Binder solution for secondary batteries

Abstract

The present invention provides a binder solution for secondary batteries comprising at least one non-aqueous solvent and at least one fluoropolymer, wherein the fluoropolymer comprises repeating units derived from a) vinylidene difluoride and b) at least one fluorinated olefin monomer comprising at least one -SO2X functional group (wherein X is selected from X' and OM, X' is selected from the group consisting of F, Cl, Br, and I, and M is selected from the group consisting of H, an alkali metal, and NH4), and b) the fluorinated olefin monomer is present in an amount of 0.1 to 10.0 mol % based on the total number of moles of repeating units. The present invention relates to a binder solution; a solid composite electrolyte comprising at least one fluoropolymer according to the present invention and at least one sulfide-based ion-conducting inorganic solid particle; a slurry for producing the solid composite electrolyte, comprising the binder solution according to the present invention and at least one sulfide-based ion-conducting inorganic solid particle, and optionally further comprising at least one electroactive material and / or at least one conductive agent; and an electrode comprising at least one fluoropolymer according to the present invention and at least one electroactive material, and optionally further comprising at least one conductive agent and / or at least one sulfide-based ion-conducting inorganic solid particle. The present invention also relates to a secondary battery comprising a positive electrode, a negative electrode, and a membrane disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the membrane comprises at least one fluoropolymer according to the present invention and optionally further comprises at least one sulfide-based ion-conducting inorganic solid particle, at least one electroactive material, and / or at least one conductive agent.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to European Patent Application No. 22189662.4, filed August 10, 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention provides a binder solution for a secondary battery, comprising at least one non-aqueous solvent and at least one fluoropolymer, wherein the fluoropolymer comprises repeating units derived from a) vinylidene difluoride and b) at least one fluorinated olefin monomer comprising at least one -SO2X functional group, wherein X is selected from X' and OM, X' is selected from the group consisting of F, Cl, Br, and I, and M is selected from the group consisting of H, an alkali metal, and NH4, and b) the fluorinated olefin monomer is present in an amount of 0.1 to 10.0 mol % based on the total number of moles of the repeating units. The present invention relates to a solution; a solid composite electrolyte comprising at least one fluoropolymer according to the present invention and at least one sulfide-based ion-conducting inorganic solid particle; a slurry for producing the solid composite electrolyte comprising the binder solution according to the present invention and at least one sulfide-based ion-conducting inorganic solid particle, optionally further comprising at least one electroactive material and / or at least one conductive agent; and an electrode comprising at least one fluoropolymer according to the present invention and at least one electroactive material, optionally further comprising at least one conductive agent and / or at least one sulfide-based ion-conducting inorganic solid particle. The present invention also relates to a secondary battery comprising a positive electrode, a negative electrode, and a membrane disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the membrane comprises at least one fluoropolymer according to the present invention and optionally further comprises at least one sulfide-based ion-conducting inorganic solid particle, at least one electroactive material, and / or at least one conductive agent. [Background technology]

[0003] Lithium-ion batteries have held a dominant position in the market of rechargeable energy storage devices for decades thanks to their many advantages, such as light weight, reasonable energy density, and good cycle life. Nevertheless, better safety and higher energy density have been constantly required with the development of high power applications such as electric vehicles, hybrid electric vehicles, grid energy storage, etc.

[0004] First, solid-state batteries have been considered as the next generation of energy storage devices, in which highly flammable liquid electrolytes are replaced by solid electrolytes that can substantially eliminate the risk of fire and / or explosion. Organic polymers, inorganic materials, and composite materials have been actively researched as solid electrolytes, each of which has its own advantages and disadvantages. In particular, composite materials, i.e., inorganic electrolytes dispersed in polymers, such as those containing sulfide particles dispersed in a polymer matrix, are considered the most promising solutions on an industrial scale, given the high ionic conductivity of sulfide-based solid electrolytes, as well as the good mechanical properties and easy processability of polymers. Nevertheless, there are still other drawbacks that need to be addressed, such as poor solvent compatibility of sulfide materials, which significantly limits the choice of polymers that can be used to fabricate electrolytes; poor adhesion to electrode current collectors; the rather complicated process for fabricating solid composite electrolytes; and the relatively weak flexibility of solid composite electrolytes.

[0005] U.S. Patent Application Publication No. 2015 / 096169 A1 (Kureha Corporation and Toyota) discloses that a positive electrode for a sulfide-based solid-state battery formed from a slurry containing a fluorine-based copolymer having a specific amount of VDF units (40-70 mol%) exhibits good adhesion to the current collector.

[0006] WO 2021 / 039950 (Fujifilm) describes an inorganic solid electrolyte-containing composition comprising an inorganic solid electrolyte, a polymer binder, and a dispersion medium, where the polymer binder comprises a fluorine-based copolymer containing a VDF component and 21 to 65 mol% hexafluoropropylene (HFP) component. The composition exhibits greater than 60% adsorption to the inorganic solid electrolyte and is effective in controlling excessive viscosity increase, re-solidification, or sedimentation of the inorganic particles, enabling the achievement of solid-state batteries with excellent cycling characteristics. In particular, the polymer binder exhibits a tensile failure strain of 500% or more.

[0007] Second, due to the favorable characteristics of lithium metal, resulting from its low redox potential and high specific capacity, the use of lithium metal as an anode has been actively investigated since the 1970s, in parallel with the development of solid-state electrolytes for solid-state batteries. Lithium metal batteries typically use conventional liquid electrolytes, such as carbonate-based and / or ether-based electrolytes, which have low viscosity and high ionic conductivity. These liquid electrolytes decompose at the beginning of cycling, forming a passivation layer, eventually leading to dendrite growth and subsequent side reactions between the liquid electrolyte and the deposited reactive lithium ions. These have been significant issues that have hindered the commercialization of lithium metal batteries.

[0008] The basic requirements for a suitable electrolyte for lithium metal batteries are the same as those for conventional liquid electrolytes for lithium-ion batteries: high ionic conductivity, low melting and boiling points, electrochemical stability, and safety. In addition to these basic requirements, a suitable electrolyte for lithium metal batteries must also provide solutions to the aforementioned drawbacks. Various approaches have been attempted to reduce or inhibit the formation of lithium dendrites and improve the cycling performance of lithium metal batteries, such as uniformly coating a polymer layer on the lithium metal surface.

[0009] WO 2018 / 054715 A1 (Solvay Specialty Polymers Italy) describes a specific multilayer assembly comprising a metal layer and a coating layer, in which the growth of lithium dendrites on a lithium metal anode is inhibited using a sulfonyl group-containing fluoropolymer, the fluoropolymer containing repeat units derived from at least one fluorinated olefin monomer having at least one -SO2X functional group (wherein X is selected from the group consisting of H, alkali metals, and NH4) in an amount of 5.0 to 50.0 mol %, preferably 10.0 to 25.0 mol %, based on the total number of moles of repeat units in the fluoropolymer.

[0010] JP 2014 / 210929 A (Daikin Industries, Ltd.) discloses a method for producing a fluorinated copolymer containing repeat units derived from a fluorine-containing ethylenic monomer and a monomer containing a -SO3Li group in the side chain, which copolymer exhibits high ionic conductivity and excellent stability when used in lithium metal batteries.

