Acylated crosslinked copolymer aliphatic polycarbonate, polymer binder for all-solid-state batteries, and all-solid-state secondary battery

Abstract

To provide a novel polymer useful for a polymer binder for an all-solid-state battery, or the like.SOLUTION: An acylated, crosslinked, copolymerized aliphatic polycarbonate is a crosslinked, copolymerized aliphatic polycarbonate composed of an oxygen-containing heterocycle diol comprising an aliphatic polyol and a spiro structure. The acylated, crosslinked, copolymerized aliphatic polycarbonate is characterized by a structure with a polymeric molecular terminal capped with an acyl group. The ratio of acyl groups at the polymeric molecular terminals to hydrogen atoms is expressed as a polymeric average density (eq / T): (100:0)-(65:35).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to acylated crosslinked copolymer aliphatic polycarbonate, a polymer binder for all-solid-state batteries, and an all-solid-state secondary battery. [Background technology]

[0002] In lithium-ion secondary batteries, a liquid electrolyte dissolved in a non-aqueous solvent is used as the electrolyte.

[0003] In contrast, all-solid-state rechargeable batteries use a solid material as the electrolyte. These batteries are manufactured using this solid electrolyte and other solid materials that constitute the battery, such as the positive electrode compound and the negative electrode compound. Therefore, all-solid-state rechargeable batteries utilize a binder to bind the various solid materials that make up the battery.

[0004] Patent Document 1 discloses a method for manufacturing a positive electrode, a negative electrode, and a solid electrolyte layer by binding solid materials together using a binder resin such as polyvinylpyrrolidone or butylene rubber as a binder.

[0005] Patent Document 2 discloses the use of polyvinyl acetal resin as a binder.

[0006] Furthermore, in Patent Document 3, the present inventors disclosed a three-dimensional crosslinked copolymer polycarbonate as a resin binder for a binder. Specifically, they disclosed a three-dimensional crosslinked copolymer polycarbonate having structural units derived from two types of aliphatic diols, structural units derived from a polyol having three or more hydroxyl groups, and structural units derived from a diol having an ether bond. This resin binder has improved bonding properties with solid materials such as inorganic solid electrolytes and aluminum, and has excellent moldability and ionic conductivity, so it can increase the surface area of ​​electrodes in all-solid-state secondary batteries and improve battery performance. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-137869 [Patent Document 2] Japanese Patent Publication No. 2014-212022 [Patent Document 3] International Publication No. 2020 / 203881 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, all-solid-state rechargeable batteries require further performance improvements, and the binders used in them also need to have superior properties, such as better adhesion. Novel polymers that are useful for these applications are therefore desired.

[0009] The object of the present invention is to provide a novel polymer useful as a polymer binder for all-solid-state batteries and the like. [Means for solving the problem]

[0010] As a result of their research to solve the above problems, the inventors discovered that acylation of the terminal hydroxyl groups of a cross-linked copolymer aliphatic polycarbonate containing specific structural units at a specific ratio results in excellent bonding properties with aluminum foil, and that reducing the amount used can improve ion conductivity inside the battery. Based on these findings, the inventors completed the present invention.

[0011] The acylated crosslinked copolymer aliphatic polycarbonate according to the first aspect of the present invention comprises structural units represented by the following formulas (1) to (4): [ka] (In formula (1), R 1 (where x represents an aliphatic hydrocarbon residue with 2 to 20 carbon atoms, and x represents an integer between 3 and 100.) [ka] (In formula (2), R2 represents the following formula (2-1)

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0012] Preferably, the acyl group represented by R 5 is an acetyl group or a benzoyl group.)

[0013] The above R1 However, x represents an aliphatic hydrocarbon residue with 8 to 12 carbon atoms, and x represents an integer between 60 and 90. The aforementioned R 2 However, R in equation (2-1) above 2’’ This represents an aliphatic hydrocarbon residue with 1 to 2 carbon atoms, The aforementioned R 3 However, the number of spiro atoms is 1 to 2, and the heteroatom is either an oxygen atom or a sulfur atom. The aforementioned R 4 However, it is preferable that m represents an aliphatic hydrocarbon residue with 2 to 4 carbon atoms, and m represents an integer between 1 and 3.

[0014] The aforementioned R 1 is an alkylene group having 10 carbon atoms, and the R 2 However, R in equation (2-1) above 2’’ is an alkylene group having 1 carbon atom, and the R 3 The group is a 2,2'-(2,4,8,10,-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropanediyl group, and the R 4 It is preferable that is an alkylene group having 2 carbon atoms and m is an integer of 3.

[0015] It is preferable that the proportion of structural units represented by formulas (1) to (4) is in molar ratio (1):(2):(3):(4) = 40-50:0.4-0.8:10-50:10-35.

[0016] A polymer binder for all-solid-state batteries according to a second aspect of the present invention comprises the acylated crosslinked copolymer aliphatic polycarbonate and a lithium salt.

[0017] The lithium salt preferably contains LiTFSI.

[0018] A third aspect of the present invention relates to an all-solid-state secondary battery comprising the acylated crosslinked copolymer aliphatic polycarbonate.

[0019] A solid-state secondary battery according to a fourth aspect of the present invention includes the polymer binder for the solid-state battery. [Effects of the Invention]

[0020] The acylated crosslinked copolymer aliphatic polycarbonate of the present invention provides a novel polymer useful for polymer binders for all-solid-state batteries and the like. [Brief explanation of the drawing]

[0021] . [Figure 1] 1H-NMR spectrum of the crosslinked copolymer aliphatic polycarbonate according to Production Example 1. [Figure 2] 13C-NMR spectrum of the cross-linked copolymer aliphatic polycarbonate according to Production Example 1. [Figure 3] 1H-NMR spectrum of the acylated crosslinked copolymer aliphatic polycarbonate according to Example 1. [Figure 4] 13C-NMR spectrum of the acylated crosslinked copolymer aliphatic polycarbonate according to Example 1. [Modes for carrying out the invention]

[0022] The acylated crosslinked copolymer aliphatic polycarbonate of the present invention contains structural units represented by the following formulas (1) to (4): [ka] (In formula (1), R 1 (where x represents an aliphatic hydrocarbon residue with 2 to 20 carbon atoms, and x represents an integer between 3 and 100.) [ka] (In formula (2), R 2 The following equation (2-1) [ka] Represents R 2’ and R 2’’ Each of these independently represents an aliphatic hydrocarbon residue with 0 to 5 carbon atoms, and R 2’’’(This represents a hydrogen atom or an aliphatic hydrocarbon residue with 1 to 5 carbon atoms.) [ka] (In formula (3), R 3 (This represents an aliphatic hydrocarbon residue that has a spiro structure and may contain heteroatoms in its structure.) [ka] (In formula (4), R 4 (where m represents an aliphatic hydrocarbon residue with 2 to 10 carbon atoms, and m represents an integer between 1 and 30.) The polymer molecule ends have one of the structures represented by the following formulas (5-1) to (5-4), where the terminal group bonded to the carbonate oxygen atom at the left end of formulas (1) to (4) is R at the right end of formulas (1) to (4). 1 ~R 4 The terminal group that is bonded to has a structure represented by the following formula (6), [ka] (In equations (5-1) to (5-4) and equation (6), R 5 Each of these independently represents either a hydrogen atom or an acyl group. The ratio of acyl groups to hydrogen atoms at the polymer molecule terminals, as represented by formulas (5-1) to (5-4) and formula (6), is (100:0) to (65:35) in terms of the polymer average concentration (eq / T).

[0023] As described later, the acylated crosslinked copolymer aliphatic polycarbonate of the present invention can be used, for example, in combination with a lithium salt as a polymer binder for all-solid-state batteries, and in the production of an all-solid-state secondary battery by forming a slurry using a hydrophobic solvent and impregnating it between the positive electrode mixture, the negative electrode mixture, and the solid electrolyte.

