Multifunctional carbon fiber battery based on modified sulfide electrolyte and preparation method thereof

Abstract

The invention belongs to the technical field of solid-state batteries, and provides a multifunctional carbon fiber battery based on modified sulfide electrolyte and a preparation method of the multifunctional carbon fiber battery. The multifunctional carbon fiber battery comprises a carbon fiber woven cloth positive electrode coated with a positive electrode active material, a modified sulfide electrolyte, a carbon fiber woven cloth negative electrode coated with a negative electrode active material and a glass fiber woven cloth diaphragm, the preparation method of the modified sulfide electrolyte comprises the following steps: mixing a sulfide electrolyte with a fluorine-containing Lewis acid solution, and sequentially carrying out ball milling treatment and heating treatment to obtain the modified sulfide electrolyte. According to the invention, the modified sulfide electrolyte is combined with the carbon fiber woven cloth and the glass fiber woven cloth which are coated with the positive electrode active material or the negative electrode active material, so that an integrated structural energy storage function of a carbon fiber reinforced matrix, the sulfide electrolyte and the positive and negative electrode materials is realized, and mechanical enhancement and energy storage functions can be simultaneously exerted; the comprehensive performance of the battery is improved; the overall quality of the battery is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly relates to a multifunctional carbon fiber battery based on a modified sulfide electrolyte and a preparation method thereof. Background Art

[0002] With the increasing demand for high-energy-density and high-safety lithium batteries, all-solid-state batteries have received extensive attention. As a key component of all-solid-state batteries, sulfide electrolytes have become one of the hotspots in the current research field of all-solid-state batteries due to their high ionic conductivity and good mechanical processing performance at room temperature. However, existing research shows that sulfide electrolytes have the following limitations:

[0003] 1. Poor air stability: Sulfide electrolytes are extremely hygroscopic, which can lead to a decrease in their ionic conductivity and even decomposition and failure.

[0004] 2. Poor interfacial stability with the lithium metal anode: It may form interfacial side reactions, resulting in an overly thick interfacial impedance layer and rapid attenuation of battery performance.

[0005] 3. The requirements for the engineering preparation process are relatively harsh, with strong activity, and it is difficult to be applied to composite materials with integrated structure and function.

[0006] In recent years, in order to solve the problems of sulfide electrolytes in terms of air stability and interfacial stability, some people have tried to construct a polymer coating layer on the surface of the electrolyte to improve the compatibility with lithium metal. However, when introducing a relatively thick polymer layer, this method will significantly reduce the overall conductivity of the electrolyte, thereby affecting the performance of the battery. Some people have also tried to introduce elements such as F and Cl for chemical doping during the preparation process. Although this method improves the stability between the electrolyte and lithium, it often leads to a decrease in the bulk conductivity, affecting the energy transfer efficiency of the battery. Some people have also used chemical vapor deposition or other surface modification methods to form a nanoscale protective layer on the surface of the electrolyte. Although this method can alleviate the oxidation or hydrolysis problems of the electrolyte to a certain extent, the process is extremely complex, causing a large obstacle to large-scale production and limiting its application and promotion in actual production.

[0007] In addition, for the direction of integrated structural energy storage, if the active materials in the battery can be combined with fiber reinforcements to construct a new type of carbon fiber battery with "load-bearing - energy storage" multifunctionality, it will greatly expand the application value of the battery in the lightweight of aerospace and new energy vehicles. In the prior art, certain progress has been made in the research of loading positive or negative electrode materials on the carbon fiber matrix. However, if a truly usable all-solid-state battery structure is to be realized in "fiber composite + sulfide electrolyte", further problems such as electrolyte modification and compatibility need to be solved.

[0008] Therefore, how to construct a stable layer on the surface of sulfide electrolyte, which has little impact on ion transport attenuation, can form a stable bonding layer with carbon fiber, positive electrode and negative electrode materials, and can resist the erosion of moisture and oxygen has become a difficult problem to be solved urgently at present. Summary of the Invention

[0009] In view of this, the present invention provides a multifunctional carbon fiber battery based on a modified sulfide electrolyte and a preparation method thereof to solve the problems of poor air stability of the existing sulfide electrolyte, poor resistance to erosion of moisture and oxygen, poor interfacial stability between the sulfide electrolyte and the lithium metal negative electrode, and poor compatibility between the modified sulfide electrolyte and the carbon fiber material.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention provides a multifunctional carbon fiber battery based on a modified sulfide electrolyte, including a carbon fiber woven fabric positive electrode coated with a positive electrode active material, a modified sulfide electrolyte, a carbon fiber woven fabric negative electrode coated with a negative electrode active material, and a glass fiber woven fabric separator.

[0012] Preferably, the preparation method of the modified sulfide electrolyte is: mixing the sulfide electrolyte with a fluorinated Lewis acid solution, and successively performing ball milling treatment and heat treatment to obtain the modified sulfide electrolyte.

[0013] Preferably, the thickness of the modified sulfide electrolyte is 10 - 1000 μm.

[0014] Preferably, the sulfide electrolyte includes one or more of argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type, and argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type doped with metal elements; the metal elements include one or more of Al, Nb, and Ta.

[0015] Preferably, the positive electrode active material includes one or more of NCM811 ternary positive electrode material, NCM523 ternary positive electrode material, NCA ternary positive electrode material, layered lithium-rich positive electrode material, and LiFePO4; the negative electrode active material includes one or more of lithium metal, graphite, silicon alloy, and lithium silicon alloy.

[0016] Preferably, the areal density of the carbon fiber woven fabric positive electrode and the carbon fiber woven fabric negative electrode is independently 10 - 20 g / m 2 , and the thickness is independently 20 - 80 μm; the areal density of the glass fiber woven fabric separator is 5 - 15 g / m 2 , and the thickness is 10 - 30 μm.

[0017] Preferably, when the sulfide electrolyte is one or more of argyrodite, lithium germanium phosphorus sulfide, and binary Li2S-P2S5 doped with metal elements, the preparation method of the sulfide electrolyte doped with metal elements includes the following steps:

[0018] 1) Mix the metal element precursor and the sulfide electrolyte, and perform mechanochemical ball milling to obtain a mixture;

[0019] 2) Subject the mixture to solid-phase annealing and crushing in sequence to obtain a sulfide electrolyte doped with metal elements.

[0020] Preferably, the atomic fraction y of the metal element in the metal element precursor in the sulfide electrolyte in step 1) is: 0.005 ≤ y ≤ 0.30; the metal element precursor includes one or more of Li2S, P2S5, GeS2, Al2S3, LiCl, LiBr, LiI, NbF5, Ta2S5.

[0021] Preferably, the ball-to-material ratio of the mechanochemical ball milling in step 1) is 10 to 25:1, and the time is 2 to 12 h; the atmosphere of the mechanochemical ball milling is an inert atmosphere; the temperature of the solid-phase annealing in step 2) is 230 to 550 °C, and the time is 2 to 10 h; the atmosphere of the solid-phase annealing is an inert atmosphere.

[0022] Preferably, the particle size of the sulfide electrolyte doped with metal elements is 1 to 10 μm.

[0023] Preferably, the fluorinated Lewis acid solution is obtained by mixing a fluorinated Lewis acid and an organic solvent; the fluorinated Lewis acid includes one or more of trifluoromethanesulfonate, boron trifluoride, tris(pentafluorophenyl)boron, bis(pentafluorophenyl)borane, antimony pentafluoride, tantalum pentafluoride, and niobium pentafluoride; the trifluoromethanesulfonate includes one or more of aluminum trifluoromethanesulfonate, indium trifluoromethanesulfonate, and scandium trifluoromethanesulfonate; the organic solvent includes one or more of toluene, xylene, n-hexane, n-heptane, and cyclohexane.

[0024] Preferably, the mass ratio of the fluorinated Lewis acid to the organic solvent is 1:10 to 100.

[0025] Preferably, the mass ratio of the sulfide electrolyte to the fluorinated Lewis acid solution is 1 to 10:1.

[0026] Preferably, the ball milling treatment is carried out in a zirconia ball milling tank; the ball-to-material ratio of the ball milling treatment is 1 to 20:1, the time is 1 to 10 h, and the environment is an inert atmosphere.

[0027] Preferably, the temperature of the heat treatment is 200 to 400 °C, the time is 1 to 10 h, and the environment is an inert atmosphere.

