Polymer electrolyte for lithium-ion secondary battery, composite solid electrolyte for lithium-ion secondary battery, and lithium-ion secondary battery

Abstract

Provided are a polymer electrolyte for a lithium-ion secondary battery, a composite solid electrolyte for a lithium-ion secondary battery, and a lithium-ion secondary battery that have high lithium-ion conductivity and with which it is possible, even when a sulfide-based solid electrolyte is used, to suppress side reactions with the sulfide-based solid electrolyte. The present invention pertains to a polymer electrolyte for a lithium-ion secondary battery, the polymer electrolyte containing at least a lithium-ion conductive polymer, an ether-based compound, and a lithium salt compound.

Description

Polymer electrolytes for lithium-ion secondary batteries, composite solid electrolytes for lithium-ion secondary batteries, and lithium-ion secondary batteries

[0001] This invention relates to a polymer electrolyte for lithium-ion secondary batteries, a composite solid electrolyte for lithium-ion secondary batteries, and a lithium-ion secondary battery.

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between the positive electrode layer and the negative electrode layer, and have the advantage of being easier to simplify safety devices compared to liquid-system batteries that have an electrolyte containing a flammable organic solvent.

[0003] Among all-solid-state batteries, all-solid-state lithium-ion batteries have attracted attention for their high energy density due to the utilization of battery reactions involving the movement of lithium ions, and for using a solid electrolyte instead of an electrolyte containing an organic solvent as the electrolyte between the positive and negative electrodes (for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2020-107414

[0005] Sulfide-based solid electrolytes are sometimes used as inorganic solid electrolytes in all-solid-state batteries. However, sulfide-based solid electrolytes generally undergo side reactions when in contact with other materials that make up the battery, and there is a risk that the sulfide-based solid electrolyte itself may decompose. Therefore, there is a need for materials that can suppress side reactions with sulfide-based solid electrolytes and suppress the decomposition reaction of sulfide-based solid electrolytes.

[0006] Furthermore, because there are few contact points between inorganic solid electrolytes, polymer electrolytes are added to inorganic solid electrolytes to improve ionic conductivity. In conventional technology, polyether polymers mainly composed of polyethylene oxide (PEO) structures have been used as polymer electrolytes added to inorganic solid electrolytes. However, the inventors' research has revealed that there is room for improvement in terms of suppressing side reactions with sulfide-based solid electrolytes and achieving high lithium ion conductivity, even when using polyether polymers, as well as when using other polymers. Lithium ion conductivity is a property that can be determined by the product of ionic conductivity and lithium ion transport fraction. In this field, there are generally many inventions aimed at improving ionic conductivity, so the focus on ion transport fraction, which is a contradictory property to ionic conductivity, and furthermore, the focus on the properties calculated from that ion transport fraction, is a novel approach.

[0007] The present invention aims to provide a polymer electrolyte for lithium-ion secondary batteries, a composite solid electrolyte for lithium-ion secondary batteries, and a lithium-ion secondary battery that can suppress side reactions with sulfide-based solid electrolytes even when sulfide-based solid electrolytes are used, and that have high lithium-ion conductivity.

[0008] As a result of various studies conducted to achieve the above objective, the inventors of the present invention have found that a polymer electrolyte for lithium-ion secondary batteries containing at least a lithium-ion conductive polymer, an ether-based compound (particularly a specific ether-based compound), and a lithium salt compound can suppress side reactions with sulfide-based solid electrolytes even when a sulfide-based solid electrolyte is used, and also possesses high lithium-ion conductivity, thus completing the present invention.

[0009] Aspects of the present invention are as follows: Item 1 A polymer electrolyte for a lithium-ion secondary battery comprising at least a lithium-ion conductive polymer, an ether compound, and a lithium salt compound, wherein the ether compound is at least one selected from the group consisting of linear ether compounds represented by the following general formula (4) and branched ether compounds represented by the following general formula (5). (wherein R ９ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms or a group represented by -(CH ２ ) ｉ CH ２ O-R １０ . R １０ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms. g, h, and i, which are the number of repetitions, are the same or different and each is an integer of 1 to 3.) (wherein R １１ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ . R １２ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ . R １３ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms. m, which is the number of repetitions, is 0 or 1, and k and l are the same or different and each is an integer of 1 to 3.) Item 2: The polymer electrolyte for a lithium ion secondary battery according to Item 1, wherein the lithium ion conductive polymer is at least one selected from the group consisting of polyether polymers, polyacrylates, polycarbonates, polyesters, fluorine-based polymers and polymers having an anionic functional group on a side chain; and the polyether polymer comprises at least an alkyl group-containing unit which is a constituent unit derived from an alkylene oxide having an alkyl group on a side chain, and the content of the alkyl group-containing unit is 15 mol% or more based on 100 mol% of the total constituent units. Item 3: The polymer electrolyte for a lithium ion secondary battery according to Item 2, wherein the polyether polymer comprises an X unit which is a constituent unit derived from an alkylene oxide represented by the following general formula (1). (wherein R １ are the same or different, and each represents an alkyl group having 1 to 6 carbon atoms. R ２ are the same or different, and each represents a hydrogen atom or -CH ２ O{(CH ２ )ａ O} ｂ (CH ２ ) ｃ H is an alkylene glycol alkyl ether group. The repeating unit a is an integer from 1 to 10, either the same or different; the repeating unit b is an integer from 1 to 6, either the same or different; and the repeating unit c is an integer from 0 to 6, either the same or different. A is a single bond or an alkylene group having 1 to 4 carbon atoms, either the same or different.) Item 4 The polymer electrolyte for lithium-ion secondary batteries according to Item 3, wherein the polyether polymer contains a Z unit, which is a constituent unit derived from the alkylene oxide shown in the following general formula (2). (In the formula, R １ R is the same or different hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ４ They are the same or different, -CH ２ OR ８ This is a crosslinking group containing an ethylenically unsaturated double bond, represented by R. ８ A is the same or different acrylic group, methacrylic group, allyl group, or methallyl group. A is the same or different single bond or C1-C4 alkylene group.) Item 5 A composite solid electrolyte for lithium-ion secondary batteries containing a polymer electrolyte for lithium-ion secondary batteries according to any one of Items 1 to 4 and an inorganic solid electrolyte. Item 6 A composite solid electrolyte for lithium-ion secondary batteries according to Item 5, wherein the inorganic solid electrolyte is a sulfide-based solid electrolyte. Item 7 A crosslinked film using the polymer electrolyte for lithium-ion secondary batteries according to any one of Items 1 to 4. Item 8 A lithium-ion secondary battery using the polymer electrolyte for lithium-ion secondary batteries according to any one of Items 1 to 4. Item 9 A lithium-ion secondary battery having a positive electrode, an electrolyte layer, and a negative electrode, wherein at least one of the positive electrode, electrolyte layer, and negative electrode is a composite solid electrolyte for lithium-ion secondary batteries according to Item 5 or 6. Item 10 A lithium-ion secondary battery having a positive electrode, an electrolyte layer, a crosslinked film, and a negative electrode, wherein at least the crosslinked film is the crosslinked film according to Item 7.

[0010] The polymer electrolyte for lithium-ion secondary batteries of the present invention contains at least a lithium-ion conductive polymer, an ether-based compound, and a lithium salt compound. Therefore, even when a sulfide-based solid electrolyte is used, side reactions with the sulfide-based solid electrolyte can be suppressed, and high lithium-ion conductivity can be achieved.

[0011] <Polymer Electrolyte for Lithium-Ion Secondary Batteries> The polymer electrolyte for lithium-ion secondary batteries of the present invention comprises at least a lithium-ion conductive polymer, an ether compound, and a lithium salt compound, wherein the ether compound is at least one selected from the group consisting of linear ether compounds represented by general formula (4) and branched ether compounds represented by general formula (5). This suppresses side reactions with sulfide-based solid electrolytes even when sulfide-based solid electrolytes are used, and also provides high lithium-ion conductivity.

[0012] In the present invention, the reason for obtaining the above-mentioned effects is not clear, but it is presumed to be as follows: The ether-based compound exhibits high ionic conductivity (lithium ion conductivity) because it has excellent solubility for lithium salt compounds, thereby increasing the ion concentration in the electrolyte, and also exhibits excellent ion transport due to its low viscosity. Furthermore, the alkyl group tends to act as a steric hindrance, which can suitably suppress the coordination of lithium ions to polar groups such as ether oxygen, thereby suppressing side reactions with sulfide-based solid electrolytes.

[0013] The lithium-ion conductive polymer is preferably a polyether polymer, more preferably a polyether polymer containing at least alkyl group-containing units which are constituent units derived from alkylene oxides having alkyl groups in their side chains, and even more preferably the content of alkyl group-containing units is 15 mol% or more per 100 mol% of constituent units. In this case, the reason why the above effect is more favorably obtained in the present invention is not clear, but it is presumed to be as follows. Because the polyether polymer has alkyl groups in its side chains, the steric hindrance effect caused by the introduction of alkyl groups into the polyether structure can suitably suppress the coordination of lithium ions to the ether oxygen of the main chain, thereby obtaining a higher ion transport rate (lithium-ion conductivity) and suppressing side reactions with sulfide-based solid electrolytes. Although nonpolar groups such as alkyl groups do not directly coordinate with lithium ions, it is thought that they are involved in optimizing the coordination state between polar groups such as ether oxygen and lithium ions. Furthermore, it is believed that the combined use of the polyether polymer and the ether compound resulted in polar groups such as oxygen introduced into the polyether polymer and the ether compound forming a unique solvation structure with the lithium salt compound, optimizing the ion conduction pathway and thus exhibiting high lithium ion conductivity while maintaining sulfide resistance.

[0014] <<Lithium-ion conductive polymers>> Lithium-ion conductive polymers (excluding linear ether compounds represented by general formula (4) and branched ether compounds represented by general formula (5)) are not particularly limited as polymers capable of conducting lithium ions, that is, polymers having a structure and / or functional groups to which lithium ions can coordinate, and enabling the movement of lithium ions. Examples include polyether polymers, polyacrylates, polycarbonates, polyesters, fluorinated polymers, and polymers having anionic functional groups in their side chains. These can be used alone or in combination of two or more. Since the conduction of lithium ions is made possible by the oxygen atoms and anionic functional groups present in these polymers, other structures are not particularly limited. Among these, polyether polymers, fluorinated polymers, and polymers having anionic functional groups in their side chains are preferred, and polyether polymers are more preferred.

[0015] The weight-average molecular weight (Mw) of the lithium-ion conductive polymer is preferably 0.5 million to 3 million, more preferably 0.5 million to 2.5 million, even more preferably 10,000 to 2.5 million, and particularly preferably 50,000 to 2.5 million. This tends to lead to a more favorable outcome of the present invention.

[0016] The degree of dispersion (Mw / Mn) of the lithium-ion conductive polymer is preferably 1 to 40, more preferably 1 to 30, even more preferably 1 to 20, and particularly preferably 1 to 10. This tends to lead to a more favorable outcome of the present invention. In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer are measured by the method described in the examples.

[0017] <<<Polyether Polymers>>> Next, polyether polymers will be described. Polyether polymers are not particularly limited as long as they are polymers having an ether linkage (-C-O-C-) in their main chain (excluding linear ether compounds shown in general formula (4) and branched ether compounds shown in general formula (5)). Preferably, the polyether polymer contains at least alkyl group-containing units, which are constituent units derived from alkylene oxides having alkyl groups in their side chains, and the content of alkyl group-containing units is 15 mol% or more per 100 mol% of constituent units (the polyether polymer of the present invention). Hereinafter, the polyether polymer of the present invention means a polymer that contains at least alkyl group-containing units, which are constituent units derived from alkylene oxides having alkyl groups in their side chains, and the content of alkyl group-containing units is 15 mol% or more per 100 mol% of constituent units.

[0018] In this specification, the constituent units derived from alkylene oxide having an alkyl group in the side chain are not particularly limited as long as the constituent units derived from alkylene oxide have an alkyl group. Here, the side chain refers to a group attached to the main chain which is the alkylene oxide skeleton (for example, if it is unit X, which is a constituent unit derived from alkylene oxide shown in the general formula (1) below, then -C-C-A-O-), and means, for example, a methyl group, an ethyl group, an alkylene glycol alkyl ether group, etc.

[0019] The alkyl group-containing unit is not particularly limited as long as it is a constituent unit derived from an alkylene oxide having an alkyl group in its side chain, for example, among the X unit and Y unit described later, R １ The unit is an alkyl group having 1 to 6 carbon atoms, and among the Z units described later, R １ Examples include units in which the alkyl group has 1 to 6 carbon atoms. Among these, the X unit described later is preferred.

