Polymer electrolyte and secondary battery

Abstract

To provide a polymer electrolyte which has high mechanical strength and high ionic conductivity even at high temperatures and is capable of suppressing dendrite growth at an interface with a battery anode.SOLUTION: A polymer electrolyte includes a polymer having a specific free-end polyether structure and a crosslinked structure formed by a specific polyether, at least one type of microparticles selected from the group consisting of resin microparticles and metal oxide microparticles, and an alkali metal cation, wherein the volumetric swelling ratio of the polymer electrolyte, as determined by a methyl ethyl ketone immersion method, is 30 to 120%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a polymer electrolyte and a secondary battery. [Background technology]

[0002] In recent years, the issue of climate change has become more prominent, and countries around the world are making efforts to achieve carbon neutrality. To achieve carbon neutrality, the use of electricity is gaining more attention, and demand for secondary batteries as a power source is expanding. Generally, secondary batteries consist of electrodes (such as positive and negative electrodes) and an electrolyte, and charge and discharge occurs 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 smartphones to large devices such as electric vehicles. Therefore, high safety and further improvement in performance are required.

[0003] Currently, organic electrolyte solutions are mainly used as electrolytes in secondary batteries, but the organic solvents used in electrolyte solutions are often flammable and pose safety issues in the event of leakage. Therefore, solid electrolytes, which are solidified electrolytes, are attracting attention. Oxide-based, sulfide-based, and polymer-based materials are widely considered as solid electrolytes. In order to improve the charge-discharge characteristics of secondary batteries, it is generally important to increase the interface between the active material in the electrode and the electrolyte. Here, the active material is a substance that participates in the reaction that generates electricity.

[0004] Among these, sulfide-based and oxide-based solid electrolytes have excellent ionic conductivity, but it is difficult to enlarge the interface with the active material and they may not have sufficient impact resistance. Therefore, it has been proposed to use gel electrolytes, which combine an electrolyte solution with a polymer, or dry polymer-based electrolytes, which combine a polymer with a supporting electrolyte. Patent Document 1 describes a gel electrolyte containing an aprotic organic solvent. Patent Document 2 describes a gel electrolyte in which affinity with the electrolyte solution is improved by incorporating a quaternary ammonium base into the main chain, and Patent Document 3 describes a dry polymer electrolyte in which component retention of the composition is improved by adding an inorganic oxide to a polyamine. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-097993 [Patent Document 2] International Publication No. 2004 / 027789 [Patent Document 3] Japanese Patent Application Publication No. 2019-021538 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, secondary batteries have been required to have not only high safety but also better discharge characteristics and longer cycle life. Repeated charge and discharge cycles in secondary batteries can cause dendrites to grow at the interface between the electrolyte and the metal negative electrode. The growth of dendrites increases the risk of short circuits and, in some cases, can even damage the base material and packaging materials that make up the battery. The present inventors have recognized that when polymer gels such as those described in Patent Documents 1 and 2 are used, repeated charge and discharge can cause dendrite growth, which can lead to the risk of short circuits. Furthermore, the strength of the polymer gels can decrease at high temperatures, which can lead to the risk of short circuits due to impact. In addition, when using a dry polymer as in Patent Document 3, the risk of short circuit due to charging and discharging is Although the ionic conductivity is low, it is likely to decrease, and the output of the secondary battery may decrease significantly.

[0007] At least one aspect of the present disclosure is directed to a polymer electrolyte that has high mechanical strength and high ionic conductivity even at high temperatures, and that can suppress dendrite growth at the interface with a battery negative electrode. Also, at least one aspect of the present disclosure is directed to providing a secondary battery that is highly safe and has excellent battery performance. [Means for solving the problem]

[0008] According to at least one aspect of the present disclosure, there is provided a polymer electrolyte comprising: The polymer electrolyte is A structure represented by the following formula (1): A polymer having at least one structure selected from the group consisting of a structure represented by the following formula (2) and a structure represented by the following formula (3), At least one fine particle selected from the group consisting of resin fine particles and metal oxide fine particles; containing an alkali metal cation, The polymer electrolyte has a volume swelling ratio of 30 to 120% when immersed in methyl ethyl ketone. [ka] In formula (1), R 1 represents a hydrogen atom or a methyl group. 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms. 3 represents an alkyl group having 1 to 6 carbon atoms. In equation (2), R 4 R each independently represents a hydrogen atom or a methyl group. 5 , R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. In equation (3), R 7 R each independently represents a hydrogen atom or a methyl group. 8 , R 9 , R 10 R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. 11represents a trivalent organic group having 1 to 6 carbon atoms. In the formulas (1) to (3), A1, B1, D1, D2 and D3 are each independently a linking group having at least an ethylene oxide structure represented by (-CH2CH2-O-).

[0009] According to at least one aspect of the present disclosure, there is provided a secondary battery including a positive electrode, a bulk electrolyte, and a negative electrode, A secondary battery is provided in which the bulk electrolyte contains the above-described polymer electrolyte. [Effects of the Invention]

[0010] According to at least one embodiment of the present disclosure, a material having high mechanical strength even at high temperatures and high ionic strength is The present disclosure also provides a polymer electrolyte having electrical conductivity and capable of suppressing dendrite growth at the interface with the battery negative electrode. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic cross-sectional view of a secondary battery using a polymer electrolyte as the bulk electrolyte DETAILED DESCRIPTION OF THE INVENTION

[0012] 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. Note that when XX is a group, multiple XXs may be selected, and the same applies to YY and ZZ.

[0013] The present inventors have conducted extensive research to achieve the above object. The inventors have discovered that in dry polymer systems, where promotion of lithium ion migration by an electrolyte solution cannot be expected, the use of specific microparticles in a polyether acrylic resin with a special three-dimensional crosslinking structure can increase ionic conductivity while suppressing dendrite growth. The inventors speculate as follows why the polymer electrolyte according to the present disclosure has high ionic conductivity and exhibits the unexpected effect of being able to suppress dendrite growth even after repeated charge and discharge.

[0014] In dry polymer systems, where stabilization of lithium ions by an electrolyte solution is not possible, lithium ions move between polymer chains undergoing molecular motion. Therefore, in polymer systems that are three-dimensionally cross-linked to reduce the risk of short circuits due to membrane deformation at high temperatures, the movement of lithium ions is more susceptible to steric hindrance than in electrolyte systems. The polymer used in this disclosure has a three-dimensional cross-linked structure shown in formulas (2) and (3), making it resistant to deformation even at high temperatures. At the same time, the structure has a free terminal chain shown in formula (1), where one end is not bonded to other polymer chains. This prevents the polymer from forming a dense network structure, which is thought to prevent lithium ion migration from being hindered while maintaining strength.

[0015] Here, the three-dimensional crosslinked structure including the structure represented by formula (1) facilitates the mobility of lithium ions in the polymer electrolyte, thereby increasing the amount of lithium ions that move to the electrode during charge and discharge. Therefore, when local current imbalance occurs, dendrites are likely to grow. Since a decrease in lithium ion mobility increases the resistance of the polymer electrolyte, it is necessary to suppress dendrite growth while maintaining high lithium ion mobility. The polymer electrolyte of the present disclosure contains at least one fine particle selected from the group consisting of resin fine particles and metal oxide fine particles. The presence of these fine particles in the polymer of the present disclosure unexpectedly suppresses dendrite growth. Dendrites are generated by the precipitation of lithium ions during charging and gradually grow.

[0016] Although the size of lithium ions is small among common cations, it is difficult for lithium ions to enter the interior of fine particles such as resin fine particles and metal oxide fine particles. Therefore, when dendrites formed by the precipitation of lithium ions come into contact with fine particles, it is thought that the dendrites cannot grow inside the fine particles because there are almost no lithium ions inside the fine particles. In addition, since the fine particles dispersed in the polymer are usually larger than lithium ions, the fine particles are more strongly constrained by the polymer inside the polymer. do.

[0017] Therefore, when dendrites are generated and grow and come into contact with fine particles, the dendrites cannot pass through the interior or move the fine particles, and the inventors believe that adding the fine particles has the effect of inhibiting dendrite growth.

[0018] The three-dimensional crosslinked structure of the polymer has many free chains at one end that are not bonded to the polymer chain, and the extremely low crosslink density is clearly expressed as the volume swelling ratio of the polymer electrolyte measured by the methyl ethyl ketone immersion method. Specifically, the volume swelling ratio of the polymer electrolyte using methyl ethyl ketone (MEK) is 30 to 120%.

[0019] The volume swelling ratio is the ratio of the volume of a three-dimensional cross-linked polymer before and after it has been immersed in a specific solvent and has reached saturation due to the solvent. The volume swelling ratio is calculated using the following formula, where the volume of the specimen is calculated from the weight in air and the weight in water. The specific measurement method will be described later. Volume swelling rate (%) = (volume when saturated by solvent immersion) / (volume before solvent immersion) × 100

[0020] A volume swelling ratio of less than 30% for a polymer electrolyte is thought to indicate a low number of terminal free chains (the structure of formula (1)), a high number of three-dimensional cross-linked structures, or a high number of fine particles. This results in low ionic conductivity and tends to result in poor rate characteristics for secondary batteries. On the other hand, a volume swelling ratio of more than 120% for a polymer electrolyte indicates a lack of three-dimensional cross-linked structures, which tends to result in a decrease in strength, such as a decrease in impact resistance at high temperatures. The volume swelling ratio of the polymer electrolyte is preferably 50 to 110%, and more preferably 60 to 105%.

[0021] The volume swelling ratio is a method for evaluating the crosslink density of crosslinked polymers, and the JIS method uses water and toluene. In the case of polymer electrolytes for secondary batteries, polymers with relatively moderate polarity are often used because they must contain ionic components, so the solvent used for swelling ratio measurement is preferably one that has affinity for both the ionic components and the polymer. MEK has a high affinity with alkali metal salts, organic ionic liquids, and polymers of various compositions, making it particularly suitable for measuring the volume swelling ratio of polymer electrolytes. Specific measurement methods are described below.

[0022] 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.

[0023] (1) Secondary battery type The secondary battery comprises a positive electrode, a bulk electrolyte, and a negative electrode, and the bulk electrolyte contains the polymer electrolyte of the present disclosure.

[0024] An example of a secondary battery using the polymer electrolyte of the present disclosure is shown in Figure 1. The secondary battery 1 shown in Figure 1 shows an example of the schematic configuration of a secondary battery using a polymer electrolyte as a bulk electrolyte 7. A positive electrode active material 3 provided on a positive electrode current collector 2 is fixed with a positive electrode active material binder 4 to form a positive electrode 6. The positive electrode 6 may contain a conductive additive 5.

[0025] A negative electrode active material 8 provided on a negative electrode current collector 9 forms a negative electrode 10. In Fig. 1, the negative electrode active material represents metallic lithium, indium, etc. A bulk electrolyte 7 is provided between the positive electrode 6 and the negative electrode 10.

[0026] In order to more effectively achieve the effects of the present disclosure, as shown in FIGS. The electrolyte 7 is preferably a polymer electrolyte that penetrates into the positive electrode active material 3 and the negative electrode active material 8 to increase the contact area.

[0027] (Method for manufacturing solid secondary batteries) The solid secondary battery can be produced by known cell production methods such as laminate cell type, coin cell type, pressurized cell type, etc. The laminate cell type will be described below as an example.

