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

Abstract

Provided is a resin that is exceptional in terms of ion conductivity and affinity with a solid electrolyte and is suitable as a binder of a solid electrolyte. The resin is characterized by having a structure represented by formula (1).　In 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 greater, and R3 each independently represent a C3-6 divalent alkylene group. R4 represents a C3 or higher alkyl group or a phenyl group, and hydrogen atoms of the phenyl group may be substituted with a C1-3 alkyl group.

Description

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

[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.

[0002] In recent years, the demand for secondary batteries as a power source has expanded with the development of portable devices such as tablet computers and smartphones, as well as electric vehicles. 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. These 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 improvements 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 involved 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. Therefore, the use of a binder has been proposed. Patent Document 1 describes a solid electrolyte dispersion paste containing an acrylic resin. Patent Document 2 also describes a composition that improves affinity with the solid electrolyte by using a polymer binder having urethane bonds, urea bonds, etc.

[0005] JP 2019-050174 A International Publication No. 2020 / 138216

[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.

[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): 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 aspect of the present disclosure, there is provided a resin solution containing the resin and a solvent. According to at least one aspect of the present disclosure, there is provided a solid electrolyte slurry containing the resin, a solid electrolyte, and a solvent. According to at least one aspect of the present disclosure, there is provided a solid electrolyte layer containing the resin and a solid electrolyte. According to at least one aspect of the present disclosure, there is provided a positive electrode layer containing the resin and a solid electrolyte. According to at least one aspect of the present disclosure, there is provided a negative electrode layer containing the 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.

[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.

[0012] FIG. 1 is a schematic cross-sectional view of an all-solid-state battery.

[0013] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, 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 using 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 an all-solid-state battery 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): 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] After further investigation, the inventors discovered that when the molecular terminal of the polyether structure has a specific chemical structure, ionic conductivity can be maintained after high-temperature storage and the decrease in secondary battery capacity during charge-discharge cycles 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 moiety has a unit structure containing 3 to 6 carbon atoms (-R3-O- structure). The molecular terminal of the polyether moiety that is not bonded to the polymer main chain is an alkyl group or a phenyl group containing 3 or more carbon atoms via a urethane bond (R4 structure). The inventors speculate as follows about the reason why the resin according to the present disclosure exhibits the unexpected effect of preventing a decrease in the ionic conductivity of the solid electrolyte layer when used as a binder for a solid electrolyte.

[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 containing three or more carbon atoms, and the end of the polyether moiety is capped 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 solid electrolyte surface, 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, voids are unlikely to form on the surface of the solid electrolyte particles, and the ionic conductivity of the solid electrolyte layer is unlikely to decrease because the ionic conductive resin is present on the solid electrolyte surface. If the polyether moiety is small and n is 1, the interaction with carrier ions such as lithium ions is 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 containing three or more carbon atoms, the terminals of which are non-reactive hydrophobic groups formed via urethane bonds. Among polyethers, polyethers containing three or more carbon atoms have ionic conductivity but exhibit 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 present at the end of the polyether moiety confers affinity to the solid electrolyte surface, but the presence of an alkyl group or phenyl group containing 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 believed that ionic conductivity can be maintained even after high-temperature storage.

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

[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 are described in detail below with reference to the drawings. The components, materials, shapes, relative positions, and the like described in these embodiments do not limit the scope of the present disclosure.

[0022] (1) Configuration of All-Solid-State Battery 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 the 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 also include a solid electrolyte 8, a positive electrode layer binder 7, and a conductive additive 9. It is preferable to use a resin according to the present disclosure as the positive electrode layer binder 7. That is, the positive electrode layer preferably includes a 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 of Manufacturing All-Solid-State Battery) An all-solid-state battery (solid secondary battery) can be manufactured by known cell manufacturing 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 an 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 sealed in a state where they are bonded by thermocompression. 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 stacked within the aluminum laminate film for purposes such as strength and formability. A bipolar type in which multiple laminates are stacked may also be used.

