JP7013653B2 - Electrolytes - Google Patents

Description

The present disclosure, which is the invention disclosed herein, relates to an electrolyte.

Conventionally, the electrolyte used for a lithium secondary battery or the like is, for example, a PO-based alkali metal which is one or more of a phosphonic acid-based alkali metal salt, a phosphoric acid-based alkali metal salt, and a phosphinic acid-based alkali metal salt. A solvated ion liquid comprising a salt, an anion containing an imide structure, and a glyme has been proposed (see Patent Document 1). With this solvated ionic liquid, it is possible to suppress a decrease in ionic conductivity at low temperatures. The reason for this is that when a PO-based alkali metal salt is added to the glyme, an anion containing an imide structure interacts with the alkali metal cation, such as coordination, and the negative charge of the counter anion is reduced. .. As a result, it is presumed that the dissociation of the complex cation formed by the alkali metal ion and grime is promoted as it is.

Japanese Unexamined Patent Publication No. 2015-2153

However, although the above-mentioned electrolyte can suppress a decrease in ionic conductivity at a low temperature, for example, it is still insufficient, and further improvement has been desired. Further, since the solvated ionic liquid is a liquid that exhibits volatility at medium and high temperatures, it has been required to further improve the thermal stability, for example, by reducing the volatility. There is a problem that when an additive is added in order to increase the thermal stability, the ionic conductivity is lowered, and when the ionic conductivity is tried to be increased, the thermal stability is lowered.

The present disclosure has been made to solve such a problem, and further suppresses the decrease in thermal stability or further improves the thermal stability, and at the same time, reduces the ionic conductivity at low temperature. The main purpose is to provide an electrolyte that can be further suppressed.

In order to achieve the above-mentioned object, the present inventors have added inorganic particles or organic particles to a solvated ionic liquid containing glyme and an organic acid salt such as a phosphonic acid-based alkali metal salt, and the present invention is thermally stable. The present invention has been completed by finding that it is possible to further suppress the decrease in property or further improve the thermal stability and further suppress the decrease in ionic conductivity at low temperatures.

That is, the electrolytes disclosed herein are:
With grime,
Anions containing imide structures and
One or more of the Group 1 and Group 2 cations,
Organic acid salts containing one or more of phosphonic acid, phosphinic acid, phosphoric acid, carboxylic acid, boric acid, boric acid, aromatic imide and phenols.
Additive particles containing at least one of an inorganic particle containing a metal oxide having one or more of acidic, amphoteric, basic and neutral and an organic particle containing a heteroatom.
Is included.

In this electrolyte, the decrease in thermal stability can be further suppressed or the decrease in thermal stability can be further improved, and the decrease in ionic conductivity at low temperature can be further suppressed. The reason why such an effect is obtained is presumed as follows, for example. That is, an organic acid salt containing one or more of phosphonic acid, phosphinic acid, phosphoric acid, carboxylic acid, boric acid, boric acid, aromatic imide and phenols is added to a solvated ion liquid containing glyme and an imide salt. Then, it is presumed that the imide anion having the complex cation coordinated by the glyme has a composite anion structure coordinated with the cation site of the organic acid salt. In this composite anion structure, the negative charge of the anion including the imide structure is reduced by the interaction such as coordination, and as a result, the dissociation of the complex cation formed by the glyme is promoted, so that the ionic conductivity is improved. Inferred. In addition, although the composite anion structure alone does not sufficiently suppress the decrease in ionic conductivity at low temperatures, in this electrolyte, the ionic bond portion of the composite anion structure interacts with the surface of the added particles to dissociate the complex cation. It is presumed that the decrease in ionic conductivity at low temperatures is further suppressed because the properties and mobility are improved. Further, since the ionic bond portion of the composite anion structure interacts with the surface of the added particles, it is presumed that the decrease in thermal stability is further suppressed or the thermal stability is further improved.

A conceptual diagram showing the state of binding between grime and an imide salt. Explanatory drawing of the interaction between a composite anion structure and inorganic particles. FT-IR spectrum of phenylphosphonic acid and its Mg salt. Σ-T curves of solvated ionic liquids ILb, ILj, ILd, ILi. XRD pattern of solvated ionic liquid ILb after solidification. Σ-T curves before and after freezing of solvated ionic liquids ILb and ILa. Σ-T curve of an experimental example in which α-alumina is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which γ-alumina is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which fumed silica is composited with a solvated ionic liquid. Σ-T curve of an experimental example in which FSM22 is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which MgO is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which CuO is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which TiO ₂ is compounded with a solvated ionic liquid. Σ-T curve of an experimental example in which h-BN is compounded with a solvated ionic liquid. Σ-T curve of solvated ionic liquid ILa, ILe, ILf, ILg. Σ-T curve of an experimental example in which inorganic particles are composited with a solvated ionic liquid ILe. Σ-T curve of an experimental example in which inorganic particles are composited with a solvated ionic liquid ILf. Σ-T curve of an experimental example in which inorganic particles are composited with solvated ionic liquid ILg. Σ-T curve of an experimental example in which inorganic particles are composited with a solvated ionic liquid ILh. Σ-T curve of an experimental example in which organic particles are composited with a solvated ionic liquid.

The electrolytes disclosed herein include glyme, anions containing an imide structure, organic acid salts, one or more cations of Group 1 and Group 2 cations, and at least one of inorganic and organic particles. It contains additive particles containing one of them. This organic acid salt is a salt containing one or more of phosphonic acid, phosphinic acid, phosphoric acid, carboxylic acid, boric acid, boric acid, aromatic imide and phenols. Inorganic particles include metal oxides that are one or more of acidic, amphoteric, basic and neutral. The organic particles are polymers containing heteroatoms.

Grime is a general term for linear symmetric glycol diethers, and may be represented by, for example, RO (CH ₂ CH ₂ O) _n —R. In the formula, R is an alkyl group or an aryl group, and n is an integer of 1 or more. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl and the like. Examples of the aryl group include phenyl, naphthyl, anthryl and the like. n may be an integer of 1 or more, but is preferably 3 or 4. The grime may be one or more of triglime dimethyl ether (G3) and tetraglyme dimethyl ether (G4). One type of grime may be used alone, or two or more types may be mixed and used.

Examples of the anion containing an imide structure include an imide anion in which two carbonyl groups are bonded to nitrogen, a sulfonylimide anion in which two sulfonyl groups are bonded to nitrogen, and one sulfonyl group and one carbonyl group to nitrogen. It may contain a bonded sulfonylcarbonylimide anion or the like. As the anion containing an imide structure, a sulfonylimide anion or a sulfonylcarbonylimide anion is preferable, and a sulfonylimide anion is more preferable. Examples of the sulfonylimide anion include bis (trifluoromethanesulfonyl) imide anion (TFSI), bis (pentafluoroethanesulfonyl) imide anion (BETI), bis (fluorosulfonyl) imide anion (FSI), and fluorosulfonyl trifluoromethanesulfonylimide. Examples include anion (FTA), 4,4,5,5, -tetrafluoro-1,3,2-dithiazolin-1,1,3,3-tetraoxide anion (CTFSI) and the like. Examples of the sulfonylcarbonylimide anion include 2,2,2-trifluoro-N- (trifluoromethylsulfonyl) acetamide anion (TSAC). Of these, TFSI and FSI are preferable from the viewpoint of solubility in grime and ease of complex formation. The anion containing the imide structure is preferably an organic anion. The anion containing this imide structure may have an alkali metal ion as a counter cation. As the alkali metal, for example, lithium, sodium, potassium and the like are preferable, and lithium is more preferable. The alkali metal may be of the same type as or different from the cation contained in the organic acid salt, but is preferably of the same type. As the imide salt containing an anion containing an imide structure and a cation, for example, LiFSI is preferable.

