Resin composition, binder resin, polymer thin film and battery

Abstract

Disclosed is a resin composition which contains a copolymer that comprises a constituent unit represented by general formula (1) and 0.3 to 20.0% by mole (inclusive) of a constituent unit represented by general formula (2). (In general formula (1) and general formula (2), R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; L1 and L2 each independently represent a single bond or an alkylene group having 1 to 3 carbon atoms; and X1 represents a reactive group selected from among groups represented by structural formula (2-1) and structural formula (2-2).)

Description

Resin composition, binder resin, polymer thin film and battery

[0001] The present invention relates to a resin composition, a binder resin, a polymer thin film, and a battery.

[0002] Polycarbonate is used in a variety of applications, including as a material in the battery field. Polycarbonate-containing binder resins are used, for example, as binders for forming electrodes. Furthermore, polycarbonate-containing polymer thin films are used, for example, in battery separators. For example, Patent Document 1 discloses a polymer binder containing a three-dimensionally crosslinked aliphatic polycarbonate.

[0003] International Publication No. 2020 / 203882

[0004] The polymer binder described in Patent Document 1 is a binder for solid electrolytes and is not intended for use in batteries using electrolytic solutions. Therefore, when an electrode fabricated using this polymer binder is used in a battery using electrolytic solutions, there is a risk of a problem such as the polymer binder eluting into the electrolytic solution.

[0005] An object of the present invention is to provide a crosslinkable resin composition, a binder resin, a polymer thin film, and a battery.

[0006] [1] A resin composition comprising a copolymer containing a structural unit represented by the following general formula (1) and 0.3 mol % to 20.0 mol % of a structural unit represented by the following general formula (2):

[0007]

[0008] (In the general formula (1) and the general formula (2), R １ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and L １ and L ２ are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, and X １ is a reactive group selected from the groups represented by the following structural formula (2-1) and the following structural formula (2-2).

[0009]

[0010] [2] The resin composition according to [1], wherein the copolymer further comprises 0.1 mol% or more and 30.0 mol% or less of at least one structural unit selected from the group consisting of structural units represented by the following general formula (3) and structural units represented by the following general formula (4): The resin composition:

[0011]

[0012] (In the general formula (3) and the general formula (4), R ２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and L ３ and L ４ are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, and X ２ is a reactive group selected from the groups represented by the following structural formula (4-1) and the following structural formula (4-2).

[0013]

[0014] [3] The resin composition according to [1] or [2], wherein the crosslinked product of the resin composition has an elution amount of the copolymer in ethyl acetate of 10% or less, and a swelling ratio of the copolymer in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 of 100% or more.

[0015] [4] A binder resin comprising the resin composition according to any one of [1] to [3].

[0016] [5] A battery comprising the binder resin according to [4].

[0017] [6] A polymer thin film comprising the resin composition according to any one of [1] to [3].

[0018] [7] A battery comprising the polymer thin film according to [6].

[0019] According to one aspect of the present invention, a crosslinkable resin composition, a binder resin, a polymer thin film, and a battery can be provided.

[0020] 1 is a cross-sectional view schematically illustrating an example of a main part of a battery according to an embodiment of the present invention. FIG. 2 is a view for explaining the effects when the polymer thin film according to the embodiment of the present invention is used as a battery separator. １ 1 is a chart showing the results of H-NMR measurement of the copolymer produced in Example 3. １ 1 is a chart showing the results of H-NMR measurement.

[0021] The present invention will be described below by taking an embodiment as an example, but the present invention is not limited to the content of the embodiment.

[0022] [Resin Composition] A preferred example of the resin composition according to this embodiment will be described.

[0023] The resin composition according to this embodiment contains a copolymer containing a structural unit represented by general formula (1) and 0.3 mol % or more and 20.0 mol % or less of a structural unit represented by general formula (2).

[0024] The resin composition according to this embodiment has the above-described structure, and thus exhibits crosslinking properties. Furthermore, by using the resin composition according to this embodiment, a binder resin with excellent adhesion to metal foil and binding ability to inorganic materials can be obtained. Furthermore, by using the resin composition according to this embodiment, a polymer thin film with high swelling properties in electrolytes and the like can be obtained. For example, when the resin composition according to this embodiment is used as a material in the battery field, the copolymer used in the resin composition according to this embodiment has a carbonate backbone as the main polymer backbone, thereby improving compatibility with electrolytes. Therefore, when assembling a battery, the polymer thin film serving as a separator can swell after the electrolyte is injected. Furthermore, by containing 0.3 mol % or more and 20.0 mol % or less of a structural unit represented by general formula (2) having a reactive group, the crosslinking reaction proceeds appropriately, thereby achieving both a high degree of swelling and a low amount of leaching.

[0025] The resin composition according to this embodiment may contain other components as long as it contains the specific copolymer having the above-described structure, as long as the object of the present invention is not impaired.

