Preparation method of composite sulfur positive electrode and its application in all-solid-state battery

Abstract

The present invention discloses a method for preparing a composite sulfur positive electrode and its application in an all-solid-state battery, and relates to the technical field of battery material preparation. The composite sulfur positive electrode comprises: a sulfur / carbon composite material, a functional glassy sulfide electrolyte, a conductive agent and a binder. By doping and modifying the traditional glassy sulfide electrolyte, it is endowed with the ability to catalyze solid-phase sulfur conversion, reduce the solid-phase sulfur conversion energy barrier, and accelerate the solid-phase sulfur conversion kinetics. The prepared functional glassy sulfide electrolyte has excellent mechanical properties, so that the internal interface of the further prepared composite sulfur positive electrode can ensure close contact between the phases during the charge and discharge cycle, build an efficient and stable ion transport network, and significantly improve the utilization rate of active substances. The use of the composite sulfur positive electrode of the present invention to prepare an all-solid-state lithium-sulfur battery can not only improve the energy density, but also show low internal resistance and excellent charge and discharge efficiency, providing reliable technical support for the application of all-solid-state lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of battery material preparation, and in particular to a method for preparing a composite sulfur positive electrode and its application in an all-solid-state battery. Background Art

[0002] With the continuous growth of global energy demand and increasingly severe environmental problems, the development of efficient and sustainable energy storage technologies has become a major issue in today's society. Lithium-ion batteries, as the mainstream energy storage technology, are widely used in fields such as electric vehicles and renewable energy storage. However, existing lithium-ion battery technology still has certain limitations in terms of energy density, cost, and environmental friendliness, and there is an urgent need to find more promising alternative technologies.

[0003] Solid-state lithium-sulfur batteries have become a research hotspot for the next generation of battery technology due to their high energy density, low cost, and environmental friendliness. Compared to traditional lithium-ion batteries, solid-state lithium-sulfur batteries use sulfur as the positive electrode material, which greatly improves the theoretical energy density. In addition, their raw materials are more abundant, which can effectively reduce production costs. At the same time, solid-state lithium-sulfur batteries use solid electrolytes instead of organic electrolytes, which not only fundamentally solves the safety problem, but also avoids the capacity loss caused by the "shuttle effect" of sulfur active materials during the use of liquid lithium-sulfur batteries. Therefore, solid-state lithium-sulfur batteries are expected to be widely used as a new generation of battery systems with both high energy density and high safety performance.

[0004] However, solid-state lithium-sulfur batteries still face a series of technical challenges in practical applications. Among them, the slow and irreversible solid-phase sulfur conversion process of the sulfur cathode is a key factor limiting the battery capacity and stability. The factors that limit the performance of solid-state sulfur cathodes are mainly the following: First, the low ionic / electronic conductivity of the active material sulfur makes it impossible for the cathode to efficiently transport electrons during the charge and discharge process, thereby reducing the output power and efficiency of the battery; second, sulfur undergoes significant volume expansion during the charge and discharge process. This expansion leads to mechanical instability of the cathode, which in turn destroys the contact between the battery's conductive network and the electrolyte interface, increases the battery's internal resistance, and reduces the overall charge and discharge efficiency; finally, the electrochemical degradation of the solid electrolyte can also cause power loss in the ion transport network. Therefore, the development of a solid-state sulfur cathode with high electrochemical conversion power is of great significance to the development of all-solid-state lithium-sulfur batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a composite sulfur positive electrode and its application in an all-solid-state battery, so as to solve the problems of high internal resistance and low overall charge and discharge efficiency of existing all-solid-state lithium-sulfur batteries.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] The present invention discloses a method for preparing a composite sulfur positive electrode, comprising:

[0008] S1: The sulfur material and the conductive agent are mixed and ground, and then heated and kept warm under vacuum conditions to obtain a sulfur / carbon composite material;

[0009] S2: Mixing the base material and the doping sulfur material, followed by ball milling to obtain a functional glassy sulfide electrolyte;

[0010] S3: A sulfur / carbon composite material, a functional glassy sulfide electrolyte, and a conductive agent are mixed, and then subjected to ball milling reaction to obtain a composite sulfur positive electrode powder. The composite sulfur positive electrode powder is then mixed with a binder, ground, and roller-pressed to obtain a composite sulfur positive electrode; the mass ratio of the composite sulfur positive electrode powder to the binder is 1:0.008-0.06.