[0024] (Structural unit represented by formula (1)) Formula (1) according to the present invention [ka] In the structural unit represented by R 1 x represents an aliphatic hydrocarbon residue with 2 to 20 carbon atoms, and x represents an integer between 3 and 100.

[0025] R in equation (1) 1 If the carbon number is less than 2, the dispersibility of the acylated crosslinked copolymer aliphatic polycarbonate in the slurry used in the production of the all-solid-state secondary battery described later tends to decrease. As will be described later, it is desirable that the polymer binder according to the present invention permeates between the positive electrode mixture, the negative electrode mixture, and the solid electrolyte during the manufacturing process of the all-solid-state secondary battery. Therefore, since a slurry using a hydrophobic solvent is usually used in the manufacturing process, it is desirable that the acylated crosslinked copolymer aliphatic polycarbonate contained in the polymer binder of the present invention be dispersed in a hydrophobic solvent.

[0026] On the other hand, R 1 When the number of carbon atoms exceeds 20, the affinity for lithium ions tends to decrease.

[0027] R 1 This can be a single type or a combination of multiple types, R 1 It is preferable that it be a single, independent entity.

[0028] R 1 If R is a single entity, 1 It is preferably an aliphatic hydrocarbon residue having 8 to 12 carbon atoms, more preferably an alkylene group having 9 to 11 carbon atoms, and particularly preferably an aliphatic hydrocarbon residue having 10 carbon atoms.

[0029] R 1 If there are multiple types, R 1 It is preferable that R represents an alkylene group having 2 to 7 carbon atoms and an aliphatic hydrocarbon residue having 2 to 20 carbon atoms. 1 If there are multiple types, the arrangement of structural units is not particularly limited, and may be, for example, a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

[0030] R 1 When the number of carbon atoms falls within this range, polymer binders for all-solid-state batteries using acylated crosslinked copolymer aliphatic polycarbonates exhibit an excellent balance of binding properties, moldability, and ionic conductivity.

[0031] R 1 The aliphatic hydrocarbon residues involved may be linear, branched, or cyclic, but linear is preferred. Also, R 1 The aliphatic hydrocarbon residues involved may be substituted with alkoxy groups, cyano groups, primary to tertiary amino groups, halogen atoms, etc., in the main chain or side chain, but are preferably unsubstituted.

[0032] Examples of aliphatic hydrocarbon residues with 2 to 20 carbon atoms include ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, dodecane-1,12-diyl group, tetradecane-1,14-diyl group, hexadecane-1,16-diyl group, oc Chain-like aliphatic hydrocarbon groups such as tadecane-1,18-diyl group and eicosane-1,20-diyl group, branched aliphatic hydrocarbon groups such as 1-methylethane-1,2-diyl group, 2-methylpropane-1,3-diyl group, 2-methylbutane-1,4-diyl group, 2-ethylbutane-1,4-diyl group, 3-methylpentane-1,5-diyl group, 2-methylhexane-1,6-diyl group, and 5-methyldecane-1,10-diyl group, cyclopropane-1,2-diyl group, cyclo Butane-1,2-diyl group, cyclobutane-1,3-diyl group, cyclopentane-1,2-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,1-diyl group, cyclohexane-1,2-diyl group, cyclohexane-1,3-diyl group, cyclohexane-1,4-diyl group, cycloheptane-1,2-diyl group, cycloheptane-1,3-diyl group, cycloheptane-1,4-diyl group, cyclooctane-1,2-diyl group, cycloocta Examples of alicyclic hydrocarbon groups include n-1,3-diyl group, cyclooctane-1,4-diyl group, cyclooctane-1,5-diyl group, cyclononane-1,2-diyl group, cyclononane-1,3-diyl group, cyclononane-1,4-diyl group, cyclononane-1,5-diyl group, cyclodecane-1,2-diyl group, cyclodecane-1,3-diyl group, cyclodecane-1,4-diyl group, cyclodecane-1,5-diyl group, and cyclodecane-1,6-diyl group. Among these aliphatic hydrocarbon residues, linear aliphatic hydrocarbon groups are preferred, C10 alkylene groups are more preferred, and decane-1,10-diyl groups are particularly preferred.

[0033] In equation (1), x represents the number of repeating units indicated in parentheses in equation (1), and is an integer between 3 and 100. When x is less than 3, the dispersibility of the solid electrolyte, positive electrode active material, negative electrode active material, etc. in the slurry when manufacturing all-solid-state secondary batteries decreases. Also, when x exceeds 100, the viscosity of the slurry increases when it is prepared, and the coating properties of the slurry decrease.

[0034] x is preferably between 30 and 95, more preferably between 60 and 90, and particularly preferably between 70 and 80.

[0035] The polymer binder for all-solid-state batteries using the acylated crosslinked copolymer aliphatic polycarbonate of the present invention enables the formation of the positive electrode, solid electrolyte layer, or negative electrode constituting the all-solid-state secondary battery in a sheet-like form. Therefore, it is desirable that it exhibits excellent bonding properties with electrode mixtures or inorganic solid electrolytes, as well as excellent strength. Strength tends to improve as x increases.

[0036] Formula (1) [ka] Acylated crosslinked copolymer aliphatic polycarbonates containing structural units represented by can be obtained by known transesterification and acylation reactions. For example, R 1 Diol compounds, in which hydroxyl groups are bonded to the termini of aliphatic hydrocarbon residues represented by , can be carbonated by reacting them with diphenyl carbonate or phosgene to prepare oligomers in which the polymer molecule termini are hydroxyl groups. A crosslinked copolymer aliphatic polycarbonate can be obtained by copolymerizing this oligomer with other diol compounds, and an acylated crosslinked copolymer aliphatic polycarbonate can be obtained by acyling some of the hydroxyl groups at the termini of the polymer molecule using a known acylation reaction.

[0037] R 1Examples of diol compounds in which a hydroxyl group is bonded to the terminus of an aliphatic hydrocarbon residue represented by include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, and 1,20-icosanediol.

[0038] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, the ratio of the structural unit of formula (1) to the sum of the structural units of formulas (1) to (4) is not particularly limited, but is preferably 20 mol% to 70 mol%, more preferably 30 mol% to 60 mol%, even more preferably 40 mol% to 50 mol%, and particularly preferably 45 mol% to 50 mol%. Furthermore, the ratio for formula (1) is not based on the entire formula (1), but rather on the repeating unit in the parentheses of formula (1). In this specification, unless otherwise specified, the ratio of the structural unit of each formula to the sum of the structural units of formulas (1) to (4) is based on the repeating unit in the parentheses of formula (1).

[0039] (Structural unit represented by formula (2)) Formula (2) according to the present invention [ka] In the structural unit represented by R 2 The following equation (2-1) [ka] Represents R 2’ and R 2’’ Each of these independently represents an aliphatic hydrocarbon residue with 0 to 5 carbon atoms, and R 2’’’ represents a hydrogen atom or an aliphatic hydrocarbon residue having 1 to 5 carbon atoms.

[0040] Note that in equation (2-1), R 2’ and R 2’’ The case with 0 carbon atoms means that only a bond exists, representing a bond between the central carbon atom inside the parentheses and a carbonate oxygen atom in the other structure outside the parentheses. Also, the bond represented by a straight line connecting to the outside of the parentheses in the vertical direction in formula (2-1) represents a bond with a carbonate oxygen atom in the other structure, similar to the bond represented by a straight line connecting to the rightmost outside of the parentheses in the horizontal direction in formula (2-1).

[0041] R 2’ and R 2’’ The aliphatic hydrocarbon residues involved may be linear, branched, or cyclic, but linear is preferred. Also, R 2’ and R 2’’ The aliphatic hydrocarbon residues involved may be substituted with alkoxy groups, cyano groups, primary to tertiary amino groups, halogen atoms, etc., in the main chain or side chain, but are preferably unsubstituted.