[0020] In the polyether polymer of the present invention, each alkyl group-containing unit may be the same or different. Therefore, the polyether polymer of the present invention may be a polymer in which one or more units corresponding to alkyl group-containing units are combined. In the polyether polymer of the present invention, it is preferable that each unit in the alkyl group-containing unit is the same.

[0021] The alkyl group contained in the alkyl group-containing unit is R in formula (1) described later. １ The same applies to alkyl groups having 1 to 6 carbon atoms, including preferred embodiments.

[0022] The polyether polymer of the present invention preferably contains X units, which are constituent units derived from alkylene oxides represented by the following general formula (1). That is, the polyether polymer of the present invention preferably contains X units as alkyl group-containing units. In the polyether polymer of the present invention, each X unit may be the same or different. Therefore, the polyether polymer of the present invention may be a polymer in which one or more units corresponding to X units are combined. In the polyether polymer of the present invention, each unit in the X unit is preferably the same. (In the formula, R １ These are alkyl groups having 1 to 6 carbon atoms, either identical or different. ２ These are identical or different hydrogen atoms or -CH ２ O { (CH ２ ) ａ O} ｂ (CH ２ ) ｃ This is an alkylene glycol alkyl ether group represented by H. The repeating unit a is an integer from 1 to 10, either the same or different; the repeating unit b is an integer from 1 to 6, either the same or different; and the repeating unit c is an integer from 0 to 6, either the same or different. A is either the same or different, a single bond or an alkylene group having 1 to 4 carbon atoms.

[0023] R in equation (1) １The alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, etc. Among these, methyl group and ethyl group are preferred.

[0024] R in equation (1) ２ of -CH ２ O { (CH ２ ) ａ O} ｂ (CH ２ ) ｃ The alkylene glycol alkyl ether group represented by H exhibits superior molecular mobility compared to the polymer backbone and maintains an appropriate distance between oxygen atoms, resulting in a tendency to achieve higher ion transportability (lithium ion conductivity). Furthermore, in terms of sulfide resistance, maintaining an appropriate distance between ether-oxygen atoms in the backbone and side chains is thought to mitigate coordination to lithium ions, thereby further suppressing reactions with sulfide-based solid electrolytes.

[0025] R in equation (1) ２ In this equation, a is an integer from 1 to 10, but preferably an integer from 1 to 9, more preferably an integer from 2 to 9, even more preferably an integer from 2 to 8, particularly preferably an integer from 2 to 7, most preferably an integer from 2 to 6, and most preferably an integer from 2 to 4. ２ In this equation, b is an integer from 1 to 6, preferably an integer from 1 to 4, more preferably an integer from 1 to 3, even more preferably an integer from 1 to 2, and particularly preferably 1. ２ In this, c is an integer from 1 to 6, preferably an integer from 1 to 4, more preferably an integer from 1 to 3, and even more preferably an integer from 1 to 2.

[0026] R in equation (1) ２ For example, -CH ２ O { (CH ２ ) ａ O} ｂ (CH ２ ) ｃ An alkylene glycol alkyl ether group represented by H is preferred.

[0027] Examples of alkylene groups having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms, and even more preferably 1 carbon atom) in A of formula (1) include methylene groups, ethylene groups, and trimethylene groups. Among these, methylene groups and ethylene groups are preferred, and methylene groups are more preferred.

[0028] In formula (1), A is preferably a single bond, a methylene group, or an ethylene group, and more preferably a single bond or a methylene group.

[0029] Preferred embodiments of the X unit, which is a constituent unit derived from the alkylene oxide shown in formula (1), are shown below. Among these, the constituent units shown in formulas (1-1) to (1-5) are preferred, and the constituent units shown in formulas (1-1), (1-2), (1-4), and (1-5) are more preferred.

[0030] The polyether polymer of the present invention preferably contains Z units, which are constituent units derived from alkylene oxides represented by the following general formula (2), in addition to the X units. Crosslinking can enhance the mechanical properties of the polyether polymer, and further, other functional groups can be introduced to provide functionality. In the polyether polymer of the present invention, each Z unit may be the same or different. Therefore, the polyether polymer of the present invention may be a polymer in which one or more units corresponding to the X units and one or more units corresponding to the Z units are combined. In the polyether polymer of the present invention, it is preferable that each unit in the X units and each unit in the Z units are the same. (In the formula, R １ R is the same or different hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ４ They are the same or different, -CH ２ OR ８ This is a crosslinking group containing an ethylenically unsaturated double bond, represented by R. ８ A is either the same or different acrylic group, methacrylic group, allyl group, or metaallyl group. A is either the same or different single bond or alkylene group having 1 to 4 carbon atoms.

[0031] R in equation (2)１ This includes preferred embodiments, and R in formula (1) １ It is similar to R. １ A C1-C6 alkyl group is preferred. １ If the Z unit is an alkyl group having 1 to 6 carbon atoms, then the Z unit corresponds to an alkyl group-containing unit.

[0032] R in equation (2) ４ In R ８ The group is an acrylic group, a methacrylic group, an allyl group, or a methallyl group, but is preferably an acrylic group, a methacrylic group, or an allyl group, more preferably a methacrylic group or an allyl group, and even more preferably an allyl group.

[0033] A in formula (2) is the same as A in formula (1), including the preferred embodiment.

[0034] Preferred embodiments of the Z unit, which is a constituent unit derived from the alkylene oxide shown in formula (2), are shown below. Among these, the constituent units shown in formulas (2-1) to (2-4) are preferred, and the constituent units shown in formulas (2-1) and (2-3) are more preferred.

[0035] In addition to the aforementioned X units, the polyether polymer of the present invention preferably further includes a Y unit which is a constitutional unit derived from an alkylene oxide represented by the following general formula (3). This tends to optimize the amount of X units in the polymer, enhance molecular mobility, and further increase ionic conductivity or lithium ion transference number. In addition, in addition to the aforementioned X units and the aforementioned Z units, the polyether polymer of the present invention also preferably includes a Y unit which is a constitutional unit derived from an alkylene oxide represented by the following general formula (3). This allows the various functions of the X units, the Z units and the Y units to be more suitably compatible with each other, as long as they are constitutional units usable in the present invention. In the polyether polymer of the present invention, each Y unit may be the same or different. Therefore, the polyether polymer of the present invention may be a polymer obtained by combining one or more types of units corresponding to X units and one or more types of units corresponding to Y units. In addition, the polyether polymer of the present invention may also be a polymer obtained by combining one or more types of units corresponding to X units, one or more types of units corresponding to Y units, and one or more types of units corresponding to Z units. In the polyether polymer of the present invention, it is preferable that all units in the X units, all units in the Y units, and all units in the Z units are the same respectively. (wherein R １ are the same or different, each being a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ３ are the same or different, each being a hydrogen atom, -CH ２ O{(CH ２ ) ａ O} ｂ (CH ２ ) ｃ H, an alkylene glycol alkyl ether group represented by the above formula, or -CH ２ O(CH ２ ) ｄ (CHR ６ ) ｅ (CH ２ ) ｆ R ７ which is a group represented by the above formula. R ６ are the same or different, each being a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ７, which may be the same or different, each represents a hydrogen atom, a hydroxyl group, a nitrile group, a trifluoromethyl group, an alkoxy group or an optionally substituted cyclic ether group. R ３ is an alkylene glycol alkyl ether group, R １ is only a hydrogen atom. a, which is the number of repeating units, is the same or different and is an integer of 1 to 10; b, which is the number of repeating units, is the same or different and is an integer of 1 to 6; c, which is the number of repeating units, is the same or different and is an integer of 0 to 6; d, which is the number of repeating units, is the same or different and is an integer of 0 to 4; e, which is the number of repeating units, is the same or different and is an integer of 0 to 4; f, which is the number of repeating units, is the same or different and is an integer of 0 to 10. A, which may be the same or different, each represents a single bond or an alkylene group having 1 to 4 carbon atoms.)

[0036] R in formula (3) １ is the same as R in formula (1), including preferred embodiments. R １ is the same as described above. Further, as R １ , an alkyl group having 1 to 6 carbon atoms is preferred. When R １ is an alkyl group having 1 to 6 carbon atoms, the Y unit corresponds to an alkyl group-containing unit.

[0037] R in formula (3) ３ of -CH ２ O{(CH ２ ) ａ O} ｂ (CH ２ ) ｃ H, the alkylene glycol alkyl ether group represented by is the same as the alkylene glycol alkyl ether group represented by -CH ２ O{(CH ２ O{(CH ２ ) ａ O} ｂ (CH ２ ) ｃ H in R of formula (1), including preferred embodiments.

[0038] R in formula (3) ３ includes -CH ２ O(CH ２ ) ｄ (CHR ６ ) ｅ (CH２ ) ｆ R ７ A group represented by R is preferred, and in this group, ６ is an alkyl group having 1 to 4 carbon atoms, R ７ It is more preferable that is a hydrogen atom, d is an integer from 1 to 3, e is an integer from 1 to 3, and f is an integer from 1 to 8.

[0039] R in equation (3) ３ In R ６ The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, etc. Among these, methyl group and ethyl group are preferred.

[0040] R in equation (3) ３ In R ６ A C1-C4 alkyl group is preferred.

[0041] R in equation (3) ３ In R ７ Examples of alkoxy groups include alkoxy groups having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms). These alkoxy groups may be linear or branched, and include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, and n-hexyloxy groups. Among these, methoxy and ethoxy groups are preferred.

[0042] R in equation (3) ３ In R ７ The number of ring members of the cyclic ether group, which may have substituents, is preferably 3 to 10, more preferably 3 to 8, and even more preferably 3 to 6. The number of oxygen atoms in the cyclic ether group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3. In this specification, the number of ring members refers to the number of atoms that constitute the ring skeleton; for example, in the case of a 5-membered ring, it is 5.

[0043] Substituents on the cyclic ether group include carbonyl groups, C1-C4 alkyl groups, and alkoxy groups having C1-C4 alkyl groups. Among these, carbonyl groups and C1-C4 alkyl groups are preferred, and carbonyl groups are more preferred. Examples of C1-C4 alkyl groups include R ６ The same applies to alkyl groups having 1 to 4 carbon atoms and preferred embodiments. Similarly, alkyl groups having 1 to 4 carbon atoms in the alkoxy group are also R ６ The same applies to alkyl groups having 1 to 4 carbon atoms, including preferred embodiments.

[0044] R ７ A cyclic ether group that may have substituents is preferably substituted. Furthermore, it is preferable that the cyclic ether group contains a carbonate group (-O-(C=O)-O-). ７ Preferred embodiments of the cyclic ether group, which may have substituents, are shown below. * indicates a bond.

[0045] R in equation (3) ３ In R ７ Preferably, the group is a hydrogen atom, a nitrile group, a trifluoromethyl group, an alkoxy group, or an optionally substituted cyclic ether group; more preferably, a hydrogen atom, a nitrile group, or an optionally substituted cyclic ether group; and even more preferably, a hydrogen atom. ７ Preferred components include hydrogen atoms, nitrile groups, trifluoromethyl groups, and optionally substituted cyclic ether groups.

[0046] R in equation (3) ３ In this equation, d is an integer from 0 to 4, preferably an integer from 1 to 3, more preferably an integer from 1 to 2, and even more preferably an integer of 1. e is an integer from 0 to 4, preferably an integer from 1 to 3, more preferably an integer from 1 to 2, and even more preferably an integer of 1. R in equation (3) ３ In this, f is an integer between 0 and 10, but is preferably an integer between 1 and 8, more preferably an integer between 2 and 6, and even more preferably an integer between 3 and 5.

[0047] A in formula (3) is the same as A in formula (1), including the preferred embodiment.

[0048] R in equation (3) １ and R ３ It is also preferable that both atoms are hydrogen atoms. This tends to reduce the crystallinity of the polyether polymer and result in better ionic conductivity.

[0049] Preferred embodiments of the Y unit, which is a constituent unit derived from the alkylene oxide shown in formula (3), are shown below. Among these, the constituent units shown in formulas (3-1) to (3-13) are preferred, the constituent units shown in formulas (3-1), (3-7), (3-8), and (3-13) are more preferred, and the structural unit shown in formula (3-7) is even more preferred.

[0050] While preferred embodiments for units X, Y, and Z have been illustrated, combinations of preferred structures for units X and Y, combinations of preferred structures for units X and Z, and combinations of preferred structures for units X, Y, and Z are also preferred embodiments.

