Electrolyte composition and battery

Abstract

The present disclosure provides an electrolyte composition which includes: a polymer which has an ability of preferentially conducting alkali metal ions; an alkali metal salt; an additive for coating film formation; and an organic solvent.

Description

Electrolyte composition and battery

[0001] The present disclosure relates to electrolyte compositions and batteries.

[0002] Batteries such as lithium ion batteries, which charge and discharge through the movement of metal ions between a positive electrode and a negative electrode, have been the subject of vigorous research due to their high capacity. Conventionally, solutions of lithium salts containing organic solvents or ionic liquids have been known as electrolytes for lithium ion batteries and the like. Meanwhile, research into solid electrolytes, polymer electrolytes, and the like has been underway from the perspectives of safety and processability (see Patent Documents 1 and 2). In addition to lithium ion batteries, research into batteries using other alkali ions, such as sodium and potassium, which are more abundant than lithium, has also been underway.

[0003] International Publication No. 2007 / 125845 Japanese Patent Application Laid-Open No. 2021-88695

[0004] Polymer electrolytes generally adhere more easily to electrodes than solid electrolytes, and therefore tend to have lower contact resistance between the electrodes. However, the inventors' intensive studies have revealed that there is room for improvement in the resistance between the electrode and electrolyte interface.

[0005] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an electrolyte composition that allows a sufficiently large current to flow at a low voltage, and a battery including the electrolyte composition.

[0006] The present disclosure includes the following exemplary embodiments. [1] An electrolyte composition comprising a polymer capable of preferentially conducting alkali metal ions, an alkali metal salt, a film-forming additive, and an organic solvent. [2] The electrolyte composition of [1], which has a transference number of 0.5 or more. [3] The electrolyte composition of [1] or [2], in which the alkali metal salt is a lithium salt or a sodium salt. [4] The electrolyte composition of any one of [1] to [3], in which the organic solvent is one or more solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, phosphate ester-based solvents, and sulfone-based solvents. [5] The electrolyte composition of any one of [1] to [4], in which the polymer capable of preferentially conducting alkali metal ions contains one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, an alkali metal substituted carboxylic acid group, and an alkali metal substituted phenolic hydroxyl group. [6] A battery comprising the electrolyte composition of any one of [1] to [5].

[0007] According to the present disclosure, it is possible to provide an electrolyte composition that allows a sufficient amount of current to flow at a low voltage, and a battery that includes the electrolyte composition.

[0008] FIG. 1 is a diagram showing the relationship between current density and voltage value in the lithium dissolution and deposition tests of Comparative Example 1, Example 1, and Example 2.

[0009] The electrolyte composition of the present embodiment includes a polymer capable of preferentially conducting alkali metal ions, an alkali metal salt, a film-forming additive, and an organic solvent.

[0010] The electrolyte composition contains the polymer, alkali metal salt, film-forming additive, and organic solvent, allowing a sufficient current to flow at a low voltage. While the reason for this effect is not entirely clear, the inventors speculate as follows: It is known that a coating derived from an organic solvent forms on the surface of an electrode as the battery operates. When a conventional polymer electrolyte is used, the polymer electrolyte is difficult to incorporate into the coating, resulting in low ionic conductivity in the coating. This increases the resistance at the interface between the electrode and the electrolyte, necessitating a higher voltage to allow sufficient current to flow. In contrast, the electrolyte composition according to this embodiment uses the polymer in combination with an alkali metal salt and a film-forming additive. When the film-forming additive and the organic solvent decompose through an electrolytic reaction to form a film on the electrode surface, the polymer and alkali metal salt can be partially incorporated. This allows alkali metal ions to be supplied into the coating, increasing ionic conductivity, lowering the resistance at the interface between the electrode and the electrolyte and increasing the transport number. As a result, it is possible to lower the voltage required to allow sufficient current to flow.

[0011] In any case herein, examples of the "substituent" include both organic groups and groups other than organic groups (inorganic groups). In this specification, the term "organic group" refers to a group having a chemical structure in which at least one hydrogen atom has been removed from an organic compound. When referring to the "organic group" in any case herein, regardless of the valence of the organic group, examples include hydrocarbon groups or groups in which some carbon atoms of a hydrocarbon group have been replaced with heteroatoms, and groups in which at least one hydrogen atom of a hydrocarbon group or a group in which some carbon atoms of a hydrocarbon group have been replaced with heteroatoms has been substituted with a substituent. When the organic group has a ring structure, the ring may be either a heterocycle or a carbocycle, and may be either a monocycle or a fused ring. In any case herein, examples of the hydrocarbon group include both aliphatic hydrocarbon groups and aromatic hydrocarbon groups. In any case herein, examples of the aliphatic hydrocarbon group include linear hydrocarbon groups, branched hydrocarbon groups, and cyclic hydrocarbon groups. Furthermore, in any case herein, examples of the hydrocarbon group include both saturated hydrocarbon groups and unsaturated hydrocarbon groups. In this specification, an aromatic hydrocarbon group refers to a hydrocarbon group having an aromatic moiety such as a benzene ring, and may also have an aliphatic moiety. Furthermore, in this specification, a cyclic hydrocarbon group refers to a hydrocarbon group having an aliphatic carbon ring moiety, and may also have a linear or branched aliphatic moiety. The heteroatom substituting the carbon atom is not particularly limited, and examples thereof include a boron atom, an oxygen atom, a nitrogen atom, a silicon atom, a phosphorus atom, and a sulfur atom. Specifically, the organic group may contain a linking group containing a heteroatom, such as an -O- (ether bond), an -S- (thioether bond), a sulfonyl group, a sulfinyl group, a secondary amino group, or a tertiary amino group. In any case in this specification, specific examples of the organic group include a substituted or unsubstituted hydrocarbon group, and a linking group in which one or more carbon atoms (methylene groups) in the hydrocarbon group contain a heteroatom such as —O— (ether bond), —S— (thioether bond), —C(═O)—, —C(═O)O—, or —C(═O)NR— (R is a monovalent organic group) (the linking group may be a divalent linking group).In any case herein, examples of the inorganic group include an electron-withdrawing group and an electron-donating group, and specific examples thereof include a halogen atom and —NH. ２ , -NH ３ ＋ , —CN, sulfonic acid group and its salts or esters, —NO ２ etc.

[0012] <Polymer Capable of Preferentially Conducting Alkali Metal Ions> A polymer capable of preferentially conducting alkali metal ions (hereinafter also simply referred to as a polymer) may be any polymer that satisfies at least one of the following conditions (A) and (B). The polymer may simply be referred to as a polymer capable of conducting alkali metal ions. (A) When the transference number of alkali metal ions is measured at room temperature (25°C) for a composition containing 33 mass% of a polymer and 67 mass% of a nonionic plasticizer, the transference number is 0.4 or greater. (B) When the transference number of alkali metal ions is measured at room temperature (25°C) for a composition containing 31.9 mass% of a polymer, an alkali metal salt, and the remainder of a nonionic plasticizer, and having an alkali metal ion concentration of 0.3 mol / L, the transference number is 0.4 or greater.

[0013] In (A) and (B), the transference number of the alkali metal ion may be, for example, 0.5 or more, 0.6 or more, or 0.7 or more. The transference number of the alkali metal ion may be, for example, 0.9 or less.

[0014] When the polymer has an anionic functional group, the alkali metal ion contained in the alkali metal salt contained in the composition may be the same as the counter cation of the anionic functional group. The alkali metal salt may be a bis(trifluoromethanesulfonyl)imide salt (TFSI salt).

[0015] The non-ionic plasticizer may be at least one of an organic solvent and another resin such as a fluorine-based resin.

[0016] The organic solvent may be an aprotic solvent. The aprotic solvent may be at least one selected from the group consisting of carbonate-based solvents, fluorine-based solvents, and ether-based solvents. The organic solvent may be a mixed solvent of ethylene carbonate and propylene carbonate (volume ratio 1:1).

