阅读说明：本技术 一种锂硫电池固态电解质-负极粘结剂 (Solid electrolyte-cathode binder of lithium-sulfur battery ) 是由 陈庆 廖健淞 司文彬 白涛 于 2020-11-23 设计创作，主要内容包括：本发明涉及一种锂硫电池固态电解质-负极粘结剂,属于锂硫电池技术领域。本发明解决的技术问题是提供一种锂硫电池固态电解质-负极粘结剂。该方法通过PBA、HDI等合成聚氨酯后,在AAS作用下对聚氨酯进行磺酸基接枝,通过二氧化硅空心纤维进行吸附后,磺酸基改性聚氨酯充分包裹二氧化硅纤维,从而得到胶状物,即锂硫电池固态电解质-负极粘结剂；使用时,将粘结剂与PVDF电解质和金属锂负极进行压制复合。本发明方法简单,成本较低,通过有机锂离子导体粘结剂在负极与电解质膜形成具有较好机械强度的缓冲层,提高电解质膜层的机械强度,同时有效抑制金属锂与氟代有机物的自发反应,从而稳定电解质膜与负极之间的稳定性,提高锂硫电池的循环寿命。(The invention relates to a solid electrolyte-cathode binder of a lithium-sulfur battery, belonging to the technical field of lithium-sulfur batteries. The invention aims to provide a solid electrolyte-cathode binder of a lithium-sulfur battery. According to the method, after polyurethane is synthesized through PBA, HDI and the like, sulfonic group grafting is carried out on the polyurethane under the action of AAS, and after silica hollow fibers are adsorbed, the sulfonic group modified polyurethane fully wraps the silica fibers, so that jelly, namely a lithium-sulfur battery solid electrolyte-negative electrode binder, is obtained; when in use, the adhesive is pressed and compounded with the PVDF electrolyte and the metallic lithium negative electrode. The method is simple and low in cost, and the organic lithium ion conductor binder forms a buffer layer with good mechanical strength between the negative electrode and the electrolyte membrane, so that the mechanical strength of the electrolyte membrane is improved, and the spontaneous reaction of metal lithium and fluoro-organic matters is effectively inhibited, thereby stabilizing the stability between the electrolyte membrane and the negative electrode, and prolonging the cycle life of the lithium-sulfur battery.)

1. The solid electrolyte-negative electrode binder of the lithium-sulfur battery is characterized by being prepared by the following method:

a. synthesis of polyurethane: adding a catalyst into an acetone solution of poly (1, 4-butanediol adipate) diol, stirring and reacting for 5-10 min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 2-4 h at 70-80 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 10-30 wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer = 1-5: 2-7: 10-30;

b. graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into a polyurethane solution, stirring, refluxing, reacting for 20-40 min, adding silica hollow fibers for adsorption, and performing solid-liquid separation to obtain a jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 5-10: 1-4: 1-10.

2. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step a, the concentration of the acetone solution of the poly (1, 4-butylene glycol adipate) glycol is 15 wt%.

3. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step a, the protective atmosphere is nitrogen, helium, neon, argon or krypton.

4. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step a, the catalyst is dibutyltin dilaurate.

5. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step a, the using amount of the catalyst is 1-5% of the total weight of the polymerized monomers, wherein the polymerized monomers are poly adipic acid-1, 4-butanediol diol, hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer.

6. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in step a, the reaction is carried out for 3h at 75 ℃.

7. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step a, according to the weight ratio, the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =3:4:5: 21.

8. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: and b, stirring and refluxing for 30 min.

9. The lithium sulfur battery solid electrolyte-negative electrode binder according to claim 1, characterized in that: in the step b, the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 7:3: 8.

Technical Field

The invention relates to a solid electrolyte-cathode binder of a lithium-sulfur battery, belonging to the technical field of lithium-sulfur batteries.

Background

The lithium ion has high energy density, strong stability, no memory effect and long cycle life, and is widely applied as a commercial high-efficiency energy storage device. And a lithium sulfur battery is one of lithium batteries. The lithium-sulfur battery is a lithium battery with sulfur as the positive electrode and metal lithium as the negative electrode. The elemental sulfur has rich reserves in the earth, and has the characteristics of low price, environmental friendliness and the like. The lithium-sulfur battery using sulfur as the anode material has higher material theoretical specific capacity and battery theoretical specific energy which respectively reach 1675m Ah/g and 2600Wh/kg, and is far higher than the capacity (< 150 mAh/g) of a lithium cobaltate battery widely applied in commerce. And the sulfur is an element which is friendly to the environment, basically has no pollution to the environment, and is a lithium battery with very prospect.

