Solid composite electrolyte

Abstract

The present invention relates to a solid composite electrolyte comprising a) at least one fluoropolymer and b) at least one sulfide-based solid ion-conducting inorganic particles wherein the fluoropolymer a) comprises recurring units derived from: i) at least 50.0 mol% of vinylidene fluoride, the mol% being relative to the total moles of recurring units; ii) at least one C2-C8 chloro and / or bromo and / or iodo fluoroolefin; and iii) at least one C2-C8 fluoroolefin, wherein i), ii) and iii) are different from each other; relates to a slurry for producing a solid composite electrolyte, comprising a) at least one fluoropolymer according to the invention and b) sulfide-based solid ion-conducting inorganic particles, and c) at least one non-aqueous solvent; to an electrode comprising the solid composite electrolyte according to the invention, d) at least one electroactive material, and optionally e) at least one conductive agent; the present invention also relates to a solid-state battery comprising a positive electrode, a negative electrode, and a membrane, at least one of which comprises the solid composite electrolyte according to the present invention. The invention also relates to a binder solution for a solid-state battery, comprising a) at least one fluoropolymer according to the invention and c) at least one non-aqueous solvent.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of European patent application No. 22189660.8 filed on August 10, 2022, the entire contents of which are incorporated by reference into this application for all purposes. Technical Field

[0003] The present invention relates to a solid composite electrolyte comprising a) at least one fluoropolymer and b) at least one sulfide-based solid ion-conducting inorganic particle, wherein the fluoropolymer a) comprises repeating units derived from: i) at least 50.0 mol% of vinylidene fluoride (VDF), mol% being relative to the total molar number of the repeating units; ii) at least one C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin; and iii) at least one C2-C8 fluoroolefin, wherein i), ii) and iii) are different from each other; to a slurry for making a solid composite electrolyte, the slurry comprising a) at least one fluoropolymer according to the present invention and b) sulfide-based solid ion-conducting inorganic particles, and c) at least one non-aqueous solvent; to an electrode comprising the solid composite electrolyte according to the present invention, d) at least one electroactive material, and optionally e) at least one conductive agent; and to a solid-state battery comprising a positive electrode, a negative electrode and a membrane, at least one of the positive electrode, the negative electrode and the membrane comprising the solid composite electrolyte according to the present invention. The present invention also relates to a binder solution for solid-state batteries, the binder solution comprising a) at least one fluoropolymer according to the present invention and c) at least one non-aqueous solvent. Background Art

[0004] Lithium-ion (Li-ion) batteries have maintained a dominant position in the rechargeable energy storage device market for decades due to their multiple advantages such as light weight, reasonable energy density, and good cycle life. Nevertheless, with the development of high-power applications such as electric vehicles, hybrid electric vehicles, grid energy storage, etc., there is a continuous demand for better safety and higher energy density.

[0005] Solid-state batteries have been considered as energy storage devices of the next generation, in which highly flammable liquid electrolytes are replaced by solid electrolytes, thereby substantially eliminating the risk of ignition and / or explosion. As solid electrolytes, organic polymers, inorganics and composite materials have been actively studied, each of which has its own advantages and disadvantages. In particular, considering the high ionic conductivity of sulfide-based solid electrolytes and the good mechanical properties and ease of processing of polymers, composite materials (i.e., inorganic solid electrolytes dispersed in polymers, such as those containing particles based on sulfides dispersed in polymer matrices) are considered to be the most promising solutions on an industrial scale. However, there are still shortcomings to be further resolved, such as the poor solvent compatibility of sulfide materials, which largely limits the selection of polymers that can be used to manufacture electrolytes; insufficient cohesion between polymers and sulfide materials; low adhesion to the current collector of the electrode; the process of manufacturing solid composite electrolytes is quite complicated, etc.

[0006] Fluorinated polymers such as VDF-based polymers have been widely used as binders in conventional Li-ion batteries. Due to their good oxidation resistance, they have been mainly used in the formulations for forming electrodes of Li-ion batteries, particularly for the formulations for forming electrodes of positive electrodes, and their use as binders for sulfide-based solid electrodes and / or electrolyte layers has also been actively studied in the art. For example, US10511052 B2 (Idemitsu Kosan) discloses fluorinated polymers as binders for sulfide-based solid electrolytes, such as VDF-hexafluoropropylene (HFP), VDF-tetrafluoroethylene (TFE), VDF-HFP-TFE, and TFE-HFP. Furthermore, JP5675694B2 (Kureha and Toyota) describes a method for producing electrodes and electrolyte layers containing sulfide-based solid electrolytes, which contain fluorinated polymers as binders, in particular VDF-based copolymers with a VDF content of 40 to 70 mol %, such as VDF-HFP, VDF-chlorotrifluoroethylene (CTFE), VDF-TFE-HFP, preferably VDF-TFE-HFP.

[0007] In this regard, it is well known in the art that VDF-based / fluorinated binders exhibit low cohesive strength in solid electrolyte particles and / or in electroactive materials inside solid electrolyte layers and / or electrodes. As a result, relatively high levels of binders are applied to solid electrolyte layers and electrodes, which leads to a significant reduction in ionic conductivity. This has been one of the main problems of solid-state battery technology. Another key problem is that VDF-based / fluorinated binders exhibit low adhesion strength to current collectors, leading to electrode delamination and ultimately battery failure.

[0008] US2015 / 096169 A1 (Kureha and Toyota) discloses that a positive electrode for a sulfide-based solid-state battery exhibits good adhesion to a current collector, the positive electrode being formed with a slurry containing a fluorine-based copolymer having a specific amount of VDF units (between 40 and 70 mol%). In particular, US'169 implements VDF-TFE-HFP (55 / 25 / 20 in mol%) as a binder, which exhibits higher adhesion than an amino-modified hydrogenated binder.

[0009] WO 2021 / 039950 (Fujifilm) describes a composition containing an inorganic solid electrolyte, comprising an inorganic solid electrolyte, a polymer binder and a dispersion medium, wherein the polymer binder comprises a fluorine-based copolymer containing a VDF component and 21 to 65 mol% of an HFP component, exhibiting an adsorption of more than 60% on the inorganic solid electrolyte and effectively controlling excessive viscosity increase, recondensation or sedimentation of the inorganic particles, thereby achieving a solid-state battery with excellent cycle characteristics. In particular, in order to improve the adhesion characteristics of the electrode, WO'950 proposes the use of specific functional groups such as carboxylic acid groups, phosphoric acid groups and hydroxyl groups in the VDF-HFP copolymer.

[0010] In particular, CN 113451638 A (Qingtao Kunshan Energy Development Co. Ltd.) describes a sulfide-based solid electrolyte membrane, characterized in that the membrane comprises a polymer membrane having a 3D structure and a sulfide-based solid electrolyte, the sulfide-based solid electrolyte membrane being manufactured by electrospinning of the membrane and subsequently infiltrating the sulfide material therein. The polymer membrane is a VDF-based copolymer represented by VDF-A or a VDF-based terpolymer represented by VDF-AB, wherein A is selected from the group consisting of trifluoroethylene (TrFE), HFP and methyl methacrylate, and B is selected from the group consisting of CTFE, 1,1-chlorofluoroethylene and chlorodifluoroethylene. However, CN'638A only implements VDF-TrFE copolymers and does not provide any further insights into fluoropolymers having an optimal combination of at least three different monomers and a solvent compatible with sulfide materials.

