Electrolyte solution and power storage device

Abstract

Provided is an electrolyte solution with which it is possible to improve the cycle characteristics of a power storage device. This electrolyte solution contains a solvent, a silyl compound that includes at least one silyl group, and a complex compound that includes lithium.

Description

Electrolyte solution and energy storage device

[0001] The present disclosure relates to an electrolyte solution and an energy storage device.

[0002] In recent years, with the popularization of electronic devices such as portable electronic terminals typified by smartphones and notebook personal computers, and hybrid vehicles, electric vehicles, etc., secondary batteries play an important role as their power sources. Examples of these secondary batteries include aqueous solution batteries, non-aqueous electrolyte batteries, and all-solid-state batteries. In particular, a lithium-ion secondary battery including a positive electrode and a negative electrode capable of occluding and releasing lithium ions, etc., and a non-aqueous electrolyte has a high voltage, a high energy density, is excellent in safety, and has various advantages compared with other secondary batteries in terms of environmental problems and the like.

[0003] In a lithium-ion secondary battery using a non-aqueous electrolyte solution that is currently in practical use, for example, a composite oxide of lithium and a transition metal is used as the positive electrode active material, and a material capable of inserting and extracting lithium ions is used as the negative electrode active material. And, in order to improve the characteristics of the lithium-ion secondary battery, improvement of the characteristics of the non-aqueous electrolyte solution responsible for the transfer of lithium ions is required. As such a non-aqueous electrolyte solution, a non-protic organic solvent contains LiBF ４ 、LiPF [[ID=1十二]] ６ 、LiClO ４ 、LiN(SO ２ CF ３ ) ２ 、LiN(SO ２ CF ２ CF ３ ) ２ and other electrolytes dissolved in the electrolyte solution are used.

[0004] A non-aqueous electrolyte solution in which electrolytes such as LiBF ４ 、LiPF ６ etc. are dissolved has a high conductivity representing the transfer of lithium ions, and LiBF ４ 、LiPF ６The high oxidative decomposition voltage of these components is known to result in a stable high voltage, contributing to the high voltage and high energy density characteristics of lithium-ion secondary batteries. However, non-aqueous electrolytes for such lithium-ion secondary batteries require improvements such as increased lithium-ion conductivity for lower electrical resistance, improved cycle characteristics to maintain high capacity even after repeated charging and discharging, low resistance characteristics in the initial stages, and maintenance of high performance at high temperatures.

[0005] To improve these characteristics, several non-aqueous electrolytes have been proposed for use in energy storage devices such as lithium-ion secondary batteries. For example, Patent Document 1 (WO2014 / 175225) describes the following general formula: X-(O-A(Z)-O-B － (Y)(F)M ＋ -) ｎ A non-aqueous electrolyte containing a complex compound represented by -R (wherein X, Y, Z, and R are alkyl groups, A is P=O, and M is an alkali metal) has been proposed. This is said to improve the initial resistance characteristics of energy storage devices.

[0006] Patent Document 2 (Japanese Unexamined Patent Publication No. 2020-194771) states that M ＋ PO ３ (F) A － (In the formula, M ＋ A non-aqueous electrolyte has been proposed that contains a complex compound having a substructure represented by (where is a monovalent metal and A is a boron atom or a phosphorus atom) as the electrolyte. This is said to improve the high-temperature charging and storage characteristics of energy storage devices, in particular, by suppressing the increase in resistance during storage.

[0007] Patent document 3 (WO2019 / 180945) contains the following formulas: (Li) ｍ (A) ｎ (UF ｘ ) ｙ (Li) ｍ (Si) ｎ (O) ｑ (UF ｘ ) ｙ(A is O, S, P, or N; U is B or P; m and n are 1-6; q is 1-12; x is 3 or 5; y is 1-6) (Li) ｍ (O) ｎ (B) ｐ (OWF ｑ ) ｘ (W is B or P, m, p, x are 1 to 15, n is 0 to 15, q is 3 or 5) (Li) ｍ (B) ｐ (O) ｎ (OR) ｙ (OWF ｑ ) ｘ (W is B or P, n is 0 to 15, p, m, x, and y are 1 to 12, q is 3 or 5, and R is hydrogen, alkyl group, etc.) (Li) ｍ (O) ｎ (B) ｐ (OOC-(A) ｚ -COO) ｙ (OWF ｑ ) ｘ An electrolyte for energy storage devices is disclosed, comprising a lithium-containing complex compound represented by (W is B or P, A is an alkylene group of carbon 1 to 6, m, p, x and y are 1 to 20, n is 0 to 15, z is 0 or 1, and q is 3 or 5). With such an electrolyte, energy storage devices such as lithium-ion secondary batteries with good initial characteristics and excellent cycle characteristics can be obtained, and because the electrolyte itself has excellent lithium-ion conductivity, an all-solid-state lithium secondary battery can be obtained.

[0008] Patent Document 4 (Japanese Patent Publication No. 2001-319685) describes a non-aqueous electrolyte containing a non-aqueous solvent and a lithium electrolyte, wherein at least one hydrogen atom of phosphoric acid or polyphosphate is of the following formula: -X(-R １ ) (-R ２ ) (-R ３ ) (In the formula, X is a Si atom, etc., and R １ ~R ３It has been disclosed that a phosphoric acid compound substituted with a group represented by (where is an alkyl group having 1 to 10 carbon atoms) is added to a non-aqueous electrolyte. This is said to result in a non-aqueous electrolyte with high energy density and superior safety when used in lithium secondary batteries.

[0009] Japanese Patent Publication No. WO2014 / 175225, Japanese Patent Publication No. 2020-194771; Japanese Patent Publication No. WO2019 / 180945, Japanese Patent Publication No. 2001-319685

[0010] As described above, various electrolytes have been proposed for use in energy storage devices such as lithium-ion secondary batteries, but there is a need to develop further electrolytes that can improve the cycle characteristics of energy storage devices.

[0011] The present inventors have now discovered that the cycle characteristics of an energy storage device can be improved by using an electrolyte containing a silyl compound having at least one silyl group and a complex compound having lithium.

[0012] Therefore, an object of the present invention is to provide an electrolyte that can improve the cycle characteristics of an energy storage device.

[0013] The present disclosure provides the following embodiments: [Embodiment 1] An electrolyte comprising a solvent, a silyl compound having at least one silyl group, and a complex compound having lithium. [Embodiment 2] The electrolyte according to Embodiment 1, wherein the silyl compound has a phosphorus atom and / or a boron atom. [Embodiment 3] The electrolyte according to Embodiment 1 or 2, wherein the silyl compound has a phosphorus atom. [Embodiment 4] The electrolyte according to any one of Embodiments 1 to 3, wherein the silyl compound has at least two silyl groups. [Embodiment 5] The electrolyte according to any one of Embodiments 1 to 4, wherein the silyl compound further has a vinyl group. [Embodiment 6] The electrolyte according to any one of Embodiments 1 to 5, wherein the complex compound has a boron trifluoride group and / or a boron difluoride group. [Embodiment 7] The electrolyte according to any one of Embodiments 1 to 6, wherein the complex compound has a phosphorus atom. [Embodiment 8] The electrolyte according to any one of Embodiments 1 to 7, wherein the complex compound has a P=O group and / or a P=S group. [Aspect 9] The electrolyte according to any one of aspects 1 to 8, wherein the complex compound has a P=O group. [Aspect 10] The electrolyte according to any one of aspects 1 to 8, wherein the complex compound has a P=S group. [Aspect 11] The electrolyte according to any one of aspects 1 to 10, wherein the electrolyte is obtained by adding a mixture of the silyl compound and the complex compound to the solvent. [Aspect 12] An energy storage device comprising: a positive electrode; a negative electrode; and an electrolyte according to any one of aspects 1 to 11, which is present at least between the positive electrode and the negative electrode. [Aspect 13] The energy storage device according to aspect 12, wherein the electrolyte is heat-treated. [Aspect 14] The energy storage device according to aspect 12 or 13, wherein the electrolyte is gel-like. [Aspect 15] The energy storage device according to any one of aspects 12 to 14, wherein the electrolyte is filled between the positive electrode and the negative electrode in an unheat-treated state and then heat-treated. [Aspect 16] The energy storage device according to any one of aspects 12 to 14, wherein the electrolyte is filled between the positive electrode and the negative electrode after or while being heat-treated. [Aspect 17] The energy storage device according to any one of aspects 12 to 16, wherein the energy storage device is a lithium-ion secondary battery.

[0014] The electrolyte of the present invention comprises a solvent, a silyl compound, and a complex compound. The silyl compound has at least one silyl group. The complex compound has lithium. By using an electrolyte containing a silyl compound having at least one silyl group and a complex compound having lithium, the cycle characteristics of an energy storage device can be improved. The cycle characteristics of an energy storage device can be evaluated, for example, by measuring the capacity retention rate in the examples described later.

[0015] Furthermore, it is anticipated that the demand for energy storage devices with superior durability at high temperatures will increase in the future. In this regard, the electrolyte of the present invention can contribute to improving cycle characteristics and suppressing the rise in resistance values ​​associated with high temperatures, even when energy storage devices are used or stored at high temperatures (for example, in an atmosphere of 45°C).

[0016] Silyl compounds have at least one silyl group, and preferably at least two silyl groups. The upper limit of the number of silyl groups in a silyl compound is not particularly limited, but is typically 20 or less, and more typically 10 or less. Preferred examples of silyl groups include trimethylsilyl, triethylsilyl, triisopropylsilyl, butyldimethylsilyl, tributylsilyl, trimethoxysilyl, triethoxysilyl, tributoxysilyl, and triphenylsilyl.

[0017] The silyl compounds are preferably phosphorus-based silyl compounds, borate-based silyl compounds, carboxylic acid-based silyl compounds, sulfate-based silyl compounds, sulfonic acid-based silyl compounds, or combinations thereof, and are more preferably having a phosphorus atom and / or a boron atom. Examples of silyl compounds having a phosphorus atom include the phosphorus-based silyl compounds mentioned above, and preferred examples of phosphorus-based silyl compounds include phosphate-based silyl compounds, thiophosphate-based silyl compounds, phosphophosphate-based silyl compounds, and phosphinate-based silyl compounds. Preferred examples of silyl compounds having a boron atom include borate-based silyl compounds and compounds having a silyl group as reaction products of silyl compounds and boron halogenated salts.

