Solid-state electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention relates to a solid-state electrolyte membrane, a preparation method thereof and a solid-state battery, and belongs to the technical field of solid-state electrolyte materials. The solid electrolyte membrane is provided with a honeycomb structure framework, and the honeycomb structure framework is filled with a lithium-conducting copolymer and a lithium salt; the honeycomb structure framework is prepared from the following raw materials: a fluorine-containing polymer, an inorganic nano filler and a lithium-conducting polymer. The solid electrolyte membrane prepared by the embodiment of the invention meets at least one of the following indexes: the thickness of the solid electrolyte is 1-30 [mu] m, and the conductivity at room temperature is gt; 5.0 * 10 <-4 > S.cm <-1 >, and the ion transference number is gt; and 0.80, so that an ultrathin solid electrolyte structure which has rapid lithium ion transmission, high mechanical strength and a stable interface is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of solid electrolyte materials, and particularly relates to a solid electrolyte membrane, a preparation method thereof, and a solid-state battery. Background Art

[0002] Solid-state batteries are considered to be one of the most promising battery technologies because they achieve excellent safety by replacing flammable liquid electrolytes with non-flammable solid electrolytes. In addition, they significantly improve the energy density of the battery by matching a high-capacity positive electrode and a lithium metal negative electrode (3860 mAh g -1 ). As a key component of solid-state batteries, solid electrolytes can not only provide ion transport channels but also act as a separator between the positive and negative electrodes, which has an important impact on battery performance. Therefore, in order to realize the practical application of solid-state batteries, it is urgent to develop high-performance solid electrolytes.

[0003] In order to improve the actual energy density of solid-state batteries, thinning the thickness of solid electrolytes has become an irresistible trend. However, it is still a great challenge to prepare an ultra-thin solid electrolyte that can simultaneously match a high-loading positive electrode and a thin lithium metal negative electrode to achieve a high energy density. Therefore, it is necessary to design a solid electrolyte structure that has good lithium-ion transport and a stable electrode-electrolyte interface while ensuring mechanical strength. Summary of the Invention

[0004] The present application provides a solid electrolyte membrane, a preparation method thereof, and a solid-state battery to solve the following technical problems: how to improve the lithium-ion conduction ability and mechanical strength of the solid electrolyte membrane.

[0005] In a first aspect, an embodiment of the present application provides a solid electrolyte membrane, which has a honeycomb structure framework filled with a lithium-conducting copolymer and a lithium salt;

[0006] The raw materials of the honeycomb structure framework include a fluoropolymer, an inorganic nano-filler, and a lithium-conducting polymer.

[0007] Optionally, the fluoropolymer includes at least one of the following: poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride), poly(vinylidene fluoride-trifluoroethylene), poly(vinylidene fluoride-trichlorofluoroethylene).

[0008] Optionally, the lithium salt includes at least one of the following: lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate.

[0009] Optionally, the inorganic nano-filler includes at least one of the following: boron nitride nano-materials, boron nitride nano-materials coated with porous silica, alumina nano-materials, cerium oxide nano-materials.

[0010] Optionally, the lithium-conductive polymer includes at least one of the following: lithiated perfluorosulfonic acid resin, lithiated lignin, and lithiated cellulose.

[0011] Optionally, the weight of the inorganic nanofiller is 0 to 5% and greater than 0 of the weight of the fluoropolymer; and / or,

[0012] the weight of the lithium-conductive polymer is 0 to 20% and greater than 0 of the weight of the fluoropolymer.

[0013] Optionally, the weight of the inorganic nanofiller is 0.5% to 5% of the weight of the fluoropolymer; and / or, the weight of the lithium-conductive polymer is 1% to 20% of the weight of the fluoropolymer.

[0014] Optionally, the solid electrolyte membrane meets at least one of the following indicators: the thickness of the solid electrolyte is 1 μm to 30 μm, the conductivity at room temperature is >5.0×10 -4 S·cm -1 , the ion transference number is >0.80, and the tensile strength is >20 MPa.