[0011] In this regard, Jarvis et al. [The use of novel VDF-HFP-CTFE terpolymers in lithium-ion polymer cells] (Journal of Power Sources 119-121 (2003) 465-468) disclose a gel polymer electrolyte consisting of a plasticized VDF-HFP-CTFE terpolymer, in which an organic carbonate mixture is absorbed as a liquid electrolyte in a conventional Li-ion battery, wherein the document also describes that the introduction of CTFE into VDF-HFP increases the electrolyte absorption capacity (due to its low melt flow index) compared to PVDF homopolymer and VDF-HFP copolymer, while maintaining structural integrity. However, Jarvis et al. do not provide any clues at all about its use as a binder for solid-state batteries (e.g. in sulfide-based solid composite electrolytes).

[0012] Therefore, there remains a continuing need in this field for solutions that overcome the shortcomings of sulfide-based solid composite electrolytes. Summary of the invention

[0013] A first object of the present invention is a solid composite electrolyte comprising a) at least one fluoropolymer and b) at least one sulfide-based solid ion-conducting inorganic particle, wherein the fluoropolymer a) comprises repeating units derived from: i) at least 50.0 mol % of vinylidene fluoride (VDF), the mol % being relative to the total moles of the repeating units; ii) at least one C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin; and iii) at least one C2-C8 fluoroolefin, wherein i), ii) and iii) are different from each other.

[0014] A second object of the present invention is a slurry for making a solid composite electrolyte, the slurry comprising a) a fluoropolymer and b) sulfide-based solid ion-conducting inorganic particles, and c) at least one non-aqueous solvent.

[0015] A third object of the present invention is an electrode comprising a solid composite electrolyte according to the invention, d) at least one electroactive material, and optionally e) at least one conducting agent.

[0016] A fourth object of the present invention is a solid-state battery, comprising a positive electrode, a negative electrode and a membrane located between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode and the membrane comprises a solid composite electrolyte according to the present invention, optionally d) at least one electroactive material and / or e) at least one conductive agent.

[0017] A fifth object of the present invention is a binder solution for solid-state batteries, the binder solution comprising a) at least one fluoropolymer according to the present invention and c) at least one non-aqueous solvent.

[0018] The inventors have surprisingly found that the solid composite electrolyte according to the present invention can provide a particularly advantageous combination of properties, such as excellent adhesion of the electrode to the current collector and significantly enhanced cohesive strength within the membrane, while maintaining good ionic conductivity, which is notably achieved by using the fluoropolymer according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure 1 is a cross-section of a pressure cell for AC impedance spectroscopy, developed in-house at Solvay to measure the ionic conductivity of membranes. In the pressure cell, the membrane is pressed between 2 stainless steel electrodes during impedance measurements.

[0020] Figure 2 represents the equivalent circuit used to simulate the conductivity behavior of the solid composite electrolyte, where R1 and R2 represent the bulk resistance and grain boundary resistance, respectively, and Q2 and Q3 represent the grain boundary and electrode contributions, respectively. DETAILED DESCRIPTION

[0021] Ratios, concentrations, amounts and other numerical data may be presented in the form of a range herein. It should be understood that the use of such a range format is only for convenience and brevity, and should be flexibly interpreted as including not only the numerical values ​​explicitly mentioned as range limits, but also all individual numerical values ​​or sub-ranges included within this range, as if each numerical value and sub-range were explicitly mentioned. In the context of the present invention, the term 'percent by weight' (wt%) indicates the content of a specific component in a mixture, which is calculated as the ratio between the weight of the component and the total weight of the mixture. As used herein, unless otherwise expressly stated, the concentration of repeating units in 'percent by mole' (mol%) refers to the concentration relative to the total number of repeating units in the polymer.

[0022] It should be understood that the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the claimed invention. Therefore, various changes and modifications described herein will be apparent to those skilled in the art. In addition, for the sake of clarity and brevity, descriptions of well-known functions and configurations may be omitted.

[0023] The present invention provides a solid composite electrolyte, which comprises:

[0024] a) at least one fluoropolymer; and

[0025] b) at least one sulfide-based solid ion-conducting inorganic particle;

[0026] wherein the fluoropolymer a) comprises repeating units derived from:

[0027] i) at least 50.0 mol% of vinylidene fluoride (VDF), the mol% being relative to the total moles of repeating units;

[0028] ii) at least one C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin; and

[0029] iii) at least one C2-C8 fluoroolefin,

[0030] wherein i), ii) and iii) are different from each other.

[0031] In one embodiment, i) vinylidene fluoride accounts for at least 60.0 mol %, the mol % being relative to the total moles of repeating units.

[0032] In another embodiment, i) vinylidene fluoride accounts for at least 70.0 mol %, the mol % being relative to the total moles of repeating units.

[0033] In one embodiment, the C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefins ii) 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.

[0034] In a specific embodiment, the C2-C8 chloro- and / or brominated- and / or iodinated fluoroolefin ii) is cis-1,2-dichloro-1,2-difluoroethylene or trans-1,2-dichloro-1,2-difluoroethylene, preferably trans-1,2-dichloro-1,2-difluoroethylene.

[0035] In a preferred embodiment, the C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin ii) is CTFE.

[0036] In one embodiment, the C2-C8 fluoroolefin iii) is selected from the group consisting of:

[0037] -C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP);

[0038] - Hydrogen-containing C2-C8 fluoroolefins, such as vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoroisobutylene;

[0039] - having the formula CH2=CH-R f (per)fluoroalkylethylene, wherein R f is a C1-C6 (per)fluoroalkyl group;

[0040] -Has the formula CF2=CFOR f (per)fluoroalkyl vinyl ether (PAVE), wherein R f is a C1-C6 (per)fluoroalkyl group;

[0041] - a (per)fluorooxyalkyl vinyl ether of the formula CF2=CFOX, wherein X is a C1-C ... 12 ((Per)fluoro)oxyalkyl;

[0042] - (per)fluorodioxole having the formula:

[0043]

[0044] Where R f3 , R f4 , R f5 and R f6 are the same as or different from each other and are independently selected from fluorine atoms and C1-C6 (per)fluoroalkyl groups optionally containing at least one oxygen atom; and

[0045] -Has the formula CFX2=CX2OCF2OR" f (per)fluoromethoxyvinyl ether (MOVE), where R" f is selected from a linear or branched C1-C6 (per)fluoroalkyl group, a C5-C6 cyclic (per)fluoroalkyl group, and a linear or branched C2-C6 (per)fluorooxyalkyl group containing 1 to 3 chain oxygen atoms, and X2 is F or H; preferably, R" f is -CF2CF3(MOVE1), -CF2CF2OCF3(MOVE2), or -CF3(MOVE3), and X2 is F.

[0046] In a specific embodiment, the C2-C8 fluoroolefin iii) is selected from the group consisting of vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), hexafluoroisobutylene, and combinations thereof.

[0047] In a preferred embodiment, the C2-C8 fluoroolefin iii) is HFP.

[0048] In another preferred embodiment, the C2-C8 fluoroolefin iii) is TrFE.

[0049] In one embodiment, the fluoropolymer further comprises repeating units derived from:

[0050] - C2-C8 non-fluorinated olefins, such as ethylene, propylene; and / or

[0051] - a hydrophilic (meth)acrylic monomer having the formula:

[0052]

[0053] wherein R1, R2 and R3 are the same or different from each other and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups, and R OH is a hydrogen atom or a C1-C5 hydrocarbon moiety containing at least one hydroxyl group.

[0054] In a specific embodiment, the hydrophilic (meth)acrylic monomer is selected from the group consisting of acrylic acid (AA), methacrylic acid (MA), hydroxyethyl (meth)acrylate, 2-hydroxypropyl acrylate, hydroxyethylhexyl (meth)acrylate, butyl acrylate, and the like, and combinations thereof.