[0018] The silyl compound preferably has a vinyl group. Preferred examples of silyl compounds having a vinyl group include bis(trimethylsilyl) vinylphosphonate, bis(trimethylsilyl) allylphosphonate, bis(trimethylsilyl) allyl phosphate, diallyl phosphate, trimethylsilyl acrylate, and bis(trimethylsilyl) maleate.

[0019] The concentration of the silyl compound in the electrolyte is preferably 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, even more preferably 0.5 to 20% by mass, and particularly preferably 1 to 10% by mass.

[0020] Preferred examples of silyl compounds include, as mentioned above, phosphorus-based silyl compounds, borate-based silyl compounds, carboxylic acid-based silyl compounds, sulfate-based silyl compounds, sulfonic acid-based compounds, and combinations thereof. In particular, it is more preferable that the silyl compounds include phosphorus-based silyl compounds and / or phosphonate-based silyl compounds.

[0021] Phosphorus-based silyl compounds preferably have a siloxy group or thiosilane group bonded to a P=O group or a P=S group, and more preferably have a siloxy group bonded to a P=O group. That is, silyl compounds preferably have a structure in which a silyl group is bonded to a P (phosphorus atom) constituting these groups via an O (oxygen atom) or S (sulfur atom). Examples of phosphorus-based silyl compounds include phosphate-based silyl compounds, thiophosphate-based silyl compounds, phosphophosphate-based silyl compounds, and phosphinate-based silyl compounds, as described above. Preferred examples of phosphate-based silyl compounds include tris(trimethylsilyl) phosphate, tetra(trimethylsilyl) diphosphate, hexa(trimethylsilyl) tetraphosphate, and trimethylsilyl polyphosphate. Preferred examples of thiophosphate silyl compounds include tris(trimethylsilyl) monothiophosphate, tris(trimethylsilyl) dithiophosphate, tris(trimethylsilyl) trithiophosphate, and tris(trimethylsilyl) tetrathiophosphate. Preferred examples of phosphonic acid silyl compounds include bis(trimethylsilyl) phosphonate, bis(trimethylsilyl) methylphosphonate, bis(trimethylsilyl) vinylphosphonate, bis(trimethylsilyl) allylphosphonate, and bis(trimethylsilyl) fluorophosphate. Preferred examples of phosphinic acid silyl compounds include trimethylsilyl phosphinate, trimethylsilyl dimethylphosphinate, and trimethylsilyl difluorophosphate.

[0022] The silyl compounds may also preferably include compounds having a silyl group as reaction products of the above-mentioned phosphorus-based silyl compounds with boron halide salts or phosphorus halide salts. Preferred examples of reaction products of phosphorus-based silyl compounds with boron halide salts or phosphorus halide salts include bis(trimethylsilyl)lithium phosphate / boron trifluoride, bis(trimethylsilyl)lithium thiophosphate / boron trifluoride, (trimethylsilyl)lithium phosphate / boron trifluoride, (trimethylsilyl)lithium phosphate / boron trifluoride, (trimethylsilyl) methylphosphonate / boron trifluoride, (trimethylsilyl) vinylphosphonate / boron trifluoride, (trimethylsilyl)lithium allylphosphonate / boron trifluoride, and (trimethylsilyl)lithium fluorophosphate / boron trifluoride. Furthermore, the reaction products of phosphate-based silyl compounds with boron-halide salts or phosphorus-halide salts can preferably be synthesized, for example, by utilizing the silyl halide reaction described later.

[0023] The borate-based silyl compound preferably has a siloxy group or a thiosilane group bonded to a boron atom (B). That is, the silyl compound preferably has a structure in which a silyl group is bonded to this boron atom via an oxygen atom (O) or a sulfur atom (S). Preferred examples of borate-based silyl compounds include tris(trimethylsilyl) borate, tris(trimethoxysilyl) borate, tris(triethylsilyl) borate, tris(triethoxysilyl) borate, tris(dimethylvinylsilyl) borate, and tris(diethylvinylsilyl) borate.

[0024] Carboxylic acid silyl compounds preferably have a siloxy group or a thiosilane group bonded to a C=O group. That is, silyl compounds preferably have a structure in which a silyl group is bonded to a carbon atom (C) constituting the C=O group via an oxygen atom (O) or a sulfur atom (S). Preferred examples of carboxylic acid silyl compounds include trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate, bis(trimethylsilyl) oxalate, bis(trimethylsilyl) malonate, bis(trimethylsilyl) pentanediate, and bis(trimethylsilyl) hexanediate.

[0025] Each of the sulfate-based silyl compounds and sulfonic acid-based silyl compounds preferably has a siloxy group or a thiosilane group bonded to an S=O group, and more preferably has a siloxy group bonded to an S=O group. That is, the silyl compound preferably has an S=O group and a structure in which a silyl group is bonded to the S (sulfur atom) constituting the S=O group via an O (oxygen atom) or S (sulfur atom). Preferred examples of sulfate-based silyl compounds include bis(trimethylsilyl) sulfate, bis(trimethylsilyl) sulfite, bis(trimethylsilyl) hyposulfite, trimethylsilyl methyl sulfate, and trimethylsilyl ethyl sulfate. Preferred examples of sulfonic acid-based silyl compounds include sulfonic acid (trimethylsilyl) and trifluorosulfonic acid (trimethylsilyl).

[0026] The complex compound contains lithium. In particular, the complex compound contains lithium ions (Li ＋ It is preferable that lithium is present in the form of ). Furthermore, it is preferable that the complex compound has a phosphorus atom, and more preferably has a P=O group and / or a P=S group. Preferred examples of complex compounds having a phosphorus atom will be described later.

[0027] The complex compound preferably has a boron halide group and / or a phosphorus halide group. In this specification, "boron halide group" means a group in which one or more halogen atoms are bonded to a boron atom. In this specification, "phosphorus halide group" means a group in which one or more halogen atoms are bonded to a phosphorus atom. A preferred example of a boron halide group is a boron fluoride group. A preferred example of a boron fluoride group is a boron trifluoride group and / or a boron difluoride group. A preferred example of a phosphorus halide group is a phosphorus fluoride group. A preferred example of a phosphorus fluoride group is a phosphorus pentafluoride group and / or a phosphorus tetrafluoride group. In particular, the complex compound preferably has a boron trifluoride group and / or a boron difluoride group. In this way, the presence of a boron halide group or a phosphorus halide group in the complex compound allows the bonding reaction with the silyl compound by dehalogenation to proceed favorably in the electrolyte. In this way, compounds formed by the bonding of silyl compounds and complex compounds in the electrolyte can be produced, which can further improve the cycle characteristics when used in energy storage devices. It can also contribute to improvements in various characteristics such as charge / discharge efficiency and resistance.

[0028] The concentration of the complex compound in the electrolyte is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, even more preferably 0.5 to 30% by mass, and particularly preferably 10 to 30% by mass.

[0029] According to a preferred embodiment of the present invention, the electrolyte is given by the following formula (1): P(=S)(-X １ ) (-X ２ ) (-X ３ ) (1) contains a complex compound represented by the above formula (1). １ , X ２ and X ３ Each is independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, an alkoxy group, an alkenyloxy group, an alkylthio group, an aryl group, a halogen atom, a substituted or unsubstituted siloxy group, a substituted or unsubstituted thiosilane, and a structure represented by formula (2) described later. And X １ , X ２and X ３ At least one of these is a structure represented by formula (2). In formula (1) above, S (sulfur atom) is bonded to P (phosphorus atom) by a double bond, X １ , X ２ and X ３ Each of them is bonded to P.

[0030] The above equation (2) is as follows: -A-U － (-F) ｘ (-R)(M) ＋ ) (2) In the above formula (2), A is an oxygen atom or a sulfur atom. U is a boron atom or a phosphorus atom. M ＋ R is an alkali metal ion or a quaternary ammonium ion. x is an integer from 1 to 4. R is one selected from the group consisting of alkyl groups, alkenyl groups, alkoxy groups, alkenyloxy groups, aryl groups, halogen atoms, the structure represented by formula (3) described later, and the structure represented by formula (4) described later. In formula (2) above, each of the x F (fluorine atoms) is U － It combines with R and U － It is bonded to the cation M. ＋ However, U is an anion. － It exists in correspondence with the above. x may be any of 1, 2, 3, and 4, preferably 2 or 4. When U in formula (2) is a boron atom, x is preferably 1 or 2, more preferably 2. On the other hand, when U in formula (2) is a phosphorus atom, x is preferably 2 to 4, more preferably 3 or 4, and even more preferably 4.

[0031] The above equation (3) is as follows: -A-U － (-F) ｙ (M ＋ ) (3) In the above formula (3), A is an oxygen atom or a sulfur atom. U is a boron atom or a phosphorus atom. M ＋ is an alkali metal ion or a quaternary ammonium ion. y is an integer from 1 to 5. In the above formula (3), each of the y F (fluorine atoms) is U － It is bonded to the cation M. ＋is the anion U － and exists correspondingly. y can be any of 1, 2, 3, 4, and 5, preferably 3 or 5. When U in formula (3) is a boron atom, y is preferably 1 to 3, more preferably 2 or 3, and particularly preferably 3. On the other hand, when U in formula (3) is a phosphorus atom, y is preferably 2 to 5, more preferably 3 to 5, still more preferably 4 or 5, and particularly preferably 5.

[0032] The above-mentioned formula (4) is as follows: -A-D(-X ４ )(-X ５ ) (4). In the above formula (4), A is an oxygen atom or a sulfur atom. D is a P=O group or a P=S group. X ４ and X ５ are each independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, an alkoxy group, an alkenyloxy group, an aryl group, a halogen atom, a substituted or unsubstituted siloxy group, and the structure represented by the above formula (3). In the above formula (4), each of X ４ and X ５ is bonded to P (that is, the phosphorus atom possessed by D).

