Resin, resin solution, solid electrolyte slurry, solid electrolyte layer, positive electrode layer, negative electrode layer, and all-solid-state battery

Abstract

To provide a resin which is excellent in affinity for solid electrolytes and ion conductivity and is suitable as a binder of a solid electrolyte.SOLUTION: The resin has a structure represented by the following formula (1). In the formula (1), R1 represents a hydrogen atom or a C1-3 alkyl group; R2 represents a C1-6 divalent alkylene group; n represents an integer of 2 or more, and each R3 independently represents a C3-6 divalent alkylene group; and R4 represents a C3 or higher alkyl group or a phenyl group, and a hydrogen atom of the phenyl group may be substituted with a C1-3 alkyl group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a resin suitable for a solid electrolyte binder in a solid secondary battery, a resin solution, a solid electrolyte slurry, a solid electrolyte layer, a positive electrode layer, a negative electrode layer, and an all-solid-state battery. [Background technology]

[0002] In recent years, with the development of portable devices such as tablet computers and smartphones, as well as electric vehicles, the demand for secondary batteries as their power source has been expanding. Secondary batteries generally consist of electrodes (positive and negative electrodes) and an electrolyte, and charge and discharge occur through the movement of ions between the electrodes via the electrolyte. Such secondary batteries are used in a wide range of applications, from small devices such as mobile phones to large devices such as electric vehicles. Therefore, high safety and further improvement in performance are required.

[0003] To prevent fires and improve safety, solid-state secondary batteries have been developed, replacing conventional flammable liquid electrolytes with solid electrolytes. Sulfide-based and oxide-based materials are being widely investigated as solid electrolytes.

[0004] To improve the performance of secondary batteries, it is generally important to increase the contact interface between the active material and solid electrolyte in the electrode, as well as the contact interface between solid electrolyte particles. Here, the active material refers to a substance that participates in the reaction that generates electricity. While sulfide-based and oxide-based solid electrolytes have excellent ionic conductivity, it is difficult to increase the interface with the active material and they may not have sufficient strength, so the use of a binder has been proposed. Patent Document 1 describes a solid electrolyte dispersion paste containing an acrylic resin, and Patent Document 2 describes a composition that uses a polymer binder having a urethane bond, a urea bond, or the like to improve affinity with the solid electrolyte. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-050174 [Patent Document 2] International Publication No. 2020 / 138216 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, solid secondary batteries have been required to have not only high safety but also higher performance and mass productivity. When resins such as those described in Patent Documents 1 and 2 are used as binders for the positive electrode layer and solid electrolyte layer, the strength of each layer is improved. However, depending on the dispersion conditions, the affinity with the solid electrolyte may be insufficient, and the ionic conductivity of the binder may be insufficient, resulting in an increase in the internal resistance of the secondary battery. Furthermore, when stored at high temperatures for long periods, the internal resistance of the secondary battery may increase due to a reaction at the interface between the solid electrolyte and the binder. Therefore, a polymer electrolyte that has high affinity with the solid electrolyte, high ionic conductivity, and reduced risk of reaction with the solid electrolyte even at high temperatures is desired.

[0007] The present disclosure is directed to a resin that has excellent affinity with a solid electrolyte and excellent ionic conductivity and is suitable as a binder for the solid electrolyte. Another aspect of the present disclosure is directed to providing a resin solution, a solid electrolyte slurry, a solid electrolyte layer, a positive electrode layer, a negative electrode layer, and an all-solid-state battery that have excellent performance and high-quality characteristics. [Means for solving the problem]

[0008] According to at least one embodiment of the present disclosure, there is provided a resin characterized by having a structure represented by the following formula (1): [ka] In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R2 represents a divalent alkylene group having 1 to 6 carbon atoms. n represents an integer of 2 or greater, and each R3 independently represents a divalent alkylene group having 3 to 6 carbon atoms. R4 represents an alkyl group having 3 or more carbon atoms or a phenyl group, and the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms.

[0009] According to at least one embodiment of the present disclosure, there is provided a resin solution comprising the resin and a solvent. According to at least one embodiment of the present disclosure, there is provided a solid electrolyte slurry including the above resin, a solid electrolyte, and a solvent. According to at least one embodiment of the present disclosure, there is provided a solid electrolyte layer including the resin and a solid electrolyte. According to at least one embodiment of the present disclosure, there is provided a positive electrode layer including the resin and a solid electrolyte. According to at least one embodiment of the present disclosure, there is provided a negative electrode layer including the above resin and a solid electrolyte.

[0010] Furthermore, according to at least one aspect of the present disclosure, there is provided an all-solid-state battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer, wherein at least one layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the resin. [Effects of the Invention]

[0011] According to one aspect of the present disclosure, a resin, a resin solution, and a solid electrolyte slurry that have excellent affinity with a solid electrolyte and excellent ionic conductivity and are suitable as a binder for the solid electrolyte can be obtained. In addition, another aspect of the present disclosure can provide a solid electrolyte layer, a positive electrode layer, a negative electrode layer, and an all-solid-state battery that have excellent performance and high-quality characteristics. [Brief explanation of the drawings]

[0012] [Figure 1] Schematic cross-section of an all-solid-state battery DETAILED DESCRIPTION OF THE INVENTION

[0013] In the present disclosure, the expression "XX or more and YY or less" or "XX to YY" representing a numerical range means a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. In addition, when a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. In addition, in the present disclosure, for example, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means XX, YY, ZZ, a combination of XX and YY, or XX and Z. It means any of a combination of XX and Z, a combination of YY and ZZ, or a combination of XX, YY and ZZ.

[0014] The present inventors have conducted extensive research to achieve affinity with solid electrolytes and ionic conductivity, and have found that the use of a polyether (meth)acrylic resin modified with a polyether having a unit structure with three or more carbon atoms in a solid electrolyte binder for all-solid-state batteries makes it possible to suppress a decrease in the ionic conductivity of the solid electrolyte layer.

[0015] That is, the present disclosure relates to a resin having a structure represented by the following formula (1): [ka] In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R2 represents a divalent alkylene group having 1 to 6 carbon atoms. n represents an integer of 2 or greater, and each R3 independently represents a divalent alkylene group having 3 to 6 carbon atoms. R4 represents an alkyl group having 3 or more carbon atoms or a phenyl group, and the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms.

[0016] As a result of further investigation, the present inventors have found that when the molecular terminal of the polyether structure has a specific chemical structure, the ionic conductivity after high-temperature storage can be maintained and the decrease in secondary battery capacity during charge-discharge cycling can be suppressed. That is, the resin of the present disclosure satisfies the following conditions. A resin having a structure in which polyether monoacrylate is polymerized, in which the polyether portion has a unit structure with 3 to 6 carbon atoms (-R3-O- structure) The molecular end of the polyether moiety that is not bonded to the polymer main chain is an alkyl group or phenyl group having 3 or more carbon atoms via a urethane bond (R4 structure). The inventors speculate as follows about the reason why the use of the resin according to the present disclosure as a binder for a solid electrolyte produces the unexpected effect of making it difficult for the ionic conductivity of the solid electrolyte layer to decrease.

