Electrolyte separator for solid state batteries

Abstract

A solid electrolyte separator for an electrochemical storage device is described. The solid electrolyte separator includes an electrolyte containing a lithium ion conductive compound and a binder containing a copolymer. The lithium ion conductive compound includes sulfur, and the copolymer has repeating units containing a carboxylic acid group or its conjugate base. A masterbatch product, a method for producing the solid electrolyte separator, and an electrochemical storage device are also described.

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte separator for an electrochemical storage device. The present invention also relates to a masterbatch product, a method for producing a solid electrolyte separator, and an electrochemical storage device having a solid electrolyte separator. [Background technology]

[0002] The future of electric transportation depends on novel battery chemistries that offer higher energy density and lower cost than prior art lithium-ion batteries. Lithium-sulfur batteries (LiSBs) offer high theoretical capacity (1675 mAh g -1 ), making them one of the most promising candidates due to the abundance of sulfur in the Earth's crust. Despite decades of research and development, widespread use of LiSBs has been hindered by rapid capacity fade caused by the polysulfide shuttle effect, as well as lithium metal precipitation and low stripping efficiency.

[0003] Replacing liquid electrolytes with solid electrolytes is the most promising approach to addressing these issues. Various materials have been investigated for potential use as solid electrolytes, each with its own unique advantages and disadvantages. Among these, polymers are easily processable, provide good interfacial contact with the active material, and suppress polysulfide shuttles. However, their practical application is severely limited by their limited ionic conductivity, narrow electrochemical stability range, and insufficient mechanical strength, which prevents lithium filament growth. On the other hand, inorganic ceramics possess sufficient electrochemical and mechanical properties to suppress both polysulfide shuttles and dendrites. Sulfide-based solid electrolytes are particularly promising because they are compatible with sulfur cathodes, exhibit excellent lithium-ion conductivity at room temperature comparable to liquid electrolytes, and have the added advantage of being easily processable. Regarding mechanical properties, the softness of the material facilitates densification, while its brittleness hinders its scalability in thin film applications.

[0004] The present invention is directed to alleviating one or more of the problems of the prior art discussed above. Summary of the Invention

[0005] The present invention provides a solid-electrolyte (SE) separator for use in electrochemical storage devices, particularly solid-state batteries (SSBs), especially all-solid-state batteries (ASSBs). The solid-electrolyte separator includes an electrolyte containing a lithium ion-conducting compound and a binder containing a copolymer, where the lithium-conducting compound contains sulfur and the copolymer has repeating units containing a carboxylic acid group or its carboxylic acid anion (or carboxylate anion).

[0006] Conventional sulfide-based solid electrolytes (SEs) can provide excellent lithium ion conductivity, but are brittle and lack sufficient mechanical performance for industrial use. The present inventors have discovered that by combining (i) a sulfur-containing lithium ion-conducting compound and (ii) a binder containing a copolymer having a repeating unit containing a carboxylic acid group or its conjugate base, a solid electrolyte separator can be obtained that has excellent electrochemical properties as well as useful mechanical strength. The solid electrolyte separator of the present invention is flexible and easily processable, while also possessing high ionic conductivity. The solid electrolyte separator of the present invention is particularly suitable for use with a Li metal anode.

[0007] To this end, the inclusion of a binder as defined in accordance with the present invention in a solid electrolyte separator contributes mechanical properties that allow the solid electrolyte to be provided as a thin separator. The solid electrolyte separator according to the present invention has an increased energy density.

[0008] Conventional sulfide-based solid electrolytes can react with polar materials, such as polar solvents or polar binders. Due to the chemical stability of sulfide-based solid electrolytes, non-polar binders are used. However, these binders have low solubility and poor compatibility and dispersibility with ion-conducting compounds. Non-polar binders generally result in poor adhesion and bonding with electrode elements, which can cause problems during the manufacture of solid electrolyte separators. On the other hand, polar binders improve processability and enhance adhesion between the electrolyte and electrode elements.

[0009] Surprisingly, it has been found that by using a binder containing a copolymer having repeating units containing a carboxylic acid group or its conjugate base, it is possible to provide a solid electrolyte separator that has good adhesion to electrode elements and can be processed in a non-polar solvent, despite the polar functional groups contained in the binder. The electrolyte material in the solid electrolyte separator of the present invention can provide a stable interfacial electrochemical action with Li metal.

[0010] The present invention further provides a masterbatch product for producing a solid electrolyte separator, the masterbatch product comprising a lithium ion conductive compound, a copolymer, and a solvent, wherein the lithium ion conductive compound comprises sulfur, and the copolymer has a repeating unit comprising a carboxylic acid group or its conjugate base.

[0011] The present invention also provides a method for producing a solid electrolyte separator for an electrochemical storage device, comprising: (i) mixing a lithium ion conductive compound, a copolymer, and a solvent to produce a masterbatch product; and (ii) calendering (or rolling) the masterbatch product to form a separator, wherein the lithium ion conductive compound comprises sulfur and the copolymer has repeat units comprising a carboxylic acid group or a conjugate base thereof.

[0012] Advantageously, the manufacturing method of the present invention provides a simple and highly flexible method for producing solid electrolyte separators. The sulfide-based solid electrolyte and binder readily form a solid electrolyte-polymer composite without requiring a high-energy mixing process. While not wishing to be bound by theory, this result is believed to be due to the formation of polar-polar intermolecular bonds between the carboxylic acid groups of the binder and the solvent. This complex or composite can be calendered to form a thin separator, e.g., on the order of 50 μm or less. Using a binder according to the present invention facilitates the production of a solid electrolyte in the form of a thin separator. Such solid electrolyte separators can achieve high energy densities.

[0013] A further aspect of the present invention provides an electrochemical storage device comprising a first electrode, a second electrode, and a solid electrolyte separator of the present invention disposed between the first and second electrodes.

[0014] Advantageously, solid electrolyte separators can be easily assembled into full cells, e.g., lithium-sulfur batteries, and are compatible with Li metal anodes. Batteries containing solid electrolyte separators also have the advantage of operating at practical and commercially relevant conditions, e.g., 30 °C and stack pressures <1 MPa. Their electrochemical performance is excellent, potentially demonstrating excellent limiting current density and cycling stability, especially under practical conditions. [Brief explanation of the drawings]

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] FIG. 1a is a schematic diagram of a method for producing a solid electrolyte separator.

[0017] Figure 1b shows a photograph of the final solid electrolyte separator product.

[0018] Figure 1c shows the spectra obtained from FT-IR analysis of solid electrolyte separators fabricated using 3, 5, and 10 wt% XNBR binder (TSE-X3, TSE-X5, and TSE-X10, respectively).

[0019] Figure 1d shows the spectra obtained from Raman spectroscopy of solid electrolyte separators fabricated with 3, 5, and 10 wt% XNBR binder (TSE-X3, TSE-X5, and TSE-X10, respectively).

[0020] Figure 1e shows the spectra obtained from XRD analysis of solid electrolyte separators fabricated with 3, 5, and 10 wt% XNBR binder (TSE-X3, TSE-X5, and TSE-X10, respectively).

[0021] Figure 1f shows the results of measuring the Young's modulus by compression and the ionic conductivity by EIS.

[0022] Figure 2a is a schematic diagram of the XPS analysis with in situ Li sputtering.

[0023] Figure 2b shows the XPS spectrum of the solid electrolyte separator with continuous in situ deposition of Li metal.

[0024] Figure 2c shows the XPS spectrum of the in situ Li-sputtered solid electrolyte pellet.

[0025] FIG. 3a shows the LSV curves of the solid electrolyte and the PDOL electrolyte composite at 2.0 to 5.0 V.

[0026] Figure 3b shows the Nyquist plot of the Li / thin solid electrolyte / Li cell over time.

