A gel electrolyte membrane for lithium-sulfur batteries, a preparation method and an energy storage device

Abstract

The application provides a gel electrolyte film for a lithium-sulfur battery, comprising a base film and a polymer electrolyte based on solidification of the base film, the raw material of the polymer electrolyte comprising a halogenated amide additive, a monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, an ether solvent, a lithium salt and an initiator. The gel electrolyte film provided by the application can inhibit the'shuttle effect' of LiPSs and avoid consumption of positive and negative active materials, thereby improving the cycle capacity and electrochemical performance of the lithium-sulfur battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a gel electrolyte film for lithium-sulfur batteries, a preparation method and an energy storage device. BACKGROUND

[0002] Lithium ion batteries with graphite as the negative electrode have now approached their theoretical energy density, but with the continuous development of battery technology, people have increasingly high requirements for high energy density batteries. Among them, lithium-sulfur batteries based on conversion reaction and lithium metal negative electrode have extremely high theoretical specific capacity (1675 mAh / g) and theoretical specific energy (2600 Wh / kg), and sulfur is abundant in reserves, low in price and environmentally friendly, so lithium-sulfur batteries have become one of the most promising battery solutions.

[0003] Because the active material sulfur (S) in the lithium-sulfur battery has a solid-liquid-solid conversion mechanism during the cycle process, lithium polysulfides (LiPSs) are easily dissolved in the electrolyte, and the dissolved LiPSs are easily shuttled to the negative electrode in the electrolyte to react irreversibly with lithium metal, resulting in loss of active material, i.e., the "shuttling effect" occurs; at the same time, the active metal lithium negative electrode is prone to side reactions with the electrolyte and forms dead lithium and lithium dendrites, thereby greatly reducing the cycle life and safety of the battery.

[0004] In lithium-sulfur batteries, using a solid-state electrolyte instead of a traditional liquid electrolyte can effectively suppress the dissolution of LiPSs and interfacial side reactions, thereby alleviating the "shuttling effect" and inhibiting the growth of lithium dendrites. However, the ionic conductivity of organic polymer solid-state electrolytes is often insufficient at room temperature, and inorganic solid-state electrolytes have poor processability and formability, making them difficult to be practically applied. One solution is to use a gel polymer instead of a solid-state electrolyte, however, although the use of a gel polymer electrolyte can effectively suppress the occurrence of the "shuttling effect", there is still a serious problem that the gel polymer electrolyte usually includes monomers such as polycarbonate and polyacrylic acid, which are mostly chemically reacted irreversibly with LiPSs, thereby causing loss of active material, and how to ensure that the gel polymer electrolyte suppresses the "shuttling effect" while avoiding consumption of the positive and negative active materials has become a major difficulty in current research. SUMMARY

[0005] To solve the problems in the prior art, the present application provides a gel electrolyte film for lithium-sulfur batteries, which suppresses the "shuttling effect" of LiPSs while avoiding consumption of the positive and negative active materials, thereby optimizing the electrochemical performance and cycle capacity of lithium-sulfur batteries.

[0006] In a first aspect, the present application provides a gel electrolyte membrane for a lithium-sulfur battery, comprising a base membrane and a polymer electrolyte based on solidification of the base membrane, wherein the raw material of the polymer electrolyte comprises a halogenated amide additive, a monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, an ether solvent, a lithium salt, and an initiator.

[0007] In a second aspect, the present application further provides an energy storage device using the gel electrolyte membrane as a separator and / or a semi-solid electrolyte.

[0008] As a further aspect, the energy storage device comprises a battery cell.

[0009] As some preferred aspects, the halogenated amide additive is selected from a chain halogenated amide additive having an end amide group and a halogen element substitution number less than or equal to 3.

[0010] As further preferred aspects, the chain halogenated amide additive having an end amide group and a halogen element substitution number less than or equal to 3 can be further preferably a chain halogenated amide additive having an end amide group and a halogen element substitution number less than or equal to 3 and a carbon chain length less than or equal to 6.

[0011] As further preferred aspects, the carbon chain length can be further preferably 4, and further, the carbon chain length can be further preferably 3, 2, or 1.

[0012] As some preferred aspects, the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond is preferably a symmetric monomer containing a double-end unsaturated carbon-carbon double bond and a disulfide bond.

[0013] As a further aspect, the raw material of the polymer electrolyte can further comprise a halogenated sulfonamide additive.

[0014] As further preferred aspects, the halogenated sulfonamide can be further preferably a chain halogenated sulfonamide having a symmetric structure.

[0015] As a further aspect, the ether solvent is selected from any one or several of a simple ether solvent, a polyether solvent, and a cyclic ether solvent.

[0016] As a further aspect, the lithium salt is selected from any one or several of an organic lithium salt and an inorganic lithium salt.

[0017] As a further aspect, the organic lithium salt is selected from any one or several of a fluorine-substituted lithium sulfonate, a lithium oxalate, and a lithium borate.

[0018] As a further aspect, the inorganic lithium salt is selected from any one or several of a fluorine-substituted inorganic lithium borate, a fluorine-substituted inorganic lithium phosphate, a fluorine-substituted inorganic lithium chlorate, and an inorganic lithium nitrate.

[0019] As a further solution, the initiator is selected from any one of ketone compounds and phosphorus oxides.

[0020] As a further solution, the polymer electrolyte raw material further comprises a second solvent, which is selected from any one or several of ester solvents or acetal solvents.

[0021] As a further solution, the ester solvent is selected from any one or several of chain carbonate solvents, carboxylate solvents, and phosphate solvents.

[0022] As a further solution, the mass ratio of the ether solvent to the second solvent in the gel electrolyte membrane is selected from 0.2 to 2.

[0023] As a further solution, the base film is selected from glass cellulose films, cellulose films, and porous polyolefin compound films, and one or more coating layers can be arranged on the base film.

[0024] As a further solution, the coating layer is not limited in principle, and can be selected from any one or several of polymer materials, carbon materials, and oxide materials.

