A bifunctional composite lithium-conducting diaphragm and a preparation method and application thereof

Abstract

The present application relates to a kind of bifunctional composite lithium-conducting diaphragm and its preparation method and application bifunctional composite lithium-conducting diaphragm, bifunctional composite lithium-conducting diaphragm includes: ion conducting layer, and respectively coated in ion conducting layer two sides of positive electrode transition layer and negative electrode transition layer;Ion conducting layer includes base film and fills in the solid-state electrolyte of base film aperture;Positive electrode side transition layer and negative electrode side transition layer all include: electronic conductor, binder and solid-state electrolyte;Electronic conductor in positive electrode side transition layer and negative electrode side transition layer respectively island structure distribution of dispersion, and the mass fraction of electronic conductor in positive electrode side transition layer and negative electrode side transition layer respectively, all below the critical value of forming continuous conductive network, to block electron directly through diaphragm structure from positive electrode side to the direct cross-layer leakage of negative electrode side;Bifunctional composite lithium-conducting diaphragm is applied to lithium battery, can reduce the surface resistance of lithium battery, inhibit the volume expansion of pole piece, improve the cycle performance of lithium battery.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, and in particular to a bifunctional composite lithium-conducting separator, its preparation method, and its application. Background Technology

[0002] In lithium-ion batteries, traditional polyolefin separators rely on electrolytes for ion conduction, which presents safety hazards such as low conductivity (<0.5 mS / cm), poor thermal stability (<150℃), and flammability. While the rigid electrolyte layer of all-solid-state batteries (such as LLZO, LATP) can improve safety, its high Young's modulus (>100 GPa) leads to poor electrode / electrolyte interface contact, poor ion conductivity, and an interface impedance as high as >1000 Ω·cm. 2 .

[0003] While existing composite membrane technologies (such as ceramic-coated membranes) can enhance mechanical strength, they cannot simultaneously achieve high ion conductivity and optimized interface impedance, and in particular, they lack synergistic suppression of silicon anode expansion (>300%) and lithium dendrite growth.

[0004] Therefore, there is an urgent need to develop a separator solution that combines high ion conductivity, interface adaptability, environmental stability, and compatibility with existing liquid battery production lines to support the gradual upgrade of high energy density batteries from liquid to semi-solid / all-solid state. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a bifunctional composite lithium-conducting separator, its preparation method, and its applications. This invention introduces a solid electrolyte material with a particle size Dv50 less than or equal to the membrane pore size into a large-pore base membrane to form an ion-conducting layer. This creates a continuous and stable ion conduction channel within the separator, improving the overall ion migration efficiency and endowing it with excellent ion conductivity and interfacial stability. Furthermore, positive and negative electrode transition layers containing electronic conductors are attached to both sides of the ion-conducting layer, forming a unique "sandwich structure" bifunctional composite lithium-conducting separator. This bifunctional composite lithium-conducting separator exhibits significant ion transport capabilities, interfacial compatibility, and thermal stability. By controlling the content of electronic conductors, the separator also achieves high safety, providing strong support for high-performance battery systems.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a bifunctional composite lithium-conducting separator, the bifunctional composite lithium-conducting separator comprising: an ion-conducting layer, and a positive electrode transition layer and a negative electrode transition layer respectively coated on both sides of the ion-conducting layer; the ion-conducting layer comprises a base film and a first solid electrolyte filling the pores of the base film;

[0007] The positive electrode side transition layer includes: a first electronic conductor, a first binder, and a second solid electrolyte;

[0008] The negative electrode side transition layer includes: a second electronic conductor, a second binder, and a third solid electrolyte;

[0009] The dual-functional composite lithium-conducting separator is used in lithium-ion batteries. The positive electrode transition layer is in contact with the positive electrode of the lithium-ion battery, and the negative electrode transition layer is in contact with the negative electrode. The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte form a continuous ion channel. The first electronic conductor and the second electronic conductor are respectively distributed in a dispersed island structure in the positive electrode transition layer and the negative electrode transition layer. The mass fraction of the first electronic conductor in the positive electrode transition layer and the mass fraction of the second electronic conductor in the negative electrode transition layer are both lower than the critical value for forming a continuous conductive network, thereby blocking direct cross-layer leakage of electrons from the positive electrode side to the negative electrode side through the separator structure.

[0010] Preferably, the base film is a large-pore base film, including: a base film formed of any one of the following materials: polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET), or a double-layer composite base film or a triple-layer composite base film formed by a combination of the above materials;

[0011] The pore size r of the base film satisfies 500nm≤r≤5μm; the particle size DV50 of the first solid electrolyte is 50nm~500nm, and the particle size DV50 of the first solid electrolyte is ≤ the pore size r of the base film.

[0012] The mass fraction of the first electronic conductor in the positive electrode side transition layer is less than or equal to 30%, and the mass fraction of the second electronic conductor in the negative electrode side transition layer is less than or equal to 30%, both of which are below the critical value for forming a continuous conductive network.

[0013] Preferably, the thickness of both the positive electrode side transition layer and the negative electrode side transition layer is between 3 μm and 20 μm;

[0014] The first electronic conductor and the second electronic conductor include: carbon-based electronic conductors and / or metal oxide electronic conductors; the first electronic conductor and the second electronic conductor may be the same or different, and the particle size DV50 is less than or equal to 100 nm;

[0015] The first adhesive and the second adhesive comprise either a water-based adhesive or an oil-based adhesive; the first adhesive and the second adhesive may be the same or different.

[0016] The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each include one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte; the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte may be the same as or different from each other.

[0017] The ion-conducting layer further includes a dispersant; the dispersant includes: a dispersant for an aqueous system or a dispersant for an organic solvent system; the mass ratio of the first solid electrolyte to the dispersant is 85-95:5-15.

[0018] More preferably, the carbon-based electronic conductor includes one or more of conductive carbon black, graphite conductive agent, graphene, and carbon nanotubes; the metal oxide electronic conductor includes indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO).

[0019] The aqueous binder includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); the oil-based binder includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN).

[0020] The oxide-based solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, and NASICON-type oxide solid electrolyte;

[0021] The sulfide-based solid electrolyte includes one or more of the following: silver sulfide germanium ore type solid electrolyte, LGPS type solid electrolyte, and Thio-LISICON type solid electrolyte;

[0022] The fluoride-based solid electrolyte includes one or more of the following: garnet-type fluoride-oxide solid electrolyte, NASICON-type oxide solid electrolyte, layered fluoride-oxide solid electrolyte, and disordered rock salt fluoride-oxide solid electrolyte;

[0023] The dispersant in the aqueous system includes one or more of polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether; the dispersant in the organic solvent system includes one or more of acidic phosphate esters, phosphate ester amine salts, polyvinylpyrrolidone, oleic acid, stearic acid, triethanolamine oleate, triethanolamine, and ethylenediamine.

