Solid electrolyte, curable composition, and power storage device

Abstract

This solid electrolyte contains: a molecular crystal containing an alkali metal salt and an organic molecule having at least one atom selected from the group consisting of a sulfur atom, an oxygen atom, a nitrogen atom, and a phosphorus atom; and a (meth) acrylic crosslinked polymer substantially not containing a structural unit derived from a (meth) acrylate having an ether group (excluding an ether group in a heterocyclic ring).

Description

Solid electrolyte, curable composition and electricity storage device

[0001] [Cross-Reference to Related Applications] This application claims priority to Japanese Patent Application No. 2023-202028, filed on November 29, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a solid electrolyte, a curable composition, and an electricity storage device.

[0002] Various types of energy storage devices have been put to practical use, including various secondary batteries such as nickel-metal hydride secondary batteries and lithium-ion secondary batteries, as well as electric double-layer capacitors. Among these, lithium-ion secondary batteries are used in a wide range of applications due to their high energy density and battery capacity. In recent years, sodium-ion secondary batteries, potassium-ion secondary batteries, and magnesium-ion secondary batteries have been attracting attention as post-lithium-ion secondary batteries that use elements that replace the rare metal lithium.

[0003] Lithium-ion secondary batteries, which are widely used as energy storage devices, have a negative electrode, a positive electrode, and an electrolyte, and are charged and discharged by transferring lithium ions between the electrodes via the electrolyte. Organic electrolyte solutions have traditionally been used primarily as electrolytes. In recent years, solid or gel electrolytes using inorganic or organic materials have been proposed as a way to eliminate concerns about electrolyte leakage and short circuits within batteries due to overcharge and overdischarge.

[0004] While organic solid electrolytes have the advantage of excellent adhesion to electrodes due to the moderate flexibility and high formability of organic materials, they tend to have lower ionic conductivity than, for example, inorganic solid electrolytes. Therefore, in order to improve their practicality, various studies have been conducted on the development of new materials for constituting organic solid electrolytes (see, for example, Patent Document 1 and Non-Patent Document 1).

[0005] Patent Literature 1 discloses a solid electrolyte for electrochemical devices, which includes a composite of a plastic crystal matrix electrolyte doped with an ionic salt and a crosslinked polymer structure having a weight-average molecular weight of 100 to 5,000 and a linear polymer having one functional group chemically bonded as a side chain. Here, the plastic crystal matrix is ​​a material in which molecules or ions exhibit rotational disorder while the centers of gravity occupy aligned positions in a crystal lattice structure, thereby exhibiting plasticity. Furthermore, Non-Patent Literature 1 discloses the formation of a crystalline organic solid electrolyte using a soft solid crystal composed of lithium chloride and isoquinoline.

[0006] Special table 2014-504788 publication

[0007] Ionics, 2018, Vol. 24, pp. 343-349

[0008] The organic solid electrolyte described in Patent Document 1 has good ionic conductivity but poor flexibility and bendability. Furthermore, the crystalline organic solid electrolyte (i.e., molecular crystalline electrolyte) described in Non-Patent Document 1 has poor bendability due to its regular crystalline structure and also has insufficient ionic conductivity at room temperature. In particular, when a solid electrolyte layer is produced using a crystalline organic solid electrolyte as a raw material, for example, by powder compaction, cracks are likely to occur at the crystal interface. From the perspective of obtaining a high-performance electricity storage device that can easily produce a solid electrolyte layer and is resistant to damage or performance degradation even when an external force is applied to the electricity storage device, a solid electrolyte that exhibits high ionic conductivity at room temperature, which is a typical usage environment, while also having good bendability is required.

[0009] The present disclosure has been made in view of the above circumstances, and has as one object to provide a solid electrolyte that exhibits high ionic conductivity at room temperature while having good flexibility, and as another object to provide a curable composition for producing the solid electrolyte, and an electricity storage device including the solid electrolyte.

[0010] The present inventors have conducted extensive research to solve the above problems and have found that a solid electrolyte containing a molecular crystal having a specific organic molecule and an alkali metal salt as structural units in a crystal lattice, and a specific polymer, exhibits high ionic conductivity at room temperature while also having good flexibility. According to the present disclosure, the following solid electrolyte, curable composition, and electricity storage device are provided.

[0011] [1] A solid electrolyte comprising: a molecular crystal containing an organic molecule having at least one atom selected from the group consisting of sulfur, oxygen, nitrogen, and phosphorus atoms, and an alkali metal salt; and a (meth)acrylic crosslinked polymer substantially free of structural units derived from a (meth)acrylate having an ether group (excluding ether groups in a heterocyclic ring). [2] The solid electrolyte of [1], wherein the mass ratio of the molecular crystal to the (meth)acrylic crosslinked polymer (molecular crystal / (meth)acrylic crosslinked polymer) is 90 / 10 to 10 / 90. [3] The solid electrolyte of [1] or [2], wherein the (meth)acrylic crosslinked polymer contains structural units derived from a monofunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring). [4] The solid electrolyte of any of [1] to [3], wherein the (meth)acrylic crosslinked polymer contains structural units derived from a polyfunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring). [5] The solid electrolyte according to [4], wherein the polyfunctional (meth)acrylate contains a compound represented by the following formula (1): (In formula (1), W １ and W ２ each independently represents a hydrogen atom or a methyl group; X １ , X ２ , Y and Z each independently represent an alkylene group having 2 to 6 carbon atoms; E １ and E ２each independently represent an ester bond, and m and n each independently represent an integer of 0 to 5.) [6] The solid electrolyte of any of [1] to [5], wherein the organic molecule is at least one selected from the group consisting of nitrile compounds and sulfone compounds. [7] The solid electrolyte of any of [1] to [6], wherein the alkali metal salt includes an imide-based alkali metal salt. [8] A curable composition used in the production of a solid electrolyte, comprising: a molecular crystal containing at least one organic molecule selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms, and an alkali metal salt; a monofunctional (meth)acrylate having no ether groups (excluding ether groups in heterocyclic rings); and a polyfunctional (meth)acrylate having no ether groups (excluding ether groups in heterocyclic rings). [9] The curable composition of [8], wherein the polyfunctional (meth)acrylate includes a compound represented by the following formula (1): (In formula (1), W １ and W ２ each independently represents a hydrogen atom or a methyl group; X １ , X ２ , Y and Z each independently represent an alkylene group having 2 to 6 carbon atoms; E １ and E ２ each independently represent an ester bond, and m and n each independently represent an integer of 0 to 5.

[10] The curable composition of [8] or [9], further containing a polymerization initiator.

[11] The curable composition of any one of [8] to

[10] , which is an active energy ray-curable type.

[12] A solid electrolyte that is a cured product of the curable composition of any one of [8] to

[11] .

[13] An electricity storage device comprising the solid electrolyte of any one of [1] to [7].

[0012] According to the present disclosure, a solid electrolyte having good flexibility while exhibiting high ionic conductivity at room temperature can be obtained. Furthermore, by using the solid electrolyte of the present disclosure as an electrolyte for an electricity storage device such as a secondary battery or a capacitor, it is possible to obtain an electricity storage device that combines ionic conductivity with the safety ensured by the solidification of the electrolyte.

[0013] FIG. 1 is a schematic diagram of a press die used to prepare the sample pellets.

[0014] The solid electrolyte, curable composition, and electricity storage device of the present disclosure will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. "(meth)acrylo" means acrylo and / or methacrylo. "(meth)acrylate" means acrylate and / or methacrylate.

[0015] <<Solid Electrolyte>> The solid electrolyte of the present disclosure contains the following component (X) and component (Y): Component (X): a molecular crystal containing an organic molecule having at least one atom selected from the group consisting of a sulfur atom, an oxygen atom, a nitrogen atom, and a phosphorus atom, and an alkali metal salt; Component (Y): a (meth)acrylic crosslinked polymer that is substantially free of structural units derived from a (meth)acrylate having an ether group (excluding ether groups in heterocycles). The molecular crystal and (meth)acrylic crosslinked polymer contained in the solid electrolyte of the present disclosure will be described in detail below.

[0016] <Component (X): Molecular Crystal> The molecular crystal (hereinafter also referred to as "molecular crystal (X)") contained in the solid electrolyte of the present disclosure includes, as a structural unit of the crystal, an organic molecule (hereinafter also referred to as "organic molecule (M)") having at least one atom selected from the group consisting of a sulfur atom, an oxygen atom, a nitrogen atom, and a phosphorus atom, and an alkali metal salt.

[0017] The molecular crystal (X) is a crystalline organic material in which organic molecules and alkali metal salts, which are structural units in a crystal lattice, are regularly arranged. It is known that molecular crystals are constructed when the organic molecules and alkali metal salts have a specific molecular weight ratio. The molecular crystal (X) has an ion conduction path due to the regular arrangement of the structural units, and Li ions are transported through the ion conduction path. ＋ It is believed that hopping conduction provides excellent ionic conductivity.

[0018] The ratio of the organic molecule (M) to the alkali metal salt contained in the molecular crystal (X) is not particularly limited. The ratio of the organic molecule (M) to the alkali metal salt in the molecular crystal may be 0.1 to 10 moles of the organic molecule (M) per mole of the alkali metal salt. From the viewpoint of increasing ionic conductivity, the ratio of the organic molecule (M) to the alkali metal salt in the molecular crystal is preferably 0.2 to 5.0 moles, more preferably 0.25 to 4.0 moles, and even more preferably 0.5 to 2.0 moles, of the organic molecule (M) per mole of the alkali metal salt.