[0027] Figure 3c shows the Nyquist plot of the Li / solid electrolyte pellet / Li cell over time.

[0028] FIG. 3d shows a circuit for fitting the Nyquist plots of FIGS. 3b and 3c.

[0029] Figure 3e shows various solid electrolyte CCDs.

[0030] Figure 3f shows the detailed Li plating / stripping curves for the Li / solid electrolyte pellet / Li CCD case.

[0031] Figure 3g shows the detailed Li plating / stripping curves for the Li / solid electrolyte thin film / Li CCD case.

[0032] Figure 3h shows a symmetric Li-Li cell with a thin solid electrolyte at 0.1 mA cm -1 , 500h Cycle Results are shown.

[0033] Figure 3i is a detailed cycling profile of symmetric Li-Li at a specific time taken from Figure 3h.

[0034] Figure 3j is the Nyquist plot of a symmetric Li-Li cell with a thin membrane solid electrolyte separator after 500 hours of cycling.

[0035] Figure 4a shows a schematic diagram of the integrated solid-state battery system, along with a FIB-SEM image of the solid electrolyte separator.

[0036] Figure 4b is a schematic of the in situ polymerization process.

[0037] Figure 4c shows the research trends of solid-state lithium-sulfur batteries according to the operating conditions of the battery.

[0038] Figure 4d shows a photograph of PDOL and the weight change of PDOL after drying.

[0039] Figure 5a shows the initial discharge curves under galvanostatic conditions for LiSBs with liquid electrolyte and thin solid electrolyte.

[0040] Figure 5b shows the EIS characterization results of the solid-state LiSB with a thin solid electrolyte during the first cycle; the left panel shows the points selected for EIS testing in the voltage profile, and the right panel shows the EIS spectra at each point in the cycle.

[0041] Figure 5c shows the EIS characteristics of the solid LiSB with liquid electrolyte during the first cycle; the left panel shows the points selected for EIS testing in the voltage profile, and the right panel shows the EIS spectra at each point during the cycle.

[0042] Figure 5d shows the results of a battery cycling test of a solid-state Li-S coin cell using TSE.

[0043] Figure 5e shows the results of battery cycling tests on liquid Li-S coin cells.

[0044] Figure 5f shows the results of cell cycling at different current densities. DETAILED DESCRIPTION OF THE INVENTION

[0045] <Definition> Unless expressly stated to the contrary, reference to a repeat unit or monomer, whether or not represented by a structural formula, encompasses all stereoisomers, including cis and trans isomers, and optical isomers (e.g., R and S enantiomers), of the repeat unit or monomer, respectively.

[0046] The various hydrocarbon-containing moieties (or groups) described herein are designated by prefixes that designate the minimum and maximum number of carbon atoms in the moiety, e.g., "C a-b " can be written using the following. For example, C a-b Alkyl refers to an alkyl moiety having a number of carbon atoms from integer "a" to integer "b".

[0047] As used herein, the terms "alkyl" and "alkyl group" refer to a branched or unbranched saturated hydrocarbon chain. Unless otherwise specified, an alkyl group typically contains from 1 to 4 carbon atoms and is unsubstituted. Representative examples include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, and t-butyl.

[0048] As used herein, the terms "alkylene" and "alkylene group" refer to a linear saturated hydrocarbon chain. Unless otherwise specified, the hydrocarbon chain is unbranched, such as when substituted with other groups. Unless otherwise specified, an alkylene group typically contains from 2 to 4 carbon atoms, e.g., 2, 3, or 4 carbon atoms, and may be substituted or unsubstituted. Representative examples include, but are not limited to, ethylene (-CH2CH2-) and propylene (-CH2CH2CH2-).

[0049] As used herein, the terms "alkenylene" and "alkenylene group" refer to a linear saturated hydrocarbon chain containing at least one double bond, preferably one double bond. Unless otherwise specified, such as when substituted with other groups, the hydrocarbon chain is unbranched. Unless otherwise specified, an alkenyl group typically contains 2 to 4 carbon atoms, e.g., 2, 3, or 4 carbon atoms, and may be substituted or unsubstituted. Representative examples include, but are not limited to, ethynyl, propen-1-yl, propen-2-yl, and buten-3-yl.

[0050] As used herein, the terms "phenyl" and "phenyl group" refer to an unsubstituted phenyl ring.

[0051] The terms "a" or "an" in PCT specifications have an open meaning and, when used in connection with a feature, allow for one or more of the feature to be present. The terms "a" or "an" include "one or more" and "at least one," and can be used interchangeably therebetween.

[0052] As used herein, the terms "comprising" and "having" have an open-ended meaning and include the semi-open-ended term "consisting essentially of" and the open-ended term "consisting of," and can be used interchangeably therebetween.

[0053] <Binders and copolymers> The solid electrolyte separator includes a binder, which may include or consist essentially of a copolymer.

[0054] As used herein, the term "copolymer" has its conventional meaning in the art and refers to a polymer formed by combining at least two different monomers (e.g., two monomers having different configurations) in the same polymer chain.

[0055] The copolymer may be an alternating copolymer, a block copolymer, or a graft copolymer, and preferably the copolymer is a block copolymer or a graft copolymer, more preferably a block copolymer.

[0056] Generally, the copolymer is a bipolymer, terpolymer, or quaterpolymer. Preferably, the copolymer is a bipolymer or terpolymer, and more preferably a terpolymer. When a bipolymer, terpolymer, or quaterpolymer, the copolymer is typically a block copolymer.

[0057] The copolymer has repeating units containing a carboxylic acid group (e.g., —COOH) or its conjugate base. The conjugate base of the carboxylic acid group is a carboxylate anion (e.g., —COO - The carboxylate anion may have a counter cation. The counter cation may be a lithium cation (e.g., Li + ) is preferable. This can be advantageous when the solid electrolyte separator is used in a Li-ion battery.

[0058] For ease of reference, the repeat unit having a carboxylic acid group or its conjugate base will be referred to herein as the "first repeat unit." The term "first" in this context is used to distinguish this repeat unit from other repeat units described below. In this regard, the term "first" should not be construed as imposing any limitations on the repeat unit, whether structural or functional.

[0059] The copolymer, and in particular the first repeat unit, can be derived from or obtained from the first monomer. The first repeat unit may be derived or obtained directly from the first monomer. In other words, the first monomer does not undergo any other chemical transformations prior to its use in forming the first repeat unit of the copolymer. As noted above, the term "first" in this context is used to distinguish this monomer from other monomers described below.

[0060] The first monomer may contain a carboxylic acid group or its conjugate base. The carboxylic acid group or its conjugate base in the first monomer is typically the carboxylic acid group or its conjugate base in the first repeating unit. The carboxylic acid group or its conjugate base is a polar functional group. Therefore, the portion of the copolymer having the first repeating unit is relatively polar.

[0061] The first monomer may be acrylic acid, methacrylic acid, or maleic acid, preferably acrylic acid or methacrylic acid, more preferably methacrylic acid. Alternatively, the first repeat unit may be derived or obtained from acrylic acid, methacrylic acid, or maleic acid, preferably acrylic acid or methacrylic acid, more preferably methacrylic acid.

[0062] Additionally or alternatively, the first monomer may include a hydrolyzable precursor group that generates a carboxylic acid group or its conjugate base, the hydrolyzable precursor group being intended to generate the carboxylic acid group or its conjugate base of the first repeat unit.

[0063] The hydrolyzable precursor group may be a carboxylic acid ester group, a carboxylic acid anhydride group, or a carboxylic acid amide group. After polymerization of the first monomer containing the hydrolyzable precursor group, the resulting polymer may be subjected to hydrolysis conditions to convert the hydrolyzable precursor group to a carboxylic acid group or its conjugate base.