[0015] In a second aspect, an embodiment of the present application provides a method for preparing the solid electrolyte membrane according to any one of the first aspect, the method comprising:

[0016] Mixing a fluoropolymer, an inorganic nanofiller, a lithium-conductive polymer, and a first solvent to obtain a mixed slurry;

[0017] Coating the mixed slurry on the surface of a substrate and drying to obtain a base film with a honeycomb structure framework;

[0018] Mixing a lithium salt, a photoinitiator, and a monomer to obtain a precursor solution;

[0019] Soaking the base film with a honeycomb structure framework in the precursor solution to obtain a base film containing the precursor solution;

[0020] Curing the base film containing the precursor solution to obtain a solid electrolyte membrane.

[0021] In a third aspect, an embodiment of the present application provides a solid-state battery, the solid-state battery including the solid electrolyte membrane according to any one of the first aspect.

[0022] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0023] The honeycomb structure of the solid electrolyte membrane provided by the embodiments of the present application is a structure with high strength and stability. In the solid electrolyte membrane, the honeycomb structure framework can provide good mechanical support for the entire membrane. The pores of the honeycomb structure can serve as ion conduction channels, which helps lithium ions to be more orderly transported in the solid electrolyte membrane and improves the lithium ion conduction ability. The lithium-conducting copolymer can promote the dissociation of lithium salts and provide a transport channel for lithium ions. Under the action of the lithium-conducting copolymer, the lithium ions in the lithium salt are promoted to dissociate and migrate between the molecular chains or internal channels of the lithium-conducting copolymer, and the lithium-conducting copolymer and lithium salt filled in the honeycomb structure framework together constitute the main body of ion conduction, improving the lithium ion conduction ability of the solid electrolyte membrane. And the honeycomb structure framework can make the lithium-conducting copolymer and lithium salt be evenly distributed in the membrane, thereby improving the uniformity of ion conduction and the lithium ion conduction ability. Among the raw materials of the honeycomb structure framework, the fluoropolymer, as the raw material of the honeycomb structure framework, has flexibility, low crystallinity and a relatively high relative dielectric constant, which helps the dissociation of lithium salts. The inorganic nano-fillers have abundant Lewis acid sites, which can capture TFSI - anions and restrict the movement of TFSI - anions, promoting the dissociation of lithium salts and increasing the lithium ion transference number; the lithium-conducting polymer has an ion exchange effect, shielding the shuttle of TFSI - anions, thereby enhancing the lithium ion conduction ability of the solid electrolyte. Therefore, the honeycomb structure can evenly disperse external stress, and the addition of inorganic nano-fillers with extremely high Young's modulus and strength and flexible lithium-conducting polymers endows the functional honeycomb with high mechanical strength. The introduction of the lithium-conducting copolymer forms an interpenetrating structure, further improving the mechanical strength of the solid electrolyte membrane; the inorganic nano-fillers have an anion anchoring effect, and the lithium-conducting polymer has an ion exchange effect. Under the synergy of the two materials, the lithium ion conduction is promoted. In summary, the lithium ion conduction ability and mechanical strength of the solid electrolyte membrane are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings here are incorporated into the specification and constitute a part of this specification, showing the embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0025] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a schematic flow chart of a preparation method of a solid electrolyte membrane provided by an embodiment of the present application;

[0027] Figure 2 Cross-sectional SEM image of a solid electrolyte membrane SSE@PH-BN / LN provided in Embodiment 1 of the present application;

[0028] Figure 3 Planar SEM image of a functionalized honeycomb skeleton PH-BN / LN of a solid electrolyte membrane provided in Embodiment 1 of the present application;

[0029] Figure 4 Planar SEM image of a solid electrolyte membrane SSE@PH-BN / LN provided in Embodiment 1 of the present application;

[0030] Figure 5 Comparison chart of the mechanical properties of a solid electrolyte membrane provided in Embodiment 1 of the present application and Comparative Examples 1 to 3;

