Resin composition, binder resin, polymer film, and battery

Abstract

A resin composition containing a copolymer containing a structural unit represented by general formula (1) and 0.3-20.0 mol% of a structural unit represented by general formula (2). (In general formula (1) and general formula (2), R1 is a hydrogen atom or an alkyl group having 1-3 carbon atoms, L1 and L2 are each independently a single bond or an alkylene group having 1-3 carbon atoms, and X1 is any reactive group among the groups represented by structural formula (2-1) and structural formula (2-2). ) # imgabs0 #.

Description

Technical Field

[0001] The present invention relates to a resin composition, an adhesive resin, a polymer film, and a battery. Background Art

[0002] Polycarbonate has been used for various purposes, and has also been used, for example, as a material in the field of batteries. An adhesive resin containing polycarbonate is used, for example, as a binder for forming an electrode. In addition, a polymer film containing polycarbonate is used, for example, as a separator for a battery.

[0003] For example, Patent Document 1 discloses a polymer adhesive containing a three-dimensional crosslinked aliphatic polycarbonate.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2020 / 203882 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] The polymer adhesive described in Patent Document 1 is an adhesive for a solid electrolyte and is not contemplated for use in a battery using an electrolytic solution. Therefore, when an electrode made of the polymer adhesive is used in a battery using an electrolytic solution, there is a risk of a problem such as elution of the polymer adhesive into the electrolytic solution.

[0009] An object of the present invention is to provide a resin composition having crosslinkability, and an adhesive resin, a polymer film, and a battery.

[0010] Means for Solving the Problems

[0011] [1] A resin composition comprising a copolymer containing 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% or more and 20.0 mol% or less,

[0012] [Chemical Formula 1]

[0013]

[0014] In the above general formula (1) and the above general formula (2), R 1 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and L 1 and L 2 are each independently a single bond or an alkylene group having 1 or more and 3 or less carbon atoms, and X 1 is any reactive group among the groups represented by the following structural formula (2-1) and the following structural formula (2-2),

[0015] [Chemical Formula 2]

[0016] .

[0017] [2] The resin composition according to [1], wherein,

[0018] The above copolymer further contains at least one structural unit selected from the structural unit represented by the following general formula (3) and the structural unit represented by the following general formula (4), and the content is 0.1 mol% or more and 30.0 mol% or less,

[0019] [Chemical Formula 3]

[0020]

[0021] In the above general formula (3) and the above general formula (4), R 2 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and L 3 and L 4 are each independently a single bond or an alkylene group having 1 or more and 3 or less carbon atoms, and X 2 is any reactive group among the groups represented by the following structural formula (4-1) and the following structural formula (4-2),

[0022] [Chemical Formula 4]

[0023] .

[0024] [3] The resin composition according to [1] or [2], wherein,

[0025] In the crosslinked product of the above resin composition,

[0026] The amount of the above copolymer dissolved in ethyl acetate is 10% or less,

[0027] The swelling ratio of the above copolymer in a mixed solvent having a volume ratio of ethylene carbonate to dimethyl carbonate of 1:1 is 100% or more.

[0028] [4] An adhesive resin comprising the resin composition according to any one of [1] to [3].

[0029] [5] A battery comprising the adhesive resin according to [4].

[0030] [6] A polymer film comprising the resin composition according to any one of [1] to [3].

[0031] [7] A battery comprising the polymer film according to [6].

[0032] According to one aspect of the present invention, a resin composition having crosslinkability, an adhesive resin, a polymer film, and a battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. is a cross-sectional view schematically showing an example of the main part of the battery of the present embodiment.

[0034] Figure 2 FIG. is a diagram for explaining the effect when the polymer film of the present embodiment is used as a battery separator.

[0035] Figure 3 FIG. shows the 1 1H-NMR measurement results of the copolymer produced in Example 1.

[0036] Figure 4 FIG. shows the 1 1H-NMR measurement results of the copolymer produced in Example 3.

