Positive pole piece, solid-state battery and preparation method of positive pole piece

Abstract

The invention provides a positive pole piece, a solid-state battery and a preparation method of the positive pole piece, and belongs to the technical field of secondary batteries, and the positive pole piece comprises a positive current collector and a positive active material layer. Wherein the positive electrode active material layer is arranged on the positive electrode current collector, the interface layer is arranged on the positive electrode active material layer, the interface layer comprises a first polymer, and the first polymer comprises polyether sulfonate. According to the positive pole piece provided by the invention, the polymer interface layer formed by cross-linking polyether sulfonate is arranged on the surface of the positive active material layer, so that the interface contact and ion transmission efficiency between the positive pole piece and the solid electrolyte membrane are effectively improved based on good ionic conductivity, chemical stability and mechanical flexibility of the interface layer; the interface impedance between the positive pole piece and the solid electrolyte membrane is reduced, and the side reaction of a contact interface is inhibited, so that the rate capability and the cycle life of the solid-state battery are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a positive electrode sheet, a solid-state battery, and a method for preparing the positive electrode sheet. Background Technology

[0002] As a next-generation energy storage technology solution, the core advantage of solid-state batteries lies in using non-flammable solid electrolytes instead of organic liquid electrolytes, which simplifies battery design, improves battery safety and energy density, and widens the battery operating temperature range, thus potentially solving battery safety issues fundamentally.

[0003] However, in current solid-state battery structures formed using hot-pressing processes, numerous microscopic voids remain at the interface between the positive electrode and the solid electrolyte membrane. This leads to increased interfacial impedance due to poor contact. Furthermore, the positive electrode active material and solid electrolyte at the interface are prone to oxidation side reactions under high voltage, causing the positive electrode active material to fail and disrupting the lithium-ion transport path at the interface. These defects all contribute to increased polarization and rapid capacity decay during charge-discharge cycles.

[0004] Therefore, it is necessary to design a positive electrode sheet, a solid-state battery, and a method for preparing the positive electrode sheet to improve the above-mentioned problems. Summary of the Invention

[0005] This invention provides a positive electrode sheet, a solid-state battery, and a method for preparing the positive electrode sheet. By constructing an interface layer between the positive electrode sheet and the solid electrolyte membrane that enables ion conduction and shields side reactions, the invention effectively improves the problems of increased battery polarization and reduced cycle life caused by poor contact and chemical stability between the positive electrode sheet and the solid electrolyte membrane.

[0006] In a first aspect, the present invention provides a positive electrode sheet, which includes a positive current collector, a positive active material layer, and an interface layer.

[0007] The positive electrode active material layer is disposed on the positive electrode current collector; the interface layer is disposed on the positive electrode active material layer, and the interface layer includes a first polymer, which includes a polyether sulfonate.

[0008] In one example of the present invention, the first polymer is formed by polymerization of a sulfur-containing cyclic lactone monomer, wherein the sulfur-containing cyclic lactone monomer includes at least one of 1,3-propanesulfonic acid lactone, 1,4-butanesulfonic acid lactone, 2,2,2-trifluoroethylsulfonic acid lactone and its substituted derivatives.

[0009] In one example of the present invention, the thickness of the interface layer is 5~25nm.

[0010] In one example of the present invention, the interface layer further includes a second polymer, which forms an interpenetrating polymer network with the first polymer. The second polymer is formed by polymerization of vinyl monomers, which contain Lewis basic nitrogen atoms.

[0011] In one example of the present invention, the vinyl monomers include at least one of dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, dimethylaminobutyl acrylate, dipropylaminoethyl acrylate, and dimethylaminoethyl methacrylate.

[0012] In one example of the present invention, the mass ratio of the first polymer to the second polymer is 3:(1~5).

[0013] In one example of the present invention, the thickness of the interface layer is 10~60nm.

[0014] In one example of the present invention, the interface layer further includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(fluorosulfonylimide), lithium bis(perfluoroethyl)sulfonylimide, lithium difluoro(oxalate)borate, and lithium bis(oxalate)borate.

[0015] In a second aspect, the present invention also provides a method for preparing a positive electrode sheet, the method comprising: An unmodified electrode sheet is provided, the unmodified electrode sheet comprising a positive current collector and a positive active material layer disposed on the positive current collector; A lithium salt, a sulfur-containing cyclic lactone monomer, and a first initiator are mixed in an organic solvent to prepare a polymerization precursor solution; the first initiator is used to initiate the polymerization of the sulfur-containing cyclic lactone monomer. The polymer precursor solution is coated onto the unmodified electrode sheet and then dried by heating to obtain the positive electrode sheet.

[0016] In one example of the present invention, the step of preparing the polymer precursor solution includes: mixing lithium salt, sulfur-containing cyclic lactone monomer, first initiator, vinyl monomer, and second initiator in an organic solvent according to a preset mass ratio to prepare a polymerization precursor solution; the second initiator is used to initiate the polymerization of the vinyl monomer.

[0017] In a third aspect, the present invention also provides a solid-state battery comprising a negative electrode, a solid electrolyte membrane, and a positive electrode as described in any of the foregoing examples, or a positive electrode prepared by any of the foregoing examples.