[0028] The present invention also provides a method for preparing the above-mentioned multifunctional carbon fiber battery based on a modified sulfide electrolyte, which includes the following steps:

[0029] Sprinkle the modified sulfide electrolyte on both sides of a glass fiber woven cloth separator, and perform hot pressing and sintering to obtain a composite modified sulfide electrolyte layer. Then, sequentially stack and assemble a carbon fiber woven cloth positive electrode coated with a positive electrode active material, the composite modified sulfide electrolyte layer, and a carbon fiber woven cloth negative electrode coated with a negative electrode active material to obtain a multifunctional carbon fiber battery based on a modified sulfide electrolyte; the atmosphere for the hot pressing and sintering is an inert atmosphere, the temperature is 250-350 °C, the pressure is 20-40 MPa, and the time is 1-2 h; the thickness of the composite modified sulfide electrolyte layer is 30-120 μm, and the density is ≥95%;

[0030] and / or sequentially perform hot pressing and laminating assembly on a carbon fiber woven cloth positive electrode coated with a positive electrode active material, a modified sulfide electrolyte, a glass fiber woven cloth separator, and a carbon fiber woven cloth negative electrode coated with a negative electrode active material to obtain a multifunctional carbon fiber battery based on a modified sulfide electrolyte; the method for the hot pressing and laminating assembly includes a low-temperature-long-time process or a high-temperature-short-time process; the temperature of the low-temperature-long-time process is 130-180 °C, the pressure is 6-9 MPa, and the time is 1.3-1.6 h; the temperature of the high-temperature-short-time process is 220-260 °C, the pressure is 18-20 MPa, and the time is 20-30 min.

[0031] Through the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The present invention constructs a fluoride-enriched interfacial layer in-situ on the surface of sulfide by using a fluorinated Lewis acid, which can significantly enhance the anti-erosion ability of the electrolyte to moisture and oxygen, and improve its stability in the environment. At the same time, it can also improve the interfacial stability and compatibility between the electrolyte and the negative electrode material (such as metallic lithium), inhibit interfacial side reactions and reduce interfacial impedance. Moreover, in the process of preparing the modified sulfide electrolyte of the present invention, a low-polarity solvent is selected as the organic solvent in the fluorinated Lewis acid solution, combined with the ball milling process, which helps to achieve a more efficient and stable uniformization effect of particle surface modification, and maximally retains the original high ionic conductivity of the sulfide electrolyte. In addition, the present invention combines the modified sulfide electrolyte with an ultra-thin carbon fiber woven cloth or a glass fiber woven cloth coated with a positive electrode active material or a negative electrode active material, which can realize the integrated structural energy storage function of "carbon fiber reinforced matrix - sulfide electrolyte - positive and negative electrode materials", and can simultaneously exert the mechanical enhancement and energy storage functions, improve the comprehensive performance of the battery and reduce the overall mass. In the overall structure, the modified sulfide electrolyte serves as both the electrolyte matrix material and the structural matrix, synergistically toughens, stiffens and reduces cracks with the carbon fiber reinforced matrix, endowing the battery with the dual functions of high energy density and excellent mechanical properties. Detailed Embodiments

[0033] The present invention provides a multifunctional carbon fiber battery based on a modified sulfide electrolyte, including a carbon fiber woven cloth positive electrode coated with a positive electrode active material, a modified sulfide electrolyte, a carbon fiber woven cloth negative electrode coated with a negative electrode active material, and a glass fiber woven cloth separator.

[0034] In the present invention, the preparation method of the modified sulfide electrolyte is: mixing the sulfide electrolyte with a fluorinated Lewis acid solution, and successively performing ball milling treatment and heat treatment to obtain the modified sulfide electrolyte.

[0035] In the present invention, the thickness of the modified sulfide electrolyte is 10 - 1000 μm, preferably 20 - 800 μm, further preferably 25 - 600 μm, and more preferably 30 - 500 μm. If the thickness is too thin, it may be difficult to ensure the isolation and mechanical properties, and if it is too thick, it will affect the energy density of the battery.

[0036] In the present invention, the sulfide electrolyte includes one or more of argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type, and argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type doped with metal elements; the argyrodite type preferably includes one or more of Li6PS5Cl and Li6PS5Br; the lithium germanium phosphorus sulfur type preferably includes Li 10 GeP2S 12 ; the binary Li2S - P2S5 type preferably includes Li 5.5 PS4.5 Cl 1.5 ; The metal element includes one or more of Al, Nb, and Ta. By doping the metal element, the intrinsic conductivity of the sulfide electrolyte can be improved.

[0037] In the present invention, the positive electrode active material includes one or more of NCM811 ternary positive electrode material, NCM523 ternary positive electrode material, NCA ternary positive electrode material, layered lithium-rich positive electrode material, and LiFePO4; the negative electrode active material includes one or more of metallic lithium, graphite, silicon alloy, and lithium-silicon alloy.

[0038] In the present invention, the areal density of the carbon fiber woven fabric positive electrode and the carbon fiber woven fabric negative electrode is independently 10 - 20 g / m 2 , preferably 12 - 18 g / m 2 , more preferably 13 - 16 g / m 2 , even more preferably 14 - 15 g / m 2 ; the thickness is independently 20 - 80 μm, preferably 25 - 70 μm, more preferably 26 - 60 μm, even more preferably 30 μm; the areal density of the glass fiber woven fabric separator is 5 - 15 g / m 2 , preferably 6 - 9 g / m 2 , more preferably 7 - 8 g / m 2 ; the thickness is 10 - 30 μm, preferably 12 - 25 μm, more preferably 13 - 20 μm, even more preferably 15 μm.

[0039] In the present invention, when the sulfide electrolyte is one or more of argyrodite-type, lithium-germanium-phosphorus-sulfur-type, and binary Li2S-P2S5-type doped with metal elements, the preparation method of the sulfide electrolyte doped with metal elements includes the following steps:

[0040] 1) Mix the metal element precursor and the sulfide electrolyte, and perform mechanochemical ball milling to obtain a mixture;

[0041] 2) Subject the mixture to solid-phase annealing and crushing in sequence to obtain the sulfide electrolyte doped with metal elements.

[0042] In the present invention, the atomic fraction y of the metal element in the metal element precursor in the sulfide electrolyte in step 1) is: 0.005 ≤ y ≤ 0.30, preferably 0.01 ≤ y ≤ 0.25, more preferably 0.03 ≤ y ≤ 0.20, even more preferably 0.05 ≤ y ≤ 0.15; the metal element precursor includes one or more of Li2S, P2S5, GeS2, Al2S3, LiCl, LiBr, LiI, NbF5, and Ta2S5.

[0043] In the present invention, the ball-to-material ratio of the mechanochemical ball milling in step 1) is 10 to 25:1, preferably 12 to 22:1, further preferably 15 to 20:1, and more preferably 16 to 18:1; the time is 2 to 12 h, preferably 3 to 10 h, further preferably 5 to 9 h, and more preferably 6 to 8 h; the atmosphere of the mechanochemical ball milling is an inert atmosphere, preferably one or more of argon atmosphere and nitrogen atmosphere.

[0044] In the present invention, the temperature of the solid-phase annealing in step 2) is 230 to 550 °C, preferably 250 to 520 °C, further preferably 260 to 500 °C, and more preferably 300 to 400 °C; the time is 2 to 10 h, preferably 3 to 9 h, further preferably 3.5 to 8.5 h, and more preferably 4 to 6 h; the atmosphere of the solid-phase annealing is an inert atmosphere, preferably one or more of argon atmosphere and nitrogen atmosphere.

[0045] In the present invention, the particle size of the sulfide electrolyte doped with metal elements is 1 to 10 μm, preferably 2 to 8 μm, further preferably 3 to 7 μm, and more preferably 5 to 6 μm.

[0046] In the present invention, the preparation method of the carbon fiber woven cloth positive electrode coated with the positive electrode active material is preferably: mixing the positive electrode active material with a conductive agent, a binder and a solvent to obtain a positive electrode slurry, and then coating the positive electrode slurry on the carbon fiber woven cloth and drying to obtain the carbon fiber woven cloth positive electrode coated with the positive electrode active material.