[0011] Preferably, the sulfur material in S1 is elemental sulfur; the conductive agent is at least one of carbon nanotubes, carbon fibers, Super P and acetylene black; and the mass ratio of the sulfur material to the conductive agent is 1:0.2-0.8.

[0012] Preferably, the basic materials in S2 are lithium sulfide, phosphorus pentasulfide and lithium iodide; the mass ratio of lithium sulfide to phosphorus pentasulfide is 1:1.3-2, and the mass ratio of lithium sulfide to lithium iodide is 1:1.6-2.3.

[0013] Preferably, the doping sulfur material in S2 is at least one of titanium disulfide, tin disulfide, indium sulfide, ferrous sulfide, silicon sulfide and copper sulfide; the mass ratio of lithium sulfide and doping sulfur material in the base material is 1:0.2-0.6.

[0014] Preferably, the mass ratio of the sulfur / carbon composite material to the functional glassy sulfide electrolyte in S3 is 1:0.8-1.3, and the mass ratio of the sulfur / carbon composite material to the conductive agent is 1:0.01-0.04.

[0015] Preferably, the binder in S3 is at least one of polytetrafluoroethylene and a xylan derivative; the xylan derivative is prepared from arabinoxylan, methyl dicocoylamine instead of a tertiary amine, and 2-(3-(chloromethyl)benzyl)ethylene oxide. Xylan derivatives have excellent binding ability, wettability, and stability. Using xylan derivatives as binders to prepare composite sulfur cathodes can effectively reduce the electrochemical impedance of all-solid-state lithium-sulfur batteries made with composite sulfur cathodes and improve their discharge capacity, with the discharge capacity remaining high even after 200 cycles.

[0016] Preferably, the mixing and grinding temperature in S1 is 20-30° C., and the grinding time is 0.3-1 h; the heating temperature is 150-160° C., and the holding time is 4-24 h.

[0017] Preferably, the ball milling reaction speed in S2 is 400-800 rpm, the reaction temperature is 20-30° C., and the reaction time is 10-22 h.

[0018] Preferably, the ball milling reaction speed in S3 is 300-600 rpm, the reaction temperature is 20-30°C, and the reaction time is 5-10h; the composite sulfur cathode powder and the binder are mixed and ground at a temperature of 20-30°C, a grinding time of 10-25min, and the number of roller pressings is 3-6 times.

[0019] The invention discloses an all-solid-state battery, comprising a composite sulfur positive electrode prepared by the above method.

[0020] The present invention discloses a method for preparing a composite sulfur positive electrode, comprising:

[0021] S1: The sulfur material and the conductive agent are mixed, ground at 20-30°C for 0.3-1h, and then heated to 150-160°C under vacuum conditions and kept warm for 4-24h to obtain a sulfur / carbon composite material;

[0022] S2: The base material and the doping sulfur material are mixed, and then ball milled at a speed of 400-800 rpm and 20-30°C for 10-22 h to obtain a functional glassy sulfide electrolyte;

[0023] S3: The sulfur / carbon composite material, the functional glassy sulfide electrolyte and the conductive agent are mixed, and the mixture is ball-milled at a speed of 300-600 rpm and a temperature of 20-30°C for 5-10 hours to obtain a composite sulfur positive electrode powder. The composite sulfur positive electrode powder is then mixed with a binder, ground at a temperature of 20-30°C for 10-25 minutes, and rolled 3-6 times to obtain a composite sulfur positive electrode.

[0024] Preferably, the sulfur material in S1 is elemental sulfur.

[0025] Preferably, the conductive agent in S1 is at least one of carbon nanotubes, carbon fibers, Super P and acetylene black.

[0026] More preferably, the mass ratio of the sulfur material to the conductive agent is 1:0.2-0.8.

[0027] Preferably, the basic materials in S2 are lithium sulfide, phosphorus pentasulfide and lithium iodide.

[0028] More preferably, the mass ratio of lithium sulfide to phosphorus pentasulfide is 1:1.3-2.

[0029] More preferably, the mass ratio of lithium sulfide to lithium iodide is 1:1.6-2.3.

[0030] Preferably, the doping sulfur material in S2 is at least one of titanium disulfide, tin disulfide, indium sulfide, ferrous sulfide, silicon sulfide and copper sulfide.