[0033] According to another preferred embodiment of the present invention, the electrolytic solution contains a complex compound represented by the following formula (5): D(-X ６ )(-X ７ )(-X ８ ) (5). In the above formula (5), D is a P=O group or a P=S group. X ６ , X ７ and X ８ are each independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, an alkoxy group, an alkenyloxy group, a substituted or unsubstituted siloxy group, a substituted or unsubstituted thiolsilane, and the structure represented by the following formula (6). Alternatively, two groups selected from the group consisting of X ６ , X ７ and X ８ may be such that one group is an oxygen atom and is bonded to the other group to form a ring structure. And X ６ , X７ and X ８ At least one of them is a structure represented by equation (6). In equation (5) above, X ６ , X ７ and X ８ Each of these is bonded to P (i.e., the phosphorus atom that D possesses).

[0034] The above-mentioned equation (6) is as follows:

[0035] Equation (6) above represents an oligomer of a molecular structure having a structure formed by linking each of the repeating units shown in parentheses, and the order in which the repeating units are linked is arbitrary. In equation (6) above, j is [ ] ｊ k represents the number of repetitions in the repetition unit enclosed in brackets, and is an integer between 1 and 10. ｋ The number of repetitions in the enclosed repeating unit is an integer between 0 and 10. A is an oxygen atom or a sulfur atom. B is a boron atom. D is a P=O group or a P=S group. G is a halogen atom. M ＋ X is an alkali metal ion or a quaternary ammonium ion. ９ This includes hydrogen atoms, alkyl groups, alkenyl groups, halogen atoms, alkoxy groups, alkenyloxy groups, substituted or unsubstituted siloxy groups, substituted or unsubstituted thiosilanes, and [ ] ｊ It is one of the types selected from the group consisting of structures enclosed by the brackets.

[0036] According to yet another preferred embodiment of the present invention, the electrolyte is the following formula (7): D(-X １０ ) (-X １１ ) (-X １２ ) (7) contains a complex compound represented by the above formula (7). In the above formula (7), D is a P=O group or a P=S group. １０ , X １１ and X １２ Each is independently selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, an alkoxy group, an alkenyloxy group, a substituted or unsubstituted siloxy group, a substituted or unsubstituted thiosilane, and a structure represented by formula (8) described later. Alternatively, X １０ , X １１ and X １２Two groups selected from the group consisting of may be one oxygen atom and bond with the other group to form a ring structure. １０ , X １１ and X １２ At least one of them is a structure represented by equation (8). In equation (7) above, X １０ , X １１ and X １２ Each of these is bonded to P (i.e., the phosphorus atom that D possesses).

[0037] The above-mentioned equation (8) is as follows:

[0038] Equation (8) above represents an oligomer of a molecular structure having a structure formed by linking each of the repeating units shown in parentheses, and the order in which the repeating units are linked is arbitrary. In equation (8) above, l is [ ] ｌ The number of repetitions in the repetition unit enclosed in brackets is an integer between 1 and 10. m is [ ] ｍ The number of repetitions in the repetition unit enclosed in brackets is an integer between 0 and 10. n is [ ] ｎ The number of repetitions in the enclosed repeating unit is an integer between 0 and 10. A is an oxygen atom or a sulfur atom. B is a boron atom. C is a carbon atom. D is a P=O group, a P=S group, or a boron atom. G is a halogen atom. M ＋ X is an alkali metal ion or a quaternary ammonium ion. １３ This is one selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, an alkoxy group, an alkenyloxy group, a substituted or unsubstituted siloxy group, and a substituted or unsubstituted thiosilane.

[0039] In formula (8) above, Z indicates that the preceding and succeeding carbon atoms are directly bonded, or is one selected from the group consisting of substituted or unsubstituted alkylene groups, substituted or unsubstituted alkenylene groups, substituted or unsubstituted phenylene groups, and alkylene groups having an ether group or a thioether group in the main chain. Preferred examples of Z include alkylene groups having 1 to 12 carbon atoms, alkenylene groups having 2 to 8 carbon atoms including an unsaturated bond, phenylene groups, ether groups having 2 to 6 carbon atoms with oxygen in the main chain, and thioether groups having 2 to 6 carbon atoms with sulfur in the main chain. Preferred examples of the structure in formula (8): -CO-Z-CO- include -CO-CO-, -CO-(CH ２ ) -CO-, -CO-(CH ２ ) ２ -CO-, -CO-(CH ２ ) ３ -CO-, -CO-(CH ２ ) ４ -CO-, -CO-(CH ２ ) ８ -CO-, -CO-(CH=CH)-CO-, -CO-(C ６ H ４ ) -CO-, -CO-(CH ２ OCH ２ ) -CO-, -CO-(CH ２ CH ２ OCH ２ CH ２ ) -CO-, -CO-(CH ２ SCH ２ )-CO-, and -CO-(CH ２ CH ２ SCH ２ CH ２ )-CO- is one example.

[0040] In the above formulas (1) to (8), if there are two or more A in the complex compound, the multiple As may be the same or different from each other. If there are two or more D in the complex compound, the multiple Ds may be the same or different from each other. If there are two or more Gs in the complex compound, the multiple Gs may be the same or different from each other. If there is M in the complex compound ＋ If there are two or more, there are multiple M＋ They may be the same or different from each other (however, M ＋ At least one of them is Li ＋ (This is the case.) If there are two or more U atoms in the complex compound, the multiple U atoms may be the same or different from each other. If there are two or more Z atoms in the complex compound, the multiple Z atoms may be the same or different from each other.

[0041] The following describes preferred embodiments of the complex compounds represented by the above formulas (1) to (8). First, X １ ~X １３ The alkyl groups in and R are each preferably linear or cyclic alkyl groups having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms. Preferred examples of alkyl groups include methyl, ethyl, propyl, butyl, hexyl, cyclopropyl, cyclobutyl, cyclohexyl, hydroxyethyl, trifluoromethyl, and hexafluoroethyl groups.

[0042] X １ ~X １３ The alkenyl groups in and R are each preferably alkenyl groups having 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms. Preferred examples of alkenyl groups include vinyl groups, propenyl groups (e.g., allyl groups), isopropenyl groups, 2-methyl-1-propenyl groups, butenyl groups, and heptenyl groups.

[0043] X １ ~X １３ The alkoxy groups in and R are each preferably alkoxy groups having 1 to 9 carbon atoms, more preferably 1 to 5 carbon atoms. Preferred examples of alkoxy groups include methoxy, ethoxy, butoxy, hexyloxy, trifluoromethyloxy, and trifluoroethyloxy groups.

[0044] X １ ~X １３The alkenyloxy groups in and R are each preferably alkenyloxy groups having 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms. Preferred examples of alkenyloxy groups include vinyloxy groups, propenyloxy groups (e.g., allyloxy groups), isopropenyloxy groups, 2-methyl-1-propenyloxy groups, butenyloxy groups, and heptenyloxy groups.

[0045] X １ ~X ３ The alkylthio groups in each are preferably alkylthio groups having 1 to 9 carbon atoms, more preferably 1 to 5 carbon atoms. Preferred examples of alkylthio groups include methylthio group, ethylthio group, propylthio group, butylthio group, hexylthio group, cyclopropylthio group, cyclobutylthio group, cyclohexylthio group, trifluoromethylthio group, trifluoroethylthio group, and hexafluoropropylthio group.

[0046] X １ ~X ５ The aryl groups in and R are preferably aryl groups having 6 to 15 carbon atoms. Preferred examples of aryl groups include phenyl, tolyl, 1-naphthyl, 2-naphthyl, 2-furyl, 3-furyl, 2-pyrrolyl, 3-pyrrolyl, and benzyl groups.

[0047] X １ ~X １３ Examples of halogen atoms in G and R include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Among these, the halogen atom is preferably a fluorine (F) and / or a chlorine (Cl), and more preferably a fluorine (F), because the bond with the phosphorus and boron atoms is stable.

[0048] X １ ~X １３Preferred examples of substituted or unsubstituted siloxy groups in include trimethylsiloxy, triethylsiloxy, triisopropylsiloxy, butyldimethylsiloxy, tributylsiloxy, trimethoxysiloxy, triethoxysiloxy, and tributoxysiloxy.

[0049] X １ ~X ３ and X ６ ~X １３ Preferred examples of substituted or unsubstituted thiosilanes in this context include trimethylthiosilane, triethylthiosilane, triisopropylthiosilane, butyldimethylthiosilane, tributylthiosilane, trimethoxythiosilane, triethoxythiosilane, and tributoxythiosilane. Substituted or unsubstituted thiosilanes have a structure in which a substituted or unsubstituted silyl group is bonded to a sulfur atom (S), and are also referred to as substituted or unsubstituted silylthio groups.

[0050] M ＋ Examples of alkali metal ions or quaternary ammonium ions represented by Li include ＋ Na ＋ _K ＋ , Rb ＋ , Cs ＋ , Fr ＋ , and NH ４ ＋ Among these, M ＋ Li ＋ and / or NH ４ ＋ Li ＋ This is more preferable. The complex compounds represented by the above formulas (1) to (8) are M ＋ Li ＋ It has at least one of the following:

[0051] A preferred example of the complex compound represented by the above formulas (1) to (4) is P(=S)(-SB － F ３ Li ＋ ) ３ , P(=S)(-OB － F ３ Li ＋ ) ３ , P(=S)(-OB－ 0. ３ Li ＋ ) ) ２ (-33) － 0. ３ Li ＋ )、P(S)-OB － 0. ３ Li ＋ (-OC(O ２ 38 ３ ) ) ２ 、P(=S)-O － 0. ３ Li ＋ ) ) ２ -OCH ２ 38 ３ )、P(S)-OB － 0. ３ Li ＋ (-OC(O ２ 3832 ２ ) ) ２ 、P(=S)-O － 0. ３ Li ＋ ) ) ２ -OCH ２ 3832 ２ )、P(S)-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ (-9) － 0. ３ Li ＋ ))、P(S)-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ -OP=O(-OB － 0. ３ Li ＋ ) ) ２ ))、P(S)-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ (e)(e)(e) － 0. ３Li ＋ )))、P(S)(-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ -OP=O(-3H ３ )(-9) － 0. ３ Li ＋ )))、P(S)(-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ -OP=O(-C(H ２ )(-9) － 0. ３ Li ＋ )))、P(S)(-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ -OP=O(-3H ２ 3832 ２ )(-9) － 0. ３ Li ＋ )))、P(S)(-OB － 0. ３ Li ＋ ) ) ２ (-9) － 0. ２ Li ＋ -OP(=O)-0)(-MB － 0. ３ Li ＋ )))、P(S)(-OB － 0. ３ Li ＋ )(Oｳi(3H ３ ) ) ３ ) ) ２ 、P(=S)-O － 0. ３ Li ＋ ) ) ２ (Oｳi(3H ３ ) ) ３ )、P(=S)-P)-OB －F ３ Li ＋ ) ２ , P(=S)(-F)(-OB － F ３ Li ＋ ) (-OCH ２ CH ３ ), P(=S)(-F)(-OB － F ３ Li ＋ ) (-OSi(CH ３ ) ３ ), P(=S)(-F)(-OB － F ３ Li ＋ ) (-OCH ２ CH ３ ), and P(=S)(-F)(-OB － F ３ Li ＋ ) (-SB － F ３ Li ＋ ) are some examples.