[0030] (Positive electrode current collector) Examples of the positive electrode current collector include 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] (Positive Electrode 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 , (C ２ F) ｍ , MnO ２ , TiS ２ , MoS ２ , FeS ２ , Li ｘＡ CoO ２ , Li ｘＡ NiO ２ , Li ｘＡ MnO ２ , Li ｘＡ Co ｙ Ni １－ｙ O ２ , Li ｘＡ Co ｙ M１－ｙ O ｚ , Li ｘＡ Ni １－ｙ M ｙ O ｚ , Li ｘＢ Mn ２ O ４ , Li ｘＢ Mn ２－ｙ M ｙ O ４ (In each of 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, z = 2.0 to 2.3), vanadium oxide and its lithium compound, niobium oxide and its lithium compound, conjugated polymers using organic conductive substances, olivine-based compounds, etc. Note that the xA and xB values ​​in each of the above composition formulas are values ​​before the start of charge and discharge, and increase or decrease with charge and discharge. The positive electrode active material can be used alone or in combination of two or more.

[0032] (Conductive auxiliary material) The conductive auxiliary material can be, for example, a material commonly used in secondary batteries such as lithium-ion secondary batteries. For example, 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 auxiliary material 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. The active material binder may be an active material binder other than the resin according to the present disclosure.

[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 satisfies 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 fixes 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 together, and the solid electrolyte binder 10 is a resin according to the present disclosure; and (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 fixes 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 pressing a premixed positive electrode mixture onto the surface of the positive electrode current collector 5, or by applying a positive electrode mixture slurry to the surface, drying the slurry, and then rolling the slurry as needed. The positive electrode layer 2 can also be prepared by kneading a positive electrode active material, a conductive additive, and a positive electrode layer binder. The positive electrode mixture slurry can also be prepared, for example, by dissolving or dispersing the positive electrode active material, solid electrolyte, conductive additive, and positive electrode layer binder in a medium such as dehydrated xylene, butyl butyrate, mesitylene, anisole, or isobutyronitrile.

[0039] (Negative electrode current collector) Examples of the negative electrode current collector include 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.

[0040] (Negative Electrode Active Material) Examples of the negative electrode active material include metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, and various alloy materials. Among these, from the viewpoint of capacity density, metals, oxides, carbon materials, silicon, silicon compounds, tin, tin compounds, and the like are preferred. Examples of metals include metallic Li and In—Li, and examples of oxides include Li ４ Ti ５ O １２ (LTO: lithium titanate). Examples of carbon materials include various natural graphites, coke, partially graphitized carbon, carbon fiber, spherical carbon, various artificial graphites, and amorphous carbon. Examples of silicon compounds include silicon-containing alloys, silicon-containing inorganic compounds, silicon-containing organic compounds, and solid solutions. Examples of tin compounds include SnO. Ｂ (0<B<2), SnO ２ , SnSiO ３ , Ni ２ Sn ４ , Mg ２ Examples include Sn.

[0041] 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, a solid electrolyte is disposed between a positive electrode and a negative electrode as a lithium ion migration layer, and may also be used as a bulk electrolyte that functions as a separator. Furthermore, by mixing the solid electrolyte into the active material layers of the positive and negative electrodes, it can also be used as an auxiliary agent that improves 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] The oxide-based solid electrolyte is Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３ and Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３Nasicon-type compounds such as Li ６．２５ L.A. ３ ZR ２ Al ０．２５ O １２ The oxide-based solid electrolyte may be a garnet-type compound such as Li ０．３３ Li ０．５５ TiO ３ The oxide-based solid electrolyte includes perovskite-type compounds such as Li １４ Zn(GeO ４ ) ４ Lithium-type compounds such as Li ３ P.O. ４ and Li ４ SiO ４ , Li ３ BO ３ Specific examples of sulfide-based solid electrolytes include Li ６ P.S. ５ Cl, 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 P.O. ４ -P ２ S ５ , Li ２ S-P ２ S ５ The solid electrolyte may be crystalline or amorphous, or may be glass ceramics. ２ S-P ２ S ５ The description of Li ２ S and P ２ S ５ The term "sulfide-based solid electrolyte" refers to a sulfide-based solid electrolyte formed using raw materials containing the above.

[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):

[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 each R3 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. 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 that can be used 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, and 1,6-tetrahexylene oxide.