[0031] More preferably, the mass ratio of lithium sulfide to the doping sulfur material in the base material is 1:0.2-0.6.

[0032] Preferably, the mass ratio of the sulfur / carbon composite material to the functional glassy sulfide electrolyte in S3 is 1:0.8-1.3.

[0033] Preferably, the mass ratio of the sulfur / carbon composite material to the conductive agent in S3 is 1:0.01-0.04.

[0034] Preferably, the binder in S3 is at least one of polytetrafluoroethylene and a xylan derivative.

[0035] Preferably, the mass ratio of the composite sulfur cathode powder to the binder in S3 is 1:0.008-0.06.

[0036] The present invention discloses a method for preparing a xylan derivative, specifically comprising:

[0037] Water and sodium hydroxide were added to arabinoxylan. Methyl dicocoylamine was then added to replace the tertiary amine and 2-(3-(chloromethyl)benzyl)ethylene oxide at 20-30°C. The mixture was stirred for 0.5-1.5 hours and then heated to 60-70°C for 3-6 hours. After the reaction, the pH was adjusted to neutral, and ethanol was added, allowed to stand, and filtered to obtain a precipitate. The precipitate was then Soxhlet extracted with ethanol for 40-50 hours, and finally dried and ground to obtain a xylan derivative.

[0038] Preferably, the mass ratio of arabinoxylan to water is 1 g:70-90 ml.

[0039] Preferably, the mass ratio of arabinoxylan to sodium hydroxide is 1:0.2-0.8.

[0040] Preferably, the mass ratio of arabinoxylan to methyl dicocoylamine used instead of tertiary amine is 1:1-2.

[0041] Preferably, the mass ratio of methyl dicocoylamine to tertiary amine and 2-(3-(chloromethyl)benzyl)ethylene oxide is 1:1-1.6.

[0042] Preferably, the reagent used to adjust the pH is a hydrochloric acid solution, which consists of hydrochloric acid and water, and the usage ratio of hydrochloric acid to water is 1g:20-30ml.

[0043] More preferably, in the preparation of the composite sulfur positive electrode, in addition to using xylan derivatives, polydimethylsiloxane-polyethylene glycol can also be used. The combined use of polydimethylsiloxane-polyethylene glycol can further improve the performance of the xylan derivative, thereby further effectively reducing the electrochemical impedance of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode, and improving the discharge capacity and cycle performance.

[0044] Preferably, the mass ratio of the xylan derivative to the polydimethylsiloxane-polyethylene glycol is 1:0.02-0.12.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention provides a preparation method of a composite sulfur positive electrode and its application in an all-solid-state battery. The composite sulfur positive electrode comprises: a sulfur / carbon composite material, a functional glassy sulfide electrolyte, a conductive agent and a binder. Functional glassy sulfide electrolytes have the advantages of no grain boundaries, high density after cold pressing into sheets, and good mechanical properties. Using functional glassy sulfide electrolytes as positive electrode fillers suppresses structural collapse caused by uneven stress distribution within the composite sulfur positive electrode during charge and discharge, ensures close contact between the various phases within the composite sulfur positive electrode, and improves battery cycle stability. Through doping modification, the functional glassy sulfide electrolyte has both high ionic and electronic conductivity. At the same time, the metal cations doped in the functional glassy sulfide electrolyte can act as solid-phase sulfur catalytic sites, significantly reducing the solid-phase conversion energy barrier of the active substance sulfur, promoting the positive electrode reaction kinetics, thereby reducing battery polarization and improving the utilization rate of the active substance, thereby improving the battery capacity and rate performance. The functional glassy sulfide electrolyte proposed in the present invention has excellent redox reversibility, can provide stable additional capacity during charge and discharge, reduce the additional use of inactive components, and further improve the energy density of the battery system. The solid-state lithium-sulfur battery using the composite sulfur positive electrode developed by the present invention has the characteristics of excellent cycle performance, high charge and discharge specific capacity, good safety, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0048] Figure 1 This is the SEM image of the functional glassy sulfide electrolyte;

[0049] Figure 2This is the SEM image of the composite sulfur cathode powder;

[0050] Figure 3 This is the SEM image of the composite sulfur positive electrode;

[0051] Figure 4 This is a graph showing the charge and discharge measurement results of an all-solid-state lithium-sulfur battery made with a composite sulfur positive electrode according to Example 1;

[0052] Figure 5 This is a graph showing the charge and discharge test results of the all-solid-state lithium-sulfur battery made with the composite sulfur positive electrode of Comparative Example 3. DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] The following first describes the concepts involved in this application with reference to the accompanying drawings. It should be noted that the following description of each concept is intended only to make the content of this application easier to understand and does not limit the scope of protection of this application. At the same time, the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The following detailed description of this application will be made with reference to the accompanying drawings and in conjunction with the embodiments.