[0055] In another specific embodiment, the fluoropolymer comprises repeating units derived from C2-C8 non-fluorinated olefins and / or hydrophilic (meth)acrylic monomers in an amount of 0.1 to 10.0 mol%, preferably 0.2 to 5.0 mol%, more preferably 0.2 to 2.0 mol%, the mol% being relative to the total moles of the repeating units.

[0056] In a preferred embodiment, the hydrophilic (meth)acrylic monomer is AA.

[0057] In another preferred embodiment, the hydrophilic (meth)acrylic monomer is MA.

[0058] In a specific embodiment, the fluoropolymer is a terpolymer of VDF-CTFE-HFP.

[0059] In another specific embodiment, the fluoropolymer is a terpolymer of VDF-CTFE-TrFE.

[0060] In another specific embodiment, the fluoropolymer is a tetrapolymer of VDF-CTFE-HFP-AA.

[0061] In the present invention, the fluoropolymer can be produced by a suspension or emulsion polymerization method.

[0062] In some embodiments, the fluoropolymer is a fluoroelastomer.

[0063] In the present invention, the term "fluoroelastomer" is intended to designate the fluoropolymer resins serving as the base component for obtaining true elastomers. True elastomers are defined by ASTM, Special Technical Bulletin, No. 184, as materials that can be stretched to twice their intrinsic length at room temperature and, after holding them under tension for 5 minutes, recover within the same time to within 10% of their initial length once they are released.

[0064] Typically, fluoroelastomers are amorphous, exhibit low crystallinity (i.e., have less than 20 vol% crystalline phase), and have a glass transition temperature (T g In most cases, the fluoroelastomer advantageously has a T below 10°C, preferably below 5°C, more preferably below 0°C, even more preferably below -5°C. g .

[0065] 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.

[0066] In the present invention, the term "sulfide-based solid ion-conductive inorganic particle" is not particularly limited as long as it is a solid electrolyte material containing one or more sulfur atoms in the molecular structure or composition.

[0067] The sulfide-based solid ion-conductive inorganic particles preferably contain Li, S, and an element of Groups 13 to 15 (e.g., P, Si, Sn, Ge, Al, As, Sb, or B) to increase Li ion conductivity.

[0068] The sulfide-based solid ion-conducting inorganic particles according to the present invention are preferably selected from the group consisting of:

[0069] - Lithium tin phosphide ("LSPS") materials, such as Li 10 SnP2S 12 ;

[0070] - Lithium phosphide ("LPS") materials, such as glasses, crystals or glass ceramics having the following formula: (Li2S) x -(P2S5) y , where x+y=1 and 0≤x≤1; Li7P3S 11 ;Li7PS6;Li4P2S6;Li 9.6 P3S 12 and Li3PS4;

[0071] - doped LPS, such as Li2CuPS4; Li 1+2x Zn 1-x PS4, where 0≤x≤1; Li 3.33 Mg 0.33 P2S6; and Li 4- 3x Sc x P2S6, where 0≤x≤1;

[0072] -With formula Li x P y S z A lithium phosphorus sulfide oxygen ("LPSO") material of O, wherein 0.33≤x≤0.67, 0.07≤y≤0.2, 0.4≤z≤0.55;

[0073] - Lithium phosphide materials containing X ("LXPS"), wherein X is Si, Ge, Sn, As, or Al, such as Li 10 SnP2S 12 , Li 10 GeP2S 12 , Li 10 SiP2S 12 , and Li2S-P2S5-SnS;

[0074] - lithium phosphorus oxysulfide containing X ("LXPSO"), wherein X is Si, Ge, Sn, As or Al;

[0075] -Lithium silicon sulfide ("LSS") materials, such as 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 , and Li2S-SiS2-Al2S3;

[0076] -Lithium boron sulfide materials, such as Li3BS3 and Li2S-B2S3-LiI;

[0077] -Lithium tin sulfide materials and lithium arsenide materials, such as Li 0.8 Sn 0.8 S2, Li4SnS4, Li 3.833 Sn 0.833 As 0.166 S4, Li3AsS4-Li4SnS4, and Ge-substituted Li3AsS4;

[0078] -Has the general formula Li a PS b X c A lithium phosphorus sulfide material, wherein X represents at least one halogen element selected from the group consisting of Cl, Br and I or a combination thereof; and 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, such as Li4PS4Cl 、 Li7P2S8Cl, and Li7P2S8I; and

[0079] - combinations thereof.

[0080] In a more preferred embodiment, the sulfide-based solid ion-conducting inorganic particles are of the general formula Li a PS b X c Lithium phosphide materials, more particularly Argyrodite-type sulfide materials having the formula Li6PS5X, wherein X is Cl, Br, or I.

[0081] In another preferred embodiment, the argyrodite-type sulfide material having the formula Li6PS5Y lacks sulfur and / or lithium, such as Li 6-x PS 5-x Cl 1+x (where 0≤x≤0.5), or doped with heteroatoms.

[0082] Particularly preferred sulfide-based solid ion-conducting particles are lithium tin phosphide ("LSPS") materials (e.g., Li 10 SnP2S 12 ) and argyrodite-type sulfide materials (e.g. Li6PS5Cl).

[0083] In one embodiment, the amount of the sulfide-based solid ion-conducting inorganic particles b) is at least 40.0 wt%, preferably at least 60.0 wt%, more preferably at least 70 wt%, even more preferably at least 80.0 wt% and 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% and most preferably at most 98.0 wt%, based on the total weight of the solid composite electrolyte.

[0084] In a specific embodiment, the amount of the sulfide-based solid ion-conductive inorganic particles b) 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.

[0085] In a more specific embodiment, the amount of the sulfide-based solid ion-conductive inorganic particles b) is 95.0 to 99.0 wt % based on the total weight of the solid composite electrolyte.

[0086] In the present invention, b) at least one sulfide-based solid ion-conductive inorganic particle is different from a lithium salt conventionally used as an essential element of a lithium secondary battery.

[0087] The term "lithium salt" is intended herein to mean a substance that needs to be dissolved in a solvent to ensure ion conduction.

[0088] In lithium secondary batteries, the liquid electrolyte is mainly composed of lithium salts in non-aqueous organic solvents, in which lithium ions (i.e., Li + cations) act as charge carriers, so that the liquid electrolyte acts as a cation (i.e., Li + The conductive pathway for the movement of cations from the cathode to the anode during discharge. The dissolution of lithium salts is through the solvent - Li + The interaction is carried out, that is, Li + The dissociation of cation-(counter) anion interactions is critical. Therefore, many simple lithium salts are excluded from use in electrolytes because their strong cation-anion interactions result in high lattice energies and thus poor solubility in relevant aprotic solvents (e.g., LiCl, LiF, Li2O, etc.). Non-limiting examples of lithium salts notably include 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 (Li2B10 F 10 ), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium bis(trifluoromethanesulfonyl)imide Li(SO2CF3)2N (LiTFSI), and mixtures thereof.

[0089] Li + Cationic conductivity is derived from both the total ionic conductivity and the cation transfer number. Considering that the cation transfer number in non-aqueous organic solvents is low, for example, typically less than 0.5, ionic conductivity plays a key role in battery performance.

[0090] In short, a liquid electrolyte in which at least one lithium salt is dissolved in at least one non-aqueous organic solvent plays a key role as one of the main components of a conventional lithium secondary battery.