[0031] Figure 6 Comparison chart of the ionic conductivity and lithium ion transference number of a solid electrolyte membrane provided in Embodiment 1 and Comparative Examples 1 to 3;

[0032] Figure 7 Full cell cycle stability test chart of a solid electrolyte membrane SSE@PH-BN / LN provided in Embodiment 1. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0034] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0035] In this application, unless otherwise stated, the directional terms such as "upper" and "lower" specifically refer to the drawing directions in the attached drawings. Additionally, in the description of this application's specification, terms such as "comprising" and "including" mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this text, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one of the following items", or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0036] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in this application can be obtained through market purchases or can be prepared by existing methods.

[0037] In a first aspect, an embodiment of this application provides a solid electrolyte membrane, which has a honeycomb structure framework, and a lithium-conducting copolymer and a lithium salt are filled in the honeycomb structure framework;

[0038] The raw materials of the honeycomb structure framework include a fluoropolymer, an inorganic nano-filler, and a lithium-conducting polymer.

[0039] The solid electrolyte membrane is a core component in a solid-state battery, and its principle of action is as follows: during battery charging, lithium ions are released from the positive electrode and migrate to the negative electrode through the solid electrolyte membrane; during discharging, lithium ions are released from the negative electrode and return to the positive electrode through the solid electrolyte membrane, thereby realizing the charge and discharge cycle of the battery. The solid electrolyte membrane provides a channel for the transmission of lithium ions between the positive and negative electrodes, and at the same time isolates the positive and negative electrodes to prevent short circuits.

[0040] The honeycomb structure is a structure with high strength and stability. In the solid electrolyte membrane, the honeycomb structure framework can provide good mechanical support for the entire membrane. The pores of the honeycomb structure can serve as ion conduction channels, which helps lithium ions to be transported more orderly in the solid electrolyte membrane and improves the lithium ion conduction ability. The lithium-conducting copolymer can promote the dissociation of lithium salts and provide a transport channel for lithium ions. Under the action of the lithium-conducting copolymer, the lithium ions in the lithium salt are promoted to dissociate and migrate between the molecular chains or internal channels of the lithium-conducting copolymer. The lithium-conducting copolymer and lithium salt filled in the honeycomb structure framework together constitute the main body of ion conduction, improving the lithium ion conduction ability of the solid electrolyte membrane. And the honeycomb structure framework can make the lithium-conducting copolymer and lithium salt be evenly distributed in the membrane, thus improving the uniformity of ion conduction and the lithium ion conduction ability.

[0041] The fluoropolymer, inorganic nano-filler and lithium-conducting polymer are blended to obtain a unique functionalized honeycomb structure framework. The lithium-conducting copolymer and lithium salt are filled in this framework to form a solid electrolyte with high lithium ion conduction performance, high mechanical strength and good interfacial stability. Under the combined action of the fluoropolymer, inorganic nano-filler and lithium-conducting polymer, a functionalized honeycomb framework can be formed, which has the function of promoting the dissociation of lithium salts and the selective conduction of lithium ions. Therefore, this honeycomb structure framework has the functions of enhancing mechanical strength, conducting lithium ions and capturing anions.

[0042] Specifically, among the raw materials of the honeycomb structure framework, the fluoropolymer, as the raw material of the honeycomb structure framework, has flexibility, low crystallinity and a relatively high relative dielectric constant, which helps the dissociation of lithium salts. The inorganic nano-filler has abundant Lewis acid sites, which can capture TFSI - anions and restrict the movement of TFSI - anions, promoting the dissociation of lithium salts and increasing the lithium ion transference number. The lithium-conducting polymer has an ion exchange effect, shielding the shuttle of TFSI - anions, thus enhancing the lithium ion conduction ability of the solid electrolyte, enabling the solid electrolyte membrane to match both the high-loading cathode and the thin lithium metal anode, and improving the energy density of the solid-state battery. Therefore, the honeycomb structure can evenly disperse external stress, and the addition of inorganic nano-fillers with extremely high Young's modulus and strength and flexible lithium-conducting polymers endows the functionalized honeycomb with high mechanical strength. The introduction of the lithium-conducting copolymer forms an interpenetrating structure, further improving the mechanical strength of the solid electrolyte membrane. The inorganic nano-filler has an anion anchoring effect, and the lithium-conducting polymer has an ion exchange effect. Under the synergy of the two materials, the lithium ion conduction is promoted. In summary, the lithium ion conduction ability and mechanical strength of the solid electrolyte membrane are improved.

