Sulfur positive electrode composite material and preparation method, and full solid-state lithium-sulfur battery and preparation method

Abstract

The application discloses a sulfur positive electrode composite material and a preparation method thereof, a full-solid-state lithium-sulfur battery and a preparation method thereof, and the preparation method of the sulfur positive electrode composite material is as follows: carbon nanotubes, a surfactant, a binder and a solvent are mixed to form a slurry, then the slurry is coated on a copper foil, and then drying, peeling and winding are carried out to obtain a macroporosity carbon nanotube paper; the carbon nanotube paper is cut to a certain size and rolled into a paper tube, and then the paper tube is packaged into a quartz tube preloaded with sulfur powder, vacuumizing is carried out, and then heating and heat preservation are carried out for a period of time, and then natural cooling is carried out to room temperature to obtain a sulfur positive electrode composite material containing stable gamma-S; the sulfur positive electrode composite material is combined with a solid electrolyte to prepare a sulfur positive electrode sheet with a structure of solid electrolyte / sulfur positive electrode (containing solid electrolyte) / aluminum foil net / sulfur positive electrode (containing solid electrolyte) / solid electrolyte; and the lithium is used as a negative electrode, and the sulfur positive electrode sheet is used as a positive electrode to assemble a battery. The full-solid-state lithium-sulfur battery prepared by using the sulfur positive electrode composite material containing stable gamma-S has good cycle performance and good rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, specifically relating to a sulfur cathode composite material containing stable γ-S and its preparation method, and an all-solid-state lithium-sulfur battery and its preparation method. Background Technology

[0002] Elemental sulfur possesses a high theoretical specific capacity (1675 mAh / g) when used as the cathode in secondary lithium-sulfur batteries. Furthermore, sulfur is inexpensive, abundant, and environmentally friendly, making it considered one of the most promising cathode materials for next-generation high-energy-density chemical power sources. However, the poor conductivity of elemental sulfur and its volume expansion during charging and discharging, along with the dissolution and diffusion of polysulfide ions generated during discharge, limit the further development and application of lithium-sulfur batteries.

[0003] The present invention is made to address the aforementioned problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention proposes a sulfur cathode composite material containing stable γ-S and its preparation method, as well as an all-solid-state lithium-sulfur battery and its preparation method. Using high-porosity carbon nanotube paper as a substrate, this invention successfully prepares a sulfur cathode composite material containing stable γ-S. This composite material is then combined with a solid electrolyte to prepare a sulfur cathode sheet with a structure of solid electrolyte / sulfur cathode (containing solid electrolyte) / aluminum foil / sulfur cathode (containing solid electrolyte) / solid electrolyte. Using lithium as the negative electrode and the sulfur cathode sheet as the positive electrode, the battery is assembled, resulting in an all-solid-state lithium-sulfur battery with good cycle performance and excellent rate capability.

[0005] The technical solution of this invention is as follows:

[0006] This invention provides a method for preparing a sulfur cathode composite material containing stable γ-S, comprising the following steps:

[0007] S1. Carbon nanotubes, surfactants, and binders are mixed with solvent in a certain proportion to form a slurry, which is then coated onto copper foil, dried, peeled off, and wound up to obtain carbon nanotube paper with high porosity.

[0008] S2. Cut the carbon nanotube paper obtained in step S1 to a certain size and roll it into a paper tube and seal it in a quartz tube pre-filled with sulfur powder. After vacuuming, heat it to 180-200℃ and keep it at that temperature for 12-24 hours. Let it cool naturally to room temperature to obtain a sulfur cathode composite material containing stable γ-S.

[0009] Preferably, in step S1, the mass ratio of carbon nanotubes, surfactants and binders is (85-95):(0.5-2.5):(4.5-12.5); and in step S2, the mass ratio of sulfur powder added to carbon nanotubes contained in the carbon nanotube paper packed into the quartz tube is (3-5.5):(1.5-3).

[0010] Preferably, the solvent is one of water and alcohol, or a mixture of both;

[0011] The surfactant is polyethylene glycol, and the molecular weight of polyethylene glycol is 400 to 10,000.

[0012] The binder is PVPk30, PVA1750, or highly substituted hydroxypropyl cellulose (H-HPC).

