Polymer electrolyte and secondary battery

Abstract

Provided is a polymer electrolyte which is not susceptible to decrease in strength even in a high-temperature range and which has high ionic conductivity at normal temperature and lower temperatures even if a liquid electrolyte is not contained therein. The polymer electrolyte contains a polymer having a specific polyether structure having a free end, a specific cross-linked structure by means of a polyether, and a specific nitrogen-containing aromatic cationic group. The polymer electrolyte additionally comprises a lithium salt; and the volume swelling ratio of the polymer electrolyte measured by a methyl ethyl ketone impregnation method is 40%-120%.

Description

Technical Field

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

[0002] In recent years, with the development of portable devices such as tablet terminals and smartphones, and electric vehicles, the demand for secondary batteries as their power sources has increased. Generally, each secondary battery is composed of electrodes (a positive electrode and a negative electrode) and an electrolyte, and charging and discharging are performed by the movement of ions between the electrodes via the electrolyte. Such secondary batteries are widely used, from small devices such as mobile phones to large devices such as electric vehicles. Therefore, further improvement in high safety and performance is required.

[0003] In order to prevent disasters caused by the fire of secondary batteries and to improve safety, solid-state secondary batteries in which a solid electrolyte replaces a conventional flammable electrolyte are being developed. Sulfide-based, oxide-based, and polymer-based materials are widely studied as solid electrolytes.

[0004] In order to improve the charge and 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. Although sulfide-based and oxide-based solid electrolytes have excellent ionic conductivity, it is difficult to expand the interface with the active material, and the impact resistance may be insufficient. Therefore, the use of a gel electrolyte in which an electrolyte is combined with a polymer has been proposed.

[0005] Patent Document 1 describes a gel electrolyte containing a polyether and an ionic liquid. Patent Document 2 describes a gel electrolyte having improved affinity with an electrolyte due to the introduction of a quaternary ammonium base into the main chain. In addition, Patent Document 3 describes a polymer electrolyte containing a crosslinked polymer and a linear polymer.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: JP-A-2017-090677

[0009] Patent Document 2: WO 2004 / 027789

[0010] Patent Document 3: JP-A-2015-173017 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] In recent years, in addition to high safety, there has been a demand for lithium-ion secondary batteries with higher charge / discharge characteristics. When a polymer gel as in Patent Documents 1 and 2 is used as an electrolyte, or when a polymer electrolyte using a linear polymer as in Patent Document 3 is used, the strength at high temperatures may decrease, and there may be a risk of short circuit due to impact. At the same time, when the liquid electrolyte is removed from the three-dimensional crosslinked polymer gel to improve safety at high temperatures, the ionic conductivity may decrease. Therefore, a polymer electrolyte having excellent ionic conductivity and suppressing a decrease in impact resistance and the risk of short circuit even at high temperatures is required.

[0013] At least one aspect of the present disclosure relates to a polymer electrolyte that exhibits little strength reduction even in a high temperature range and has high ionic conductivity from room temperature to low temperature without depending on a liquid electrolyte. At least one aspect of the present disclosure relates to providing a secondary battery with high safety and high-class characteristics.

[0014] Means for solving the problems

[0015] At least one aspect of the present disclosure provides a polymer electrolyte,

[0016] The polymer electrolyte includes a polymer having the following structure:

[0017] A structure represented by the following formula (1),

[0018] 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), and

[0019] At least one structure selected from the group consisting of a structure represented by the following formula (4) and a structure represented by the following formula (5),

[0020] The polymer electrolyte further includes a lithium salt, and

[0021] The polymer electrolyte has a volume swelling ratio measured by the methyl ethyl ketone impregnation method of 40% to 120%:

[0022] [Chemical formula 1]

[0023]

[0024] (In formula (1), R 1 represents a hydrogen atom or a methyl group. R 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms. R 3 represents an alkyl group having 1 to 6 carbon atoms.

[0025] In formula (2), R 4 each independently represents a hydrogen atom or a methyl group. R5 and R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms.

[0026] In formula (3), R 7 each independently represents a hydrogen atom or a methyl group. R 8 , R 9 and R 10 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms. R 11 represents a trivalent organic group having 1 to 6 carbon atoms.

[0027] In 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-).)

[0028] [Chemical formula 2]

[0029]

[0030] (In formula (4), R 12 represents a hydrogen atom or a methyl group.

[0031] R 13 represents a divalent linking group. R 14 represents an alkyl group having 1 to 4 carbon atoms. R 15 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R 13 to R 15 each bond to 3 elements selected from the group consisting of 2 nitrogen atoms and 3 carbon atoms constituting the imidazolium ring structure. However, one of R 13 to R 15 bonds to the cationic nitrogen atom in the imidazolium ring structure. X1 - represents an anion.)

[0032] [Chemical formula 3]

[0033]

[0034] (In formula (5), R 16 represents a hydrogen atom or a methyl group. R 17 represents a divalent linking group. R 19 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R 17 and R 19 one of which bonds to the nitrogen atom constituting the pyridinium ring structure, and the other bonds to any one of the 5 carbon atoms constituting the pyridinium ring structure. X2 - represents an anion.)

[0035] In addition, at least one aspect of the present disclosure provides a secondary battery having a positive electrode, a host electrolyte, and a negative electrode, wherein

[0036] at least one of the positive electrode, the host electrolyte, and the negative electrode contains the above polymer electrolyte.

[0037] Advantages of the Invention

[0038] According to at least one aspect of the present disclosure, a polymer electrolyte can be obtained which exhibits little strength reduction even in a high temperature range and has high ionic conductivity from room temperature to low temperature without relying on a liquid electrolyte. According to at least one aspect of the present disclosure, a secondary battery with high safety and high-class characteristics can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic cross-sectional view of a secondary battery using the polymer electrolyte of the present disclosure as a host electrolyte.

[0040] Figure 2 is a schematic cross-sectional view of a secondary battery using the polymer electrolyte of the present disclosure as a binder for a positive electrode active material.

[0041] Figure 3 is a schematic cross-sectional view of a secondary battery using the polymer electrolyte of the present disclosure as a binder for a positive electrode active material, a host electrolyte, and a binder for a negative electrode active material. DETAILED DESCRIPTION

[0042] In the present disclosure, unless otherwise specified, the phrase "from XX to YY" or "XX to (~)YY" indicating a numerical range means a numerical range including the lower limit and the upper limit as endpoints. In addition, when numerically ranging is described stepwise, the upper and lower limits of each numerical range can be freely combined. Further, in the present disclosure, for example, the phrase "at least one selected from the group consisting of XX, YY, and ZZ" means any one of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, and a combination of XX, YY, and ZZ.

[0043] To achieve the above object, the present inventors conducted in-depth research. First, the present inventors found that in a dry polymer system in which the advancement of lithium ions by a liquid electrolyte cannot be expected, the ionic conductivity can be increased by using a polyether acrylic resin having a special three-dimensional crosslinked morphology.

[0044] ​​​As a result of further research, the present inventors have found that high ionic conductivity can be maintained even at low temperatures only when the molecule contains an anion and a cationic group having a nitrogen-containing heterocyclic structure, and this finding has enabled the present inventors to obtain the above polymer electrolyte. In other words, the polymer electrolyte of the present disclosure satisfies the following conditions.

[0045] - The three-dimensional crosslinked structure of the polymer has many terminal free chains that are not bonded to the polymer chains at one end and has a very low crosslinking density.

[0046] - The three-dimensional crosslinked structure of the polymer has an anion and a cationic group having a nitrogen-containing aromatic structure.

[0047] Regarding the reason why the polymer electrolyte according to the present disclosure exhibits the unexpected effect of having high ionic conductivity without relying on a liquid electrolyte, the present inventors speculate as follows. In a dry polymer system where it is not desired to stabilize lithium ions with a liquid electrolyte, lithium ions move between polymer chains that undergo molecular motion. Therefore, a polymer system that has been three-dimensionally crosslinked to suppress the risk of short circuit due to film deformation at high temperatures is more susceptible to steric hindrance than a liquid system.

[0048] The polymer used in the present disclosure has a three-dimensional crosslinked structure (the structures of Formula (2) and Formula (3)) and is not easily deformed even at high temperatures. At the same time, this structure has many terminal free chains where one end is not bonded to other polymer chains (the structure of Formula (1)). This is clearly the reason why the polymer does not form a dense network structure and is unlikely to hinder the movement of lithium ions while maintaining strength.

[0049] Furthermore, the nitrogen-containing aromatic cation structure bonded in the polymer structure and the anion (the structures of Formula (4) and Formula (5)) reduces the difference in polarity between the lithium salt, which is the supporting electrolyte contained, and the polymer, does not cause precipitation of the lithium salt, and increases the amount that can be dissolved. In particular, it is considered that since the cation having a nitrogen-containing aromatic structure has high stability as a cation, the dissociation rate of the lithium salt is also improved by interacting with the anion of the lithium salt.

[0050] Furthermore, it is considered that the nitrogen-containing aromatic cation structure bonded in the above polymer structure suppresses three-dimensional regularity and reduces the crystallinity of the polymer, thus suppressing the decrease in ionic conductivity at low temperatures.

[0051] The fact that the three-dimensional crosslinked structure of the polymer has many terminal free chains that are not bonded to the polymer chains at one end and has a very low crosslinking density is clearly manifested as the volume swelling rate of the polymer electrolyte measured by the methyl ethyl ketone impregnation method. Specifically, the volume swelling rate of the polymer electrolyte measured using methyl ethyl ketone (MEK) is 40% to 120%.

[0052] The volume swelling ratio represents the ratio of the volume of a three-dimensional crosslinked polymer before and after being immersed in a specific solvent until the swelling caused by the solvent becomes saturated. The volume swelling ratio is calculated using the following formula, where the volume of the test specimen is calculated from its weight in air and its weight in water. The specific measurement method is described below.

[0053] Volume swelling ratio (%) = (Volume after being immersed in the solvent and reaching swelling saturation) / (Volume before being immersed in the solvent) × 100

[0054] It is considered that a volume swelling ratio of the polymer electrolyte less than 40% indicates few terminal free chains (the structure of formula (1)) and many three-dimensional crosslinked structures. Therefore, the ionic conductivity may be low, and the rate characteristics of the secondary battery may also be reduced. At the same time, a volume swelling ratio of the polymer electrolyte exceeding 120% indicates a lack of three-dimensional crosslinked structures, which may lead to a reduction in strength at high temperatures, such as a reduction in impact resistance.

[0055] The volume swelling ratio of the polymer electrolyte is preferably 60% to 110%, and more preferably 70% to 105%.

[0056] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The components, materials, shapes, and their relative positions described in these embodiments do not limit the scope of the present disclosure.

[0057] (1) Embodiments of the secondary battery

[0058] The secondary battery includes a positive electrode, a solid electrolyte, and a negative electrode, and at least one of the positive electrode, the solid electrolyte, and the negative electrode contains the polymer electrolyte of the present disclosure. For example, the solid electrolyte is a polymer electrolyte.

[0059] Examples of secondary batteries using the polymer electrolyte of the present disclosure are shown in Figures 1 to 3 as follows. Figure 1 The secondary battery 1 shown represents an example of the schematic configuration of a secondary battery using a polymer electrolyte as the solid electrolyte 7. The positive electrode active material 3 provided on the positive electrode current collector 2 is fixed by the positive electrode active material binder 4 to form the positive electrode 6. The positive electrode 6 may contain a conductive auxiliary material 5.

[0060] The negative electrode active material 8 provided on the negative electrode current collector 9 forms the negative electrode 10. In Figure 1 the negative electrode active material represents metallic lithium, indium, etc. The solid electrolyte 7 is provided between the positive electrode 6 and the negative electrode 10.