[0055] Example 1:

[0056] Preparation of the sulfur / carbon composite: Elemental sulfur and carbon nanotubes were mixed and ground at 25°C for 0.5 h to obtain a mixture. The mixture was then heated to 155°C under vacuum and held for 12 h to obtain the sulfur / carbon composite. The mass ratio of sulfur to carbon nanotubes was 1:0.43.

[0057] Preparation of a functional glassy sulfide electrolyte: Lithium sulfide, phosphorus pentasulfide, lithium iodide, and titanium disulfide were mixed and ball-milled at 550 rpm and 25°C for 20 h to produce Li3PS4-LiI-TiS2, the functional glassy sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide was 1:1.61, the mass ratio of lithium sulfide to lithium iodide was 1:1.93, and the mass ratio of lithium sulfide to titanium disulfide was 1:0.32.

[0058] Preparation of the composite sulfur cathode: A sulfur / carbon composite, a functional glassy sulfide electrolyte, and carbon nanotubes were mixed and ball-milled at 500 rpm and 25°C for 6 hours to produce composite sulfur cathode powder. The composite sulfur cathode powder was then mixed with polytetrafluoroethylene (PTFE) and ground at 25°C for 15 minutes, followed by roller pressing five times to produce the composite sulfur cathode. The mass ratio of the sulfur / carbon composite to the functional glassy sulfide electrolyte was 1:1, the mass ratio of the sulfur / carbon composite to the carbon nanotubes was 1:0.022, and the mass ratio of the composite sulfur cathode powder to the PTFE was 1:0.01.

[0059] Example 2:

[0060] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0061] Preparation of a functional glassy sulfide electrolyte: Lithium sulfide, phosphorus pentasulfide, lithium iodide, and tin disulfide were mixed and ball-milled at 550 rpm and 25°C for 20 h to produce Li3PS4-LiI-SnS2, the functional glassy sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide was 1:1.61, the mass ratio of lithium sulfide to lithium iodide was 1:1.93, and the mass ratio of lithium sulfide to tin disulfide was 1:0.52.

[0062] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this embodiment is different from that in Example 1, except that the functional glassy sulfide electrolyte used is the functional glassy sulfide electrolyte prepared in this embodiment, and the other conditions and parameters are the same as in Example 1.

[0063] Example 3:

[0064] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0065] Preparation of a functional glassy sulfide electrolyte: Lithium sulfide, phosphorus pentasulfide, lithium iodide, and indium sulfide were mixed and ball-milled at 550 rpm and 25°C for 20 h to produce Li3PS4-LiI-In2S3, the functional glassy sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide was 1:1.61, the mass ratio of lithium sulfide to lithium iodide was 1:1.93, and the mass ratio of lithium sulfide to indium sulfide was 1:0.23.

[0066] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this embodiment is different from that in Example 1, except that the functional glassy sulfide electrolyte used is the functional glassy sulfide electrolyte prepared in this embodiment, and the other conditions and parameters are the same as in Example 1.

[0067] Example 4:

[0068] Preparation of xylan derivatives: Water and sodium hydroxide were added to arabinoxylan. Methyl dicocoylamine was then added at 25°C to replace the tertiary amine and 2-(3-(chloromethyl)benzyl)ethylene oxide. The mixture was stirred for 0.8 h and then heated to 65°C for 5 h. After the reaction, hydrochloric acid solution was added to adjust the pH to neutral. Ethanol was then added and the mixture was allowed to stand at 4°C for 12 h. The precipitate was filtered and Soxhlet extracted with ethanol for 48 h. Finally, it was dried and ground to obtain the xylan derivative. The mass ratio of arabinoxylan to water is 1g:80ml, the mass ratio of arabinoxylan to sodium hydroxide is 1:0.4, the mass ratio of arabinoxylan to methyl dicocoylamine instead of tertiary amine is 1:1.5, the mass ratio of methyl dicocoylamine instead of tertiary amine and 2-(3-(chloromethyl)benzyl)ethylene oxide is 1:1.2, and the hydrochloric acid solution is composed of hydrochloric acid and water, and the usage ratio of hydrochloric acid to water is 1g:27.4ml.

