Sulfide-based solid composite electrolyte membrane

Abstract

The present invention relates to a method for producing a free-standing solid composite electrolyte membrane, comprising: a) mixing (i) at least one sulfide-based solid, ionically conductive inorganic particle and (ii) at least one tetrafluoroethylene (TFE) (co)polymer to form a paste; and b) calendering or extruding the paste to produce a membrane. The present invention also relates to a free-standing solid composite electrolyte membrane comprising (i) at least one sulfide-based solid, ionically conductive inorganic particle and (ii) at least one TFE (co)polymer, wherein the (ii) at least one TFE (co)polymer is in an amount of 1.0 to 20.0 wt. %, preferably 2.0 to 15.0 wt. %, and more preferably 3.0 to 10.0 wt. %, based on the total weight of the membrane.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority under European Patent Application No. 19195191.2 filed on 3 September 2019, and the entire contents of this application are incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for producing a self-supporting solid composite electrolyte membrane, comprising the steps of a) (i) mixing at least one sulfide-based solid ion-conducting inorganic particle and (ii) at least one tetrafluoroethylene (TFE) polymer to form a paste, and b) calendering or extruding the paste to produce a membrane. The present invention also relates to a self-supporting solid composite electrolyte membrane comprising (i) at least one sulfide-based solid ion-conducting inorganic particle and (ii) at least one TFE polymer, wherein the amount of (ii) at least one TFE polymer is 1.0 to 20.0% by weight, preferably 2.0 to 15.0% by weight, and more preferably 3.0 to 10.0% by weight, based on the total weight of the membrane. [Background technology]

[0003] Lithium-ion batteries have maintained a dominant position in the rechargeable energy storage device market for over 20 years due to their many advantages, including being lightweight, having a moderate energy density, and a good cycle life. Nevertheless, current lithium-ion batteries still suffer from problems with safety and relatively low energy density when it comes to the energy density required for high-power applications such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and grid energy storage. This is due to the presence of the liquid electrolyte, which underlies such drawbacks.

[0004] Conventional lithium-ion batteries primarily use organic carbonate-based liquid electrolytes, which inherently makes them prone to leakage and the generation of flammable volatile gases.

[0005] Therefore, solid-state batteries (SSBs) are considered to be next-generation energy storage devices because they offer a higher energy density and are safer than conventional Li-ion batteries with liquid electrolyte systems. In SSBs, highly flammable liquid electrolytes are replaced by solid electrolytes, substantially eliminating any risk of ignition and / or explosion.

[0006] There are three types of solid electrolytes: (i) solid polymer electrolytes, (ii) inorganic electrolytes, and (iii) composite electrolytes.

[0007] (i) Solid polymer electrolytes exhibit excellent mechanical properties and processability but have the drawback of low ionic conductivity. Prior art polymer-based conductors, such as high molecular weight poly(ethylene oxide) in which Li salts are dissolved, have two main drawbacks. First, due to the crystallinity of the polymer, sufficient conductivity can only be obtained at temperatures above the melting temperature, so its usability is limited to high-temperature applications only. Second, such solid polymer electrolytes are significantly plasticized by incorporating salts, resulting in poor mechanical properties.

[0008] (ii) Inorganic electrolytes exhibit high ionic conductivity but are brittle due to insufficient mechanical properties. Garnet-type Li-ion conductive materials, such as oxide-based inorganic electrolytes like Li7La3Zr2O 12 (LLZO), have the problem of low grain boundary conductivity. This is because Li-ion transport is greatly hindered at the grain boundaries between oxide inorganic particles and at the interfaces between the solid electrolyte and the electrodes. Therefore, these materials rely on a sintering process to fuse the particles and then construct conductive paths. Although only hot pressing has succeeded in shortening the sintering time, this requires special and expensive equipment, which is a major obstacle to mass production on a commercial scale. Furthermore, the possibility of thin film forming by hot pressing has not yet been demonstrated. In contrast, sulfide-based inorganic electrolytes have 10 -4 Scm -1Exhibiting high conductivity exceeding [a certain threshold], the interparticle contact resistance of sulfide particles can be easily eliminated by conventional cold pressing. In particular, neither sintering nor hot pressing is necessarily required. Nevertheless, sulfide-based inorganic electrolytes remain brittle, and the feasibility of forming thin films by cold pressing on a commercial scale has yet to be demonstrated.

[0009] (iii) Composite electrolytes, such as those consisting of sulfide particles dispersed in a polymer matrix, offer the potential to combine the high ionic conductivity of inorganic electrolytes with the excellent mechanical properties and processability of polymers. Therefore, these composite electrolytes are considered to be the most promising solution on an industrial scale.

[0010] While sulfide-based composite electrolytes offer the potential to overcome the shortcomings of other solid electrolytes, particularly (composite) oxide electrolytes, and polymer electrolytes with their interesting ionic conductivity and mechanical properties, several drawbacks of sulfide-based composite electrolytes, such as their high solvent reactivity, remain unconquered.