[0051] In formulas (1) to (3), * represents a bond, and when located at the end of a polymer, it is a hydrogen atom, a hydroxyl group, or an alkoxy group.

[0052] In the polyether polymer of the present invention, it is preferable that the skeletal structure (number of carbon atoms in the alkylene in the alkylene oxide) is the same in all constituent units. Specifically, it is preferable that all A are the same in each X unit, each Y unit, and each Z unit.

[0053] In the polyether polymer of the present invention, the content of alkyl group-containing units, which are constituent units derived from alkylene oxides having alkyl groups in their side chains, is 15 mol% or more, and may be 100 mol%, but is preferably 15 to 99.9 mol%, more preferably 15 to 98.9 mol%. The lower limit is more preferably 20 mol% or more, particularly preferably 30 mol% or more, most preferably 40 mol% or more, most preferably 50 mol% or more, still most preferably 60 mol% or more, particularly most preferably 70 mol% or more, still preferably 80 mol% or more, and even more preferably 90 mol% or more. Within this range, sufficient sulfide resistance tends to be obtained. In this specification, the notation "~" means greater than or equal to the value before the notation "~" and less than or equal to the value after the notation "~". In this specification, the content of alkyl group-containing units means the total content when multiple types of constituent units are included as alkyl group-containing units. The same applies to the content of other components.

[0054] In the polyether polymer of the present invention, all alkyl group-containing units may be X units. Therefore, the content of X units, which are constituent units derived from the alkylene oxide represented by the general formula (1), in 100 mol% of the constituent units is preferably the same as the content of alkyl group-containing units.

[0055] In the polyether polymer of the present invention, the content of Z units, which are constituent units derived from alkylene oxides represented by general formula (2), is preferably 0.1 to 20 mol%, more preferably 0.3 to 10 mol%, and even more preferably 0.5 to 5 mol% in 100 mol% of constituent units. Within this range, sufficient mechanical strength to withstand compression and the like tends to be obtained.

[0056] In the polyether polymer of the present invention, the content of Y units, which are constituent units derived from the alkylene oxide represented by the general formula (3), in 100 mol% of constituent units is preferably 0 to 79 mol%, more preferably 3 to 60 mol%, and even more preferably 5 to 55 mol%. Within this range, sufficient sulfide resistance is obtained, and lithium ion conductivity tends to increase.

[0057] In the polyether polymer of the present invention, the total content of X units and Z units in 100 mol% of constituent units is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, particularly preferably 98 mol% or more, and may be 100 mol%.

[0058] In the polyether polymer of the present invention, the total content of X units, Y units, and Z units in 100 mol% of constituent units is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, particularly preferably 98 mol% or more, and may be 100 mol%.

[0059] In this specification, the content of each constituent unit in a polyether polymer can be determined by the nuclear magnetic resonance (NMR) spectrum of the polymer.

[0060] The polyether polymer of the present invention may have units other than X, Y, and Z units, such as units having a thioether group or units having a sulfonyl group, as long as it does not depart from the spirit of the invention. These can be used individually or in combination of two or more.

[0061] The weight-average molecular weight (Mw) of the polyether polymer of the present invention is preferably 0.5 million to 3 million, more preferably 0.5 million to 2.5 million, even more preferably 10,000 to 2.5 million, and particularly preferably 50,000 to 2.5 million. This tends to lead to a more favorable outcome of the effects of the present invention.

[0062] The degree of dispersion (Mw / Mn) of the polyether polymer of the present invention is preferably 1 to 40, more preferably 1 to 30, even more preferably 1 to 20, and particularly preferably 1 to 10. This tends to lead to a more favorable outcome of the effects of the present invention. In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer are measured by the method described in the examples.

[0063] The polyether polymer of the present invention may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer. A random copolymer is preferred because it disrupts the crystallinity of the polymer, resulting in better ion transportability (lithium ion conductivity).

[0064] Preferred embodiments of the polyether polymer of the present invention are as follows: <<<Embodiment 1-1>>> A polymer having an X unit content of 40 mol% or more.

[0065] <<<Aspect 1-2>>> A polymer containing X units and Z units, wherein the content of X units is 80 mol% or more.

[0066] <<

[0067] (In formula (1-a), R １ , R ２ R in equation (1) １ , R ２ (It is similar to this.) (In formula (3-a), R １ , R ３ R in equation (3) １ , R ３ (It is similar to this.) (In formula (2-a), R １ , R ４ R in equation (2) １ , R ４ (It is similar to this.)

[0068] The polymerization method for the polyether polymer of the present invention is not particularly limited, and conventional polymerization reactions can be used. Those skilled in the art can appropriately produce the polyether polymer of the present invention using the above monomers by known polymerization methods, etc. For example, a ring-opening polymerization catalyst such as an organoaluminum-based catalyst system, an organozinc-based catalyst system, or an organotin-phosphate ester condensate catalyst system as a coordination anion initiator, and a K counterion. ＋ Polyether polymers can be obtained by reacting each monomer with or without a solvent at a reaction temperature of 0 to 120°C under stirring, using an anionic initiator such as potassium alkoxide, diphenylmethyl potassium, or potassium hydroxide, or a cationic initiator such as a Lewis acid such as boron trifluoride, diethyl ether complex, aluminum(III) chloride, or tin(IV) chloride.

[0069] Furthermore, the compounds represented by formula (1-a), formula (2-a), and formula (3-a) may be commercially available, but if synthesized, they can be obtained, for example, by the reaction of oxetane alcohols with alkyl ether halides.

[0070] Furthermore, the polyether polymer of the present invention, in which A is a methylene group, can be obtained by synthesis using the above monomers. However, those skilled in the art can appropriately select the monomer according to the A of the polyether polymer to be produced.

[0071] The polymer electrolyte for lithium-ion secondary batteries of the present invention preferably contains the polyether polymer of the present invention. Here, the polyether polymer of the present invention may be used alone or in combination of two or more types.

[0072] The polymer electrolyte for lithium-ion secondary batteries of the present invention is preferably a polymer solid electrolyte that is solid at room temperature. In this specification, a solid electrolyte means an electrolyte that is solid (does not exhibit fluidity) at room temperature. Here, in this specification, room temperature refers to the temperature range in which the power supply is expected to operate normally. The temperature range in which the power supply is expected to operate normally has an upper limit of about 120°C, and in some cases about 60°C, and a lower limit of about -40°C, and in some cases about -20°C.

[0073] In the polymer electrolyte for lithium-ion secondary batteries of the present invention, the content of the polyether polymer of the present invention in 100% by mass of the lithium-ion conductive polymer is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass. This tends to more favorably obtain the effects of the present invention. In this specification, the content of each polymer can be determined by nuclear magnetic resonance spectroscopy.

[0074] <<<Polyacrylates>>> Polyacrylates are not particularly limited as long as they are polymers obtained by polymerizing acrylic acid, methacrylic acid, and / or derivatives thereof. Examples of polyacrylates include alkyl acrylate polyacrylates such as polymethyl acrylate, polyethyl acrylate, and polybutyl acrylate, acrylic acid-based polyacrylates such as acrylic acid polymers, partially neutralized acrylic acid polymers, and crosslinked acrylic acid polymers, and functional group-containing polyacrylates such as hydroxyethyl acrylate polymers, carboxyl group-containing acrylate polymers, and epoxy group-containing acrylate polymers. Examples of polymethacrylates include alkyl methacrylate polymethacrylates such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate, functional group-containing polymethacrylates such as hydroxyethyl methacrylate polymers, carboxyl group-containing methacrylate polymers, and epoxy group-containing methacrylate polymers. Of these, alkyl acrylate-based polyacrylates and alkyl methacrylate-based polymethacrylates are more preferred, alkyl methacrylate-based polymethacrylates are even more preferred, and polymethyl methacrylates are particularly preferred.

[0075] <<<Polycarbonates>>> Polycarbonates are not particularly limited as long as they are polymers having a carbonate bond (-O-(C=O)-O-) in their main chain. Examples of polycarbonates include aromatic polycarbonates such as bisphenol A type polycarbonate, branched aromatic polycarbonate, and bisphenol S type polycarbonate; aliphatic polycarbonates such as polypropylene carbonate, polyethylene carbonate, and polybutylene carbonate; polycarbonate-based polyols such as aliphatic polycarbonate diol, branched polycarbonate polyol, and dendrimer-type polycarbonate polyol; bio-based polycarbonates such as isosorbide polycarbonate, limonene polycarbonate, and mass-balance type polycarbonate derived from bio-materials; and siloxane copolymer polycarbonates, polycarbonate / ABS blend resins, and polycarbonate / polyester blend resins. Among these, aliphatic polycarbonate is more preferred, and polypropylene carbonate is even more preferred.

[0076] <<<Polyester>>> Polyester is not particularly limited as long as it is a polymer having an ester bond (-COO-) in its main chain. Examples of polyesters include aliphatic polyesters such as polycaprolactone, polybutylene succinate, and polybutylene adipate; aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and biodegradable or copolymerized polyesters such as polylactic acid, poly(butylene adipate-co-terephthalate), and poly(ethylene-co-vinyl alcohol) ester. Of these, aliphatic polyester is more preferred, and polycaprolactone is even more preferred.

[0077] <<<Polymers Having Anionic Functional Groups>>> Polymers having anionic functional groups in their side chains are not particularly limited as long as they have anionic functional groups in their side chains. The anionic functional group is not particularly limited as long as it is an anionic functional group, and examples include sulfonimide groups, sulfonate groups, carboxylate groups, borate groups, phosphonate groups, phosphate groups, etc. These can be used alone or in combination of two or more. Among these, sulfonimide groups, borate groups, sulfonate groups, and phosphate groups are preferred, and sulfonimide groups are more preferred. A specific example of such a group is trifluoromethanesulfonylimide (TFSI) － ) group, fluoromethanesulfonylimide (FSI － ) group, tetraarylborate group, oxaloborate group, alkylsulfonate group, polystyrenesulfonate group, alkylphosphate group are more preferred, and fluoromethanesulfonylimide (FSI － ) group, trifluoromethanesulfonyliimide (TFSI － A group is even more preferable. The structure of the main chain of a polymer having anionic functional groups in its side chains is not particularly limited.

[0078] <<<Fluorine-based polymers>>> Fluorine-based polymers are not particularly limited as long as they have structural units containing fluorine atoms and are polymers that allow lithium ion movement due to their polarity or amorphousness. Examples of fluorine-based polymers include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), vinylidene fluoride chlorotrifluoroethylene copolymer (VDF-CTFE), tetrafluoroethylene hexafluoropropylene copolymer (FEP), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene copolymer (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), and polychlorotrifluoroethylene (PCTFE). Among these, polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) is preferred.

[0079] <<Ether-based compounds>> The polymer electrolyte for lithium-ion secondary batteries of the present invention contains ether-based compounds. In this specification, ether-based compounds refer to linear ether-based compounds represented by the following general formula (4) and branched ether-based compounds represented by the following general formula (5).

[0080] The ether compounds used in the present invention are not particularly limited, but it is preferable that they be at least one compound selected from the group consisting of linear ether compounds represented by the following general formula (4) and branched ether compounds represented by the following general formula (5). (In the formula, R ９ These are identical or different alkyl groups having 1 to 4 carbon atoms, or -(CH ２ ) ｉ CH ２ O-R １０ It is a group represented by R. １０ (The elements are the same or different alkyl groups having 1 to 4 carbon atoms. The repeating elements, g, h, and i, are the same or different integers from 1 to 3.) (In the formula, R １１ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ That is. R １２ These are identical or different alkyl groups having 1 to 4 carbon atoms, or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ That is. R １３ (The elements are the same or different alkyl groups having 1 to 4 carbon atoms. The repeating number m is 0 or 1, and k and l are the same or different integers from 1 to 3.)

[0081] R in general formula (4) ９The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, etc. Among these, methyl group and ethyl group are preferred.

[0082] The number of repetitions of general formula (4), g and h, are the same or different integers from 1 to 3, preferably from 1 to 2, and more preferably from 1.

[0083] R in general formula (4) ９ - (CH2) ｉ CH ２ O-R １０ The group R represented by １０ The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, etc. Among these, methyl group and ethyl group are preferred.

[0084] The number of repetitions i in general formula (4) is an integer from 1 to 3, preferably an integer from 2 to 3.

[0085] R in general formula (4) ９ Of these, at least one is preferably an alkyl group having 1 to 4 carbon atoms.