[0047] In the present invention, the mass ratio of the positive electrode active material to the conductive agent, the binder and the solvent is preferably 80 to 92:2 to 10:2 to 8:60 to 200, preferably 82 to 90:3 to 8:3 to 7:75 to 180, and more preferably 85 to 89:5 to 6:5 to 6:80 to 100; the conductive agent preferably includes one or more of conductive carbon black, acetylene black, graphene, reduced graphene oxide, single-walled or multi-walled carbon nanotubes (CNT) and vapor-grown carbon fibers (VGCF); the binder preferably includes one or more of polyvinylidene fluoride (PVDF), PVDF-HFP, polyimide (PI), styrene-butadiene rubber-carboxymethyl cellulose (SBR-CMC), polyacrylic acid (PAA), hydroxypropyl methyl cellulose (HPMC), modified acrylate, thermoplastic epoxy, and fluorinated polyolefin; the solvent preferably includes one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, toluene, xylene, cyclohexane, n-hexane, n-heptane and deionized water; the solid content of the positive electrode slurry is preferably 33 to 60 wt%, further preferably 45 to 55 wt%, and more preferably 50 wt%.

[0048] In the present invention, the atmosphere for drying is preferably an inert atmosphere, more preferably one or more of an argon atmosphere and a nitrogen atmosphere; the temperature is preferably 120 to 160 °C, further preferably 130 to 150 °C, and more preferably 140 °C; the time is preferably 5 to 30 min, further preferably 6 to 25 min, and more preferably 10 to 20 min; the coating thickness of the carbon fiber woven cloth positive electrode coated with the positive electrode active material is preferably 10 to 50 μm, further preferably 12 to 40 μm, and more preferably 15 to 30 μm; the thickness of the carbon fiber woven cloth positive electrode coated with the positive electrode active material is preferably 40 to 110 μm, further preferably 50 to 100 μm, and more preferably 60 to 70 μm.

[0049] In the present invention, when the negative electrode active material is one or more of metallic lithium, silicon alloy, and lithium-silicon alloy, the preparation method of the carbon fiber woven cloth negative electrode coated with the negative electrode active material is preferably: rolling the negative electrode active material into a thin sheet, and then laminating it on the carbon fiber woven cloth to obtain the carbon fiber woven cloth negative electrode coated with the negative electrode active material; when the negative electrode active material is metallic lithium, the thickness of the thin sheet is preferably 5 to 60 μm, further preferably 6 to 50 μm, and more preferably 8 to 20 μm; when the negative electrode active material is silicon alloy and / or lithium-silicon alloy, the thickness of the thin sheet is preferably 5 to 60 μm, further preferably 6 to 50 μm, and more preferably 15 to 40 μm; the lamination is preferably to place the thin sheet on the carbon fiber woven cloth for hot pressing, so that the thin sheet is softened and embedded between the carbon fiber bundles to achieve mechanical interlocking; the temperature of the hot pressing is preferably 60 to 90 °C, further preferably 65 to 85 °C, and more preferably 70 °C; the pressure is preferably 0.3 to 1 MPa, further preferably 0.4 to 0.8 MPa, and more preferably 0.6 MPa; the lamination is also preferably to coat the surfaces of the thin sheet and the carbon fiber woven cloth with an ion-conductive adhesive layer, and then place the thin sheet on the carbon fiber woven cloth for hot lamination; the thickness of the ion-conductive adhesive layer is preferably 2 to 5 μm, further preferably 2.5 to 4.5 μm, and more preferably 3 to 4 μm; the ion-conductive adhesive layer is preferably PEO-(LiTFSI), PVDF-HFP / ionic liquid, PVDF containing 5 wt% Ketjenblack, or B-stage epoxy-imidazole glue; the temperature of the hot lamination is preferably 60 to 120 °C, further preferably 70 to 110 °C, and more preferably 80 to 90 °C; the pressure is preferably 0.2 to 0.8 MPa, further preferably 0.3 to 0.6 MPa, and more preferably 0.4 to 0.5 MPa.

[0050] In the present invention, when the negative electrode active material is graphite or a mixture of graphite and one or more of metallic lithium, silicon alloy, and lithium silicon alloy, the method for preparing the carbon fiber woven cloth negative electrode coated with the negative electrode active material is preferably as follows: Mix the negative electrode active material with a conductive agent, a binder, and a solvent to obtain a negative electrode slurry, and then coat the negative electrode slurry on the carbon fiber woven cloth and dry it to obtain the carbon fiber woven cloth negative electrode coated with the negative electrode active material.

[0051] In the present invention, the mass ratio of the negative electrode active material, the conductive agent, the binder, and the solvent is preferably 80-94:1-8:2-8:70-200, more preferably 82-92:2-7:3-7:80-130, and still more preferably 85-90:3-6:4-6:90-100; the conductive agent preferably includes one or more of carbon black, acetylene black, Ketjenblack EC-600JD, graphene, and carbon nanotubes; the binder preferably includes one or more of PVDF, SBR-CMC, PAA, PVDF-HFP, and PI; the solvent preferably includes one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, toluene, xylene, cyclohexane, 1,3-dioxolane, 1,2-dimethoxyethane, and deionized water; the solid content of the negative electrode slurry is preferably 35-60 wt%, more preferably 40-55 wt%, and still more preferably 45-50 wt%.

[0052] In the present invention, the atmosphere for drying is preferably an inert atmosphere, more preferably one or more of an argon atmosphere and a nitrogen atmosphere; the temperature is preferably 80-150 °C, more preferably 90-120 °C, and still more preferably 95-100 °C; the time is preferably 5-30 min, more preferably 8-25 min, and still more preferably 10-20 min; the coating thickness of the carbon fiber woven cloth negative electrode coated with the negative electrode active material is preferably 15-35 μm, more preferably 17-30 μm, and still more preferably 22-25 μm; the thickness of the carbon fiber woven cloth negative electrode coated with the negative electrode active material is preferably 45-120 μm, more preferably 50-100 μm, and still more preferably 60-70 μm.

[0053] In the present invention, the fluorinated Lewis acid solution is obtained by mixing a fluorinated Lewis acid and an organic solvent; the fluorinated Lewis acid includes one or more of trifluoromethanesulfonate, boron trifluoride, pentafluorophenylboron, antimony pentafluoride, tantalum pentafluoride, and niobium pentafluoride; the trifluoromethanesulfonate includes one or more of aluminum trifluoromethanesulfonate, indium trifluoromethanesulfonate, and scandium trifluoromethanesulfonate, preferably aluminum trifluoromethanesulfonate; the organic solvent includes one or more of toluene, xylene, n-hexane, n-heptane, and cyclohexane, preferably includes one or more of toluene, xylene, and cyclohexane. By selecting the above-mentioned organic solvents with moderate boiling points and low polarities, the penetration and reaction degrees during the modification process can be controlled.

[0054] In the present invention, the mass ratio of the fluorinated Lewis acid to the organic solvent is 1:10 to 100, preferably 1:15 to 50, further preferably 1:20 to 35, and more preferably 25 to 30.

[0055] In the present invention, the mass ratio of the sulfide electrolyte to the fluorinated Lewis acid solution is 1 to 10:1, preferably 2 to 8:1, further preferably 3 to 6:1, and more preferably 4 to 5:1.

[0056] In the present invention, the ball milling treatment is carried out in a zirconia ball milling tank; the ball-to-material ratio of the ball milling treatment is 1 to 20:1, preferably 5 to 18:1, further preferably 8 to 15:1, and more preferably 10 to 12:1; the time of the ball milling treatment is 1 to 10 h, preferably 2 to 8 h, further preferably 3 to 6 h, and more preferably 4 to 5 h; the environment of the ball milling treatment is an inert atmosphere, preferably one or more of an argon atmosphere and a nitrogen atmosphere; by adjusting the ball milling time and the ball-to-material ratio, the uniformization of the surface modification of the sulfide particles can be achieved, and agglomeration and local overreaction can be reduced.

[0057] In the present invention, the temperature of the heat treatment is 200 to 400 °C, preferably 220 to 360 °C, further preferably 250 to 350 °C, and more preferably 260 to 300 °C; within this temperature range of the heat treatment, the solvent residue can be effectively removed and the formation of the surface fluorination layer can be promoted, while avoiding the decomposition of the sulfide body due to too high a temperature; the time of the heat treatment is 1 to 10 h, preferably 2 to 8 h, further preferably 3 to 6 h, and more preferably 4 to 5 h; the environment of the heat treatment is an inert atmosphere, preferably one or more of an argon atmosphere and a nitrogen atmosphere.