[0061] Figure 2 The secondary battery 1 shown represents an example of the schematic configuration of a secondary battery using a polymer electrolyte as the positive electrode active material binder 4. In Figure 2In the embodiment shown, the positive electrode 6 includes a polymer electrolyte. For example, the positive electrode 6 has a positive electrode active material 3 and a positive electrode active material binder 4 that fixes the positive electrode active material, and the positive electrode active material binder 4 is the polymer electrolyte of the present disclosure. In Figure 2 the configuration shown, the host electrolyte 7 represents an oxide-based or sulfide-based inorganic solid electrolyte. Other features are the same as those in Figure 1 the above.

[0062] Figure 3 The secondary battery 1 shown in the above represents an example of a schematic configuration of a secondary battery that uses a polymer electrolyte as the positive electrode active material binder 4, the host electrolyte 7, and the negative electrode active material binder 11. In Figure 3 the embodiment shown, the positive electrode, the host electrolyte, and the negative electrode include a polymer electrolyte. That is, the positive electrode 6 has a positive electrode active material 3 and a positive electrode active material binder 4 that fixes the positive electrode active material, and the positive electrode active material binder 4 is the polymer electrolyte of the present disclosure. In addition, the host electrolyte 7 is the polymer electrolyte of the present disclosure. In addition, the negative electrode 10 has a negative electrode active material 8 and a negative electrode active material binder 11 that fixes the negative electrode active material 8, and the negative electrode active material binder 11 is the polymer electrolyte of the present disclosure. In Figure 3 the configuration shown, the negative electrode active material 8 represents a carbon material such as graphite. Other features are the same as those in Figure 1 the above.

[0063] In order to more effectively achieve the effects of the present disclosure, as shown in Figure 1 and Figure 3 the above, preferably, the host electrolyte 7 is a polymer electrolyte that penetrates the positive electrode active material 3 and the negative electrode active material 8 and increases the contact area.

[0064] (Method for manufacturing a solid-state secondary battery)

[0065] The solid-state secondary battery can be manufactured by a known battery manufacturing method such as a laminated battery type, a button battery type, or a pressure battery type. Hereinafter, the laminated battery type will be described as an example.

[0066] A laminate is obtained in which a positive electrode, a solid electrolyte, and a negative electrode are disposed between a positive electrode current collector and a negative electrode current collector. Electrode tabs are welded to the positive and negative electrode current collectors. The laminate in which the positive electrode current collector, the positive electrode, the solid electrolyte, the negative electrode, and the negative electrode current collector are laminated in this order is wrapped and sealed with an aluminum laminated film while reducing the pressure using a vacuum packaging machine. The ends of the electrode tabs are exposed to the outside of the laminated film, and the tabs and the aluminum laminated film are sealed in a state where they are thermocompression bonded. After sealing, if necessary, pressure can be applied using an isostatic pressure device or the like. The solid electrolyte may be a solid electrolyte or a polymer electrolyte, and both can be used in the laminate. In addition to the above laminate, for the purpose of improving strength and formability, other layers such as an elastic material and a resin material may be laminated inside the aluminum laminated film. A bipolar type in which a plurality of laminates are laminated may also be used.

[0067] (Positive electrode current collector)

[0068] Examples of the positive electrode current collector include metal foils. Examples of the metal include aluminum, stainless steel, copper, silver, gold, platinum, nickel, and palladium. The metal may be used alone or in combination of two or more.

[0069] (Positive electrode active material)

[0070] The positive electrode active material may be selected from those commonly used in secondary batteries such as lithium ion secondary batteries. Examples thereof include (CF) m , (C2F) m , MnO2, TiS2, MoS2, FeS2, Li xA CoO2, Li xA NiO2, Li xA MnO2, Li xA Co y Ni 1-y O2, Li xA Co y M 1-y O z , Li xA Ni 1-y M y O z , Li xB Mn2O4, Li xB Mn 2-y M yO4 (in the above formulas, M is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B; xA = 0 to 1.2, xB = 0 to 2.0, y = 0 to 0.9, z = 2.0 to 2.3), vanadium oxide and its lithium compounds, niobium oxide and its lithium compounds, conjugated polymers using organic conductive materials, olivine compounds, etc.

[0071] The values of xA and xB in the above respective compositional formulas are the values before the start of charge and discharge, and increase and decrease with charge and discharge. The positive electrode active material can be used alone or in combination of two or more.

[0072] (Conductive auxiliary material)

[0073] The conductive auxiliary material can be selected from those commonly used in secondary batteries such as lithium ion secondary batteries. Examples thereof include graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and pyrolytic carbon black, conductive fibers such as carbon fibers and metal fibers, 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 phenyl derivatives. The conductive auxiliary material can be used alone or in combination of two or more.

[0074] (Active material binder)

[0075] The active material binder can be selected from those commonly used in secondary batteries such as lithium ion secondary batteries. Examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, polyaromatic amide resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, hexyl polyacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropropylene, styrene-butadiene rubber, and carboxymethyl cellulose.

[0076] The polymer electrolyte of the present disclosure can be used as a host electrolyte, can be used as a positive electrode active material binder, can be used as a negative electrode active material binder, or can be used as a host electrolyte, a positive electrode active material binder, and a negative electrode active material binder.

[0077] In other words, preferably, the secondary battery satisfies at least one of the following (i) to (iii).

[0078] (i) The positive electrode 6 has a positive electrode active material 3 and a positive electrode active material binder 4 that fixes the positive electrode active material, and the positive electrode active material binder 4 is the polymer electrolyte of the present disclosure.

[0079] (ii) The main electrolyte 7 is the polymer electrolyte of the present disclosure.

[0080] (iii) The negative electrode 10 has a negative electrode active material 8 and a negative electrode active material binder 11 that fixes the negative electrode active material 8, and the negative electrode active material binder 11 is the polymer electrolyte of the present disclosure.

[0081] Particularly preferably, the polymer electrolyte of the present disclosure is used as the positive electrode active material binder because, in this case, lithium ions can easily reach the deep part from the surface of the positive electrode 6. The active material binder can be used alone or in combination of two or more.

[0082] The positive electrode 6 can be manufactured, for example, by pressing and bonding a positive electrode mixture to the surface of the positive electrode current collector 2, or by coating a positive electrode mixture slurry, drying, and further rolling as needed 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 also 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, or ethylene glycol ether.

[0083] (Negative electrode current collector)

[0084] Examples of the negative electrode current collector include metal foils. Examples of the metal include aluminum, stainless steel, copper, silver, gold, platinum, nickel, and palladium. The metal can be used alone or in combination of two or more.

[0085] (Negative electrode active material)

[0086] Examples of the negative electrode active material include metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, and various alloy materials. Among them, from the viewpoint of capacity density, metals, oxides, carbon materials, silicon, silicon compounds, tin, and tin compounds are preferred.

[0087] Examples of the metal include metallic Li and In-Li, and examples of the oxide include Li4Ti5O 12 (LTO: lithium titanate). Examples of the carbon material include various types of natural graphite, coke, carbon during the graphitization process, carbon fiber, spherical carbon, various types of artificial graphite, and amorphous carbon. Examples of the silicon compound include silicon-containing alloys, silicon-containing inorganic compounds, silicon-containing organic compounds, and solid solutions. Examples of the tin compound include SnO B (0 < B < 2), SnO2, SnSiO3, Ni2Sn4, and Mg2Sn.

[0088] The negative electrode material may also contain a conductive auxiliary material. Examples of the conductive auxiliary material 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 pyrolytic carbon black. When using a polymer electrolyte as the host electrolyte, graphite is particularly suitable as the negative electrode active material.

[0089] Examples of the conductive auxiliary material include conductive fibers such as carbon fibers, carbon nanotubes, and metal fibers, metal powders such as carbon fluoride, aluminum powder, conductive whiskers such as zinc oxide, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenyl dielectrics.

[0090] (Solid electrolyte)

[0091] In a secondary battery, the solid electrolyte is disposed between the positive electrode and the negative electrode as a lithium ion moving layer, and can also be used as the host electrolyte that also serves as a separator. By mixing with the active material layers of the positive and negative electrodes, it can also be used as an aid to enhance the conductivity of lithium ions.

[0092] The polymer electrolyte of the present disclosure can be suitable for use as both the host electrolyte and the auxiliary material. This expands the contact interface between the host electrolyte and the positive and negative electrode active materials, and also has flexibility to follow the expansion and contraction of the positive and negative electrode active materials, thereby improving the characteristics of the secondary battery.

[0093] For the host electrolyte and the auxiliary material, a solid electrolyte other than the polymer electrolyte can be used. Examples of the solid electrolyte other than the polymer electrolyte include oxide-based solid electrolytes, sulfide-based solid electrolytes, and complex hydride-based solid electrolytes.

[0094] Examples of the oxide-based solid electrolyte include NASICON-type compounds such as Li 1.5 Al 0.5 Ge 1.5 (PO4)3 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3, garnet-type compounds such as Li 6.25 LA3ZR2Al 0.25 O 12 . Examples of the oxide-based solid electrolyte include perovskite-type compounds such as Li 0.33 Li 0.55 TiO3. Examples of the oxide-based solid electrolyte also include LISICON-type compounds such as Li 14Zn(GeO4)4 and acidic 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, Li2S-P2S5, etc.

[0095] The solid electrolyte can be crystalline or amorphous, or can be glass-ceramic. The symbols such as Li2S-P2S5 refer to sulfide-based solid electrolytes made from raw materials containing Li2S and P2S5.

[0096] The polymer electrolyte of the present disclosure can be used as a host electrolyte, a positive electrode active material binder, or a negative electrode active material binder. Hereinafter, the configuration of the polymer electrolyte according to one embodiment of the present disclosure will be described in detail.

[0097] The polymer electrolyte of the present disclosure is preferably a solid electrolyte or a semi-solid electrolyte, such as a dry polymer electrolyte or a gel electrolyte. In other words, a non-liquid electrolyte is preferred. A dry polymer electrolyte is more preferred. The polymer electrolyte preferably substantially does not contain liquid components such as a liquid electrolyte.

[0098] <Polymer Electrolyte>

[0099] The polymer electrolyte according to one embodiment of the present disclosure has a polymer with 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 crosslinked structure with the following structure.

[0100] - A structure represented by formula (1).

[0101] - At least one structure selected from the group consisting of the structure represented by formula (2) and the structure represented by formula (3).

[0102] - At least one structure selected from the group consisting of the structure represented by formula (4) and the structure represented by formula (5).

[0103] The polymer electrolyte has a structure represented by the following formula (1).

[0104] [Chemical formula 4]

[0105]

[0106] In formula (1), R 1 represents a hydrogen atom or a methyl group. R 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). R 3represents an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1).

[0107] In formula (1), A1 is a linking group having at least an ethylene oxide structure represented by (-CH2CH2-O-).

[0108] The structure represented by formula (1) is preferably a structure represented by the following formula (1-1).

[0109] [Chemical formula 5]

[0110]

[0111] In formula (1-1), R 1 represents a hydrogen atom or a methyl group. R 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). R 3 represents an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1). m1 and n1 are average addition mole numbers, m1 is an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n1 is an integer of 0 or more (preferably 5% to 25% of m1, more preferably 11% to 25% of m1).

[0112] 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). At least one structure selected from the group consisting of the structure represented by formula (2) and the structure represented by formula (3) may be the structure represented by formula (2). This structure can form a three-dimensional crosslinked structure.

[0113] [Chemical formula 6]

[0114]

[0115] In formula (2), R 4 each independently represents a hydrogen atom or a methyl group. R 5 and 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).

[0116] In formula (3), R 7 each independently represents a hydrogen atom or a methyl group. R 8 , R 9 and R 10 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 2 to 4). R 11 represents a trivalent organic group having 1 to 6 carbon atoms (preferably 1 to 3, more preferably 1).

[0117] In Formulas (2) and (3), B1, D1, D2, and D3 each independently represent a linking group having at least an ethylene oxide structure represented by (-CH2CH2-O-).