[0086] R in general formula (5) １１ and R １２ The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, etc. Among these, methyl group and ethyl group are preferred.

[0087] R in general formula (5) １１ and R １２ -{(CH2) ｋ CH ２ O}ｌ -R １３ The group R represented by １３ The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, etc. Among these, methyl group and ethyl group are preferred.

[0088] The number of repetitions m in general formula (5) is either 0 or 1. It is preferable that m is 1.

[0089] The number of repetitions of general formula (5), k and l, are the same or different integers from 1 to 3, preferably from 1 to 2, and more preferably from 1. It is preferable that both k and l are 1.

[0090] R in general formula (5) １１ R of general formula (5) is preferred to be an alkyl group having 1 to 4 carbon atoms. １２ At least one of them is -{(CH ２ ) ｋ CH ２ O} ｌ R １３ It is preferable that R １２ At least two of them are -{(CH ２ ) ｋ CH ２ O} ｌ R １３ It is more preferable that R １２ All of them are - { (CH ２ ) ｋ CH ２ O} ｌ R １３ It is even more preferable that this be the case.

[0091] Specific examples of linear ether compounds represented by general formula (4) are, but are not limited to, 1-methoxy-3-(3-methoxypropoxy)propane (formula (4-1)), 1-methoxy-4-(3-methoxypropoxy)butane (formula (4-2)), 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)), 2,6,10,14-tetraoxapentadecane (formula (4-4)), 2,6,11,15-tetraoxahexadecane (formula (4-5)), 2,6,10,1 Examples include 5-tetraoxahexadecane (formula (4-6)), 2,7,11,16-tetraoxaheptadecane (formula (4-7)), and 2,7,12,17-tetraoxaoctadecane (formula (4-8)). Among these, formulas (4-1), (4-2), (4-3), (4-4), (4-5), and (4-6) are preferred, formulas (4-3), (4-4), (4-5), and (4-6) are more preferred, and formulas (4-3), (4-4), and (4-5) are even more preferred.

[0092]

[0093] Specific examples of branched ether compounds represented by general formula (5) are, but are not limited to, 1,3-dimethoxy-2-(methoxymethyl)propane (formula (5-1)), 1,3-dimethoxy-2-(methoxymethyl)-2-methylpropane (formula (5-2)), 1-methoxy-2,2-bis(methoxymethyl)butane (formula (5-3)), 1,3-diethoxy-2-(ethoxymethyl)propane (formula (5-4)), 1,3-diethoxy-2-(ethoxymethyl)-2-methylpropane (formula (5-5)), and 1-ethoxy-2,2-bis(ethoxymethyl)butane. ¹(Formula (5-6)), 7-((2-methoxyethoxy)methyl)-2,5,9,12-tetraoxatridecane(Formula (5-7)), 7-((2-methoxyethoxy)methyl)-7-methyl-2,5,9,12-tetraoxatridecane(Formula (5-8)), 7-ethyl-((2-methoxyethoxy)methyl)-2,5,9,12-tetraoxatridecane(Formula (5-9)), 10-((2-methoxyethoxy)methyl)-2,5,8,12,15-pentaoxahexadecane(Formula (5-10)), 10-((2-methoxyethoxy)methyl)-10-methyl Lu-2,5,8,12,15-pentaoxahexadecane (formula (5-11)), 10-ethyl-10-((2-methoxyethoxy)methyl)-2,5,8,12,15-pentaoxahexadecane (formula (5-12)), 10-((2-methoxyethoxy)methyl)-2,5,8,12,15,18-hexaoxanonadecane (formula (5-13)), 10-((2-methoxyethoxy)methyl)-10-methyl-2,5,8,12,15,18-hexaoxanonadecane (formula (5-14)), 10-ethyl-10-((2-methoxyethoxy)methyl)-2 ,5,8,12,15,18-Hexaoxanonadecane (Formula (5-15)),10-((2-(2-methoxyethoxy)ethoxy)methyl)-2,5,8,12,15,18-Hexaoxanonadecane (Formula (5-16)),10-((2-(2-methoxyethoxy)ethoxy)methyl)-10-methyl-2,5,8,12,15,18-Hexaoxanonadecane (Formula (5-17)),10-Ethyl-10-((2-(2-methoxyethoxy)ethoxy)methyl)-2,5,8,12,15,18-Hexaoxanonadecane (Formula (5-18)),1,2,3-Trimethoxypropane (Formula (5-19)), 1,2,3-Triethoxypropane (Formula (5-20)), 1,3-Dimethoxy-2-(2-Methoxyethoxy)propane (Formula (5-21)), 6-(Methoxymethyl)-2,5,8,11-Tetraoxadodecane (Formula (5-22)), 7-(2-Methoxyethoxy)-2,5,9,12-Tetraoxatridecane (Formula (5-23)), 10-(2-Methoxyethoxy)-2,5,8,12,15-Pentaoxahexadecane (Formula (5-24)) )), 10-(2-methoxyethoxy)-2,5,8,12,15,18-hexaoxanonadecane (formula (5-25)), 10-(2-(2-methoxyethoxy)ethoxy)-2,5,8,12,15,18-hexaoxanonadecane (formula (5-26)), 13-(2-methoxyethoxy)-2,5,8,11,15,18-hexaoxanonadecane (formula (5-27)), 13-(2-(2-methoxyethoxy)ethoxy)-2,5,8,11,15,18,21-heptaoxadocosane Examples include (Formula (5-28)), 13-(2-methoxyethoxy)-2,5,8,11,15,18,21,24-octaoxapentacosane (Formula (5-29)), and among these, formulas (5-2), (5-3), (5-5), (5-6), (5-8), (5-9), (5-11), (5-12), (5-14), (5-15), (5-17), (5-18), (5-21), (5-22), (5-23), (5-24), (5-25), (5-26), and (5-27) are preferred. It is more preferable that the formulas are (5-5), (5-6), (5-8), (5-9), (5-11), (5-12), (5-14), (5-15), (5-22), (5-23), (5-24), (5-25), (5-26), (5-27), even more preferable that the formulas are (5-5), (5-6), (5-8), (5-9), (5-11), (5-12), (5-14), (5-15), (5-23), (5-25), (5-26), and particularly preferable that the formulas are (5-6) and (5-9).

[0094]

[0095] The linear ether compounds represented by general formula (4) and the branched ether compounds represented by general formula (5) may be used individually or in combination of two or more types.

[0096] In the polymer electrolyte for lithium-ion secondary batteries of the present invention, the lower limit of the content of ether compounds (total content of linear ether compounds represented by general formula (4) and branched ether compounds represented by general formula (5)) per 100 parts by mass of lithium-ion conductive polymer (preferably polyether polymer, more preferably polyether polymer of the present invention) is 50 parts by mass or more, preferably 150 parts by mass or more, more preferably 200 parts by mass or more, even more preferably 250 parts by mass or more, and most preferably 300 parts by mass or more. The upper limit is 1000 parts by mass or less, preferably 900 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 700 parts by mass or less, and most preferably 600 parts by mass or less. This tends to more favorably obtain the effects of the present invention.

[0097] <<Lithium Salt Compounds>> As lithium salt compounds, those with a broad potential window, such as those commonly used in lithium-ion batteries, are preferred. Examples of lithium salt compounds include LiBF ４ LiPF ６ LiClO ４ LiCF ３ SO ３ , Li(CF ３ SO ２ ) ２ N, LiN (CF ３ SO ２ ) ２ (LiTFSI), LiN(SFO ２ ) ２ (LiFSI), LiN(C ２ F ５ SO ２ ) ２ ,LiN[CF ３ SC (C ２ F ５ SO ２ ) ３ ] ２These are some examples. These may be used individually or in combination of two or more types.

[0098] In the polymer electrolyte for lithium-ion secondary batteries of the present invention, the lower limit of the content of the lithium salt compound per 100 parts by mass of the lithium-ion conductive polymer (preferably a polyether polymer, more preferably the polyether polymer of the present invention) is 20 parts by mass or more, preferably 40 parts by mass or more, even more preferably 80 parts by mass or more, and most preferably 100 parts by mass or more. On the other hand, the upper limit is 700 parts by mass or less, more preferably 600 parts by mass or less, even more preferably 500 parts by mass or less, and particularly preferably 400 parts by mass or less. This tends to more favorably obtain the effects of the present invention.

[0099] In the polymer electrolyte for lithium-ion secondary batteries of the present invention, the total content of the lithium-ion conductive polymer (preferably a polyether polymer), ether compounds (linear ether compounds represented by general formula (4) and branched ether compounds represented by general formula (5)), and lithium salt compounds is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and may be 100% by mass, based on 100% by mass of the polymer electrolyte for lithium-ion secondary batteries of the present invention. This tends to more favorably obtain the effects of the present invention.

[0100] <<Room Temperature Molten Salt>> The polymer electrolyte for lithium-ion secondary batteries of the present invention may contain a room temperature molten salt. A room temperature molten salt means a salt that is liquid in at least a portion of its form at room temperature.

[0101] Room-temperature molten salts are also called ionic liquids, and known examples include pyridine-based, aliphatic amine-based, and alicyclic amine-based quaternary ammonium organic cations. These may be used individually or in combination of two or more types. Examples of quaternary ammonium organic cations include imidazolium ions such as dialkylimidazolium and trialkylimidazolium, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, and piperidinium ions.

[0102] <<Plasticizer>> The polymer electrolyte for lithium-ion secondary batteries of the present invention may contain a plasticizer. The plasticizer is not particularly limited, but dicyano compounds and branched ether compounds are preferred. These may be used alone or in combination of two or more. When the polymer electrolyte for lithium-ion secondary batteries of the present invention contains a plasticizer, it is preferable to crosslink the lithium-ion conductive polymer (preferably the polyether polymer of the present invention) after blending the plasticizer. This suppresses the outflow of the plasticizer.

[0103] <<Other Components>> In addition to the components listed above, the polymer electrolyte for lithium-ion secondary batteries of the present invention may also contain, for example, reaction initiators, crosslinking aids, binders, etc. These may be used individually or in combination of two or more types. Reaction initiators and crosslinking aids will be described in detail when describing the crosslinked film. The polymer electrolyte for lithium-ion secondary batteries of the present invention may be crosslinked or uncrosslinked.

[0104] The polymer electrolyte for lithium-ion secondary batteries of the present invention can be prepared using conventionally known methods, for example, by adding and mixing an ether compound, a lithium salt compound, etc., to a lithium-ion conductive polymer (preferably the polyether polymer of the present invention). It may also be dried if necessary.

[0105] The lithium ion conductivity (at 25°C) of the polymer electrolyte for lithium-ion secondary batteries of the present invention is preferably 5 × 10⁻⁶. －６ (S / cm) or more, more preferably 1 × 10 －５ (S / cm) or more, more preferably 5 x 10 －５ (S / cm) or more, particularly preferably 8 x 10 －５ (S / cm) or more, and there is no particular upper limit, but for example, 1 × 10 －３ The following applies. In this specification, the lithium-ion conductivity of an electrolyte for lithium-ion secondary batteries is calculated by the product of the ionic conductivity and the lithium-ion transport fraction, and is specifically measured by the method described in the examples.

[0106] <Composite Solid Electrolyte for Lithium-Ion Secondary Batteries> The composite solid electrolyte for lithium-ion secondary batteries of the present invention (sometimes simply referred to as a composite solid electrolyte) comprises an inorganic solid electrolyte and a polymer electrolyte for lithium-ion secondary batteries of the present invention (ether-based compound, lithium-ion conductive polymer (preferably the polyether polymer of the present invention)). Since the composite solid electrolyte of the present invention contains a polymer electrolyte for lithium-ion secondary batteries of the present invention (ether-based compound, lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) in addition to the inorganic solid electrolyte, it is considered that the contact area at the interface between the electrode material layer and the solid electrolyte layer is larger compared to cases where the solid electrolyte is formed by inorganic solid electrolyte alone. As a result, the interfacial resistance between the electrode and the electrolyte is reduced, and excellent charge and discharge characteristics are exhibited. Furthermore, even within the composite solid electrolyte, it is considered that the polymer electrolyte for lithium-ion secondary batteries of the present invention (ether-based compound, lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) reduces the resistance inside the composite solid electrolyte by bringing the particles of the inorganic solid electrolyte into close contact. Here, the polymer electrolyte for lithium-ion secondary batteries of the present invention (ether-based compound, lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) may be used alone or in combination of two or more types.