[0053] R4 is a terminal functional group bonded to the urethane group at the end of the polyether moiety, and represents an alkyl group having 3 or more carbon atoms, or a phenyl group. Examples of alkyl groups having 3 or more carbon atoms include a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, and a 2-methylhexyl group. That is, the number of carbon atoms in the alkyl group of R4 is preferably 3 to 8. When R4 is a phenyl group, a 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).

[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 small 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. When the average number of moles is within the above range, the ionic conductivity of the resin is improved, thereby achieving higher ionic conductivity. The (meth)acryloyl residue is a form in which a (meth)acryloyl group is addition-polymerized, and is represented, for example, by the following structure in formula (1):

[0059]

[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 formula (1) or formula (1-1), the arrangement of the polyether unit structures may be a block copolymer or a random copolymer. Random copolymerization is preferred.

[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.

[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, introducing the structure represented by formula (2) into a polymer structure can reduce crystallinity. 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, a sufficient amount of ions can be contained while also improving ionic conductivity due to reduced crystallinity. The structure contained in the resin can be confirmed by analysis using known means, such as pyrolysis GC / MS, FT-IR, or 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 fluoroalkylsulfonylimide anions, fluorosulfonylimide anions, fluoroalkylsulfonate anions, fluorosulfonate anions, fluoroalkylcarboxylate anions, fluoroalkylmethide anions, fluoroborate anions, fluorophosphate anions, dicyanamide anions, thiocyanate anions, bisoxalatoborate anions, perchlorate anions, and derivatives thereof.

[0068] More specifically, the anions contained in the supporting electrolyte are bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoromethanesulfonate anion (CF ３ -SO ３ － ), hexafluorophosphate anion (PF ６ － ), fluoroborate anion (BF ４ － ), 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 even more 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, the supporting electrolyte 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 the following formula (4): Polyether mono(meth)acrylate, one end of which is blocked with an alkyl group having 3 or more carbon atoms or a phenyl group via a urethane group.

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

[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). A known polymerization initiator may be contained in the resin polymerization as needed. Examples of the polymerization initiator include thermal polymerization initiators. 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] (Method for forming solid electrolyte layer, positive electrode layer, negative electrode layer) The method for forming the solid electrolyte layer, positive electrode layer, or 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, positive electrode layer, or negative electrode layer.

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

[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) will be 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. Thereafter, the temperature was lowered to 25°C, and stirring was continued until the vessel internal pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 40°C for 30 minutes, after which 1.10 parts by mass of an alkali adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and 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] Next, the obtained polyether monoacrylate was dissolved in 39.0 ml of methyl ethyl ketone, and 14.82 parts by mass of phenyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by a reaction at 70°C for 5 hours. The reaction solution temperature was then lowered 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 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-1.

[0081] (Polyether Monoacrylates 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 for 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-substituted 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 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 carried out 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 vessel internal pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 40°C for 30 minutes, after which 1.10 parts by mass of an alkali adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and 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.

[0083] Next, the obtained polyether monoacrylate was dissolved in 39.0 ml of methyl ethyl ketone, and 12.38 parts by mass of butyl isocyanate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.08 parts by mass of dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was allowed to react at 70°C for 6 hours. The reaction solution temperature was then lowered 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 reaction solution after washing, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-5.

[0084] (Polyether Monoacrylates A-6 to A-9) Terminally urethane-modified polyether monoacrylates A-6 to A-9 were obtained in the same manner as 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 (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.03 parts by mass of butylhydroxytoluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.02 parts by mass of boron trifluoride diethyl ether complex (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a nitrogen-substituted 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 58.1 parts by mass of 1,2-epoxyhexane (manufactured by 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 carried out 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 vessel internal pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 40°C for 30 minutes, after which 1.10 parts by mass of an alkali adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and 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] Next, the obtained polyether monoacrylate was dissolved in 39.0 ml of methyl ethyl ketone, and 8.23 ​​parts by mass of isopropyl 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, and the reaction was carried out at 70°C for 6 hours. The reaction solution temperature was then lowered 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 pure water. The organic phase was separated from the reaction solution after washing, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-10.

[0087]

[0088] The structures of the obtained polyether mono(meth)acrylates are shown in formula (5) and Table 2.