[0037] SYMBOL DESCRIPTION

[0038] 10... positive electrode, 11... positive electrode mixture layer, 13... positive electrode current collector, 20... negative electrode, 21... negative electrode mixture layer, 23... negative electrode current collector, 30... electrolyte layer, 31... separator, 33... electrolytic solution, 100... battery. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] Hereinafter, the present invention will be described by way of examples. The present invention is not limited to the content of the embodiments.

[0040] [Resin Composition]

[0041] A preferred example of the resin composition of the present embodiment will be described.

[0042] The resin composition of the present embodiment contains a copolymer containing a structural unit represented by the general formula (1) and a structural unit represented by the general formula (2) in an amount of 0.3 mol% or more and 20.0 mol% or less.

[0043] According to the resin composition of the present embodiment, it has crosslinkability by having the above constitution. In addition, by using the resin composition of the present embodiment, an adhesive resin excellent in adhesion to a metal foil and adhesion to an inorganic material can be obtained. In addition, by using the resin composition of the present embodiment, a polymer film having high swelling properties with respect to an electrolytic solution or the like can be obtained.

[0044] Further, for example, when the resin composition of the present embodiment is used as a material in the battery field, for the copolymer used in the resin composition of the present embodiment, by setting the main polymer skeleton as a carbonate skeleton, the compatibility with the electrolyte is improved. Therefore, when assembling a battery, after injecting the electrolyte, the polymer thin film serving as a separator can be swollen. Further, by containing 0.3 mol% or more and 20.0 mol% or less of the structural unit represented by the general formula (2) having a reactive group, the crosslinking reaction proceeds moderately, and thus, high swelling degree and low elution amount can be achieved at the same time.

[0045] The resin composition of the present embodiment only needs to contain a specific copolymer having the above-described constitution, and may contain other components as long as the object of the present invention is not impaired.

[0046] (Copolymer)

[0047] The copolymer contained in the resin composition of the present embodiment is a copolymer containing the structural unit represented by the following general formula (1) and 0.3 mol% or more and 20.0 mol% or less of the structural unit represented by the following general formula (2).

[0048] [Chemical formula 5]

[0049]

[0050] In the general formula (1) and the general formula (2),

[0051] R 1 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

[0052] L 1 and L 2 are each independently a single bond or an alkylene group having 1 or more and 3 or less carbon atoms, preferably a methylene group or an ethylene group, and particularly preferably a methylene group.

[0053] X 1 is any reactive group among the groups represented by the following structural formula (2-1) and the following structural formula (2-2). It should be noted that the wavy line in the structural formula indicates the bonding position.

[0054] [Chemical formula 6]

[0055]

[0056] Such a copolymer may be a random copolymer or a block copolymer. From the viewpoint of ease of synthesis, the above copolymer is preferably a random copolymer.

[0057] In the case where the copolymer contained in the resin composition of the present embodiment is, for example, a copolymer formed of a structural unit represented by the general formula (1) and a structural unit represented by the general formula (2), the constituent ratio is as described below.

[0058] With respect to all the structural units, the ratio of the structural unit represented by the general formula (2) must be 0.3 mol% or more and 20 mol% or less. If this ratio is less than 0.3 mol%, the dissolution amount becomes high. On the other hand, if this ratio exceeds 20.0 mol%, there is a problem that the crosslinking density of the copolymer becomes high and the swelling property decreases.

[0059] From the same viewpoint, the ratio of the structural unit represented by the general formula (2) is preferably 1.0 mol% or more, more preferably 1.5 mol% or more, and further preferably 1.8 mol% or more. On the other hand, the ratio of the structural unit represented by the general formula (2) is preferably 19.0 mol% or less, more preferably 18.0 mol% or less, further preferably 12.0 mol% or less, and particularly preferably 6.0 mol% or less.