[0118] In Formulas (1) to (3), preferably, 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 preferred.

[0119] In addition, to the extent that the effects of the present disclosure are not impaired, 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). The diol structure is represented by -O-R x -O-, where R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms).

[0120] The structure represented by Formula (2) is preferably the structure represented by the following Formula (2-1).

[0121] [Chemical Formula 7]

[0122]

[0123] In Formula (2-1), R 4 each independently represents a hydrogen atom or a methyl group. R 5 and R 6 each independently represent a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 2 to 4 carbon atoms). m2 and n2 are the average addition mole numbers, m2 is an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n2 is an integer of 0 or more (preferably 5% to 25% of m2, more preferably 11% to 25% of m2).

[0124] To the extent that the effects of the present disclosure are not impaired, the chain sandwiched between two -COO- may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms). For example, a diol structure may be included between the ethylene oxide structure and the propylene oxide structure. The diol structure is represented by -O-R x -O-, where R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms).

[0125] The structure represented by Formula (3) is preferably the structure represented by the following Formula (3-1).

[0126] [Chemical Formula 8]

[0127]

[0128] In formula (3-1), R 7 each independently represents a hydrogen atom or a methyl group. R 8 , R 9 and R 10 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 2 to 4 carbon atoms). R 11 represents a trivalent organic group (preferably a hydrocarbon group) having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 carbon atom). m3 and n3 are average addition molar numbers, and m3 independently represents an integer of 1 or more (preferably 1 to 110, more preferably 13 to 46), and n3 independently represents an integer of 0 or more (preferably 5% to 25% of m3, more preferably 11% to 25% of m3).

[0129] Within the extent that does not impair the effects of the present disclosure, the chain sandwiched between -COO- and R 11 may further contain a diol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms). For example, a diol structure may be included between an ethylene oxide structure and a propylene oxide structure. The diol structure is represented by -O-R x -O-, where R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms).

[0130] The average addition molar number Meo of the ethylene oxide structure per mole of (meth)acryloyl residues in the polymer contained in the polymer electrolyte is preferably 2.5 moles or more. Meo is more preferably 13 to 46. Within the above range, the crosslinking density of the polymer main chain becomes more appropriate, so that high lithium ion conductivity can be obtained while maintaining the strength at high temperatures. The (meth)acryloyl residue is an addition polymerization form of (meth)acryloyl, and is represented, for example, by the following structure in formula (1).

[0131] [Chemical formula 9]

[0132]

[0133] In addition, in the polymer contained in the polymer electrolyte, the average addition molar number Mpo of the propylene oxide structure per mole of (meth)acryloyl residues is preferably 5% to 25% of the average addition molar number Meo of the ethylene oxide structure per mole of (meth)acryloyl residues, more preferably 11% to 25%. Within the above range, even if the molecular weight between crosslinking points is large, the crystallinity of the polymer main chain is suppressed, and especially at low temperatures, it is easier to suppress the hindrance of lithium ion movement.

[0134] The average addition molar numbers Meo and Mpo can be quantified by decomposing the polymer electrolyte using pyrolysis GC / MS and creating calibration curves for the fragments derived from (meth)acryloyl residues, the fragments derived from ethylene oxide structures, and the fragments derived from propylene oxide structures, respectively.

[0135] In the polymer electrolyte of the present disclosure, the three-dimensional crosslinked structure of the polymer has a very low crosslinking density as described above, and the polymer chains have many free chains that are not bonded to other polymer chains at one end. Such a crosslinked structure can be obtained, for example, by reacting the following materials.

[0136] - Polyether mono(meth)acrylate.

[0137] - At least one selected from the group consisting of polyether di(meth)acrylate and polyether tri(meth)acrylate.

[0138] - At least one selected from the group consisting of imidazolium-based ionic compounds having an unsaturated reactive functional group and pyridinium-based ionic compounds having an unsaturated reactive functional group.

[0139] (Polyether mono(meth)acrylate)

[0140] 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 polyethylene glycol-propylene glycol copolymer mono(meth)acrylate can be used. When using polyethylene glycol-propylene glycol copolymer mono(meth)acrylate, the molar ratio of the ethylene glycol structure to the propylene glycol structure is preferably from 100:0 to 50:50, and more preferably from 80:20 to 95:5.

[0141] When the molar ratio of the ethylene glycol structure:propylene glycol structure is within this range, the lithium ion transportability through polyethylene glycol can be maintained at a high level, and by combining with the structures of formula (4) and / or formula (5), it becomes easier to suppress the hindrance of lithium ion movement due to polymer crystallization.

[0142] Polyether mono(meth)acrylate is represented, for example, by the following formula (1').

[0143] [Chemical formula 10]

[0144]

[0145] In formula (1’), R 1 , R 2 , R 3 , m1 and n1 are the same as those in formula (1-1).

[0146] (Polyether di(meth)acrylate)

[0147] The 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 polyethylene glycol-propylene glycol copolymer di(meth)acrylate can be used. When using the polyethylene glycol-propylene glycol copolymer di(meth)acrylate, the molar ratio of ethylene glycol structure:propylene glycol structure is preferably from 100:0 to 50:50, more preferably from 80:20 to 95:5.

[0148] When the molar ratio of ethylene glycol structure:propylene glycol structure is within this range, the lithium ion transportability of polyethylene glycol can be maintained at a high level, and by combining with the structure of formula (4) and / or formula (5), it becomes easier to suppress the hindrance of lithium ion movement due to polymer crystallization.

[0149] The polyether di(meth)acrylate is represented, for example, by the following formula (2').

[0150] [Chemical formula 11]

[0151]

[0152] In formula (2'), R 4 , R 5 , R 6 , m2 and n2 are the same as those in formula (2-1).

[0153] To the extent that the effects of the present disclosure are not impaired, the chain sandwiched between two -COO- groups may further contain a glycol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms). For example, a glycol structure can be included between the ethylene oxide structure and the propylene oxide structure. The glycol structure is represented by -O-R x -O-, where R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms).

[0154] (Polyether tri(meth)acrylate)

[0155] 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 polyethylene glycol-propylene glycol copolymer tri(meth)acrylate can be used. When using the polyethylene glycol-propylene glycol copolymer tri(meth)acrylate, the molar ratio of ethylene glycol structure:propylene glycol structure is preferably from 100:0 to 50:50, more preferably from 80:20 to 95:5.

[0156] When the molar ratio of the ethylene glycol structure to the propylene glycol structure is within this range, the lithium ion transportability of polyethylene glycol can be maintained at a high level, and by combining with the structures of formula (4) and / or formula (5), it becomes easier to suppress the hindrance of lithium ion movement due to polymer crystallization.

[0157] The polyether tri(meth)acrylate is represented, for example, by the following formula (3').

[0158] [Chemical formula 12]

[0159]

[0160] In formula (3'), R 7 , R 8 , R 9 , R 10 , R 11 , m3 and n3 are the same as those in formula (3-1). To the extent that the effects of the present disclosure are not impaired, the chain sandwiched between -COO- and R 11 may further contain a glycol structure having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms). For example, a glycol structure may be included between the ethylene oxide structure and the propylene oxide structure. The glycol structure is represented by -O-R x -O-, where R x is an alkylene group having 1 to 6 carbon atoms (preferably 4 to 6 carbon atoms).

[0161] The structures represented by formula (1), formula (2) and formula (3) (preferably formula (1-1), (2-1) and (3-1)) can be obtained, for example, by using a polyether polyol obtained by ring-opening polymerization of ethylene oxide and propylene oxide.

[0162] The arrangement of the ethylene oxide structure represented by (-CH2-CH2-O-) and the propylene oxide structure represented by (-CH2-CH(CH3)-O-) in formula (1-1), formula (2-1) and formula (3-1) (and formula (1'), formula (2') and formula (3')) can be a block copolymer or a random copolymer. A random copolymer is preferred.

[0163] The mass content of the structure represented by formula (1) in the polymer contained in the polymer electrolyte is represented by A. The total mass content of the structure represented by formula (2) and the structure represented by formula (3) in the polymer (preferably the mass content of the structure represented by formula (2)) is represented by B. The mass ratio A:B of A to B is preferably from 70:30 to 98:2. More preferably from 88:12 to 96:4, and even more preferably from 90:10 to 95:5.

[0164] The mass ratio of A:B can specifically be adjusted by the ratio of polyether mono(meth)acrylate to polyether di(meth)acrylate and / or tri(meth)acrylate.

[0165] When the mass ratio of A:B is within the above range, the polymer does not have an overly dense network structure and is less likely to impede the movement of lithium ions while maintaining strength, so it is particularly preferred.

[0166] In the polymer electrolyte, preferably, 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) is 1 to 110 (more preferably 14 to 58). Within these ranges, the crosslinking density of the polymer main chain becomes appropriate, such that the ionic conductivity of the polymer electrolyte is higher while maintaining strength at high temperatures, and the rate performance of the secondary battery is also improved.

[0167] In the polymer electrolyte, m1:n1 in formula (1-1) is preferably 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)) is 80:20 to 95:5 (more preferably 85:15 to 95:5).

[0168] Within the above range, even if the molecular weight between crosslinking points is large, the crystallinity of the polymer main chain is suppressed, and especially at low temperatures, it becomes easier to suppress the hindrance of lithium ion movement.

[0169] <Nitrogen-containing aromatic cationic group>

[0170] The polymer in the polymer electrolyte has at least one structure selected from the group consisting of the structure represented by the following formula (4) and the structure represented by the following formula (5).

[0171] For example, the structure represented by the following formula (4) can be exemplified by the reaction product of an imidazolium-based ionic compound having an unsaturated reactive functional group.

[0172] [Chemical formula 13]

[0173]

[0174] In formula (4), R 12 represents a hydrogen atom or a methyl group.

[0175] R 13 represents a divalent linking group. R 14represents an alkyl group having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 or 2, and even more preferably 1). R 15 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).

[0176] In formula (4), R 13 to R 15 each bond to three elements selected from the group consisting of two nitrogen atoms and three carbon atoms constituting the imidazolium ring structure. However, one of R 13 to R 15 bonds to the cationic nitrogen atom in the imidazolium ring structure. X1 - represents an anion. Preferably, R 13 bonds to the cationic nitrogen atom constituting the imidazolium ring structure. Additionally, preferably, R 14 bonds to the nitrogen atom constituting the imidazolium ring structure.

[0177] As the linking group, R 13 specifically represents a straight-chain or branched-chain 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 alkylene group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even preferably 1) with a carbonyl oxygen alkylene group containing an ester bond (-COO-). Preferably, the carbonyl in the divalent organic group containing an ester bond bonds to the carbon bonded to R 12

[0178] Furthermore, the imidazolium ring structure may have substituents such as an alkyl group, a substituted alkyl group (substituted by a halogen, etc.), or a halogen.

[0179] For example, the structure represented by the following formula (5) is a reaction product of a pyridinium-based ionic compound having an unsaturated reactive functional group.

[0180] [Chemical formula 14]

[0181]

[0182] In formula (5), R 16 represents a hydrogen atom or a methyl group.

[0183] R 17 represents a divalent linking group. R 19 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).

[0184] In formula (5), R 17 or R 19 ​Any one of them is bonded to the nitrogen atom constituting the pyridinium ring structure, and the other is bonded to one of the five carbon atoms constituting the pyridinium ring structure. X2 - represents an anion. Preferably, R 17 is bonded to the cationic nitrogen atom constituting the pyridinium ring structure.

[0185] R used as a linking group 17 specifically 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 a carbonyl oxyalkylene group having an ester bond (-COO-) or an alkylene group with 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 or 2, and even more preferably 1). Preferably, the carbonyl in the divalent organic group containing an ester bond is bonded to the carbon bonded to R 16 bonded.

[0186] The pyridinium ring structure may have substituents such as an alkyl group, a substituted alkyl group (substituted by a halogen, etc.) or a halogen.