[0028] A laminate is obtained in which a positive electrode, bulk electrolyte, and negative electrode are disposed between a positive electrode current collector and a negative electrode current collector. Electrode tabs are welded to the positive electrode and negative electrode current collectors. The laminate, in which the positive electrode current collector, positive electrode, bulk electrolyte, negative electrode, 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 to the outside of 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. Examples of bulk electrolytes include solid electrolytes and polymer electrolytes, and both may be used in the laminate. In addition to the above-mentioned laminate, other layers such as elastic materials and 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.

[0029] (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.

[0030] (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 y O4 (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 charging and discharging, and increase or decrease with charging and discharging. The positive electrode active material can be used alone or in combination of two or more.

[0031] (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.

[0032] (active material binder) As the active material binder, those commonly used in secondary batteries such as lithium ion secondary batteries can be used, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polypropylene, etc. Examples of the polymerizable monomer include triamide imide, 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. The active material binder may be used alone or in combination of two or more.

[0033] The positive electrode 6 can be produced, for example, by pressing a positive electrode mixture onto the surface of the positive electrode current collector 2, or by applying a positive electrode mixture slurry, drying it, and further rolling it as necessary to form the positive electrode 6. It can also be prepared by kneading a positive electrode active material, a conductive auxiliary material, and a positive electrode active material binder. The positive electrode mixture slurry can be prepared, for example, by dissolving or dispersing a positive electrode active material, a conductive auxiliary material, and an active material binder in a medium such as dehydrated N-methyl-2-pyrrolidone, acetonitrile, methyl ethyl ketone, ethylene glycol ethers, etc.

[0034] (Negative electrode current collector) Examples of the negative electrode current collector include, for example, a metal foil. Examples of the metal include aluminum, stainless steel, copper, silver, gold, platinum, nickel, palladium. The metal may be used alone or in combination of two or more.

[0035] (Negative electrode active material) Examples of the negative electrode active material include, for example, metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, various alloy materials, etc. Among them, from the viewpoint of capacity density, metals, oxides, carbon materials, silicon, silicon compounds, tin, tin compounds, etc. are preferable.

[0036] Examples of the metal include, for example, metallic Li and In-Li. It is known that a metallic Li electrode has an extremely high energy density when used as a lithium ion secondary battery. Examples of the oxide include, for example, Li4Ti5O 12 (LTO: lithium titanate), etc. Examples of the carbon material include, for example, various natural graphites (graphite), coke, carbon in the process of graphitization, carbon fibers, spherical carbon, various artificial graphites, amorphous carbon, etc. Examples of the silicon compound include, for example, silicon-containing alloys, silicon-containing inorganic compounds, silicon-containing organic compounds, solid solutions, etc. Examples of the tin compound include, for example, SnO B (0 < B < 2), SnO2, SnSiO3, Ni2Sn4, Mg2Sn, etc.

[0037] 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.

[0038] 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.

[0039] (solid electrolyte) In secondary 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. They can also be used as auxiliary agents to improve the conductivity of lithium ions by being mixed into the active material layers of the positive and negative electrodes.

[0040] The polymer electrolyte of the present disclosure can be suitably used as both a bulk electrolyte and an auxiliary material, which allows the contact interface between the bulk electrolyte and the positive and negative electrode active materials to be large, and further has flexibility that allows it to follow the expansion and contraction of the positive and negative electrode active materials, thereby improving the characteristics of the secondary battery.

[0041] The bulk electrolyte and auxiliary material may be a solid electrolyte other than a polymer electrolyte, such as an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a complex hydride-based solid electrolyte. Oxide-based solid electrolytes are Li 1.5 Al 0.5 Ge 1.5 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7 Nasicon-type compounds such as (PO4)3, Li 6.25LA3ZR2Al 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 of sulfide-based solid electrolytes include silicon-type compounds such as Zn(GeO4)4, and acid compounds such as Li3PO4, Li4SiO4, and Li3BO3. Specific examples of sulfide-based solid electrolytes include Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5. 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.

[0042] The polymer electrolyte of the present disclosure is preferably used as a bulk electrolyte. The configuration of the polymer electrolyte according to one embodiment of the present disclosure will be described in detail below.

[0043] The polymer electrolyte of the present disclosure is preferably a solid electrolyte or semi-solid electrolyte such as a dry polymer electrolyte or a gel electrolyte. That is, a non-liquid electrolyte is preferred. A dry polymer electrolyte is more preferred. The polymer electrolyte preferably does not substantially contain a liquid component, such as a liquid electrolyte.

[0044] <Polymer electrolyte> A polymer electrolyte according to an embodiment of the present disclosure includes a polymer having the following structure: The polymer is, for example, a vinyl polymer. The polymer electrolyte is, for example, a polyether acrylic resin having a three-dimensional cross-linked structure having the following structure: The structure represented by formula (1) At least one structure selected from the group consisting of a structure represented by formula (2) and a structure represented by formula (3)

[0045] The polymer electrolyte has a structure represented by the following formula (1): [ka]

[0046] In formula (1), R 1 represents a hydrogen atom or a methyl group. 2 R represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). 3 represents an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1). A1 in formula (1) is a linking group having at least an ethylene oxide structure represented by (-CH2CH2-O-).

[0047] The structure represented by formula (1) is preferably a structure represented by the following formula (1-1). [ka]

[0048] In formula (1-1), R 1 represents a hydrogen atom or a methyl group. 2 R represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). 3 represents an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1). m1 and n1 represent the average number of moles added, m1 represents an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n1 represents an integer of 0 or more (preferably 5% to 25% of m1, more preferably 11% to 25% of m1).

[0049] The polymer electrolyte has at least one structure selected from the group consisting of the structure represented by the following formula (2) and the structure represented by the following formula (3). The at least one structure selected from the group consisting of the structure represented by the formula (2) and the structure represented by the formula (3) may be the structure represented by formula (2). This structure can form a three-dimensional crosslinked structure. [ka]

[0050] In equation (2), R 4 R each independently represents a hydrogen atom or a methyl group. 5 , R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). In equation (3), R 7 R each independently represents a hydrogen atom or a methyl group. 8 , R 9 , R 10 R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). 11 represents a trivalent organic group having 1 to 6 carbon atoms (preferably 1 to 3, more preferably 1).

[0051] In formulas (2) and (3), B1, D1, D2, and D3 are each independently a linking group having at least an ethylene oxide structure represented by (—CH2CH2—O—). In formulas (1) to (3), it is preferable that A1, B1, D1, D2, and D3 each independently further have a propylene oxide structure represented by (-CH2CH(CH3)-O-). The arrangement of the ethylene oxide structure and the propylene oxide structure may be a block copolymer or a random copolymer. A random copolymer is preferable. When the polymer has an ethylene oxide structure, the transportability of ions such as lithium ions can be improved.

[0052] Furthermore, A1, B1, D1, D2 and D3 may each independently further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms) to the extent that the effect of the present disclosure is not impaired. x -O-, R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6).

[0053] The structure represented by formula (2) is preferably a structure represented by the following formula (2-1). [ka]

[0054] In formula (2-1), R 4 R each independently represents a hydrogen atom or a methyl group. 5 , R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). m2 and n2 represent the average number of moles added, m2 represents an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n2 represents an integer of 0 or more (preferably 5% to 25% of m2, more preferably 11% to 25% of m2).

[0055] The chain sandwiched between two -COO- may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms) to the extent that the effect of the present disclosure is not impaired. For example, a diol structure may be contained between ethylene oxide structures, between propylene oxide structures, or between an ethylene oxide structure and a propylene oxide structure. The diol structure may be -OR x -O-, R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6).

[0056] The structure represented by formula (3) is preferably a structure represented by the following formula (3-1). [ka]

[0057] In formula (3-1), R 7 R each independently represents a hydrogen atom or a methyl group. 8 , R 9 , R 10 R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). 11represents a trivalent organic group (preferably a hydrocarbon group) having 1 to 6 carbon atoms (preferably 1 to 3, more preferably 1). m3 and n3 represent the average number of moles added, m3 each independently represents an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n3 each independently represents an integer of 0 or more (preferably 5% to 25% of m3, more preferably 11% to 25% of m3).

[0058] -COO- and R to an extent that does not impair the effect of the present disclosure. 11 The chain sandwiched between these may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6). For example, between ethylene oxide structures, between propylene oxide structures, or between an ethylene oxide structure and a propylene oxide structure. A diol structure may be contained between the -OR structure. x -O-, R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6).

[0059] In the polymer contained in the polymer electrolyte, the average number of moles of ethylene oxide structures added per mole of (meth)acryloyl residues, Meo, is preferably 2.5 moles or more. Meo is more preferably 6 to 46, and even more preferably 13 to 46. Within the above range, the crosslinking density of the polymer main chain becomes more appropriate, thereby maintaining strength at high temperatures and achieving high lithium ion 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:

[0060] [ka]

[0061] Furthermore, in the polymer contained in the polymer electrolyte, the average number of moles of propylene oxide structures added per mole of (meth)acryloyl residues, Mpo, is preferably 5 to 25%, and more preferably 11 to 25%, of the average number of moles of ethylene oxide structures added per mole of (meth)acryloyl residues, Meo. By being in this range, the crystallinity of the polymer main chain is suppressed even if the molecular weight between crosslinking points is large, and inhibition of lithium ion migration, particularly at low temperatures, is more easily suppressed.

[0062] The average numbers of moles added Meo and Mpo can be measured by decomposing the polymer electrolyte using pyrolysis GC / MS, and quantifying the fragments derived from (meth)acryloyl residues, the fragments derived from ethylene oxide structures, and the fragments derived from propylene oxide structures using calibration curves.

[0063] It can be confirmed that the polymer has the structure of formula (1) and at least one structure selected from the group consisting of the structure of formula (2) and the structure of formula (3) by, for example, pyrolysis GC / MS, FT-IR or NMR analysis.

[0064] In the polymer electrolyte of the present disclosure, the three-dimensional crosslinked structure of the polymer has a very low crosslink density as described above, and the polymer chains have many free chains at one end that are not bonded to other polymer chains, etc. Such a crosslinked structure can be obtained, for example, by reacting the following materials: Polyether mono(meth)acrylate At least one (meth)acrylate selected from the group consisting of polyether di(meth)acrylate and polyether tri(meth)acrylate

[0065] (Polyether mono(meth)acrylate) The polyether mono(meth)acrylate can form a structure represented by formula (1) (preferably formula (1-1)). As the polyether mono(meth)acrylate, for example, at least one selected from the group consisting of polyethylene glycol mono(meth)acrylate and mono(meth)acrylate of polyethylene glycol-propylene glycol copolymer can be used. When the mono(meth)acrylate of polyethylene glycol-propylene glycol copolymer is used, the ethylene glycol structure:propylene glycol structure The molar ratio is preferably 100:0 to 50:50, and more preferably 80:20 to 95:5.

[0066] When the molar ratio of ethylene glycol structure:propylene glycol structure is within this range, the transportability of ions such as lithium ions by polyethylene glycol can be maintained at a high level, and it becomes easier to suppress the inhibition of the movement of ions such as lithium ions due to crystallization of the polymer.

[0067] The polyether mono(meth)acrylate is represented by, for example, the following formula (1'). [ka] In formula (1'), R 1 , R 2 , R 3 , m1 and n1 are the same as in formula (1-1).