[0069] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0070] The preparation of the functional glassy sulfide electrolyte is the same as in Example 1.

[0071] Preparation of the composite sulfur cathode: A sulfur / carbon composite, a functional glassy sulfide electrolyte, and carbon nanotubes were mixed and ball-milled at 500 rpm and 25°C for 6 hours to produce composite sulfur cathode powder. Water was added to the xylan derivative, followed by the composite sulfur cathode powder, which was then mixed and ground at 25°C for 15 minutes. Roller-pressed five times, the resulting composite sulfur cathode was dried. The mass ratio of the sulfur / carbon composite to the functional glassy sulfide electrolyte was 1:1, the mass ratio of the sulfur / carbon composite to the carbon nanotubes was 1:0.022, the mass ratio of the xylan derivative to water was 1 g:100 ml, and the mass ratio of the composite sulfur cathode powder to the xylan derivative was 1:0.01.

[0072] Example 5:

[0073] The preparation of xylan derivatives was the same as in Example 4.

[0074] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0075] The preparation of the functional glassy sulfide electrolyte is the same as in Example 1.

[0076] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this embodiment is compared with that in Example 4, except that the mass ratio of the composite sulfur positive electrode powder and the xylan derivative is 1:0.04, and other conditions and parameters are the same as in Example 4.

[0077] Example 6:

[0078] The preparation of xylan derivatives was the same as in Example 4.

[0079] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0080] The preparation of the functional glassy sulfide electrolyte is the same as in Example 1.

[0081] Preparation of the composite sulfur cathode: A sulfur / carbon composite, a functional glassy sulfide electrolyte, and carbon nanotubes were mixed and ball-milled at 500 rpm and 25°C for 6 hours to obtain composite sulfur cathode powder. Polydimethylsiloxane-polyethylene glycol and water were added to the xylan derivative, followed by the composite sulfur cathode powder, which was then mixed and ground at 25°C for 15 minutes. The mixture was roller-pressed five times and finally dried to obtain the composite sulfur cathode. The mass ratio of the sulfur / carbon composite to the functional glassy sulfide electrolyte was 1:1, the mass ratio of the sulfur / carbon composite to the carbon nanotubes was 1:0.022, the mass ratio of the xylan derivative to the polydimethylsiloxane-polyethylene glycol was 1:0.03, the mass ratio of the xylan derivative to water was 1 g:100 ml, and the mass ratio of the composite sulfur cathode powder to the xylan derivative was 1:0.01.

[0082] Example 7:

[0083] The preparation of xylan derivatives was the same as in Example 4.

[0084] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0085] The preparation of the functional glassy sulfide electrolyte is the same as in Example 1.

[0086] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this embodiment is compared with that in Example 6, except that the mass ratio of the amount of xylan derivative and polydimethylsiloxane-polyethylene glycol used is 1:0.08, and other conditions and parameters are the same as in Example 6.

[0087] Comparative Example 1:

[0088] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0089] Preparation of a functional glassy sulfide electrolyte: Lithium sulfide, phosphorus pentasulfide, and lithium iodide were mixed and ball-milled at 550 rpm and 25°C for 20 h to produce Li3PS4-LiI, the functional glassy sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide was 1:1.61, and the mass ratio of lithium sulfide to lithium iodide was 1:1.93.

[0090] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this comparative example is compared with that in Example 1, except that the functional glassy sulfide electrolyte used is the functional glassy sulfide electrolyte prepared in this comparative example, and the other conditions and parameters are the same as in Example 1.

[0091] Comparative Example 2:

[0092] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0093] Preparation of a functional glassy sulfide electrolyte: Lithium sulfide and phosphorus pentasulfide were mixed and ball-milled at 550 rpm and 25°C for 20 h to produce Li3PS4, the functional glassy sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide was 1:1.61.

[0094] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this comparative example is compared with that in Example 1, except that the functional glassy sulfide electrolyte used is the functional glassy sulfide electrolyte prepared in this example, and the other conditions and parameters are the same as in Example 1.