[0011] In other words, although sulfide-based solid composite electrolytes have been studied as a solution, manipulating / designing the polymer binders and surface chemistry of sulfide-based materials within sulfide-based composite electrolytes has proven to be far more complex than anticipated. This problem stems from the extremely poor solvent compatibility of sulfide-based solid electrolytes, which ultimately limits the choice of binders.

[0012] Therefore, several attempts have been made to overcome the drawbacks of sulfide-based solid composite electrolytes.

[0013] In the Journal of The Electrochemical Society, 164(9) A2075-A2081 (2017) ("Selection of Binder and Solvent for Solution-processed All-Solid-State-Battery"), Lee et al. experimented with various combinations of solvent and binder, using a solid composite electrolyte containing Li3PS4 (75Li2S-25P2S5), nitrile butadiene rubber (NBR) as the binder, and p-xylene as the solvent, at room temperature with a capacitance of approximately 0.4 mScm. -1 We succeeded in achieving the required ionic conductivity.

[0014] To understand the effect of binder type on ionic conductivity, the minimum amount of binder required to obtain a mechanically stable sheet, and the uniformity, density, and flexibility of the resulting solid electrolyte membrane, LSPS (Li) containing various non-conductive binders including polyisobutene (PIB), styrene-butadiene rubber (SBR), poly(methyl methacrylate) (PMMA), poly(ethylene vinyl acetate) (PEVA), and hydrogenated nitrile butadiene rubber (HNBR) is used. 10 SnP2S 12 Composite materials were also tested by Riphaus et al. in the Journal of the Electrochemical Society, 165(16)A3993-A3999 (2018) ("Slurry-based Processing of Solid Electrolytes: A comparative Binder Study"). As a result, they concluded that the ionic conductivity is affected to varying degrees by the amount of binder, depending on the binder distribution pattern. Generally, the ionic pathways are increasingly restricted by the binder content, so the lower the weight fraction of the binder, the higher the ionic conductivity. However, this is only true if there is enough polymer as a binder to ensure proper adhesion between the particles of the solid electrolyte. In particular, Riphaus et al. focused only on slurry-based processing of sulfide-based composite electrolytes.

[0015] U.S. Patent No. 9,300,011 B2 (Toyota Jidosha Kabushiki Kaisha) discloses a solid electrolyte layer comprising a sulfide electrolyte material produced from Li2S and P2S5, having crosslinked sulfur of S3P-S-PS3 units of 10 mol% or less, and a hydrophobic polymer as a binder, particularly a hydrocarbon-based polymer such as SBR or styrene-ethylene-butadiene rubber (SEBR). The purpose is to obtain a sulfide-based solid composite electrolyte in which an increase in resistance due to deterioration of the sulfide material is suppressed. Further, this also focuses on slurry-based processing of only the solid electrolyte.

[0016] Therefore, prior art sulfide-based solid composite electrolytes are mainly produced by a wet casting process, in which solid ion-conductive inorganic particles are placed in a solution of a binder and a solvent to form a slurry, which is then cast onto a support and then dried to remove the solvent. Usually, such a wet process requires a large amount of solvent to produce the slurry, and as a result, evaporation of the solvent and its recycling ultimately lead to complex processing and a significant increase in manufacturing costs. In addition to these problems, there is another difficulty in finding a solvent that is compatible with both the sulfide material and the polymer binder in the sulfide-based composite electrolyte.

[0017] Therefore, there is a continuing need in this field for a method of manufacturing a sulfide-based composite electrolyte using a minimum amount of solvent and even without the presence of a solvent.

[0018] Inada et al. in Solid State Ionics, 158(2003)275 - 280 (“Fabrication and properties of composite solid-state electrolytes”), as ionic conductive inorganic particles, thio-LISICON (lithium germanium thiophosphate, Li 3.25 Ge 0.25 P 0.75A composite inorganic solid electrolyte containing S4) and an SBR copolymer as a polymeric binder is manufactured by dry and wet processes, and the composite inorganic solid electrolyte containing SBR manufactured by the dry process is manufactured by the wet process (0.35·10- 4 Scm -1 Higher conductivity (5.74·10) than those manufactured by ) -4 Scm -1 This demonstrates that the granular domain structure of the polymer formed during the dry process is better suited to having higher ionic conductivity. However, the dry process used in this literature still has drawbacks when it comes to the mass production of large, thin solid electrolyte membranes required for batteries.

[0019] Fluorinated polymers, such as vinylidene difluoride (VDF) polymers, are used as binders due to their excellent oxidation resistance and are mainly utilized in cathode formulations in lithium-ion batteries. Although some reports suggest the use of fluorinated binders in sulfide composite materials, typical fluorinated binders are difficult to solubilize in solvents compatible with sulfide materials.

[0020] Due to its insolubility, TFE polymers are typically processed into pastes at temperatures several degrees above room temperature (35-55°C) using techniques such as calendering and cold extrusion. By adding shear during calendering and cold extrusion, TFE polymer particles are fibrillated, forming a three-dimensional (3-D) structure consisting of nodes, fibrils interconnecting the nodes, and free space between the fibrils and nodes. Furthermore, TFE polymers are compatible with sulfide-based solid ion-conducting inorganic particles and exhibit excellent resistance to oxidation in solid composite electrolytes.