[0011] However, the demand for more reliable and safe secondary batteries based on lithium metal anodes still needs to be met, as solutions to overcome the shortcomings of sulfide-based solid composite electrolytes and / or lithium metal batteries are continually sought in these fields. Furthermore, regardless of the battery type and generation, there is always the ultimate goal of meeting the increasing demand for batteries with higher energy density while also having greater reliability. Summary of the Invention

[0012] A first object of the present invention is a binder solution for secondary batteries comprising at least one non-aqueous solvent and at least one fluoropolymer, wherein the fluoropolymer comprises repeating units derived from a) vinylidene difluoride (VDF) and b) at least one fluorinated olefin monomer comprising at least one -SO2X functional group, wherein X is selected from X' and OM, X' is selected from the group consisting of F, Cl, Br, and I, and M is selected from the group consisting of H, an alkali metal, and NH4, and b) the fluorinated olefin monomer is present in an amount of 0.1 to 10.0 mol % relative to the total number of moles of repeating units.

[0013] A second object of the present invention is a solid composite electrolyte comprising at least one fluoropolymer according to the invention and at least one sulfide-based ionically conductive inorganic solid particle.

[0014] A third object of the present invention is a slurry for producing a solid composite electrolyte comprising the binder solution according to the present invention and at least one sulfide-based ionically conductive inorganic solid particle, optionally further comprising at least one electroactive material and / or at least one conductive agent.

[0015] A fourth object of the present invention is an electrode comprising at least one fluoropolymer according to the invention and at least one electroactive material, optionally further comprising at least one conductive agent and / or at least one sulfide-based ionically conductive inorganic solid particle.

[0016] A fifth object of the present invention is a secondary battery comprising a positive electrode, a negative electrode and a membrane arranged between the positive and negative electrodes, wherein at least one of the positive electrode, the negative electrode and the membrane comprises at least one fluoropolymer according to the present invention and optionally further comprises at least one sulfide-based ionically conductive inorganic solid particle, at least one electroactive material and / or at least one conductive agent.

[0017] The inventors have surprisingly found that the fluoropolymers according to the invention can provide a particularly advantageous combination of properties in secondary batteries, such as excellent adhesion to current collectors and better cohesion within the film, while maintaining good ionic conductivity, both in solid-state batteries, in particular those containing sulfide-based solid composite electrolytes, and in current generation batteries containing conventional liquid electrolytes, not limited to lithium metal batteries. [Brief explanation of the drawings]

[0018] [Figure 1] Cross-section of an AC impedance spectroscopy pressure cell developed within Solvay to measure the ionic conductivity of films. In the pressure cell, the film is pressed between two stainless steel electrodes during impedance measurements. [Figure 2] Figure 1 shows an equivalent circuit for modeling the conductive behavior of solid composite electrolytes, where R1 and R2 represent the bulk and grain boundary resistances, respectively, and Q2 and Q3 represent the grain boundary and electrode contributions, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0019] Ratios, concentrations, amounts, and other numerical data may be expressed in range format herein. It should be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the upper and lower limits of the range, but also all individual numerical values or subranges encompassed within the range, as if each numerical value and subrange were explicitly recited. In the context of the present invention, the term "weight percent" (wt%) refers to the content of a particular component in a mixture, calculated as the ratio between the weight of the component and the total weight of the mixture. As used herein, the concentration of a repeat unit in "percent by mole" (mol%) refers to the concentration relative to the total number of repeat units in the polymer, unless otherwise specified.

[0020] It should be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. Accordingly, various changes and modifications described herein will be apparent to those skilled in the art. Additionally, descriptions of well-known functions and constructions may be omitted for clarity and brevity.

[0021] The present invention provides a binder solution for a secondary battery, comprising at least one non-aqueous solvent and at least one fluoropolymer, The fluoropolymer a) vinylidene difluoride (VDF); b) at least one fluorinated olefin monomer containing at least one -SO2X functional group, wherein X is selected from X' and OM, X' is selected from the group consisting of F, Cl, Br, and I, and M is selected from the group consisting of H, an alkali metal, and NH4; b) the fluorinated olefin monomer is present in an amount of 0.1 to 10.0 mol % based on the total number of moles of the repeating units; A binder solution for a secondary battery is provided.

[0022] In one embodiment, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is present in an amount of at least 0.1 mol%, preferably at least 0.2 mol%, more preferably at least 0.3 mol%, and / or at most 10.0 mol%, preferably at most 5.0 mol%, more preferably at most 2.0 mol%, and most preferably at most 1.5 mol%, based on the total number of moles of repeat units.

[0023] In certain embodiments, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is present in an amount of 0.1 to 5.0 mol %, preferably 0.2 to 2.0 mol %, and more preferably 0.2 to 1.5 mol %, based on the total number of moles of repeat units.

[0024] In another particular embodiment, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is present in an amount of 0.3 to 1.0 mole % based on the total number of moles of repeat units.

[0025] In one embodiment, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is selected from the group consisting of: Formula: CF2 = CF(CF2) p Halogenated sulfonyl fluoroolefins of the formula SO2X' (wherein p is an integer of 0 to 10, preferably 1 to 6, more preferably p is 2 or 3, and preferably X' = F); Formula: CF2 = CF-O-(CF2) m Halogenated sulfonyl fluorovinyl ethers of SO2X' (wherein m is an integer of 1 to 10, preferably 1 to 6, more preferably 2 to 4, even more preferably m is 2, and preferably X' = F); Formula: CF2 = CF-(OCF2CF(R F1 )) w -O-CF2(CF(R F2 )) y SO2X' (wherein w is an integer of 0 to 2, and R F1 and R F2 are the same or different and independently represent F, Cl, or C1-C optionally substituted with one or more ether oxygen atoms. 10 is a fluoroalkyl group, y is an integer of 0 to 6, preferably w is 1, and R F1 is -CF3, y is 1, and R F2 is F, preferably X′═F; and Halogenated sulfonyl aromatic fluoroolefins of the formula CF2=CF-Ar-SO2X' or CF2=CF-O-Ar-SO2X', where Ar is C5-C 15 and preferably X'=F).

[0026] In a preferred embodiment, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is selected from the group consisting of sulfonyl fluorides, i.e., those where X' = F. More preferably ... m The sulfonyl fluorovinyl ether is selected from the group of sulfonyl fluorovinyl ethers SO2F (wherein m is an integer of 1 to 6, preferably 2 to 4).

[0027] In certain embodiments, b) the fluorinated olefin monomer comprising at least one -SO2X functional group is perfluoro-5-sulfonyl fluoride-3-oxa-1-pentene (CF2=CF-O-CF2CF2-SO2F) (hereinafter "VEFS").

[0028] In a more preferred embodiment, the fluoropolymer is a copolymer of VDF-VEFS, where the VEFS is present in an amount of 0.2 to 2.0 mole % based on the total number of moles of repeat units.

[0029] In some embodiments, the fluoropolymer further comprises c) additional repeat units derived from at least one C2-C8 (per)fluoroolefin different from a) and b) and / or C2-C8 chloro- and / or bromo- and / or iodofluoroolefin.