Conventionally, lithium hexafluorophosphate, which is a liquid electrolyte used in lithium ion batteries including lithium sulfur batteries, is very unstable and easily decomposed to cause battery gassing, and is very easily burned and exploded at high temperature, short circuit, overcharge, or physical impact. Despite the protection mechanism added by the external encapsulation, it still has a large safety hazard.

The solid lithium ion battery uses the solid electrolyte to replace the liquid electrolyte, and can fundamentally solve the safety problem and the temperature use region problem of the liquid lithium ion battery. For example, the invention patent application No. 201680028992.6 discloses a glass-ceramic electrolyte for a lithium-sulfur battery, mainly relating to a lithium-sulfur electrochemical cell comprising as components (a) an electrolyte comprising lithium metal or lithium alloy and lithium ions conductively connected thereto, (B) a glass ceramic membrane comprising an amorphous phase, as component (C) a liquid electrolyte comprising at least one solvent and at least one lithium salt, as component (D) sulfur as an electrode for a cathode active material. The patent also relates to batteries comprising a lithium-sulfur electrochemical cell as defined herein. The patent further relates to the use of a glass ceramic membrane as defined herein as a separator in (i) a lithium-sulfur electrochemical cell or (ii) a battery comprising at least one lithium-sulfur electrochemical cell.

The above patents mainly refer to lithium-sulfur batteries prepared by using glass-ceramic electrolyte, however, the lithium ion conductivity of the current glass-ceramic electrolyte-based solid-state batteries is relatively low, and the lithium-sulfur batteries are difficult to meet the practical use. Many researchers have concentrated on the research of polymer gel electrolytes, which have high ion mobility by introducing a liquid solvent into the polymer.

The invention patent application No. 200910043325.7 discloses an all-solid polymer electrolyte for a lithium sulfur battery and its preparation. The invention designs and synthesizes a novel main chain sulfur-containing polymer electrolyte. Grafting PEG on the main chain of organic dihalide compound, polymerizing by sulfur-sulfur bond to prepare the sulfur-containing polymer (PSPEG), mixing the sulfur-containing polymer with lithium salt by taking THF as solvent, and volatilizing the THF solvent to obtain the sulfur-containing polymer electrolyte. The polymer electrolyte combines the advantages of polysulfide compound and low molecular weight PEG, and the sulfur-containing polymer main chain has certain rigidity so as to enhance the mechanical property of the electrolyte. Meanwhile, the sulfur-containing main chain enables the polymer to have better adhesive property, and can improve the compatibility of the electrolyte and the electrode material. The small-component PEG grafted by the side chain has lower glass transition temperature, ether oxygen groups on the PEG chain can be complexed with lithium ions, the aim of transmitting the lithium ions is achieved by swinging back and forth near the main chain of the polymer, and the PEG has higher ionic conductivity. However, the polymer has a complex structure and high cost.

At present, the typical polymers used in the field comprise PVDF, PVC, PAN, PVP, PMMA and the like, the materials are low in price and wide in source, and meanwhile, the lithium ion conductivity of the materials is relatively moderate, so that the materials are very attractive in the prospect of technological production. However, although PVDF has a high dielectric constant to promote ionization of lithium salt, and can improve the mobility of lithium ions, it is difficult to coordinate with lithium ions, and the stability of the interface between the fluorinated polymer and lithium metal is poor, and lithium fluoride is easily formed, which causes loss of active lithium. Therefore, the method has very important practical significance for improving the interface stability of the PVDF electrolyte by modification.

Disclosure of Invention

The invention provides a solid electrolyte-cathode binder of a lithium-sulfur battery, aiming at the problem of poor stability of a PVDF-based electrolyte and cathode interface in the existing lithium-sulfur battery.

The invention provides a solid electrolyte-cathode binder of a lithium-sulfur battery, which is characterized by being prepared by the following method:

a. synthesis of polyurethane: adding a catalyst into an acetone solution of poly (1, 4-butylene glycol) adipate (PBA), stirring and reacting for 5-10 min under a protective atmosphere, then sequentially adding Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI) and HDI Trimer (HT), reacting for 2-4 h at 70-80 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 10-30 wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer = 1-5: 2-7: 10-30;

b. graft modification: adding ethylenediamine ethanesulfonic acid sodium (AAS) into a polyurethane solution, stirring and refluxing for reaction for 20-40 min, adding silica hollow fibers for adsorption, and then carrying out solid-liquid separation to obtain a jelly, namely a lithium-sulfur battery solid electrolyte-negative electrode binder; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 5-10: 1-4: 1-10.