[0017] The fluororesin is preferably a resin having a carbon chain as the main chain. The carbon chain may be formed by radical polymerization of an ethylenically unsaturated group. The fluororesin may be PVDF-HFP.

[0018] The polymer may contain at least one of a structural unit having an anionic functional group and an alkali metal ion as a counter cation of the anionic functional group (hereinafter also referred to as structural unit (A)), and a structural unit having a functional group that functions as an anion receptor (hereinafter also referred to as structural unit (B)). The polymer may contain one or more types of structural unit (A). The polymer may also contain one or more types of structural unit (B).

[0019] The polymer may contain, as the alkali metalated group, one or more groups selected from the group consisting of an alkali metalated sulfonylimide group, an alkali metalated sulfonic acid group, an alkali metalated carboxylic acid group, and an alkali metalated phenolic hydroxyl group.

[0020] Here, in this specification, an alkali metalated group refers to a group in which an anionic functional group, which is a conjugate base of the acid form of the group, forms a salt with an alkali metal ion. Specific examples include an alkali metalated sulfonylimide group, an alkali metalated sulfonic acid group, an alkali metalated carboxylic acid group, and an alkali metalated phenolic hydroxyl group. An alkali metalated sulfonylimide group is a sulfonylimide acid group (-SO ２ -NH-SO ２ - group) in which H is substituted with an alkali metal element A ２ -NA-SO ２ - group ([-SO ２ -N-SO ２ -] －A ＋ The alkali metal sulfonic acid group refers to a sulfonic acid group (—SO ３ H group) in which H is replaced by an alkali metal element A. ３ A group ([-SO ３ ] － A ＋ The alkali metal carboxylic acid group refers to a —COOA group ([—COO] group) in which H of a carboxylic acid group (—COOH group) is substituted with an alkali metal element A. － A ＋ The alkali metal phenolic hydroxyl group refers to an —OA group (—O group) in which H of the —OH group, which is a phenolic hydroxyl group, is substituted with an alkali metal element A. － A ＋ This refers to the group.

[0021] The structure of the polymer is not particularly limited, but examples thereof include those having a carbon chain as the main chain, and the carbon chain may be formed by radical addition polymerization of a monomer having an ethylenically unsaturated group.

[0022] The alkali metal element A may include at least one selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, may include at least one selected from the group consisting of lithium, sodium, and potassium, may include at least one of lithium and sodium, may include lithium, or may be lithium.

[0023] The content of one alkali metal element among the alkali metal elements contained in the polymer may be, for example, 80 mol% or more, 85 mol% or more, or 90 mol% or more. The one alkali metal element may be potassium, sodium, or lithium, or may be sodium or lithium.

[0024] The structural unit (A) may contain at least one of a structural unit represented by the following formula (A1) and a structural unit represented by the following formula (A2). (In formula (A1), Y is a monovalent group converted to an alkali metal. R １ ~R ３are each independently a hydrogen atom or a monovalent substituent, or R １ and R ２ One of them is R ３ and form a ring together, and the other is a hydrogen atom or a monovalent substituent. １ ~R ３ may have the above-mentioned alkali metalated group. (In formula (A2), Z is a divalent group converted to an alkali metal. R ４ and R ５ are each independently a hydrogen atom or a monovalent substituent, or R ４ and R ５ are joined together to form a ring. ４ and R ５ may have the above-mentioned alkali metalated group.

[0025] In addition, in formula (A1), R １ ~R ３ and Y are omitted, and in formula (A2), R ４ , R ５ The structure excluding Z is also simply called an ethylene unit.

[0026] In formula (A1), Y may contain one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, an alkali metal substituted carboxylic acid group, and an alkali metal substituted phenolic hydroxyl group, or may contain one or more groups selected from the group consisting of an alkali metal substituted sulfonic acid group, an alkali metal substituted carboxylic acid group, and an alkali metal substituted phenolic hydroxyl group. One or more functional groups may be used as Y.

[0027] In formula (A1), R １ ~R ３ The monovalent substituent as R may be a monovalent organic group. １ ~R ３ When R is a monovalent substituent, the substituent may be a monovalent organic group. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. １ ~R ３At least one of the groups may be a hydrogen atom, or all of the groups may be hydrogen atoms. Examples of the monovalent organic group include a methyl group.

[0028] In formula (A1), R １ and R ２ One of them is R ３ When R forms a ring together with １ or R ２ and R ３ In formula (A2), R forms a divalent substituent bonded to two carbon atoms of the ethylene unit of formula (A1). ４ and R ５ are taken together to form a ring, R ４ and R ５ form divalent substituents bonded to two carbon atoms of the ethylene unit of formula (A2), respectively. These rings may be either carbocyclic or heterocyclic. The number of ring members of these rings may be 4 to 10, or 5 to 8, or may be 5 or 6. A substituent may be bonded to the carbon atom or heteroatom that is a ring member.

[0029] In formula (A1), when Y contains an alkali metal-modified carboxylic acid group (-COOA group, A is an alkali metal), Y may be the -COOA group itself, or may be a monovalent organic group having a -COOA group. When Y is a monovalent organic group, the number of carbon atoms contained in the organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. The monovalent organic group may have one or more -COOA groups, or may have one -COOA group. In addition to the -COOA group, Y may have an electron-withdrawing group such as a halogen atom.

[0030] In formula (A1), Y is -R ９ -COOA, where R ９ is a divalent organic group or a covalent bond. The number of carbon atoms in the divalent organic group may be, for example, 1 to 19, 1 to 14, 1 to 9, 1 to 4, or 1 or 2.

[0031] In formula (A1), when Y has an alkali metal-substituted phenolic hydroxyl group, Y may be a group having one or more -OA groups (A is an alkali metal element) directly bonded to a carbon atom that is a member of an aromatic ring such as a benzene ring, a naphthalene ring, or an anthracene ring. Another ring structure may be condensed with the aromatic ring. For example, Y may have a group represented by any of the following formulas (A21) to (A26). Y may be directly covalently bonded to a carbon atom of the ethylene unit in formula (A1), or may be bonded via a linking group (for example, a divalent linking group). (In formula (A21), R Ａ１ ~R Ａ５ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ａ３ The group may be an —OA group. Ａ２ and R Ａ４ or R Ａ１ , R Ａ２ , R Ａ４ , and R Ａ５ each independently represents a hydrogen atom, an —OA group, a methyl group, an ethyl group, or a monovalent organic group having 1 to 20 carbon atoms (provided that when the monovalent organic group is a saturated hydrocarbon group, it is a methyl group, an ethyl group, or a group having 6 to 20 or 6 to 15 carbon atoms; and when the monovalent organic group is an alkoxy group, it is a group having 4 to 20 or 4 to 15 carbon atoms). In formula (A22), R Ｂ１～ R Ｂ７ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ｂ３ ~R Ｂ６ At least one of the groups may be an —OA group. Ｃ１～ R Ｃ９ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ｃ２ ~R Ｃ８ At least one of the groups may be an —OA group. Ｄ１～ R Ｄ６ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ｄ３～ R Ｄ６At least one of the groups may be an —OA group. Ｅ１～ R Ｅ９ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ｅ２ ~R Ｅ８ At least one of the groups may be an —OA group. Ｆ１～ R Ｆ９ At least one of the groups is an -OA group, and the rest are hydrogen atoms or monovalent substituents. Ｆ１～ R Ｆ９ At least one of the groups may be an —OA group.

[0032] The groups represented by formulae (A21) to (A26) may have 1 to 3 -OA groups, may have 1 or 2 -OA groups, or may have 1 -OA group.

[0033] In formulas (A21) to (A26), the monovalent substituent is preferably an electron-withdrawing group. Examples of the electron-withdrawing group include a halogen atom, a sulfonic acid group or a salt thereof, a sulfonic acid ester, a nitro group, and a nitrile group. The halogen atom may be any of F, Cl, Br, and I.

[0034] In addition, in formulae (A21) to (A26), the monovalent substituent may be an organic group having 1 to 20 carbon atoms. The number of carbon atoms in the organic group may be, for example, 1 to 15, 1 to 10, 1 to 5, or 1 to 3.

