Material for polymer electrolyte, polymer electrolyte, and electric storage element

Abstract

To provide a material for polymer electrolyte capable of forming a polymer electrolyte that can achieve an electric storage element with suppressed gas generation, a polymer electrolyte containing the material for polymer electrolyte, and an electric storage element containing the polymer electrolyte.SOLUTION: A material for polymer electrolyte is a compound containing a cyclic structure that is a Diels-Alder reaction product of a conjugated diene moiety of a conjugated diene compound and a cyclic dienophile moiety of a dienophile compound having the cyclic dienophile moiety.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polymer electrolyte material, a polymer electrolyte, and an electricity storage device. [Background technology]

[0002] Non-Patent Document 1 describes a self-repairable polymer binder formed by a reversible Diels-Alder reaction, which is used as a material for constituting a Si negative electrode. Non-Patent Document 1 describes that a compound having a 3D cross-linked polymer network is formed by adding 1,6-bismaleimide (BMI) as a cross-linking agent to furfurylamine-functionalized polyacrylic acid (FPAA) and performing a thermal Diels-Alder (DA) reaction using a click chemistry method, and that this is used as a binder for a Si negative electrode. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Rajeev KK, Jaebin Nam, Eunsoo Kim, Yeonho Kim, Tae-Hyun Kim, Electrochimica Acta, 364 (2020) 137311 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a polymer electrolyte material capable of forming a polymer electrolyte capable of realizing an electricity storage element in which gas generation is suppressed, a polymer electrolyte containing the polymer electrolyte material, and an electricity storage element containing the polymer electrolyte. [Means for solving the problem]

[0005] A polymer electrolyte material according to one aspect of the present invention is a compound containing a ring structure which is a Diels-Alder reaction product between a conjugated diene portion of a conjugated diene compound and a cyclic dienophile portion of a dienophile compound having a cyclic dienophile portion.

[0006] A polymer electrolyte material according to another aspect of the present invention is a compound having a structure represented by the following formula (1): [ka] (In the formula, element A may or may not be present, element A is O or C, and * represents a bond.)

[0007] A polymer electrolyte according to yet another aspect of the present invention includes the above-mentioned polymer electrolyte material.

[0008] An electricity storage element according to yet another aspect of the present invention includes a positive electrode, a negative electrode, and the above-described polymer electrolyte. Effect of the Invention

[0009] According to a polymer electrolyte material according to one aspect of the present invention, a polymer electrolyte capable of realizing an electricity storage element in which gas generation is suppressed can be formed.

[0010] According to the polymer electrolyte according to another aspect of the present invention, an electricity storage element in which gas generation is suppressed can be formed.

[0011] In the electric storage device according to another aspect of the present invention, gas generation is suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing the skeletal structure of a polymer electrolyte material according to Example 1. [Diagram 2] FIG. 2 is a diagram showing the skeletal structure of a polymer electrolyte material according to Comparative Example 1. [Diagram 3] FIG. 2 is a transparent perspective view showing one embodiment of an energy storage element. [Figure 4] 1 is a schematic diagram showing an embodiment of an energy storage device formed by assembling a plurality of energy storage elements; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First, the polymer electrolyte material disclosed in this specification will be described.

[0014] [1] A polymer electrolyte material according to one aspect of the present invention is a compound containing a ring structure which is a Diels-Alder reaction product between a conjugated diene portion of a conjugated diene compound and a cyclic dienophile portion of a dienophile compound having a cyclic dienophile portion.

[0015] According to the polymer electrolyte material described in the above [1], a polymer electrolyte can be formed that can realize an electricity storage element in which gas generation is suppressed.

[0016] [2] In the polymer electrolyte material according to the above [1], the conjugated diene moiety of the conjugated diene compound may be a furan ring.

[0017] According to the polymer electrolyte material described in the above [2], since the conjugated diene moiety is a furan ring, a compound containing a ring structure, which is a Diels-Alder reaction product, can be easily formed.

[0018] [3] In the polymer electrolyte material according to the above [1] or [2], the dienophile compound may have at least four cyclic dienophile moieties.

[0019] According to the polymer electrolyte material described in [3], since the dienophile compound has at least four cyclic dienophile moieties, the structure of the compound containing the ring structure, which is the Diels-Alder reaction product, can be made to have a uniform network structure. As a result, it is expected that the electrochemical reaction in the energy storage element using the polymer electrolyte material will be uniform.

[0020] [4] A polymer electrolyte material according to another aspect of the present invention is a compound having a structure represented by the following formula (1): [ka] (In the formula, element A may or may not be present, element A is O or C, and * represents a bond.)

[0021] According to the polymer electrolyte material described in the above item [4], a polymer electrolyte can be formed that can realize an electricity storage element in which gas generation is suppressed.

[0022] [5] In the polymer electrolyte material according to any one of [1] to [4] above, the polymer electrolyte material may have a repeating unit structure containing ether oxygen.

[0023] According to the polymer electrolyte material described in [5] above, since the polymer electrolyte material has a repeating unit structure containing an ether oxygen, the polymer electrolyte material can be made suitable as a polymer electrolyte.

[0024] [6] The polymer electrolyte material according to any one of [1] to [5] above may contain a sulfide bond.

[0025] According to the polymer electrolyte material described in [6] above, since the polymer electrolyte material contains a sulfide bond, it is possible to form a polymer electrolyte that can realize an energy storage element in which gas generation is further suppressed.

[0026] [7] A polymer electrolyte according to another aspect of the present invention comprises the polymer electrolyte material according to any one of the above [1] to [6].

[0027] According to the polymer electrolyte described in the above [7], it is possible to realize an electricity storage element in which gas generation is suppressed.

[0028] [8] An electricity storage element according to another aspect of the present invention includes a positive electrode, a negative electrode, and the polymer electrolyte described in [7] above.