[0089] 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 (manufactured by Tokyo Chemical Industry Co., Ltd.) was suspended in 100 mL of THF and 0.5 mL of N,N-dimethylformamide, and then 20 mL (0.28 mol) of thionyl chloride was added and stirred for 3 hours. This 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 solution was again concentrated under reduced pressure 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 (manufactured by Tokyo Chemical Industry Co., Ltd.) and 27.3 mL (0.20 mol) of triethylamine (manufactured by Kishida Chemical Co., Ltd.) dissolved in 50 mL of tetrahydrofuran, and the mixture was stirred for 2 hours, after which 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 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and the mixture was stirred overnight. Unreacted lithium hydride was filtered off using Celite filtration, and the filtrate was dried under reduced pressure to obtain ionic compound B-1.

[0092] (Synthesis of Ionic Compound B-2) Ionic 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 (manufactured by Atomax Chemical Products Co., Ltd.) was dissolved in 50 mL of THF, and 5.17 g (0.06 mol) of methacrylic acid (manufactured by Kishida Chemical Co., Ltd.) 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, and then dissolved again in 50 mL of THF, to which 2.41 g (0.06 mol) of potassium hydride (manufactured by Merck & Co., Ltd.) was added, followed by stirring at room temperature for 2 hours. The white solid obtained after drying under reduced pressure was used as the starting material, and ionic compound B-3 was obtained 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 (manufactured by Hong Kong Chemhere Products Co., Ltd.) and 6.07 g (0.06 mol) of triethylamine (manufactured by 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 (manufactured by Merck & Co.) was dissolved in 50 mL of ethanol, and the oily liquid obtained above and 0.022 g (0.20 mmol) of hydroquinone (manufactured by Kanto Chemical Co., Inc.) 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 for ionic compound B-2.

[0095] (Synthesis of Ionic Compound B-5) Ionic Compound B-5 was obtained in the same manner as in the preparation of Ionic Compound B-2, except that the reactant was changed from trifluoromethanesulfonamide (manufactured by Tokyo Chemical Industry Co., Ltd.) to 5.94 g (0.06 mol) of sulfamoylfluoride (manufactured by Atomax Chemical Products Co., Ltd.).

[0096] (Synthesis of Ionic Compound B-6) Ionic Compound B-6 was obtained in the same manner as for Ionic Compound B-1, except that the reactant was changed from trifluoromethanesulfonamide (manufactured by Tokyo Chemical Industry Co., Ltd.) to 18.0 g (0.06 mol) of nonafluorobutane-1-sulfonamide (manufactured by Enamine Co., Ltd.).

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

[0098]

[0099] <Resin Synthesis> [Example 1] 300.0 parts by mass of toluene was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen gas inlet tube, and the temperature was raised to 110°C under a nitrogen gas stream. Next, a mixture of 100.0 parts by mass of terminally urethane-modified polyether monoacrylate A-1 and 0.2 parts by mass of an initiator (trade name Kayaester O, manufactured by Nouryon Chemical Industries, 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. Next, the temperature was 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 previously dehydrated n-butyl butyrate was added, stirred, and dissolved to obtain Resin 1 according to Example 1.

[0100] The weight average molecular weight was measured using an HLC-8120GPC (manufactured by Tosoh Corporation) as a measuring instrument, two TSKgel Super HM-M (manufactured by Tosoh Corporation) columns, and THF as a solvent. The measurement was performed at a temperature of 40 ° C., a THF flow rate of 0.6 ml / min, with the measurement sample being a 0.1 mass% THF solution, and an RI (refractive index) detector. A calibration curve was created using several monodisperse standard polystyrenes (manufactured by Tosoh Corporation) as standard samples for creating a calibration curve, 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, 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 stream. 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 initiator (product name Kayaester O, manufactured by Kayaku Nouryon 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 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, stirred, and dissolved 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 ion compound were changed as shown in Table 4.