[0042] R 2’ and R 2’’ Examples of aliphatic hydrocarbon residues with 0 to 5 carbon atoms related to R include chain-like aliphatic hydrocarbon groups such as methane-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, and pentane-1,5-diyl group; branched aliphatic hydrocarbon groups such as 1-methylethane-1,2-diyl group, 2-methylpropane-1,3-diyl group, 2-methylbutane-1,4-diyl group, and 2-ethylbutane-1,4-diyl group; and alicyclic hydrocarbon groups such as cyclopropane-1,2-diyl group, cyclobutane-1,2-diyl group, cyclobutane-1,3-diyl group, cyclopentane-1,2-diyl group, and cyclopentane-1,3-diyl group. 2’ and R 2’’ As mentioned above, an aliphatic hydrocarbon residue with zero carbon atoms refers to a bond between a central carbon atom and a carbonate oxygen atom or the like in another structure. Among these aliphatic hydrogen residues, linear aliphatic hydrocarbon groups are preferred. Furthermore, aliphatic hydrocarbon residues with 1 to 2 carbon atoms are preferred, and methane-diyl groups (methylene groups) are more preferred.

[0043] R 2’’’ The aliphatic hydrocarbon residues involved may be linear, branched, or cyclic, but linear is preferred. Also, R 2’’’ The aliphatic hydrocarbon residues involved may be substituted with alkoxy groups, cyano groups, primary to tertiary amino groups, halogen atoms, etc., in the main chain or side chain, but are preferably unsubstituted.

[0044] R 2’’’ Examples of aliphatic hydrocarbon residues with 1 to 5 carbon atoms include linear aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, and pentyl groups; branched aliphatic hydrocarbon groups such as 2-methylethyl (isopropyl), 2-methylpropyl, 2,2-dimethylethyl (t-butyl), and 2-methylbutyl groups; and alicyclic hydrocarbon groups such as cyclopropyl, cyclobutyl, and cyclopentyl groups.

[0045] The structural unit represented by equation (2) functions as a crosslinking structure that crosslinks other structural units in three dimensions. This results in a more uniform crosslinking structure, improving the dispersibility of the polymer binder for all-solid-state batteries in hydrophobic solvents.

[0046] Acylated crosslinked copolymer aliphatic polycarbonates containing the structural unit represented by formula (2) can be obtained by known transesterification and acylation reactions. For example, an oligomer having the structural unit represented by formula (1) in which both molecular ends are hydroxyl groups, a diol compound having the structure represented by the parentheses in formula (3), a diol compound having the structure represented by the parentheses in formula (4), and R in formula (2-1) 2’ and R 2’’ A crosslinked copolymer aliphatic polycarbonate can be obtained by carbonate bonding a triol compound or tetraol compound, in which a hydroxyl group is bonded to the terminal end of a hydrocarbon residue represented by , with diphenyl carbonate or the like. Then, an acylated crosslinked copolymer aliphatic polycarbonate can be obtained by acyling some of the hydroxyl groups at the terminal ends of the polymer molecule using a known acylation reaction.

[0047] R in equation (2-1) 2’ and R 2’’ Examples of triol compounds or tetraol compounds in which a hydroxyl group is bonded to the terminus of a hydrocarbon residue represented by include glycerin, trimethylolpropane, and pentaerythritol. These triol compounds or tetraol compounds may be used individually or in combination of two or more. In the present invention, the use of pentaerythritol is preferred.

[0048] Another method for producing acylated crosslinked copolymer aliphatic polycarbonates containing the structural unit represented by formula (2) is to use a compound having three or four carboxyl groups instead of the aforementioned triol or tetraol compounds.

[0049] Compounds having three or more carboxyl groups include 1,3,5-pentanetricarboxylic acid and 1,2,3,4-butanetetracarboxylic acid.

[0050] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, the ratio of structural units of formula (2) to the sum of structural units of formulas (1) to (4) is not particularly limited, but is preferably 0.01 mol% to 10 mol%, more preferably 0.05 mol% to 5 mol%, even more preferably 0.1 mol% to 1 mol%, particularly preferably 0.4 mol% to 0.8 mol%, and most preferably 0.4 mol% to 0.6 mol%. Here, for formula (1), the ratio is based on the repeating unit in parentheses in formula (1), not on the entire formula (1).

[0051] When the ratio of structural units in formula (2) is reduced, the crosslinking density tends to decrease, which in turn reduces the adhesion of the polymer binder with metal salts in solid solution. Conversely, when the ratio of structural units in formula (2) is too high, the crosslinking density increases, leading to gelation and a decrease in dispersibility in hydrophobic solvents.

[0052] (Structural unit represented by formula (3)) Formula (3) according to the present invention [ka] In the structural unit represented by R 3 This represents an aliphatic hydrocarbon residue that has a spiro structure and may contain heteroatoms in its structure.

[0053] Examples of the heteroatom include oxygen atoms, sulfur atoms, and nitrogen atoms, and it is preferable that the heteroatom is an oxygen atom or a sulfur atom, and more preferably that the heteroatom is an oxygen atom.

[0054] The structure represented by formula (3) is thought to contribute to the dispersibility in hydrophobic solvents used in the manufacture of all-solid-state batteries. The acylated crosslinked copolymer aliphatic polycarbonate of the present invention is preferable because having this structure improves the affinity of the polymer binder using the acylated crosslinked copolymer aliphatic polycarbonate of the present invention to hydrophobic solvents, and reduces the cohesive force in hydrophobic solvents, resulting in improved dispersibility in hydrophobic solvents.

[0055] R in equation (3) 3 The hydrocarbon residue having a spiro structure represented by may be a hydrocarbon residue having a bicyclic spiro structure with one spiro atom, or a tricyclic or more spiro structure with two or more spiro atoms, but it is preferably a hydrocarbon residue having a bicyclic or tricyclic spiro structure with 1 to 2 spiro atoms, and more preferably a hydrocarbon residue having a bicyclic spiro structure with one spiro atom. The number of atoms forming the ring is preferably 4 or more, and more preferably 6 or more. Furthermore, it is even more preferable that some of the carbon atoms forming the ring are substituted with heteroatoms such as oxygen atoms.

[0056] R in equation (3) 3 The presence of a hydrocarbon residue with a spiro structure increases its bulkiness, improving its dispersibility in the slurry used when creating all-solid-state batteries. Furthermore, if some of the carbon atoms forming the ring are substituted with heteroatoms, the affinity with lithium salt increases, which is even more preferable.

[0057] Examples of hydrocarbon residues having a two-cyclic or more spiro structure include the spiro[2.2]pentane-1,4-diyl group, spiro[3.3]heptane-2,6-diyl group, spiro[4.4]nonane-2,7-diyl group, spiro[5.5]undecane-3,9-diyl group, spiro[3.5]nonane-2,7-diyl group, spiro[2.6]nonane-1,6-diyl group, spiro[4.5]decane-1,5-diyl group, dispiro[4.2.4.2]tetradecane-1,11-diyl group, dispiro[4.1.5.2]tetradecane-2,12-diyl group, 1,1'-spirobi[indene]-8,8'-diyl group, and 1H,1'H-2,2'-spirobi[naphthalene]-9,9'-diyl group.

[0058] Examples of hydrocarbon residues having a spiro structure in which some of the ring-forming atoms are substituted with heteroatoms such as oxygen atoms include the 2,2'-(2,4,8,10,-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropanediyl group (generic monomer name: spiroglycol), the 2,2',3,3'-tetrahydro-1,1'-spirobi[indene]-7,7'-diyl group, the 4,8-dihydro-1H,1'H-2,4'-spirobi[quinoline]-6',7-diyl group, and the 4,4,4',4'-tetramethyl-2,2'-spirobi[chroman]-7,7'-diyl group. Among these, the 2,2'-(2,4,8,10,-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropanediyl group is preferred.