[0019] (Organic Molecule (M)) The number of at least one atom selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms contained in the organic molecule (M) is not particularly limited. In the organic molecule (M), the number of at least one atom selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms is preferably 1 to 8, and more preferably 2 to 6, per molecule. Of these, the organic molecule (M) preferably contains a total of 2 or more, and more preferably 2 to 6, of at least one atom selected from sulfur atoms, oxygen atoms, and nitrogen atoms per molecule.

[0020] The molecular weight of the organic molecule (M) is, for example, 300 or less, preferably 250 or less, and more preferably 200 or less. The lower limit of the molecular weight of the organic molecule (M) is, for example, 20 or more, preferably 40 or more, and more preferably 50 or more. From the viewpoint of promoting crystallization of the mixture of the organic molecule (M) and the alkali metal salt, the total number of carbon atoms per molecule of the organic molecule (M) is preferably 16 or less, more preferably 10 or less, even more preferably 8 or less, and even more preferably 6 or less.

[0021] Specific examples of the organic molecule (M) include organic molecules having a sulfur atom, such as sulfone compounds, sulfide compounds, thiol compounds, thioester compounds, thiocarbonate compounds, sulfoxide compounds, and sulfamide compounds. Examples of organic molecules having a nitrogen atom include nitrile compounds, amine compounds, and amide compounds. Examples of organic molecules having a phosphorus atom include phosphine compounds, phosphine oxide compounds, and phosphinimine compounds. Examples of organic molecules having an oxygen atom include organic molecules having an oxygen atom among the examples of organic molecules having a sulfur atom, organic molecules having an oxygen atom among the examples of organic molecules having a nitrogen atom, and organic molecules having an oxygen atom among the examples of organic molecules having a phosphorus atom, as well as ether compounds, ester compounds, ketone compounds, and carbonate compounds.

[0022] In terms of being able to further increase the ionic conductivity of the molecular crystal (X), the organic molecule (M) is preferably at least one selected from the group consisting of an organic molecule having a sulfur atom and an oxygen atom, an organic molecule having a nitrogen atom, and an organic molecule having a phosphorus atom.

[0023] Organic molecules having sulfur atoms and oxygen atoms As the organic molecules having sulfur atoms and oxygen atoms, sulfone compounds can be preferably used. Preferred examples of sulfone compounds include those represented by the following formula (2): (In formula (2), R １ and R ２ are each independently an alkyl group or an alkoxy group, or R １ and R ２ and represents a cyclic structure formed by bonding together, and the total number of carbon atoms in formula (2) is 2 to 16.

[0024] The molecule represented by the above formula (2) (hereinafter also referred to as "molecule (M-1)") has a sulfonyl group (-SO ２ -) in the above formula (2). １ and R ２When R is an alkyl group or an alkoxy group, the alkyl group and the alkoxy group may be linear or branched. １ and R ２ The number of carbon atoms in each group of R １ and R ２ There are no particular limitations on the number of carbon atoms in R as long as the total number of carbon atoms in R is 2 to 16. From the viewpoint of inducing crystallization in the mixture of the organic molecule (M) and the alkali metal salt, １ and R ２ Each of the groups preferably has 1 to 3 carbon atoms, more preferably 1 or 2.

[0025] R in the above formula (2) １ and R ２ But, R １ and R ２ When R represents a cyclic structure formed by bonding R and R, the cyclic structure may have a saturated ring skeleton or an unsaturated bond in the ring skeleton. １ and R ２ The number of carbon atoms in the cyclic structure formed by bonding R is preferably 2 to 8, more preferably 2 to 6, and even more preferably 3 to 5. １ and R ２ The ring skeleton of the cyclic structure formed by bonding the above may have an alkyl group (for example, a methyl group or an ethyl group) bonded thereto.

[0026] In order to improve the ionic conductivity of the molecular crystal (X), R １ and R ２ is R １ and R ２ and more preferably, the cyclic structure has a saturated ring skeleton.

[0027] The total number of carbon atoms in the above formula (2) is 2 to 16. From the viewpoint of promoting crystallization of the mixture of molecule (M-1) and an alkali metal salt, the total number of carbon atoms in the above formula (2) is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 5.

[0028] Specific examples of the molecule (M-1) include R１ and R ２ are each an alkyl group or an alkoxy group, examples of which include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, dioctyl sulfone, dimethyl sulfate, and diethyl sulfate. １ and R ２ But, R １ and R ２ Examples of the ring structure formed by bonding include tetrahydrothiophene 1,1-dioxide, 3-methylsulfolane, 3-sulfolene, 1,3-propane sultone, 1,4-butane sultone, 1,3,2-dioxathiolane 2,2-dioxide, etc. As the molecule (M-1), one type may be used alone, or two or more types may be used in combination.

[0029] Nitrogen-containing organic molecules Nitrogen-containing organic molecules include nitrile compounds. Preferred examples of nitrile compounds include those represented by the following formula (3): (In formula (3), R ３ represents a hydrocarbon chain, R ４ and R ５ each independently represents a hydrogen atom, an alkyl group, or a cyano group, and the total number of carbon atoms in formula (3) is 16 or less.

[0030] The molecule represented by the above formula (3) (hereinafter also referred to as "molecule (M-2)") is a molecule having two or more cyano groups (-CN). ３ R may be a saturated hydrocarbon chain or may have an unsaturated bond. R is a suitable ionic conductive material for obtaining a molecular crystal having excellent ionic conductivity. ３ Preferably, R represents a saturated hydrocarbon chain. ３ has, for example, 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and more preferably 2 to 4 carbon atoms.

[0031] R ４ or R ５ When R is an alkyl group, the alkyl group may be linear or branched. ４ or R ５The alkyl group represented by R is preferably linear. ４ and R ５ The number of carbon atoms in each group is preferably 0 to 3, and more preferably 0 or 1, from the viewpoint of causing crystallization by mixing (A) the organic molecule with the alkali metal salt.

[0032] The total number of carbon atoms in the above formula (3) may be 16 or less. From the viewpoint of promoting crystallization of the mixture of molecule (M-2) and an alkali metal salt, the total number of carbon atoms in the above formula (3) is preferably 8 or less, more preferably 6 or less.

[0033] Specific examples of the molecule (M-2) include succinonitrile, adiponitrile, 3-hexenedinitrile, 1,3,5-pentanetricarbonitrile, tert-butylmalononitrile, 1,2,2,3-propanetetracarbonitrile, etc. As the molecule (M-2), one type may be used alone, or two or more types may be used in combination.

[0034] Organic Molecules Having a Phosphorus Atom Examples of organic molecules having a phosphorus atom include ethylenebis(dimethylphosphine), ethylenebis(diphenylphosphine), methyl(diphenyl)phosphine oxide, triphenylphosphine oxide, methyl(diphenyl)phosphine imine, and triphenylphosphine imine.

[0035] From the viewpoint of ease of production of the molecular crystal, the organic molecule (M) is preferably at least one selected from the group consisting of nitrile compounds and sulfone compounds. In addition, in terms of more excellent ionic conductivity of the molecular crystal, at least one selected from the group consisting of molecules (M-1) and molecules (M-2) is more preferable, and R １ and R ２ and a molecule representing a cyclic structure formed by bonding R ３ It is more preferable that the organic molecule (M) is at least one selected from the group consisting of molecules in which M represents a saturated hydrocarbon chain. As the organic molecule (M), one type may be used alone, or two or more types may be used in combination.

[0036] (Alkali Metal Salt) The alkali metal salt is not particularly limited as long as it is a salt that generates alkali metal ions. Examples of the alkali metal salt include lithium salt, sodium salt, and potassium salt.

[0037] Specific examples of alkali metal salts include Li ２ CO ３ , LiBr, LiCl, LiI, LiSCN, LiBF ４ , LiAsF ６ , LiClO ４ , C.H. ３ COOLi, CF ３ COOLi, LiCF ３ SO ３ , LiPF ６ , LiC(CF ３ SO ２ ) ３ , lithium bis(fluorosulfonyl)imide (Li ＋ (FSO ２ ) ２ N － ), lithium bis(trifluoromethanesulfonyl)imide (Li ＋ (CF ３ SO ２ ) ２ N － and salts of the anions of these lithium salts with alkali metals other than lithium (for example, sodium, potassium, etc.). Among these, lithium salts or sodium salts are preferred, and lithium salts are more preferred, in that they have high ionic dissociation properties and can further increase the ionic conductivity of the molecular crystal (X).

[0038] In view of being able to further increase the ionic conductivity of the molecular crystal (X), the alkali metal salt constituting the molecular crystal (X) preferably contains an imide-based alkali metal salt. In view of high ionic dissociation, the imide-based alkali metal salt is preferably an imide-based lithium salt, and among the imide-based lithium salts, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide is particularly preferred, lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide is more preferred, and lithium bis(fluorosulfonyl)imide is even more preferred.

[0039] The molecular weight of the alkali metal salt is, for example, 500 or less, preferably 400 or less, more preferably 350 or less, and even more preferably 300 or less. The lower limit of the molecular weight of the alkali metal salt is, for example, 20 or more, preferably 50 or more, more preferably 100 or more, and even more preferably 150 or more. One type of alkali metal salt may be used alone, or two or more types may be used in combination.