[0035] In the formula (A1), when Y is a sulfonic acid group modified with an alkali metal, examples of Y include groups represented by the following formula (A3). (In formula (A3), R １９ is a covalent bond or a divalent organic group. A is an alkali metal element.

[0036] In formula (A3), the divalent organic group may have, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3 carbon atoms.

[0037] The alkali metal sulfonic acid group is —SO ３ A, -CH２ -SO ３ A, -C ６ H ４ -SO ３ Examples include A.

[0038] The structural unit (A2) may be a group containing a maleimide ring having an alkali metal-modified group, and examples thereof include the following structural unit (A4). (In formula (A4), X is a divalent organic group having 1 to 20 carbon atoms, and Y １ is a halogen atom or a monovalent organic group having 1 to 20 carbon atoms, and A ＋ represents an alkali metal ion, and * represents the position where the structural unit (A4) is bonded to another structural unit.

[0039] In formula (A4), the number of carbon atoms that X has may be, for example, 1 to 15, 2 to 10, or 3 to 8.

[0040] In formula (A4), the hydrocarbon group represented by X may be a phenylene group, an alkylene group having 1 to 8 carbon atoms, a polyoxyalkylene group, or a group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms such as fluorine atoms, or a divalent group having a substituted or unsubstituted phenylene group, or a phenylene group or substituted phenylene group. The substituted phenylene group refers to a functional group in which at least some of the hydrogen atoms constituting the phenylene group have been substituted with an alkyl group, a halogen atom, an electron-withdrawing group, or the like.

[0041] In formula (A4), Y １ is a monovalent organic group, Y １ The number of carbon atoms contained in Y may be, for example, 1 to 15, 1 to 10, 1 to 8, 1 to 5, or 1 to 3. １The hydrocarbon group as Y may be a phenyl group, an alkyl group having 1 to 5 carbon atoms, or a group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms such as fluorine atoms, or may be a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 3 carbon atoms such as a trifluoromethyl group. The fluorinated alkyl group may be a perfluorinated alkyl group. １ When is a halogen atom, the halogen atom may be a fluorine atom or a chlorine atom, and may be a fluorine atom.

[0042] The structural unit (B) functions as an anion receptor. An anion receptor is a chemical species that captures anions by forming electrostatic interactions, hydrogen bonds, acid-base complexes, or the like with anions. The structural unit (B) captures the counter anion of the alkali metal ion in the alkali metal salt and promotes dissociation between the counter anion and the alkali metal ion. This increases the mobility of the alkali metal ion. Meanwhile, since the counter anion is captured by the polymer via the structural unit (B), the mobility of the counter anion decreases. This is thought to result in an improvement in the transport number of the alkali metal ion. Furthermore, the increased mobility of the alkali metal ion also tends to improve the conductivity of the alkali metal ion. Low-molecular-weight chemical species (compounds, etc.) that function as anion receptors are known, and examples of such compounds include those described in U.S. Patent Nos. 6,022,643, 5,705,689, and 6,120,941.

[0043] The functional group functioning as an anion receptor may have Lewis acidity. In this case, the functional group can capture the anion by accepting the unshared electron pair of the anion and forming an acid-base complex. Examples of such functional groups include functional groups having an electron-deficient atom. Note that an electron-deficient atom refers to an atom that is covalently bonded to another atom but the electrons in the outermost shell of the atom do not form an octet. Examples of electron-deficient atoms include atoms belonging to Group 13 of the periodic table, and more specifically, may be at least one of aluminum and boron, or may be boron.

[0044] The functional group having a function as an anion receptor may be a group having an azaether moiety. The group having an azaether moiety is a group having an azaether compound as a substituent, and the azaether compound is formed by converting —O— of an ether compound to —NR Ｅ - (where R Ｅ is a hydrogen atom or an organic group). The azaether moiety may be either a linear azaether moiety or a cyclic azaether moiety, or may have both a linear azaether moiety and a cyclic azaether moiety. The group having an azaether moiety may have an electron-withdrawing group in, for example, the hydrocarbon moiety.

[0045] The structural unit (B) may contain at least one structural unit represented by the following formula (B). (In formula (B), W is a functional group having a function as an anion receptor, and R １１ ~R １３ are each independently a hydrogen atom or a monovalent substituent, or R １１ and R １３ One of them is R １２ and form a ring together, and the other is a hydrogen atom or a monovalent substituent. * indicates the position where the structural unit (B) is bonded to another structural unit. R １１ ~R １３ may be hydrogen atoms, or all of may be hydrogen atoms.)

[0046] In addition, in formula (B), R １１~R １３ The structure excluding W is also simply called an ethylene unit.

[0047] In formula (B), R １１ ~R １３ is a monovalent substituent, the monovalent substituent may be a monovalent organic group. The number of carbon atoms in the organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3.

[0048] The monovalent substituent may have an electron-withdrawing group or may be the electron-withdrawing group itself. The electron-withdrawing group may be bonded to the monovalent organic group, or the monovalent organic group may be the electron-withdrawing group. Examples of the electron-withdrawing group include a halogen atom, a sulfonic acid group or a salt thereof, a sulfonic acid ester, a nitro group, and a nitrile group. The halogen atom may be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0049] In formula (B), R １１ and R １３ One of them is R １２ When R forms a ring together with １１ or R １２ and R １３ form divalent substituents bonded to two carbon atoms of the ethylene unit of formula (B), respectively. These rings may be either carbocyclic or heterocyclic. The number of ring members of these rings may be, for example, 4 to 10, 5 to 8, 5, or 6. A substituent may be bonded to the carbon atom or heteroatom that is a ring member.

[0050] In formula (B), W preferably has a group represented by formula (B1) below. (In formula (B1), W Ｂ is an atom belonging to group 13 of the periodic table, and R １５ is a covalent bond or a divalent organic group, and R １６ and R １７ are each independently a hydrogen atom, an —OH group, a halogen atom, or a monovalent organic group, or are joined together to form a ring. １６ and R １７ may be the same group or different groups.)

[0051] W Ｂ may be at least one of an aluminum atom and a boron atom, and may be a boron atom.

[0052] In formula (B1), R １５ When W is a divalent organic group, the number of carbon atoms in the divalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. The divalent organic group may be a hydrocarbon group, a halogen-substituted hydrocarbon group, or a hydrocarbon group or a halogen-substituted hydrocarbon group connected to W via an ether bond. Ｂ The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group. １５ may be a covalent bond.

[0053] In formula (B1), R １６ or R １７ is a halogen atom, R １６ or R １７ may be any of a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and may also be a fluorine atom.

[0054] In formula (B1), R １６ or R １７ When R is a monovalent organic group, the number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. ６ or R ７ is a hydrocarbon group, a halogen-substituted hydrocarbon group, or a hydrocarbon group or a halogen-substituted hydrocarbon group connected to W via an ether bond Ｂ The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group.

[0055] The group represented by formula (B1) may be a group represented by formula (B1a) below or a group represented by formula (B1b) below. (In formula (B1a), R １５ is a covalent bond or a divalent organic group, and X １１ and X １２ are each independently an oxygen atom or a covalent bond. １１ is a covalent bond, R ２１ is a hydrogen atom, a halogen atom, or a monovalent organic group. １１ is an oxygen atom, R ２１ is a hydrogen atom or a monovalent organic group. １２ is a covalent bond, R ２２ is a hydrogen atom, a halogen atom, or a monovalent organic group. １２ is an oxygen atom, R ２２ is a hydrogen atom, a halogen atom, or a monovalent organic group. １１ and X １２ When each is an oxygen atom, they may be oxygen atoms that form an ether bond. (In formula (B1b), R １５ is a covalent bond or a divalent organic group, and X １３ and X １４ are each an oxygen atom or a covalent bond, and R ２３ is a divalent organic group.

[0056] In formula (B1a), R ２１ Or R ２２ When R is a monovalent organic group, the monovalent organic group may be a monovalent hydrocarbon group or a monovalent halogen-substituted hydrocarbon group. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group. ２１ Or R ２２ When is a halogen atom, the halogen atom may be a fluorine atom.