[0025] As a further solution, the gel electrolyte membrane has a Raman scattering peak at 512 cm -1 in the Raman spectrum measurement, and the standard deviation of the peak position is within 2 cm -1 .

[0026] In a third aspect, the present solution further provides a method for preparing a gel electrolyte membrane, and the specific steps are as follows:

[0027] S1: under an inert atmosphere, dissolving a lithium salt in an ether solvent, adding a halogenated amide additive and a monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, then adding an initiator, and uniformly mixing to obtain a precursor solution;

[0028] S2: in a dry environment, immersing a base film in the precursor solution, taking it out after complete wetting, and irradiating with ultraviolet light to obtain a gel electrolyte membrane.

[0029] As a further solution, in the step S1, the inert atmosphere is selected from any one of helium, neon, argon, krypton, xenon, and radon.

[0030] As a further solution, in the step S1, the lithium salt is selected from a total mass content in the polymer electrolyte selected from 5% to 50%.

[0031] As a further solution, in the step S1, the lithium salt is selected from a total mass content in the polymer electrolyte selected from 10% to 30%.

[0032] As a further development, in step S1 the lithium salt concentration is selected from the range of 0.1 mol / L to 5 mol / L.

[0033] As a further development, in step S1 the lithium salt concentration is selected from the range of 1.5 mol / L to 3 mol / L.

[0034] As a further development, in step S1 the total mass content of lithium salt in the polymer electrolyte is selected from the range of 1 % to 45 %.

[0035] As a further development, in step S1 the total mass content of lithium salt in the polymer electrolyte is selected from the range of 20 % to 38 %.

[0036] As a further development, in step S1 the total mass content of halogenated amide additive in the polymer electrolyte is selected from the range of 0.1 % to 5 %.

[0037] As a further development, in step S1 the total mass content of halogenated amide additive in the polymer electrolyte is selected from the range of 0.5 % to 2 %.

[0038] As a further development, in step S1 the total mass content of monomer containing unsaturated carbon-carbon double bond and disulfide bond in the polymer electrolyte is selected from the range of 2 % to 10 %.

[0039] As a further development, in step S1 the total mass content of monomer containing unsaturated carbon-carbon double bond and disulfide bond in the polymer electrolyte is selected from the range of 5 % to 8 %.

[0040] As a further development, in step S1 the total mass content of initiator in the polymer electrolyte is selected from the range of 0.1 % to 2 %.

[0041] As a further development, in step S1 the total mass content of initiator in the polymer electrolyte is selected from the range of 0.5 % to 1 %.

[0042] As a further development, in step S1 a halogenated sulfonamide additive can also be added.

[0043] As a further development, in step S1 the total mass content of halogenated sulfonamide additive in the polymer electrolyte is selected from the range of 0.1 % to 5 %.

[0044] As a further development, in step S1 the total mass content of halogenated sulfonamide additive in the polymer electrolyte is selected from the range of 0.5 % to 2 %.

[0045] As a further development, in step S2 the dry environment means that the water content of the environment is less than 1 ppm.

[0046] As a further solution, the ultraviolet light irradiation time is selected from 1 min to 8 min.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] The present invention utilizes an ether solvent, providing a stable environment for the dissolution and conversion of lithium polysulfide. Furthermore, by introducing monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, the introduction of additional polymers is avoided, while also suppressing the "shuttle effect." The addition of a halogenated amide additive further enhances the dissolution and conversion of lithium polysulfide while suppressing the "shuttle effect," thereby avoiding the consumption of positive and negative electrode active materials. Furthermore, the introduction of the halogenated sulfonamide additive further optimizes the cycling performance of lithium-sulfur batteries. The combined effects of the ether solvent, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, and halogenated amide additive suppress the "shuttle effect," avoid the consumption of positive and negative electrode active materials, and significantly enhance the cycling performance of lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0050] Figure 1 This is the state diagram of polymer electrolyte before and after polymerization;

[0051] Figure 2 This is a comparison chart of the first discharge specific capacity of Example 1 and Comparative Example 1;

[0052] Figure 3 This is a comparison chart of the coulombic efficiency of Example 1 and Comparative Example 1 after 50 cycles;

[0053] Figure 4 Schematic diagram of the dynamic disulfide bond exchange reaction.

[0054] Figure 5 These are Raman spectra of the polymer monomer, semi-solid electrolyte, and semi-solid electrolyte with added lithium polysulfides (LiPSs) in Example 1. DETAILED DESCRIPTION

[0055] For ease of understanding, the present invention will be described in more detail below, and examples of the present invention are given, but the scope of the present invention is not limited thereby.

[0056] In a first aspect, the present invention proposes a gel electrolyte membrane for a lithium-sulfur battery, comprising a base membrane and a polymer electrolyte solidified based on the base membrane, wherein the polymer electrolyte raw materials include a halogenated amide additive, a monomer containing unsaturated carbon-carbon double bonds and disulfide bonds, an ether solvent, a lithium salt, and an initiator.