[0024] More preferably, the garnet-type oxide solid electrolyte specifically comprises: Li7Al3B12O 12Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf;

[0025] The perovskite-type oxide solid electrolyte specifically includes: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr;

[0026] The NASICON-type oxide solid electrolyte specifically includes: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf;

[0027] The sulfosilver germanite-type solid electrolyte comprises: Li6PS5N, wherein N includes any one of Cl, Br, and I elements;

[0028] The LGPS-type sulfide solid electrolyte specifically includes: Li 11-z M 2-z P 1+z S 12 , where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn;

[0029] The Thio-LISICON type sulfide solid electrolyte specifically includes: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1;

[0030] The fluoride-based solid electrolyte specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; wherein M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; wherein M2 is one or more of Nb, Sb, Bi, V, and Ta; and wherein M3 is one or more of W, Cr, Mo, and Mn.

[0031] In a second aspect, the present invention provides a method for preparing the bifunctional composite lithium-conducting separator described in the first aspect, the method comprising:

[0032] The first solid electrolyte, dispersant and first solvent are mixed and dispersed evenly to obtain a mixed slurry;

[0033] The base film is immersed in the mixed slurry, left to stand under vacuum, and then placed in an oven for drying to obtain an ion-conducting layer.

[0034] The first electronic conductor, the first binder, and the second solid electrolyte are added to the second solvent and dispersed evenly to obtain the positive electrode side slurry;

[0035] The second electronic conductor, the second binder, and the third solid electrolyte are added to the third solvent and dispersed evenly to obtain the negative electrode side slurry;

[0036] The positive electrode slurry and the negative electrode slurry are coated on both sides of the ion conduction layer, and then dried in an oven to obtain a bifunctional composite lithium conductive membrane.

[0037] Preferably, the mass ratio of the first solid electrolyte to the dispersant is 85-95:5-15; the first solvent includes deionized water or ethanol; and the solid content of the mixed solution is 5wt%-20wt%.

[0038] The vacuum degree is less than or equal to 0.1 MPa, and the settling time is 10 to 30 minutes;

[0039] The drying process is carried out at a temperature of 50℃ to 100℃ for 30 minutes to 5 hours.

[0040] Preferably, the mass ratio of the second solid electrolyte, the first electronic conductor, and the second solid electrolyte is [60-80]:[10-30]:[5-10]; the second solvent includes either deionized water or N-methylpyrrolidone; and the solid content of the positive electrode slurry is 5wt% to 30wt%.

[0041] The mass ratio of the third solid electrolyte, the second electronic conductor, and the second binder is [60-80]:[10-30]:[5-10]; the third solvent includes either deionized water or N-methylpyrrolidone; the solid content of the negative electrode slurry is 5wt% to 30wt%.

[0042] Preferably, the coating method includes any one of: blade coating, roller coating, microgravure coating, and spray coating;

[0043] The drying temperature is 80℃~160℃, and the time is 1 hour~10 hours.

[0044] Thirdly, the present invention provides a lithium battery, the lithium battery comprising the bifunctional composite lithium-conducting separator described in the first aspect, or comprising the bifunctional composite lithium-conducting separator prepared by the preparation method described in the second aspect.

[0045] This invention provides a bifunctional composite lithium-conducting separator, its preparation method, and its application. By introducing a solid electrolyte material with a particle size Dv50 less than or equal to the membrane pore size into a large-pore base membrane to form an ion-conducting layer, a continuous and stable ion conduction channel is constructed inside the separator, improving the overall ion migration efficiency of the system and endowing it with excellent ion conductivity and interfacial stability. Furthermore, a positive electrode transition layer and a negative electrode transition layer containing electronic conductors are respectively attached to both sides of the ion-conducting layer, forming a special "sandwich structure." Due to the large difference in surface energy between the electronic conductor and the solid electrolyte, which acts as an ion conductor... During solvent evaporation, spontaneous phase separation occurs. The anchoring effect of the binder preferentially coats the solid electrolyte with a polarity matching that of the binder, squeezing the electronic conductors into isolated islands. This results in the electronic conductors being distributed in a dispersed island structure in the transition layers on both the positive and negative sides. By controlling the mass fraction of the electronic conductors in both the positive and negative transition layers to be below the critical value for forming a continuous conductive network, a continuous electronic conduction network cannot be formed between the electronic conductors. This blocks direct cross-layer leakage of electrons through the membrane structure from the positive side to the negative side, preventing short circuits.

[0046] The bifunctional composite lithium-conducting separator proposed in this invention has significant ion transport capability, interface compatibility and thermal stability, and achieves high safety by controlling the content of electronic conductors, providing strong support for high-performance battery systems.

[0047] The strategy of this invention is to replace the "inert physical coating" of traditional alumina separator with "active ion filling + intelligent interface coating", upgrading the separator from a "passive isolation component" to an "active lithium conduction and interface regulation core", which achieves the technical effects of improving ionic conductivity, reducing interface impedance, improving the mechanical strength of the separator, and improving battery cycle life. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the preparation method of the bifunctional composite lithium conductive membrane provided in an embodiment of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] This invention provides a dual-functional composite lithium-conducting separator, comprising: an ion-conducting layer, and a positive electrode transition layer and a negative electrode transition layer respectively coated on both sides of the ion-conducting layer.

[0052] First, the structural composition of the ion-conducting layer will be explained.

[0053] The ion-conducting layer in the bifunctional composite lithium-conducting separator provided in this embodiment of the invention includes: a base film and a first solid electrolyte filling the pores of the base film.

[0054] Specifically, the base membrane is a large-pore base membrane, including: a base membrane formed from any one of the following materials: polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET), or a bilayer composite base membrane or a trilayer composite base membrane formed from a combination of the above materials; the pore size r of the base membrane satisfies 500nm≤r≤5μm; the particle size Dv50 of the first solid electrolyte is 50nm~500nm, and the particle size DV50 of the first solid electrolyte is ≤ the pore size r of the base membrane.

[0055] The first solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte.