[0029] According to the energy storage element described in [8] above, gas generation can be suppressed.

[0030] A polymer electrolyte material according to one embodiment of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiment.

[0031] ≪Materials for polymer electrolytes≫ A polymer electrolyte material according to one embodiment of the present invention is a compound containing a ring structure that is a Diels-Alder reaction product between a conjugated diene portion of a conjugated diene compound and a cyclic dienophile portion of a dienophile compound having a cyclic dienophile portion.

[0032] Here, the term "polymer electrolyte material" refers to a material that can be used to form a polymer electrolyte. A polymer electrolyte can be formed by including at least a carrier ion such as an alkali metal ion together with the polymer electrolyte material of the present invention.

[0033] For example, a polymer electrolyte can be formed as a composition containing the polymer electrolyte material of the present invention and an electrolytic solution. Also, a polymer electrolyte can be formed as a composition containing the polymer electrolyte material of the present invention and an electrolyte salt. Also, a polymer electrolyte can be formed by introducing a site capable of dissociating carrier ions into the polymer electrolyte material of the present invention.

[0034] <Conjugated diene compounds> The conjugated diene compound used in the polymer electrolyte material according to one embodiment of the present invention is not particularly limited, and may be any compound having at least one conjugated diene moiety.

[0035] The conjugated diene compound according to one embodiment may be linear or cyclic. The conjugated diene compound may have a substituent such as an alkyl group introduced into the conjugated diene skeleton. The alkyl group introduced may have, for example, 1 to 6 carbon atoms and may have any of a linear, branched, and cyclic structure.

[0036] The chain-like conjugated diene compound may be linear or branched. Examples of the chain-like conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and the like.

[0037] Examples of the cyclic conjugated diene moiety include a furan ring, a thiophene ring, a pyrrole ring, a cyclopentadiene ring, 1,3-butadiene, a thiophene-1-oxide ring, a thiophene-1,1-dioxide ring, a cyclopenta-2,4-dienone ring, a 2H-pyran ring, a cyclohex-1,3-diene ring, a 2H-pyran 1-oxide ring, a 1,2-dihydropyridine ring, a 2H-thiopyran-1,1-dioxide ring, a cyclohex-2,4-dienone ring, a pyran-2-one ring, and a structure derived from anthracene. These structures may further have substituents.

[0038] When the cyclic dienophile moiety of the dienophile compound having a cyclic dienophile moiety undergoes a Diels-Alder reaction, the reaction product has a ring structure without a crosslink when the conjugated diene compound is linear. On the other hand, when the conjugated diene compound is cyclic, the reaction product has a ring structure with a crosslink of the elements that constituted the ring.

[0039] From the viewpoint of more highly expressing the effects of the present invention, the conjugated diene compound preferably has a cyclic conjugated diene moiety. Further, from the viewpoint of the reactivity of the Diels-Alder reaction, the cyclic conjugated diene moiety is preferably a ring selected from a furan ring, a thiophene ring, a cyclopentadiene ring, a thiophene-1,1-dioxide ring, and anthracene. Among them, since the reactivity is high and the effects of the present invention are highly expressed, the conjugated diene moiety of the conjugated diene compound is particularly preferably a furan ring.

[0040] In addition, the conjugated diene compound used in the polymer electrolyte material according to one embodiment of the present invention preferably has at least two conjugated diene moieties. If the conjugated diene compound has at least two conjugated diene moieties, the polymer electrolyte material of the present invention containing a ring structure that is a Diels-Alder reaction product with a dienophile compound becomes a compound with a higher molecular weight, so that the structural stability is improved, and the polymer electrolyte material can be more suitable as a component of an electricity storage element.

[0041] The polymer electrolyte material according to one embodiment of the present invention has a specific ring structure. Therefore, in an energy storage element using a polymer electrolyte containing the polymer electrolyte material, when a component that causes gas generation is generated inside the energy storage element, the component is expected to be captured by the ring structure.

[0042] The conjugated diene compound used in the polymer electrolyte material according to one embodiment of the present invention is particularly preferably a compound having at least two furan rings as a conjugated diene moiety, such as difurfuryl sulfide, furfuryl disulfide, tri(2-furyl)phosphine, tri(3-furyl)phosphine sulfide, etc.

[0043] In particular, when the conjugated diene compound contains a sulfide bond, the polymer electrolyte material according to one embodiment of the present invention contains a sulfide bond. When the polymer electrolyte material contains a sulfide bond, the energy storage element using the polymer electrolyte containing the polymer electrolyte material can more effectively suppress gas generation. As a result, the effects of the present invention can be enjoyed to a greater extent.

[0044] Furthermore, the conjugated diene compound used in the polymer electrolyte material according to one embodiment of the present invention is not limited to a low molecular weight compound, and may be a high molecular weight compound, so long as it has at least one conjugated diene moiety in the compound.

[0045] When the conjugated diene compound is a polymer compound, the repeating unit is not particularly limited. Examples of the skeleton constituting the repeating unit include an ether skeleton, a siloxane skeleton, and a vinylidene fluoride skeleton.

[0046] When the conjugated diene compound is a polymer compound, the skeleton of the repeating unit is preferably an ether skeleton. The structure of the ether skeleton of the repeating unit is not particularly limited, but examples thereof include a polyethylene oxide structure, a branched polypropylene oxide structure, and a linear polypropylene oxide structure. Among them, a polyethylene oxide structure in which an oxyethylene group is a repeating unit is preferable.

[0047] <Dienophile compounds> The dienophile compound used in the polymer electrolyte material according to one embodiment of the present invention is not particularly limited as long as it has a cyclic dienophile moiety. The dienophile compound used in the polymer electrolyte material according to one embodiment of the present invention may have at least one cyclic dienophile moiety in the compound.