[0095] Comparative Example 3:

[0096] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0097] Preparation of sulfide electrolyte: Lithium sulfide, phosphorus pentasulfide and lithium chloride were mixed and ball milled at 550 rpm and 25 °C for 20 h to obtain Li 5.5 PS 4.5 Cl 1.5 , that is, sulfide electrolyte. The mass ratio of lithium sulfide to phosphorus pentasulfide is 1:1.21, and the mass ratio of lithium sulfide to lithium chloride is 1:0.7.

[0098] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this comparative example is compared with that in Example 1, except that the functional glassy sulfide electrolyte is replaced by a sulfide electrolyte, and the other conditions and parameters are the same as in Example 1.

[0099] Comparative Example 4:

[0100] The preparation of xylan derivatives was the same as in Example 4.

[0101] The preparation of the sulfur / carbon composite material is the same as in Example 1.

[0102] The preparation of the functional glassy sulfide electrolyte is the same as in Example 1.

[0103] Preparation of composite sulfur positive electrode: The preparation of the composite sulfur positive electrode in this comparative example is compared with that in Example 4, except that the mass ratio of the composite sulfur positive electrode powder and the xylan derivative used is 1:0.002, and other conditions and parameters are the same as in Example 4.

[0104] Experimental Example 1:

[0105] The functional glassy sulfide electrolyte, composite sulfur cathode powder and composite sulfur cathode prepared in Example 1 were subjected to scanning electron microscopy (SEM) testing. The SEM image of the functional glassy sulfide electrolyte is shown in FIG. Figure 1 As shown, the particle size range of the functional glassy sulfide electrolyte is 1-3 μm; the SEM image of the composite sulfur cathode powder is as follows Figure 2 As shown, the particle size range of the composite sulfur cathode powder is 2-5 μm; the SEM image of the composite sulfur cathode is as shown Figure 3 As shown, the thickness of the composite sulfur cathode is 40-50 μm.

[0106] Experimental Example 2:

[0107] The electrochemical impedance spectroscopy (EIS) was performed under argon conditions by assembling the cathode shell, composite sulfur cathode, electrolyte film, lithium sheet, gasket, spring, and anode shell in this order, pressing and sealing, to obtain an all-solid-state lithium-sulfur battery. The electrochemical impedance spectroscopy (EIS) was measured using a Blue Electric Battery Testing System and an electrochemical workstation. The composite sulfur cathode was prepared using the composite sulfur cathodes described in Examples 1-7 and Comparative Examples 1-4. The electrolyte film was prepared by mixing, grinding, and shearing a sulfide solid electrolyte and polytetrafluoroethylene (PTFE). The mass ratio of the sulfide solid electrolyte to the PTFE was 1:0.01.

[0108] Table 1 Results of electrochemical impedance spectroscopy

[0109]

[0110] The electrochemical impedance measurement results of the all-solid-state lithium-sulfur batteries prepared by the composite sulfur positive electrodes prepared in Examples 1-7 and Comparative Examples 1-4 are shown in Table 1. Compared with Comparative Examples 1-2, Example 1-3 shows that the composite sulfur positive electrode prepared by doping with titanium disulfide, tin disulfide and indium sulfide has a better effect, that is, the electrochemical impedance of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode of Examples 1-3 is lower, and the dynamics of lithium ions at the electrode interface is better; Compared with Comparative Example 3, Example 1 shows that the composite sulfur positive electrode made of functional glassy sulfide electrolyte can reduce the electrochemical impedance of the all-solid-state lithium-sulfur battery prepared; Compared with Example 4, Example 1 shows that the use of xylan derivatives can effectively reduce the electrochemical impedance of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode; Compared with Example 5, Example 4 shows that increasing the amount of xylan derivatives used within a certain range can reduce The electrochemical impedance of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode; Example 4 is compared with Example 6, which shows that on the basis of using the xylan derivative, the use of polydimethylsiloxane-polyethylene glycol can further reduce the electrochemical impedance of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode; Example 6 is compared with Example 7, which shows that increasing the usage of polydimethylsiloxane-polyethylene glycol within a certain range can reduce the electrochemical impedance of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode; Example 4 is compared with Comparative Example 4, which shows that the usage of the xylan derivative needs to be within a certain range. Too low an amount has no obvious effect on reducing the electrochemical impedance of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode.