[0040] The melting point of the alkali metal salt under atmospheric pressure is, for example, 60° C. or higher, preferably 70° C. or higher, and more preferably 80° C. or higher. There is no particular upper limit to the melting point of the alkali metal salt, but it may be, for example, 300° C. or lower, or 250° C. or lower.

[0041] The molecular crystal (X) may further contain a structural unit different from the organic molecule (M) and the alkali metal salt, provided that the effect of the present disclosure is not impaired. However, in consideration of the ionic conductivity and ease of production of the molecular crystal (X), the molecular crystal (X) is preferably a molecular crystal composed of the organic molecule (M) and the alkali metal salt.

[0042] In the solid electrolyte of the present disclosure, the content of the molecular crystal (X) is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 75% by mass or more, based on the total amount of the solid electrolyte, from the viewpoint of exhibiting good ionic conductivity. The upper limit of the content of the molecular crystal (X) is preferably 99% by mass or less, more preferably 95% by mass or less, based on the total amount of the solid electrolyte, from the viewpoint of ensuring flexibility.

[0043] (Method for Producing Molecular Crystal) The molecular crystal (X) can be produced using an organic molecule (M) and an alkali metal salt as raw materials. The method for producing the molecular crystal (X) is not particularly limited. The molecular crystal (X) can be produced, for example, by a method (hereinafter also referred to as a "first production method") including a step of mixing the organic molecule (M) and an alkali metal salt while applying mechanical energy (hereinafter also referred to as a "mechanical mixing step"); a method (hereinafter also referred to as a "second production method") including a step of dissolving the organic molecule (M) and the alkali metal salt in a solvent (hereinafter also referred to as a "dissolving step") and a step of removing the solvent from the solution in which the organic molecule (M) and the alkali metal salt are dissolved in the solvent (hereinafter also referred to as a "solvent removing step"); or the like.

[0044] First Production Method Mechanical Mixing Step In the mechanical mixing step, the organic molecules (M) and the alkali metal salt are mixed while applying mechanical energy to a substance containing the organic molecules (M) and the alkali metal salt by means of impact, shear, compression, friction, etc. (hereinafter also referred to as "mechanical mixing") This preferably causes changes in the physicochemical properties of the organic molecules (M), the alkali metal salt, or both.

[0045] The compounding ratio of the organic molecule (M) to the alkali metal salt is not particularly limited and may be set depending on the types of the organic molecule (M) and the alkali metal salt. The compounding ratio of the organic molecule (M) to the alkali metal salt may be, for example, 0.1 to 10 moles of the organic molecule (M) per mole of the alkali metal salt. The compounding ratio of the organic molecule (M) to the alkali metal salt is preferably 0.2 to 5.0 moles, more preferably 0.25 to 4.0 moles, and even more preferably 0.5 to 2.0 moles, of the organic molecule (M) per mole of the alkali metal salt, in order to obtain a molecular crystal exhibiting excellent ionic conductivity.

[0046] The method for mixing the organic molecule (M) and the alkali metal salt while applying mechanical energy is not particularly limited. In the mechanical mixing step, the organic molecule (M) and the alkali metal salt can be mixed using various devices, such as a ball mill, a bead mill, a blender, a homogenizer, a stamp mill, a homomixer, or a disperser-type mixer. Furthermore, when producing molecular crystals on a small scale, the organic molecule (M) and the alkali metal salt can also be mechanically mixed using a mortar and pestle. The mechanical mixing of the organic molecule (M) and the alkali metal salt can be performed in a dry or wet manner. Furthermore, the mechanical mixing of the organic molecule (M) and the alkali metal salt can be performed at room temperature or at a low temperature. For example, when the melting point of the organic molecule (M) is lower than room temperature, the organic molecule in a liquid state can be mechanically mixed with the alkali metal salt. Furthermore, the organic molecule in a solid state can be mechanically mixed with the alkali metal salt at a temperature lower than the melting point of the organic molecule (M).

[0047] The organic molecules (M) and the alkali metal salt may be mechanically mixed while being heated. However, in order to suppress volatilization or sublimation of the organic molecules (M), the heating in the mechanical mixing step is preferably carried out at a temperature lower than the heating temperature in the heating step optionally carried out after the mechanical mixing step. Specifically, in the mechanical mixing step, the organic molecules (M) and the alkali metal salt are mechanically mixed at, for example, 50°C or lower. The temperature when mechanically mixing the organic molecules (M) and the alkali metal salt is preferably 40°C or lower, more preferably 35°C or lower. The time for mechanical mixing varies depending on the amount and type of the organic molecules (M) and the alkali metal salt used, but may be, for example, 1 to 60 minutes, or 1 to 30 minutes.

[0048] When producing a molecular crystal by the first production method, the first production method preferably further includes a step of heating the mixture obtained by the mechanical mixing step (i.e., a mixture of organic molecules (M) and an alkali metal salt) (hereinafter also referred to as the "heating step"). This heating step can make the organic molecules (M) and the alkali metal salt in the mixture more uniform, thereby further increasing the ionic conductivity of the molecular crystal (X). In particular, a method that combines the mechanical mixing step and the heating step is thought to generate intermolecular interactions between the alkali metal ions derived from the alkali metal salt and the organic molecules (M) due to the mechanical mixing, thereby making it possible to suppress volatilization or sublimation of the organic molecules (M) during heat treatment. This has the advantage of making it easier to obtain a molecular crystal of the desired composition.

[0049] Heating Step In the heating step, the temperature and method for heating the mixture are not particularly limited. The heating temperature of the mixture may be set appropriately depending on the types of organic molecules (M) and alkali metal salt used as raw materials. From the viewpoint of making the organic molecules (M) and alkali metal salt in the mixture more uniform, it is preferable that in the heating step of the first production method, the mixture is heated at a temperature equal to or higher than the melting point of the mixture of organic molecules (M) and alkali metal salt obtained by mechanical mixing. Setting the heating temperature equal to or higher than the melting point of the mixture melts the mixture, thereby promoting uniform mixing of the organic molecules (M) and alkali metal salt.

[0050] The temperature at which the mixture is heated is preferably higher than the melting point of the mixture, from the viewpoint of homogenizing the organic molecules (M) and the alkali metal salt in the mixture by melting the mixture. Furthermore, from the viewpoint of promoting homogenization of the organic molecules (M) and the alkali metal salt in the mixture, the heating temperature of the mixture is more preferably 5°C or higher, and even more preferably 7°C or higher, than the melting point of the mixture (unit: °C). With regard to the upper limit of the heating temperature of the mixture, from the viewpoint of suppressing volatilization or sublimation of the components contained in the mixture, when the melting point of the mixture is expressed as Mp (unit: °C), it is preferably (Mp + 20)°C or lower, and more preferably (Mp + 15)°C or lower. The heating time is not particularly limited as long as it homogenizes the organic molecules (M) and the alkali metal salt in the mixture. The heating time is, for example, 1 minute to 3 hours, preferably 15 minutes to 2 hours, and more preferably 30 minutes to 2 hours. Furthermore, the heat treatment is usually carried out under normal pressure, but may also be carried out under pressure or reduced pressure.

[0051] When the mixture is heated, it is preferable to heat the mixture while stirring it, thereby further homogenizing the organic molecule (M) and the alkali metal salt. The stirring method is not particularly limited, and examples thereof include a magnetic stirrer, a stirring rod, a stirrer with stirring blades, and external circulation stirring. Stirring may also be performed using a mechanical operation that can generate a larger shear force, such as a homomixer, a disperser-type mixer, or a homogenizer.

[0052] After heating a mixture containing an organic molecule (M) and an alkali metal salt, the heated mixture can be crystallized by lowering the temperature of the heated mixture, thereby obtaining the desired molecular crystal. The temperature of the heated mixture can be lowered by gradually cooling the mixture (e.g., slowly lowering the temperature at room temperature over 1 to 48 hours). Alternatively, the heated mixture can be rapidly cooled (e.g., by placing the heated mixture in a thermostatic bath at a temperature lower than room temperature (e.g., 15°C or lower) for a short period of time). From the viewpoint of favorable crystallization of the heated mixture, gradually lowering the temperature of the mixture is preferable. The fact that the product obtained by this production method is a molecular crystal containing an organic molecule (M) and an alkali metal salt can be determined by powder X-ray diffraction measurement of the product. Details of the measurement method follow those described in the Examples below.

[0053] Second Manufacturing Method - Dissolution Step When the boiling point of the organic molecule (M) is high (e.g., 100°C or higher), the second manufacturing method may be used to manufacture the molecular crystal (X). An organic solvent can be preferably used as the solvent for dissolving the organic molecule (M) and the alkali metal salt. The organic solvent is preferably a solvent that can dissolve the organic molecule (M) and the alkali metal salt, has a moderately low boiling point (e.g., 100°C or lower), and a low dielectric constant. Examples of such organic solvents include dimethyl carbonate, tetrahydrofuran, and ethyl acetate. When dissolving the organic molecule (M) and the alkali metal salt in the solvent, it is preferable to stir the mixture to homogenize the organic molecule (M) and the alkali metal salt. The stirring method is not particularly limited, and the stirring methods exemplified in the first manufacturing method can be used as appropriate.

[0054] Solvent Removal Step The method for removing the solvent from the solution in which the organic molecule (M) and the alkali metal salt are dissolved is not particularly limited as long as it can remove the solvent from the solution. As a method for removing the solvent, heat treatment is preferred because it can remove the solvent simply and efficiently. The heat treatment may be carried out under normal pressure, but may also be carried out under increased pressure or reduced pressure. When a solvent with a high boiling point is used in the dissolving step, it is preferable to carry out the heat treatment under reduced pressure in order to suppress decomposition of the organic molecule (M) and the alkali metal salt.