[0048] The compound having a cyclic dienophile moiety may be any compound containing a double bond or triple bond capable of reacting with a conjugated diene compound. The compound having a cyclic dienophile moiety preferably has a double bond, and may have a substituent such as an alkyl group introduced therein. The alkyl group may have 1 to 6 carbon atoms, and may have any of a linear, branched, and cyclic structure.

[0049] Examples of the cyclic dienophile moiety include groups having a structure derived from styrene, maleic anhydride, maleic acid, maleic acid monoesters, maleic acid diesters, maleimides, fumaric acid, itaconic acid, acrolein, acrylic acid, methacrylic acid, acryloyl chloride, methacryloyl chloride, acrylic acid esters, methacrylic acid esters, 1,4-benzoquinone, 1,4-naphthoquinone, 2,5-dihydrofurans, and pyrrolines, etc. These may have a substituent at the double bond or at a portion adjacent to the double bond.

[0050] Among these, the cyclic dienophile moiety is preferably a maleimide group, since it has high reactivity and can maximize the effects of the present invention.

[0051] The dienophile compound used in the polymer electrolyte material according to one embodiment of the present invention preferably has a plurality of cyclic dienophile moieties. The cyclic dienophile moiety is a moiety that is subjected to the Diels-Alder reaction when preparing the polymer electrolyte material according to one embodiment of the present invention. Therefore, if the dienophile compound has a plurality of reactive moieties, the polymer electrolyte material of the present invention is more easily polymerized or has a crosslinked structure. As a result, the effect of the present invention can be enjoyed to a greater extent.

[0052] Since the polymer electrolyte material according to one embodiment of the present invention has a specific ring structure, when a component that causes gas generation is generated inside an electricity storage element using a polymer electrolyte containing the polymer electrolyte material, the component is expected to be captured by the ring structure, and as a result, an increase in the volume of the electricity storage element due to the gas generated inside the electricity storage element can be suppressed.

[0053] The dienophile compound preferably has at least four cyclic dienophile moieties. If the dienophile compound has at least four cyclic dienophile moieties, the polymer electrolyte material of the present invention containing a ring structure that is a Diels-Alder reaction product can be made into a compound having a uniform network structure. As a result, when a polymer electrolyte is formed using the polymer electrolyte material, the polymer concentration in the system can be reduced.

[0054] As a dienophile compound having four cyclic dienophile moieties, for example, a dienophile compound having one cyclic dienophile moiety on each branch of a compound having a four-branch structure can be mentioned. A dienophile compound having four cyclic dienophile moieties can also be obtained as a commercial product, for example, 4arm-PEG20K-Maleimide (Mw=20,000) (Sigma-Aldrich). 4arm-PEG20K-Maleimide is a compound having a maleimide group at the end of each branch.

[0055] In addition, the dienophile compound used in the polymer electrolyte material according to one embodiment of the present invention is not limited to a low molecular weight compound, and may be a polymer compound as long as it has at least one cyclic dienophile moiety in the compound.

[0056] When the dienophile compound is a polymer compound, the repeating unit is not particularly limited. Examples of the skeleton that constitutes the repeating unit include an ether skeleton, a siloxane skeleton, and a vinylidene fluoride skeleton.

[0057] When the dienophile compound is a polymer compound, the skeleton of the repeating unit is preferably an ether skeleton.The structure of the skeleton of the repeating unit is not particularly limited, but may be, for example, a polyethylene oxide structure, a branched polypropylene oxide structure, or a linear polypropylene oxide structure.Among them, a polyethylene oxide structure in which an oxyethylene group is a repeating unit is preferred.

[0058] <Ring structure of Diels-Alder reaction product> A polymer electrolyte material according to one embodiment of the present invention is a compound containing a ring structure which is a Diels-Alder reaction product between the conjugated diene portion of the above-mentioned conjugated diene compound and the cyclic dienophile portion of the above-mentioned dienophile compound having a cyclic dienophile portion.

[0059] As an example of the formation of a ring structure possessed by a polymer electrolyte material according to one embodiment of the present invention, reaction formula (A) by the Diels-Alder reaction between a conjugated diene compound having a furan ring as a conjugated diene moiety and a dienophile compound having a maleimide group as a cyclic dienophile moiety is shown below.

[0060] [ka]

[0061] The Diels-Alder reaction combines the furan ring, which was the conjugated diene moiety, with the maleimide group, which was the cyclic dienophile moiety, to form a compound with a new ring structure.

[0062] Such new ring structures include, for example, the ring structures of the following chemical formulas (2), (3), and (4).

[0063] [ka] (In chemical formula (2), * represents a bond.)

[0064] The ring structure represented by chemical formula (2) is the ring structure shown in the above chemical reaction formula (A), and is a ring structure that is a Diels-Alder reaction product of a conjugated diene compound having a furan ring as a conjugated diene moiety and a dienophile compound having a maleimide group as a cyclic dienophile moiety. The ring structure shown in chemical formula (2) has a bridge of oxygen (O), which was a constituent element of the furan ring.

[0065] [ka] (In chemical formula (3), * represents a bond.)

[0066] The ring structure represented by chemical formula (3) is a ring structure that is a Diels-Alder reaction product between a conjugated diene compound having a cyclopentadiene ring as a conjugated diene moiety and a dienophile compound having a maleimide group as a cyclic dienophile moiety. The ring structure shown in chemical formula (3) has a bridge of carbon (C), which was a constituent element of the cyclopentadiene ring.

[0067] [ka] (In chemical formula (4), * represents a bond.)

[0068] The ring structure represented by chemical formula (4) is a ring structure that is a Diels-Alder reaction product of a conjugated diene compound having butadiene as a conjugated diene moiety and a dienophile compound having a maleimide group as a cyclic dienophile moiety. The ring structure shown in chemical formula (4) is formed from butadiene, which is a chain-like conjugated diene, so it does not have a bridge like chemical formulas (2) and (3).