[0021] U.S. Patent Publication 2014 / 0238576A1 (Linda Zhong) describes a dry process for manufacturing electrodes, particularly cathodes, by utilizing the fibrillation feature of TFE polymers. However, this dry process, among other solutions, failed to solve the problem of requiring a large amount of binder to support other particles and form an electrode film, thereby producing an electrode with sufficient density. The large amount of binder blocks the surface area of ​​the active material, further reducing the energy density of the battery, and this can also block the flow of electricity between active material particles. As a result, the resistance between particles increases, and the energy density of the battery decreases. Consequently, U.S. Patent Publication 2014 / 0238576A1 ultimately claimed a wet process, rather than a dry process, for manufacturing electrodes.

[0022] In recent years, Hippauf et al., in *Energy Storage Materials* (available online as of May 24, 2019) ("Overcoming binder limitations of sheet-type solid-state cathodes using a solvent-free dry-film approach"), demonstrated the production of solid cathodes using a dry process that minimizes the amount of binder while replacing the slurry-based binder with a TFE polymer. They also describe the production of a "self-supporting" solid electrolyte membrane with a binder content of 0.30 wt% using the same process. While lowering the binder content certainly increases ionic conductivity, the mechanical properties of the resulting membrane are too low to obtain a thin, self-supporting membrane, making such membranes impractical. Furthermore, because the paste is too hard to process, Hippauf et al. were unable to increase the PTFE content beyond 1 wt% in the process to improve the mechanical properties of the resulting membrane.

[0023] Therefore, in this field, there is a continuing need for dry processes to produce thinner, self-supporting sulfide-based solid composite electrolyte membranes while maintaining the processability, high ionic conductivity, and excellent mechanical properties of TFE polymers. [Overview of the project]

[0024] The first object of the present invention is, a) A step of mixing (i) at least one sulfide-based solid ion-conducting inorganic particles and (ii) at least one tetrafluoroethylene (TFE) polymer to form a paste, and b) A process of manufacturing a film by calendering or extruding the paste, A method for producing a self-supporting solid composite electrolyte membrane, comprising: The present invention provides a method in which step a) mixing comprises a1) homogenizing a mixture of (i) at least one sulfide-based solid ion-conducting inorganic particles and (ii) at least one TFE polymer into a powder, and a2) blending the powders into a paste.

[0025] A second object of the present invention is a self-supporting solid composite electrolyte membrane comprising (i) at least one sulfide-based solid ion-conducting inorganic particle and (ii) at least one TFE polymer, wherein (ii) the amount of the at least one TFE polymer is 1.0 to 20.0% by weight, preferably 2.0 to 15.0% by weight, and more preferably 3.0 to 10.0% by weight, based on the total weight of the membrane.

[0026] A third object of the present invention is a solid-state battery comprising the self-supporting solid composite electrolyte membrane described above.

[0027] A fourth object of the present invention is the use of the above-described self-supporting solid composite electrolyte membrane in a solid-state battery to improve ionic conductivity and mechanical properties.

[0028] Surprisingly, the inventors have discovered that the method for producing a self-supporting solid composite electrolyte membrane according to the present invention can provide a thin, self-supporting membrane with excellent processability without necessarily requiring the presence of a solvent. In addition, the self-supporting solid composite electrolyte membrane according to the present invention provides a particularly advantageous combination of properties, such as excellent ionic conductivity and mechanical properties. [Brief explanation of the drawing]

[0029] [Figure 1] This is a cross-sectional view of a pressure cell for AC impedance spectroscopy developed in Solvay to measure the ionic conductivity of a film. In the pressure cell, the film is pressed between two stainless steel electrodes during impedance measurement. [Modes for carrying out the invention]

[0030] definition Throughout this specification, unless the context requires otherwise, the words “comprise” or “include” or variations thereof, such as “comprises,” “comprising,” “includes,” and “including,” are understood to mean that they encompass the steps or groups of steps of the element or method described, but do not exclude any other steps or groups of steps of the element or method. In a preferred embodiment, the words “comprise” and “include,” and variations thereof, mean “consisting of only.”

[0031] As used herein, the singular forms "a," "an," and "the" include their plural forms unless the context explicitly indicates otherwise. The term "and / or" encompasses the meanings of "and" and "or," as well as all other possible combinations of elements related to this term.

[0032] The term "between ~ and ~" should be understood to include the boundary point.

[0033] The “alkyl” group as used herein includes saturated hydrocarbons having one or more carbon atoms, including linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl; cyclic alkyl groups (or “cycloalkyl,” “alicyclic,” or “carbocyclic” groups) 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 groups and cycloalkyl-substituted alkyl groups.

[0034] The term "aliphatic group" refers to organic moieties that typically have between 1 and 18 carbon atoms and are characterized by a straight or branched chain. In complex structures, the chain may be branched, cross-linked, or otherwise bridging. Aliphatic groups include alkyl groups, alkenyl groups, and alkynyl groups.