[0060] With respect to all the structural units, the ratio of the structural unit represented by the general formula (1) must be 80.0 mol% or more and 99.7 mol% or less. In addition, the ratio of the structural unit represented by the general formula (1) is preferably 81.0 mol% or more, more preferably 82.0 mol% or more, further 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 the general formula (1) is preferably 99.0 mol% or less, more preferably 98.5 mol% or less, and further preferably 98.2 mol% or less.

[0061] Preferably, the copolymer contained in the resin composition of the present embodiment further contains at least one structural unit selected from the structural unit represented by the following general formula (3) and the structural unit represented by the following general formula (4) in an amount of 0.1 mol% or more and 30.0 mol% or less.

[0062] By forming a copolymer having an ether skeleton such as the structural unit represented by the general formula (3) or the general formula (4), the glass transition temperature of the copolymer is lowered and the film is softened, so that an increase in ionic conductivity can be expected.

[0063] [Chemical formula 7]

[0064]

[0065] In the general formula (3) and the general formula (4),

[0066] R 2 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

[0067] L 3 and L 4 are each independently a single bond or an alkylene group having 1 or more and 3 or less carbon atoms, preferably a methylene group or an ethylene group, and particularly preferably a methylene group.

[0068] X 2 is any reactive group among the groups represented by the following structural formula (4-1) and the following structural formula (4-2). It should be noted that the wavy line in the structural formula indicates the bonding position.

[0069] [Chemical formula 8]

[0070]

[0071] In the case where the copolymer contained in the resin composition of the present embodiment is, for example, a copolymer formed of a structural unit represented by the general formula (1), a structural unit represented by the general formula (2), a structural unit represented by the general formula (3), and a structural unit represented by the general formula (4), the constituent ratio is as described below.

[0072] The ratio of the structural unit represented by the general formula (2) is as described above.

[0073] With respect to all the structural units, the total ratio of the structural unit represented by the general formula (3) and the structural unit represented by the general formula (4) is preferably 0.1 mol% or more and 30.0 mol% or less. If their total ratio is less than 0.1 mol%, there is a tendency that the effects brought about by the ether skeleton cannot be fully exhibited. On the other hand, if their total ratio exceeds 30.0 mol%, the compatibility with the electrolyte deteriorates, the degree of swelling decreases, and there is a tendency for the ionic conductivity to decrease.

[0074] From the same viewpoint, their total ratio is preferably 1.0 mol% or more, more preferably 2.0 mol% or more. On the other hand, their total ratio is preferably 25.0 mol% or less, more preferably 20.0 mol% or less, and particularly preferably 10.0 mol% or less.

[0075] With respect to all the structural units, the ratio of the structural unit represented by the general formula (1) is preferably 50.0 mol% or more and 99.6 mol% or less. In addition, the ratio of the structural unit represented by the 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 the general formula (1) is preferably 98.0 mol% or less, more preferably 94.0 mol% or less.

[0076] Regarding the molecular weight measured by the method shown in the measurement example of the copolymer of the present embodiment, when expressed as the weight-average molecular weight (Mw), it is preferably 5,000 or more and 5,000,000 or less, more preferably 10,000 or more and 1,000,000 or less.

[0077] In addition, regarding the molecular weight measured by the method shown in the measurement example of the copolymer of the present embodiment, when expressed as the number-average molecular weight (Mn), it is preferably 3,000 or more and 3,000,000 or less, more preferably 5,000 or more and 500,000 or less.

[0078] In addition, the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) is preferably 1 or more and 10 or less, more preferably 1.1 or more and 5 or less. By making the molecular weight and molecular weight distribution of the above copolymer within the above ranges, sufficient processability can be achieved when formed into a film shape. In addition, when the above copolymer is used as an adhesive, by making the molecular weight and molecular weight distribution of the above copolymer within the above ranges, when producing an electrode paste, the viscosity of the paste can be made appropriate, sedimentation of the active material and conductive assistant can be suppressed, and sufficient dispersibility of the active material and conductive assistant can be obtained.