[0069] A polymer electrolyte material according to another embodiment of the present invention is a compound having a structure represented by the following formula (1). [ka] (In the formula, element A may or may not be present, element A is O or C, and * represents a bond.)

[0070] Examples of the ring structure of the above formula (1) include the ring structures of the above chemical formulas (2), (3), and (4).

[0071] <Structure other than the ring structure of the Diels-Alder reaction product> As long as the polymer electrolyte material according to one embodiment of the present invention has a ring structure which is the Diels-Alder reaction product, other molecular structures are not particularly limited.

[0072] (Repeating unit structure containing ether oxygen) The polymer electrolyte material according to one embodiment of the present invention preferably has a repeating unit structure containing ether oxygen. The polymer electrolyte material according to one embodiment of the present invention has a repeating unit structure containing ether oxygen, and thus can be a polymer electrolyte material suitable for use as a polymer electrolyte. That is, when the polymer electrolyte is solid, the polymer chain contains a structure having the property of coordinating with carrier ions, and therefore ion conduction in the polymer solid electrolyte is reliably expressed. In addition, when the polymer electrolyte is gel-like, the solvent retention is improved, and therefore even if the volume ratio of the polymer constituting the gel-like polymer electrolyte is low, the polymer electrolyte can have excellent structure retention.

[0073] The repeating unit structure containing ether oxygen may be contained in the conjugated diene compound to be subjected to the Diels-Alder reaction, in the dienophile compound, or in both.

[0074] The repeating unit structure containing ether oxygen is not particularly limited, but examples thereof include a polyethylene oxide structure, a branched polypropylene oxide structure, a linear polypropylene oxide structure, etc. Among these, a polyethylene oxide structure in which an oxyethylene group is a repeating unit is preferred.

[0075] (sulfide bond) The polymer electrolyte material according to one embodiment of the present invention preferably contains a sulfide bond. By containing a sulfide bond in the polymer electrolyte material, an energy storage element using a polymer electrolyte containing the polymer electrolyte material can more effectively suppress gas generation. As a result, the effects of the present invention can be enjoyed to a greater extent.

[0076] ≪Polymer electrolyte≫ A polymer electrolyte according to one embodiment of the present invention includes the polymer electrolyte material of the present invention. The polymer electrolyte according to one embodiment of the present invention may optionally include other components as long as it includes the polymer electrolyte material of the present invention.

[0077] The polymer electrolyte according to one embodiment of the present invention may be in the form of a gel or a solid. In particular, the polymer electrolyte is preferably in the form of a gel, since it can provide a polymer electrolyte with high ionic conductivity.

[0078] The other components contained in the polymer electrolyte according to one embodiment of the present invention are not particularly limited, and may be known materials contained in the polymer electrolyte constituting the storage element. When the polymer electrolyte according to one embodiment of the present invention is in a gel state, the other components may include, for example, a solvent or an electrolytic solution. When the polymer electrolyte according to one embodiment of the present invention is in a solid state, the other components may include, for example, an electrolyte salt or another ionic compound that shares a carrier ion with the polymer electrolyte material of the present invention.

[0079] <Solvent or electrolyte> When the polymer electrolyte according to one embodiment of the present invention contains a solvent or an electrolytic solution, the solvent or the electrolytic solution is impregnated into the polymer network of the polymer electrolyte material of the present invention.

[0080] By impregnating the polymer network of the polymer electrolyte material with a solvent or electrolytic solution, a polymer electrolyte having high ionic conductivity can be obtained.

[0081] The solvent or electrolyte contained in the polymer electrolyte according to one embodiment of the present invention is not particularly limited, and may be one that is commonly used in electrolytes for lithium secondary batteries. The electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt containing carrier ions such as alkali metal ions. The solvent contains, for example, a non-aqueous solvent.

[0082] (Non-aqueous solvent) Examples of non-aqueous solvents constituting the solvent or electrolyte include ether compounds, ester compounds, amide compounds, chain carbonate compounds, cyclic carbonate compounds, and nitrile compounds, and these can be used alone or in combination of two or more.

[0083] Among these, it is preferable to contain a chain carbonate compound, a cyclic carbonate compound, or a mixture thereof.

[0084] Examples of cyclic carbonate compounds include ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate.

[0085] Examples of the chain carbonate compound include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC).

[0086] In particular, cyclic carbonate compounds such as ethylene carbonate (EC) and propylene carbonate (PC) have a high dielectric constant and facilitate dissociation of the electrolyte salt in the polymer electrolyte. For this reason, a polymer electrolyte with high ionic conductivity can be obtained by appropriately mixing a low-viscosity, low-dielectric-constant chain carbonate compound such as ethyl methyl carbonate (EMC), diethyl carbonate (DEC), or dimethyl carbonate (DMC) with a generally high-viscosity cyclic carbonate compound.

[0087] Furthermore, by using fluoroethylene carbonate (FEC) containing fluorine atoms as the cyclic carbonate compound, it is possible to obtain an electricity storage element that exhibits excellent charge-discharge cycle performance and favorable high-rate discharge performance.

[0088] In addition, the non-aqueous solvent containing fluorine atoms forms a good coating, which gives the storage element excellent performance, but also generates gas due to decomposition. However, the polymer electrolyte containing the polymer electrolyte material of the present invention is expected to have the effect of capturing the components that cause gas generation, so that gas generation can be suppressed. Therefore, the polymer electrolyte material of the present invention can be used together with a non-aqueous solvent containing fluorine atoms to enjoy the effects of the present invention to a greater extent.