[0064] The first monomer may be a carboxylic acid ester, anhydride or amide of acrylic acid, methacrylic acid or maleic acid, preferably a carboxylic acid ester, anhydride or amide of acrylic acid or methacrylic acid, more preferably a carboxylic acid ester, anhydride or amide of methacrylic acid, or the first repeat unit may be derived or obtained from a carboxylic acid ester, anhydride or amide of acrylic acid, methacrylic acid or maleic acid, preferably a carboxylic acid ester, anhydride or amide of acrylic acid or methacrylic acid, more preferably a carboxylic acid ester, anhydride or amide of methacrylic acid.

[0065] In general, it is preferred that the first repeat unit contains a carboxylic acid group, preferably as the only functional group of the repeat unit, i.e., the first repeat unit contains no other functional groups.

[0066] The first repeat unit has the formula (1): JPEG2025533352000002.jpg35150 (in the formula, R 1 is hydrogen or methyl, Q is selected from a carboxylic acid group (—COOH) or its conjugate base and a hydrolyzable precursor group that produces a carboxylic acid group or its conjugate base, and z is greater than 1.

[0067] In the definition of Q, "its conjugate base" and "hydrolyzable precursor group" are as defined above.

[0068] The first repeat unit is represented by formula (1a) or formula (1b), preferably formula (1b): JPEG2025533352000003.jpg38164 (R in the formula 1 (when present in formula (1a)) and z are as defined above in relation to formula (1)).

[0069] In formula (1) and formula (1a), R 1 is preferably hydrogen.

[0070] In formula (1), formula (1a) and formula (1b), the parameter "z" represents the number of first repeat units in the copolymer.

[0071] For each copolymer molecule, z represents an integer number of repeat units, which is greater than one.

[0072] However, when multiple copolymer molecules are contained in the binder of the solid electrolyte separator of the present invention, there is a distribution in the number of repeating units represented by formula (1), formula (1a), and formula (1b). In this case, the parameter "z" may be defined as an average number such that the copolymer has a total amount of carboxylic acid groups and their conjugate bases of 1 to 15 wt% (e.g., based on the total weight of the copolymer). More preferably, the parameter "z" may be defined as an average number such that the copolymer has a total amount of carboxylic acid groups and their conjugate bases of 5 to 12.5 wt% (e.g., based on the total weight of the copolymer). Even more preferably, the parameter "z" may be defined as an average number such that the copolymer has a total amount of carboxylic acid groups and their conjugate bases of 7 to 10 wt% (e.g., based on the total weight of the copolymer). Even more preferably, the parameter "z" may be defined as an average number such that the copolymer has a total amount of carboxylic acid groups and their conjugate bases of 10 wt% (e.g., based on the total weight of the copolymer).

[0073] The copolymer may include a second repeat unit, the second repeat unit having a different chemical structure than the chemical structure of the first repeat unit.

[0074] The term "second" in reference to a "second repeat unit" or "second monomer" is used to distinguish that repeat unit or monomer, respectively, from other repeat units or monomers described herein. In this context, the term "second" should not be construed as imposing any limitation, whether structural or functional, on the repeat unit or monomer.

[0075] The second repeat unit is a hydrocarbyl repeat unit. The hydrocarbyl repeat unit is a non-polar portion of the copolymer. Therefore, the portion of the copolymer containing the second repeat unit is non-polar.

[0076] Typically, the hydrocarbyl repeat unit has a backbone, which may contain two or more carbon atoms and is optionally substituted with one or more side groups, and preferably is optionally substituted with a single (e.g., only one) side group.

[0077] The backbone is a component of the second repeat unit that forms the main polymer chain of at least a portion of the copolymer. Side groups are groups that are covalently attached to the backbone but do not form part of the main polymer chain.

[0078] The second iteration is equation (2): JPEG2025533352000004.jpg53156, where the dashed bond indicates that the presence of a side group is optional (e.g., the side group is an optional substituent).

[0079] In general, or in formula (2), the backbone is C 2-4 Alkylene group and C 2-4 The alkenylene group may be selected from alkenylene groups, the backbone of which is optionally substituted with side groups, preferably a single side group.

[0080] In general, or in formula (2), the side chain group is C 1-4 It may be selected from alkyl groups and phenyl groups.

[0081] In equation (2), x is greater than 1.

[0082] The skeleton is C 2-3 Alkylene group and C 3-4 Preferably, the backbone is selected from an alkenylene group, and more preferably, the backbone is selected from a C2 alkylene group and a C4 alkenylene group.

[0083] The side chain group is C 1-2 It is generally preferred to select from alkyl and phenyl groups, and more preferably the side chain groups are selected from methyl and phenyl groups.

[0084] When the backbone is a C2 alkylene group, it is preferred that the backbone is unsubstituted or substituted with one side group selected from methyl, ethyl and phenyl, preferably methyl and phenyl.

[0085] When the backbone is a C4 alkenylene group, it is preferred that the backbone is unsubstituted.

[0086] The second repeat unit is one of formula (2a), (2b) or (2c), preferably formula (2c): JPEG2025533352000005.jpg60131, where the term "Ph" represents a phenyl group and x is as defined herein.

[0087] For each copolymer molecule, x represents an integer number of repeat units and is greater than one.

[0088] When multiple copolymer molecules are contained in the binder of the solid electrolyte separator of the present invention, there is a distribution in the number of repeating units represented by formula (2) or formulas (2a) to (2c). When only second repeating units represented by formula (2) or formulas (2a) to (2c) are present in addition to the first repeating units, the parameter "x" may be defined as an average number so that the copolymer has a total content of second repeating units represented by formula (2) or formulas (2a) to (2c) of 85 to 99 wt% (e.g., based on the total weight of the copolymer). Preferably, the average number may be defined so that the copolymer has a total content of second repeating units represented by formula (2) or formulas (2a) to (2c) of 87.5 to 95 wt% (e.g., based on the total weight of the copolymer). More preferably, the average number may be defined so that the copolymer has a total content of second repeating units represented by formula (2) or formulas (2a) to (2c) of 90 to 93 wt% (e.g., based on the total weight of the copolymer). Even more preferably, the copolymer may be defined as having a total content of second repeat units represented by formula (2) or formulas (2a) to (2c) of 90 wt % (e.g., based on the total weight of the copolymer), as an average number.

[0089] The copolymer may include a third repeat unit, the third repeat unit having a different chemical structure than the chemical structure of the first repeat unit.

[0090] The third repeat unit may have the same or a different chemical structure than the chemical structure of the second repeat unit.

[0091] When the second and third repeat units share the same chemical structure, it is preferred that the second repeat unit is not directly bonded to the third repeat unit, and more preferably, the first repeat unit is located between the second and third repeat units in the copolymer.

[0092] In general, it is preferred that the third repeat unit have a chemical structure that is different from the chemical structure of the second repeat unit.

[0093] The term "third" in reference to a "third repeat unit" or a "third monomer" is used to distinguish the repeat unit or monomer, respectively, from other repeat units or monomers described herein. The term "third" in this context should not be construed as imposing any limitation, whether structural or functional, on the repeat unit or monomer, respectively. For example, the presence of a "third repeat unit" does not require the presence of a "second repeat unit."

[0094] The third repeat unit has the formula (3): JPEG2025533352000006.jpg36118, where W is selected from a nitrile group (e.g., —CN) and a phenyl group; and and y is greater than 1).

[0095] Depending on the identity of W, the third repeat unit may be non-polar (for example, when W is a phenyl group) or mildly polar (for example, when W is a nitrile group).

[0096] Thus, the third repeat unit is of formula (3a) or formula (3b): JPEG2025533352000007.jpg34119, where y is as defined herein.

[0097] In each copolymer molecule, y represents an integer number of repeat units and is greater than one.