[0059] The hydrocarbon residues having a spiro structure may be saturated or unsaturated, and the main chain or side chain may be substituted with alkoxy groups, cyano groups, primary to tertiary amino groups, halogen atoms, etc.

[0060] The structural units represented by formula (3) can exist in blocks or randomly in acylated cross-linked copolymer aliphatic polycarbonates.

[0061] Here, when the structural units represented by formula (3) exist as blocks in the main chain, it is preferable that the structural units represented by formula (3) are linked together in units of 1 to 10 to form blocks, more preferably in units of 1 to 5, and particularly preferably in units of 1 to 3. Linking in units of 3 or less improves the dispersibility of the polymer binder in hydrophobic solvents.

[0062] Acylated crosslinked copolymer aliphatic polycarbonates containing the structural unit represented by formula (3) can be obtained by known transesterification reactions. For example, an oligomer having the structural unit represented by formula (1) in which both molecular ends are hydroxyl groups, and R in formula (2-1) 2’ and R 2’’ A crosslinked copolymer aliphatic polycarbonate can be obtained by carbonate bonding a triol compound or tetraol compound having a hydroxyl group bonded to the terminal end of a hydrocarbon residue represented by formula (4), a diol compound having the structure represented by the parentheses in formula (4), and a diol compound having the structure represented by the parentheses in formula (3) with diphenyl carbonate or the like. An acylated crosslinked copolymer aliphatic polycarbonate can then be obtained by acyling some of the hydroxyl groups at the terminal ends of the polymer molecule using a known acylation reaction.

[0063] Diol compounds having the structure represented in parentheses in formula (3) include spiro[2.2]pentane-1,4-diol, spiro[3.3]heptane-2,6-diyl group, spiro[4.4]nonane-2,7-diol, spiro[5.5]undecane-3,9-diol, spiro[3.5]nonane-2,7-diol, spiro[2.6]nonane-1,6-diol, spiro[4.5]decane-1,5-diol, dispiro[4.2.4.2]tetradecane-1,11-diol, dispiro[4.1.5.2]tetradecane-2,12-diol, 1,1'-spirob[ Examples include indene-8,8'-diol, 1H,1'H-2,2'-spirobio[naphthalene]-9,9'-diol, 2,2'-(2,4,8,10,-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropanediol (also known as spiroglycol), 2,2',3,3'-tetrahydro-1,1'-spirobio[indene]-7,7'-diyl group, 4,8-dihydro-1H,1'H-2,4'-spirobio[quinoline]-6',7-diol, and 4,4,4',4'-tetramethyl-2,2'-spirobio[chroman]-7,7'-diol. Among these, spiroglycol is preferred.

[0064] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, the ratio of structural units of formula (3) to the sum of structural units of formulas (1) to (4) is not particularly limited, but is preferably 5 mol% to 55 mol%, more preferably 10 mol% to 50 mol%, even more preferably 20 mol% to 35 mol%, and particularly preferably 25 mol% to 33 mol%. Here, for formula (1), the ratio is based on the repeating unit in parentheses in formula (1), not on the entire formula (1).

[0065] (Structural unit represented by formula (4)) Formula (4) according to the present invention [ka] In the structural unit represented by R 4represents an aliphatic hydrocarbon residue with 2 to 10 carbon atoms, and m represents an integer between 1 and 30.

[0066] The structural unit represented by formula (4) is thought to contribute to the adhesion of the polymer binder to the positive / negative electrode active material, solid electrolyte, and current collector, which are the materials to which the polymer binder is bound in an all-solid-state battery. The acylated crosslinked copolymer aliphatic polycarbonate polymer of the present invention is preferable because having this structure increases the flexibility and polarity of the polymer binder, resulting in improved adhesion to the materials to which it is bound.

[0067] R in equation (4) 4 The group is not particularly limited as long as it is an aliphatic hydrocarbon residue with 2 to 10 carbon atoms, but it is preferably an alkylene group with 2 to 4 carbon atoms. When the number of carbon atoms is 2 or more, the flexibility of the polymer tends to improve.

[0068] In formula (4), m is not particularly limited as long as it is an integer between 1 and 30, but is preferably an integer between 1 and 20, more preferably an integer between 2 and 10, even more preferably an integer between 3 and 5, is particularly preferably an integer between 1 and 3, and is most preferably 3. When m is 1 or greater, the flexibility of the acylated crosslinked copolymer aliphatic polycarbonate increases, and when it is 5 or less, the adhesion to metal tends to improve.

[0069] R in equation (4) 4Examples of aliphatic hydrocarbon residues with 2 to 10 carbon atoms include chain-like aliphatic hydrocarbon groups such as ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group, as well as branched aliphatic hydrocarbon groups such as 1-methylethane-1,2-diyl group, 2-methylpropane-1,3-diyl group, 2-methylbutane-1,4-diyl group, 2-ethylbutane-1,4-diyl group, 3-methylpentane-1,5-diyl group, 3-methylpentane-1,5-diyl group, and 2-methylhexane-1,6-diyl group. Among these, an alkylene group with 2 carbon atoms, i.e., an ethane-1,2-diyl group (ethylene group), is preferred.

[0070] R in equation (4) 4 The aliphatic hydrocarbon residues involved may be saturated or unsaturated, and the main chain or side chain may be substituted with alkoxy groups, cyano groups, primary to tertiary amino groups, halogen atoms, etc.

[0071] The structural units represented by formula (4) can exist in blocks or randomly in acylated crosslinked copolymer aliphatic polycarbonates.

[0072] When the structural units represented by formula (4) exist as blocks, it is preferable that the structural units represented by formula (4) are linked together in units of 1 to 10 to form blocks, more preferably in units of 1 to 5, and particularly preferably in units of 1 to 3. Linking in units of 3 or less is preferable because it allows for both dispersibility and binding properties of the polymer binder in hydrophobic solvents.

[0073] Acylated crosslinked copolymer aliphatic polycarbonates containing the structural unit represented by formula (4) can be obtained by known transesterification reactions. For example, an oligomer having the structural unit represented by formula (1) in which both molecular ends are hydroxyl groups, and R in formula (2-1) 2’ and R 2’’A crosslinked copolymer aliphatic polycarbonate can be obtained by carbonate bonding a triol compound or tetraol compound having a hydroxyl group bonded to the terminal end of a hydrocarbon residue represented by formula (3), a diol compound having the structure represented by the parentheses in formula (3), and a diol compound having the structure represented by the parentheses in formula (4) with diphenyl carbonate or the like. An acylated crosslinked copolymer aliphatic polycarbonate can then be obtained by acyling some of the hydroxyl groups at the terminal ends of the polymer molecule using a known acylation reaction.

[0074] Examples of diol compounds having the structure represented by the parentheses in formula (4) include diethylene glycol, triethylene glycol, and polyethylene glycol. Among these, triethylene glycol is preferred.

[0075] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, the ratio of the structural unit of formula (4) to the total sum of the structural units of formulas (1) to (4) is not particularly limited, but is preferably 5 mol% to 40 mol%, more preferably 10 mol% to 35 mol%, even more preferably 15 mol% to 30 mol%, and particularly preferably 18 mol% to 22 mol%. Here, for formula (1), the ratio is based on the repeating unit in parentheses in formula (1), not on the entire formula (1).

[0076] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, structural units other than those of formulas (1) to (4) may be included as long as the effects of the present invention are not impaired. However, the ratio of the total amount of structural units of formulas (1) to (4) in the acylated crosslinked copolymer aliphatic polycarbonate is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and most preferably 99 mol% or more.