[0018] The positive electrode provided by this invention has a polymer interface layer formed by crosslinking polyether sulfonate on the surface of the positive electrode active material layer. Based on the good ionic conductivity, chemical stability and mechanical flexibility of the interface layer, it can effectively improve the interfacial contact and ion transport efficiency between the positive electrode and the solid electrolyte membrane, reduce the interfacial impedance between the positive electrode and the solid electrolyte membrane, and suppress the occurrence of side reactions at the contact interface, thereby effectively improving the rate performance and cycle life of the solid battery. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of the present invention is for describing specific implementation schemes and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0020] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as part of the scope of the invention.

[0021] In a first aspect, the present invention provides a positive electrode sheet comprising a positive current collector, a positive active material layer, and an interface layer. The positive current collector can be a foil material with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel, or carbon; besides foil materials, the positive current collector can also be any one or more combinations of various forms such as film, mesh, porous, foam, or nonwoven fabric. The positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on at least one side of the positive current collector, specifically, the positive active material layer is disposed on either or both of the two surfaces of the positive current collector. The interface layer can be disposed on the positive active material layer.

[0022] The interface layer includes a first polymer, which is a polyether sulfonate. The interface layer comprises a polymer network formed by crosslinking the first polymer, the polyether sulfonate. Based on the good flexibility and flowability of the polyether sulfonate material, this polymer network can effectively fill the microscopic gaps at the interface between the positive electrode active material layer and the solid electrolyte membrane. This allows the positive electrode active material layer and the solid electrolyte membrane to achieve continuous solid-solid interface contact through the interface layer, thereby significantly reducing the interfacial impedance between the positive electrode and the solid electrolyte membrane.

[0023] The first polymer, polyether sulfonate, serves as a single-ion conductor material for lithium ions (i.e., only allowing Li-ion ions to pass through). + Through the conductive material), the interface layer can rely on the first polymer to form an "organic-inorganic hybrid" three-dimensional continuous single-ion conductive network between the positive electrode active material layer and the solid electrolyte membrane, thereby constructing a high-mobility lithium-ion transport channel between the positive electrode active material layer and the solid electrolyte membrane. Under the action of the single-ion conductive network constructed by the first polymer, the lithium-ion transference number (t) between the positive electrode active material and the solid electrolyte at the contact interface is high. + The value approaches 1, thereby eliminating the space charge layer and concentration polarization caused by the co-movement of cations and anions during lithium-ion translocation, avoiding the accumulation of anions at the contact interface, and thus effectively reducing the interfacial impedance between the positive electrode and the solid electrolyte film, greatly improving the battery polarization problem and enhancing the battery's rate performance.

[0024] Simultaneously, based on the electronic insulation properties of the first polymer, the interface layer can also construct an insulating barrier between the positive electrode active material layer and the solid electrolyte membrane. Besides preventing direct contact between the positive electrode active material and the solid electrolyte membrane, it can also fundamentally cut off the electron transfer pathways that lead to the oxidation of the solid electrolyte (such as sulfide electrolytes). This effectively suppresses oxidation side reactions at the interface between the positive electrode and the solid electrolyte membrane under high voltage, ensuring the chemical stability of the interface and further improving the battery's cycle life. Furthermore, due to its excellent flexibility, the interface layer can effectively absorb the compressive stress on the solid electrolyte membrane caused by the volume expansion of the positive electrode during charging and discharging, thus ensuring the long-term stability of the interface structure between the positive electrode and the fixed electrolyte membrane. This maintains the improvement in battery rate performance while effectively enhancing the battery's cycle life.

[0025] In some embodiments, the first polymer contains a sulfonate group (-[-O-(CH2)2-SO2-]-), and the anionic group (-SO3-) in the sulfonate group... - This allows lithium ions to shuttle freely, giving the first polymer the material properties of a lithium-ion single-ion conductor. Specifically, the anionic group (-SO3) in the sulfonate group... -The lithium-ion channels of the first polymer are covalently bonded to the main chain of the first polymer crosslinked network. This ensures that the lithium-ion channels of the first polymer are uniformly distributed in the interface layer along with the main chain, thereby ensuring that the interface layer has uniform ionic conductivity in space. This reduces the interfacial impedance between the positive electrode and the solid electrolyte membrane, while avoiding concentration polarization caused by uneven lithium-ion transport rates at the contact interface.

[0026] In some embodiments, the first polymer is formed by ring-opening polymerization of a sulfur-containing cyclic lactone monomer. The sulfur-containing cyclic lactone monomer may be selected from one or more combinations of 1,3-propanesulfonic acid lactone, 1,4-butanesulfonic acid lactone, 2,2,2-trifluoroethylsulfonic acid lactone, and substituted derivatives thereof, wherein the substituted derivative may be a halogenated, alkyl, aryl, or fluoroalkyl substituted derivative of the materials listed above.

[0027] In some embodiments, the thickness of the interface layer can be any value within the range of 5 to 25 nm, for example, the interface layer thickness can be 5 nm, 7 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm, 23 nm, or 25 nm. When the interface layer contains only the first polymer and the interface layer thickness is within the above range, the optimal improvement effect on interfacial ionic conductivity and chemical stability can be achieved. If the interface layer is too thick, it will lead to an increase in the interfacial impedance between the positive electrode and the solid electrolyte film, affecting the interface layer's effect on improving battery rate performance. If the interface layer is too thin, it will be difficult for the interface layer to completely shield the side reactions between the positive electrode active material and the solid electrolyte, thereby affecting the interface layer's effect on improving battery cycle life.