[0013] The present invention also provides a sulfur cathode composite material containing stable γ-S, which is prepared by the above-described preparation method.

[0014] This invention also provides an all-solid-state lithium-sulfur battery, comprising a lithium anode and a sulfur cathode. The sulfur cathode contains a sulfur cathode composite material with stable γ-S, and carbon nanotube paper serves as the cathode framework, providing a good internal conductive network for the sulfur cathode. The carbon nanotubes can effectively lock the γ-S phase, ensuring its stable existence. During charging and discharging, γ-S can reversibly convert monoclinic sulfur into Li2S without forming intermediate polysulfides. The porous structure of the carbon nanotube paper can also effectively alleviate the volume expansion problem of the sulfur cathode during battery charging and discharging, thereby improving the cycle stability of the battery.

[0015] Preferably, the sulfur cathode sheet is composed of a first solid electrolyte layer, a first sulfur cathode, an aluminum foil mesh, a second sulfur cathode, and a second solid electrolyte layer arranged sequentially, wherein the first sulfur cathode and the second sulfur cathode both include a sulfur cathode composite material containing stable γ-S.

[0016] The aluminum foil mesh is a microporous aluminum foil mesh with a pore size of 20–50 μm.

[0017] Preferably, the first solid electrolyte layer and the second solid electrolyte layer are made of the same material, both including a superion conductor solid electrolyte, a solid polymer electrolyte framework material and a solid lithium salt, and the superion conductor solid electrolyte, the solid polymer electrolyte framework material and the solid lithium salt together constitute a mixed solid polymer electrolyte.

[0018] The superionic conductor solid electrolyte is Li 10 GeP2S 12 (Abbreviated as LGPS), the solid polymer electrolyte framework material is polyethylene oxide (PEO), and the solid lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0019] The mass ratio of the solid polymer electrolyte contained in the sulfur cathode sheet to the mass ratio of the carbon nanotubes contained in the sulfur cathode sheet is (0.5-3):(1.5:3).

[0020] Li 10 GeP2S 12 The total mass accounts for 1-5% of the total mass of the mixed solid polymer electrolyte; the molar ratio of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide is 18:1.

[0021] Preferably, the number of sulfur positive electrode sheets and the number of lithium negative electrode sheets are both at least one, the sulfur positive electrode sheets and the lithium negative electrode sheets correspond one-to-one, the sulfur positive electrode sheets and the lithium negative electrode sheets are arranged alternately in sequence, one sulfur positive electrode sheet and the corresponding lithium negative electrode sheet form a combination, and two or more combinations are connected in parallel or in series.

[0022] The present invention also provides a method for preparing the above-mentioned all-solid-state lithium-sulfur battery, comprising the following steps:

[0023] A1. In an argon-filled glove box, a certain proportion of PEO and LiTFSI are dissolved in anhydrous acetonitrile. A certain amount of LGPS is added under vigorous stirring, and stirring is continued to form a homogeneous solution. The homogeneous solution is cast into a polytetrafluoroethylene mold, which is pre-filled with sequentially arranged sulfur cathode composite material containing stable γ-S / aluminum foil mesh / sulfur cathode composite material containing stable γ-S. Then, it is transferred to a vacuum bag-autoclave to form a composite, thus obtaining a sulfur cathode sheet.

[0024] A2. Using lithium foil as the negative electrode and the sulfur positive electrode as described above, an all-solid-state lithium-sulfur battery is assembled.

[0025] Preferably, the vacuum bag-autoclave forming process parameters are: working temperature 40-50℃; working pressure 0.3-1.6MPa; working time 8-12h; dynamic vacuuming.

[0026] The beneficial effects of this invention are:

[0027] 1) This invention uses special process conditions to successfully prepare a sulfur cathode composite material containing stable γ-S. This γ-S is different from typical orthorhombic α-phase sulfur. Its redox mechanism has changed. During the charging and discharging process, monoclinic sulfur can be reversibly converted into Li2S without forming intermediate polysulfides, thus avoiding the dissolution and shuttle effect of polysulfides.