The organic acid salt contains one or more of phosphonic acid, phosphinic acid, phosphoric acid, carboxylic acid, boric acid, boric acid, aromatic imide and phenols. This organic acid salt may be, for example, one or more of a phosphonic acid-based metal salt, a phosphoric acid-based metal salt, a boronic acid-based metal salt, and a boric acid-based metal salt. As the phosphonic acid-based metal salt, for example, those represented by the formulas (1) and (2) are preferable. Further, as the boronic acid-based metal salt, for example, those represented by the formulas (3) and (4) are preferable.

In the formulas (1) to (4), R is one or more selected from the group consisting of hydrogen, halogen, alkyl group, aryl group, alkylaryl group, aralkyl group and oxyalkylene group, or a polymer having the same. Is. The alkyl group may have, for example, a straight chain or a branched chain having about 1 to 20 carbon atoms. Examples of such a group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a tetradecane group and the like. Examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group and the like. Examples of the alkylaryl group include a tolyl group and a xylyl group. Examples of the aralkyl group include a benzyl group and a phenethyl group. The oxyalkylene group may have, for example, about 1 to 20 oxyalkylene units. When having two or more oxyalkylene units, the oxyalkylene unit may be one kind or two or more kinds. Examples of the oxyalkylene unit include an oxymethylene unit, an oxyethylene unit, and an oxypropylene unit. As the polymer, a polymerizable compound (monomer) using a part of the above-mentioned monomers such as an alkyl group, an aryl group, and an oxyalkylene group as a polymerizable substituent is used, and if necessary, other polymerizable compounds. It may be obtained by adding (monomer) and polymerizing. Such a polymer may be an oligomer obtained by polymerizing about 2 to 100 monomers, or may be a polymer obtained by polymerizing 100 or more monomers. Further, in the above-mentioned R, the alkyl group, the aryl group, the alkylaryl group, the aralkyl group and the oxyalkylene group, and the polymer having the group may be halogenated at the terminal. At this time, all the ends may be halogenated, or some ends may be halogenated. Fluorine is preferable as the halogen. Examples of the halogenated terminal include an alkyl group having a fluorinated terminal, such as a trifluoromethyl group, a pentafluoroethyl group, and a 2- (tridecafluorohexyl) ethyl group. As such a phosphonic acid, for example, one or more of phenylphosphonic acid and xylenediphosphonic acid is preferable. Further, as the boronic acid-based metal salt, for example, phenylboronic acid or the like is preferable.

In the formulas (1) and (3), M ¹ and M ² are alkali metals and may be of the same type or different types, but are preferably of the same type. These may be alkali metals, but lithium, sodium, potassium and the like are preferable, and lithium is more preferable. In formulas (2) and (4), M ³ is preferably a cation of a Group 2 element. This is preferably magnesium, strontium, calcium, barium and the like, with magnesium being more preferred.

In the formula (1), as the one in which R is an alkyl group, the one shown in the formula (5) or the like can be preferably used. In the formula (5), n = 0 to 19 can be set. As the alkyl group in which R is fluorinated at the terminal, the one represented by the formula (6) or the like can be preferably used. In the formula (6), n + m = 0 to 19 can be set. Of these, n = 0 to 3, m = 3 to 10, and the like are preferable. As the aryl group of R, those represented by the formula (7) can be preferably used. In the following, among those represented by the formula (7), those in which M ¹ and M ² are Li are also referred to as PhPOLi. As the R having an oxyalkylene group, those represented by the formula (8) can be preferably used. In the formula (8), for example, n = 1 to 20 can be set, and when it is desired to have a relatively low viscosity, n = 1 to 5 is preferable, and a relatively high viscosity (semi-solid or semi-solid) or (Including solid), n = 6 to 20 is preferable. The equations (5) to (8) can also be applied to the equations (2) to (4).

As the phosphoric acid-based alkali metal salt, for example, those represented by the formulas (9) and (10) are preferable. Further, as the boric acid-based metal salt, for example, those represented by the formulas (11) and (12) are preferable. In the formulas (9) to (12), any one or more of the above-mentioned formulas (1) to (8) can be applied to R, M ¹ , M ² and M ³ .

As the phosphinic acid-based alkali metal salt, for example, the one represented by the formula (13) is preferable. In the formula (13), examples of R ¹ and R ² include those exemplified as R of the phosphonic acid-based alkali metal salt. R ¹ and R ² may be of the same type or different types. Further, in the formula (13), M is an alkali metal, preferably lithium, sodium, potassium and the like, and more preferably lithium. More specifically, as shown in the formula (13), for example, an alkali metal salt of diethylphosphinic acid, an alkali metal salt of dimethylphosphinic acid, an alkali metal salt of diphenylphosphinic acid, an alkali metal salt of phenylphosphinic acid, etc. Can be mentioned.

Examples of the carboxylic acid include terephthalic acid, isophthalic acid and benzoic acid, of which terephthalic acid is preferable. Examples of the aromatic imide include pyromellitic acid diimide, 1,4,5,8-naphthalenetetracarboxylic dianimide and phthalimide, of which pyromellitic acid diimide is preferable. Examples of phenols include cresol and phenol, of which cresol is preferable.

The cation contained in this electrolyte is one or more of the group 1 cations and the group 2 cations. This cation is a counter cation of an anion containing an imide structure or a cation contained in an organic acid salt. Group 1 cations are ions of alkali metals such as Li, Na, and K, and Li ions are preferable. The group 2 cation is a divalent cation such as Be, Mg, Ca, Sr, Ba, and Mg is preferable.

The ratio of the glyme, the organic acid salt and the imide salt in this electrolyte is not particularly limited, but those containing 0.2 mol equivalent or more and 2 mol equivalent or less of the imide salt with respect to the glyme are preferable, and 0.5. More preferably, it contains a molar equivalent or more and 1.5 molar equivalent or less. The coordination number to the alkali metal ion is generally 4 to 6, and since the oxygen atom in the glyme molecule coordinates to it, such a range is preferable. Further, those containing 0.15 mol equivalent or more and 1.7 mol equivalent or less of the organic acid salt with respect to the imide salt are preferable, and those containing 0.3 mol equivalent or more and 1.2 mol equivalent or less are more preferable. This is because the organic acid salt complexes with the imide salt and promotes the dissociation of the metal ion (derived from the imide salt) coordinated by the glyme.

In this electrolyte, the added particles are added to the electrolyte in a range of 15% by mass or more and 75% by mass or less based on the total of the glyme, the anion salt containing the imide structure (imide salt), the organic acid salt, and the added particles. It is preferable that it is contained. In this range, the decrease in the thermal stability of the electrolyte can be further suppressed or the thermal stability can be further improved, and the decrease in the ionic conductivity at a low temperature can be further suppressed, which is preferable. This content can be appropriately selected depending on the type of grime or imide salt contained and the desired wet state. For example, if the content of the added particles is 60% by mass or less, 50% by mass or less, 40% by mass or less, the electrolyte can be brought into a state close to that of a wet powder. Alternatively, if the content of the added particles is 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, the electrolyte can be brought into a state close to powder with less wetting.

The added particles include inorganic particles and organic particles. The inorganic particles may have an average particle size of 5 nm or more and 300 nm or less. The average particle size is an average value obtained by observing the inorganic particles with an electron microscope (SEM) and measuring the diameters of the particles included in the observed image. The average particle size of the inorganic particles can be appropriately selected as long as the desired characteristics can be obtained. The average particle size may be, for example, 100 nm or less or 50 nm or less. Alternatively, the average particle size may be 50 nm or more or 100 nm or more. The inorganic particles may contain, for example, one or more of aluminum oxide, silicon oxide, copper oxide, titanium oxide, magnesium oxide, zeolite and boron nitride. Examples of aluminum oxide include α-alumina and γ-alumina. Examples of silicon oxide include fumed silica, spherical silica, and trimethylsilylated products thereof. Examples of titanium oxide include rutile type and anatase type, and anatase type is preferable. Examples of the zeolite include mesoporous silica FSM22, FSM16, MCM41 and the like. Examples of the boron nitride include hexagonal-boron nitride (h-BN) and the like. As the inorganic particles, for example, aluminum oxide, silicon oxide, copper oxide, magnesium oxide and the like are preferable.