[0187] From the viewpoint of lithium ion transportability, the polyether component of the polyether (meth)acrylate as the main component of the polymer is preferably polyethylene glycol. However, polyethylene glycol has high crystallinity, and in order to suppress crystallization, especially at low temperatures, a method of copolymerizing a propylene glycol structure with poor lithium ion transportability in a certain proportion is used. Therefore, it is difficult to achieve high ionic conductivity only with a polyether composition having the structures of formulas (1) to (3).

[0188] At the same time, the structures of formulas (4) and (5) are cationic structures with a planar structure having a relatively large molecular size, so that introducing them into the polymer structure can reduce crystallinity. Therefore, by using the structures of formulas (4) and (5), crystallization at low temperatures can be suppressed while reducing the number of propylene glycol units with poor lithium ion transportability in the polyether composition. Therefore, high ionic conductivity can be maintained even at low temperatures.

[0189] In addition, by introducing the structures of formulas (4) and (5) into the polymer structure, the polymer itself becomes ionic, and the affinity with the lithium salt is improved compared to when the structures of formulas (4) and (5) are absent. Therefore, more lithium salt can be dissolved without precipitation.

[0190] Furthermore, the imidazolium group represented by formula (4) and the pyridinium group represented by formula (5) have high stability as cations and a high dissociation rate with anions. Therefore, considering the interaction between the imidazolium group or pyridinium group and the anion of the lithium salt contained as a supporting electrolyte and promoting the dissociation of the lithium salt, the ionic conductivity is improved.

[0191] With respect to a total of 100 parts by mass of the structures represented by Formula (1), Formula (2), and Formula (3), the total content of the structure represented by Formula (4) and the structure represented by Formula (5) in the polymer structure is preferably from 1 part by mass to 15 parts by mass, more preferably from 2 parts by mass to 5 parts by mass.

[0192] When the contents of Formula (4) and Formula (5) are within this range, due to the reduced crystallinity, higher levels of both improved compatibility with the supporting electrolyte and improved ionic conductivity can be achieved.

[0193] These reaction states can be confirmed by analysis using known means such as pyrolysis GC / MS, FT-IR, and NMR.

[0194] An imidazolium-based ionic compound having an unsaturated reactive functional group capable of forming the structure shown in Formula (4) is represented, for example, by the following Formula (4’). Further, a pyridinium-based ionic compound having an unsaturated reactive functional group capable of forming the structure shown in Formula (5) is represented, for example, by the following Formula (5’).

[0195] [Chemical Formula 15]

[0196]

[0197] In Formula (4’) and Formula (5’), R 12 ~R 19 , X1 - and X2 - are the same as those explained in Formula (4) and Formula (5).

[0198] <Anion>

[0199] Examples of the anions X1 - and X2 - shown in Formula (4) and Formula (5) include fluoroalkylsulfonylimide anions, fluorosulfonylimide anions, fluoroalkylsulfate anions, fluorosulfate anions, fluoroalkylcarboxylate anions, fluoroalkylmethyl anions, tetrafluoroborate anions, hexafluorophosphate anions, dicyanamide anions, thiocyanate anions, bis(oxalato)borate anions, perchlorate anions, and derivatives thereof.

[0200] Specific examples of the fluoroalkylsulfonylimide anion include fluoroalkylsulfonylimide anions having a fluoroalkyl group with 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.

[0201] A specific example of the fluorosulfonylimide anion is the bis(fluorosulfonyl)imide anion.

[0202] Specific examples of the fluoroalkylsulfonate anion include trifluoromethanesulfonate anion, fluoromethanesulfonate anion, perfluoroethanesulfonate anion, perfluoropropanesulfonate anion, perfluorobutanesulfonate anion, perfluoropentanesulfonate anion, perfluorohexanesulfonate anion, and perfluorooctanesulfonate anion.

[0203] Specific examples of the fluoroalkylcarboxylate anion include trifluoroacetate anion, perfluoropropionate anion, perfluorobutyrate anion, perfluorovalerate anion, and perfluorohexanoate anion.

[0204] Specific examples of the fluoroalkylmethyl anion include fluorinated alkylsulfonylmethyl anions such as tris(trifluoromethanesulfonyl)methyl anion, tris(perfluoroethanesulfonyl)methyl anion, tris(perfluoropropanesulfonyl)methyl anion, tris(perfluorobutanesulfonyl)methyl anion, tris(perfluoropentanesulfonyl)methyl anion, tris(perfluorohexanesulfonyl)methyl anion, and tris(perfluorooctanesulfonyl)methyl anion.

[0205] A specific example of the tetrafluoroborate anion is the tetrafluoroborate anion.

[0206] A specific example of the hexafluorophosphate anion is the hexafluorophosphate anion.

[0207] Among these anions, at least one selected from the group consisting of fluoroalkylsulfonylimide anions, fluorosulfonylimide anions, tetrafluoroborate anions, dicyanamide anions, and thiocyanate anions is particularly preferred because it reduces the decrease in conductivity in a low-temperature environment.

[0208] More specifically, selected from the group consisting of bis(trifluoromethanesulfonyl)imide anion, bis(fluorosulfonyl)imide anion, trifluoromethanesulfonate anion (CF3-SO3 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), dicyanamide anion (N(CN)2 - ) and thiocyanate anion (SCN- At least one anion in the group is preferred.

[0209] <Lithium salt>

[0210] The polymer electrolyte contains a lithium salt. The lithium salt is preferably included as a supporting electrolyte in a lithium ion secondary battery. Examples of the lithium salt include at least one selected from the group consisting of LiBF4, LiPF6, LiN(SO2CF3)2, LiN(SO2F)2, LiN(SO2C2F5)2, LiAlCl4, LiSBF6, LiSCN, LiCF3SO3, LiAsF6, LiClO4, LiN(CN)2, lithium lower aliphatic carboxylate, LiCl, LiBr, and LiI.

[0211] Among them, in terms of chemical stability to the lithium-based positive electrode active material, at least one selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2), and LiN(C2F5SO2)2 is preferred. The lithium salt can be used alone or in combination of two or more.

[0212] Relative to 100 parts by mass of the polymer in the polymer electrolyte, the content of the lithium salt is preferably 5 to 40 parts by mass, and more preferably 7 to 20 parts by mass. When the content of the lithium salt is within this range, the lithium salt is well compatible with the polymer and does not precipitate, and a high ionic conductivity is obtained.

[0213] The polymer electrolyte is preferably a solidified product of an electrolyte solution.

[0214] The electrolyte solution can be, for example, a mixture of the following materials.

[0215] - Polyether mono(meth)acrylate.

[0216] - At least one selected from the group consisting of polyether di(meth)acrylate and polyether tri(meth)acrylate.

[0217] - At least one selected from the group consisting of imidazolium-based ionic compounds having an unsaturated reactive functional group and pyridinium-based ionic compounds having an unsaturated reactive functional group.

[0218] - Lithium salt.

[0219] If necessary, the electrolyte solution can contain a known polymerization initiator. Examples of the polymerization initiator include a photoinitiator.

[0220] <Liquid electrolyte>

[0221] Within the extent that does not impair the effects of the present disclosure and does not impair the safety at high temperatures, the polymer electrolyte may contain a liquid electrolyte. Examples of the liquid electrolyte include ionic liquids and non-aqueous electrolytes.

[0222] Specific examples of the ionic liquid include combinations of the following cations and anions.

[0223] The cation may be at least one selected from the group consisting of quaternary ammonium, imidazolium, pyridinium, pyrrolidinium, and piperidinium.

[0224] The anion may be at least one selected from the group consisting of fluoroalkylsulfonylimide anions, fluorosulfonylimide anions, fluoroalkylsulfate anions, fluorosulfate anions, fluoroalkylcarboxylate anions, fluoroalkylmethyl anions, fluoroborate anions, fluorophosphate anions, dicyanamide anions, thiocyanate anions, bis(oxalato)borate anions, perchlorate anions, and their derivatives.

[0225] The non-aqueous electrolyte is a liquid in which about 1 mole 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.

[0226] Although including a liquid electrolyte can improve the ionic conductivity, in order to avoid a decrease in mechanical strength at high temperatures, preferably, relative to 100 parts by mass of the polymer contained in the polymer electrolyte, the liquid electrolyte is included in an amount of, for example, 10 parts by mass or less, 5 parts by mass or less, 1 part by mass or less, or 0.5 part by mass or less.

[0227] The polymer electrolyte may contain, as needed, non-conductive fillers such as silica, quartz powder, titanium oxide, zinc oxide, and calcium carbonate. By adding a non-conductive filler to the coating for forming the electrolyte layer, when the coating is applied in the electrolyte layer forming step, the filler functions as a film-forming aid. Relative to 100 parts by mass of the polymer for forming the electrolyte layer, the content of such non-conductive filler is preferably 0.1 part by mass to 10 parts by mass.

[0228] In addition, if necessary, within the range that does not impede the effects of the present disclosure, the polymer electrolyte may contain conductive fillers. As the conductive fillers, conductive fine particles such as carbon black, zinc oxide, tin oxide, and titanium oxide can be used.

[0229] In particular, when using the polymer electrolyte as a binder for a positive or negative electrode active material, by including a conductive filler in the polymer electrolyte, the internal resistance of the secondary battery can be reduced. Relative to 100 parts by mass of the polymer contained in the polymer electrolyte, the content of the conductive filler is preferably 0.5 part by mass to 5 parts by mass.

[0230] (Method for forming polymer electrolyte layer)

[0231] The method for forming the polymer electrolyte layer is not particularly limited. For example, the above polymer electrolyte material is used and mixed by a known method to obtain an electrolyte solution for forming the polymer electrolyte layer. After coating the electrolyte solution by a known coating method such as bar coating, spin coating or roll coating, the polymer material contained in the electrolyte solution is polymerized by a known means such as UV to form a polymer electrolyte layer. The polymer electrolyte layer can be formed at a desired position, such as on the positive electrode or the negative electrode.

[0232] The thickness of the polymer electrolyte layer as the main electrolyte is preferably 5.0 μm to 100.0 μm.

[0233] Examples

[0234] Specific examples and comparative examples related to the present disclosure are shown below. However, the present disclosure is not limited to the following examples and comparative examples.

[0235] First, polyether acrylate having the structures shown in Formula (1) and Formula (2) is synthesized. A synthesis example of polyether monoacrylate having the structure shown in Formula (1) is shown below.

[0236] (Synthesis of polyether monoacrylate)

[0237] (Polyether monoacrylate A-1)

[0238] A total of 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, 1041 parts by mass of a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced over 260 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 180 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Then, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 6000.

[0239] Next, 100 parts by mass of the obtained polyether monoalcohol, 1.26 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 2.02 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 5 hours while removing the water generated by the reaction to the outside of the system.

[0240] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of a 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-1.

[0241] (Polyether monoacrylate A-2)

[0242] A total of 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 95:5 was continuously introduced in an amount of 976 parts by mass over 240 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 180 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in the pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Then, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 5000.

[0243] Next, 100 parts by mass of the obtained polyether monoalcohol, 1.51 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 2.42 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 5 hours while removing the water generated by the reaction to the outside of the system.

[0244] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-2.

[0245] (Polyether monoacrylate A-3)

[0246] Polyether monoacrylate A-3 was obtained in the same manner as polyether monoacrylate A-2, except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 8:2.

[0247] (Polyether monoacrylate A-4)

[0248] A total of 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 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced in an amount of 984 parts by mass over 240 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 150 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in the pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Thereafter, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 2000.

[0249] Next, 100 parts by mass of the obtained polyether monoalcohol, 3.78 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 6.05 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0250] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of a 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-4.

[0251] (Polyether monoacrylate A-5)

[0252] A total of 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced in an amount of 946 parts by mass over 240 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 130 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in the pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Thereafter, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 1000.

