Solid electrolyte and power storage device

Abstract

A solid electrolyte according to the present invention contains: a molecular crystal that includes, as constituent units, an organic molecule that includes at least one type of atom selected from the group that consists of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorous atoms and an alkali metal salt; and a non-crosslinked polymer that has a principal chain that does not substantially include a repeating unit represented by -(R-O)- (in which R is an alkylene group).

Description

Solid electrolytes and energy storage devices

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Japanese Patent Application No. 2024-105384, filed on June 28, 2024, the entire contents of which are incorporated herein by reference. The present disclosure relates to solid electrolytes and electricity storage devices.

[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. Conventionally, nonaqueous electrolytes have been used primarily as the electrolyte. However, nonaqueous electrolytes contain flammable organic solvents, which raise concerns about electrolyte leakage and short-circuiting within the battery due to overcharging and overdischarging.

[0004] In response to this, solid electrolytes using organic materials instead of organic electrolytes have been proposed in recent years as a technology to eliminate concerns about electrolyte leakage and short circuits inside batteries due to overcharging and overdischarging. For example, crystalline organic solid electrolytes have the advantage of having plastic deformability and excellent adhesion to electrodes because alkali metal salts and organic molecules are bonded through relatively weak intermolecular interactions such as hydrogen bonds, electrostatic interactions, and van der Waals forces. On the other hand, crystalline organic solid electrolytes tend to have lower ionic conductivity than inorganic solid electrolytes. Therefore, various studies have been conducted to develop new materials for organic solid electrolytes in order to improve their practicality (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 polymer crosslinked 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. 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 described in Non-Patent Document 1 has poor bendability due to its regular crystalline structure and insufficient ionic conductivity at room temperature. In particular, when a solid electrolyte layer is produced using the crystalline organic solid electrolyte as a raw material, for example, by powder compaction, cracks are likely to occur at the crystal interface, resulting in poor handleability. From the perspective of obtaining a high-performance electricity storage device that can easily produce a solid electrolyte layer and is resistant to damage and 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 also having good flexibility, and another object to provide an electricity storage device including the solid electrolyte.

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a solid electrolyte containing a molecular crystal containing a specific organic molecule and an alkali metal salt as structural units in a crystal lattice, as well as a specific polymer, exhibits high ionic conductivity at room temperature and also has good flexibility. That is, according to the present disclosure, the following solid electrolyte and electricity storage device are provided.

[0011] [1] A solid electrolyte comprising a molecular crystal containing, as structural units, 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, and a non-crosslinked polymer having substantially no repeating unit represented by -(R-O)- (wherein R is an alkylene group) in its main chain. [2] A solid electrolyte comprising: a molecular crystal having an entropy of fusion of 20JK －１ mol －１ or more. [3] The solid electrolyte according to [1] or [2], wherein the mass ratio of the molecular crystal to the non-crosslinked polymer (molecular crystal / non-crosslinked polymer) is 99 / 1 to 50 / 50, where the total amount of the molecular crystal and the non-crosslinked polymer is 100. [4] The solid electrolyte according to any one of [1] to [3], wherein the weight average molecular weight of the non-crosslinked polymer is 2,500 to 1,000,000. [5] The solid electrolyte according to any one of [1] to [4], wherein the organic molecule is at least one selected from the group consisting of sulfone, nitrile, and amide. [6] The solid electrolyte according to any one of [1] to [4], wherein the counter anion constituting the alkali metal salt is (FSO ２ ) ２ N － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) (CF ３ SO ２ ) N － , P.F. ６ － or BF ４ － [7] An electricity storage device comprising the solid electrolyte according to any one of [1] to [6].

[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 high 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 composite electrolyte and the 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): molecular crystal Component (Y): non-crosslinked polymer having substantially no repeating unit represented by -(R-O)- (wherein R is an alkylene group) in its main chain. Each component contained in the solid electrolyte of the present disclosure will be described in detail below. Note that, unless otherwise specified, each component may be contained alone or in combination of two or more.

[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 contains 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. That is, the molecular crystal (X) contains the organic molecule (M) and the alkali metal salt as structural units of the crystal.

[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 formed when the organic molecules and alkali metal salts are in a specific molar ratio. The molecular crystal (X) has ion conduction paths due to the regular arrangement of the structural units, and is thought to exhibit excellent ion conductivity due to carrier hopping conduction through the ion conduction paths.

[0018] The fact that a substance containing an organic molecule (M) and an alkali metal salt as structural units is a molecular crystal and not a plastic crystal can be evaluated by combining analysis of the X-ray diffraction spectrum and measurement of the entropy of fusion. Specifically, this is as follows.

[0019] (Analysis of X-ray diffraction spectrum) When an X-ray diffraction spectrum is obtained that has a sharp peak in the angle measurement range (2θ=5-60 deg) and is different from the organic molecule and alkali metal salt used as raw materials (however, if the organic molecule used as raw material is liquid at room temperature, the X-ray diffraction spectrum will be different from that of the alkali metal salt), it can be determined that a molecular crystal containing an organic molecule and an alkali metal salt has been produced. Details of the measurement method follow the method described in the Examples below.

[0020] (Measurement of Entropy of Fusion) According to Timmermans' empirical rule, the entropy of fusion is 20 JK. －１ mol －１ On the other hand, if the entropy of fusion of a material containing organic molecules and alkali metal salts is 20 JK, the material has a plastic crystalline phase and can be evaluated as a plastic crystal. －１ mol －１ If the above is true, it can be determined that the substance does not have a plastic crystal phase and is not a plastic crystal. In other words, plastic crystals transition from a crystalline phase to a liquid phase via a plastic crystal phase when melted, whereas molecular crystals have the property of directly transitioning from a crystalline phase to a liquid phase when melted, and the two are different substances. The fusion entropy of a substance can be measured by differential scanning calorimetry (DSC measurement). Details of the measurement method follow the method described in the examples below.

[0021] The ratio of the organic molecule (M) to the alkali metal salt contained in the molecular crystal (X) is not particularly limited, as long as a mixture of the organic molecule (M) and the alkali metal salt constitutes a molecular crystal. 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.

[0022] (Organic Molecules (M)) The number of organic molecules (M) constituting the molecular crystal is not particularly limited. The organic molecules (M) constituting the molecular crystal may be one type alone or a combination of two or more types.

[0023] The number of atoms of at least one kind selected from the group consisting of sulfur atoms, oxygen atoms, nitrogen atoms, and phosphorus atoms (the total number when two or more kinds are present) contained in the organic molecule (M) is not particularly limited. In the organic molecule (M), the number of atoms of at least one kind 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 two or more, and more preferably two to six, of at least one kind of atom selected from sulfur atoms, oxygen atoms, and nitrogen atoms per molecule.

[0024] 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.

[0025] 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. Organic molecules having a nitrogen atom, such as nitrile compounds, amine compounds, and amide compounds. Organic molecules having a phosphorus atom, such as phosphine compounds, phosphine oxide compounds, and phosphinimine compounds. Organic molecules having an oxygen atom, such as 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, include ether compounds, ester compounds, ketone compounds, and carbonate compounds.

[0026] In terms of being able to further increase the ionic conductivity of the molecular crystal, the organic molecule (M) is preferably at least one selected from the group consisting of organic molecules having a sulfur atom and an oxygen atom, organic molecules having a nitrogen atom, and organic molecules having a phosphorus atom.

[0027] (Organic molecule having sulfur atom and oxygen atom) As the organic molecule having sulfur atom and oxygen atom, sulfone can be preferably used. Preferred examples of sulfone include those represented by the following formula (1): (In formula (1), R １ and R ２ are each independently an alkyl group or an alkoxy group, or R １ and R ２ and bond to form a cyclic structure, and the total number of carbon atoms in formula (1) is 2 to 16.

[0028] The molecule represented by the above formula (1) (hereinafter also referred to as "organic molecule (M-1)") has a sulfonyl group (-SO ２ -) in the above formula (1). 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 the organic molecule (M-1) as long as the total number of carbon atoms in the organic molecule (M-2) and the alkali metal salt is 2 to 16. From the viewpoint of inducing crystallization in the mixture of the organic molecule (M-1) 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.

[0029] R in the above formula (1) １ and R ２ But, R １ and R ２ When R is bonded to form a ring structure, the ring structure may have a saturated ring skeleton or may have an unsaturated bond in the ring skeleton. １ and R ２ The number of carbon atoms in the ring 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 structure formed by bonding the above may have an alkyl group (for example, a methyl group or an ethyl group) bonded to the ring skeleton.