According to the lithium-sulfur battery solid electrolyte-cathode binder, after polyurethane is synthesized through PBA, HDI and the like, sulfonic group grafting is carried out on the polyurethane under the action of AAS, after silica hollow fibers are adsorbed, the sulfonic group modified polyurethane fully wraps the silica fibers, and the binder with good mechanical strength is obtained. The method can form a buffer layer with better mechanical strength between the cathode and the electrolyte membrane through the organic lithium ion conductor binder, improve the mechanical strength of the electrolyte membrane layer, and effectively inhibit spontaneous reaction of metal lithium and fluoro-organic matters, thereby stabilizing the stability between the electrolyte membrane and the cathode.

And a, synthesizing polyurethane, wherein the step a is mainly used for synthesizing polyurethane, the adopted polymerization monomers are poly adipic acid-1, 4-butanediol ester diol, hexamethylene diisocyanate, isophorone diisocyanate and HDI tripolymer, and the polymerization reaction is carried out under the catalytic action of a catalyst to obtain a polyurethane solution.

Poly adipic acid-1, 4-butanediol diol, abbreviated as PBA, is polyester polyol formed by condensation polymerization of adipic acid and 1, 4-T-alcohol, is insoluble in water and easily soluble in organic solvents such as acetone, toluene and ethyl acetate.

Hexamethylene diisocyanate, HDI for short, is a lipid capable of reacting with active hydrogen-containing groups such as water, alcohols and amines. The HDI is stable at normal temperature and has active chemical property, and the HDI is adopted as one of the polymerization monomers of the polyurethane.

Isophorone diisocyanate, abbreviated as IPDI, is a curing agent for hydroxyl prepolymer (namely polypropylene glycol) required by polyurethane adhesive of composite propellant, and is also one of important monomers for synthesizing polyurethane in the invention.

HDI trimer, abbreviated as HT, is a product of the trimerization reaction of Hexamethylene Diisocyanate (HDI) under the catalytic action, and is also one of important monomers for synthesizing polyurethane in the invention.

Preferably, in step a, the concentration of the acetone solution of poly (1, 4-butylene adipate) glycol is 15 wt%.

Step a of the present invention needs to be performed under a protective atmosphere to avoid oxidation reactions or other side reactions, and protective atmospheres commonly used in the art are all suitable for the present invention.

The polymerized monomer in the step a needs to be polymerized under the action of a catalyst. Conventional polyurethane synthesis catalysts are suitable for use in the present invention. In order to improve the synthesis effect and thus the stability of the final battery, it is preferable that the catalyst is dibutyltin dilaurate.

The amount of the catalyst is 1-5% of the total weight of the polymerized monomers in the step a, wherein the polymerized monomers are poly (1, 4-butylene adipate) glycol, hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer.

The temperature and time of the polymerization reaction also have certain influence on the reaction, the reaction temperature is too high, the time is too long, not only is the energy consumption increased, but also the quality of the synthesized polyurethane is influenced, and the reaction temperature is too low, the time is too short, and the reaction is incomplete or even does not occur. The inventor finds that the reaction is suitable for 2-4 hours at the temperature of 70-80 ℃.

Preferably, in step a, the reaction is carried out at 75 ℃ for 3 h.

In the step a, the mixture ratio of each reaction monomer also influences the performance of the polyurethane after reaction. It was found that the weight ratio of poly (1, 4-butylene adipate glycol): hexamethylene diisocyanate: isophorone diisocyanate: when the HDI trimer = 1-5: 2-7: 10-30, the obtained polyurethane is good in performance, and the obtained battery is good in performance.

And as the optimal scheme, in the step a, the weight ratio of poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =3:4:5: 21. In this case, the polyurethane produced has the best properties and the best battery performance.

b, adding ethylenediamine ethanesulfonic acid sodium (AAS) into a polyurethane solution, stirring and refluxing for reaction for 20-40 min, adding silica hollow fibers for adsorption, and then carrying out solid-liquid separation to obtain a jelly, namely a lithium-sulfur battery solid electrolyte-cathode binder, wherein the original lithium in the step is as follows: the sulfonic group grafting is carried out on the polyurethane under the action of AAS, after the adsorption is carried out on the hollow silica fibers, the sulfonic group modified polyurethane fully wraps the silica fibers, so that the silica fibers as a binder have better mechanical strength, meanwhile, the sulfonic group is a strong acid group, the transfer capacity of lithium ions can be effectively improved, and meanwhile, the modified polyurethane is used for physically isolating a metal lithium cathode from PVDF and inhibiting a fluorinated polymer from reacting with metal lithium to form lithium fluoride.

Preferably, in step b, stirring and refluxing are carried out for 30 min.

Preferably, in the step b, the weight ratio of the polyurethane solution to the ethylenediamine-based ethanesulfonic acid sodium salt to the silica hollow fibers is 7:3: 8.