[0107] Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. These may be used individually or in combination of two or more types. In the composite solid electrolyte of the present invention, the inorganic solid electrolyte is included, for example, in particulate form, and the particles of the inorganic solid electrolyte are tightly bonded together with the polymer electrolyte for lithium-ion secondary batteries of the present invention (lithium-ion conductive polymer (preferably the polyether polymer of the present invention)).

[0108] Oxide-based solid electrolytes are not particularly limited as long as they contain oxygen, have ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and possess electronic insulating properties.

[0109] Specific compounds that make up oxide-based solid electrolytes include Liｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍ O ｎ (M is at least one element from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, and x satisfies 5 ≤ ​​x ≤ 10, y satisfies 1 ≤ y ≤ 4, z satisfies 1 ≤ z ≤ 4, m satisfies 0 ≤ m ≤ 2, and n satisfies 5 ≤ ​​n ≤ 20.) Li ｘ B ｙ M ｚ O ｎ (In the formula, M is at least one element from C, S, Al, Si, Ga, Ge, In, and Sn, x satisfies 0 ≤ x ≤ 5, y satisfies 0 ≤ y ≤ 1, z satisfies 0 ≤ z ≤ 1, and n satisfies 0 ≤ n ≤ 6.) Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (wherein 1≦x≦3, 0≦y≦1, 0≦z≦2, 0≦a≦1, 1≦m≦7, 3≦n≦13), Li （３－２ｘ） M ｘ DO (where x is a number between 0 and 0.1, M represents a divalent metal atom, and D represents a halogen atom or a combination of two or more halogen atoms), Li ｘ Si ｙ O ｚ (1≦x≦5, 0<y≦3, 1≦z≦10), Li ｘ S ｙ O ｚ (1≦x≦3, 0<y≦2, 1≦z≦10), Li ３ BO ３ -Li ２ SO ４ Li ２ O-B ２ O ３ -P ２ O ５ Li ２ O-SiO ２ Li ６ BaLa ２ Ta ２ O １２Li ３ PO （４－３／２ｗ） N ｗ (where w < 1), Li has a LISICON (Lithium superionic conductor) type crystal structure. ３．５ Zn ０．２５ GeO ４ La having a perovskite-type crystal structure ０．５５ Li ０．３５ TiO ３ LiTi having a NASICON (Natrium superionic conductor) type crystal structure ２ P ３ O １２ Li （１＋ｘ＋ｙ） (Al, Ga) ｘ (Ti, Ge) （２－ｘ） Si ｙ P （３－ｙ） O １２ (where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1), Li having a garnet-type crystal structure ７ La ３ Zr ２ O1 ２ Examples include the following. Phosphorus compounds containing Li, P, and O are also desirable. For example, lithium phosphate (Li ３ PO ４ Examples include LiPON and LiPOD (where D is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.), in which some of the oxygen in lithium phosphate is replaced with nitrogen. LiAON (where A is at least one selected from Si, B, Ge, Al, C, Ga, etc.) can also be preferably used.

[0110] Among them, Li ｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍ O ｎ(M is at least one element from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, and x satisfies 5 ≤ ​​x ≤ 10, y satisfies 1 ≤ y ≤ 4, z satisfies 1 ≤ z ≤ 4, m satisfies 0 ≤ m ≤ 2, and n satisfies 5 ≤ ​​n ≤ 20.) Li ７ La ３ Zr ２ O １２ (LLZ), Li ３ BO ３ Li ３ BO ３ -Li ２ SO ４ Li ３ BO ３ -Li ２ CO ３ Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (However, 1 ≤ x ≤ 3, 0 ≤ y ≤ 1, 0 ≤ z ≤ 2, 0 ≤ a ≤ 1, 1 ≤ m ≤ 7, 3 ≤ n ≤ 13 is preferred.)

[0111] Sulfide-based solid electrolytes are not particularly limited as long as they contain sulfur, have ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and possess electronic insulating properties.

[0112] The sulfide-based solid electrolyte may be a glass-based sulfide solid electrolyte or a glass-ceramic sulfide solid electrolyte. These may be used individually or in combination of two or more. The glass-based sulfide solid electrolyte can be obtained by vitrifying the raw materials. The glass-ceramic sulfide solid electrolyte can be obtained, for example, by heat-treating the glass-based sulfide solid electrolyte. Furthermore, it is preferable that the sulfide-based solid electrolyte has a crystalline structure. Examples of crystalline structures include the Thio-LISICON type crystal structure, the LGPS type crystal structure, and the argyrodite type crystal structure.

[0113] Examples of glassy sulfide solid electrolytes include Li ２ S-P ２ S ５ Li ２S-LiI-P ２ S ５ Li ２ S-LiI-Li ２ O-P ２ S ５ Li ２ S-LiBr-P ２ S ５ Li ２ S-Li ２ O-P ２ S ５ Li ２ S-Li ３ PO ４ -P ２ S ５ Li ２ S-P ２ S ５ -P ２ O ５ Li ２ S-P ２ S ５ -SiS ２ Li ２ S-P ２ S ５ - SnS, Li ２ S-P ２ S ５ - Al ２ S ３ Li ２ S-GeS ２ Li ２ S-GeS ２ Examples include -ZnS. These can be used individually or in combination of two or more.

[0114] Examples of sulfide-based solid electrolytes having a crystalline structure include Li １０ GeP ２ S １２ Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ Li ９．４２ Si １．０２ P ２．１ S ９．９６ O ２．２４ LGPS-type sulfide solid electrolytes such as Li ６ PS ５ Cl, Li ６．６ Ge ０．６ P０．４ S ５ I, Li ７ Ge ３ PS １２ Algyrodite-type sulfide solid electrolytes such as Li ４．２７５ Ge ０．６１ Ga ０．２５ S ４ Li ４ SnS ４ β-Li ３ PS ４ Examples of Thio-LisICON type sulfide solid electrolytes include the following. Among these, argyrodite type sulfide solid electrolytes and Thio-LisICON type sulfide solid electrolytes are preferred, and argyrodite type sulfide solid electrolytes are more preferred. These may be used individually or in combination of two or more.

[0115] From the viewpoint of improving the electrical characteristics of all-solid-state lithium-ion secondary batteries, sulfide-based solid electrolytes with high ionic conductivity are preferable. Specifically, the ionic conductivity is 1 × 10⁻⁶. －４ It is preferable that the S / cm is greater than or equal to 1 × 10 －３ A ratio of S / cm or higher is more preferable.

[0116] As the inorganic solid electrolyte, sulfide-based solid electrolytes are preferred. The ether-based compounds and the polyether polymers of the present invention can suppress side reactions with sulfide-based solid electrolytes and have high lithium-ion conductivity, thus more favorably exhibiting the effects of the present invention.

[0117] When the inorganic solid electrolyte is in particulate form, the particle size can be, for example, 0.01 to 100 μm, preferably 0.1 to 20 μm.

[0118] In the composite solid electrolyte for lithium-ion secondary batteries of the present invention, the mass ratio of the inorganic solid electrolyte to the polymer electrolyte for lithium-ion secondary batteries of the present invention (lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) is not particularly limited. However, from the viewpoint of more favorably exhibiting excellent charge-discharge characteristics in the secondary battery, the content of the polymer electrolyte for lithium-ion secondary batteries of the present invention (lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) per 100 parts by mass of inorganic solid electrolyte is preferably 0.1 to 1000 parts by mass, more preferably 0.5 to 800 parts by mass, even more preferably 5 to 600 parts by mass, and particularly preferably 10 to 400 parts by mass.

[0119] In the composite solid electrolyte for lithium-ion secondary batteries of the present invention, the total content of the inorganic solid electrolyte and the polymer electrolyte for lithium-ion secondary batteries of the present invention is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and may be 100% by mass, based on 100% by mass of the composite solid electrolyte for lithium-ion secondary batteries of the present invention. This tends to more favorably obtain the effects of the present invention.

[0120] The composite solid electrolyte for lithium-ion secondary batteries of the present invention contains a polymer electrolyte for lithium-ion secondary batteries in addition to an inorganic solid electrolyte. Therefore, unlike when using only an inorganic solid electrolyte, it can be suitably molded into a sheet. The thickness of the composite solid electrolyte of the present invention when applied to a secondary battery is not particularly limited, but for example, it is about 0.01 to 1 mm, preferably about 0.05 to 0.3 mm.

[0121] The composite solid electrolyte for lithium-ion secondary batteries of the present invention may also contain, in addition to the polymer electrolyte for lithium-ion secondary batteries of the present invention, for example, reaction initiators, crosslinking aids, binders, etc. These may be used individually or in combination of two or more types.

[0122] The composite solid electrolyte for lithium-ion secondary batteries of the present invention can be prepared using conventionally known methods, for example, by mixing an inorganic solid electrolyte with the polymer electrolyte for lithium-ion secondary batteries of the present invention (a lithium-ion conductive polymer (preferably the polyether polymer of the present invention)). Specifically, it can be produced by dispersing an inorganic solid electrolyte in a solvent containing the polymer electrolyte for lithium-ion secondary batteries of the present invention (a lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) to prepare a composite solid electrolyte slurry, and then spraying and drying the slurry in hot air to obtain the composite solid electrolyte; by heating and evaporating the solvent of the dispersed slurry under atmospheric pressure or reduced pressure to dry it out; or by applying the dispersed slurry to a current collector sheet, etc., and drying it.

[0123] As the dispersion solvent, one that does not react with the inorganic solid electrolyte is preferred. Specifically, butyl butyrate, toluene, ortho-xylene, tetralin, acetonitrile, isobutyronitrile, anisole, methyl isobutyl ketone, diisobutyl ketone, etc., can be used alone or in combination. Even if the obtained dispersion slurry is a homogeneous solution, and even if the solute that does not dissolve in the dispersion solvent is an inorganic solid electrolyte and / or the polymer electrolyte for lithium-ion secondary batteries of the present invention, it can be prepared by the above general preparation method. When removing the dispersion solvent, it is desirable to remove as much residual solvent and water as possible from the composite solid electrolyte obtained. For example, this can be achieved by heating at 30°C to 200°C for 1 to 48 hours under vacuum. The dried composite solid electrolyte of the present invention has high lithium-ion conductivity as well as binding properties, so the electrolyte powder itself can be pressure-molded and used as a solid electrolyte material. Furthermore, by performing pressure heat treatment, the porosity can be reduced and the particle interface adhesion can be increased. When an inorganic solid electrolyte is pressure-molded alone, it has almost no binding properties, resulting in a thick electrolyte film. However, with a composite solid electrolyte, the binding properties of the lithium-ion secondary battery polymer electrolyte (lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) make it possible to produce a thinner solid electrolyte.

[0124] The composite solid electrolyte of the present invention may be crosslinked or uncrosslinked, but it is preferable that it be crosslinked. By crosslinking the composite solid electrolyte of the present invention, the bonding strength between the inorganic solid electrolyte in the composite solid electrolyte and the polymer electrolyte for lithium-ion secondary batteries of the present invention (lithium-ion conductive polymer (preferably the polyether polymer of the present invention)) can be further improved, and short circuits in the battery due to confinement pressure and dendrite deposition can be more effectively prevented. Crosslinking can be achieved by applying heat or by irradiating with active energy rays such as ultraviolet light.

[0125] In the case of thermal crosslinking, radical initiators selected from organic peroxides, azo compounds, etc., are used. These may be used alone or in combination of two or more. As organic peroxides, those commonly used for crosslinking applications are used, such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, etc. As azo compounds, those commonly used for crosslinking applications are used, such as azonitrile compounds, azoamide compounds, azoamidine compounds, etc. The amount of radical initiator added varies depending on the type, but is usually in the range of 0.1 to 10 parts by mass, based on 100 parts by mass of lithium-ion conductive polymer (preferably polyether polymer (ion-conducting polymer)).

[0126] For crosslinking irradiated with active energy rays, alkylphenone-based, benzophenone-based, acylphosphine oxide-based, titanocene-based, triazine-based, bisimidazole-based, and oxime ester-based radical initiators are used. These may be used individually or in combination of two or more types. The amount of these radical polymerization initiators added varies depending on the type, but is usually in the range of 0.01 to 5.0 parts by mass, based on 100 parts by mass of lithium-ion conductive polymer (preferably polyether polymer (ion-conducting polymer)).

[0127] When crosslinking a complex solid electrolyte, crosslinking aids may be used as needed. Examples of crosslinking aids include ethylene glycol diacrylate, ethylene glycol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane triacrylate, allyl methacrylate, allyl acrylate, diallyl maleate, triallyl isocyanurate, maleimide, phenyl maleimide, maleic anhydride, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane. These may be used individually or in combination of two or more types.

