Preparation method of sulfur-polyether copolymer composite positive electrode and lithium-sulfur battery

Abstract

The application discloses a preparation method of a sulfur-polyether copolymer composite positive electrode and a lithium-sulfur battery. The preparation method comprises the following steps: (1) mixing an ether monomer solution and a solvent, adding lithium salt and an initiator, stirring until clear and transparent, and obtaining a precursor solution; (2) mixing the precursor solution with sulfur powder, putting the mixture into a beating box for ball milling, and then drying to obtain a sulfur-polyether copolymer; and (3) taking the sulfur-polyether copolymer, conductive graphite, acetylene black and polyvinylidene fluoride as raw materials to prepare a positive electrode slurry; coating the positive electrode slurry on a carbon-coated aluminum foil, drying, and obtaining a sulfur-polyether copolymer composite positive electrode. In the sulfur-polyether copolymer, the surfaces of part of the sulfur powder are coated with polyether polymers, so that the ion transmission rate and the electrochemical stability of the positive electrode can be enhanced; the surfaces of the remaining part of the sulfur powder are not coated with polyether polymers, and the remaining part of the sulfur powder is exposed, so that the remaining part of the sulfur powder can be combined with conductive agents to enhance the conductivity of the positive electrode. The sulfur-polyether copolymer composite positive electrode can make the lithium-sulfur battery have excellent conductivity and chemical stability, and can greatly improve the cycle performance and the rate performance of the lithium-sulfur battery under different current densities.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a method for preparing a sulfur@polyether copolymer composite cathode and a lithium-sulfur battery. Background Technology

[0002] Due to their unique physicochemical properties, the combination of polymers with sulfur remains crucial for achieving cathode modification. Polymers typically possess abundant functional groups, which exhibit strong chemisorption of polysulfides, effectively suppressing their shuttle effect. Conductive polymers are among the most widely used polymers, and based on these advantages, their application in lithium-sulfur batteries has increased significantly in recent years. The composite forms of conductive polymers and sulfur mainly include two types: one is the formation of a "polymer-encapsulated sulfur" core-shell structure, such as composites of polythiophene (PTh) / S, polypyrrole (PPy) / S, polyvinylcarbazole (PVK) / S, polyaniline (PANi) / S, and poly(3,4-ethylenedioxythiophene) (PEDOT) / S. These composites primarily rely on the physical confinement of sulfur within the polymer shell to stabilize the cathode, exhibiting superior electrochemical performance. Another type is the core-shell structure of "S-encapsulated polymer". For example, S is composited onto the surface of a conductive polymer matrix (mainly including PPy nanowires and nanotubes, PANi nanotubes and hollow PANi spheres, etc.) by melting or chemical deposition. The polymer acts as a conductive agent, dispersant, adsorbent and buffer for volume changes in the composite material, and provides a better carrier for the deposition of S.

[0003] Although conductive polymer composite sulfur cathode materials have shown significant advantages in the modification of lithium-sulfur battery cathodes, they still face the following challenges in practical applications: (1) The conductive polymers commonly used generally have a non-localized π-electron conjugated structure, which limits their conductivity. Further enhancement of conductivity is still required through copolymerization or doping. (2) Conductive polymer materials are generally rigid, which is not conducive to electrolyte penetration and the formation of ion-conducting networks. Furthermore, their effect on suppressing electrode volume expansion is not ideal. (3) The adsorption and fixation effect on polysulfides is still relatively weak. More importantly, the insulation problem between sulfur and lithium sulfide ions cannot be solved. This defect will also greatly limit the practical application of composite materials in the modification of lithium-sulfur battery cathodes.

[0004] The purpose of this application is to develop a method for preparing a sulfur@polyether copolymer composite cathode and a lithium-sulfur battery, so as to solve some of the defects in the above-mentioned technical background. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for preparing a sulfur@polyether copolymer composite cathode and a lithium-sulfur battery. In the sulfur@polyether copolymer prepared in this application, part of the sulfur powder surface is coated with a polyether polymer, which can enhance the ion transport rate and electrochemical stability of the cathode; the remaining sulfur powder surface is not coated with a polyether polymer, and the remaining sulfur powder is exposed, which can combine with a conductive agent to enhance the conductivity of the cathode. The sulfur@polyether copolymer composite cathode of this application can enable lithium-sulfur batteries to have excellent conductivity and chemical stability, and can significantly improve the cycle performance and rate performance of lithium-sulfur batteries at different current densities.