The organic particles may be a polymer having one or more of a carbon chain containing fluorine, a nitrile group and a polyether structure. The organic particles include, for example, a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP: formula 14), polyacrylonitrile (PAN: formula 15), polyethylene oxide (PEO: formula 16), and polytetrafluoroethylene. (PTFE) and the like, of which PVdF-HFP, PAN, PEO and the like are preferable. Note that x, y, and n in the equations (14) to (16) are arbitrary numbers. In addition, examples of the organic particles include various aliphatic polymers and aromatic polymers. Examples of the aliphatic polymer include polyester (PET, etc.), polyamide (nylon 66, nylon 6, etc.), polyamine (polyallylamine, etc.), and polyvinyl polymers such as polyacrylamide (PAAm), polyvinylpyridine (PVPy), and polyacrylic acid (polyacrylic acid). PAA), polymethacrylate (PMMA, etc.), polyurethane and the like can be mentioned. Examples of the aromatic polymer include poly (m-phenylene isophthalamide) and poly (p-phenylene terephthalamide) of aromatic polyamide (aramid), aromatic polyester (allylate), and poly (p-phenylene ether) of aromatic polyether. (PPO, etc.), Polyethersulfonate (PES), Polyetheretherketone (PEEK), Polyetherketone (PEK), Polyimide (PI), Polybenzoazoles Polybenzoimidazole (PBI), Polybenzoxazole (PBO) , Polybenzothiazole (PBT), polycarbonate (PC), and phenolic resins. These polymers may be homopolymers or copolymers, and their morphology may be linear or hyperbranched.

The electrolyte may be a liquid, a solid, or a semi-solid (wet powder) having properties intermediate between the liquid and the solid, but a wet powder or a solid is preferable. This is because it has high thermal stability and is easy to handle. This electrolyte may exist as a self-supporting membrane. When the above-mentioned organic acid salt is a polymer (formula (5), (6), (8)), and when a polymer compound of organic particles is compounded, it can be a self-supporting film.

This electrolyte has a conductivity retention rate (σ _-30 / σ ₈₀ ), which is the ratio of the ionic conductivity σ ₈₀ at 80 ° C to the ionic conductivity σ _-30 at -30 ° C, when the conductivity is 2 × 10 ^-4 or more. It is preferably 1 × 10 ^-3 or more, and more preferably 1 × 10 -3 or more. In this range, the ionic conductivity is stable in a wide temperature range, which is preferable. Further, the electrolyte preferably has an ion conductivity of σ _-30 at −30 ° C. of 3 × 10 ^-3 mS / cm or more, and more preferably 1 × 10 ⁻² mS / cm or more.
In particular, when the ionic conductivity σ _-30 at −30 ° C. is 3 × 10 ^-3 mS / cm or more, the ionic conductivity is higher than that of the conventional glyme-based solvated ionic liquid, which is preferable.

Examples of applications of this electrolyte include alkali metal ion batteries such as lithium ion batteries, and constituent materials such as capacitors, fuel cells, and solar cells.

In the electrolyte described above, the decrease in thermal stability can be further suppressed or the thermal stability can be further improved, and the decrease in ionic conductivity at low temperature can be further suppressed. The reason why such an effect is obtained is presumed as follows. Here, it will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the state of binding of grime, an imide salt, and an organic acid salt. In FIG. 1, a case where the glyme is triglime, the imide salt is LiFSI, and the organic acid salt is a phosphonic acid-based lithium salt will be described as an example. The same can be considered for other configurations. FIG. 1A shows a case where the molar ratio of triglime, LiFSI and the phosphonic acid-based lithium salt is 1: 1: 0, that is, the case where the phosphonic acid-based lithium salt is not added. FIG. 1 (b) shows a case where the molar ratio of triglyme, LiFSI, and a phosphonic acid-based lithium salt is 1: 1: 1. FIG. 1 (c) shows a case where the molar ratio of triglyme, LiFSI, and a phosphonic acid-based lithium salt is 2: 1: 1. FIG. 1 (d) shows a case where the molar ratio of triglyme, LiFSI, and a phosphonic acid-based lithium salt is 2: 2: 1.

As shown in FIG. 1 (a), in the mixture of triglyme and LiFSI, the oxygen moiety of the oxyethylene group in triglyme and the FSI of LiFSI are combined with each other to form a solvate compound. Conceivable. When an organic acid salt such as a phosphonic acid-based lithium salt is added thereto, as shown in FIGS. 1 (b) to 1 (d), the state of charge of glyme and LiFSI changes due to the presence of phosphonic acid-based lithium. , It is thought that the interaction works. The composition of the (contact ion pair) solvate compound in FIG. 1 (a) is a salt composed of a weak acid, which is a complex cation whose acidity is weakened by the coordination of glyme, and an FSI anion, which is a weak base. When a salt formed by a strong ionic bond composed of Li ion, which is a strong acid, and an organic phosphonate anion, which is a strong base, is added, the complex is compounded with the salt of {Glyme + LiFSI} as it is. It is presumed to have an anionic structure. In this complex, it is presumed that the other sulfonyl group of the FSI anion interacts (coordinates) with the Li ion of the organic phosphonate Li to stabilize this complex anion structure. It is considered that the Vehicle mechanism, which improves the mobility (dissociation) of the grime-Li ⁺ complex cation, works better because the negative charge density of the FSI anion is dispersed and lowered by this interaction. In addition, the Grottus mechanism that the aggregate becomes large by becoming a stable complex salt, the connection of the grime tunnel is improved, and the interaction of FSI anions is weakened, so that the movement of Li ions in the grime tunnel is improved. It is believed to work better. It is considered that these actions can suppress the decrease in ionic conductivity.

Further, although this composite anion structure can suppress a decrease in ionic conductivity, it is not yet sufficient in the low temperature region because freezing and solidification due to supercooling or the like are observed. FIG. 2 is an explanatory diagram of the interaction between the composite anion structure and the inorganic particles. FIG. 2B is a schematic diagram of an electrolyte in which an acidic metal oxide (silica, zirconia, etc.) is compounded as inorganic particles in a solvated ionic liquid to which lithium phenylphosphonate is added. In this electrolyte, it is presumed that the anion portion of the composite anion structure forms a hydrogen bond with a hydroxyl group on the inorganic particles, for example, to improve the mobility (dissociative property) of the Glyme-Li complex cation (Vehicle). Promotion of mechanism). Further, as a result, a uniform layer of the composite anion is formed on the surface of the acidic metal oxide, and in the vicinity thereof, the connection of the grime tunnel is further improved, so that the movement of the Li cation in the tunnel is improved. Is inferred (promotion of the Tunnel mechanism). FIG. 2 (c) is a schematic diagram of an electrolyte in which an amphoteric or basic metal oxide (α-alumina, γ-alumina, MgO, CuO, etc.) is compounded as an inorganic particle in a solvated ionic liquid to which lithium phenylphosphonate is added. be. In this electrolyte, the cation moiety present in the composite anion structure can interact with, for example, the oxygen moiety of the inorganic particles. Therefore, in this case as well, it is considered that the composite of the inorganic particles promotes the Vehicle mechanism and the Grottus mechanism, and the decrease in the ionic conductivity at low temperature can be suppressed. It is presumed that even if an organic polymer having a hetero atom (PVdF-HFP, PAN, PEO, etc.) is used instead of the inorganic particles, the decrease in ionic conductivity in the low temperature region can be suppressed by the same effect. To.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be carried out in various embodiments as long as it belongs to the technical scope of the present invention.

Hereinafter, an example in which the above-mentioned electrolyte is specifically produced will be described. Experimental Examples 0-1 to 13, 1-4, 2-3, 3-3, 4, 4-3, 5-2, 6-2, 7-2, 8-2, 12-2, 13- 2, 13-4 and 13-6 correspond to Comparative Examples, and the others correspond to Examples.