[0253] Next, 100 parts by mass of the obtained polyether monoalcohol, 7.56 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 12.1 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0254] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of a 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-5.

[0255] (Polyether monoacrylate A-6)

[0256] A total of 112 parts by mass of 1-butanol (Tokyo Chemical Industry Co., Ltd.) and 5 parts by mass of potassium hydroxide (Kojundo Chemical Laboratory Co., Ltd.) were placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced at 937 parts by mass over 240 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 120 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. After that, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 600.

[0257] Next, 100 parts by mass of the obtained polyether monoalcohol, 12.6 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 20.2 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0258] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-6.

[0259] (Polyether monoacrylate A-7)

[0260] 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, 927 parts by mass of a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced over 220 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 120 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in the pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. After that, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether monoalcohol with an Mn of 400.

[0261] Next, 100 parts by mass of the obtained polyether monoalcohol, 18.9 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 24.2 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0262] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monoacrylate A-7.

[0263] (Polyether monoacrylate A-8)

[0264] Polyether monoacrylate A-8 was obtained in the same manner as polyether monoacrylate A-5 except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 9:1.

[0265] (Polyether monoacrylate A-9)

[0266] Polyether monoacrylate A-9 was obtained in the same manner as polyether monoacrylate A-5, except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0267] (Polyether monoacrylate A-10)

[0268] A polyether monoalcohol with Mn of 600 was obtained in the same manner as the preparation of polyether monoacrylate A-6, except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0269] Next, 100 parts by mass of the obtained polyether monoalcohol, 15.0 parts by mass of methacrylic acid (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 20.2 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and reacted for 6 hours while removing the water generated by the reaction to the outside of the system.

[0270] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monomethacrylate A-10.

[0271] (Polyether monoacrylate A-11)

[0272] A polyether monoalcohol with Mn of 400 was obtained in the same manner as the preparation of polyether monoacrylate A-7, except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0273] Next, 100 parts by mass of the obtained polyether monoalcohol, 22.6 parts by mass of methacrylic acid (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 24.2 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0274] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of a 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether monomethacrylate A-11.

[0275] The obtained polyether mono(meth)acrylate is shown in Table 1.

[0276] Next, a synthesis example of a polyether diacrylate that can form the structure represented by formula (2) will be described.

[0277] <Synthesis of Polyether Diacrylate>

[0278] (Polyether Diacrylate B-1)

[0279] A total of 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 8:2 was continuously introduced in an amount of 1041 parts by mass over 280 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 170 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Thereafter, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added. And the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether diol with an Mn of 6000.

[0280] Next, 100 parts by mass of the obtained polyether diol, 2.52 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 2.02 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.08 parts by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 5 hours while removing the water generated by the reaction to the outside of the system.

[0281] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-1.

[0282] (Polyether diacrylate B-2)

[0283] A polyether diol with an Mn of 5000 was obtained in the same manner as 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.

[0284] Next, 100 parts by mass of the obtained polyether diol, 3.02 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 2.42 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.08 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115°C, and the reaction was carried out for 5 hours while removing the water generated by the reaction to the outside of the system.

[0285] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of a 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-2.

[0286] (Polyether diacrylate B-3)

[0287] A total of 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 9:1, 955 parts by mass, was continuously introduced over 220 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 150 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Then, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether diol with an Mn of 2000.

[0288] Next, 100 parts by mass of the obtained polyether diol, 7.56 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 6.05 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 5 hours while removing the water generated by the reaction to the outside of the system.

[0289] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-3.

[0290] (Polyether diacrylate B-4)

[0291] A total of 205 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 placed in 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 while maintaining the pressure inside the container at about 0.5 MPa, 899 parts by mass of a gas mixture of ethylene oxide / propylene oxide with a molar ratio of 9:1 was continuously introduced over 210 minutes. The temperature was maintained at 100 °C and the reaction was carried out for 110 minutes until the pressure inside the container became 0.2 MPa or less. Then, the temperature was raised to 130 °C over 30 minutes, and the mixture was stirred until the change in the pressure inside the container became 0.01 MPa / 30 minutes. A total of 20 parts by mass of pure water was added to the obtained polymer, and the mixture was stirred at 90 °C for 30 minutes. Then, 50 g of the basic adsorbent Kyowaad 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for another 30 minutes. Then, the basic adsorbent was removed by filtration, and the mixture was dried under reduced pressure at 130 °C to obtain a polyether diol with an Mn of 400.

[0292] Next, 100 parts by mass of the obtained polyether diol, 37.8 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 24.2 parts by mass of p-toluenesulfonic 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 placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system.

[0293] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-4.

[0294] (Polyether diacrylate B-5)

[0295] A polyether diol with an Mn of 600 was obtained in the same manner as the preparation of polyether diacrylate B-4, except that the amount of 1,4-butanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 137 parts by mass.

[0296] Next, 100 parts by mass of the obtained polyether diol, 25.2 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 20.2 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and reacted for 6 hours while removing the water generated by the reaction to the outside of the system.

[0297] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-5.

[0298] (Polyether diacrylate B-6)

[0299] A polyether diol with an Mn of 1000 was obtained in the same manner as the preparation of 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.

[0300] Next, 100 parts by mass of the obtained polyether diol, 15.1 parts by mass of acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 12.1 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and reacted for 6 hours while removing the water generated by the reaction to the outside of the system.

[0301] Then, the temperature of the reaction solution was lowered to room temperature, and the mixture was washed twice with 120 g of 5% aqueous sodium hydroxide solution and further washed three times with 120 g of pure water. The organic phase was separated from the washed reaction solution by fractional distillation, and the solvent was distilled off under reduced pressure to obtain polyether diacrylate B-6.

[0302] (Polyether diacrylate B-7)

[0303] Polyether diacrylate B-7 was obtained in the same manner as polyether diacrylate B-2 except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 9:1.

[0304] (Polyether diacrylate B-8)

[0305] A polyether diol with Mn of 1000 was obtained in the same manner as the preparation of polyether diacrylate B-6 except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0306] Next, 100 parts by mass of the obtained polyether diol, 18.1 parts by mass of methacrylic acid (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 12.1 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C, and the reaction was carried out for 6 hours while removing the water generated by the reaction to the outside of the system. Then, polyether diacrylate B-8 was obtained in the same manner as polyether diacrylate B-6.

[0307] (Polyether diacrylate B-9)

[0308] A polyether diol with Mn of 600 was obtained in the same manner as the preparation of polyether diacrylate B-5 except that the molar ratio of the ethylene oxide / propylene oxide mixed gas was changed to 5:5.

[0309] Next, 100 parts by mass of the obtained polyether diol, 30.0 parts by mass of methacrylic acid (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 20.2 parts by mass of p-toluenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.11 part by mass of hydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 250 ml of toluene were placed in a Dean-Stark reactor equipped with a stirring device. The mixture was heated and stirred at 115 °C for 5 hours while removing the water generated by the reaction to the outside of the system. Then, polyether diacrylate B-9 was obtained in the same manner as polyether diacrylate B-6.

[0310] The obtained polyether di(meth)acrylates are shown in Table 2.

[0311] [Table 1]

[0312] Table 1

[0313]

[0314] The polyether composition ratio represents the mole fraction. EO represents ethylene oxide, and PO represents propylene oxide [Table 2]

[0315] Table 2

[0316]

[0317] The polyether composition ratio represents the molar ratio. EO represents ethylene oxide, and PO represents propylene oxide

[0318] (Synthesis of reactive ionic compounds)

[0319] (Ionic compound C-1)

[0320] 1-Allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as ionic compound C-1.

[0321] (Synthesis of ionic compound C-2)

[0322] Dissolve a total of 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.) in 35.0 g of acetonitrile. Heat and stir the reaction mixture at 30 °C for 24 hours, then cool to room temperature and wash 3 times with 100 ml of diethyl ether. Subsequently, add 2 g of activated carbon and 20 ml of ethanol. After stirring at room temperature for 1 hour, filter out the activated carbon and distill off the solvent under reduced pressure.

[0323] Dissolve the obtained product in 160 ml of pure water, add 33.7 g (0.18 mol) of lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) as an anion raw material, and stir the mixture at room temperature for 4 hours. Next, extract the reaction solution 2 times with 100.0 g of ethyl acetate. Next, wash the separated ethyl acetate layer 3 times with 60 g of ion-exchanged water. Then, distill off the ethyl acetate under reduced pressure to obtain the ionic compound C-2.

[0324] (Synthesis of ionic compound C-3)

[0325] Dissolve a total of 15.0 g (0.12 mol) of 1-methyl-5-(prop-2-en-1-yl)-1H-imidazole (manufactured by AURORA FineChemicAls Ltd) in tetrahydrofuran. Next, place the reaction system under a nitrogen atmosphere and cool it with ice. Next, dropwise add 19.2 g (0.14 mol) of methyl iodide (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 30.0 g of tetrahydrofuran over 30 minutes. Heat the reaction solution under reflux for 12 hours, then add 100 ml of water and distill off the solvent under reduced pressure. Add a total of 100 ml of ethanol to the residue and stir at room temperature. Remove the insoluble matter by filtration through diatomaceous earth and distill off the solvent again under reduced pressure.

[0326] Dissolve the obtained product in 160 ml of pure water, add 18.7 g (0.12 mol) of lithium hexafluorophosphate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an anion raw material, and stir the mixture at room temperature for 1 hour. Next, extract the reaction solution 2 times with 80.0 g of ethyl acetate. Next, wash the separated ethyl acetate layer 3 times with 60 g of ion-exchanged water. Then, distill off the ethyl acetate under reduced pressure to obtain the ionic compound C-3.

[0327] (Synthesis of Ionic Compound C-4)

[0328] A total of 15.0 g (0.12 mol) of 1-butylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 30.0 g of tetrahydrofuran. Next, the reaction system was placed under a nitrogen atmosphere and ice-cooled. Next, 24.1 g (0.13 mol) of 8-bromo-1-octene (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 80.0 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. A total of 100 ml of ethanol was added to the residue and stirred at room temperature. The insoluble matter was removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0329] The obtained product was dissolved in 160 ml of pure water, 34.7 g (0.12 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-4.

[0330] (Synthesis of Ionic Compound C-5)

[0331] A total of 15.0 g (0.11 mol) of 1H-imidazole, 1-butyl-5-methyl- (manufactured by Hong Kong Chemhere Co., Ltd.) was dissolved in 30.0 g of tetrahydrofuran. Next, the reaction system was placed under a nitrogen atmosphere and ice-cooled. Then, 19.5 g (0.12 mol) of 6-bromo-1-hexene (Tokyo Chemical Industry Co., Ltd.) dissolved in 60.0 g of tetrahydrofuran was 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. A total of 100 ml of ethanol was added to the residue and stirred at room temperature. The insoluble matter was removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0332] The obtained product was dissolved in 160 ml of pure water, 9.79 g (0.11 mol) of sodium dicyanamide (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an anion raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain the ionic compound C-5.

[0333] (Synthesis of ionic compound C-6)

[0334] A total of 15.0 g (0.18 mol) of 1-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 35.0 g of tetrahydrofuran. Next, the reaction system was placed under a nitrogen atmosphere, and then 32.2 g (0.18 mol) of 2-bromoethyl acrylate (manufactured by Merck Co., Ltd.) 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. A total of 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matters were removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0335] The obtained product was dissolved in 160 ml of pure water, 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 raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain the ionic compound C-6.

[0336] (Synthesis of ionic compound C-7)

[0337] Dissolve a total of 15.0 g (0.18 mol) of 1-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) in 35.0 g of tetrahydrofuran. Next, place the reaction system under a nitrogen atmosphere and add dropwise 39.8 g (0.18 mol) of 4-bromobutyl methacrylate (manufactured by Hong Kong Chemhere Co., Ltd.) dissolved in 40.0 g of tetrahydrofuran over 30 minutes. Heat the reaction solution under reflux for 6 hours, then add 100 ml of water and distill off the solvent under reduced pressure. Add a total of 100 ml of ethanol to the residue and stir at room temperature. Remove the insoluble matter by filtration through diatomaceous earth and distill off the solvent again under reduced pressure.