[0098] When multiple copolymer molecules are contained in the binder of the solid electrolyte separator of the present invention, there is a distribution in the number of repeating units represented by formulas (3), (3a), and (3b). When only third repeating units represented by formulas (3), (3a), and (3b) are present in addition to the first repeating units, the parameter "y" may be defined as an average number so that the copolymer has a total content of third repeating units represented by formulas (3), (3a), and (3b) of 85 to 99 wt% (e.g., based on the total weight of the copolymer). Preferably, the average number may be defined so that the copolymer has a total content of third repeating units represented by formulas (3), (3a), and (3b) of 87.5 to 95 wt% (e.g., based on the total weight of the copolymer). More preferably, the average number may be defined so that the copolymer has a total content of third repeating units represented by formulas (3), (3a), and (3b) of 90 to 93 wt% (e.g., based on the total weight of the copolymer). Even more preferably, the copolymer may be defined as having a total content of the third repeat units represented by formula (3), formula (3a) and formula (3b) of 90 wt % (e.g., based on the total weight of the copolymer), as an average number.

[0099] The copolymer, and in particular the third repeat unit, may be derived from or obtained from a third monomer. The third repeat unit may be derived directly from or obtained from a third monomer. In other words, the third monomer does not undergo any other chemical transformations prior to its use in forming the third repeat unit of the copolymer.

[0100] The third monomer may be styrene or acrylonitrile. Alternatively, the third repeat unit may be derived from or obtained from styrene or acrylonitrile.

[0101] The copolymer comprises a first repeat unit and at least one of a second repeat unit and a third repeat unit. Thus, the copolymer comprises a first repeat unit, and (i) a second repeat unit, or (ii) a third repeat unit, or (iii) The second repeating unit and the third repeating unit It may include any of the following.

[0102] In embodiments where the copolymer comprises a first repeat unit, a second repeat unit, and a third repeat unit, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 1 to 15 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 42.5 to 79 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 20 to 42.5 wt% (e.g., based on the total weight of the copolymer). Preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 5 to 12.5 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 47.5 to 65 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 30 to 40 wt% (e.g., based on the total weight of the copolymer). More preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 7 to 10 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 51 to 60 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 33 to 39 wt% (e.g., based on the total weight of the copolymer). Even more preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 10 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 51 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 39 wt% (e.g., based on the total weight of the copolymer).

[0103] In yet another embodiment, when the copolymer comprises a first repeat unit, a second repeat unit, and a third repeat unit, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 1 to 15 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 20 to 42.5 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 42.5 to 79 wt% (e.g., based on the total weight of the copolymer). Preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 5 to 12.5 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 30 to 40 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 47.5 to 65 wt% (e.g., based on the total weight of the copolymer). More preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 7 to 10 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 33 to 39 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 51 to 60 wt% (e.g., based on the total weight of the copolymer).Even more preferably, parameter "z" may be defined as an average number such that the copolymer has a total content of carboxylic acid groups and their conjugate bases of 10 wt% (e.g., based on the total weight of the copolymer), parameter "x" may be defined as an average number such that the copolymer has a total content of second repeat units of 39 wt% (e.g., based on the total weight of the copolymer), and parameter "y" may be defined as an average number such that the copolymer has a total content of third repeat units of 51 wt% (e.g., based on the total weight of the copolymer).

[0104] When the copolymer comprises a second repeat unit and a third repeat unit, it is preferred that the third repeat unit has a chemical structure different from that of the second repeat unit.

[0105] When the second repeating unit is represented by formula (2b), the third repeating unit is preferably represented by formula (3a).

[0106] When the copolymer comprises a second repeat unit and a third repeat unit, it is generally preferred that the second repeat unit be of formula (2c).

[0107] The copolymer may comprise a structure represented by formula (4), formula (5), or formula (6), or may consist essentially of formula (4), formula (5), or formula (6): JPEG2025533352000008.jpg77151 (in the formula, R 1 , x (if present), y (if present), and z are as defined herein).

[0108] The copolymer has the formula (7): Preferably, the structure comprises or consists essentially of the structure represented by formula (7): JPEG2025533352000009.jpg37130.

[0109] Typically, the copolymer is a carboxylated rubber, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, or a carboxylated polystyrene. Preferably, the copolymer is a carboxylated rubber, an ethylene-methacrylic acid copolymer, or a carboxylated polystyrene, and more preferably, the copolymer is a carboxylated rubber.

[0110] As used herein, the term "rubber", particularly in the context of carboxylated rubber, generally refers to synthetic rubber, not natural rubber, which is typically butadiene rubber (BR).

[0111] The carboxylated rubber may be carboxylated polybutadiene, carboxylated nitrile butadiene rubber, or carboxylated styrene butadiene rubber. Preferably, the carboxylated rubber is carboxylated nitrile butadiene rubber.

[0112] Generally, the copolymer has a total content of carboxylic acid groups and their conjugate bases of 15 wt% or less (e.g., based on the total weight of the copolymer). The copolymer preferably has a total content of carboxylic acid groups and their conjugate bases of less than 15 wt% (e.g., based on the total weight of the copolymer), more preferably 10 wt% or less, and even more preferably less than 10 wt%. For example, the copolymer may have a total content of carboxylic acid groups and their conjugate bases of 1 to 15 wt% (e.g., based on the total content of the copolymer), preferably 5 to 12.5 wt% (e.g., based on the total content of the copolymer), and more preferably 7 to 10 wt% (e.g., based on the total content of the copolymer).

[0113] Typically, the copolymers have a total content of carboxylic acid groups and their conjugate bases of 1, 2, 3, 4, 5, 6, 7, 8 or 9 wt % (eg, based on the total weight of the copolymer).

[0114] The copolymers of the present invention, particularly carboxylated nitrile butadiene rubber, have advantageous properties. Some of these properties are due to the polar (e.g., -CN and -COOH) and nonpolar portions of the copolymer molecules. The copolymers also have elasticity and adhesive properties, and are compatible with nonpolar solvents despite containing polar functional groups in at least one repeat unit. This is surprising because other polymer binders with polar functional groups (e.g., polyvinylidene fluoride, polyacrylic acid) exhibit high reactivity toward sulfide-based solid electrolyte materials such as LPSCl.

[0115] The copolymer is preferably soluble in a non-polar solvent such as toluene (e.g., at 25°C). Preferably, the solvent has a polarity index of less than 4.0 based on Snyder's polarity index (e.g., as described in "Classification of the Solvent Properties of Common Liquids, LRSnyder., Journal of Chromatography, 92 (1978), 223-224"). More preferably, the polarity index is less than 3.0, and even more preferably less than 2.5. Typically, the polarity index is measured at ambient temperature, e.g., room temperature (e.g., between 20°C and 30°C, especially 25°C), and atmospheric pressure (e.g., 1 atmosphere).

[0116] Generally, the solid electrolyte separator comprises a binder in a total weight range of 0.50 to 20.00 wt% (e.g., based on the total weight of the solid electrolyte separator), preferably 1.00 to 15.00 wt%, more preferably 3.00 to 10.00 wt%, for example, 3.50 to 7.50 wt% (e.g., about 5.00 wt%). Total binder contents anywhere between the aforementioned values ​​are contemplated. For example, the binder may be present in the solid electrolyte separator in a total content of 4.00, 5.00, 6.00, 7.00, 8.00, and 9.00 wt%, or any range therein.

[0117] For solid electrolyte separators with binder contents less than 3 wt%, the amount of binder may be insufficient to hold the solid electrolyte particles together, resulting in flaky composites, while solid electrolyte separators containing more than 10 wt% binder may be too sticky to process.

[0118] <Electrolytes and lithium ion conductive compounds> The solid electrolyte separator comprises an electrolyte, preferably a solid electrolyte.

[0119] The electrolyte, particularly the solid electrolyte, may comprise or consist essentially of lithium ion conducting compounds, which contain sulfur.