[0030] In certain embodiments, the C2-C8 (per)fluoroolefin is selected from the group consisting of: · C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP); · Hydrogen-containing C2-C8 fluoroolefins, such as vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoroisobutylene; ·Formula CH2=CH-R f (per)fluoroalkylethylene (wherein R f is a C1-C6 (per)fluoroalkyl group; ·Formula CF2=CFORf (Per)fluoroalkyl vinyl ethers (PAVEs) of the formula (wherein R f is a C1-C6 (per)fluoroalkyl group; (Per)fluorooxy-alkyl vinyl ethers of formula CF2=CFOX, where X is a C1-C alkyl group containing at least one catenary oxygen atom 12 ((per)fluoro)oxyalkyl); (Per)fluorodioxole of the formula: [ka] (In the formula, R f3 , R f4 , R f5 , and R f6 are the same or different and are independently selected from C1-C6 (per)fluoroalkyl groups which may contain a fluorine atom and optionally at least one oxygen atom; and ·Formula CFX2=CX2OCF2OR” f (per)fluoromethoxyvinyl ether (MOVE) (wherein R f is selected from linear or branched C1-C6 (per)fluoroalkyl, C5-C6 cyclic (per)fluoroalkyl, linear or branched C2-C6 (per)fluorooxyalkyl containing 1-3 catenary oxygen atoms, X2 is F or H, preferably R" f is -CF2CF3(MOVE1), -CF2CF2OCF3(MOVE2), or -CF3(MOVE3), where X2=F).

[0031] In more specific embodiments, the C2-C8 (per)fluoroolefin is selected from the group consisting of vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), hexafluoroisobutylene, and combinations thereof.

[0032] In a preferred embodiment, the C2-C8 (per)fluoroolefin is HFP.

[0033] In another preferred embodiment, the C2-C8 (per)fluoroolefin is TFE.

[0034] In another specific embodiment, the C2 to C8 chloro and / or bromo and / or iodofluoroolefins are selected from the group consisting of 1,1-chlorofluoroethylene (CFE), chlorodifluoroethylene (CDFE), bromotrifluoroethylene, chlorotrifluoroethylene (CTFE), 1,2-dichloro-1,2-difluoroethylene, iodotrifluoroethylene, and combinations thereof.

[0035] In a more specific embodiment, the C2 to C8 chloro and / or bromo and / or iodofluoroolefin is cis-1,2-dichloro-1,2-difluoroethylene or trans-1,2-dichloro-1,2-difluoroethylene, preferably trans-1,2-dichloro-1,2-difluoroethylene.

[0036] In a preferred embodiment, the C2-C8 chloro and / or bromo and / or iodofluoroolefin is chlorotrifluoroethylene (CTFE).

[0037] In a more preferred embodiment, the fluoropolymer is a VDF-HFP-VEFS terpolymer, wherein HFP is present in an amount of 10.0 to 30.0 mol %, preferably 13.0 to 25.0 mol %, more preferably 15.0 to 20.0 mol %, and VEFS is present in an amount of 0.1 to 10.0 mol %, preferably 0.1 to 5.0 mol %, more preferably 0.2 to 1.5 mol %, where mol % is based on the total number of moles of repeat units.

[0038] In another more preferred embodiment, the fluoropolymer is a VDF-CTFE-VEFS terpolymer, wherein CTFE is present in an amount of 10.0 to 30.0 mol %, preferably 13.0 to 25.0 mol %, more preferably 15.0 to 20.0 mol %, and VEFS is present in an amount of 0.1 to 10.0 mol %, preferably 0.1 to 5.0 mol %, more preferably 0.2 to 1.5 mol %, where mol % is based on the total number of moles of repeat units.

[0039] In some embodiments, the fluoropolymer is a fluoroelastomer.

[0040] In the present invention, the term "fluoroelastomer" is intended to denote fluoropolymer resins that serve as building blocks for obtaining true elastomers, which are defined by ASTM Special Technical Bulletin No. 184 as materials that can be stretched to twice their natural length at room temperature and that simultaneously return to within 10% of their original length when released after being held under tension for 5 minutes.

[0041] Generally, fluoroelastomers are amorphous, have low crystallinity, i.e., less than 20% by volume of crystalline phase, and have a glass transition temperature (T g In most cases, the fluoroelastomer advantageously has a T of less than 10°C, preferably less than 5°C, more preferably less than 0°C, and even more preferably less than -5°C. g It has.

[0042] The term "amorphous" herein is intended to mean a polymer having a heat of fusion of less than 5.0 J / g, preferably less than 3.0 J / g, and more preferably less than 2.0 J / g, as measured by differential scanning calorimetry (DSC) according to ASTM D3418 at a heating rate of 10°C / min.

[0043] There are no particular limitations on the non-aqueous solvent as long as it can dissolve the fluoropolymer of the present invention.

[0044] However, when a non-aqueous solvent is used in the presence of sulfide-based ionically conductive inorganic solid particles in addition to a fluoropolymer, the non-aqueous solvent must be compatible with the sulfide-based ionically conductive inorganic solid particles, i.e., the solvent must not adversely affect the ionic conductivity of the sulfide-based solid composite electrolyte. To this end, the solvent is required to exhibit high polarity, preferably with a high dielectric constant, to dissolve the fluoropolymer, but preferably without electrophilic sites, to limit the solvent's interaction with the sulfide particles and avoid their degradation.

[0045] In certain embodiments, the non-aqueous solvent is selected from the group consisting of nitrile-containing solvents, ethers, esters, thiols, thioethers, ketones, and tertiary amines.

[0046] In a preferred embodiment, the non-aqueous solvent is a nitrile-containing solvent of the general formula R-CN, where R represents an alkyl group. Non-limiting examples of nitrile-containing solvents are acetonitrile, butyronitrile, valeronitrile, isobutylnitrile, and the like.

[0047] In another preferred embodiment, the non-aqueous solvent is an ether of the general formula R1-O-R2, where R1 and R2 independently represent alkyl groups. Ether solvents include cyclic ethers based on 3-, 5-, or 6-membered rings. Cyclic ethers may be substituted with alkyl groups, may have unsaturation, or may have additional functional elements such as nitrogen or oxygen atoms in the ring. Non-limiting examples of (cyclic) ether solvents include diethyl ether, 1,2-dimethoxy ether, cyclopentyl methyl ether, diethyl ether, dibutyl ether, 1,3-dioxolane, 1,3-dioxane, anisole, tetrahydrofuran, methyltetrahydrofuran, and tetrahydropyran.

[0048] In another preferred embodiment, the non-aqueous solvent is an ester of the general formula R-COO-R, where R and R independently represent alkyl groups. Non-limiting examples of ester solvents include butyl butyrate and ethyl benzoate. In a more preferred embodiment, the non-aqueous solvent is butyl butyrate.

[0049] In another preferred embodiment, the non-aqueous solvent is a thiol of the general formula R5=SH or a thioether of the general formula R6-S-R7, where R5, R6, and R7 are independently alkyl groups. Thioether solvents include cyclic thioethers based on 3-, 5-, or 6-membered rings. Cyclic thioethers may be substituted with alkyl groups, may have unsaturation, or may have additional functional elements such as nitrogen or oxygen atoms in the ring. Non-limiting examples of thiol solvents include ethanethiol, tert-dodecyl mercaptan, thiophenol, tert-butyl mercaptan, octanethiol, dimethyl sulfide, ethyl methyl sulfide, and methyl benzyl sulfide.

[0050] In another preferred embodiment, the non-aqueous solvent is a ketone of the general formula R8R9C=O, where R8 and R9 independently represent an alkyl group. Non-limiting examples of ketone solvents include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, benzophenone, etc. In a more preferred embodiment, the non-aqueous solvent is methyl isobutyl ketone.