[0043] In some embodiments, the fluoropolymer includes at least one of the following: polyvinylidene fluoride - hexafluoropropylene, polyvinylidene fluoride, polyvinylidene fluoride - trifluoroethylene, polyvinylidene fluoride - chlorotrifluoroethylene.

[0044] The fluoropolymer can be one or a combination of more than one of polyvinylidene fluoride - hexafluoropropylene (PVDF - HFP), polyvinylidene fluoride (PVDF), polyvinylidene fluoride - trifluoroethylene (PVDF - TFE), polyvinylidene fluoride - chlorotrifluoroethylene (PVDF - CTFE).

[0045] In some embodiments, the lithium salt includes at least one of the following: lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate.

[0046] The lithium salt can be one or a combination of more than one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate.

[0047] In some embodiments, the inorganic nanofiller includes at least one of the following: boron nitride nanomaterials, boron nitride nanomaterials coated with porous silica, alumina nanomaterials, cerium oxide nanomaterials.

[0048] The inorganic nanofiller can be one or a combination of more than one of boron nitride nanomaterials, boron nitride nanomaterials coated with porous silica, alumina nanomaterials, cerium oxide nanomaterials, all of which can promote the dissociation of lithium salts and increase the ion transference number. Among them, boron nitride has abundant Lewis acid sites, which helps to promote the dissociation of lithium salts. Therefore, the honeycomb structure can evenly disperse external stress, and the addition of boron nitride materials with extremely high Young's modulus and strength and flexible lithium - conducting polymers endows the functional honeycomb with high mechanical strength. The introduction of lithium - conducting copolymers forms an interpenetrating structure, further improving the mechanical strength of the ultrathin solid electrolyte membrane; boron nitride nanomaterials have an anion - anchoring effect, and lithium - conducting polymers have an ion - exchange effect. Under the synergy of the two materials, the lithium - ion transport is promoted; the polymer solid electrolyte is in close contact with the positive and negative electrode interfaces, which is beneficial to interfacial ion transport. The nanomaterials can be one morphology or a combination of more than one of nanotubes, nanofibers, nanosheets, quantum dots.

[0049] In some embodiments, the lithium - conducting polymer includes at least one of the following: lithiated perfluorosulfonic acid resin, lithiated lignin, lithiated cellulose.

[0050] The lithium - conducting polymer can be one or a combination of more than one of lithiated perfluorosulfonic acid resin, lithiated lignin, lithiated cellulose, all of which have a cation - exchange effect and the function of promoting the selective conduction of lithium ions.

[0051] In some embodiments, the weight of the inorganic nano-filler is 0 to 5% and greater than 0 of the weight of the fluoropolymer; and / or,

[0052] the weight of the lithium-conducting polymer is 0 to 20% and greater than 0 of the weight of the fluoropolymer.

[0053] In some embodiments, the weight of the inorganic nano-filler is 0.5% to 5% of the weight of the fluoropolymer; and / or,

[0054] the weight of the lithium-conducting polymer is 1% to 20% of the weight of the fluoropolymer.