[0058] The present invention also provides a preparation method of the above-mentioned multifunctional carbon fiber battery based on the modified sulfide electrolyte, comprising the following steps:

[0059] The modified sulfide electrolyte is spread on both sides of a glass fiber woven fabric separator, and then hot-pressed and sintered to obtain a composite modified sulfide electrolyte layer. Subsequently, a carbon fiber woven fabric positive electrode coated with a positive electrode active material, the composite modified sulfide electrolyte layer, and a carbon fiber woven fabric negative electrode coated with a negative electrode active material are stacked and assembled in sequence to obtain a multifunctional carbon fiber battery based on the modified sulfide electrolyte. This method can omit a separate separator, enabling the modified sulfide electrolyte powder and fibers to form a composite membrane.

[0060] The atmosphere for the hot-pressing sintering is an inert atmosphere, preferably one or more of an argon atmosphere and a nitrogen atmosphere; the temperature is 250 - 350 °C, preferably 280 - 330 °C, further preferably 290 - 310 °C, and more preferably 300 °C; the pressure is 20 - 40 MPa, preferably 22 - 38 MPa, further preferably 25 - 35 MPa, and more preferably 30 MPa; the time is 1 - 2 h, preferably 1.2 - 1.8 h, further preferably 1.3 - 1.6 h, and more preferably 1.5 h; the thickness of the composite modified sulfide electrolyte layer is 30 - 120 μm, preferably 35 - 100 μm, further preferably 39 - 85 μm, and more preferably 42 - 50 μm; the relative density is ≥ 95%, preferably 95.5 - 97%, further preferably 95.7 - 96.8%, and more preferably 96 - 96.5%;

[0061] and / or a carbon fiber woven fabric positive electrode coated with a positive electrode active material, the modified sulfide electrolyte, a glass fiber woven fabric separator, and a carbon fiber woven fabric negative electrode coated with a negative electrode active material are hot-pressed and laminated in sequence to obtain a multifunctional carbon fiber battery based on the modified sulfide electrolyte.

[0062] The method for the hot-pressing lamination assembly includes a low-temperature - long-time process or a high-temperature - short-time process; for the low-temperature - long-time process, the temperature is 130 - 180 °C, preferably 140 - 170 °C, further preferably 145 - 160 °C, and more preferably 150 °C; the pressure for the low-temperature - long-time process is 6 - 9 MPa, preferably 6.2 - 8.8 MPa, further preferably 6.5 - 8.5 MPa, and more preferably 7 MPa; the time for the low-temperature - long-time process is 1.3 - 1.6 h, preferably 1.4 - 1.5 h, and more preferably 1.45 h; for the high-temperature - short-time process, the temperature is 220 - 260 °C, preferably 230 - 255 °C, further preferably 240 - 250 °C, and more preferably 245 °C; the pressure for the high-temperature - short-time process is 18 - 20 MPa, preferably 18.2 - 19.8 MPa, further preferably 18.5 - 19.5 MPa, and more preferably 19 MPa; the time for the high-temperature - short-time process is 20 - 30 min, preferably 22 - 28 min, and more preferably 25 min.

[0063] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0064] Example 1

[0065] Preparation of modified sulfide electrolyte: 2 g of argyrodite-type sulfide electrolyte Li6PS5Cl was dispersed in a fluorinated Lewis acid solution with a mass ratio of 1:20 of aluminum trifluoromethanesulfonate to toluene, and then put into a 50 mL zirconia ball milling tank for ball milling. Among them, the ball-to-material ratio was controlled to be 10:1, the ball milling time was 3 h, the ball milling environment was an argon atmosphere, and after the ball milling was completed, it was heated at a temperature of 300 °C and an argon atmosphere for 5 h to obtain a modified sulfide electrolyte.

[0066] Preparation of multifunctional carbon fiber battery: The NCM811 ternary cathode material was mixed with conductive carbon black, PVDF and N-methyl-2-pyrrolidone according to a mass ratio of 18:1:1:40 to obtain a cathode slurry (solid content 33 wt%), and then the cathode slurry was applied to the unfolded carbon fiber woven fabric (areal density 15 g / m -2 with a wet coating amount of 0.12 kg·m 2 , thickness 30 μm) by a slot die head, and vacuum dried at a temperature of 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with NCM811 with a dry film thickness of 25 μm and an overall thickness of 55 μm for standby; the metallic lithium was rolled into a thin sheet with a thickness of 12 μm, and then hot pressed in an argon glove box at a condition of 0.5 MPa and 70 °C for 1 min to be adhered to another carbon fiber woven fabric (areal density 15 g / m 2 , thickness 30 μm) to obtain a carbon fiber woven fabric anode electrode sheet coated with metallic lithium; finally, the modified sulfide electrolyte was first cold pressed into a dense sheet with a thickness of 60 μm; then the cathode electrode sheet, the anode electrode sheet, the modified electrolyte dense sheet and the glass fiber woven fabric separator (areal density 8 g / m 2, with a thickness of 15 μm) were all cut into a size of 40 mm × 40 mm, dried at 120 °C under vacuum for 2 h, cooled and placed in a glove box with residual water < 50 ppm to ensure no residual polar solvent. Then, a carbon fiber woven cloth negative electrode sheet coated with metallic lithium (carbon fiber side up) was placed at the bottom layer, and then the glass fiber woven cloth separator was aligned and stacked, followed by placing a 60-μm-thick modified sulfide electrolyte sheet, and then a carbon fiber woven cloth positive electrode sheet coated with NCM811 (active side down) was placed on the topmost layer. After assembly, it was put into a flat cold press and pre-pressed and degassed for 30 s at room temperature and 5 MPa to ensure the sheets were well adhered. Then, under an argon atmosphere, hot pressing and lamination assembly were carried out using a high-temperature and short-time process, controlling the temperature at 260 °C, the pressure at 20 MPa, and the time at 30 min to achieve dense bonding between layers. After cooling to 50 °C, samples were taken to obtain a multifunctional carbon fiber battery with a thickness of 150 μm.

[0067] A Cu / Ni current collector with a size of 10 mm × 5 mm and a nickel plating thickness of 25 μm was welded to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then, it was heat-sealed into a small-sized flat battery of 55 mm × 55 mm using a 60-μm polyimide-aluminum plastic composite bag with a 5-mm side seal.

[0068] The modified sulfide electrolyte prepared in this example was placed in an environment with a relative humidity of 30% indoors and left standing for 8 h, and the conductivity of the modified sulfide electrolyte before and after standing was detected. At the same time, the unmodified argyrodite-type sulfide electrolyte Li6PS5Cl was left standing using the same method. After detection, the conductivity of the modified sulfide electrolyte prepared in this example only decreased by 10% after standing for 8 h, while the unmodified electrolyte decreased by more than 30%. That is, the air stability of the modified sulfide electrolyte in this example was significantly improved compared to the unmodified electrolyte.

[0069] The small-sized flat battery prepared in this example was subjected to constant current charge-discharge tests at room temperature (25 °C), with a charging cut-off voltage of 4.2 V and a discharging cut-off voltage of 2.5 V. The test results showed that the initial discharging capacity was 165 mAh / g, and the capacity retention rate after 50 cycles reached 91%, indicating that the modified layer of the modified sulfide electrolyte effectively inhibited the interfacial side reactions and maintained good ion transport performance.

[0070] The multifunctional carbon fiber battery prepared in this example was subjected to EIS testing, applying a small AC perturbation signal with an amplitude of 5 mV, and the initial interfacial impedance of the battery was measured to be 95 Ω·cm at 10 mHz - 1 MHz 2 ; the interfacial impedance after 80 cycles was 120 Ω·cm 2 .

[0071] Example 2

[0072] Preparation of modified sulfide electrolyte: 5 g of binary Li2S-P2S5 type sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 was dispersed in a fluorinated Lewis acid solution with a mass ratio of 1:30 of antimony pentafluoride to xylene, and then put into a 100 mL zirconia ball mill jar for ball milling. Among them, the ball-to-material ratio was controlled to be 15:1, the ball milling time was 6 h, the ball milling environment was an argon atmosphere, and after the ball milling was completed, it was heated at a temperature of 200 °C and an argon atmosphere for 6 h to obtain the modified sulfide electrolyte.