[0068] (Polyether di(meth)acrylate) Polyether di(meth)acrylate can form a structure represented by formula (2) (preferably formula (2-1)). As the polyether di(meth)acrylate, for example, at least one selected from the group consisting of polyethylene glycol di(meth)acrylate and di(meth)acrylate of polyethylene glycol-propylene glycol copolymer can be used. When di(meth)acrylate of polyethylene glycol-propylene glycol copolymer is used, the molar ratio of ethylene glycol structure:propylene glycol structure is preferably 100:0 to 50:50, and more preferably 80:20 to 95:5.

[0069] When the molar ratio of ethylene glycol structure:propylene glycol structure is within this range, the transportability of ions such as lithium ions by polyethylene glycol can be maintained at a high level, and it becomes easier to suppress the inhibition of the movement of ions such as lithium ions due to crystallization of the polymer.

[0070] The polyether di(meth)acrylate is represented, for example, by the following formula (2'). [ka] In formula (2'), R 4 , R 5 , R 6 , m2 and n2 are the same as in formula (2-1).

[0071] The chain sandwiched between two -COO- may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms) to the extent that the effect of the present disclosure is not impaired. For example, a diol structure may be contained between ethylene oxide structures, between propylene oxide structures, or between an ethylene oxide structure and a propylene oxide structure. The diol structure may be -OR x -O-, R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6).

[0072] (Polyether tri(meth)acrylate) The polyether tri(meth)acrylate can form a structure represented by formula (3) (preferably formula (3-1)). As the polyether tri(meth)acrylate, for example, at least one selected from the group consisting of polyethylene glycol tri(meth)acrylate and tri(meth)acrylate of polyethylene glycol-propylene glycol copolymer can be used. When the tri(meth)acrylate of polyethylene glycol-propylene glycol copolymer is used, the molar ratio of ethylene glycol structure:propylene glycol structure is preferably 100:0 to 50:50, and more preferably 80:20 to 95:5.

[0073] When the molar ratio of ethylene glycol structure:propylene glycol structure is within this range, the transportability of ions such as lithium ions by polyethylene glycol can be maintained at a high level, and it becomes easier to suppress the inhibition of the movement of ions such as lithium ions due to crystallization of the polymer.

[0074] The polyether tri(meth)acrylate is represented, for example, by the following formula (3'). [ka]

[0075] In formula (3'), R 7 , R 8 , R 9 , R 10 , R 11 , m3, and n3 are the same as in formula (3-1). 11 The chain sandwiched between these may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6). For example, a diol structure may be contained between ethylene oxide structures, between propylene oxide structures, or between an ethylene oxide structure and a propylene oxide structure. The diol structure may be a -OR x -O-, R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6).

[0076] The structures represented by formula (1), formula (2), and formula (3) (preferably formula (1-1), formula (2-1), and formula (3-1)) can be obtained, for example, by using a polyether polyol obtained by ring-opening polymerization of ethylene oxide and propylene oxide. In addition, ethylene oxide represented by (-CH2-CH2-O-) in formula (1-1), formula (2-1), and formula (3-1) (and formula (1'), formula (2'), and formula (3')) The arrangement of the propylene oxide structure represented by the structure (—CH2—CH(CH3)—O—) may be a block copolymer or a random copolymer, preferably a random copolymer.

[0077] The mass content of the structure represented by formula (1) in the polymer contained in the polymer electrolyte is defined as A. The mass content of the structure represented by formula (2) and the structure represented by formula (3) in the polymer (preferably the content of the structure represented by formula (2)) is defined as B. The mass ratio A:B of A to B is preferably 70:30 to 98:2, more preferably 88:12 to 96:4, and even more preferably 90:10 to 95:5.

[0078] The mass ratio A:B can be adjusted by specifically adjusting the ratio between polyether mono(meth)acrylate and polyether di(meth)acrylate and / or tri(meth)acrylate. When the mass ratio A:B is within the above range, the polymer does not have an excessively dense network structure, and the polymer maintains its strength while less likely to inhibit the movement of lithium ions, which is particularly preferable.

[0079] In the polymer electrolyte, it is preferable that m1+n1 in formula (1-1) is 1 to 110 (more preferably 14 to 58), and m2+n2 in formula (2-1) and / or m3+n3 in formula (3-1) (preferably m2+n2 and m3+n3) are 1 to 110 (more preferably 14 to 58). By being in the above ranges, the crosslink density of the polymer main chain becomes appropriate, so that the ionic conductivity of the polymer electrolyte is higher while maintaining strength at high temperatures, and the rate characteristics of the secondary battery are also improved.

[0080] In the polymer electrolyte, it is preferred that m1:n1 in formula (1-1) is 80:20 to 95:5 (more preferably 80:20 to 90:10), and m2:n2 in formula (2-1) and / or m3:n3 in formula (3-1) (preferably m2:n2 in formula (2-1) and m3:n3 in formula (3-1)) are 80:20 to 95:5 (more preferably 85:15 to 95:5). Within the above range, the crystallinity of the polymer main chain is suppressed even if the molecular weight between crosslinking points is large, and it becomes easier to suppress the inhibition of lithium ion migration, particularly at low temperatures.

[0081] The polymer electrolyte of the present disclosure preferably has ionic functional groups as shown in the following formulas (4) to (7) for the purpose of imparting ionicity to the polymer itself and improving affinity with lithium salts. That is, the polymer preferably contains at least one structure selected from the group consisting of a structure represented by the following formula (4), a structure represented by the following formula (5), a structure represented by the following formula (6), and a structure represented by the formula (7).

[0082] <Fluorine sulfonylimide anionic group> It is preferable that the polymer further contains a structure represented by the following formula (4). The structure represented by formula (4) makes it possible to maintain a high level of ionic conductivity while reducing the crystallinity of the resin. The structure represented by formula (4) may be a structure represented by formula (4B). For example, the structure represented by formula (4) may be a reaction product of a fluorine sulfonylimide-based ionic compound having an unsaturated reactive functional group. [ka]

[0083] In formulas (4) and (4B), R 12 represents a hydrogen atom or a methyl group. 13 represents a divalent linking group. 14 represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms (preferably 1 to 2). + represents a cation, for example, an alkali metal cation. The cation preferably represents at least one selected from the group consisting of a lithium ion, a sodium ion, and a potassium ion. X + may be an alkali metal cation contained in the polymer electrolyte. That is, when the polymer contains the structure of formula 4(B), X + The cation included as may be an alkali metal cation in the polymer electrolyte.

[0084] R 13 The divalent linking group in the formula (I) preferably contains a linear or branched alkylene group having 1 to 7 carbon atoms (preferably 2 to 4 carbon atoms). 30 -(wherein the carbonyl group is R 12 is preferably bonded to the carbon atom to which R is bonded. 30 is preferably a linear or branched alkylene group having 1 to 7 (preferably 2 to 4) carbon atoms.

[0085] The polymer may be a polymer having a structure represented by the following formula (5), a structure represented by the following formula (6), or a structure represented by the following formula (7). The structure can reduce the crystallinity of the resin while maintaining a high level of ionic conductivity.

[0086] <Nitrogen-containing aromatic cationic group> The polymer preferably contains a structure represented by the following formula (5): For example, the structure represented by the following formula (5) may be a reaction product of an imidazolium-based ionic compound having an unsaturated reactive functional group. [ka]

[0087] In equation (5), R 15 represents a hydrogen atom or a methyl group. R 16 represents a divalent linking group. 17 R represents an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 or 2, and even more preferably 1). 18 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 or 2, and even more preferably 1).

[0088] In equation (5), R 16 ~R 18 Each of R is bonded to three elements selected from the group consisting of two nitrogen atoms and three carbon atoms that constitute the imidazolium ring structure. 16 ~R 18 One of X1 is attached to the cationic nitrogen atom in the imidazolium ring structure. - represents an anion. Preferably, R 16 is bonded to the cationic nitrogen atom constituting the imidazolium ring structure. 17 is bonded to the nitrogen atom that constitutes the imidazolium ring structure.

[0089] R as a linking group 16Specifically, represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1), or a divalent organic group containing an ester bond. The divalent organic group containing an ester bond is preferably an ester bond (-COO-) or a carbonyloxyalkylene having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1). Preferably, the carbonyl group in the divalent organic group containing an ester bond is R 15 is bonded to the carbon to which it is bonded.

[0090] The imidazolium ring structure may have a substituent such as an alkyl group, a substituted alkyl group (substituted with a halogen or the like), or a halogen.

[0091] The polymer preferably contains a structure represented by the following formula (6). For example, the polymer may contain a structure represented by the following formula (6): ) is a reaction product of a pyridinium-based ionic compound having an unsaturated reactive functional group. [ka]

[0092] In equation (6), R 19 represents a hydrogen atom or a methyl group. R 20 represents a divalent linking group. 21 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 or 2, and even more preferably 1). In equation (6), R 20 and R 21 One of the X2 bonds to the nitrogen atom that constitutes the pyridinium ring structure, and the other bond to one of the five carbon atoms that constitute the pyridinium ring structure. - represents an anion. Preferably, R 20 is attached to the cationic nitrogen atom that constitutes the pyridinium ring structure.

[0093] R as a linking group 20Specifically, represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1), or a divalent organic group containing an ester bond. The divalent organic group containing an ester bond is preferably an ester bond (-COO-) or a carbonyloxyalkylene having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1). Preferably, the carbonyl group in the divalent organic group containing an ester bond is R 19 is bonded to the carbon to which it is bonded.

[0094] The pyridinium ring structure may have a substituent such as an alkyl group, a substituted alkyl group (substituted with halogen or the like), or a halogen.

[0095] <Ammonium cationic group> The polymer preferably contains a structure represented by the following formula (7): For example, the structure represented by the following formula (7) may be a reaction product of an ammonium-based ionic compound having an unsaturated reactive functional group. [ka] In equation (7), R 22 represents a hydrogen atom or a methyl group. R 23 represents a divalent linking group. 24 ~R 26 each independently represents an alkyl group having 1 to 8 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1). X 3- represents an anion.

[0096] R as a linking group 22Specifically, R represents a straight-chain or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1), or a divalent organic group containing an ester bond. The divalent organic group containing an ester bond is preferably an ester bond (-COO-) or a carbonyloxyalkylene having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1). Preferably, the carbonyl group in the divalent organic group containing an ester bond is R 12 is bonded to the carbon to which it is bonded.

[0097] The total content of the structures represented by formulas (4) to (7) in the polymer structure is preferably 1 to 15 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the total of the structures represented by formulas (1), (2), and (3). When the contents of formulas (4) to (7) are within this range, it is possible to achieve both improved compatibility with the supporting electrolyte and improved ionic conductivity at a higher level by reducing the crystallinity of the polyethylene glycol structure in the polymer.

[0098] The state after these reactions can be confirmed by analysis using known means such as pyrolysis GC / MS, FT-IR, and NMR.

[0099] The ionic compounds having an unsaturated reactive functional group capable of forming the structures represented by the formulas (4) to (7) are represented by, for example, the following formulas (4') to (7'). [ka]

[0100] In formulas (4') to (7'), R 12 ~R 26 ,X - ,X1 - ,X2 - ,X3 - is the same as that explained in equations (4) to (7).

[0101] <cation> The cation X + shown in formula (4) is, for example, at least one selected from the group consisting of a lithium ion, a sodium ion, and a potassium ion. The cation may be selected depending on the carrier in the secondary battery. For example, lithium is selected for a lithium-ion secondary battery that uses lithium cobalt oxide or the like as the positive electrode active material, and sodium is selected for a sodium-sulfur secondary battery.