[0077] In the acylated crosslinked copolymer aliphatic polycarbonate of the present invention, the proportion of structural units represented by formulas (1) to (4) is preferably (1):(2):(3):(4) = 40-50:0.4-0.8:10-50:10-35 in molar ratio. Here, for formula (1), the ratio is based on the repeating unit in parentheses in formula (1), not on the entire formula (1).

[0078] The weight-average molecular weight (Mw) of the acylated crosslinked copolymer aliphatic polycarbonate of the present invention is not particularly limited, but is approximately 5.0 × 10⁻⁶. 3 ~1.0×10 6 Preferably, it is 1.0 × 10 4 ~7.0×10 4 It is preferable that this is the case. 4.0 × 10 4 ~5.0×10 4 It would be preferable if this were the case.

[0079] The method for producing the acylated crosslinked copolymer aliphatic polycarbonate according to the present invention is not particularly limited, for example, R 1 Diol compounds in which a hydroxyl group is bonded to the terminus of an aliphatic hydrocarbon residue represented by are reacted with diphenyl carbonate or phosgene to carbonate them and prepare oligomers in advance, and the oligomer and R in formula (2-1) 2’ and R 2’’ A triol compound or tetraol compound having a hydroxyl group bonded to the terminal end of a hydrocarbon residue represented by , a diol compound having the structure represented by the parentheses in formula (3), and a diol compound having the structure represented by the parentheses in formula (4) can be randomly polymerized by reacting them with diphenyl carbonate or phosgene to form carbonate bonds, thereby obtaining a crosslinked copolymer aliphatic polycarbonate. A portion of the hydroxyl groups at the terminal ends of the polymer molecule can then be acylated using a known acylation reaction to obtain an acylated crosslinked copolymer aliphatic polycarbonate.

[0080] Also, R 1React a diol compound having a hydroxyl group bonded to the end of an aliphatic hydrocarbon residue represented by [formula] with diphenyl carbonate or phosgene to carbonate it to prepare an oligomer containing a structural unit represented by formula (1). React a diol compound having the structure represented by the inner brackets in formula (3) with diphenyl carbonate or phosgene to carbonate it to prepare an oligomer containing a structural unit represented by formula (3). React a diol compound having the structure represented by the inner brackets in formula (4) with diphenyl carbonate or phosgene to carbonate it to prepare an oligomer containing a structural unit represented by formula (1). React these oligomers with a triol compound or a tetraol compound having a hydroxyl group bonded to the end of a hydrocarbon residue represented by R 2’ and R 2’’ in formula (2-1) by reacting with diphenyl carbonate or phosgene to form a carbonate bond for block polymerization, whereby a crosslinked copolymerized aliphatic polycarbonate can be obtained.

[0081] (Acylation) The acylated crosslinked copolymerized aliphatic polycarbonate according to the present invention is an acylated crosslinked copolymerized aliphatic polycarbonate in which a part of the hydroxyl groups at the polymer molecule ends of the crosslinked copolymerized aliphatic polycarbonate is acylated at a specific ratio. That is, the polymer molecule ends of the acylated crosslinked copolymerized aliphatic polycarbonate according to the present invention are each one of the structures represented by the following formulas (5-1) to (5-4) for the end groups bonded to the carbonate oxygen atoms at the left end portions in formulas (1) to (4), and the end groups bonded to R 1 ~R 4 at the right end portions in formulas (1) to (4) are the structures represented by the following formula (6).

Chemical formula

[0082] When the average polymer concentration (eq / T) is in the range of (100:0) to (65:35), the adhesion of the polymer binder containing acylated crosslinked copolymer aliphatic polycarbonate to aluminum foil is improved.

[0083] If the polymer binder has high adhesive properties, the amount of polymer binder used can be reduced, which in turn lowers the resistance inside the all-solid-state battery and is expected to improve ion conductivity.

[0084] Examples of acyl groups in acylated crosslinked copolymer aliphatic polycarbonates include formyl group (also known as methyl group), acetyl group (also known as ethanol group), propionyl group (also known as propanoyl group), benzoyl group, and acryl group (also known as propenoyl group). Among these, acetyl group and benzoyl group are preferred, and acetyl group is particularly preferred.

[0085] (Polymer binder) A polymer binder according to a second aspect of the present invention may contain an acylated crosslinked copolymer aliphatic polycarbonate and a lithium salt. The inclusion of a lithium salt is preferable because it improves the ionic conductivity of the polymer binder. The ratio of acylated crosslinked copolymer aliphatic polycarbonate to lithium salt in the polymer binder is, for example, 100 to 200 parts by mass of lithium salt per 100 parts by mass of acylated crosslinked copolymer aliphatic polycarbonate.

[0086] For example, when sulfides are used as the solid electrolyte in an all-solid-state secondary battery, the sulfides may become brittle or deform due to heat, potentially reducing their ionic conductivity. Therefore, it may not be possible to remove the binder by heat treatment. In the present invention, by incorporating a lithium salt into the polymer binder, it is possible to obtain the effect of assisting ionic conductivity in the positive electrode, negative electrode, or solid electrolyte layer without ultimately removing the binder.

[0087] Lithium salts that can be incorporated into polymer binders include LiN(SO2F)2 (common name: LiFSI), LiN(SO2CF3)2 (common name: LiTFSI), LiN(SO2C2H5)2, LiPF6, and LiBF4. These lithium salts may also contain other components such as inorganic salts of alkali metals. Among these, LiTFSI is preferred.

[0088] The polymer binder of the present invention is also used to bind the positive electrode mixture, negative electrode mixture, and solid electrolyte of an all-solid-state secondary battery. That is, it is desirable that the polymer binder of the present invention penetrates between the positive electrode mixture, negative electrode mixture, and solid electrolyte during the manufacturing process. When manufacturing an all-solid-state secondary battery that uses sulfides in the solid electrolyte layer, a slurry using a hydrophobic solvent such as chloroform, anisole, or butyl butyrate is preferred in the manufacturing process. Since the polymer binder of the present invention disperses well in hydrophobic solvents, it is suitably used when sulfides are used in the solid electrolyte layer.

[0089] Examples of hydrophobic solvents include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane, and decane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogen-substituted hydrocarbons such as chloroform, dichloromethane, and carbon tetrachloride; halogen-substituted aromatic hydrocarbons such as chlorobenzene and bromobenzene; aromatic ethers such as anisole; aliphatic esters such as butyl butyrate; and aliphatic carbonates such as diethyl carbonate. Butyl butyrate and diethyl carbonate are particularly preferred.

[0090] Therefore, from the viewpoint of having high dispersibility in hydrophobic solvents, the polymer binder of the present invention preferably has a dispersion rate of 70% or more of butyl butyrate or diethyl carbonate, and more preferably 80% or more.

[0091] However, the variance rate is calculated using the following formula (a). Variance rate (%) = (Amount of residual material / Theoretical amount) × 100 ... (a) In the above formula, "theoretical amount" refers to the mass of polymer binder (g) calculated from the concentration (mass%) of the polymer binder in the dispersion and the mass (g) of the collected dispersion, assuming that the entire amount of sample polymer binder is dispersed in butyl butyrate or diethyl carbonate. "Residual amount" refers to the actual mass (g) of sample polymer binder remaining after the collected dispersion is dried to remove the butyl butyrate or diethyl carbonate.

[0092] Furthermore, when a solid electrolyte is incorporated into a polymer binder, solid electrolytes generally have low solubility in hydrophobic solvents. Therefore, they may not disperse in the hydrophobic solvent, and the solid electrolyte may separate and precipitate. For this reason, when incorporating a solid electrolyte into the polymer binder of the present invention, using an acylated crosslinked copolymer aliphatic polycarbonate allows for dispersion in a hydrophobic solvent. Specifically, the acylated crosslinked copolymer aliphatic polycarbonate and the solid electrolyte are mixed and dispersed in a hydrophilic solvent such as THF, and the dispersion is dried to volatilize the solvent, thereby incorporating the solid electrolyte into the polymer binder.