[0030] The R in the above formula (1) is preferable in that it can make the ionic conductivity of the molecular crystal (X) more excellent. １ and R ２ is R １ and R ２ and more preferably, the cyclic structure has a saturated ring skeleton.

[0031] The total number of carbon atoms in the above formula (1) is 2 to 16. From the viewpoint of promoting crystallization of the mixture of the organic molecule (M-1) and the alkali metal salt, the total number of carbon atoms in the above formula (1) is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 5.

[0032] Specific examples of the organic molecule (M-1) include R １ 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 compounds that bond to form a cyclic structure include tetrahydrothiophene 1,1-dioxide (sulfolane), 3-methylsulfolane, 3-sulfolene, 1,3-propane sultone, 1,4-butane sultone, and 1,3,2-dioxathiolane 2,2-dioxide.

[0033] (Nitrogen Atom-Containing Organic Molecule) As the nitrogen atom-containing organic molecule, at least one selected from the group consisting of compounds having a nitrile group and an amide group can be preferably used.

[0034] Preferred examples of the nitrile include those represented by the following formula (2): (In formula (2), 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 (2) is 16 or less.

[0035] The molecule represented by the above formula (2) (hereinafter also referred to as "organic 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.

[0036] R ４ or R ５When R is an alkyl group, the alkyl group may be linear or branched. ４ and R ５ The number of carbon atoms in each group is preferably 0 to 3, more preferably 0 or 1, from the viewpoint of causing crystallization by mixing the organic molecule (M-2) with an alkali metal salt.

[0037] The total number of carbon atoms in the above formula (2) may be 16 or less. From the viewpoint of promoting crystallization of the mixture of the organic molecule (M-2) and the alkali metal salt, the total number of carbon atoms in the above formula (2) is preferably 8 or less, more preferably 6 or less.

[0038] Specific examples of the organic molecule (M-2) include succinonitrile, adiponitrile, 3-hexenedinitrile, 1,3,5-pentanetricarbonitrile, tert-butylmalononitrile, and 1,2,2,3-propanetetracarbonitrile.

[0039] The organic molecule having an amide group preferably has two or more amide groups in one molecule in terms of high heat resistance. Specific examples of the organic molecule having an amide group include malonamide, succinamide, glutaramide, adipamide, N,N,N',N'-tetramethylmalonamide, N,N,N',N'-tetraethylmalonamide, N,N,N',N'-tetramethylsuccinamide, and terephthalamide.

[0040] (Organic Molecule Having a Phosphorus Atom) Specific 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.

[0041] From the viewpoint of ease of production of molecular crystals, at least one selected from the group consisting of sulfones, nitriles, and amides can be preferably used as the organic molecule (M). In addition, the organic molecule (M-2) is more preferred in that a solid electrolyte having superior ionic conductivity can be obtained while improving the flexibility of the solid electrolyte by combining a non-crosslinked polymer with a molecular crystal. ３ Preferably, represents a saturated hydrocarbon chain.

[0042] Alkali Metal Salt The alkali metal salt is not particularly limited as long as it generates alkali metal ions. Examples of the alkali metal salt include lithium salt, sodium salt, and potassium salt.

[0043] 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(oxalate)borate, imide-based lithium salts, and the like; and salts of the anions of these lithium salts with alkali metal ions other than lithium ions (for example, sodium ions, potassium ions, etc.).

[0044] The imide-based lithium salt is a lithium salt containing an imide-based anion as a counter anion. Specific examples of the imide-based lithium salt include lithium bis(fluorosulfonyl)imide (Li ＋ (FSO ２ ) ２ N － ), lithium bis(trifluoromethanesulfonyl)imide (Li ＋ (CF ３ SO ２ ) ２ N－ ), lithium (fluorosulfonyl) (trifluoromethanesulfonyl) imide, and the like.

[0045] Among these, the alkali metal salt constituting the molecular crystal is preferably a lithium salt or a sodium salt, more preferably a lithium salt, in that it is possible to obtain a molecular crystal having high ionic dissociation property and higher ionic conductivity. ６ or LiBF ４ In terms of higher ion dissociation, the counter anion constituting the alkali metal salt is preferably (FSO ２ ) ２ N － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) (CF ３ SO ２ ) N － , P.F. ６ － or BF ４ － It is preferable that:

[0046] 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.

[0047] 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. The alkali metal salt constituting the molecular crystal may be one type alone or two or more types.

[0048] The melting point of the alkali metal salt 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.

[0049] 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 invention 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.

[0050] (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.

[0051] 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.

[0052] 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, so as to obtain a molecular crystal containing the organic molecule (M) and the alkali metal salt as structural units. 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.

[0053] 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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 has 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.

[0061] 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.

[0062] The method for producing the molecular crystal (X) is not limited to the above. For example, the molecular crystal (X) may be produced by the method of heating and mixing the organic molecule (M) and the alkali metal salt without performing mechanical mixing in the first production method described above.

[0063] The fact that the product obtained by the above-mentioned production method is a molecular crystal containing an organic molecule (M) and an alkali metal salt as structural units and is not a plastic crystal can be evaluated by combining powder X-ray diffraction measurement of the product and measurement of the entropy of fusion. Details of the measurement method follow the method described in the Examples below.

[0064] The molecular crystal contained in the solid electrolyte of the present disclosure exhibits ionic conductivity. Specifically, the ionic conductivity of the molecular crystal at 25° C. is 1.0×10 －５ It is preferable that the ionic conductivity of the molecular crystal at 25° C. is 1.0×10 S / cm or more. －５ In order to obtain a solid electrolyte having excellent ionic conductivity, the ionic conductivity of the molecular crystal at 25° C. is preferably 1.5×10 S / cm or more. －５ S / cm or more, and －５ S / cm or more, and more preferably 3.0×10 －５ It is more preferable that the ionic conductivity of the molecular crystal is 25 S / cm or more. The ionic conductivity of the molecular crystal is a value measured at 25°C using an AC impedance method. The details of the method for measuring the ionic conductivity follow the method described in the examples below.

[0065] In the solid electrolyte of the present disclosure, the content of the molecular crystals is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total amount of the solid electrolyte, from the viewpoint of obtaining a solid electrolyte exhibiting good ionic conductivity. The upper limit of the content of the molecular crystals is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less, based on the total amount of the solid electrolyte, from the viewpoint of ensuring the flexibility of the solid electrolyte.

[0066] <Component (Y): Non-Crosslinked Polymer> The non-crosslinked polymer contained in the solid electrolyte of the present disclosure is a polymer that exhibits ionic conductivity in the presence of a molecular crystalline electrolyte and that does not substantially have a repeating unit represented by -(R-O)- (where R is an alkylene group) in its main chain. It is believed that using a non-crosslinked polymer as a binder can make the molecular motion of the polymer more active, making it easier to form ion conduction paths in the solid electrolyte, thereby improving the ionic conductivity of the solid electrolyte.

[0067] Here, the polymer having a repeating unit represented by -(R-O)- in the main chain is typically a polymer obtained by polymerization using alkylene oxides or cyclic ethers as a monomer, and -(R-O) ｒ The main chain of the solid electrolyte has a polyalkylene structure represented by the formula (where r is an integer of 2 or more). R generally has 2 or more carbon atoms, and may have 2 to 10 carbon atoms. In other words, the non-crosslinked polymer contained in the solid electrolyte of the present disclosure is a polymer different from polyether-based polymers such as polyalkylene oxides and polyethers.

[0068] In this specification, "substantially free of repeating units represented by -(R-O)- in the main chain" means that the non-crosslinked polymer does not exhibit properties derived from repeating units represented by -(R-O)-. However, it is acceptable for the non-crosslinked polymer to have a small amount of repeating units represented by -(R-O)- in the main chain to the extent that the effects of the present invention are not impaired. Specifically, the proportion of repeating units represented by -(R-O)- in the non-crosslinked polymer is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on the total amount of repeating units constituting the main chain of the non-crosslinked polymer. In addition, the non-crosslinked polymer does not have any repeating units represented by -(R-O)-. ｒ It is preferred that the main chain does not have a structure represented by - (where r is an integer of 2 or more).