[0006] Therefore, the present invention provides a method for preparing a sulfur@polyether copolymer composite cathode, comprising:

[0007] (1) Mix the ether monomer solution and solvent, add lithium salt and initiator, and stir until clear and transparent to obtain the precursor solution;

[0008] (2) The precursor solution and sulfur powder were mixed and placed in a pulping box for ball milling, and then dried to obtain sulfur@polyether copolymer;

[0009] (3) Using sulfur@polyether copolymer, conductive graphite, acetylene black and polyvinylidene fluoride (PVDF) as raw materials, a positive electrode slurry is prepared; the positive electrode slurry is coated on carbon-coated aluminum foil and dried to obtain a sulfur@polyether copolymer composite positive electrode.

[0010] Preferably, in step (1), the ether monomers include aziridine crosslinking agent TTMAP, 1,3-dioxolane DOL and / or glycidyl 2,2,3,3-tetrafluoropropyl ether.

[0011] Preferably, in step (1), the solvent is N-methylpyrrolidone (NMP), and the volume ratio of the ether monomer solution to the solvent is (0.5-1.5):(5-20).

[0012] Preferably, in step (1), the lithium salt includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium hexafluorophosphate (LiPF6), and the molar ratio of the ether monomer to the lithium salt is 0.9:1-1.2:1.

[0013] Preferably, in step (1), the initiator includes lithium bis(trifluoromethanesulfonylimide)LiTFSI and / or lithium hexafluorophosphateLiPF6, and the molar ratio of ether monomer to initiator is (0.8-1.5):(1-2).

[0014] Preferably, in step (2), the volume ratio of the ether monomer solution to the mass of the sulfur powder is (150-250) μL: (0.5-1.5) g.

[0015] Preferably, in step (2), the ball milling speed is 200-400 r / min and the ball milling time is 40-55 h; the drying process includes: drying in a blower oven for 10-15 h, and then transferring to a vacuum oven for 10-15 h.

[0016] Preferably, in step (3), the mass ratio of sulfur@polyether copolymer: conductive graphite: acetylene black: PVDF is (60-70): (10-20): (10-20): (3-9).

[0017] Preferably, in step (3), the thickness of the sulfur@polyether copolymer composite cathode is 200-300 μm and the diameter is 7-15 mm.

[0018] This application also provides a lithium-sulfur battery, including a lithium negative electrode, a polyethylene separator, and a positive electrode, wherein the positive electrode is a sulfur@polyether copolymer composite positive electrode prepared by the method described above.

[0019] Compared with the prior art, the advantages and positive effects of the present invention include:

[0020] (1) The preparation process of the sulfur@polyether copolymer of this application is carried out at room temperature, which has low environmental requirements and does not require prior template preparation. It has the advantages of being simple, easy to operate, and energy-saving. The sulfur@polyether copolymer has high production efficiency and can be mass-produced.

[0021] (2) The ether monomers of this application can undergo effective and uniform in-situ polymerization on the surface of sulfur powder, achieving controllable coating and ensuring the formation of a sulfur@polyether copolymer with a semi-coated morphology and core-shell structure. In the sulfur@polyether copolymer prepared in this application, part of the sulfur powder surface is coated with polyether polymer, which can enhance the ion transport rate and electrochemical stability of the positive electrode; the remaining part of the sulfur powder surface is not coated with polyether polymer, and the remaining sulfur powder is exposed, which can combine with the conductive agent to enhance the conductivity of the positive electrode.

[0022] (3) The preferred ether monomer in this application is TTMAP. TTMAP has excellent ion conductivity, as well as high thermal stability, excellent chemical stability, and low volatility. While increasing the ion conductivity of sulfur, it can effectively block the dissolution of sulfur and polysulfides. Secondly, the polyether polymer TTMAP has excellent flexibility and mechanical stability, which is conducive to the penetration of electrolyte and the formation of ion-conducting network. It has a good buffering effect on the volume expansion and / or volume contraction of sulfur during battery charging and discharging, ensuring the structural stability of the positive electrode. This can greatly improve the cycle performance and rate performance of lithium-sulfur batteries at different current densities. In addition, the polyether polymer TTMAP contains abundant ester C=O and nitrogen rings, which have excellent fixation and absorption effects on polysulfides and can effectively block the dissolution of polysulfides.