[0091] In this regard, recent advances in the field of batteries involve the use of solid substances as electrolyte materials, and among others, solid ion-conducting inorganic particles based on sulfides are promising materials. In such solid-state batteries, the solid electrolyte replaces the function / role of the liquid electrolyte. Although many efforts have been made to understand the ion transport mechanism in solid electrolytes, the Li+ transport mechanism within the solid electrolyte (i.e., the interface between the electrode and the electrolyte (electrode / solid electrolyte interface and the active material / solid electrolyte interface within the electrode)) is still unclear. + The cation diffusion behavior still lacks a deep understanding.

[0092] Like liquid electrolytes, solid electrolytes are ionic conductors that deliver ions between two electrodes. However, unlike liquid electrolytes, solid electrolytes do not need to dissociate / dissolve into Li + The solid electrolyte is conductive by the presence of cations. For example, the lithium cations in lithium argyrodite Li6PS5X (X = Cl, Br or I) are + The cation diffusion mechanism plays a role as Li + However, it dissociates into Li in the non-aqueous solvent that constitutes the liquid electrolyte. + Different from the lithium salts of the cations and the corresponding counteranions, it is understood that the lithium sites within Li6PS5X form local cages, in which multiple hopping processes may occur, namely bimodal hopping, intracage hopping, and intercage hopping, thereby generating Li +Cation diffusion / transport (Reddy et al., Sulfide and oxide inorganic solid electrolytes for All-Solid-State LiBatteries: Nanomaterials 2020, 10, 1606; doi: 10.3390 / nano10081606). That is, unlike liquid electrolytes, only one species in solid electrolytes is mobile and these structures have the mobile species (i.e., Li + cations), corresponding to a cooperative conduction mechanism.

[0093] In view of the above, lithium salts are significantly different from sulfide-based solid ion-conducting inorganic particles containing lithium species in their inorganic structure, because lithium salts need to be dissolved in a solvent to ensure ion conduction, while sulfide-based solid ion-conducting inorganic particles have an intrinsic ionic conductivity higher than 0.1 mS / cm at room temperature, which is due to the diffusion of sublattices of mobile lithium species in their inorganic skeletons.

[0094] In the present invention, the solid composite electrolyte does not contain a lithium salt.

[0095] The solid composite electrolyte of the present invention is characterized by high adhesion properties to a current collector when it is used to manufacture an electrode (eg, a positive electrode) of a solid-state battery.

[0096] In the present invention, the nature of the "current collector" depends on whether the electrode provided thereby is a positive electrode or a negative electrode. If the electrode of the present invention is a positive electrode, the current collector typically comprises, preferably consists of, at least one metal selected from the group consisting of aluminum (Al), nickel (Ni), titanium (Ti) and alloys thereof, preferably Al. If the electrode of the present invention is a negative electrode, the current collector typically comprises, preferably consists of, 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.

[0097] A second object of the present invention is a slurry for making a solid composite electrolyte, the slurry comprising a) at least one fluoropolymer, b) at least one sulfide-based solid ion-conducting inorganic particle, and c) at least one non-aqueous solvent.

[0098] Fluoropolymer is as defined in the present invention.

[0099] There is no particular limitation on the non-aqueous solvent, as long as the non-aqueous solvent c) is able to dissolve the fluoropolymer a) and is compatible with the sulfide-based solid ion-conductive inorganic particles b), which means that the solvent has no negative impact on the ionic conductivity of the resulting solid composite electrolyte.

[0100] In one embodiment, the non-aqueous solvent c) is selected from the group consisting of nitrile-containing solvents, ethers, esters, thiols, thioethers, ketones and tertiary amines.

[0101] In a preferred embodiment, the non-aqueous solvent c) is a nitrile-containing solvent having the general formula R-CN, wherein R represents an alkyl group. Non-limiting examples of nitrile-containing solvents are acetonitrile, butyronitrile, valeronitrile, isobutyronitrile, and the like.

[0102] In another preferred embodiment, the non-aqueous solvent c) is an ether with the general formula R1-O-R2, wherein R1 and R2 independently represent an alkyl group. Ether solvents include cyclic ethers based on 3, 5 or 6 rings. Cyclic ethers can be substituted with an alkyl group, can have unsaturation and can have additional functional elements such as nitrogen or oxygen atoms inside the ring. Non-limiting examples of (cyclic) ether solvents are diethyl ether, 1,2-dimethoxy ether, cyclopentyl methyl ether, diethyl ether, dibutyl ether, 1,3-dioxolane, anisole, tetrahydrofuran, methyltetrahydrofuran, tetrahydropyran, etc.

[0103] In another preferred embodiment, the non-aqueous solvent c) is an ester having the general formula R3-COO-R4, wherein R3 and R4 independently represent an alkyl group. Non-limiting examples of ester solvents are butyl butyrate, ethyl benzoate, and the like.

[0104] In another preferred embodiment, the non-aqueous solvent c) is a thiol with the general formula R5=SH or a thioether with the general formula R6-S-R7, wherein R5, R6 and R7 are independently alkyl. The thioether solvent includes a cyclic thioether based on a 3, 5 or 6-membered ring. The cyclic thioether can be substituted by an alkyl group, can have unsaturation and can have additional functional elements such as nitrogen or oxygen atoms in the ring. Non-limiting examples of thiol solvents are ethanethiol, tert-dodecyl mercaptan, thiophenol, tert-butyl mercaptan, octanethiol, dimethyl sulfide, ethyl methyl sulfide, methyl benzyl sulfide, etc.

[0105] In another preferred embodiment, the non-aqueous solvent c) is a ketone having the general formula R8R9C=O, wherein R8 and R9 independently represent an alkyl group. Non-limiting examples of ketone solvents are methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, benzophenone, etc., preferably methyl isobutyl ketone.

[0106] In another preferred embodiment, the non-aqueous solvent c) is a solvent having the general formula R 10 R 11 R12 N tertiary amine, where R 10 , R 11 and R 12 and independently represent an alkyl group. The N atom of the tertiary amine may be embedded in a 3-, 5-, or 6-membered ring. Non-limiting examples of tertiary amine solvents are triethylamine, dimethylbutylamine, tributylamine, cyclohexyldimethylamine, N-ethylpiperidine, and the like.

[0107] In the present invention, R1 to R 12 The alkyl groups of the present invention refer to "alkyl" including saturated hydrocarbons having one or more carbon atoms, including: straight chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclic alkyl groups (or "cycloalkyl" or "alicyclic" or "carbocyclyl") such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl, branched alkyl groups such as isopropyl, tert-butyl, sec-butyl and isobutyl, and alkyl-substituted alkyl groups such as alkyl-substituted cycloalkyl and cycloalkyl-substituted alkyl groups, as defined above. In addition, the alkyl group may include functional groups such as one or more unsaturated, ether, carbonyl, carboxyl, hydroxyl, sulfhydryl, thiol, sulfoxyl, sulfonic acid, nitrile, nitro, nitroso, azo, amide, imide, amino, imine or halogen.

[0108] In a preferred embodiment, the non-aqueous solvent c) includes nitrile-containing solvents, such as acetonitrile; ethers, such as tetrahydrofuran, 2-methyl-tetrahydrofuran, 2,5-dimethyl-tetrahydrofuran, 1,3-dioxolane, diethyl ether and 1,2-dimethoxy ether; esters, such as butyl butyrate; and ketones, such as methyl isobutyl ketone.

[0109] In a more preferred embodiment, the non-aqueous solvent c) is an ester, such as butyl butyrate.

[0110] In another more preferred embodiment, the non-aqueous solvent c) is a ketone, such as methyl isobutyl ketone.