[0028] In some embodiments, the interface layer further includes a second polymer formed by polymerization of vinyl monomers. The vinyl monomers forming the second polymer contain Lewis basic nitrogen atoms; for example, the vinyl monomers may contain primary, secondary, or tertiary amine groups with Lewis basic nitrogen atoms. The groups containing Lewis basic nitrogen atoms in the second polymer can instantly and irreversibly capture and neutralize corrosive byproducts generated by the hydrolysis of solid electrolytes, such as hydrogen sulfide (H2S) gas generated by the hydrolysis of sulfide electrolytes. This effectively prevents the chemical corrosion of the positive electrode material by the decomposition byproducts of the solid electrolyte, ensuring the structural integrity of the positive electrode sheet and the long-term stability of the contact interface.

[0029] In the interface layer, the second polymer and the first polymer form a dense, pinhole-free interpenetrating polymer network (IPN), which can reduce the porosity of the interface layer and ensure a tighter contact between the positive electrode active material layer and the solid electrolyte membrane. This allows the positive electrode active material layer and the solid electrolyte membrane to achieve seamless interface contact through the interface layer, thereby further improving the rate performance and cycle performance of the battery.

[0030] In some embodiments, the vinyl monomers include at least one of dimethylaminomethyl acrylate (DMAMA), dimethylaminoethyl acrylate (DMAEA), dimethylaminopropyl acrylate (DMAPA), dimethylaminobutyl acrylate (DMABA), dipropylaminoethyl acrylate (DPAEA), and dimethylaminoethyl methacrylate (MADAMA).

[0031] In some embodiments, the mass ratio of the first polymer to the second polymer in the interface layer is 3:(1~5), for example, the mass ratio of the first polymer to the second polymer can be 3:1, 3:2, 3:3, 3:4, or 3:5; optionally, the mass ratio of the first polymer to the second polymer can be 1:1. Although the second polymer has a cleaning effect on corrosive substances at the contact interface, the addition of the second polymer also increases the thickness of the interface layer and dilutes the lithium-ion channel density in the interface layer. Therefore, when the mass ratio of the first polymer to the second polymer in the interface layer is within the above-mentioned suitable range, the optimal improvement effect of the interface layer on the ionic conductivity and chemical stability of the interface layer can be achieved. If the mass ratio of the first polymer to the second polymer is too high (i.e., the content of the second polymer is too low), the second polymer will have difficulty completely capturing corrosive substances at the contact interface; if the mass ratio of the first polymer to the second polymer is too low (i.e., the content of the first polymer is too low), the ionic conductor material in the interface layer will be severely diluted, affecting the improvement effect of the interface layer on the ionic conductivity of the contact interface.

[0032] In some embodiments, the thickness of the interface layer can be any value within the range of 10-60 nm, for example, the interface layer thickness can be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, or 60 nm. When the interface layer simultaneously contains a first polymer and a second polymer, an interface layer thickness within the above range can achieve optimal improvement in both interfacial ionic conductivity and chemical stability. If the interface layer is too thick, it will increase the interfacial impedance between the positive electrode and the solid electrolyte membrane, affecting the interface layer's improvement effect on battery rate performance. If the interface layer is too thin, it will be difficult for the interface layer to completely shield the side reactions between the positive electrode active material and the solid electrolyte, thereby affecting the interface layer's improvement effect on battery cycle life.

[0033] In some embodiments, the interface layer also includes a lithium salt. The lithium salt mixed into the interface layer can provide sufficient conductive charge carriers, thereby further improving the ionic conductivity of the interface layer, reducing the interfacial impedance between the positive electrode and the solid electrolyte membrane, and improving the rate performance of the battery.

[0034] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(fluorosulfonylimide), lithium bis(perfluoroethyl)sulfonylimide, lithium difluoro(oxalate)borate, and lithium bis(oxalate)borate.

[0035] In some embodiments, the mass content of lithium salt in the interface layer is any value in the range of 20% to 30%, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%.

[0036] Furthermore, it should be noted that in this application, the positive electrode active material layer includes positive electrode active material, solid electrolyte positive electrode binder and positive electrode conductive agent. The mass content of the above components in the positive electrode active material layer is not limited, and the content of each component can be adjusted according to the functional requirements of the battery. For example, the mass ratio of positive electrode active material, solid electrolyte, positive electrode binder and positive electrode conductive agent can be (50~97):(1~50):(0~3):(1~3):(0.01~0.5).

[0037] In this application, the positive electrode active material used in the positive electrode sheet can be any conventional positive electrode active material, and the type of positive electrode active material is not limited. For example, the positive electrode active material is selected from one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), and lithium-rich manganese oxide (LRMO).