[0056] Among them, oxide-based solid electrolytes include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes; garnet-type oxide solid electrolytes specifically include: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON type oxide solid electrolytes specifically include: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0057] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include:

[0058] (100-u)Li2S-uP2S5, (100-u)Li2S-uSiS2, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0059] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; specifically, fluoride oxide-based solid electrolytes include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the first solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0060] In an optional embodiment, the ion-conducting layer further includes a dispersant, wherein the mass ratio of the first solid electrolyte to the dispersant is 85–95:5–15; the dispersant includes: a dispersant for aqueous systems or a dispersant for organic solvent systems; the dispersant can be selected according to the type of system; the dispersant for aqueous systems includes, but is not limited to, one or more of polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether; the dispersant for organic solvent systems includes, but is not limited to, one or more of acidic phosphate esters, phosphate ester amine salts, polyvinylpyrrolidone, oleic acid, stearic acid, triethanolamine oleate, triethanolamine, and ethylenediamine.

[0061] Secondly, the transition layer on the positive electrode side will be explained.

[0062] The positive electrode-side transition layer in the bifunctional composite lithium-conducting separator provided in this embodiment of the invention comprises: a first electronic conductor, a first binder, and a second solid electrolyte. The positive electrode-side transition layer is in contact with the positive electrode sheet of the lithium-ion battery.

[0063] Specifically, the transition layer on the positive electrode side is between 3μm and 20μm, and can be any value within this range, such as 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0064] The first electronic conductor includes: carbon-based electronic conductors and / or metal oxide electronic conductors; wherein, the carbon-based electronic conductors include one or more of conductive carbon black, graphite conductive agent, graphene, and carbon nanotubes; the metal oxide electronic conductors include: indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO); specifically, the graphite conductive agent includes one or more of KS-6, KS-15, SFG-6, and SFG-15; the conductive carbon black includes one or more of acetylene black, Super P, Super S, 350G, carbon fiber (VGCF), carbon nanotubes (CNTs), Ketjen black, and activated carbon; and the particle size DV50 of the first electronic conductor is less than or equal to 100 nm.

[0065] The first adhesive includes any one of an aqueous adhesive or an oil-based adhesive; wherein the aqueous adhesive includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); and the oil-based adhesive includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN).

[0066] The second solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte; wherein, the oxide-based solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, and NASICON-type oxide solid electrolyte; the garnet-type oxide solid electrolyte specifically includes: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON type oxide solid electrolytes specifically include: Li 1+y A3y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0067] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include:

[0068] (100-u)Li2S-uP2S5, (100-u)Li2S-uSiS2, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0069] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; specifically, fluoride oxide-based solid electrolytes include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 uOne or more of O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the second solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0070] Next, the transition layer on the negative electrode side will be explained.

[0071] The negative electrode-side transition layer in the bifunctional composite lithium-conducting separator provided in this embodiment of the invention includes: a second electronic conductor, a second binder, and a third solid electrolyte; the negative electrode-side transition layer is in contact with the negative electrode sheet.

[0072] Specifically, the thickness of the transition layer on the negative electrode side is between 3μm and 20μm, and can be any value within this range, such as 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0073] The second electronic conductor includes: carbon-based electronic conductors and / or metal oxide electronic conductors; wherein, the carbon-based electronic conductors include one or more of conductive carbon black, graphite conductive agents, graphene, and carbon nanotubes; the metal oxide electronic conductors include: indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO); specifically, the graphite conductive agents include one or more of KS-6, KS-15, SFG-6, and SFG-15; the conductive carbon black includes one or more of acetylene black, Super P, Super S, 350G, carbon fiber (VGCF), carbon nanotubes (CNTs), Ketjen black, and activated carbon; and the particle size DV50 of the first electronic conductor is less than or equal to 100 nm. The first electronic conductor and the second electronic conductor may be of the same or different types.

[0074] The second adhesive includes either a water-based adhesive or an oil-based adhesive; wherein, the water-based adhesive includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); and the oil-based adhesive includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN). The first adhesive and the second adhesive may be of the same or different types.

[0075] The third type of solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte.

[0076] Among them, oxide-based solid electrolytes include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes.

[0077] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include:

[0078] (100-u)Li2S-uP2S5, (100-u)Li2S-uSiS2, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0079] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; garnet-type oxide solid electrolytes specifically include: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-xB2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON type oxide solid electrolytes specifically include: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf; fluoride oxide-based solid electrolytes specifically include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the third solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0080] The first, second, and third solid electrolytes may be of the same or different types, and all are preferably Li. x La y M1 z M2 w M3 uO6F, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; and M3 is one or more of W, Cr, Mo, and Mn. Because this Li... x La y M1 z M2 w M3 u O6F fluoride oxide-based solid electrolytes are characterized by high density, high purity, high volumetric energy density, low internal resistance, and excellent ion conduction performance. After being bridged with a eutectic coating layer on its surface, they exhibit even better processability and electrochemical performance.

[0081] Due to the fluoride-based solid electrolyte Li x La y M1 z M2 w M3 u O6F possesses a rigid framework structure with tunable elemental composition. The introduction of diverse coordination environments through multivalent cation doping facilitates the formation of open channels conducive to lithium-ion transport. Simultaneously, fluorine doping further enhances the material's polarity and interfacial wettability, improving interfacial contact with the electrolyte and electrodes and reducing interfacial impedance. Furthermore, the fluorine oxide-based solid electrolyte Li... x La y M1 z M2 w M3 u The particle size control of O6F, which matches the large-pore polymer base membrane, helps it to be uniformly embedded in the membrane pores without clogging the micropores, thereby giving it excellent ionic conductivity and interfacial stability while maintaining the mechanical support function of the membrane.

[0082] The dual-function composite lithium-conducting separator provided by this invention is used in lithium-ion batteries. The positive electrode transition layer is in contact with the positive electrode of the lithium-ion battery, and the negative electrode transition layer is in contact with the negative electrode. The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte form a continuous ion channel. The first electronic conductor and the second electronic conductor are distributed in a dispersed island structure in the positive electrode transition layer and the negative electrode transition layer, respectively. The mass fraction of the first electronic conductor in the positive electrode transition layer and the mass fraction of the second electronic conductor in the negative electrode transition layer are both lower than the critical value for forming a continuous conductive network, thereby blocking the direct cross-layer leakage of electrons from the positive electrode side to the negative electrode side through the separator structure.

[0083] Specifically, the mass fraction of the first electronic conductor in the positive electrode transition layer is less than or equal to 30%, and the mass fraction of the second electronic conductor in the negative electrode transition layer is less than or equal to 30%, both of which are below the critical value for forming a continuous conductive network. That is, when the mass percentage of the first electronic conductor in the total mass of the first electronic conductor, the first binder, and the second solid electrolyte is less than or equal to 30%, and when the mass percentage of the second electronic conductor in the total mass of the second electronic conductor, the second binder, and the third solid electrolyte is less than or equal to 30%, the first and second electronic conductors are distributed in a dispersed island-like structure in the positive electrode transition layer and the negative electrode transition layer, respectively. A continuous conductive network will not be formed between the first and second electronic conductors, thereby blocking the direct cross-layer leakage of electrons from the positive electrode side to the negative electrode side through the membrane structure.