[0338] Dissolve the obtained product in 160 ml of pure water, add 28.1 g (0.18 mol) of lithium trifluoromethanesulfonate (product name: EF-15, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) as anionic raw material, and stir the mixture at room temperature for 3 hours. Next, extract the reaction solution twice with 100.0 g of ethyl acetate. Next, wash the separated ethyl acetate layer three times with 60 g of ion-exchanged water. Then, distill off the ethyl acetate under reduced pressure to obtain the ionic compound C-7.

[0339] (Synthesis of ionic compound C-8)

[0340] Dissolve a total of 15.0 g (0.19 mol) of pyridine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 26.9 g (0.20 mol) of allyl bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) in 35.0 g of acetonitrile. Heat and stir the reaction mixture at 30 °C for 24 hours, then cool to room temperature and wash three times with 100 ml of diethyl ether. Subsequently, add 2 g of activated carbon and 20 ml of ethanol. After stirring at room temperature for 1 hour, filter out the activated carbon and distill off the solvent under reduced pressure.

[0341] The obtained product was dissolved in 160 ml of pure water, and 54.5 g (0.19 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-8.

[0342] (Synthesis of ionic compound C-9)

[0343] Ionic compound C-9 was obtained in the same manner as ionic compound C-8, except that the anion raw material was changed to 35.5 g (0.19 mol) of lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Inc.).

[0344] (Synthesis of ionic compound C-10)

[0345] The reaction system was placed under a nitrogen atmosphere, and then 19.7 g (0.14 mol) of methyl iodide (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 80.0 g of tetrahydrofuran was added dropwise to 15.0 g (0.13 mol) of 4-allylpyridine (manufactured by Arch Bioscience Company) 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. A total of 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matter was removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0346] The obtained product was dissolved in 160 ml of pure water, and 14.3 g (0.13 mol) of sodium tetrafluoroborate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an anion raw material, and the mixture was stirred at room temperature for 3 hours. 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. Then, ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-10.

[0347] (Synthesis of ionic compound C-11)

[0348] Over 30 minutes, a total of 30.8 g (0.16 mol) of 8-bromo-1-octene (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 80.0 g of tetrahydrofuran was added dropwise to 15.0 g (0.16 mol) of 4-methylpyridine (manufactured by Tokyo Chemical Industry Co., Ltd.). The reaction solution was heated under reflux for 10 hours, after which 100 ml of water was added and the solvent was distilled off under reduced pressure. A total of 80 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matters were removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0349] The obtained product was dissolved in 160 ml of pure water, 45.9 g (0.16 mol) of lithium bis(trifluoromethanesulfonyl)imide (product name: EF-N115, manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.) was added as an anion raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain the ionic compound C-11.

[0350] (Synthesis of ionic compound C-12)

[0351] Over 30 minutes, a total of 12.3 g (0.086 mol) of methyl iodide (manufactured by Tokyo Chemical Industry Co., Ltd.) dissolved in 80.0 g of tetrahydrofuran was added dropwise to 15.0 g (0.079 mol) of 2-pyridin-3-ylethyl methacrylate (manufactured by Hong Kong ChemheRe Co., Ltd.). The reaction solution was heated under reflux for 5 hours, after which 100 ml of water was added and the solvent was distilled off under reduced pressure. A total of 100 ml of ethanol was added to the residue and stirred at room temperature. Insoluble matters were removed by filtration through diatomaceous earth, and the solvent was distilled off again under reduced pressure.

[0352] The obtained product was dissolved in 160 ml of pure water, 14.8 g (0.079 mol) of lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) was added as an anion raw material, and the mixture was stirred at room temperature for 1 hour. Next, the reaction solution was extracted twice with 40.0 g of ethyl acetate. Next, the separated ethyl acetate layer was washed three times with 30 g of ion-exchanged water. Then, ethyl acetate was distilled off under reduced pressure to obtain the ionic compound C-12.

[0353] (Synthesis of Ionic Compound C-13)

[0354] A total of 15.0 g (0.19 mol) of pyridine (manufactured by Tokyo Chemical Industry Co., Ltd.) and 42.0 g (0.19 mol) of 4-bromobutyl methacrylate (manufactured by Hong Kong Chemhere Co., Ltd.) were dissolved in 60.0 g of acetonitrile. The reaction mixture was heated and stirred at 60 °C for 12 hours, then cooled to room temperature and washed three times with 100 ml of diethyl ether. Subsequently, 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 out and the solvent was distilled off under reduced pressure.

[0355] The obtained product was dissolved in 160 ml of pure water, 15.4 g (0.19 mol) of sodium thiocyanate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an anion raw material, and the mixture was 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. Then, ethyl acetate was distilled off under reduced pressure to obtain ionic compound C-13.

[0356] The chemical structures of the obtained reactive ionic compounds C-1 to C-13 are shown below.

[0357] [Chemical Formula 16]

[0358]

[0359] (Preparation of Electrolyte Solution of Polymer Electrolyte)

[0360] [Example 1]

[0361] The following materials were mixed and stirred as materials for the polymer electrolyte.

[0362] - Polyether monoacrylate NK ester M-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 50.0 parts by mass

[0363] - Polyether diacrylate B-1: 50.0 parts by mass

[0364] - Ionic compound C-3: 2.0 parts by mass

[0365] - Lithium bis(trifluoromethanesulfonyl)imide (Li·TFSI) (manufactured by Kishida Chemical Co., Ltd.): 10.0 parts by mass

[0366] - Initiator Omnirad 184 (IGM RESINS B.V.): 2.0 parts by mass

[0367] Next, methyl ethyl ketone (hereinafter referred to as MEK) was added to make the total solid ratio 60% by mass, and then it was mixed with an electric stirrer to prepare an electrolyte solution.

[0368] (Measuring the volume swelling ratio by the MEK impregnation method)

[0369] Test pieces for the volume swelling ratio by the MEK impregnation method were prepared using the electrolyte solutions of the respective examples. A prescribed amount of the dispersion for forming the surface layer of each example was added to an aluminum mold coated with a fluororesin on the surface so that the film thickness was 200 μm. Then, the mold was placed on a sunflower stand and dried until the viscosity increased to the extent that the surface of the film did not flow, and then the mold was placed on a horizontal table and dried at 60 °C for 2 hours.

[0370] Then, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.), in an air atmosphere with a cumulative light dose of 5000 mJ / cm 2 The surface of the film was irradiated with UV light to crosslink and cure the polymer electrolyte.

[0371] After curing, the mold was placed in an environment of 23 °C and 40% RH for 24 hours, and the electrolyte membrane was peeled off from the aluminum mold to prepare a sheet with a film thickness of 200 μm. The obtained polymer electrolyte sheet was cut into 50 mm × 50 mm and placed in an environment of 23 °C and 40% RH for 24 hours to prepare test pieces.

[0372] First, the initial weight in air (W1) and the initial weight in water (W2) were measured in an environment of 23 °C and 40%. Next, the test piece after measuring the initial weight was immersed in MEK at 23 °C for 48 hours. Immediately after the test piece was taken out of MEK, the MEK on the surface was wiped with a non-woven fabric, and the test piece was put into 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.

[0373] Volume swelling ratio (%) = ((W3 - W4) - (W1 - W2)) / (W1 - W2) × 100

[0374] W1: Initial weight in air

[0375] W2: Initial weight in water

[0376] W3: Weight after immersion in air

[0377] W4: Weight after immersion in water

[0378] (Measurement of ionic conductivity at normal temperature (25 °C))

[0379] The electrolyte solution obtained in Example 1 was coated on an aluminum plate with a thickness of 100 μm using a bar coater and dried at 60 °C for 30 minutes. Next, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by MarioNetwork Co., Ltd.), with a cumulative light dose of 5000 mJ / cm 2 The surface of the film was irradiated with UV light, and the polymer electrolyte membrane of Example 1 was crosslinked and cured. The thickness of the cured film was 60 μm.

[0380] The obtained polymer electrolyte membrane was punched out together with the aluminum substrate to a diameter of 50 mm and vacuum dried at 80 °C for 48 hours. Then, the polymer electrolyte membrane was placed in a glove box purged with argon (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 R B (Ω) was determined from the real impedance intercept of the obtained Cole-Cole plot, and the ionic conductivity was calculated using the following formula:

[0381] σ = L / RB × S (σ: Ionic conductivity (S·cm -1 ), L: Sample thickness (cm), S: Sample area (cm 2 ))

[0382] (Measurement of ionic conductivity at low temperature (5 °C))

[0383] A polymer electrolyte membrane was formed on the aluminum plate in the same manner as the measurement of ionic conductivity at normal temperature. Then, the polymer electrolyte membrane was placed in a glove box purged with argon (temperature 25 °C, dew point -70 °C) and loaded into a all-solid-state battery evaluation unit (manufactured by Hohsen Corp.).

[0384] The evaluation unit into which the polymer electrolyte membrane was introduced was placed in a low-temperature environmental test machine and left at 5 °C for 1 hour. Then, the ionic conductivity at low temperature was measured in the same manner as the above measurement.

[0385] <Preparation of secondary battery>

[0386] 1. Constitution using the polymer electrolyte of the present disclosure as a main electrolyte

[0387] (Preparation of negative electrode)

[0388] A 20 mm × 20 mm, 60 μm-thick lithium foil (manufactured by Honjo Metal Co., Ltd.) was laminated on a 20 mm × 30 mm, 20 μm-thick copper foil, leaving a 10 mm non-laminated end portion on one side, and then pressed to prepare a negative electrode. The total thickness of the prepared negative electrode was 70 μm. A nickel-plated 5 mm-wide copper tab was joined to the non-laminated end portion on one side of the negative electrode.

[0389] (Preparation of positive electrode)

[0390] A total of 100 parts by mass of lithium cobaltate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 7 parts by mass of Kureha KH Polymer L#1120 (manufactured by Kureha Corporation) as an active material binder and 5 parts by mass of Denka Black Li-100 (manufactured by Denka Corporation) as a conductive auxiliary material, and 40 parts by mass of N-methylpyrrolidone was added and mixed and stirred. Then, the resulting slurry was coated on a 15 mm × 25 mm, 20 μm-thick rolled aluminum foil, leaving a 10 mm non-coated end portion on one side, and then dried at 100 °C for 30 minutes and pressed to obtain a positive electrode. The thickness of the positive electrode was 80 μm.

[0391] A 5 mm-wide aluminum tab was attached to the non-coated end portion on one side of the positive electrode.

[0392] (Formation of polymer electrolyte layer)

[0393] The electrolyte solution was coated on the entire surface of the obtained positive electrode coated with the active material using a bar coater, and after air-drying at 23 °C for 10 minutes, it was then dried at 60 °C for 30 minutes. Next, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.), the film surface was irradiated with UV light to cure it. The thickness of the cured film was 60 μm. 2 The film surface was irradiated with UV light for curing. The thickness of the cured film was 60 μm.

[0394] (Preparation of secondary battery using polymer electrolyte as main electrolyte)

[0395] The positive electrode coated with the polymer electrolyte was vacuum dried at 80 °C for 48 hours. Then, the polymer electrolyte membrane was placed in a glove box purged with argon (temperature 25 °C, dew point -70 °C), and a polyimide sheet stamped into a window frame shape was attached to cover the outer peripheral portion of the positive electrode surface to form a short-circuit prevention layer. Next, the polymer electrolyte layer of the positive electrode coated with the polymer electrolyte was laminated to correspond to the lithium layer of the negative electrode. The laminate was sandwiched between aluminum laminated films and vacuum packaged to obtain a secondary battery according to Example 1.