[0038] The type of solid electrolyte used in the positive electrode is not limited, and the solid electrolyte can be at least one of sulfide electrolytes, halide electrolytes, oxide electrolytes, and polymer electrolytes. For example, sulfide electrolytes include Li7P3S. 11 Li6PS5Cl, Li 10 GeP2S 12 At least one of the following: ; as an example, halide electrolytes include at least one of Li3YCl6, Li3InCl6, Li3YBr6 and their derivatives; as an example, oxide electrolytes include at least one of lithium lanthanum zirconium oxide (LLZO), lithium titanium aluminum phosphate (LATP), lithium lanthanum titanate (LLTO) and their derivatives; as an example, polymer-based electrolytes include at least one of PEO-LiTFSI and PVDF-HFP.

[0039] The type of material used for the positive electrode binder in the positive electrode sheet is not limited. For example, the positive electrode binder can be selected from polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene propylene Diene monomers, styrene Butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer are among one or more combinations thereof.

[0040] The type of positive electrode conductive agent used in the positive electrode sheet is not limited. The positive electrode conductive agent can be selected from at least one of graphite, graphene, carbon black, carbon fiber and carbon nanotubes, as well as fluorination or oxidation modification of the above materials.

[0041] In a second aspect, the present invention also provides a method for preparing a positive electrode sheet, the method comprising the following steps: S1. Provide unmodified electrode sheets; S2. Lithium salt, sulfur-containing cyclic lactone monomer and first initiator are mixed in an organic solvent to prepare a polymerization precursor solution; S3. The polymerization precursor solution is coated onto the unmodified electrode sheet and then dried by heating to obtain the positive electrode sheet.

[0042] In step S1, the provided unmodified electrode sheet can be a finished positive electrode sheet without an interface layer formed on its surface. The unmodified electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector.

[0043] In step S2, the sulfur-containing cyclic lactone monomer and the first initiator are mixed in an organic solvent at a mass ratio of (50~100):1.

[0044] In step S2, the first initiator is used to initiate the polymerization of sulfur-containing cyclic lactone monomers. In some embodiments, the first initiator is a cationic polymerization initiator, for example, the polymerization initiator may be selected from one or more combinations of organic sulfonate compounds (such as methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, isopropyl trifluoromethanesulfonate) and Lewis acid compounds (such as BF3·Et2O, AlCl3, FeCl3).

[0045] In some embodiments, the organic solvent may be any low-boiling-point, aprotic, volatile solvent, such as one or more combinations of toluene, xylene, chlorobenzene, acetonitrile, butyronitrile, ethyl methyl carbonate, dimethyl carbonate, ethyl acetate, butyl butyrate, dichloromethane, and dichloroethane.

[0046] Furthermore, in some embodiments, when preparing an interface layer containing an interpenetrating polymer network of a first polymer and a second polymer, step S2 of preparing the polymer precursor solution includes: mixing a sulfur-containing cyclic lactone monomer, a first initiator, a vinyl monomer, and a second initiator in an organic solvent according to a preset mass ratio to prepare a polymerization precursor solution. The mass ratio of the sulfur-containing cyclic lactone monomer, the first initiator, the vinyl monomer, and the second initiator is (150~300):1:(50~250):(2~10).

[0047] In some embodiments, the second initiator may be selected from one or more combinations of azobisisobutyronitrile (AIBN), azobis(2,4-dimethylpentanonitrile) (ADVN), 1,1'-azobis(cyclohexanecarboxynitrile) (CAN), benzoyl peroxide (BPO), lauroyl peroxide (LPO), di-tert-butyl peroxide (DTBP), dicumyl peroxide (DCP), or tert-butyl peroxide (TBPB).

[0048] In step S3, the polymerization precursor solution is coated onto the surface of the positive electrode active material layer of the unmodified electrode. Then, the unmodified electrode coated with the polymerization precursor solution is heated and dried to allow the organic solvent in the polymerization precursor solution to evaporate and promote the in-situ cross-linking of polymer monomers in the polymerization precursor solution under the catalysis of the corresponding initiator to form polymers (such as sulfur-containing cyclic lactone monomers polymerizing to form the first polymer under the action of the first initiator, and vinyl monomers polymerizing to form the second polymer under the action of the second initiator), thereby forming an interface layer on the surface of the positive electrode.

[0049] In some embodiments, in step S3, the drying temperature of the electrode coated with the polymerization precursor solution is 50°C to 80°C, and the drying time is 8 to 12 hours.

[0050] In a third aspect, the present invention also provides a solid-state battery, which can be a solid-state lithium-ion secondary battery. The solid-state battery includes a negative electrode, a solid electrolyte membrane, and a positive electrode from any of the above embodiments. The solid electrolyte membrane is disposed between the positive and negative electrode to isolate the positive and negative electrode and serves as a lithium-ion conductor between the positive and negative electrode.

[0051] The solid electrolyte membrane can be any solid electrolyte membrane used in various systems in the art. For example, in some embodiments, the solid electrolyte membrane includes a solid electrolyte and a membrane layer binder. The mass ratio of the solid electrolyte to the membrane layer binder in the solid electrolyte membrane is (90~100):(0.5~10). The solid electrolyte is selected from at least one of sulfide electrolytes, halide electrolytes, oxide electrolytes, and polymer electrolytes. The membrane layer binder is selected from any one of nitrile rubber (NBR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and linear triblock copolymers, or a combination of several of these in any proportion.