[0111] In one embodiment, the slurry may further comprise a second solvent, such as saturated and aromatic hydrocarbons, such as, but not limited to, linear and branched alkanes (eg, heptane), cyclic alkanes (eg, cyclohexane), and aromatic compounds (eg, xylene and toluene).

[0112] In the present invention, the slurry can be suitably prepared by a method comprising mixing the following by any method known to those skilled in the art: a) fluoropolymer, b) sulfide-based solid ion-conductive inorganic particles, and c) non-aqueous solvent. In a preferred embodiment, the slurry is prepared by a method comprising dissolving a) fluoropolymer in c) non-aqueous solvent, then adding c) sulfide-based solid ion-conductive inorganic particles, and mixing the resulting mixture.

[0113] In the present invention, the amount of a) fluoropolymer in the slurry is such as to provide a solid composite electrolyte comprising an amount of the fluoropolymer a) in the range of at least 1.0 wt%, preferably at least 1.5 wt%, more preferably 2.0 wt%, and / or at most 20.0 wt%, preferably at most 15.0 wt%, more preferably at most 10.0 wt%, most preferably at most 5.0 wt%, relative to the total weight of the fluoropolymer a) and the sulfide-based solid ion-conductive inorganic particles b).

[0114] In a specific embodiment, the amount of a) fluoropolymer in the slurry is such as to provide a solid composite electrolyte containing a certain amount of the fluoropolymer a), the 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% relative to the total weight of the fluoropolymer a) and the sulfide-based solid ion-conductive inorganic particles b). Therefore, the resulting solid composite electrolyte exhibits good cohesion between the fluoropolymer a) and the sulfide-based solid ion-conductive inorganic particles b) while maintaining good ionic conductivity.

[0115] The slurry according to the present invention is typically applied to the foil of at least one inert flexible carrier by a technique selected from the following: casting, spraying, spin spraying, roller coating, blade coating, slot 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 between 10 ° C and 200 ° C, preferably between 20 ° C and 80 ° C. An additional drying step at a temperature between 20 ° C and 150 ° C, preferably between 50 ° C and 80 ° C, in an oven under vacuum can be suitably performed to completely remove the solvent. Those skilled in the art can select the optimal duration and temperature of the drying step considering the boiling point of the solvent. The dry film thus obtained can be further subjected to an additional compression step, such as calendaring, uniaxial or isostatic compression method, to reduce porosity and increase the density of the solid composite electrolyte.

[0116] In another embodiment, the slurry may further comprise d) at least one electroactive material, and optionally e) at least one conductive agent.

[0117] In a preferred embodiment, the electroactive material d) is used in a positive electrode.

[0118] In the present invention, the term "positive electrode" is intended to denote in particular an electrode of an electrochemical cell, wherein reduction occurs during discharge, whereas the term "negative electrode" is intended to denote in particular an electrode of an electrochemical cell, wherein oxidation occurs during discharge.

[0119] In the present invention, the term "electroactive material" is intended to denote a material that is capable of incorporating or inserting lithium ions into its structure and releasing a large amount of lithium ions therefrom during the charging and discharging phases of a battery.

[0120] In the case of forming a positive electrode for a solid-state battery, the electroactive material for the positive electrode is not particularly limited. It may include a composite metal chalcogenide having the formula LiMQ2, where M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr, and V and Q is a chalcogen element such as O and S. Among these, a lithium-based composite metal oxide having the formula LiMO2, where M is the same as defined above, is preferably used. Preferred examples thereof may include LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1) and spinel-structured LiMn2O4. Another preferred example thereof may include a lithium-nickel-manganese-cobalt-based metal oxide having the formula LiNi x Mn y Co z O2 (x + y + z = 1, referred to as NMC), such as LiNi 1 / 3 Mn 1 / 3Co 1 / 3 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, and a lithium-nickel-cobalt-aluminum-based metal oxide having the formula LiNi x Co y Al z O2 (x + y + z = 1, referred to as NCA), such as LiNi 0.8 Co 0.15 Al 0.05 O2.

[0121] As an alternative, still in the case of forming a positive electrode for a lithium metal battery, the electroactive material of the positive electrode may include a compound having the formula M1M2(JO4) f E 1-fAn electroactive material based on lithiated or partially lithiated transition metal oxyanions, where M1 is lithium, which may be partially replaced by another alkali metal that is less than 20% of the M1 metal; M2 is a transition metal selected from Fe, Mn, Ni, or mixtures thereof at an oxidation level of +2, which may be partially replaced by one or more additional metals that are at an oxidation level between +1 and +5 and are less than 35% of the M2 metal, including 0; JO4 is any oxyanion, where J is P, S, V, Si, Nb, Mo, or combinations thereof; E is a fluoride anion, a hydroxide anion, or a chloride anion; f is the mole fraction of the JO4 oxyanion, generally including between 0.75 and 1.

[0122] 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.

[0123] More preferably, the electroactive material of the positive electrode has 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, where J is S, V, Si, Nb, Mo, or combinations thereof. Even more preferably, the electroactive material is a phosphate-based electroactive material having the formula Li(Fe x Mn 1-x )PO4, where 0 ≤ x ≤ 1, preferably x = 1, that is, lithium iron phosphate having the formula LiFePO4.

[0124] In a preferred embodiment, the electroactive material of the positive electrode is selected from the group consisting of: 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); spinel-structured LiMn2O4; lithium-nickel-manganese-cobalt-based metal oxide (NMC) having the formula LiNi x Mn y Co z O2 (x + y + z = 1), lithium-nickel-cobalt-aluminum-based metal oxide (NCA) having the formula LiNi x Co y Al z O2 (x + y + z = 1), lithium-cobalt-based metal oxide (NCO), lithium-nickel-manganese-based metal oxide (LNMO), and LiFePO4.

[0125] In a more preferred embodiment, the electroactive material is for the positive electrode and is selected from the group consisting of NMC, NCA, NCO, and LNMO.

[0126] In the present invention, the term "conductive agent" is intended to specifically refer to a material for ensuring that the electrode has good charge and discharge properties and provides additional conductivity. Non-limiting examples of conductive agents are carbonaceous materials and metal powders or fibers, such as carbon black, carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), graphite, graphene, graphite fibers, etc. Examples of carbon black include Ketjen black and acetylene black. Metal powders or fibers include nickel and aluminum powders or fibers.

[0127] In a specific embodiment, the amount of a) fluoropolymer in the slurry is such as to provide a solid composite electrolyte comprising an amount of the fluoropolymer a) in the range of 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% relative to the total weight of the fluoropolymer a), the sulfide-based solid ion-conducting inorganic particles b), the electroactive material c) and optionally e) at least one conductive agent. Thus, the resulting electrode exhibits excellent adhesion to the current collector.

[0128] A third object of the present invention is an electrode comprising a solid composite electrolyte according to the invention, d) at least one electroactive material, and optionally e) at least one conducting agent.

[0129] In one embodiment, the electroactive material d) is used in a positive electrode.

[0130] In one embodiment, the electrode comprises at least one fluoropolymer according to the present invention, at least one electroactive material for a positive electrode, and at least one sulfide-based solid ion-conducting inorganic particle.

[0131] In a specific embodiment, the positive electrode comprises a VDF-CTFE-HFP terpolymer as a fluoropolymer, Li6PS5Cl as a sulfide-based solid ion-conducting inorganic particle, LiNi as an electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2, and optionally carbon black as a conductive agent.

[0132] In another specific embodiment, the positive electrode comprises a VDF-CTFE-TrFE terpolymer as a fluoropolymer, Li6PS5Cl as a sulfide-based solid ion-conducting inorganic particle, LiNi as an electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2O2, and optionally carbon black as a conductive agent.