[0057] To suppress the shuttle problem of polysulfides in the electrolyte, we first used ether solvents as solvents, taking advantage of the high solubility of ether solvents for lithium polysulfides to provide a stable environment for the dissolution and conversion of lithium polysulfides. Subsequently, by introducing monomers containing unsaturated carbon-carbon double bonds and disulfide bonds into the polymer electrolyte, we were able to effectively utilize the dynamic exchange reaction of disulfide bonds ( Figure 4 ) interacts with lithium polysulfide, thereby inhibiting the shuttle of polysulfide in the electrolyte. Figure 5 As shown in Figure 2, the characteristic Raman peak of disulfide bond SS (~512 cm -1 ), however, the Raman peak of SS disappeared after adding LiPSs, and the peak at ~534 cm -1 A new S-S8 appeared in the position 2- Raman peaks confirm the cleavage of disulfide bonds in the polymer backbone and the dynamic reorganization process with LiPSs. At the same time, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds can further rely on unsaturated carbon-carbon double bonds for polymerization, avoiding the introduction of additional polymers ( Figure 1 ), which largely avoids the loss of positive and negative electrode active materials caused by the introduction of polycarbonate and polyamide monomers. However, relying solely on monomers containing unsaturated carbon-carbon double bonds and disulfide bonds cannot completely avoid the consumption of positive electrode active materials. On the basis of introducing monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, we further introduced halogenated amide additives. On the one hand, we believe that the amide group with strong polarity in the halogenated amide additive can promote the dissolution and conversion of lithium polysulfide by forming hydrogen bonds with the lone pair electrons of sulfur (S) and forming dipole-dipole interactions with sulfur atoms, thereby preventing the deposition and deactivation of polysulfides caused by the dynamic exchange reaction of disulfide bonds in semi-solid lithium-sulfur batteries; on the other hand, the presence of halogen elements in the halogenated amide additive can also bind to the lithium in the battery to form a LiF-rich SEI film at the lithium negative electrode, thereby inhibiting the interfacial side reactions between the sulfur-containing polymer and the lithium metal, thereby improving the electrochemical performance of the lithium-sulfur battery. Under the combined action of halogenated amide additives, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, and ether solvents, we suppress the "shuttle effect" while avoiding the consumption of positive and negative electrode active materials, thereby optimizing the performance of lithium-sulfur batteries.

[0058] Secondly, this solution also proposes an energy storage device that uses a gel electrolyte membrane as a separator and / or a semi-solid electrolyte.

[0059] As a further solution, the energy storage device comprises a battery cell.

[0060] As some preferred solutions, the halogenated amide additive is selected from chain halogenated amide additives with end amide group and halogen element substitution number less than or equal to 3. For halogenated amide additives, the presence of halogen element can bind with lithium in the battery, forming SEI film rich in LiF at the lithium negative electrode, when the halogen element substitution number is greater than 3, it may lead to an over-thick or uneven SEI layer, which in turn affects the first coulombic efficiency and the first specific discharge capacity of the battery; in addition, we believe that the selection of chain halogenated amide additives helps to further utilize its chain structure to provide more hydrogen bonding and dipole-dipole interaction sites, and to strengthen the binding force with polysulfides, thereby optimizing the battery cycle performance.

[0061] As a further preferred solution, the chain halogenated amide additive with end amide group and halogen element substitution number less than or equal to 3 can be further preferred to be a chain halogenated amide additive with end amide group and halogen element substitution number less than or equal to 3 and carbon chain length less than or equal to 6.

[0062] As a further preferred solution, the carbon chain length can be further preferred to be 4, and further, the carbon chain length can be further preferred to be 3, 2, or 1.

[0063] As some preferred non-limiting examples, the chain halogenated amide with end amide group and halogen element substitution number less than or equal to 3 and carbon chain length less than or equal to 4 is selected from trifluoroacetamide chloroacetamide iodoacetamide dichloroacetamide fluoroiodoacetamide fluorochloroacetamide chlorofluoroacetamide bromofluoroacetamide bromochloroacetamide any one of them.

[0064] As some preferred solutions, the monomer containing unsaturated carbon-carbon double bond and disulfide bond is preferably a symmetric monomer containing double-end unsaturated carbon-carbon double bond and disulfide bond. The presence of symmetric structure helps to build more ordered and stable ion channels during polymerization, thereby improving the first specific discharge capacity and the first coulombic efficiency of the battery, and further, the ordered polymer can better intercept lithium polysulfide dissolved in the electrolyte, thereby inhibiting the occurrence of "shuttle effect".

[0065] As some preferred non-limiting examples, the symmetric monomer containing double-end unsaturated carbon-carbon double bond and disulfide bond can be selected from N, N-bis(acryloyl) cystamine diallyl disulfide any one of the foregoing.

[0066] As a further solution, the polymer electrolyte raw material can further comprise a halogenated sulfonamide additive.

[0067] The halogenated sulfonamide additive contains halogen elements and sulfonamide functional groups. When the halogenated sulfonamide additive is introduced into the gel electrolyte membrane, firstly, the oxygen in the amino group of the halogenated sulfonamide can interact with the amide group in the halogenated amide additive as a hydrogen bond acceptor, thereby affecting the behavior of polysulfides; secondly, the electrophilicity of the halogenated sulfonamide additive itself enables it to act on polysulfide anions through non-covalent interactions such as ion-dipole interactions, thereby stabilizing polysulfides and promoting their dissolution; thirdly, the presence of halogen elements in the halogenated sulfonamide additive helps to further interact with sulfur atoms in polysulfides, promoting the dissociation of polysulfides; under the combined action of the halogenated sulfonamide additive, the halogenated amide additive, the monomer containing unsaturated carbon-carbon double bonds and disulfide bonds, and the ether solvent, we further reduce the loss of positive and negative active materials, optimize the cycle efficiency and cycle capacity retention rate.

[0068] As a further preferred solution, the halogenated sulfonamide can be further preferably a chain halogenated sulfonamide with a symmetrical structure. The chain halogenated sulfonamide with a symmetrical structure can provide more uniform and effective interaction with polysulfides, preventing their uneven distribution and deposition in the electrolyte. At the same time, the symmetrical chain halogenated sulfonamide can also introduce higher content of halogen elements, thereby further improving the stability of the SEI film and optimizing the cycle performance of the battery.

[0069] As some preferred non-limiting examples, the chain halogenated sulfonamide with a symmetrical structure can be triflic anhydride N-methyl bis[(trifluoromethyl)sulfonyl]imide bis(trifluoromethane)sulfonimide any one of the foregoing.

[0070] As a further solution, the ether solvent is selected from any one or several of simple ether solvents, polyether solvents, and cyclic ether solvents.

[0071] As a further solution, the simple ether solvent refers to a structure of R-O-R', wherein R and R' can be alkyl or aryl groups. Exemplarily, it can be selected from one or several of diethyl ether, dipropyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, cyclopentyl methyl ether, and 2-methyl tetrahydrofuran.