[0052] The negative electrode can be a negative electrode used in various systems in this field.

[0053] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer coated on at least one side of the negative current collector. The negative active material layer includes a negative active material, a solid electrolyte, a negative binder, and a negative conductive agent. The preparation process of this type of negative electrode sheet is as follows: the negative active material, solid electrolyte, negative conductive agent, and negative binder are mixed in a mass ratio of (70~90):(5~25):(1~5):(1~3), deionized water is added as a solvent, and then the mixture is thoroughly stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative current collector, and the negative current collector is dried at room temperature and then transferred to an oven for drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0054] The negative electrode current collector can be made of foil with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel or carbon. In addition to foil, the negative electrode current collector can also be made of any one or more of the following forms: film, mesh, porous, foam or non-woven fabric.

[0055] The negative electrode active material is selected from one or more of the following: tin, artificial graphite (single crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (bulk graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon or organosilicon), silicon oxide, silicon carbide, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles).

[0056] The solid electrolyte is selected from at least one of sulfide electrolytes, halide electrolytes, oxide electrolytes and polymer electrolytes.

[0057] The negative electrode conductive agent is selected from one or more of carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers, or a mixture of two or more in any proportion.

[0058] The negative electrode binder is selected from any one of polyvinylidene fluoride (PVDF), fluoroethylene-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and styrene-butadiene rubber (SBR), or a combination of several of these in any proportion.

[0059] In other embodiments, the negative electrode can be a lithium metal sheet, an indium metal sheet, or a lithium-containing alloy sheet (such as a lithium-tin-indium alloy sheet, a lithium-silicon alloy sheet, a lithium-tin alloy sheet, or a lithium-aluminum alloy sheet). For example, in one example, the negative electrode is selected from a lithium metal sheet.

[0060] An example of a solid-state battery assembly method is described below: A positive electrode is integrated onto one side of a solid electrolyte membrane, for example, by placing the solid electrolyte membrane on the positive active material layer of the positive electrode, and pressing the solid electrolyte membrane and the positive electrode together under a pressure of 200 MPa. Then, a negative electrode is integrated onto the other side of the solid electrolyte membrane, for example, by placing the negative electrode on the other side of the solid electrolyte membrane, so that the negative active material layer of the negative electrode is in contact with the solid electrolyte membrane, and pressing the negative electrode together with the solid electrolyte membrane and the positive electrode under a pressure of 200 MPa. After sealing and encapsulating the pressed cell under a vacuum or inert atmosphere, a solid-state lithium-ion battery is obtained.

[0061] The technical solution of the present invention will be described in detail below through several specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by conventional methods in the art.

[0062] Example 1 This embodiment provides a positive electrode sheet, which includes a positive current collector, a positive active material layer, and an interface layer. The positive active material layer is located on the positive current collector, and the interface layer is located on the positive active material layer. The interface layer includes a first polymer formed by the polymerization of 1,3-propanesulfonic acid lactone. All operations in the preparation of this positive electrode sheet are carried out in an argon glove box with an oxygen content of <0.1ppm and a water content of <0.1ppm. The preparation method of this positive electrode sheet is as follows: (1) Provide unmodified electrode sheets with no interface layer modification on the surface. The unmodified electrode sheets are from Ningbo Rongbai New Energy and are model S800 nickel cobalt manganese oxide.

[0063] (2) Dissolve 1500 mg of 1,3-propanesulfonic acid lactone (PS monomer) and 500 mg of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 2 mL of anhydrous acetonitrile, and then stir magnetically for 15 minutes at room temperature until all solids are completely dissolved; then add 29 mg of the first initiator MeOTf to the anhydrous acetonitrile and stir briefly again for about 1 minute to ensure that the initiator is evenly dispersed to obtain the polymerization precursor solution.

[0064] (3) The unmodified electrode sheet is flattened and fixed on the glass plate of the adjustable gap coating machine. The polymerization precursor solution is uniformly coated on one end of the unmodified electrode sheet. The blade gap of the coating machine is set to 20 μm, so that the coating machine scrapes the blade from the solution end to the other end on the surface of the unmodified electrode sheet at a constant speed of about 5 mm / s, so that the surface of the unmodified electrode sheet is uniformly coated with the polymerization precursor solution. Then, the unmodified electrode sheet coated with the polymerization precursor solution is placed in a preheated oven and heated at 60°C for 2 hours under vacuum. Then, the temperature is raised to 80°C and heated at a constant temperature for 1 hour. Finally, it is vacuum heated at 60°C for 12 hours. After drying, a positive electrode sheet with a 5 nm thick interface layer on the surface is obtained.

[0065] Example 2 This embodiment provides a positive electrode sheet with the same system as in Example 1. The difference between this embodiment and Example 1 is that in step (2), 3000 mg of 1,3-propanesulfonic acid lactone, 1000 mg of lithium bis(trifluoromethanesulfonyl)imide and 58 mg of MeOTf are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 30 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 10 nm.

[0066] Example 3 This embodiment provides a positive electrode sheet with the same system as in Example 1. The difference between this embodiment and Example 1 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 1500 mg of lithium bis(trifluoromethanesulfonyl)imide and 88 mg of MeOTf are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 50 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 15 nm.