[0120] Typically, the solid electrolyte is a sulfide solid electrolyte and includes a lithium ion conducting compound. Such sulfide solid electrolytes are known in the art.

[0121] Solid electrolytes, especially sulfide solid electrolytes, have the general formula Li 7-p BS 6-p X p wherein B is phosphorus or arsenic, X is Cl, Br or I, and p is 0 to 1.

[0122] Preferably, B is phosphorus.

[0123] Preferably, X is Cl or Br.

[0124] Preferably, p is 1.

[0125] More preferably, the electrolyte, especially the sulfide solid electrolyte, is Li6PS5Cl (LPSCl) or Li6PS5Br (LPSBr), and even more preferably Li6PS5Cl (LPSCl).

[0126] Electrolytes, particularly sulfide solid electrolytes, have the general formula Li4-q Ge (1-q) P q S4, where q is 0 to 1. Such materials are typically known as thio-LISICON materials.

[0127] Electrolytes, especially sulfide solid electrolytes, include Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li3PS4, and Li7P3S 11 , LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, Li 10 GeP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li7P3S 11 , Li x PS y Cl z , Li x PS y Br z , Li x PS y Cl z Br 1-z , Li x PS y F z , Li x PS y F z Cl 1-z and Li x PS y F z Br 1-z Li x PS y Cl z , Li x PS y Br z , Li x PS y Cl z Br 1-z , Li x PS y F z ,Lix PS y F z Cl 1-z and Li x PS y F z Br 1-z where x, y, and z are each greater than 0.

[0128] <Solid electrolyte separator> Typically, the solid electrolyte separator has a thickness of 50 μm or less. For example, the solid electrolyte separator may have a thickness of 1 to 50 μm, preferably 2 to 30 μm, and in this context, references to thickness refer to the maximum measured thickness of the solid electrolyte.

[0129] The solid electrolyte separator may have a thickness of 40 μm, or 30 μm, or 20 μm, or 10 μm, or for example 5 microns. Advantageously, the solid electrolyte separator may have a thickness of 50 microns or less, which contributes to the solid electrolyte separator having a high energy density.

[0130] Solid electrolyte separators typically have a resistance of 0.1 to 1.0 mS cm -1 , e.g., 0.3 to 0.75 mS cm -1 It has an ionic conductivity of

[0131] The solid electrolyte separator may have a Young's modulus of 0.5 to 5 GPa, preferably 1 to 3 GPa. The Young's modulus is measured according to the method specified in ASTM D695.

[0132] <Masterbatch products> The present invention also provides a masterbatch product, which comprises a lithium ion conductive compound and the copolymer described above.

[0133] The masterbatch product further comprises a solvent, which is preferably a non-polar solvent.

[0134] The non-polar solvent may be an aromatic non-polar solvent, for example, the aromatic non-polar solvent may be toluene, xylene, or benzene.

[0135] In another embodiment, the non-polar solvent can be an aliphatic non-polar solvent. For example, the aliphatic non-polar solvent can be pentane, hexane, or heptane.

[0136] Typically, the masterbatch product comprises a total solvent content of 1 to 50 wt% (eg, based on the total weight of the masterbatch product).

[0137] Advantageously, masterbatch products can be formed without the need for high-energy mixing. Without wishing to be bound by theory, this is believed to be the result of promoting the formation of polar-polar intermolecular bonds between the carboxylic acid groups of the copolymer in the solvent. When the solvent is a nonpolar solvent, such as toluene, the intermolecular interactions between the polar functional groups are enhanced and are not masked by the solvation effect of the nonpolar solvent.

[0138] <Manufacturing method> The present invention also provides a method for producing a solid electrolyte separator. This manufacturing method is (i) mixing a lithium ion conductive compound, a copolymer, and a solvent (e.g., to form a masterbatch product as described above); and (ii) calendaring the masterbatch product mixture to form a separator; It may comprise or consist essentially of:

[0139] The step of mixing the lithium ion conductive compound, the copolymer, and the solvent may be a step of dispersing the lithium ion conductive compound and the copolymer in the solvent.

[0140] Calendering of the masterbatch product may be carried out to form separators having thicknesses of 50 microns or less, particularly those thicknesses mentioned above.

[0141] Calendering the masterbatch product may involve passing the masterbatch product through rollers to form a separator.

[0142] Advantageously, the manufacturing method of the present invention is simple and only requires the basic processing steps to form a solid electrolyte separator. Thus, advantageously, the solid electrolyte separator can be manufactured using a simple and flexible manufacturing method.

[0143] Formation of the masterbatch product (e.g., the first step of the manufacturing process) is preferably carried out at ambient temperature, e.g., room temperature (e.g., between 20°C and 30°C, especially 25°C), and ambient pressure (e.g., 1 atmosphere).

[0144] As mentioned above, the solvent is preferably a non-polar solvent.

[0145] The non-polar solvent may be an aromatic non-polar solvent, for example, the aromatic non-polar solvent may be toluene, xylene, or benzene.

[0146] In another embodiment, the non-polar solvent can be an aliphatic non-polar solvent. For example, the aliphatic non-polar solvent can be pentane, hexane, or heptane.

[0147] <Electrochemical storage device> The present invention also provides an electrochemical storage device, comprising a first electrode, a second electrode, and a solid electrolyte separator positioned between the first electrode and the second electrode, the solid electrolyte separator being in accordance with the present invention.

[0148] Typically, the electrochemical storage device is a solid state battery (SSB), preferably an all solid state battery (ASSB).

[0149] The second electrode has a different composition than the first electrode to ensure that a potential difference can exist between the first and second electrodes.

[0150] Generally, the first electrode is the cathode and the second electrode is the anode.

[0151] Typically, the first electrode or cathode comprises sulfur. Preferably, the first electrode or cathode is a tape-cast sulfur electrode.

[0152] In principle, any kind of second electrode can be used in the electrochemical energy storage device, in particular the second electrode comprises lithium. Typically the second electrode or anode comprises lithium.

[0153] The second electrode or anode comprising lithium may comprise a lithium metal electrode or an alloy of lithium and silicon. Preferably, the second electrode is a lithium metal electrode.

[0154] The electrochemical energy storage device may include a charger as part of the system, particularly if it is an all-solid-state battery, which serves to recharge the electrochemical storage device.

[0155] Typically, after assembly of the electrochemical storage device, the solid electrolyte separator according to the first aspect of the present invention is integrated with a supplemental electrolyte.

[0156] In electrochemical storage devices, the solid electrolyte separator typically further comprises an integrated auxiliary electrolyte, which comprises an ion-conducting polymer, such as a polydioxolane (PDOL) auxiliary electrolyte.

[0157] Advantageously, and without wishing to be bound by theory, it is believed that the integrated auxiliary electrolyte provides a chemically stable ion conduction path at the electrode-electrolyte interface. Therefore, the need to operate the cell under high stack pressure to allow sufficient contact between the solid electrolyte and the electrode is alleviated. Advantageously, the cell operates at a low stack pressure, for example, 1 MPa or less. Therefore, a cell that can be operated under more convenient conditions is provided.

[0158] The electrochemical storage device can have a stable cycle count of at least 100 cycles, eg, at least 200 cycles, at least 500 cycles, and at least 800 cycles measured at 30° C. and a stack pressure of <1 MPa.

[0159] Example Preparation and characterization details 1. Synthesis of solid electrolyte separator Li6PS5Cl (LPSCl, 99.9%, approximately 1 μm, obtained from Ampcera Inc.) and carboxylated nitrile butadiene rubber (XNBR, Krynac® X750, obtained from Arlanxeo) binder (3 wt%) were added to anhydrous toluene (99.8%, obtained from Sigma-Aldrich) and mixed using a vortex mixer or an agate mortar and pestle. Immediately after mixing the LPSCl and XNBR, a composite solid electrolyte (SE) was obtained.