[0069] A "repeating unit" is a basic unit of the chemical structure of a polymer, and the chemical formula of a polymer is expressed as an integer multiple of the number of repeating units. Basically, one molecule of a monomer introduces one repeating unit having a structure corresponding to that monomer into a polymer, or introduces a structure consisting of two or more consecutive repeating units into a polymer. In the latter case, the structure consisting of two or more consecutive repeating units corresponds to one molecule of the monomer.

[0070] As the non-crosslinked polymer, a polymer that exhibits higher ionic conductivity at room temperature (25°C) in the presence of a molecular crystalline electrolyte than an organic electrolyte consisting of a polyether polymer and a molecular crystalline electrolyte is preferably used. Examples of such non-crosslinked polymers include nitrile group-containing polymers, polyester polymers, polycarbonate polymers, fluorine-containing polymers, olefin polymers, (meth)acrylic polymers, and polyvinyl acetal polymers. Note that the non-crosslinked polymers may be used alone or in combination of two or more.

[0071] Nitrile Group-Containing Polymers Examples of nitrile group-containing polymers include polymers containing structural units derived from nitrile group-containing vinyl monomers. Examples of nitrile group-containing vinyl monomers include (meth)acrylonitrile, ethacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile. The nitrile group-containing polymer is preferably a polymer containing repeating units derived from (meth)acrylonitrile. In the nitrile group-containing polymer, the proportion of repeating units derived from (meth)acrylonitrile is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total repeating units constituting the nitrile group-containing polymer.

[0072] Polyester-Based Polymers Examples of polyester-based polymers include polymers containing a repeating unit represented by the following formula (3). (In formula (3), R ５ represents a hydrogen atom or an alkyl group, and m represents an integer of 0 to 10.

[0073] In the above formula (3), R ５ is preferably a hydrogen atom or a methyl group from the viewpoint of availability of raw materials and ease of synthesis of a polyester polymer. m is preferably 0 to 8, more preferably 0 to 6, and even more preferably 0 to 4, from the viewpoint of availability of raw materials. Furthermore, m is preferably 1 or more, more preferably 2 to 8, and even more preferably 2 to 6, in order to provide the resulting solid electrolyte with better ionic conductivity and flexibility.

[0074] Monomers used to introduce the repeating unit represented by formula (3) above into a polymer include lactones and lactides. Specific examples of these include lactones such as β-propiolactone, γ-butyrolactone, β-butyrolactone, pivalolactone, δ-valerolactone, and ε-caprolactone. Lactides include glycolide obtained by dehydration condensation of two glycolic acid molecules, dilactide obtained by dehydration condensation of two lactic acid molecules, and tetramethylglycolide. When the above lactides are used as monomers, a structure consisting of two consecutive repeating units represented by formula (3) above is introduced into the polymer per lactide molecule. That is, a structure consisting of two consecutive repeating units represented by formula (3) above corresponds to one lactide molecule.

[0075] Among the above, the monomer constituting the polyester polymer is preferably at least one selected from the group consisting of γ-butyrolactone, δ-valerolactone, ε-caprolactone, and dilactide, in that a composite electrolyte having superior ionic conductivity can be obtained.

[0076] The number of repeating units represented by formula (3) contained in the polyester polymer can be appropriately set depending on the desired molecular weight of the polyester polymer. The number of repeating units represented by formula (3) contained in the polyester polymer is, for example, 10 to 1,500, preferably 20 to 1,200, more preferably 30 to 1,000, and even more preferably 30 to 800.

[0077] The polyester polymer may further contain a repeating unit different from the repeating unit in formula (3) above, as long as the effects of the present invention are not impaired. Examples of the other repeating unit include dioxepanone, ethylene oxalate, dioxanone, γ-nonalactone, γ-decalactone, γ-undecalactone, cyclopentadecanolide, and cyclohexedecanolide.

[0078] In the polyester polymer, the proportion of the repeating units represented by the formula (3) is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, based on all repeating units constituting the polyester polymer. By setting the proportion of the repeating units represented by the formula (3) in the polyester polymer within the above range, a solid electrolyte with superior ionic conductivity can be obtained.

[0079] The polyester polymer may have a hydroxyl group or carboxyl group derived from the monomer at its terminal. Alternatively, the terminal of the polyester polymer may be modified by utilizing a hydroxyl group or carboxyl group present at the polymer terminal. By modifying the terminal hydroxyl group or terminal carboxyl group of the polyester polymer, it is possible to improve the heat resistance (durability) of the polyester polymer or reduce the crystallinity of the polyester polymer. When the terminal structure of the polyester polymer is an alkyl group, the alkyl group is preferably a linear or branched alkyl group having 3 to 20 carbon atoms, from the viewpoint of improving the heat resistance of the polyester polymer and promoting a reduction in crystallinity.

[0080] The method for producing the polyester polymer is not particularly limited, and the polyester polymer can be produced by any conventionally known method. In terms of being able to produce the polyester polymer simply and inexpensively, it is preferred to produce the polyester polymer by ring-opening polymerization using at least one monomer selected from the group consisting of the lactones and lactides described above.

[0081] Polycarbonate-Based Polymers Examples of polycarbonate-based polymers include polymers containing a repeating unit represented by the following formula (4). (In formula (4), R ６ represents an alkylene group.)

[0082] In the above formula (4), R ６ The carbon number is preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 6, in terms of the ease of availability of raw materials and the ability to provide the resulting solid electrolyte with better ionic conductivity and flexibility.

[0083] The number of repeating units represented by the formula (4) contained in the polycarbonate polymer can be appropriately set depending on the desired molecular weight of the polycarbonate polymer. The number of repeating units represented by the formula (4) contained in the polycarbonate polymer is, for example, 10 to 1,500, preferably 20 to 1,200, more preferably 30 to 1,000, and even more preferably 30 to 800.

[0084] In the polycarbonate-based polymer, the proportion of the repeating unit represented by the above formula (4) is preferably 80 mass% or more, more preferably 85 mass% or more, even more preferably 90 mass% or more, and even more preferably 95 mass% or more, based on the total repeating units constituting the polycarbonate-based polymer. By setting the proportion of the repeating unit represented by the above formula (4) in the polycarbonate-based polymer within the above range, a solid electrolyte with superior ion conductivity can be obtained. The polycarbonate-based polymer may further have a repeating unit different from the repeating unit in the above formula (4) (for example, a repeating unit derived from bisphenol A) within a range that does not impair the effects of the present invention.

[0085] The method for producing the polycarbonate polymer is not particularly limited, and the polycarbonate polymer can be produced by any conventionally known method. For example, the polycarbonate polymer can be produced by using a dihydroxy compound as a raw material and a phosgene method or an ester exchange method.

[0086] Fluorine-containing polymer The fluorine-containing polymer may be a polymer containing a repeating unit having a fluorine atom. As the fluorine-containing polymer, a polymer containing carbon atoms in the main skeleton and having fluorine atoms bonded to the carbon atoms can be preferably used. Specifically, the fluorine-containing polymer preferably contains a repeating unit represented by the following formula (5) as the repeating unit having a fluorine atom: -[CR ７ R ８ -CFR ９ ]-(5) (In formula (5), R ７ , R ８ and R ９are each independently a hydrogen atom, a fluorine atom, a chlorine atom, an alkyl group having 1 to 3 carbon atoms, a perfluoroalkyl group having 1 to 3 carbon atoms, or a perfluoroalkyloxy group having 1 to 3 carbon atoms.

[0087] Specific examples of the repeating unit represented by the above formula (5) include -[CH ２ -CHF]-, -[CH ２ -CF ２ ]-,-[CHF-CF ２ ] -, -[CF ２ -CF ２ ] -, -[CF ２ -CFCF ３ ]-,-[CHF-CFCF ３ ] -, -[CF ２ -CF (OCF ３ ) )]-, -[CF ２ -CF(OC ２ F ５ ) )]-, -[CF ２ The repeating unit represented by the above formula (5) is, among these, -[CH ２ -CHF]-, -[CH ２ -CF ２ ]-,-[CHF-CF ２ ] -, -[CF ２ -CF ２ ] -, -[CF ２ -CFCF ３ ]- and -[CHF-CFCF ３ ]- is preferred.

[0088] In the fluorine-containing polymer, the proportion of the repeating units having fluorine atoms is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, based on the total repeating units constituting the fluorine-containing polymer. The fluorine-containing polymer may have only one kind of repeating unit having a fluorine atom, or may have two or more kinds of repeating units having a fluorine atom.