[0079] (Method for producing copolymer)

[0080] The method for producing the copolymer contained in the resin composition of the present embodiment is not particularly limited and can be obtained by a known method. For example, it can be produced by the method described below.

[0081] As described in the examples below, it 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 form a structural unit represented by the general formula (3), and by polymerizing a part of propylene oxide while undergoing ring-opening with carbon dioxide, a structural unit represented by the general formula (1) is formed.

[0082] The polymerization catalyst used in the copolymerization reaction of the epoxide monomer and carbon dioxide is not particularly limited, and examples thereof include metal Salen complex catalysts such as cobalt Salen catalyst and organozinc catalysts.

[0083] Regarding the amount of the polymerization catalyst used in the copolymerization reaction of the epoxide monomer and carbon dioxide, for example, in the case of a metal Salen complex catalyst, relative to 1 mole of the epoxide monomer, it is preferably 0.05 mole or less, more preferably 0.01 mole or less, and particularly preferably 0.001 mole or less.

[0084] In addition, in the case of using a metal Salen complex catalyst, a cocatalyst can be used. As the cocatalyst, for example, preferably a salt compound. As the above specific examples of the salt compound are not particularly limited. From the viewpoint of high reactivity, preferably bis(triphenylphosphoranylidene)ammonium chloride, piperidine, bis(triphenylphosphoranylidene)ammonium fluoride, ammonium pentafluorobenzoate, tetra-n-butylammonium chloride, etc.

[0085] It should be noted that for the polymerization conditions, the optimal conditions vary depending on the type of catalyst. For example, the pressure of carbon dioxide 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.

[0086] In addition, for the polymerization temperature, for example, in the case of a cobalt Salen complex catalyst, from the viewpoint of well exerting the catalyst effect and promoting the reaction rate, it is preferably around room temperature (25 °C).

[0087] In the method of copolymerizing an epoxide monomer and carbon dioxide, examples of the epoxide monomer that can be used as a starting material include: ethylene oxide, propylene oxide, 1,2-epoxybutane, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether, etc. It should be noted that for the molar ratio of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) in the copolymer, due to differences in reactivity, it sometimes does not match the mixing ratio based on the molar ratio of the epoxide monomer that becomes the structural unit represented by the general formula (1) and the epoxide monomer that becomes the structural unit represented by the general formula (2).

[0088] (Properties of the crosslinked product of the resin composition)

[0089] In the crosslinked product of the resin composition of the present embodiment, the elution amount of the copolymer in ethyl acetate is preferably 40% or less, more preferably 30% or less, further preferably 20% or less, particularly preferably 10% or less, and very preferably 7% or less. Since the low molecular weight components of the eluted copolymer become irreversible capacity, it is preferably that the elution amount is as low as possible. The lower limit value of the elution amount of the copolymer is not particularly limited. For example, it can be 1% or more, can also be 0.1% or more, and can also be 0%.

[0090] In the crosslinked product of the resin composition of the present embodiment, it is preferred that the elution amount of the copolymer in ethyl acetate is in the above range, and the swelling degree of the copolymer in a mixed solvent with a volume ratio of ethylene carbonate to dimethyl carbonate of 1:1 is 100% or more.

[0091] Preferably, the crosslinked product of the resin composition of the present embodiment has high swelling properties with respect to electrolytes and carbonate solvents used as solvents for electrolytes. From this perspective, the swelling degree of the copolymer with respect to the mixed solvent having a volume ratio of ethylene carbonate to dimethyl carbonate of 1:1 is preferably 100% or more, more preferably 200% or more, further preferably 300% or more, particularly preferably 500% or more, very preferably 700% or more, and most preferably 900% or more. The upper limit value of the swelling degree is not particularly limited and can be, for example, 2000% or less.

