtain a slurry. The mass ratio of the binder, conductive agent and S / C@LLZO composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:2:7. S302. The slurry obtained in S301 is coated onto a current collector (carbon-coated aluminum foil), and after drying, pressing, and cutting, an S / C / LLZO composite cathode material is obtained; the areal density of the slurry coating is 2.0 mg / cm³ based on the mass of sulfur. 2 The drying conditions are as follows: first, dry by blowing air at a temperature of 80℃ for 2 hours, and then dry by vacuum at a temperature of 60℃ for 12 hours; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0048] Comparative Example 2 The preparation method of the S / C / Co9S8 composite cathode material in this comparative example is as follows: S1. Preparation of Co9S8 quantum dots: 2.0 mmol of cobalt salt (cobalt nitrate, Co(NO3)2·6H2O) and 6.0 mmol of sulfur source (thiourea, CH4N2S) were dissolved in 50 mL of solvent (20% ethylene glycol aqueous solution). Then, 0.5 g of surfactant (polyvinylpyrrolidone, PVP, Mw≈40000) was added. The mixture was magnetically stirred at 2000 rpm for 120 min and then subjected to hydrothermal reaction at 160 °C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min to collect the precipitate. The precipitate was washed three times with deionized water and then three times with anhydrous ethanol. The washed precipitate was dispersed in anhydrous ethanol and ultrasonicated at 1000 W for 60 min to obtain a Co9S8 quantum dot colloidal solution with a concentration of 5 mg / mL. S2. Preparation of precursors for sulfur / carbon composite S / C / Co9S8 composite cathode materials: S201. Preparation of C / Co9S8 composite host material: 0.9 g of porous carbon material (commercial multi-walled carbon nanotubes MWCNTs) and 0.1 g of Co9S8 quantum dot colloidal solution with a concentration of 5 mg / mL obtained from S1 were added to 50 mL of anhydrous ethanol. After ultrasonic dispersion at 1000 W for 2 h, the solvent was evaporated by stirring at 80 °C to obtain C / Co9S8 composite host material. S202, Preparation of S / C / Co9S8 composite cathode material precursor: A melt diffusion method was used to load sulfur powder into the porous structure of the C / Co9S8 composite host material obtained in S201, and then naturally cooled to room temperature to obtain the S / C / Co9S8 composite cathode material precursor. The melt diffusion method was as follows: the sulfur powder and the C / Co9S8 composite host material were physically ground and mixed, and then heat-treated at 155°C for 10 hours under argon protection. The mass ratio of the sulfur powder to the C / Co9S8 composite host material was 55:45. S3. Preparation of S / C / Co9S8 composite cathode material: S301. Dissolve the binder (polyvinylidene fluoride, PVDF) in N-methylpyrrolidone (NMP) to obtain an N-methylpyrrolidone solution of the binder. Then add the conductive agent (conductive carbon black, Super P) and the S / C / Co9S8 composite cathode material precursor obtained in S202. Stir and mix in a planetary mixer at 2000 rpm for 6 hours to obtain a slurry. The mass ratio of the binder, conductive agent and S / C / Co9S8 composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:2:7. S302. The slurry obtained in S301 is coated onto a current collector (carbon-coated aluminum foil), and after drying, pressing, and cutting, an S / C / Co9S8 composite cathode material is obtained; the areal density of the slurry coating is 2.0 mg / cm³ based on the mass of sulfur. 2 The drying conditions are as follows: first, dry by blowing air at a temperature of 80℃ for 2 hours, and then dry by vacuum at a temperature of 60℃ for 12 hours; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0049] Performance testing: The positive electrode sheets prepared in Example 1, Comparative Example 1, and Comparative Example 2 were used as working electrodes, and lithium metal sheets were used as counter electrodes and reference electrodes. Conventional electrolytes and separators were used to assemble CR2032 coin cells in an argon glove box. Electrochemical testing results showed that after 200 cycles at 0.5 C, the discharge specific capacity retention rate of the battery in Example 1 was as high as 85%, with extremely low capacity decay per cycle. The battery in Comparative Example 1, lacking a strong catalytic center, had low initial capacity and rapid capacity decay. The battery in Comparative Example 2 had a higher initial capacity, but poor cycle stability and significant capacity decay, indicating that the Co9S8 quantum dots without the LLZO modification layer may be deactivated or aggregated during cycling, and ion transport is limited. This fully demonstrates the synergistic advantages of the core-shell Co9S8@SE composite quantum dot and carbon matrix composite strategy designed in this invention.