[0028] 2) The sulfur cathode composite material containing stable γ-S uses carbon nanotube paper with large porosity as the substrate. The carbon nanotube paper serves as the cathode framework, providing a good internal conductive network for the sulfur cathode. The carbon nanotubes can effectively lock the γ-S phase, making it stable. The porous structure of the carbon nanotube paper can also effectively alleviate the volume expansion problem of the sulfur cathode during battery charging and discharging, thereby improving the cycle stability of the battery.

[0029] 3) The preparation method of sulfur cathode composite material containing stable γ-S is simple, and the assembled all-solid-state lithium-sulfur battery has good cycle performance and good rate performance. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the cross-section of a polytetrafluoroethylene (PTFE) mold.

[0031] Figure 2a This is a schematic diagram of an all-solid-state lithium-sulfur battery using a series-connected assembly, as shown in Example 1.

[0032] Figure 2b This is a schematic diagram of an all-solid-state lithium-sulfur battery using a combination of parallel components, as shown in Example 1.

[0033] Figure 3 The charge-discharge cycle curve of the all-solid-state lithium-sulfur battery prepared in Example 2 at 0.05C under 60°C conditions is shown.

[0034] Figure 4 The all-solid-state lithium-sulfur battery prepared in Example 3 is shown in charge-discharge curves at different rates under 60°C.

[0035] Figure 5 The all-solid-state lithium-sulfur battery prepared in Example 3 is shown in the long-cycle charge-discharge curve at 1.0C high rate under 60°C conditions.

[0036] Figure 1 In the middle: 1-0 is a polytetrafluoroethylene mold; 1-1 to 1-5 are polytetrafluoroethylene gaskets (the thickness of the solid electrolyte can be controlled by changing the height of the gaskets); 1-6 is the solid electrolyte; 1-7 is a sulfur cathode composite material (containing solid electrolyte); 1-8 is an aluminum foil mesh.

[0037] In Figure 2: 2-1 is the lithium anode sheet; 2-2 is the first solid electrolyte layer; 2-3 is the first sulfur cathode; 2-4 is the aluminum foil mesh; 2-5 is the second sulfur cathode; 2-6 is the second solid electrolyte layer (2-2, 2-3, 2-4, 2-5 and 2-6 constitute the sulfur cathode sheet). Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] This invention relates to a method for preparing a sulfur cathode composite material containing stable γ-S, and a method for preparing a sulfur cathode sheet and an all-solid-state lithium-sulfur battery based on this sulfur cathode composite material, comprising the following steps:

[0040] Step 1: Preparation of sulfur cathode composite material containing stable γ-S

[0041] Using water and / or alcohol as solvents, carbon nanotubes, surfactants and binders are mixed with the solvent in a mass ratio of (85-95):(0.5-2.5):(4.5-12.5) to form a slurry, which is then coated onto copper foil, dried, peeled off and wound up to obtain high-porosity carbon nanotube paper.

[0042] The obtained carbon nanotube paper is cut to a suitable size and rolled into a paper tube and sealed into a quartz tube pre-filled with sulfur powder. The mass ratio of the added sulfur powder to the carbon nanotube paper in the quartz tube is (3-5.5):(1.5-3). After vacuuming, it is heated to 180-200℃ and kept at this temperature for 12-24 hours. After naturally cooling to room temperature, a sulfur cathode composite material containing stable γ-S is obtained.

[0043] Step 2: Preparation of sulfur cathode sheet

[0044] In an argon-filled glove box, a certain proportion of PEO (molecular weight 600,000) and LiTFSI were mixed and then added to anhydrous acetonitrile. The mixture was stirred until completely dissolved. Under vigorous stirring, 1–5% (by weight of the total weight of the mixed solid polymer electrolyte) of Li was added. 10 GeP2S 12 (LGPS) was stirred for 24 hours to form a homogeneous solution. The homogeneous solution was then cast into a polytetrafluoroethylene (PTFE) mold. The PTFE mold was pre-filled with sequentially arranged sulfur cathode composite material containing stable γ-S / microporous aluminum foil mesh / sulfur cathode composite material containing stable γ-S. The mixture was then placed in a vacuum bag and transferred to an autoclave for molding. The vacuum bag-autoclave molding process parameters were: working temperature 40-50℃; working pressure 0.3-1.6MPa; working time 8-12 hours; dynamic vacuuming was used to obtain a sulfur cathode sheet with the structure of solid electrolyte / sulfur cathode (containing solid electrolyte) / aluminum foil mesh / sulfur cathode (containing solid electrolyte) / solid electrolyte. The corresponding structures were named sequentially as the first solid electrolyte layer, the first sulfur cathode, the aluminum foil mesh, the second sulfur cathode, and the second solid electrolyte layer.