[0052] For reference, P(=S)(-OB) － F ３ Li ＋ ) ３ The structural formula is shown below.

[0053] Also, P(=S)(-OB － F ３ Li ＋ ) ２ (-OB － F ２ Li ＋ (-OP(=O)(-CH ２ CHCH ２ ) (-OB － F ３ Li ＋ The structural formula for ))) is shown below.

[0054] Furthermore, P(=S)(-OB) － F ３ Li ＋ ) ２ (-OSi(CH ３ ) ３ The structural formula of ) is shown below.

[0055] Preferred examples of complex compounds represented by formulas (5) and (6) above are shown below.

[0056] Preferred examples of the complex compounds represented by formulas (7) and (8) above are shown below.

[0057] The complex compounds represented by formulas (1) to (8) above may be produced by any method. Preferred methods for producing these complex compounds are described below.

[0058] In the first method, the complex compound is synthesized by reacting a boron halide compound or a phosphorus halide compound with a phosphorus-based salt. This method preferably includes a step of bringing the boron halide compound or phosphorus halide compound into contact with a phosphorus-based salt in the presence or absence of a solvent to allow the reaction to proceed.

[0059] For example, a phosphorus-based salt is added to a liquid containing a boron halide compound or a phosphorus halide compound dissolved or dispersed in a solvent under an inert atmosphere (e.g., an argon or nitrogen atmosphere). In this case, the phosphorus-based salt may be added while the liquid containing the boron halide compound or phosphorus halide compound is cooled (e.g., below 20°C). The solvent is not particularly limited as long as it is inert to the above reaction. Preferred examples of solvents include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, pyridine, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. The reaction can be desirablely carried out by holding or stirring the liquid after the addition of the phosphorus-based salt at a temperature of preferably 0 to 80°C for preferably 1 to 24 hours. The crude complex compound can be obtained by concentrating the reaction mixture and removing the solvent. A high-purity complex compound can be obtained by purifying, washing, and drying the obtained crude complex compound under reduced pressure.

[0060] Preferred examples of boron halide compounds include boron trihalide, boron trihalide dimethyl ether complex, boron trihalide diethyl ether complex, boron trihalide di-n-butyl ether complex, boron trihalide ditert-butyl ether complex, boron trihalide tert-butyl methyl ether complex, boron trihalide tetrahydrofuran complex, boron trihalide methanol complex, boron trihalide ethanol complex, boron trihalide propanol complex, boron trihalide butanol complex, boron trihalide phenol complex, boron trihalide ethylene carbonate complex, boron trihalide ethyl methyl carbonate complex, boron trihalide dimethyl carbonate complex, boron trihalide diethyl carbonate complex, boron trihalide sulfolane complex, boron trihalide acetate complex, aqueous solutions of these compounds with phosphorus-based salts, and compounds having boron halide groups as reaction products.

[0061] The halogen contained in the boron halide compound is preferably fluorine, chlorine, or a combination thereof, and more preferably fluorine. Preferred examples of boron fluoride compounds include boron trifluoride, boron trifluoride dimethyl ether complex, boron trifluoride diethyl ether complex, boron trifluoride di-n-butyl ether complex, boron trifluoride ditert-butyl ether complex, boron trifluoride tert-butyl methyl ether complex, boron trifluoride tetrahydrofuran complex, boron trifluoride methanol complex, boron trifluoride ethanol complex, and trifluoride Examples include boron-propanol complexes, boron trifluoride-butanol complexes, boron trifluoride-phenol complexes, boron trifluoride-ethylene carbonate complexes, boron trifluoride-ethylmethyl carbonate complexes, boron trifluoride-dimethyl carbonate complexes, boron trifluoride-diethyl carbonate complexes, boron trifluoride-sulfolane complexes, boron trifluoride-acetic acid complexes, aqueous solutions of boron trifluoride, and compounds having a boron fluoride group as reaction products of these with phosphorus-based salts. Among these, boron trifluoride, boron trifluoride dimethyl ether complex, boron trifluoride diethyl ether complex, boron trifluoride methanol complex, boron trifluoride ethanol complex, boron trifluoride propanol complex, boron trifluoride butanol complex, boron trifluoride ethylene carbonate complex, boron trifluoride ethylmethyl carbonate complex, boron trifluoride dimethyl carbonate complex, boron trifluoride diethyl carbonate complex, boron trifluoride sulfolane complex, or combinations thereof are more preferred, and boron trifluoride, boron trifluoride methanol complex, boron trifluoride butanol complex, boron trifluoride ethylene carbonate complex, boron trifluoride ethylmethyl carbonate complex, boron trifluoride dimethyl carbonate complex, boron trifluoride diethyl carbonate complex, or combinations thereof are even more preferred.

[0062] Preferred examples of boron chloride compounds include boron trichloride, boron trichloride diethyl ether complex, boron trichloride methanol complex, boron trichloride ethanol complex, boron trichloride butanol complex, and compounds having a boron chloride group as reaction products of these with phosphorus-based salts.

[0063] Preferred examples of phosphorus halogenated compounds include phosphorus pentafluoride and phosphorus pentafluoride complexes. Phosphorus pentafluoride complexes are formed from phosphorus pentafluoride and oxygen of an oxygen-containing compound, and are obtained by contacting phosphorus pentafluoride with an oxygen-containing compound. Preferred examples of oxygen-containing compounds include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Preferred examples of phosphorus pentafluoride complexes include phosphorus pentafluoride ethylene carbonate complex, phosphorus pentafluoride dimethyl carbonate complex, phosphorus pentafluoride diethyl carbonate complex, and phosphorus pentafluoride ethylmethyl carbonate complex. Among these, phosphorus pentafluoride, phosphorus pentafluoride dimethyl carbonate complex, phosphorus pentafluoride diethyl carbonate complex, phosphorus pentafluoride ethylmethyl carbonate complex, or combinations thereof are more preferred.

[0064] Phosphorus salts are compounds having a P=O group or a P=S group and containing an alkali metal ion or a quaternary ammonium ion. Furthermore, phosphorus salts have at least one lithium ion as the alkali metal ion. Preferred examples of phosphorus salts include salts of phosphinic acid, dimethylphosphinic acid, phosphonic acid, methylphosphonic acid, vinylphosphonic acid, phosphoric acid, diphosphate, polyphosphate, methyl phosphate, ethyl phosphate, monothiophosphate, dithiophosphate, trithiophosphate, tetrathiophosphate, diethyldithiophosphate, etc., with an alkali metal ion or a quaternary ammonium ion, and reaction products of these with boron halide compounds or phosphorus halide compounds that have a P=O group or a P=S group and contain an alkali metal ion or a quaternary ammonium ion.

[0065] In the second method, the complex compound is synthesized by reacting a boron halide salt or a phosphorus halide salt with a phosphorus compound. This method preferably includes a step (hereinafter referred to as the "first step") to allow the bonding reaction between the boron halide salt or phosphorus halide salt and the phosphorus compound to proceed by dehalogenation silylation. The above method may further include a step (hereinafter referred to as the "second step") after the first step, in which additional reaction raw materials containing a boron halide salt or a phosphorus halide salt and / or a phosphorus compound are added to allow an additional bonding reaction by dehalogenation silylation to proceed.

[0066] The silyl dehalogenation reaction proceeds even in the absence of a solvent, but a solvent may be added as needed. Furthermore, the silyl dehalogenation reaction can be efficiently carried out by controlling the reaction temperature. The reaction temperature is not particularly limited as long as it allows the silyl dehalogenation reaction to proceed efficiently. For example, the reaction temperature can be selected in the range of 10 to 150°C depending on the type of solvent used, and the reaction can be more preferably promoted in the range of 20 to 120°C. Also, from the viewpoint of ease of controlling the reaction rate, the range of 40 to 100°C is particularly preferred.

[0067] The molar ratio of boron in the boron halide salt or phosphorus in the phosphorus halide salt to the silyl group of the phosphorus compound in each of the first and second steps can be appropriately determined depending on the target chemical structure of the resulting complex compound, and is not particularly limited.

[0068] The boron halide salt or phosphorus halide salt preferably contains an anion having a halogen atom bonded to a boron atom or phosphorus atom, and an alkali metal ion or quaternary ammonium ion, and is capable of carrying out a silyl dehalogenation reaction. Furthermore, the boron halide salt or phosphorus halide salt contains at least one lithium ion as the alkali metal ion. Preferred examples of boron halide salts and phosphorus halide salts include complex salts having diboron halide or triboron halide groups in the molecule, tetraborate salts, monophosphate salts, diphosphate salts, tetraphosphate salts, pentaphosphate salts, hexaphosphate salts, carboxylic acid complex salts, phosphinate complex salts, phosphonate complex salts, phosphoric acid complex salts, phosphoric acid complex salts, condensed phosphoric acid complex salts, thiophosphate complex salts, and reaction products of these with phosphorus compounds that have a halogen atom bonded to a boron atom or a phosphorus atom, lithium oxide-triboron halide complex salts, and lithium sulfide-triboron halide complex salts. In this specification, for convenience, the number of boron halide groups may be omitted in the names of complex salts, but these complex salts have a predetermined number of boron halide groups depending on their structure.