[0084] The percentage of the mass of the first electronic conductor to the total mass of the first electronic conductor, the first binder, and the second solid electrolyte is less than or equal to 30%, and can be any value within this range, such as: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable. The percentage of the mass of the second electronic conductor to the total mass of the second electronic conductor, the second binder, and the third solid electrolyte is less than or equal to 30%, and can be any value within this range, such as: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0085] This invention provides a method for preparing a bifunctional composite lithium-conducting separator, such as... Figure 1 As shown, the preparation method includes the following steps.

[0086] Step 110: Mix the first solid electrolyte, dispersant and first solvent, and disperse them evenly to obtain a mixed slurry.

[0087] The mass ratio of the first solid electrolyte to the dispersant is 85-95:5-15.

[0088] Specifically, the first solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte.

[0089] Oxide-based solid electrolytes include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes. Garnet-type oxide solid electrolytes specifically include: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON-type oxide solid electrolytes specifically include: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0090] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0091] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; specifically, fluoride oxide-based solid electrolytes include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the first solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0092] The dispersant is a commonly used dispersant, including dispersants for aqueous systems or organic solvent systems, which can be selected according to the type of system. Dispersants for aqueous systems include, but are not limited to, one or more of polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether. Dispersants for organic solvent systems include, but are not limited to, one or more of acidic phosphate esters, phosphate ester amine salts, polyvinylpyrrolidone, oleic acid, stearic acid, triethanolamine oleate, triethanolamine, and ethylenediamine. Polyvinylpyrrolidone is preferred as the dispersant, as it can be used in both aqueous and organic solvent systems.

[0093] The first solvent includes deionized water or ethanol.

[0094] The solid content of the mixed solution is 5 wt% to 20 wt%.

[0095] The method for achieving uniform dispersion in this step is a conventional method, which can be achieved using a mixer, ultrasonic disperser, etc. For example, when using a mixer, stir at a speed of 500 rpm to 1200 rpm for 1 to 10 hours.

[0096] Step 120: Immerse the base film in the mixed slurry, let it stand under vacuum, and then put it in an oven for drying to obtain the ion-conducting layer.

[0097] The base membrane is a macroporous base membrane, which includes a base membrane formed from any one of the following materials: polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET), or a bilayer composite base membrane or a trilayer composite base membrane formed from a combination of the above materials; the pore size r of the base membrane satisfies 500nm≤r≤5μm; the particle size DV50 of the first solid electrolyte is 50nm~500nm, and the particle size DV50 of the first solid electrolyte is ≤ the pore size r of the base membrane.

[0098] In this invention, pore size refers to the diameter of the internal pores in a large-pore base film, a meaning known in the art. Pore size can be measured using instruments and conventional methods known in the art; in this example, the pore size of the base film can be directly measured using a scanning electron microscope (SEM).

[0099] The vacuum degree is less than or equal to 0.1 MPa, and the standing time is 10 to 30 minutes.

[0100] The drying process is carried out at a temperature of 50℃ to 100℃ for 30 minutes to 5 hours.

[0101] Step 130: Add the first electronic conductor, the first binder, and the second solid electrolyte to the second solvent and disperse them evenly to obtain the positive electrode side slurry;

[0102] The mass ratio of the second solid electrolyte, the first electronic conductor, and the second solid electrolyte is [60-80]:[10-30]:[5-10]; the second solvent includes either deionized water or N-methylpyrrolidone; the solid content of the positive electrode slurry is 5wt% to 30wt%. The method for uniform dispersion in this step is a conventional method, such as using a mixer to stir at a speed of 500 rpm to 1200 rpm for 1 to 10 hours.

[0103] The first electronic conductor includes: carbon-based electronic conductors and / or metal oxide electronic conductors; wherein, the carbon-based electronic conductors include one or more of conductive carbon black, graphite conductive agent, graphene, and carbon nanotubes; the metal oxide electronic conductors include: indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO); specifically, the graphite conductive agent includes one or more of KS-6, KS-15, SFG-6, and SFG-15; the conductive carbon black includes one or more of acetylene black, Super P, Super S, 350G, carbon fiber VGCF, carbon nanotubes (CNTs), Ketjen black, and activated carbon; and the particle size DV50 of the first electronic conductor is less than or equal to 100 nm.

[0104] The first adhesive includes any one of an aqueous adhesive or an oil-based adhesive; wherein the aqueous adhesive includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); and the oil-based adhesive includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN).

[0105] The second solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte.

[0106] Specifically, oxide-based solid electrolytes include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes. Garnet-type oxide solid electrolytes specifically include: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON-type oxide solid electrolytes specifically include: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0107] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-vGe 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0108] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; specifically, fluoride oxide-based solid electrolytes include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the second solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0109] Step 140: Add the second electronic conductor, the second binder and the third solid electrolyte to the third solvent and disperse them evenly to obtain the negative electrode side slurry.

[0110] The mass ratio of the third solid electrolyte, the second electronic conductor, and the second binder is [60-80]:[10-30]:[5-10]; the third solvent includes either deionized water or N-methylpyrrolidone (NMP); the solid content of the negative electrode slurry is 5wt% to 30wt%. The method for achieving uniform dispersion in this step is a conventional method, such as using a mixer at a speed of 500 rpm to 1200 rpm for 1 to 10 hours.

[0111] Specifically, the second electronic conductor includes: carbon-based electronic conductors and / or metal oxide electronic conductors; wherein, carbon-based electronic conductors include one or more of conductive carbon black, graphite conductive agents, graphene, and carbon nanotubes; metal oxide electronic conductors include: indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO); specifically, graphite conductive agents include one or more of KS-6, KS-15, SFG-6, and SFG-15; conductive carbon black includes one or more of acetylene black, Super P, Super S, 350G, carbon fiber VGCF, carbon nanotubes (CNTs), Ketjen black, and activated carbon; and the particle size DV50 of the second electronic conductor is less than or equal to 100 nm. The second electronic conductor may be the same as or different from the first electronic conductor.

[0112] The second adhesive includes any one of an aqueous adhesive or an oil-based adhesive; wherein, the aqueous adhesive includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); and the oil-based adhesive includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN). The second adhesive may be the same as or different from the first adhesive.

[0113] The third solid electrolyte may be the same as or different from the first and second solid electrolytes; the third solid electrolyte includes one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte.