[0017] In a solid electrolyte layer, the binder binds the solid electrolyte particles together and increases the strength of the solid electrolyte layer. However, if the surface affinity between the solid electrolyte particles and the binder is insufficient, voids are likely to form on the surface of the solid electrolyte particles. Furthermore, if the ionic conductivity of the binder at the interface between the solid electrolyte particles and the binder is insufficient, carrier ions such as lithium ions have difficulty moving within the binder. As a result of the above, it is thought that the use of a binder reduces the ionic conductivity of the solid electrolyte layer.

[0018] The resin according to the present disclosure is a hydrophobic polyether in which the polyether moiety in the structure has a unit structure with three or more carbon atoms, and the end of the polyether moiety is blocked with a hydrophobic functional group via a urethane bond. The urethane bond at the end of the polyether moiety is a polar group and has affinity with the surface of the solid electrolyte, and the polyether moiety adjacent to the urethane bond has ionic conductivity. Therefore, when the resin according to the present disclosure is used as a binder, the surface of the solid electrolyte particles is blocked with a hydrophobic functional group. It is believed that the ionic conductivity of the solid electrolyte layer is less likely to decrease because voids are less likely to occur and the ionic conductive resin is present on the surface of the solid electrolyte. If the polyether portion is small and n is 1, the interaction with carrier ions such as lithium ions will be significantly reduced, which may result in a decrease in ionic conductivity. Therefore, n is 2 or more.

[0019] The resin according to the present disclosure is a polyether having a unit structure of three or more carbon atoms, the terminal of which is a non-reactive hydrophobic group via a urethane bond. Among polyethers, polyethers having three or more carbon atoms have ionic conductivity but low interaction with lithium in the solid electrolyte, and are therefore thought to be less likely to react with other components even when in contact with a sulfide-based solid electrolyte. Furthermore, the urethane bond at the end of the polyether moiety confers affinity to the solid electrolyte surface, but the presence of an alkyl group or phenyl group having three or more carbon atoms at the adjacent terminal position is thought to inhibit reaction between the urethane bond and components such as lithium in the solid electrolyte. Therefore, it is thought that ionic conductivity can be maintained even after high-temperature storage.

[0020] Furthermore, the resin preferably further has a structure represented by the following formula (2). [ka]

[0021] When the resin contains the structure of formula (2), the ionic conductivity of the binder is further increased when the resin is used as a binder, and it is believed that the decrease in the ionic conductivity of the solid electrolyte layer is further suppressed. Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. The components, materials, shapes, relative arrangements, etc. described in these embodiments do not limit the scope of the present disclosure.

[0022] (1) All-solid-state battery structure The all-solid-state battery has a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and at least one layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains a resin according to the present disclosure. It is preferable that the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contain a resin according to the present disclosure. It is preferable that the all-solid-state battery contains a resin according to the present disclosure as a binder.

[0023] An example of a secondary battery, which is an all-solid-state battery, using the resin of the present disclosure is shown in Fig. 1. The all-solid-state battery 1 shown in Fig. 1 is an example in which a resin is used as a binder for a solid electrolyte layer 3. The solid electrolyte layer 3 is provided between a positive electrode layer 2 provided on a positive electrode current collector 5 and a negative electrode layer 4 provided on a negative electrode current collector 13.

[0024] The positive electrode layer 2 includes at least a positive electrode active material 6, and may include a solid electrolyte 8, a positive electrode layer binder 7, and a conductive additive 9. The positive electrode layer binder 7 may include a resin according to the present disclosure. That is, the positive electrode layer preferably contains the resin according to the present disclosure and a solid electrolyte.

[0025] The solid electrolyte layer 3 includes a solid electrolyte 8 and a solid electrolyte binder 10. It is preferable to use a resin according to the present disclosure as the solid electrolyte binder 10. That is, it is preferable that the solid electrolyte layer includes a resin according to the present disclosure and a solid electrolyte.

[0026] The negative electrode layer 4 includes at least a negative electrode active material 11, and may also include a solid electrolyte 8, a negative electrode layer binder 12, and a conductive additive 9. It is preferable to use a resin according to the present disclosure as the negative electrode layer binder 12. That is, it is preferable that the negative electrode layer includes a resin according to the present disclosure and a solid electrolyte. In addition to the configuration shown in the figure, for example, metallic lithium can also be used as the negative electrode layer 4.

[0027] In order to more effectively achieve the effects of the present disclosure, it is preferable that the solid electrolyte layer 3 contains a resin according to the present disclosure as a binder 10, as a solid electrolyte binder, as shown in Fig. 1. Furthermore, it is preferable that the positive electrode layer binder 7 in the positive electrode layer 2 and the negative electrode layer binder 12 in the negative electrode layer 4 contain a resin according to the present disclosure.

[0028] (Method for manufacturing all-solid-state batteries) All-solid-state batteries (solid-state secondary batteries) can be fabricated by known cell fabrication methods such as laminate cell type, coin cell type, pressurized cell type, etc. The laminate cell type will be described below as an example.

[0029] A laminate is obtained in which a positive electrode layer, a solid electrolyte, and a negative electrode layer are disposed between a positive electrode current collector and a negative electrode current collector. Electrode tabs are welded to the positive electrode current collector and the negative electrode current collector. The laminate, in which the positive electrode current collector, positive electrode layer, solid electrolyte layer, negative electrode layer, and negative electrode current collector are stacked in this order, is wrapped in aluminum laminate film and sealed under reduced pressure using a vacuum packaging machine. The ends of the electrode tabs are exposed outside the laminate film, and the tabs and the aluminum laminate film are bonded together by thermocompression, and the product is sealed. After sealing, if necessary, pressure may be applied using an isostatic pressure device or the like. The solid electrolyte may include a polymer electrolyte. In addition to the above laminate, other layers such as elastic materials or resin materials may be laminated within the aluminum laminate film for the purposes of strength, formability, etc. Also, a bipolar type in which multiple laminates are stacked may be used.

[0030] (Positive electrode current collector) The positive electrode current collector may be, for example, a metal foil. Examples of metals include aluminum, stainless steel, copper, silver, gold, platinum, nickel, and palladium. The metals may be used alone or in combination of two or more.

[0031] (Cathode active material) As the positive electrode active material, for example, a material commonly used in secondary batteries such as lithium ion secondary batteries can be used. For example, (CF) m , (C2F) m , MnO2, TiS2, MoS2, FeS2, Li xA CoO2, Li xA NiO2, Li xA MnO2, Li xA Co y Ni 1-y O2, Li xA Co y M 1-y O z , Li xA Ni 1-y M y O z , Li xB Mn2O4, Li xB Mn 2-y M yO4 (in the above formulas, M represents at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B; xA=0 to 1.2, xB=0 to 2.0, y=0 to 0.9, and z=2.0 to 2.3), vanadium oxides and lithium compounds thereof, niobium oxides and lithium compounds thereof, conjugated polymers using organic conductive substances, and olivine-based compounds. The xA and xB values ​​in the above composition formulas are values ​​before the start of charge / discharge. The positive electrode active material can be used alone or in combination of two or more.