[0069] Preferred examples of carboxylic acid complex salts include oxalate / boron trihalide complex salts, maleate / boron trihalide complex salts, fumarate / boron trihalide complex salts, citraconate / boron trihalide complex salts, adipinate / boron trihalide complex salts, glutarate / boron trihalide complex salts, succinate / boron trihalide complex salts, tartrate / boron trihalide complex salts, malonate / boron trihalide complex salts, glycolate / boron trihalide complex salts, diglycolate / boron trihalide complex salts, thiodiacetate / boron trihalide complex salts, and thiodipropionate / boron trihalide complex salts.

[0070] Preferred examples of phosphinate-based complex salts include phosphinate-boron trihalide complex salts, dimethylphosphinate-boron trihalide complex salts, and difluorophosphate-boron trihalide complex salts.

[0071] Preferred examples of phosphonic acid complex salts include phosphonate / boron trihalide complex salts, methylphosphonate / boron trihalide complex salts, vinylphosphonate / boron trihalide complex salts, and fluorophosphate / boron trihalide complex salts.

[0072] Preferred examples of phosphate-based complex salts include phosphate-boron trihalide complex salts, methyl phosphate-boron trihalide complex salts, and ethyl phosphate-boron trihalide complex salts.

[0073] Preferred examples of condensed phosphate complex salts include diphosphate-boron trihalide complex salts, metaphosphate-boron trihalide complex salts, and polyphosphate-boron trihalide complex salts.

[0074] Preferred examples of thiophosphate complex salts include monothiophosphate-boron trihalide complex salts, dithiophosphate-boron trihalide complex salts, trithiophosphate-boron trihalide complex salts, and tetrathiophosphate-boron trihalide complex salts.

[0075] Fluorine is preferred as the halogen in the boron halide or phosphorus halide salt. Lithium ions are preferred as the cation in the boron halide or phosphorus halide salt. In particular, lithium boron fluoride salts are preferred.

[0076] Preferred examples of boron fluoride-based lithium salts include lithium tetrafluoroborate, lithium oxide / boron trifluoride complex salt, lithium sulfide / boron trifluoride complex salt, lithium oxalate / boron trifluoride complex salt, lithium maleate / boron trifluoride complex salt, lithium fumarate / boron trifluoride complex salt, lithium citraconate / boron trifluoride complex salt, lithium aconitate / boron trifluoride complex salt, and lithium thiodiacetate / boron trifluoride. Lithium complex salts, lithium thiopropionate / boron trifluoride complex salts, lithium adipicate / boron trifluoride complex salts, lithium glutarate / boron trifluoride complex salts, lithium succinate / boron trifluoride complex salts, lithium tartrate / boron trifluoride complex salts, lithium malonate / boron trifluoride complex salts, lithium glycolate / boron trifluoride complex salts, lithium diglycolate / boron trifluoride complex salts, lithium borate / boron trifluoride complex Salts, lithium phosphinate / boron trifluoride complex salts, lithium dimethylphosphinate / boron trifluoride complex salts, lithium phosphoneate / boron trifluoride complex salts, methylphosphoneate / boron trifluoride complex, lithium vinylphosphoneate / boron trifluoride complex salts, lithium phosphate / boron trifluoride complex salts, lithium diphosphate / boron trifluoride complex salts, lithium polyphosphate / boron trifluoride complex salts, lithium phosphate / boron trifluoride Examples include fluorine complex salts, methyllithium phosphate / boron trifluoride complex salts, ethyllithium phosphate / boron trifluoride complex salts, lithium monothiophosphate / boron trifluoride complex salts, lithium dithiophosphate / boron trifluoride complex salts, lithium trithiophosphate / boron trifluoride complex salts, lithium tetrathiophosphate / boron trifluoride complex salts, and reaction products of these with phosphorus-based compounds that have two or more fluorine atoms bonded to a boron atom.

[0077] The phosphorus-based compound is preferably a compound having a siloxy group or thiosilane group bonded to a P=O group or a P=S group. Preferred examples of phosphorus-based compounds include phosphinic acid, phosphonic acid, vinylphosphonic acid, phosphoric acid, diphosphate, triphosphate, tetraphosphate, polyphosphate, monothiophosphate, dithiophosphate, trithiophosphate, tetrathiophosphate, diethyldithiophosphate, and derivatives thereof. More preferred examples of phosphorus-based compounds include trimethylsilyl phosphinate, trimethylsilyl dimethylphosphinate, bis(trimethylsilyl) phosphonate, bis(trimethylsilyl) vinylphosphonate, bis(trimethylsilyl) allylphosphonate, tris(trimethylsilyl) phosphate, tetra(trimethylsilyl) diphosphate, trimethylsilyl polyphosphate, tris(trimethylsilyl) monothiophosphate, tris(trimethylsilyl) dithiophosphate, tris(trimethylsilyl) trithiophosphate, tris(trimethylsilyl) tetrathiophosphate, and reaction products of these with boron halide salts or phosphorus halide salts.

[0078] The complex compound can also be a lithium-containing complex compound disclosed in the aforementioned Patent Document 3 (WO2019 / 180945), etc.

[0079] The electrolyte is preferably obtained by adding a mixture of a silyl compound and a complex compound to a solvent. The silyl compound and / or complex compound in the electrolyte may be dissolved in the solvent or dispersed in the solvent. The electrolyte may also contain a compound in which the silyl compound and the complex compound are bonded by the dehalogenation silyl reaction described above. A gel-like electrolyte can also be obtained by generating a compound in which the silyl compound and the complex compound are bonded by the dehalogenation silyl reaction or the like. In this specification, "gel-like" means an amorphous, highly viscous fluid state, or an amorphous state that does not have fluidity.

[0080] The solvent is preferably an organic solvent (non-aqueous solvent). The organic solvent preferably contains carbonate esters (also called carbonates), carboxylic acid esters, sulfone compounds, nitrile compounds, or combinations thereof, and more preferably contains carbonate esters from the viewpoint of enhancing ionic conductivity.

[0081] The carbonate ester preferably contains both cyclic carbonate esters and linear carbonate esters, and more preferably contains all three types: saturated cyclic carbonate esters, unsaturated cyclic carbonate esters, and linear carbonate esters. The volume ratio of cyclic carbonate ester to linear carbonate ester in the electrolyte is not particularly limited, but from the viewpoint of improving the degree of dissociation and solubility of the complex compound, low viscosity, and high ionic conductivity, it is preferably 10 / 90 to 70 / 30, and more preferably 20 / 80 to 50 / 50. On the other hand, the amount of unsaturated cyclic carbonate ester contained in the total organic solvent is preferably 0.01 to 10% by volume, and more preferably 0.1 to 5% by volume.

[0082] Preferred examples of saturated cyclic carbonate esters include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate, and 4,5-difluoroethylene carbonate. More preferred examples include ethylene carbonate, propylene carbonate, and fluoroethylene carbonate. Propylene carbonate is particularly preferred because it allows for the acquisition of a stable electrolyte over a wide temperature range.

[0083] Preferred examples of unsaturated cyclic carbonate esters include vinylene carbonate and its derivatives, as well as alkenylethylene carbonate. Preferred examples of vinylene carbonate derivatives include vinylene carbonate, fluorovinylene carbonate, methylvinylene carbonate, fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, and dipropylvinylene carbonate. Preferred examples of alkenylethylene carbonates include 4-vinylethylene carbonate, 4-vinyl-4-methylethylene carbonate, 4-vinyl-4-ethylethylene carbonate, and 4-vinyl-4-n-propylethylene carbonate.

[0084] Preferred examples of linear carbonate esters include linear carbonate esters having 3 to 9 carbon atoms, and specific examples include ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and methyl trifluoroethyl carbonate. In the above compounds, the propyl group may independently be an n-propyl group or an isopropyl group, and the butyl group may independently be an n-butyl group, an isobutyl group, or a t-butyl group. Among these, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, or a combination thereof is preferred.

[0085] The carboxylic acid ester may be a cyclic carboxylic acid ester, a linear carboxylic acid ester, or a combination of both. Preferred examples of cyclic carboxylic acid esters (also called lactones) include those with 3 to 9 carbon atoms, specifically γ-butyrolactone, γ-valerolactone, γ-caprolactone, and ε-caprolactone. Among these, γ-butyrolactone, γ-valerolactone, or a combination thereof is more preferred. Preferred examples of linear carboxylic acid esters include those with 3 to 9 carbon atoms, specifically methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, and t-butyl propionate. Among these, ethyl acetate, methyl propionate, ethyl propionate, or a combination thereof is more preferred.

[0086] Preferred examples of sulfone compounds include dimethyl sulfone, diethyl sulfone, ethylmethyl sulfone, methylpropyl sulfone, sulfolane, 2-methylsulfolane, and 3-methylsulfolane.

[0087] Preferred examples of nitrile compounds include acetonitrile, succinonitrile, adiponitrile, and benzonitrile.

[0088] The organic solvent may further contain other solvents such as ether compounds and phosphate ester compounds. Preferred examples of ether compounds include cyclic ether compounds, linear ether compounds, linear glycol ether compounds, and fluorine-containing ether compounds. Preferred examples of cyclic ether compounds include tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, dioxolane, and 4-methyldioxolane. A preferred example of a linear ether compound is dimethyl ether. Preferred examples of linear glycol ethers include those having 3 to 6 carbon atoms, specifically dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, and ethoxymethoxyethane. Among these, dimethoxyethane, diethoxyethane, or combinations thereof are more preferred. Specific examples of fluorine-containing ethers include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3,3-pentafluoropropyl ether, and ethoxy-2,2,2-trifluoroethoxyethane.