[0089] The fluorine-containing polymer may be composed solely of repeating units having fluorine atoms, or may further contain repeating units not having fluorine atoms. Specific examples of monomers constituting repeating units having no fluorine atoms include olefins such as ethylene, propylene, n-butene, and isobutene; carboxyl group-containing monomers such as (meth)acrylic acid, vinylacetic acid, and pentenoic acid; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, vinyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 2-hydroxyethyl allyl ether, and 4-hydroxybutyl allyl ether; amide group-containing monomers such as N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, and N-vinyl-γ-valerolactam; and ester group-containing monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, vinyl acetate, isopropenyl acetate, vinyl butyrate, vinyl isobutyrate, vinyl versatate, and vinyl benzoate.

[0090] Specific examples of the fluorine-containing polymer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride, polytrifluoroethylene, polypentafluoropropylene, vinylidene fluoride / hexafluoropropylene copolymer (PVDF-HFP), tetrafluoroethylene / hexafluoropropylene copolymer, vinylidene fluoride / tetrafluoroethylene copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / tetrafluoroethylene / hexafluoropropylene copolymer, polychlorotrifluoroethylene, chlorotrifluoroethylene / trifluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, vinylidene fluoride / hexafluoropropane / (meth)acrylic acid copolymer, and vinylidene fluoride / pentafluoropropylene copolymer.

[0091] Furthermore, a fluororubber may be used as the fluorine-containing polymer. Specific examples of the fluororubber include vinylidene fluoride rubber, tetrafluoroethylene / propylene rubber, tetrafluoroethylene / propylene / vinylidene fluoride rubber, and ethylene / hexafluoropropylene rubber.

[0092] Among the above, the fluorine-containing polymer is preferably at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride, polytrifluoroethylene, polypentafluoropropylene, vinylidene fluoride / hexafluoropropylene copolymer (PVDF-HFP), tetrafluoroethylene / hexafluoropropylene copolymer, and vinylidene fluoride / tetrafluoroethylene copolymer, and more preferably at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypentafluoropropylene, and vinylidene fluoride / hexafluoropropylene copolymer (PVDF-HFP).

[0093] Olefin-Based Polymers Examples of olefin-based polymers include polymers containing structural units derived from α-olefins having 2 to 20 carbon atoms. Specific examples include homopolymers of α-olefins having 2 to 20 carbon atoms and copolymers of α-olefins having 2 to 20 carbon atoms with other monomers. Specific examples of α-olefins having 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 4-methyl-1-hexene, 1-octene, 4,4-dimethyl-1-hexene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene.

[0094] In the olefin polymer, the proportion of structural units derived from α-olefins having 2 to 20 carbon atoms is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on all repeating units constituting the olefin polymer. The α-olefins constituting the olefin polymer may be one type or two or more types.

[0095] The olefin polymer may contain repeating units derived from other vinyl monomers in addition to repeating units derived from α-olefins. Examples of other vinyl monomers constituting the olefin polymer include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half esters or half amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-aconitic acid; maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, Examples of suitable carboxylic acid anhydrides include 3,4,5,6-tetrahydrophthalic anhydride; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate; styrenes such as styrene and methylstyrene; conjugated dienes such as 1,3-butadiene, isoprene, 1,3-pentadiene, and 1,3-hexadiene; and vinyl ethers such as vinyl acetate.

[0096] Preferred examples of olefin polymers include polypropylene, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / ethylene / 1-octene copolymer. Furthermore, examples of olefin polymers copolymerized with other vinyl monomers include ethylene / ethyl acrylate copolymer and ethylene / vinyl acetate copolymer. When a copolymer is used, a random copolymer, a block copolymer, or a graft copolymer can be appropriately selected. Among the above, polypropylene, a propylene / ethylene copolymer, or a propylene / 1-butene copolymer is preferred as the olefin polymer.

[0097] (Meth)acrylic Polymer As the (meth)acrylic polymer, a polymer containing a repeating unit derived from a (meth)acrylic acid alkyl ester can be preferably used, since it can provide a solid electrolyte that exhibits a good balance between ionic conductivity and flexibility.

[0098] Examples of the (meth)acrylic acid alkyl ester constituting the (meth)acrylic polymer include (meth)acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms in the ester moiety. Specific examples thereof include 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, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, stearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0099] From the viewpoint of obtaining a solid electrolyte having excellent ionic conductivity while ensuring the formability and flexibility of the solid electrolyte, the (meth)acrylic acid alkyl ester constituting the (meth)acrylic polymer is preferably a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms in the ester moiety, and more preferably a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms in the ester moiety, among the above.

[0100] The (meth)acrylic polymer may contain repeating units derived from other vinyl monomers in addition to repeating units derived from (meth)acrylic acid alkyl esters. Examples of other vinyl monomers constituting the (meth)acrylic polymer include (meth)acrylic acid, aliphatic cyclic (meth)acrylic acid esters, aromatic (meth)acrylic acid esters, alkoxyalkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, polyalkylene glycol mono(meth)acrylates, (meth)acrylates having a heterocyclic structure, and zwitterionic mono(meth)acrylates.

[0101] In the (meth)acrylic polymer, the proportion of repeating units derived from a (meth)acrylic acid alkyl ester is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 95% by mass or more, based on the total repeating units constituting the (meth)acrylic polymer. The method for producing the (meth)acrylic polymer is not particularly limited, and the polymer can be produced by appropriately using a conventionally known method such as radical polymerization.

[0102] Polyvinyl acetal polymers are polymers obtained by acetalizing polyvinyl alcohol with an aldehyde, and contain a structural unit having an acetal group (acetal group unit) and a structural unit having a hydroxyl group (hydroxyl group unit). Polyvinyl acetal polymers typically contain a structural unit having an acetyl group (acetyl group unit) in addition to the acetal group unit and the hydroxyl group unit. The polyvinyl acetal polymer used as component (Y) may be modified with an ethylenically unsaturated monomer such as an α-olefin or a (meth)acryloyl group-containing compound. In the polyvinyl acetal polymer, the content of the structural unit having an acetal group is, for example, 40 to 95% by mass, or may be 60 to 90% by mass, based on the total repeating units constituting the polyvinyl acetal polymer.

[0103] As the polyvinyl acetal polymer, commercially available polyvinyl acetal resins can also be used, such as the "S-LEC" series from Sekisui Chemical Co., Ltd. and the "Mobital" series from Kuraray Co., Ltd.

[0104] As the non-crosslinked polymer, at least one selected from the group consisting of a nitrile group-containing polymer, a polyester polymer, a polycarbonate polymer, a fluorine-containing polymer, an olefin polymer, a (meth)acrylic polymer, and a polyvinyl acetal polymer is preferred, in that it can provide a solid electrolyte that exhibits high ionic conductivity and is excellent in formability and flexibility. Among these, at least one selected from the group consisting of a nitrile group-containing polymer, a polyester polymer, a fluorine-containing polymer, and an olefin polymer is more preferred, in that it provides a solid electrolyte that exhibits high ionic conductivity and is excellent in formability and flexibility, and at least one selected from the group consisting of a nitrile group-containing polymer, a fluorine-containing polymer, and an olefin polymer is even more preferred.

[0105] The weight-average molecular weight (Mw) of the non-crosslinked polymer contained in the solid electrolyte of the present disclosure is preferably 2,500 or more, more preferably 5,000 or more, even more preferably 10,000 or more, and even more preferably 20,000 or more, from the viewpoints of obtaining a solid electrolyte that is high in strength and ion conductivity and of improving the formability of the solid electrolyte. The upper limit of the Mw of the non-crosslinked polymer is preferably 1,000,000 or less, more preferably 800,000 or less, and even more preferably 500,000 or less, from the viewpoints of ensuring appropriate fluidity of the non-crosslinked polymer and ensuring flexibility of the solid electrolyte.

[0106] The preferred range of Mw of the non-crosslinked polymer can be set by appropriately combining the upper and lower limits of the preferred ranges of Mw described above. The range of Mw of the non-crosslinked polymer is preferably 2,500 to 1,000,000, more preferably 5,000 to 800,000, even more preferably 10,000 to 500,000, and still more preferably 20,000 to 500,000.

[0107] For a non-crosslinked polymer, the molecular weight distribution (Mw / Mn), which is the ratio of Mw to the number average molecular weight (Mn), is preferably 4.5 or less, more preferably 4.0 or less, and even more preferably 3.5 or less, from the viewpoint of obtaining a solid electrolyte exhibiting good ionic conductivity. In this specification, the Mw and Mn of the non-crosslinked polymer are polystyrene-equivalent values ​​determined by gel permeation chromatography (GPC).