[0072] As a further option, the polyether-based solvent refers to an ether-based solvent containing multiple ether linkages, typically ether oxygen bridge connected ethylene glycol units, exemplary can be selected from one or more of dimethyl ether of ethylene glycol, diethyl ether of ethylene glycol, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether.

[0073] As a further option, the cyclic ether-based solvent refers to one or more of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, tetrahydropyran having a cyclic structure, and wherein one or more oxygen atoms are in the ring.

[0074] As a further option, the lithium salt is selected from any one or more of an organic lithium salt and an inorganic lithium salt.

[0075] As a further option, the organic lithium salt is selected from any one or more of a fluorine-substituted lithium sulfonate, a lithium oxalate, and a lithium borate.

[0076] As a further option, the lithium sulfonate is selected from any one or more of lithium bistrifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium perfluorobutanesulfonate, lithium perfluorobutanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium 1,1,2,2-tetrafluoroethanesulfonate, lithium hexafluoropropylsulfonate, lithium perfluorooctanesulfonate, lithium pentafluorobenzenesulfonate, lithium 1,2,2-trifluoroethanesulfonate, lithium octafluoropropylsulfonate.

[0077] As a further option, the lithium borate is selected from any one or more of lithium difluorodihydroxyborate, lithium fluoroborate, lithium fluoromethyleneborate, lithium trifluoropropanolborate.

[0078] As a further option, the inorganic lithium salt is selected from any one or more of a fluorine-substituted inorganic lithium borate, a fluorine-substituted inorganic lithium phosphate, a fluorine-substituted inorganic lithium chlorate, an inorganic lithium nitrate.

[0079] As a further option, the fluorine-substituted inorganic lithium borate is selected from any one or more of lithium tetrafluoroborate, lithium difluoroborate, lithium fluoroborate, lithium trifluoroborate, lithium fluorophosphoborate, lithium perfluoropropylborate.

[0080] As a further option, the fluorine-substituted inorganic lithium phosphate is selected from any one or more of lithium fluorophosphate, lithium fluorometaphosphate, lithium bis(fluorooxophosphoryl)nitrosylate, lithium fluorophosphite, lithium trifluorophosphate, lithium hexafluorophosphate.

[0081] As a further option, the fluorine-substituted inorganic lithium chlorate is selected from any one or more of lithium perchlorate, lithium difluorochlorate, lithium trifluorochlorate, lithium tetrafluorochlorate, lithium pentafluorochlorate.

[0082] As a further option, the inorganic lithium nitrate is selected from lithium nitrate.

[0083] As a further aspect, the initiator is selected from any one of ketone compounds and phosphorus oxides.

[0084] As a further aspect, the ketone compound is selected from any one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-l-phenylpropanone, benzophenone, 2-isopropylthioxanthone.

[0085] As a further aspect, the phosphorus oxide is selected from any one of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, diphosphorus trioxide, diphosphorus pentoxide, phosphoric anhydride, Na3PO4, phosphorus oxychloride, hypophosphorous acid, nitro phosphoric acid.

[0086] As a further aspect, the polymer electrolyte material further comprises a second solvent selected from any one or several of ester solvents or acetal solvents.

[0087] As a further aspect, the ester solvent is selected from any one or several of chain carbonate solvents, carboxylic acid ester solvents, phosphoric acid ester solvents.

[0088] As a further aspect, the chain carbonate solvent comprises at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

[0089] As a further aspect, the carboxylic acid ester solvent comprises at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, methyl isobutyrate, ethyl butyrate, methyl trimethylacetate, and ethyl trimethylacetate.

[0090] As a further aspect, the phosphoric acid ester solvent comprises at least one of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphite, and ethoxy(pentafluoro)cyclotriphosphazene.

[0091] As a further aspect, the acetal solvent is selected from any one or several of dimethylaluminum, diethylaluminum, dimethylaluminum, diethylaluminum, 1,1,2,2-tetraethoxyethane.

[0092] As a further aspect, the mass ratio of the ether solvent to the second solvent in the gel electrolyte membrane is selected from 0.2 to 2.

[0093] As a further aspect, the base film is selected from glass cellulose film, cellulose film, and porous polyolefin compound film, and one or more coating layers can be provided on the base film.

[0094] As a further solution, the porous polyolefin compound film is selected from any one or several of a polyethylene porous film, a polypropylene film, a polytetrafluoroethylene coated polyolefin film, a polyvinyl alcohol crosslinked polyolefin film, an ethylene-propylene copolymer porous film, an ultra-high molecular weight polyethylene porous film, an ethylene-vinyl acetate copolymer film, a polyacrylonitrile coated polyolefin film, a polyethylene blended porous film with polylactic acid, an ethylene-octene copolymer porous film.

[0095] As a further solution, the coating layer is in principle not limited, for example, can be selected from any one or several of a polymer material, a carbon material, an oxide material.

[0096] As a further solution, the polymer material is selected from any one or several of polyethylene glycol, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyurethane, polymethyl methacrylate, polystyrene, polyvinylidene fluoride-hexafluoropropylene copolymer.

[0097] As a further solution, the carbon material is selected from any one or several of carbon nanotubes, graphene, carbon nanofibers, porous carbon, graphitic carbon, carbon black, nitrogen-doped carbon.

[0098] As a further solution, the oxide material is selected from any one or several of Al2O3, zirconium oxide, titanium oxide, silicon oxide, magnesium oxide, tin oxide, yttrium oxide, cerium oxide.

[0099] As a further solution, the gel electrolyte film has a Raman scattering peak at 512 cm -1 in the Raman spectrum measurement, the standard deviation of the peak position is 2 cm -1 or less.