[0092] (Crosslinking method of resin composition)

[0093] From the perspective of easily obtaining a polymer film formed by crosslinking a copolymer, the resin composition of the present embodiment preferably uses a photoinitiator. In the resin composition of the present embodiment, when a photoinitiator is used, the film containing the copolymer reacts with the reactive groups (allyl group and (meth)acryloyl group) on the side chains of the copolymer in the film to undergo crosslinking.

[0094] The photoinitiator is not particularly limited, and known compounds can be cited. The photoinitiator is preferably a photoinitiator that is sensitive to ultraviolet light. The photoinitiator can be used alone or in combination of two or more.

[0095] Specific examples of the photoinitiator include, for example: 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-hydroxycyclohexyl phenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; ketal compounds such as benzyl dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-benzoyl-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenones such as benzoic anhydride and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone; benzophenone compounds such as camphorquinone; halogenated ketones, acylphosphines, acylphosphonates, and oligo[2-hydroxy-2-methyl-1-(4-(1-methylethenyl)phenyl)acetone], etc.

[0096] The content of the photopolymerization initiator is, for example, preferably 0.1 part by mass or more and 10 parts by mass or less, more preferably 0.5 part by mass or more and 7.5 parts by mass or less, and further preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the copolymer.

[0097] By irradiating an energy ray to a molded article obtained by molding the resin composition of the present embodiment into a given shape, the copolymer is crosslinked, and a thin film as a crosslinked product of the copolymer can be obtained. The type of the energy ray is not particularly limited, and from the viewpoints of reactivity and operability, ultraviolet rays are preferred. The apparatus for irradiating the molded article with ultraviolet rays is not particularly limited. For example, it may be an apparatus equipped with an ultraviolet LED lamp, may be an apparatus equipped with a high-pressure mercury lamp, or may be an apparatus equipped with a metal halide lamp.

[0098] The conditions for irradiating the molded article with ultraviolet rays are not particularly limited. Examples of the maximum illuminance and the integrated light quantity at the time of irradiating ultraviolet rays include the following conditions. The maximum illuminance is preferably 5 mW / cm 2 or more and 1000 mW / cm 2 or less. The integrated light quantity is preferably 50 mJ / cm 2 or more and 5000 mJ / cm 2 or less.

[0099] [Adhesive resin]

[0100] The adhesive resin of the present embodiment contains the resin composition of the present embodiment. When the adhesive resin of the present embodiment is used as a material for the binder layer in an electrode of a secondary battery, the adhesive resin of the present embodiment has excellent swelling properties with respect to the electrolytic solution, and also has excellent adhesion to the metal foil and adhesiveness to the inorganic material. The reason is not clear yet, but it is considered as follows.

[0101] In the case where an existing adhesive resin is used for the binder layer of a secondary battery such as a lithium ion battery, by suppressing the swelling properties with respect to the electrolytic solution to a low level, even if the adhesive resin swells due to the electrolytic solution, the adhesion between the binder layer and the current collector and the adhesion between the active substances in the binder layer can be obtained.

[0102] It can be considered that since the electrolyte penetrates into the binder layer in contact with the electrolyte, the binder layer has a contact region between the binder resin and the active material and a contact region between the active material and the electrolyte. Existing binder resins have low swelling properties with respect to the electrolyte. Therefore, it is difficult to exhibit ionic conductivity, and the ionic conductivity of ions such as lithium ions contained in the electrolyte is low in the contact region between the binder resin and the active material. On the other hand, in the contact region between the active material and the electrolyte, the ionic conductivity of ions such as lithium ions contained in the electrolyte is increased. In addition, since existing binder resins have low swelling properties with respect to the electrolyte, the area of the contact region between the binder resin and the active material does not expand much, and this contact area is small. On the other hand, the area of the contact region between the active material and the electrolyte is large.