[0073] Preparation of multifunctional carbon fiber battery: NCM811 ternary cathode material was mixed with Ketjenblack EC-600JD, PVDF-HFP and N-methyl-2-pyrrolidone according to a mass ratio of 18:1:1:40 to obtain a cathode slurry (solid content 33 wt%), and then the cathode slurry was wet-coated on the unfolded carbon fiber woven fabric (areal density 15 g / m -2 with a wet coating amount of 0.12 kg·m 2 , thickness 30 μm) and dried at a temperature of 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with NCM811 with a dry film thickness of 25 μm and an overall thickness of 55 μm for standby; the lithium-silicon alloy was rolled into a thin sheet with a thickness of 20 μm, and then hot-pressed in an argon glove box at 0.6 MPa and 80 °C for 1 min to be laminated on another carbon fiber woven fabric (areal density 15 g / m 2 , thickness 30 μm) to obtain a carbon fiber woven fabric negative electrode sheet coated with lithium-silicon alloy; finally, the modified sulfide electrolyte was first cold-pressed into a dense sheet with a thickness of 70 μm; then the positive electrode sheet, the negative electrode sheet, the modified electrolyte dense sheet and the glass fiber woven fabric separator (areal density 8 g / m 2, with a thickness of 15 μm) were all cut into a size of 40 mm × 40 mm, dried at 120 °C under vacuum for 2 h, cooled and placed in a glove box with residual water < 50 ppm to ensure no residual polar solvent. Then, a carbon fiber woven cloth negative electrode sheet coated with lithium-silicon alloy was placed at the bottom (with the carbon fiber side facing up), then the glass fiber woven cloth separator was aligned and stacked, then a 70-μm-thick modified sulfide electrolyte sheet was placed, and finally, a carbon fiber woven cloth positive electrode sheet coated with NCM811 was placed on the top layer (with the active side facing down). After assembly, it was put into a flat cold press and pre-pressed and degassed for 30 s at room temperature and 5 MPa to ensure the sheets were adhered. Then, under an argon atmosphere, a hot-pressing lamination assembly was carried out using a high-temperature and short-time process, controlling the temperature at 240 °C, the pressure at 18 MPa, and the time at 30 min. After hot pressing, it was cooled to 50 °C for sampling to obtain a multifunctional carbon fiber battery with a thickness of 165 μm, without wrinkles or visible holes on the surface.

[0074] A Cu / Ni current collector with a size of 10 mm × 5 mm and nickel plating of 25 μm was welded to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then, it was heat-sealed into a small-sized flat battery of 55 mm × 55 mm using a 60-μm polyimide-aluminum plastic composite bag, with a side seal of 5 mm.

[0075] The modified sulfide electrolyte prepared in this example was placed in an environment with a relative humidity of 40% indoors and left standing for 5 h, and the conductivity of the modified sulfide electrolyte before and after standing was detected. At the same time, for the unmodified binary Li2S-P2S5 type sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 The same method as above was used for standing. After detection, the conductivity of the modified sulfide electrolyte prepared in this example only decreased by 15% after standing for 5 h, while the unmodified electrolyte decreased by more than 35%. This shows that the air stability of the modified sulfide electrolyte in this example has been significantly improved compared to the unmodified electrolyte.

[0076] The small-sized flat battery prepared in this example was subjected to a constant current charge-discharge test at room temperature (the same as in Example 1). The test results showed that the initial discharge capacity was 160 mAh / g, and the capacity retention rate after 80 cycles at a 0.5C rate was 88%.

[0077] Example 3

[0078] Preparation of modified sulfide electrolyte: 3 g of argyrodite-type sulfide electrolyte Li6PS5Br was dispersed in a fluorinated Lewis acid solution with a mass ratio of 1 g of boron trifluoride to a mixed solvent of toluene and n-hexane (volume ratio of toluene to n-hexane is 1:1) of 1:20, and then put into a 50 mL zirconia ball mill jar for ball milling. Among them, the ball-to-material ratio was controlled to be 8:1, the ball milling time was 2 h, and the ball milling environment was an argon atmosphere. After ball milling, it was heated at a temperature of 350 °C and an argon atmosphere for 3 h to obtain the modified sulfide electrolyte.

[0079] Preparation of multifunctional carbon fiber battery: The layered lithium-rich cathode material was mixed with acetylene black, PVDF, and N-methyl-2-pyrrolidone according to a mass ratio of 17:2:1:40 to obtain a cathode slurry (solid content of 33 wt%), and then the cathode slurry was wet-coated on the unfolded carbon fiber woven fabric (areal density of 15 g / m -2 with a wet coating amount of 0.13 kg·m 2 , and dried in vacuum at a temperature of 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with a layered lithium-rich cathode material with a dry film thickness of 28 μm and an overall thickness of 58 μm for standby; Graphite was mixed with Ketjenblack EC-600JD, SBR-CMC (mass ratio of SBR-CMC is 3:2), and a mixed solvent of deionized water and isopropanol (volume ratio of deionized water to isopropanol is 1:1) according to a mass ratio of 90:3:7:120 to obtain a negative electrode slurry, and then the negative electrode slurry was wet-coated on another carbon fiber woven fabric (areal density of 15 g / m -2 with a wet coating amount of 0.11 kg·m 2 , and dried in vacuum at a temperature of 90 °C for 10 min to obtain a carbon fiber woven fabric negative electrode sheet coated with graphite with a dry film thickness of 22 μm and an overall thickness of 52 μm; Finally, the modified sulfide electrolyte was first cold-pressed into a dense sheet with a thickness of 65 μm; Then the positive electrode sheet, negative electrode sheet, modified electrolyte dense sheet, and glass fiber woven fabric separator (areal density of 15 g / m 2, with a thickness of 15 μm) were all cut into a size of 40 mm × 40 mm, dried at 120 °C under vacuum for 2 h, cooled and placed in a glove box with residual water < 50 ppm to ensure no residual polar solvent. Then, a carbon fiber woven cloth negative electrode sheet coated with graphite was placed at the bottom (with the carbon fiber side facing up), then the glass fiber woven cloth separator was aligned and stacked, then a 65-μm-thick modified sulfide electrolyte sheet was placed, and finally a carbon fiber woven cloth positive electrode sheet coated with layered lithium-rich cathode material was placed on the top layer (with the active side facing down). After assembly, it was placed in a flat cold press and pre-pressed and degassed for 30 s at room temperature and 5 MPa to ensure the sheets were in good contact. Then, under an argon atmosphere, a hot pressing and lamination assembly was carried out using a high-temperature and short-time process, controlling the temperature at 250 °C, the pressure at 20 MPa, and the time at 25 min. After hot pressing, it was cooled to 50 °C for sampling to obtain a multifunctional carbon fiber battery with a thickness of 165 μm.

[0080] An Al / Ni current collector with a size of 10 mm × 5 mm and a nickel plating thickness of 25 μm was welded to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then it was heat-sealed into a small flat battery with a size of 55 mm × 55 mm using a 60-μm polyimide-aluminum plastic composite bag, with a side seal of 5 mm.

[0081] The small flat battery prepared in this example was subjected to a constant current charge-discharge test at room temperature (the same as in Example 1). The test results showed that the initial discharge capacity (0.1C, 25 °C) was 215 mAh / g (calculated based on the mass of the layered lithium-rich material), the first-week efficiency reached 92%, the capacity retention rate after 100 cycles at a 1C rate was 85%, and the capacity retention after bending was > 95% (200 MPa, three-point bending).

[0082] The modified sulfide electrolyte prepared in this example was left standing in an environment with a relative humidity of 35% indoors for 10 h and then the battery was assembled. Then, the battery was subjected to a constant current charge-discharge test using the same method as in Example 1. The results showed that the conductivity of the battery remained at 88%, indicating that the modified sulfide electrolyte layer prepared in this example has an effective protective effect on the battery.

[0083] Example 4

[0084] Preparation of the modified sulfide electrolyte: 4 g of lithium germanium phosphorus sulfur type sulfide electrolyte Li 10 GeP2S 12 was dispersed in a fluorinated Lewis acid solution with a mass ratio of 1:25 of indium trifluoromethanesulfonate to cyclohexane, and then put into a 50-mL zirconia ball mill jar for ball milling. Among them, the ball-to-material ratio was controlled at 12:1, the ball milling time was 4 h, the ball milling environment was an argon atmosphere, and after ball milling was completed, it was heated at a temperature of 250 °C and an argon atmosphere for 4 h to obtain the modified sulfide electrolyte.