[0114] Specifically, oxide-based solid electrolytes include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes. Garnet-type oxide solid electrolytes specifically include: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; perovskite oxide solid electrolytes specifically include: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; NASICON type oxide solid electrolytes specifically include: Li 1+y A3 y B3 2-y(PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0115] Sulfide-based solid electrolytes include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes; specifically, sulfide-germanium sulfide-type solid electrolytes include Li6PS5N, where N includes any one of Cl, Br, and I elements; LGPS-type sulfide solid electrolytes specifically include: Li 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; Thio-LISICON type sulfide solid electrolytes specifically include: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0116] Fluoride oxide-based solid electrolytes include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes; specifically, fluoride oxide-based solid electrolytes include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 uOne or more of O6F, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; M3 is one or more of W, Cr, Mo, and Mn; the third solid electrolyte is preferably Li. x La y M1 z M2 w M3 u O6F.

[0117] Step 150: The positive electrode slurry and the negative electrode slurry are coated on both sides of the ion conduction layer, and then dried in an oven to obtain a bifunctional composite lithium conductive membrane.

[0118] Specifically, a positive electrode slurry (or a negative electrode slurry) is first coated on one side of the ion conduction layer and dried in an oven. Then, a negative electrode slurry (or a positive electrode slurry) is coated on the other side of the ion conduction layer and dried in an oven to obtain a bifunctional composite lithium-conducting separator.

[0119] The coating method includes any one of the following: blade coating, roller coating, microgravure coating, and spray coating; the thickness of the coating on both the positive and negative electrode sides is 1μm to 10μm; the drying oven can be a regular oven or a vacuum drying oven, as long as the solvent is removed; the drying temperature is 80℃ to 160℃, and the time is 1 hour to 10 hours, in order to remove the solvent in the slurry.

[0120] In this invention, particle size Dv50 refers to the volumetric median particle size of the material, representing the particle size corresponding to 50% of the material's volume distribution, a meaning known in the art. The particle size Dv50 of the material in this invention can be determined using instruments and conventional methods known in the art. Specifically, 1g of material is weighed and added to 20ml of deionized water, followed by 50ul of a 1% (w / w) aqueous solution of ethyl phenyl polyethylene glycol dispersant. The mixture is sonicated for 5 minutes, and then the dispersion is added to a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. for particle size determination. The Dv50 value is then read.

[0121] The bifunctional composite lithium-conducting separator prepared by the above-described preparation method provided in this invention can be applied to lithium batteries. The bifunctional composite lithium-conducting separator proposed in this invention can significantly improve the ion transport capability, interface compatibility, and high safety of lithium batteries, providing strong support for high-performance lithium battery systems.

[0122] To better understand the technical solution provided by this invention, the following examples illustrate the preparation process and characteristics of the bifunctional composite lithium-conducting separator of this invention.

[0123] Example 1

[0124] This embodiment provides a preparation process for a bifunctional composite lithium-conducting separator, as detailed below.

[0125] (1) Preparation of fluoride oxide-based solid electrolyte Li 1.25 La 0.58 Specifically, Nb₂O₆F is prepared by mixing Li₂CO₃, La₂O₃, Nb₂O₅, and LiF in a molar ratio of 0.625:0.29:1:1, and then placing the mixture in a tube furnace. Nitrogen gas is introduced into the tube furnace at a flow rate of 1.5 L / min. Under the nitrogen atmosphere, the temperature is increased to 1000℃ at a heating rate of 2℃ / min and held for 6 hours to obtain a fluoride solid electrolyte Li₂O₆F with a particle size Dv₅₀ of 100 nm. 1.25 La 0.58 Nb2O6F.

[0126] (2) The fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Nb2O6F and polyvinylpyrrolidone were mixed with ethanol at a mass ratio of 90:10 and dispersed evenly to obtain a mixed slurry with a solid content of 20wt%.

[0127] (3) Immerse the PE base film with a pore size of 5μm into the mixed slurry, let it stand for 30min under a vacuum of 0.1Mpa, and then put it in an oven at 60℃ for 2 hours to remove the solvent and obtain the ion-conducting layer.

[0128] (4) Indium tin oxide, polyvinylidene fluoride and fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Nb2O6F was added to NMP at a mass ratio of 10:20:70 and dispersed evenly to obtain a positive electrode slurry with a solid content of 20wt%.

[0129] (5) Carbon nanotubes (CNTs), PVDF, and fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Nb2O6F was added to deionized water at a mass ratio of 10:20:70 and dispersed evenly to obtain a negative electrode slurry with a solid content of 20wt%.

[0130] (6) First, a positive electrode slurry is coated on one side of the ion conduction layer and dried in a vacuum drying oven at 160°C for 2 hours. Then, a negative electrode slurry is coated on the other side of the ion conduction layer and dried in a vacuum drying oven at 90°C for 2 hours to form a sandwich structure with a 10μm positive electrode transition layer and a 10μm negative electrode transition layer attached to both sides of the ion conduction layer, thus obtaining a bifunctional composite lithium conductive membrane.

[0131] The bifunctional composite lithium-conducting membrane prepared in this embodiment was tested, and the test items and methods are as follows. The test results are detailed in Table 1.

[0132] 1. Ionic conductivity and surface resistivity tests are as follows.

[0133] (1) Ionic conductivity was tested using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation. Specifically, the bifunctional composite lithium-conducting membrane prepared in this embodiment was first cut into circular pieces with a diameter of 17 mm and sandwiched between two stainless steel (SS) inert electrodes before being installed in a battery for testing. To ensure the accuracy of the test, the test battery was placed in a constant temperature chamber for temperature control. In the EIS test, the frequency range was set from 0.01 Hz to 1 MHz, and the amplitude voltage was set to 10 mV to accurately measure the resistance of the bifunctional composite lithium-conducting membrane. Next, by analyzing the Nyquist impedance spectrum, the ionic conductivity of the electrolyte can be calculated using the following formula: In the determination of ionic conductivity, d in the formula represents the thickness of the bifunctional composite lithium-ion separator, R is the impedance value read from the Nyquist impedance diagram of EIS, and S represents the effective contact area between the bifunctional composite lithium-ion separator and the stainless steel inert electrode. To ensure the accuracy of the measurement, when testing the ionic conductivity at different temperatures, the constant temperature chamber needs to be set to the target temperature and maintained for half an hour to allow the test battery to reach thermal equilibrium. This step ensures the stability of the test environment, thereby allowing for accurate measurement of the ionic conductivity of the solid electrolyte at various temperatures. The ionic conductivity tests of this invention are all conducted at 25±2℃ and humidity less than 50%.

[0134] (2) Calculate the surface resistance. The formula is: Surface resistance = impedance value R × area S of the bifunctional composite lithium conductive membrane.