[0160] The resulting composite was placed between Si-coated polyethylene terephthalate (PET) films (50 μm thick), and the composite was repeatedly calendered to form a film. The thickness of the solid electrolyte film was controlled by the settings of the calendering machine (MTI Corp., MSK-2150). After calendering, toluene volatilized, and only a negligible amount (<1 wt%) of toluene remained in the calendered solid electrolyte material.

[0161] After the film was dried under vacuum at room temperature overnight, the separator was placed between stainless steel plungers and cold-pressed under a uniaxial pressure of 200 MPa for 3 min.

[0162] All preparation steps were carried out in an Ar-filled glove box (MBRAUN, MB 200B, H2O < 0.1 ppm, O2 < 0.1 ppm).

[0163] The above method for preparing solid electrolyte separators was repeated two more times, except that the carboxylated nitrile butadiene rubber content was changed to 5 wt% and 10 wt% in each preparation. Thus, hereinafter, sample TSE-X3 contained 3 wt% carboxylated nitrile butadiene rubber, sample TSE-X5 contained 5 wt% carboxylated nitrile butadiene rubber, and sample TSE-X10 contained 10 wt% carboxylated nitrile butadiene rubber.

[0164] 2. Preparation of cathode auxiliary electrolyte (catholyte) A solid electrolyte separator (prepared using the method in section 1) was assembled into the cell.

[0165] During the cell assembly process, catholyte was injected into a tape-cast sulfur cathode. To prepare the catholyte, a sulfur content of 1 mg was used. -2 The nanoparticles were impregnated with 10 μL of a 2 M solution of lithium bis(fluorosulfonyl)imide (LiFSI) in 1,3-dioxolane (DOL) per nanoparticle, followed by in situ polymerization. The solution was prepared by mixing dry DOL (dried over molecular sieves for 24 h) and LiFSI (dried at 70 °C under vacuum for 24 h).

[0166] After impregnation, the assembled cell was stored at room temperature for 6 h. All processing steps were carried out in an Ar-filled glove box.

[0167] 3. Characterization Method All characterization techniques were carried out at a temperature of 30°C without exposure to air.

[0168] Fourier transform infrared spectroscopy (FT-IR, NICOLET iS50, Thermo Fisher Scientific) was performed at 3200-1200 cm -1 The measurements were carried out by attenuated total reflectance (ATR) in the spectral range of

[0169] X-ray diffraction (XRD, Miniflex, Rigaku) ​​using Cu Kα radiation was used to analyze the structure of the LPSCl powder and the solid electrolyte separator. Measurements were performed after covering the samples with polyimide film to avoid exposure to air.

[0170] Raman spectroscopy measurements were collected using a Raman microscope (in via Relex, Renishaw, combined with an inverted Leica microscope). A 633 nm laser (output power <300 μW) was used as the excitation source, and a ×50 objective (Olympus) was used to focus the sample. To avoid exposure to air, the sample was covered with glass or polyimide film. The collected Raman spectra were baseline corrected and peak-fitted using a Lorentizian-Gaussian mixed function. To ensure a good signal-to-noise ratio for peak separation, the spectra were acquired for 2 seconds, with 24 acquisitions.

[0171] X-ray photoelectron spectroscopy (XPS) spectra were collected using an Al Kα X-ray source with a Phi XPS VersaProbe III. For XPS measurements during in situ Li deposition, Li metal foil (Sigma-Aldrich, thickness = 380 μm) was sputtered at 2 kV accelerating voltage and 1 μA Ar. + The beam current was set at 1.5 V. The angle between the sputter gun and the sample surface was 33°. The estimated sputter depth rate was 0.7 Å min -1Therefore, the thickness of Li after deposition was about 14 nm. The solid electrolyte (pellets and separator) and Li metal were transferred to the XPS chamber using a vacuum transfer container to eliminate exposure to air.

[0172] To clarify the cross-sectional morphology of the electrodes, cross-sections were fabricated using a plasma focused ion beam scanning electron microscope (PFIB-SEM). PFIB cross-sections were fabricated using a Thermo Fisher Helios G4 Plasma-FIB. It should be noted that the entire sample may have some redeposition due to the FIB. However, since similar milling and polishing steps were used for each sample, the possibility of redeposition is considered to be comparable across samples. Therefore, the polishing process was chosen to minimize the possibility of redeposition. The sample surfaces were protected with evaporated Pt, and cross-sections and polishing were performed at a constant voltage of 30 kV with a current reduced to 15 nA.

[0173] The Young's modulus was measured according to the method specified in ASTM D695.

[0174] Electrochemical impedance spectroscopy (EIS) was performed using a VMP-3 potentiostat (Biologic, France) at a potential amplitude of 10 mV and a frequency range of 1 MHz to 0.01 Hz. SE pellets were pressed into a PEEK die at 370 MPa, and two carbon-coated Al foil (10 mm diameter) current collectors were pressed onto the pellet at 300 MPa for 3 min. The ionic conductivity of SE was measured using a homemade battery cell under a stack pressure of 9 MPa or a coin cell (CR2032, Hoshen Co., Ltd., Japan) under a stack pressure of <1 MPa, both at 30 °C.

[0175] For symmetric Li-Li cycling tests, two Li metal anodes with a diameter of 12.7 mm and a thickness of 100 μm were attached to either side of the ISE separator in a coin cell. The symmetric cells were cycled at various current densities as mentioned in the "Results" section.

[0176] Li-S full cells were assembled in the form of coin cells and pouch cells. A commercially available cathode (BE-70E, NEI Corp., 3.75 mg cm) consisting of 70 wt% sulfur, 20 wt% carbon black, and 10 wt% polyvinylidene fluoride binder was used as the cathode. -2 The lithium-ion battery cells (12.7 mm in diameter for coin cells and 20 mm x 20 mm for pouch cells) were used with Li metal anodes (100 μm thick, Sigma Aldrich), which were polished and calendered before use to remove the surface layer. For the Li-S cells, the impregnation precursor solution was added to account for the sulfur content (electrolyte / sulfur = 10 μL / mg-S sulfur). Cycling tests of the Li-S cells were performed at a constant current of 0.05 C between 1.5 and 2.8 V using a BCS-800 battery cycler (Biologic, France) after three activation cycles at a rate of 0.01 C.

[0177] Results and Discussion Characterization of solid electrolyte separators FT-IR was used to investigate the effect of the binder on intermolecular bonding. With the addition of the binder, the FT-IR spectrum (Figure 1c) showed increased bands at 1730 and 1697 cm due to the carboxyl groups of XNBR (carbonyl stretching vibrations of monovalent and hydrogen-bonded carboxylic acids, respectively). -1 The peak shifts to the lower wavenumber side. -1 The broad peak shift near the P 5+ and Li + Carboxylate (-COO) - The shift of the corresponding FT-IR peak to lower wavenumbers supports this interpretation and indicates the formation of intermolecular bonds between LPSCl and XNBR.

[0178] Raman spectroscopy and X-ray diffraction (XRD) analyses were carried out to confirm the chemical and structural stability of the Li6PS5Cl solid electrolyte separator. Raman spectra (Fig. 1d) showed peaks at 199, 272, 425, 573, and 600 cm for all samples. -1 All of these peaks are PS4 in Li6PS5Cl. 3- This may be due to vibration modes.

[0179] From the XRD pattern of the solid electrolyte (Fig. 1e), the prominent diffraction peaks at 25.5°, 30.0°, 31.4°, 45.0°, 47.9°, and 52.4° were assigned to the (220), (311), (222), (422), (511), and (440) planes of LPSCl, respectively, which is consistent with the pattern of pure LPSCl without any evidence of decomposition to Li2S.

[0180] These results confirm that Li6PS5Cl is chemically stable during the fabrication of solid electrolyte separators.