[0055] The method for producing the molecular crystal (X) is not limited to the above. For example, the molecular crystal (X) may be produced by a method in which the organic molecule (M) and the alkali metal salt are heated and mixed without mechanical mixing in the first production method described above.

[0056] <Component (Y): (meth)acrylic crosslinked polymer> The (meth)acrylic crosslinked polymer (hereinafter also referred to as "(meth)acrylic crosslinked polymer (Y)") which is component (Y) is a polymer mainly composed of structural units derived from (meth)acrylate (i.e., a monomer having a (meth)acryloyl group). However, the (meth)acrylic crosslinked polymer (Y) does not substantially contain structural units derived from (meth)acrylate having an ether group (excluding ether groups in a heterocyclic ring). Hereinafter, "a (meth)acrylate having an ether group (excluding ether groups in a heterocyclic ring)" will also be referred to as "(meth)acrylate (E1)," and "a structural unit derived from a (meth)acrylate having an ether group (excluding ether groups in a heterocyclic ring)" will also be referred to as "ether group-containing unit."

[0057] In the (meth)acrylic crosslinked polymer (Y), the proportion of the structural units derived from (meth)acrylate is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y). When the proportion of the structural units derived from (meth)acrylate in the (meth)acrylic crosslinked polymer (Y) is within the above range, a crystal structure derived from the molecular crystal (X) is likely to appear, thereby further increasing the ionic conductivity of the solid electrolyte.

[0058] The term "ether group" refers to "-O-" contained in the structural formula represented by R-O-R (wherein each of the two R's is independently a hydrocarbon group). That is, each of the two bonds extending from the oxygen atom constituting the ether group is bonded to a hydrocarbon structure. Herein, "substantially free of structural units derived from (meth)acrylates having ether groups (excluding ether groups in heterocycles)" means that the (meth)acrylic crosslinked polymer (Y) does not exhibit properties derived from ether group-containing units. However, it is acceptable for the (meth)acrylic crosslinked polymer (Y) to contain a trace amount of ether group-containing units to the extent that the effects of the present disclosure are not impaired. Specifically, the proportion of ether group-containing units in the (meth)acrylic crosslinked polymer (Y) is typically 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.1% by mass or less, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y). It is particularly preferred that the (meth)acrylic crosslinked polymer (Y) contains no ether group-containing units.

[0059] The (meth)acrylate (E1) has an ether group in the molecule, excluding the ether group in the heterocyclic ring. Examples of the (meth)acrylate (E1) include polyalkylene glycol mono(meth)acrylates such as alkoxyalkyl (meth)acrylate, aryloxyalkyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polyethylene glycol-polypropylene glycol mono(meth)acrylate; and polyalkylene glycol polyfunctional (meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, diacrylate of an ethylene oxide adduct of bisphenol A, and diacrylate of a propylene oxide adduct of bisphenol A.

[0060] The (meth)acrylic crosslinked polymer (Y) contains, as a monomer unit, a structural unit derived from a (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring). Hereinafter, the "(meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring)" will also be referred to as "(meth)acrylate (E2)."

[0061] The (meth)acrylate (E2) may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate, as long as it does not have any ether groups other than the ether groups in the heterocycle. That is, the (meth)acrylate (E2) does not have any ether groups present at positions other than the ether groups in the heterocycle, but may or may not have any ether groups present in the heterocycle. In terms of being able to obtain a solid electrolyte with high ion conductivity by a simple method, the (meth)acrylic crosslinked polymer (Y) preferably contains, as a monomer unit, a structural unit derived from a monofunctional (meth)acrylate that does not have any ether groups other than the ether groups in the heterocycle, and more preferably contains a structural unit derived from a monofunctional (meth)acrylate that does not have any ether groups other than the ether groups in the heterocycle and a structural unit derived from a polyfunctional (meth)acrylate that does not have any ether groups other than the ether groups in the heterocycle. In the following, the "monofunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring)" will also be referred to as the "monofunctional (meth)acrylate (E2-1)," and the "polyfunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring)" will also be referred to as the "polyfunctional (meth)acrylate (E2-2)."

[0062] Monofunctional (meth)acrylate (E2-1) Examples of the monofunctional (meth)acrylate (E2-1) include (meth)acrylic acid alkyl esters, aliphatic cyclic (meth)acrylic acid esters, aromatic (meth)acrylic acid esters, (meth)acrylic acid hydroxyalkyl esters, mono(meth)acrylates having a heterocyclic structure, and zwitterionic mono(meth)acrylates.

[0063] Specific examples of these include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Of these, the (meth)acrylic acid alkyl esters are preferably compounds in which the alkyl group constituting the alkyl ester moiety has 1 to 12 carbon atoms, more preferably compounds in which 2 to 8 carbon atoms, and even more preferably compounds in which 2 to 6 carbon atoms.

[0064] Specific examples of the aliphatic cyclic esters of (meth)acrylic acid include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0065] Specific examples of aromatic esters of (meth)acrylic acid include phenyl (meth)acrylate and benzyl (meth)acrylate.

[0066] Specific examples of the hydroxyalkyl (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0067] Examples of mono(meth)acrylates having a heterocyclic structure include mono(meth)acrylates having a cyclic carbonate structure, a cyclic ether structure, an oxazolidone ring structure, a cyclic amide structure, an oxazoline ring structure, or a morpholine ring structure as the heterocyclic structure. Among these, mono(meth)acrylates having a cyclic carbonate structure, a cyclic ether structure, an oxazolidone ring structure, or a morpholine ring structure are preferred. Specific examples thereof include (2-oxo-1,3-dioxolan-4-yl)methyl(meth)acrylate, 2-((2-oxo-1,3-dioxolan-4-yl)methoxy)ethyl(meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl(meth)acrylate, oxazolidone(meth)acrylate, and (meth)acryloylmorpholine. Among these, mono(meth)acrylates having a cyclic carbonate structure are particularly preferred because they can provide a solid electrolyte with excellent ion conductivity.

[0068] The dipolar ionic mono(meth)acrylate may be any monomer having a cationic moiety and an anionic moiety in the same molecule. Examples of the dipolar ionic mono(meth)acrylate include sulfobetaine (meth)acrylates such as 3-[[2-((meth)acryloyloxy)ethyl]dimethylammonio]propane-1-sulfonic acid, 4-[[2-((meth)acryloyloxy)ethyl]dimethylammonio]butane-1-sulfonic acid, 3-[(3-(meth)acrylamidopropyl)dimethylammonio]propane-1-sulfonic acid, and 4-[(3-(meth)acrylamidopropyl)dimethylammonio]butane-1-sulfonic acid. ) acrylate; carboxybetaine type (meth)acrylates such as 2-[[2-((meth)acryloyloxy)ethyl]dimethylammonio]acetic acid, 3-[[2-((meth)acryloyloxy)ethyl]dimethylammonio]propionate, and 3-[(3-(meth)acrylamidopropyl)dimethylammonio]propanoate; phosphobetaine type (meth)acrylates such as 2-((meth)acryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate; and the like. Of these, sulfobetaine type (meth)acrylates are preferred as the zwitterionic mono(meth)acrylate.

[0069] In terms of being able to obtain a solid electrolyte exhibiting superior ion conductivity, the (meth)acrylic crosslinked polymer (Y) preferably contains, as a structural unit derived from the monofunctional (meth)acrylate (E2-1), a structural unit derived from at least one selected from the group consisting of a (meth)acrylic acid alkyl ester, a mono(meth)acrylate having a heterocyclic structure, and a zwitterionic mono(meth)acrylate. Furthermore, the monofunctional (meth)acrylate (E2-1) is preferably a non-crosslinkable monomer, and specifically, preferably does not have a crosslinkable group such as a carboxyl group, a hydroxyl group, a primary amino group, or the like.

[0070] In terms of further improving the flexibility of the solid electrolyte, a monofunctional (meth)acrylate constituting the (meth)acrylic crosslinked polymer (Y) is preferably one having a relatively low glass transition temperature in the homopolymer. Specifically, a monofunctional (meth)acrylate (E2-1) having a glass transition temperature in the homopolymer of 80°C or less is preferably used. The monofunctional (meth)acrylate (E2-1) has a glass transition temperature of preferably 65°C or less, more preferably 50°C or less, and even more preferably 20°C or less. In this specification, the glass transition temperature of the polymer is a value calculated according to the FOX formula.

[0071] In the (meth)acrylic crosslinked polymer (Y), the proportion of the structural units derived from the monofunctional (meth)acrylate (E2-1) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y), from the viewpoint of imparting sufficient flexibility to the solid electrolyte. The upper limit of the proportion of the structural units derived from the monofunctional (meth)acrylate (E2-1) is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y), from the viewpoint of introducing an appropriate crosslinked structure into the polymer to obtain a solid electrolyte that exhibits a good balance between flexibility and ionic conductivity.