[0032] (Conductive additive) The conductive additive can also be one commonly used in secondary batteries such as lithium-ion secondary batteries. Examples include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fiber and metal fiber, metal powders such as aluminum powder, conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene derivatives. The conductive additives can be used alone or in combination of two or more.

[0033] (active material binder) The active material binder is preferably a resin according to the present disclosure, but other active material binders than the resin according to the present disclosure may also be used.

[0034] Other active material binders that can be used include those commonly used in secondary batteries such as lithium-ion secondary batteries, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose.

[0035] The resin according to the present disclosure may be used as a binder for a solid electrolyte layer, as a binder for a positive electrode active material, as a binder for a negative electrode active material, or as a binder for a solid electrolyte, a binder for a positive electrode active material, and a binder for a negative electrode active material.

[0036] That is, it is preferable that the all-solid-state battery satisfy at least one of the following (i) to (iii). (i) The positive electrode layer 2 has a positive electrode active material 6, a solid electrolyte 8, and a positive electrode layer binder 7 that binds the positive electrode active material 6 and the solid electrolyte 8 together, and the positive electrode layer binder 7 is a resin according to the present disclosure. (ii) The solid electrolyte layer 3 has a solid electrolyte 8 and a solid electrolyte binder 10 that fixes the solid electrolyte, and the solid electrolyte binder 10 is a resin according to the present disclosure. (iii) The negative electrode layer 4 has a negative electrode active material 11, a solid electrolyte 8, and a negative electrode layer binder 12 that binds the negative electrode active material 11 and the solid electrolyte 8 together, and the negative electrode layer binder 12 is a resin according to the present disclosure.

[0037] It is particularly preferable to use a resin according to the present disclosure as the positive electrode active material binder 7, since lithium ions can easily reach from the surface to the depths of the positive electrode layer 2. The resin as the positive electrode layer binder 7 may be used alone or in combination of two or more.

[0038] The positive electrode layer 2 can be produced, for example, by crimping a positive electrode mixture previously mixed on the surface of the positive electrode current collector 5, or by applying and drying a positive electrode mixture slurry, and further rolling it as necessary. It can also be prepared by kneading a positive electrode active material, a conductive auxiliary material, and a positive electrode layer binder. The positive electrode mixture slurry can also be prepared, for example, by dissolving or dispersing a positive electrode active material, a solid electrolyte, a conductive auxiliary material, and a positive electrode layer binder in a medium such as dehydrated xylene, butyl butyrate, mesitylene, anisole, isobutyronitrile, etc.

[0039] <​​​​​​​​​​​​​​​​​​The negative electrode material may also contain a conductive additive. Examples of the conductive additive include graphite, such as natural graphite and artificial graphite, and carbon black, such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. When a polymer electrolyte is used as the bulk electrolyte, graphite is particularly suitable as the negative electrode active material.

[0042] Examples of the conductive additive include conductive fibers such as carbon fibers, carbon nanotubes, and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene dielectrics.

[0043] (solid electrolyte) In all-solid-state batteries, solid electrolytes are sometimes used as bulk electrolytes that are disposed between the positive and negative electrodes as a lithium ion migration layer and also function as separators. Furthermore, by mixing them into the active material layers of the positive and negative electrodes, they can be used as auxiliary agents to improve the conductivity of lithium ions.

[0044] The resin according to the present disclosure can be suitably used as a binder in any of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer, thereby enabling the contact interface between the solid electrolyte, the positive electrode active material, and the negative electrode active material to be enlarged, and furthermore, having flexibility that allows the resin to follow the expansion and contraction of the positive electrode active material and the negative electrode active material, thereby improving the characteristics of the secondary battery.

[0045] The auxiliary materials for the solid electrolyte layer, the positive electrode layer, and the negative electrode layer can be solid electrolytes, such as oxide-based solid electrolytes, sulfide-based solid electrolytes, and complex hydride-based solid electrolytes.

[0046] Oxide-based solid electrolytes are 1.5 Al 0.5 Ge 1.5 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7Nasicon-type compounds such as (PO4)3, Li 6.25 LA3ZR2Al 0.25 O 12 In addition, oxide-based solid electrolytes include garnet-type compounds such as Li 0.33 Li 0.55 Perovskite-type compounds such as TiO3 are also included. Oxide-based solid electrolytes include Li 14 Examples include lithiated compounds such as Zn(GeO4)4, and acid compounds such as Li3PO4, Li4SiO4, and Li3BO3. Specific examples of sulfide-based solid electrolytes include Li6PS5Cl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, Examples include LiI-Li3PO4-P2S5, Li2S-P2S5, etc. The solid electrolyte may be crystalline or amorphous, or may be glass ceramics. Note that the term "Li2S-P2S5" refers to a sulfide-based solid electrolyte made using raw materials containing Li2S and P2S5.

[0047] The resin according to the present disclosure can be used as a solid electrolyte binder for a solid electrolyte layer, a positive electrode layer binder, and a negative electrode layer binder. The configuration of the resin according to an embodiment of the present disclosure will be described in detail below.

[0048] <Resin> A resin according to an embodiment of the present disclosure has a polymer having the following structure: For example, a polyether (meth)acrylic resin having the following structure:

[0049] The resin according to the present disclosure has a structure represented by the following formula (1): [ka]

[0050] In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms (preferably 1 or 2, more preferably 1). R2 represents a divalent alkylene group having 1 to 6 carbon atoms (preferably 2 to 6). n represents an integer of 2 or more, and R3 each independently represents an alkylene group having 3 to 6 carbon atoms. That is, multiple R3s represented by n may be the same or different from each other. n is the average number of moles added. n is preferably 2 to 50, more preferably 5 to 50, and even more preferably 5 to 30. R4 represents an alkyl group having 3 or more carbon atoms or a phenyl group, and the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms.

[0051] In formula (1), R3 represents the number of carbon atoms in the unit structure of the polyether moiety. In the resin according to the present disclosure, the polyether moiety in the structure is a hydrophobic polyether having a unit structure with 3 to 6 carbon atoms. The polyether unit structure preferably has 4 to 5 carbon atoms, which provides excellent ionic conductivity and is less likely to react with the solid electrolyte. In other words, it is preferable that each R3 is independently an alkylene group with 4 to 5 carbon atoms.

[0052] Examples of the unit structure of the polyether moiety include: 1,2-propylene oxide, 1,3-propylene oxide, 1-ethyl-1,2-ethylene oxide, 1,4-tetramethylene oxide, 1-methyl-1,3-propylene oxide, 2-methyl-1,3-propylene oxide, 2-methyl-1,4-tetramethylene oxide, 1,5-pentamethylene oxide, 1-n-butyl-1,2-ethylene oxide, 1,6-tetrahexylene oxide can be used.

[0053] R4 is a terminal functional group bonded to a urethane group at the end of the polyether moiety, and has 3 or more carbon atoms. represents an alkyl group or a phenyl group. Examples of alkyl groups having 3 or more carbon atoms include propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and 2-methylhexyl. That is, the alkyl group for R4 preferably has 3 to 8 carbon atoms. When R4 is a phenyl group, the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 4 carbon atoms (more preferably 1 carbon atom), but an unsubstituted phenyl group is preferred.