[0181] The mechanical and electrochemical properties of the solid electrolyte separator were analyzed, and the Young's modulus and ionic conductivity results are shown in Figure 1f and Table 1 below. [Table 1] JPEG2025533352000010.jpg47141

[0182] Therefore, as shown by the results in Table 1 and Figure 1f, increasing the binder content improves the flexibility of the solid electrolyte separator (as indicated by a decrease in Young's modulus), but also decreases ionic conductivity because the binder is not ionically conductive. TSE-X3 exhibited the highest Young's modulus value and the highest ionic conductivity among the solid electrolytes tested. Conversely, TSE-X10 exhibited the lowest Young's modulus value but the lowest ionic conductivity among the solid electrolytes tested. Further testing was conducted on TSE-X5, which has Young's modulus and ionic conductivity values ​​between those of TSE-X3 and TSE-X10.

[0183] Sulfide-based solid electrolytes (SEs) decompose upon contact with Li metal, producing LiS, LiCl, and Li x It is known that TSEs form an unevenly conductive interface consisting of P. This uneven interface may affect the Li plating / stripping behavior, potentially leading to reduced ionic conductivity at the interface, non-uniform precipitation, accelerated Li filament growth, and degradation during battery cycling. Therefore, the interface stability between Li metal and TSE was evaluated by X-ray photoelectron spectroscopy (XPS) using Li metal and binder-free pellet-type LPSCl solid electrolyte as a comparison (Figure 2).

[0184] To further investigate the chemical changes at the Li metal and solid electrolyte interface, XPS was also performed. XPS analysis showed that Ar was deposited on the solid electrolyte, as shown schematically in Figure 2a. + In situ deposition of Li metal was performed by the beam. The XPS spectrum (Figure 2b) obtained from the analysis of the TSE surface shows a gradual shift in the Li 1s spectrum to lower binding energies, indicating the formation of a solid electrolyte interphase (SEI) upon reaction with the solid electrolyte surface. Further deposition leads to metallic Li (Li) observed at a binding energy around 52.5 eV. 0 ) leading to the expression of traits characteristic of the species.

[0185] Furthermore, a doublet feature characteristic of Li2S (highlighted in orange) was observed in the S 2p spectrum, consistent with the reported component of the SEI between Li metal and LPSCl.

[0186] In the P 2p spectrum, unlike the binder-free solid electrolyte pellet (Fig. 2c), x The formation of P is difficult to observe.

[0187] These results indicate that the prepared solid electrolyte separators have a stable solid electrolyte interface (SEI) with LiS as the dominant component in contact with Li metal, which is clearly different from the SEI fabricated using binder-free solid electrolyte pellets. Therefore, this indicates that XNBR also influences the interfacial chemistry and contributes to improving its stability.

[0188] Cell Evaluation To determine the practical limits of this SE system with a Li metal anode, linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and limiting current density (CCD) tests were performed to investigate its electrochemical limits (Figure 3). Figure 3a shows the maximum current density (V) of 0.1 mV s. -1 This figure shows the electrochemical stability of the TSE separator as measured by linear sweep voltammetry at 1000 V. The TSE exhibited a wide electrochemical stability region up to 6.0 V, as expected from its predominantly sulfide composition. The stability of both of these components falls within the range required for the TSE to be used in solid-state LiSBs. Symmetric Li-Li coin cells were assembled and tested by EIS and CCD on the SE pellet and TSE under practical conditions (30 °C, <1 MPa (specific to coin cells)) without stack pressure.

[0189] Figures 3b and 3c show the impedance spectra of the TSE and SE pellets, respectively, assembled into a symmetric Li / SE / Li cell. Using a fitted equivalent circuit model (Figure 3d), the Nyquist plots were plotted to obtain the interfacial resistance (R) between the Li metal and the SE. int ) and the bulk resistance of the SE (R b After maintaining contact between the Li metal and the TSE for more than 36 hours, the R int The change in R is small, indicating a stable interface between the SE and Li (Fig. 3b). On the other hand, for the pellet SE, R int and R bincreases continuously during the same time period, suggesting high reactivity between Li metal and LPSCl (Fig. 3c). These results are consistent with the formation of a stable SEI layer between the TSE and Li metal, as shown in Fig. 2.

[0190] Based on the stable electrochemical properties of TSE with Li metal, we set the current density from 0.01 to 0.4 mA cm for each electrolyte. -2 The Li plating / stripping behavior was investigated by increasing the current to 0.325 mA cm (Figs. 3e, 3f, 3g and Table 2). As shown in Figs. 3e, 3f, and 3g, on average, the symmetric Li-Li cell with a pellet SE of approximately 600 μm thickness achieved a current of 0.325 mA cm. -2 On the other hand, TSEs with a thickness of <50 μm (1 / 12 the thickness of the pellet) showed a short circuit after applying a current density of 0.3 mA cm -2 This performance may be attributed to the dense microstructure of the TSE with low porosity (average 4.47%).

[0191] Furthermore, to evaluate the stability of the TSE under long-term cycling, a symmetric Li-Li cell was assembled and tested at 0.1 mA cm -2 (0.05mAh·cm -2 ) for 500 h (Fig. 3h). After cycling, the overpotential and interfacial resistance did not change significantly (Figs. 3i and 3j), indicating that the interface between the TSE and Li metal maintained good contact without significant short-circuiting during repeated Li plating / stripping.

[0192] Therefore, TSE is practical for commercial production, exhibits good stability with respect to Li metal, and can withstand extended battery cycling without failure. [Table 2] JPEG2025533352000011.jpg36155

[0193] We prepared a monolithic solid-state battery with a tape-cast sulfur cathode containing a cathode auxiliary electrolyte (catholyte), as shown in Figure 4a. The catholyte is chemically stable and contains ionically conductive polydioxolane (PDOL), which provides an ion-conducting pathway at the cathode-electrolyte interface (cathode / TSE). This was achieved by impregnating the sulfur cathode with 2 M lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in 1,3-dioxolane (DOL) after cell assembly was complete. The LiFSI acted as an initiator, and the solution polymerized in situ to form polydioxolane (PDOL) (Figure 4b).

[0194] The selection of DOL as a soluble precursor followed by an in situ polymerization step is intentional. First, other non-polar solvents, such as toluene, xylene, and benzene, readily dissolve sulfur-based materials despite their apparent chemical compatibility with sulfide-based SEs. This complicates the fabrication of film-type cathode composites with high sulfur content. Second, DOL maintains the solid state of the TSE upon completion of the in situ polymerization step while providing an ionically conductive solid (~0.308 mS cm). -1 ) is polymerized into a PDOL-based polymer. This is demonstrated by the negligible weight change of the catholyte before and after polymerization of LiFSI-DOL when it is dried under vacuum at 80 °C for 24 h (Figure 4c). Furthermore, the catholyte forms ionic pathways within the cathode and TSE, enhancing the contact between these layers by improving wettability. This impregnation with PDOL effectively enables the operation of the assembled cell at practical stack pressures (<1 MPa) and room temperature, marking a step toward an ideal solid-state battery system (Figure 4d).

[0195] Commercially available S-cathode (3.54 mg cm -2TSEs were assembled into full cells in combination with a Li metal anode (100 μm thick) and a 1 M S content of 0.05% S and tested under realistic conditions (stack pressure <1 MPa, 30 °C). The galvanostatic (constant current) initial discharge profiles of lithium-sulfur batteries (LiSBs) with liquid electrolyte (1 M LiTFSI, 0.8 M LiNO3DOL / DME) and TSE were compared (Fig. 5a). While the Li-S cell with liquid electrolyte (LE) exhibits two plateaus in the voltage profile, the solid-state Li-S cell with TSE only forms a plateau at approximately 2.15 V, which indicates the direct reaction of S to Li2S (S + 2Li), similar to that observed in conventional solid-state LiSBs with pelleted solid electrolyte. + +2e - =Li2S).