[0133] In another specific embodiment, the positive electrode comprises VDF-CTFE-HFP-AA as a fluoropolymer, Li6PS5Cl as a sulfide-based solid ion-conducting inorganic particle, LiNi as an electroactive material for the positive electrode. 0.6 Mn 0.2 Co 0.2 O2, and optionally carbon black as a conductive agent.

[0134] A fourth object of the present invention is a solid-state battery, comprising a positive electrode, a negative electrode and a membrane located between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode and the membrane comprises a solid composite electrolyte according to the present invention, optionally d) at least one electroactive material and / or e) at least one conductive agent.

[0135] In the present invention, the term "membrane" is intended to mean in particular an ion-permeable membrane placed between the positive electrode and the negative electrode. Its function is to allow lithium ions to pass through while blocking electrons and ensuring physical isolation between the electrodes.

[0136] A fifth object of the present invention is a binder solution for solid-state batteries, the binder solution comprising a) at least one fluoropolymer according to the present invention and c) at least one non-aqueous solvent.

[0137] The non-aqueous solvent is as defined in the present invention.

[0138] When the binder solution according to the present invention is used to prepare a solid composite electrolyte, a person skilled in the art can easily select an appropriate amount of c) non-aqueous solvent to achieve uniform dissolution of a) fluoropolymer and proper evaporation thereof. Such a solid composite electrolyte can be used as a membrane between a positive electrode and a negative electrode or as an electrode of a solid-state battery.

[0139] Should the disclosure of any patents, patent applications, and publications incorporated herein by reference conflict with the description of the present application to the extent that it might render a term unclear, the present invention shall take precedence.

[0140] The present invention will now be described in more detail with reference to the following examples, which are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0141] Examples

[0142] raw materials

[0143] - Crystalline sulfide-based solid ion-conducting inorganic particles LPSCl (Li6PS5Cl), commercially available from NEI Corporation;

[0144] -NMC622( NMC KHX12), commercially available from Umicore;

[0145] -Conductive carbon (C-NERGY TM SUPER C65T), commercially available from Imerys;

[0146] - butyl butyrate (BB), commercially available from Sigma Aldrich; and

[0147] - Methyl isobutyl ketone (MIBK), commercially available from Sigma-Aldrich.

[0148] Fluoropolymers:

[0149] -Polymer 1: VDF-CTFE-HFP (80.0 / 10.0 / 10.0 in mol%), synthesized in-house at Solvay Specialty Polymers Italy SpA

[0150] -Polymer 2: VDF-CTFE-HFP (79.0 / 15.0 / 6.0 in mol%), synthesized in-house at Solvay Specialty Polymers Italy

[0151] -Polymer 3: VDF-CTFE-HFP-AA (78.7 / 9.9 / 9.9 / 0.5 in mol%), synthesized in-house at Solvay Specialty Polymers Italy

[0152] - Polymer 4: VDF-CTFE-TrFE (in mol % 63.5 / 7.5 / 29.0), 300, commercially available from Solvay Specialty Polymers Italy

[0153] - Polymer 5: VDF-HFP (in mol % 78.5 / 21.5), N935, commercially available from Solvay Specialty Polymers Italy (T g =-19℃)

[0154] - Polymer 6: VDF-TFE-HFP (in mol % 60.0 / 20.0 / 20.0), T538, commercially available from Solvay Specialty Polymers Italy

[0155] - Polymer 7: VDF-TFE-HFP (in mol % 65.0 / 19.0 / 16.0), TN, commercially available from Solvay Specialty Polymers Italy.

[0156] Synthesis of polymers 1-3

[0157] Polymer 1:

[0158] In a steel vertical autoclave equipped with baffles and a stirrer operating at 550 rpm, 1.3 L of demineralized water were introduced. The temperature was brought to a reaction temperature of 75°C. 4.0×10 5 Pa (absolute pressure) VDF and 3.0×10 5 Pa (absolute pressure) of HFP. A gaseous mixture of VDF-CTFE-HFP with a nominal molar ratio of 80.0 / 10.0 / 10.0 was added by using a compressor until a pressure of 20.0×10 5 The pressure is Pa (absolute pressure).

[0159] Before starting the reaction, the composition of the gaseous mixture present in the head of the autoclave as analyzed by gas chromatography was 72.6 mol% of VDF, 14.2 mol% of CTFE and 13.2 mol% of HFP. 40.0 cc of an ethyl acetate solution (3% w / w) of ammonium persulfate ((NH4)2S2O8) and 2.0 mL of pure ethyl acetate were fed into the autoclave.

[0160] The polymerization pressure was maintained constant until the polymerization was completed. When 200.0 g of the mixture had been fed, the feed was stopped, the reactor was cooled to room temperature and degassed to remove residue. The latex as produced was discharged and further degassed with nitrogen for 24 hours. The resulting polymer was separated by using aluminum sulfate (Al2(SO4)3) using a standard separation procedure, and then dried in a ventilated oven at 90°C for 24 hours.

[0161] Polymer 2:

[0162] Polymer 2 was synthesized in a similar manner to polymer 1. After the introduction of 1.3 L of demineralized water, the temperature was brought to a reaction temperature of 75° C. 3.8×10 5 Pa (absolute pressure) VDF and 4.0×10 5 Pa (absolute pressure) of HFP. A gaseous mixture of VDF-CTFE-HFP with a nominal molar ratio of 79.0 / 15.0 / 6.0 was added by using a compressor until a pressure of 20.0×10 5 The pressure is Pa (absolute pressure).

[0163] Before starting the reaction, the composition of the gaseous mixture present in the head of the autoclave as analyzed by gas chromatography was 78.3 mol% of VDF, 14.6 mol% of CTFE and 7.1 mol% of HFP. 45.0 cc of an ethyl acetate solution of ammonium persulfate (3% w / w) and 3 mL of pure ethyl acetate were fed into the autoclave.

[0164] The polymerization pressure was maintained constant until the polymerization was completed. When 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 the residue. The latex as produced was discharged and further degassed with nitrogen for 24 hours. The resulting polymer was then separated with aluminum sulfate using a standard separation procedure and dried in a ventilated oven at 90 ° C for 24 hours.

[0165] Polymer 3:

[0166] In a steel vertical autoclave equipped with baffles and a stirrer operating at 650 rpm, 1.3 L of demineralized water were introduced. The temperature was brought to a reaction temperature of 80° C. 3.0×10 5 Pa (absolute pressure) VDF and 3.0×10 5 Pa (absolute pressure) of HFP. A gaseous mixture of VDF-CTFE-HFP with a nominal molar ratio of 80.0 / 10.0 / 10.0 was added by using a compressor until a pressure of 26.0×10 5 Pa's pressure.

[0167] Before starting the reaction, the composition of the gaseous mixture present in the head of the autoclave as analyzed by gas chromatography was 72.7 mol% of VDF, 12.9 mol% of CTFE and 14.4 mol% of HFP. 40.0 mL of an ethyl acetate solution of ammonium persulfate (3% w / w) and 5.0 mL of an acrylic acid solution (2% w / w) were fed into the autoclave. 10 mL of an ethyl acetate solution of ammonium persulfate (3% w / w) and 5.0 mL of an acrylic acid solution (2% w / w) were fed into the autoclave for every 20.0 g of polymerization. The polymerization pressure was maintained constant until the end of the polymerization.

[0168] When 200.0 g of the gaseous mixture had been fed, the feed was stopped and the reactor was cooled to room temperature. The latex as produced was discharged and frozen for 48 hours. The resulting polymer was washed with demineralized water after melting and dried in a ventilated oven at 80° C. for 48 hours.