[0026] (Copolymer) The copolymer contained in the resin composition according to this embodiment includes a copolymer containing a structural unit represented by the following general formula (1) and 0.3 mol % or more and 20.0 mol % or less of a structural unit represented by the following general formula (2):

[0027]

[0028] In the general formula (1) and the general formula (2), R １ L is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group. １ and L ２ are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a methylene group or an ethylene group, and particularly preferably a methylene group. １ is a reactive group selected from the groups represented by the following structural formula (2-1) and the following structural formula (2-2). The wavy line in the structural formula indicates the bonding position.

[0029]

[0030] Such a copolymer may be a random copolymer or a block copolymer, but from the viewpoint of ease of synthesis, the copolymer is preferably a random copolymer.

[0031] The copolymer contained in the resin composition according to this embodiment, for example, a copolymer consisting of a structural unit represented by general formula (1) and a structural unit represented by general formula (2), has the following composition ratio. The ratio of the structural unit represented by general formula (2) must be 0.3 mol% or more and 20 mol% or less relative to all structural units. If this ratio is less than 0.3 mol%, the amount of elution will be high. On the other hand, if this ratio exceeds 20.0 mol%, the crosslinking density of the copolymer will be high and the swelling property will be reduced. From the same viewpoint, the ratio of the structural unit represented by general formula (2) is preferably 1.0 mol% or more, more preferably 1.5 mol% or more, and even more preferably 1.8 mol% or more. On the other hand, the ratio of the structural unit represented by general formula (2) is preferably 19.0 mol% or less, more preferably 18.0 mol% or less, even more preferably 12.0 mol% or less, and particularly preferably 6.0 mol% or less.

[0032] The ratio of the structural unit represented by general formula (1) must be 80.0 mol% or more and 99.7 mol% or less relative to all structural units. Also, the ratio of the structural unit represented by general formula (1) is preferably 81.0 mol% or more, more preferably 82.0 mol% or more, even more preferably 88.0 mol% or more, and particularly preferably 94.0 mol% or more. On the other hand, the ratio of the structural unit represented by general formula (1) is preferably 99.0 mol% or less, more preferably 98.5 mol% or less, and even more preferably 98.2 mol% or less.

[0033] The copolymer contained in the resin composition according to this embodiment preferably further contains 0.1 mol % to 30.0 mol % of at least one structural unit selected from the group consisting of structural units represented by the following general formula (3) and structural units represented by the following general formula (4): By using a copolymer containing an ether skeleton such as the structural unit represented by general formula (3) or general formula (4), the glass transition temperature of the copolymer is lowered and the thin film becomes flexible, which is expected to result in high ionic conductivity.

[0034]

[0035] In the general formula (3) and the general formula (4), R ２ L is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group. ３ and L ４ are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a methylene group or an ethylene group, and particularly preferably a methylene group. ２ is a reactive group selected from the groups represented by the following structural formula (4-1) and the following structural formula (4-2). The wavy line in the structural formula indicates the bonding position.

[0036]

[0037] The copolymer contained in the resin composition according to this embodiment, for example, a copolymer consisting of a structural unit represented by general formula (1), a structural unit represented by general formula (2), a structural unit represented by general formula (3), and a structural unit represented by general formula (4), has the following composition ratio. The ratio of the structural unit represented by general formula (2) is as described above. The total ratio of the structural unit represented by general formula (3) and the structural unit represented by general formula (4) is preferably 0.1 mol% or more and 30.0 mol% or less with respect to all structural units. If the total ratio of these is less than 0.1 mol%, the effect of the ether skeleton tends to be insufficient. On the other hand, if the total ratio of these exceeds 30.0 mol%, the compatibility with the electrolyte solution tends to be poor, the degree of swelling tends to be reduced, and the ionic conductivity tends to be reduced. From the same viewpoint, the total ratio of these is preferably 1.0 mol% or more, and more preferably 2.0 mol% or more. On the other hand, the total ratio of these is preferably 25.0 mol % or less, more preferably 20.0 mol % or less, and particularly preferably 10.0 mol % or less.

[0038] The ratio of the structural unit represented by general formula (1) is preferably 50.0 mol% or more and 99.6 mol% or less relative to all structural units. Also, the ratio of the structural unit represented by general formula (1) is preferably 55.0 mol% or more, more preferably 60.0 mol% or more. On the other hand, the ratio of the structural unit represented by general formula (1) is preferably 98.0 mol% or less, more preferably 94.0 mol% or less.

[0039] The molecular weight of the copolymer according to this embodiment, measured by the method shown in the measurement examples, is preferably 5,000 to 5,000,000 in weight average molecular weight (Mw), and more preferably 10,000 to 1,000,000 in number average molecular weight (Mn). The molecular weight of the copolymer according to this embodiment, measured by the method shown in the measurement examples, is preferably 3,000 to 3,000,000 in number average molecular weight (Mn), and more preferably 5,000 to 500,000 in number average molecular weight (Mw / Mn). The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is preferably 1 to 10, and more preferably 1.1 to 5. Having the molecular weight and molecular weight distribution of the copolymer within the above ranges ensures sufficient handleability when molded into a film. Furthermore, when the copolymer is used as a binder, the molecular weight and molecular weight distribution of the copolymer within the above ranges ensures that the viscosity of the slurry is appropriate during electrode slurry preparation, suppresses sedimentation of the active material and conductive additive, and ensures sufficient dispersibility of the active material and conductive additive.