[0051] In another preferred embodiment, the non-aqueous solvent is a compound of the general formula R 10 R 11 R 12 N is a tertiary amine, and R 10 , R 11 , and R 12 each independently represents an alkyl group. The N atom of the tertiary amine may be embedded inside a 3-, 5-, or 6-membered ring. Non-limiting examples of tertiary amine solvents include triethylamine, dimethylbutylamine, tributylamine, cyclohexyldimethylamine, N-ethylpiperidine, etc.

[0052] In the present invention, R to R 12 The alkyl group refers to an "alkyl group" containing saturated carbon atoms having one or more carbon atoms, such as straight-chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.; cyclic alkyl groups (or "cycloalkyl" or "alicyclic" or "carbocyclic" groups) such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl; branched-chain alkyl groups such as isopropyl, tert-butyl, sec-butyl, and isobutyl; and alkyl-substituted alkyl groups such as the alkyl-substituted cycloalkyl and cycloalkyl-substituted alkyl groups defined above. Furthermore, the alkyl group may contain one or more unsaturated functional groups such as ether, carbonyl, carboxyl, hydroxyl, thio, thiol, thioxy, sulfo, nitrile, nitro, nitroso, azo, amido, imido, amino, imino, or halogen.

[0053] In another particular embodiment, the non-aqueous solvent is an organic carbonate, which may be partially or fully fluorinated. In the present invention, the organic carbonate may be either cyclic or acyclic. Non-limiting examples of organic carbonates include, among others, ethylene carbonate (1,3-dioxolan-2-one), propylene carbonate, 4-methylene-1,3-dioxolan-2-one, 4,5-dimethylene-1,3-dioxolan-2-one, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, propyl butyl carbonate, dibutyl carbonate, di-tert- butyl carbonate, butylene carbonate, mono- and difluoroethylene carbonate, mono- and difluoropropylene carbonate, mono- and difluorobutylene carbonate, 3,3,3-trifluoropropylene carbonate, fluorinated dimethyl carbonate, fluorinated diethyl carbonate, fluorinated ethyl methyl carbonate, fluorinated dipropyl carbonate, fluorinated dibutyl carbonate, fluorinated methyl propyl carbonate, and fluorinated ethyl propyl carbonate.

[0054] In another specific embodiment, the non-aqueous solvent is selected from the group consisting of acyclic amides, lactams, lactones, cyclic sulfones, sulfoxides, and tertiary phosphines. Non-limiting examples of non-aqueous solvents include, among others, dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyrolactone, γ-valerolactone, sulfolane, dimethyl sulfoxide, and hexamethylphosphoramide. In a more preferred embodiment, the non-aqueous solvent is N-methylpyrrolidone.

[0055] A second object of the present invention is a solid composite electrolyte comprising at least one fluoropolymer and at least one sulfide-based ion-conducting inorganic solid particle, wherein the fluoropolymer is a) vinylidene difluoride (VDF); b) at least one fluorinated olefin monomer containing at least one -SO2X functional group, wherein X is selected from X' and OM, X' is selected from the group consisting of F, Cl, Br, and I, and M is selected from the group consisting of H, an alkali metal, and NH4; and b) the fluorinated olefin monomer is present in an amount of 0.1 to 10.0 mole % based on the total number of moles of the repeating units.

[0056] Fluoropolymer is as defined in the present invention.

[0057] In the present invention, the term "sulfide-based solid, ionically conductive inorganic particles" is not particularly limited as long as it is a solid electrolyte material that contains sulfur atoms in its molecular structure or composition.

[0058] The sulfide-based solid, ionically conductive inorganic particles preferably contain Li, S, and an element from Groups 13-15, such as P, Si, Sn, Ge, Al, As, Sb, or B, to increase Li-ion conductivity.

[0059] The sulfide-based solid, ionically conductive inorganic particles according to the present invention preferably comprise: Li 10 SnP2S 12 Lithium tin phosphorus sulfide ("LSPS") materials, such as; ·Formula (Li2S) x -(P2S5) y (wherein x+y=1 and 0≦x≦1), Li7P3S 11 , Li7PS6, Li4P2S6, Li 9.6 P3S 12 and lithium phosphosulfide ("LPS") materials, such as glasses, crystalline, or glass-ceramics of the type Li3PS4; ·Li2CuPS4, Li 1+2x Zn 1-x PS4 (in the formula, 0≦x≦1), Li 3.33 Mg 0.33 P2S6, and Li 4-3x Sc xDoped LPS, such as P2S6 (where 0≦x≦1); ·Express Li x P y S z Lithium Phosphorus Sulfide Oxygen (“LPSO”) materials of formula O, where 0.33≦x≦0.67, 0.07≦y≦0.2, and 0.4≦z≦0.55; Li 10 SnP2S 12、 Li 10 GeP2S 12 , Li 10 SiP2S 12 and X-containing lithium phosphorus sulfide materials ("LXPS"), where X is Si, Ge, Sn, As, or Al, such as Li2S-P2S5-SnS; · X-containing lithium phosphorus sulfide oxygen ("LXPSO"), where X is Si, Ge, Sn, As, or Al; ·Li2SiS3, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Lithium silicon sulfide ("LSS") materials, such as Li2S-SiS2-Al2S3; Lithium boron sulfide materials, such as Li3BS3 and Li2S-B2S3-LiI; Li 0.8 Sn 0.8 S2, Li4SnS4, Li 3.833 Sn 0.833 As 0.166 Lithium tin sulfide and lithium arsenide materials, such as S4, Li3AsS4-Li4SnS4, and Ge-substituted Li3AsS4; Li4PS4Cl 、 Li7P2S8Cl, Li7P2S8I, and the like a PS b X c(wherein X represents at least one halogen element selected from the group consisting of Cl, Br, and I, or a combination thereof; a represents a number from 2.0 to 7.0; b represents a number from 3.5 to 6.0; and c represents a number from 0 to 3.0) is selected from the group consisting of:

[0060] In a more preferred embodiment, the sulfide-based solid, ionically conductive inorganic particles have the general formula Li a PS b X c and more particularly, argyrodite-type sulfide materials of the formula Li6PS5X, where X is Cl, Br, or I.

[0061] In another preferred embodiment, the argyrodite-type sulfide material of formula Li6PS5X is sulfur and / or lithium deficient, e.g., Li6PS5X, where 0≦x≦0.5. 6-x PS 5-x Cl 1+x , or doped with heteroatoms.

[0062] Particularly preferred sulfide-based solid ionically conductive particles are lithium tin phosphosulfide (“LSPS”) materials (e.g., Li 10 SnP2S 12 ) and argyrodite-type sulfide materials (e.g., Li6PS5Cl).

[0063] In one embodiment, the amount of sulfide-based solid, ionically conductive inorganic particles is at least 40.0 wt.%, preferably at least 60.0 wt.%, more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, most preferably at least 90.0 wt.%, and / or at most 99.8 wt.%, preferably at most 99.5 wt.%, more preferably at most 99.0 wt.%, most preferably at most 98.0 wt.%, based on the total weight of the solid composite electrolyte.

[0064] In certain embodiments, the amount of sulfide-based solid, ionically conductive inorganic particles is 40.0 to 99.8 wt. %, preferably 60.0 to 99.5 wt. %, more preferably 70.0 to 99.0 wt. %, even more preferably 80.0 to 99.0 wt. %, and most preferably 90.0 to 99.0 wt. %, based on the total weight of the solid composite electrolyte.