[0067] Example 4 This embodiment provides a positive electrode sheet with the same system as in Example 1. The difference between this embodiment and Example 1 is that in step (2), 6000 mg of 1,3-propanesulfonic acid lactone, 2000 mg of lithium bis(trifluoromethanesulfonyl)imide and 116 mg of MeOTf are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 60 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 20 nm.

[0068] Example 5 This embodiment provides a positive electrode sheet with the same system as in Example 1. The difference between this embodiment and Example 1 is that in step (2), 7500 mg of 1,3-propanesulfonic acid lactone, 2500 mg of lithium bis(trifluoromethanesulfonyl)imide and 145 mg of MeOTf are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 75 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 25 nm.

[0069] Example 6 This embodiment provides a positive electrode sheet with the same system as in Example 1. The difference between this embodiment and Example 1 is that the interface layer includes an interpenetrating polymer network formed by a first polymer and a second polymer. The first polymer is formed by polymerizing 1,3-propanesulfonate lactone, and the second polymer is formed by polymerizing dimethylaminoethyl acrylate. The difference in the preparation process is that in step (2), 4500 mg of 1,3-propanesulfonate lactone, 1500 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 30 mg of azobisisobutyronitrile (AIBN), and 2000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 60 μm to make the interface layer thickness of the positive electrode sheet surface 20 nm.

[0070] Example 7 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 3000 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 60 mg of azobisisobutyronitrile (AIBN), and 2500 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 75 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 25 nm.

[0071] Example 8 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 4500 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 90 mg of azobisisobutyronitrile (AIBN), and 3000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 85 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 30 nm.

[0072] Example 9 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 6000 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 120 mg of azobisisobutyronitrile (AIBN) and 3500 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 90 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 35 nm.

[0073] Example 10 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 7500 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 150 mg of azobisisobutyronitrile (AIBN) and 4000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 100 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 40 nm.

[0074] Example 11 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 1500 mg of 1,3-propanesulfonic acid lactone, 1500 mg of dimethylaminoethyl acrylate (DMAEA), 29 mg of MeOTf, 30 mg of azobisisobutyronitrile (AIBN), and 1000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 30 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 10 nm.

[0075] Example 12 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 3000 mg of 1,3-propanesulfonic acid lactone, 3000 mg of dimethylaminoethyl acrylate (DMAEA), 58 mg of MeOTf, 60 mg of azobisisobutyronitrile (AIBN), and 2000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 60 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 20 nm.

[0076] Example 13 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 4500 mg of 1,3-propanesulfonic acid lactone, 4500 mg of dimethylaminoethyl acrylate (DMAEA), 88 mg of MeOTf, 90 mg of azobisisobutyronitrile (AIBN), and 3000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 80 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 30 nm.

[0077] Example 14 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 6000 mg of 1,3-propanesulfonic acid lactone, 6000 mg of dimethylaminoethyl acrylate (DMAEA), 116 mg of MeOTf, 120 mg of azobisisobutyronitrile (AIBN) and 4000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 100 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 40 nm.

[0078] Example 15 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 7500 mg of 1,3-propanesulfonic acid lactone, 7500 mg of dimethylaminoethyl acrylate (DMAEA), 145 mg of MeOTf, 150 mg of azobisisobutyronitrile (AIBN) and 5000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 150 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 60 nm.

[0079] Example 16 This embodiment provides a positive electrode sheet with the same system as in Example 6. The difference between this embodiment and Example 6 is that in step (2), 3000 mg of 1,3-propanesulfonic acid lactone, 3000 mg of dimethylaminoethyl acrylate (DMAEA), 588 mg of MeOTf, 600 mg of azobisisobutyronitrile (AIBN) and 20000 mg of lithium bis(trifluoromethanesulfonyl)imide are weighed and dissolved in 2 mL of anhydrous acetonitrile; in step (3), the polymerization precursor solution is uniformly coated on the unmodified electrode sheet with a gap of 300 μm so that the thickness of the interface layer on the surface of the positive electrode sheet is 200 nm.

[0080] Comparative Example 1 Comparative Example 1 provides the same unmodified electrode as Example 1 as the positive electrode.

[0081] The positive electrode sheets prepared in Examples 1 to 16 and Comparative Example 1 were assembled into lithium-ion solid-state batteries. The parameters of the positive electrode sheets in Examples 1 to 16 and Comparative Example 1 are shown in Table 1. The rate performance and cycle performance of the solid-state batteries assembled in Examples 1 to 16 and Comparative Example 1 were tested to verify the improvement effect of the positive electrode sheets on the rate performance and cycle performance of the batteries. The test results are shown in Table 2, and the test methods are as follows: The assembly process of the solid-state battery is as follows: Solid electrolyte powder is placed in a mold sleeve with a diameter of φ12mm and pressed under a pressure of 200MPa for 5 minutes to obtain a solid electrolyte block with a diameter of φ12mm; wherein, the solid electrolyte is Li6PS5Cl. Using lithium metal sheets as negative electrode sheets, the positive and negative electrode sheets prepared in Examples 1 to 16 and Comparative Example 1 are cut into small circular pieces with a diameter of φ12mm. The prepared positive and negative electrode sheets are placed on both sides of the solid electrolyte block in the mold sleeve for assembly. After assembly, the pressure is increased to 100MPa and the nut at the top of the column is tightened to maintain a constant pressure, thus obtaining an all-solid-state lithium-ion battery.