[0128] <Lithium-ion secondary battery> The lithium-ion secondary battery of the present invention is a lithium-ion secondary battery using the polymer electrolyte for lithium-ion secondary batteries of the present invention. The lithium-ion secondary battery of the present invention is not particularly limited as long as the polymer electrolyte for lithium-ion secondary batteries of the present invention is used. A preferred embodiment is a lithium-ion secondary battery using the composite solid electrolyte for lithium-ion secondary batteries of the present invention. As a stacked configuration of the secondary battery, for example, there is a stacked configuration in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in order, but it is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention in at least one of each layer, and it is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention as the solid electrolyte layer.

[0129] <<Crosslinked Film>> In the secondary battery of the present invention, a crosslinked film of the polymer electrolyte for lithium-ion secondary batteries of the present invention may be placed between the positive electrode and the solid electrolyte layer, and between the negative electrode and the solid electrolyte layer, at least one of the two. By placing the crosslinked film, the interfacial resistance of the electrodes and the solid electrolyte layer can be further reduced.

[0130] The crosslinked film is preferably formed by crosslinking a polymer electrolyte for lithium-ion secondary batteries of the present invention, which is a composition comprising at least a lithium salt compound, an ether compound, and a lithium-ion conductive polymer (preferably the polyether polymer of the present invention). That is, the crosslinked film is a crosslinked film of a composition comprising a lithium salt compound, an ether compound, and a lithium-ion conductive polymer (preferably the polyether polymer of the present invention). The lithium salt compound, ether compound, lithium-ion conductive polymer (preferably the polyether polymer of the present invention), and the polymer electrolyte for lithium-ion secondary batteries of the present invention are as described above.

[0131] A reaction initiator and a crosslinking aid may be added to the polymer electrolyte for lithium-ion secondary batteries of the present invention to form a crosslinked film. Examples of reaction initiators include thermal reaction initiators and photoreaction initiators. These may be used individually or in combination of two or more types.

[0132] As a thermal reaction initiator, a radical initiator selected from organic peroxides, azo compounds, etc., is used. As organic peroxides, those commonly used for crosslinking applications such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters are used, and as azo compounds, those commonly used for crosslinking applications such as azonitrile compounds, azoamide compounds, and azoamidine compounds are used. The amount of radical initiator added varies depending on the type, but is usually in the range of 0.1 to 10 parts by mass per 100 parts by mass of ion-conducting polymer.

[0133] Radical initiators such as alkylphenones, benzophenones, acylphosphine oxides, titanocenes, triazines, bisimidazoles, and oxime esters are used as photoinitiators. The amount of these radical polymerization initiators added varies depending on the type, but is usually in the range of 0.01 to 5.0 parts by mass per 100 parts by mass of the ion-conducting polymer.

[0134] As crosslinking aids, ethylene glycol diacrylate, ethylene glycol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, allyl acrylate, diallyl maleate, triallyl isocyanurate, maleimide, phenyl maleimide, maleic anhydride, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane can be used as desired. These may be used alone or in combination of two or more types.

[0135] The polymer electrolyte for lithium-ion secondary batteries of the present invention may contain organic solvents. Examples of organic solvents include toluene, xylene, benzene, acetonitrile, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and THF (tetrahydrofuran). These may be used individually or in combination of two or more.

[0136] One method for producing a crosslinked film is to mix and dissolve the polymer electrolyte for lithium-ion secondary batteries of the present invention in an organic solvent to form a composition, cast the composition onto a substrate (e.g., a PET film or a Teflon® plate), remove the solvent, and then produce a crosslinked film by heating or irradiation with active energy rays such as ultraviolet light. Alternatively, a crosslinked film can also be produced by directly casting the composition onto the surface of a solid electrolyte layer.

[0137] The thickness of the crosslinked film is preferably in the range of 0.1 μm to 200 μm, and more preferably in the range of 0.5 μm to 100 μm.

[0138] In the secondary battery of the present invention, the crosslinked film is preferably a crosslinked film using the polymer electrolyte for lithium-ion secondary batteries of the present invention. However, the crosslinked film may also be a crosslinked film using a composition containing an ion-conducting polymer containing a lithium salt compound other than the polymer electrolyte for lithium-ion secondary batteries of the present invention.

[0139] <<Specific Configuration of Lithium-ion Secondary Battery>> Examples of the laminated configuration of the secondary battery of the present invention include the following configurations. It is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention as the solid electrolyte layer. It is also preferable that the crosslinked film is a crosslinked film using the polymer electrolyte for lithium-ion secondary batteries of the present invention. Laminated configuration in which the positive electrode, solid electrolyte layer, and negative electrode are laminated in order; Laminated configuration in which the positive electrode, crosslinked film, and negative electrode are laminated in order; Laminated configuration in which the positive electrode, crosslinked film, solid electrolyte layer, crosslinked film, and negative electrode are laminated in order; Laminated configuration in which the positive electrode, solid electrolyte layer, crosslinked film, and negative electrode are laminated in order; Laminated configuration in which the positive electrode, crosslinked film, solid electrolyte layer, and negative electrode are laminated in order; Laminated configuration in which the positive electrode, solid electrolyte layer, crosslinked film, and negative electrode are laminated in order.

[0140] In the secondary battery of the present invention, it is preferable that the solid electrolyte layer and the crosslinked film using the polymer electrolyte for lithium-ion secondary batteries of the present invention are in contact. Since the crosslinked film is a crosslinked body of the polymer electrolyte for lithium-ion secondary batteries of the present invention, it has high lithium-ion conductivity and high flexibility compared to inorganic materials. Therefore, the contact area between the crosslinked film and the solid electrolyte layer is increased, and as a result, the interfacial resistance of the solid electrolyte layer is effectively reduced, and it is believed that the secondary battery of the present invention exhibits excellent charge and discharge characteristics. In addition, in the secondary battery of the present invention, it is also preferable that the crosslinked film is in contact with the electrode material layer of the electrode, and it is also preferable that the crosslinked film is in contact with both the electrode material layer and the solid electrolyte layer.

[0141] The secondary battery of the present invention comprises at least a positive electrode, a negative electrode, and a solid electrolyte layer. As described above, it is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention as the solid electrolyte of any of the layers. Furthermore, as described above, if the secondary battery of the present invention comprises a crosslinked film, it is preferable to use a crosslinked film using the polymer electrolyte for lithium-ion secondary batteries of the present invention as the crosslinked film.

[0142] While known materials can be used for both the positive and negative electrodes, examples of electrodes include those that have an electrode material layer, i.e., a positive electrode material layer or a negative electrode material layer, on the current collector.

[0143] Known current collectors can be used for the positive and negative electrodes. Specifically, for the positive electrode, metals such as aluminum, nickel, stainless steel, gold, platinum, and titanium can be used as current collectors. For the negative electrode, metals such as copper, nickel, stainless steel, gold, platinum, and titanium can be used as current collectors.

[0144] Furthermore, the positive electrode material layer and the negative electrode material layer each contain at least a positive electrode active material and a negative electrode active material, and may also contain a conductive additive, a binder, and a thickener. If necessary, they may also contain the aforementioned inorganic solid electrolyte or the composite solid electrolyte for lithium-ion secondary batteries of the present invention.

[0145] The positive electrode active material used in this invention is LiMO ２ LiM ２ O ４ Li ２ MO ３ LiMEO ４ This is a lithium metal-containing composite oxide powder having one of the following compositions: Here, M mainly consists of a transition metal and contains at least one of Co, Mn, Ni, Cr, Fe, and Ti. While M consists of a transition metal, other elements such as Al, Ga, Ge, Sn, Pb, Sb, Bi, Si, P, and B may also be added. E contains at least one of P and Si. The particle size of the positive electrode active material is preferably 50 μm or less, and more preferably 20 μm or less. These active materials are 3V(vs.Li / Li) ＋ It has an electromotive force of ) or greater.

[0146] Specific examples of positive electrode active materials include lithium cobalt oxide, lithium nickel oxide, nickel / cobalt / lithium manganese oxide (ternary system), spinel-type lithium manganese oxide, and lithium iron phosphate.

[0147] The negative electrode active material used in this invention is either a carbon material (natural graphite, artificial graphite, amorphous carbon, etc.) having a structure (intercalary compound) capable of intercalating and releasing alkali metal ions such as lithium ions, or a metal such as lithium, aluminum-based compounds, tin-based compounds, silicon-based compounds, or titanium-based compounds capable of intercalating and releasing alkali metal ions such as lithium ions. In the case of a powder, the particle size is preferably 10 nm to 100 μm, and more preferably 20 nm to 20 μm. It may also be used as a mixed active material of metal and carbon material.

[0148] When using conductive additives, known conductive additives can be used, including graphite, furnace black, acetylene black, conductive carbon black such as Ketjen black, carbon fibers such as carbon nanotubes, or metal powders. One or more of these conductive additives may be used.

[0149] As a binder, one or more compounds selected from fluororesins such as PVDF, fluororubber, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber, acrylic polymers, and vinyl polymers can be used. These binders are added in amounts of 5 parts by mass or less, more preferably 3 parts by mass or less, for example, 0.01 to 2 parts by mass, relative to 100 parts by mass of the active material.

[0150] Specific examples of thickeners include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose and their salts (alkali metal salts such as sodium salts, ammonium salts), polyvinyl alcohol, polyacrylates, polyethylene oxide, etc. One or more of these thickeners may be used. These thickeners are added in amounts of 5 parts by mass or less, more preferably 3 parts by mass or less, for example, 0.01 to 2 parts by mass, relative to 100 parts by mass of the active material. Furthermore, if the viscosity of the coating solution is low, a thickener can be used in combination.

[0151] The method for manufacturing the positive electrode and negative electrode, which comprise a current collector and positive electrode material layer and negative electrode material layer, is not particularly limited and general methods can be used. For example, a paste (coating liquid) of the positive electrode material and negative electrode material, consisting of a positive electrode active material or negative electrode active material, a conductive additive, a binder, an organic solvent such as butyl butyrate, and a thickener if necessary, is uniformly applied to the surface of the current collector to an appropriate thickness using methods such as the doctor blade method or the silkscreen method.

[0152] For example, in the doctor blade method, negative electrode active material powder, positive electrode active material powder, conductive additive, binder, etc., are dispersed in an organic solvent to form a slurry, which is then applied to a metal electrode substrate. After application, the slurry is uniformly spread to an appropriate thickness using a blade with a predetermined slit width. After the active material is applied, the electrodes are dried to remove excess organic solvent, for example, by using hot air at 100°C or under reduced pressure at 80°C. After drying, the electrodes are manufactured by press molding using a press device.

[0153] The method for manufacturing the secondary battery of the present invention is not particularly limited, and it consists of at least a positive electrode, a negative electrode, and a solid electrolyte, and is manufactured by a known method. For example, in the case of a coin-type lithium-ion battery, the positive electrode, solid electrolyte, and negative electrode are inserted into an outer casing. Then, the sealing body is joined to the casing by tab welding or the like, the sealing body is sealed, and the casing is crimped to obtain a rechargeable battery. The shape of the battery is not limited, but examples include coin-type, cylindrical, and sheet-type batteries, and a structure in which two or more batteries are stacked is also possible.

[0154] The secondary battery of the present invention is preferably an all-solid-state battery. This makes it possible to create a secondary battery with higher safety.

[0155] The polymer electrolyte for lithium-ion secondary batteries, the composite solid electrolyte for lithium-ion secondary batteries, and the lithium-ion secondary batteries of the present invention can suppress side reactions with sulfide-based solid electrolytes and have high lithium-ion conductivity, making them useful in battery storage systems for vehicles such as electric vehicles and hybrid vehicles, battery storage systems for household power storage, and battery storage systems for electronic devices such as mobile phones and personal computers.

[0156] The present invention will be specifically described by examples and comparative examples. However, the present invention is not limited to these. In the event of any discrepancy between the descriptions in the text and the descriptions in the tables, the descriptions in the tables shall prevail.

[0157] [Synthesis Example 1] 100 parts by mass of 1-chloro-4-methoxybutane and 81 parts by mass of potassium hydroxide were added to a flask for the synthesis of 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)), and the mixture was stirred at 100°C for 1 hour. While maintaining stirring, 235 parts by mass of 4-methoxybutanol were added dropwise, and after the addition was complete, the reaction was carried out at 120°C for 20 hours. After the reaction was complete, water was added to obtain the organic layer. The obtained organic layer was concentrated and then purified by vacuum distillation to obtain 101 parts by mass of 1-methoxy-4-(4-methoxybutoxy)butane.