[0169] Preparation of solid composite electrolytes

[0170] Examples 1 and 5 (E1 and E5) of the present invention

[0171] A solid composite electrolyte of E1 composed of 95.0 parts by weight (pbw) of LPSC1 and 5.0 pbw of polymer 1 was produced in film form as follows:

[0172] A 10.0 wt% polymer solution was prepared by weighing 1.0 g of polymer 1 and 9.0 g of BB. Subsequently, 3.705 g of LPSCl, 1.95 g of the 10.0 wt% polymer solution and 0.345 g of BB were mixed with 4 glass balls under magnetic stirring at 400 rpm for a minimum of 6 hours. The solid content of the slurry and the casting speed were adjusted so that the slurry viscosity was maintained between 2.0 and 10.0 Pa.s during casting. The obtained slurry was cast on a flexible support ( FN). The wet film was dried on a hot plate at 50°C for one hour and then placed in an oven under vacuum at 80°C during the night. The samples were stored in mini grip bags and then placed in sealed bags. All experiments were performed in an argon-filled glove box.

[0173] The solid composite electrolyte of E5 was prepared in the same manner as E1, except that MIBK was used instead of BB as the solvent.

[0174] Examples 2 and 6 of the present invention (E2 and E6)

[0175] The solid composite electrolyte of E2 was prepared in the same manner as E1, except that polymer 2 was used instead of polymer 1. The solid composite electrolyte of E6 was prepared in the same manner as E2, except that MIBK was used instead of BB as the solvent.

[0176] Examples 3 and 7 of the present invention (E3 and E7)

[0177] The solid composite electrolyte of E3 was prepared in the same manner as E1, except that polymer 3 was used instead of polymer 1. The solid composite electrolyte of E7 was prepared in the same manner as E3, except that MIBK was used instead of BB as the solvent.

[0178] Example 4 (E4) of the present invention

[0179] The solid composite electrolyte of E4 was prepared in the same manner as E1, except that polymer 4 was used instead of polymer 1.

[0180] Comparative Examples 1-2 (CE1-CE2)

[0181] The solid composite electrolyte of CE1 was prepared in the same manner as E1, except that polymer 5 was used instead of polymer 1. The solid composite electrolyte of CE2 was prepared in the same manner as CE1, except that MIBK was used instead of BB as the solvent.

[0182] Comparative Example 3 (CE3)

[0183] The solid composite electrolyte of CE3 was prepared in the same manner as E1, except that polymer 6 was used instead of polymer 1.

[0184] Comparative Example 4 (CE4)

[0185] The solid composite electrolyte of CE4 was prepared in the same manner as E1, except that polymer 7 was used instead of polymer 1.

[0186] Measurement of cohesive forces in solid composite electrolytes E1-E4, CE1, CE3 and CE4

[0187] A strip of dry, self-supporting solid composite electrolyte was fixed to a rigid Al plate (2.6 cm * 10 cm) using double-sided tape (width 25 mm; thickness 0.24 mm). Using an electric tensile / compression force test bench (ESM303 from Mark-10 Corporation) equipped with a flat circular tip, a second double-sided tape (diameter: 1 cm and thickness: 0.24 mm) fixed to the bottom of the circular tip was pressed to the second surface of the solid composite electrolyte with a force of 200 N for 1 min. In the second step, the tip was removed (pulled off) 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) and part of it remained on the rigid Al support, while the other part remained on the tip connected to the test bench. The force required to separate the membrane into two parts is recorded in Table 1 as the average of 5 independent pull-off measurements. The pull-off test was carried out in a dry room with a dew point of -40°C.

[0188] Measurement of ionic conductivity of solid composite electrolytes E1-E4 and CE1

[0189] The ionic conductivity of the solid composite electrolytes of E1-E4 and CE1 in film form was measured by AC impedance spectroscopy with an in-house developed pressure cell, where the membrane was pressed between two stainless steel electrodes during the impedance measurement. The cross section of the pressure cell is Figure 1 Shown in.

[0190] The impedance spectrum was measured at a pressure of 370 MPa and a temperature of 20° C. AC impedance measurements were performed with a potentiostat (VMP-300, BioLogic Science Instruments SAS, France) in the frequency range of 1000 Hz to 4.7 MHz.

[0191] The Nyquist plot of solid composite electrolytes shows the typical behavior of solid electrolytes (inorganic, polymer or composite materials) with semicircular and Warburg type impedances in the high frequency region and low frequency region, respectively. According to the equivalent circuit R1(R2 / Q2)Q3 (see Figure 2 ) is used to simulate the conductive behavior of the composite electrolyte, where R is the resistance and Q is the constant phase element, where R1 and R2 represent the bulk resistance and grain boundary resistance, respectively, and Q2 and Q3 represent the grain boundary and electrode contributions, respectively.

[0192] The intercept of the semicircle with the real axis at high frequencies is attributed to the bulk resistance (R1), while the intercept with the real axis at low frequencies is attributed to the total resistance of the membrane (R1+R2). This total resistance R is conventionally used to calculate the conductivity of solid composite electrolytes. Therefore, the ionic conductivity σ is obtained using the equation σ=d / (R x A), where d is the thickness of the membrane and A is the area of ​​the stainless steel electrode. The SI unit of ionic conductivity is Siemens / meter (S / m), where S is ohm -1 , and 1 millisiemens / cm (mS / cm) is the decimal part of the SI unit, that is, 1 mS / cm=0.1 S / m. The ionic conductivities of the solid composite electrolytes of E1-E4, CE1, CE4, and CE5 are reported in Table 1.

[0193] Preparation of positive electrodes E1-E7 and CE1-CE4

[0194] The positive electrodes of E1-E4, CE1, CE3 and 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 to 7) were produced as follows:

[0195] A 10.0 wt% binder solution was prepared by weighing 1.0 g of fluoropolymer and 9.0 g of BB. Subsequently, 1.0 g of LPSCl, 0.1 g of conductive carbon, 3.7 g of NMC622 and 2.0 g of 10.0 wt% binder solution were mixed with 4 glass balls under magnetic stirring at 400 rpm for at least 6 hours. The slurry as obtained was cast on an Al current collector using an automatic film applicator from ECO. The solid content and casting speed of the slurry were adjusted so that the slurry viscosity was maintained between 2.0 and 10.0 Pa.s during casting and so as to obtain 25.0 to 30.0 mg / cm 2 The wet film was dried on a hot plate at 50°C for one hour, placed in an oven under vacuum at 80°C during the night, stored in a mini grip bag, and then placed in a sealed bag. The experiments were performed in an argon-filled glove box.

[0196] The cathodes of E5-E7 and CE2 were produced in the same manner as described above, except that MIBK was used instead of BB as the solvent.

[0197] Measurement of the adhesion characteristics of the cathode to the Al current collector (peel test): E1-E7 and CE1-CE4

[0198] The adhesion strength of the positive electrode to the Al current collector is evaluated using a 180° peel test. The electrode strips (2cm*10cm) of the dried electrode are fixed on a rigid Al plate (2.6cm*10cm) with the electrode facing down and the current collector facing up using double-sided tape (width 25mm; thickness 0.24mm). Using an electric tension / compression tester (ESM303, from Mark-10), an angle of 180° is maintained and the Al current collector is peeled off from the electrode at a constant speed of 300mm / min. The force required to remove the Al current collector from the electrode is recorded in Table 1, which is the average value of 3 independent strips generated by 3 independent electrodes using 3 independent slurries with the same composition. The peel test was carried out in a dry room with a dew point of -40°C.