[0082] The solid-state battery cycle performance test process is as follows: At 25℃, within the operating voltage range of 2.4V~4.25V, the solid-state battery is charged and discharged three times at a constant current rate of 0.1C / 0.1C. After capacitation, the battery is charged and discharged at a current rate of 0.3C / 0.3C, and the first charge capacity and first discharge capacity are recorded. The first discharge specific capacity is obtained by dividing the first discharge capacity by the mass of the negative electrode, and the first coulombic efficiency is obtained by dividing the first discharge capacity by the first charge capacity. Then, the battery is charged and discharged at a current rate of 1C / 1C, and the specific discharge capacity C0 of the first cycle and the specific discharge capacity C after 300 cycles are recorded during the charge and discharge cycles. 300 The capacity retention rate C after 300 battery cycles was calculated. 300 / C0.

[0083] The solid-state battery rate performance testing process is as follows: At 25℃, within the operating voltage range, the solid-state battery is charged and discharged three times at a constant current rate of 0.1C / 0.C to complete the battery's capacity determination. After capacity determination, the solid-state battery is subjected to a constant current mode charge and discharge once at a constant current rate of 0.1C / 0.1C, and the capacity of this charge and discharge is recorded as the baseline capacity C. 0.1 C. Charge the solid-state battery in constant current and constant voltage mode at a constant rate of 0.3C (i.e., constant current charging to the upper limit of the operating cutoff voltage, then constant voltage charging until the current is less than 0.05C); after resting for 15 minutes, discharge the battery to the lower limit of the operating cutoff voltage at a constant rate of 0.1C, and record the discharge capacity C. 0.1 The battery was then charged and discharged three times. The solid-state battery was charged in constant current / constant voltage mode at a constant rate of 0.3C; after resting for 15 minutes, the battery was discharged to the lower limit of the operating cutoff voltage at a constant rate of 0.3C, and the discharge capacity C was recorded. 0.3 The battery was then charged and discharged three times. The solid-state battery was charged in constant current / constant voltage mode at a constant rate of 0.3C; after resting for 15 minutes, the battery was discharged to the lower limit of the operating cutoff voltage at a constant rate of 0.5C, and the discharge capacity C was recorded. 0.5 The solid-state battery was charged at a constant current and constant voltage (DCV) of 0.3C. After resting for 15 minutes, it was discharged to the lower limit of the operating cutoff voltage at a constant current of 1C, and the discharge capacity C1 was recorded. This process was repeated three times. The solid-state battery was then charged at a constant current and constant voltage (DCV) of 0.3C. After resting for 15 minutes, it was discharged to the lower limit of the operating cutoff voltage at a constant current of 2C, and the discharge capacity C2 was recorded. This process was repeated three times. The capacity retention rate of the solid-state battery at each DCV rate was calculated. The capacity retention rate is (C... x / C0.1C)×100%, C x The discharge capacity was measured at 0.3C, 0.5C, 1C, and 2C rates.

[0084] Table 1: Preparation parameters of the positive electrode sheet provided in Examples 1 to 16 and Comparative Example 1

[0085] Table 2: Performance test results of batteries prepared in Examples 1 to 16 and Comparative Example 1

[0086] Comparing the test results of Examples 1 to 5 and Comparative Example 1, it can be seen that, compared to the positive electrode sheet in Comparative Example 1 without an interface layer on its surface, the embodiments disclosed in this application, by forming an interface layer formed by PS monomer crosslinking on the surface of the positive electrode sheet, can effectively improve and protect the interfacial contact between the positive electrode active material layer and the solid electrolyte membrane. Simultaneously, the crosslinked single-ion conductor material can construct uniformly distributed lithium-ion transport channels at the interface between the positive electrode active material layer and the solid electrolyte membrane. This interface layer can reduce the interfacial impedance between the positive electrode sheet and the solid electrolyte membrane while maintaining the structural stability and electrochemical stability of the interface between the positive electrode sheet and the solid electrolyte membrane. This results in a significant improvement in the rate performance and cycle performance of the battery compared to when no interface layer is provided on the positive electrode surface. The 2C discharge rate retention rate of the battery is significantly increased to 60%~70% (approximately 20% higher than Comparative Example 1), and the 300-cycle capacity retention rate is also approximately 30% higher than Comparative Example 1.

[0087] Comparing the test results of Examples 1 to 5 and Examples 6 to 10, it can be seen that when a second polymer is introduced into the interface layer as in Examples 6 to 10 to form an interpenetrating polymer network of the first and second polymers, the high ionic conductivity of the interface layer can be maintained while effectively absorbing hydrogen sulfide gas generated by the hydrolysis of sulfide electrolyte in the solid electrolyte membrane. This ensures that the positive electrode active material is not corroded by electrolyte byproducts during cycling, thereby significantly improving the cycle life of the battery while maintaining its high rate performance. Specifically, compared to Examples 1 to 5, the increased interface layer thickness and the addition of non-conductive polymers in Examples 6 to 10 slightly increase the interfacial impedance of the positive electrode surface, resulting in a slight decrease in the 2C discharge rate retention (within 10%). However, the battery's 300-cycle capacity retention can still be increased to over 80%, thus meeting the requirements for commercial applications.