[0045] Step 3: Assembly of the all-solid-state lithium-sulfur battery

[0046] Using lithium foil as the negative electrode and the aforementioned sulfur positive electrode, an all-solid-state lithium-sulfur battery is assembled. The number of sulfur positive electrodes and lithium negative electrodes is at least one, with a one-to-one correspondence between them. The sulfur positive electrodes and lithium negative electrodes are arranged alternately, with one sulfur positive electrode and its corresponding lithium negative electrode forming a unit. When there are two or more units, they are connected in parallel or series.

[0047] Example 1

[0048] Step 1: Preparation of sulfur cathode composite material containing stable γ-S

[0049] CNTs, PEG1000, and PVPk30 were weighed according to a mass ratio of carbon nanotubes:surfactant:binder = 85:2.5:12.5. PEG and PVPk30 were dissolved in appropriate amounts of 1:1 (v:v) alcohol aqueous solution to prepare 0.5wt% PEG solution and 10wt% PVP solution, respectively. While stirring, CNTs were added to the PEG solution in small amounts several times. After continuous stirring and ultrasonic dispersion, a PVP solution equivalent to 1 / 20 volume of the ultrasonically dispersed carbon nanotube slurry was added. Stirring was continued to prepare a uniform slurry, which was then coated onto copper foil, dried, peeled off, and wound to obtain high-porosity carbon nanotube paper. The resulting carbon nanotube paper was 50 μm thick and had an areal density of 13.3 g / m³. 2 Porosity 86.7%;

[0050] Carbon nanotube paper was cut to a size of 1m*1m and rolled into a paper tube and sealed into a quartz tube pre-filled with 20g of sulfur powder. After vacuuming, it was heated to 190℃ and kept at this temperature for 20h. It was then naturally cooled to room temperature to obtain a sulfur cathode composite material containing stable γ-S.

[0051] Step 2: Preparation of sulfur cathode sheet

[0052] In an argon-filled glove box, PEO (molecular weight 600,000) and LiTFSI were mixed and dissolved in anhydrous acetonitrile at a molar ratio of 18:1 (PEO to anhydrous acetonitrile molar ratio 1:8). Under vigorous stirring, 1% (LiGPS, Li...) of the total weight of the mixed solid polymer electrolyte (i.e., the total mass of LGPS, PEO, and LiTFSI) was added. 10 GeP2S 12 Continue stirring for 24 hours to form a homogeneous solution; then cast the homogeneous solution into a polytetrafluoroethylene mold (e.g., Figure 1As shown, a polytetrafluoroethylene mold pre-places a series of sequentially arranged sulfur cathode composite material containing stable γ-S / microporous aluminum foil mesh / sulfur cathode composite material containing stable γ-S. These are then placed in a vacuum bag and transferred to an autoclave for molding. The vacuum bag-autoclave molding process parameters are set as follows: working temperature 45℃; working pressure 0.5MPa; working time 12h; dynamic vacuuming. This produces a sulfur cathode sheet with a structure of solid electrolyte / sulfur cathode (containing solid electrolyte) / aluminum foil mesh / sulfur cathode (containing solid electrolyte) / solid electrolyte. The corresponding structures are named sequentially: first solid electrolyte layer, first sulfur cathode, aluminum foil mesh, second sulfur cathode, and second solid electrolyte layer.

[0053] Step 3: Assembly of the all-solid-state lithium-sulfur battery

[0054] Using lithium foil as the negative electrode and the aforementioned sulfur positive electrode, the number of sulfur positive electrode and the number of lithium negative electrode are both at least one. The sulfur positive electrode and the lithium negative electrode are in one-to-one correspondence. Alternatively, the sulfur positive electrode and the lithium negative electrode can be arranged alternately in sequence, that is, the battery is assembled by stacking multiple layers of sulfur positive electrode, lithium negative electrode, sulfur positive electrode, lithium negative electrode, etc., to obtain an all-solid-state lithium-sulfur battery.