[0072] Polyfunctional (meth)acrylates (E2-2) Examples of the polyfunctional (meth)acrylates (E2-2) (i.e., crosslinkable monomers) include polyol poly(meth)acrylates such as alkylene diol di(meth)acrylates (e.g., 1,6-hexanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, etc.), trimethylolpropane tri(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri- or tetra(meth)acrylate, ditrimethylolpropane tri- or tetra(meth)acrylate, diglycerin tri- or tetra(meth)acrylate, and dipentaerythritol tri-, tetra-, penta-, or hexa(meth)acrylate; (In formula (1), W １ and W ２ each independently represents a hydrogen atom or a methyl group; X １ , X ２ , Y and Z each independently represent an alkylene group having 2 to 6 carbon atoms; E １ and E ２ each independently represent an ester bond, and m and n each independently represent an integer of 0 to 5; zwitterionic polyfunctional (meth)acrylates such as bis[2-[(meth)acryloyloxy)ethyl](methyl)ammonio]propane-1-sulfonic acid; and the like.

[0073] In the above formula (1), W １ and W ２ Each of X is preferably a hydrogen atom in terms of high photocurability. １ , X ２ The alkylene group having 2 to 6 carbon atoms represented by Y or Z may be linear or branched. m and n each preferably represent an integer of 0 to 2, more preferably 0 or 1. Specific examples of the compound represented by formula (1) include hydroxypivalic acid neopentyl glycol di(meth)acrylate.

[0074] Among the above, bifunctional (meth)acrylates can be preferably used as the polyfunctional (meth)acrylate (E2-2), from the viewpoint of promoting the formation of a crystalline structure derived from molecular crystals and increasing the ionic conductivity of the solid electrolyte. Among them, the compound represented by the above formula (1) can be preferably used as the polyfunctional (meth)acrylate (E2-2).

[0075] In the (meth)acrylic crosslinked polymer (Y), the proportion of the structural units derived from the polyfunctional (meth)acrylate (E2-2) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y), from the viewpoint of introducing a crosslinked structure into the polymer appropriately. The upper limit of the proportion of the structural units derived from the polyfunctional (meth)acrylate (E2-2) is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of structural units constituting the (meth)acrylic crosslinked polymer (Y), from the viewpoint of suppressing a decrease in ionic conductivity.

[0076] In the solid electrolyte of the present disclosure, the content of the (meth)acrylic crosslinked polymer (Y) is preferably 1% by mass or more, and more preferably 5% by mass or more, relative to the total amount of the solid electrolyte, from the viewpoint of obtaining a solid electrolyte exhibiting good flexibility. The upper limit of the content of the (meth)acrylic crosslinked polymer (Y) is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less, relative to the total amount of the solid electrolyte, from the viewpoint of obtaining a solid electrolyte exhibiting good ionic conductivity.

[0077] In the solid electrolyte of the present disclosure, the mass ratio of the molecular crystal (X) to the (meth)acrylic crosslinked polymer (Y), expressed as "molecular crystal / (meth)acrylic crosslinked polymer," is preferably 90 / 1 to 10 / 90. When the mass ratio of the molecular crystal (X) to the (meth)acrylic crosslinked polymer (Y) is within the above range, a solid electrolyte can be obtained that exhibits good flexibility while enhancing the ionic conductivity of the solid electrolyte. In terms of achieving both the ionic conductivity and flexibility of the solid electrolyte, the mass ratio of the molecular crystal (X) to the (meth)acrylic crosslinked polymer (Y) is more preferably 90 / 10 to 20 / 80, even more preferably 90 / 10 to 30 / 70, even more preferably 80 / 20 to 30 / 70, even more preferably 70 / 30 to 30 / 70, and even more preferably 60 / 40 to 40 / 60. The mass ratio expressed as "molecular crystal / (meth)acrylic crosslinked polymer" is the ratio of each component when the total amount of the molecular crystal (X) and the (meth)acrylic crosslinked polymer (Y) is taken as 100.

[0078] <Other Components> The solid electrolyte of the present disclosure may further contain components (hereinafter also referred to as "other components") different from the above-described molecular crystal (X) and (meth)acrylic crosslinked polymer (Y). Examples of the other components include inorganic fillers, inorganic electrolytes (e.g., ceramic electrolytes, glass electrolytes, etc.), binders, conductive additives, positive electrode active materials, and negative electrode active materials.

[0079] The inorganic filler can be used for purposes such as improving the strength and ionic conductivity of the solid electrolyte. Examples of inorganic fillers include oxides, nitrides, and carbides. Specific examples of these include oxides such as zinc oxide, silicon monoxide, silicon dioxide (silica), aluminum oxide (alumina), magnesium oxide, titanium oxide, and iron oxide. Nitrides include silicon nitride, boron nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, and magnesium nitride. Carbides include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide. The solid electrolyte of the present disclosure may contain only one type of inorganic filler, or may contain two or more types.

[0080] When the solid electrolyte of the present disclosure contains an inorganic filler, from the viewpoint of obtaining a solid electrolyte that exhibits good ion conductivity, the solid electrolyte preferably contains an oxide (i.e., an inorganic oxide) as the inorganic filler, and particularly preferably contains silica.

[0081] When the solid electrolyte of the present disclosure contains an inorganic filler, the content of the inorganic filler in the solid electrolyte is preferably 30 mass% or less, more preferably 25 mass% or less, even more preferably 20 mass% or less, and still more preferably 10 mass% or less, relative to the total amount of the solid electrolyte.

[0082] <Method for Producing Solid Electrolyte> The method for producing the solid electrolyte of the present disclosure is not particularly limited as long as it can produce a solid electrolyte exhibiting desired properties. Methods for producing the solid electrolyte of the present disclosure include, for example, [1] a method of mixing a molecular crystal (X) and a (meth)acrylic crosslinked polymer (Y); and [2] a method of curing a curable composition containing the molecular crystal (X) and raw materials for the (meth)acrylic crosslinked polymer (Y) (such as the monomer components constituting the (meth)acrylic crosslinked polymer (Y)). Of these, the method [2] is preferred because it is simple and can produce a solid electrolyte with high ionic conductivity.

[0083] Curable Composition The curable composition used in producing the solid electrolyte of the present disclosure (hereinafter also referred to as "solid electrolyte composition") contains the following components (X), (y1), and (y2). Component (X): a molecular crystal containing an organic molecule having at least one atom selected from the group consisting of a sulfur atom, an oxygen atom, a nitrogen atom, and a phosphorus atom, and an alkali metal salt. Component (y1): a monofunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring). Component (y2): a polyfunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring).

[0084] Here, the component (X) contained in the solid electrolyte composition is the molecular crystal (X) described above. Furthermore, the component (y1) corresponds to the monofunctional (meth)acrylate that will constitute the (meth)acrylic crosslinked polymer (Y), and the component (y2) corresponds to the polyfunctional (meth)acrylate that will constitute the (meth)acrylic crosslinked polymer (Y). That is, the component (y1) is the monofunctional (meth)acrylate (E2-1), and the component (y2) is the polyfunctional (meth)acrylate (E2-2). Details of each component are as described above, and therefore, description thereof will be omitted here.

[0085] In the solid electrolyte composition, the content of component (X) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the solid electrolyte composition. Furthermore, the content of component (X) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on the total amount of the solid electrolyte composition. By setting the amount of component (X) in the solid electrolyte composition within the above range, a solid electrolyte that combines ionic conductivity and flexibility can be obtained.

[0086] In order to enhance the flexibility of the solid electrolyte, the content of component (y1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, relative to 100 parts by mass of the molecular crystal (X) contained in the composition for a solid electrolyte. In order to suppress a decrease in ion conductivity, the content of component (y1) is preferably 800 parts by mass or less, more preferably 700 parts by mass or less, even more preferably 600 parts by mass or less, and even more preferably 500 parts by mass or less, relative to 100 parts by mass of the molecular crystal (X) contained in the composition for a solid electrolyte.

[0087] In order to sufficiently promote the crosslinking reaction, the content of component (y2) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the molecular crystal (X) contained in the composition for a solid electrolyte. Furthermore, from the viewpoint of suppressing a decrease in ion conductivity, the content of component (y2) is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less, relative to 100 parts by mass of the molecular crystal (X) contained in the composition for a solid electrolyte.

[0088] The solid electrolyte composition may further contain a component different from the component (X), the component (y1), and the component (y2). Examples of such a component include a polymerization initiator and a solvent.

[0089] (Polymerization Initiator) As the polymerization initiator, known polymerization initiators such as thermal decomposition type and photoinitiation type can be used. Preferably, a photoinitiation type polymerization initiator (photopolymerization initiator) is used. Specific examples of the photopolymerization initiator include benzoin and its alkyl ethers, acetophenones, anthraquinones, thioxanthones, ketals, benzophenones, xanthones, acylphosphine oxides, α-diketones, and α-hydroxyketones. Furthermore, when the solid electrolyte composition is an active energy ray-curable type, a benzoic acid-based or amine-based photosensitizer may be used in combination as needed to improve the sensitivity of the solid electrolyte composition to the active energy ray irradiated thereto.

[0090] In the solid electrolyte composition, the content of the polymerization initiator can be, for example, 0.1 to 50 parts by mass relative to 100 parts by mass of the total of component (y1) and component (y2) blended into the solid electrolyte composition. From the viewpoint of sufficiently carrying out the polymerization reaction of component (y1) and component (y2), the content of the polymerization initiator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the total of component (y1) and component (y2). Furthermore, in order to avoid blending an excessive amount of polymerization initiator while sufficiently proceeding with the polymerization reaction, the content of the polymerization initiator is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0091] The solid electrolyte composition may contain a solvent such as an organic solvent, but is preferably used as a solventless type that does not contain a solvent. A solventless curable composition is advantageous in that it allows the thickness of the solid electrolyte to be easily adjusted and does not require a step of removing the solvent, thereby simplifying the production process.