[0158] [Synthesis Example 2] 8 parts by mass of 1,3-propanediol, 17.7 parts by mass of potassium hydroxide, and 82.1 parts by mass of dimethyl sulfoxide were added to a flask for the synthesis of 2,6,10,14-tetraoxapentadecane (formula (4-4)), and the mixture was stirred at room temperature for 1 hour. While maintaining stirring, 48.3 parts by mass of 1-bromo-3-methoxypropane was added dropwise, and the reaction was carried out for 20 hours after the addition was complete. After the reaction was complete, water was added, and the mixture was extracted twice with toluene. The resulting organic layer was concentrated and then purified by vacuum distillation to obtain 8.4 parts by mass of 2,6,10,14-tetraoxapentadecane.

[0159] [Synthesis Example 3] 10 parts by mass of 1,4-butanediol, 18.7 parts by mass of potassium hydroxide, and 86.7 parts by mass of dimethyl sulfoxide were added to a flask for the synthesis of 2,6,11,15-tetraoxahexadecane (formula (4-5)), and the mixture was stirred at room temperature for 1 hour. While maintaining stirring, 51 parts by mass of 1-bromo-3-methoxypropane were added dropwise, and the reaction was carried out for 20 hours after the addition was complete. After the reaction was complete, water was added, and the mixture was extracted twice with toluene. The resulting organic layer was concentrated and purified by vacuum distillation to obtain 11.4 parts by mass of 2,6,11,15-tetraoxahexadecane.

[0160] [Synthesis Example 4] 30 parts by mass of trimethylolpropane, 76 parts by mass of potassium hydroxide, and 350 parts by mass of dimethyl sulfoxide were added to a flask for the synthesis of 1-ethoxy-2,2-bis(ethoxymethyl)butane (formula (5-6)), and the mixture was stirred at room temperature for 1 hour. While maintaining stirring, 210 parts by mass of iodoethane was added dropwise, and the reaction was carried out for 20 hours after the addition was complete. After the reaction was complete, water was added, and the mixture was extracted twice with toluene. The resulting organic layer was concentrated and then purified by vacuum distillation to obtain 27.9 parts by mass of 1-ethoxy-2,2-bis(ethoxymethyl)butane.

[0161] [Synthesis Example 5] 20 parts by mass of trimethylolpropane, 50.2 parts by mass of potassium hydroxide, and 232.9 parts by mass of dimethyl sulfoxide were added to a flask for the synthesis of 7-ethyl-((2-methoxyethoxy)methyl)-2,5,9,12-tetraoxatridecane (formula (5-9)), and the mixture was stirred at room temperature for 1 hour. While maintaining stirring, 93.2 parts by mass of 1-bromo-2-methoxyethane was added dropwise, and the reaction was carried out for 20 hours after the addition was complete. After the reaction was complete, water was added, and the mixture was extracted twice with toluene. The obtained organic layer was concentrated and then purified by vacuum distillation to obtain 21.1 parts by mass of 7-ethyl-((2-methoxyethoxy)methyl)-2,5,9,12-tetraoxatridecane.

[0162] The structures of the obtained ether compounds are summarized below, along with the results of their chemical structure identification (NMR).

[0163]

[0164]

[0165]

[0166]

[0167]

[0168] [Synthesis Example 6] To a flask for the synthesis of cyclic ether compound 1 (MBOx), 320 parts by mass of 3-ethyl-3-oxetane methanol and 694 parts by mass of potassium hydroxide were added, and the solvent was added. The mixture was stirred at room temperature for 1 hour. The reaction mixture was cooled to 10°C, and while maintaining stirring, 967 parts by mass (2.1 equivalents) of 1-bromo-4-methoxybutane were added dropwise. After the addition was complete, the reaction was carried out for 44 hours. Subsequently, an oil-water separation operation was performed, and the resulting organic layer was concentrated to obtain 420 parts by mass of cyclic ether compound 1 (MBOx).

[0169] [Synthesis Example 7] Synthesis of Cyclic Ether Compound 2 (MPOx) The synthesis was carried out in the same manner as in Synthesis Example 6, except that 1-bromo-4-methoxybutane was replaced with 1-bromo-3-methoxypropane, to obtain Cyclic ether compound 2 (MPOx).

[0170] [Synthesis Example 8] Synthesis of cyclic ether compound 3 (AllOx) The synthesis was carried out in the same manner as in Synthesis Example 6, except that 1-bromo-4-methoxybutane was replaced with allyl bromide, to obtain cyclic ether compound 3 (AllOx).

[0171] The structures of the obtained cyclic ether compounds are summarized below, along with the results of their chemical structure identification (NMR).

[0172]

[0173]

[0174]

[0175] [Synthesis Example 9] Synthesis of Polymerization Catalyst for Polyether Polymers 10 parts by mass of tributyltin chloride and 35 parts by mass of tributyl phosphate were placed in a three-necked flask equipped with a stirrer, thermometer, and distillation apparatus, and heated at 250°C for 20 minutes while stirring under a nitrogen stream. The distillate was removed by distillation, and a solid condensation material was obtained as the residue. This was used as a polymerization catalyst in the following polymerization examples.

[0176] [Polymerization Example 1] Polymerization of Polyether Polymer 1 (P(PO / EO / AGE)) The inside of a 3 L glass four-necked flask was purged with nitrogen, and 1.0 part by mass of the polymerization catalyst shown in Synthesis Example 9, 16.8 parts by mass of ethylene oxide (EO) adjusted to a moisture content of 10 ppm or less, 53.8 parts by mass of propylene oxide (PO), 5.4 parts by mass of allyl glycidyl ether (AGE), 0.12 parts by mass of tert-butanol, and 333 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 24 parts by mass of ethylene oxide were added sequentially. The polymerization temperature at this time was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was stopped by adding methanol. After removing Polyether Polymer 1 by decantation, it was dried at 25°C under normal pressure for 24 hours, and then at 40°C under reduced pressure for 10 hours to obtain Polyether Polymer 1.

[0177] [Polymerization Example 2] Polymerization of Polyether Polymer 2 (P(BO / EO / AGE)) The inside of a 3 L glass four-necked flask was purged with nitrogen, and 1.0 part by mass of the polymerization catalyst shown in Production Example 2, 14.9 parts by mass of ethylene oxide adjusted to a moisture content of 10 ppm or less, 59.1 parts by mass of 1,2-butylene oxide (BO), 4.8 parts by mass of allyl glycidyl ether, 0.12 parts by mass of tert-butanol, and 333 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 21.2 parts by mass of ethylene oxide were added sequentially. The polymerization temperature at this time was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was stopped by adding methanol. After removing Polyether Polymer 2 by decantation, it was dried at 25°C under normal pressure for 24 hours, and then at 40°C under reduced pressure for 10 hours to obtain Polyether Polymer 2.

[0178] [Polymerization Example 3] Polymerization of polyether polymer 3 (P(MBOx / AllOx)) 98.4 parts by mass of cyclic ether compound 1 (MBOx), 1.6 parts by mass of cyclic ether compound 3 (AllOx), and 1,2-dichloroethane as a solvent were added, and the mixture was cooled to 0°C while stirring. BF was added as a polymerization initiator while maintaining the temperature. ３ ・Et ２1.6 parts by mass of oxygen were added over 5 minutes to achieve a total composition of 2 mol% of the polyether polymer, and the polymerization reaction was carried out for a further 2 hours. A 4 M NaCl / 1 M NaOH aqueous solution was added to stop the reaction, and oil-water separation was performed. Subsequently, the mixture was purified by reprecipitation and vacuum-dried at 50°C to obtain polyether polymer 3.

[0179] [Polymerization Example 4] Polymerization of polyether polymer 4 (P(MBOX)) 100 parts by mass of cyclic ether compound 1 (MBOX) and 1,2-dichloroethane as a solvent were added and cooled to 0°C while stirring. BF was added as a polymerization initiator while maintaining the temperature. ３ ・Et ２ 1.6 parts by mass of oxygen were added over 5 minutes to achieve a total composition of 2 mol% of the polyether polymer, and the polymerization reaction was carried out for a further 2 hours. A 4 M NaCl / 1 M NaOH aqueous solution was added to stop the reaction, and oil-water separation was performed. Subsequently, the mixture was purified by reprecipitation and vacuum-dried at 50°C to obtain polyether polymer 4.

[0180] [Polymerization Example 5] Polymerization of polyether polymer 5 (P(MPOx)) 100 parts by mass of cyclic ether compound 2 (MPOx) and 1,2-dichloroethane as a solvent were added and cooled to 0°C while stirring. BF was added as a polymerization initiator while maintaining the temperature. ３ ・Et ２ 1.6 parts by mass of oxygen were added over 5 minutes to achieve a total composition of 2 mol% of the polyether polymer, and the polymerization reaction was carried out for a further 2 hours. A 4 M NaCl / 1 M NaOH aqueous solution was added to stop the reaction, and oil-water separation was performed. Subsequently, the mixture was purified by reprecipitation and vacuum-dried at 50°C to obtain polyether polymer 5.

[0181] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the obtained polyether polymer were measured. The results are shown in Table 1. The content of each unit shown in Table 1 was calculated from the NMR spectrum.

[0182] <Weight-average molecular weight (Mw), number-average molecular weight (Mn)> The molecular weight of the polyether polymers obtained in polymerization examples 1 to 5 was measured in polystyrene equivalent using tetrahydrofuran (THF) gel permeation chromatography (GPC). Based on the measurement results, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were calculated. For the measurements, a Shimadzu LC-2030 (RID-20A) and four linked GPC columns KF-801, KF-803L, KF-806L, and KF-807L from Resonaq Corporation were used. The flow rate was 1.0 mL / min, the concentration was 10 mg of polymer / 8 mL of THF, the injection volume was 100 μL, and the column temperature was 40°C.

[0183]

[0184] [Example 1] (Polymer electrolyte 1) 100 parts by mass of P(PO / EO / AGE) obtained in Polymerization Example 1, 483 parts by mass of 2,6,10,14-tetraoxapentadecane (formula (4-4)) from Synthesis Example 2 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ Polymer electrolyte 1 was prepared by stirring and mixing 233 parts by mass of N, 17 parts by mass of trimethylolpropane trimethacrylate as a crosslinking aid, and 2 parts by mass of Percadox 16 (manufactured by Nurion, compound name: bis(4-tert-butylcyclohexyl)peroxydicarbonate) as a thermal reaction initiator.

[0185] [Examples 2-8] (Polymer electrolytes 2-8) Polymer electrolytes 2-8 were prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 2.

[0186] [Example 9] (Polymer Electrolyte 9) Polymer electrolyte 9 was prepared in the same manner as in Example 1, except that 100 parts by mass of P(MBOX / AllOx) obtained in Polymerization Example 3 was used, 458 parts by mass of 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)) from Synthesis Example 1 was used as the ether compound, 2 parts by mass of Karenz MT BD-1 (manufactured by Resonaq, compound name: 1,4-bis(3-mercaptobutyryloxy)butane) was used as a crosslinking aid, and 1 part by mass of Irgacure 1173 (manufactured by BASF, compound name: 2-hydroxy-2-methyl-1-phenylpropanone) was used as the photoreaction initiator.

[0187] [Example 10] (Polymer electrolyte 10) 100 parts by mass of P(MBOX / AllOx) obtained in Polymerization Example 3, 400 parts by mass of 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)) from Synthesis Example 1 as an ether compound, 100 parts by mass of 7-ethyl-((2-methoxyethoxy)methyl)-2,5,9,12-tetraoxatridecane (formula (5-9))) from Synthesis Example 5, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 10 was prepared by stirring and mixing 233 parts by mass of N.

[0188] [Examples 11, 12] (Polymer electrolytes 11, 12) Polymer electrolytes 11 and 12 were prepared in the same manner as in Example 10, except that the composition was changed as shown in Table 2.

[0189] [Example 13] (Polymer electrolyte 13) 100 parts by mass of polymethyl methacrylate (PMMA, weight-average molecular weight 800,000, manufactured by Tokyo Chemical Industry Co., Ltd.), 500 parts by mass of 1-ethoxy-2,2-bis(ethoxymethyl)butane (formula (5-6)) from Synthesis Example 4 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 13 was prepared by stirring and mixing 233 parts by mass of N.