[0035] The term "(Cn~Cm)" used herein, which refers to organic groups where n and m are integers, indicates that the group may contain between n and m carbon atoms per group.

[0036] Ratios, concentrations, quantities, and other numerical data may be expressed in range form as herein. Such range forms are used solely for convenience and brevity and should be understood to be interpreted flexibly to include not only the numerical values ​​explicitly listed as limits of the range, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were explicitly listed. For example, a temperature range of approximately 120°C to approximately 150°C should be interpreted to include not only the explicitly listed limit of approximately 120°C to approximately 150°C, but also subranges such as 125°C to 145°C, 130°C to 150°C, and individual quantities within specified ranges, such as small quantities, such as 122.2°C, 140.6°C, and 141.3°C.

[0037] The method for producing a self-supporting solid composite electrolyte membrane and the components of the self-supporting solid composite electrolyte membrane according to the present invention will be described in detail below. It should be understood that both the above summary and the following detailed description are illustrative and intended to provide a further explanation of the claimed invention. Accordingly, the various variations and modifications described herein will be obvious to those skilled in the art. Furthermore, for clarity and brevity, well-known descriptions of functions and structures may be omitted.

[0038] The present invention a) A step of mixing (i) at least one sulfide-based solid ion-conducting inorganic particle and (ii) at least one tetrafluoroethylene (TFE)(co)polymer to form a paste, and b) A process of manufacturing a film by calendering or extruding the paste, A method for producing a self-supporting solid composite electrolyte membrane, comprising: The present invention provides a method in which step a) mixing comprises a1) homogenizing (i) at least one sulfide-based solid ion-conducting inorganic particle and (ii) at least one TFE(co)polymer to form a powder, and a2) blending the powders to form a paste.

[0039] In the present invention, the term "self-supporting solid composite electrolyte membrane" refers to a lithium-ion conductive composite material membrane that has a self-supporting shape at room temperature without a support and can be in the form of a foldable and flexible self-supporting membrane. The solid composite electrolyte membrane according to the present invention does not flow to take the shape of its container, nor does it expand to fill the entire available volume. On the other hand, the solid composite electrolyte according to the present invention can be molded in various ways due to its flexibility and can therefore accommodate any changes in volume or shape that may occur during charging and discharging of a lithium battery.

[0040] In this invention, the term "paste" refers to a non-flowing, dry or wet pseudoplastic solid that can be molded into various shapes when sufficient stress is applied.

[0041] Sulfide-based solid ion-conducting inorganic particles In the present invention, the term "sulfide-based solid ion-conducting inorganic particles" is not particularly limited, as long as it is a solid electrolyte material containing sulfur atoms in its molecular structure or composition.

[0042] The sulfide-based solid ion-conducting inorganic particles preferably contain Li, X (where X is P, Si, Sn, Ge, Al, As, or B) and S to enhance Li ion conductivity.

[0043] The sulfide-based solid ion-conducting inorganic particles according to the present invention are more preferably selected from the group consisting of the following: - Li 10 SnP2S 12 Lithium tin sulfide ("LSPS") materials such as; - Formula (Li2S) x -(P2S5) y (x+y=1 and 0≦x≦1), Li7P3S 11 Li7PS6, Li4P2S6, Li 9.6 P3S 12 , and lithium phosphate sulfide ("LPS") materials such as glass, crystal, or glass ceramics of Li3PS4; - Li2CuPS4, Li Li 1+2x Zn 1-x PS4 (0 ≤ x ≤ 1), Li 3.33 Mg 0.33 P2S6 and Li 4-3x Sc x Doped LPS such as P2S6 (0≦x≦1); - Formula Li x P y S z Lithium phosphorus sulfide oxygen ("LPSO") material with O(0.33≦x≦0.67, 0.07≦y≦0.2, 0.4≦z≦0.55); - Li 10 GeP2S 12 and Li 10 SiP2S 12Lithium phosphide materials containing X such as Si, Ge, Sn, As, or Al ("LXPS"); - Lithium phosphide oxygen ("LXPSO") containing X, where X is Si, Ge, Sn, As, or Al; - Lithium silicon sulfide ("LSS") materials; - Lithium borosilicate materials such as Li3BS3 and Li2S-B2S3-LiI; - Li 0.8 Sn 0.8 S 2、 Li4SnS4, Li 3.833 Sn 0.833 As 0.166 S4, Li3AsS4-Li4SnS 4、 Lithium tin sulfide materials and lithium arsenide materials such as Ge-substituted Li3AsS4; and - Silver-germanium ore-type sulfide materials of the formula Li6PS5Y (where Y is Cl, Br, or I), this compound may be deficient in sulfur, lithium, or halogen (e.g., Li6-xPS5-xCl 1+x (0 ≤ x ≤ 0.5)), or heteroatoms may be doped.

[0044] Particularly preferred sulfide solid electrolytes are lithium tin-phosphorus sulfide ("LSPS") materials (e.g., Li 10 SnP2S 12 ) and silver-germanium ore-type sulfide materials (e.g., Li6PS5Cl)).