[0102] <anion> Anion X1 represented by formulas (5) to (7) - , X2 - , X3 - For example, 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.

[0103] Specific examples of the fluoroalkylsulfonylimide anion include fluoroalkylsulfonylimide anions having a fluoroalkyl group having from 1 to 6 carbon atoms, such as bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, bis(heptafluoropropanesulfonyl)imide anion, bis(nonafluorobutanesulfonyl)imide anion, bis(dodecafluoropentanesulfonyl)imide anion, and bis(perfluorohexanesulfonyl)imide anion, and cyclic fluoroalkylsulfonylimide anions such as N,N-hexafluoropropane-1,3-disulfonylimide. Examples of the anion include a fluoroalkylsulfonylimide anion.

[0104] A specific example of the fluorosulfonylimide anion is a bis(fluorosulfonyl)imide anion. Specific examples of the fluoroalkylsulfonate anion include trifluoromethanesulfonate anion, fluoromethanesulfonate anion, perfluoroethanesulfonate anion, perfluoropropanesulfonate anion, perfluorobutanesulfonate anion, perfluoropentanesulfonate anion, perfluorohexanesulfonate anion, and perfluorooctanesulfonate anion.

[0105] Specific examples of the fluoroalkyl carboxylate anion include a trifluoroacetate anion, a perfluoropropionate anion, a perfluorobutyrate anion, a perfluorovalerate anion, and a perfluorocaproate anion. Specific examples of the fluoroalkyl methide anion include fluorinated alkylsulfonyl methide anions such as tris(trifluoromethanesulfonyl)methide anion, tris(perfluoroethanesulfonyl)methide anion, tris(perfluoropropanesulfonyl)methide anion, tris(perfluorobutanesulfonyl)methide anion, tris(perfluoropentanesulfonyl)methide anion, tris(perfluorohexanesulfonyl)methide anion, and tris(perfluorooctanesulfonyl)methide anion.

[0106] A specific example of the fluoroborate anion is tetrafluoroborate anion. A specific example of the fluorophosphate anion is hexafluorophosphate anion.

[0107] Among these anions, at least one selected from the group consisting of a fluoroalkylsulfonylimide anion, a fluorosulfonylimide anion, a fluoroborate anion, a dicyanamide anion, and a thiocyanate anion is particularly preferred because it reduces the decrease in conductivity in a low-temperature environment.

[0108] More specifically, bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoromethanesulfonic acid anion (CF3-SO3 - ), hexafluorophosphate anion (PF6 - ), fluoroborate anion (BF4 - ), dicyanamide anion (N(CN)2 - ), thiocyanate anion (SCN - ) is preferred. More preferably, bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, hexafluorophosphate anion (PF6 - ), and at least one anion selected from the group consisting of:

[0109] <Alkali metal cation> The polymer electrolyte is characterized by containing an alkali metal cation. The alkali metal cation may be at least one selected from the group consisting of lithium cation, sodium cation, potassium cation, rubidium cation, and cesium cation. The alkali metal cation is preferably at least one selected from the group consisting of lithium ion, sodium ion, and potassium ion.

[0110] Alkali metal cations may be contained as a supporting electrolyte in the polymer electrolyte layer. In this case, the cation of the alkali metal salt serving as the supporting electrolyte functions as a carrier in the secondary battery, and is therefore selected appropriately depending on the type of battery. For example, in a lithium secondary battery, Therefore, the alkali metal cation is selected from metal salts containing lithium cations.

[0111] When the polymer has a structure represented by formula (4B), X + At least one cation selected from the group consisting of lithium ions, sodium ions, and potassium ions contained as the cation may be an alkali metal cation.

[0112] <Supporting electrolyte> Examples of the supporting electrolyte include lithium salts, sodium salts, potassium salts, rubidium salts, and cesium salts. The alkali metal salt used as the supporting electrolyte has an anion that is the counterion of the cation. For example, BF4 - , PF6 - , N(SO2CF3)2 - , N(SO2F)2 - , N(SO2C2F5)2 - , B(OCH(CF3)2)4 - , B(OCH(CF3)2)4 - , AlCl4 - , SBF6 - , SCN - , CF3SO3 - , AsF6 - , ClO4 - , N(CN)2 - , lower aliphatic carboxylic acid anion, CO3 2- , Cl - , Br - , I - At least one selected from the group consisting of:

[0113] For example, when lithium ions are selected as the alkali metal cation, at least one selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiN(SOCF)), lithium bis(fluorosulfonyl)imide (LiN(SOF)), and LiN(CFS0) is preferred due to its chemical stability with the positive electrode active material. One lithium salt may be used alone, or two or more may be used in combination. Similarly, for other alkali metal cations such as sodium and potassium, it is preferable to select a similar paired anion.

[0114] The content of the supporting electrolyte is preferably 5 to 40 parts by mass, more preferably 7 to 20 parts by mass, per 100 parts by mass of the polymer in the polymer electrolyte. When the content of the supporting electrolyte is within this range, the supporting electrolyte is well compatible with the polymer, does not precipitate, and high ionic conductivity is obtained.

[0115] <Fine particles> The polymer electrolyte is characterized by containing at least one fine particle selected from the group consisting of resin fine particles and metal oxide fine particles, and the fine particles exert an effect of inhibiting dendrite growth.

[0116] The resin fine particles include, for example, at least one particle selected from the group consisting of acrylic resin fine particles, melamine formaldehyde resin fine particles, styrene resin fine particles, silicone resin fine particles, epoxy resin fine particles, etc. The resin fine particles are preferably at least one particle selected from the group consisting of acrylic resin fine particles, melamine formaldehyde resin fine particles, etc.

[0117] Examples of the metal oxide fine particles include at least one fine particle selected from the group consisting of silica fine particles, glass fine particles, alumina fine particles, titanium oxide fine particles, zirconium oxide fine particles, strontium titanate fine particles, calcium titanate fine particles, sodium titanate fine particles, barium titanate fine particles, potassium niobate fine particles, etc. The metal oxide fine particles are preferably at least one fine particle selected from the group consisting of silica fine particles, titanium oxide fine particles, alumina fine particles, and barium titanate fine particles.

[0118] The volume average particle size of the primary particles of these fine particles is preferably 10 to 200 nm, more preferably 20 to 80 nm. When the particle size range of the fine particles is within this range, both ionic conductivity and the effect of inhibiting dendrite growth can be achieved at a higher level.

[0119] The volume average particle size is an average particle size calculated from the volume of a sphere calculated from the radius when the projected area is converted into a circle. Specifically, it is measured by the following procedure. The polymer electrolyte is cut into a thin slice of a predetermined thickness (e.g., 1 μm). Then, a fracture surface is formed by freeze fracturing, cross polishing, focused ion beam (FIB), or other methods. The FIB method is used in consideration of the smoothness of the fracture surface and pretreatment for observation. Furthermore, pretreatment such as staining or vapor deposition may be performed to facilitate observation of the particles.

[0120] The fractured surface is formed, and the pre-processed section is photographed using a scanning electron microscope (SEM). To ensure accuracy of the average grain size, the SEM is used for observation at 1,000 to 100,000 magnifications. The acquired photographed images of the fracture surface are converted to 8-bit grayscale using image processing software ("Luzex" (trade name, manufactured by Nireco Corporation)) to obtain a monochrome image with 256 gradations. Next, the image is processed so that the fine particles in the fracture surface appear white, and after binarization, the image processing software is used to calculate the circular equivalent diameter of each fine particle. Then, assuming that the fine particles are spherical, the volume of the sphere is calculated from the circular equivalent diameter.

[0121] The polymer electrolyte is divided into 20 equal sections, and one thin section sample is cut from each section. The images are then captured, and the measurements are obtained. The volume-average particle size is calculated by multiplying the obtained circle-equivalent diameter by the volume of each sphere and dividing the sum by the total volume of the spheres.

[0122] These fine particles may be subjected to a surface treatment such as hydrophobic treatment or hydrophilic treatment, for example, hydrophobic treatment using an organosilicon compound, an organotitanium compound, or the like as a treatment agent. The fine particles preferably have at least one surface functional group selected from the group consisting of hydroxyl groups, carboxyl groups, carbonyl groups, amino groups, etc. This is more preferable because the fine particles have a higher affinity with the polymer. Furthermore, aggregation in the polymer can be suppressed, resulting in a higher dendrite suppression effect.

[0123] The content of the fine particles is preferably 2 to 30 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the polymer in the polymer electrolyte. When the content of the fine particles is within this range, both high ionic conductivity and the dendrite growth suppression effect can be achieved at a higher level. The content of these can be confirmed by analysis using known means such as TG.

[0124] <Liquid electrolyte> The polymer electrolyte of the present disclosure may contain a liquid electrolyte, such as an ionic liquid or a non-aqueous electrolyte solution, as long as the effects of the present disclosure are not impaired and safety at high temperatures is not impaired.

[0125] Specific examples of ionic liquids include the following combinations of cations and anions: The cation may be at least one selected from the group consisting of quaternary ammonium, imidazolium, pyridinium, pyrrolidinium, and piperidinium. The anion may be selected from the group consisting of a fluoroalkylsulfonylimide anion, a fluorosulfonylimide anion, a fluoroalkylsulfonate anion, a fluorosulfonate anion, a fluoroalkylcarboxylate 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. At least one selected from the following can be mentioned.

[0126] The non-aqueous electrolyte is a liquid in which approximately 1 mol of a lithium salt is dissolved in a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of the lithium salt include LiPF6, LiBF4, and LiClO4.

[0127] Although the inclusion of a liquid electrolyte may improve ionic conductivity, in order to avoid a decrease in mechanical strength at high temperatures, the amount of the liquid electrolyte is preferably 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less per 100 parts by mass of the polymer that forms the polymer electrolyte.

[0128] Furthermore, the polymer electrolyte may contain a conductive filler, if necessary, within a range that does not impair the effects of the present disclosure. As the conductive filler, conductive fine particles such as carbon black, zinc oxide, tin oxide, and titanium oxide can be used. The content of the conductive filler is preferably 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the resin that forms the polymer electrolyte.

[0129] (Method for forming a polymer electrolyte layer) The method for forming the polymer electrolyte layer is not particularly limited. For example, the above-mentioned polymer electrolyte materials are mixed by a known method to obtain an electrolyte solution for forming the polymer electrolyte layer. The electrolyte solution is applied by a known application method such as barcode coating, spin coating, or roll coating, and then the polymer material contained in the charge chamber solution is polymerized by a known means such as UV to form the polymer electrolyte layer.

[0130] The thickness of the polymer electrolyte layer as a bulk electrolyte is preferably 5.0 μm or more and 100.0 μm or less. If necessary, the electrolyte solution may contain a known polymerization initiator, such as a photopolymerization initiator, or a known organic solvent such as methyl ethyl ketone. [Example]

[0131] 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.

[0132] First, polyether acrylates were synthesized that form the structures represented by formula (1) and formula (2). A synthesis example of a polyether monoacrylate that can form the structure represented by formula (1) is shown below. <Synthesis of polyether mono(meth)acrylate> (Polyether monoacrylate A-1) 15.5 parts by mass of 1-hexanol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an 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 1041 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 8:2 was continuously introduced over 260 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 180 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 90°C for 30 minutes, after which 50 g 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 130°C to obtain a polyether monool with Mn of 6000.

[0133] Next, 100 parts by mass of the resulting polyether monool, 1.26 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 2.02 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether monoacrylate A-1.