[0023] (4) The sulfur@polyether copolymer synthesized by the ring-opening copolymerization reaction in this application can exhibit significant swelling and good gelation behavior in organic electrolytes. While promoting electrolyte penetration, it can effectively block the dissolution of sulfur and polysulfides. At the same time, its excellent mechanical stability can effectively alleviate the volume strain of the electrode. The lithium-sulfur battery assembled with the sulfur@polyether copolymer composite cathode has significantly improved cycle performance and rate performance at different current densities. More importantly, the ether oxygen group (-COC-) of polyether polymers helps the dissociation of lithium salts and can achieve efficient lithium-ion transport through "complexation-decomplexation" with lithium ions.

[0024] (5) No additional substances are introduced during the entire coating preparation process; LiTFSI and LiPF6 are common lithium salts in lithium batteries, which will not react with the electrolyte or cause side reactions in the battery, thus ensuring higher safety.

[0025] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a SEM image of the sulfur@polyether copolymer composite cathode prepared in Example 1 of the present invention.

[0027] Figure 2 This is a TEM image of the sulfur@polyether copolymer composite cathode prepared in Example 1 of the present invention.

[0028] Figure 3 This is a TEM image of sulfur powder;

[0029] Figure 4 The graphs show the rate performance test results of the lithium-sulfur batteries in Example 2 and Comparative Example 1 of this invention.

[0030] Figure 5The graphs show the cycle performance test results of the lithium-sulfur batteries in Example 2 and Comparative Example 1 of this invention.

[0031] Figure 6 This is a visual absorption test diagram of the ether polymer TTMAP on polysulfide solutions. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, after reading this invention, those skilled in the art can make various modifications or alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The method for preparing the sulfur@polyether copolymer composite cathode of the present invention includes:

[0034] (1) Mix the ether monomer solution and solvent and add lithium salt, stir until clear and transparent to obtain the precursor solution;

[0035] The ether monomers include at least one of the following: propidium crosslinking agent TTMAP, 1,3-dioxolane DOL, and glycidyl 2,2,3,3-tetrafluoropropyl ether.

[0036] The preferred ether monomer in this application is TTMAP. TTMAP possesses excellent ion conductivity, along with high thermal stability, excellent chemical stability, and low volatility. It increases the ion conductivity of sulfur while effectively preventing the dissolution of sulfur and polysulfides. Secondly, the polyether polymer TTMAP exhibits excellent flexibility and mechanical stability, facilitating electrolyte penetration and the formation of an ion-conducting network. It also provides a good buffer against the volume expansion and / or contraction of sulfur during battery charging and discharging, ensuring the structural stability of the cathode. This allows for significant improvements in the cycle performance and rate performance of lithium-sulfur batteries at different current densities. Furthermore, the abundant ester C=O groups and nitrogen rings in TTMAP provide excellent fixation and absorption of polysulfides, effectively preventing their dissolution.

[0037] The solvent is N-methylpyrrolidone (NMP), and the volume ratio of the ether monomer solution to the solvent is (0.5-1.5):(5-20). Preferably, the volume ratio of the ether monomer solution to the solvent is (0.8-1.2):(8-15).

[0038] The solvent in this application allows the ether monomer solution and sulfur powder to be fully and uniformly mixed, enabling the ether monomer to undergo effective and uniform in-situ polymerization on the surface of the sulfur powder, forming a polyether copolymer with a semi-encapsulated morphology and a core-shell structure.

[0039] The lithium salts include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium hexafluorophosphate (LiPF6). The lithium salts used in this application exhibit high electrochemical stability and conductivity, and have a low probability of side reactions, thus providing electrochemical stability and conductivity for lithium-sulfur batteries.

[0040] The molar ratio of ether monomer to lithium salt is 0.9:1-1.2:1, preferably 1:1; this allows the lithium salt to maximize the ionic conductivity and electrochemical stability of the polyionic liquid copolymer.

[0041] The initiator can be lithium hexafluorophosphate (LiPF6), a common lithium salt with good thermal stability and solubility, which can improve battery stability and conductivity. LiPF6 can also be used as an initiator to induce ring-opening of ether monomers, completing polymerization on the surface of sulfur powder.

[0042] The molar ratio of ether monomer to initiator is (0.8-1.5):(1-2), preferably (0.9-1.2):(1.3-1.7).