[0040] (Method for Producing Copolymer) The method for producing the copolymer contained in the resin composition according to this embodiment is not particularly limited and can be obtained by a known method, but can be produced, for example, by the following method. As described in the examples below, the copolymer can be produced by copolymerizing an epoxide monomer such as propylene oxide with carbon dioxide in the presence of a polymerization catalyst. Specifically, propylene oxide undergoes ring-opening to become a structural unit represented by general formula (3), and a portion of the propylene oxide undergoes ring-opening while polymerizing with carbon dioxide to become a structural unit represented by general formula (1).

[0041] The polymerization catalyst used in producing the copolymer is not particularly limited, and examples thereof include metal salen complex catalysts such as cobalt salen catalysts, and organozinc catalysts.

[0042] The amount of polymerization catalyst used in the copolymerization reaction of epoxide monomer and carbon dioxide, for example, in the case of a metal salen complex catalyst, is preferably 0.05 mol or less, more preferably 0.01 mol or less, and particularly preferably 0.001 mol or less, per 1 mol of epoxide monomer. Furthermore, when using a metal salen complex catalyst, a co-catalyst can be used. For example, an onium salt compound is preferred as the co-catalyst. Specific examples of the onium salt compound are not particularly limited, but from the viewpoint of high reaction activity, bis(triphenylphosphoranylidene)ammonium chloride, piperidine, bis(triphenylphosphoranylidene)ammonium fluoride, ammonium pentafluorobenzoate, tetra-n-butylammonium chloride, and the like are preferred.

[0043] Although the optimum polymerization conditions vary depending on the type of catalyst, for example, the carbon dioxide pressure in the reaction vessel is 0.1 MPa or more and 10 MPa or less, preferably 0.5 MPa or more and 5 MPa or less. Furthermore, in the case of a cobalt salen complex catalyst, for example, the polymerization temperature is preferably about room temperature (25° C.) from the viewpoint of favorable catalytic action and an accelerated reaction rate.

[0044] In the method of copolymerizing an epoxide monomer with carbon dioxide, examples of the epoxide monomer used as a starting material include ethylene oxide, propylene oxide, 1,2-butylene oxide, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether. Note that, due to differences in reactivity, the molar ratio of the constituent unit represented by general formula (1) to the constituent unit represented by general formula (2) in the copolymer may not match the molar mixing ratio of the epoxide monomer serving as the starting material for the constituent unit represented by general formula (1) and the epoxide monomer serving as the starting material for the constituent unit represented by general formula (2).

[0045] (Characteristics of Crosslinked Resin Composition) In the crosslinked resin composition according to this embodiment, the amount of copolymer eluted in ethyl acetate is preferably 40% or less, more preferably 30% or less, even more preferably 20% or less, particularly preferably 10% or less, and very preferably 7% or less. Since the eluted low molecular weight components of the copolymer become irreversible capacity, it is desirable that the elution amount be as low as possible. The lower limit of the elution amount of the copolymer is not particularly limited, and may be, for example, 1% or more, 0.1% or more, or 0%.

[0046] In the crosslinked product of the resin composition according to this embodiment, it is preferable that the amount of elution of the copolymer with ethyl acetate is within the above range, and that the degree of swelling of the copolymer with a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 is 100% or more.

[0047] The crosslinked resin composition according to this embodiment preferably has high swelling properties in the electrolyte solution and carbonate-based solvents used as the solvent for the electrolyte solution. From this viewpoint, the degree of swelling of the copolymer in the above-mentioned mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 is preferably 100% or more, more preferably 200% or more, even more preferably 300% or more, particularly preferably 500% or more, very preferably 700% or more, and most preferably 900% or more. The upper limit of this swelling degree is not particularly limited and may be, for example, 2000% or less.

[0048] (Method of crosslinking resin composition) The resin composition according to the present embodiment preferably uses a photopolymerization initiator, from the viewpoint of facilitating the production of a polymer thin film in which the copolymer is crosslinked. When a photopolymerization initiator is used in the resin composition according to the present embodiment, the thin film containing the copolymer is crosslinked by reaction of reactive groups (allyl groups and (meth)acryloyl groups) on the side chains of the copolymer in the thin film.

[0049] The photopolymerization initiator is not particularly limited, and examples thereof include known compounds. The photopolymerization initiator is preferably a photopolymerization initiator that is sensitive to ultraviolet light. The photopolymerization initiator may be used alone or in combination of two or more types.

[0050] Specific examples of the photopolymerization initiator include α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenones such as benzoylbenzoic acid and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone; benzophenone compounds such as camphorquinone; halogenated ketones, acylphosphinoxides, acylphosphonates, and oligo[2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone].

[0051] The content of the photopolymerization initiator is, for example, preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 7.5 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the copolymer.