[0396] <Evaluation of battery characteristics>

[0397] (Rate characteristics)

[0398] The theoretical capacity was determined from the total mass of lithium cobaltate contained in the positive electrode. A charge / discharge test was performed on the prototype secondary battery at 25 °C using a charge / discharge device BCS-805 (manufactured by BioLogic Co., Ltd.).

[0399] The theoretical capacity was determined from the total mass of lithium cobaltate contained in the positive electrode, and in the first cycle,

[0400] - Charging was performed at a charging rate of 0.05C and a cut-off value of 3.9V for 2 hours by constant current charging, and

[0401] - Discharging was performed at a discharging rate of 0.05C and a cut-off value of 2.0V for 1 hour by constant current discharging.

[0402] Then, the same charging and discharging were performed by increasing the charging rate and discharging rate by 0.05C each time, and the rate at which the battery could be charged and discharged without exceeding the cut-off value was determined as the rate characteristics.

[0403] (Strength evaluation at high temperature)

[0404] A prototype secondary battery was subjected to one impact in a 25 °C environment using a film impact tester QC-633 (manufactured by Cometech Testing MAchines Co., Ltd.) with an impact front diameter of 38.1 mm, a load of 120 g, and a height of 150 mm. Then, a short-circuit test was performed on the battery using a tester. Five batteries were produced for each example, and a total of 5 impact tests were performed, and the number of short-circuited batteries was counted.

[0405] Then, the impact tester and the secondary battery were placed in an environmental test chamber set to 60 °C and left for 2 hours. The same test was performed, and the number of short-circuited batteries in the high-temperature test was counted.

[0406] [Examples 2 to 34]

[0407] In addition to changing the types and amounts of polyether mono(meth)acrylate, polyether di(meth)acrylate, ionic compound, and supporting electrolyte as shown in Table 3, polymer electrolytes and secondary batteries according to Examples 2 to 34 were prepared in the same manner as in Example 1.

[0408] [Table 3]

[0409] Table 3

[0410]

[0411] The structures of the materials used during polymerization are as follows.

[0412] M-230G (methoxypolyethylene glycol methacrylate; in formula (1-1), R 1 : methyl, R 2 : ethylene-(CH2)2-, R 3 : methyl, m1: 23, n1: 0)

[0413] AM-130G (methoxypolyethylene glycol #600 acrylate; in formula (1-1), R 1 : hydrogen atom, R 2 : ethylene, R 3 : methyl, m1: 13, n1: 0)

[0414] AM-230G (methoxypolyethylene glycol #1000 acrylate; in formula (1-1), R 1 : hydrogen atom, R 2 : ethylene, R 3 : methyl, m1: 23, n1: 0)

[0415] AM-90G (methoxypolyethylene glycol #400 acrylate; in formula (1-1), R 1 : hydrogen atom, R 2 : ethylene, R 3 : methyl, m1: 9, n1: 0)

[0416] M-450G (methoxypolyethylene glycol methacrylate; in formula (1-1), R 1 : methyl, R 2 : ethylene, R 3 : methyl, m1: 45, n1: 0)

[0417] A-1000PER (in formula (2-1), R 4 : hydrogen atom, R 5 : ethylene or propylene, R 6 : ethylene or propylene, m2: 17, n2: 4)

[0418] A-1000 (Polyethylene Glycol #1000 Diacrylate; in formula (2-1), R 4 : a hydrogen atom, R 5 : an ethylene group, R 6 : an ethylene group, m2: 23, n2: 0)

[0419] A-400 (Polyethylene Glycol #400 Diacrylate; in formula (2-1), R 4 : a hydrogen atom, R 5 : an ethylene group, R 6 : an ethylene group, m2: 9, n2: 0)

[0420] A-600 (Polyethylene Glycol #600 Diacrylate; in formula (2-1), R 4 : a hydrogen atom, R 5 : an ethylene group, R 6 : an ethylene group, m2: 14, n2: 0)

[0421] A-GLY-20E (Ethoxylated Glycerol Triacrylate, in formula (3-1), R 7 : a hydrogen atom, R 8 : an ethylene group, R 9 : an ethylene group, R 10 : an ethylene group, R 11 : -CH2(CH-)CH2-, m3: 20 as the sum of formula (3-1), n3: 0)

[0422] 9G: Polyethylene Glycol #400 Dimethacrylate (in formula (2-1), R 4 : a methyl group, R 5 : an ethylene group, R 6 : an ethylene group, m2: 9, n2: 0)

[0423] 14G: Polyethylene Glycol #600 Dimethacrylate (in formula (2-1), R 4 : a methyl group, R 5 : an ethylene group, R 6 : an ethylene group, m2: 14, n2: 0)

[0424] All of the above are manufactured by Shin-Nakamura Chemical Co., Ltd.

[0425] MEMA-4000: (Polyethylene Glycol #4000 Dimethacrylate (in formula (2-1), R 4 : a methyl group, R 5 : an ethylene group, R 6 : an ethylene group, m2: 90, n2: 0)), manufactured by Toho Chemical Co., Ltd.

[0426] PEGDA-4000: (polyethylene glycol diacrylate; in formula (2-1), R 4 : a hydrogen atom, R 5 : an ethylene group, R 6 : an ethylene group, m2: 90, n2: 0), manufactured by Techno Chemical Co., Ltd.

[0427] Li·FSI represents lithium bis(fluorosulfonyl)imide.

[0428] 2. Configuration using the polymer electrolyte of the present disclosure as a binder for the positive electrode active material

[0429] [Example 35]

[0430] (Preparation of the negative electrode)

[0431] A 20 μm-thick lithium foil (manufactured by Honjo Metal Co., Ltd.) with a size of 20 mm × 20 mm was laminated on a 20 mm × 30 mm, 20 μm-thick copper foil, leaving a 10 mm non-laminated end on one side, and then pressed to prepare the negative electrode. The total thickness of the negative electrode was 70 μm. A nickel-plated 5 mm-wide copper tab was joined to the non-laminated end on one side of the negative electrode.

[0432] (Solid electrolyte)

[0433] A 20 mm × 20 mm, 0.18 mm-thick LICGC sheet (manufactured by Ohara Inc.) was used.

[0434] (Preparation of the positive electrode)

[0435] A total of 100 parts by mass of lithium cobaltate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 18 parts by mass of the electrolyte solution (60% solid) from Example 1 as a binder for the active material and 5 parts by mass of Denka Black Li-100 (manufactured by Denka Corporation) as a conductive auxiliary material, and 40 parts by mass of N-methylpyrrolidone was added and mixed and stirred. Then, the resulting slurry was coated on a 15 mm × 25 mm, 20 μm-thick rolled aluminum foil, leaving a 10 mm non-coated end on one side, and then dried at 100 °C for 30 minutes. Then, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.) with a cumulative light dose of 7000 mJ / cm 2The film surface is cured by irradiating with UV light. After curing, pressing is performed to obtain a positive electrode with a thickness of 80 μm. An aluminum tab with a width of 5 mm is joined to the non-coated end portion on one side of the positive electrode.

[0436] (Preparation of a secondary battery using a polymer electrolyte as a positive electrode active material binder)

[0437] The positive electrode having a polymer electrolyte as an active material binder is vacuum dried at 80 °C for 48 hours. Then, the polymer electrolyte film is placed in an argon replacement glove box (temperature 25 °C, dew point -70 °C) and laminated in the order of positive electrode / solid electrolyte / negative electrode. The laminate is sandwiched between aluminum laminated films and vacuum packaged to obtain a secondary battery using the polymer electrolyte of the present disclosure as a positive electrode active material binder according to Example 35.

[0438] [Examples 36 to 39]

[0439] Except for changing the electrolyte solution (polymer electrolyte) as shown in Table 7, secondary batteries according to Examples 36 to 39 are prepared in the same manner as in Example 35. The evaluation results such as rate characteristics are shown in Table 7.

[0440] 3. Configuration using the polymer electrolyte of the present disclosure as a host electrolyte, a positive electrode active material binder, and a negative electrode active material binder

[0441] [Example 40]

[0442] (Preparation of the negative electrode)

[0443] A total of 100 parts by mass of graphite powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is mixed with 20 parts by mass of the electrolyte solution (60% solid) of Example 1 as an active material binder and 5 parts by mass of Denka Black Li-100 (manufactured by Denka Co., Ltd.) as a conductive auxiliary material, and 80 parts by mass of N-methylpyrrolidone is added and mixed and stirred. Then, the resulting slurry is coated on a copper foil of 20 mm × 30 mm and 20 μm, leaving a non-coated end portion of 10 mm on one side, and then dried at 100 °C for 30 minutes. Then, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.) with an accumulated light dose of 8000 mJ / cm 2The surface of the film is irradiated with UV light for curing. After curing, pressing is performed to obtain a negative electrode with a thickness of 80 μm. Negative electrode active material non-coated portions are provided at both ends, and a nickel-plated 5 mm-wide copper current collector tab is joined to one of the negative electrode active material non-coated portions. Negative electrode active material non-coated portions where neither side is coated with the negative electrode active material are provided at both ends, and a nickel-plated 5 mm-wide copper current collector tab is joined to one of the negative electrode active material non-coated portions.

[0444] (Preparation of the positive electrode)

[0445] A total of 100 parts by mass of lithium cobaltate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 18 parts by mass of the electrolyte solution (60% solid) from Example 1 as an active material binder, and 5 parts by mass of Denka Black Li-100 (manufactured by Denka Corporation) as a conductive auxiliary material are mixed, 40 parts by mass of N-methylpyrrolidone is added, and the mixture is mixed and stirred. Then, the resulting slurry is coated on a 20-μm-thick rolled aluminum foil and dried at 60 °C for 30 minutes. Then, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.), with a cumulative light dose of 7000 mJ / cm 2 The surface of the film is irradiated with UV light for curing. After curing, pressing is performed to obtain a positive electrode with a thickness of 80 μm. Positive electrode active material non-coated portions where neither side is coated with the positive electrode active material are provided at both ends, and a 5 mm-wide aluminum current collector tab is joined to one of the positive electrode active material non-coated portions.

[0446] (Formation of the polymer electrolyte layer)

[0447] The electrolyte solution of Example 1 is coated on the obtained positive electrode using a bar coater, then air-dried at 23 °C for 10 minutes, and then dried at 60 °C for 30 minutes. Then, using a high-pressure mercury UV irradiation device (product name: Handy 1000, manufactured by Mario Network Co., Ltd.), with a cumulative light dose of 5000 mJ / cm 2 The surface of the film is irradiated with UV light for curing. The thickness of the cured film is 60 μm.

[0448] (Preparation of a secondary battery using a polymer electrolyte as the main electrolyte, positive electrode active material binder, and negative electrode active material binder)

[0449] The positive electrode and the negative electrode coated with a polymer electrolyte were vacuum-dried at 80 °C for 48 hours. Then, the polymer electrolyte membrane was placed in a glove box purged with argon (temperature 25 °C, dew point -70 °C), and a polyimide sheet stamped into a window frame shape was attached to cover the outer peripheral portion of the positive electrode surface to form a short-circuit prevention layer. Next, the polymer electrolyte layer of the positive electrode coated with the polymer electrolyte was laminated to correspond to the active material layer of the negative electrode. The laminate was sandwiched between aluminum laminated films and vacuum-packaged to obtain a secondary battery according to Example 40 in which the polymer electrolyte of the present disclosure was used as the main electrolyte, the positive electrode active material binder, and the negative electrode active material binder.

[0450] [Examples 41 to 44]

[0451] Except for changing the electrolyte solution (polymer electrolyte) as shown in Table 7, secondary batteries of Examples 41 to 44 were prepared in the same manner as in Example 40. The evaluation results of rate characteristics and the like are shown in Table 7.

[0452] [Comparative Example]

[0453] [Comparative Example 1]

[0454] The following materials were mixed and stirred as materials for the polymer electrolyte.