[0043] The initiator of this application can initiate the ring-opening polymerization of ether monomers, so that the ether monomers are polymerized uniformly on the surface of sulfur powder. At the same time, it can avoid the excessive polymerization of ether monomers, which would lead to the generation of bubbles, and can ensure the formation of a polyether copolymer with a semi-encapsulated morphology and a core-shell structure.

[0044] This application, by adjusting the amounts of lithium salt and initiator, enables effective and uniform in-situ polymerization of ether monomers on the surface of sulfur powder, achieving controllable coating and ensuring the formation of a semi-coated, core-shell structured polyether copolymer. In the polyether copolymer prepared in this application, part of the sulfur powder surface is coated with the ether polymer, which enhances the ion transport rate and electrochemical stability of the positive electrode; the remaining sulfur powder surface is not coated with the ether polymer, and the exposed sulfur powder can combine with the conductive agent to enhance the conductivity of the positive electrode.

[0045] (2) The precursor solution and sulfur powder were mixed and placed in a pulping box for ball milling, and then dried to obtain sulfur@polyether copolymer;

[0046] The volume ratio of the ether monomer solution to the mass of the sulfur powder is (150-250) μL : (0.5-1.5) g, preferably (180-220) μL : (0.8-1.2) g. This allows the ether monomer to undergo effective and uniform in-situ polymerization on the surface of the sulfur powder, forming a polyether copolymer with a semi-encapsulated morphology and a core-shell structure.

[0047] The ball milling speed is 200-400 r / min, and the ball milling time is 40-55h. Through ball milling, ether monomers can undergo effective and uniform in-situ polymerization on the surface of sulfur powder to form a polyether copolymer with a semi-encapsulated morphology and a core-shell structure.

[0048] The drying process includes: drying in a forced-air oven for 10-15 hours, and then transferring to a vacuum oven for 10-15 hours.

[0049] (3) Using sulfur@polyether copolymer, conductive graphite, acetylene black and polyvinylidene fluoride (PVDF) as raw materials, a positive electrode slurry is prepared; the positive electrode slurry is coated on carbon-coated aluminum foil and dried to obtain a sulfur@polyether copolymer composite positive electrode.

[0050] The mass ratio of sulfur@polyether copolymer: conductive graphite: acetylene black: PVDF is (60-70): (10-20): (10-20): (3-9). Reacting within the above mass ratio range can yield a structurally stable positive electrode, which can improve the ion transport rate, conductivity and electrochemical stability of the positive electrode.

[0051] The conductive graphite and acetylene black of this application can effectively solve the problem of sulfur's non-conductivity and effectively enhance the conductivity of the positive electrode.

[0052] The PVDF binder in this application can ensure the effective adhesion of sulfur@polyether copolymer, conductive graphite and acetylene black to each other, prevent the sulfur@polyether copolymer and / or conductive graphite and / or acetylene black from falling off after drying, and ensure the formation of a structurally stable sulfur@polyether copolymer composite cathode.

[0053] The thickness of the sulfur@polyether copolymer composite cathode is 200-300 μm and the diameter is 7-15 mm.

[0054] The present invention also provides a lithium-sulfur battery, which is assembled into a button lithium-sulfur battery using a lithium anode, a polyethylene separator, a lithium-sulfur electrolyte and a sulfur@polyether copolymer composite cathode prepared by the method described in the present invention.

[0055] The advantages and positive effects of this invention include:

[0056] (1) The preparation process of the sulfur@polyether copolymer of this application is carried out at room temperature, which has low environmental requirements and does not require prior template preparation. It has the advantages of being simple, easy to operate, and energy-saving. The sulfur@polyether copolymer has high production efficiency and can be mass-produced.

[0057] (2) The ether monomers of this application can undergo effective and uniform in-situ polymerization on the surface of sulfur powder, achieving controllable coating and ensuring the formation of a sulfur@polyether copolymer with a semi-coated morphology and core-shell structure. In the sulfur@polyether copolymer prepared in this application, part of the sulfur powder surface is coated with polyether polymer, which can enhance the ion transport rate and electrochemical stability of the positive electrode; the remaining part of the sulfur powder surface is not coated with polyether polymer, and the remaining sulfur powder is exposed, which can combine with the conductive agent to enhance the conductivity of the positive electrode.