[0108] In the solid electrolyte of the present disclosure, the mass ratio of the molecular crystals to the non-crosslinked polymer, when expressed as "molecular crystals / non-crosslinked polymer," is preferably 99 / 1 to 50 / 50. When the mass ratio of the molecular crystals to the non-crosslinked polymer is within the above range, a solid electrolyte having a well-balanced improved ionic conductivity and flexibility can be obtained. In terms of being able to improve the ionic conductivity and flexibility of the solid electrolyte in a well-balanced manner, the mass ratio of the molecular crystals to the non-crosslinked polymer is more preferably 99 / 1 to 55 / 45, even more preferably 98 / 2 to 60 / 40, even more preferably 98 / 2 to 65 / 35, and even more preferably 95 / 5 to 70 / 30. Note that the mass ratio expressed as "molecular crystals / non-crosslinked polymer" is the ratio of each component when the total amount of the molecular crystals and the non-crosslinked polymer is 100.

[0109] The solid electrolyte of the present disclosure may further contain components (other components) other than the molecular crystals and non-crosslinked polymer described above, as long as the effects of the present invention are not impaired. For example, an alkali metal salt may be further blended as another component to enhance the ionic conductivity of the solid electrolyte. Examples of alkali metal salts include those similar to the alkali metal salts used in producing molecular crystals. When an alkali metal salt is further blended into the solid electrolyte, the alkali metal salt to be blended may be the same as or different from the alkali metal salt constituting the molecular crystal. From the viewpoint of fully achieving the effect of enhancing the ionic conductivity of the solid electrolyte, it is preferable that the alkali metal salt blended together with the molecular crystals and non-crosslinked polymer is the same as the alkali metal salt constituting the molecular crystal.

[0110] When an alkali metal salt is blended into the solid electrolyte, the content of the alkali metal salt is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total amount of the molecular crystal, non-crosslinked polymer, and alkali metal salt used in producing the solid electrolyte, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the total amount of the molecular crystal, non-crosslinked polymer, and alkali metal salt used in producing the solid electrolyte.

[0111] Examples of other components include, in addition to alkali metal salts, inorganic fillers, conductive additives, positive electrode active materials, negative electrode active materials, antioxidants, colorants, etc. However, in consideration of the ionic conductivity and ease of production of the solid electrolyte, it is preferable to use as few components as possible other than the alkali metal salts. Specifically, the content of components other than the alkali metal salts is, for example, 5% by mass or less, or may be 2% by mass or less, or may be 1% by mass or less, based on the total amount of the solid electrolyte.

[0112] <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 the desired properties. The solid electrolyte of the present disclosure can be produced by mixing molecular crystals and a non-crosslinked polymer (mixing step), and molding the mixture as needed. The solid electrolyte of the present disclosure is preferable in that it can produce a solid electrolyte exhibiting high ionic conductivity without requiring a firing step during the production of the solid electrolyte, and is less subject to process constraints. Furthermore, a solid electrolyte with high ionic conductivity can be produced by a simple method of mixing molecular crystals and a non-crosslinked polymer, and molding the mixture as needed.

[0113] In the mixing step for producing a solid electrolyte, the molecular crystals and the non-crosslinked polymer may be mixed uniformly, and the method is not particularly limited. The process of mixing the molecular crystals and the non-crosslinked polymer may be performed by dry mixing or wet mixing using a liquid. Of these, wet mixing is preferred. By employing wet mixing, the components can be mixed more uniformly, thereby relatively improving the ionic conductivity of the solid electrolyte.

[0114] As the liquid used in the wet mixing, various organic solvents can be appropriately used. From the viewpoint of increasing the uniformity of the molecular crystals and the non-crosslinked polymer and increasing the flexibility of the solid electrolyte, the liquid used in the wet mixing is preferably an organic solvent capable of dissolving the non-crosslinked polymer, and more preferably an organic solvent capable of dissolving the non-crosslinked polymer and dissolving or dispersing the molecular crystals. Such a solvent can be appropriately selected depending on the types of non-crosslinked polymer and molecular crystal used in the production of the solid electrolyte. Examples of such solvents include ethers such as 1,2-dimethoxyethane and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and heptane; esters such as ethyl acetate; carbonates such as dimethyl carbonate and ethyl methyl carbonate; amides such as N-methylformamide, N-methylacetamide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; and nitriles such as acetonitrile. The liquid used in the wet mixing may be a single solvent or a mixed solvent of two or more solvents.

[0115] When a solvent is used when mixing the molecular crystals and the non-crosslinked polymer, the amount of the solvent used may be set appropriately. From the viewpoint of achieving uniform mixing, the amount of the solvent used may be, for example, 50 to 2,000 parts by mass per 100 parts by mass of the total amount of components other than the solvent used in producing the solid electrolyte. The mixing of the molecular crystals and the non-crosslinked polymer may be performed at room temperature, at a low temperature, or under heating.

[0116] When the molecular crystals and the non-crosslinked polymer are mixed by dry mixing, the mixing of the molecular crystals and the non-crosslinked polymer may be carried out using various devices, such as a ball mill, a planetary ball mill, a bead mill, a blender, a homogenizer, a stamp mill, a homomixer, a disperser mixer, etc. When the solid electrolyte is produced on a small scale, the mixing may be carried out using a mortar and pestle.

[0117] The mixture obtained by mixing the molecular crystals and the non-crosslinked polymer may be used as a solid electrolyte by molding or forming into a thin film. When a mixture containing the molecular crystals and the non-crosslinked polymer is molded to obtain a molded body, the molding method is not particularly limited, and known molding methods can be appropriately adopted. Specific examples of molding methods include extrusion molding, transfer molding, pressure molding, slip casting, mold cast molding, tape casting, etc. The shape of the molded body is not particularly limited, and can be appropriately set depending on the application and shape of the electricity storage device. The shape of the molded body is, for example, rectangular or circular.

[0118] When using wet mixing, it is preferable to remove the solvent from the mixture of molecular crystals and non-crosslinked polymer (solvent removal step). There are no particular restrictions on the method for removing the solvent, and known desolvation methods can be appropriately adopted. For example, the solvent may be removed by heating, or by natural drying, air blowing, or reduced pressure treatment. Desolvation may also be performed by appropriately combining two or more of these treatments. When removing the solvent by heating, the heating temperature can be appropriately set depending on the type of solvent, but can be, for example, 30 to 120°C, and preferably 35 to 100°C. The heating time is, for example, 30 minutes to 72 hours. The heating treatment may be performed under atmospheric pressure or under reduced pressure. From the perspective of removing the solvent from the mixture at as low a temperature as possible, it is recommended to perform the desolvation treatment under reduced pressure and at a heating temperature of 80°C or less.

[0119] By the above-described operations, a solid electrolyte having high ionic conductivity can be obtained by a relatively simple method. The solid electrolyte obtained in this manner exhibits high ionic conductivity. Therefore, by using the solid electrolyte of the present disclosure as an electrolyte material for an electricity storage device, an electricity storage device having high ionic conductivity can be obtained.

[0120] Specifically, the ionic conductivity of a molded body of the present disclosure having a thickness of about 0.20 mm (specifically, 0.20±0.05 mm) measured at 25°C using an AC impedance method is 1.0 × 10 －７From the viewpoint of obtaining an electricity storage device with excellent performance, the ionic conductivity under the same conditions is preferably 2.0 × 10 S / cm or more. －７ S / cm or more, and more preferably 1.0×10 －６ More preferably, it is 1.0×10 S / cm or more. －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.

[0121] <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 described above. Examples of the device include a secondary battery, a capacitor, etc. When the device of the present disclosure 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.

[0122] The following describes an all-solid-state lithium-ion secondary battery, which is one embodiment of the device. The lithium-ion secondary battery is a laminate including an electrode layer made of a positive electrode layer and a negative electrode layer, and a solid electrolyte layer, with the solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer so that the solid electrolyte layer is in contact with the electrode layer.