[Abbreviations for raw materials, etc.]
G3: Triethyleneglycoldimethylether; manufactured by Tokyo Chemical Industry, molecular weight: 178.2
G4: Tetraethyleneglycoldimethylether; manufactured by Tokyo Chemical Industry, molecular weight: 222.3
LiTFSI: Lithium Bis (trifluoromethanesulfonyl) imide; manufactured by Kishida Chemical, molecular weight: 287.1
LiFSI: Lithium Bis (fluorosulfonyl) imide; manufactured by Kishida Chemical, molecular weight: 187.1
n-BuLi: n-Butyl Lithium; 1.6M in hexane, manufactured by Aldrich, molecular weight: 64.1
TMS-Br: Trimethylsilyl Bromide; manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 153.09
THF: Tetrahydrofuran; dehydrated product, manufactured by Wako Pure Chemical Industries, Ltd. MeOH: Methylalcohol; manufactured by Wako Pure Chemical Industries, Ltd. PhPOH: Phenylphosphonic acid; manufactured by Tokyo Chemical Industry, molecular weight: 158.1
XyPOE: Xylenebis (phosphonic acid ester) ester; manufactured by Tokyo Chemical Industry, molecular weight: 378.3
PhBOH: Phenylboronic acid; manufactured by Tokyo Chemical Industry, molecular weight: 121.9
Mg (OAc) ₂ : Magnesium acetate; manufactured by Wako Pure Chemical Industries, molecular weight: 214.5
SiO ₂ (380): fumed silica (specific surface area 380 m ² / g); Aerosil FSM: mesoporous silica (pore diameter 4 nm, specific surface area 400 m ² / g); Taiyo Kagaku α-Al ₂ O ₃ : α-alumina (Average particle size 0.3 μm); Buehler γ-Al ₂ O ₃ : γ-alumina (specific surface area 150 m ² / g); Nikki Universal TiO ₂ : Anatase type (specific surface area 300 m ² / g) ); Ishihara Sangyo h-BN: Hexagonal boron nitride (average particle size 1 μm); Aldrich PVdF-HFP: Polyvinylidene fluoride and hexafluoropropylene copolymer; Aldrich PAN: Polyacrylonitrile; Aldrich PEO: Polyethylene oxide; made by Aldrich

[Preparation of samples (ILb, ILj, ILi, ILd)]
G3, G4, LiTFSI, LiFSI were prepared. Then, in a glove box filled with Ar gas, an equimolar amount (50.0 mmol) of G4 (11.11 g) or G3 (8.91 g) and LiTFSI (14.36 g) or LiFSI (9) are placed in a 20 mL sample bottle. .36 g) was taken, sealed and taken out, and heated to obtain four uniform solutions. The solvent ionic liquid (ILb: G3 + LiFSI), the solvate ionic liquid (ILj: G3 + LiTFSI), the solvate ionic liquid (ILi: G4 + LiFSI), and the solvate ionic liquid (ILd: G4 + LiTFSI), respectively. The ILb crystallized when left at a temperature of 10 ° C. or lower for 2 months after preparation.

[Making ILa]
In a glove box filled with Ar gas, 0.79 g of PhPOH that has been sufficiently dried in advance and 6 mL of THF are placed in an eggplant flask containing a stirrer, and after sealing, cooled in a low-temperature constant temperature bath cooled to -30 ° C. did. The reaction was carried out by slowly adding 6.3 mL of a solution of n-BuLi with a syringe under an Ar gas stream. At this time, a white precipitate was formed immediately after the start of addition of n-BuLi to form a dispersion liquid. After the addition was completed, the reaction was carried out at room temperature for 1.5 hours continuously, and after the reaction was completed, the solvent was removed by reducing the pressure while heating to 50 ° C. to obtain PhPOLi, which is a pale yellow cream-like product. In addition, PhPOLi means that the hydrogen of the OH group of PhPOH was replaced with Li. Next, in a glove box filled with Ar gas, this product is taken out into agate, 3.65 g of ILb is added and mixed uniformly, and a paste-like yellow dispersion ILa {(G3 + LiFSI) + 0.5 PhPOLi} is added. Obtained. The ILa remained liquid even when left at a temperature of 10 ° C. or lower for 3 months, but solidified instantly when stirred with a spatula. It was found that the tendency of solidification can be suppressed by adding PhPOLi to ILb, but it is a partial action.

[Making ILe]
4.43 g of PhPOH and 6.01 g of Mg (OAc) ₂ were taken in an eggplant flask containing a stirrer, 32 mL of methanol was added, and the mixture was stirred at room temperature for 2 hours. Then, 200 mL of water was added, and stirring was performed for 1.5 hours while heating in an oil bath at 110 ° C. After the product was filtered off, it was washed with 200 mL of water on a funnel and dried overnight to obtain PhPOMg, which is a white plate-like product. When this PhPOMg was measured by FT-IR, as shown in FIG. 3, the broad ν (OH) absorption peak (2700 to 2560 cm ^-1 ) of the P—OH bond disappeared in the product, but 1105 cm. From the fact that an absorption peak based on ν (P = O) and ν (P—O—C) between ^-1 and 1145 cm ^-1 and an absorption peak based on the PC (aromatic) bond of 1440 cm ^-1 can be seen. , The formation of PhPOMg was confirmed. Next, in a glove box filled with Ar gas, this product (0.90 g) was taken out into agate, 3.65 g of ILb was added and mixed uniformly, and the white emulsion dispersion ILe {(G3 + LiFSI) +0.5 PhPOMg} was obtained. The ILe remained liquid even when left at a temperature of 10 ° C. or lower for 3 months, but solidified instantly when stirred with a spatula.

[Preparation of ILf]
In a glove box filled with Ar gas, 0.61 g of PhBOH was taken in a eggplant flask containing a stirrer, 5 mL of THF was added to dissolve the mixture, and the mixture was cooled in a low temperature constant temperature bath cooled to −30 ° C. after sealing. The reaction was carried out by slowly adding 6.3 mL of a solution of n-BuLi with a syringe under an Ar gas stream. At this time, it became a uniform transparent liquid after the addition of n-BuLi, but when it was stirred at −30 ° C. for 1 hour, a white precipitate was formed and it became a dispersion liquid. After the addition was completed, the reaction was carried out at room temperature for 1.5 hours continuously, and after the reaction was completed, the solvent was removed by reducing the pressure while heating to 50 ° C. to obtain PhBOLi, which is a white cream-like product. Next, in a glove box filled with Ar gas, this product is taken out into agate, 3.65 g of ILb is added and mixed uniformly, and a paste-like yellow dispersion ILf {(G3 + LiFSI) + 0.5PhBOLi} is added. Obtained.

[Preparation of ILg]
First, XyPOH was synthesized by hydrolysis of XyPOE. It was carried out according to the method described in the literature (J. Mater. Chem., 2007, 17, 4563) and Japanese Patent Application Laid-Open No. 2008-69093. In a glove box filled with Ar gas, take 3.07 g of XyPOE in a eggplant flask containing a stirrer, dissolve it in 20 mL of methylene chloride, close it tightly, and react by combining a cooling tube, a dropping funnel and an Ar gas introduction tube. Assembled the device. 6.6 mL of TMS-Br was added dropwise over 30 minutes with stirring at room temperature. Then, the reaction was carried out by stirring at room temperature for 6 hours. After completion of the reaction, the apparatus was reassembled for distillation and desolvated under reduced pressure. 17 mL of methanol was added into the flask under an Ar gas stream, and the mixture was stirred overnight at room temperature. After desolving with an evaporator, the mixture was vacuum dried and then dispersed in 35 mL of acetonitrile. The solid content was separated by filtration, further washed with acetonitrile, and dried to obtain XyPOH. Next, as with PhPOLi, 0.80 g of XyPOH was dissolved in 6 mL of THF, and then 7.5 mL of 1.6 M n-BuLi solution was used to prepare XyPOLi. Finally, 0.22 g of this XyPOLi was taken out into agate in a glove box filled with Ar gas, and 1.11 g of ILb was added and mixed uniformly to obtain a gray powder ILg {(G3 + LiFSI) +0.25XyPOLi}.