[0089] In addition, the electrolyte may contain known additives used in known electrolytes to improve the performance of the storage element, such as propane sultone (PS), ethylene sulfite (ES), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), tris(trimethylsilyl)phosphate (TMSP), tris(2,2,2-trifluoroethyl)phosphate (TFEP), and tris(trifluoroethyl)phosphite (TFEPi).

[0090] (Electrolyte salt) The electrolyte salt constituting the electrolytic solution is not particularly limited, and any known electrolyte salt can be used. Among them, an alkali metal salt is preferable, and a lithium salt is more preferable. The electrolyte salt may contain salts other than alkaline metal salts such as magnesium salts and onium salts.

[0091] The lithium salt is LiPF 6 , LiPO 2 F 2 , LiBF 4 , LiClO 4 , LiN(SO 2 F) 2 Inorganic lithium salts such as LiSO 3 CF 3 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiN(SO 2 CF 3 )(SO 2 C 4 F 9 ), LiC(SO 2 CF 3 ) 3 , LiC(SO 2 C 2 F 5 ) 3 and the like.

[0092] <Polymer compounds that serve as non-aqueous electrolytes> When the polymer electrolyte according to one embodiment of the present invention is in a solid state, the polymer electrolyte contains an electrolyte salt such as an alkali metal salt that supplies carrier ions, in addition to the polymer electrolyte material of the present invention, which is an essential component. The electrolyte salt such as an alkali metal salt may be in a state in which the anion portion is fixed to a polymer compound that becomes a non-aqueous electrolyte and is capable of dissociating carrier ions.

[0093] The polymer electrolyte according to one embodiment of the present invention may further contain, for example, a room temperature molten salt, an ionic liquid, or the like.

[0094] When the polymer electrolyte according to one embodiment of the present invention is in a solid state, the electrolyte salt contained in the polymer electrolyte is the same as the electrolyte salt constituting the above-mentioned electrolytic solution.

[0095] <Polymer compound for gelation> The polymer electrolyte of the present invention may further contain a polymer compound for gelling a solvent or an electrolytic solution in addition to the polymer electrolyte material according to one embodiment of the present invention. By further containing such a polymer compound, the polymer electrolyte can be made into a gel even in cases where gelling is insufficient using only the polymer electrolyte material of the present invention, which is an essential component of the polymer electrolyte of the present invention.

[0096] The polymer compound for gelling the polymer electrolyte is not particularly limited as long as it functions as a gelling agent. Examples of such polymer compounds include those having an ether skeleton, a siloxane skeleton, a vinylidene fluoride skeleton, etc. as a skeleton constituting the repeating units.

[0097] The skeleton of the repeating unit of the polymer compound is preferably an ether skeleton. The structure of the skeleton of the repeating unit is not particularly limited, but examples thereof include a polyethylene oxide structure, a branched polypropylene oxide structure, and a linear polypropylene oxide structure. Among them, a polyethylene oxide structure in which an oxyethylene group is a repeating unit is preferable.

[0098] <Method of manufacturing polymer electrolyte> The polymer electrolyte according to one embodiment of the present invention can be obtained, for example, by mixing the polymer electrolyte material of the present invention with other components such as an electrolytic solution and heating the mixture. The heating temperature and time are not particularly limited and can be appropriately set depending on the materials used.

[0099] <Electricity storage element> The electric storage element according to one embodiment of the present invention includes a positive electrode, a negative electrode, and the polymer electrolyte of the present invention. The electric storage element according to one embodiment of the present invention may include other components as long as it includes the positive electrode, the negative electrode, and the polymer electrolyte of the present invention as essential components. Examples of the other components include an intermediate layer, a separator, and a container disposed between the positive electrode substrate and the positive electrode active material layer in the positive electrode.

[0100] <Positive electrode> The positive electrode constituting the electric storage element according to one embodiment of the present invention is not particularly limited, and any known positive electrode used in electric storage elements can be used. The positive electrode has, for example, a positive electrode substrate and a positive electrode active material layer disposed on the positive electrode substrate directly or via an intermediate layer.

[0101] (Positive electrode substrate) The positive electrode substrate is electrically conductive. Whether or not it has "electrical conductivity" is determined by the volume resistivity measured in accordance with JIS-H-0505 (1975) of 10 7 The threshold value is Ω·cm.

[0102] Examples of the material of the positive electrode substrate include metals such as aluminum, titanium, tantalum, and stainless steel, and alloys thereof. Among them, from the viewpoints of potential resistance, high electrical conductivity, and cost balance, the material of the positive electrode substrate may be aluminum or an aluminum alloy.

[0103] Examples of the form of the positive electrode substrate include foil, vapor deposition film, mesh, and porous material. From the viewpoint of cost, the form of the positive electrode substrate may be foil. Therefore, the positive electrode substrate is preferably an aluminum foil or an aluminum alloy foil. Examples of aluminum or aluminum alloy include A1085P, A3003P, and A1N30P as specified in JIS-H-4000 (2014) or JIS-H-4160 (2006).

[0104] (Cathode active material layer) The positive electrode active material layer is a layer formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture forming the positive electrode active material layer may contain any components such as a polymer electrolyte, a conductive agent, a binder, a thickener, and a filler, as necessary, in addition to the positive electrode active material, which is an essential component.

[0105] The positive electrode active material used in the positive electrode constituting the electricity storage element according to one embodiment of the present invention is not particularly limited, and any known positive electrode active material that is applied to electricity storage elements can be used.

[0106] The positive electrode active material used in lithium ion secondary batteries is usually a material capable of absorbing and releasing lithium ions. Examples of such positive electrode active materials include α-NaFeO 2 Examples of the lithium transition metal composite oxides include those having a lithium transition metal complex oxide having a spinel type crystal structure, polyanion compounds, chalcogen compounds, and sulfur.