[0054] The content of the structure represented by formula (1) in the resin is preferably 50 to 100% by mass, more preferably 75 to 98% by mass, and even more preferably 85 to 97% by mass.

[0055] The structure represented by formula (1) preferably includes a structure represented by the following formula (1-1) or a structure represented by formula (1-2). [ka]

[0056] In formula (1-1) and formula (1-2), n1, n2, and n3 are the average number of moles added. n1 represents an integer of 1 or more (preferably 1 to 30, more preferably 1 to 12), n2 represents an integer of 1 or more (preferably 1 to 50, more preferably 5 to 30), and n3 represents an integer of 4 or more (preferably 4 to 50, more preferably 5 to 30). R1, R2, and R4 are the same as in formula (1).

[0057] The chain sandwiched between -COO- and -CONH- may further contain a polyether unit structure having 2 or less carbon atoms or 7 or more carbon atoms, to the extent that the effects of the present disclosure are not impaired. When a polyether unit structure having 2 or less carbon atoms, i.e., ethylene oxide, is contained, the content is preferably low from the viewpoint of chemical stability with respect to the solid electrolyte. It is more preferable that the chain is substantially free of polyether unit structures having 2 or less carbon atoms.

[0058] In the resin according to the present disclosure, the average number of moles n of polyether unit structures added per mole of (meth)acryloyl residue is 2 moles or more. The average number of moles added is preferably 2 to 50, more preferably 5 to 50, even more preferably 5 to 30, and even more preferably 4 to 20. By keeping the number of moles within the above range, the ionic conductivity of the resin is improved, resulting in a higher ionic conductivity. The (meth)acryloyl residue is a form in which a (meth)acryloyl group is addition polymerized, and is represented by the following structure in formula (1), for example.

[0059] [ka]

[0060] The polyether unit structure in the structure represented by formula (1) (preferably formula (1-1) or formula (2-1)) can be obtained, for example, by ring-opening polymerization of alkylene oxide or dehydration condensation of alkylene diol. In the formula (1) or (1-1), the arrangement of the polyether unit structures may be a block copolymer or a random copolymer, and is preferably a random copolymer.

[0061] <Ionic functional group> The resin having the structure represented by formula (1) preferably further has a structure represented by the following formula (2).

[0062] For example, the structure represented by the following formula (2) can be a reaction product of a sulfonylimide ionic compound having an unsaturated reactive functional group. [ka]

[0063] In formula (2), R5 represents a hydrogen atom or a methyl group. R6 represents a divalent linking group, preferably represented by -COO-A-, where A is preferably an alkylene group having 1 to 10 carbon atoms (more preferably 1 to 8 carbon atoms). R7 represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms. X + is at least one selected from the group consisting of lithium ions, sodium ions, and potassium ions.

[0064] Since the structure represented by formula (2) is an anionic structure with a relatively large molecular size, the formula By introducing the structure represented by (2) into the polymer structure, crystallinity can be reduced. Therefore, crystallization can be suppressed in the resin of the present disclosure. As a result, it is possible to impart flexibility to the solid electrolyte layer, the positive electrode layer, and the negative electrode layer, and it is also possible to maintain high ionic conductivity even at low temperatures.

[0065] The content of the structure represented by formula (2) in the resin according to the present disclosure is preferably 0.5 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the structure represented by formula (1). When the content of formula (2) is within this range, it is possible to expect an improvement in ionic conductivity due to a decrease in crystallinity while containing a sufficient amount of ions. The structure contained in the resin can be confirmed by analysis using known means such as pyrolysis GC / MS, FT-IR, and NMR.

[0066] Cation X shown in formula (2) + The cation may be at least one selected from the group consisting of lithium ions, sodium ions, and potassium ions. The cation may be selected depending on the carrier in the secondary battery. For example, lithium may be selected for a lithium-ion secondary battery that uses lithium cobalt oxide or the like as the positive electrode active material, and sodium may be selected for a sodium-sulfur secondary battery.

[0067] <Supporting electrolyte> The resin according to the present disclosure preferably contains at least one supporting electrolyte selected from the group consisting of lithium salts, sodium salts, and potassium salts. For example, the resin may be a resin mixture containing the supporting electrolyte. Examples of anion species contained in the supporting electrolyte include: Examples of the anion include a fluoroalkylsulfonylimide anion, a fluorosulfonylimide anion, a fluoroalkylsulfonate anion, a fluorosulfonate anion, a fluoroalkylcarboxylic acid anion, a fluoroalkylmethide anion, a fluoroborate anion, a fluorophosphate anion, a dicyanamide anion, a thiocyanate anion, a bisoxalatoborate anion, a perchlorate anion, and derivatives thereof.

[0068] More specifically, the anions contained in the supporting electrolyte are bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoromethanesulfonate anion (CF3-SO3 - ), hexafluorophosphate anion (PF6 - ), fluoroborate anion (BF4 - ), dicyanamide anion (N(CN)2 - ), thiocyanate anion (SCN - ) is preferred.

[0069] The anion is preferably at least one selected from the group consisting of a fluoroalkylsulfonylimide anion and a fluorosulfonylimide anion in terms of chemical stability with respect to the positive electrode active material and the solid electrolyte, and more preferably at least one selected from the group consisting of a bis(trifluoromethanesulfonyl)imide anion and a bis(fluorosulfonyl)imide anion.

[0070] The supporting electrolyte may be used alone or in combination of two or more. + The cation may be at least one selected from the group consisting of lithium ions, sodium ions, and potassium ions. The cation may be selected depending on the carrier in the secondary battery.

[0071] The content of the supporting electrolyte in the resin mixture is preferably 1 to 40 parts by mass, more preferably 1 to 20 parts by mass, and most preferably 1 to 7 parts by mass, relative to 100 parts by mass of the resin. When the content of the supporting electrolyte is within this range, it is well compatible with the resin and does not precipitate, and high ionic conductivity is obtained.

[0072] The resin according to the present disclosure is, for example, a polymer (copolymer) of a compound represented by the following formula (3) and, if necessary, a material represented by formula (4). Polyether mono(meth)acrylate, one end of which is terminated with an alkyl group having 3 or more carbon atoms or a phenyl group via a urethane group [ka]

[0073] Sulfonylimide ionic compounds with unsaturated reactive functional groups [ka]

[0074] The compound represented by formula (3) corresponds to the structure represented by formula (1), and the compound represented by formula (4) corresponds to the structure represented by formula (2). In formula (3), R1, R2, R3, n, and R4 are the same as those in formula (1). In addition, in formula (4), R5, R7, and X + is the same as in formula (2). R16 is an alkylene group having 1 to 10 carbon atoms (more preferably 1 to 8 carbon atoms). For the polymerization of the resin, a known polymerization initiator may be used as needed, such as a thermal polymerization initiator. The weight average molecular weight of the resin is preferably 20,000 to 200,000, 50,000 to 150,000, or 60,000 to 130,000.