[0085] Preparation of a multifunctional carbon fiber battery: Mix the LiFePO4 cathode material with carbon black, PVDF, and N-methyl-2-pyrrolidone in a mass ratio of 18:1:1:40 to obtain a cathode slurry (solid content 33 wt%), and then apply the cathode slurry onto the unfolded carbon fiber woven fabric (areal density 15 g / m -2 with a wet coating amount of 0.12 kg·m 2 , thickness 30 μm) using a slot die head, and vacuum dry at 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with LiFePO4 with a dry film thickness of 26 μm and an overall thickness of 56 μm for standby; Roll the metallic lithium into a thin sheet with a thickness of 10 μm, and then laminate it onto another carbon fiber woven fabric (areal density 15 g / m 2 , thickness 30 μm) by hot pressing at 0.3 MPa and 70 °C for 1 min in an argon glove box to obtain a carbon fiber woven fabric anode electrode sheet coated with metallic lithium; Finally, first cold press the modified sulfide electrolyte into a dense sheet with a thickness of 60 μm; Then cut all the cathode electrode sheet, anode electrode sheet, modified electrolyte dense sheet, and glass fiber woven fabric separator (areal density 10 g / m 2 , thickness 15 μm) into a size of 40 mm × 40 mm, and dry at 120 °C under vacuum for 2 h. After cooling, place it in a glove box with residual water < 50 ppm to ensure no polar solvent residue. Then place the carbon fiber woven fabric anode electrode sheet coated with metallic lithium (carbon fiber side up) at the bottom, then align and stack the glass fiber woven fabric separator, then place the 60-μm-thick modified sulfide electrolyte sheet, and then place the carbon fiber woven fabric cathode electrode sheet coated with LiFePO4 (active side down) on the top layer. After assembly, put it into a flat cold press, pre-press and exhaust for 30 s at room temperature and 5 MPa to ensure the sheets are well adhered, and then use a low-temperature and long-time process for hot pressing and lamination assembly in an argon atmosphere, control the temperature at 160 °C, the pressure at 7 MPa, and the time at 1.5 h. After hot pressing is completed, cool to 50 °C and sample to obtain a multifunctional carbon fiber battery with a thickness of 150 μm.

[0086] Weld an Al / Ni current collector with a size of 10 mm × 5 mm and nickel plating of 25 μm to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; Then use a 60-μm polyimide-aluminum plastic composite bag to thermally seal it into a small flat battery with a size of 55 mm × 55 mm and a side seal of 5 mm.

[0087] The small-sized coin cells prepared in this example were subjected to constant current charge-discharge tests at room temperature (the same as in Example 1). The test results showed that the initial discharge specific capacity could reach 150 mAh / g, the capacity retention rate after 100 cycles at a rate of 0.5C was 90%, and the rate performance at 0.5C was good.

[0088] The modified sulfide electrolyte prepared in this example was left standing in an environment with a relative humidity of 35% indoors for 48 h, and the conductivity of the modified sulfide electrolyte before and after standing was detected. At the same time, for the unmodified lithium-germanium-phosphorus-sulfur type sulfide electrolyte Li 10 GeP2S 12 The same method as above was used for standing. After detection, the conductivity of the modified sulfide electrolyte prepared in this example remained ≥80% after standing for 48 h, while the conductivity of the unmodified electrolyte was only 55%. That is, the air stability of the modified sulfide electrolyte in this example was more excellent.

[0089] Example 5

[0090] Preparation of the modified sulfide electrolyte: 3 g of the binary Li2S-P2S5 type sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 was dispersed in a fluorinated Lewis acid solution with a mass ratio of 1:30 of a mixture of 1.5 g of niobium pentafluoride and scandium trifluoromethanesulfonate (the mass ratio of niobium pentafluoride to scandium trifluoromethanesulfonate was 1:1) to a mixed solvent of xylene and n-heptane (the volume ratio of xylene to n-heptane was 1:1). Then, it was put into a 100 mL zirconia ball mill jar for ball milling. Among them, the ball-to-material ratio was controlled to be 10:1, the ball milling time was 5 h, the ball milling environment was an argon atmosphere, and after the ball milling was completed, it was heated at a temperature of 300 °C and in an argon atmosphere for 6 h to obtain the modified sulfide electrolyte.

[0091] Preparation of the multifunctional carbon fiber battery: The NCM523 ternary cathode material was mixed with carbon black, PVDF, and N-methyl-2-pyrrolidone according to a mass ratio of 90:5:5:60 to obtain a cathode slurry (solid content 33 wt%). Then, the cathode slurry was coated on the unfolded carbon fiber woven fabric (areal density 15 g / m -2 with a wet coating amount of 0.10 kg·m 2, on a carbon fiber woven fabric with a basis weight of 15 g / m² and a thickness of 30 μm, and vacuum dried at 140 °C for 15 min to obtain a positive electrode sheet of carbon fiber woven fabric coated with NCM523 with a dry film thickness of 22 μm and an overall thickness of 52 μm, for standby; mix a mixed powder of graphite and silicon alloy (mass ratio of graphite to silicon alloy is 8:2), carbon black, PVDF and NMP according to a mass ratio of 18:1:1:38 to obtain a negative electrode slurry, and then apply the negative electrode slurry onto another carbon fiber woven fabric (basis weight of 15 g / m² -2 with a wet coating amount of 0.12 kg·m 2 , thickness of 30 μm), and vacuum dried at 140 °C for 15 min to obtain a negative electrode sheet of carbon fiber woven fabric coated with graphite and silicon alloy with a dry film thickness of 25 μm and an overall thickness of 55 μm; finally, first cold press the modified sulfide electrolyte into a dense sheet with a thickness of 65 μm; then cut the positive electrode sheet, negative electrode sheet, modified electrolyte dense sheet and glass fiber woven fabric separator (basis weight of 10 g / m² 2 , thickness of 15 μm) into a size of 40 mm × 40 mm, and dry at 120 °C under vacuum for 2 h, cool and place in a glove box, with residual water < 50 ppm, ensuring no polar solvent residue. Then place the negative electrode sheet of carbon fiber woven fabric coated with graphite and silicon alloy (carbon fiber side up) at the bottom layer, then align and stack the glass fiber woven fabric separator, then place the 65-μm-thick modified sulfide electrolyte sheet, and then place the positive electrode sheet of carbon fiber woven fabric coated with NCM523 (active surface down) on the top layer. After assembly, put it into a flat cold press, pre-press and exhaust for 30 s at room temperature and 5 MPa to ensure the sheets are well adhered, and then carry out hot pressing and lamination assembly using a high-temperature and short-time process under an argon atmosphere, controlling the temperature at 240 °C, pressure at 18 MPa, and time at 25 min. After hot pressing, cool to 50 °C for sampling to obtain a multifunctional carbon fiber battery with a thickness of 165 μm.

[0092] Weld an Al / Ni current collector with a size of 10 mm × 5 mm and nickel plating of 25 μm to the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then use a 60-μm-thick polyimide-aluminum plastic composite bag to thermally seal into a small-sized flat battery with a size of 55 mm × 55 mm and a side seal of 5 mm.

[0093] Place the modified sulfide electrolyte prepared in this example in an environment with a relative humidity of 50% and a temperature of 25 °C indoors for 6 h, and detect the conductivity of the modified sulfide electrolyte before and after standing. The results show that the conductivity of the modified sulfide electrolyte prepared in this example decreased by less than 12% after standing for 6 h, indicating that the fluorinated layer on the surface of the modified sulfide electrolyte inhibits moisture erosion.

[0094] The small-sized sheet battery prepared in this example was subjected to constant current charge and discharge tests at room temperature (same as Example 1). The test results showed that the initial discharge capacity was 170 mAh / g, the capacity retention after 120 cycles at a rate of 0.5C was 88%, and after 50 cycles at a rate of 1C, the capacity decay was <6%.

[0095] As can be seen from the above examples, the fluorinated Lewis acid modification route adopted in the present invention can significantly improve the stability between the sulfide electrolyte and air, the negative electrode (especially the lithium negative electrode or silicon alloy). At the same time, by using carbon fiber woven fabric and glass fiber woven fabric, a carbon fiber structure battery with the integration of mechanical enhancement and energy storage was successfully constructed, providing a new solution for the lightweight and structural integration of all-solid-state batteries.