[0100] In a third aspect, the present solution further proposes a method for preparing a gel electrolyte film, the specific steps are:

[0101] S1: under an inert atmosphere, dissolve the lithium salt in an ether solvent, then add the halogenated amide additive and the monomer containing unsaturated carbon-carbon double bond and disulfide bond, then add the initiator, mix uniformly to obtain a precursor solution;

[0102] S2: immerse the base film in the precursor solution in a dry environment, take it out after complete wetting, and irradiate it with ultraviolet light to obtain a gel electrolyte film.

[0103] As a further solution, in step S1, the inert atmosphere is selected from any one of helium, neon, argon, krypton, xenon, radon.

[0104] As a further solution, in step S1, the lithium salt is selected from a total mass content in the polymer electrolyte selected from 5%-50%.

[0105] As a further solution, in step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 10% to 30%.

[0106] As a further solution, in step S1, the concentration of the lithium salt is selected from 0.1 mol / L to 5 mol / L.

[0107] As a further solution, in step S1, the concentration of the lithium salt is selected from 1.5 mol / L to 3 mol / L.

[0108] As a further solution, in step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 1% to 45%.

[0109] As a further solution, in step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 20% to 38%.

[0110] As a further solution, the total mass content of the halogenated amide additive in the polymer electrolyte in step S1 is selected from 0.1% to 5%.

[0111] As a further solution, the total mass content of the halogenated amide additive in the polymer electrolyte in step S1 is selected from 0.5% to 2%.

[0112] As a further solution, in step S1, the total mass content of monomers containing unsaturated carbon-carbon double bonds and disulfide bonds in the polymer electrolyte is selected from 2% to 10%.

[0113] As a further solution, in step S1, the total mass content of monomers containing unsaturated carbon-carbon double bonds and disulfide bonds in the polymer electrolyte is selected from 5% to 8%.

[0114] As a further solution, in step S1, the total mass content of the initiator in the polymer electrolyte is selected from 0.1% to 2%.

[0115] As a further solution, in step S1, the total mass content of the initiator in the polymer electrolyte is selected from 0.5% to 1%.

[0116] As a further solution, a halogenated sulfonamide additive may be added in step S1.

[0117] As a further solution, in step S1, the total mass content of the halogenated sulfonamide additive in the polymer electrolyte is selected from 0.1% to 5%.

[0118] As a further solution, in step S1, the total mass content of the halogenated sulfonamide additive in the polymer electrolyte is selected from 0.5% to 2%.

[0119] As a further solution, the drying environment in step S2 refers to an environment with a water content of less than 1 ppm.

[0120] As a further solution, the ultraviolet irradiation time is selected from 1 min to 8 min.

[0121] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0122] The chemical raw materials involved in the following examples and comparative examples are all prior art and are all obtained by commercial purchase. The experimental devices, testing devices, etc. involved in the following examples and comparative examples are all conventional devices in the art, without special requirements and limitations.

[0123] Example 1

[0124] Preparation of gel electrolyte membrane

[0125] S1: In an argon-protected glove box, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) with a concentration of 1.5 mol / L and a mass ratio of 22.4% in the electrolyte was dissolved in a 1:1:1 mass ratio of 1,3-dioxolane, ethylene glycol dimethyl ether and methylal dimethyl alcohol mixed solvent. 1% of the total mass of the electrolyte was added trifluoroacetamide additive, 1% of the total mass was added bis(trifluoromethane)sulfonylimide, 8% of the total mass was added N,N-bis(acryloyl)cystamine monomer, and 1% of the total mass of the monomer was added 1-hydroxycyclohexyl phenyl ketone initiator. Continuous stirring obtained a precursor solution.

[0126] S2: In an environment with a water content of less than 1 ppm, the polypropylene-based film was immersed in the precursor solution, taken out after complete wetting, and a UV light was used for continuous irradiation for 2 min to obtain a gel electrolyte membrane.

[0127] Preparation of battery

[0128] In an environment with a water content of less than 1 ppm, a gel electrolyte membrane was used as a separator, a mass ratio of 7:2:1 of sulfur / carbon nanotube / porous carbon material was used as a positive electrode, and lithium metal was used as a negative electrode to assemble a semi-solid lithium-sulfur battery.

[0129] Example 2

[0130] The preparation method is the same as that in Example 1, except that bis(trifluoromethane)sulfonylimide is not added.

[0131] Example 3

[0132] The preparation method is the same as that of Example 1, except that trifluoroacetamide is replaced by pentafluoropropionamide.

[0133] Example 4

[0134] The preparation method is the same as that of Example 1, except that N,N-bis(acryloyl)cystamine monomer is replaced by allyl propyl disulfide.

[0135] Example 5

[0136] The preparation method is the same as that of Example 1, except that bis(trifluoromethane)sulfonimide is replaced by trifluoromethane sulfonamide.

[0137] Example 6

[0138] The preparation method is the same as that of Example 1, except that bis(trifluoromethane)sulfonimide accounts for 0.1% of the total mass of the electrolyte.

[0139] Example 7

[0140] The preparation method is the same as that of Example 1, except that N,N-bis(acryloyl)cystamine monomer accounts for 4% of the total mass of the electrolyte.

[0141] Example 8

[0142] The preparation method is the same as that of Example 1, except that trifluoroacetamide accounts for 3% of the total mass of the electrolyte.

[0143] Example 9

[0144] The preparation method is the same as that of Example 1, except that the concentration of LiTFSI is 2 mol / L, and the mass accounts for 27.8% in the electrolyte.

[0145] Example 10

[0146] The preparation method is the same as that of Example 1, except that the ultraviolet curing time is 5 min.

[0147] Example 11

[0148] The preparation method is the same as that of Example 1, except that the polypropylene-based film is replaced by an Al2O3-coated polypropylene film.

[0149] Comparative Example 1

[0150] The preparation method is the same as that of Example 1, except that trifluoroacetamide is not added.

[0151] Comparative Example 2

[0152] The preparation method is the same as that of Example 1, except that N,N-bis(acryloyl)cystamine is not added.