[0093] The all-solid-state secondary battery of the present invention has a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrodes, and at least one of these contains or is used in the manufacture of the polymer binder of the present invention. In addition, the all-solid-state secondary battery of the present invention may contain or be used in the manufacture of a binder other than the polymer binder of the present invention. Examples of binders other than the polymer binder of the present invention include styrene-butadiene rubber, PVDF, PTFE, acrylic resin, etc.

[0094] As a solid electrolyte used in the solid electrolyte layer, Z2S-M x S y solid sulfides represented by are exemplified. However, in the formula, Z is Li or Na, M is P, Si, Ge, B, Al or Ga, and x and y are numbers based on the stoichiometry according to the type of M. M x S y Examples of include solid sulfides such as P2S5, SiS2, GeS2, B2S3, Al2S3, Ga2S3, etc.

[0095] Z2S-M x S y Examples of include Li2S-P2S5, Li2S-SiS2, etc. Further, the above-mentioned solid sulfides may contain different M x S y .

[0096] Furthermore, solid sulfides represented by Z2S-M n S m -ZX can also be used as a solid electrolyte. However, in the formula, Z is Li, M is P, Si, Ge, B, Al or Ga, X is Cl, Br or I, and n and m are numbers based on the stoichiometry according to the type of M.

[0097] M n S m Examples of include solid sulfides such as P2S5, SiS2, GeS2, B2S3, Al2S3, Ga2S3, etc.

[0098] Z2S-M n S m Examples of -ZX include Li2S-P2S5-LiCl, Li2S-P2S5-LiBr-LiCl, Li2S-SiS2-LiBr, etc.

[0099] As a solid sulfide electrolyte used in the solid electrolyte layer, in addition to the above, for example, Li 10 GeP2S 12 (common name: LGPS), Li 10 SnP2S 12Li6PS5Cl is used. These solid sulfides may be used individually or in combination.

[0100] In addition to solid sulfides, Li7La3Zr2O 12 (Common name: LLZO), Li 1.3 Al 0.3 Ti 1.7 Solid oxides such as (PO4)3 (generic name: LATP) can also be used as solid electrolytes. These solid electrolytes may be used individually or in combination.

[0101] A preferred solid electrolyte is Li2S-P2S5, and it is particularly preferred that the molar ratio of Li2S to P2S5 be Li2S:P2S5 = 50:50 to 95:5.

[0102] The positive electrode contains a positive electrode active material and the solid electrolyte, and may further contain the polymer binder of the present invention.

[0103] As the positive electrode active material, known positive electrode active materials usable in all-solid-state secondary batteries can be used. Examples include LiCoO2, LiNiO2, and Li 1+x Ni 1 / 3 Mn 1 / 3 Co 1 / 3 O2 (where x is a positive number), LiMn2O4, Li 1+x Mn 2-x-y M y O4 (where M is at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, and x and y are positive numbers), Li x TiO y Examples include (where x and y are positive numbers), LiMPO4 (where M is Fe, Mn, Co, or Ni), etc.

[0104] In addition to the positive electrode active material, solid electrolyte, and polymer binder of the present invention, the positive electrode may also contain other components such as conductive additives.

[0105] Examples of conductive additives include carbon black such as acetylene black and Ketjenblack, carbon nanotubes, natural graphite, artificial graphite, and vapor-grown carbon fiber (VGCF®). The content of other components in the positive electrode is not particularly limited, but it is preferable that the content be 10% by mass or less.

[0106] The positive electrode may be formed on the current collector. As the current collector, for example, a metal such as aluminum formed into a plate shape can be used.

[0107] The negative electrode includes a negative electrode active material and the solid electrolyte, and may further include the polymer binder of the present invention. As the negative electrode active material, known negative electrode active materials usable in all-solid-state secondary batteries can be used. Examples include carbon materials such as mesocarbon microbeads, graphite, hard carbon, and soft carbon, and Li4Ti5O 12 Examples include lithium titanium oxide and metals such as Li.

[0108] In addition to the negative electrode active material and solid electrolyte, the negative electrode may contain other components such as alkali metal inorganic salts and conductive additives. Other components for the negative electrode can be those exemplified in the description of the solid electrolyte layer. The content of these other components in the negative electrode is preferably 10% by mass or less.

[0109] The negative electrode may be formed on the current collector. As the current collector, for example, a plate-shaped copper or stainless steel metal can be used.

[0110] The all-solid-state secondary battery of the present invention consists of a positive electrode, a solid electrolyte layer, and a negative electrode, forming one cell. An all-solid-state secondary battery may be constructed with only one cell, or multiple cells may be connected in series or parallel to form an assembly.

[0111] The positive electrode, negative electrode, or solid electrolyte layer can be obtained by a process of dissolving or dispersing raw materials, i.e., the substances described in each description and the polymer binder of the present invention, in an organic solvent to obtain a slurry (slurry manufacturing process), and a process of coating the slurry onto a substrate and drying it (coating and drying process).

[0112] As the organic solvent, one that does not affect the properties of the solid electrolyte and active material and dissolves or disperses the polymer binder of the present invention is used. Specifically, saturated chain hydrocarbons such as n-pentane, n-hexane, heptane, n-octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane; halogen-substituted saturated chain hydrocarbons such as carbon tetrachloride, chloroform, and dichloroethane; saturated cyclic hydrocarbons such as cyclohexane, cycloheptane, and cyclooctane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogen-substituted aromatic hydrocarbons such as chlorobenzene and bromobenzene; dioxane, methyl ethyl ketone, trioxaundecane, trioxanonanane, and Examples include oxygen-containing chain hydrocarbons such as lyoxapentadecane and diethylene glycol dimethyl ether, nitrogen-containing saturated hydrocarbons such as triethylamine, propanenitrile, dimethyldiazohexane, trimethyltriazonanane, N,N,N',N'-tetramethylethylenediamine, and N,N,N',N”,N”-pentamethyldiethylenetriamine, oxygen-containing aromatic hydrocarbons such as anisole, aliphatic esters such as butyl butyrate, and aliphatic carbonates such as dimethyl carbonate, diethyl carbonate, and propylene carbonate. When sulfides are used in the solid electrolyte layer, hydrophobic solvents such as chloroform, anisole, butyl butyrate, and diethyl carbonate are preferred as organic solvents. The organic solvent is used in an amount sufficient to coat the solution or dispersion of the raw materials.

[0113] The conditions for dissolving or dispersing the solid electrolyte and the polymer binder of the present invention in an organic solvent are not particularly limited, as long as sufficient dissolution or dispersion is achieved. Dissolution or dispersion can be carried out at room temperature (e.g., 25°C), and may be cooled or heated as needed. Dissolution or dispersion may also be carried out under atmospheric pressure, reduced pressure, or increased pressure as needed.

[0114] By applying slurries of raw materials for the positive electrode, negative electrode, or solid electrolyte onto a substrate, and then drying the resulting coating, the positive electrode, negative electrode, and solid electrolyte layers can be obtained.

[0115] The substrate to which the slurry is applied is not particularly limited. For example, if the production of the solid electrolyte slurry is carried out simultaneously with the production of the positive electrode, the current collector, the solid electrolyte layer, or the positive electrode can be used as the substrate. Examples of application methods include application using an applicator, doctor blade, or bar coater, brush application, roll coating, spray coating, and electrospray coating.

[0116] The positive electrode, solid electrolyte layer, and negative electrode obtained in this manner are stacked in this order, and then pressed together in the stacking direction to fix them to each other, forming a laminate. By heat-treating the laminate as needed, the all-solid-state secondary battery of the present invention can be obtained.