[0055] The weight of the inorganic nano-filler can be 0 to 5% of the weight of the fluoropolymer, which can improve the mechanical strength of the solid electrolyte membrane and also enhance the lithium-ion conduction performance. If the weight of the inorganic nano-filler is higher than 5%, it may cause agglomeration of the inorganic nano-filler and uneven dispersion of the inorganic nano-filler in the base membrane. The weight of the lithium-conducting polymer can be 0 to 20% of the weight of the fluoropolymer, which can enable the lithium-conducting polymer to be stably dispersed in the fluoropolymer. The flexibility of the lithium-conducting polymer helps to improve the mechanical properties of the solid electrolyte membrane, and the ion exchange effect of the lithium-conducting polymer can promote the transport of lithium ions. If the weight of the lithium-conducting polymer is higher than 20%, it may lead to a decrease in the pore content in the functionalized framework and a significant reduction in the liquid absorption capacity of the precursor solution, which is not conducive to the transport of lithium ions in the solid electrolyte membrane. Exemplarily, the weight of the inorganic nano-filler can be 0.5%, 1%, 2%, 3%, 4%, 5%, etc. of the weight of the fluoropolymer; the weight of the lithium-conducting polymer can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc. of the weight of the fluoropolymer.

[0056] In some embodiments, the solid electrolyte membrane meets at least one of the following indicators: the thickness of the solid electrolyte is 1 μm to 30 μm, the conductivity at room temperature is >5.0×10 -4 S·cm -1 ⁻¹, the ion transference number is >0.80, and the tensile strength is >20 MPa.

[0057] This solid electrolyte membrane has excellent lithium-ion conduction ability and realizes an ultra-thin thickness. This solid electrolyte membrane is in close contact with the positive and negative electrode interfaces, which is beneficial to interfacial ion transport. In addition, this solid electrolyte membrane can form a soft-pack full battery with the NCM811 positive electrode and the lithium metal negative electrode at the same time and conduct stable cycling.

[0058] In a second aspect, the embodiments of the present application provide a preparation method of the solid electrolyte membrane according to any one of the first aspect,Figure 1 Schematic flow chart of a method for preparing a solid electrolyte membrane provided by an embodiment of the present application; please refer to Figure 1 , the method includes:

[0059] S1. Mix a fluoropolymer, an inorganic nanofiller, a lithium-conducting polymer, and a first solvent to obtain a mixed slurry;

[0060] Mixing the fluoropolymer, the inorganic nanofiller, the lithium-conducting polymer, and the first solvent evenly disperses each component in the solvent, laying a foundation for the subsequent formation of a honeycomb structure framework with uniform structure and properties. Among them, the first solvent can be one or a combination of more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, acetone, and water.

[0061] S2. Coat the mixed slurry on the surface of a substrate and dry it to obtain a base film with a honeycomb structure framework;

[0062] Coating the mixed slurry on the surface of the substrate, common coating methods include doctor blade coating, spin coating, etc. The coating process can control the thickness and uniformity of the film to ensure the quality of the base film. The purpose of drying is to remove the first solvent, enabling the fluoropolymer, the inorganic nanofiller, and the lithium-conducting polymer to form a solid honeycomb structure framework. During the drying process, as the solvent volatilizes, the polymer molecules gradually aggregate and solidify to form a honeycomb-like framework with a certain pore structure. The substrate provides support and a flat surface for the formation of the base film. Among them, the thickness of the base film with the honeycomb structure framework is 5 μm to 10 μm.

[0063] S3. Mix a lithium salt, a photoinitiator, and a monomer to obtain a precursor solution;

[0064] Mixing the lithium salt, the photoinitiator, and the monomer to obtain a uniform precursor solution, so that it can be fully filled into the pores of the honeycomb structure framework subsequently. Among them, the monomer can be ethylene carbonate and / or polyethylene glycol diacrylate, polyethylene glycol diacrylate / ethylene carbonate = 0 to 20%, the concentration of the lithium salt is 1 mol / L to 2 mol / L, and the photoinitiator is 0.5% to 5% of the weight of the monomer. The photoinitiator can be 2-hydroxy-2-methyl-1-phenylpropanone.