[0123] The materials constituting the positive electrode layer and the negative electrode layer are not particularly limited and can be appropriately selected from materials known as electrode materials for lithium-ion secondary batteries. For example, the positive electrode layer may be configured to include a positive electrode current collector and a positive electrode mixture layer. The positive electrode current collector can be a metal foil such as aluminum or stainless steel. The positive electrode mixture layer is a layer containing a positive electrode active material and is disposed on the surface of the positive electrode current collector. Examples of the positive electrode active material include metal oxides having a layered rock salt, spinel, or olivine crystal structure. The negative electrode layer may be configured to include a negative electrode current collector and a negative electrode mixture layer. The negative electrode current collector can be a metal foil such as copper foil or lithium foil. The negative electrode mixture layer is a layer containing a negative electrode active material and is disposed on the surface of the negative electrode current collector. Examples of the negative electrode active material include metallic lithium and graphite.

[0124] The solid electrolyte layer is formed of a solid electrolyte containing the above-mentioned molecular crystals and a non-crosslinked polymer. The thickness of the solid electrolyte layer is not particularly limited and can be appropriately set depending on the application of the secondary battery, etc. The thickness of the solid electrolyte layer is, for example, 5 to 5,000 μm. From the viewpoint of realizing a smaller, lighter, and higher-capacity all-solid-state secondary battery by making the thickness of the solid electrolyte layer as thin as possible, the thickness of the solid electrolyte layer is preferably 50 μm or less, and more preferably 20 μm or less.

[0125] The method for producing the solid electrolyte layer and the 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 layer, a solid electrolyte layer, and a negative electrode layer may be produced by sandwiching a molded body of the solid electrolyte of the present disclosure as a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and preferably performing a pressure treatment for bonding. The laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is usually housed in a case and used as a secondary battery.

[0126] The device is not limited to the above-described configuration in which the carrier for ion conduction is lithium ions, but may also be a secondary battery in which other ions, such as sodium ions, are used as carriers. The device may also be a capacitor. One form of the capacitor includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, with the solid electrolyte disposed between the positive electrode layer and the negative electrode layer so that the solid electrolyte layer is in contact with each electrode layer.

[0127] The power storage device including the solid electrolyte of the present disclosure can be used in a variety of applications, 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.

[0128] The present invention will be specifically described below based on examples. However, the present invention is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0129] <<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 at -40 ° C. or less, 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, so that the molar ratio was 1: 2, 0.2156 g (116.8 parts by mass) of lithium bis(fluorosulfonyl)imide, 0.1846 g (100.0 parts by mass) of succinonitrile were weighed out, and the mixture was mechanically mixed at room temperature (25 ° C.) for 5 minutes 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: under a nitrogen atmosphere) at a heating rate of 10 ° C. per minute, and a large endothermic peak (melting point) was observed at 60 ° C. Although succinonitrile before mixing exhibited plasticity, the mixture did not exhibit plasticity, confirming that it was not a plastic crystal. The mixture was transferred to a vial and stirred with a magnetic stirrer set at 70 °C for 1 hour, and it was confirmed that it was uniformly dissolved (heating step). The resulting melt was then allowed to cool to room temperature, yielding a white solid.

[0130] 2. Confirmation of Crystallinity by Powder X-ray Diffraction Measurement (XRD Measurement) Powder X-ray diffraction measurement was performed on the obtained white solid 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 produced. 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) ２ In 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.

[0131] 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 When the melting point is smaller than 100°C, the substance has a plastic crystal 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 111.8 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.

[0132] 4. Measurement of ionic conductivity Using the press mold 10 shown in Figure 1, sample pellets were prepared in a dry room with a dew point of -40°C or less. First, the molecular crystal (Li(FSI)(SN) ２ A die set 11 containing 0.0200 g of ZnO was placed on the lower punch, and an upper punch 13 was placed on the die set 11. The molecular crystals were compressed using a hydraulic press at a pressure of 10 MPa for 1 minute to obtain circular sample pellets with a diameter of 1 cm and a thickness of 200 μm. Next, the sample pellets were sealed in an all-solid-state battery evaluation cell (KP-SolidCell, manufactured by Hosen Co., Ltd.) in a dry room with a dew point of -40°C or lower. Ionic conductivity measurements were performed using the all-solid-state battery evaluation cell containing the sample pellets. To measure ionic conductivity, first, the sealed cell containing the sample pellets was heat-treated in a thermostatic chamber at 40°C (corresponding to the heat treatment temperature in Table 1), while the resistance value was measured by AC impedance measurement. The heat treatment was terminated when the resistance value 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 using the following formula (1). The AC impedance measurement for calculating the ionic conductivity was carried out after the cell was kept at the measurement temperature in a thermostatic bath for 2 hours. 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 sample pellet during measurement (unit: cm ２ ), and L represents the distance between the electrodes (unit: cm).) Li(FSI)(SN) of Production Example 1 ２ The ionic conductivity of 1.2 × 10 at 25 ° C. －４ The viscosity was S / cm.

[0133] [Production Examples 2, 3, and 5] A white solid 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. XRD measurement was performed on the obtained white solid, and it was found that the molecular crystals (Li(FSI)(SL), Li(FSI)(SA), and Li ２ (TFSI) ２ (SN) ３) was confirmed. In the composition formulas of the molecular crystals of Production Examples 2, 3, and 5, bis(fluorosulfonyl)imide anion is abbreviated as FSI, bis(trifluoromethanesulfonyl)imide anion as TFSI, tetrahydrothiophene 1,1-dioxide as SL, succinamide as SA, and succinonitrile as SN. The molecular crystals obtained were subjected to DSC measurement in the same manner as in Production Example 1, and the melting point of Li(FSI)(SL) was found to be 73°C and the entropy of fusion was 88.3 JK. －１ mol －１ The melting point of Li(FSI)(SA) is 104°C and the entropy of fusion is 81.3 JK －１ mol －１ , Li ２ (TFSI) ２ (SN) ３ The melting point of is 59°C and the entropy of fusion is 71.7 JK －１ mol －１ From these measurement results, it was confirmed that none of the white solids obtained in Production Examples 2, 3, and 5 had a plastic crystal phase and were not plastic crystals. In addition, the molecular crystals (Li(FSI)(SL), Li(FSI)(SA), Li ２ (TFSI) ２ (SN) ３ The ionic conductivity was measured at 25° C. using a heat treatment temperature as shown in Table 1. The measurement results are shown in Table 1.

[0134] [Production Example 4] In a dry room maintained at a dew point of -40°C or less, 0.4307 g of lithium hexafluorophosphate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as an alkali metal salt and 0.6129 g of adiponitrile (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as an organic molecule were weighed out to a molar ratio of 1:2 and transferred to a vial. 8 g of dimethyl carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added thereto, and the mixture was stirred for 1 hour using a magnetic stirrer set at 25°C, and it was confirmed that the mixture was uniformly dissolved. The resulting solution was cast onto a PTFE (polytetrafluoroethylene) petri dish, and to remove the solvent, the mixture was dried on a hot plate at 60°C for 5 hours, and then vacuum dried in a vacuum dryer at 60°C for 12 hours or more. This resulted in a white solid. XRD measurement was performed on the resulting white solid, and a molecular crystal (Li(PF ６ ) (AdN) ２ It was confirmed that the molecular crystal of Production Example 4 was adiponitrile, abbreviated as AdN. The molecular crystal obtained was subjected to DSC measurement in the same manner as in Production Example 1, and the result was Li(PF ６ ) (AdN) ２ The melting point of is 180°C and the entropy of fusion is 72.9 JK －１ mol －１ From the measurement results, it was confirmed that the white solid obtained in Production Example 4 does not have a plastic crystal phase and is not a plastic crystal. In addition, the molecular crystal (Li(PF ６ ) (AdN) ２ The ionic conductivity was measured at 25° C. using a heat treatment temperature of 165° C. The measurement results are shown in Table 1.

[0135]

[0136] The details of the compounds used in Table 1 are as follows: LiFSI: lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.) LiPF ６: Lithium hexafluorophosphate [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] LiTFSI: Lithium bis(trifluoromethanesulfonyl)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.] SA: Succinamide [manufactured by Tokyo Chemical Industry Co., Ltd.] AdN: Adiponitrile [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.]

[0137] <<Production of Polymer and Physical Properties>> [Production Example 6] 1. Synthesis of Polymer PCL (Polycaprolactone) 100 parts of ε-caprolactone, 0.33 parts of 1-butanol, 0.17 parts of tin(II) 2-ethylhexanoate, and a stirrer were placed in a 100 mL test tube and stirred at 95°C for 96 hours in dry air (dew point -60°C or lower). ε-Caprolactone and 1-butanol were used that had been dehydrated using molecular sieves. The polymer solution was poured into a large amount of isopropanol to precipitate the polymer. The precipitate was collected by filtration under reduced pressure and dried in vacuo to obtain polymer PCL.