[0052] The resin composition according to the present embodiment is molded into a predetermined shape, and a molded product is irradiated with energy rays to crosslink the copolymer, thereby obtaining a thin film of the crosslinked copolymer. The type of energy rays is not particularly limited, but ultraviolet rays are preferred in terms of reactivity and workability. The device for irradiating the molded product with ultraviolet rays is not particularly limited, and may be, for example, a device equipped with an ultraviolet LED lamp, a device equipped with a high-pressure mercury lamp, or a device equipped with a metal halide lamp.

[0053] The conditions for irradiating the molded product with ultraviolet light are not particularly limited. The maximum irradiance and the integrated amount of light when irradiating the molded product with ultraviolet light are, for example, as follows: maximum irradiance: 5 mW / cm ２ More than 1000mW / cm ２ The integrated light amount is preferably 50 mJ / cm or less. ２ More than 5000mJ / cm ２ It is preferable that:

[0054] [Binder Resin] The binder resin according to the present embodiment includes the resin composition according to the present embodiment. When the binder resin according to the present embodiment is used as a material for a composite layer in an electrode of a secondary battery, the binder resin according to the present embodiment has excellent swelling properties in an electrolytic solution, and also has excellent adhesion to a metal foil and binding properties for inorganic materials. The reason for this is unclear, but is thought to be as follows.

[0055] When used in composite layers of lithium-ion secondary batteries, conventional binder resins have low swelling properties in response to an electrolyte solution, thereby maintaining adhesion between the composite layer and the current collector and binding between the active materials in the composite layer even when the binder resin swells with the electrolyte solution. It is believed that a composite layer in contact with an electrolyte solution has a contact area between the binder resin and the active material, and a contact area between the active material and the electrolyte solution, due to the electrolyte solution penetrating into the composite layer. Because conventional binder resins have low swelling properties in response to an electrolyte solution, they are less likely to exhibit ionic conductivity, resulting in low ionic conductivity of lithium ions and other ions contained in the electrolyte solution in the contact area between the binder resin and the active material. On the other hand, the ionic conductivity of lithium ions and other ions contained in the electrolyte solution is improved in the contact area between the active material and the electrolyte solution. Furthermore, because conventional binder resins have low swelling properties in response to an electrolyte solution, the area of ​​contact between the binder resin and the active material does not expand significantly, resulting in a small contact area, while the area of ​​contact between the active material and the electrolyte solution is large. Although it is thought that the electrolyte solution is unlikely to decompose in the contact area between the binder resin and the active material, a decomposition layer of the electrolyte solution called an SEI (Solid Electrolyte Interphase) layer is likely to be formed in the contact area between the active material and the electrolyte solution. When a conventional binder resin is used in the composite layer, as described above, the area of ​​the contact area between the active material and the electrolyte solution is large, and therefore the area where the SEI layer is formed is also large, which tends to shorten the life of the electrolyte solution.

[0056] In contrast, when the binder resin according to the present embodiment is used in a composite layer of a lithium-ion secondary battery or the like, the binder resin according to the present embodiment contains a copolymer having a carbonate skeleton as the main polymer backbone, thereby improving compatibility with the electrolyte solution and exhibiting high swelling in the electrolyte solution. Furthermore, the binder resin according to the present embodiment swells significantly upon contact with the electrolyte solution, thereby exhibiting ionic conductivity. Furthermore, because the binder resin according to the present embodiment has high swelling in the electrolyte solution, the area of ​​contact between the binder resin and the active material increases, while the area of ​​contact between the active material and the electrolyte solution decreases. Therefore, when the binder resin according to the present embodiment is used, ionic conductivity is exhibited in the contact area between the binder resin and the active material, and the electrolyte solution is less likely to decompose. Therefore, the area where an SEI layer is formed in the contact area between the active material and the electrolyte solution is reduced. Therefore, when the binder resin according to the present embodiment is used in a composite layer of a lithium-ion secondary battery or the like, it is believed that this contributes to improving the life of the electrolyte solution, which in turn leads to improved battery performance. However, if the swelling property with respect to the electrolyte is too high, the adhesion to the metal foil and the binding property of the inorganic material tend to decrease.

[0057] The binder resin according to this embodiment has excellent adhesion to metal foil and excellent binding ability for inorganic materials, and therefore can be applied to applications requiring such properties. The binder resin according to this embodiment is preferably applied to battery applications, for example. In this case, the binder resin according to this embodiment is preferably a binder resin for battery electrodes, and is also preferably a binder resin for electrodes of secondary batteries such as lithium ion batteries. The binder resin according to this embodiment may be used as a binder resin for a composite layer in a positive electrode, or may be used as a binder resin for a composite layer in a negative electrode.