[0104] [Example 18] 300.0 parts by mass of toluene was charged into a reaction vessel equipped with a stirrer, thermometer, reflux tube, dropping device, and nitrogen gas inlet tube, and the temperature was raised to 110 ° C. under a nitrogen gas stream. Next, a mixture of 100.0 parts by mass of terminally urethane-modified polyether monoacrylate A-9 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. Next, the temperature was lowered to 30 ° C., and the 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.) and 100.0 parts by mass of previously dehydrated n-butyl butyrate were added as a supporting electrolyte, followed by stirring and dissolution, to obtain resin 18 according to Example 18.

[0105] Example 19 Resin 19 according to 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 tube, 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 stream. 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 (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 the 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 (manufactured by Kishida Chemical Co., Ltd.) and 100.0 parts by mass of pre-dehydrated isobutyronitrile were added as a supporting electrolyte, followed by stirring and dissolution to obtain Resin 20 according to Example 20. The weight average molecular weight of Resin 20 was 89,000.

[0107]

[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. Next, the temperature was 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. The weight average molecular weight of Resin 1C was 66,000.

[0109] [Comparative Examples 2 and 3] Resin 2C according to Comparative Example 2 and Resin 3C according to Comparative Example 3 were obtained in the same manner as in Comparative Example 1, except that the polyether monoacrylate was changed as shown in Table 5. 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 weight of polypropylene glycol monomethacrylate Blemmer PP-1000 (manufactured by NOF Corporation) was dissolved in 39.0 ml of methyl ethyl ketone, 3.40 parts by weight of ethyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.08 parts by weight of dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the reaction was carried out at 70 ° C. for 6 hours. The reaction solution temperature was then lowered 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 reaction solution after washing, and the solvent was distilled off under reduced pressure to obtain terminally urethane-modified polyether monoacrylate A-11. Hereinafter, 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 temperature was then lowered 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 reaction solution after washing, 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 in 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]

[0114]

[0115]

[0116]

[0117]

[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 as a dispersion medium was added 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 onto a polypropylene sheet using a doctor blade, dried under reduced pressure at 140° C. for 3 hours, and allowed to cool to 25° C. The obtained solid electrolyte layer had a thickness of 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 (manufactured by KEYSIGHT), 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 Pellet) For comparison, a sulfide electrolyte was compacted without using a binder, and the ionic conductivity was measured. Specifically, 200 mg of an argyrodite-type sulfide electrolyte LPSCl (manufactured by Sigma-Aldrich Japan) was weighed as a solid electrolyte, placed in a ceramic cylinder, and compressed to 4 ton / cm. ２The pellet was pressed at a pressure of 1000 kJ / cm2. The thickness of the obtained circular pellet was measured. Next, both sides of the pellet were sandwiched between SUS sheets, and the pellet was pressed by bolts to prepare a pressed powder cell. Hereinafter, the ionic conductivity was 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 pressed 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 to determine the ionic conductivity of the solid electrolyte layer and the initial maintenance rate of the ionic conductivity. 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 had been measured was kept at 60°C for 7 days. Thereafter, the cell was left at 25°C for 3 hours, and the ionic conductivity was measured again in the same manner as in the initial state 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 retention rate after high-temperature storage. The results are shown in Table 8.

[0125]

[0126] Because the resins according to Examples 1 to 20 have the structure represented by formula (1), solid electrolyte layers using these resins as binders maintain higher ionic conductivity than those made by compacting only the solid electrolyte, and the decrease in ionic conductivity is suppressed even after high-temperature storage. 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 include a supporting electrolyte, show higher initial ionic conductivity retention rates. 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 four or more carbon atoms, also show 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 not having 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 is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present disclosure. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2024-041908, filed March 18, 2024, the entire contents of which are incorporated herein by reference.

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 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.

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

3. The resin according to claim 1 or 2, further having a structure represented by the following formula (2): In formula (2), R5 represents a hydrogen atom or a methyl group, R6 represents a divalent linking group, and 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. The resin according to any one of claims 1 to 3, further comprising at least one supporting electrolyte selected from the group consisting of lithium salts, sodium salts, and potassium salts.

5. The resin according to any one of claims 1 to 4, wherein the content of the structure represented by formula (1) in the resin is 50 to 100 mass %.

6. The resin according to any one of claims 1 to 5, 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, wherein at least one layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the resin described in any one of claims 1 to 6.

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