[0455] - Polyether monomethacrylate NK-Ester M-40G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 70 parts by mass

[0456] - Polyether dimethacrylate 4G (manufactured by Shin-Nakamura Chemical Co., Ltd.): 30 parts by mass

[0457] Lithium bis(trifluoromethanesulfonyl)imide (manufactured by Kishida Chemical Co., Ltd.): 5.0 parts by mass Initiator Omnirad 184 (manufactured by IGM RESINS B.V.): 2.0 parts by mass

[0458] Next, methyl ethyl ketone was added so that the total solid ratio was 60% by mass, and the mixture was mixed with an electric stirrer to prepare an electrolyte solution.

[0459] The polymer electrolyte and the secondary battery of Comparative Example 1 were prepared in the same manner as in Example 1.

[0460] [Comparative Examples 2 to 6]

[0461] Except for changing the types and amounts of the polyether mono(meth)acrylate, polyether di(meth)acrylate, ionic compound, and supporting electrolyte as shown in Table 4, the polymer electrolytes and secondary batteries of Comparative Examples 2 to 6 were prepared in the same manner as in Example 1.

[0462] The secondary batteries of Comparative Examples 1 to 6 were constructed using the polymer electrolyte as the main electrolyte. The evaluation results of the rate characteristics and the like are shown in Table 6.

[0463] [Table 4]

[0464] Table 4

[0465]

[0466] The structures of the materials used during polymerization were as follows.

[0467] M-40G: Methoxytetraethylene glycol methacrylate (in formula (1-1), R 1 : Methyl, R 2 : Ethylene, R 3 : Methyl, m1: 3, n1: 0)

[0468] 4G: Polyethylene glycol #200 dimethacrylate (in formula (2-1), R 4 : Methyl, R 5 : Ethylene, R 6 : Ethylene, m2: 4, n2: 0)

[0469] APG-400: Polypropylene glycol #400 diacrylate (in formula (2-1), R 4 : Hydrogen atom, R 5 : Propylene, R 6 : Propylene, m2: 0, n2: 7)

[0470] AM-90G, AM-130G, and A-600 are as described above.

[0471] All of the above were manufactured by Shin-Nakamura Chemical Co., Ltd.

[0472] PA-500: Hydroxypolypropylene glycol monoacrylate (in formula (1-1), R 1 : Hydrogen atom, R 2 : Propylene, R 3 : Hydroxyl, m1: 0, n1: 5), manufactured by Toho Chemical Co., Ltd.

[0473] [Comparative Example 7]

[0474] A secondary battery according to Comparative Example 7 was prepared in the same manner as in Example 35, except that the positive electrode active material binder was 7 parts by mass of Kureha KH Polymer L#1120 (manufactured by Kureha Co., Ltd.).

[0475] [Comparative Examples 8 to 10]

[0476] Secondary batteries according to Comparative Examples 8 to 10 were prepared in the same manner as in Example 35, except that the polymer electrolyte used was changed as shown in Table 8.

[0477] The secondary batteries of Comparative Examples 7 to 10 were constructed using a polymer electrolyte as the positive electrode active material binder. The evaluation results of the rate characteristics and the like are shown in Table 8.

[0478] [Comparative Examples 11 to 14]

[0479] Secondary batteries according to Comparative Examples 11 to 14 were prepared in the same manner as in Example 40, except that the polymer electrolyte used was changed as shown in Table 8.

[0480] The secondary batteries of Comparative Examples 11 to 14 were constructed using a polymer electrolyte as the positive electrode active material binder, the matrix electrolyte, and the negative electrode active material binder. The evaluation results of the rate characteristics and the like are shown in Table 8.

[0481] The polymer electrolytes and secondary batteries obtained in Examples 2 to 44 and Comparative Examples 1 to 14 were evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 5, 6, 7, and 8.

[0482] [Table 5]

[0483] Table 5

[0484]

[0485] In Tables 5 and 6, Mpo% is the ratio of the average addition mole number Mpo to the average addition mole number Meo.

[0486] [Table 6]

[0487] Table 6

[0488]

[0489] The polymer electrolytes according to Embodiments 1 to 34 have a structure of Formula (1), at least one of the structures of Formula (2) and Formula (3), and at least one of the structures of Formula (4) and Formula (5) in the polymer structure, and have a volume swelling ratio of 40% to 120%. As a result, these polymer electrolytes exhibit high ionic conductivity at both 25°C and 5°C. In addition, a secondary battery using the polymer electrolyte according to Embodiments 1 to 34 as a host electrolyte has both high rate characteristics and high impact resistance at high temperatures.

[0490] In addition, in Embodiments 7, 8, 11, 13, 14, 18, and 19, where 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 is 70:30 to 98:2, m1 + n1 in Formula (1-1) is 14 to 58, and m2 + n2 in Formula (2-1) is 14 to 58, exhibit particularly high ionic conductivity and also have good rate characteristics of the secondary battery.

[0491] Meanwhile, the polymer electrolytes of Comparative Example 1 that do not have the structure of Formula (4) or Formula (5) in the polymer structure, Comparative Examples 2 and 6 that do not have the structure of Formula (1), and Comparative Example 3 with a volume swelling ratio less than 40% exhibit low ionic conductivity and very poor rate characteristics of the secondary battery.

[0492] In addition, secondary batteries using the polymer electrolytes of Comparative Examples 4 and 5 with a volume swelling ratio greater than 120% or without three-dimensional crosslinking show a significant reduction in impact resistance at high temperatures.

[0493] [Table 7]

[0494] Table 7

[0495]

[0496] [Table 8]

[0497] Table 8

[0498]

[0499] Similar to the case of using the polymer electrolyte as a host electrolyte, the secondary batteries according to Embodiments 35 to 39 that use the polymer electrolyte of the present disclosure as a positive electrode active material binder and the secondary batteries according to Embodiments 40 to 44 that use the polymer electrolyte as a positive electrode active material binder, a host electrolyte, and a negative electrode active material binder have high rate characteristics and high impact resistance at high temperatures.

[0500] Meanwhile, the rate characteristics of the secondary batteries that do not have the structure of formula (4) or formula (5) in the polymer structure in Comparative Examples 8 and 11 are poor, the rate characteristics of the secondary batteries that do not have the structure of formula (1) in Comparative Examples 9 and 10 are poor, and the rate characteristics of the secondary battery with a volume swelling rate of less than 40% in Comparative Example 12 are poor. In addition, the secondary batteries with a volume swelling rate greater than 120% or without three-dimensional crosslinking in Comparative Examples 13 and 14 show a significant reduction in impact resistance at high temperatures.

[0501] The present disclosure is not limited to the above embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present disclosure. Therefore, the appended claims are intended to disclose the scope of the present disclosure.

[0502] This application claims priority based on Japanese Patent Application No. 2022-188705 filed on November 25, 2022, the entire content of which is incorporated herein by reference.

Claims

1. A polymer electrolyte, The polymer electrolyte contains a polymer having a structure represented by the following formula (1), 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), and at least one structure selected from the group consisting of a structure represented by the following formula (4) and a structure represented by the following formula (5), The polymer electrolyte further contains a lithium salt, and the volume swelling rate of the polymer electrolyte measured by the methyl ethyl ketone impregnation method is 40% to 120%: In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms, R 3 represents an alkyl group having 1 to 6 carbon atoms; In formula (2), R 4 each independently represents a hydrogen atom or a methyl group, R 5 and R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms; In formula (3), R 7 each independently represents a hydrogen atom or a methyl group, R 8 , R 9 and R 10 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms, and R 11 represents a trivalent organic group having 1 to 6 carbon atoms; In 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-; In formula (4), R 12 represents a hydrogen atom or a methyl group, R 13 represents a divalent linking group, R 14 represents an alkyl group having 1 to 4 carbon atoms, R 15 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 13 ~R 15 each is bonded to 3 elements selected from the group consisting of 2 nitrogen atoms and 3 carbon atoms constituting the imidazolium ring structure. However, one of R 13 ~R 15 is bonded to the cationic nitrogen atom in the imidazolium ring structure, and X1 - represents an anion; In formula (5), R 16 represents a hydrogen atom or a methyl group, R 17 represents a divalent linking group, R 19 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R 17 and one of R 19 is bonded to the nitrogen atom constituting the pyridinium ring structure, and the other is bonded to any one of the 5 carbon atoms constituting the pyridinium ring structure, X2 - represents an anion.

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

3. The polymer electrolyte according to claim 1 or 2, wherein A1, B1, D1, D2 and D3 each independently further have a propylene oxide structure represented by -CH2CH(CH3)-O-.

4. The polymer electrolyte according to claim 3, wherein the average number of moles Mpo of the propylene oxide structure added per mole of (meth)acryloyl residue in the polymer is 5% to 25% of the average number of moles of the ethylene oxide structure added per mole of (meth)acryloyl residue in the polymer.

5. The polymer electrolyte according to any one of claims 1 to 4, wherein when the mass content of the structure represented by the formula (1) in the polymer contained in the polymer electrolyte is represented by A, and the total mass content of the structure represented by the formula (2) and the structure represented by the formula (3) is represented by B, the mass ratio A:B is 70:30 to 98:

2.

6. The polymer electrolyte according to any one of claims 1 to 5, wherein 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), and the structure represented by the formula (3) is a structure represented by the following formula (3-1): In formula (1-1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear or branched alkylene group having 1 to 6 carbon atoms, R 3 represents an alkyl group having 1 to 6 carbon atoms, m1 and n1 are average addition molar numbers, m1 is an integer of 1 or more, and n1 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; In formula (2-1), R 4 each independently represents a hydrogen atom or a methyl group, R 5 and R 6 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms, m2 and n2 are average addition moles, m2 represents an integer of 1 or more, and n2 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- can be a block copolymer or a random copolymer. The chain sandwiched between two -COO- may further include a glycol structure having 1 to 6 carbon atoms; In formula (3-1), R 7 each independently represents a hydrogen atom or a methyl group, R 8 , R 9 and R 10 each independently represents a linear or branched alkylene group having 1 to 6 carbon atoms, R 11 represents a trivalent organic group having 1 to 6 carbon atoms, m3 and n3 are average addition molar numbers, m3 each independently represents an integer of 1 or more, and n3 each 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- can be a block copolymer or a random copolymer. The chain sandwiched between -COO- and R 11 may further include a diol structure having 1 to 6 carbon atoms.

7. The polymer electrolyte according to claim 6, wherein m1 + n1 in the formula (1-1) is 14 to 58, and m2 + n2 in the formula (2-1) and / or m3 + n3 in the formula (3-1) is 14 to 58.

8. The polymer electrolyte according to claim 6 or 7, wherein m1:n1 in the formula (1-1) is 80:20 to 95:5, and m2:n2 in formula (2-1) and / or m3:n3 in formula (3) is from 80:20 to 95:

5.

9. The polymer electrolyte according to any one of claims 1 to 8, wherein the polymer electrolyte is a dry polymer electrolyte.

10. A secondary battery comprising a positive electrode, a body electrolyte, and a negative electrode, wherein at least one selected from the group consisting of the positive electrode, the body electrolyte, and the negative electrode comprises the polymer electrolyte according to any one of claims 1 to 9.

11. A secondary battery comprising a positive electrode, a body electrolyte, and a negative electrode, wherein the secondary battery satisfies at least any one of the following (i) to (iii): (i) The positive electrode has a positive electrode active material and a positive electrode active material binder that fixes the positive electrode active material, and the positive electrode active material binder is the polymer electrolyte according to any one of claims 1 to 9; (ii) The body electrolyte is the polymer electrolyte according to any one of claims 1 to 9; and (iii) The negative electrode has a negative electrode active material and a negative electrode active material binder that fixes the negative electrode active material, and the negative electrode active material binder is the polymer electrolyte according to any one of claims 1 to 9.

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