When the adhesive is used, the adhesive, the PVDF electrolyte and the metallic lithium negative electrode are directly pressed and compounded. Wherein, the compounding method is a common bonding and pressing method.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the organic lithium ion conductor binder forms a buffer layer with good mechanical strength between the negative electrode and the electrolyte membrane, so that the mechanical strength of the electrolyte membrane is improved, and the spontaneous reaction of metal lithium and fluoro-organic matters is effectively inhibited, thereby stabilizing the stability between the electrolyte membrane and the negative electrode and prolonging the cycle life of the lithium-sulfur battery.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.

Example 1

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 5min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 4h at 70 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 10wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =1: 5:2: 10; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 1 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into a polyurethane solution, stirring, refluxing and reacting for 20min, adding silicon dioxide hollow fibers for adsorption, and then carrying out solid-liquid separation to obtain a jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 5:1: 1.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Example 2

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 10min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 2h at 80 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 30wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =5:1: 7: 10; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 5 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into polyurethane solution, stirring, refluxing, reacting for 40min, adding silica hollow fiber for adsorption, and performing solid-liquid separation to obtain jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 10: 4: 10.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Example 3

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 6min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 2.5h at 72 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 20wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =4:1:7: 18; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 3 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into polyurethane solution, stirring, refluxing, reacting for 30min, adding silica hollow fiber for adsorption, and performing solid-liquid separation to obtain jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 6:2: 3.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Example 4

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 9min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 3.5h at 78 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 12wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =4:3:3: 25; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 4 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into a polyurethane solution, stirring, refluxing and reacting for 25min, adding silicon dioxide hollow fibers for adsorption, and then carrying out solid-liquid separation to obtain a jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 8:3: 5.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Example 5

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 9min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 2.5h at 75 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 25wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =4:4:5: 15; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 4 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into a polyurethane solution, stirring, refluxing and reacting for 35min, adding silicon dioxide hollow fibers for adsorption, and then carrying out solid-liquid separation to obtain a jelly, namely a lithium-sulfur battery solid electrolyte-negative electrode binder; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 8:2: 9.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Example 6

The solid electrolyte-cathode binder of the lithium-sulfur battery is prepared by the following method:

a. synthesis of polyurethane: adding an acetone solution of anhydrous poly (1, 4-butanediol adipate) diol into a container with a reflux device, adding dibutyltin dilaurate as a catalyst, stirring and reacting for 10min under a protective atmosphere, then sequentially adding hexamethylene diisocyanate, isophorone diisocyanate and HDI trimer, reacting for 3h at 75 ℃, and cooling to room temperature to obtain a polyurethane solution; wherein the concentration of the acetone solution of the poly adipic acid-1, 4-butanediol ester diol is 15wt%, and the weight ratio of the poly adipic acid-1, 4-butanediol ester diol: hexamethylene diisocyanate: isophorone diisocyanate: HDI trimer =3:4:5: 21; wherein the protective atmosphere is nitrogen, and the dosage of the catalyst is 4 percent of the total weight of the poly adipic acid-1, 4-butanediol ester diol, the hexamethylene diisocyanate, the isophorone diisocyanate and the HDI tripolymer.

b. Graft modification: adding ethylenediamine ethanesulfonic acid sodium salt into polyurethane solution, stirring, refluxing, reacting for 30min, adding silica hollow fiber for adsorption, and performing solid-liquid separation to obtain jelly, namely a solid electrolyte-cathode binder of the lithium-sulfur battery; wherein the weight ratio of the polyurethane solution to the ethylenediamine ethanesulfonic acid sodium salt to the silicon dioxide hollow fibers is 7:3: 8.

c. And pressing and compounding the binder, the PVDF electrolyte and the metallic lithium cathode, and taking elemental sulfur as a positive electrode to prepare the lithium-sulfur battery. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

Comparative example 1

The adhesive is not used, the PVDF electrolyte and the metallic lithium cathode are directly pressed and compounded to be used as a composite pole piece, and elemental sulfur is used as a positive pole, so that the lithium-sulfur battery is prepared. The cycle performance of the cell was measured at 80 ℃ and 0.2 ℃ and the results are shown in Table 1.

TABLE 1

Numbering	10-cycle capacity retention (%)	Retention ratio of 50 cycles capacity (%)
			Example 1	91.1	74.6
Example 2	90.4	75.7
			Example 3	91.8	74.2
Example 4	91.7	76.8
			Example 5	91.2	77.3
Example 6	92.5	79.7
			Comparative example 1	88.1	49.8

In examples 1 to 5, the binder having a good isolation layer is introduced between the solid electrolyte and the lithium metal negative electrode, so that the lithium metal negative electrode is effectively prevented from directly contacting and reacting with the fluorinated electrolyte, and the capacity retention rate is significantly improved compared with that of comparative example 1.