[0057] In formula (B1a), R ２１ and R ２２ are each independently —F, —CH ３ , -C ２ H ５, -C ３ H ７ , -C ６ H ５ (phenyl group), —C ６ H ｎ F ５－ｎ (n is an integer of 0 to 4, and may be an integer of 0 to 3), -CF ３ , -CH ２ CF ３ , -CH ２ CF ３ F ７ , -CH(CF ３ ) ２ , -C(CF ３ ) ２ -C ６ H ５ , -C(CF ３ ) ３ , -C ６ H ｎ (CF ３ ) ５－ｎ (n is an integer from 0 to 4, and may be 1 or 2.)

[0058] In formula (B1b), the divalent organic group may have, for example, 1 to 20, 1 to 15, 2 to 10, or 3 to 8 carbon atoms. The divalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group. The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group.

[0059] In formula (B1b), R ２３ is -C ２ H ４ -, -C ３ H ６ -, -C ４ H ８ -, -C ５ H １０ -, -C ６ H １２ -, -C ７ H １４ -, -C ８ H １６ -, -C ９ H １８ -, -C １０ H ２０-, etc., or compounds in which the hydrogen atoms of these groups are partially or entirely substituted with fluorine atoms. More specifically, R ２３ is -C(CH ３ ) ２ -C(CH ３ ) ２ - may be.

[0060] The polymer may further contain a structural unit (C) that is neither the structural unit (A) nor the structural unit (B). The structural unit (C) may contain a structural unit (C) represented by the following formula (C): (In formula (C), R ２５ is a hydrogen atom or a monovalent substituent, and R ２６ ~R ２８ are each independently a hydrogen atom or a monovalent substituent, or R ２６ and R ２７ is a hydrogen atom or a monovalent substituent, and the other is R ２８ and form a ring. * indicates the bonding site of the structural unit (C) to other structural units.

[0061] In formula (C), R ２５ may be a monovalent organic group. The monovalent organic group is -Z １ -R ２９ R ２５ may have, for example, 1 to 40 carbon atoms, 1 to 20 carbon atoms, 2 to 15 carbon atoms, or 4 to 13 carbon atoms. １ is a divalent linking group, for example, a covalent bond, —O—, —S—, —C(═O)—, —C(═O)O—, —OC(═O)—, or —C(═O)NR ３８ -or-NR ３９ It may be a group represented by C(=O)-.

[0062] Above Z １ is a covalent bond, —O—, —S—, —C(═O)—, —C(═O)O—, or —OC(═O)—, R ２９ is a hydrogen atom or a monovalent organic group. １ -C(=O)NR ３８ -, then R ２９ , R ３８are each a hydrogen atom or a monovalent organic group, or R ２９ is R ３８ The above Z forms a ring together with １ But, -NR ３９ When C(=O)-, R ２９ , R ３９ are each a hydrogen atom or a monovalent organic group, or R ２９ is R ３９ It forms a ring together with R. ２９ , R ３８ and R ３９ The monovalent organic group as R may have 1 to 20 organic groups, or 1 to 10 organic groups. ３８ When is a monovalent organic group, it may be a monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0063] Above Z １ is a covalent bond or —C(═O)O—, R ２９ may be a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. １ is a covalent bond and R ２９ When R is a hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group. ２９ may be a monovalent organic group other than a hydrocarbon group or a hydrocarbon group having a ring structure. １ When R is —O—, W may be an alkyl ether and may be a monovalent organic group other than the group represented by W—H. ２６ ~R ２８ When R is a monovalent organic group, the monovalent organic group is ２５ The same examples as those given above are included.

[0064] In the group having an aromatic ring, a monovalent substituent may be bonded to the aromatic ring. Examples of the monovalent substituent include a monovalent organic group, and examples of the monovalent organic group include a substituted or unsubstituted hydrocarbon group, a group represented by the formula: -R ４１ - (W １ -R ４２ ) ｎ -W ２ R ４３ Examples include groups represented by the formula: -R ４１ - (W １ -R４２ ) ｎ -W ２ R ４３ The group represented by the formula (I) may be bonded to the para position of the benzene ring. １ may be a divalent group such as -O-, -S-, -C(=O)- or -C(=O)O-, or may be -O-. ２ may be a divalent group such as —O—, —S—, —C(═O)— or —C(═O)O—, or may be —O—.

[0065] R ４１ is a covalent bond or a divalent organic group. The divalent organic group may be a divalent hydrocarbon group. The divalent hydrocarbon group may have, for example, 1 to 8, 1 to 5, or 1 to 3 carbon atoms. The hydrogen atoms bonded to the divalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the divalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. The divalent hydrocarbon group may be either an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group, or may be a linear or branched aliphatic hydrocarbon group. Specific examples of the divalent hydrocarbon group include a methylene group, an ethylene group, a 1,2-propylene group, a 1,3-propylene group, or a group in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine atoms, and may be a methylene group.

[0066] R ４２is a divalent organic group and may be a divalent hydrocarbon group. The divalent hydrocarbon group may have, for example, 1 to 8, 1 to 5, or 1 to 3 carbon atoms. The hydrogen atoms bonded to the divalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the divalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. The divalent hydrocarbon group may be either an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group, and may be a linear or branched aliphatic hydrocarbon group. Specific examples of the divalent hydrocarbon group include a methylene group, an ethylene group, a 1,2-propylene group, a 1,3-propylene group, or a group in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine atoms, and may be an ethylene group. n may be, for example, 1 to 10, 1 to 5, or 1 to 3. n may be an integer or a rational number (for example, n is an average value across the structural units (B) contained in the polymer). ４２ When there are multiple, they may be different or the same.

[0067] R ４３ may be a hydrogen atom or a divalent hydrocarbon group. The number of carbon atoms in the monovalent hydrocarbon group may be, for example, 1 to 8, 1 to 5, or 1 to 3. The hydrogen atom bonded to the monovalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the monovalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. The monovalent hydrocarbon group may be either an aromatic hydrocarbon group or an aliphatic hydrocarbon group, and may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group, and may be a linear or branched aliphatic hydrocarbon group. Specific examples of the divalent hydrocarbon group include a methyl group, an ethyl group, an isopropyl group, an n-propyl group, or a group in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine atoms, and may be a methyl group.

[0068] The structural unit (C) may contain at least one structural unit derived from a monomer represented by the following formula (C1). (wherein m is 0 to 4 and n is 0 to 10. R ２０ may be a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The alkyl group may be a methyl group or an ethyl group, or may be a methyl group.

[0069] In formula (C1), m may be, for example, 1 to 3, 1 to 2, or 1. m may be an integer or an average value across all structural units derived from the monomer represented by formula (C1) contained in the polymer (in this case, m is a rational number). In formula (C1), n ​​may be, for example, 1 to 4, or 1 to 3. n may be an integer or an average value across all structural units derived from the monomer represented by formula (C1) contained in the polymer (in this case, n is a rational number).

[0070] R ２６ and R ２７ One of them is R ２８ When the structural unit (C) forms a ring together with the structural unit (C), the ring may have, for example, 4 to 10, 4 to 8, or 5 to 7 ring members. The structural unit (C) may be the following structural unit (C2). (In formula (C2), X represents an oxygen atom or —NR ２４ - is a tertiary amino group represented by R ２４ is a monovalent organic group, and R ２５ and R ２６ are each independently a hydrogen atom or a monovalent substituent.

[0071] R ２４ The number of carbon atoms contained in R may be, for example, 1 to 20, 1 to 15, or 2 to 10. ２４ may be a hydrocarbon group or a hydrocarbon group substituted with fluorine, and may be an ethyl group, a 2,2,2-trifluoroethyl group, an n-dodecyl group, a cyclohexyl group, or a benzyl group.

[0072] The ratio of the structural unit (A) to all structural units contained in the polymer may be, for example, 0.2 to 0.95, 0.2 to 0.8, 0.3 to 0.7, or 0.4 to 0.6.