[0092] In addition to the above, other components that may be blended in the solid electrolyte composition include various additives such as antioxidants, ultraviolet absorbers, flame retardants, mildew inhibitors, colorants, etc. The contents of these can be appropriately set depending on the respective compounds within a range that does not cause a decrease in performance.

[0093] - Production of Solid Electrolyte One embodiment of the solid electrolyte of the present disclosure is a cured product obtained by curing the above-described solid electrolyte composition. This makes it possible to obtain a solid electrolyte that is less susceptible to cracking at crystal interfaces, without requiring molding processes such as powder compaction. The solid electrolyte composition is preferably an active energy ray-curable composition that is cured by active energy rays such as ultraviolet rays or electron beams. In this case, the solid electrolyte of the present disclosure can be produced by irradiating the solid electrolyte composition with active energy rays to cure the composition.

[0094] One embodiment of the method for producing a solid electrolyte according to the present disclosure includes a method including the following mixing step and curing step: Mixing step: A step of mixing component (X), component (y1), and component (y2) to obtain a solid electrolyte composition; Curing step: A step of irradiating the solid electrolyte composition with active energy rays to cure it.

[0095] (Mixing Step) In the mixing step for producing a solid electrolyte composition, the molecular crystal (X), the component (y1), and the component (y2) may be mixed uniformly, and the method for doing so is not particularly limited. The molecular crystal (X), the component (y1), and the component (y2) may be mixed while heating, from the viewpoint of homogenizing the components and obtaining a solid electrolyte exhibiting good ionic conductivity.

[0096] When the molecular crystal (X), component (y1), and component (y2) are mixed while being heated, the heating temperature and method are not particularly limited. From the viewpoint of obtaining a composition in which the molecular crystal (X), component (y1), and component (y2) are homogenized, the mixture is preferably heated to a temperature higher than the melting point of the molecular crystal (X). The heating time is not particularly limited as long as it is long enough to homogenize the components in the mixture. The heating time is, for example, 1 minute to 3 hours, and preferably 3 minutes to 2 hours. Furthermore, the heat treatment is usually carried out under normal pressure, but may also be carried out under increased pressure or reduced pressure.

[0097] When the mixture is heated, it is preferable to heat the mixture while stirring the mixture to further homogenize the molecular crystal (X), component (y1), and component (y2). The stirring method is not particularly limited, and examples thereof include a magnetic stirrer, a stirring rod, a stirrer with stirring blades, and external circulation stirring. Mechanical operations that can generate greater shear force, such as a homomixer, a disperser-type mixer, or a homogenizer, may also be used for stirring. When other components, such as a polymerization initiator, are contained in the solid electrolyte composition, the other components may be blended before mixing the molecular crystal (X), component (y1), and component (y2), or after mixing the molecular crystal (X), component (y1), and component (y2). From the viewpoint of homogenizing the composition and suppressing variations in the curing reaction, it is preferable to blend the other components in advance before the heat treatment of the molecular crystal (X), component (y1), and component (y2).

[0098] After heating the mixture containing the molecular crystal (X), the component (y1), and the component (y2), the temperature of the mixture after heating may be lowered to promote crystallization of the mixture after heating. When lowering the temperature of the mixture after heating, the mixture may be gradually cooled (e.g., slowly lowered at room temperature over 1 to 48 hours). Alternatively, the mixture after heating may be rapidly cooled (e.g., the mixture after heating may be placed in a thermostatic bath at a temperature lower than room temperature (e.g., 15°C or lower) for a short period of time). From the viewpoint of favorable crystallization of the mixture after heating, it is preferable to gradually lower the temperature of the mixture.

[0099] (Curing Step) In the subsequent curing step, the mixture obtained in the mixing step (i.e., the solid electrolyte composition) is irradiated with active energy rays to cure the solid electrolyte composition. For example, the solid electrolyte composition is first applied to a substrate or placed in a mold. Next, the solid electrolyte composition is cured by irradiating it with active energy rays such as ultraviolet rays or electron beams. This allows the solid electrolyte of the present disclosure to be produced as a cured product of the solid electrolyte composition.

[0100] Examples of the active energy rays irradiated to the solid electrolyte composition include ultraviolet rays, visible light, and electron beams. Of these, ultraviolet rays or electron beams are preferred as the active energy rays irradiated to the solid electrolyte composition. The active energy rays may be irradiated to only one side or both sides of the substrate coated with the solid electrolyte composition. The irradiation energy can be appropriately set depending on the type of active energy rays, the formulation of the solid electrolyte composition, and the like.

[0101] For example, when ultraviolet rays are used as the active energy rays, the wavelength is, for example, 250 to 400 nm. Examples of ultraviolet irradiation devices include high-pressure mercury lamps, metal halide lamps, ultraviolet electrodeless lamps, and ultraviolet light-emitting diodes (UV-LEDs). The cumulative light amount is 0.5 J / cm. ２ More than 1.0 J / cm is preferable. ２ More preferably, 1.5 J / cm or more ２ The upper limit of the cumulative light amount is more preferably 250 J / cm in order to minimize the influence on each component in the solid electrolyte composition and to reduce energy consumption. ２ Preferably, 200 J / cm or less ２ The following is more preferred:

[0102] The illuminance and irradiation time of the ultraviolet light can be appropriately set so that the integrated light amount is a desired amount. For example, the illuminance is 1.0 mW / cm ２ More than 2.0 mW / cm is preferable. ２ More preferably, the upper limit of the illuminance is 100 mW / cm. ２ Preferably, 80 mW / cm or less ２ The following is more preferred:

[0103] When electron beams are used as the active energy rays, examples of electron beam irradiation devices include Cockcroft-Walton type, Van de Graaff type, and resonant transformer type devices. The absorbed dose of the electron beam is preferably 1 to 200 kGy, more preferably 10 to 100 kGy. The acceleration voltage of the electron beam may be appropriately set within a range of 80 to 300 kV depending on the thickness of the substrate, etc. The oxygen concentration of the electron beam irradiation atmosphere is preferably 500 ppm or less, more preferably 300 ppm or less.

[0104] The solid electrolyte of the present disclosure can be obtained by molding a cured product containing a molecular crystal (X) and a (meth)acrylic crosslinked polymer (Y) into a desired shape. The finally obtained molded product may be used as is as a solid electrolyte layer of an electricity storage device. In this case, a plurality of molded products may be stacked to form a solid electrolyte layer of an electricity storage device. When the solid electrolyte of the present disclosure is obtained as a molded product, the shape of the molded product is not particularly limited and can be appropriately set depending on the shape of the electricity storage device to which it is applied. The shape of the molded product is, for example, rectangular or circular. The thickness of the molded product is, for example, 5 to 5,000 μm, preferably 5 to 3,500 μm, and more preferably 10 to 3,000 μm.

[0105] The solid electrolyte obtained as described above exhibits high ionic conductivity at room temperature (25°C). Therefore, by using the solid electrolyte of the present disclosure as an electrolyte material for an electricity storage device, an electricity storage device with high ionic conductivity can be obtained. Specifically, for a solid electrolyte having a thickness of about 300 μm (specifically, 300±30 μm), the ionic conductivity measured at 25°C using an AC impedance method is 1.0×10 －７ From the viewpoint of obtaining an electricity storage device with excellent performance, the ionic conductivity under the same conditions is preferably 1.0 × 10 S / cm or more. －６ S / cm or more, and more preferably 1.0×10 －５ The ionic conductivity is more preferably 25 S / cm or more. Details of the method for measuring the ionic conductivity follow the method described in the examples below.

[0106] <Electricity Storage Device> The electricity storage device of the present disclosure (hereinafter also referred to as "the device") includes the solid electrolyte of the present disclosure. Specific embodiments of the device include a secondary battery, a capacitor, and the like. When the device is a secondary battery, one embodiment is an all-solid-state battery, and a lithium-ion secondary battery is preferred in terms of excellent ionic conductivity.

[0107] An all-solid-state lithium-ion secondary battery, which is one embodiment of the device, will now be described. A lithium-ion secondary battery is a laminate comprising electrodes consisting of a positive electrode and a negative electrode, and a solid electrolyte, with the solid electrolyte being disposed between the positive electrode and the negative electrode so that the solid electrolyte is in contact with the electrode. The materials constituting the positive electrode and the negative electrode are not particularly limited, and can be appropriately selected from materials known as electrode materials for lithium-ion secondary batteries. For example, a metal foil such as aluminum or stainless steel can be used as the positive electrode current collector. A metal foil such as copper foil or lithium foil can be used as the negative electrode current collector.

[0108] In the lithium ion secondary battery of the present disclosure, the solid electrolyte is formed using a molecular crystalline electrolyte containing an organic molecule (M) and an alkali metal salt, and a (meth)acrylate-based crosslinked polymer (Y). The thickness of the solid electrolyte is not particularly limited and can be appropriately set depending on the application of the secondary battery, etc. The thickness of the solid electrolyte is, for example, 5 to 500 μm.