[0058] [Polymer thin film] The polymer thin film according to this embodiment contains the resin composition according to this embodiment. The polymer thin film according to this embodiment provides a polymer thin film with high swelling properties in electrolyte solutions and the like. The reason for this is unclear, but is thought to be as follows. The copolymer used in the polymer thin film according to this embodiment has a carbonate skeleton as the main polymer backbone, which improves compatibility with electrolyte solutions. Therefore, when assembling a battery, the polymer thin film serving as a separator can swell after the electrolyte solution is injected. Furthermore, by including a predetermined amount of a structural unit represented by general formula (2) having a reactive group, the crosslinking reaction proceeds appropriately, making it possible to achieve both a high degree of swelling and a low amount of elution.

[0059] The polymer thin film according to this embodiment has high swelling properties in an electrolyte solution or the like, and can therefore be applied to applications requiring such properties. The polymer thin film according to this embodiment is preferably applied to, for example, battery applications. In this case, the polymer thin film according to this embodiment is preferably used as, for example, a battery separator, and is also preferably used as a battery separator for a secondary battery such as a lithium ion battery. Furthermore, the polymer thin film according to this embodiment is preferably used as, for example, an anode protective film that covers at least a portion of the anode of a battery, and is also preferably used as an anode protective film for a secondary battery such as a lithium ion battery.

[0060] [Battery] Next, a preferred example of the battery according to this embodiment will be described.

[0061] The battery according to this embodiment is a battery to which the resin composition according to this embodiment is applied. The battery according to this embodiment includes the binder resin according to this embodiment as a material constituting the electrodes of the battery. The battery according to this embodiment also includes the polymer thin film according to this embodiment as, for example, a battery separator. The battery is composed of a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. By adopting such a configuration, a battery with excellent characteristics can be obtained. The battery is preferably a secondary battery, and more preferably a lithium-ion secondary battery or the like. The structure of the battery according to this embodiment is not particularly limited, and may be a stacked structure or a wound structure.

[0062] An example of a battery using the polymer thin film according to this embodiment will now be described with reference to the drawings, in which some parts are shown enlarged or reduced in size for ease of explanation.

[0063] FIG. 1 shows an example of a battery using the polymer thin film according to this embodiment. The battery 100 shown in FIG. 1 is a lithium-ion secondary battery. As shown in FIG. 1, the battery 100 includes a positive electrode 10, a negative electrode 20, and an electrolyte layer 30 between the positive electrode 10 and the negative electrode 20. The positive electrode 10 is composed of a positive electrode current collector 13 and a positive electrode composite layer 11 laminated on the positive electrode current collector 13. The negative electrode 20 is composed of a negative electrode current collector 23 and a negative electrode composite layer 21 laminated on the negative electrode current collector 23. The electrolyte layer 30 is composed of an electrolyte solution 33 and a separator 31 impregnated with the electrolyte solution 33, and the separator 31 separates the positive electrode 10 side from the negative electrode 20 side. The battery 100 has a laminated structure in which a positive electrode current collector 13, a positive electrode composite layer 11, an electrolyte layer 30, a negative electrode composite layer 21, and a negative electrode current collector 23 are laminated in this order from the positive electrode current collector 13 toward the negative electrode current collector 23, and this laminated structure is housed inside a container (not shown). In the battery 100, the positive electrode composite layer 11 and the negative electrode composite layer 21 preferably contain a binder resin (not shown) according to the present embodiment. In this case, the positive electrode composite layer 11 and the negative electrode composite layer 21 contain the electrolyte solution 33 due to penetration of the electrolyte solution 33 from the electrolyte layer 30, and the binder resin (not shown) according to the present embodiment is swollen by the electrolyte solution 33. In the battery 100, the polymer thin film according to the present embodiment is preferably used as the separator 31. In the battery 100, the polymer thin film according to the present embodiment is preferably used as an anode protective film (not shown) that covers at least a portion of the negative electrode composite layer 21.

[0064] The battery using the polymer thin film according to this embodiment has the above-described configuration, which allows the suppression of dendrite formation. While the reason for this is unclear, it is believed to be as follows. When the polymer thin film according to this embodiment is used as separator 31, after the electrolyte solution is injected during battery assembly, separator 31 and electrolyte solution 33 are separated as shown in FIG. 2(A). In this state, gaps due to fine irregularities exist between negative electrode composite layer 21 and separator 31. The inventors speculate that dendrites precipitate in these gaps. Meanwhile, because separator 31 using the polymer thin film according to this embodiment has high swelling properties in electrolyte solution 33, separator 31 swells as shown in FIG. 2(B) after some time has passed since the electrolyte solution was injected. This swelling of separator 31 then eliminates the gap between negative electrode composite layer 21 and separator 31 as shown in FIG. 2(C). Therefore, when the polymer thin film according to this embodiment is used as separator 31, the suppression of dendrite formation can be achieved.

[0065] Although an example of the battery according to the present embodiment has been described above with reference to Figures 1 and 2, the example of the battery according to the present embodiment is not limited to this. The battery according to the present embodiment can adopt various forms as long as it uses the polymer thin film according to the present embodiment.

[0066] Examples of materials used for the positive electrode current collector and the negative electrode current collector include metal foils or metal plates such as copper, aluminum, nickel, titanium, and stainless steel, as well as carbon sheets and carbon nanotube sheets.