[0135] 2. Electrochemical window test: Lithium metal sheet is used as reference electrode and counter electrode, and stainless steel sheet (SS) is used as working electrode. A bifunctional composite lithium conductive membrane is used in the middle. The electrolyte is LiPF6 with a molar concentration of 1 mol / L. The solvent of the electrolyte is a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1.

[0136] During testing, lithium / stainless steel (Li|SS) batteries were assembled inside a glove box, and then linear sweep voltammetry (LSV) tests were performed in a constant temperature chamber at room temperature. The scan rate was set to 1 millivolt per second (mV / s), scanning from the open-circuit voltage to 6V.

[0137] 3. Cyclic performance test: To test the cycle stability of the full battery assembled with the dual-functional composite lithium-conducting membrane, lithium iron phosphate (LFP) was selected as the positive electrode active material to prepare the LFP positive electrode, and commercial silicon-carbon negative electrode was selected as the negative electrode active material. The membrane used in this embodiment is the dual-functional composite lithium-conducting membrane. The electrolyte is LiPF6 with a molar concentration of 1 mol / L. The solvent of the electrolyte is a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1. The battery is assembled into a "LFP positive electrode | dual-functional composite lithium-conducting membrane | silicon-carbon negative electrode" soft-pack battery using conventional methods. During the assembly process, it is important to ensure that the LFP positive electrode is in contact with the positive electrode side coating of the dual-functional composite lithium-conducting membrane, and the silicon-carbon negative electrode is in contact with the negative electrode side coating of the dual-functional composite lithium-conducting membrane.

[0138] Then, a blue-light tester was used to perform 200 cycles of cyclic testing at 3C current density, and the capacity retention rate was calculated and recorded.

[0139] 4. Test the electrode expansion rate. Measure the thickness of the silicon-carbon negative electrode before assembling the full cell. After the full cell has been cycled 200 times, disassemble the silicon-carbon negative electrode after testing and measure the thickness before and after the test. Calculate the expansion rate = (thickness after cycling - initial thickness) / initial thickness.

[0140] Example 2

[0141] This embodiment provides a preparation process for a bifunctional composite lithium-conducting separator, which differs from Embodiment 1 in that a different solid electrolyte is used. Step (1) involves preparing a fluorine oxide-based solid electrolyte, Li. 1.25 La 0.58Ta₂O₆F was prepared by mixing Li₂CO₃, La₂O₃, Ta₂O₅, and LiF in a molar ratio of 0.625:0.29:1:1. The mixture was then placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 1.5 L / min. Under the nitrogen atmosphere, the temperature was increased to 1000 °C at a rate of 2 °C / min and held for 6 hours to obtain a fluoride solid electrolyte Li₂O₆F with a particle size Dv₅₀ of 100 nm. 1.25 La 0.58 Ta2O6F.

[0142] The solid electrolytes used in steps (2), (4), and (5) are all the prepared fluoride oxide-based solid electrolytes, Li. 1.25 La 0.58 Ta2O6F. The other preparation processes are the same as in Example 1.

[0143] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0144] Example 3

[0145] This embodiment provides a preparation process for a bifunctional composite lithium-conducting separator, which differs from Embodiment 1 in that the particle size of the solid electrolyte and the pore size of the base film are different. Steps (2), (4), and (5) use a fluorine oxide-based solid electrolyte, Li. 1.25 La 0.58 The particle size Dv50 of Nb2O6F is 200 nm. The average pore size of the PE-based film is 5 μm, and the other preparation processes are the same as in Example 1.

[0146] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0147] Example 4

[0148] This embodiment provides a preparation process for a bifunctional composite lithium conductive membrane. The difference from Embodiment 1 is that the raw materials for preparing the slurry in steps (4) and (5) are different, as detailed below.

[0149] Steps (1) to (3) are the same as in Example 1.

[0150] Step (4): Add AZO, Super P, PVDF-HFP and fluoride-based solid electrolyte Li 1.25 La 0.58Nb2O6F was added to NMP at a mass ratio of 10:10:10:70 and dispersed evenly to obtain a positive electrode slurry with a solid content of 20wt%.

[0151] Step (5) involves combining ITO, carbon nanotubes (CNTs), CMC, PVDF, and the fluoride-based solid electrolyte Li. 1.25 La 0.58 Nb2O6F was added to deionized water at a mass ratio of 10:10:10:70 and dispersed evenly to obtain a negative electrode slurry with a solid content of 20wt%.

[0152] Step (6) is the same as in Example 1.

[0153] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0154] Example 5

[0155] This embodiment provides a preparation process for a bifunctional composite lithium conductive membrane. The difference from Embodiment 1 is that the thickness of the positive electrode transition layer and the negative electrode transition layer in step (6) is 5 μm. The other preparation processes are the same as in Embodiment 1.

[0156] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0157] Example 6

[0158] This embodiment provides a preparation process for a bifunctional composite lithium-conducting separator, which differs from Embodiment 1 in that the solid electrolyte in steps (2), (4), and (5) all uses commercially available Li-340. 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) solid electrolyte, and the other preparation processes are the same as in Example 1.

[0159] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0160] Example 7

[0161] This embodiment provides a bifunctional composite lithium-conducting separator. The preparation process differs from that in Embodiment 1 in that the solid electrolyte used in steps (2), (4), and (5) is commercially available Li7La3Zr2O. 12(LLZO) solid electrolyte, and the other preparation processes are the same as in Example 1.

[0162] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0163] Example 8

[0164] This embodiment provides a preparation process for a bifunctional composite lithium-conducting separator, which differs from Embodiment 1 in that the solid electrolyte in steps (2), (4), and (5) all uses commercially available Li-340. 0.33 La 0.56 TiO3 (LLTO) solid electrolyte, the other preparation process is the same as in Example 1.

[0165] The performance of the bifunctional composite lithium-conducting separator prepared in this embodiment was tested, and a lithium-ion battery was assembled using the bifunctional composite lithium-conducting separator prepared in this embodiment for testing. The specific process was the same as in Example 1.

[0166] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0167] Comparative Example 1

[0168] This comparative example directly uses commercially available PE separators for performance testing, and uses PP separators to assemble lithium-ion batteries for testing. The specific process is the same as in Example 1.

[0169] Comparative Example 2

[0170] This comparative example provides a method for preparing a composite membrane. The difference from Example 1 is that the solid electrolyte in steps (2), (4), and (5) is inert filler alumina (Al2O3). The other preparation processes are the same as in Example 1.

[0171] The performance of the separator prepared in this comparative example was tested, and the separator prepared in this comparative example was assembled into a lithium-ion battery for testing. The specific process was the same as in Example 1.