[0117] The heat treatment of the laminate can be carried out under an inert atmosphere such as nitrogen or argon, as needed. The heat treatment may also be carried out under normal pressure, reduced pressure, or increased pressure. Furthermore, it is preferable to heat the laminate at a temperature below which the crystal structure of the solid electrolyte does not change. A more preferable heat treatment temperature is between T-25°C and T+50°C, where T°C is the decomposition start temperature of the polymer binder of the present invention. The heat treatment time varies depending on the size and number of layers of the laminate and the heat treatment temperature, but is usually 3 to 60 minutes, and more preferably 5 to 30 minutes. The solid electrolyte layer, positive electrode, and negative electrode may also be heat treated individually, or they may be treated after being laminated.

[0118] (Examples) The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited thereto.

[0119] <Weight average molecular weight, molecular weight distribution> The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined from the weight-average molecular weight (Mw) and number-average molecular weight (Mn) values, measured using standard polystyrene equivalents by gel permeation chromatography (GPC). The molecular weight distribution (Mw / Mn) is expressed as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn).

[0120] GPC measurements were performed using a Waters Corporation WATERS410 differential refractometer as the detector, a MODEL510 high-performance liquid chromatography pump, and two Shodex GPC HFIP-806L columns connected in series. The measurement conditions were a flow rate of 1.0 mL / min, chloroform as the solvent, and 0.1 mL of a 0.2 mg / mL sample solution injected.

[0121] <Glass transition temperature> The glass transition temperature was measured using a differential scanning calorimeter (Q20) manufactured by T·A· Instruments Inc. by heating a 10 mg sample from -160°C to 100°C at a rate of 20°C / min under a nitrogen atmosphere.

[0122] <Polymer structure> The polymer structure was determined in a deuterated chloroform solution using a JEOL Ltd. JNM-ECA600 nuclear magnetic resonance spectrometer. 1 H-NMR and 13 The structure was confirmed by measuring 1C-NMR.

[0123] <Hydrophobic solvent dispersibility> The dispersibility of polycarbonate was evaluated using the following method. 0.4 g of polymer, 0.6 g of LiTFSI, and 5.7 g of THF were added to a 30 mL vial, mixed well, dried at 65°C for 5 hours, and then dried again under reduced pressure at 65°C for 24 hours. Next, butyl butyrate or diethyl carbonate was added to a 30 mL vial so that the polymer binder accounted for 10% by mass, and the mixture was stirred at 25°C for 3 hours. After stopping the stirring, the mixture was allowed to stand for 0 minutes and 24 hours, and 1 g of the mixture was dispensed into a weighed 30 mL vial. In the case of butyl butyrate, it was dried at 160°C for 3 hours, followed by drying under reduced pressure at 65°C for 2 hours. In the case of diethyl carbonate, it was dried at 130°C for 3 hours, followed by drying under reduced pressure at 65°C for 2 hours. After drying, a 30 mL vial was weighed, and the mass of the residue was calculated. From the calculated amount of residue, the dispersion rate of the solution was calculated using the following formula (c). Dispersion rate = residual amount / theoretical residual amount × 100 (c) ○ (Good): Dispersion rate is 90% or higher × (Poor): Variance rate less than 90%

[0124] <Heat resistance> The heat resistance of the polymer binder film was evaluated using the 5% weight loss temperature (Td5). The 5% weight loss temperature (Td5) was measured using a Rigaku TG-DTA 8122 / C-SL detector. A 15 mg sample was heated in a nitrogen atmosphere from 20°C to 110°C at a rate of 10°C / min, held for 10 minutes, and then further heated to 500°C and held for 30 minutes. The weight after holding at 110°C for 10 minutes was used as the baseline, and the temperature at which a 5% weight loss occurred was defined as the 5% weight loss temperature (Td5).

[0125] <Aluminum foil adhesive strength> 2.5 mL of a THF dispersion containing 30% by mass of a polymer binder was uniformly spread onto an aluminum foil sheet, covering an area of ​​150 mm in length and 60 mm in width. Next, the sheet sample was dried at 100°C for 1 hour, and then further dried under reduced pressure at 60°C for 2 hours. Another aluminum foil was placed on top of the obtained sheet sample and pressed at 60°C and 0.5 MPa for 2 minutes. The pressed aluminum sheet was cut to 200 mm in length and 25 mm in width, including the polymer portion, to prepare a sample for peel testing. The peel test sample was set in a Shimadzu AG-100B with a 20 mm gap between the chucks, and the peel force (N) was measured at a speed of 10 mm / min. The average value of the peel force between 60 and 100 mm within the 200 mm measurement range was calculated and used as the adhesive strength of the polymer binder to the aluminum foil.

[0126] <Ionic conductivity measurement> Ionic conductivity was obtained by the following method. The polymer binder films obtained using the method described later were each cut into circles with a diameter of 6 mm, sandwiched between two stainless steel plates, and the impedance of the polymer binder films was measured. An impedance analyzer manufactured by Biologic was used to measure impedance at a frequency range of 100 to 1,000,000 Hz and an amplitude voltage of 10 mV, at temperatures of 30 to 80°C. From the obtained impedance, the ionic conductivity was calculated using the following formula (b). σ = L / (R × S) ... (b) In equation (b) above, σ is the ionic conductivity (S / cm), R is the impedance (Ω), and S is the cross-sectional area of ​​the polymer binder film (cm²). 2 ), where L is the thickness (cm) of the polymer binder film.

[0127] <Manufacturing Example 1> The following procedure was used to synthesize cross-linked copolymer aliphatic polycarbonates.

[0128] (Preparation of oligomers) In a 0.3 L three-necked flask equipped with a stirrer, nitrogen gas inlet tube, thermometer, vacuum controller, and reflux condenser, 69.71 g (0.40 mol) of 1,10-decanediol, 77.1 g (0.36 mol) of diphenyl carbonate (Aldrich), and 0.30 mg (4 μmol) of sodium bicarbonate were added, and the mixture was heated to 200 °C while stirring. Next, the temperature was increased at 0.5 °C / min while reducing the pressure to 1 kPa / min, and the mixture was stirred for 2 hours. After that, the polymerization reaction was carried out under reduced pressure at 260 °C for 15 minutes, and the mixture was stirred to obtain the oligomer.

[0129] (Copolymer reaction) Next, 0.28 g (0.002 mol) of pentaerythritol (manufactured by Wako Pure Chemical Industries, Ltd.), 36.89 g (0.12 mol) of spiroglycol, 12.14 g (0.08 mol) of triethylene glycol, 44.7 g (0.21 mol) of diphenyl carbonate, and 0.18 mg (2 μmol) of sodium bicarbonate were added to the aforementioned 0.3 L three-necked flask, and the temperature was raised to 200 °C while stirring. Then, the temperature was raised at 0.5 °C / min while reducing the pressure to 1 kPa / min, and the mixture was stirred for 2 hours. Subsequently, under reduced pressure, the mixture was stirred at 260 °C for 30 minutes to carry out the polymerization reaction. After the reaction was complete, the three-necked flask was cooled to obtain cross-linked copolymer aliphatic polycarbonate R1. The weight-average molecular weight of the obtained cross-linked copolymer aliphatic polycarbonate R1 was 2.9 × 10⁻⁶. 4 (Mw / Mn = 2.0). The structure of the obtained cross-linked copolymer aliphatic polycarbonate R1 was: 1 H-NMR, 13 This was confirmed by 13C-NMR (Figures 1 and 2).

[0130] <Example 1> The cross-linked copolymer aliphatic polycarbonate R1 obtained in Production Example 1 was acylated by the following procedure.