[Preparation of ILa and ILb in which inorganic nanoparticles are composited]
The inorganic nanoparticles include α-Al ₂ O ₃ of an amphoteric oxide, γ-Al ₂ O ₃ , fumed silica SiO ₂ (380) of an acidic oxide, mesoporous silica FSM22, and MgO of a basic oxide. CuO, TiO ₂ (anatase) with neutral inorganic nanoparticles and high hydration, and hexagonal / boron nitride h-BN with neutral inorganic nanoparticles with high hydrophobicity were used. By mixing the inorganic nanoparticles with ILa, a composite having a total content of the inorganic nanoparticles of 22% by mass, 50% by mass, and 55% by mass was prepared. The composites of ILb and these inorganic nanoparticles were also prepared in the same manner, but the contents were 25% by mass, 55% by mass, and 61% by mass.

An example in which α-Al ₂ O ₃ is used as the inorganic nanoparticles will be described as a representative. 0.36 g of ILa and 0.45 g of pre-dried α-Al ₂ O ₃ are uniformly ground on agate and mixed in a glove box filled with Ar gas to form a product as a white putty-like wet powder. IL4a (55% by mass) was obtained. The theoretical composition of IL4a is {(G3 + LiFSI) + 0.5PhPOLi} + α-Al ₂ O ₃ (55% by mass).

[Preparation of ILe, ILf, ILg in which inorganic nanoparticles are composited]
Using the solvated ionic liquids ILe, ILf, and ILg, and using α-Al ₂ O ₃ , γ-Al ₂ O ₃ , and SiO ₂ (380) as the inorganic nanoparticles, the inorganic nanoparticles are compounded in the same manner as above. A solvated ionic liquid was prepared. The contents of the inorganic nanoparticles were 50% by mass, 55% by mass and 56% by mass.

[Preparation of ILh in which inorganic nanoparticles are compounded]
A solvated ionic liquid ILh {(G4 + LiFSI) + 0.5PhPOLi} was prepared by the same procedure as above. Further, using this solvent-containing ionic liquid ILh and using TiO ₂ , α-Al ₂ O ₃ and fumed silica SiO ₂ (380) as the inorganic nanoparticles, a solvent in which the inorganic nanoparticles are composited in the same manner as described above. Japanese ionic liquids IL16h, IL4h, and IL6h were prepared. The contents of the inorganic nanoparticles were 53% by mass, 44% by mass and 48% by mass, respectively.

[Preparation of ILa and ILb in which organic nanoparticles are compounded]
Instead of the inorganic nanoparticles, the organic polymer compounds PVdF-HFP, PAN and PEO were used, and the organic nanoparticles were complexed with the solvated ionic liquids ILa and ILb in the same manner as described above. The content of the organic nanoparticles was 55% by mass for ILa and 60% by mass for ILb.

Tables 1 and 2 summarize the prepared electrolytes in which the solvated ionic liquid and the added particles are combined. The experimental example numbers are as shown in Tables 1 and 2. The abbreviations are "4" for α-Al ₂ O ₃ , "3" for γ-Al ₂ O ₃ , "6" for SiO ₂ (380), "7" for FSM22, and "14" for MgO. Each sample was distinguished by adding "15" to CuO, "16" to TiO ₂ , "17" to h-BN, "8" to PVdF-HFP, "9" to PAN, and "10" to PEO. .. The specific structures of the solvated ionic liquids ILa, ILe, ILf, ILg, and ILh are formulas (17) to (21).

(Measurement of ionic conductivity)
Each sample was placed inside each measurement cell (diameter φ = 10 mm) in a glove box filled with Ar. Then, it was sandwiched between stainless steel electrodes to remove air bubbles and sealed. After measuring the film thickness at that time, place the measuring cell in a constant temperature bath and place it in a constant temperature bath at 25 ° C, 10 ° C, -10 ° C, -30 ° C, -10 ° C, 10 ° C, 25 ° C, 45 ° C, 60 ° C, 70. The temperature was adjusted to ° C., 80 ° C., 80 ° C., 70 ° C., 60 ° C., 45 ° C., and 25 ° C. Impedance measurement was performed after holding at each temperature for 1 hour. However, the temperature was kept below freezing for 1.5 hours. This impedance measurement was performed at 0.5 pts / sec between 0.1 MHz and 1.0 Hz with an amplitude voltage of 100 mV. The value of the real axis section of Z'in the obtained Cole-Cole plot or | Z | in which θ is the minimum in the Bode diagram was obtained as the resistance value (R). From this value (R), the film thickness t (cm), and the electrode area S (cm ² ), the ionic conductivity σ (Scm ^-1 ) was calculated according to the following equation. The results are shown in FIGS. 4 to 20. The unit of T on the horizontal axis in FIGS. 4 to 20 is Kelvin (K).
σ = 1 / R × t / S

(TG-DTA measurement)
Using a TG-DTA measuring device (Thermo plus TG8120 manufactured by Rigaku Co., Ltd.), 15 mg of a sample was heated at 10 ° C./min on a Pt pan under an Ar air flow (50 mL / min), and thermogravimetric analysis was performed. The standard sample was α-Al ₂ O ₃ .

(Experimental results and discussion)
Tables 1 and 2 show the abbreviations of Experimental Examples 0 to 16, the temperature (° C) of -10% by mass of TG, mainly the thermal decomposition temperature Td (° C) of LiFSI, the heat absorption temperature peak temperature (° C), 80 ° C, 25. Conductivity maintenance rate (σ _-30 /), which is the value obtained by dividing the ionic conductivity at -30 ° C (σ ₈₀ , σ ₂₅ , σ _-30 ) and the ionic conductivity at -30 ° C by the ionic conductivity at 80 ° C. σ ₈₀ ), the smoothness of the σ-T curve, and the composition of the sample are shown together. In addition, "His" in the table indicates that hysteresis exists. In Tables 1 and 2, the ionic conductivity at 25 ° C is shown by separating the initial 25 ° C, the value of 25 ° C after raising the temperature from -30 ° C, and the 25 ° C at the time of cooling from 80 ° C by "-". rice field.

(Experimental examples 0-1 to 0-10)
FIG. 4 is a σ−T curve of solvated ionic liquids ILb, ILj, ILi, and ILd. Hysteresis was observed on the σ-T curve for ILb, ILj, and ILi. At this time, ILb, ILj, ILi, and ILd were liquid. In addition, ILb was solidified by being left to stand during the winter season (temperature of 10 ° C. or lower). When XRD measurement was performed on this frozen solid, a regular XRD pattern considered to be based on crystals was obtained. FIG. 5 is an XRD pattern of the solvated ionic liquid ILb after solidification. Therefore, it is considered that ILb exhibited hysteresis due to the occurrence of a supercooled state when the sample was cooled from 25 ° C. Then, it was presumed that the σ value decreased in the low temperature region (-10 to -30 ° C., etc.) when the temperature was raised after the sample was frozen by cooling. On the other hand, in ILd, such hysteresis was not observed in the σ-T curve. Therefore, it was considered that ILd has a lower melting point and can maintain a stable liquid under these measurement conditions.

FIG. 6 is a σ−T curve before and after freezing of the solvated ionic liquids ILb and ILa. In ILb, the σ value drops significantly in the low temperature region, but in the frozen solidified one, the Core-Cole plot is greatly disturbed when the temperature rises from -30 ° C to -10 ° C, and no numerical value can be obtained (ND). : No data). On the other hand, in ILa as well, a decrease in the σ value due to freezing was observed in the low temperature region, but the degree was small. From this result, it was confirmed that the addition effect of PhPOLi acts on ILb, although it is not sufficient. Below, the added particles were compounded with respect to this ILa, and the improvement of ionic conductivity and thermal stability in the low temperature region was examined.