[0055] A sulfur positive electrode and a corresponding lithium negative electrode form an assembly. These assemblies are connected in parallel or series. Inside the cell, a high-voltage, all-solid-state lithium-sulfur battery cell is formed through series connection. Figure 2a As shown; high-capacity all-solid-state lithium-sulfur battery cells are obtained by connecting them in parallel inside the cell, such as... Figure 2b As shown.

[0056] Example 2

[0057] Step 1: Preparation of sulfur cathode composite material containing stable γ-S

[0058] CNTs, PEG600, and PVA1750 were weighed according to a mass ratio of carbon nanotubes:surfactant:binder = 90:2:8. PEG and PVA were dissolved in appropriate amounts of water to prepare 0.5wt% PEG solutions and 5wt% PVA solutions, respectively. While stirring, CNTs were added to the PEG solutions in small amounts several times. After continuous stirring and ultrasonic dispersion, a PVA solution equivalent to 1 / 10 volume of the ultrasonically dispersed carbon nanotube slurry was added. Stirring was continued to prepare a uniform slurry, which was then coated onto copper foil, dried, peeled off, and wound up to obtain high-porosity carbon nanotube paper. The resulting carbon nanotube paper had a thickness of 55 μm and an areal density of 15.8 g / m³. 2 Porosity 85.6%;

[0059] Carbon nanotube paper was cut to a size of 1m*1m and rolled into a paper tube and sealed into a quartz tube pre-filled with 24g of sulfur powder. After vacuuming, it was heated to 200℃ and kept at this temperature for 20h. It was then naturally cooled to room temperature to obtain a sulfur cathode composite material containing stable γ-S.

[0060] Step 2: Preparation of sulfur cathode sheet

[0061] In an argon-filled glove box, PEO (molecular weight 600,000) and LiTFSI were mixed and dissolved in anhydrous acetonitrile at a molar ratio of 18:1 (PEO to anhydrous acetonitrile molar ratio 1:8). Under vigorous stirring, 2% (by weight of) LGPS (Li ester) of the total weight of the mixed solid polymer electrolyte (i.e., LGPS, PEO, and LiTFSI) was added. 10 GeP2S 12 Continue stirring for 24 hours to form a homogeneous solution; then cast the homogeneous solution into a polytetrafluoroethylene mold (e.g., Figure 1 As shown, a polytetrafluoroethylene mold pre-places a series of sequentially arranged sulfur cathode composite material containing stable γ-S / microporous aluminum foil mesh / sulfur cathode composite material containing stable γ-S. These are then placed in a vacuum bag and transferred to an autoclave for molding. The vacuum bag-autoclave molding process parameters are set as follows: working temperature 45℃; working pressure 0.5MPa; working time 12h; dynamic vacuuming. This produces a sulfur cathode sheet with a structure of solid electrolyte / sulfur cathode (containing solid electrolyte) / aluminum foil mesh / sulfur cathode (containing solid electrolyte) / solid electrolyte. The corresponding structures are named sequentially: first solid electrolyte layer, first sulfur cathode, aluminum foil mesh, second sulfur cathode, and second solid electrolyte layer.

[0062] Step 3: Assembly of the all-solid-state lithium-sulfur battery

[0063] Using lithium foil as the negative electrode and the aforementioned sulfur positive electrode, with one sulfur positive electrode and one lithium negative electrode, the battery is assembled to obtain an all-solid-state lithium-sulfur battery.

[0064] The electrochemical performance of the battery in this embodiment was tested at 60°C, such as... Figure 3 As shown, the battery has an initial discharge capacity of up to 2005 mAh·g at 0.05C. -1 The capacity remained stable at 1496 mAh·g after the 30th cycle. -1 .