[0172] Comparative Example 3

[0173] This comparative example provides a method for preparing a separator. The difference from Example 1 is that steps (4) and (5) are not performed, that is, the positive electrode slurry and the negative electrode slurry are not coated on both sides of the base membrane, and the ion conduction layer of step (3) is used directly as the separator.

[0174] The performance of the separator prepared in this comparative example was tested, and the separator prepared in this comparative example was assembled into a lithium-ion battery for testing. The specific process was the same as in Example 1.

[0175] Comparative Example 4

[0176] This comparative example provides a method for preparing a diaphragm, which differs from Example 1 in that the mass percentage of the electronic conductor in steps (4) and (5) both exceeds 30%. Step (4) involves indium tin oxide, polyvinylidene fluoride, and a fluoride-based solid electrolyte Li. 1.25 La 0.58 The mass ratio of Nb₂O₆F is 35:15:50; Step (5) Carbon nanotubes (CNTs), PVDF, and fluoride-based solid electrolyte Li 1.25 La 0.58 The mass ratio of Nb2O6F was 35:15:50, and the other preparation processes were the same as in Example 1.

[0177] The separator prepared in this comparative example was assembled into a full cell for cycle performance testing. The specific assembly and testing process was the same as in Example 1. The full cell containing the separator of Comparative Example 4 could not cycle for 200 cycles. This is because when the mass ratio of electronic conductors exceeds the threshold value, the electronic conductors easily form network connection channels, which will lead to a real electronic short circuit in the ionic conductivity test and cause a huge background current in the electrochemical window test, which seriously interferes with the judgment of the decomposition potential. Its behavior is similar to that of a short circuit. Similarly, in the cycle test of the full cell, it will cause the battery to fail rapidly through mechanisms such as continuous self-discharge, lithium dendrite growth, and interfacial side reactions. Essentially, it is an electrochemically driven progressive short circuit.

[0178] Table 1 summarizes the test data for Examples 1-8 and Comparative Examples 1-3.

[0179]

[0180] Table 1

[0181] As can be seen from the test data in Table 1, the ionic conductivity of Examples 1-8 is much higher than that of Comparative Example 1, the sheet resistance of Examples 1-8 is significantly lower than that of Comparative Example 1, the electrochemical window of Examples 1-8 is significantly higher than that of Comparative Example 1, the cycle capacity retention rate of Examples 1-8 after 200 cycles is significantly higher than that of Comparative Example 1, and the silicon-carbon electrode expansion rate of Examples 1-8 is significantly lower than that of Comparative Example 1. This is because the bifunctional composite lithium-conducting separator of Examples 1-8 of the present invention has significant ion transport capability, interface compatibility and thermal stability, and by controlling the content of electronic conductors, the separator has high safety, which can effectively improve the electrochemical performance of the battery. In contrast, the traditional PE separator used in Comparative Example 1, although its ionic conductivity and electrochemical window are mediocre, cannot cope with the expansion problem of silicon-carbon anode, resulting in poor cycle performance.

[0182] The ionic conductivity of Examples 1-8 is much higher than that of Comparative Example 2, the sheet resistance of Examples 1-8 is significantly lower than that of Comparative Example 2, the electrochemical window of Examples 1-8 is significantly higher than that of Comparative Example 2, the cycle capacity retention rate of Examples 1-8 after 200 cycles is significantly higher than that of Comparative Example 2, and the silicon-carbon electrode expansion rate of Examples 1-8 is significantly lower than that of Comparative Example 2. This is because the bifunctional composite lithium-conducting separator of Examples 1-8 of the present invention has significant ion transport capability, interface compatibility and thermal stability, and by controlling the content of electronic conductors, the separator has high safety, which can effectively improve the electrochemical performance of the battery. In contrast, the separator of Comparative Example 2 uses inert alumina filler and does not use a high-ionic-conductor solid electrolyte. The intermediate layer cannot provide additional ion channels, resulting in the inability to improve the ionic conductivity and other properties. Lithium ions cannot migrate quickly and deposit uniformly, affecting the cycle performance.

[0183] The ionic conductivity of Examples 1-5 is much higher than that of Comparative Example 3, the sheet resistance of Examples 1-5 is significantly lower than that of Comparative Example 3, the electrochemical window of Examples 1-5 is significantly higher than that of Comparative Example 3, the cycle capacity retention rate of Examples 1-5 after 200 cycles is significantly higher than that of Comparative Example 3, and the silicon-carbon electrode expansion rate of Examples 1-5 is significantly lower than that of Comparative Example 3. This is because the bifunctional composite lithium-conducting separator of Examples 1-5 of the present invention has significant ion transport capability, interface compatibility and thermal stability, and the separator has high safety by controlling the content of electronic conductors, which can effectively improve the electrochemical performance of the battery. In contrast, Comparative Example 3 does not have a "sandwich structure". Although the ionic conductivity and sheet resistance are improved, it does not have a transition layer between the positive and negative electrodes, which reduces its compatibility with the positive and negative electrodes and prevents it from performing as expected.

[0184] Although the ionic conductivity of Examples 6-8 is lower than that of Comparative Example 3, and the sheet resistance is higher, the electrochemical window of Examples 6-8 is significantly larger than that of Comparative Example 3. The silicon-carbon electrode expansion rate of Examples 6-8 is also significantly lower than that of Comparative Example 3. Therefore, the cycle capacity retention rate of Examples 6-8 after 200 cycles is better than that of Comparative Example 3. This is because Comparative Example 3 directly uses an ion-conducting layer. Although the ionic conductivity and sheet resistance are improved, there is no transition layer between the positive and negative electrodes, resulting in reduced compatibility with the positive and negative electrodes and a weaker ability to suppress electrode expansion, thus leading to poorer cycle performance compared to Examples 6-8.

[0185] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bifunctional composite lithium-conducting separator, characterized in that, The dual-function composite lithium-conducting membrane includes: an ion-conducting layer, and a positive electrode-side transition layer and a negative electrode-side transition layer respectively coated on both sides of the ion-conducting layer; the ion-conducting layer includes a base film and a first solid electrolyte filling the pores of the base film; The positive electrode side transition layer includes: a first electronic conductor, a first binder, and a second solid electrolyte; The negative electrode side transition layer includes: a second electronic conductor, a second binder, and a third solid electrolyte; The dual-functional composite lithium-conducting separator is used in lithium-ion batteries. The positive electrode transition layer is in contact with the positive electrode of the lithium-ion battery, and the negative electrode transition layer is in contact with the negative electrode of the lithium-ion battery. The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte form a continuous ion channel. The first electronic conductor and the second electronic conductor are respectively distributed in a dispersed island structure in the positive electrode transition layer and the negative electrode transition layer. The mass fraction of the first electronic conductor in the positive electrode transition layer is less than or equal to 30%, and the mass fraction of the second electronic conductor in the negative electrode transition layer is less than or equal to 30%, both of which are lower than the critical value for forming a continuous conductive network, thereby blocking the direct cross-layer leakage of electrons from the positive electrode side to the negative electrode side through the separator structure. The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte are the same.