[0075] (Methods for forming solid electrolyte layers, positive electrode layers, and negative electrode layers) The method for forming the solid electrolyte layer, the positive electrode layer, or the negative electrode layer is not particularly limited. For example, the above-mentioned resin is mixed with a solid electrolyte, a positive electrode active material, or a negative electrode active material, and a solvent by a known method to obtain a slurry for forming each layer. The slurry is applied by a known application method such as bar coating, doctor blade coating, or roll coating, and then the solvent contained in the applied slurry is dried by heating under reduced pressure to form the solid electrolyte layer, the positive electrode layer, or the negative electrode layer.

[0076] The present disclosure provides a resin solution comprising a resin according to the present disclosure and a solvent. The present disclosure also provides a solid electrolyte slurry comprising a resin according to the present disclosure, a solid electrolyte, and a solvent. The solvent is not particularly limited, and any known solvent capable of dissolving the resin can be used. Examples of the solvent include n-butyl n-butyrate, isobutyronitrile, toluene, xylene, mesitylene, dibutyl ether, butyronitrile, dibutyl ketone, and anisole. The resin concentration in the resin solution and solid electrolyte slurry is not particularly limited, and can be appropriately set depending on the intended use. Just do that. [Example]

[0077] Specific examples and comparative examples according to the present disclosure are shown below, but the present disclosure is not limited to the following examples and comparative examples.

[0078] First, polyether acrylates that form the structure represented by formula (1) were synthesized. A synthesis example of a polyether monoacrylate that can form the structure represented by formula (1) is shown below.

[0079] <Synthesis of terminal urethane-modified polyether monoacrylate> (Terminal urethane modified polyether monoacrylate A-1) 15.0 parts by mass of 2-hydroxyethyl methacrylate (Tokyo Chemical Industry Co., Ltd.), 0.01 parts by mass of butylhydroxytoluene (Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.02 parts by mass of boron trifluoride diethyl ether complex (Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a nitrogen-purged autoclave and stirred under reduced pressure at 120°C to dissolve and dehydrate. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 16.06 parts by mass of propylene oxide gas was continuously introduced over 30 minutes while maintaining the vessel internal pressure at 0.5 MPa. The reaction was carried out for 180 minutes while maintaining the temperature at 60°C. The temperature was then lowered to 25°C and the mixture was stirred until the change in pressure inside the vessel reached 0.01 MPa / 30 minutes. 20 parts by mass of pure water was added to the resulting polymer and the mixture was stirred at 40°C for 30 minutes. Then, 1.10 parts by mass of an alkali adsorbent, Kyoward 600 (Kyowa Chemical Industry Co., Ltd.), was added and the mixture was stirred for another 30 minutes. The alkali adsorbent was then removed by filtration, and the mixture was dried under reduced pressure at 120°C to obtain polyether monoacrylate.

[0080] The resulting polyether monoacrylate was then dissolved in 39.0 ml of methyl ethyl ketone, and 14.82 parts by mass of phenyl isocyanate (Tokyo Chemical Industry Co., Ltd.) was added, followed by a reaction at 70°C for 5 hours. The reaction solution was then cooled to room temperature, and the solution was washed twice with 40 ml of a 2% aqueous potassium hydroxide solution, and then twice with 40 ml of purified water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-1.

[0081] (Polyether monoacrylate A-2, A-3, A-4) Terminally urethane-modified polyether monoacrylates A-2, A-3, and A-4 were obtained in the same manner as terminally urethane-modified polyether monoacrylate A-1, except that the amount of propylene oxide added was changed as shown in Table 1. In A-4, 2-hydroxyethyl methacrylate was replaced with 2-hydroxypropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in the amount shown in Table 1, and 1,2-butylene oxide was used in addition to propylene oxide in the amount shown in Table 1.

[0082] (Polyether monoacrylate A-5) 15.0 parts by mass of 2-hydroxypropyl methacrylate (Tokyo Chemical Industry Co., Ltd.), 0.03 parts by mass of butylhydroxytoluene (Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.02 parts by mass of boron trifluoride diethyl ether complex (Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a nitrogen-purged autoclave and stirred under reduced pressure at 120°C to dissolve and dehydrate. The system was then depressurized to -0.1 MPa at 100°C, and 54.00 parts by mass of 1,2-butylene oxide gas was continuously introduced over 30 minutes while maintaining the vessel internal pressure at approximately 0.5 MPa. The reaction was allowed to proceed for 240 minutes while maintaining the temperature at 70°C. The temperature was then lowered to 25°C, and the mixture was stirred until the change in pressure inside the vessel reached 0.01 MPa / 30 minutes. 20 parts by mass of pure water was added to the resulting polymer, and the mixture was stirred at 40°C for 30 minutes. 1.10 parts by mass of an alkali adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was then added, and the mixture was stirred for another 30 minutes. The alkali adsorbent was then removed by filtration, and the mixture was dried under reduced pressure at 120°C to obtain the polyether. Termonoacrylate was obtained.

[0083] The resulting polyether monoacrylate was then dissolved in 39.0 ml of methyl ethyl ketone, and 12.38 parts by mass of butyl isocyanate (Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.08 parts by mass of dibutyltin dilaurate (Tokyo Chemical Industry Co., Ltd.) were added, followed by a reaction at 70°C for 6 hours. The reaction solution was then cooled to room temperature, and the mixture was washed twice with 40 ml of a 2% aqueous potassium hydroxide solution, and then twice with 40 ml of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-5.

[0084] (Polyether monoacrylate A-6 to A-9) Terminally urethane-modified polyether monoacrylates A-6 to A-9 were obtained in the same manner as for terminally urethane-modified polyether monoacrylate A-5, except that the types and amounts of the starting material, alkylene oxide compound, and isocyanate compound were changed as shown in Table 1.

[0085] (Polyether monoacrylate A-10) 15.0 parts by mass of 6-hydroxyhexyl methacrylate (Tokyo Chemical Industry Co., Ltd.), 0.03 parts by mass of butylhydroxytoluene (Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.02 parts by mass of boron trifluoride diethyl ether complex (Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a nitrogen-purged autoclave and stirred under reduced pressure at 120°C to dissolve and dehydrate. The system was then depressurized to -0.1 MPa at 100°C, and 58.1 parts by mass of 1,2-epoxyhexane (Tokyo Chemical Industry Co., Ltd.) gas was continuously introduced over 30 minutes while maintaining the vessel internal pressure at approximately 0.5 MPa. The reaction was allowed to proceed for 280 minutes while maintaining the temperature at 80°C. The temperature was then lowered to 25°C and the mixture was stirred until the change in pressure inside the vessel reached 0.01 MPa / 30 minutes. 20 parts by mass of pure water was added to the resulting polymer and the mixture was stirred at 40°C for 30 minutes. Then, 1.10 parts by mass of an alkali adsorbent, Kyoward 600 (Kyowa Chemical Industry Co., Ltd.), was added and the mixture was stirred for another 30 minutes. The alkali adsorbent was then removed by filtration, and the mixture was dried under reduced pressure at 120°C to obtain polyether monoacrylate.

[0086] The resulting polyether monoacrylate was then dissolved in 39.0 ml of methyl ethyl ketone, and 8.23 ​​parts by mass of isopropyl isocyanate (Tokyo Chemical Industry Co., Ltd.) and 0.08 parts by mass of dibutyltin dilaurate (Tokyo Chemical Industry Co., Ltd.) were added, followed by a reaction at 70°C for 6 hours. The reaction solution was then cooled to room temperature, and the mixture was washed twice with 40 ml of a 2% aqueous potassium hydroxide solution, and then twice with 40 ml of purified water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-10.