[0088] Comparing the test results of Examples 6 to 10, it can be seen that when the mass ratio of the first polymer to the second polymer is within the aforementioned suitable range, the optimal improvement effect of the interface layer on the interfacial ionic conductivity and chemical stability can be achieved. If the mass ratio of the first polymer to the second polymer is too high (i.e., the content of the second polymer is too low), the second polymer will have difficulty playing a sufficient purifying role at the contact interface, affecting the improvement effect of the interface layer on the battery cycle life; if the mass ratio of the first polymer to the second polymer is too low (i.e., the content of the first polymer is too low), the ionic conductor material in the interface layer will be severely diluted, affecting the improvement effect of the interface layer on the ionic conductivity of the contact interface.

[0089] Comparing the test results of Examples 11 to 16, it can be seen that when the thickness of the interface layer containing both the first and second polymers is within a suitable range of 10 nm to 60 nm, optimal improvement in both battery rate performance and cycle performance can be achieved. For example, when the interface layer thickness is as low as 10 nm, the battery exhibits extremely strong rate performance, with its 2C rate discharge capacity retention rate exceeding 70%, while the battery's 300-cycle capacity retention rate remains above 80%, thus demonstrating excellent cycle performance. The battery is suitable for scenarios with extremely high instantaneous power requirements. When the interface layer thickness is between 20 nm and 40 nm, the battery can achieve both high rate performance and long cycle life. For example, in Example 13, the battery achieved a 91.5% 300-cycle capacity retention rate while still retaining an excellent 64% 2C rate discharge capacity retention rate. When the interface layer thickness is between 40nm and 60nm, the cycle life of the battery is greatly improved, and its capacity retention rate after 300 cycles reaches an astonishing 94.8%. However, the effect of the interface layer on improving the rate performance of the battery is reduced.

[0090] However, when the interface layer thickness increases to 200 nm, the excessively thick polymer layer generates enormous internal stress during polymerization and drying, leading to brittle fracture and delamination of the coating itself. These physical defects not only fail to provide protection but also create a large number of new, unstable reaction interfaces, resulting in more severe side reactions and poorer conductivity pathways than in the unmodified state. Consequently, the rate performance of the battery is significantly reduced, and the cycle life of the battery is also relatively decreased.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A positive electrode sheet, characterized by, The positive electrode active material layer is provided on the positive electrode current collector. The interface layer is provided on the positive electrode active material layer, and the interface layer comprises a first polymer, and the first polymer comprises a polyether sulfonate. The first polymer is formed by polymerization of a sulfur-containing lactone monomer, and the sulfur-containing lactone monomer comprises at least one of 1,3-propane sulfonolactone, 1,4-butane sulfonolactone, 2,2,2-trifluoroethyl sulfonolactone, and a substituted derivative thereof. The thickness of the interface layer is 5-25 nm.

2. The cathode electrode of claim 1, wherein, The interface layer further comprises a second polymer, and the second polymer forms an interpenetrating polymer network with the first polymer, and the second polymer is formed by polymerization of a vinyl-based monomer, and the vinyl-based monomer comprises a Lewis basic nitrogen atom.

3. The cathode electrode of claim 1, wherein, The vinyl-based monomer comprises at least one of dimethylamino methyl acrylate, dimethylamino ethyl acrylate, dimethylamino propyl acrylate, dimethylamino butyl acrylate, dipropylamino ethyl acrylate, and dimethylamino ethyl methacrylate.

4. The cathode electrode of claim 1, wherein, The mass ratio of the first polymer to the second polymer is 3:(1-5); and / or, the thickness of the interface layer is 10-60 nm.

5. The cathode electrode of claim 4, wherein, The interface layer further comprises a lithium salt, and the lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethyl) sulfonylimide, lithium bisfluorosulfonylimide, lithium bis(perfluoroethylsulfonyl) imide, lithium difluoro(oxalato)borate, and lithium bis(oxalato)borate.

6. The cathode electrode of claim 4, wherein, The positive electrode active material layer is provided on the positive electrode current collector.

7. The cathode sheet of claim 1, wherein, The lithium salt, the sulfur-containing lactone monomer, and a first initiator are mixed in an organic solvent to form a polymer precursor solution; the first initiator is used to initiate polymerization of the sulfur-containing lactone monomer.

8. A method of producing the positive electrode sheet according to any one of claims 1 to 7, characterized by, The polymer precursor solution is coated on the unmodified electrode sheet, and after heating and drying, a positive electrode sheet is obtained. The step of forming the polymer precursor solution comprises: The lithium salt, the sulfur-containing lactone monomer, a first initiator, a vinyl-based monomer, and a second initiator are mixed in an organic solvent according to a preset mass ratio to form a polymer precursor solution; the second initiator is used to initiate polymerization of the vinyl-based monomer. The positive electrode sheet of any one of claims 1-7, or the positive electrode sheet prepared by the preparation method of claim 8 or 9.

9. The production method according to claim 8, characterized by, ​ ​ 10. A solid state battery, characterized by ​

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