[0153] Comparative Example 3

[0154] The preparation method is the same as that of Example 1, except that no ethylene glycol dimethyl ether is added.

[0155] Comparative Example 4

[0156] The preparation method is the same as that of Example 1, except that lithium bis-trifluoromethanesulfonimide (LiTFSI) with a concentration of 1 mol / L and a mass ratio of 16% in the electrolyte is dissolved in a 1:1 mass ratio of 1,3-dioxolane and ethylene glycol dimethyl ether mixed solvent as a liquid electrolyte to replace the precursor solution.

[0157] Comparative Example 5

[0158] The preparation method is the same as that of Example 1, except that it is prepared by in-situ thermal polymerization, that is, the precursor solution is injected into the battery, and the battery is assembled and heated at 60°C for 3h.

[0159] Test conditions of Examples 1-11 and Comparative Examples 1-5 are shown in Table 1.

[0160] Test method: The lithium-sulfur battery is tested by constant current charge and discharge cycling at 0.2C rate in the voltage range of 2.8-1.2V at 25°C.

[0161] Initial discharge specific capacity = initial discharge capacity / mass of active sulfur

[0162] Initial coulombic efficiency = (initial discharge capacity / initial charge capacity)*100%

[0163] 50th cycle capacity retention rate = (50th discharge capacity / initial discharge capacity)*100%

[0164] 50th coulombic efficiency = (50th discharge capacity / 50th charge capacity)*100%

[0165] Raman spectrum test

[0166] Labram HR is used to test the Raman spectrum, and the test wavelength is 532nm.

[0167] Test results of Examples 1-11 and Comparative Examples 1-5 are shown in Table 2.

[0168] Table 1

[0169]

[0170]

[0171]

[0172] Table 2

[0173]

[0174]

[0175] From Examples 1-11, Comparative Examples 1-5, it can be observed that Examples 1-11 as a whole exhibit higher initial specific discharge capacity, first cycle coulombic efficiency than Comparative Examples 1-5, indicating that the gel electrolyte membrane can ensure higher ionic conductivity in the battery. After 50 cycles, Examples 1-11 as a whole still exhibit better cycle capacity retention and coulombic efficiency than Comparative Examples 1-5, indicating that the gel electrolyte membrane can effectively inhibit the "shuttle effect" while avoiding the loss of positive and negative active materials, thereby effectively optimizing the cycle performance of lithium-sulfur batteries.

[0176] From Example 1, Comparative Examples 1-3, it can be observed that ( Figures 2-3 ) whether it is a halogenated amide additive, a monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, or an ether solvent, all play an important role in improving the ionic conductivity of lithium-sulfur batteries, inhibiting the "shuttle effect", and avoiding the consumption of positive and negative active materials. In Comparative Example 1-3, when the halogenated amide additive and the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond are absent, Comparative Example 1-2 exhibits lower 50th cycle capacity retention and 50th cycle coulombic efficiency than the absence of ether solvent, which may be because in the gel electrolyte membrane, the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond needs to work synergistically with the halogenated amide additive, inhibiting the "shuttle effect" while activating polysulfides with the halogenated amide additive to avoid the loss of positive and negative active materials, so Example 1 exhibits much better cycle capacity than Comparative Example 1-2 ( Figure 3 ). In addition, the addition of the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond can also construct efficient ion channels using the self-polymerization of the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, and when the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond is absent, Comparative Example 2 exhibits lower initial specific discharge capacity and first cycle coulombic efficiency than Comparative Example 1. In Comparative Example 3, we observed that when no ether solvent is added as a solvent, the overall performance of Comparative Example 3 is greatly affected, which may be because the lack of ether solvent can lead to a decrease in the solubility of lithium polysulfide, thus affecting the initial coulombic efficiency and specific capacity of Comparative Example 3, and during subsequent cycles, although the presence of halogenated amide additives, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, and halogenated sulfonamide additives can optimize the cycle performance of lithium-sulfur batteries to some extent, the lack of ether solvent may not provide a stable environment for the dissolution and conversion of lithium polysulfide, thus affecting the cycle performance.

[0177] Comparative Example 4 uses electrolyte instead of gel electrolyte. It can be clearly observed from Comparative Example 4 that the specific discharge capacity and coulombic efficiency of the first cycle of Comparative Example 4 are affected compared to Example 1. This may be because the serious dissolution and shuttle effect of polysulfides in the liquid electrolyte leads to serious loss of active material, while the use of gel electrolyte can effectively alleviate the shuttle effect of polysulfides, so Example 1 exhibits better specific discharge capacity and coulombic efficiency of the first cycle than Comparative Example 4.

[0178] Example 1, Comparative Example 5 shows the influence of polymerization method on the performance of lithium-sulfur batteries. When Comparative Example 5 is prepared by in-situ thermal polymerization, it can be observed that the specific discharge capacity of Comparative Example 5 is only 735.8 mAh / g in the first cycle, the coulombic efficiency of the first cycle is only 55.2%, and the capacity retention rate of Comparative Example 5 is only 75.2% after 50 cycles, and the coulombic efficiency of the 50th cycle is only 78.5%, which are all lower than Example 1. This may be because when the curing is not performed by ultraviolet curing, the monomers containing unsaturated carbon-carbon double bonds and disulfide bonds may not be fully polymerized, and a complete and stable ion-conducting pathway cannot be constructed, and the dynamic exchange reaction of disulfide bonds cannot be fully utilized to inhibit the shuttle of polysulfides in the electrolyte. At the same time, during the in-situ thermal initiation polymerization process, the monomers that are not fully polymerized have many lone pair electrons, which are prone to interface side reactions with lithium metal, thereby deteriorating the battery performance.