(About Experimental Examples 1-1 to 4)
FIG. 7 shows Experimental Examples 1-1 to 3 in which α-alumina, which is an amphoteric metal oxide, is compounded with the solvated ionic liquid ILa, and Experimental Example 1 in which α-alumina is compounded with the solvated ionic liquid ILb. It is a σ-T curve of -4. The skeleton of these composites changed from wet powder to powder as α-alumina increased. In Experimental Example 1-4 (IL4b (61%)), the decrease in σ value is remarkable in the low temperature region of the σ-T curve, whereas in Experimental Examples 1-1 to 3, σ- The T curve showed a smooth curve, and no sharp decrease in σ value was observed in the low temperature region. Experimental Examples 1-1 and 2 showed the same σ-T curve as ILa containing no α-alumina, and exceeded 1 mS / cm at 25 ° C. As shown in Table 1, their T (-10%) was 202 ° C. and 212 ° C., which greatly exceeded ILa's 163 ° C. and Experimental Example 1-4's 174 ° C. By compounding α-alumina with ILa, it was confirmed that the ionic conductivity in the low temperature region was improved and the thermal stability was significantly improved.

(About Experimental Examples 2-1 to 3)
FIG. 8 shows Experimental Examples 2-1 and 2 in which γ-alumina, which is an amphoteric metal oxide, is compounded with the solvated ionic liquid ILa, and Experimental Example 2 in which γ-alumina is compounded with the solvated ionic liquid ILb. It is a σ-T curve of -3. The skeleton of these composites changed from wet powder to powder as γ-alumina increased. In Experimental Example 2-3 (IL3b (25%)), a large hysteresis was shown in the low temperature region of the σ-T curve and measurement was not possible at -30 ° C, whereas in Experimental Examples 2-1 and 2, any of them The σ-T curve showed a smooth curve even in the content of sigma, and no sharp decrease in sigma value was observed in the low temperature region. Experimental Example 2-1 showed the same σ-T curve as ILa containing no γ-alumina, and exceeded 1 mS / cm at 25 ° C. As shown in Table 1, the T (-10%) was 178 ° C, which was higher than 163 ° C of ILa and 160 ° C of Experimental Example 2-3. By compounding γ-alumina with ILa, it was confirmed that the ionic conductivity in the low temperature region was improved and the thermal stability was significantly improved.

(About Experimental Examples 3-1 to 4)
FIG. 9 shows Experimental Examples 3-1 to 2 in which fumed silica (380), which is an acidic metal oxide, is compounded with the solvated ionic liquid ILa, and fumed silica (380) with respect to the solvated ionic liquid ILb. ) Is a composite of the σ-T curves of Experimental Examples 3-3-4. The skeletons of these composites changed from wet powder to powder as the amount of fumed silica (380) increased. In Experimental Examples 3-1 to 4, a smooth curve was shown in the low temperature region of the σ-T curve, and no sharp decrease in the σ value was observed in the low temperature region. The σ values at 25 ° C. were about 2 mS / cm in Experimental Examples 3-1 and 3, and 0.3 mS / cm and 1.2 mS / cm in Experimental Examples 3-2 and 4, respectively. On the other hand, the T (-10%) was 184 ° C. and 197 ° C. in Experimental Examples 3 and 1 and 197 ° C., which exceeded 163 ° C. in ILa, whereas the temperature in Experimental Examples 3-3 and 4 was 162 ° C. and 89 ° C. It was ° C. When the fumed silica (380) is composited, the ionic conductivity in the low temperature region is sufficiently improved by using the solvated ionic liquid ILb to which the organic acid salt PhPOLi is not added, but the organic acid salt is used. Addition of a certain PhPOLi was found to improve thermal stability at the same time.

(About Experimental Examples 4-1 to 3)
FIG. 10 shows Experimental Examples 4-1 and 2 in which mesoporous silica FSM22, which is an acidic metal oxide, is combined with the solvated ionic liquid ILa, and Experimental Example 4 in which FSM22 is combined with the solvated ionic liquid ILb. It is a σ−T curve of -3. The skeletons of these composites changed from wet powder to powder as FSM22 increased. In Experimental Examples 4-1 to 3, a smooth curve was shown in the low temperature region of the σ-T curve, and no sharp decrease in the σ value was observed in the low temperature region. The σ value at 25 ° C. was 0.7 mS / cm in Experimental Example 4-1 but decreased to about 0.001 mS / cm in Experimental Examples 4-2 and 3. The reason why the σ value decreases due to the increase in the content is that, for example, FSM22 has pores of 40 nm, and the decrease in the density of OH groups on the particle surface affected the interaction with the anion part. It was speculated that there was. On the other hand, the T (-10%) was 188 ° C. and 203 ° C. in Experimental Examples 4-1 and 2, which was higher than 163 ° C. in ILa, while it was lower than 159 ° C. in Experimental Example 4-3. In the case of compounding FSM22, in a relatively low range such as 40% by mass or less, more preferably 30% by mass or less, the ionic conductivity in the low temperature region is improved and the thermal stability is improved. Was recognized.

(About Experimental Examples 5-1 and 2)
FIG. 11 shows Experimental Example 5-1 in which MgO, which is a basic metal oxide, is compounded with the solvated ionic liquid ILa, and Experimental Example 5-2 in which MgO is compounded with the solvated ionic liquid ILb. It is a σ−T curve. As for the skeleton of these composites, Experimental Example 5-1 is a wet powder and Experimental Example 5-2 is a powder. In Experimental Example 5-2 (IL14b (61%)), a small hysteresis is shown in the low temperature region of the σ-T curve and a decrease in the σ value is observed, whereas in Experimental Example 5-1 the σ-T curve is shown. It showed a smooth curve, and no sharp decrease in σ value was observed in the low temperature region. Experimental Example 5-1 showed 0.4 mS / cm at 25 ° C. As shown in Table 1, the T (-10%) was 213 ° C, which was higher than 163 ° C of ILa and 199 ° C of Experimental Example 5-2. When complexing MgO, which is a basic metal oxide, using a solvated ionic liquid containing PhPOLi, which is an organic acid salt, improves ionic conductivity and thermal stability in the low temperature region. It was observed, and the difference from the solvated ionic liquid without PhPOLi, which is an organic acid salt, was clear.

(About Experimental Examples 6-1 and 2)
FIG. 12 shows Experimental Example 6-1 in which CuO, which is a basic metal oxide, is compounded with the solvated ionic liquid ILa, and Experimental Example 6-2 in which CuO is compounded with the solvated ionic liquid ILb. It is a σ−T curve. The skeleton of these composites is a wet powder. In Experimental Example 6-2 (IL15b (61%)), a small hysteresis was shown in the low temperature region of the σ-T curve and a decrease in the σ value was observed, whereas in Experimental Example 6-1 the σ-T curve showed a small hysteresis. There was a decrease, but the hysteresis disappeared. Experimental Example 6-1 showed 1 mS / cm at 25 ° C. As shown in Table 2, its T (-10%) was 206 ° C, which was much higher than ILa's 163 ° C. By compounding CuO with the solvated ionic liquid ILa, it was found that the ionic conductivity in the low temperature region was improved and the thermal stability was significantly improved.

(About Experimental Examples 7-1 and 2)
FIG. 13 shows Experimental Example 7-1 in which TiO ₂ (anathase), which is a neutral metal oxide having high hydration to the solvated ionic liquid ILa, is complexed, and TiO ₂ to the solvated ionic liquid ILb. It is a σ-T curve of Experimental Example 7-2 in which. TiO ₂ (anathase) has a strong structure with high motility near the surface when dried under atmospheric pressure at 85 ° C for 2 hours, and the proportion of those showing acidity due to the decrease in basic water landing. Increases and the surface becomes acidic. In this example, TiO ₂ was vacuum dried at 75 ° C. overnight, and the same combined effect as that of the acidic metal oxide can be expected. The skeleton of these composites is powder. In Experimental Example 7-2 (IL16b (61%)), a small hysteresis is shown in the low temperature region of the σ-T curve and a decrease in the σ value is observed, whereas in Experimental Example 7-1, the σ-T curve is shown. It showed a smooth curve, and no sharp decrease in σ value was observed in the low temperature region. Experimental Example 7-1 showed 0.8 mS / cm at 25 ° C. As shown in Table 2, its T (-10%) was 162 ° C, which was equivalent to 163 ° C of ILa. By complexing TiO ₂ with the solvated ionic liquid ILa, no improvement in thermal stability was observed, but improvement in ionic conductivity in the low temperature region was observed. It is presumed that the reason why the improvement in thermal stability was not observed was that the OH group on the surface of TiO ₂ was derived from the adsorbed water, so that it could not contribute to the improvement in thermal characteristics.