[0131] (Acylation reaction) In a 1 L three-necked flask equipped with a stirrer, thermometer, and reflux condenser, 5 g of cross-linked copolymer aliphatic polycarbonate R1 obtained in Production Example 1, 69 g (0.9 mol) of pyridine, and 600 mL of NMP were added and stirred at room temperature for 30 minutes. Next, 104 g (1.0 mol) of acetic anhydride was added, and the temperature was raised to 70°C and stirred for 6 hours. After returning to room temperature, methanol was added to the reaction mixture to precipitate the polymer, and the mixture was filtered. The residue was transferred to a beaker, dissolved with chloroform, and separated three times with pure water. After separation, the chloroform phase was added to methanol, and the precipitate was recovered by filter filtration. The weight-average molecular weight of the obtained acylated cross-linked copolymer aliphatic polycarbonate was 4.6 × 10⁶. 4 (Mw / Mn = 1.6). The glass transition temperature of the acylated cross-linked copolymer aliphatic polycarbonate was -25°C. The structure of the acylated cross-linked copolymer aliphatic polycarbonate was 1 H-NMR, 13 This was confirmed by 13C-NMR (Figures 3 and 4). The concentrations of acetyl and hydroxyl groups in the polymer were calculated from Figures 3 and 4. The unit of concentration was the number of equivalents per ton of polymer (eq / T). From the obtained concentrations of acetyl and hydroxyl groups, the acetylation rate (acylation rate) was calculated using the following formula (c). Acetylation rate (acylation rate) = Acetyl group concentration / (Acetyl group concentration + Hydroxyl group concentration) × 100 ... (c) The acetylation rate (acylation rate) of the acylated cross-linked copolymer aliphatic polycarbonate was found to be 75%.

[0132] (Manufacturing of polymer binders) The acylated cross-linked copolymer aliphatic polycarbonate obtained in Example 1 was mixed with LiTFSI weighed to a LiTFSI content of 60% by mass, and the mixture was thoroughly stirred in THF to obtain a dispersion of a polymer binder with a concentration of 30% by mass.

[0133] The dispersibility of polymer binders was evaluated using butyl acetate and diethyl carbonate as hydrophobic solvents. Both butyl acetate and diethyl carbonate showed dispersion rates of 90% or higher, indicating good performance. The results are shown in Table 1.

[0134] (Manufacturing of polymer binder membranes) One mL of a THF dispersion of polymer binder was uniformly applied to one side of an aluminum foil film using a micropipette, covering a 5 cm square area. After drying at 65°C for 3 hours, it was further dried under reduced pressure at 65°C for 4 hours to obtain a polymer binder film consisting of a transparent polymer binder with a LiTFSI content of 60% by mass. The Tg of the obtained polymer binder film was measured to be -55°C, indicating heat resistance (T d5 The temperature was 267°C. Furthermore, the adhesion strength of the obtained polymer binder film to aluminum foil was measured to be 8.8 N. The results are shown in Table 1.

[0135] <Comparative Example 1> Without acylation of the cross-linked copolymer aliphatic polycarbonate R1 from Production Example 1, a polymer binder and a polymer binder film were prepared using the same procedure as in Example 1, and Tg, heat resistance, aluminum foil adhesion, and hydrophobic solvent dispersibility were measured. The results are shown in Table 1. The aluminum foil adhesion of the polymer binder film using the cross-linked copolymer aliphatic polycarbonate R1 was inferior to that of Example 1.

[0136] [Table 1]

[0137] Even a cross-linked copolymer aliphatic polycarbonate with all -OH ends (Comparative Example 1) exhibits relatively high adhesive strength. However, in order to increase the area of ​​batteries and stabilize the cycle characteristics during charging and discharging, it is important to suppress delamination of the electrode layer, and further improvement in the adhesive strength to the current collector foil is necessary for the polymer binder. In the acylated cross-linked copolymer aliphatic polycarbonate according to the present invention (Example 1), the adhesive strength has increased as described above. In the adhesive strength test, an adhesive strength of 1N corresponds to the holding of 100g of metal particles, so the increase of 1.8N compared to Comparative Example 1, as shown in Example 1, can be said to greatly contribute to increasing the area of ​​all-solid-state batteries.

Claims

1. It includes structural units represented by the following formulas (1) to (4), 【Chemistry 1】 (In formula (1), R １ (where x represents an aliphatic hydrocarbon residue with 2 to 20 carbon atoms, and x represents an integer between 3 and 100.) 【Chemistry 2】 (In formula (2), R ２ The following equation (2-1) 【Transformation 3】 Represents R ２’ and R ２’’ Each of these independently represents an aliphatic hydrocarbon residue with 0 to 5 carbon atoms, and R ２’’’ (This represents a hydrogen atom or an aliphatic hydrocarbon residue having 1 to 5 carbon atoms.) 【Chemistry 4】 (In formula (3), R ３ (This represents an aliphatic hydrocarbon residue that has a spiro structure and may contain heteroatoms in its structure.) 【Transformation 5】 (In formula (4), R ４ (where m represents an aliphatic hydrocarbon residue with 2 to 10 carbon atoms, and m represents an integer between 2 and 30.) The polymer molecular terminals are such that the terminal groups bonded to the carbonate oxygen atoms at the left end portions in the above formulas (1) to (4) are respectively any of the structures represented by the following formulas (5-1) to (5-4), and the terminal groups bonded to R １ ~R ４ at the right end portions in the above formulas (1) to (4) are structures represented by the following formula (6). 【Transformation 6】 (In equations (5-1) to (5-4) and equation (6), R ５ Each of these independently represents either a hydrogen atom or an acyl group. The ratio of acyl groups to hydrogen atoms at the polymer molecule terminals, as represented by formulas (5-1) to (5-4) and formula (6), is (100:0) to (65:35) in terms of the polymer average concentration (eq / T), The acyl group represented by R5 is selected from the group consisting of a formyl group, an acetyl group, a propionyl group, a benzoyl group, and an acryl group. Acylated cross-linked copolymer aliphatic polycarbonate.

2. The aforementioned R ５ The acylated crosslinked copolymer aliphatic polycarbonate according to claim 1, wherein the acyl group represented by is an acetyl group or a benzoyl group.

3. The aforementioned R １ However, x represents an aliphatic hydrocarbon residue with 8 to 12 carbon atoms, and x represents an integer between 60 and 90. The aforementioned R ２ However, R in equation (2-1) above ２’’ This represents an aliphatic hydrocarbon residue with 1 to 2 carbon atoms, The aforementioned R ３ However, the number of spiro atoms is 1 to 2, and the heteroatom is either an oxygen atom or a sulfur atom. The aforementioned R ４ The acylated crosslinked copolymer aliphatic polycarbonate according to claim 1 or 2, wherein m represents an aliphatic hydrocarbon residue having 2 to 4 carbon atoms, and m represents an integer between 2 and 3.

4. The aforementioned R １ is an alkylene group having 10 carbon atoms, and the R ２ However, R in equation (2-1) above ２’’ is an alkylene group having 1 carbon atom, and the R ３ is a 2,2'-(2,4,8,10,-tetraoxaspiro[5.5]undecane-3,9-diyl)dipropanediyl group, and the R ４ The acylated crosslinked copolymer aliphatic polycarbonate according to any one of claims 1 to 3, wherein is an alkylene group having 2 carbon atoms and m is an integer of 3.

5. The acylated crosslinked copolymer aliphatic polycarbonate according to claim 1, wherein the proportion of structural units represented by formulas (1) to (4) is (1):(2):(3):(4) = 40-50:0.4-0.8:10-50:10-35 in molar ratio.

6. A polymer binder for all-solid-state batteries comprising an acylated crosslinked copolymer aliphatic polycarbonate and a lithium salt according to any one of claims 1 to 5.

7. The polymer binder for all-solid-state batteries according to claim 6, wherein the lithium salt comprises LiTFSI.

8. An all-solid-state secondary battery comprising an acylated crosslinked copolymer aliphatic polycarbonate according to any one of claims 1 to 5.

9. An all-solid-state secondary battery comprising the polymer binder for all-solid-state batteries according to claim 6 or 7.

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