[0050] The long-cycle performance of the electrodes of Example 1, Comparative Examples 1 and 2 was compared at a current density of 0.5C. The results are as follows: Figure 4 As shown: Example 1 (catalytic nanoscale quantum dot composite cathode, i.e., core-shell Co9S8@LLZO composite quantum dot / carbon composite electrode) exhibits excellent cycle stability and rate performance: its initial discharge specific capacity reaches 810 mAh / g, and after 200 charge-discharge cycles, the discharge specific capacity can still be maintained at about 680 mAh / g, with a capacity retention rate as high as 84%, and there is no obvious capacity cliff decay during cycling, with extremely low single-cycle capacity decay rate. This excellent performance is due to the synergistic effect of the core-shell structure: the internal Co9S8 quantum dots provide abundant catalytic active sites for the conversion reaction of polysulfides, effectively suppressing the shuttle effect of polysulfides; the outer LLZO modification layer constructs a continuous and stable ion transport channel, while physically confining and chemically anchoring the Co9S8 quantum dots, preventing them from agglomerating, dissolving or deactivating during cycling; the carbon matrix significantly improves the overall conductivity of the electrode and alleviates the volume stress changes during charge and discharge. The three work together to ensure the long-term cycle stability of the electrode.

[0051] The electrochemical performance of Comparative Example 1 (S / C / LLZO composite cathode material, i.e., the control electrode without a strong catalytic center) was significantly worse than that of Example 1: its initial discharge specific capacity was only 630 mAh / g, significantly lower than that of Example 1, and its capacity continued to decay during cycling, showing a significant precipitous drop after 150 cycles, and finally dropping below 100 mAh / g after about 170 cycles, resulting in complete electrode failure. These results indicate that in the absence of highly active catalytic centers such as Co9S8, the electrode cannot effectively catalyze the conversion reaction of polysulfides, leading to a severe polysulfide shuttle effect, continuous loss of active material, and consequently, low initial capacity and extremely poor cycling stability.

[0052] Comparative Example 2 (S / C / Co9S8 composite cathode material, i.e., Co9S8 quantum dot / carbon composite electrode without LLZO modification layer) had an initial discharge specific capacity of 470 mAh / g. Although it possessed certain catalytic activity, its cycling stability was far worse than that of Example 1: the capacity decayed rapidly during cycling, and after 100 cycles, the capacity was less than 20% of the initial value, only about 90 mAh / g. The electrode completely failed after about 120 cycles. This result demonstrates that when Co9S8 catalytic centers are present without the protection of an LLZO modification layer, Co9S8 quantum dots are prone to aggregation, dissolution, and deactivation during cycling. Furthermore, the lack of continuous ion transport channels leads to increased ion diffusion resistance and intensified electrode polarization, ultimately causing a precipitous capacity decay and preventing long-term cycling stability.

[0053] The comparison results of the three sets of electrodes fully demonstrate that the composite strategy of the core-shell structure Co9S8@LLZO composite quantum dots and carbon matrix designed in this invention, through the multi-dimensional synergistic effect of catalysis, confinement, ion transport and conductivity, simultaneously solves the problems of polysulfide shuttle, catalytic center deactivation and limited ion transport in lithium-sulfur batteries, showing significant technical advantages.