[0138] 2. Molecular Weight Measurement The molecular weight of the polymer was measured using gel permeation chromatography (hereinafter also referred to as "GPC") according to the following procedure. The weight average molecular weight and number average molecular weight (hereinafter also referred to as "Mw" and "Mn", respectively) of the polymer PCL were Mw 26,800 and Mn 18,700. <Procedure> A sample solution was obtained by dissolving 4 mg of polymer PCL in 4 mL of tetrahydrofuran. This sample solution was filtered through a polytetrafluoroethylene membrane filter, and 100 μL was injected into a GPC apparatus, and Mw and Mn were measured under the following conditions. Column: 4 columns of TSKgel SuperMultiporeHZ-M manufactured by Tosoh Corporation Temperature: 40°C Eluent: Tetrahydrofuran Detector: Differential refractometer Flow rate: 600 μL / min Standard material: Polystyrene

[0139] 3. Glass Transition Temperature Measurement The glass transition temperature of the polymer PCL was determined using a differential scanning calorimeter (TA Instruments, DSC250, measurement atmosphere: nitrogen atmosphere) according to the following procedure. The glass transition temperature of the polymer PCL1 was -65°C. <Procedure> A heat flux curve was obtained by subjecting 5 mg of polymer sealed in an aluminum pan to DSC measurement at a heating rate of 10°C per minute in the range of -80°C to 100°C. The glass transition temperature was determined from the intersection of the baseline of the heat flux curve and the tangent at the inflection point.

[0140] <<Production and Evaluation of Solid Electrolyte>> [Example 1] Li(FSI)(SN) as molecular crystal ２ (Production Example 1 above), PAN (polyacrylonitrile, Mw 150,000, manufactured by Sigma-Aldrich) as a non-crosslinked polymer was added to Li(FSI)(SN) in a mass ratio of 80:20. ２ 0.4000 g of PAN and 0.1000 g of PAN were weighed into a vial. 4.0 g of DMF (N,N-dimethylformamide superdehydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a solvent to obtain a mixture. Next, the mixture was stirred for 2 hours using a magnetic stirrer set at 60°C, obtaining a solution in which the mixture was uniformly dissolved (mixing step). The obtained solution was cast onto a PTFE petri dish, and to remove the solvent, it was heated at room temperature on a hot plate at 60°C for 5 hours, and then vacuum-dried in a vacuum dryer at 60°C for 12 hours or more (solvent removal step). This resulted in a flexible solid electrolyte.

[0141] (Measurement of Ionic Conductivity) In a dry room maintained at a dew point of −40°C or less, 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 210 μm for ionic conductivity measurement. The sample pellets were then encapsulated in an all-solid-state battery evaluation cell (KP-SolidCell, manufactured by Hosen Co., Ltd.). Ionic conductivity measurements were performed using the all-solid-state battery evaluation cell encapsulating the sample pellets. To measure ionic conductivity, the resistance value was measured by AC impedance measurement while the all-solid-state battery evaluation cell encapsulating the sample pellets was heat-treated in a thermostatic chamber at 40°C (corresponding to the heat treatment temperature in Table 2). The resistance value decreased with 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 using the above formula (1). The AC impedance measurement for calculating the ionic conductivity was carried out after the cell was kept at the measurement temperature in a thermostatic chamber for 2 hours. The ionic conductivity of the solid electrolyte of Example 1 at 25°C was 4.6 × 10 －４ The viscosity was S / cm.

[0142] (Evaluation of Flexibility) In a dry room where the dew point was maintained at -40°C or below, the solid electrolyte was punched using a punch and a hammer to obtain circular sample pellets with a diameter of 10 mm and a thickness of 210 μm as sample pellets for evaluating the flexibility of the solid electrolyte. The sample pellets were wrapped around a polyethylene round rod with a diameter of 20 mm, and the state of the bent sample pellets was observed to evaluate the flexibility according to the following criteria. As a result, the solid electrolyte of Example 1 showed no abnormalities in appearance even when the sample pellets were bent, and was evaluated as "Good." This confirmed that the solid electrolyte of Example 1 had flexibility. Good: No abnormalities in appearance were observed in the sample pellets. Fair: Fine cracks were observed in the sample pellets. Bad: Clear cracks were observed in the sample pellets, or parts of the sample pellets peeled off.

[0143] [Examples 2 to 4, 12, 13, 16 to 18] Solid electrolytes were obtained in the same manner as in Example 1, except that the types and amounts of raw materials and the heat treatment temperature for ionic conductivity measurement were changed as shown in Tables 2, 3, and 4. In Tables 2, 3, and 4, polyvinylidene fluoride (KF Polymer W#1300, Mw 350,000, manufactured by Kureha Corporation) was used as PVDF-1. Polymethyl methacrylate (Mw 800,000, manufactured by Tokyo Chemical Industry Co., Ltd.) was used as PMMA. Polyvinylidene fluoride (KF Polymer W#9300, Mw 1,000,000, manufactured by Kureha Corporation) was used as PVDF-2. Polyvinyl acetal resin (S-LEC BH-3, Mw 108,000, manufactured by Sekisui Chemical Co., Ltd.) was used as PVB. Using the solid electrolyte of each Example, ionic conductivity was measured at 25°C in the same manner as in Example 1. The results of the ionic conductivity measurements are shown in Tables 2, 3, and 4. In addition, using the solid electrolyte of each Example, a flexibility evaluation test was performed in the same manner as in Example 1. The results are shown in Tables 2, 3, and 4.

[0144] [Example 5] Li(FSI)(SN) as molecular crystal ２ (Production Example 1 above), PEC (polyethylene carbonate, QPAC25, Mw 198,000, manufactured by EMPOWER) as a non-crosslinked polymer was mixed with Li(FSI)(SN) in a mass ratio of 70:30. ２0.3502 g of α- and 0.1506 g of PEC were weighed into a vial, and 2.0 g of acetonitrile (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a solvent to obtain a mixture. The mixture was then stirred for 2 hours using a magnetic stirrer set at 60°C, resulting in a solution in which the mixture was uniformly dissolved (mixing process). The solid electrolyte obtained by drying the solution in the same manner as in Example 1 was sticky and difficult to handle, so aluminum foil was used as the substrate and a solid electrolyte was obtained using the following method. The resulting solution was cast onto aluminum foil (thickness: 17 μm) using an applicator. To remove the solvent from the solution on the aluminum foil, the aluminum foil on which the solution was cast was heated on a hot plate at 60°C for 5 hours and then vacuum-dried in a vacuum dryer at 60°C for 12 hours or more (solvent removal process). This resulted in a flexible solid electrolyte formed on the aluminum foil (thickness of the layer excluding the aluminum foil: 40 μm). Using the obtained solid electrolyte with the aluminum foil still attached, the ionic conductivity at 25°C was measured in the same manner as in Example 1. The measurement results of the ionic conductivity are shown in Table 2. Furthermore, the obtained solid electrolyte was used with the aluminum foil still attached, and a flexibility evaluation test was carried out in the same manner as in Example 1. The results are shown in Table 2.

[0145] [Example 6] Li(FSI)(SN) as molecular crystal ２ (Production Example 1 above), PO (polypropylene-co-butylene, propylene / butylene=80 / 20 (mol%), Tafmer XM7080, Mw 353,000, manufactured by Mitsui Chemicals, Inc.) as a non-crosslinked polymer was added to Li(FSI)(SN) in a mass ratio of 80:20. ２ 0.4000 g of PO and 0.1000 g of PO were weighed into a vial, and 4.0 g of toluene (ultra-dehydrated) (Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a solvent to obtain a mixture. Next, the mixture was stirred for 2 hours with a magnetic stirrer set at 25°C, and PO was uniformly dissolved and Li(FSI)(SN) ２A solution in which the above components were dispersed was obtained (mixing step). The obtained solution was cast onto a PTFE dish. To remove the solvent from the solution on the dish, the dish into which the solution had been cast was heated on a hot plate at 60°C for 5 hours, and then vacuum-dried in a vacuum dryer at 60°C for 12 hours or more (solvent removal step). This resulted in a flexible solid electrolyte. Using the obtained solid electrolyte, heat treatment was performed in the same manner as in Example 1, except that the heat treatment temperature was 50°C, and then ionic conductivity at 25°C was measured in the same manner as in Example 1. The results of the ionic conductivity measurement are shown in Table 2. Furthermore, a flexibility evaluation test was performed using the obtained solid electrolyte in the same manner as in Example 1. The results are shown in Table 2.