[0065] In a more specific embodiment, the amount of sulfide-based solid, ionically conductive inorganic particles is 95.0 to 99.0 wt %, based on the total weight of the solid composite electrolyte.

[0066] In the present invention, the sulfide-based solid, ionically conductive inorganic particles are different from the lithium salts conventionally used as essential components of lithium secondary batteries.

[0067] The term "lithium salt" is intended herein to mean a substance that must be dissolved in a solvent to ensure ionic conduction.

[0068] In lithium secondary batteries, the liquid electrolyte consists primarily of a lithium salt in a non-aqueous organic solvent, where the liquid electrolyte serves as a conductive path for the movement of cations, i.e., Li + Lithium ions (i.e., Li) pass from the cathode to the anode during discharge. + cations) are used as charge carriers. The dissolution of lithium salts is achieved by + By interaction, i.e., Li +Cation dissolution - (counter)ion interactions are crucial. Thus, many simple lithium salts, such as LiCl, LiF, Li2O, etc., are precluded from electrolyte use because their strong cation-anion interactions result in high lattice energies and thus poor solubility in relevant aprotic solvents. Non-limiting examples of lithium salts include, among others, lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonate (LiSbF6), lithium hexafluorotantalate (LiTaF6), lithium tetrachloroaluminate (LiAlCl4), lithium tetrafluoroborate (LiBF4), lithium chloroborate (Li2B 10 Cl 10 ), lithium fluoroborate (LiB 10 F 10 ), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium bis(trifluoromethanesulfonyl)imide Li(SO2CF3)2N (LiTFSI), and mixtures thereof.

[0069] Li + Cation conductivity originates from both total ionic conductivity and cation transference number. Given that the cation transference number in non-aqueous organic solvents is low, e.g., typically less than 0.5, ionic conductivity plays a crucial role in battery performance.

[0070] In short, a liquid electrolyte, in which at least one lithium salt is dissolved in at least one non-aqueous organic solvent, plays a vital role as one of the main components of a conventional lithium secondary battery.

[0071] In this regard, recent advances in the field of batteries involve the use of solid materials as electrolyte materials, and sulfide-based solid ionically conductive inorganic particles are particularly promising materials. In such solid-state batteries, the solid electrolyte replaces the function / role of the liquid electrolyte. Much effort has been made to understand the ion transport mechanism in solid electrolytes, but the Li transport mechanism within the solid electrolyte, i.e., between the electrode and electrolyte interfaces (both the electrode / solid electrolyte interface and the active material / solid electrolyte interface in the electrode), is still unclear. + The cation diffusion behavior, however, still lacks a deep understanding.

[0072] Like liquid electrolytes, solid electrolytes are ionic conductors that deliver ions between two electrodes. However, unlike liquid electrolytes, solid electrolytes require the addition of Li to make them conductive. + The lithium cation in lithium argyrodite Li6PS5X (where X = Cl, Br, or I) is, for example, Li + Li as a pathway for cations + However, the Li in the non-aqueous solvent that constitutes the liquid electrolyte plays a role in the cation diffusion mechanism. + Unlike lithium salts, which dissociate into a cation and the corresponding counteranion, the lithium site in Li6PS5X is thereby + It is understood that the diffusion / transport of cations occurs by forming localized cages where multiple jump processes, i.e., doublet jumps, intracage jumps, and intercage jumps, are possible (Sulfide and oxide inorganic solid electrolytes for All-Solid-State Li Batteries: Nanomaterials 2020, 10, 1606; doi:10.3390 / nano10081606 by Reddy et al.). That is, unlike liquid electrolytes, only one species in solid electrolytes is mobile, and the structure is determined by the mobile species, i.e., Li, which corresponds to the cooperative conduction mechanism. +It has partial site occupancy of cations.

[0073] In view of the above, lithium salts are distinctly different from sulfide-based solid, ionically conductive inorganic particles that contain lithium species within their inorganic structure in that lithium salts need to be dissolved in a solvent to ensure ionic conduction, whereas sulfide-based solid, ionically conductive inorganic particles have intrinsic ionic conductivities of greater than 0.1 mS / cm at room temperature, which are attributed to the sublattice diffusion of mobile lithium species in the inorganic framework.

[0074] In the present invention, the solid composite electrolyte does not contain a lithium salt.

[0075] The solid composite electrolyte of the present invention is characterized by having high adhesive properties to current collectors when used to manufacture electrodes, particularly positive electrodes, of solid state batteries.

[0076] In the present invention, the type of "current collector" depends on whether the electrode provided thereby is a positive electrode or a negative electrode. When the electrode of the present invention is a positive electrode, the current collector typically comprises at least one metal selected from the group consisting of aluminum (Al), nickel (Ni), titanium (Ti), and alloys thereof, preferably Al. When the electrode of the present invention is a negative electrode, the current collector typically comprises at least one metal selected from the group consisting of lithium (Li), sodium (Na), zinc (Zn), magnesium (Mg), copper (Cu), and alloys thereof, preferably Cu.

[0077] The solid composite electrolyte of the present invention is also characterized by high cohesion between the fluoropolymer and the sulfide-based ionically conductive inorganic solid particles when used to fabricate a membrane disposed between a positive electrode and a negative electrode.

[0078] A third object of the present invention is a slurry for producing a solid composite electrolyte, which contains a binder solution according to the present invention and at least one sulfide-based ion-conductive inorganic solid particle, and optionally further contains at least one electroactive material and / or at least one conductive agent.

[0079] In the present invention, the term "electroactive material" is intended to mean a material that can be incorporated into or inserted into its structure during the charging and discharging stages of a battery and can substantially release lithium ions therefrom.

[0080] When forming a positive electrode, the electroactive material for the positive electrode is not particularly limited. It can include a composite metal chalcogenide of the formula LiMQ2 (M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr, V, etc., and Q is a chalcogen such as O and S). Among these, it is preferable to use a lithium-based composite metal oxide of the formula LiMO2 (M is the same as defined above). Preferred examples thereof include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1), and spinel-structured LiMn2O4. Another preferred example is, for example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, etc., lithium nickel manganese cobalt-based metal oxides of the formula LiNi x Mn y Co z O2 (x + y + z = 1, called NMC), and, for example, lithium nickel cobalt aluminum-based metal oxides of the formula LiNi 0.8 Co 0.15 Al 0.05 O2, etc., of the formula LiNi x Co y Al z O2 (x + y + z = 1, called NCA).

[0081] Alternatively, when forming a positive electrode in the same manner, the electroactive material of the positive electrode may be of the formula M1M2(JO4): f E 1-f wherein M1 is lithium, which may be partially replaced by another alkali metal occupying less than 20% of the M1 metal; M2 is a transition metal in oxidation level +2 selected from Fe, Mn, Ni, or a mixture thereof, which may be partially replaced by one or more additional metals in oxidation levels +1 to +5 occupying less than 35% (including 0) of the M2 metal; JO4 is any oxyanion where J is any of P, S, V, Si, Nb, Mo, or a combination thereof; E is a fluoride, hydroxide, or chloride anion; and f is the mole fraction of the JO4 oxyanion, typically comprised between 0.75 and 1.

[0082] M1M2(JO4) as defined above f E 1-f The electroactive material is preferably phosphate-based and may have an ordered or modified olivine structure.