[0087] [Table 1]

[0088] The structure of the obtained polyether mono(meth)acrylate is shown in formula (5) and Table 2. [ka]

[0089] [Table 2] In Table 2, m represents the number of moles of ether unit structure 1 added, and n represents the number of moles of ether unit structure 2 added when a plurality of ether unit structures are present.

[0090] <Synthesis of reactive ionic compounds> (Ionic Compound B-1) 15.0 g (0.06 mol) of 3-Sulfopropyl Methacrylate Potassium Salt (Tokyo Chemical Industry Co., Ltd.) was dissolved in 100 mL of THF and N,N- After suspending the mixture in 0.5 mL of dimethylformamide, 20 mL (0.28 mol) of thionyl chloride was added and stirred for 3 hours. The mixture was concentrated under reduced pressure, and the residue was dissolved in dichloromethane. After washing with 50 mL of pure water and 50 mL of brine, the mixture was concentrated under reduced pressure again to obtain a pale yellow liquid.

[0091] The resulting pale yellow liquid was added to a solution of 9.20 g (0.06 mol) of trifluoromethanesulfonamide (Tokyo Chemical Industry Co., Ltd.) and 27.3 mL (0.20 mol) of triethylamine (Kishida Chemical Co., Ltd.) dissolved in 50 mL of tetrahydrofuran. The mixture was stirred for 2 hours, and then the reaction solution was concentrated under reduced pressure. The resulting residue was dissolved in dichloromethane, washed with 150 mL of pure water, and the organic layer was dried under reduced pressure to obtain a yellow liquid. The resulting yellow liquid was dissolved in 300 mL of tetrahydrofuran, and 1.43 g (0.18 mol) of lithium hydride (Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred overnight. Unreacted lithium hydride was removed by filtration through Celite, and the filtrate was dried under reduced pressure to obtain ionic compound B-1.

[0092] (Synthesis of ionic compound B-2) Ion compound B-2 was obtained in the same manner as for ionic compound B-1, except that the starting material was changed to 15.9 g (0.06 mol) of 3-sulfopropyl acrylate potassium salt (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0093] (Synthesis of ionic compound B-3) 7.78 g (0.07 mol) of hydroxymethanesulfonate (Atomax Chemical Products) was dissolved in 50 mL of THF, and 5.17 g (0.06 mol) of methacrylic acid (Kishida Chemical) and molecular sieves were added, followed by stirring at 80 °C for 3 hours. The filtrate was filtered through Celite and dried under reduced pressure, then dissolved again in 50 mL of THF, and 2.41 g (0.06 mol) of potassium hydride (Merck) was added and stirred at room temperature for 2 hours. The white solid obtained after drying under reduced pressure was used as the starting material to obtain ionic compound B-3 in the same manner as for ionic compound B-1.

[0094] (Synthesis of ionic compound B-4) 12.9 g of 1-HEPTANESULFONYL CHLORIDE, 7-HYDROXY (Hong Kong Chemhere Products) and 6.07 g (0.06 mol) of triethylamine (Kishida Chemical Co., Ltd.) were added to 80 mL of dichloromethane and stirred at room temperature. After washing with 100 mL of pure water, the organic phase was dried under reduced pressure to obtain an oily liquid. 5.64 g (0.06 mol) of sodium acrylate (Merck) was dissolved in 50 mL of ethanol, and the oily liquid obtained above and 0.022 g (0.20 mmol) of hydroquinone (Kanto Chemical Co., Ltd.) were added and stirred at 70 °C for 5 hours. The pale yellow solid obtained after drying under reduced pressure was used as the starting material to obtain ionic compound B-4 in the same manner as ionic compound B-2.

[0095] (Synthesis of ionic compound B-5) Ionic compound B-5 was obtained in the same manner as for ionic compound B-2, except that the reactant was changed from trifluoromethanesulfonamide (Tokyo Chemical Industry Co., Ltd.) to 5.94 g (0.06 mol) of sulfamoyl fluoride (Atomax Chemical Products).

[0096] (Synthesis of ionic compound B-6) The same procedure as for ionic compound B-1 was repeated except that the reactant was changed from trifluoromethanesulfonamide (Tokyo Chemical Industry Co., Ltd.) to 18.0 g (0.06 mol) of nonafluorobutane-1-sulfonamide (Enamine Co., Ltd.). Ionic compound B-6 was obtained.

[0097] The structures of the resulting reactive ion compounds B-1 to B-6 are shown in formula (6) and Table 3. [ka]

[0098] [Table 3]

[0099] <Resin synthesis> [Example 1] A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen gas inlet tube was charged with 300.0 parts by mass of toluene, and the temperature was raised to 110° C. under a nitrogen gas flow. Next, 100.0 parts by mass of terminally urethane-modified polyether monoacrylate A-1, an initiator (trade name A mixture of 0.2 parts by mass of Kayaester O (manufactured by Nouryon Chemical Co., Ltd.) was added dropwise over 2 hours, and the mixture was heated under reflux for an additional 5 hours while maintaining the temperature at 110°C. The temperature was then lowered to 30°C, and the toluene was distilled off under reduced pressure. The mixture was allowed to cool to room temperature, and 100.0 parts by mass of n-butyl n-butyrate that had been previously dehydrated was added and dissolved by stirring, yielding Resin 1 according to Example 1.

[0100] The weight-average molecular weight was measured using an HLC-8120GPC (Tosoh Corporation) as the measuring instrument, two TSKgel SuperHM-M (Tosoh Corporation) columns, and THF as the solvent. Measurements were performed at a temperature of 40°C and a THF flow rate of 0.6 ml / min using a 0.1 mass% THF solution as the measurement sample and an RI (refractive index) detector. A calibration curve was created using several monodisperse standard polystyrenes (Tosoh Corporation) as standard samples, and the weight-average molecular weight was calculated from the retention time of the measurement sample obtained based on this. The weight average molecular weight of Resin 1 according to Example 1 was 76,000.

[0101] [Examples 2 to 10] Resins 2 to 10 according to Examples 2 to 10 were obtained in the same manner as in Example 1, except that the terminal urethane-modified polyether monoacrylate was changed as shown in Table 4.

[0102] [Example 11] A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen gas inlet tube was charged with 300.0 parts by mass of acetonitrile, and the temperature was raised to 80°C under a nitrogen gas flow. Next, a mixture of 95.0 parts by mass of terminally urethane-modified polyether monoacrylate A-2, 5 parts by mass of reactive ion compound B-1, and 0.2 parts by mass of an initiator (trade name Kayaester O, manufactured by Nouryon Chemical Co., Ltd.) was added dropwise over 2 hours, and the mixture was heated to reflux for an additional 6 hours while maintaining the temperature at 82°C. Next, the temperature was lowered to 30°C, and then acetonitrile was distilled off under reduced pressure. The mixture was allowed to cool to room temperature, and 100.0 parts by mass of pre-dehydrated isobutyronitrile was added and dissolved by stirring to obtain Resin 11 according to Example 11. The weight average molecular weight of Resin 11 was 92,000.