[0190] [Example 14] (Polymer electrolyte 14) 100 parts by mass of polypropylene carbonate (PPC, weight-average molecular weight 50,000, manufactured by Sigma-Aldrich), 400 parts by mass of 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)) from Synthesis Example 1 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ Polymer electrolyte 14 was prepared by stirring and mixing 474 parts by mass of N.

[0191] [Example 15] (Polymer electrolyte 15) 100 parts by mass of polycaprolactone (PCL, weight-average molecular weight 80,000, manufactured by Sigma-Aldrich), 400 parts by mass of 1-methoxy-4-(4-methoxybutoxy)butane (formula (4-3)) from Synthesis Example 1 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 15 was prepared by stirring and mixing 472 parts by mass of N.

[0192] [Example 16] (Polymer electrolyte 16) 100 parts by mass of an anionic functional group-containing polymer (EK02 0103, manufactured by Polykey), 500 parts by mass of 1-ethoxy-2,2-bis(ethoxymethyl)butane (formula (5-6)) from Synthesis Example 4 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 16 was prepared by stirring and mixing 233 parts by mass of N.

[0193] [Example 17] (Polymer electrolyte 17) 100 parts by mass of polyvinylidene-co-hexafluoropropylene (PVDF-HFP, KYNAR FLEX 2500-20, Arkema), 500 parts by mass of 1-ethoxy-2,2-bis(ethoxymethyl)butane (formula (5-6)) from Synthesis Example 4 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 17 was prepared by stirring and mixing 233 parts by mass of N.

[0194] [Comparative Example 1] (Polymer Electrolyte 18) 100 parts by mass of P(MBOx / AllOx) obtained in Polymerization Example 3, 483 parts by mass of dibutyl ether as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 18 was prepared by stirring and mixing 233 parts by mass of N, 17 parts by mass of trimethylolpropane trimethacrylate as a crosslinking aid, and 2 parts by mass of Percadox 16 as a thermal reaction initiator.

[0195] [Comparative Example 2] (Polymer Electrolyte 19) 100 parts by mass of polyethylene oxide (PEO, weight-average molecular weight 20,000, manufactured by Fujifilm Wako Pure Chemical Industries) as the polyether polymer, 204 parts by mass of tetraglyme as the ether compound, and Li(CF) as the lithium salt compound. ３ SO ２ ) ２ A polymer electrolyte 19 was prepared by stirring and mixing 113 parts by mass of N.

[0196] [Comparative Example 3] 100 parts by mass of maleic anhydride graft SEBS (ToughTec M1943, molecular weight 50,000, manufactured by Asahi Kasei), 500 parts by mass of 1-ethoxy-2,2-bis(ethoxymethyl)butane (formula (5-6)) from Synthesis Example 4 as an ether compound, and Li(CF) as a lithium salt compound. ３ SO ２ ) ２ Although 230 parts by mass of N were stirred and mixed, the polymer was not compatible with the ether-based compound, and a polymer electrolyte could not be prepared.

[0197] [Degradation Evaluation of Sulfide Solid Electrolytes] (Examples 1-9, Comparative Example 1) Polymer electrolytes 1-9 and 18 were each coated onto a SUS spacer, and polymer electrolyte crosslinked films (thickness 100 μm) were fabricated by heat treatment in an oxygen-blocking environment. Polymer electrolyte 9, which used a photoreaction initiator, was exposed to UV light at a wavelength of 365 nm to produce a polymer electrolyte crosslinked film (thickness 100 μm). This crosslinked film was bonded to an argyrodite-type sulfide solid electrolyte (manufactured by NEI, Li6PS5Cl) pellet to produce a composite of sulfide solid electrolyte and polymer electrolyte crosslinked material, which was then heat-treated at 60°C for one week. The sulfide solid electrolyte from the above composite was filled into a solid NMR sample tube, and a 31P-NMR test was performed using a nuclear magnetic resonance spectrometer (NMR). (Examples 10-17, Comparative Example 2) Polymer electrolytes 10-17 and 19 were each dissolved in isobutyronitrile to a solid content concentration of 10% by mass to prepare polymer electrolyte solutions. 0.4 parts by mass of argyrodite-type sulfide solid electrolyte (NEI Corporation, Li6PS5Cl) and 1.0 part by mass of the polymer electrolyte solution (polymer electrolyte: 0.1 parts by mass) were added and mixed. The solvent was removed by vacuum heating and drying to prepare a composite of the sulfide solid electrolyte and the polymer electrolyte. The composite was packed into a solid NMR sample tube and subjected to heat treatment at 60°C for one week. A 31P-NMR test was performed using a nuclear magnetic resonance spectrometer (NMR) under the same test conditions as above. (31P-NMR test) Measurements were performed using an NMR spectrometer (spectrometer name: ECA400WB, JEOL Ltd.). As an evaluation method, resistance was assessed by checking for the presence or absence of spectra derived from PS43- units contained in the sulfide solid electrolyte and spectra derived from P2S74- units generated by the decomposition reaction of the sulfide solid electrolyte. A result of ○ indicated that the spectra generated by the decomposition reaction of the sulfide solid electrolyte were not detected, while a × indicated that the spectra generated by the decomposition reaction of the sulfide solid electrolyte were detected. A ○ result indicates that side reactions with sulfide-based solid electrolytes can be suppressed. Measurement temperature: Room temperature. Rotation speed: 10 kHz. Number of integrations: 8. Repeat waiting time: 2,000 seconds. Chemical shift standard substance: Ammonium dihydrogen phosphate (1 ppm).

[0198] [Evaluation of Ionic Conductivity of Polymer (Polyether) Electrolytes] <Fabrication of SUS Blocking Cells> (Examples 1-9, Comparative Example 1) Polymer electrolytes 1-9 and 18 were each coated onto a SUS spacer, and a polymer electrolyte crosslinked film (film thickness 100 μm) was fabricated by heat treatment with oxygen blocked off. A SUS spacer was then attached to the counter electrode to fabricate a SUS blocking cell. Polymer electrolyte 9, which used a photoreaction initiator, was exposed to UV light with a wavelength of 365 nm, and the same procedure as above was performed. A SUS spacer was then attached to the counter electrode to fabricate a SUS blocking cell. (Examples 10-17, Comparative Example 2) Polymer electrolytes 10-17 and 19 were each coated onto a SUS spacer to fabricate a polymer electrolyte film (film thickness 100 μm), and a SUS spacer was attached to the counter electrode to fabricate a SUS blocking cell.

[0199] <AC Impedance Test> An AC impedance test was performed using the SUS blocking cell prepared above and a potentiometer / galvanostat (device name: BioLogic SP-300). The resistance (Ω) of the polymer electrolyte was calculated from the diameter of the semicircular arc in the real axis direction obtained from the Cole-Cole plot. In addition, the ionic conductivity of the cell was calculated from the cell thickness and surface area using the following formula. The test temperature was 25°C. Measurements were performed with a voltage amplitude of 20 mV and a measurement frequency range of 7 MHz to 1 Hz. σ = 1 / R × (d / A) σ: Ionic conductivity of polymer electrolyte (S / cm) R: Resistance of polymer electrolyte (Ω) d: Thickness of polymer electrolyte (cm) A: Surface area of ​​polymer electrolyte (cm) ２ )

[0200] [Evaluation of Li ion transport fraction of polymer (polyether) electrolyte] <Preparation of evaluation cell> A polymer electrolyte was coated onto a Li foil, and a polymer electrolyte crosslinked film (film thickness 100 μm) was prepared by performing heat treatment and exposure treatment with oxygen blocked as needed. Subsequently, a Li foil was bonded to the counter electrode to prepare a Li symmetric cell. <Measurement of interfacial resistance before and after polarization (AC impedance test)> An AC impedance test was performed using the Li symmetric cell prepared above with a potentiometer / galvanostat apparatus. The interfacial resistance value was calculated from the size of the semicircle derived from the interfacial resistance obtained from the Cole-Cole plot. The test temperature was 25°C, and the measurement was performed with a voltage amplitude of 7 mV and a measurement frequency range of 7 MHz to 100 mHz. <Chronoamperometry test> After performing the AC impedance test, the open-circuit voltage (OCV) for 1 minute was measured, and then a chronoamperometry measurement was performed. The test temperature was 25°C. The measurement was performed with a DC voltage of 7 mV for a measurement time of 3 hours, and the initial current value and the steady-state current value after 3 hours were measured. <Calculation of Li ion transport fraction> Using the initial current value and steady-state current value obtained in the above test (measurement of interfacial resistance value before and after polarization and chronoamperometry test), the Li ion transport fraction can be calculated from the following formula: tLi+ = (Is × (V - I0 × R0)) / (I0 × (V - Is × Rs)) tLi+: Li ion transport fraction of polymer electrolyte I0: Initial current value of chronoamperometry test (mA) Is: Steady-state current value of chronoamperometry test (mA) R0: Interfacial resistance value before polarization (Ω) Rs: Interfacial resistance value after polarization (Ω) V: DC voltage (mV)

[0201] [Evaluation of Lithium Ion Conductivity] Lithium ion conductivity (lithium ion conductivity) can be determined by the product of the above-mentioned ionic conductivity and lithium ion transport fraction. If the lithium ion conductivity is 5 × 10⁻⁶ －６ A value of (S / cm) or higher was considered good. Lithium-ion conductivity = Ionic conductivity × Lithium-ion transport number

[0202]

[0203] Table 2 shows that the polymer electrolytes described in Examples 1 to 17, which contain at least lithium-ion conductive polymers (polyether polymers, polyacrylates, polycarbonates, polyesters, anionic functional group-containing polymers, and fluorine-based polymers from Polymerization Examples 1 to 5, containing at least 15 mol% or more of constituent units derived from alkylene oxides having alkyl groups in their side chains), ether compounds, and lithium salt compounds, can suppress side reactions with sulfide-based solid electrolytes and have high Li-ion conductivity.

[0204] The polymer electrolyte for lithium-ion secondary batteries, the composite solid electrolyte for lithium-ion secondary batteries, and the lithium-ion secondary batteries of the present invention can suppress side reactions with sulfide-based solid electrolytes even when sulfide-based solid electrolytes are used, and have high lithium-ion conductivity. Therefore, they can be usefully used in batteries for vehicles such as electric vehicles and hybrid vehicles, batteries for household power storage, and batteries for electronic devices such as mobile phones and personal computers.

Claims

1. A polymer electrolyte for a lithium ion secondary battery, comprising at least a lithium ion conductive polymer, an ether-based compound, and a lithium salt compound, wherein said ether-based compound is at least one selected from the group consisting of a linear ether-based compound represented by the following general formula (4) and a branched ether-based compound represented by the following general formula (5). (wherein, R ９ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms, or a group represented by -(CH ２ ) ｉ CH ２ O-R １０ ; R １０ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms; g, h, and i, which are the number of repetitions, are the same or different, and each is an integer of 1 to 3.) (wherein, R １１ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ ; R １２ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms, or -{(CH ２ ) ｋ CH ２ O} ｌ R １３ ; R １３ are the same or different, and each represents an alkyl group having 1 to 4 carbon atoms; m, which is the number of repetitions, is 0 or 1, and k and l are the same or different, and each is an integer of 1 to 3.) 2. The lithium-ion conductive polymer is at least one selected from the group consisting of polyether polymers, polyacrylates, polycarbonates, polyesters, fluorinated polymers, and polymers having anionic functional groups in their side chains, and the polyether polymer contains at least alkyl group-containing units which are constituent units derived from alkylene oxides having alkyl groups in their side chains, and the content of alkyl group-containing units is 15 mol% or more in 100 mol% of constituent units, according to claim 1, which is a polymer electrolyte for a lithium-ion secondary battery.

3. A composite solid electrolyte for a lithium-ion secondary battery, comprising a polymer electrolyte for a lithium-ion secondary battery according to claim 1 or 2 and an inorganic solid electrolyte.

4. A crosslinked film using a polymer electrolyte for lithium-ion secondary batteries according to claim 1 or 2.

5. A lithium-ion secondary battery using a polymer electrolyte for lithium-ion secondary batteries according to claim 1 or 2.

6. A lithium-ion secondary battery having a positive electrode, an electrolyte layer, and a negative electrode, wherein at least one of the positive electrode, electrolyte layer, and negative electrode is a composite solid electrolyte for lithium-ion secondary batteries as described in claim 3.

7. A lithium-ion secondary battery having a positive electrode, an electrolyte layer, a crosslinked film, and a negative electrode, wherein at least the crosslinked film is the crosslinked film described in claim 4.

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