(About Experimental Examples 8-1 and 2)
FIG. 14 shows Experimental Example 8-1 in which hexagonal-boron nitride (h-BN), which is a neutral metal oxide hydrophobic to the solvated ionic liquid ILa, is composited, and the solvated ionic liquid ILb. It is a σ-T curve of Experimental Example 8-2 in which h-BN was compounded. The skeleton of these composites is powder. In Experimental Examples 8-1 and 8, the σ-T curve showed a smooth curve, and no decrease in the σ value was observed in the low temperature region. Experimental Example 8-1 showed 0.3 mS / cm at 25 ° C., and Experimental Example 8-2 showed almost the same value as 0.4 mS / cm at 25 ° C. It was speculated that the reason for this is that, for example, since h-BN is a neutral and hydrophobic inorganic particle, there is no site on the surface where an FSI anion or a composite anion can be combined, and it is simply physically adsorbed. .. As shown in Table 2, the T (-10%) of Experimental Example 8-1 was 194 ° C, which was much higher than 163 ° C of ILa. When h-BN is complexed, the ionic conductivity in the low temperature region is sufficiently improved even if a solvent-containing ionic liquid ILb to which the organic acid salt PhPOLi is not added is used, but when the organic acid salt is added, heat is generated. At the same time, improvement in stability was observed.

(About Experimental Examples 0-11 to 13)
FIG. 15 is a σ-T curve of Experimental Examples 0-11 to 13 (ILE, ILf, ILg) using PhPOMg, PhBOLi, and XyPOLi, which are organic acid salts different from the organic acid salt PhPOLi. As shown in FIGS. 15 and 1, in the solvated ionic liquid to which these were added, the σ value in the low temperature region was significantly reduced. In the following, the effect of combining these with inorganic particles was examined.

(About Experimental Examples 9-1 to 3)
FIG. 16 is a σ-T curve of Experimental Examples 9-1 to 3 in which γ-alumina, α-alumina and fumed silica (380) are combined with a solvated ionic liquid ILe to which magnesium phenylphosphonate is added. The skeletons of these composites are from wet powder to powder. By compounding the inorganic particles with ILe, the σ-T curve showed a smooth curve in each case, and almost no sharp decrease in the σ value was observed in the low temperature region. Experimental Examples 9-1 to 9-3 were 0.2 mS / cm, 0.8 mS / cm, and 0.3 mS / cm, respectively, at 25 ° C., which were higher than 0.03 mS / cm of ILe. As shown in Table 2, their T (-10%) were 165 ° C, 198 ° C and 194 ° C, respectively, which were comparable to those of the solvated ionic liquid ILe at 191 ° C. By compounding the inorganic particles with the solvated ionic liquid ILe, improvement of ionic conductivity in the low temperature region was observed.

(About Experimental Examples 10-1 to 3)
FIG. 17 is a σ-T curve of Experimental Examples 10-1 to 3 in which γ-alumina, α-alumina and fumed silica (380) are combined with a solvated ionic liquid ILf to which lithium phenylboronic acid is added. The skeletons of these composites are from wet powder to powder. By compounding the inorganic particles with ILf, the σ-T curve showed a smooth curve in each case, and almost no sharp decrease in the σ value was observed in the low temperature region. Experimental Examples 10-1 to 3 were 0.2 mS / cm, 0.6 mS / cm, and 0.3 mS / cm, respectively, at 25 ° C., which were higher than the ILf of 0.02 mS / cm. As shown in Table 2, their T (-10%) were 167 ° C, 183 ° C and 176 ° C, respectively, which greatly exceeded the 148 ° C of the solvated ionic liquid ILe. By complexing the inorganic particles with the solvated ionic liquid ILf, it was found that the ionic conductivity was improved in the low temperature region and the thermal stability was improved.

(About Experimental Examples 11-1 and 11-1)
FIG. 18 is a σ-T curve of Experimental Examples 11-1 and 11-1 in which γ-alumina and fumed silica (380) are combined with a solvated ionic liquid ILg to which lithium xylenebisphosphonate is added. The skeleton of these composites is powder. By compounding the inorganic particles with ILg, the σ-T curve showed a smooth curve in each case, and almost no sharp decrease in the σ value was observed in the low temperature region. In Experimental Examples 11-1 and 11-1 and 2, 0.2 mS / cm and 0.4 mS / cm, respectively, at 25 ° C., which were about the same as 0.4 mS / cm of ILg. As shown in Table 2, their T (-10%) were 162 ° C and 193 ° C, respectively, which were comparable to 188 ° C of the solvated ionic liquid ILg. By compounding the inorganic particles with the solvated ionic liquid ILg, improvement in ionic conductivity in the low temperature region was observed.

(About Experimental Examples 12-1 to 4)
FIG. 19 shows Experimental Examples 12-1, 3 and 4 in which TiO ₂ , α-alumina and fumed silica (380) are combined with the solvated ionic liquid ILh using G4 and LiFSI, and the solvated ionic liquid ILi. It is a σ-T curve of Experimental Example 12-2 in which TiO ₂ is compounded with respect to the above. Note that FIG. 19 also shows the measurement results of the solvated ionic liquids ILh and ILi. The skeletons of these composites are from wet powder to powder. In ILh in which PhPOLi is added to ILi, the ionic conductivity in the low temperature region is slightly improved, but the presence of hysteresis and the decrease in σ value in the low temperature region are almost the same. However, by compounding the inorganic particles with ILh, the σ-T curve showed a smooth curve in each case, and a sharp decrease in the σ value was hardly observed in the low temperature region. Experimental Examples 12-1, 3 and 4 were 0.5 mS / cm, 0.3 mS / cm and 0.2 mS / cm, respectively, at 25 ° C. As shown in Table 2, the T (-10%) of Experimental Examples 12-1 and 12-1 and 12 is 178 ° C. and 157 ° C., respectively, and Experimental Example 12-1 has slightly higher ionic conductivity and is thermally stable. It turned out that the sex is also high. The T (-10%) of Experimental Examples 12-3 and 4 was 205 ° C. and 214 ° C., respectively, which were higher than those of the solvated ionic liquid ILi at 198 ° C. By complexing the inorganic particles with the solvated ionic liquid ILh, it was found that the ionic conductivity was improved and the thermal stability was improved in the low temperature region.

(About Experimental Examples 13-1 to 6)
FIG. 20 is a σ-T curve of Experimental Examples 13-1 to 6 in which PVdF-HFP, PAN, and PEO of organic polymer compounds are composited as organic particles with respect to solvated ionic liquids ILa and ILb. The skeletons of these composites are from wet powder to powder. Looking at the composite of the solvated ionic liquid ILb and the organic particles, the σ value in the low temperature region is improved, but the σ-T curve becomes a smooth curve only in Experimental Example 13-6. In Experimental Examples 13-2 and 4, some hysteresis remained in the low temperature region. That is, the degree of this improvement depended on the structure of the organic particles. On the other hand, in Experimental Examples 13-1, 3 and 5 in which the solvated ionic liquid ILa to which PhPOLi was added and the organic particles were combined, the σ-T curve showed a smooth curve in each case, and the σ-T curve showed a sharp curve in the low temperature region. There was almost no decrease in the σ value. Experimental Examples 13-1, 3 and 5 were 0.2 to 0.3 mS / cm at 25 ° C., respectively. This result was presumed to be due to the fact that the adsorption mechanism of the estimated composite anion by the ionic site was expressed at the heteroatom site of the organic particles in the same manner as that of the inorganic particles. As shown in Table 2, the T (-10%) of Experimental Examples 13-3 and 5 was 130 ° C. and 106 ° C., respectively, which were similar to those of Experimental Examples 13-4 and 6 at 138 ° C. and 111 ° C. rice field. The T (-10%) of Experimental Example 13-1 was 183 ° C, which was higher than that of Experimental Example 13-2 at 159 ° C, and an improvement in thermal stability was observed. The advantage of being able to combine with organic particles at a high content is that a film-like electrolyte can be obtained. Since the solid content is higher than that of a general gel electrolyte, the electrolyte membrane is easy to handle. The preparation method is not particularly limited, but what is shown here is an electrolyte membrane which is powder-molded in a σ measuring cell.