[0103] [Examples 12 to 17] Resins 12 to 17 according to Examples 12 to 17 were obtained in the same manner as in Example 11, except that the type and amount of the terminally urethane-modified polyether monoacrylate and the type and amount of the reactive ionic compound were changed as shown in Table 4.

[0104] [Example 18] A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen gas inlet tube was charged with 300.0 parts by mass of toluene, and the temperature was raised to 110° C. under a nitrogen gas flow. Next, 100.0 parts by mass of terminally urethane-modified polyether monoacrylate A-9, an initiator (trade name A mixture of 0.2 parts by mass of Kayaester O (manufactured by Nouryon Chemical Co., Ltd.) was added dropwise over 2 hours, and the mixture was heated under reflux for an additional 5 hours while maintaining the temperature at 110°C. Next, the temperature was lowered to 30°C, and then toluene was distilled off under reduced pressure. The mixture was allowed to cool to room temperature, and 5.0 parts by mass of lithium bis(trifluoromethanesulfonyl)imide (manufactured by Kishida Chemical Co., Ltd.) as a supporting electrolyte and 100.0 parts by mass of n-butyl n-butyrate that had been previously dehydrated were added and dissolved by stirring, thereby obtaining Resin 18 according to Example 18.

[0105] [Example 19] Resin 19 of Example 19 was obtained in the same manner as in Example 18, except that the type and amount of the reactive ionic compound were changed as shown in Table 4.

[0106] [Example 20] A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen gas inlet tube was charged with 300.0 parts by mass of acetonitrile, and the temperature was raised to 80°C under a nitrogen gas flow. Next, a mixture of 97.0 parts by mass of terminally urethane-modified polyether monoacrylate A-9, 3 parts by mass of reactive ion compound B-1, and 0.2 parts by mass of initiator (product name: Kayaester O, manufactured by Nouryon Chemical Co., Ltd.) was added dropwise over 2 hours, and the mixture was heated to reflux for an additional 6 hours while maintaining the temperature at 82°C. Next, the temperature was lowered to 30°C, and then acetonitrile was distilled off under reduced pressure. The mixture was allowed to cool to room temperature, and 2.0 parts by mass of lithium bis(fluorosulfonyl)imide (Kishida Chemical Co., Ltd.) as a supporting electrolyte and 100.0 parts by mass of pre-dehydrated isobutyronitrile were added and dissolved by stirring to obtain Resin 20 according to Example 20. Resin 20 had a weight average molecular weight of 89,000.

[0107] [Table 4]

[0108] [Comparative Example 1] A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen gas inlet tube was charged with 300.0 parts by mass of acetonitrile and heated to 110°C under a nitrogen gas stream. Next, a mixture of 100.0 parts by mass of methoxypolyethylene glycol monoacrylate Light Acrylate 130A (manufactured by Kyoeisha Chemical Co., Ltd.) and 0.2 parts by mass of an initiator (trade name Kayaester O, manufactured by Nouryon Chemical Co., Ltd.) was added dropwise over 2 hours, and the mixture was heated to reflux for an additional 5 hours while maintaining the temperature at 110°C. The temperature was then lowered to 30°C, and the acetonitrile was distilled off under reduced pressure. The mixture was allowed to cool to room temperature, and 100.0 parts by mass of pre-dehydrated isobutyronitrile was added and dissolved by stirring to obtain Resin 1C according to Comparative Example 1. Resin 1C had a weight average molecular weight of 66,000.

[0109] [Comparative Examples 2 and 3] The same as Comparative Example 1 except that the polyether monoacrylate was changed as shown in Table 5. Thus, resin 2C according to comparative example 2 and resin 3C according to comparative example 3 were obtained. The structures of the monoacrylates used in Comparative Examples 1 to 3 are shown in formula (7) and Table 6.

[0110] Comparative Example 4 15.0 parts by mass of polypropylene glycol monomethacrylate Blemmer PP-1000 (NOF Corporation) was dissolved in 39.0 ml of methyl ethyl ketone, and 3.40 parts by mass of ethyl isocyanate (Tokyo Chemical Industry Co., Ltd.) and 0.08 parts by mass of dibutyltin dilaurate (Tokyo Chemical Industry Co., Ltd.) were added, followed by a reaction at 70°C for 6 hours. The reaction solution was then cooled to room temperature, and the solution was washed twice with 40 ml of a 2% aqueous potassium hydroxide solution, and then twice with 40 ml of purified water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-11. Resin 4C according to Comparative Example 4 was obtained in the same manner as Comparative Example 1, except that the monoacrylate was changed as shown in Table 5.

[0111] Comparative Example 5 15.0 parts by mass of methacrylic acid 2-(2-hydroxy-propoxy)-propyl ester (manufactured by Hong Kong Chemhere Co., Ltd.) was dissolved in 39.0 ml of methyl ethyl ketone, and 8.03 parts by mass of butyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.08 parts by mass of dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, followed by a reaction at 70°C for 6 hours. The reaction solution was then cooled to room temperature, and the mixture was washed twice with 40 ml of 2% aqueous potassium hydroxide solution and then twice with 40 ml of purified water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-12. Resin 5C according to Comparative Example 5 was obtained in the same manner as Comparative Example 1, except that the monoacrylate was changed as shown in Table 5.

[0112] The structure of the terminally urethane-modified polyether monomethacrylate used in Comparative Examples 4 and 5 is shown in formula (8) and Table 7.

[0113] [Table 5]

[0114] [ka]

[0115] [Table 6]

[0116] [ka]

[0117] [Table 7]

[0118] The ionic conductivity of the solid electrolyte layer using the resins according to the examples and comparative examples will be described below. All operations were carried out in an argon-substituted glove box (temperature 25°C, dew point -70°C).

[0119] <Preparation of Slurry for Forming Solid Electrolyte Layer> 35.0 parts by mass of n-butyl n-butyrate was added as a dispersion medium to 50.0 parts by mass of argyrodite-type sulfide LPSCl (manufactured by Sigma-Aldrich Japan) as a solid electrolyte and 2.5 parts by mass of resin 1 according to Example 1. The mixture was then mixed and stirred for 30 minutes using a planetary mixer to obtain a slurry for forming a solid electrolyte layer according to Example 1.

[0120] <Formation of solid electrolyte layer> The obtained solid electrolyte forming slurry was applied to a polypropylene sheet using a doctor blade. The solid electrolyte layer was coated on the substrate, dried under reduced pressure at 140° C. for 3 hours, and allowed to cool to 25° C. The thickness of the resulting solid electrolyte layer was 90 μm.