[0196] To further investigate the reaction processes occurring during discharge and charge, EIS spectra were collected at various points during the charge-discharge cycle of cells using TSE and LE, as shown in Figures 5b and 5c, respectively. The direct solid-solid conversion reaction using TSE resulted in a much larger absolute change in resistance than that using LE. During discharge from the initial state to 1.5 V, the charge-transfer resistance gradually increased due to the direct conversion of S to LiS, while the presence of a soluble liquid acting as a medium meant that the LE cell exhibited a lower intermediate resistance. During recharge, the impedance spectra returned to a similar shape to the initial state, indicating that LiS converted back to S. This indicates that TSE can be reversibly cycled without significant changes in resistance or trapping of S species.

[0197] As shown in Figure 5d, the TSE was cycled at 0.05 C as a solid-state LiSB coin cell. The coin cell exhibited stable cycling and high coulombic efficiency (approximately 99%). Furthermore, after 50 cycles, the solid-state LiSB achieved a capacity of 410 mAh g -1 This is the discharge capacity of the Li-S cell using LE (433 mAh g -1, Fig. 5e). In Fig. 5f, the fabricated solid-state Li-S cells exhibited stable battery cycling at various current densities from 0.02 C to 0.2 C. The cells exhibited capacities of 722, 484, 314, 176, 90, and 310 mAh g -1 (0.02, 0.05, 0.1, 0.15, 0.2, and 0.1 C, respectively) and showed excellent reversibility (maintained 98.7%) even after the current density was returned to 0.1 C. This also indicates that a stable interface is formed between the SE and the cathode without significant effects from the polysulfide shuttle or Li filament growth.

[0198] conclusion Thin (less than 50 μm), flexible solid electrolyte separators were fabricated by a facile method. Full cells using solid electrolyte separators integrated with ion-conducting cathode auxiliary electrolytes were also prepared. The integrated solid-state system exhibited excellent electrochemical performance under practical conditions (<1 MPa stack pressure at 30 °C), including 0.3 mA cm in a symmetric Li-Li cell. -2 equivalent to a CCD and 0.1mA cm -2 These include 500 hours of stable cycling in a Li-S full cell with a Li metal anode and a commercially available sulfur cathode, and over 50 cycles in a Li-S full cell with a Li metal anode and a commercially available sulfur cathode.

Claims

1. an electrolyte containing a lithium ion conductive compound; a binder containing a copolymer; Including, The lithium ion conductive compound contains sulfur, and the copolymer has a repeating unit containing a carboxylic acid group or a conjugate base thereof. Solid electrolyte separators for electrochemical storage devices.

2. 2. The solid electrolyte separator according to claim 1, wherein the copolymer is a block copolymer.

3. 3. The solid electrolyte separator according to claim 1, wherein the repeating unit containing a carboxylic acid group or a conjugate base thereof is derived from acrylic acid, methacrylic acid, or maleic acid.

4. 4. The solid electrolyte separator according to claim 1, wherein the copolymer is a carboxylated rubber, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, or a carboxylated polystyrene.

5. 5. The solid electrolyte separator according to claim 4, wherein the carboxylated rubber is a carboxylated nitrile butadiene rubber or a carboxylated styrene butadiene rubber.

6. 6. The solid electrolyte separator according to claim 1, wherein the copolymer has a total content of carboxylic acid groups and their conjugate bases of 15 wt % or less.

7. 7. The solid electrolyte separator according to claim 1, wherein the binder is contained in a total amount of 3.00 to 10.00 wt %, preferably about 5.00 wt %.

8. The solid electrolyte separator according to any one of claims 1 to 7, wherein the electrolyte is a sulfide solid electrolyte.

9. The electrolyte has the general formula Li ７－ｐ B.S. ６－ｐ X ｐ wherein B is phosphorus or arsenic, X is Cl, Br or I, and p is 0 to 1. Preferably, the electrolyte is Li ６ P.S. ５ The solid electrolyte separator according to any one of claims 1 to 8, wherein the solid electrolyte separator is SiO2.

10. The electrolyte has the general formula Li ４－ｑ Ge （１－ｑ） P ｑ S ４ 9. The solid electrolyte separator according to claim 1, wherein q is 0 to 1.

11. The electrolyte is Li ２ S - P ２ S ５ - LiCl, Li ２ S - SiS ２ 、LiI - Li ２ S - SiS ２ 、LiI - Li ２ S - P ２ S ５ 、LiI - Li ２ S - P ２ O ５ 、LiI - Li ３ PO ４ - P ２ S ５ 、Li ２ S - P ２ S ５ 、Li ３ PS ４ 、Li ７ P ３ S １１ The electrolyte is Li ２ S - B ２ S ３ 、Li ３ PO ４ - Li ２ S - Si ２ S, Li ３ PO ４ - Li ２ S - SiS ２ 、LiPO ４ - Li ２ S - SiS, Li １０ GeP ２ S １２ 、Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ 、Li ７ P ３ S １１ 、Li ｘ PS ｙ Cl<上标 ｚ 、Li ｘ PS ｙ Br ｚ 、 Li ｘ PS ｙ Cl ｚ Br １－Ｚ 、Li ｘ PS ｙ F ｚ 、Li ｘ P.S. ｙ F ｚ Cl １－ｚ and Li ｘ P.S. ｙ F ｚ Br １－ｚ The solid electrolyte separator according to any one of claims 1 to 8, wherein x, y, and z are selected from the following, and x, y, and z are all greater than 0.

12. The solid electrolyte separator according to any one of claims 1 to 11, which has a thickness of 50 µm or less.

13. 0.1~1.0mS・cm －１ The solid electrolyte separator according to any one of claims 1 to 12, having an ionic conductivity of

14. The solid electrolyte separator according to any one of claims 1 to 13, having a Young's modulus of 0.5 to 5.0 GPa.

15. lithium ion conductive compounds, copolymers, and solvent A masterbatch product for producing a solid electrolyte separator, comprising: A masterbatch product in which the lithium ion conductive compound contains sulfur and the copolymer has a repeating unit containing a carboxylic acid group or a conjugate base thereof.

16. 16. The masterbatch product according to claim 15, wherein the lithium ion conductive compound is as defined in any one of claims 8 to 11 and / or the copolymer is as defined in any one of claims 2 to 7.

17. 1. A method for manufacturing a solid electrolyte separator for an electrochemical storage device, comprising: (i) mixing a lithium ion conductive compound, a copolymer, and a solvent to produce a masterbatch product; and (ii) Calendaring the masterbatch product to produce a separator. wherein the lithium ion conductive compound contains sulfur, and the copolymer has a repeating unit containing a carboxylic acid group or a conjugate base thereof.

18. 18. The method according to claim 17, wherein the solvent is a non-polar solvent, preferably an aromatic non-polar solvent.

19. The method according to claim 18, wherein the non-polar solvent is toluene, xylene or benzene.

20. 15. An electrochemical storage device comprising a first electrode, a second electrode, and the solid electrolyte separator according to any one of claims 1 to 14, wherein the solid electrolyte separator is disposed between the first electrode and the second electrode.

21. 21. The electrochemical storage device of claim 20, wherein the solid electrolyte separator further comprises an integrated auxiliary electrolyte.

22. 22. The electrochemical storage device of claim 21, wherein the integrated auxiliary electrolyte comprises polydioxolane (PDOL).

23. 23. The electrochemical energy storage device according to any one of claims 20 to 22, wherein the first electrode is a cathode and the second electrode is an anode.

24. The electrochemical energy storage device according to any one of claims 20 to 23, wherein the first electrode contains sulfur.

25. 25. The electrochemical energy storage device according to any one of claims 20 to 24, wherein the second electrode comprises lithium.

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