[0134] (Polyether monoacrylate A-2) 18.6 parts by mass of 1-hexanol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 976 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 95:5 was continuously introduced over 240 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 180 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 90°C for 30 minutes, after which 50 g 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 130°C to obtain a polyether monool with Mn of 5000.

[0135] Next, 100 parts by mass of the resulting polyether monool, 1.51 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 2.42 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether monoacrylate A-2.

[0136] (Polyether monoacrylate A-3) 33.7 parts by mass of 1-butanol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 984 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 8:2 was continuously introduced over 240 minutes while maintaining the vessel pressure at approximately 0.5 MPa. The reaction was continued for 150 minutes while maintaining the temperature at 100°C, until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and the mixture was stirred until the vessel pressure change reached 0.01 MPa / 30 minutes. 20 parts by mass of pure water was added to the resulting polymer and stirred at 90°C for 30 minutes. After stirring, 50 g of the alkaline adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and the mixture was stirred for an additional 30 minutes. Next, the alkali adsorbent was removed by filtration, and the residue was dried under reduced pressure at 130°C to obtain a polyether monool having an Mn of 2000.

[0137] Next, 100 parts by mass of the resulting polyether monool, 3.78 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 6.05 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 6 hours while removing the water produced by the reaction from the system. The reaction solution was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-3.

[0138] (Polyether monoacrylate A-4) 67.4 parts by mass of 1-butanol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 946 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 8:2 was continuously introduced over 240 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 130 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes and stirred until the vessel pressure change reached 0.01 MPa / 30 minutes. 20 parts by mass of pure water was added to the resulting polymer and stirred at 90°C for 30 minutes. After stirring, 50 g of the alkaline adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and stirred for an additional 30 minutes. Next, the alkali adsorbent was removed by filtration, and the residue was dried under reduced pressure at 130°C to obtain a polyether monool having an Mn of 1000.

[0139] Next, 100 parts by mass of the resulting polyether monool, 7.56 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 12.1 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 6 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether monoacrylate A-4.

[0140] (Polyether monoacrylate A-5) 169 parts by mass of 1-butanol (Tokyo Chemical Industry Co., Ltd.) and 8 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 927 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 8:2 was continuously introduced over 220 minutes while maintaining the vessel pressure at approximately 0.5 MPa. The reaction was continued for 120 minutes while maintaining the temperature at 100°C, until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and the mixture was stirred until the vessel pressure change 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 90°C for 30 minutes. After this, 50 g of the alkaline adsorbent Kyoward 600 (Kyowa Chemical Industry Co., Ltd.) was added and the mixture was stirred for an additional 30 minutes. Next, the alkali adsorbent was removed by filtration, and the residue was dried under reduced pressure at 130°C to obtain a polyether monool with Mn of 400.

[0141] Next, 100 parts by mass of the resulting polyether monool, 18.9 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 24.2 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 6 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether monoacrylate A-5.

[0142] (Polyether monomethacrylate A-6) 1-butanol (Tokyo Chemical Industry Co., Ltd.) 112 parts by mass, potassium hydroxide (High Purity Chemical Research Five parts by mass of a propylene oxide (manufactured by Kyowa Chemical Industry Co., Ltd.) was placed in an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 937 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 5:5 was continuously introduced over 240 minutes while maintaining the vessel internal pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 120 minutes until the vessel internal pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel internal pressure change 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 90°C for 30 minutes. After that, 50 g of an alkali adsorbent, Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.), was added, and the mixture was stirred for an additional 30 minutes. Next, the alkali adsorbent was removed by filtration, and the residue was dried under reduced pressure at 130°C to obtain a polyether monool with Mn of 600.

[0143] Next, 100 parts by mass of the resulting polyether monool, 12.6 parts by mass of methacrylic acid (Nippon Shokubai Co., Ltd.), 20.2 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 6 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether monomethacrylate A-6.

[0144] (Polyether monoacrylate A-7) Polyether monoacrylate A-7 was obtained in the same manner as Polyether monoacrylate A-4, except that the molar fraction of the ethylene oxide / propylene oxide mixed gas was changed to 5:5. The polyether mono(meth)acrylates obtained are shown in Table 1.

[0145] Next, a synthesis example of a polyether di(meth)acrylate capable of forming the structure represented by formula (2) will be shown. <Synthesis of polyether diacrylate> (Polyether diacrylate B-1) 13.7 parts by mass of 1,4-butanediol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 1,041 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 8:2 was continuously introduced over 280 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 170 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 90°C for 30 minutes, after which 50 g of an alkali adsorbent, Kyoward 600 (manufactured by 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 130°C to obtain a polyether diol with Mn of 6000.

[0146] Next, 100 parts by mass of the resulting polyether diol, 2.52 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 2.02 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction solution was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-1.

[0147] (Polyether diacrylate B-2) A polyether diol having an Mn of 5000 was obtained in the same manner as in the preparation of polyether diacrylate B-1, except that the amount of 1,4-butanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 16.4 parts by mass.

[0148] Next, 100 parts by mass of the resulting polyether diol, 3.02 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 2.42 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction solution was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-2.

[0149] (Polyether diacrylate B-3) 41.0 parts by mass of 1,4-butanediol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 955 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 9:1 was continuously introduced over 220 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 150 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 90°C for 30 minutes, after which 50 g of an alkali adsorbent, Kyoward 600 (manufactured by 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 130°C to obtain a polyether diol with Mn of 2000.

[0150] Next, 100 parts by mass of the resulting polyether diol, 7.56 parts by mass of acrylic acid (Nippon Shokubai Co., Ltd.), 6.05 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction solution was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-3.

[0151] (Polyether dimethacrylate B-4) A polyether diol having an Mn of 1000 was obtained in the same manner as polyether diacrylate B-3, except that the amount of 1,4-butanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 82.0 parts by mass and the molar fraction of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0152] Next, 100 parts by mass of the resulting polyether diol, 18.1 parts by mass of methacrylic acid (Mitsubishi Gas Chemical Company, Inc.), 12.1 parts by mass of paratoluenesulfonic acid (Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 6 hours while removing the water produced by the reaction from the system. The reaction mixture was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of purified water. The organic phase was separated from the washed reaction mixture, and the solvent was removed under reduced pressure to obtain polyether dimethacrylate B-4.

[0153] (Polyether dimethacrylate B-5) 137 parts by mass of 1,4-butanediol (Tokyo Chemical Industry Co., Ltd.) and 2 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were added to an autoclave and stirred under reduced pressure at 120°C for dissolution and dehydration. Next, the pressure inside the system was reduced to -0.1 MPa at 100°C, and 899 parts by mass of a gas mixture of ethylene oxide and propylene oxide at a molar fraction of 5:5 was continuously introduced over 210 minutes while maintaining the vessel pressure at approximately 0.5 MPa. While maintaining the temperature at 100°C, the reaction was carried out for 110 minutes until the vessel pressure dropped to 0.2 MPa or less. The temperature was then raised to 130°C over 30 minutes, and stirring was continued until the vessel pressure change reached 0.01 MPa / 30 minutes. To the resulting polymer, 20 parts by mass of pure water was added and stirred at 90°C for 30 minutes, after which 50 g of an alkali adsorbent, Kyoward 600 (manufactured by 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 130°C to obtain a polyether diol with Mn of 600.

[0154] Next, 100 parts by mass of the resulting polyether diol, 30.0 parts by mass of methacrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 20.2 parts by mass of paratoluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 parts by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were added to a Dean-Stark reactor equipped with a stirrer. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water produced by the reaction from the system. The reaction solution was then cooled to room temperature and washed twice with 120 g of a 5% aqueous solution of sodium hydroxide, and then three times with 120 g of pure water. The organic phase was separated from the washed reaction solution, and the solvent was distilled off under reduced pressure to obtain polyether dimethacrylate B-5. The polyether di(meth)acrylates obtained are shown in Table 2.

[0155] [Table 1] The polyether composition ratios are expressed as mole fractions, where EO represents ethylene oxide and PO represents propylene oxide.

[0156] [Table 2] The polyether composition ratios are expressed as mole fractions, where EO represents ethylene oxide and PO represents propylene oxide.

[0157] <Synthesis of reactive ionic compounds> (Synthesis of ionic compound C-1) 15.9 g (0.06 mol) of 3-sulfopropyl acrylate potassium salt (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. The suspension was concentrated under reduced pressure, and the residue was dissolved in dichloromethane, washed with 50 mL of pure water and 50 mL of brine, and then concentrated under reduced pressure again to obtain a pale yellow liquid. 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, and the mixture was stirred for 2 hours. The reaction mixture was then 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 C-1.

[0158] (Synthesis of ionic compound C-2) 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 C-2 in the same manner as ionic compound C-1.

[0159] (Ionic Compound C-3) 1-Allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Tokyo Chemical Industry Co., Ltd.) was used as ionic compound C-3.

[0160] (Synthesis of ionic compound C-4) 15.0 g (0.18 mol) of 1-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) and 27.1 g (0.20 mol) of allyl bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 35.0 g of acetonitrile. The reaction mixture was heated and stirred at 30°C for 24 hours, then cooled to room temperature, and The mixture was washed three times with 100 ml of ethyl ether, and then 2 g of activated carbon and 20 ml of ethanol were added. After stirring at room temperature for 1 hour, the activated carbon was filtered off and the solvent was distilled off under reduced pressure.

[0161] The resulting product was dissolved in 160 ml of pure water, and 33.7 g (0.18 mol) of lithium bis(fluorosulfonyl)imide (Kanto Chemical Co., Ltd.) was added as an anion source and stirred at room temperature for 4 hours. The reaction solution was then extracted twice with 100.0 g of ethyl acetate. The separated ethyl acetate layer was then washed three times with 60 g of ion-exchanged water. The ethyl acetate was then distilled off under reduced pressure to obtain ionic compound C-4.

[0162] (Synthesis of ionic compound C-5) 15.0 g (0.12 mol) of 1-methyl-5-(Prop-2-en-1-yl)-1H-imidazole (AURORA Fine Chemicals Ltd.) was dissolved in tetrahydrofuran. The reaction system was then placed under a nitrogen atmosphere and ice-cooled. Subsequently, 19.2 g (0.14 mol) of methyl iodide (Tokyo Chemical Industry Co., Ltd.) dissolved in 30.0 g of tetrahydrofuran was added dropwise over 30 minutes. The reaction solution was heated under reflux for 12 hours, after which 100 ml of water was added and the solvent was distilled off under reduced pressure. 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matter was removed by filtration through Celite, and the solvent was again distilled off under reduced pressure.

[0163] The resulting product was dissolved in 160 ml of pure water, and 18.7 g (0.12 mol) of lithium hexafluorophosphate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an anion source and stirred at room temperature for 1 hour. Next, the reaction solution was extracted twice with 80.0 g of ethyl acetate. Next, the separated ethyl acetate layer was washed three times with 60 g of ion-exchanged water. Subsequently, the ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-5.

[0164] (Synthesis of ionic compound C-6) 15.0 g (0.18 mol) of 1-methylimidazole (Tokyo Chemical Industry Co., Ltd.) was dissolved in 35.0 g of tetrahydrofuran. The reaction system was then placed under a nitrogen atmosphere, and 32.2 g (0.18 mol) of 2-bromoethyl acrylate (Merck & Co.) dissolved in 80.0 g of tetrahydrofuran was added dropwise over 30 minutes. The reaction solution was heated under reflux for 6 hours, after which 100 ml of water was added and the solvent was distilled off under reduced pressure. 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matter was removed by filtration through Celite, and the solvent was again distilled off under reduced pressure.