[0067] The positive electrode mixture layer is preferably composed of, for example, a positive electrode active material such as a lithium-containing composite oxide, a conductive additive such as a carbon-based material, and the binder resin according to this embodiment.

[0068] The negative electrode mixture layer is preferably composed of a negative electrode active material such as acetylene black, carbon nanotubes, carbon nanofibers, or graphene, and the binder resin according to this embodiment.

[0069] The electrolyte layer is preferably composed of, for example, an electrolyte solution and a separator that is a polymer thin film according to this embodiment.

[0070] In the battery according to this embodiment, the electrolyte preferably contains a lithium salt and a carbonate-based solvent. From the viewpoint of easily improving the effect of suppressing dendrite formation, the molar ratio of the lithium salt to the carbonate-based solvent (the lithium salt / the carbonate-based solvent) is preferably 1 / 6 or more and 1 / 1 or less. This molar ratio is more preferably 1 / 4 or more and 1 / 1 or less, and even more preferably 1 / 3 or more and 1 / 1 or less.

[0071] Specific examples of the lithium salt include lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium 2-trifluoromethyl-4,5-dicyanoimidazolate, lithium 4,5-dicyano-1,2,3-triazolate, lithium bis(pentafluoroethylsulfonyl)imide, lithium borofluoride, lithium bis(oxalato)borate, lithium nitrate, lithium chloride, lithium bromide, and lithium fluoride. One or more of these exemplified lithium salts can be used as the lithium salt.

[0072] Specific examples of carbonate solvents include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. The carbonate solvent may be one or more of these exemplified lithium salts. Here, the carbonate solvent in this embodiment refers to a compound having a carbonate skeleton in its molecular structure.

[0073] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention.

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0075] Measurements and evaluations in the following examples and comparative examples were carried out by the methods shown below.

[0076] [Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)] Measurement was performed using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8320GPC") under the following conditions, and the values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: A column in which "TSKgel guard column Super H-H", "TSKgel Super HM-H", "TSKgel Super HM-H", and "TSKgel Super H2000" (all manufactured by Tosoh Corporation) were connected in sequence Column temperature: 40°C Developing solvent: tetrahydrofuran (copolymer concentration: 1% by mass) Standard substance: polystyrene Injection volume: 20 μL Flow rate: 0.60 mL / min Detector: differential refractometer

[0077] [Measurement of elution amount] The thin film obtained in each of the examples and comparative examples described below was weighed to be about 300 mg. The mass of the thin film at this time was ０ This thin film was wrapped in a polyester mesh (mesh size 200). The mass of the thin film wrapped in the polyester mesh was weighed, and the mass of the thin film was subtracted to calculate the mass of the polyester mesh alone. Next, the thin film wrapped in the polyester mesh was immersed in ethyl acetate at 23°C for 48 hours. Thereafter, the thin film wrapped in the polyester mesh was removed from the ethyl acetate, dried in an oven at 120°C for 2 hours, and then air-dried in an environment at a temperature of 23°C and a relative humidity of 50% for 2 hours. The mass after air-drying was weighed, and the mass of the thin film alone after immersion was calculated by subtracting the mass of the polyester mesh alone. This mass was used as M １ The amount of elution was calculated using the following formula (F1): Amount of elution (%) = {(M ０ -M １ ) / M ０}×100 (F1) In formula (F1), M ０ is the mass of the thin film weighed before wrapping it in the polyester mesh, M １indicates the mass of the thin film only after immersion in ethyl acetate.

[0078] [Measurement of swelling degree] The thin films obtained in each of the examples and comparative examples described below were cut into pieces of approximately 3 cm (length) x approximately 3 cm (width), and the obtained thin film pieces were weighed to be approximately 1 g. The mass at this time was W ０ This thin film piece was wrapped in a polyester mesh (mesh size 200), and the mass of the thin film piece wrapped in the polyester mesh was weighed, and the mass of the thin film piece was subtracted to calculate the mass of the polyester mesh alone. The piece was immersed in a carbonate-based solvent [composition: a mixed solvent of ethylene carbonate / dimethyl carbonate = 1 / 1 (volume ratio)] for 24 hours to cause swelling. Thereafter, the thin film piece wrapped in the polyester mesh was pulled out, the solvent on the surface was wiped with a paper wiper, and the mass was measured. The mass of the swollen thin film piece was calculated by subtracting the mass of the polyester mesh alone. This mass was taken as W １ Then, the swelling degree was calculated using the following formula (F2): Swelling degree (%) = {(W １ -W ０ ) / W ０}×100 ... (F2) In formula (F2), W ０ is the mass of the thin film piece weighed before wrapping it in the polyester mesh, W １ indicates the mass of the thin film piece only after swelling.