[0179] Example 1, 2 shows the compounding effect of halogenated sulfonamide additives in gel electrolyte film. When the halogenated sulfonamide additive is added, Example 1 exhibits higher cycle capacity retention rate and 50th cycle coulombic efficiency than Example 2, which may be because the amino group in the sulfonamide group can interact with the amide group, thereby affecting the behavior of polysulfides; secondly, the electrophilicity of the halogenated sulfonamide additive enables it to stabilize polysulfides and promote the dissolution of polysulfides through non-covalent interaction with polysulfide anions; in addition, the presence of halogen elements in the halogenated sulfonamide also helps to promote the dissociation of polysulfides. Under the compounding effect of the halogenated sulfonamide additive, Example 1 exhibits good capacity retention rate (84.3%) and 50th cycle coulombic efficiency (89.6%).

[0180] Example 1, 3 shows the influence of halogenated amide additives with different structures on the performance of gel electrolyte film. It can be observed from Example 1 that when trifluoroacetamide is used as an additive, Example 1 exhibits better first cycle capacity and specific discharge capacity than Example 3, which may be because the SEI film constructed by fluorine elements in trifluoroacetamide is more moderate in thickness than the SEI film constructed by pentafluoroacetamide, which can protect the battery while improving the specific discharge capacity and coulombic efficiency of the first cycle of the battery, so Example 1 exhibits better electrochemical performance than Example 3.

[0181] Example 1, 4 demonstrates the influence of monomers with different structures containing unsaturated carbon-carbon double bonds and disulfide bonds on the performance of gel electrolyte films. When N, N-bis(acryloyl)cystamine is used as an additive, Example 1 exhibits better initial specific discharge capacity and first-cycle coulombic efficiency than Example 4. After 50 cycles, Example 1 also exhibits better cycle capacity retention and 50th cycle coulombic efficiency. This may be because, compared to allyl propyl disulfide, N, N-bis(acryloyl)cystamine with a symmetrical structure and double-end unsaturated carbon-carbon double bonds can combine with the base film during polymerization, building more uniform and orderly ion channels, and a more uniform disulfide bond interception network, fully inhibiting the "shuttle effect", so Example 1 exhibits better cycle performance.

[0182] Example 1, 5 demonstrates the influence of halogenated sulfamide structure on battery performance. When the halogenated sulfamide used is a chain halogenated sulfamide with a symmetrical structure, Example 1 exhibits better initial specific discharge capacity and first-cycle coulombic efficiency than Example 5, and better cycle performance in subsequent cycles. This may be because the chain halogenated sulfamide with a symmetrical structure can provide more uniform and effective interactions with polysulfides, while also providing a higher content of halogen elements, thereby optimizing battery performance.

[0183] Examples 1, 6-9 demonstrate the influence of halogenated amide additives, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, the proportion of halogenated sulfamide additives in the electrolyte, and the concentration of lithium salt on battery performance. As can be observed from Examples 6-9, the proportion of halogenated amide additives, monomers containing unsaturated carbon-carbon double bonds and disulfide bonds, halogenated sulfamide additives in the electrolyte, and the concentration of lithium salt should all be controlled and coordinated with each other. The reason why Example 1 exhibits better performance than Examples 6-9 is that the addition amount of each component in Example 1 can fully play the compounding effect of each other, thereby optimizing battery performance.

[0184] Example 1, 10 demonstrates the influence of UV curing time on battery performance. It can be observed that when the UV curing time is 2 min, Example 1 exhibits better initial specific discharge capacity than Example 10, while Example 10 exhibits better cycle capacity retention and coulombic efficiency after 50 cycles. This may be because longer curing time will increase the degree of polymerization of the monomer containing unsaturated carbon-carbon double bonds and disulfide bonds, thereby improving the inhibition of the "shuttle effect". At the same time, when the curing time is 2 min, Example 1 has higher ionic conductivity, so the initial specific discharge capacity and first-cycle coulombic efficiency are both better.

[0185] Example 1, 11 discusses the influence of the base film. It can be observed that both Example 1 and Example 11 exhibit good initial discharge capacity and cycle performance, indicating that different base films uniformly exhibit good performance.

[0186] Each technical feature of the above-described embodiments can be combined with any other technical feature, and for the sake of brevity, not all possible combinations are described, but it is understood that the scope of the present specification includes all possible combinations. Although the above has shown and described the embodiments of the present application, it is to be understood that the above-described embodiments are merely illustrative of the principles of the present application, and are not to be taken in a limiting sense. Those skilled in the art can readily devise numerous alternative ways to implement the same without departing from the scope of the present application. Furthermore, the different embodiments or examples described in the specification can be combined with each other, and the features of the different embodiments or examples can be combined with each other, unless they are mutually contradictory.

Claims

1. A gel electrolyte film for a lithium-sulfur battery, characterized by, The gel electrolyte film includes a base film and a polymer electrolyte based on solidification of the base film, and has a Raman scattering peak at 512 cm -1 in the Raman spectrum measurement, the standard deviation of the peak position is 2 cm -1 or less; the gel electrolyte film is obtained by polymerizing and solidifying a precursor solution after the base film is soaked in the precursor solution, the precursor solution including a halogenated amide additive, a monomer containing an unsaturated carbon-carbon double bond and a disulfide bond, an ether solvent, a lithium salt, and an initiator.

2. The gel electrolyte film according to claim 1, wherein The halogenated amide additive is selected from a chain halogenated amide additive with an end amide group and a halogen element substitution number less than or equal to 3.

3. The gel electrolyte film according to claim 2, wherein The chain halogenated amide additive with an end amide group and a halogen element substitution number less than or equal to 3 has a carbon chain length less than or equal to 6.

4. The gel electrolyte film according to claim 2, wherein The chain halogenated amide additive with an end amide group and a halogen element substitution number less than or equal to 3 has a carbon chain length less than or equal to 4.

5. The gel electrolyte film according to claim 4, wherein The chain halogenated amide having a carbon chain length of 4 or less, having an end amide group, and having a halogen element substitution number of 3 or less is selected from any one of , , , , , , , , .

6. The gel electrolyte film according to claim 1, wherein The monomer containing an unsaturated carbon-carbon double bond and a disulfide bond is a symmetric monomer containing double-end unsaturated carbon-carbon double bonds and disulfide bonds.