[0109] The method for producing a lithium ion secondary battery is not particularly limited, and known methods can be appropriately adopted depending on the battery structure, etc. For example, a laminate including a positive electrode, a solid electrolyte, and a negative electrode may be produced by annealing a molded body formed using a molecular crystalline electrolyte and a (meth)acrylate-based crosslinked polymer (Y) and sandwiching the resulting solid electrolyte between a positive electrode and a negative electrode. Alternatively, a laminate including a positive electrode, a solid electrolyte, and a negative electrode may be produced by sandwiching an electrolyte material including a molecular crystalline electrolyte and a (meth)acrylate-based crosslinked polymer (Y) between a positive electrode and a negative electrode in a container and then annealing the container. A laminate including a positive electrode, a solid electrolyte, and a negative electrode is usually housed in a case and used as a secondary battery.

[0110] The device is not limited to the above-described configuration in which the carrier for ion conduction is lithium ions, and may be a secondary battery in which other ions, such as sodium ions, are used as carriers. The device may also be a capacitor. One embodiment of the capacitor includes an anode body, a cathode body, and a solid electrolyte, with the solid electrolyte disposed between the anode body and the cathode body so that the solid electrolyte is in contact with the electrode.

[0111] The power storage device including the solid electrolyte can be used for a variety of purposes, specifically as a power source for various mobile devices such as mobile phones, personal computers, smartphones, game consoles, and wearable devices; various moving objects such as electric vehicles, hybrid vehicles, robots, and drones; and various electric and electronic devices such as digital cameras, video cameras, music players, power tools, and home appliances.

[0112] The present disclosure will be specifically described below based on examples. However, the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0113] <<Production and structural confirmation of molecular crystal electrolyte>> [Production Example 1] 1. Production of molecular crystals In a dry room where the dew point was maintained below -40 ° C., lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) as an alkali metal salt and succinonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) as an organic molecule were weighed out in a molar ratio of 1: 2, and 0.2156 g of lithium bis(fluorosulfonyl)imide and 0.1846 g of succinonitrile were mechanically mixed for 5 minutes at room temperature (25 ° C.) using a mortar to obtain a mixture (mechanical mixing step). The melting point of the mixture was measured using a differential scanning calorimeter (TA Instruments, DSC250, measurement atmosphere: nitrogen atmosphere) at a heating rate of 10 ° C. per minute, and a large endothermic peak (melting point) was observed at 60 ° C. Note that although succinonitrile before mixing exhibited plasticity, the mixture did not exhibit plasticity. The mixture was transferred to a vial and stirred with a magnetic stirrer at a set temperature of 70°C for 1 hour, and it was confirmed that the mixture was dissolved uniformly (heating step). Thereafter, the resulting melt was allowed to cool to room temperature, and a white solid was obtained.

[0114] 2. Confirmation of Crystallinity by Powder X-ray Diffraction Measurement The obtained white solid was subjected to powder X-ray diffraction measurement using an X-ray diffractometer (D8 ADVANCE, manufactured by Bruker AXS). CuKα was used as the X-ray source, with an applied voltage of 40 kV and a current of 40 mA. The measurement range was 2θ = 5-60 deg, the scanning speed was 2.3 deg / min, and the step angle was 0.02 deg. If an X-ray diffraction spectrum having a sharp peak at an angle within the measurement range is observed, this indicates that the measured sample (solid) is crystalline. Therefore, if an X-ray diffraction spectrum having a sharp peak at an angle within the measurement range and different from that of the organic molecule and alkali metal salt used as raw materials is obtained, it can be determined that molecular crystals composed of organic molecules and alkali metal salts have been formed. Powder X-ray diffraction measurement was performed on the white solid obtained as described above, and an X-ray diffraction spectrum having a sharp peak at an angle within the measurement range and different from that of the raw material was observed. From this, it can be seen that the obtained white solid has crystallinity, that is, molecular crystal (this is called "Li(FSI)(SN) ２In the composition formula of the molecular crystal of Production Example 1, bis(fluorosulfonyl)imide anion is abbreviated as FSI, and succinonitrile is abbreviated as SN.

[0115] 3. Confirmation of Crystalline Phase by Differential Scanning Calorimetry (DSC Measurement) The obtained white solid was subjected to DSC measurement using a differential scanning calorimeter (TA Instruments, DSC250, measurement atmosphere: nitrogen atmosphere) in the range of -80°C to 100°C at a heating rate of 10°C per minute. According to Timmermans' empirical rule, the entropy of fusion is 20 JK. －１ mol －１ If the melting point is smaller than 100°C, the substance has a plastic crystalline phase and can be said to be a plastic crystal. As a result of DSC measurement, an endothermic peak (melting point) was observed around 60°C (confirmed by visual observation). The melting entropy was calculated to be 110.97 JK －１ mol －１ Therefore, Li(FSI)(SN) ２ It was confirmed that the material does not have a plastic crystal phase and is not a plastic crystal.

[0116] [Production Example 2] A molecular crystal (Li(FSI)(SL)) was obtained by the same procedure as in Production Example 1, except that the types and amounts of raw materials and the heating temperature in the heating step were changed as shown in Table 1. In the composition formula of the molecular crystal of Production Example 2, bis(fluorosulfonyl)imide anion is abbreviated as FSI and tetrahydrothiophene 1,1-dioxide is abbreviated as SL. The obtained molecular crystal was subjected to DSC measurement in the same manner as in Production Example 1, and it was confirmed that Li(FSI)(SL) did not have a plastic crystal phase and was not a plastic crystal.

[0117]

[0118] <<Production and Evaluation of Solid Electrolyte>> [Example 1] (Preparation of Curable Composition for Solid Electrolyte) Li(FSI)(SN) was used as a molecular crystal. ２(Production Example 1 above), 0.2702 g, 0.0227 g, 0.0057 g, and 0.0029 g of n-butyl acrylate (manufactured by Toagosei Co., Ltd.) as a monofunctional (meth)acrylic monomer, Light Acrylate HPP-A (manufactured by Kyoeisha Chemical Co., Ltd.) as a polyfunctional (meth)acrylic monomer (crosslinkable monomer), and 2-hydroxy-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization initiator were weighed out and transferred to a vial to obtain a mixture. Next, the mixture was stirred for 30 minutes with a magnetic stirrer set at 70°C, and a solid electrolyte composition A1 was obtained as a solution in which the mixture was uniformly dissolved.

[0119] (Production of Solid Electrolyte) A mold with a 6 mm diameter circular hole in a 0.3 mm thick silicone rubber sheet was attached to a 1 cm x 1 cm x 1 mm stainless steel plate, and the warm solid electrolyte composition A1 was poured into the hole. A PET film (38 μm thick) was then placed over the hole to prevent air bubbles from forming. Two 1 mm thick slide glasses (manufactured by Matsunami Glass Industry Co., Ltd., white slide glass S1112) were sandwiched between the top and bottom of the film, and the whole was fixed with clips. When the solid electrolyte composition A1 cooled to room temperature, crystals were precipitated. Next, ultraviolet light with a wavelength of 365 nm (illuminance 60 mW / cm) was applied from the PET film side using an ultraviolet irradiation device (ultraviolet curing device manufactured by Minaga Electric Mfg. Co., Ltd., mercury xenon lamp, lamp height 10 mm). ２ ) for 360 seconds (cumulative light dose of 21.6 J / cm ２ ), and solid electrolyte B1 (thickness 300 μm) was obtained as a cured product by irradiation with active energy rays. An ultraviolet integrating actinometer [UV Power Puck II (center wavelength of light receiving part: 355 nm) manufactured by EIT Corporation] was used to measure the illuminance. The reaction rate of the monofunctional (meth)acrylic monomer and the crosslinkable monomer was >96%. The slide glass, PET film, and silicone rubber sheet were removed, and a test piece was obtained in which solid electrolyte B1 was formed into a circular shape on a stainless steel plate. Solid electrolyte B1 was cloudy, and XRD measurement revealed that the Li(FSI)(SN) obtained in Production Example 1 ２It was confirmed that the diffraction pattern was at the same position as the diffraction pattern of the molecular crystals of 1. From this result, it can be said that in the cured product of the solid electrolyte composition A1 (i.e., solid electrolyte B1), the molecular crystals that had once dissolved by heating were cooled to room temperature and went through the curing reaction of the monofunctional (meth)acrylic monomer and the crosslinkable monomer, and then precipitated again as molecular crystals.

[0120] (Measurement of Ionic Conductivity) Using the solid electrolyte B1 as a sample for measuring ionic conductivity, the ionic conductivity was measured according to the following formula (1): σ = L / (R × S) (1) (In formula (1), σ is the ionic conductivity (unit: S / cm), R is the resistance (unit: Ω), and S is the cross-sectional area of ​​the composite electrolyte at the time of measurement (unit: cm ２ ), and L represents the distance between the electrodes (unit: cm). The ionic conductivity of solid electrolyte B1 was measured at 25°C and found to be 2.5 × 10 －５ S / cm.

[0121] (Evaluation of Flexibility) Solid electrolyte B1 was used as a sample pellet for evaluating flexibility, and was wound around a polyethylene round rod with a diameter of 20 mm. The state of the bent sample pellet was observed, and the flexibility was evaluated according to the following criteria. As a result, the sample pellet showed no abnormal appearance even when bent, and was judged to be "Good". This confirmed that solid electrolyte B1 has flexibility. Good: No abnormal appearance was observed in the sample pellet. Fair: Fine cracks were observed in the sample pellet. Bad: Clear cracks were observed in the sample pellet, or part of the sample pellet peeled off.