[0065] S4. Immerse the base film with the honeycomb structure framework in the precursor solution to obtain a base film containing the precursor solution;

[0066] Immersing the base film with the honeycomb structure framework in the precursor solution may utilize capillary action and diffusion principles to enable the precursor solution to fully fill the pores of the honeycomb structure framework. Among them, the immersion time can be 0.5 h to 24 h.

[0067] S5. Cure the base film containing the precursor solution to obtain a solid electrolyte membrane.

[0068] Curing the base film containing the precursor solution is usually to make the photoinitiator generate free radicals by means of light irradiation, initiate the polymerization reaction of monomers, and form a lithium-conducting copolymer. The lithium-conducting copolymer and the lithium salt filled therein together constitute a filling phase with high lithium ion conduction performance, which combines with the honeycomb structure skeleton to finally form a solid electrolyte membrane. Among them, the curing method can be ultraviolet light irradiation, the wavelength of the ultraviolet lamp is 365 nm, and the curing time is 1 min to 10 min.

[0069] The preparation method of this solid electrolyte membrane is realized based on the above solid electrolyte membrane. The specific composition of this solid electrolyte membrane can refer to the above embodiments. Since the preparation method of this solid electrolyte membrane adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0070] In a third aspect, an embodiment of the present application provides a solid-state battery, and the solid-state battery includes the solid electrolyte membrane according to any one of the first aspect.

[0071] This solid-state battery is realized based on the above solid electrolyte membrane. The specific composition of this solid electrolyte membrane can refer to the above embodiments. Since this solid-state battery adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0072] The following further elaborates the present application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions indicated in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions or conditions recommended by the manufacturer.

[0073] Example 1

[0074] A solid electrolyte membrane, which has a honeycomb structure skeleton filled with a lithium-conducting copolymer and a lithium salt; the raw materials of the honeycomb structure skeleton include a fluoropolymer, an inorganic nano-filler, and a lithium-conducting polymer.

[0075] The fluoropolymer is polyvinylidene fluoride-hexafluoropropylene (weight ratio is 0.83), the inorganic nano-filler is boron nitride nanotube, the lithium-conducting polymer is a lithiated perfluorosulfonic acid resin solution, the boron nitride nanotube is 1% of the mass of polyvinylidene fluoride-hexafluoropropylene, and the lithiated perfluorosulfonic acid resin solution is 20% of the mass of polyvinylidene fluoride-hexafluoropropylene;

[0076] The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, and the raw material monomers of the lithium-conducting copolymer are ethylene carbonate and polyethylene glycol diacrylate.

[0077] A method for preparing a solid electrolyte membrane, comprising:

[0078] S11. Mix a fluoropolymer, an inorganic nanofiller, a lithium-conducting polymer, and a first solvent to obtain a mixed slurry;

[0079] S21. Coat the mixed slurry on the surface of a substrate and dry it to obtain a base membrane with a honeycomb structure skeleton;

[0080] Specifically: Stir polyvinylidene fluoride-hexafluoropropylene, boron nitride nanotubes, and a lithiumated perfluorosulfonic acid resin solution in a mixed solvent of water and acetone, coat it on an aluminum foil, and vacuum dry it at 60 °C to obtain a unique functionalized honeycomb skeleton PH-BN / LN.

[0081] S31. Mix a lithium salt, a photoinitiator, and a monomer to obtain a precursor solution;

[0082] Specifically: Mix ethylene carbonate, polyethylene glycol diacrylate, lithium bis(trifluoromethanesulfonyl)imide, and 2-hydroxy-2-methyl-1-phenylpropanone and stir to obtain a precursor solution. Among them, polyethylene glycol diacrylate / ethylene carbonate = 15%, the concentration of lithium bis(trifluoromethanesulfonyl)imide is 1.5 mol / L, and 2-hydroxy-2-methyl-1-phenylpropanone is 0.5% of the total weight of polyethylene glycol diacrylate and ethylene carbonate.

[0083] S41. Immerse the base membrane with a honeycomb structure skeleton (for 6 h) in the precursor solution to obtain a base membrane containing the precursor solution;

[0084] S51. Cure the base membrane containing the precursor solution to obtain a solid electrolyte membrane.