[0165] The resulting product was dissolved in 160 ml of purified water, and 51.7 g (0.18 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion source and stirred at room temperature for 1 hour. Next, the reaction solution was extracted twice with 100.0 g of ethyl acetate. Next, the separated ethyl acetate layer was washed three times with 60 g of ion-exchanged water. Subsequently, the ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-6.

[0166] (Synthesis of ionic compound C-7) 15.0 g (0.19 mol) of pyridine (Tokyo Chemical Industry Co., Ltd.) and 26.9 g (0.20 mol) of allyl bromide (Tokyo Chemical Industry Co., Ltd.) were dissolved in 35.0 g of acetonitrile. The reaction mixture was heated and stirred at 30°C for 24 hours, then cooled to room temperature and washed three times with 100 ml of diethyl ether. 2 g of activated carbon and 20 ml of ethanol were then added, and the mixture was stirred at room temperature for 1 hour. The activated carbon was then filtered, and the solvent was distilled off under reduced pressure.

[0167] The obtained product was dissolved in 160 ml of pure water, and lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, Mitsubishi Materials Electronics) was added as an anion source. 54.5 g (0.19 mol) of ethanol (manufactured by Seisakusho) was added and stirred at room temperature for 1 hour. The reaction solution was then extracted twice with 100.0 g of ethyl acetate. The separated ethyl acetate layer was then washed three times with 60 g of ion-exchanged water. The ethyl acetate was then distilled off under reduced pressure to obtain ionic compound C-7.

[0168] (Synthesis of ionic compound C-8) 15.0 g (0.11 mol) of allyltrimethylammonium chloride (Combi-Blocks Inc.) was dissolved in 160 mL of purified water. 31.7 g (0.11 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion source and stirred at room temperature for 1 hour. Next, the reaction solution was extracted twice with 100.0 g of ethyl acetate. Next, the separated ethyl acetate layer was washed three times with 60 g of ion-exchanged water. Subsequently, the ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-8.

[0169] (Synthesis of ionic compound C-9)

[0170] 15.0 g (0.10 mol) of (DIMETHYLAMINO)METHYL 2-METHYLPROP-2-ENOATE (manufactured by Hong Kong Chemhere Co., Ltd.) was dissolved in 30.0 g of tetrahydrofuran. The reaction system was then placed under a nitrogen atmosphere and ice-cooled. 20.2 g (0.10 mol) of 1-bromooctane (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 60.0 g of tetrahydrofuran was then added dropwise over 30 minutes. The reaction solution was heated under reflux for 9 hours, after which 100 ml of water was added and the solvent was distilled off under reduced pressure. 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matter was removed by filtration through Celite, and the solvent was again distilled off under reduced pressure. The resulting product was dissolved in 160 ml of purified water, and 30.1 g (0.10 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion source and stirred at room temperature for 1 hour. The reaction solution was then extracted twice with 100.0 g of ethyl acetate. The separated ethyl acetate layer was then washed three times with 60 g of ion-exchanged water. The ethyl acetate was then distilled off under reduced pressure to obtain ionic compound C-9.

[0171] The chemical structures of the resulting reactive ion compounds C-1 to C-9 are shown below. [ka]

[0172] <Preparation of polymer electrolyte solution> [Example 1] As materials for the polymer electrolyte, the following materials were mixed and stirred. Polyether monoacrylate NK Ester M-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 50.0 parts by mass Polyether diacrylate B-1: 50.0 parts by mass Ionic compound C-5: 2.0 parts by mass Lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) (Kishida Chemical Co., Ltd.): 10.0 parts by mass Fine particles D-11 (aerosil 200 manufactured by Nippon Aerosil Co., Ltd.): 10.0 parts by mass Initiator Omnirad 184 (manufactured by IGM Resins BV): 2.0 parts by mass Next, methyl ethyl ketone (hereinafter referred to as MEK) was added so that the total solid content ratio became 60% by mass, and then the mixture was mixed by stirring with a motor to prepare an electrolyte solution.

[0173] (Measurement of volume swelling ratio using MEK immersion method) Test pieces for measuring volume swelling ratio by MEK immersion were prepared as follows using the electrolyte solution of each example. A predetermined amount of the surface layer-forming dispersion of each example was added to an aluminum mold with a fluororesin coating on the surface to achieve a film thickness of 200 μm. The mold was then placed on a sunflower stand and dried until the viscosity increased to the point where the film surface did not flow. After that, the mold was placed on a horizontal stand and dried at 60°C for 2 hours. Next, a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network) was used to irradiate the air with an integrated light dose of 5000 mJ / cm. 2 The membrane surface was irradiated with UV light so that the polymer electrolyte was crosslinked and cured. After curing, the electrolyte membrane was left in an environment of 23°C and 40% RH for 24 hours, and then peeled off from the aluminum mold to prepare a sheet with a thickness of 200 μm. The obtained polymer electrolyte sheet was cut into 50 mm × 50 mm pieces and left in an environment of 23°C and 40% RH for 24 hours to prepare test specimens.

[0174] First, the initial weight in air (W1) and the initial weight in water (W2) were measured in an environment of 23°C and 40% RH. Next, the test piece after the initial weight measurement was immersed in MEK at 23°C for 48 hours. Immediately after removing the test piece from MEK, the MEK on the surface was wiped off with a nonwoven fabric, and the test piece was placed in a pre-weighed weighing bottle, and the weight after immersion in air (W3) and the weight after immersion in water (W4) were measured. The volume swelling ratio after immersion in MEK was calculated using the following formula. Volume swelling rate (%) = ((W3-W4)-(W1-W2)) / (W1-W2) x 100 W1: Initial weight in air W2: Initial weight in water W3: Weight after immersion in air W4: Weight after immersion in water

[0175] (Ionic conductivity measurement at room temperature (25°C)) The electrolyte solution obtained in Example 1 was applied to a 100 μm thick aluminum plate using a bar coater and dried for 30 minutes at 60° C. Next, a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.) was used to apply an accumulated light dose of 5000 mJ / cm 2 2 The membrane surface was irradiated with UV light so as to crosslink and cure the polymer electrolyte membrane of Example 1. The membrane thickness after curing was 60 μm.

[0176] The obtained polymer electrolyte membrane was punched together with the aluminum substrate to a diameter of 50 mm and vacuum dried at 80°C for 48 hours. The polymer electrolyte membrane was then placed in an argon-substituted glove box (temperature 25°C, dew point -70°C), and the AC impedance between the electrodes was measured using an impedance analyzer E4990A (manufactured by KEYSIGHT) at an applied voltage of 10 mV and a frequency range of 100 MHz to 1 Hz. 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 ))

[0177] (Ionic conductivity measurement at low temperature (5℃)) A polymer electrolyte membrane was formed on an aluminum plate in the same manner as in the measurement of ionic conductivity at room temperature. The polymer electrolyte membrane was then placed in an argon-substituted glove box (temperature 25°C, dew point -70°C) and incorporated into an all-solid-state battery evaluation cell (manufactured by Hosensha). The evaluation cell incorporating the polymer electrolyte membrane was placed in a low-temperature environmental tester and left for 1 hour at 5° C. Thereafter, the ionic conductivity at low temperature was determined in the same manner as in the above measurement.

[0178] <Preparation of secondary battery> Configuration using the polymer electrolyte of the present disclosure as a bulk electrolyte (Preparation of negative electrode) A 20mm x 20mm, 60μm-thick lithium foil (manufactured by Honjo Metals Co., Ltd.) was laminated onto a 20mm x 30mm, 20μm-thick copper foil, leaving a 10mm unlaminated edge on one side, and then pressed together to produce a negative electrode. The total thickness of the resulting negative electrode was 70μm. A 5mm-wide copper tab with nickel plating on one unlaminated edge was attached to the negative electrode.

[0179] (Preparation of positive electrode) 100 parts by weight of lithium cobalt oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 7 parts by weight of Kureha KF Polymer L#1120 (manufactured by Kureha Corporation) as an active material binder and 5 parts by weight of Denka Black Li-100 (manufactured by Denka Corporation) as a conductive additive, and 40 parts by weight of N-methylpyrrolidone was added and mixed and stirred. The resulting slurry was then coated onto a 15mm x 25mm, 20μm thick rolled aluminum foil, leaving a 10mm uncoated edge on one side, dried at 100°C for 30 minutes, and pressed to obtain a positive electrode. The positive electrode had a thickness of 80μm. An aluminum tab having a width of 5 mm was attached to one uncoated end of the positive electrode.

[0180] (Formation of polymer electrolyte layer) An electrolyte solution was applied to the entire active material-coated surface of the obtained positive electrode using a bar coater, and the coating was air-dried at 23° C. for 10 minutes, and then dried at 60° C. for 30 minutes. Next, a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network) was used to irradiate the coating with an accumulated light dose of 5000 mJ / cm. 2 The film surface was irradiated with UV light to cure the film, and the film thickness after curing was 60 μm.

[0181] (Fabrication of secondary batteries using polymer electrolytes as bulk electrolytes) The positive electrode coated with the polymer electrolyte was vacuum dried at 80°C for 48 hours. The polymer electrolyte film was then placed in an argon-substituted glove box (temperature 25°C, dew point -70°C), and a polyimide sheet punched into a window frame shape was attached to cover the outer periphery of the positive electrode surface to form a short-circuit prevention layer. Next, the polymer electrolyte-coated positive electrode and the lithium layer of the negative electrode were laminated so that they corresponded to each other. The laminate was sandwiched between aluminum laminate films and vacuum-packed to obtain a secondary battery according to Example 1.

[0182] <Battery characteristic evaluation> (rate characteristics) The theoretical capacity was calculated from the total mass of lithium cobalt oxide contained in the positive electrode. A charge / discharge test was carried out on the prototype secondary battery at 25°C using a charge / discharge device BCS-805 (manufactured by Biologic Co., Ltd.). The theoretical capacity was calculated from the total mass of lithium cobalt oxide contained in the positive electrode, and the first cycle consisted of charging at a constant current of 0.05C with a cutoff voltage of 3.9V for 2 hours, followed by discharging at a constant current of 0.05C with a cutoff voltage of 2.0V for 1 hour. Next, the charge and discharge rates were increased by 0.05C each time, and the same charge and discharge were performed. The rate at which the charge and discharge could be performed without exceeding the cutoff value was taken as the rate characteristic.

[0183] (Strength evaluation at high temperatures) The prototype secondary batteries were subjected to impact once using a thin film impact tester QC-633 (manufactured by Cometech Testing Machines) at 25°C, with an impact tip diameter of 38.1 mm, a load of 120 g, and a height of 150 mm, and then a short circuit test was performed using a tester. Five batteries were produced for each example, and the impact test was performed five times in total, and the number of batteries that short-circuited was counted. Next, the impact tester and secondary battery were placed in an environmental tester set to 60°C, and after leaving them for 2 hours, the same test was carried out, and the number of batteries that developed short circuits during the high-temperature test was counted.

[0184] (Short circuit occurrence evaluation) The prototype secondary battery was repeatedly charged and discharged in an environment of 40°C. Charging was performed at a charge rate of 0.05C and a charge voltage of 4.0V, and discharging was performed at a discharge rate of 0.05C and a discharge voltage of 3.0V, and the number of cycles was counted until abnormal voltage behavior occurred during charging and discharging. Next, the electrodes were removed from the batteries after evaluation, and the electrodes were observed using a digital microscope VHX-5000 (manufactured by Keyence Corporation) with 50x and 500x objective lenses to see if there were any deposits on the surfaces.