[0089] The electrolyte may further contain other electrolytes and / or additives in addition to the silyl compound and complex compound described above. Preferred examples of such electrolytes include lithium salts (excluding the lithium-containing complex compounds described above), specifically LiPF ６ LiAsF ６ LiBF ４ LiClO ４ LiBrO ４ LiIO ４ LiCF ３ SO ３ , LiN (FSO ２ ) ２ ,LiN(CF ３ SO ２ ) ２ ,LiN(C ２ F ５ SO ２ ) ２ ,LiN(CF ３ SO ２ ) (C２ F ５ SO ２ ), LiiN(CF ３ SO ２ )(C ４ F ９ SO ２ ), Li""("F ３ SO ２ ) ３ 、Li+PF(FF ３ ) ５ 、Li)PF ２ (CF) ３ ) ４ 、Li)PF ３ (CF) ３ ) ３ 、Li)PF ２ (C ２ F ５ ) ４ 、Li)PF ３ (C ２ F ５ ) ３ 、Li+PF(n-C ３ F ７ ) ５ 、Li)PF ２ (n-C ３ F ７ ) ４ 、Li)PF ３ (n-C ３ F ７ ) ３ 、LiPF(iso-C ３ F ７ ) ５ 、Li)PF ２ (ｳso-C) ３ F ７ ) ４ 、Li)PF ３ (ｳso-C) ３ F ７ ) ３ 、LiiB(CF ３ ) ４ 、Liidt(Cd ３ ) ３ 、Liida ２ (CF) ３ ) ２ 、Liida ３ (CF) ３ ), Liic(C ２ F ５ ) ４ 、LiiBF(C ２F ５ ) ３ LiBF ２ (C ２ F ５ ) ２ LiBF ３ (C ２ F ５ ), LiB(n-C ３ F ７ ) ４ , LiBF(n-C ３ F ７ ) ３ LiBF ２ (n-C ３ F ７ ) ２ LiBF ３ (n-C ３ F ７ ), LiB(iso-C ３ F ７ ) ４ , LiBF(iso-C ３ F ７ ) ３ LiBF ２ (iso-C ３ F ７ ) ２ , and LiBF ３ (iso-C ３ F ７ ) are some examples. Among these, LiPF ６ LiBF ４ LiCF ３ SO ３ , LiN (FSO ２ ) ２ ,LiN(CF ３ SO ２ ) ２ ,LiN(C ２ F ５ SO ２ ) ２ ,LiN(CF ３ SO ２ ) (C ２ F ５ SO ２ ), LiN (CF ３ SO ２ ) (C ４ F ９ SO ２ ), or a combination thereof, is particularly preferred.

[0090] The cations present in the electrolyte include at least lithium cations. The electrolyte may further contain sodium cations and / or quaternary ammonium cations in addition to lithium cations. From the viewpoint of improving charge-discharge characteristics and suppressing an increase in internal resistance, the concentration of total cations (especially total lithium cations) in the electrolyte is preferably 0.1 to 5.0 mol / L, and more preferably 0.7 to 2.5 mol / L.

[0091] Preferred examples of additives that may be included in the electrolyte include cyclic carbonate compounds, sulfur-containing compounds, cyclic acid anhydrides, carboxylic acid compounds, boron-containing compounds, phosphorus-containing compounds, and isocyanate compounds, from the viewpoint of improving the lifespan and resistance performance of the energy storage device. These additives may be used individually or in combination of two or more. When the electrolyte contains these additives, the concentration of the additives in the electrolyte is preferably 0.01 to 5% by mass, and more preferably 0.1 to 2% by mass.

[0092] Preferred examples of cyclic carbonate compounds include halogenated ethylene carbonates, vinylene carbonates and their derivatives, and alkenyl ethylene carbonates. Preferred examples of vinylene carbonate derivatives include vinylene carbonate, fluorovinylene carbonate, methylvinylene carbonate, fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, and dipropylvinylene carbonate. Preferred examples of alkenyl ethylene carbonates include 4-vinylethylene carbonate, 4-vinyl-4-methylethylene carbonate, 4-vinyl-4-ethylethylene carbonate, and 4-vinyl-4-n-propylethylene carbonate.

[0093] Preferred examples of sulfur-containing compounds include 1,3-propanesultone (PS), propensultone, ethylene sulfite, hexahydrobenzo[1,3,2]dioxathiolan-2-oxide (also known as 1,2-cyclohexanediol cyclic sulfite), 5-vinyl-hexahydro1,3,2-benzodioxathiol-2-oxide, 1,4-butanediol dimethanesulfonate, 1,3-butanediol dimethanesulfonate, methylenemethanedisulfonic acid, ethylenemethanedisulfonic acid, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, divinylsulfone, 1,2-bis(vinylsulfonyl)methane, 1,3,2-dioxathiolan-2,2-dioxide, tetrakis(vinylsulfonylmethyl)methane, and pentaerythritol bicyclic sulfate.

[0094] Preferred examples of cyclic acid anhydrides include glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, succinic anhydride, diglycolic anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentanetetracarboxylic acid dianhydride, 4-cyclohexene-1,2-dicarboxylic acid anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, phenylsuccinic acid anhydride, 2-phenylglutaric acid anhydride, phthalic anhydride, pyromellitic anhydride, fluorosuccinic acid anhydride, and tetrafluorosuccinic acid anhydride. Examples include aqueous carboxylic acid anhydrides, 1,2-ethanedisulfonic acid anhydride, 1,3-propanedisulfonic acid anhydride, 1,4-butanedisulfonic acid anhydride, 1,2-benzenedisulfonic acid anhydride, tetrafluoro-1,2-ethanedisulfonic acid anhydride, hexafluoro-1,3-propanedisulfonic acid anhydride, octafluoro-1,4-butanedisulfonic acid anhydride, 3-fluoro-1,2-benzenedisulfonic acid anhydride, 4-fluoro-1,2-benzenedisulfonic acid anhydride, and 3,4,5,6-tetrafluoro-1,2-benzenedisulfonic acid anhydride.

[0095] Preferred examples of carboxylic acid compounds include lithium oxalate, lithium malonate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, lithium adipate, lithium glutarate, lithium acetonedicarboxylate, lithium 2-oxobutyrate, lithium oxalacetate, lithium 2-oxoglutarate, lithium acetoacetate, lithium 3-oxocyclobutanecarboxylate, lithium 3-oxocyclopentanecarboxylate, lithium 2-oxovalerate, lithium pyruvate, and lithium glyoxylate. Examples include lithium 3,3-dimethyl-2-oxobutyrate, lithium 2-hydroxypropionate, lithium 2-methyllactate, lithium tartrate, lithium cyanoacetate, lithium 2-mercaptopropionate, lithium methylenebis(thioglycolate)thiodicuccinate, lithium 3-(methylthio)propionate, lithium 3,3'-thiodipropionate, lithium dithiodiglycolate, lithium 2,2'-thiodiglycolate, lithium thiazolidinedione-2,4-dicarboxylate, and lithium acetylthioacetate.

[0096] A preferred example of a boron-containing compound is LiBF ２ (C ２ O ４ ), LiB(C ２ O ４ ) ２ LiBF ２ (CO ２ CH ２ CO ２ ), LiB(CO ２ CH ２ CO ２ ) ２ LiB(CO) ２ CF ２ CO ２ ) ２ LiBF ２ (CO ２ CF ２ CO ２ ), LiBF ３ (CO ２ CH ３ ), LiBF ３ (CO ２ CF ３ ), LiBF ２ (CO ２CH ３ ) ２ LiBF ２ (CO ２ CF ３ ) ２ LiBF(CO) ２ CH ３ ) ３ LiBF(CO) ２ CF ３ ) ３ LiB(CO) ２ CH ３ ) ４ LiB(CO) ２ CF ３ ) ４ Li ２ B ２ O ７ , and Li ２ B ２ O ４ These are some examples.

[0097] Preferred examples of phosphorus-containing compounds include trimethyl phosphate, methyl metaphosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, dimethyl phosphate, dimethyl methylphosphonate, diethyl phosphate, diethyl fluorophosphate, diethyl vinylphosphonate, phosphonic anhydride, methylphosphonic anhydride, propylphosphonic anhydride, vinylphosphonic anhydride, and lithium difluorophosphate.

[0098] Preferred examples of isocyanate compounds include alkyl isocyanates such as methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tert-butyl isocyanate, cycloalkyl isocyanates such as cyclohexyl isocyanate, allyl isocyanate, propargyl isocyanate, monomethylene diisocyanate, dimethyl diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, and 1,4-di Examples include socyanato-2-butene, toluene diisocyanate, xylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diirbis(methylisocyanate), bicyclo[2.2.1]heptane-2,6-diirbis(methylisocyanate), isophorone diisocyanate, carbonyl diisocyanate, 1,4-diisocyanatobutane-1,4-dione, and trimethylhexamethylene diisocyanate.

[0099] Energy Storage Device The electrolyte of the present invention is preferably used in energy storage devices. That is, according to a preferred embodiment of the present invention, an energy storage device is provided comprising a positive electrode, a negative electrode, and the electrolyte present at least between the positive electrode and the negative electrode. The energy storage device may be a liquid-type energy storage device comprising a liquid electrolyte, a semi-solid energy storage device comprising a gel-like electrolyte, or a semi-solid energy storage device comprising both a solid electrolyte and an electrolyte. In particular, the electrolyte contained in the energy storage device is preferably in gel form. For example, the electrolyte can be gelled by subjecting it to heat treatment, thereby promoting the bonding of the silyl compound and the complex compound by the dehalogenation silyl reaction described above. Alternatively, the electrolyte may be gelled by adding a commercially available gelling agent to the electrolyte.

[0100] Therefore, it is preferable that the electrolyte is heat-treated. The heat treatment of the electrolyte may be performed before, during, or after filling the battery cell. That is, the electrolyte may be filled between the positive and negative electrodes in an unheat-treated state and then heat-treated. Alternatively, the electrolyte may be filled between the positive and negative electrodes after or while being heat-treated. The heat treatment conditions can be appropriately determined according to the type of electrolyte (for example, the type and concentration of silyl compounds and complex compounds contained in the electrolyte) and are not particularly limited. For example, by holding the electrolyte or a power storage device equipped with the electrolyte in an atmosphere of 20 to 150°C, preferably 30 to 120°C, for 0.1 to 300 hours, preferably 3 to 150 hours, the gelation of the electrolyte by a dehalogenated silyl reaction or the like can be desirablely promoted. The heat treatment of the electrolyte may be performed in the presence of oxygen or in the presence of an inert gas and is not particularly limited.