[0103] It can be considered that although the electrolyte is not easily decomposed in the contact region between the binder resin and the active material, a decomposition layer of the electrolyte called the SEI (Solid Electrolyte Interphase) layer is easily formed in the contact region between the active material and the electrolyte. When an existing binder resin is used as the binder layer, as described above, since the area of the contact region between the active material and the electrolyte is large, the area where the SEI layer can be formed also becomes large. Thus, the life of the electrolyte is easily reduced.

[0104] In contrast, when the binder resin of the present embodiment is used for the binder layer of a secondary battery such as a lithium ion battery, the binder resin of the present embodiment contains a copolymer having a carbonate skeleton as the main polymer skeleton. Thus, the compatibility with the electrolyte is improved, and therefore, it has high swelling properties with respect to the electrolyte. Moreover, the binder resin of the present embodiment swells significantly when in contact with the electrolyte, thereby exhibiting ionic conductivity. In addition, since the binder resin of the present embodiment has high swelling properties with respect to the electrolyte, the area of the contact region between the binder resin and the active material becomes large. On the other hand, the area of the contact region between the active material and the electrolyte becomes small. Therefore, it can be considered that when the binder resin of the present embodiment is used, ionic conductivity can be exhibited in the contact region between the binder resin and the active material, and the electrolyte is not easily decomposed. It can be considered that in the contact region between the active material and the electrolyte, the area where the SEI layer is formed is suppressed. Thus, it can be considered that when the binder resin of the present embodiment is used for the binder layer of a secondary battery such as a lithium ion battery, it contributes to the improvement of the life of the electrolyte, and it can be considered that as a result, the battery performance is improved. However, when the swelling property with respect to the electrolyte is too high, the adhesion to the metal foil and the adhesion to the inorganic material are easily reduced.

[0105] The adhesive resin of the present embodiment has excellent adhesion to the metal foil and adhesiveness to the inorganic material, and thus can be applied to uses that require such characteristics. The adhesive resin of the present embodiment is, for example, preferably applicable to the use of a battery. In this case, the adhesive resin of the present embodiment is, for example, preferably an adhesive resin for a battery electrode, and is also preferably an adhesive resin for an electrode of a secondary battery such as a lithium ion battery. The adhesive resin of the present embodiment can also be applied as an adhesive resin for a binder layer in a positive electrode, and can also be applied as an adhesive resin for a binder layer in a negative electrode.

[0106] [Polymer film]

[0107] The polymer film of the present embodiment contains the resin composition of the present embodiment. According to the polymer film of the present embodiment, a polymer film having high swelling properties with respect to an electrolytic solution or the like can be obtained. The reason for this has not been determined, but the following can be considered. The copolymer used in the polymer film of the present embodiment improves the compatibility with the electrolytic solution by setting the main polymer skeleton as a carbonate skeleton. Therefore, when assembling the battery, after injecting the electrolytic solution, the polymer film as a separator can be swollen. Moreover, by containing a given amount of the structural unit represented by the general formula (2) having a reactive group, the crosslinking reaction proceeds moderately, and thus it is possible to achieve both a high swelling degree and a low elution amount.

[0108] The polymer film of the present embodiment has high swelling properties with respect to an electrolytic solution or the like, and thus can be applied to uses that require such characteristics. The polymer film of the present embodiment is, for example, preferably applicable to the use of a battery. In this case, the polymer film of the present embodiment is, for example, preferably a separator for a battery, and is also preferably a separator for a secondary battery such as a lithium ion battery. In addition, the polymer film of the present embodiment is, for example, preferably a negative electrode protective film that covers at least a part of the negative electrode of the battery, and is also preferably a negative electrode protective film of a secondary battery such as a lithium ion battery.

[0109] [Battery]

[0110] Next, a preferred example of the battery of the present embodiment will be described.