[0058] (3) The preferred ether monomer in this application is TTMAP. TTMAP has excellent ion conductivity, as well as high thermal stability, excellent chemical stability, and low volatility. While increasing the ion conductivity of sulfur, it can effectively block the dissolution of sulfur and polysulfides. Secondly, the polyether polymer TTMAP has excellent flexibility and mechanical stability, which is conducive to the penetration of electrolyte and the formation of ion-conducting network. It has a good buffering effect on the volume expansion and / or volume contraction of sulfur during battery charging and discharging, ensuring the structural stability of the positive electrode. This can greatly improve the cycle performance and rate performance of lithium-sulfur batteries at different current densities. In addition, the polyether polymer TTMAP contains abundant ester C=O and nitrogen rings, which have excellent fixation and absorption effects on polysulfides and can effectively block the dissolution of polysulfides.

[0059] (4) The polyether copolymer synthesized by ring-opening copolymerization exhibits significant swelling and good gelation behavior in organic electrolytes. While promoting electrolyte penetration, it effectively blocks the dissolution of sulfur and polysulfides. Furthermore, its excellent mechanical stability effectively alleviates electrode volume strain. Batteries assembled with TTMAP@S show significant improvements in cycle performance and rate performance at different current densities. More importantly, the ether radical (-COC-) in polyether polymers facilitates the dissociation of lithium salts and enables efficient lithium-ion transport through a complexation-decomplexation process.

[0060] (5) No additional substances are introduced during the entire coating preparation process; LiTFSI and LiPF6 are common lithium salts in lithium batteries, which will not react with the electrolyte or cause side reactions in the battery, thus ensuring higher safety. Example 1

[0061] The preparation method of the sulfur@polyether copolymer composite cathode in this embodiment includes:

[0062] (1) Take 200 uL of trifunctional aziridine crosslinking agent TTMAP solution and 2000 uL of N-methylpyrrolidone NMP solution, add 0.058 g of LiTFSI and 0.046 g of LiPF6, stir until clear and transparent to obtain precursor solution.

[0063] (2) The precursor solution was mixed with 1g of S powder and placed in a pulping box. The mixture was ball-milled at 300 r / min for 48 h. The mixture was then dried in a forced-air oven for 12 h and then transferred to a vacuum oven for 12 h to obtain a sulfur@polyether copolymer.

[0064] (3) Using polyvinylidene fluoride (PVDF) as a binder, a positive electrode slurry was prepared in a ratio of sulfur@polyether copolymer: conductive graphite: acetylene black: PVDF = 65:15:15:5. Then, a 250 μm thick positive electrode slurry was coated onto a carbon-coated aluminum foil, dried, and cut into 10 mm diameter discs as the positive electrode.

[0065] Figure 1 This is a SEM image of the sulfur@polyether copolymer composite cathode prepared in Example 1 of this invention. Figure 1 The SEM images show that the sulfur powder surface has a semi-coated structure, which is the ether polymer TTMAP. The presence of the polymer can improve the ion conductivity of sulfur. Simultaneously, it can be seen that there are uncoated portions of the sulfur powder surface. These uncoated sulfur powder particles can combine with the conductive agent during the preparation of the cathode. In other words, part of the sulfur powder surface is coated with the polyether polymer, which can enhance the ion transport rate and electrochemical stability of the cathode; the remaining sulfur powder surface is uncoated and exposed, allowing it to combine with the conductive agent and enhance the conductivity of the cathode.

[0066] The sulfur@polyether copolymer composite positive electrode of this application is a semi-encapsulated structure. As can be seen from the figure, the polyether polymer coating layer coats the sulfur powder relatively uniformly.

[0067] Figure 2 This is a TEM image of the sulfur@polyether copolymer composite cathode prepared in Example 1 of this invention. Figure 3 TEM image of sulfur powder; by Figure 2 and Figure 3 The comparison also shows that the sulfur powder surface of the sulfur@polyether copolymer composite cathode prepared in Example 1 has a semi-coated structure, which is the ether polymer TTMAP. The presence of the polymer can improve the ion conductivity of sulfur. At the same time, it can be seen that there are parts of the sulfur powder surface that are not coated by the polymer. The uncoated sulfur powder can combine with the conductive agent during the preparation of the cathode. Figure 3 The image shows the TEM morphology of sulfur powder. It can be seen that the surface of pure sulfur is smooth and flat, and there are no other components covering the surface of pure sulfur.