[0101] Preferred examples of energy storage devices include secondary batteries (e.g., lithium-ion secondary batteries), electric double-layer capacitors, and hybrid batteries in which one of the positive or negative electrodes is a battery and the other is an electric double layer, with lithium-ion secondary batteries being particularly preferred. The shape of the energy storage device is not particularly limited and can be in various shapes such as cylindrical, prismatic, aluminum laminate, coin-shaped, or button-shaped.

[0102] The following describes a preferred embodiment of a lithium-ion secondary battery as an example. A lithium-ion secondary battery is a secondary battery that charges and discharges by the movement of lithium ions between a positive electrode and a negative electrode, and is composed of a positive electrode, a negative electrode, a separator, an electrolyte, etc.

[0103] A preferred example of a negative electrode is a configuration in which a negative electrode active material is formed on a current collector such as copper foil, expanded metal, carbon material, or a composite material thereof. Preferred examples of negative electrode active materials constituting the negative electrode include carbon materials capable of insertion and removal of lithium ions, metallic lithium, lithium-containing alloys, silicon or silicon alloys capable of alloying with lithium, or tin or tin alloys, tin oxide or silicon oxide capable of insertion and removal of lithium ions, transition metal oxides capable of insertion and removal of lithium ions, transition metal nitrogen compounds capable of insertion and removal of lithium ions, and mixtures thereof, as well as mixtures obtained by inter-coating these materials.

[0104] Preferred carbon materials for the negative electrode active material include pyrolysis carbons, cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), graphites, calcined organic polymer compounds (e.g., phenolic resin, furan resin, etc., that have been calcined and carbonized), carbon fibers, activated carbon, and graphite (e.g., natural graphite, artificial graphite, carbon-coated graphite, graphite-coated graphite, resin-coated graphite, etc.). The carbon material is particularly preferred if the interplanar spacing (d002) of the (002) plane, as measured by X-ray diffraction, is 0.340 nm or less. Furthermore, the true density is 1.70 g / cm³. ３ Highly crystalline carbon materials having properties similar to graphite are preferred. By using such a carbon material as the negative electrode, the energy density of the energy storage device can be increased. Furthermore, as carbon materials, those containing boron, those coated with metals such as gold, platinum, silver, copper, Sn, and Si, and those coated with salts such as magnesium salts and calcium salts can be used.

[0105] Furthermore, (i) silicon that can be alloyed with lithium, (ii) silicon coated with carbon, (iii) silicon supported on carbon, (iv) silicon alloys, (v) tin or tin alloys, (v) tin oxide or silicon oxide that can insert and remove lithium ions, and (vi) transition metal oxides that can insert and remove lithium ions all have a higher theoretical capacity per unit weight than the carbon materials mentioned above and are suitable as negative electrode active materials.

[0106] The negative electrode may contain polyvinylidene fluoride-based binders, latex-based binders, etc., to improve the adhesion of the negative electrode active material to the current collector, and may also contain carbon black, amorphous whisker carbon, carbon nanofibers, etc., as conductive additives.

[0107] A preferred configuration for the positive electrode is one in which a positive electrode active material is formed on a current collector such as aluminum, titanium, or stainless steel foil, expanded metal, carbon material, or a composite material thereof. The positive electrode active material constituting the positive electrode can be formed from various materials that can be charged and discharged. Examples include lithium-containing transition metal oxides, lithium-containing transition metal composite oxides using one or more transition metals, transition metal oxides, transition metal sulfides, metal oxides, olivine-type metallic lithium salts, etc. Furthermore, LiCoO ２ LiNiO ２ LiMn ２ O ４ LiMnO ２ Li ｘ MO ２ A composite oxide of lithium and one or more transition metals (lithium transition metal composite oxide), represented as (where M is one or more transition metals, and x is a value that varies depending on the charge / discharge state of the energy storage device, usually 0.05 ≤ x ≤ 1.20), a metal composite oxide in which some of the transition metal atoms that make up the main body of these lithium transition metal composite oxides are replaced with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Yb, FeS ２ TiS ２ , V ２ O ５ MoO ３ MoS ２ Chalcogenides of transition elements such as polyacetylene and polypyrrole polymers can also be used. Among these, it is particularly preferable to construct the positive electrode active material with a lithium transition metal composite oxide that allows for the insertion and removal of lithium ions, or a metal composite oxide in which some of the transition metal atoms are replaced by other metals.

[0108] Furthermore, it is also possible to use positive electrode active materials in which a substance with a different composition from the main positive electrode active material is attached to the surface. Examples of surface-attached substances include carbon, metal oxides, metal sulfides, metal carbonates, and composite mixtures thereof. Preferred examples of metal oxides include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide, as well as composite mixtures thereof. Preferred examples of metal sulfides include lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate. Preferred examples of metal carbonates include carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and composite mixtures thereof.

[0109] The positive electrode may contain polyvinylidene fluoride-based binders, latex-based binders, etc., to improve the adhesion of the positive electrode active material to the current collector, and may also contain carbon black, amorphous whiskers, graphite, carbon nanofibers, etc., to improve the electron conductivity within the positive electrode.

[0110] The separator electrically insulates the positive electrode from the negative electrode and is preferably a membrane that allows lithium ions to pass through. Preferred examples of separators include porous membranes such as microporous polymer films. As microporous polymer films, porous polyolefin films are preferred, and specifically, porous polyethylene films, porous polypropylene films, or multilayer films of porous polyethylene films and polypropylene films are preferred. If necessary, an insulating layer may be further coated on the surface of these films. A polymer electrolyte can also be used as the separator. As polymer electrolytes, for example, polymer substances in which lithium salts are dissolved, polymer substances swollen with an electrolyte, etc., can be used, but are not limited to these.

[0111] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.

[0112] <Battery Fabrication> A lithium-ion secondary battery was fabricated as follows to evaluate the electrolyte prepared in the following example.

[0113] (1) Preparation of the positive electrode: 5% by mass of polyvinylidene fluoride as a binder, 4% by mass of acetylene black as a conductive agent, and a positive electrode active material (LiNi) which is a composite oxide powder of lithium, nickel, manganese, and cobalt. ０．６ Mn ０．２ Co ０．２ O ２ A positive electrode composite was prepared by mixing 91% by mass of ) with ). N-methylpyrrolidone was added to this positive electrode composite to make a paste. The paste-like positive electrode composite was applied to both sides of an 18 μm thick aluminum foil current collector, and after drying off the solvent, the positive electrode was obtained by rolling it with a roll press.

[0114] (2) Preparation of the negative electrode A slurry was prepared by mixing 95.8% by mass of artificial graphitizable carbon powder, 2.0% by mass of styrene-butadiene rubber (SBR) as a binder, and a 2.2% by mass aqueous solution of carboxymethylcellulose, and using water as a dispersion medium. This slurry was applied to both sides of a 12 μm thick copper foil, and after drying off the solvent, the negative electrode was obtained by rolling it with a roll press.

[0115] (3) Fabrication of the battery cell The obtained positive and negative electrodes were wound around a separator with a thickness of 23 μm to obtain a flattened wound electrode group. This flattened wound electrode group was placed in a case to fabricate a rectangular parallelepiped battery cell with dimensions of 30 mm (length) x 30 mm (width) x 2.0 mm (thickness).

[0116] (4) Fabrication of Lithium-ion Secondary Batteries Using the fabricated battery cells, lithium-ion secondary batteries were fabricated according to the following procedures (a) to (c). (a) 0.55 g of the electrolyte for each example was weighed out and poured into the filling port of the battery cell, and after depressurizing, the filling port was sealed. As will be described later, for certain examples, the battery cell was kept in an atmosphere at a predetermined temperature for a predetermined time. In this way, sealed battery cells were obtained. (b) With the sealed battery cells kept in an atmosphere of 25°C, they were charged to 4.2 V at 8 mA and then discharged to 3.0 V at 8 mA. (c) The internal gas of the battery cells discharged to 3.0 V was removed by depressurizing, and a lithium-ion secondary battery was obtained.

[0117] <Battery Evaluation> To evaluate the charge-discharge characteristics of the fabricated battery, the initial charge-discharge efficiency, -10°C resistance, capacity retention rate, and resistance change rate were measured as follows.

[0118] (Initial Charge / Discharge Efficiency) The sealed battery cell prepared in (4)(a) above was charged at 25°C with a current of 20mA until the voltage from 0V reached 4.2V. Then, while maintaining the voltage at 4.2V, charging was continued until the current value reached 4mA. The total current value consumed until the current value reached 4mA was defined as the initial charge capacity value. Subsequently, the battery in the above charged state was discharged at 25°C with a current of 20mA until the voltage reached 3.0V. The total current value consumed until the voltage reached 3.0V was defined as the initial discharge capacity value. The initial charge / discharge efficiency (%) was then calculated using the following formula: Initial charge / discharge efficiency (%) = [(Initial discharge capacity value) / (Initial charge capacity value)] × 100

[0119] (-10°C Resistance Value) The fabricated lithium-ion secondary battery was charged to a State of Charge (SOC) of 50% in a 25°C atmosphere, and then discharged for 10 seconds at a rate of 0.2C in a -10°C atmosphere. The voltage of the battery after discharge was measured. The same procedure was followed to measure the voltage of the battery after discharging for 10 seconds each at rates of 0.5C, 1.0C, and 2.0C in a -10°C atmosphere. The DC resistance value was determined using the voltage measurements for each rate of 0.2C, 0.5C, 1.0C, and 2.0C, and was defined as the -10°C resistance value.