[0185] It can be confirmed that the polymer electrolyte has at least one structure selected from the group consisting of the structure of formula (1) and the structure of formula (2) and the structure of formula (3) by, for example, pyrolysis GC / MS, FT-IR or NMR analysis. The polymer electrolyte obtained in this example was analyzed using a pyrolysis apparatus (trade name: Pyrofoil Sampler JPS-700, manufactured by Japan Analytical Industry Co., Ltd.) and a GC / MS apparatus (trade name: FocusGC / ISQ, manufactured by Thermo Fisher Scientific) at a pyrolysis temperature of 590°C and helium as a carrier gas. As a result, from the obtained fragment peaks, it was confirmed that the polymer electrolyte had at least one structure selected from the group consisting of the structure represented by formula (1), the structure represented by formula (2), and the structure represented by formula (3).

[0186] Test pieces for measuring the volumetric swelling ratio by the MEK immersion method can also be obtained by removing them from the secondary battery. Test pieces can be obtained by removing the bulk electrolyte from the secondary battery obtained in this example and removing the positive and negative electrodes. It was confirmed that the volumetric swelling ratios by the MEK immersion method of the test piece removed from the secondary battery and the test piece prepared in this example were the same value.

[0187] [Examples 2 to 34] Polymer electrolytes and secondary batteries according to Examples 2 to 34 were produced in the same manner as in Example 1, except that the types and amounts of materials used were changed as shown in Tables 3 and 4.

[0188] [Table 3] In the table, the primary particle size indicates the volume average particle size of the primary particles.

[0189] [Table 4]

[0190] The structures of the materials used when polymerized are as follows: M-230G (methoxypolyethylene glycol methacrylate, R in formula (1-1) 1 : Methyl group, R 2 : Ethylene group -(CH2)2-, R 3 : methyl group, m1:23, n1:0) AM-90G (methoxypolyethylene glycol #400 acrylate, R in formula (1-1) 1 : Hydrogen atom, R 2 : ethylene group, R 3 : methyl group, m1:9, n1:0) A-1000PER (R in Equation (2-1) 4 : Hydrogen atom, R 5 : ethylene group or propylene group, R 6 : ethylene group or propylene group, m2: 17, n2: 4) A-1000 (polyethylene glycol #1000 diacrylate, R in formula (2-1) 4 : Hydrogen atom, R 5 : ethylene group, R 6 : ethylene group, m2: 23, n2: 0) A-400 (polyethylene glycol #400 diacrylate, R in formula (2-1) 4 : Hydrogen atom, R 5 : ethylene group, R 6 : ethylene group, m2:9, n2:0) A-GLY-20E (ethoxylated glycerin triacrylate, R in formula (3-1) 7 : Hydrogen atom, R 8 : ethylene group, R 9 : ethylene group, R 10 : ethylene group, R 11 :-CH2(CH-)CH2-, m3: 20 as the total of formula (3-1), n3: 0) 14G: Polyethylene glycol #600 dimethacrylate (R in formula (2-1) 4 : Methyl group, R 5 : ethylene group, R 6 : ethylene group, m2:14, n2:0) All of the above are manufactured by Shin-Nakamura Chemical Co., Ltd.

[0191] MEMA-4000: (Polyethylene glycol #4000 dimethacrylate (in formula (2-1), R4 is a methyl group, R5 is an ethylene group, R6 is an ethylene group, m2 is 90, n2 is 0)) manufactured by Toho Chemical Industry Co., Ltd. Li·TFSI stands for lithium bis(trifluoromethanesulfonyl)imide. Li·FSI indicates lithium bis(fluorosulfonyl)imide.

[0192] <Comparative Example> [Comparative Example 1] As materials for the polymer electrolyte, the following materials were mixed and stirred. Polyether monomethacrylate NK-ester M-40G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 70.0 parts by mass Polyether dimethacrylate 4G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 30.0 parts by mass Lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) (Kishida Chemical Co., Ltd.): 10.0 parts by mass Fine particles D-1 (TTO-51(A) manufactured by Ishihara Sangyo Kaisha): 90.0 parts by mass Initiator Omnirad 184 (manufactured by IGM Resins BV): 2.0 parts by mass Next, MEK was added so that the total solid content ratio was 60% by mass, and then the mixture was mixed with a motor to prepare an electrolyte solution. Thereafter, in the same manner as in Example 1, a polymer electrolyte and a secondary battery according to Comparative Example 1 were produced.

[0193] [Comparative Examples 2 to 6] Polymer electrolytes and secondary batteries according to Comparative Examples 2 to 6 were produced in the same manner as in Example 1, except that the types and amounts of materials used were changed as shown in Table 5.

[0194] [Table 5]

[0195] The structures of the materials used when polymerized are as follows: M-40G: methoxytetraethylene glycol methacrylate (R in formula (1-1) 1 : Methyl group, R 2 : ethylene group, R 3 : Methyl group, m1:3, n1:0 4G: polyethylene glycol #400 diacrylate (R in formula (2-1) 4 : Methyl group, R 5 : ethylene group, R 6 : ethylene group, m2:4, n2:0) A-600: polyethylene glycol #600 diacrylate (R in formula (2-1) 4 : Hydrogen atom, R 5 : ethylene group, R 6 : ethylene group, m2:14, n2:0) AM-130G: methoxypolyethylene glycol #600 acrylate (R in formula (1-1) 1 : Hydrogen atom, R 2 : ethylene group, R 3 : methyl group, m1: 13, n1: 0) APG-400: polypropylene glycol #400 diacrylate (R in formula (2-1) 4 : Hydrogen atom, R 5 : propylene group, R 6 : propylene group, m2: 0, n2: 7) The AM-90G is as described above. All of the above are manufactured by Shin-Nakamura Chemical Co., Ltd. PA-500: Hydroxypolypropylene glycol monoacrylate (R in formula (1-1) 1 : Hydrogen atom, R 2 : propylene group, R 3 : hydroxyl group, m1:0, n1:5) manufactured by Toho Chemical Co., Ltd.

[0196] The obtained polymer electrolytes and secondary batteries according to Examples 1 to 34 and Comparative Examples 1 to 6 were evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 6 and 7. In Tables 6 and 7, Mpo% is the ratio of the average number of moles added Mpo to the average number of moles added Meo.

[0197] [Table 6]

[0198] [Table 7]

[0199] The polymer electrolytes according to Examples 1 to 34 contain the above formula (1), formula (2) and / or formula (3), specific fine particles, and alkali metal cations in the polymer structure, and have a volume swelling ratio of 30 to 120%, and therefore exhibit high ionic conductivity in both 25°C and 5°C environments. Furthermore, the secondary batteries using the polymer electrolytes of Examples 1 to 34 as bulk electrolytes had both high rate characteristics and high impact resistance at high temperatures, and were long-life secondary batteries with many cycles before short circuiting occurred.

[0200] Furthermore, Examples 6, 7, 9, and 10 to 17, in which the mass ratio A:B of the content A of the structure of formula (1) to the content B of the structure of formula (2) in the polymer structure was 70:30 to 98:2, m1+n1 in formula (1-1) was 14 to 58, and m2+n2 in formula (2-1) was 14 to 58, exhibited particularly high ionic conductivity and the rate characteristics of the secondary battery were also good.

[0201] In Examples 2 to 9, 12, 14, 15, 17 to 20, 23, and 25 to 27, in which the primary particles of at least one selected from resin fine particles and metal oxide fine particles have a volume average particle size of 20 to 80 nm, the number of cycles until a short circuit occurred was further increased.

[0202] On the other hand, the polymer electrolytes of Comparative Examples 2 and 5, which did not have the structure of formula (1) in the polymer structure, and Comparative Example 1, which had a volume swelling ratio of less than 30%, had low ionic conductivity and resulted in very poor rate characteristics of the secondary battery. In the evaluation of short circuit occurrence, although no dendrites were observed on the electrode surface, the low ionic conductivity caused the voltage during charge and discharge to exhibit unsteady behavior, resulting in a low number of cycles.

[0203] Furthermore, secondary batteries using polymer electrolytes according to Comparative Examples 3 and 4, which had a volume swelling rate of over 120% or no three-dimensional crosslinking, showed a significant decrease in impact resistance at high temperatures. The number of cycles required for short circuiting also decreased. This is thought to be because, although fine particles were present in the system, there was little or no crosslinking, and the fine particles moved due to dendrite growth, weakening the dendrite growth suppression effect.

[0204] In Comparative Example 6, which did not contain at least one particle selected from resin particles and metal oxide particles, the number of cycles until a short circuit occurred was small, and dendrites were observed on the surface of the battery electrode.