[0096] Example 6

[0097] Preparation of a modified sulfide electrolyte doped with a metal element: Weigh a total of 3 g of Li2S, P2S5, LiCl, and Al2S3 according to the chemical ratio of Li6P 0.95 Al 0.05 S5Cl (the atomic fraction of Al is 5%), then mix it with 3 g of the thiogermanate-type sulfide electrolyte Li6PS5Cl, and perform mechanochemical ball milling for 4 h under a ball-to-material ratio of 10:1, a rotation speed of 400 rpm, and an argon atmosphere to obtain a mixture; then perform solid-phase annealing on the mixture in an argon atmosphere at a temperature of 280 °C for 4 h, and take the powder after cooling to obtain a sulfide electrolyte doped with a metal element with a conductivity (at 25 °C) of 1.4×10 -2 S / cm and a particle size of 3 μm (the conductivity of the sulfide electrolyte without doping with a metal element is 9.5×10 -3 S / cm); then use the same preparation method as in Example 1 to prepare a modified sulfide electrolyte doped with a metal element, and then use the same preparation method as in Example 1 to prepare a carbon fiber woven fabric positive electrode sheet coated with NCM811 and a carbon fiber woven fabric negative electrode sheet coated with metallic lithium for standby; directly spread the modified sulfide electrolyte powder doped with a metal element between the positive electrode sheet and the negative electrode sheet, and perform hot pressing and lamination assembly using a high-temperature and short-time process in an argon atmosphere, controlling the temperature at 250 °C, the pressure at 20 MPa, and the time at 20 min to obtain a multifunctional carbon fiber battery with a total thickness of 150 μm.

[0098] Weld an Al / Ni current collector with a size of 10 mm×5 mm and a nickel plating thickness of 25 μm to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then use a 60-μm polyimide-aluminum plastic composite bag to heat-seal it into a small-sized sheet battery with a size of 55 mm×55 mm and a side seal of 5 mm.

[0099] The small-sized coin cells prepared in this example were subjected to constant current charge-discharge tests and EIS tests (same as Example 1) at room temperature. The test results showed that the initial discharge capacity was 168 mAh / g, the capacity retention after 100 cycles at 1C rate was 90%, and the initial interfacial impedance was 85 Ω·cm 2 It can be seen that after doping the modified sulfide electrolyte with metal elements, the conductivity of the electrolyte can be significantly improved. At the same time, due to the omission of the separator, a 15-μm insulating layer is reduced, and the interfacial impedance is decreased.

[0100] Example 7

[0101] Preparation of modified sulfide electrolyte doped with metal elements: Weigh a total of 4 g of Li2S, GeS2, P2S5 and NbF5 according to the chemical ratio of Li 10 Ge 0.90 Nb 0.10 P2S 12 (the atomic fraction of Nb is 10%), and then mix it with 2 g of lithium-germanium-phosphorus-sulfur type sulfide electrolyte Li 10 GeP2S 12 and carry out mechanochemical ball milling for 6 h under a ball-to-material ratio of 12:1, a rotation speed of 500 rpm and an argon atmosphere to obtain a mixture; then anneal the mixture in an argon atmosphere at a temperature of 420 °C for 3 h, take the powder after cooling, and obtain a sulfide electrolyte doped with metal elements with a conductivity (25 °C) of 1.2×10 -2 S / cm and a particle size of 2 μm; then use the same preparation method as in Example 4 to prepare a modified sulfide electrolyte doped with metal elements.

[0102] Preparation of multifunctional carbon fiber battery: Mix the layered lithium-rich cathode material with acetylene black, PVDF and N-methyl-2-pyrrolidone according to a mass ratio of 17:2:1:40 to obtain a cathode slurry (solid content is 33 wt%), and then coat the cathode slurry on the unfolded carbon fiber woven fabric (areal density is 15 g / m -2 ) with a wet coating amount of 0.10 kg·m 2 and vacuum dry it at a temperature of 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with a layered lithium-rich cathode material with a dry film thickness of 28 μm and an overall thickness of 58 μm for standby; mix the mixed powder of graphite and silicon alloy (mass ratio of graphite to silicon alloy is 8:2), Ketjenblack EC-600JD, PVDF and NMP according to a mass ratio of 90:3:7:170 to obtain a negative electrode slurry, and then coat the negative electrode slurry on another carbon fiber woven fabric (areal density is 15 g / m -2 ) with a wet coating amount of 0.12 kg·m2 , on a carbon fiber woven fabric with a thickness of 30 μm, and vacuum dried at a temperature of 140 °C for 15 min to obtain a negative electrode sheet of carbon fiber woven fabric coated with graphite and silicon alloy with a dry film thickness of 25 μm and an overall thickness of 55 μm; finally, the modified sulfide electrolyte was first cold pressed into a dense sheet with a thickness of 70 μm; then the positive electrode sheet, the negative electrode sheet, the modified electrolyte dense sheet and the glass fiber woven fabric separator (areal density of 10 g / m 2 , with a thickness of 15 μm) were all cut into a size of 40 mm × 40 mm, dried at 120 °C under vacuum for 2 h, cooled and placed in a glove box with residual water < 50 ppm to ensure no residual polar solvent. Then, a negative electrode sheet of carbon fiber woven fabric coated with graphite and silicon alloy (carbon fiber side up) was placed on the bottom layer, then the glass fiber woven fabric separator was aligned and stacked, then a 70-μm-thick modified sulfide electrolyte sheet was placed, and finally, a positive electrode sheet of carbon fiber woven fabric coated with layered lithium-rich cathode material (active side down) was placed on the top layer. After assembly, it was placed in a flat cold press and pre-pressed and degassed at room temperature and 5 MPa for 30 s to ensure that the sheets were in good contact. Then, under an argon atmosphere, a hot pressing and lamination assembly was carried out using a high-temperature and short-time process, controlling the temperature at 240 °C, the pressure at 18 MPa, and the time at 25 min. After hot pressing, it was cooled to 50 °C for sampling to obtain a multifunctional carbon fiber battery with a thickness of 170 μm.

[0103] One Al / Ni current collector with a size of 10 mm × 5 mm and a nickel plating thickness of 25 μm was welded to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this example; then it was heat-sealed into a small flat battery with a size of 55 mm × 55 mm using a 60-μm polyimide-aluminum plastic composite bag, with a side seal of 5 mm.

[0104] The small flat battery prepared in this example was subjected to a constant current charge-discharge test at room temperature (same as Example 1). The test results showed that the first-week efficiency was 93%; the capacity remained at 91% after 150 cycles at a 0.5C rate; and the capacity remained at 97% after bending at 200 MPa.

[0105] Example 8

[0106] Preparation of a modified sulfide electrolyte doped with a metal element: Li2S, P2S5, LiCl and Ta2S5 were weighed in a chemical ratio of Li 5.5 P 0.85 Ta 0.15 S 4.5 Cl 1.5 (the atomic fraction of Ta was 15%) with a total amount of 3 g, and then mixed with 1.5 g of a binary Li2S-P2S5 type sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5Mix and carry out mechanochemical ball milling for 5 h under a ball-to-material ratio of 10:1, a rotation speed of 400 rpm, and an argon atmosphere to obtain a mixture; then carry out solid-phase annealing of the mixture in an argon atmosphere at a temperature of 300 °C for 6 h, take the powder after cooling, and obtain a sulfide electrolyte doped with metal elements with a conductivity (25 °C) of 8.5×10 -3 S / cm and a particle size of 3 μm; then prepare a modified sulfide electrolyte doped with metal elements by using the same preparation method as in Example 5.