2. The bifunctional composite lithium-conducting separator according to claim 1, characterized in that, The base film is a large-pore base film, including: a base film formed by any one of the following materials: polypropylene PP, polyethylene PE, polyvinylidene fluoride PVDF, polyethylene oxide PEO, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP, polyvinyl alcohol PVA, polymethyl methacrylate PMMA, and polyethylene terephthalate PET, or a double-layer composite base film or a triple-layer composite base film formed by a combination of the above materials. The pore size r of the base film satisfies 500nm≤r≤5μm; the particle size DV50 of the first solid electrolyte is 50nm~500nm, and the particle size DV50 of the first solid electrolyte is ≤ the pore size r of the base film.

3. The bifunctional composite lithium-conducting separator according to claim 1, characterized in that, The thickness of both the positive electrode side transition layer and the negative electrode side transition layer is between 3 μm and 20 μm. The first electronic conductor and the second electronic conductor include: carbon-based electronic conductors and / or metal oxide electronic conductors; the first electronic conductor and the second electronic conductor may be the same or different, and the particle size DV50 is less than or equal to 100 nm; The first adhesive and the second adhesive comprise either a water-based adhesive or an oil-based adhesive; the first adhesive and the second adhesive may be the same or different. The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each comprise one or more of the following: oxide-based solid electrolyte, sulfide-based solid electrolyte, fluoride oxide-based solid electrolyte, and solid polymer electrolyte; the ion-conducting layer further comprises a dispersant; the dispersant comprises a dispersant for an aqueous system or a dispersant for an organic solvent system; the mass ratio of the first solid electrolyte to the dispersant is 85-95:5-15.

4. The bifunctional composite lithium-conducting separator according to claim 3, characterized in that, The carbon-based electronic conductors include one or more of conductive carbon black, graphite conductive agents, graphene, and carbon nanotubes; the metal oxide electronic conductors include indium tin oxide (ITO) and / or aluminum-doped zinc oxide (AZO). The aqueous binder includes one or more of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), and chitosan (CS); the oil-based binder includes one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyethylene oxide (PEO), and polyacrylonitrile (PAN). The oxide-based solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, and NASICON-type oxide solid electrolyte; The sulfide-based solid electrolyte includes one or more of the following: silver sulfide germanium ore type solid electrolyte, LGPS type solid electrolyte, and Thio-LISICON type solid electrolyte; The fluoride-based solid electrolyte includes one or more of the following: garnet-type fluoride-oxide solid electrolyte, NASICON-type oxide solid electrolyte, layered fluoride-oxide solid electrolyte, and disordered rock salt fluoride-oxide solid electrolyte; The dispersant in the aqueous system includes one or more of polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, fatty alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether; the dispersant in the organic solvent system includes one or more of acidic phosphate esters, phosphate ester amine salts, polyvinylpyrrolidone, oleic acid, stearic acid, triethanolamine oleate, triethanolamine, and ethylenediamine.

5. The bifunctional composite lithium-conducting separator according to claim 4, characterized in that, The garnet-type oxide solid electrolyte specifically includes: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; The perovskite-type oxide solid electrolyte specifically includes: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; The NASICON-type oxide solid electrolyte specifically includes: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf; The sulfosilver germanite-type solid electrolyte comprises: Li6PS5N, wherein N includes any one of Cl, Br, and I elements; The LGPS-type solid electrolyte specifically includes: Li 11-z M 2-z P 1+z S 12 , where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; The Thio-LISICON type solid electrolyte specifically includes: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1; The fluoride-based solid electrolyte specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or Li x La y M1 z M2 w M3 u One or more of O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3; 0 ≤ z ≤ 2, 0 ≤ w ≤ 2, 0 ≤ u ≤ 2, z + w + u = 2; wherein M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; wherein M2 is one or more of Nb, Sb, Bi, V, and Ta; and wherein M3 is one or more of W, Cr, Mo, and Mn.

6. A method for preparing a bifunctional composite lithium-conducting separator according to any one of claims 1-5, characterized in that, The preparation method includes: The first solid electrolyte, dispersant and first solvent are mixed and dispersed evenly to obtain a mixed slurry; The base film is immersed in the mixed slurry, left to stand under vacuum, and then placed in an oven for drying to obtain an ion-conducting layer. The first electronic conductor, the first binder, and the second solid electrolyte are added to the second solvent and dispersed evenly to obtain the positive electrode side slurry; The second electronic conductor, the second binder, and the third solid electrolyte are added to the third solvent and dispersed evenly to obtain the negative electrode side slurry; The positive electrode slurry and the negative electrode slurry are coated on both sides of the ion conduction layer, and then dried in an oven to obtain a bifunctional composite lithium conductive membrane.

7. The method for preparing the bifunctional composite lithium-conducting separator according to claim 6, characterized in that, The mass ratio of the first solid electrolyte to the dispersant is 85–95:5–15; the first solvent includes deionized water or ethanol; the solid content of the mixed slurry is 5 wt%–20 wt%. The vacuum level under the vacuum condition is less than or equal to 0.1 MPa, and the settling time is 10 to 30 minutes; The drying process is carried out at a temperature of 50℃ to 100℃ for 30 minutes to 5 hours.

8. The method for preparing the bifunctional composite lithium-conducting separator according to claim 6, characterized in that, The mass ratio of the second solid electrolyte, the first electronic conductor, and the first binder is 60-80:10-30:5-10; the second solvent includes either deionized water or N-methylpyrrolidone; the solid content of the positive electrode side slurry is 5wt% to 30wt%. The mass ratio of the third solid electrolyte, the second electronic conductor, and the second binder is 60-80:10-30:5-10; the third solvent includes either deionized water or N-methylpyrrolidone; the solid content of the negative electrode slurry is 5wt% to 30wt%.

9. The method for preparing the bifunctional composite lithium-conducting separator according to claim 6, characterized in that, The coating method includes any one of the following: blade coating, roller coating, microgravure coating, and spray coating; The drying temperature is 80℃~160℃, and the time is 1 hour~10 hours.

10. A lithium battery, characterized in that, The lithium battery includes the bifunctional composite lithium-conducting separator as described in any one of claims 1-5, or the bifunctional composite lithium-conducting separator prepared by the preparation method described in any one of claims 6-9.

Images