[0121] <Evaluation of ionic conductivity> (Measurement of ionic conductivity of solid electrolyte layer) The solid electrolyte layer formed on the polypropylene sheet was peeled off and sandwiched between SUS sheets to prepare a cell. Using an impedance analyzer E4990A (Keysight Corporation), the AC impedance between the electrodes was measured at an applied voltage of 10 mV and a frequency range of 100 MHz to 1 Hz, and the bulk resistance value R was calculated from the real impedance intercept of the obtained Cole-Cole plot. B (Ω) was measured, and the ionic conductivity was calculated using the following formula. σ=L / R B ×S (σ: ionic conductivity (S·cm -1 ), L: sample thickness (cm), S: sample area (cm 2 ))

[0122] (Ionic conductivity of sulfide electrolyte compacted pellets) For comparison, the sulfide electrolyte was compressed without a binder and the ionic conductivity was measured. Specifically, 200 mg of the argyrodite-type sulfide electrolyte LPSCl (Sigma-Aldrich Japan) was weighed out and placed in a ceramic cylinder. The pressure was 4 ton / cm. 2 The pellet was pressed at a pressure of 1000 kJ / cm. The thickness of the resulting circular pellet was measured. Next, both sides of the pellet were sandwiched between SUS sheets and the pellet was pressed with bolts to create a pressed powder cell. The ionic conductivity was then determined in the same manner as in the evaluation of the solid electrolyte layer. The obtained (ionic conductivity of the solid electrolyte layer including the binder / ionic conductivity of the sulfide electrolyte compacted powder pellet) was defined as the initial maintenance rate of ionic conductivity.

[0123] The same procedure was carried out for the resins of Examples 2 to 20 and Comparative Examples 1 to 5, and the ionic conductivity of the solid electrolyte layer and the initial maintenance rate of the ionic conductivity were determined. The results are shown in Table 8.

[0124] (Measurement of ionic conductivity of solid electrolyte layer after high-temperature storage) The cell in which the ionic conductivity of the solid electrolyte layer was measured was kept at 60°C for 7 days, then left at 25°C for 3 hours, and the ionic conductivity was measured again in the same manner as the initial measurement to determine the ionic conductivity after high-temperature storage. The obtained (ionic conductivity after high-temperature storage / initial ionic conductivity) was defined as the ionic conductivity maintenance rate after high-temperature storage. The results are shown in Table 8.

[0125] [Table 8]

[0126] Since the resins according to Examples 1 to 20 have the structure represented by formula (1), the solid electrolyte layers using these as binders maintain high ionic conductivity compared to those made by compacting only the solid electrolyte, and the decrease in ionic conductivity is suppressed even after storage at high temperatures. In particular, Examples 11 to 17 and 20, which have the structure represented by formula (2) in addition to the structure represented by formula (1), and Examples 18 and 19, which contain a supporting electrolyte, show higher initial retention rates of ionic conductivity. Furthermore, Examples 5 to 10 and 14 to 20, in which the polyether moiety contained in the structure represented by formula (1) has an ether unit structure having 4 or more carbon atoms, also exhibit high values ​​for the ionic conductivity retention rate after high-temperature storage.

[0127] On the other hand, in Comparative Examples 1 to 5, which are resins that do not have the structure represented by formula (1), the ionic conductivity of the solid electrolyte layer using these as binders was significantly reduced, and a significant reduction in ionic conductivity was also observed during high-temperature storage.

[0128] The present disclosure relates to the following configurations. (Configuration 1) A resin characterized by having a structure represented by the following formula (1): TIFF2025142505000023.tif51153In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R2 represents a divalent alkylene group having 1 to 6 carbon atoms. n represents an integer of 2 or greater, and each R3 independently represents a divalent alkylene group having 3 to 6 carbon atoms. R4 represents an alkyl group having 3 or more carbon atoms or a phenyl group, and the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms. (Configuration 2) The resin according to configuration 1, wherein in formula (1), R3's are each independently a divalent alkylene group having 4 to 5 carbon atoms. (Configuration 3) 3. The resin according to claim 1, further comprising a structure represented by the following formula (2): TIFF2025142505000024.tif59153In formula (2), R5 represents a hydrogen atom or a methyl group, and R6 represents a divalent linking group. R7 represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms. X +is at least one selected from a lithium ion, a sodium ion, and a potassium ion. (Configuration 4) 4. The resin according to any one of aspects 1 to 3, further comprising at least one supporting electrolyte selected from the group consisting of lithium salts, sodium salts, and potassium salts. (Configuration 5) 5. The resin according to any one of aspects 1 to 4, wherein the content of the structure represented by formula (1) in the resin is 50 to 100% by mass. (Configuration 6) 6. The resin according to any one of aspects 1 to 5, wherein the resin is a binder for a solid electrolyte. (Configuration 7) A resin solution comprising the resin according to any one of Aspects 1 to 6 and a solvent. (Configuration 8) 7. A solid electrolyte slurry comprising the resin according to any one of aspects 1 to 6, a solid electrolyte, and a solvent. (Configuration 9) A solid electrolyte layer comprising the resin according to any one of aspects 1 to 6 and a solid electrolyte. (Configuration 10) A positive electrode layer comprising the resin according to any one of Configurations 1 to 6 and a solid electrolyte. (Configuration 11) A negative electrode layer comprising the resin according to any one of configurations 1 to 6 and a solid electrolyte. (Configuration 12) An all-solid-state battery having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, 7. An all-solid-state battery, wherein at least one layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the resin according to any one of configurations 1 to 6. [Explanation of symbols]

[0129] 1: Secondary battery, 2: Positive electrode layer, 3: Solid electrolyte layer, 4: Negative electrode layer, 5: Positive electrode current collector, 6: Positive electrode active material, 7: Positive electrode layer binder, 8: Solid electrolyte, 9: Conductive additive, 10: Solid electrolyte binder, 11: Negative electrode active material, 12: negative electrode layer binder, 13: negative electrode current collector

Claims

1. A resin characterized by having a structure represented by the following formula (1): In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R2 represents a divalent alkylene group having 1 to 6 carbon atoms. n represents an integer of 2 or more, and each R3 independently represents a divalent alkylene group having 3 to 6 carbon atoms. R4 represents an alkyl group having 3 or more carbon atoms or a phenyl group, and the hydrogen atom of the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms.

2. The resin according to claim 1, wherein in the formula (1), each R3 is independently a divalent alkylene group having 4 to 5 carbon atoms.

3. The resin according to claim 1 , further having a structure represented by the following formula (2): In formula (2), R5 represents a hydrogen atom or a methyl group, and R6 represents a divalent linking group. R7 represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms. X ＋ is at least one selected from a lithium ion, a sodium ion, and a potassium ion.

4. 10. The resin of claim 1, wherein the resin further comprises at least one supporting electrolyte selected from the group consisting of lithium salts, sodium salts, and potassium salts.

5. The resin according to claim 1, wherein the content of the structure represented by formula (1) in the resin is 50 to 100 mass%.

6. The resin of claim 1 , wherein the resin is a binder for a solid electrolyte.

7. A resin solution comprising the resin according to any one of claims 1 to 6 and a solvent.

8. A solid electrolyte slurry comprising the resin according to any one of claims 1 to 6, a solid electrolyte, and a solvent.

9. A solid electrolyte layer comprising the resin according to any one of claims 1 to 6 and a solid electrolyte.

10. A positive electrode layer comprising the resin according to any one of claims 1 to 6 and a solid electrolyte.

11. An anode layer comprising the resin according to any one of claims 1 to 6 and a solid electrolyte.

12. An all-solid-state battery having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, An all-solid-state battery, wherein at least one layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the resin according to any one of claims 1 to 6.

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