[0045] TFE(copolymer) The TFE(co)polymer according to the present invention is a TFE (tetrafluoroethylene) homopolymer, a TFE copolymer comprising repeating units of a TFE monomer and repeating units different from the TFE monomer, or a blend thereof.

[0046] The TFE copolymer according to the present invention is distinct from melt-processable TFE copolymers and is typically intended to represent a TFE copolymer modified with a small amount of repeating units different from the TFE monomer, while maintaining the intrinsic fibrillation properties of the resulting TFE copolymer.

[0047] A useful criterion for distinguishing the TFE copolymer according to the present invention from melt-processable TFE copolymers is the amorphous index (AI), particularly as described by Remoynihan in the Journal of the American Chemical Society, 1959, vol. 81, pp. 1045-1050 ("The Molecular Structure of Perfluorocarbon Polymers: Infrared Studies on Polytetrafluoroethylene"). Approximately 778 cm² -1 The intensity of the IR absorption band centered around and approximately 2367 cm -1 The ratio of the intensity of another IR absorption band, centered around , has been shown to correlate appropriately and reliably with the proportion of amorphous phase in the TFE copolymer. In other words, this IR intensity ratio has been found to be directly proportional to the content of conformational disorder in the polymer chains.

[0048] The TFE copolymer of the present invention may comprise repeating units of a TFE monomer and repeating units different from the TFE monomer, such as repeating units derived from a per(halo)fluoroolefin. A per(halo)fluoroolefin is an ethylenically unsaturated fluorinated olefin that does not contain hydrogen atoms and may contain one or more halogen atoms other than fluorine, particularly chlorine or bromine. Preferably, the per(halo)fluoroolefin monomer is a C3-C8 perfluoroolefin such as hexafluoropropylene.

[0049] In certain embodiments, the TFE copolymer contains at least one repeating unit derived from a per(halo)fluoroolefin different from the TFE monomer in an amount of 0.01 to 0.25 mol%, preferably 0.05 to 0.175 mol%, relative to the total number of moles of repeating units of the TFE copolymer.

[0050] In preferred embodiments, the at least one per(halo)fluoroolefin, distinct from the TFE monomer, is hexafluoropropylene.

[0051] In another specific embodiment, the TFE copolymer is present in an amount of 0.005 to 0.025 mol% relative to the total number of moles of repeating units of the TFE copolymer, as given by the formula CF2 = CF - OR f (In the formula, R f It contains repeating units derived from at least one perfluoro(oxy)alkyl vinyl ether (which is a C1-C6 perfluoroalkyl and may contain one or more etheric oxygen atoms).

[0052] In another preferred embodiment, at least one perfluoro(oxy)alkyl vinyl ether is a perfluoropropyl vinyl ether.

[0053] In one embodiment, (ii) at least one TFE(co)polymer is determined by infrared spectroscopy and is approximately 778 cm⁻¹ -1 The intensity of the wavelength band centered around and approximately 2367 cm -1 It has an AI of 0.22 or less, preferably 0.017 or less, and more preferably 0.012 or less, which is defined as the ratio between the intensity of the wavelength band centered on .

[0054] In reality, for compressed tablets of TFE copolymer manufactured under a press of approximately 10 tons of pressure, 4000-400 cm -1 FT-IR analysis is performed using a spectrophotometer with a spectral range of approximately 778 cm². -1 (OD 778 The optical density or intensity of the absorption band centered at ) is determined, and 2367 cm⁻¹ is determined. -1 (OD 2367It is normalized to the optical density of the composite band centered on ). As a result, the AI ​​is determined as follows: AI=(OD 778 ) / (OD 2367 ).

[0055] Among the repeating units suitable as comonomers in TFE copolymers, the following can be listed: - C3-C8 perfluoroolefins, such as hexafluoropropene (HFP) and hexafluoroisobutene; - Equation CF2 = CF - OR f perfluoroalkyl vinyl ether (wherein R f These are C1-C3 perfluoroalkyls (selected from, for example, -CF3, -C2F5, or -C3F7), i.e., perfluoromethyl vinyl ether (formula CF2=CFOCF3), perfluoroethyl vinyl ether (formula CF2=CFOC2F5), perfluoropropyl vinyl ether (formula CF2=CFOC3F7), and mixtures thereof; - Perfluoro(oxy)alkyl vinyl ether of the formula CF2=CF-OX (wherein X is a C1-C having one or more ether groups) 12 (It is a perfluoro(oxy)alkyl), for example, formula CF2 = CF-O-CF 2- Ure f1 perfluoromethoxyvinyl ether (wherein R f1 is a linear or branched C1-C6 perfluoroalkyl group, a cyclic C5-C6 perfluoroalkyl group, or a linear or branched C2-C6 perfluorooxyalkyl group, preferably R f1 -CF 3、 -CF2CF3 or CF2CF2OCF3), for example, perfluoropropyl vinyl ether; and - The following formula: [ka] (In the formula, X1 and X2 are equal to or different from each other, and are selected from F and CF3, preferably F.) Perfluorodioxole containing [a specific characteristic].