[0107] α-NaFeO 2 As an example of a lithium transition metal composite oxide having a crystalline structure, Li[Li x Ni (1-x) ]O 2 (0≦x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O 2 (0≦x<0.5, 0<γ<1), Li[Li x Co (1-x) ]O 2 (0≦x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O 2 (0≦x<0.5, 0<γ<1), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O 2 (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1), Li[Li x Ni γ Co β Al (1-x-γ-β) ]O 2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn 2 O 4 , Li x Ni γ Mn (2-γ) O 4 Examples of polyanion compounds include LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 ,Li 3 V 2 (PO 4 ) 3 , Li 2 MnSiO 4 , Li 2 CoPO 4 Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. The atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more of them may be used in combination.

[0108] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass to 99% by mass, more preferably 70% by mass to 98% by mass, and even more preferably 80% by mass to 95% by mass. By setting the content of the positive electrode active material in the above range, both high energy density and manufacturability of the positive electrode active material layer can be achieved.

[0109] The conductive agent is not particularly limited as long as it is a material having electrical conductivity. Examples of such conductive agents include carbonaceous materials, metals, conductive ceramics, and the like. Examples of carbonaceous materials include graphite, non-graphitic carbon, graphene-based carbon, and the like. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, carbon black, and the like. Examples of carbon black include furnace black, acetylene black, ketjen black, and the like. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), fullerene, and the like. Examples of the conductive agent include powder and fiber. As the conductive agent, one of these materials may be used alone, or two or more of them may be mixed and used. These materials may also be used in combination. For example, a material in which carbon black and CNT are combined may be used. Among these, carbon black is preferable from the viewpoint of electronic conductivity and coatability, and acetylene black is preferable among them.

[0110] The content of the conductive agent in the positive electrode active material layer is preferably from 1 mass % to 10 mass %, and more preferably from 3 mass % to 9 mass %. By setting the content of the conductive agent in the above range, the energy density of the electricity storage element can be increased.

[0111] Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, and fluororubber; and polysaccharide polymers.

[0112] The content of the binder in the positive electrode active material layer is preferably 1% by mass to 10% by mass, more preferably 3% by mass to 9% by mass. By setting the content of the binder in the above range, the positive electrode active material can be stably maintained.

[0113] <Negative electrode> The negative electrode constituting the electric storage element according to one embodiment of the present invention is not particularly limited, and a known negative electrode used in an electric storage element can be used. The negative electrode has, for example, a negative electrode substrate and a negative electrode active material layer disposed on the negative electrode substrate directly or via an intermediate layer.

[0114] (Negative electrode substrate) The negative electrode substrate is conductive. Examples of the material of the negative electrode substrate include metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, alloys thereof, and carbonaceous materials. Among these, copper or copper alloys are preferred.

[0115] Examples of the form of the negative electrode substrate include foil, vapor deposition film, mesh, and porous material. From the viewpoint of cost, the form of the negative electrode substrate may be foil. Therefore, the negative electrode substrate is preferably copper foil or copper alloy foil. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

[0116] When the negative electrode active material described below has electrical conductivity, the negative electrode active material may be used as it is as a negative electrode without using a negative electrode substrate.

[0117] (Negative electrode active material layer) The negative electrode active material layer is a layer formed from a so-called negative electrode mixture containing a negative electrode active material. The negative electrode mixture forming the negative electrode active material layer may contain any components such as a polymer electrolyte, a conductive agent, a binder, a thickener, and a filler, as necessary, in addition to the negative electrode active material which is an essential component.

[0118] The negative electrode active material used in the negative electrode constituting the electricity storage element according to one embodiment of the present invention is not particularly limited, and any known negative electrode active material that is applied to electricity storage elements can be used.

[0119] The negative electrode active material used in the lithium ion secondary battery is usually a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include metal Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide;4 Ti 5 O 12 , LiTiO 2 Lithium compounds such as TiNb 2 O 7 Examples of the titanium-containing oxide include titanium-containing oxides such as titanium oxide, titanium carbide, polyphosphate compounds, silicon carbide, and carbon materials such as graphite and non-graphitizable carbon (easily graphitizable carbon or non-graphitizable carbon).

[0120] Among these, metallic Li is preferable because it can increase the discharge capacity of the negative electrode active material and improve the energy density of the storage element. Metallic Li may be pure metallic Li consisting essentially of lithium element, or may be a lithium alloy containing other metal elements. Examples of lithium alloys include lithium silver alloys, lithium zinc alloys, lithium calcium alloys, lithium aluminum alloys, lithium magnesium alloys, and lithium indium alloys. Lithium alloys may contain multiple metal elements other than lithium element.

[0121] In the negative electrode active material layer, the above-mentioned negative electrode active materials may be used alone or in combination of two or more kinds, if necessary.

[0122] The content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass to 99% by mass, more preferably 90% by mass to 98% by mass. By setting the content of the negative electrode active material in the above range, both high energy density and manufacturability of the negative electrode active material layer can be achieved.

[0123] <separator> The separator can be appropriately selected from known separators. As the separator, for example, a separator composed only of a base material layer, a separator having a heat-resistant layer containing heat-resistant particles and a binder formed on one or both surfaces of the base material layer, etc. can be used. Examples of the shape of the base material layer of the separator include woven fabric, non-woven fabric, porous resin film, etc. Among these shapes, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of the liquid retention property of the non-aqueous electrolyte. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of the shut-down function, and polyimides and aramids are preferable from the viewpoint of oxidation decomposition resistance. As the base material layer of the separator, a material obtained by compounding these resins may be used.

[0124] In addition, in a power storage element using metallic Li as the negative electrode active material, the decomposition of the electrolyte solution becomes large, and gas is generated due to the decomposition. However, since the polymer electrolyte containing the polymer electrolyte material of the present invention has the effect of adsorbing the generated gas, gas generation can be suppressed. Therefore, by using the polymer electrolyte material of the present invention together with metallic Li as the negative electrode active material, the effects of the present invention can be more highly enjoyed.