[0054] Example 2

[0055] The preparation method of the catalytic nanoscale quantum dot composite cathode in this embodiment is as follows: S1. Preparation of Co9S8 quantum dots: 2.0 mmol of cobalt salt (cobalt chloride) and 6.0 mmol of sulfur source (thioacetamide) were dissolved in 50 mL of solvent (20% ethylene glycol aqueous solution). Then, 0.5 g of surfactant (hexadecyltrimethylammonium bromide) was added. The mixture was magnetically stirred at 2000 rpm for 120 min and then subjected to hydrothermal reaction at 120 °C for 12 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min to collect the precipitate. The precipitate was washed three times with deionized water and then three times with anhydrous ethanol. The washed precipitate was dispersed in anhydrous ethanol and ultrasonicated at 1000 W for 60 min to obtain a Co9S8 quantum dot colloidal solution with a concentration of 5 mg / mL. S2, Modified solid electrolyte: S201, Secondary hydrothermal reaction: While stirring, the Co9S8 quantum dot colloidal solution obtained in S1 was added dropwise to the solid electrolyte precursor solution. After ultrasonic mixing for 30 min at a power of 1000 W, a 28% ammonia solution was added dropwise to the system until the pH value reached 10. The mixture was then transferred to a new 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 140 °C for 16 h. After naturally cooling to room temperature, the mixture was centrifuged at 2000 rpm for 120 min, and the precipitate was collected. After washing with ethanol and drying at 80 °C for 12 h, the composite powder modified with solid electrolyte was obtained. The solid electrolyte precursor solution is prepared by dissolving 3.0 mmol LiNO3, 0.5 mmol La(NO3)3·6H2O and 1.0 mmol ZrOCl2·8H2O in 25 mL of deionized water to obtain the solid electrolyte precursor solution. S202, Annealing: Under an argon atmosphere, the composite powder of modified solid electrolyte obtained in S201 was heated from room temperature to 400℃ at a heating rate of 2℃ / min, held at that temperature for 4h, and then naturally cooled to room temperature to obtain Co9S8@LLZO composite quantum dot powder with a core-shell structure. S3. Preparation of sulfur / carbon composite S / C / Co9S8@LLZO composite cathode material precursor: S301, Preparation of C / Co9S8@LLZO composite host material: 0.5g of porous carbon material (mesoporous carbon) and 0.1g of Co9S8@LLZO composite quantum dot powder with a core-shell structure obtained from S202 were added to 50mL of anhydrous ethanol. After ultrasonic dispersion at 1000W for 2h, the solvent was evaporated by stirring at 80℃ to obtain C / Co9S8@LLZO composite host material. S302, Preparation of S / C / Co9S8@LLZO composite cathode material precursor: A melt diffusion method was used to load sulfur powder into the porous structure of the C / Co9S8@LLZO composite host material obtained in S301, and then naturally cooled to room temperature to obtain the S / C / Co9S8@LLZO composite cathode material precursor. The melt diffusion method was as follows: the sulfur powder and the C / Co9S8@LLZO composite host material were physically ground and mixed, and then heat-treated at 160°C for 6 hours under argon protection. The mass ratio of the sulfur powder to the C / Co9S8@LLZO composite host material was 55:45. S4. Preparation of catalytic nanoscale quantum dot composite cathode: S401. Dissolve the binder (polyvinylidene fluoride, PVDF) in N-methylpyrrolidone (NMP) to obtain an N-methylpyrrolidone solution of the binder. Then add the conductive agent (conductive carbon black, Super P) and the S / C / Co9S8@LLZO composite cathode material precursor obtained in S302. Stir and mix in a planetary mixer at 2000 rpm for 6 hours to obtain a slurry. The mass ratio of the binder, conductive agent and S / C / Co9S8@LLZO composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:1:8. S402. The slurry obtained in S401 is coated onto a current collector (nickel foam), and after drying, pressing, and cutting, a catalytic nanoscale quantum dot composite cathode is obtained; the areal density of the slurry coating is 2.5 mg / cm³ based on the mass of sulfur. 2 The drying conditions are as follows: first, dry by blowing air at a temperature of 80℃ for 2 hours, and then dry by vacuum at a temperature of 50℃ for 24 hours; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0056] This embodiment also provides the application of the prepared catalytic nanoscale quantum dot composite cathode, which is used to prepare solid-state lithium-sulfur batteries.