(Consideration of mechanism)
First, the effect of adding an organic acid salt (lithium phenylphosphonate) on a solvated ionic liquid will be considered using {(G3 + LiFSI) + 0.5PhPOLi} as an example. As shown in FIG. 1, when triglyme and LiFSI are mixed in equal molar amounts, it is considered that the oxygen moiety of oxyethylene in triglyme and the FSI anion are bonded to the lithium cation to form a solvate compound. This solvate compound has a contact ion pair (CIP) in which the pair structure is formed by ionic bonding the FSI anion to the Li + complex cation coordinated to the glyme and at the same time coordinating the sulfonyl group to Li +. ) It is presumed to have a type structure. When this solvate compound is placed under potential, the entire complex cation of Li + coordinated to grime is considered to move (see, for example, J. Am. Chem. Soc., 2011, 133, 13121). Therefore, under potential, the structure of this solvate compound changes from a contact ion pair (CIP) type to a solvent-separated ion pair (SSIP), and then becomes a highly solvated free ion, thereby conducting an ion conduction mechanism (Vehicle). Mechanism) is conceivable. At the same time, it is considered that the mechanism of hopping conduction of Li + in the tunnel of grime formed by the aggregate of solvated compounds (Grotthus mechanism) also acts. Therefore, in such a case, it is considered that the movement of the grime-Li complex cation is restricted because the equilibrium movement from CIP to SIPP (→ free ion) is suppressed at a low temperature such as −30 ° C. On the other hand, when an organic acid such as phenylphosphonic acid is added, it is considered that an interaction works such that the charge state of grime or LiFSI changes depending on its presence (see FIG. 1 (d) and the like). The structure of the catalytic ion-solvate compound is a salt consisting of a weak acid, which is a complex cation whose acidity is weakened by the coordination of glyme, and an FSI anion, which is a weak base. When a salt composed of a strong acid Li + and a strong base phenylphosphonate anion and formed by a strong ionic bond is added thereto, as shown in FIG. 2 (a), a salt of glyme + LiFSI as it is. It was presumed that the structure would be complex with 2 equivalents. In this complex salt, it was speculated that the other sulfonyl group of the FSI anion interacts with Li + of lithium phenylphosphonate to stabilize the complex salt structure. It was considered that this interaction further disperses and lowers the negative charge density of the FSI anion, so that the Vehicle mechanism that improves the mobility (dissociation) of the grime-Li complex cation works better. In addition, the stable complex salt enlarges the aggregates and improves the connection of the grime tunnel, and also weakens the interaction of FSI anions, which improves the movement of Li cations in the grime tunnel. The Grotthus mechanism was also thought to work better. It is considered that these actions can suppress the decrease in ionic conductivity at low temperatures.

By the way, it has been found that the solvated ionic liquid (G3 + LiFSI) composed of triglyme and LiFSI may freeze in the cold winter season. On the other hand, the solvated ionic liquid (G4 + LiTFSI) composed of tetraglyme and LiTFSI remained liquid without any freezing. It is considered that this is because the ionic interaction between the Li complex cation coordinated to grime and the FSI anion is not sufficiently weakened when the molecular weight of grime or disulfonylimide anion is smaller. .. In this case, it is considered that the effect of adding lithium phenylphosphonate improves the ionic conductivity at low temperatures, but does not prevent the solvated ionic liquid from freezing.

FIG. 2B schematically shows an electrolyte in which an acidic metal oxide (silica, zirconia, etc.) is complexed as an inorganic particle in a solvated ionic liquid (G3 + LiFSI) to which lithium phenylphosphonate is added. It is conceivable that the anion portion of this composite anion structure, for example, forms a hydrogen bond with a hydroxyl group on the inorganic particles to promote the Vehicle mechanism that improves the mobility (dissociation) of the glyme-Li complex cation. In addition, as a result, a uniform layer of composite anions is formed on the surface of the acidic metal oxide, and in the vicinity thereof, the connection of the grime tunnel is further improved, so that the movement of the Li cation in the tunnel is improved. The promoting action of the Grotthus mechanism is also considered.

FIG. 2 (c) shows an electrolyte in which an amphoteric or basic metal oxide (α-alumina, γ-alumina, MgO, CuO, etc.) is compounded as an inorganic particle in a solvent-containing ionic liquid (G3 + LiFSI) to which lithium phenylphosphonate is added. Is schematically shown. The cation moiety present in this composite anion structure can interact with, for example, the oxygen moiety of the inorganic particles. Therefore, in this case as well, it is considered that the composite of the inorganic nanoparticles promotes the Vehicle mechanism and the Grottus mechanism, and the decrease in the ionic conductivity at low temperature can be suppressed. It is presumed that even if an organic polymer having a hetero atom (PVdF-HFP, PAN and PEO) is used instead of the inorganic particles, the decrease in ionic conductivity in the low temperature region can be suppressed by the same effect. ..

Since the promoting effect of the composite of the added particles is exhibited on the surface of the particles, the entire electrolyte does not need to be liquid. Therefore, it is not necessary to keep the addition amount of the added particles to several mass% or less as in the Soggy Sand effect, and even if the added particles are added in an amount of 22% by mass or more and 55% by mass or more to form a powdery electrolyte, ions in the low temperature region are obtained. The decrease in conductivity is suppressed. Further, in such an electrolyte, the ionic conductivity at room temperature or higher shows a magnitude comparable to that of a solvated ionic liquid. In this way, in the electrolyte in which the added particles are compounded with the solvated ionic liquid to which lithium phenylphosphonate is added, the number of flame-retardant particles is increased, so that the thermal stability is improved. It was confirmed by the increase in the temperature decrease by 10% by mass.

The electrolyte disclosed herein can be used as a constituent material of, for example, an alkali metal ion secondary battery, a capacitor, a fuel cell, a solar cell and the like.

Claims (3)

It ’s an electrolyte,
Grime as a main component, which is one or more of triglime dimethyl ether (G3) and tetraglyme dimethyl ether (G4),
An anion containing an imide structure, which is a bis (fluorosulfonyl) imide anion (FSI),
Cations that are lithium ions and
Phenylphosphonic acid, xylenediphosphonic acid, organic acid salt which is one or more of phenylboronic acid, and
Including inorganic particles containing a metal oxide which is one or more of acidic, amphoteric, basic and neutral, and additive particles containing at least one of organic particles containing a heteroatom.
The added particles are contained in the electrolyte in a range of 15% by mass or more and 75% by mass or less with respect to the total of the grime, the anion salt containing the imide structure, and the added particles.
An anion containing the imide structure is contained in the grime in a range of 0.5 molar equivalent or more and 1.5 molar equivalent or less.
The organic acid salt is contained in the range of 0.15 molar equivalent or more and 1.2 molar equivalent or less with respect to the anion containing the imide structure.
The inorganic particles are one or more of copper oxide, magnesium oxide, zeolite and boron nitride, an electrolyte. The electrolyte according to claim 1, wherein the inorganic particles have an average particle size of 5 nm or more and 300 nm or less. The electrolyte according to claim 1 or 2, wherein the organic particles are a polymer having one or more of a carbon chain containing fluorine, a nitrile group and a polyether structure.

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