[0125] <Polymer electrolyte> The polymer electrolyte used in the power storage element according to one embodiment of the present invention is the polymer electrolyte of the present invention described above. The polymer electrolyte of the present invention is not particularly limited as long as it is included in the configuration of the power storage element, and for example, it can be used in a form impregnated in the pores of any of the components constituting the power storage element such as the positive electrode, negative electrode, and separator.

[0126] <Method for manufacturing a power storage element> The method for manufacturing a power storage element according to one embodiment of the present invention is not particularly limited, and known methods can be applied.

[0127] For example, the method includes a step of disposing a separator between a positive electrode and a negative electrode and housing the separator in a container, and a step of injecting a polymer electrolyte material containing a conjugated diene compound and a dienophile compound having a cyclic dienophile moiety into the container. After injecting the polymer electrolyte material, the polymer electrolyte material is heated to obtain an electricity storage element containing the polymer electrolyte according to one aspect of the present invention.

[0128] FIG. 3 is a schematic diagram of a rectangular energy storage element 1, which is one embodiment of the energy storage element. The figure is a see-through view of the inside of a container. In the energy storage element 1 shown in FIG. 3, an electrode group 2 is housed in a container 3. The electrode group 2 is formed by winding a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material with a separator interposed therebetween. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 4', and the negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 5'.

[0129] Here, the positive electrode, the negative electrode, and the separator may each contain an electrolyte in their pores, but the present invention is characterized in that the electrolyte contained in any one of the positive electrode, the negative electrode, and the separator is a polymer electrolyte containing the polymer electrolyte material according to one embodiment of the present invention.

[0130] The configuration of the energy storage element according to one embodiment of the present invention is not particularly limited, and examples include a cylindrical battery, a prismatic battery (a rectangular battery), and a flat battery. The present invention can also be realized as an energy storage device including a plurality of the above-mentioned energy storage elements. One embodiment of the energy storage device is shown in FIG. 4. In FIG. 4, an energy storage device 30 includes a plurality of energy storage units 20. Each of the energy storage units 20 includes a plurality of energy storage elements 1. The energy storage device 30 can be installed as a power source for automobiles such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). EXAMPLES

[0131] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0132] Example 1 (Example using furan-maleimide polymer electrolyte material) (Preparation of positive electrode) As the positive electrode active material, LiNi 0.5 Co 0.2 Mn 0.3 O 2 A lithium transition metal composite oxide represented by formula (NCM523) was used. A positive electrode mixture paste was prepared using N-methylpyrrolidone (NMP) as a dispersion solvent, containing the positive electrode active material, acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder in a mass ratio (solid content equivalent) of 92:4:4.

[0133] A 20 μm thick aluminum foil was used as the positive electrode substrate, and the positive electrode mixture paste prepared above was applied to one side of the aluminum foil, dried at 100° C. under atmospheric pressure for 30 minutes, and then pressed to obtain a positive electrode with a positive electrode active material layer. The coating amount of the positive electrode mixture was 26 mg / cm in terms of solid content. 2 The prepared positive electrode was dried at 120° C. under reduced pressure for 15 hours.

[0134] (Preparation of negative electrode) A copper foil having a thickness of 8 μm was used as the negative electrode substrate, and a lithium metal foil having a thickness of 100 μm (lithium metal 100% by mass) was laminated as a negative electrode active material layer on one side of the copper foil, followed by pressing to obtain a negative electrode.

[0135] (Preparation of electrolyte) Fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 30 volume %:70 volume % to obtain a mixed solvent. 6 A solution was prepared by dissolving the above in a concentration of 1.5 mol / kg, and this was used as the electrolyte.

[0136] (Preparation of single-layer pouch cells) Next, the positive electrode and the negative electrode prepared above were laminated with a separator made of a polyolefin microporous film interposed therebetween to prepare an electrode assembly. The prepared electrode assembly was placed in a container made of an aluminum resin composite film and sealed except for a liquid injection port.

[0137] (Preparation of polymer electrolyte) As a conjugated diene compound, difurfuryl sulfide (Tokyo Chemical Industry Co., Ltd.) having two furan rings at the molecular end, represented by chemical formula (5), was prepared. As a dienophile compound having a cyclic dienophile moiety, 4arm-PEG20K-Maleimide (Mw=20,000) (Sigma-Aldrich Co., Ltd.), which has a four-branched molecular structure represented by chemical formula (6) and has maleimide groups at the branched ends, was prepared.

[0138] [ka]

[0139] [ka]

[0140] 100 mg of 4arm-PEG20K-Maleimide was dissolved in 1800 mg of the non-aqueous electrolyte prepared above to obtain "Solution A". 19.425 mg of difurfuryl sulfide was dissolved in 1369 mg of the non-aqueous electrolyte prepared above to obtain "Solution B". 138.9 mg of "Solution B" was added to the total amount of "Solution A" to obtain "Mixed Solution 1". 0.5 mL of the obtained "Mixed Solution 1" was taken and poured into the injection port of the single-layer pouch cell prepared above, and the injection port was then sealed under reduced pressure. All of the above operations were performed under an argon atmosphere with a dew point of -50°C or less.

[0141] The monolayer pouch cell sealed above was sandwiched between two stainless steel plates with screw holes at the four corners, and M4 screws were inserted into the screw holes at the four corners of the two plates to tighten them, and the pressure applied to the monolayer pouch cell was adjusted to 0.2 MPa. As a polymerization acceleration step, the monolayer pouch cell was left in a thermostatic chamber at 40°C for 10 days. As a result, a Diels-Alder reaction proceeded between the furan ring and the maleimide group, and a gel-like polymer electrolyte containing a furan-maleimide polymer electrolyte material having a network structure shown in Figure 1 was formed. In Figure 1, A is a portion derived from difurfuryl sulfide, and B is a portion derived from 4arm-PEG20K-Maleimide. In this way, the energy storage element (monolayer pouch cell) according to Example 1 was obtained.