[0111] The battery of the present embodiment is a battery to which the resin composition of the present embodiment is applied. The battery of the present embodiment contains the adhesive resin of the present embodiment as a material for forming the electrodes of the battery. In addition, the battery of the present embodiment contains, for example, the polymer film of the present embodiment as a separator for the battery. 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 having excellent characteristics can be obtained. In addition, as the battery, a secondary battery is preferred, and a secondary battery such as a lithium ion battery is more preferred. The structure of the battery of the present embodiment is not particularly limited, and may be a laminated structure or a wound structure.

[0112] Here, an example of a battery using the polymer film of the present embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, for ease of explanation, there are parts shown enlarged or reduced.

[0113] Figure 1 An example of a battery as an example of using the polymer film of the present embodiment is shown. Figure 1 The battery 100 shown is a lithium ion secondary battery. As Figure 1 shown, the battery 100 includes a positive electrode 10, a negative electrode 20, and an electrolyte layer 30 disposed 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 mixture 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 mixture layer 21 laminated on the negative electrode current collector 23. The electrolyte layer 30 is composed of an electrolytic solution 33 and a separator 31 impregnated with the electrolytic solution 33. Through the separator 31, the positive electrode 10 side and the negative electrode 20 side are separated from each other. The battery 100 has a laminated structure in which the positive electrode current collector 13, the positive electrode mixture layer 11, the electrolyte layer 30, the negative electrode mixture layer 21, and the 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).

[0114] In the battery 100, the positive electrode mixture layer 11 and the negative electrode mixture layer 21 preferably contain the binder resin (not shown) of the present embodiment. In this case, the positive electrode mixture layer 11 and the negative electrode mixture layer 21 contain the electrolytic solution 33 by impregnating the electrolytic solution 33 of the electrolyte layer 30, and the binder resin of the present embodiment (not shown) swells due to the electrolytic solution 33.

[0115] In the battery 100, it is preferable to use the polymer film of the present embodiment as the separator 31.

[0116] In the battery 100, it is preferable to use the polymer film of the present embodiment as a negative electrode protective film (not shown) that covers at least a part of the negative electrode mixture layer 21.

[0117] According to the battery using the polymer film of the present embodiment, by having the above-described configuration, generation of dendritic crystals can be suppressed. The reason has not been determined yet, but the following can be considered. When the polymer film of the present embodiment is used as the separator 31, after injecting the electrolytic solution during battery assembly, as Figure 2As shown in (A), the separator 31 and the electrolyte 33 are separated. In such a state, there is a gap caused by fine unevenness between the negative electrode mixture layer 21 and the separator 31. Moreover, the inventors et al. inferred that dendritic crystals would precipitate in this part. On the other hand, the separator 31 using the polymer film of the present embodiment has high swelling property with respect to the electrolyte 33. Therefore, after a period of time when the electrolyte is injected, as Figure 2 shown in (B), the separator 31 swells. Moreover, due to such swelling of the separator 31, as Figure 2 shown in (C), the gap between the negative electrode mixture layer 21 and the separator 31 disappears. Therefore, when using the polymer film of the present embodiment as the separator 31, the generation of dendritic crystals can be suppressed.

[0118] Above, with reference to Figure 1 and Figure 2 an example of the battery of the present embodiment has been described, but the examples of the battery of the present embodiment are not limited thereto. The battery of the present embodiment only needs to use the polymer film of the present embodiment and can adopt various forms.

[0119] Examples of the 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.

[0120] 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 auxiliary such as a carbonaceous material, and the binder resin of the present embodiment.

[0121] The negative electrode mixture layer is preferably composed of, for example, a negative electrode active material such as acetylene black, carbon nanotubes, carbon nanofibers, graphene, and the binder resin of the present embodiment.

[0122] The electrolyte layer is preferably composed of, for example, an electrolyte and a separator which is the polymer film of the present embodiment.