[0083] More preferably, the electroactive material of the positive electrode is of the formula Li 3-x M' y M” 2-y (JO4)3, where 0≦x≦3, 0≦y≦2, M′ and M″ are the same or different metals, at least one of which is a transition metal, JO4 is preferably PO4, which may be partially replaced by another oxyanion, and J is S, V, Si, Nb, Mo, or a combination thereof. More preferably, the electroactive material has the formula Li(Fe x Mn 1-x )PO4 (0≦x≦1, preferably x=1), i.e., lithium iron phosphate, LiFePO4.

[0084] In a preferred embodiment, the electroactive material of the positive electrode is LiMQ2 (where M is at least one metal selected from Co, Ni, Fe, Mn, Cr, and V, and Q is O or S); LiNi x Co 1-x O2 (0 < x < 1); LiMn2O4 having a spinel structure; the formula LiNi x Mn y Co z O2 (x + y + z = 1) lithium nickel manganese cobalt-based metal oxide (NMC), the formula LiNi x Co y Al z O2 (x + y + z = 1) lithium nickel cobalt aluminum-based metal oxide (NCA), lithium cobalt-based metal oxide (LCO), lithium nickel manganese-based metal oxide (LNMO), and LiFePO4, and is selected from the group consisting of

[0085] In a more preferred embodiment, the electroactive material of the positive electrode is selected from the group consisting of NMC, NCA, LCO, and LNMO.

[0086] In the present invention, the term "conductive agent" is specifically intended to mean a material used to ensure that the electrode has good charge and discharge performance and to provide additional electrical conductivity. Non-limiting examples of conductive agents are carbonaceous materials and metal powders or fibers, such as carbon black, carbon nanotubes (CNT), vapor-grown carbon fibers (VGCF), graphite, graphene, graphite fibers, etc. Examples of carbon black include ketjen black and acetylene black. Examples of metal powders or fibers include nickel and aluminum powders or fibers.

[0087] In one embodiment, the amount of fluoropolymer in the slurry is such as to provide an electrode comprising at least 1.0 wt. %, preferably at least 1.5 wt. %, more preferably 2.0 wt. %, and / or in an amount in the range of at most 20.0 wt. %, preferably at most 15.0 wt. %, more preferably at most 10.0 wt. %, and most preferably at most 5.0 wt. %, based on the total weight of the fluoropolymer, the sulfide-based ionically conductive inorganic solid particles, the electroactive material, and the optional conductive agent.

[0088] In certain embodiments, the amount of fluoropolymer in the slurry is such that an electrode is obtained comprising fluoropolymer in an amount ranging from 1.0 to 20.0 wt %, preferably 1.5 to 15.0 wt %, more preferably 2.0 to 10.0 wt %, and most preferably 2.0 to 5.0 wt %, based on the total weight of the fluoropolymer, sulfide-based ionically conductive inorganic solid particles, electroactive material, and optional conductive agent, such that the resulting electrode exhibits excellent adhesion to the current collector.

[0089] The slurry according to the present invention is typically applied onto at least one foil of an inert flexible support by a technique selected from casting, spray coating, rotary spray coating, roll coating, doctor blading, slot-die coating, gravure coating, inkjet printing, spin coating, and screen printing. In one embodiment, the wet film thus obtained typically has a thickness of 10 to 400 μm, preferably 50 to 200 μm. The wet film is then dried at a temperature of 10°C to 200°C, preferably 20°C to 80°C. An additional drying step in an oven under vacuum at a temperature of 20°C to 150°C, preferably 50°C to 80°C, can be appropriately carried out to completely remove the solvent. Those skilled in the art can select the optimal duration and temperature of the drying step depending on the boiling point of the solvent. The dried film thus obtained can be further subjected to an additional compression step, such as calendering, uniaxial or isostatic compression, to reduce the porosity and increase the density of the solid composite electrolyte.

[0090] A fourth object of the present invention is an electrode comprising at least one fluoropolymer according to the invention and at least one electroactive material, optionally further comprising at least one conductive agent and / or at least one sulfide-based ionically conductive inorganic solid particle.

[0091] In one embodiment, the electroactive material is for the positive electrode.

[0092] In certain embodiments, the electrode comprises at least one fluoropolymer according to the present invention and at least one positive electroactive material.

[0093] In another particular embodiment, the electrode comprises at least one fluoropolymer according to the present invention, at least one positive electrode electroactive material, and at least one sulfide-based ionically conductive inorganic solid particle.

[0094] In the present invention, the positive electrode is characterized by high adhesion to the current collector of the secondary battery.

[0095] In a particular embodiment, the positive electrode comprises a VDF-VEFS copolymer as the fluoropolymer and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2 and, optionally, carbon black as a conductive agent.

[0096] In another particular embodiment, the positive electrode comprises a VDF-CTFE-VEFS terpolymer as the fluoropolymer and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2 and, optionally, carbon black as a conductive agent.

[0097] In another particular embodiment, the positive electrode comprises a VDF-HFP-VEFS terpolymer as the fluoropolymer and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2O2 and, optionally, carbon black as a conductive agent.

[0098] In some embodiments, an electrode comprises a fluoropolymer according to the present invention, at least one sulfide-based ionically conductive inorganic solid particle, at least one electroactive material, and optionally at least one conductive agent.

[0099] In a more specific embodiment, the positive electrode comprises a VDF-VEFS copolymer as the fluoropolymer, Li6PS5Cl as the sulfide-based ion-conducting inorganic solid particles, and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2 and, optionally, carbon black as a conductive agent.

[0100] In another more specific embodiment, the positive electrode comprises a VDF-CTFE-VEFS terpolymer as the fluoropolymer, Li6PS5Cl as the sulfide-based ion-conducting inorganic solid particles, and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2 and, optionally, carbon black as a conductive agent.

[0101] In another more specific embodiment, the positive electrode comprises a VDF-HFP-VEFS terpolymer as the fluoropolymer, Li6PS5Cl as the sulfide-based ion-conducting inorganic solid particles, and LiNi as the electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2 and, optionally, carbon black as a conductive agent.

[0102] A fifth object of the present invention is a secondary battery comprising a positive electrode, a negative electrode and a membrane arranged between the positive and negative electrodes, wherein at least one of the positive electrode, the negative electrode and the membrane comprises at least one fluoropolymer according to the present invention and optionally further comprises at least one sulfide-based ionically conductive inorganic solid particle, at least one electroactive material and / or at least one conductive agent.

[0103] In some embodiments, the secondary battery is a solid-state battery.

[0104] In the present invention, the term "membrane" is intended to mean in particular an ion-permeable membrane placed between the positive and negative electrodes, whose function is to block electrons and ensure physical separation between the electrodes while allowing lithium ions to pass through.

[0105] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference conflicts with the statements of this application to the extent that a term may be unclear, the statements of this application shall control.