[0073] The ratio of the structural unit (C) to all structural units contained in the polymer may be, for example, 0.05 to 0.8, 0.2 to 0.8, 0.3 to 0.7, or 0.4 to 0.6. The ratio of the structural unit (C) to all structural units contained in the polymer may be, for example, 0.8 or less, 0.7 or less, 0.6 or less, or 0.3 or less.

[0074] The total proportion of the structural units (A) and (C) relative to all structural units contained in the polymer may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 0.95 or more. The total proportion of the structural units (A) and (C) relative to all structural units contained in the polymer may be, for example, less than 1.0, or 0.97 or less. The total proportion of the structural units (A) and (C) relative to all structural units contained in the polymer may be, for example, 0.5 or more and less than 1.0, or 0.5 to 0.97.

[0075] The content of the structural unit (A) relative to the total mass of the polymer may be, for example, 25 to 95 mass %, 40 to 90 mass %, or 50 to 90 mass %.

[0076] The content of the structural unit (C) relative to the total mass of the polymer may be, for example, 5 to 75 mass%, 10 to 60 mass%, or 10 to 50 mass%, and the content of the structural unit (C) relative to the total mass of the polymer may be, for example, 75 mass% or less, 60 mass% or less, 50 mass% or less, or 25 mass% or less.

[0077] The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 90% by mass or more, 95% by mass or more, or 98% by mass or more. The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 100% by mass or less, less than 100% by mass, or 99% by mass or less. The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 90 to 100% by mass.

[0078] When the polymer contains the structural unit (B), the molar ratio m of the structural unit (B) to all structural units contained in the polymer may be, for example, 0.2 to 0.8, 0.25 to 0.75, 0.3 to 0.7, 0.35 to 0.65, or 0.4 to 0.6. The content of the structural unit (B) relative to the total mass of the polymer may be, for example, greater than 10% by mass and 95% by mass or less, 15 to 95% by mass, 20 to 80% by mass, 25 to 60% by mass, or 30 to 45% by mass.

[0079] The number average molecular weight (Mn) of the polymer may be, for example, 5,000 to 400,000, 8,000 to 200,000, 10,000 to 150,000, or 10,000 to 100,000. The weight average molecular weight (Mw) of the polymer may be, for example, 5,000 to 600,000, 10,000 to 450,000, 20,000 to 200,000, or 20,000 to 100,000. The molecular weight distribution (Mw / Mn) of the polymer may be, for example, 1.0 to 5.0, 1.2 to 3.0, or 1.3 to 2.5. The number average molecular weight and weight average molecular weight of the polymer can be measured, for example, by gel permeation chromatography.

[0080] There is no particular limitation on the method for producing a polymer capable of preferentially conducting alkali metal ions. For example, it can be produced by subjecting a corresponding monomer to radical addition polymerization.

[0081] The content of the polymer in the electrolyte composition may be, for example, 1 to 80 mass %, 3 to 70 mass %, 5 to 60 mass %, or 10 to 40 mass % relative to the total amount of the electrolyte composition.

[0082] <Film-forming additive> The film-forming additive contained in the electrolyte composition of the present embodiment is a compound capable of forming a film (solid electrolyte interface, SEI) on the electrode surface by an electrolytic reaction. Therefore, the film-forming additive may be an SEI-forming agent.

[0083] The coating-forming additive may be at least one of an electrolytically oxidatively polymerizable compound and an electrolytically reductively polymerizable compound, but may also be an electrolytically reductively polymerizable compound. By using the electrolytically reductively polymerizable compound, a coating can be formed on the negative electrode.

[0084] Examples of the film-forming additive include carbonate compounds, aliphatic polyunsaturated compounds, aromatic compounds having a vinyl group, unsaturated ester compounds, unsaturated nitrile compounds, polyester compounds, vinyl ester compounds of carboxylic acids, cyclic acid anhydrides, cyclic imide compounds, phosphonate ester compounds, vinyl group-containing silane compounds, furan derivatives containing two double bonds in each molecule, sulfur-based compounds, organic nitro compounds, halogenated cyclic esters, nitrate ester compounds, nitrite ester compounds, aromatic ester compounds, aromatic isocyanate compounds, boron-based compounds, halogenated organic compounds, polydimethylsiloxane, electrolytic reduction-polymerizable compounds such as silanes, etc. The electrolyte composition may contain one or more film-forming additives.

[0085] The film-forming additives also include electrolytically oxidatively polymerizable compounds such as pyrrole, aniline, thiophene, and derivatives thereof.

[0086] The film-forming additives include compounds that can be used as organic solvents. When the electrolyte composition of this embodiment contains a compound that can be used as a film-forming additive and an organic solvent, it may further contain another compound as the organic solvent, or it may further contain another compound as the film-forming additive. In other words, the electrolyte composition of this embodiment may contain one or more compounds each as the organic solvent and the film-forming additive (i.e., a total of two or more compounds).

[0087] The carbonate compound may be a cyclic carbonate compound or a chain carbonate compound. The carbonate compound may be a carbonate compound substituted with an ethylenically unsaturated group such as a vinyl group or a halogen atom such as a fluorine atom. Examples of the carbonate compound include ethylene carbonate, vinylene carbonate, vinylethylene carbonate, allyl ethyl carbonate, and fluoroethylene carbonate (4-fluoro-1,3-dioxane-2-one).

[0088] Examples of aliphatic polyunsaturated compounds include conjugated unsaturated compounds such as butadiene. Examples of aromatic compounds having a vinyl group include vinylpyridines such as 2-vinylpyridine, methyl cinnamate, and styrene. Examples of unsaturated ester compounds include (meth)acrylic acid esters and α-cyanoacrylic acid esters. Examples of unsaturated nitrile compounds include α,β-unsaturated nitrile compounds such as (meth)acrylonitrile. Examples of polyvalent ester compounds include dialkylmalonic acid ester compounds such as dimethylmalonic acid ester, diethylmalonic acid ester, di-n-hexylmalonic acid ester, and dicyclohexylmalonic acid ester. Examples of vinyl ester compounds of carboxylic acids include vinyl acetate and divinyl adipate. Examples of cyclic acid anhydrides include maleic anhydride. Examples of cyclic imide compounds include compounds having a carbon-carbon unsaturated bond in the ring, such as maleimide, and compounds not having a carbon-carbon unsaturated bond in the ring, such as succinimide. Examples of organic nitro compounds include nitro compounds having an ethylenically unsaturated group, such as nitroethylene (nitroethene).

[0089] Sulfur compounds include SO ２Examples of sulfur dioxide (sulfur dioxide), polysulfides, sulfite ester compounds, sulfonate ester compounds, sulfate ester compounds, sulfone compounds, etc. The sulfonate ester compound may be a cyclic sulfonate ester compound. Examples of sulfonate esters include 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and 1,4-butene sultone. The sulfate ester compound may be a cyclic sulfate ester compound. Examples of sulfate ester compounds include propylene sulfate, butylene sulfate, and ethylene propyl sulfate. Examples of sulfite ester compounds include cyclic alkyl sulfite ester compounds and aromatic (aryl) sulfite ester compounds. Examples of sulfite esters include ethylene sulfite and propylene sulfite. The sulfone compound may be a cyclic sulfone compound. Examples of sulfone compounds include sulfolane, 3-methylsulfolane, 3-sulfolene, and 2-sulfolene.

[0090] Boron compounds include B ２ O ３ (boron oxide), organic boron compounds, boroxine compounds, etc.

[0091] The film-forming additive may include at least one of vinylene carbonate and fluoroethylene carbonate.

[0092] The content of the film-forming additive in the electrolyte composition may be, for example, 0.01 to 100 parts by mass, 0.1 to 80 parts by mass, 1 to 50 parts by mass, 1 to 30 parts by mass, or 5 to 25 parts by mass relative to 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions.

[0093] <Alkali Metal Salt> The electrolyte composition of the present embodiment contains an alkali metal salt. Since the electrolyte composition contains an alkali metal, when a coating is formed from the coating-forming additive, the coating contains alkali metal ions, which is thought to improve the ionic conductivity of the coating formed on the electrode surface.