[0142] Comparative Example 1 (Example using thiol-maleimide polymer electrolyte material) (Preparation of polymer electrolyte) Pentaerythritol tetra(3-mercaptopropionate) (Tokyo Chemical Industry Co., Ltd.), represented by chemical formula (7), and 4arm-PEG20K-Maleimide (Mw=20,000) (Sigma-Aldrich Co., Ltd.), which has a four-branched molecular structure represented by chemical formula (6) and has maleimide groups at the branched ends, were prepared.

[0143] [ka]

[0144] [ka]

[0145] 0.149 mL of pentaerythritol tetra(3-mercaptopropionate) was dissolved in 1 mL of the non-aqueous electrolyte prepared above to obtain "solution C". 20 mg of 2,2'-azoisobutyronitrile (AIBN) was dissolved in 1 mL of the non-aqueous electrolyte prepared above to obtain "solution D". 195 mg of 4arm-PEG20K-Maleimide was dissolved in 2.76 mL of the non-aqueous electrolyte prepared above to obtain "solution E". 0.0287 mL of "solution C" and 0.204 mL of "solution D" were added to the total amount of "solution E", respectively, to obtain "mixed solution 2". A storage element (single layer pouch cell) was prepared in the same manner as in Example 1, except that 0.5 mL was taken from the obtained "mixed solution 2" and poured, and the polymerization acceleration step was left in a constant temperature bath at 60 ° C. for 24 hours. This was used as the storage element (single layer pouch cell) according to Comparative Example 1.

[0146] In the energy storage element (single-layer pouch cell) of Comparative Example 1, a thiol-ene reaction represented by reaction formula (B) proceeded between the thiol group and the maleimide group, and a gel-like polymer electrolyte containing a thiol-maleimide polymer electrolyte material having a network structure shown in Figure 2 was formed. In Figure 2, C is a portion derived from pentaerythritol tetra(3-mercaptopropionate), and D is a portion derived from 4arm-PEG20K-Maleimide.

[0147] [ka]

[0148] <Comparative Example 2> A storage element (single-layer pouch cell) according to Comparative Example 2 was produced in the same manner as in Example 1, except that 0.5 mL of the non-aqueous electrolyte prepared above was injected instead of mixed solution 1, and the polymerization acceleration process was not performed.

[0149] [Charge / discharge test] A charge / discharge test was carried out in a thermostatic chamber set at 25°C using the energy storage elements (single-layer pouch cells) according to Example 1 and Comparative Examples 1 and 2. Prior to the charge / discharge test, the pressure applied to the energy storage elements (single-layer pouch cells) was changed to 0.35 MPa. Charging was performed at a constant current / constant voltage (CCCV) with a charging current of 0.22C and a charge cut-off voltage of 4.4V, and the charge was terminated until the charging current reached 0.05C. Discharging was performed at a constant current (CC) with a discharging current of 0.22C and a discharge cut-off voltage of 2.7V. A rest period of 5 minutes was provided after each charging and discharging. This charge / discharge was repeated for 201 cycles. For the first time and every 50 cycles, charging / discharging was carried out in the same manner as in the charge / discharge test described above, except that the charging current and discharging current were set to 0.1C, as a capacity confirmation test. The discharge capacity at the 201st cycle relative to the discharge capacity at the first cycle (initial capacity) was calculated as a percentage, and this was taken as the "discharge capacity maintenance rate (%)". The "discharge capacity retention rate (%)" is shown in Table 1.

[0150] <Volume measurement> After the first charge / discharge cycle and after the 201st charge / discharge cycle, the volume of each storage element (single-layer pouch cell) was measured by Archimedes' method, and the increase in volume was calculated from the difference between the volume after the first charge / discharge cycle and the volume after the 201st charge / discharge cycle. The results are shown in Table 1.

[0151] [Table 1]

[0152] As can be seen from Table 1, the energy storage elements (single-layer pouch cells) according to Example 1 and Comparative Examples 1 and 2 all exhibited good charge-discharge cycle performance. On the other hand, the energy storage elements using the polymer electrolyte material according to one embodiment of the present invention showed suppressed gas generation and suppressed volume increase of the energy storage elements.

[0153] (Explanation of symbols) 1 Energy storage element 2 electrode groups 3 containers 4 Positive terminal 4' Positive lead 5 Negative terminal 5' Negative lead 20 Energy Storage Unit 30 Energy storage device

Claims

1. A material for polymer electrolytes, which is a compound containing a ring structure that is a Diels-Alder reaction product between a conjugated diene portion of a conjugated diene compound and a cyclic dienophile portion of a dienophile compound having the cyclic dienophile portion.

2. The polymer electrolyte material according to claim 1 , wherein the conjugated diene moiety is a furan ring.

3. The polymer electrolyte material according to claim 1 , wherein the dienophile compound has at least four of the cyclic dienophile moieties.

4. A polymer electrolyte material, which is a compound having a structure represented by the following formula (1): 【Chemistry 1】 (In the formula, element A may or may not be present, element A is O or C, and * represents a bond.)

5. The polymer electrolyte material according to claim 1 or 4, which has a repeating unit structure containing an ether oxygen atom.

6. The polymer electrolyte material according to claim 1 or 4, which contains a sulfide bond.

7. A polymer electrolyte comprising the material for a polymer electrolyte according to claim 1 or 4.

8. A positive electrode and A negative electrode; The polymer electrolyte according to claim 7 ; A storage element comprising:

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