[0199] As shown in Table 1, in all positive electrodes according to the present invention (i.e., E1 to E7), excellent adhesion properties to the Al current collector (distinct from those of CE1 to CE4) were clearly observed while maintaining reasonable ionic conductivity. Although E4 showed relatively low adhesion properties, E4 exhibited the highest ionic conductivity and excellent cohesion. In particular, E3 and E7 showed even better adhesion properties with polymer 3 (VDF-CTFE-HFP-AA) than E1 and E5 with polymer 1 (VEF-CTFE-HFP).

[0200] Table 1

[0201]

[0202]

Claims

1. A solid composite electrolyte comprising: a) at least one fluoropolymer; and b) at least one sulfide-based solid ion-conducting inorganic particle; wherein the fluoropolymer a) comprises repeating units derived from: i) at least 50.0 mol% of vinylidene fluoride (VDF), the mol% being relative to the total moles of repeating units; ii) at least one C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin; and iii) at least one C2-C8 fluoroolefin, wherein i), ii) and iii) are different from each other.

2. The solid composite electrolyte according to claim 1, wherein i) Vinylidene fluoride accounts for at least 60.0 mol%, the mol% being relative to the total moles of the repeating units.

3. The solid composite electrolyte according to claim 1 or 2, wherein: The C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefins ii) 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.

4. The solid composite electrolyte according to any one of claims 1 to 3, wherein The C2-C8 fluoroolefin iii) is selected from the group consisting of: -C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP); - Hydrogen-containing C2-C8 fluoroolefins, such as vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoroisobutylene; - having the formula CH2=CH-R f (per)fluoroalkylethylene, wherein R f is a C1-C6 (per)fluoroalkyl group; -Has the formula CF2=CFOR f (per)fluoroalkyl vinyl ether (PAVE), wherein R f is a C1-C6 (per)fluoroalkyl group; - a (per)fluorooxyalkyl vinyl ether of the formula CF2=CFOX, wherein X is a C1-C ... 12 ((Per)fluoro)oxyalkyl; - (per)fluorodioxole having the formula: Where R f3 , R f4 , R f5 and R f6 are the same as or different from each other and are independently selected from fluorine atoms and C1-C6 (per)fluoroalkyl groups optionally containing at least one oxygen atom; and -Has the formula CFX2=CX2OCF2OR" f (per)fluoromethoxyvinyl ether (MOVE), where R" f is selected from a linear or branched C1-C6 (per)fluoroalkyl group, a C5-C6 cyclic (per)fluoroalkyl group, and a linear or branched C2-C6 (per)fluorooxyalkyl group containing 1 to 3 chain oxygen atoms, and X2 is F or H; preferably, R" f is -CF2CF3(MOVE1), -CF2CF2OCF3(MOVE2), or -CF3(MOVE3), and X2 is F.

5. The solid composite electrolyte according to any one of claims 1 to 4, wherein The fluoropolymer a) further comprises repeating units derived from: - C2-C8 non-fluorinated olefins, such as ethylene, propylene; and / or - a hydrophilic (meth)acrylic monomer having the formula: wherein R1, R2 and R3 are the same or different from each other and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups, and R OH is a hydrogen atom or a C1-C5 hydrocarbon moiety containing at least one hydroxyl group.

6. The solid composite electrolyte according to claim 5, wherein: The hydrophilic (meth)acrylic monomer is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, 2-hydroxypropyl acrylate, hydroxyethylhexyl (meth)acrylate, and combinations thereof.

7. The solid composite electrolyte according to any one of claims 1 to 6, wherein The fluoropolymer a) has a heat of fusion as measured according to ASTM D3418 of less than 5.0 J / g, preferably less than 3.0 J / g, more preferably less than 2.0 J / g.

8. The solid composite electrolyte according to any one of claims 1 to 7, wherein The sulfide-based solid ion-conducting inorganic particles b) are selected from the group consisting of: -Lithium tin phosphide ("LSPS") materials, such as Li 10 SnP2S 12 ; - Lithium phosphosulfide ("LPS") materials, such as glasses, crystals or glass ceramics having the formula: (Li2S) x -(P2S5) y , where x+y=1 and 0≤x≤1; Li7P3S 11 ;Li7PS6;Li4P2S6;Li 9.6 P3S 12 and Li3PS4; -doped LPS, such as Li2CuPS4; Li Li 1+2x Zn 1-x PS4, where 0≤x≤1; Li 3.33 Mg 0.33 P2S6; and Li 4- 3x Sc x P2S6, where 0≤x≤1; -With formula Li x P y S z A lithium phosphorus sulfide oxygen ("LPSO") material of O, wherein 0.33≤x≤0.67, 0.07≤y≤0.2, 0.4≤z≤0.55, 0≤w≤0.15; - Lithium phosphide materials containing X ("LXPS"), where X is Si, Ge, Sn, As, Al, such as Li 10 GeP2S 12 and Li 10 SiP2S 12 ; - lithium phosphorus oxysulfide containing X ("LXPSO"), wherein X is Si, Ge, Sn, As, Al; - lithium silicon sulfide ("LSS") materials; -Lithium boron sulfide materials, such as Li3BS3 and Li2S-B2S3-LiI; -Lithium tin sulfide materials and lithium arsenide materials, such as Li 0.8 Sn 0.8 S2, Li4SnS4, Li 3.833 Sn 0.833 As 0.166 S4, Li3AsS4-Li4SnS4, Ge-substituted Li3AsS4; and -Has the general formula Li a PS b X c A lithium phosphorus sulfide material, wherein X represents at least one halogen element selected from the group consisting of Cl, Br and I or a combination thereof; and 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.

9. A slurry for making a solid composite electrolyte, comprising a) at least one fluoropolymer and b) at least one sulfide-based solid ion-conducting inorganic particle according to any one of claims 1 to 8, and c) at least one non-aqueous solvent.

10. The slurry according to claim 9, wherein The non-aqueous solvent c) is selected from the group consisting of nitrile-containing solvents, ethers, esters, thiols, thioethers, ketones, and tertiary amines, preferably butyl butyrate and / or methyl isobutyl ketone.

11. The slurry according to claim 9 or 10, further comprising d) at least one electroactive material and optionally e) at least one conductive agent.

12. The slurry according to claim 11, wherein The electroactive material d) is for the positive electrode and is selected from the group consisting of: having the formula LiNi x Mn y Co z O2 (x + y + z = 1) based on lithium-nickel-manganese-cobalt metal oxide, having the formula LiNi x Co y Al z O2 (x+y+z=1)-based lithium-nickel-cobalt-aluminum metal oxide, lithium-cobalt metal oxide, and lithium-nickel-manganese metal oxide.

13. An electrode comprising the solid composite electrolyte according to any one of claims 1 to 8, d) at least one electroactive material, and optionally e) at least one conductive agent.

14. A solid-state battery comprising a positive electrode, a negative electrode and a membrane located between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode and the membrane comprises a solid composite electrolyte according to any one of claims 1 to 8, optionally further comprising d) at least one electroactive material and / or e) at least one conductive agent.

15. A binder solution for a solid-state battery comprising a) at least one fluoropolymer and c) at least one non-aqueous solvent, wherein the fluoropolymer a) comprises repeating units derived from: i) at least 50.0 mol % of vinylidene fluoride (VDF), the mol % being relative to the total moles of repeating units; ii) at least one C2-C8 chlorinated and / or brominated and / or iodinated fluoroolefin; and iii) at least one C2-C8 fluoroolefin, wherein i), ii) and iii) are different from each other.

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