[0111] Experimental Example 3:

[0112] To measure the constant current discharge capacity, under argon, the positive electrode shell, composite sulfur positive electrode, electrolyte film, lithium sheet, gasket, spring, and negative electrode shell were assembled in this order and sealed tightly to produce an all-solid-state lithium-sulfur battery. The constant current discharge capacity of the all-solid-state lithium-sulfur battery was measured using a Blue Electric Battery Testing System and an electrochemical workstation at a current density of 0.1C. The test cycles were the first and 200 cycles. The composite sulfur positive electrodes were those prepared in Examples 1-7 and Comparative Examples 1-4.

[0113] Table 2 0.1C discharge capacity measurement results

[0114]

[0115] The discharge capacity of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode prepared in Examples 1-7 and Comparative Examples 1-4 at 0.1C is shown in Table 2. Compared with Comparative Examples 1-2, Examples 1-3 show that the composite sulfur positive electrode prepared by doping with titanium disulfide, tin disulfide and indium sulfide has better effect, that is, the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode of Examples 1-3 exhibits a larger discharge capacity; Compared with Comparative Example 3, Example 1 shows that the composite sulfur positive electrode made of functional glassy sulfide electrolyte can improve the discharge capacity of the prepared all-solid-state lithium-sulfur battery; Compared with Example 4, Example 1 shows that the use of xylan derivatives can effectively improve the discharge capacity of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode; Compared with Example 5, Example 4 shows that increasing the amount of xylan derivatives used within a certain range can improve the discharge capacity of the prepared The discharge capacity of the all-solid-state lithium-sulfur battery made of the composite sulfur positive electrode is improved; compared with Example 6, Example 4 shows that on the basis of using the xylan derivative, the use of polydimethylsiloxane-polyethylene glycol can further improve the discharge capacity of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode; compared with Example 7, Example 6 shows that increasing the amount of polydimethylsiloxane-polyethylene glycol within a certain range can improve the discharge capacity of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode; compared with Comparative Example 4, Example 4 shows that the amount of xylan derivative used needs to be within a certain range. Too low an amount has no obvious effect on improving the discharge capacity of the all-solid-state lithium-sulfur battery made of the prepared composite sulfur positive electrode.

[0116] Experimental Example 4:

[0117] The constant current discharge capacity was measured in this experimental example. The difference between the measurement method in this experimental example and that in Experimental Example 2 was that the current density was 0.5C. Other conditions and parameters were the same as those in Experimental Example 2.

[0118] Table 3 0.5C discharge capacity measurement results

[0119]

[0120] The discharge capacity of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode prepared in Examples 1-7 and Comparative Examples 1-4 is measured at 0.5C as shown in Table 3. Compared with Comparative Examples 1-2, Examples 1-3 show that the composite sulfur positive electrode prepared by doping with titanium disulfide, tin disulfide and indium sulfide has better effect, that is, the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode of Examples 1-3 exhibits a larger discharge capacity; Compared with Comparative Example 3, Example 1 shows that the composite sulfur positive electrode made of functional glassy sulfide electrolyte can improve the discharge capacity of the prepared all-solid-state lithium-sulfur battery; Compared with Example 4, Example 1 shows that the use of xylan derivatives can effectively improve the discharge capacity of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode; Compared with Example 5, Example 4 shows that increasing the amount of xylan derivatives used within a certain range can improve the discharge capacity of the prepared The discharge capacity of an all-solid-state lithium-sulfur battery using a composite sulfur cathode is shown in Figure 4. Comparison between Example 4 and Example 6 demonstrates that the use of polydimethylsiloxane-polyethylene glycol, in addition to a xylan derivative, can further improve the discharge capacity of an all-solid-state lithium-sulfur battery using a composite sulfur cathode. Comparison between Example 6 and Example 7 demonstrates that increasing the amount of polydimethylsiloxane-polyethylene glycol within a certain range can improve the discharge capacity of an all-solid-state lithium-sulfur battery using a composite sulfur cathode. Comparison between Example 4 and Comparative Example 4 demonstrates that the amount of xylan derivative used must be within a certain range; a lower amount has no significant effect on improving the discharge capacity of an all-solid-state lithium-sulfur battery using a composite sulfur cathode. The discharge capacity measurements at 0.5C show the same trend as those at 0.1C.