[0094] The alkali metal salts include MF, MCl, MBr, MI, and MNO, where M is an alkali metal. ３ , MClO４ , MPF ６ , MBF ４ , M ２ SO ４ , M[(C ｈ F ２ｈ＋１ ) SO ３ ] (h is 0 to 3), M[(C ｈ F ２ｈ＋１ ) SO ２ ] ２ N (h is 0 to 3), M{[(C ｈ F ２ｈ＋１ ) SO ２ ]N[(C ｉ F ２ｉ＋１ ) SO ２ ]} (h and i are 0 to 3), MBOB (BOB is bisoxalatoborate), etc. One or more alkali metal salts may be used. M is not particularly limited as long as it is an alkali metal, and may contain lithium, sodium, or potassium, or may contain lithium or sodium, or may contain potassium. In other words, the alkali metal salt may contain, for example, at least one selected from the group consisting of lithium salts, sodium salts, and potassium salts, and may be a lithium salt or a sodium salt. The alkali metal element contained in the alkali metal salt may be the same alkali metal element as the alkali metal element contained in the structural unit (A).

[0095] The content of the alkali metal salt in the electrolyte composition may be, for example, 0.1 to 250 molar parts, 2.5 to 200 molar parts, 5 to 180 molar parts, or 10 to 150 molar parts, calculated as the alkali metal ions contained in the alkali metal salt, relative to 100 moles of the total amount of the structural units (A) and (B) contained in the polymer capable of preferentially conducting alkali metal ions. The content of the alkali metal salt in the electrolyte composition may be, for example, 10 to 200 parts by mass, 20 to 150 parts by mass, 30 to 100 parts by mass, or 40 to 75 parts by mass, relative to 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions contained in the electrolyte composition.

[0096] <Organic Solvent> The organic solvent may be an aprotic solvent, which may be a compound other than the above-mentioned additives for forming a coating film.

[0097] The organic solvent may include one or more organic solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, phosphate ester-based solvents, and sulfone-based solvents, and may include a phosphate ester. The organic solvent may include one or more solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, and phosphate ester-based solvents, and may include a carbonate-based solvent. In the electrolyte composition, the polymer capable of preferentially conducting alkali metal ions may be swollen by the organic solvent.

[0098] Examples of carbonate solvents include chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. The organic solvent may be a mixed solvent containing two or more carbonate solvents, such as a mixed solvent containing one or more cyclic carbonate solvents and one or more chain carbonate solvents, or a mixed solvent containing two or more cyclic carbonate solvents.

[0099] Examples of the ether solvent include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane; and chain ethers such as 1,2-diethoxyethane and ethoxymethoxyethane.

[0100] Examples of fluorine-based solvents include hydrofluorocarbons such as perfluorooctane; hydrofluoroethers such as methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether; hydrofluoroolefins such as 1,3,3,3-tetrafluoropropene; and 2,2,2-trifluoro-N,N-dimethylacetamide.

[0101] Examples of the phosphate ester include trimethyl phosphate (TMP), triethyl phosphate (TEP), and tris(2,2,2-trifluoroethyl) phosphate (TFEP).

[0102] Examples of the nitrile solvent include acetonitrile, succinonitrile, etc. Examples of the lactone solvent include γ-butyrolactone, etc.

[0103] Examples of the phosphate ester include trimethyl phosphate (TMP), triethyl phosphate (TEP), and tris(2,2,2-trifluoroethyl) phosphate (TFEP).

[0104] Other examples of organic solvents include sulfone-based solvents such as sulfolane and 3-methylsulfolane; solvents having a sulfonyl group such as dimethyl sulfoxide (DMSO); amide-based solvents such as dimethylformamide (DMF) and dimethylacetamide (DMA); organic solvents having a carbonyl group such as acetone (referring to carbonyl compounds other than amide compounds such as -C(=O)-, esters, ketones, and aldehydes); and nitrogen-containing aromatic compounds such as pyridine (compounds containing nitrogen as a ring member of the aromatic ring, which may be either monocyclic or fused ring systems). The organic solvent may be used alone or as a mixed solvent containing two or more organic solvents. The organic solvent may include a carbonate-based solvent and at least one of a fluorine-based solvent and a phosphate ester.

[0105] The content of the organic solvent in the electrolyte composition may be, for example, 10 to 1800 parts by mass, 50 to 1500 parts by mass, 100 to 600 parts by mass, or 150 to 450 parts by mass relative to 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions. The polymer capable of preferentially conducting alkali metal ions contained in the electrolyte composition may be swollen with the organic solvent.

[0106] The electrolyte composition may further contain other resins such as fluorine-based resins (resins other than polymers capable of preferentially conducting alkali metal ions, such as binder resins), fabrics such as nonwoven fabrics, porous materials, viscosity modifiers, anion receptors, etc. The electrolyte composition may contain, as the fluorine-based resin, a resin having a carbon chain as its main chain. The carbon chain may be formed by radical polymerization of an ethylenically unsaturated group. Examples of fluorine-based resins include poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and polyvinylidene fluoride (PVDF). The porous material may be a porous material made of resin. Specific examples include porous polyolefin membranes and porous ceramic membranes.

[0107] The content of the other resin may be, for example, 10 to 200 parts by mass, or 50 to 150 parts by mass, per 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions.

[0108] <Anion Receptor> The anion receptor is not particularly limited. The formula weight (molecular weight) of the anion receptor may be, for example, 1,000 or less, 800 or less, or 500 or less. The anion receptor may have Lewis acidity. In this case, the anion receptor can capture the anion by accepting the unshared electron pair of the anion and forming an acid-base complex. Examples of such compounds include compounds having an electron-deficient atom. Note that an electron-deficient atom refers to an atom that is covalently bonded to another atom but has fewer than eight electrons in its outermost shell. Examples of electron-deficient atoms include atoms belonging to Group 13 of the periodic table, and more specifically, may be at least one of an aluminum atom and a boron atom, or may be a boron atom.

[0109] Examples of anion receptors having a boron atom include boron compounds that function as Lewis acids, such as diborane and compounds represented by the following chemical formulas IA to IE.

[0110]

[0111] In Formulas IA and ID, R ３１and R ３３ are each a halogen atom or a monovalent organic group. The halogen atom may be a fluorine atom or a chlorine atom, or may be a fluorine atom. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. Here, the monovalent organic group is bonded to the boron atom (B) in formula IA or ID via a carbon atom in the monovalent organic group. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple R ３１ and R ３３ may be different from each other or may all be the same.

[0112] In formulas IB and IE, R ３２ and R ３４ are each a hydrogen atom or a monovalent organic group. The halogen atom may be a fluorine atom or a chlorine atom, or may be a fluorine atom. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. Here, the monovalent organic group is bonded to the oxygen atom (O) in formula IB or IE via a carbon atom in the monovalent organic group. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple R ３２ and R ３４ may be different from each other or may all be the same.

[0113] In formula IC, R ３５ is a divalent organic group, Z ２ is a covalent bond or an oxygen atom. The number of carbon atoms in the divalent organic group may be, for example, 1 to 15, 2 to 10, or 3 to 8. ３５ , two Zs ２ and the boron atom (B) form a ring, and the ring may have, for example, 4 to 8, 5, or 6 ring members. ２ When is an oxygen atom, the divalent organic group is connected to Z in formula IC by the carbon atom contained in the divalent organic group.２ It is bonded to Z. ２ When Z is a covalent bond, the divalent organic group is bonded to the boron atom (B) in formula IC via a carbon atom contained in the divalent organic group. The divalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple Z ２ may be different from each other or may all be the same.

[0114] In formula IC, R ３６ is a hydrogen atom or a monovalent organic group. The monovalent organic group may be a group that bonds to the boron atom (B) in formula IC via a carbon atom that the monovalent organic group has, but -OR ３７ R ３７ is a hydrogen atom or a monovalent organic group. ３７ The monovalent organic group represented by the formula (I) is -OR ３７ It is bonded to the oxygen atom of R. ３６ or R ３７ The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group.