[0079] [Ionic Conductivity Measurement] The lithium half-cells obtained in each of the Examples and Comparative Examples described below were measured using an AC impedance method, in which an AC voltage (applied voltage of 10 mV) is applied between the electrodes to measure the resistance component. The ionic conductivity was calculated from the real impedance intercept of the obtained Cole-Cole plot. A potentiostat / galvanostat (VMP-300, manufactured by biologic) was used for the measurement. The ionic conductivity (σ Ａ ) was calculated by the following formula (F3): Ａ =L Ａ / (R Ａ ×S Ａ ) ... (F3) In formula (F3), σ Ａ is the ionic conductivity (unit: S cm －１ ), R Ａis the resistance (unit: Ω), S Ａ is the cross-sectional area of ​​the solid electrolyte membrane at the time of measurement (unit: cm ２ ), L Ａ indicates the distance between the electrodes (unit: cm). The measurement temperature was 25°C. In addition, the ionic conductivity (σ Ａ ) was calculated.

[0080] Example 1 Synthesis of Polymerization Catalyst (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanecobalt(II) and pentafluorobenzoic acid were weighed out to a molar ratio of 1:1.1 and placed in a flask, to which was added dehydrated toluene. The flask was shielded from light with aluminum foil, and the reaction was carried out at room temperature for 20 hours. The chemical reaction formula is as follows: After completion of the reaction, the solvent was removed under reduced pressure, and the mixture was washed several times with an excess amount of hexane. This was then vacuum dried at room temperature to obtain a cobalt salen complex.

[0081]

[0082] (Synthesis of Copolymer A) A mixture of propylene oxide and allyl glycidyl ether in a molar ratio of 97:3 was used as the epoxide monomer. A synthesized cobalt salen complex was used as the polymerization catalyst, and bis(triphenylphosphoranylidene)ammonium chloride was used as the cocatalyst. The resulting mixture was weighed out in a molar ratio of epoxide monomer:catalyst:cocatalyst = 2000:1:1 and placed in a pressure vessel. 200 ppm of phenothiazine was then added, followed by ethyl acetate to achieve a monomer:ethyl acetate ratio of 50:50 (mass ratio). All of these operations were carried out with the pressure vessel purged with argon. Subsequently, the pressure vessel was purged, and carbon dioxide was introduced into the pressure vessel using a liquid pump. The pressure inside the pressure vessel was then increased to 2.0 MPa, and the polymerization reaction was carried out at 25°C for 20 hours. After the reaction was completed, chloroform was added to the contents of the pressure vessel to prepare a chloroform solution, and 1M hydrochloric acid was added. The chloroform solution was then added dropwise to stirring methanol to precipitate the product. Thereafter, the product was dried under reduced pressure in a desiccator using a diaphragm pump, and then vacuum dried at 60° C. to obtain copolymer A.

[0083] The structure of the obtained copolymer A was confirmed by nuclear magnetic resonance spectroscopy ( １ H-NMR (Biospin Avance 500, Bruker) using a solvent (CDCl ３ , containing 0.03 volume % tetramethylsilane), the molar ratio of the structural unit represented by general formula (1) (hereinafter also referred to as structural unit (1)), the structural unit represented by general formula (2) (hereinafter also referred to as structural unit (2)), the structural unit represented by general formula (3) (hereinafter also referred to as structural unit (3)), and the structural unit represented by general formula (4) (hereinafter also referred to as structural unit (4)) in copolymer A was structural unit (1): structural unit (2): structural unit (3): structural unit (4) = 94.5:2.9:2.5:0.1 (see Figure 3). The number average molecular weight Mn of the obtained copolymer A was 24,000, and the molecular weight distribution Mw / Mn was 1.1.

[0084] (Preparation of Thin Film) 1-hydroxycyclohexyl phenyl ketone was added as a photopolymerization initiator to the obtained copolymer A so that the copolymer:initiator ratio was 97:3% by mass. The solution was further diluted with ethyl acetate and stirred to prepare a thin film-forming solution with a solids concentration of 30% by mass. A first release film (manufactured by Lintec Corporation, product name "SP-PET381031") was prepared, and the prepared thin film-forming solution was applied to the release-treated surface of this release film and dried at 120°C for 1 minute to form a thin film layer with a thickness of 10 μm. Furthermore, a second release film (manufactured by Lintec Corporation, product name "SP-PET382150") was prepared, and the release-treated surface of this release film was bonded to the surface of the thin film layer. Thereafter, the thin film laminate sandwiched between the first release film and the second release film was placed on a stainless steel plate and irradiated with ultraviolet light [illuminance: 200 mW / cm] at 50°C. ２ , cumulative light amount: 1000 mJ / cm ２ and measuring using an illuminance actinometer (controller: EYE UV METER UVPF-A2, light-receiving part: EYE UV METER PD-365A2) manufactured by Eye Graphics Co., Ltd. to obtain a thin film having a thickness of 10 μm. The obtained thin film is a negative electrode protective film. The amount of elution and the degree of swelling of the obtained thin film were measured by the methods described above.