[0085] Specifically: Place the immersed membrane under an ultraviolet lamp (365 nm) for 2 min of curing to obtain a solid electrolyte sample SSE@PH-BN / LN.

[0086] Example 2

[0087] Based on the content disclosed in Example 1, the difference between Example 2 and Example 1 is that:

[0088] The boron nitride nanotubes are 1% of the mass of polyvinylidene fluoride-hexafluoropropylene, and the lithiumated perfluorosulfonic acid resin solution is 10% of the mass of polyvinylidene fluoride-hexafluoropropylene.

[0089] Example 3

[0090] Based on the disclosure of Example 1, the difference between Example 3 and Example 1 is as follows:

[0091] The boron nitride nanotubes are 5% of the mass of polyvinylidene fluoride - hexafluoropropylene, and the lithiated perfluorosulfonic acid resin solution is 20% of the mass of polyvinylidene fluoride - hexafluoropropylene.

[0092] Comparative Example 1

[0093] Based on the disclosure of Example 1, the difference between Comparative Example 1 and Example 1 is as follows: There is no inorganic nano - filler.

[0094] Comparative Example 2

[0095] Based on the disclosure of Example 1, the difference between Comparative Example 2 and Example 1 is as follows: There is no lithium - conducting polymer.

[0096] Comparative Example 3

[0097] Based on the disclosure of Example 1, the difference between Comparative Example 3 and Example 1 is as follows: There is no inorganic nano - filler and lithium - conducting polymer.

[0098] Perform performance tests on the solid - state electrolyte membranes provided in Examples 1 - 3 and Comparative Examples 1 - 3. Please refer to the index test results of the solid - state electrolyte membranes shown in Table 1.

[0099] Table 1 Index test results of the solid - state electrolyte membrane

[0100]

[0101]

[0102] As can be seen from Table 1, Examples 1 - 3 all meet the requirements for the solid - state electrolyte membrane: the thickness of the solid - state electrolyte is 1 μm to 30 μm, the conductivity at room temperature is > 5.0×10 -4 S·cm -1 , the ion transference number is > 0.80, the tensile strength is > 20 MPa, and the lithium - ion conduction ability and mechanical strength of the solid - state electrolyte membrane. In particular, Example 1 has a higher room - temperature ionic conductivity (5.5×10 -4 S·cm -1 ), transference number (0.85) and better mechanical properties (29.5 MPa); while the technical solutions of Comparative Examples 1 - 3 are not within the scope of this application, and the performances in Table 1 are somewhat worse than those of Examples 1 - 3.

[0103] Figure 2 This is the cross - sectional SEM image of a solid - state electrolyte membrane SSE@PH - BN / LN provided in Example 1 of this application; please refer to Figure 2, it can be seen that the thickness of the prepared ultra-thin solid-state electrolyte SSE@PH-BN / LN is 10 μm. Figure 3 This is a planar SEM image of the functionalized honeycomb skeleton PH-BN / LN of a solid electrolyte membrane provided in Example 1 of this application; please refer to Figure 3 , it can be seen that the prepared membrane has a honeycomb pore structure. Figure 4 This is a planar SEM image of a solid electrolyte membrane SSE@PH-BN / LN provided in Example 1 of this application; please refer to Figure 4 , it can be seen the uniformity of the prepared solid electrolyte membrane SSE@PH-BN / LN. Figure 5 This is a comparison chart of the mechanical properties of a solid electrolyte membrane provided in Example 1 and Comparative Examples 1-3 of this application; please refer to Figure 5 , it can be seen that the ultra-thin solid-state electrolyte SSE@PH-BN / LN in Example 1 has better mechanical properties (29.5 MPa). Figure 6 This is a comparison chart of the ionic conductivity and lithium ion transference number of a solid electrolyte membrane provided in Example 1 and Comparative Examples 1-3; please refer to Figure 6 , it can be observed that the ultra-thin solid-state electrolyte SSE@PH-BN / LN in Example 1 has a higher room temperature ionic conductivity (5.5×10 -4 S·cm -1 ). Figure 7 This is a full cell cycle stability test chart of a solid electrolyte membrane SSE@PH-BN / LN provided in Example 1; please refer to Figure 7 , it is observed that the initial capacity of the ultra-thin solid-state electrolyte SSE@PH-BN / LN prepared in Example 1 is 205 mAh·g -1 and the capacity retention rate after 100 cycles (91.7%).