[0205] The present disclosure has the following configuration. (Configuration 1) A polymer electrolyte, The polymer electrolyte is A structure represented by the following formula (1): A polymer having at least one structure selected from the group consisting of a structure represented by the following formula (2) and a structure represented by the following formula (3), At least one fine particle selected from the group consisting of resin fine particles and metal oxide fine particles; containing an alkali metal cation, A polymer electrolyte characterized in that the volume swelling ratio of the polymer electrolyte measured by a methyl ethyl ketone immersion method is 30 to 120%: TIFF2025174431000025.tif170153 (In Equation (1), R 1 represents a hydrogen atom or a methyl group. 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms. 3 represents an alkyl group having 1 to 6 carbon atoms. In equation (2), R 4 R each independently represents a hydrogen atom or a methyl group. 5 , R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. In equation (3), R 7 R each independently represents a hydrogen atom or a methyl group. 8 , R 9 , R 10 R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. 11 represents a trivalent organic group having 1 to 6 carbon atoms. In the formulas (1) to (3), A1, B1, D1, D2 and D3 each independently represent at least It is a linking group having an ethylene oxide structure represented by the formula: -CH2CH2-O-. (Configuration 2) The polymer electrolyte according to aspect 1, wherein the polymer further comprises a structure represented by formula (4): TIFF2025174431000026.tif68153 In equation (4), R 12 represents a hydrogen atom or a methyl group. 13 represents a divalent linking group. 14 represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms. (Configuration 3) The polymer electrolyte according to aspect 1 or 2, wherein the polymer comprises at least one structure selected from the group consisting of a structure represented by the following formula (5), a structure represented by the following formula (6), and a structure represented by the following formula (7): TIFF2025174431000027.tif242153In equation (5), R 15 represents a hydrogen atom or a methyl group. 16 represents a divalent linking group. 17 represents an alkyl group having 1 to 4 carbon atoms. 18 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 16 ~R 18 Each of R is bonded to three elements selected from the group consisting of two nitrogen atoms and three carbon atoms that constitute the imidazolium ring structure. 16 ~R 18 One of X1 is bonded to the cationic nitrogen atom in the imidazolium ring structure. - represents an anion. In equation (6), R 19 represents a hydrogen atom or a methyl group. 20 represents a divalent linking group. 21 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 20 and R 21 One of the X2 bonds to the nitrogen atom that constitutes the pyridinium ring structure, and the other bonds to one of the five carbon atoms that constitute the pyridinium ring structure. - represents an anion. In equation (7), R 22 represents a hydrogen atom or a methyl group. 23 represents a divalent linking group. 24 ~R 26Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. X3- represents an anion. (Configuration 4) 4. The polymer electrolyte according to any one of aspects 1 to 3, wherein the average number of moles Meo of the ethylene oxide structures added per mole of the (meth)acryloyl residue in the polymer is 2.5 moles or more. (Configuration 5) 5. The polymer electrolyte according to any one of configurations 1 to 4, wherein A1, B1, D1, D2, and D3 each independently further have a propylene oxide structure represented by (—CH 2 CH(CH 3 )—O—). (Configuration 6) 6. The polymer electrolyte according to claim 5, wherein in the polymer, an average number of moles Mpo of the propylene oxide structure added per mole of the (meth)acryloyl residue is 5 to 25% of an average number of moles Meo of the ethylene oxide structure added per mole of the (meth)acryloyl residue. (Configuration 7) 7. The polymer electrolyte according to any one of Aspects 1 to 6, wherein the mass ratio A:B is 70:30 to 98:2, where A is the mass content of the structure represented by formula (1) in the polymer contained in the polymer electrolyte, and B is the mass content of the structure represented by formula (2) and the structure represented by formula (3) in total. (Configuration 8) The structure represented by the formula (1) is a structure represented by the following formula (1-1): The structure represented by the formula (2) is a structure represented by the following formula (2-1): The structure represented by the formula (3) is a structure represented by the following formula (3-1): A polymer electrolyte according to any one of Configurations 1 to 7: TIFF2025174431000028.tif42153 (In equation (1-1), R 1 represents a hydrogen atom or a methyl group. 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms. 3represents an alkyl group having 1 to 6 carbon atoms. m1 and n1 represent the average number of moles added, m1 represents an integer of 1 or more, and n1 represents an integer of 0 or more. The arrangement of the ethylene oxide structure represented by (-CH2-CH2-O-) and the propylene oxide structure represented by (-CH2-CH(CH3)-O-) may be a block copolymer or a random copolymer. TIFF2025174431000029.tif42153 (In equation (2-1), R 4 R each independently represents a hydrogen atom or a methyl group. 5 , R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. m2 and n2 are the average number of moles added, m2 is an integer of 1 or more, and n2 is an integer of 0 or more. The arrangement of the ethylene oxide structure represented by (-CH2-CH2-O-) and the propylene oxide structure represented by (-CH2-CH(CH3)-O-) may be a block copolymer or a random copolymer. The chain sandwiched between two -COO- may further contain a diol structure having 1 to 6 carbon atoms. TIFF2025174431000030.tif64153 (In equation (3-1), R 7 R each independently represents a hydrogen atom or a methyl group. 8 , R 9 , R 10 R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. 11 represents a trivalent organic group having 1 to 6 carbon atoms. m3 and n3 are the average number of moles added, and each m3 independently represents an integer of 1 or more, and each n3 independently represents an integer of 0 or more. The arrangement of the ethylene oxide structure represented by (-CH2-CH2-O-) and the propylene oxide structure represented by (-CH2-CH(CH3)-O-) may be a block copolymer or a random copolymer. -COO- and R 11 The chain sandwiched between may further contain a diol structure having 1 to 6 carbon atoms. (Configuration 9) In the polymer electrolyte, m1+n1 in the formula (1-1) is 14 to 58, 9. The polymer electrolyte according to aspect 8, wherein m2+n2 in the formula (2-1) and / or m3+n3 in the formula (3-1) is 14 to 58. (Configuration 10) In the polymer electrolyte, In the formula (1-1), m1:n1 is 80:20 to 95:5, 10. The polymer electrolyte according to aspect 9, wherein m2:n2 in the formula (2-1) and / or m3:n3 in the formula (3) is 80:20 to 95:5. (Configuration 11) 11. The polymer electrolyte according to any one of aspects 1 to 10, wherein the polymer electrolyte is a dry polymer electrolyte. (Configuration 12) 12. The polymer electrolyte according to any one of aspects 1 to 11, wherein the volume average particle size of the primary particles of the fine particles is 20 to 80 nm. (Configuration 13) 13. The polymer electrolyte according to any one of aspects 1 to 12, wherein the fine particles have at least one surface functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a carbonyl group, and an amino group. (Configuration 14) 14. The polymer electrolyte according to any one of aspects 1 to 13, wherein the content of the fine particles is 2 to 30 parts by mass per 100 parts by mass of the polymer. (Configuration 15) A secondary battery comprising a positive electrode, a bulk electrolyte, and a negative electrode, 15. A secondary battery, wherein the bulk electrolyte contains the polymer electrolyte according to any one of aspects 1 to 14. [Explanation of symbols]

[0206] 1 secondary battery, 2 positive electrode current collector, 3 positive electrode active material, 4 positive electrode active material binder, 5 conductive additive, 6 positive electrode, 7 bulk electrolyte, 8 negative electrode active material, 9 negative electrode current collector, 10 negative electrode,

Claims

1. A polymer electrolyte, The polymer electrolyte is A structure represented by the following formula (1): A polymer having at least one structure selected from the group consisting of a structure represented by the following formula (2) and a structure represented by the following formula (3), At least one fine particle selected from the group consisting of resin fine particles and metal oxide fine particles; containing an alkali metal cation, A polymer electrolyte characterized in that the volume swelling ratio of the polymer electrolyte measured by a methyl ethyl ketone immersion method is 30 to 120%: (In formula (1), R １ represents a hydrogen atom or a methyl group. ２ represents a linear or branched alkylene group having 1 to 6 carbon atoms. ３ represents an alkyl group having 1 to 6 carbon atoms. In formula (2), R ４ R each independently represents a hydrogen atom or a methyl group. ５ , R ６ each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. In formula (3), R ７ R each independently represents a hydrogen atom or a methyl group. ８ , R ９ , R １０ R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. １１ represents a trivalent organic group having 1 to 6 carbon atoms. In the formulas (1) to (3), A1, B1, D1, D2 and D3 each independently represent at least (—CH ２ CH ２ is a linking group having an ethylene oxide structure represented by the formula:

2. The polymer electrolyte according to claim 1, wherein the polymer further comprises a structure represented by the following formula (4): In formula (4), R １２ represents a hydrogen atom or a methyl group. １３ represents a divalent linking group. １４ represents a fluorine atom or a perfluoroalkyl group having 1 to 4 carbon atoms.

3. The polymer electrolyte according to claim 1, wherein the polymer comprises at least one structure selected from the group consisting of a structure represented by the following formula (5), a structure represented by the following formula (6), and a structure represented by the following formula (7): In formula (5), R １５ represents a hydrogen atom or a methyl group. １６ represents a divalent linking group. １７ represents an alkyl group having 1 to 4 carbon atoms. １８ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. １６ ~R １８ is bonded to three elements selected from the group consisting of two nitrogen atoms and three carbon atoms that constitute the imidazolium ring structure. １６ ~R １８ One of X1 is bonded to the cationic nitrogen atom in the imidazolium ring structure. － represents an anion. In formula (6), R １９ represents a hydrogen atom or a methyl group. ２０ represents a divalent linking group. ２１ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ２０ and R ２１ One of X2 is bonded to the nitrogen atom constituting the pyridinium ring structure, and the other is bonded to any of the five carbon atoms constituting the pyridinium ring structure. － represents an anion. In formula (7), R ２２ represents a hydrogen atom or a methyl group. ２３ represents a divalent linking group. ２４ ~R ２６ Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. X3- represents an anion.

4. 2. The polymer electrolyte according to claim 1, wherein an average number of moles Meo of the ethylene oxide structure added per mole of the (meth)acryloyl residue in the polymer is 2.5 moles or more.

5. A1, B1, D1, D2 and D3 each independently represent (—CH ２ CH (CH ３ 2. The polymer electrolyte according to claim 1, further comprising a propylene oxide structure represented by the formula:

6. 6. The polymer electrolyte according to claim 5, wherein in the polymer, an average number of moles Mpo of the propylene oxide structure added per mole of a (meth)acryloyl residue is 5 to 25% of an average number of moles Meo of the ethylene oxide structure added per mole of a (meth)acryloyl residue.

7. 2. The polymer electrolyte according to claim 1, wherein the mass ratio A:B is 70:30 to 98:2, where A is the mass content of the structure represented by formula (1) in the polymer contained in the polymer electrolyte, and B is the mass content of the structure represented by formula (2) and the structure represented by formula (3).

8. The structure represented by the formula (1) is a structure represented by the following formula (1-1): The structure represented by the formula (2) is a structure represented by the following formula (2-1): The structure represented by the formula (3) is a structure represented by the following formula (3-1): The polymer electrolyte of claim 1: (In formula (1-1), R １ represents a hydrogen atom or a methyl group. ２ represents a linear or branched alkylene group having 1 to 6 carbon atoms. ３ represents an alkyl group having 1 to 6 carbon atoms. m1 and n1 are the average number of moles added, m1 is an integer of 1 or more, and n1 is an integer of 0 or more. (-CH ２ -CH ２ -O-) and an ethylene oxide structure represented by (-CH ２ -CH(CH ３ The arrangement of the propylene oxide structure represented by the formula (III)-O-) may be a block copolymer or a random copolymer. (In formula (2-1), R ４ R each independently represents a hydrogen atom or a methyl group. ５ , R ６ each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. m2 and n2 are the average number of moles added, m2 is an integer of 1 or more, and n2 is an integer of 0 or more. (-CH ２ -CH ２ -O-) and an ethylene oxide structure represented by (-CH ２ -CH(CH ３ The arrangement of the propylene oxide structures represented by -COO- may be a block copolymer or a random copolymer. The chain sandwiched between two -COO- may further contain a diol structure having 1 to 6 carbon atoms. (In formula (3-1), R ７ R each independently represents a hydrogen atom or a methyl group. ８ , R ９ , R １０ R each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. １１ represents a trivalent organic group having 1 to 6 carbon atoms. m3 and n3 are the average number of moles added, each m3 independently represents an integer of 1 or more, and each n3 independently represents an integer of 0 or more. (-CH ２ -CH ２ -O-) and an ethylene oxide structure represented by (-CH ２ -CH(CH ３ The arrangement of the propylene oxide structure represented by —COO— and R may be a block copolymer or a random copolymer. １１ The chain sandwiched between may further contain a diol structure having 1 to 6 carbon atoms.

9. In the polymer electrolyte, m1+n1 in the formula (1-1) is 14 to 58, 9. The polymer electrolyte according to claim 8, wherein m2+n2 in the formula (2-1) and / or m3+n3 in the formula (3-1) is 14 to 58.

10. In the polymer electrolyte, In the formula (1-1), m1:n1 is 80:20 to 95:5, 10. The polymer electrolyte according to claim 9, wherein m2:n2 in the formula (2-1) and / or m3:n3 in the formula (3) is 80:20 to 95:

5.

11. The polymer electrolyte of claim 1 , wherein the polymer electrolyte is a dry polymer electrolyte.

12. 2. The polymer electrolyte according to claim 1, wherein the volume average particle size of the primary particles of the fine particles is 20 to 80 nm.

13. 2. The polymer electrolyte according to claim 1, wherein the fine particles have at least one surface functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a carbonyl group, and an amino group.

14. 2. The polymer electrolyte according to claim 1, wherein the content of the fine particles is 2 to 30 parts by mass per 100 parts by mass of the polymer.

15. A secondary battery comprising a positive electrode, a bulk electrolyte, and a negative electrode, A secondary battery, characterized in that the bulk electrolyte contains the polymer electrolyte according to any one of claims 1 to 14.

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