[0057] The catalytic nanoscale quantum dot composite cathode prepared in this embodiment, when used in an all-solid-state lithium-sulfur battery, exhibits an initial discharge specific capacity of 1240 mAh / g, exceeding 1200 mAh / g, under 0.1C and 60 ℃ conditions. After 200 cycles, it still maintains 1020 mAh / g, demonstrating excellent capacity performance and cycle stability under high-temperature conditions. At a 0.2C rate, the initial discharge specific capacity is 1130 mAh / g, and the capacity retention rate exceeds 85% after 100 cycles. After 200 cycles, it still reaches approximately 900 mAh / g, with an average capacity decay rate of only 0.1% per cycle.

[0058] Example 3

[0059] The preparation method of the catalytic nanoscale quantum dot composite cathode in this embodiment is as follows: S1. Preparation of Co9S8 quantum dots: 2.0 mmol of cobalt salt (cobalt acetate) and 6.0 mmol of sulfur source (sodium sulfide) were dissolved in 50 mL of solvent (20% ethylene glycol aqueous solution). Then, 0.5 g of surfactant (polyethylene glycol) was added. The mixture was magnetically stirred at 2000 rpm for 120 min and then subjected to hydrothermal reaction at 180 °C for 4 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min to collect the precipitate. The precipitate was then washed three times with deionized water and three times with anhydrous ethanol. The washed precipitate was dispersed in anhydrous ethanol and sonicated at 1000 W for 60 min to obtain a Co9S8 quantum dot colloidal solution with a concentration of 5 mg / mL. S2, Modified solid electrolyte: S201, Secondary hydrothermal reaction: While stirring, the Co9S8 quantum dot colloidal solution obtained in S1 was added dropwise to the solid electrolyte precursor solution. After ultrasonic mixing for 30 min at a power of 1000 W, a 26% ammonia solution was added dropwise to the system until the pH value reached 10. The mixture was then transferred to a new 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 150 °C for 10 h. After naturally cooling to room temperature, the mixture was centrifuged at 2000 rpm for 120 min, and the precipitate was collected. After washing with ethanol and drying at 80 °C for 12 h, the composite powder modified with solid electrolyte was obtained. The solid electrolyte precursor solution is prepared by dissolving 3.0 mmol LiNO3, 0.5 mmol La(NO3)3·6H2O and 1.0 mmol ZrOCl2·8H2O in 25 mL of deionized water to obtain the solid electrolyte precursor solution. S202, Annealing: Under an argon atmosphere, the composite powder of modified solid electrolyte obtained in S201 was heated from room temperature to 600℃ at a heating rate of 2℃ / min, held at that temperature for 2h, and then naturally cooled to room temperature to obtain Co9S8@LLZO composite quantum dot powder with a core-shell structure. S3. Preparation of sulfur / carbon composite S / C / Co9S8@LLZO composite cathode material precursor: S301, Preparation of C / Co9S8@LLZO composite host material: (0.5–2) g of porous carbon material (graphene) and 0.1 g of Co9S8@LLZO composite quantum dot powder with a core-shell structure obtained from S202 were added to 50 mL of anhydrous ethanol. After ultrasonic dispersion at 1000 W for 2 h, the solvent was evaporated by stirring at 80 °C to obtain C / Co9S8@LLZO composite host material. S302, Preparation of S / C / Co9S8@LLZO composite cathode material precursor: A melt diffusion method was used to load sulfur powder into the porous structure of the C / Co9S8@LLZO composite host material obtained in S301, and then naturally cooled to room temperature to obtain the S / C / Co9S8@LLZO composite cathode material precursor. The melt diffusion method was as follows: the sulfur powder and the C / Co9S8@LLZO composite host material were physically ground and mixed, and then heat-treated at 158°C for 12 hours under argon protection. The mass ratio of the sulfur powder to the C / Co9S8@LLZO composite host material was 55:45. S4. Preparation of catalytic nanoscale quantum dot composite cathode: S401. Dissolve the binder (polyvinylidene fluoride, PVDF) in N-methylpyrrolidone (NMP) to obtain an N-methylpyrrolidone solution of the binder. Then add the conductive agent (conductive carbon black, Super P) and the S / C / Co9S8@LLZO composite cathode material precursor obtained in S302. Stir and mix in a planetary mixer at 2000 rpm for 6 hours to obtain a slurry. The mass ratio of the binder, conductive agent and S / C / Co9S8@LLZO composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:1.5:7.5. S402. The slurry obtained in S401 is coated onto a current collector (carbon-coated aluminum foil), and after drying, pressing, and cutting, a catalytic nanoscale quantum dot composite cathode is obtained; the areal density of the slurry coating is 2.2 mg / cm³ based on the mass of sulfur. 2The drying conditions are as follows: first, dry by blowing at 80°C for 2 hours, and then dry under vacuum at 80°C for 18 hours; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