[0056] The TFE(co)polymer according to the present invention has two transition temperatures at approximately 19°C and 30°C. Below 19°C, TFE(co)polymer particles easily pass through each other while maintaining their identity. However, above 19°C, the structure of the TFE(co)polymer particles loosens, and especially above the transition temperature of 19°C, they become more susceptible to mechanical shear. Therefore, shear unravels the crystalline structure of the TFE polymer and initiates a so-called fibrillation phenomenon, that is, it can form a 3D structure consisting of nodes, fibrils interconnecting the nodes, and free space between the fibrils and nodes. Fibrillation occurs when particles rub against a surface, and fibrils are drawn out from the surface of the TFE(co)polymer particles. At temperatures above 30°C, a more advanced fibrillation continues.

[0057] In certain embodiments, a1) homogenization is carried out at a temperature of 19°C or lower, preferably 10°C to 19°C.

[0058] In another specific embodiment, a2) the blending is carried out at a temperature of 30°C or higher, preferably 30°C to 150°C, more preferably 35°C to 120°C, and even more preferably 40°C to 80°C.

[0059] In one embodiment, step b) calendering or extrusion is carried out at a temperature of 30°C to 150°C, preferably 35°C to 120°C, and more preferably 40°C to 100°C.

[0060] In the present invention, in order to form a paste, (iii) at least one lubricant may be additionally present in step a). Examples of the at least one lubricant, but are not limited to, aliphatic hydrocarbons, particularly isoparaffinic hydrocarbon compounds and petroleum fractions, more specifically squalene. Preferred petroleum fractions include gasoline (C4-C4). 10 ), naphtha (C4~C 11 ), and petroleum / paraffin (C 10 ~C16 ), as well as mixtures thereof.

[0061] In a preferred embodiment, (iii) at least one lubricant is selected from the group consisting of isoparaffinic hydrocarbon compounds and petroleum fractions.

[0062] In a more preferred embodiment, (iii) at least one lubricant is squalene.

[0063] According to one embodiment, (iii) the amount of at least one lubricant is 5.0 to 35.0 parts by weight (pbw), preferably 10.0 to 30.0 pbw, more preferably 15.0 to 25.0 pbw, based on the total weight of the mixture of (i) at least one sulfide-based solid ion-conducting inorganic particles, (ii) at least one TFE(co)polymer, and (iii) at least one lubricant.

[0064] A second object of the present invention is a self-supporting solid composite electrolyte membrane comprising (i) at least one sulfide-based solid ion-conducting inorganic particles and (ii) at least one TFE(co)polymer in an amount of 1.0 to 20.0% by weight, preferably 2.0 to 15.0% by weight, and more preferably 3.0 to 10.0% by weight, based on the total weight of the membrane.

[0065] In one embodiment, (ii) at least one TFE(co)polymer has a three-dimensional (3-D) structure consisting of nodes, fibrils interconnecting the nodes, and free space between the fibrils and nodes, and (i) at least one sulfide-based solid ion-conducting inorganic particle is disposed inside the free space of the self-supporting solid composite electrolyte membrane according to the present invention.

[0066] In certain embodiments, the thickness of the self-supporting solid composite electrolyte membrane according to the present invention is 10 to 150 μm, preferably 15 to 100 μm, and more preferably 20 to 60 μm.

[0067] A third object of the present invention relates to a solid-state battery comprising the self-supporting solid composite electrolyte membrane of the present invention as detailed above. The solid-state battery of the present invention comprises a positive electrode and a negative electrode.

[0068] A further object of the present invention is the use of the above-described self-supporting solid composite electrolyte membrane in a solid-state battery to improve ionic conductivity and mechanical properties.

[0069] If any disclosure of a patent, patent application, or publication incorporated herein by reference contradicts the description of this application to such an extent that it obscures the terminology, the description herein shall prevail.

[0070] The present invention will now be described in more detail with reference to the following embodiments, but the purpose of these embodiments is merely illustrative and not to limit the scope of the invention. [Examples]

[0071] raw materials Sulfide-based solid inorganic particles: - LSPS(Li 10 SnP2S 12 (NANOMYTE® SSE-10, commercially available from NEI Corporation) - LPSCl (Li6PS5Cl), commercially available from NEI Corporation) TFE(co)polymer: Algoflon® DF132F (TFE homopolymer) and Algoflon® DF681F (TFE copolymer) (both available from Solvay Specialty Polymers Italy SpA) SEBS: Tuftec (trademark) N504 (available from Asahi Kasei Chemicals Corporation) Lubricants: Squalene (available from Sigma Aldrich) and Isopar® K (available from ExxonMobil Chemical)

[0072] Ionic conductivity The ionic conductivity of the film was measured by AC impedance spectroscopy using a pressure cell developed in-house. During the measurement, the film was pressed between two stainless steel electrodes. A cross-sectional view of the pressure cell is shown in Figure 1.

[0073] The impedance spectrum of the solid composite electrolyte according to Example 1 was determined at a pressure of 83 MPa and a temperature of 20°C.