[0120] (Capacity Retention Rate) The fabricated lithium-ion secondary battery was charged to 4.2V at a 1C rate in an atmosphere of 45°C, and then discharged to 3.0V at a 1C rate in the same atmosphere. This charge-discharge cycle was considered the first cycle, and the discharged capacity value was taken as the initial capacity value. Next, the above charge-discharge cycle was repeated under the same conditions until 200 cycles were reached, and the discharged capacity value at the 200th cycle was taken as the capacity value after the cycle. From this initial capacity value and the capacity value after the cycle, the capacity retention rate (%) was calculated using the following formula: Capacity Retention Rate = [(Capacity Value After Cycles) / (Initial Capacity Value)] × 100

[0121] (Resistance Change Rate) The fabricated lithium-ion secondary battery was charged to a State of Charge (SOC) of 50% in a 25°C atmosphere and discharged at a rate of 0.2C for 10 seconds. The voltage of the battery after discharge was measured. The voltage of the battery was measured after discharging at rates of 0.5C, 1.0C, and 2.0C for 10 seconds each, using the same procedure. The DC resistance was determined using the voltage measurements at 0.2C, 0.5C, 1.0C, and 2.0C, and was defined as the initial DC resistance. Subsequently, the lithium-ion secondary battery was charged to 4.2V at a rate of 1C in a 45°C atmosphere, and then discharged to 3.0V at a rate of 1C in the same atmosphere. This charge-discharge was considered one cycle, and the charge-discharge cycle was repeated until 200 cycles were reached. The DC resistance after each cycle was then measured under the same conditions as when the initial DC resistance was measured. From these initial DC resistance and DC resistance after each cycle, the resistance change rate (%) was calculated using the following formula. Resistance change rate = [(DC resistance after cycle) / (initial DC resistance)] × 100

[0122] Examples 1-6: Electrolytes of the present invention containing silyl compounds having a silyl group and lithium-containing complex compounds were prepared. Furthermore, batteries were fabricated and evaluated using the obtained electrolytes. Specifically, the details are as follows.

[0123] Example 1: A mixed solvent was obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC) in a volume ratio of 30:68:2. LiPF4 was added to this mixed solvent as a lithium salt. ６ A standard electrolyte was prepared by adding and dissolving the following to a concentration of 1 mol / L. To this standard electrolyte, tris(trimethylsilyl) phosphate, as a silyl compound, was added in an amount of 2.0% by mass, and lithium phosphate / boron trifluoride complex salt (P(=O)(-OB) was added as a complex compound. － F ３ Li ＋ ) ３The compound was added in such a way that its amount was 3.0% by mass. Here, the amount added refers to the ratio of the mass of the added silyl compound or complex compound to the total mass of the standard electrolyte and the added silyl compound and complex compound. In this way, an electrolyte containing the silyl compound and the complex compound was obtained.

[0124] Using the obtained electrolyte, a battery was fabricated according to the procedure described above. To evaluate the fabricated battery, the initial charge-discharge efficiency, -10°C resistance, capacity retention rate, and resistance change rate were measured as described above. The results are shown in Table 1.

[0125] Example 2: As a complex compound, instead of lithium phosphate / boron trifluoride complex salt, monothiophosphate / boron trifluoride complex salt (P(=S)(-OB) － F ３ Li ＋ ) ３ Except for the use of ( ), the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0126] The lithium monothiophosphate / boron trifluoride complex salt was synthesized as follows: First, under a nitrogen atmosphere, 200 mL of methanol was placed in an Erlenmeyer flask, and then 13.2 g of lithium monothiophosphate was dispersed in the methanol to obtain a dispersion. While cooling the obtained dispersion, 43.5 g of BF was added. ３ The methanol complex solution was added dropwise into an Erlenmeyer flask to obtain a mixture. The resulting mixture was kept at 25°C for 3 hours. After removing methanol from the mixture using an evaporator, it was washed three times with dibutyl ether and dried under reduced pressure. Thus, 20.1 g of lithium monothiophosphate / boron trifluoride complex salt (P(=S)(-OB) was obtained. － F ３ Li ＋ ) ３ ) was obtained.

[0127] Example 3: As a complex compound, instead of lithium phosphate / boron trifluoride complex salt, lithium tetrathiophosphate / boron trifluoride complex salt (P(=S)(-SB) － F ３ Li ＋ )３ Except for the use of ( ), the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0128] The lithium tetrathiophosphate / boron trifluoride complex salt was synthesized as follows: First, under an argon atmosphere, 10 wt% BF was added to an Erlenmeyer flask. ３ / 180g of ethylmethyl carbonate (MEC) complex solution was added. While cooling this complex solution, 9.6g of lithium tetrathiophosphate (Li ３ PS ４ The mixture was added to an Erlenmeyer flask over one hour to obtain a mixture. After removing ethylmethyl carbonate from the mixture using an evaporator, it was washed three times with dibutyl ether and dried under reduced pressure. Thus, 18.5 g of lithium tetrathiophosphate / boron trifluoride complex salt (P(=S)(-SB) was obtained. － F ３ Li ＋ ) ３ ) was obtained.

[0129] In Example 4, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 1, except that bis(trimethylsilyl)lithium boron trifluoride, represented by the following formula, was used as the silyl compound instead of tris(trimethylsilyl) phosphate. The results are shown in Table 1.

[0130] The bis(trimethylsilyl)lithium phosphate boron trifluoride was synthesized as follows: First, under a nitrogen atmosphere, 100 mL of ethylmethyl carbonate was placed in an Erlenmeyer flask, and then 9.4 g of lithium tetrafluoroborate was dissolved in the ethylmethyl carbonate to obtain a lithium tetrafluoroborate / ethylmethyl carbonate solution. 31.4 g of tris(trimethylsilyl) phosphate was added to this lithium tetrafluoroborate / ethylmethyl carbonate solution, and the mixture was stirred at 80°C for 3 hours to obtain a mixture. After removing the ethylmethyl carbonate from the mixture using an evaporator, the mixture was washed three times with dibutyl ether and dried under reduced pressure. Thus, bis(trimethylsilyl)lithium phosphate boron trifluoride was obtained.

[0131] Example 5 Except for using lithium monothiophosphate boron trifluoride complex salt (P(=S)(-OB － F ３ Li ＋ )) instead of lithium phosphate boron trifluoride complex salt as the complex compound, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 4. The results were as shown in Table 1.

[0132] Example 6 Except for using lithium tetrathiophosphate boron trifluoride complex salt (P(=S)(-SB － F ３ Li ＋ )) instead of lithium phosphate boron trifluoride complex salt as the complex compound, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 4. The results were as shown in Table 1.

[0133] Example 7 (Comparative) Except for using the reference electrolyte as the electrolyte without adding a silyl compound and a complex compound, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 1. The results were as shown in Table 1.

[0134]

[0135] Examples 8 to 12 The batteries were evaluated using the heat-treated electrolyte of the present invention. Specifically, it was as follows. The electrolytes of Examples 8 to 12 changed from a liquid state to a gel state by being allowed to cool to room temperature after the heat treatment.

[0136] Example 8 Except for performing the heat treatment of the battery cell by holding the sealed battery cell in an atmosphere at 60°C for 10 hours after injecting the electrolyte into the battery cell, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 1. The results were as shown in Table 2.

[0137] Example 9 Except for using trimethylsilyl polyphosphate instead of tris(trimethylsilyl) phosphate as the silyl compound, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 8. The results were as shown in Table 2.

[0138] ​​​​In Example 10, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 8, except that bis(trimethylsilyl) vinylphosphonate was used as the silyl compound instead of tris(trimethylsilyl) phosphate. The results are shown in Table 2.

[0139] In Example 11, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 8, except that bis(trimethylsilyl)lithium boron trifluoride was used as the silyl compound instead of tris(trimethylsilyl) phosphate. The results are shown in Table 2.

[0140] In Example 12, the electrolyte was prepared, and the battery was fabricated and evaluated in the same manner as in Example 8, except that tris(trimethylsilyl) monothiophosphate was used as the silyl compound instead of tris(trimethylsilyl) phosphate. The results are shown in Table 2.

[0141] Example 13 (Comparison): The electrolyte was prepared, and the battery was manufactured and evaluated in the same manner as in Example 7, except that the electrolyte was heat-treated by holding the battery cell at 60°C for 10 hours after injecting the electrolyte into the battery cell and sealing it. The results are shown in Table 2.

[0142]

[0143] In Examples 14 and 15, the electrolyte was prepared, and the batteries were manufactured and evaluated in the same manner as in Example 10, except that the ambient temperature and holding time were changed as shown in Table 3 during the heat treatment of the battery cells, and the timing of the heat treatment was changed to after step (b) in the manufacturing of lithium-ion secondary batteries described above. The results are shown in Table 3. In addition, the electrolytes in Examples 14 and 15 changed from a liquid state to a gel state after cooling at room temperature following the heat treatment.

[0144]

[0145] From the above examples, it was confirmed that batteries using the electrolyte of the present invention have excellent capacity retention, and therefore, improved cycle characteristics (especially cycle characteristics when used at high temperatures).

Claims

1. An electrolyte comprising a solvent, a silyl compound having at least one silyl group, and a complex compound having lithium.

2. The electrolyte according to claim 1, wherein the silyl compound has a phosphorus atom and / or a boron atom.

3. The electrolyte according to claim 1, wherein the silyl compound has a phosphorus atom.

4. The electrolyte according to any one of claims 1 to 3, wherein the silyl compound has at least two silyl groups.

5. The electrolyte according to any one of claims 1 to 3, wherein the silyl compound has a vinyl group.

6. The electrolyte according to any one of claims 1 to 3, wherein the complex compound has a boron trifluoride group and / or a boron difluoride group.

7. The electrolyte according to claim 6, wherein the complex compound has a phosphorus atom.

8. The electrolyte according to claim 7, wherein the complex compound has a P=O group and / or a P=S group.

9. The electrolyte according to claim 7, wherein the complex compound has a P=O group.

10. The electrolyte according to claim 7, wherein the complex compound has a P=S group.

11. The electrolyte according to any one of claims 1 to 3, wherein the electrolyte is obtained by adding a mixture of the silyl compound and the complex compound to the solvent.

12. An energy storage device comprising: a positive electrode; a negative electrode; and an electrolyte according to any one of claims 1 to 3, present at least between the positive electrode and the negative electrode.

13. The energy storage device according to claim 12, wherein the electrolyte is heat-treated.

14. The energy storage device according to claim 13, wherein the electrolyte is in the form of a gel.

15. The energy storage device according to claim 12, wherein the electrolyte is filled between the positive electrode and the negative electrode in an unheated state and then heat-treated.

16. The energy storage device according to claim 12, wherein the electrolyte is filled between the positive electrode and the negative electrode after or while being heat-treated.

17. The energy storage device according to claim 12, wherein the energy storage device is a lithium-ion secondary battery.

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