[0060] This embodiment also provides the application of the prepared catalytic nanoscale quantum dot composite cathode, which is used to prepare solid-state lithium-sulfur batteries.

[0061] The catalytic nanoscale quantum dot composite cathode prepared in this embodiment, when used in an all-solid-state lithium-sulfur battery, exhibits an initial discharge specific capacity of 1230 mAh / g, exceeding 1200 mAh / g, under 0.1C and 60 ℃ conditions. After 200 cycles, it still maintains 1020 mAh / g, demonstrating excellent capacity performance and cycle stability under high-temperature conditions. At a 0.2C rate, the initial discharge specific capacity is 1140 mAh / g, and the capacity retention rate exceeds 85% after 100 cycles. After 200 cycles, it still reaches approximately 910 mAh / g, with an average capacity decay rate of only 0.1% per cycle.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a catalytic nanoscale quantum dot composite cathode, characterized in that, The method is as follows: S1. Preparation of Co9S8 quantum dots: Cobalt salt and sulfur source were dissolved in a solvent, and then a surfactant was added. After magnetic stirring, a hydrothermal reaction was carried out at a temperature of 120℃~180℃ for 4h~12h. After natural cooling to room temperature, the precipitate was collected by centrifugation, washed, and dispersed in anhydrous ethanol. After ultrasonic treatment, a Co9S8 quantum dot colloidal solution was obtained. S2, Modified solid electrolyte: S201, Secondary hydrothermal reaction: While stirring, the Co9S8 quantum dot colloidal solution obtained in S1 was added dropwise to the solid electrolyte precursor solution. After ultrasonic mixing, ammonia was added dropwise to the system until the pH value reached 10. Then, a hydrothermal reaction was carried out at a temperature of 140℃~180℃ for 8h~16h. After naturally cooling to room temperature, the precipitate was collected by centrifugation, washed, and dried to obtain the composite powder modified with solid electrolyte. S202, Annealing: Under an argon atmosphere, the composite powder of modified solid electrolyte obtained in S201 was heated from room temperature to 400℃~600℃ at a heating rate of 2℃ / min, held at that temperature for 2h~4h, and then naturally cooled to room temperature to obtain Co9S8@SE composite quantum dot powder with core-shell structure. S3. Preparation of sulfur / carbon composite S / C / Co9S8@SE composite cathode material precursor: S301. Preparation of C / Co9S8@SE composite host material: The porous carbon material and the Co9S8@SE composite quantum dot powder with a core-shell structure obtained from S202 were added to anhydrous ethanol, ultrasonically dispersed, and then the solvent was evaporated by stirring at 80℃ to obtain the C / Co9S8@SE composite host material. S302, Preparation of S / C / Co9S8@SE composite cathode material precursor: Using a melt diffusion method, sulfur powder was loaded into the porous structure of the C / Co9S8@SE composite host material obtained in S301, and then naturally cooled to room temperature to obtain the S / C / Co9S8@SE composite cathode material precursor. S4. Preparation of catalytic nanoscale quantum dot composite cathode: S401. Dissolve the binder in N-methylpyrrolidone to obtain an N-methylpyrrolidone solution of the binder, then add the conductive agent and the S / C / Co9S8@SE composite cathode material precursor obtained in S302, stir and mix to obtain a slurry; S402. The slurry obtained in S401 is coated onto the current collector, and after drying, pressing and cutting, a catalytic nanoscale quantum dot composite cathode is obtained.

2. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The solvent in S1 is a 20% (v / v) aqueous solution of ethylene glycol; the cobalt salt is cobalt nitrate, cobalt chloride, or cobalt acetate; the sulfur source is thiourea, thioacetamide, or sodium sulfide; the surfactant is polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, or polyethylene glycol; the ratio of cobalt salt, sulfur source, solvent, and surfactant is 2.0 mmol: 6.0 mmol: 50 mL: 0.5 g; and the concentration of the Co9S8 quantum dot colloidal solution is 5 mg / mL.

3. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The conditions for magnetic stirring in S1 were: 2000 rpm for 120 min; the conditions for centrifugation were: 10000 rpm for 10 min; the washing method was: first wash with deionized water 3 times, then wash with anhydrous ethanol 3 times; the conditions for ultrasonic treatment were: 1000 W for 60 min.

4. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The solid electrolyte precursor solution described in S201 is prepared by dissolving LiNO3, La(NO3)3·6H2O and ZrOCl2·8H2O in deionized water to obtain the solid electrolyte precursor solution; the ratio of the amount of LiNO3, La(NO3)3·6H2O, ZrOCl2·8H2O and deionized water is 3.0 mmol: 0.5 mmol: 1.0 mmol: 25 mL.

5. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The ammonia water mentioned in S201 is an ammonia water solution with a mass fraction of 25% to 28%; the centrifugation conditions in S201 are 2000 rpm for 120 min; the washing method is ethanol washing; the drying conditions are 80℃ for 12 h.

6. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The porous carbon material described in S301 is a multi-walled carbon nanotube, mesoporous carbon, or graphene; the ratio of the porous carbon material, the core-shell structured Co9S8@LLZO composite quantum dot powder, and anhydrous ethanol is (0.5-2) g: 0.1 g: 50 mL; the ultrasonic dispersion conditions are: 1000 W, 2 h.

7. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The melt diffusion method described in S302 is as follows: the sulfur powder and the C / Co9S8@SE composite host material are physically ground and mixed, and then heat-treated at a temperature of 155℃~160℃ for 6h~12h under argon protection; the mass ratio of the sulfur powder to the C / Co9S8@SE composite host material is 55:

45.

8. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The binder in S401 is polyvinylidene fluoride, and the conductive agent is conductive carbon black; the mass ratio of the binder, conductive agent and S / C / Co9S8@SE composite cathode material precursor in the N-methylpyrrolidone solution of the binder is 1:(1~2):(7~8); the stirring conditions are: 2000 rpm, 6h.

9. The method for preparing a catalytic nanoscale quantum dot composite cathode according to claim 1, characterized in that, The current collector described in S402 is carbon-coated aluminum foil or nickel foam; the areal density of the slurry coating is 2.0 mg / cm³ (based on sulfur mass). 2 ~2.5mg / cm 2 The drying conditions are as follows: first, dry by blowing air at a temperature of 80℃ for 2 hours, and then dry by vacuum at a temperature of 50℃~80℃ for 12h~24h; the pressing conditions are: 10MPa, roller pressing; the catalytic nano-scale quantum dot composite positive electrode is a disc with a thickness of 40μm and a diameter of 12mm.

10. An application of a catalytic nanoscale quantum dot composite cathode prepared by the preparation method according to any one of claims 1-9, characterized in that, The catalytic nanoscale quantum dot composite cathode is used to prepare solid-state lithium-sulfur batteries.

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