7. The gel electrolyte film according to claim 6, wherein The symmetrical monomer containing a double bond and a disulfide bond is selected from any one of , .

8. The gel electrolyte film according to claim 1, wherein The precursor solution further comprises a halogenated sulfonamide additive.

9. The gel electrolyte film according to claim 8, wherein The halogenated sulfonamide additive is a chain halogenated sulfonamide with a symmetric structure.

10. The gel electrolyte film according to claim 9, wherein The chain halogenated sulfonamide having a symmetrical structure is selected from any one of , , .

11. The gel electrolyte film according to claim 1, wherein The ether solvent is selected from any one or several of simple ether solvents, which are solvents with the structure of R-O-R', wherein R and R' are alkyl or aryl groups.

12. The gel electrolyte film according to claim 1, wherein The ether solvent is selected from any one or several of polyether solvents.

13. The gel electrolyte film according to claim 1, wherein The ether solvent is selected from any one or several of cyclic ether solvents.

14. The gel electrolyte film according to claim 1, wherein The lithium salt is selected from any one or several of organic lithium salts and inorganic lithium salts.

15. The gel electrolyte film according to claim 14, wherein The organic lithium salt is selected from any one or several of fluorine-substituted lithium sulfonate salts.

16. The gel electrolyte film according to claim 14, wherein The organic lithium salt is selected from any one or several of fluorine-substituted lithium oxalate salts.

17. The gel electrolyte film according to claim 14, wherein The organic lithium salt is selected from any one or several of fluorine-substituted lithium borate salts.

18. The gel electrolyte film according to claim 14, wherein The inorganic lithium salt is selected from any one or several of fluorine-substituted inorganic lithium borate salts, fluorine-substituted inorganic lithium phosphate salts, lithium perchlorate, and inorganic lithium nitrate salts.

19. The gel electrolyte film according to claim 1, wherein The initiator is selected from any one of ketone compounds and phosphine oxides.

20. The gel electrolyte film according to claim 1, wherein The precursor solution further comprises a second solvent selected from any one or several of ester solvents or acetal solvents.

21. The gel electrolyte film according to claim 20, wherein The ester solvent is selected from any one or several of chain carbonate solvents, carboxylic acid ester solvents, and phosphate ester solvents.

22. The gel electrolyte film of claim 20, wherein The mass ratio of the ether solvent to the second solvent in the gel electrolyte membrane is selected from 0.2 to 2.

23. The gel electrolyte film of claim 1, wherein The base film is selected from glass cellulose films, cellulose films, and porous polyolefin compound films.

24. The gel electrolyte film of claim 1, wherein The base film is provided with one or more coating layers.

25. A method of preparing the gel electrolyte film according to any one of claims 1 to 24, characterized by, The specific steps for preparing the gel electrolyte membrane are as follows: S1: under an inert atmosphere, the lithium salt is dissolved in the ether solvent, and then the halogenated amide additive and the monomer containing an unsaturated carbon-carbon double bond and a disulfide bond are added, followed by the addition of the initiator, and the mixture is uniformly mixed to obtain a precursor solution; S2: in a dry environment, the base film is immersed in the precursor solution, taken out after complete wetting, and irradiated with ultraviolet light to obtain a gel electrolyte membrane.

26. The method of claim 25, wherein, In the step S1, the inert atmosphere is selected from any one of helium, neon, argon, krypton, xenon, and radon.

27. The method of claim 25, wherein, In the step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 5% to 50%.

28. The method of claim 25, wherein, In the step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 10% to 30%.

29. The method of claim 25, wherein, In the step S1, the concentration of the lithium salt is selected from 0.1 mol / L to 5 mol / L.

30. The method of claim 25, wherein, In the step S1, the concentration of the lithium salt is selected from 1.5 mol / L to 3 mol / L.

31. The method of claim 25, wherein, In the step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 1% to 45%.

32. The method of claim 25, wherein, In the step S1, the total mass content of the lithium salt in the polymer electrolyte is selected from 20% to 38%.

33. The method of claim 25, wherein, The total mass content of the halogenated amide additive in the polymer electrolyte in step S1 is selected from 0.1%-5%.

34. The method of claim 25, wherein, The total mass content of the halogenated amide additive in the polymer electrolyte in step S1 is selected from 0.5%-2%.

35. The method of claim 25, wherein, The total mass content of the monomer containing unsaturated carbon-carbon double bond and disulfide bond in the polymer electrolyte in step S1 is selected from 2%-10%.

36. The method of claim 25, wherein, The total mass content of the monomer containing unsaturated carbon-carbon double bond and disulfide bond in the polymer electrolyte in step S1 is selected from 5%-8%.

37. The method of claim 25, wherein, The total mass content of the initiator in the polymer electrolyte in step S1 is selected from 0.1%-2%.

38. The method of claim 25, wherein, The total mass content of the initiator in the polymer electrolyte in step S1 is selected from 0.5%-1%.

39. The method of claim 25, wherein, A halogenated sulfonamide additive is also added in step S1.

40. The method of claim 39, wherein, The total mass content of the halogenated sulfonamide additive in the polymer electrolyte in step S1 is selected from 0.1%-5%.

41. The method of claim 39, wherein, The total mass content of the halogenated sulfonamide additive in the polymer electrolyte in step S1 is selected from 0.5%-2%.

42. The method of claim 25, wherein, In step S2, the dry environment refers to an environment with water content less than 1 ppm.

43. The method of claim 25, wherein, In step S2, the ultraviolet light irradiation time is selected from 1 min-8 min.

44. An electrode assembly having the gel electrolyte film of any one of claims 1-24 or obtained by the method of any one of claims 25-43.

45. A battery cell having the gel electrolyte film of any one of claims 1-24 or obtained by the method of any one of claims 25-43.

46. An energy storage device having the gel electrolyte film of any one of claims 1-24 or obtained by the method of any one of claims 25-43.

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