[0074] The resistance R of the solid composite electrolyte membrane was obtained by extrapolating the quasi-linear portion of the low-frequency diffusion tail of the impedance spectrum (using a linear model). The resistance R was considered to be the point where the extrapolated curve intersects the x-axis. Based on this, the ionic conductivity σ was obtained using the formula σ = d / (R × A), where d is the membrane thickness and A is the area of ​​the stainless steel electrode.

[0075] The SI unit for ionic conductivity is siemens per meter (S / m), where S is ohms. -1 That is the case.

[0076] Mechanical properties Mechanical properties were evaluated visually in a certain manner, namely whether the film i) is self-supporting without a support, ii) is flexible, i.e., can be repeatedly bent without breakage or crack formation, and iii) has mechanical resistance to deformation. This means that it must be able to withstand the physical stresses of the pressing / calendering process, which will reduce the film thickness / porosity, and must also be compatible with roll-to-roll or stacking processes.

[0077] Comparative example 1 (Comp.Ex1): 3 g (99.85 wt%) of LSPS and 4.5 mg (0.15 wt%) of Algoflon® DF132F were homogenized at 15°C to form a powder, which was then blended at 60°C to form a paste. Due to the small amount of TFE polymer, obtaining the paste was extremely difficult. Furthermore, the resulting paste was very brittle and difficult to handle. As a result, the tensile strength of this paste was too low for calendering to produce thin films, hindering the industrialization of the process and the practical application of the resulting composite electrolyte membrane.

[0078] Comparative example 2 (Comp.Ex2): Comp.Ex2 was manufactured using the same method as Comp.1, except that the amounts of LSPS (3g, 99.7 wt%) and Algoflon® DF132F (9mg, 0.30 wt%) differed. Due to the small amount of TFE polymer, obtaining the paste was difficult. Furthermore, the resulting paste was very brittle and difficult to handle. As a result, the tensile strength of this paste was too low for calendering to produce thin films, hindering the industrialization of the process and the practical application of the resulting composite electrolyte membrane.

[0079] Comparative example 3 (Comp.Ex3): Comp.Ex3 was prepared in the same manner as Comp.Ex1, except that LPSCl was used instead of LSPS. Therefore, the amounts of LPSCl and TFE polymer were adjusted, namely 3 g (99.7 wt%) of LPSCl and 9 mg (0.30 wt%) of Algoflon® DF132F.

[0080] Comparative example 4 (Comp.Ex4): A polymer solution was prepared by dissolving 0.1 g (3 wt%) of SEBS in 2.5 g of xylene. 3.233 g (97 wt%) of LSPS was added to the polymer solution. The resulting slurry solution was cast onto a Teflon support and dried at 50°C. Complete solvent removal was ensured by vacuum drying at 80°C. A self-supporting film was obtained.

[0081] Comparative Examples 5~9 (Comp.Ex5~9): Comps 5-9 were prepared in the same manner as Comp.Ex4, except that the amounts of LSPS and SEBS differed. The compositions, along with their ionic conductivity and mechanical properties, are listed in Table 1 below.

[0082] [Table 1]

[0083] Example 1: 3.0 g (99.0 wt%) of LSPS and 30 mg (1.0 wt%) of Algoflon® DF132F were homogenized at 15°C to form a powder, which was then blended at 60°C to form a paste. The resulting paste was calendered at 40°C to form a self-supporting film. Although the resulting film did not exhibit excellent tensile strength, it was sufficient for further calendering to produce a 30 μm thin film.

[0084] Examples 2-7 Ex2-7 were manufactured in the same manner as Ex1, except that the amounts of LSPS and Algoflon® DF132F were varied to cover a TFE polymer content of 1.0-20.0% by weight. The self-supporting films obtained from Ex2-7 in this manner showed good tensile strength, and could be easily calendered to reduce their thickness to 30 μm.

[0085] A significant improvement in mechanical properties was observed as soon as the TFE polymer content reached 3.0 wt% (Ex2). When the TFE polymer content reached 10.0 wt% (Ex5), the paste became harder, requiring more shear to calender the paste into a thin film. Therefore, it was anticipated that when the TFE polymer content exceeded 10.0 wt%, the resulting paste would be extremely hard, requiring considerable force for calendering.

[0086] As the TFE polymer content increased to 10.0 wt%, the ionic conductivity of the resulting membrane continued to decrease. More precisely, excellent ionic conductivity was maintained at levels above 0.3 mS / cm up to a maximum of 10.0 wt% (Ex5). However, at even higher TFE polymer content (Ex6 and Ex7), certain signs of charge transfer resistance appeared in the corresponding impedance curves. Nevertheless, the ionic conductivity did not decrease significantly. Even with 20.0 wt% TFE polymer (Ex7), the resulting composite electrolyte membrane exhibited an ionic conductivity of approximately 0.1 mS / cm.

[0087] Examples 8-13: Ex8-13 were prepared in the same manner as Ex2-7, except that LPSCl was used instead of LSPS. Therefore, the amounts of LPSCl and TFE polymer were adjusted. The self-supporting films obtained from Ex8-13 in this way showed good tensile strength and could be easily calendered to reduce the thickness to 30 μm.