[0146] [Examples 7 and 14] A solid electrolyte was obtained by the same procedure as in Example 6, except that the types and amounts of raw materials and the heat treatment temperature for ionic conductivity measurement were changed as shown in Tables 2 and 3. Using the obtained solid electrolyte, ionic conductivity was measured at 25°C in the same manner as in Example 1. The results of the ionic conductivity measurements are shown in Tables 2 and 3. In addition, a flexibility evaluation test was performed using the obtained solid electrolyte in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0147] [Example 8] Li(FSI)(SN) as molecular crystal ２ (Production Example 1 above), PCL (Production Example 3 above, Mw 26,800) as a non-crosslinked polymer, and LiFSI (manufactured by Kanto Chemical Co., Inc.) as an alkali metal salt were mixed in a mass ratio of 94:4:2 with Li(FSI)(SN) ２0.5500 g of , 0.0255 g of PCL, and 0.0100 g of LiFSI were weighed into a vial, and 1.0 g of MIBK (methyl isobutyl ketone, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a solvent to obtain a mixture. Next, the mixture was stirred for 2 hours using a magnetic stirrer set at 25 ° C, obtaining a solution in which the mixture was uniformly dissolved (mixing step). The solid electrolyte obtained by drying the solution in the same manner as in Example 1 was sticky and difficult to handle, so a solid electrolyte was obtained by the following method. The obtained solution was cast onto aluminum foil (thickness: 17 μm) using an applicator. To remove the solvent from the solution on the aluminum foil, the aluminum foil on which the solution was cast was heated on a hot plate at 60 ° C for 5 hours, and then vacuum-dried in a vacuum dryer at 60 ° C for 12 hours or more (solvent removal step). This resulted in a flexible solid electrolyte formed on the aluminum foil (thickness of the layer excluding the aluminum foil: 40 μm). Furthermore, heat treatment was carried out in the same manner as in Example 1, except that the heat treatment temperature was set to 55°C. Then, the resulting solid electrolyte was used with the aluminum foil still attached, and the ionic conductivity at 25°C was measured in the same manner as in Example 1. The results of the ionic conductivity measurement are shown in Table 2. Furthermore, the resulting solid electrolyte was used with the aluminum foil still attached, and a flexibility evaluation test was carried out in the same manner as in Example 1. The results are shown in Table 2.

[0148] [Examples 9 to 11] Solid electrolytes were obtained by the same procedure as in Example 8, except that the types and amounts of raw materials and the heat treatment temperature for ionic conductivity measurement were changed as shown in Table 3. In Table 3, polybutyl acrylate (Alfon (registered trademark) UP-1080, Mw 5,000, manufactured by Toagosei Co., Ltd.) was used as PBA. Furthermore, ionic conductivity at 25°C was measured in the same manner as in Example 1. The results of the ionic conductivity measurements are shown in Table 3. Furthermore, a flexibility evaluation test was performed in the same manner as in Example 1 using the solid electrolytes of each example. The results are shown in Table 3.

[0149] [Example 15] Li(FSI)(SN) as molecular crystal ２(Production Example 1) and a non-crosslinked polymer, PTFE (polytetrafluoroethylene, Teflon 6-J (Teflon is a registered trademark, the same applies hereinafter), manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.), were mixed in a mass ratio of 99:1 with Li(FSI)(SN) ２ 0.2970 g of the above and 0.0031 g of PTFE were weighed out and mechanically mixed in a mortar at room temperature for 20 minutes to obtain a white solid as a solid electrolyte. The ionic conductivity of the obtained white solid at 25°C was measured in the same manner as in Example 1. The results of the ionic conductivity measurement are shown in Table 3. In addition, a flexibility evaluation test was performed in the same manner as in Example 1. The results are shown in Table 3.

[0150] [Comparative Example 1] Li(FSI)(SN) as molecular crystal ２ (Production Example 1) and PEO (polyethylene oxide, Mw 300,000, manufactured by Thermo Scientific) as a polymer were mixed in a mass ratio of 80:20 with Li(FSI)(SN) ２ 0.3999 g of PEG and 0.0997 g of PEO were weighed into a vial, and 2.0 g of acetonitrile (ultra-dehydrated) (Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a solvent to obtain a mixture. The mixture was then stirred for 2 hours using a magnetic stirrer set at 60°C, resulting in a uniformly dissolved solution (mixing process). The resulting solution was cast onto a PTFE dish, dried on a hot plate at 60°C for 5 hours to remove the solvent, and then vacuum dried in a vacuum dryer at 60°C for 12 hours or more (solvent removal process). The resulting solid electrolyte was not flexible and cracked when peeled from the PTFE dish, making it impossible to measure ionic conductivity. The results are shown in Table 4.

[0151] [Comparative Example 2] Li (FSI) (SN) ２ Using the sample pellets (from Production Example 1 above), a flexibility evaluation test was carried out in the same manner as in Example 1. The results are shown in Table 4 together with the measurement results of ionic conductivity at 25°C.

[0152]

[0153]

[0154]

[0155] Details of the compounds used in Tables 2, 3, and 4 are shown below. PAN: polyacrylonitrile (manufactured by Sigma-Aldrich Co., Ltd.) PVDF-1: polyvinylidene fluoride, KF Polymer W#1300 (manufactured by Kureha Corporation) PEC: polyethylene carbonate, QPAC25 (manufactured by Empower Co., Ltd.) PO: polypropylene-co-butylene, propylene / butylene=80 / 20 (mol %), Tafmer XM7080 (manufactured by Mitsui Chemicals, Inc.) PCL: polycaprolactone obtained in Production Example 6 PBA: polybutyl acrylate, Arfon (registered trademark) UP-1080 (manufactured by Toagosei Co., Ltd.) PMMA: polymethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) PTFE: polytetrafluoroethylene, Teflon 6-J (manufactured by Mitsui-Chemours Fluoroproducts, Inc.) PVDF-2: Polyvinylidene fluoride, KF Polymer W#9300 (manufactured by Kureha Corporation) PVB: Polyvinyl acetal, S-LEC BH-3 (manufactured by Sekisui Chemical Co., Ltd.) PEO: Polyethylene oxide (manufactured by Thermo Scientific) DMF: N,N-dimethylformamide (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) DMAc: N,N-dimethylacetamide (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) AcN: Acetonitrile (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Toluene: Toluene (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) MIBK: Methyl isobutyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) DMC: Dimethyl carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) LiFSI: Lithium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.)

[0156] <Evaluation Results> The solid electrolytes of Examples 1 to 18 exhibited high ionic conductivity at room temperature (25°C) and also exhibited high flexibility. ２ H ４ The solid electrolyte of Comparative Example 1, which contained a non-crosslinked polymer having a repeating unit represented by (-O)- in its main chain and molecular crystals, did not exhibit flexibility. The solid electrolyte of Comparative Example 2, which consisted only of molecular crystals, did not exhibit flexibility, although it had high ionic conductivity.

[0157] 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.

[0158] 10... Press mold

Claims

1. A solid electrolyte comprising: a molecular crystal containing, as structural units, 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 non-crosslinked polymer having substantially no repeating units represented by -(R-O)- (wherein R is an alkylene group) in its main chain.

2. The entropy of fusion of the molecular crystal is 20JK. －１ mol －１ The solid electrolyte according to claim 1 .

3. The solid electrolyte according to claim 1, wherein the mass ratio of the molecular crystals to the non-crosslinked polymer (molecular crystals / non-crosslinked polymer) is 99 / 1 to 50 / 50, where the total mass of the molecular crystals and the non-crosslinked polymer is 100.

4. The solid electrolyte according to claim 1, wherein the weight average molecular weight of the non-crosslinked polymer is 2,500 to 1,000,000.

5. The solid electrolyte according to claim 1, wherein the organic molecule is at least one selected from the group consisting of sulfones, nitriles, and amides.

6. The counter anion constituting the alkali metal salt is (FSO ２ ) ２ N － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) (CF ３ SO ２ ) N － , P.F. ６ － or BF ４ － The solid electrolyte according to claim 1 , 7. An electricity storage device comprising the solid electrolyte according to any one of claims 1 to 6.

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