[0115] Specific examples of boron compounds include diborane, boron trifluoride, boric acid, boroxine, trimethylborane, triethylborane, tri-n-propylborane, triisopropylborane, triphenylborane, trimethylborate, triethylborate, triphenylborate, tri-n-propylborate, triisopropylborate, 2-methoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, and 2-ethoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. Examples thereof include organic boron compounds such as oran, 2,4,6-trimethylboroxine, 2,4,6-triethylboroxine, 2,4,6-trivinylboroxine, 2,4,6-trimethoxyboroxine, 2,4,6-trimethoxyboroxine, and triphenylboroxine; and halogen-substituted hydrocarbon groups such as tris(2,2,2-trifluoroethyl)borate, 2,4,6-tris(4-fluorophenyl)boroxine, and 2,4,6-tris(3,4,5-trifluorophenyl)boroxine.

[0116] The anion receptor having an aluminum atom includes an aluminum compound that functions as a Lewis acid, and has the formula AlX １ ３ (X １ is a halogen atom, which may be a fluorine atom), the formula: Al(OR ３５ ) ３ (R ３５ is a hydrocarbon group, which may be an alkyl group.

[0117] The anion receptor may also be an azaether. An azaether is an ether compound in which —O— is replaced by —NR Ｅ - (where R Ｅ is a hydrogen atom or an organic group). The azaether may be either a linear azaether or a cyclic azaether. The azaether may have an electron-withdrawing group, for example, in the hydrocarbon moiety.

[0118] The content of the anion receptor in the electrolyte composition may be, for example, 10 to 200 parts by mole, 30 to 180 parts by mole, 50 to 150 parts by mole, or 80 to 130 parts by mole relative to 100 moles of the structural unit (A) contained in the polymer capable of preferentially conducting alkali metal ions.

[0119] Some anion receptors function as coating-forming additives. When the electrolyte composition of the present embodiment contains an anion receptor, the electrolyte composition contains one or more anion receptors, one or more organic solvents, and one or more comparative coating-forming additives (three or more in total).

[0120] The content of the other resin in the electrolyte composition may be, for example, 10 to 75 mass %, 15 to 65 mass %, 20 to 50 mass %, or 25 to 45 mass % based on the total amount of the polymer capable of preferentially conducting alkali metal ions and the other resin contained in the electrolyte composition.

[0121] The method for producing the electrolyte composition is not particularly limited, but examples include a method in which a dry film of a polymer capable of preferentially conducting alkali metal ions or a dry film made by mixing the polymer with another resin is produced, and then the dry film is impregnated with an organic solvent. The film-forming additive may be added by dissolving it in the organic solvent to be impregnated into the dry film and then allowing it to impregnate the dry film. As for the alkali metal salt, an organic solvent may be added after a dry film is produced by mixing the polymer, optionally another resin, and the alkali metal salt, or the alkali metal salt may be dissolved in an organic solvent and added to the dry film.

[0122] The electrolyte composition of this embodiment can be used as a composition for forming an electrolyte for batteries, capacitors, etc. That is, the electrolyte for batteries, etc. of this embodiment contains the electrolyte composition. Examples of the battery include batteries that charge and discharge by the movement of alkali metal ions, such as lithium ion batteries and sodium ion batteries. The battery may be a primary battery, a secondary battery, or a solid-state battery.

[0123] The battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. The positive electrode may be a layer containing a positive electrode material formed on a current collector. The negative electrode may be a layer containing a negative electrode material formed on a current collector. The following description will be given taking a lithium-ion battery as an example.

[0124] The negative electrode of the lithium ion battery is not particularly limited and may contain a negative electrode active material and, if necessary, a conductive additive, a binder, etc. Examples of the negative electrode active material include simple elements such as Li, Si, P, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys or composites containing these elements, carbon materials such as graphite, substances in which lithium ions are inserted between the layers of the carbon material, and oxides containing titanium.

[0125] The positive electrode of the lithium ion battery is not particularly limited, and may contain a positive electrode active material and, if necessary, a conductive additive, a binder, etc. The positive electrode active material is not particularly limited, and examples thereof include lithium composite metal oxides containing lithium and a transition metal element. The transition metal element may be at least one selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, and Al, and may contain Ni. Examples of lithium composite metal oxides include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , LiNi ０．５ Mn １．５ O ４ , Li ２ MnO ３ , LiNi ｘ Mn ｙ Co １－ｘ－ｙ O ２ [0<x+y<1]), LiNi ｘ Co ｙ Al １－ｘ－ｙ O ２ [0<x+y<1]), LiCr ０．５ Mn ０．５ O ２ , LiFePO ４ , Li ２ FeP ２ O ７, LiMnPO ４ , LiFeBO ３ , Li ３ V ２ (P.O. ４ ) ３ , Li ２ CuO ２ , Li ２ FeSiO ４ , Li ２ MnSiO ４ When the positive electrode active material contains an alkali metal element other than Li, specific examples thereof include those in which Li in the above specific examples is replaced with another alkali metal.

[0126] The negative electrode (negative electrode material) and the positive electrode (positive electrode material) of this embodiment may further contain a solid electrolyte material, a binding resin (binder), a conductive assistant, and the like.

[0127] The battery may have a separator. The separator may be a porous material, such as a porous resin material. Specific examples of the separator include a porous polyolefin membrane and a porous ceramic membrane.

[0128] <Synthesis of Copolymer 1> 0.558 g of monomer X represented by the following formula, 0.149 g of styrene, and 11.7 mg of azobisisobutyronitrile were dissolved in 6.7 mL of dehydrated acetonitrile, and the mixture was reacted at 60°C for 24 hours under a nitrogen atmosphere while adding tetralin as an internal standard substance to check the monomer consumption rate. The polymerization solution was dialyzed in acetonitrile and vacuum dried at 120°C to obtain 0.640 g (yield 87%) of Copolymer 1. The monomer introduction ratio was monomer X:styrene = 52:48. The monomer introduction ratio was 0.640 g (yield 87%) of Copolymer 1. １ Calculated from H-NMR.

[0129] Number average molecular weight of copolymer 1 Mn = 9.4 × 10 ４ , weight average molecular weight Mw=4.2×10 ５ The number average molecular weight and the weight average molecular weight were measured by gel permeation chromatography.

[0130]

[0131] The monomer X was synthesized by adding the following compound and an aqueous lithium acetate solution (14.0 mmol, 0.92 g) to acetic anhydride (12.3 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) and stirring at 70° C. for 3 hours.

[0132] (Examples 1 to 11 and Comparative Examples 1 to 5) <Production of Electrolyte Composition> The components were blended according to the compositions shown in Tables 1 and 2 to obtain the electrolyte compositions of the Examples and Comparative Examples. The electrolyte compositions were produced by first dissolving the copolymer obtained as described above in acetonitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 1-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), adding a lithium salt to the solution, allowing the solution to soak into a porous PE membrane, and then removing the solvent to obtain a dry membrane. An organic solvent in which a film-forming additive had been dissolved was then added to the dry membrane to swell the membrane, thereby obtaining an electrolyte composition.

[0133] The units of the contents of the organic solvent and the coating additive in the table are parts by mass relative to 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions, and the units of the contents of the alkali metal salt and the anion receptor in the table are parts by mole relative to 100 moles of the structural unit derived from the monomer X in the copolymer.

[0134] The abbreviations in the table are as follows: MI-St: Copolymer 1 synthesized as above PVDF-HFP: Poly(vinylidene fluoride-co-hexafluoropropylene) EC: Ethylene carbonate PC: Propylene carbonate DMC: Dimethyl carbonate FDMA: 2,2,2-trifluoro-N,N-dimethylacetamide TMP: Trimethyl phosphate TEP: Triethyl phosphate LiFSI: Lithium bis(fluorosulfonyl)imide LiTFSI: Lithium bis(trifluoromethanesulfonyl)imide VC: Vinylene carbonate FEC: Fluoroethylene carbonate TFB: 2,4,6-tris(4-fluorophenyl)boroxine

[0135] <Measurement of Lithium Ion Transference Number> The lithium ion transference number of the electrolyte compositions of each of the Examples and Comparative Examples was measured by the following method. The results are shown in Table 2.