[0107] Preparation of a multifunctional carbon fiber battery: Mix a NCM523 ternary cathode material, carbon black, PVDF, and N-methyl-2-pyrrolidone according to a mass ratio of 88:7:5:60 to obtain a cathode slurry (solid content: 33 wt%), then apply the cathode slurry onto an unfolded carbon fiber woven fabric (areal density: 15 g / m -2 with a wet coating amount of 0.10 kg·m 2 , and dry it in vacuum at a temperature of 140 °C for 15 min to obtain a carbon fiber woven fabric cathode electrode sheet coated with NCM523 with a dry film thickness of 22 μm and an overall thickness of 52 μm for standby; roll a metallic lithium into a thin sheet with a thickness of 10 μm, and then laminate it onto another carbon fiber woven fabric (areal density: 15 g / m 2 , thickness: 30 μm) by means of hot pressing at 0.3 MPa and 70 °C for 1 min in an argon glove box to obtain a carbon fiber woven fabric anode electrode sheet coated with metallic lithium; finally, spread the modified sulfide electrolyte on both sides of a nanofiber mat (areal density: 5 g / m 2 , thickness: 20 μm, porosity: 70%), and press it into a modified electrolyte composite sheet with a thickness of 55 μm; then cut all the cathode electrode sheet, anode electrode sheet, and modified electrolyte composite sheet into a size of 40 mm×40 mm, dry them at 120 °C in vacuum for 2 h, cool them, and place them in a glove box with residual water <50 ppm to ensure no residual polar solvent. Then place the carbon fiber woven fabric anode electrode sheet coated with metallic lithium (carbon fiber side up) at the bottom layer, then align and stack the 55-μm-thick modified electrolyte composite sheet, and then place the carbon fiber woven fabric cathode electrode sheet coated with the NCM523 ternary cathode material (active surface down) at the top layer. After assembly, put it into a flat cold press, pre-press and exhaust for 30 s at room temperature and 5 MPa to ensure the sheets are well adhered, and then carry out hot pressing and lamination assembly by means of a high-temperature and short-time process in an argon atmosphere, controlling the temperature at 250 °C, the pressure at 20 MPa, and the time at 25 min. After hot pressing is completed, cool it to 50 °C and take a sample to obtain a multifunctional carbon fiber battery with a thickness of 165 μm.

[0108] Weld an Al / Ni current collector with a size of 10 mm × 5 mm and a nickel plating thickness of 25 μm to each of the positive and negative electrodes of the multifunctional carbon fiber battery prepared in this embodiment; then use a 60-μm polyimide-aluminum plastic composite bag to thermally seal it into a small-sized flat battery with a size of 55 mm × 55 mm, and the side seal is 5 mm.

[0109] Perform constant current charge and discharge tests and EIS tests (the same as in Example 1) on the small-sized flat battery prepared in this embodiment at room temperature. The test results show that the initial discharge capacity is 173 mAh / g, the capacity after 120 cycles at a 1C rate remains at 90%, and the initial interfacial impedance is 78 Ω·cm. 2 It can be seen therefrom that Ta doping can improve the conductivity of the battery and inhibit air hydrolysis; it can still maintain low impedance and high cycle stability without a separator.

[0110] In summary, it can be seen that the technical routes of metal doping and removing the separator or using a composite separator are superior to the traditional undoped system in terms of ionic conductivity, interfacial impedance, and cycle life, and can effectively reduce the battery thickness and increase the specific energy of the battery.

[0111] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A multifunctional carbon fiber battery based on a modified sulfide electrolyte, characterized in that, It includes a carbon fiber woven cloth positive electrode coated with a positive electrode active material, a modified sulfide electrolyte, a carbon fiber woven cloth negative electrode coated with a negative electrode active material, and a glass fiber woven cloth separator; The preparation method of the modified sulfide electrolyte is: mixing a sulfide electrolyte with a fluorinated Lewis acid solution, and successively performing ball milling treatment and heat treatment to obtain the modified sulfide electrolyte; The thickness of the modified sulfide electrolyte is 10 - 1000 μm; The sulfide electrolyte includes one or more of argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type, and argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type doped with metal elements; The metal elements include one or more of Al, Nb, and Ta.

2. The multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 1, wherein The positive electrode active material includes one or more of NCM811 ternary positive electrode material, NCM523 ternary positive electrode material, NCA ternary positive electrode material, layered lithium - rich positive electrode material, and LiFePO4; The negative electrode active material includes one or more of metallic lithium, graphite, silicon alloy, and lithium - silicon alloy.

3. A multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 2, characterized in that, The areal density of the carbon fiber woven fabric positive electrode and the carbon fiber woven fabric negative electrode is independently 10 to 20 g / m 2 , and the thickness is independently 20 to 80 μm; The areal density of the glass fiber woven fabric diaphragm is 5 to 15 g / m 2 , and the thickness is 10 to 30 μm.

4. A multifunctional carbon fiber battery based on a modified sulfide electrolyte according to any one of claims 1 to 3, characterized in that, When the sulfide electrolyte is one or more of argyrodite type, lithium germanium phosphorus sulfur type, binary Li2S - P2S5 type doped with metal elements, the preparation method of the sulfide electrolyte doped with metal elements includes the following steps: 1) Mixing a metal element precursor and a sulfide electrolyte, and performing mechanochemical ball milling to obtain a mixture; 2) Sequentially performing solid - phase annealing and pulverization on the mixture to obtain a sulfide electrolyte doped with metal elements; In step 1), the atomic fraction y of the metal element in the metal element precursor in the sulfide electrolyte is: 0.005 ≤ y ≤ 0.30; the metal element precursor includes one or more of Li2S, P2S5, GeS2, Al2S3, LiCl, LiBr, LiI, NbF5, Ta2S5; In step 1), the ball - to - material ratio of the mechanochemical ball milling is 10 - 25:1, and the time is 2 - 12 h; the atmosphere of the mechanochemical ball milling is an inert atmosphere; In step 2), the temperature of the solid - phase annealing is 230 - 550 °C, and the time is 2 - 10 h; the atmosphere of the solid - phase annealing is an inert atmosphere; The particle size of the sulfide electrolyte doped with metal elements is 1 - 10 μm.

5. The multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 4, characterized in that, The fluorinated Lewis acid solution is obtained by mixing a fluorinated Lewis acid and an organic solvent; The fluorinated Lewis acid includes one or more of trifluoromethanesulfonate, boron trifluoride, tris(pentafluorophenyl)boron, bis(pentafluorophenyl)borane, antimony pentafluoride, tantalum pentafluoride, and niobium pentafluoride; The trifluoromethanesulfonate includes one or more of aluminum trifluoromethanesulfonate, indium trifluoromethanesulfonate, and scandium trifluoromethanesulfonate; The organic solvent includes one or more of toluene, xylene, n - hexane, n - heptane, and cyclohexane.

6. The multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 5, wherein, The mass ratio of the fluorinated Lewis acid to the organic solvent is 1:10 - 100.

7. A multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 5 or 6, characterized in that, The mass ratio of the sulfide electrolyte to the fluorinated Lewis acid solution is 1 - 10:

1.

8. A multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 7, characterized in that, The ball milling treatment is carried out in a zirconia ball milling tank; the ball-to-material ratio of the ball milling treatment is 1-20:1, the time is 1-10 h, and the environment is an inert atmosphere.

9. The multifunctional carbon fiber battery based on a modified sulfide electrolyte according to claim 8, wherein The temperature of the heat treatment is 200-400 °C, the time is 1-10 h, and the environment is an inert atmosphere.

10. A method for preparing a multifunctional carbon fiber battery based on a modified sulfide electrolyte according to any one of claims 1 to 9, characterized in that, It includes the following steps: Sprinkle the modified sulfide electrolyte on both sides of the glass fiber woven cloth diaphragm, and perform hot pressing sintering to obtain a composite modified sulfide electrolyte layer. Then, sequentially stack and assemble the carbon fiber woven cloth positive electrode coated with the positive electrode active material, the composite modified sulfide electrolyte layer, and the carbon fiber woven cloth negative electrode coated with the negative electrode active material to obtain a multifunctional carbon fiber battery based on the modified sulfide electrolyte; The atmosphere of the hot pressing sintering is an inert atmosphere, the temperature is 250-350 °C, the pressure is 20-40 MPa, and the time is 1-2 h; the thickness of the composite modified sulfide electrolyte layer is 30-120 μm, and the density is ≥95%; and / or sequentially stack and assemble the carbon fiber woven cloth positive electrode coated with the positive electrode active material, the modified sulfide electrolyte, the glass fiber woven cloth diaphragm, and the carbon fiber woven cloth negative electrode coated with the negative electrode active material by hot pressing to obtain a multifunctional carbon fiber battery based on the modified sulfide electrolyte; The method of the hot pressing lamination assembly includes a low-temperature-long-time process or a high-temperature-short-time process; the temperature of the low-temperature-long-time process is 130-180 °C, the pressure is 6-9 MPa, and the time is 1.3-1.6 h; the temperature of the high-temperature-short-time process is 220-260 °C, the pressure is 18-20 MPa, and the time is 20-30 min.