[0065] Example 3

[0066] Step 1: Preparation of sulfur cathode composite material containing stable γ-S

[0067] CNTs, PEG600, and H-HPC (highly substituted hydroxypropyl cellulose) were weighed according to a mass ratio of carbon nanotubes:surfactant:binder = 90:2:8. PEG and H-HPC were dissolved in appropriate amounts of water to prepare 0.5 wt% PEG solution and 10 wt% H-HPC solution, respectively. While stirring, CNTs were added to the PEG solution in small amounts several times. After continuous stirring and ultrasonic dispersion, H-HPC solution equivalent to 1 / 20 volume of the ultrasonically dispersed carbon nanotube slurry was added. Stirring was continued to prepare a uniform slurry, which was then coated onto copper foil, dried, peeled off, and wound up to obtain high-porosity carbon nanotube paper. The resulting carbon nanotube paper had a thickness of 70 μm and an areal density of 24.6 g / m³. 2 Porosity 82.4%;

[0068] Carbon nanotube paper was cut to a size of 1m*1m and rolled into a paper tube and sealed into a quartz tube pre-filled with 37g of sulfur powder. After vacuuming, it was heated to 200℃ and kept at this temperature for 20h. It was then naturally cooled to room temperature to obtain a sulfur cathode composite material containing stable γ-S.

[0069] Step 2: Preparation of sulfur cathode sheet

[0070] In an argon-filled glove box, PEO (molecular weight 600,000) and LiTFSI were mixed in a molar ratio of 18:1 and dissolved in anhydrous acetonitrile (Molar ratio of PEO to anhydrous acetonitrile 1:8). Under vigorous stirring, 5% (LiGPS, Li...) of the total weight of the mixed solid polymer electrolyte (i.e., the total mass of LGPS, PEO, and LiTFSI) was added. 10 GeP2S 12 Continue stirring for 24 hours to form a homogeneous solution; then cast the homogeneous solution into a polytetrafluoroethylene mold (e.g., Figure 1 As shown, a polytetrafluoroethylene mold pre-places a series of sequentially arranged sulfur cathode composite material containing stable γ-S / microporous aluminum foil mesh / sulfur cathode composite material containing stable γ-S. These are then placed in a vacuum bag and transferred to an autoclave for molding. The vacuum bag-autoclave molding process parameters are set as follows: working temperature 50℃; working pressure 1.0MPa; working time 12h; dynamic vacuuming. This produces a sulfur cathode sheet with a structure of solid electrolyte / sulfur cathode (containing solid electrolyte) / aluminum foil mesh / sulfur cathode (containing solid electrolyte) / solid electrolyte. The corresponding structures are named sequentially: first solid electrolyte layer, first sulfur cathode, aluminum foil mesh, second sulfur cathode, and second solid electrolyte layer.

[0071] Step 3: Assembly of the all-solid-state lithium-sulfur battery

[0072] Using lithium foil as the negative electrode and the aforementioned sulfur positive electrode, with two sulfur positive electrodes and two lithium negative electrodes in each case, the sulfur positive electrodes and lithium negative electrodes are arranged alternately, i.e., by stacking multiple layers of sulfur positive electrodes, lithium negative electrodes, sulfur positive electrodes, and lithium negative electrodes in parallel to assemble the battery, thus obtaining an all-solid-state lithium-sulfur battery.

[0073] The rate performance of the battery in this embodiment was tested at 60°C, and the results are as follows: Figure 4 , Figure 5 As shown, the battery exhibits excellent rate performance, delivering 1382.9, 902.8, and 501.7 mAh·g⁻¹ at charge / discharge rates of 0.1C, 1.0C, and 2.0C, respectively. -1 The reversible capacity; in addition, under a high-rate, long-cycle charge-discharge of 1.0C, it can still maintain 829mAh·g after 750 cycles. -1 With its reversible capacity, the battery's capacity decay rate per cycle is only 0.015%, demonstrating significantly improved cycle performance compared to traditional lithium-sulfur batteries.