[0122] [Examples 2 to 12] Solid electrolytes were obtained by the same procedure as in Example 1, except that the types and amounts of raw materials were changed as shown in Table 2. In Examples 2 to 4 and 10 to 12, precipitation of crystals was observed after the solid electrolyte composition was cooled to room temperature, while in Examples 5 to 9, precipitation of crystals was not observed after the solid electrolyte composition was cooled to room temperature. Using the solid electrolyte of each Example, measurement of ionic conductivity at 25°C and evaluation of flexibility were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0123] Comparative Example 1 In a dry room where the dew point was maintained at -40°C or less, 0.4119 g of poly(ethylene oxide) (manufactured by Thermo Scientific) was weighed into a vial as a polymer, and 2.0 g of acetonitrile (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added thereto. The vial was stirred for 60 hours using a mix rotor to dissolve the poly(ethylene oxide). 0.0879 g of lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) was added as an alkali metal salt, and 0.0879 g of Lithium bis(fluorosulfonyl)imide was added thereto. ＋ The resulting mixture was weighed out so that the molar ratio of ethylene oxide units in the poly(ethylene oxide) and the lithium bis(fluorosulfonyl)imide was 1:20. The mixture was added to a vial and stirred at room temperature for 1 hour using a magnetic stirrer, resulting in a mixture in which lithium bis(fluorosulfonyl)imide was uniformly dissolved. The mixture was cast onto a Teflon (registered trademark) Petri dish, heated on a hot plate at 90°C for 5 hours, and then vacuum-dried in a vacuum oven at 90°C for 24 hours to obtain a flexible solid electrolyte. The resulting solid electrolyte was subjected to measurement of ionic conductivity at 25°C and an evaluation test for flexibility. The ionic conductivity was measured using the following procedure, and the evaluation test for flexibility was performed in the same manner as in Example 1. The results are shown in Table 2. (Ionic Conductivity Measurement) The solid electrolyte was punched out using a punch and hammer to obtain circular sample pellets with a diameter of 10 mm and a thickness of 264 μm. The sample pellets were then encapsulated in an all-solid-state battery evaluation cell (KP-SolidCell, manufactured by Hosen Co., Ltd.). Ionic conductivity was measured using the all-solid-state battery evaluation cell encapsulating the sample pellets. In measuring the ionic conductivity, first, the resistance value was measured by AC impedance measurement while the all-solid-state battery evaluation cell containing the sample pellets was heat-treated in a thermostatic bath at 55°C. The resistance value decreased with the heat treatment time, and the heat treatment was terminated when it became constant. Next, the resistance value at 25°C was measured by AC impedance measurement. Using the obtained resistance value, the ionic conductivity (σ) was calculated according to the above formula (1). The AC impedance measurement for calculating the ionic conductivity was performed after the cell was held at the measurement temperature in the thermostatic bath for 2 hours.

[0124] [Comparative Example 2] A press die 10 consisting of a die set 11, an upper punch 12, and a lower punch 13 (see FIG. 1) was used. ２ Sample pellets were prepared using the above-mentioned Preparation Example 1 as a raw material. First, solid Li(FSI)(SN) ２ A die set 11 containing 0.0600 g of the ionic conductivity was placed on the lower punch 13, and the upper punch 12 was placed on the die set. The raw material was compressed for 1 minute at a pressure of 10 MPa using a hydraulic press to obtain circular sample pellets with a diameter of 10 mm and a thickness of 498 μm. Ionic conductivity measurements were performed using an all-solid-state battery evaluation cell containing the obtained sample pellets. To measure ionic conductivity, first, the resistance value was measured by AC impedance measurement while the all-solid-state battery evaluation cell containing the sample pellets was heat-treated in a thermostatic bath at 40°C. The resistance value decreased with heat treatment time and was terminated when it reached a constant value. Next, the resistance value at 25°C was measured by AC impedance measurement. The obtained resistance value was used to calculate the ionic conductivity (σ) using the above formula (1). The AC impedance measurement for calculating ionic conductivity was performed after the cell was held at the measurement temperature in a thermostatic bath for 2 hours. The ionic conductivity measurement results are shown in Table 2. Furthermore, a flexibility evaluation test was performed using the sample pellets prepared by the above method in the same manner as in Example 1. The results are shown in Table 2.

[0125] [Comparative Example 3] Li(FSI)(SN) as raw material ２ Instead of Li(FSI)(SL) (Production Example 2), sample pellets were prepared and enclosed in all-solid-state battery evaluation cells. AC impedance measurements were performed in the same manner as in Comparative Example 2, except that the heat treatment temperature was changed to 50°C. The results of the ionic conductivity measurements are shown in Table 2. In addition, a flexibility evaluation test was performed in the same manner as in Example 1 using the sample pellets prepared by the above method. The results are shown in Table 2.

[0126]

[0127] Details of the compounds used in Tables 1 and 2 are shown below. LiFSI: lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) SN: succinonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) SL: tetrahydrothiophene 1,1-dioxide (manufactured by Tokyo Chemical Industry Co., Ltd.) BA: n-butyl acrylate (manufactured by Toagosei Co., Ltd.) SBM23: 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propane-1-sulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) GCA: mixture of (2-oxo-1,3-dioxolan-4-yl)methyl acrylate and multifunctional acrylate (GPC area ratio of 2-oxo-1,3-dioxolan-4-yl)methyl acrylate and multifunctional acrylate = 90.05 / 9.95). The polyfunctional acrylate includes glycerin diacrylate, glycerin triacrylate, and an oligomer component having two or more acryloyl groups, and the area ratio of these is 0.03 / 6.74 / 3.18. HPP-A: Light acrylate HPP-A (manufactured by Kyoeisha Chemical Co., Ltd.). HMP: 2-hydroxy-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.). PEO: Poly(ethylene oxide) (manufactured by Thermo Scientific).

[0128] <Evaluation Results> As is clear from the results of Examples 1 to 12, the solid electrolytes containing the molecular crystal (X) and the (meth)acrylic crosslinked polymer (Y) exhibited high ionic conductivity and flexibility. In contrast, the solid electrolyte of Comparative Example 1, which contained an ether-based polymer and an alkali metal salt, exhibited flexibility but low ionic conductivity. Furthermore, the solid electrolytes of Comparative Examples 2 and 3, which were composed only of molecular crystals, exhibited high ionic conductivity but did not exhibit flexibility.

[0129] From the above results, it has become clear that a solid electrolyte containing a molecular crystal (X) and a (meth)acrylic crosslinked polymer (Y) has high ionic conductivity and flexibility. By using the solid electrolyte of the present disclosure having such properties as an electrolyte material for an electricity storage device, the electricity storage device can be easily handled during production, and can also follow bending when a bending force is applied to the electricity storage device. Therefore, by using the solid electrolyte of the present disclosure, it is possible to obtain an electricity storage device that is less likely to be damaged or its performance to be reduced even when an external force is applied to the electricity storage device, and that is highly safe.

[0130] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

[0131] 10... Press mold

Claims

1. A solid electrolyte comprising: a molecular crystal containing an organic molecule having at least one atom selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms, and an alkali metal salt; and a (meth)acrylic crosslinked polymer that is substantially free of structural units derived from a (meth)acrylate having an ether group (excluding ether groups in heterocycles).

2. The solid electrolyte according to claim 1, wherein a mass ratio of the molecular crystals to the (meth)acrylic crosslinked polymer (molecular crystals / (meth)acrylic crosslinked polymer) is 90 / 10 to 10 / 90.

3. The solid electrolyte according to claim 1, wherein the (meth)acrylic crosslinked polymer contains a structural unit derived from a monofunctional (meth)acrylate having no ether group (excluding an ether group in a heterocycle).

4. The solid electrolyte according to claim 1, wherein the (meth)acrylic crosslinked polymer contains a structural unit derived from a polyfunctional (meth)acrylate having no ether group (excluding an ether group in a heterocycle).

5. The solid electrolyte according to claim 4, wherein the polyfunctional (meth)acrylate contains a compound represented by the following formula (1): (In formula (1), W １ and W ２ each independently represents a hydrogen atom or a methyl group; X １ , X ２ , Y and Z each independently represent an alkylene group having 2 to 6 carbon atoms; １ and E ２ each independently represents an ester bond, and m and n each independently represent an integer of 0 to 5.

6. The solid electrolyte according to claim 1, wherein the organic molecule is at least one selected from the group consisting of nitrile compounds and sulfone compounds.

7. The solid electrolyte of claim 1, wherein the alkali metal salt comprises an imide-based alkali metal salt.

8. A curable composition used in the production of a solid electrolyte, comprising: a molecular crystal containing at least one organic molecule selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms, and an alkali metal salt; a monofunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring); and a polyfunctional (meth)acrylate having no ether group (excluding ether groups in a heterocyclic ring).

9. The curable composition according to claim 8, wherein the polyfunctional (meth)acrylate comprises a compound represented by the following formula (1): (In formula (1), W １ and W ２ each independently represents a hydrogen atom or a methyl group; X １ , X ２ , Y and Z each independently represent an alkylene group having 2 to 6 carbon atoms; １ and E ２ each independently represents an ester bond, and m and n each independently represent an integer of 0 to 5.

10. The curable composition according to claim 8, further comprising a polymerization initiator.

11. The curable composition according to claim 8, which is an active energy ray curable type.

12. A solid electrolyte which is a cured product of the curable composition according to any one of claims 8 to 11.

13. An electricity storage device comprising the solid electrolyte according to any one of claims 1 to 7.

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