[0136] An evaluation cell of a coin-type lithium battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the evaluation cell in the following order to prepare a test laminate (lithium / electrolyte composition / lithium).

[0137] The lithium ion transport number measurement method is introduced in Polymer, 28, 2324 (1987). That is, 10 mV is applied to the test laminate at room temperature (25° C.), and the initial current value (I ０ ) and steady-state current value (I ｓｓ ) was measured, and the interface resistance measured value R ０ and the measured interface resistance R after voltage application ＳＳ The lithium ion transport number (t Ｌｉ＋ ) was calculated. V in the formula is the applied voltage. Ｌｉ＋ =I ｓｓ (VI ０ R ０ ) / I ０ (VI ＳＳ R ＳＳ )

[0138] <Measurement of Maximum DC Current Density> An evaluation cell of a coin-type battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the evaluation cell in the following order to prepare a test laminate (lithium / electrolyte composition / lithium).

[0139] The evaluation cell was subjected to alternating positive and negative currents of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, and 2000 μA / cm ２ A constant current test was carried out in which current densities of 1000 and 15000 were applied in this order for five cycles, and the test was terminated when the voltage reached 2 V. The maximum current density that could be applied before reaching 2 V was defined as the maximum DC current density, and the voltage value at that time was determined. The results are shown in Tables 1 and 2.

[0140] FIG. 1 is a diagram showing the relationship between current density and voltage value in the lithium dissolution and deposition tests of Comparative Example 1, Example 1, and Example 2.

[0141]

[0142]

[0143] Tables 1 and 2 show that the electrolyte composition of this embodiment can pass a sufficient amount of current at a low voltage. Comparing Comparative Example 1 with Comparative Examples 2 to 5, a slight improvement in the current value is observed, demonstrating the effect of including the film-forming additive in the electrolyte composition. However, compared with the Examples, a higher voltage was required to pass the same amount of current.

[0144] <Synthesis of Copolymer 2> 0.74 g of Monomer X, 0.34 g of isobutyl vinyl ether (IBVE), and 8.2 mg of azobisisobutyronitrile were dissolved in 10 mL of dehydrated acetonitrile, and the mixture was reacted at 60°C for 24 hours under a nitrogen atmosphere while adding tetralin as an internal standard substance to check the monomer consumption rate. The polymerization solution was dialyzed in acetonitrile and vacuum dried at 120°C to obtain 0.34 g of Copolymer 2 (yield 82%). The monomer introduction ratio was Monomer X:IBVE = 62:38. The monomer introduction ratio of Copolymer 2 was １ Calculated from H-NMR.

[0145] <Synthesis of Copolymer 3> 0.94 g of Monomer X, 1.53 g of dodecyl vinyl ether (DDVE), and 16.4 mg of azobisisobutyronitrile were dissolved in 20 mL of dehydrated acetonitrile, and the mixture was reacted at 60°C for 24 hours under a nitrogen atmosphere while adding tetralin as an internal standard substance to check the monomer consumption rate. The polymerization solution was dialyzed in acetonitrile and vacuum dried at 120°C to obtain 0.64 g of Copolymer 3 (yield 44%). The monomer introduction ratio was Monomer X:DDVE = 55:45. The monomer introduction ratio of Copolymer 3 was １ Calculated from H-NMR.

[0146] <Synthesis of Copolymer 4> 0.78 g of monomer X, 0.46 g of the following monomer (B1), and 16.4 mg of azobisisobutyronitrile were dissolved in 6.7 mL of dehydrated acetonitrile, and the mixture was reacted at 60°C for 24 hours under a nitrogen atmosphere while adding tetralin as an internal standard substance to check the monomer consumption rate. The polymerization solution was dialyzed in acetonitrile and vacuum dried at 120°C to obtain 1.08 g (yield 87%) of Copolymer 4. The monomer introduction ratio was monomer X:B1 = 48:52. １ Calculated from H-NMR.

[0147] (Synthesis of Monomer B1) Monomer (B1) was synthesized as follows: ４ To 4.21 g (5 mmol) of 4-vinylphenylboronic acid (VPBA) and 4.14 g (35 mmol) of pinacol were added 175 mL of diethyl ether, and the mixture was stirred to obtain a cloudy solution. To this solution, 5.18 g (35 mmol) of 4-vinylphenylboronic acid (VPBA) was added and the mixture was stirred at room temperature for 19 hours. The solvent obtained by filtration was evaporated and the resulting solution was purified by silica gel chromatography (eluent: hexane / ethyl acetate 20 / 1 (volume ratio)), and the target monomer (B1) was obtained in a yield of 92.1%.

[0148] Examples 11 to 17 The components were blended in the compositions shown in Table 3, and the electrolyte compositions of Examples 11 to 17 were produced by the method described above, and various measurements were carried out.

[0149] <Method for Synthesizing Copolymer 5> The lithiated carboxyl group-containing copolymer of Example 1 was produced by the following method.

[0150] Saccharin methacrylamide (SacM) (1.8848 g, 7.5 mmol), styrene (St) (0.86 mL, 7.5 mmol), tetralin (0.15 mL), and azobisisobutyronitrile (24.7 mg, 0.15 mmol) were dissolved in a mixed solvent of dioxane and acetonitrile (dioxane:acetonitrile=1:1 (volume ratio)) (12.1 mL), and the solution was stirred at 60° C. for 24 hours to obtain a solution of a copolymer of saccharin methacrylamide and styrene (raw material copolymer).

[0151] Next, a 25 mM phenothiazine solution in 1,4-dioxane (45.0 mL, 1.13 mmol) and 100 equivalents of water were added to the resulting polymerization solution, and the mixture was stirred overnight. As a result, the structural units derived from saccharin methacrylamide in the raw copolymer were hydrolyzed, and the amide bonds containing saccharin moieties were converted to -COOH groups (i.e., the structural units derived from saccharin methacrylamide were converted to methacrylic acid (MAA) units), yielding a -COOH group-containing copolymer (0.61 g).

[0152] The composition ratio of the structural units in the polymer was MAA:St = 48:52 (molar ratio). １ It was calculated by measuring the H-NMR spectrum.

[0153] Then, the -COOH group-containing copolymer (0.61 g, 3.21 mmol) was dissolved in dimethylformamide (12 mL) to obtain a solution. To this solution, 2.5 equivalents of LiOH (449.1 mg, 18.82 mmol) relative to the amount of SacM initially charged when producing the raw material copolymer was added, and the mixture was stirred at room temperature (25°C) for 3 days. As a result, a copolymer in which the -COOH groups of the -COOH group-containing copolymer had been converted to -COOLi (lithiated carboxyl group-containing copolymer) was obtained (0.43 g).

[0154] Examples 18 to 24, Comparative Examples 4 and 5 Components were blended in the compositions shown in Tables 4 and 5, and electrolyte compositions were produced by the above-described method, and various measurements were carried out.

[0155]

[0156]

Claims

1. An electrolyte composition comprising a polymer capable of preferentially conducting alkali metal ions, an alkali metal salt, a film-forming additive, and an organic solvent.

2. The electrolyte composition according to claim 1, having a transport number of 0.5 or more.

3. The electrolyte composition according to claim 1 or 2, wherein the alkali metal salt is a lithium salt or a sodium salt.

4. The electrolyte composition according to claim 1 or 2, wherein the organic solvent is one or more solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, phosphate-based solvents, and sulfone-based solvents.

5. The electrolyte composition according to claim 1 or 2, wherein the polymer capable of preferentially conducting alkali metal ions contains one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, an alkali metal substituted carboxylic acid group, and an alkali metal substituted phenolic hydroxyl group.

6. A battery comprising the electrolyte composition according to claim 1 or 2.

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