[0074] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a sulfur cathode composite material containing stable γ-S, characterized in that, Includes the following steps: S1. Carbon nanotubes, surfactants, and binders are mixed with solvent in a certain proportion to form a slurry, which is then coated onto copper foil, dried, peeled off, and wound up to obtain carbon nanotube paper with high porosity. The solvent is one of water and alcohol, or a mixture of both. The surfactant is polyethylene glycol; The binder is PVPk30, PVA1750 or highly substituted hydroxypropyl cellulose; S2. Cut the carbon nanotube paper obtained in step S1 to a certain size and roll it into a paper tube and seal it in a quartz tube pre-filled with sulfur powder. After vacuuming, heat it to 180~200℃ and keep it at that temperature for 12~24h. Let it cool naturally to room temperature to obtain a sulfur cathode composite material containing stable γ-S.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of carbon nanotubes, surfactants and binders is (85~95):(0.5~2.5):(4.5~12.5); in step S2, the mass ratio of sulfur powder added to carbon nanotubes contained in the carbon nanotube paper packed in the quartz tube is (3~5.5):(1.5~3).

3. The preparation method according to claim 1, characterized in that, The molecular weight of polyethylene glycol is 400~10000.

4. A sulfur-containing cathode composite material containing stable γ-S, characterized in that, It is prepared by the preparation method according to any one of claims 1-3.

5. An all-solid-state lithium-sulfur battery, characterized in that, It includes a lithium anode and a sulfur cathode, wherein the sulfur cathode contains the sulfur cathode composite material containing stable γ-S as described in claim 4.

6. The all-solid-state lithium-sulfur battery according to claim 5, characterized in that, The sulfur cathode sheet is composed of a first solid electrolyte layer, a first sulfur cathode, an aluminum foil mesh, a second sulfur cathode, and a second solid electrolyte layer arranged sequentially. Both the first sulfur cathode and the second sulfur cathode include the sulfur cathode composite material containing stable γ-S as described in claim 4. The aluminum foil mesh is a microporous aluminum foil mesh with a pore size of 20~50μm.

7. The all-solid-state lithium-sulfur battery according to claim 6, characterized in that, The first solid electrolyte layer and the second solid electrolyte layer are made of the same material, both including a superion conductor solid electrolyte, a solid polymer electrolyte framework material and a solid lithium salt. The superion conductor solid electrolyte, the solid polymer electrolyte framework material and the solid lithium salt together constitute a mixed solid polymer electrolyte. The superionic conductor solid electrolyte is Li 10 GeP2S 12 The solid polymer electrolyte backbone material is polyethylene oxide, and the solid lithium salt is lithium bis(trifluoromethanesulfonyl)imide. The mass ratio of the solid polymer electrolyte contained in the sulfur cathode sheet to the mass ratio of the carbon nanotubes contained in the sulfur cathode sheet is (0.5~3): (1.5~3); Li 10 GeP2S 12 The total mass accounts for 1-5% of the total mass of the mixed solid polymer electrolyte; the molar ratio of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide is 18:

1.

8. The all-solid-state lithium-sulfur battery according to claim 6, characterized in that, The number of sulfur positive electrode plates and the number of lithium negative electrode plates are both at least one. There is a one-to-one correspondence between the sulfur positive electrode plates and the lithium negative electrode plates. The sulfur positive electrode plates and the lithium negative electrode plates are arranged alternately in sequence. One sulfur positive electrode plate and the corresponding lithium negative electrode plate form a combination. Two or more combinations are connected in parallel or in series.

9. A method for preparing an all-solid-state lithium-sulfur battery, characterized in that, The all-solid-state lithium-sulfur battery is the all-solid-state lithium-sulfur battery as described in claim 7, comprising the following steps: A1. In an argon-filled glove box, a certain proportion of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide are dissolved in anhydrous acetonitrile. A certain amount of Li is then added under vigorous stirring. 10 GeP2S 12 Continue stirring to form a homogeneous solution; cast the homogeneous solution into a polytetrafluoroethylene mold, the polytetrafluoroethylene mold being pre-filled with sequentially arranged sulfur cathode composite material containing stable γ-S / aluminum foil mesh / sulfur cathode composite material containing stable γ-S, and then transferred to a vacuum bag-autoclave to form a composite, thereby obtaining a sulfur cathode sheet. A2. Using lithium foil as the negative electrode and the sulfur positive electrode as described above, an all-solid-state lithium-sulfur battery is assembled.

10. The preparation method according to claim 9, characterized in that, The vacuum bag-autoclave forming process parameters are: working temperature 40~50℃; working pressure 0.3~1.6MPa; working time 8~12h; dynamic vacuuming.

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