[0085] [Example 2] (Polymerization of Copolymer B) Polymerization was carried out in the same manner as in Example 1, except that a mixture of propylene oxide and allyl glycidyl ether in a molar ratio of 90:10 was used as the epoxide monomer. The structure of the obtained copolymer B was determined in the same manner as in Example 1. １ When confirmed by H-NMR, the molar ratio of structural unit (1), structural unit (2), structural unit (3), and structural unit (4) in copolymer B was structural unit (1):structural unit (2):structural unit (3):structural unit (4)=81.7:8.4:8.9:0.9. Furthermore, the number average molecular weight Mn of the obtained copolymer B was 25,000, and the molecular weight distribution Mw / Mn was 1.2.

[0086] (Preparation of Thin Film) A thin film having a thickness of 10 μm was obtained in the same manner as in Example 1, except that copolymer B was used.

[0087] [Example 3] (Polymerization of Copolymer C) Polymerization was carried out in the same manner as in Example 1, except that a mixture of propylene oxide and 4-hydroxybutyl acrylate glycidyl ether in a molar ratio of 98:2 was used as the epoxide monomer. The structure of the obtained copolymer C was determined in the same manner as in Example 1. １ When confirmed by H-NMR, the molar ratio of structural unit (1), structural unit (2), structural unit (3), and structural unit (4) in copolymer C was structural unit (1):structural unit (2):structural unit (3):structural unit (4)=95.0:2.1:2.8:0.1 (see FIG. 4). Furthermore, the number average molecular weight Mn of the obtained copolymer C was 38,000, and the molecular weight distribution Mw / Mn was 1.2.

[0088] (Preparation of Thin Film) A thin film having a thickness of 10 μm was obtained in the same manner as in Example 1, except that Copolymer C was used.

[0089] [Example 4] (Polymerization of Copolymer D) Polymerization was carried out in the same manner as in Example 1, except that a mixture of propylene oxide and 4-hydroxybutyl acrylate glycidyl ether in a molar ratio of 95:5 was used as the epoxide monomer. The structure of the obtained copolymer D was determined in the same manner as in Example 1. １When confirmed by H-NMR, the molar ratio of structural unit (1), structural unit (2), structural unit (3), and structural unit (4) in copolymer D was structural unit (1):structural unit (2):structural unit (3):structural unit (4)=92.3:5.1:2.5:0.1. Furthermore, the number average molecular weight Mn of the obtained copolymer D was 41,000, and the molecular weight distribution Mw / Mn was 1.1.

[0090] (Preparation of Thin Film) A thin film having a thickness of 10 μm was obtained in the same manner as in Example 1, except that copolymer D was used.

[0091] Comparative Example 1 Preparation of Thin Film Polyethylene carbonate (product name "QPAC25", manufactured by EMPOWER MATERIALS) was diluted with chloroform to prepare a solution with a solids concentration of 30% by mass. The prepared solution was applied to the release-treated surface of a release film (manufactured by LINTEC CORPORATION, product name "SP-PET381031") and dried at a temperature of 90°C for 1 minute to obtain a thin film with a thickness of 10 μm.

[0092] Comparative Example 2 Preparation of Thin Film Polypropylene carbonate (product name "QPAC40", manufactured by EMPOWER MATERIALS) was diluted with ethyl acetate to prepare a solution with a solids concentration of 30% by mass. The prepared solution was applied to the release-treated surface of a release film (manufactured by LINTEC Corporation, product name "SP-PET381031") and dried at a temperature of 120°C for 1 minute to obtain a thin film with a thickness of 10 μm.

[0093]

[0094]

[0095] The results shown in Table 2 indicate that the thin films obtained in Examples 1 to 4 had a small amount of elution despite a high degree of swelling, confirming that the copolymers obtained in Examples 1 to 4 have crosslinkability.

[0096] 10... positive electrode, 11... positive electrode composite layer, 13... positive electrode current collector, 20... negative electrode, 21... negative electrode composite layer, 23... negative electrode current collector, 30... electrolyte layer, 31... separator, 33... electrolyte solution, 100... battery.

Claims

1. The copolymer includes a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2) in an amount of 0.3 mol % to 20.0 mol %: Resin composition. 【Chemistry 1】 (In the general formula (1) and the general formula (2), R １ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; L １ and L ２ each independently represents a single bond or an alkylene group having 1 to 3 carbon atoms; １ is a reactive group represented by the following structural formula (2-2): 【Chemistry 2】

2. The resin composition according to claim 1, The copolymer further contains at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (3) and a structural unit represented by the following general formula (4), in an amount of 0.1 mol % to 30.0 mol %: Resin composition. 【Chemistry 3】 (In the general formula (3) and the general formula (4), R ２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; L ３ and L ４ each independently represents a single bond or an alkylene group having 1 to 3 carbon atoms; ２ is a reactive group represented by the following structural formula (4-2): 【Chemistry 4】

3. The resin composition according to claim 1 or 2, The crosslinked product of the resin composition is the amount of the copolymer eluted in ethyl acetate is 10% or less; The swelling ratio of the copolymer in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 is 100% or more. Resin composition.

4. The resin composition according to claim 1 or 2 is included. Binder resin.

5. The binder resin according to claim 4, battery.

6. The resin composition according to claim 1 or 2 is included. Polymer thin film.

7. The polymer thin film according to claim 6 , battery.

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