[0121] Experimental Example 5:

[0122] The composite sulfur positive electrode was made into an all-solid-state lithium-sulfur battery for constant current charge and discharge test. The measurement method was the same as that of Experimental Example 3, wherein the composite sulfur positive electrode was the composite sulfur positive electrode prepared in Example 1 and Comparative Example 3. The charge and discharge measurement results of the all-solid-state lithium-sulfur battery prepared by the composite sulfur positive electrode prepared in Example 1 are shown in FIG. Figure 4 As shown in Figure 2, additional redox platforms appeared at 2.87V and 2.51V, indicating that the introduction of the functional glassy sulfide electrolyte changes the electrochemical path of the composite sulfur cathode, has excellent redox reversibility, and improves the cathode capacity. The charge and discharge test results of the composite sulfur cathode prepared in Example 3 are shown in Figure 2. Figure 5 As shown in the graph, compared with Example 1, the charge and discharge reversible capacity is lower, indicating that the introduction of the functional glassy sulfide electrolyte can indeed significantly improve the electrochemical kinetics of the composite sulfur positive electrode, reduce the sulfur solid-phase conversion energy barrier, and reduce battery polarization.

[0123] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and do not impose any form of limitation on the implementation methods of the technology of the present invention. Any person skilled in the art may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0124] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can also make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A method for preparing a composite sulfur cathode, comprising: S1: The sulfur material and the conductive agent are mixed and ground, and then heated and kept warm under vacuum conditions to obtain a sulfur / carbon composite material; S2: mixing a base material and a doping sulfur material, followed by ball milling to obtain a functional glassy sulfide electrolyte; the base material is lithium sulfide, phosphorus pentasulfide, and lithium iodide; the doping sulfur material is at least one of titanium disulfide, tin disulfide, indium sulfide, ferrous sulfide, silicon sulfide, and copper sulfide; S3: A sulfur / carbon composite material, a functional glassy sulfide electrolyte and a conductive agent are mixed, and then subjected to ball milling reaction to obtain a composite sulfur positive electrode powder. The composite sulfur positive electrode powder is then mixed with a binder, ground and rolled to obtain a composite sulfur positive electrode; the mass ratio of the composite sulfur positive electrode powder to the binder is 1:0.008-0.06; the mass ratio of the sulfur / carbon composite material to the functional glassy sulfide electrolyte is 1:0.8-1.3, and the mass ratio of the sulfur / carbon composite material to the conductive agent is 1:0.01-0.04; the binder is a xylan derivative; the xylan derivative is prepared from arabinoxylan, methyl dicocoylamine and 2-(3-(chloromethyl)benzyl)ethylene oxide.

2. The method for preparing a composite sulfur cathode according to claim 1, wherein: The sulfur material in S1 is elemental sulfur; the conductive agent is at least one of carbon nanotubes, carbon fibers, Super P and acetylene black; and the mass ratio of the sulfur material to the conductive agent is 1:0.2-0.

8.

3. The method for preparing a composite sulfur cathode according to claim 1, wherein: The mass ratio of lithium sulfide to phosphorus pentasulfide in S2 is 1:1.3-2, and the mass ratio of lithium sulfide to lithium iodide is 1:1.6-2.

3.

4. The method for preparing a composite sulfur cathode according to claim 1 or 3, characterized in that: The mass ratio of the lithium sulfide and the doping sulfur material in the base material of S2 is 1:0.2-0.

6.

5. The method for preparing a composite sulfur positive electrode according to claim 1, characterized in that: In the step S1, the mixing and grinding temperature is 20-30° C., and the grinding time is 0.3-1 h; the heating temperature is 150-160° C., and the holding time is 4-24 h.

6. The method for preparing a composite sulfur cathode according to claim 1, characterized in that: The ball milling reaction speed in S2 is 400-800 rpm, the reaction temperature is 20-30° C., and the reaction time is 10-22 h.

7. The method for preparing a composite sulfur cathode according to claim 1, characterized in that: In the S3, the ball milling reaction speed is 300-600 rpm, the reaction temperature is 20-30° C., and the reaction time is 5-10 h; the composite sulfur cathode powder and the binder are mixed and ground at a temperature of 20-30° C., the grinding time is 10-25 min, and the number of roller pressings is 3-6 times.

8. An all-solid-state battery comprising a composite sulfur cathode prepared by the method according to any one of claims 1 to 7.

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