[0106] The present invention will now be described in more detail with reference to the following examples, the purpose of which is merely illustrative and is not intended to limit the scope of the invention. [Example]

[0107] raw materials · LPSCl (Li6PS5Cl), a crystalline sulfide-based solid ionically conductive inorganic particle, commercially available from NEI Corporation; · NMC622 (Cellcore® NMC KHX12), commercially available from Umicore; Conductive carbon black (C-NERGY™ SUPER C65T), commercially available from Imerys; ·Butyl butyrate (BB), commercially available from Sigma Aldrich; · Methyl isobutyl ketone (MIBK), commercially available from Sigma Aldrich; · N-methylpyrrolidone (NMP), commercially available from Sigma Aldrich; Fluoropolymer: Polymer 1: VDF-CTFE-VEFS (79.5 / 20.0 / 0.5 (mol%)), synthesized in-house at Solvay Specialty Polymers Italy SpA Polymer 2: VDF-CTFE (80.0 / 20.0 (mol%)), synthesized in-house at Solvay Specialty Polymers Italy SpA Polymer 3: VDF-HFP (78.5 / 21.5 (mol %)), Tecnoflon® N935 (T) commercially available from Solvay Specialty Polymers Italy SpA g =-19℃) Polymer 4: VDF-CTFE-HFP (80.0 / 10.0 / 10.0 (mol%)), synthesized in-house at Solvay Specialty Polymers Italy SpA Polymer 5: VDF-CTFE-HFP (79.0 / 15.0 / 6.0 (mol%)), synthesized in-house at Solvay Specialty Polymers Italy SpA

[0108] Synthesis of polymers 1-2 and 4-5 Polymer 1: In a vertical steel autoclave equipped with baffles and a stirrer operating at 550 rpm, 1.3 L of demineralized water was introduced. The temperature was brought to the reaction temperature of 75°C, and then 6.0 x 10 5 Pa (absolute) of VDF was then introduced. A gaseous mixture of VDF / CTFE in a nominal molar ratio of 80 / 20 was then added to the mixture at 26.0 × 10 5 The addition was carried out by using a compressor until a pressure of 100 Pa (absolute) was reached.

[0109] The composition of the gas mixture present in the autoclave head, analyzed by gas chromatography, was 83.5 mol% VDF and 16.5 mol% CTFE before the start of the reaction. 30.0 cc of a 3% w / w solution of ammonium persulfate ((NH4)2S2O8) in ethyl acetate was fed into the autoclave.

[0110] When 25.0 g of the gas mixture was introduced, 2.0 mL of VEFS was initially added to the gas mixture. Subsequently, the polymerization pressure was maintained constant by continuously adding 2.0 mL of VEFS for each additional 12.5 g of gas mixture until the polymerization was complete. When 250.0 g of the mixture had been fed, the feed was stopped, the reactor was cooled to room temperature, and then degassed to remove residual, i.e., unreacted, monomers. The resulting latex was removed and further degassed with nitrogen for 24 hours. The resulting polymer was isolated using a standard isolation procedure using aluminum sulfate (Al2(SO4)3) and then dried in a ventilated oven at 90°C for 24 hours.

[0111] Polymer 2: A vertical steel autoclave equipped with baffles and a stirrer operating at 550 rpm was charged with 1.3 L of demineralized water. The temperature was increased to a reaction temperature of 75°C, and 3.5 x 10 5 A gas mixture of VDF-CTFE with a nominal molar ratio of 80 / 20 was introduced at a pressure of 20.0 × 10 Pa (absolute pressure). 5 The mixture was added using a compressor until it reached 100 Pa (absolute pressure).

[0112] The composition of the gas mixture present in the autoclave head, analyzed by gas chromatography, was 83.5 mol% VDF and 16.5 mol% CTFE before the start of the reaction. 45.0 cc of a 3% w / w solution of ammonium persulfate in ethyl acetate and 2 mL of pure ethyl acetate were fed into the autoclave.

[0113] The polymerization pressure was maintained constant by feeding the monomer mixture. After 300.0 g of the mixture had been fed, the feed was stopped, the reactor was cooled to room temperature, and degassed to remove unreacted monomers. The resulting latex was removed and further degassed with nitrogen for 24 hours. The resulting polymer was isolated using a standard isolation procedure using aluminum sulfate and then dried in a ventilated oven at 90°C for 24 hours.

[0114] Polymer 4: Polymer 4 was synthesized in a similar manner to polymer 1.

[0115] A vertical steel autoclave equipped with baffles and a stirrer operating at 550 rpm was charged with 1.3 L of demineralized water. The temperature was increased to the reaction temperature of 75°C. 4.0 x 10 5 Pa (absolute pressure) of VDF and 3.0 x 10 5 A gas mixture of VDF-CTFE-HFP in a nominal molar ratio of 80.0 / 10.0 / 10.0 was introduced at a pressure of 20.0 × 10 Pa (absolute pressure). 5 The mixture was added using a compressor until it reached 100 Pa (absolute pressure).

[0116] The composition of the gas mixture present in the autoclave head, analyzed by gas chromatography, before the start of the reaction was 72.6 mol% VDF, 14.2 mol% CTFE, and 13.2 mol% HFP. 2.0 mL of pure ethyl acetate was fed into the autoclave.

[0117] The polymerization pressure was maintained constant until the polymerization was complete. After 200.0 g of the mixture had been fed, the feed was stopped, the reactor was cooled to room temperature, and degassed to remove residual materials. The resulting latex was removed and further degassed with nitrogen for 24 hours. The resulting polymer was isolated using standard separation procedures using aluminum sulfate and then dried in a ventilated oven at 90°C for 24 hours.

[0118] Polymer 5: Polymer 5 was synthesized in a similar manner to polymer 4.

[0119] A vertical steel autoclave equipped with baffles and a stirrer operating at 550 rpm was charged with 1.3 L of demineralized water. The temperature was increased to the reaction temperature of 75°C. 3.8 x 10 5 Pa (absolute pressure) of VDF and 4.0 x 10 5 A gas mixture of VDF-CTFE-HFP in a nominal molar ratio of 79.0 / 15.0 / 6.0 was introduced at a pressure of 20.0 × 10 Pa (absolute pressure). 5The mixture was added using a compressor until it reached 100 Pa (absolute pressure).

[0120] The composition of the gas mixture present in the autoclave head, analyzed by gas chromatography, was 78.3 mol% VDF, 14.6 mol% CTFE, and 7.1 mol% HFP before the start of the reaction. 45.0 cc of a 3% w / w solution of ammonium persulfate in ethyl acetate and 3 mL of pure ethyl acetate were fed into the autoclave.

[0121] The polymerization pressure was maintained constant until the polymerization was complete. After 300.0 g of the mixture had been fed, the feed was stopped, the reactor was cooled to room temperature, and then degassed to remove residual materials. The resulting latex was removed and further degassed with nitrogen for 24 hours. The resulting polymer was then isolated using a standard separation procedure using aluminum sulfate and dried in a ventilated oven at 90°C for 24 hours.

[0122] Preparation of solid composite electrolytes E1 and CE1-CE4 Inventive Example 1 (E1) A solid composite electrolyte composed of 95.0 parts by weight (pbw) LPSCI and 5.0 pbw Polymer 1 was prepared in the form of a film as follows.

[0123] A 10.0 wt% polymer solution was prepared by weighing out 1.0 g of Polymer 1 and 9.0 g of BB. Then, 3.705 g of LPSCl, 1.95 g of the 10.0 wt% polymer solution, and 0.345 g of BB were mixed using four glass balls under magnetic stirring at 400 rpm for a minimum of 6 hours. The solids content of the slurry and the casting speed were adjusted to maintain a slurry viscosity of 2.0–10.0 Pa·s throughout the casting process. The resulting slurry was cast onto a flexible support (Kapton® FN) using an automatic film applicator manufactured by Elcometer Ltd. The wet film was dried on a hot plate at 50°C for 1 hour and then placed in an oven at 80°C under vacuum overnight. The sample was stored in a minigrip bag and then placed in a sealed bag. All experiments were performed in an argon-filled glove box.