[0068] Figure 6 This is a visual absorption test diagram of the polyether polymer TTMAP of this application for polysulfide solutions. Figure 6 (a) is an initial photograph of the polysulfide solution after the addition of polymer TTMAP; Figure 6 (b) A photograph of polymer TTMAP after immersion in a polysulfide solution for 24 hours; Figure 6 (c) A photograph of polymer TTMAP after immersion in a polysulfide solution for 48 hours. Figure 6 It can be seen that after adding the polymer TTMAP to the polysulfide solution, the color of the solution gradually becomes lighter, which indicates that the polyether polymer TTMAP of this application has excellent adsorption and fixation effect on polysulfides. Example 2

[0069] The lithium-sulfur battery of this embodiment includes: the sulfur@polyether copolymer composite positive electrode of Example 1 as the positive electrode, the lithium sheet as the negative electrode, the 19 mm polyethylene (PE) as the separator, and the coin cell assembled using lithium-sulfur electrolyte.

[0070] Comparative Example 1

[0071] The lithium-sulfur battery of this comparative example includes: sulfur (S) as the positive electrode, lithium sheet as the negative electrode, 19 mm polyethylene (PE) as the separator, and a button cell assembled using lithium-sulfur electrolyte.

[0072] Figure 4 The graphs show the rate performance test results of the lithium-sulfur batteries in Example 2 and Comparative Example 1 of this invention. The graphs show the rate performance test results of the lithium-sulfur batteries after 10 cycles at different current densities (0.1C, 0.2C, 0.5C, 1C, 2C, 0.1C). Figure 4 It can be seen that, at various current densities, the capacity of the lithium-sulfur battery in Example 2 is higher than that of the lithium-sulfur battery in Comparative Example 1; and when the current density gradually increases and finally returns to the initial 0.1C, the capacity recovery of the lithium-sulfur battery in Example 2 is good.

[0073] Figure 5 This is a cycle performance test graph for the lithium-sulfur batteries of Example 2 and Comparative Example 1 of the present invention. This graph shows the cycle performance after 300 charge-discharge cycles at a current density of 0.5C. Figure 5 As can be seen, the lithium-sulfur battery in Example 2 has high capacity, low degradation, and high retention rate, exhibiting excellent cycle performance.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing a sulfur@polyether copolymer composite cathode, characterized in that, include: (1) Mix the ether monomer solution and solvent, add lithium salt and initiator, and stir until clear and transparent to obtain the precursor solution; (2) The precursor solution and sulfur powder were mixed and placed in a pulping box for ball milling, and then dried to obtain sulfur@polyether copolymer; (3) Using sulfur@polyether copolymer, conductive graphite, acetylene black and polyvinylidene fluoride (PVDF) as raw materials, a positive electrode slurry was prepared; the positive electrode slurry was coated on carbon-coated aluminum foil and dried to obtain a sulfur@polyether copolymer composite positive electrode. Ether monomers include the aziridine crosslinking agent TTMAP. The molar ratio of ether monomers to initiators is (0.8-1.5):(1-2). In step (2), the ratio of the volume of the ether monomer solution to the mass of the sulfur powder is (150-250) μL: (0.5-1.5) g.

2. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (1), the solvent is N-methylpyrrolidone (NMP), and the volume ratio of the ether monomer solution to the solvent is (0.5-1.5):(5-20).

3. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (1), the lithium salt includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium hexafluorophosphate (LiPF6), and the molar ratio of ether monomer to lithium salt is 0.9:1-1.2:

1.

4. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (1), the initiator includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium hexafluorophosphate (LiPF6).

5. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (2), the ball milling speed is 200-400 r / min and the ball milling time is 40-55h; The drying process includes: drying in a forced-air oven for 10-15 hours, and then transferring to a vacuum oven for 10-15 hours.

6. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (3), the mass ratio of sulfur@polyether copolymer: conductive graphite: acetylene black: PVDF is (60-70): (10-20): (10-20): (3-9).

7. The method for preparing the sulfur@polyether copolymer composite cathode according to claim 1, characterized in that, In step (3), the thickness of the sulfur@polyether copolymer composite cathode is 200-300 μm and the diameter is 7-15 mm.

8. A lithium-sulfur battery, comprising a lithium negative electrode and a polyethylene separator, characterized in that, It also includes a positive electrode, which is a sulfur@polyether copolymer composite positive electrode prepared by the method for preparing the sulfur@polyether copolymer composite positive electrode according to any one of claims 1-7.

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