[0104] One or more technical solutions in the embodiments of this application at least further have the following technical effects or advantages:

[0105] (1) A unique functionalized honeycomb structure skeleton is prepared;

[0106] (2) The unique functionalized honeycomb structure skeleton is composed of flexible polyvinylidene fluoride-hexafluoropropylene, boron nitride nanomaterials with rich Lewis acid sites, and lithium-conducting polymers, which promotes the rapid transport of lithium ions through anion capture and ion exchange;

[0107] (3) The ultra-thin solid-state electrolyte membrane can match a high-loading cathode and a thin lithium metal anode and perform stable cycling.

[0108] The above description is only a specific implementation manner of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A solid electrolyte membrane, the solid electrolyte membrane having a honeycomb structure skeleton, the honeycomb structure skeleton is filled with a lithium-conducting copolymer and a lithium salt; The raw materials of the honeycomb structure skeleton include fluorine-containing polymer, inorganic nano filler and lithium-conducting polymer.

2. The solid electrolyte membrane according to claim 1, characterized in that The fluorine-containing polymer includes at least one of the following: polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, and polyvinylidene fluoride-chlorotrifluoroethylene.

3. The solid electrolyte membrane according to claim 1, characterized in that The lithium salt includes at least one of the following: lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

4. The solid electrolyte membrane according to claim 1, characterized in that The inorganic nanofiller includes at least one of the following: boron nitride nanomaterial, boron nitride nanomaterial coated with porous silicon oxide, aluminum oxide nanomaterial, and cerium oxide nanomaterial.

5. The solid electrolyte membrane according to claim 1, characterized in that The lithium-conducting polymer includes at least one of the following: lithiated perfluorosulfonic acid resin, lithiated lignin, and lithiated cellulose.

6. The solid electrolyte membrane according to any one of claims 1 to 5, characterized in that: The weight of the inorganic nanofiller is 0 to 5% and greater than 0% of the weight of the fluorine-containing polymer; and / or, The weight of the lithium conductive polymer is 0 to 20% and greater than 0% of the weight of the fluorine-containing polymer.

7. The solid electrolyte membrane according to claim 6, characterized in that The weight of the inorganic nanofiller is 0.5% to 5% of the weight of the fluorine-containing polymer; and / or, The weight of the lithium-conductive polymer is 1% to 20% of the weight of the fluorine-containing polymer.

8. The solid electrolyte membrane according to claim 1, characterized in that The solid electrolyte membrane meets at least one of the following indicators: the thickness of the solid electrolyte is 1 μm to 30 μm, and the conductivity at room temperature is >5.0×10 -4 S cm -1 , ion migration number is >0.80, and tensile strength is >20MPa.

9. A method for preparing a solid electrolyte membrane according to any one of claims 1 to 8, the method comprising: Mixing the fluorine-containing polymer, the inorganic nanofiller, the lithium-conducting polymer and the first solvent to obtain a mixed slurry; Applying the mixed slurry on the surface of a substrate and drying it to obtain a base film having a honeycomb structure skeleton; Mixing lithium salt, photoinitiator and monomer to obtain a precursor solution; Immersing the base membrane having a honeycomb structure skeleton in the precursor solution to obtain a base membrane containing the precursor solution; The base film containing the precursor solution is solidified to obtain a solid electrolyte membrane.

10. A solid-state battery, comprising the solid electrolyte membrane according to any one of claims 1 to 8.

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