[0124] Comparative example 1 (CE1) CE1 was prepared in the same manner as E1, except that polymer 2 was used instead of polymer 1.

[0125] Comparative Example 2 (CE2) The solid composite electrolyte of CE2 was prepared in the same manner as E1, except that polymer 3 was used instead of polymer 1.

[0126] Comparative Example 3 (CE3) and Comparative Example 4 (CE4) The solid composite electrolytes of CE3 and CE4 were prepared in the same manner as CE2, except that polymer 4 and polymer 5 were used instead of polymer 3, respectively.

[0127] Cohesion forces in solid composite electrolytes E1 and CE1-CE4 A strip of dried, free-standing solid composite electrolyte was fixed to a rigid aluminum plate (2.6 cm × 10 cm) using double-sided tape (25 mm wide, 0.24 mm thick). Using a motorized tension / compression test stand (Mark-10 Corporation ESM303) with a flat, rounded tip, a second piece of double-sided tape, 1 cm in diameter and 0.24 mm thick (fixed to the bottom of the rounded tip), was pressed against the second surface of the solid composite electrolyte with a force of 200 N for 1 min. In the second step, the tip was pulled away (peeled) from the surface of the solid composite electrolyte at a constant speed of 100 mm / s. As a result, the solid composite electrolyte was damaged (torn), with one part remaining on the rigid aluminum support and the other part remaining on the tip connected to the test stand. The force required to tear the film in two is recorded in Table 1 as the average of five independent peel measurements. The peel tests were conducted in a dry chamber with a dew point of -40 °C.

[0128] Ionic conductivity of solid composite electrolytes E1 and CE1-CE4 The ionic conductivities of the solid composite electrolytes E1 and CE1–CE4 in film form were measured by AC impedance spectroscopy using an in-house developed pressure cell, in which the film is pressed between two stainless steel electrodes during impedance measurements. A cross section of the pressure cell is shown in Figure 1.

[0129] Impedance spectra were determined at a pressure of 370 MPa and a temperature of 20°C. AC impedance measurements were performed in the frequency range of 1000 Hz to 4.7 MHz using a potentiostat (VMP-300, BioLogic Science Instruments SAS).

[0130] The Nyquist diagram of the solid composite electrolyte showed typical behavior of a solid electrolyte (inorganic, polymer, or composite), with semicircular and Warburg-type impedances in the high- and low-frequency regions, respectively. The conductive behavior of the composite electrolyte was modeled according to the equivalent circuit R1(R2 / Q2)Q3 (see Figure 2), where R is the resistance, Q is a constant phase element, R1 and R2 represent the bulk resistance and grain boundary resistance, respectively, and Q2 and Q3 represent the grain boundary resistance and electrode contribution, respectively.

[0131] The intercept of the semicircle with the real axis at high frequencies is due to the bulk resistance (R1), and the intercept with the real axis at low frequencies is due to the total resistance of the film (R1 + R2). This total resistance, R, is conventionally used to calculate the electrical conductivity of solid composite electrolytes. Therefore, the ionic conductivity, σ, was obtained using the formula σ = d / (R × A), where d is the thickness of the film and A is the area of the stainless steel electrode. The SI unit of ionic conductivity is siemens per meter (S / m), where S is ohm -1 and 1 millisiemens per centimeter (mS / cm) is a decimal SI unit, i.e. 1mS / cm = 0.1S / m.

[0132] Preparation of the positive electrode E1 and CE1-CE4 containing LPSCl Positive electrodes E1 and CE1-CE4, composed of 74.0 pbw NMC622, 20.0 pbw LPSCl, 2.0 pbw conductive carbon black, and 4.0 pbw fluoropolymer (selected from Polymers 1-5), were prepared as follows.

[0133] A 10.0 wt% binder solution was prepared by weighing out 1.0 g of fluoroelastomer and 9.0 g of BB. Then, 1.0 g of LPSCl, 0.1 g of conductive carbon, 3.7 g of NMC622, and 2.0 g of the 10.0 wt% binder solution were mixed using four glass balls under magnetic stirring at 400 rpm for a minimum of 6 hours. The resulting slurry was cast onto an aluminum (Al) current collector using an automatic film applicator manufactured by Elcometer Ltd. The viscosity of the slurry was adjusted to maintain a viscosity of 2.0–10.0 Pa·s and 25.0–30.0 mg / cm throughout the casting process. 2 The solids content of the slurry and the casting speed were adapted to obtain a dry electrode loading of 1000 kJ / cm². The wet films were dried on a hot plate at 50 °C for 1 h, then placed in an oven at 80 °C under vacuum overnight, stored in minigrip bags, and then placed in sealed bags. The experiments were carried out in an argon-filled glove box.

[0134] E2 and CE5-CE6 without LPSCl The positive electrodes E2 and CE5-CE6, composed of 96 pbw NMC622, 2.0 pbw conductive carbon black, and 2.0 pbw fluoropolymer (selected from polymers 1-3), were prepared as follows:

[0135] A 10.0 wt.% binder solution was prepared by weighing out 1.0 g of fluoropolymer and 9.0 g of NMP. Subsequently, 0.1 g of conductive carbon, 4.8 g of NMC622, and 1.0 g of the 10.0 wt.% binder solution were mixed with four glass spheres under magnetic stirring at 400 rpm for a minimum of 6 hours. The resulting slurry was cast onto an Al current collector using an Elcometer Ltd. automatic film applicator. The slurry viscosity during casting was adjusted to maintain a range of 2.0-10.0 Pa.s and a dry electrode loading of 25.0-30.0 mg / cm. 2The solids content of the slurry and the casting speed were adjusted to achieve the desired results. The wet films were dried on a hot plate at 50 °C for 1 h, placed in an oven at 80 °C under vacuum overnight, stored in a minigrip bag, and then placed in a sealed bag. The experiment was carried out in an argon-filled glove box.

[0136] Adhesion of positive electrode to Al current collector (peel test) The adhesive strength of the positive electrode to the Al current collector was evaluated using a 180° peel test. An electrode strip (2 cm × 10 cm) of the dried electrode was fixed onto a rigid Al plate (2.6 cm × 10 cm) using double-sided tape (25 mm wide; 0.24 mm thick), with the electrode facing downwards and the current collector facing upwards. The Al current collector was peeled from the electrode using a motorized tension / compression test bench (ESM303, manufactured by Mark-10 Corporation) while maintaining a 180° angle and at a constant speed of 300 mm / min. The force required to remove the Al current collector from the electrode was recorded in Table 1 as the average value of three independent strips produced from three independent electrodes using three independent slurries with the same composition. The peel test was conducted in a dry room with a dew point of -40°C.

[0137] Regardless of whether or not sulfide-based ion-conducting inorganic solid particles were present, all cathodes E1 and E2 clearly exhibited excellent adhesion to the Al current collector, distinguishing them from CE1 to CE6. In particular, as shown in Table 1 below, E1 exhibited the highest adhesion to the current collector and also the highest cohesion compared to CE1 to CE4, which are applicable to sulfide-based solid-state batteries. Furthermore, when MIBK was used as the solvent instead of BB in fabricating cathode E1 using polymer 1, the adhesion was measured to be greater than 245 N / m, far exceeding the 214 N / m of E1. Similarly, E2 exhibited superior adhesion compared to CE5 and CE6, which are applicable to current-generation batteries using conventional liquid electrolytes.

[0138] [Table 1]

Images