[0088] Example 14: 3 g (95.0 wt%) of LSPS and 0.16 g (5 wt%) of TFE polymer were homogenized at 15°C to form a powder. Subsequently, 0.89 g (22 pbw relative to the total weight of the mixture of LSPS, TFE polymer, and squalene) of squalene was blended with the powder and a paste was formed at 60°C. The resulting paste was calendered at 40°C to form a self-supporting film, and then the squalene was removed by vacuum drying.

[0089] Example 15 Ex15 was manufactured in the same manner as Ex14, except that LPSCl was used instead of LSPS.

[0090] Example 16 3 g (95.0 wt%) of LSPS and 0.16 g (5 wt%) of TFE polymer were homogenized at 15°C to form a powder. Subsequently, 1.7 g (35 pbw relative to the total weight of the mixture of LSPS, TFE polymer, and Isopar® K) was blended with the powder and a paste was formed at 60°C. The resulting paste was calendered at 40°C to form a self-supporting film, and then Isopar® K was removed by vacuum drying.

[0091] The addition of a lubricant promoted fibrillation, and the resulting self-supporting film exhibited excellent flexibility and good tensile strength. No significant change in ionic conductivity was observed compared to films produced without a lubricant (both Ex3 and Ex9 contained 5.0 wt% TFE polymer).

[0092] Examples 17-18 Ex17-18 were manufactured in the same manner as Ex2-3, except that Algoflon® DF681F was used instead of Algoflon® DF132F. The self-supporting films obtained in this way showed good tensile strength, and could be easily calendered to reduce the thickness to 30 μm.

[0093] All compositions of the obtained composite material films Ex1-18 are listed in Table 2 below, along with their ionic conductivity and mechanical properties.

[0094] [Table 2]

[0095] [Table 3]

[0096] All experiments were conducted under protected conditions (Ar).

Claims

1. a) A step of mixing (i) sulfide-based solid ion-conducting inorganic particles and (ii) tetrafluoroethylene (TFE) polymer or TFE copolymer to form a paste, and b) A process of manufacturing a film by calendering the paste, A method for producing a self-supporting solid composite electrolyte membrane, comprising: Step a) involves mixing a1) (i) homogenizing the mixture of sulfide-based solid ion-conducting inorganic particles and (ii) the TFE polymer or TFE copolymer to form a powder, and a2) blending the powder to form a paste. The homogenization in a1) is carried out at a temperature of 19°C or lower, and the blending in a2) is carried out at a temperature of 30°C or higher. The calendering process in step b) is carried out at a temperature of 30°C to 150°C. (ii) The amount of the TFE polymer or the TFE copolymer is 3.0 to 10.0% by weight relative to the total weight of the mixture. A method in which the sulfide-based solid ion-conducting inorganic particles are selected from silver-germanium ore-type Li₆PS₅X (X = Cl or Br), Li₁₀SnP₂S₁₂, and Li₁₀GeP₂S₁₂.

2. The method according to claim 1, wherein at least one lubricant (iii) is added to the blend of a2) in order to form a paste.

3. c) The method according to claim 2, further comprising the step of drying the film obtained from step b) to remove the lubricant.

4. (ii) The method according to any one of claims 1 to 3, wherein the amount of the TFE polymer or TFE copolymer is 3.0 to 7.5% by weight relative to the total weight of the mixture.

5. (ii) The method according to any one of claims 1 to 4, wherein the TFE copolymer contains repeating units derived from at least one per(halo)fluoroolefin different from the TFE monomer in an amount of 0.01 to 0.25 mol% with respect to the total moles of the repeating units of the TFE copolymer.

6. The method according to claim 5, wherein the at least one per(halo)fluoroolefin, which is different from the TFE monomer, is hexafluoropropylene.

7. (i) The sulfide-based solid ion-conducting inorganic particles are Li ６ PS5 Cl or Li １０ SnP ２ S １２ The method according to any one of claims 1 to 6.

8. (iii) The method according to claim 2 or 3, wherein the at least one lubricant is selected from the group consisting of isoparaffinic hydrocarbon compounds and petroleum fractions.

9. The method according to any one of claims 2, 3, and 8, wherein the amount of the at least one lubricant is 5.0 to 35.0 parts by weight (pbw) with respect to the total weight of the mixture of (i) the sulfide-based solid ion-conducting inorganic particles, (ii) the TFE polymer or TFE copolymer, and (iii) the at least one lubricant.

10. A self-supporting solid composite electrolyte membrane manufactured by the method described in any one of Claims 1 to 9.

11. The self-supporting solid composite electrolyte membrane according to claim 10, wherein the thickness of the membrane is 10 to 150 μm.

12. A solid-state battery comprising a self-supporting solid composite electrolyte membrane according to any one of claims 10 or 11.

13. Use of a self-supporting solid composite electrolyte membrane according to claim 10 or 11 in a solid-state battery for improving ionic conductivity and mechanical properties.

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