[0123] In the battery of the present embodiment, the electrolyte preferably contains a lithium salt and a carbonate solvent. From the viewpoint of easily improving the effect of suppressing the generation of dendritic crystals, the molar ratio of the lithium salt to the carbonate solvent (the above lithium salt / the above carbonate 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 further preferably 1 / 3 or more and 1 / 1 or less.

[0124] Lithium salts, for example, specifically include: lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium 2-trifluoromethyl-4,5-dicyanoimidazole, lithium 4,5-dicyano-1,2,3-triazole, lithium bis(pentafluoroethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium nitrate, lithium chloride, lithium bromide, and lithium fluoride, etc. One or more of the lithium salts exemplified above can be used.

[0125] Carbonate solvents, for example, specifically include: dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate, etc. One or more of the carbonate solvents exemplified above can be used. Here, the carbonate solvents in this embodiment represent compounds having a carbonate skeleton in the molecular structure.

[0126] It should be noted that the present invention is not limited to the above embodiments, and variations, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention.

[0127] Examples

[0128] Hereinafter, examples are listed to explain the present invention in more detail, but the present invention is not limited by any of these examples.

[0129] The measurements or evaluations in the following examples and comparative examples were carried out by the methods shown below.

[0130] [Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)]

[0131] The measurement was carried out using a gel permeation chromatography device (manufactured by Tosoh Corporation, product name "HLC-8320GPC") under the following conditions, and the values measured by standard polystyrene conversion were used.

[0132] (Measurement conditions)

[0133] · Column: A column formed by connecting "TSKgel guardcolumn SuperH-H", "TSKgel SuperHM-H", "TSKgel SuperHM-H", and "TSKgel SuperH2000" (all manufactured by Tosoh Corporation) in sequence

[0134] · Column temperature: 40 °C

[0135] · Elution solvent: Tetrahydrofuran (copolymer concentration 1 mass%)

[0136] · Standard substance: Polystyrene

[0137] · Injection volume: 20 μL

[0138] ·Flow rate: 0.60 mL / min

[0139] ·Detector: Differential refractometer

[0140] [Determination of dissolution amount]

[0141] Weigh the films obtained in each of the following Examples and Comparative Examples in such a way as to reach approximately 300 mg. Let the mass of the film at this time be M0. Wrap the film with a polyester sieve (mesh size 200). Weigh the mass of the film wrapped with the polyester sieve, subtract the mass of the film, and thus calculate the mass of the polyester sieve alone. Next, immerse the film wrapped with the polyester sieve in ethyl acetate at 23 °C for 48 hours. Then, take out the film wrapped with the polyester sieve from ethyl acetate, dry it in an oven at 120 °C for 2 hours, and further air-dry it in an environment at a temperature of 23 °C and a relative humidity of 50% for 2 hours. Weigh the mass after air-drying, subtract the mass of the above-mentioned polyester sieve alone, and thus calculate the mass of the film after immersion only. Let the mass at this time be M1. Then, use the following mathematical formula (F1) to calculate the dissolution amount.

[0142] Dissolution amount (%) = {(M0 - M1) / M0} × 100 ··· (F1)

[0143] In the mathematical formula (F1), M0 represents the mass of the film weighed before being wrapped with the polyester sieve, and M1 represents the mass of the film only after immersion in ethyl acetate.

[0144] [Determination of swelling degree]

[0145] Cut the films obtained in each of the following Examples and Comparative Examples into approximately 3 cm (long) × approximately 3 cm (wide), and weigh the obtained film pieces in such a way as to reach approximately 1 g. Let the mass at this time be W0. Wrap the film pieces with a polyester sieve (mesh size 200), weigh the mass of the film pieces wrapped with the polyester sieve, subtract the mass of the film pieces, and thus calculate the mass of the polyester sieve alone. Immerse them in a carbonate solvent [composition: a mixed solvent of ethylene carbonate / dimethyl carbonate = 1 / 1 (volume ratio)] for 24 hours to cause swelling. Then, lift the film pieces wrapped with the polyester sieve, wipe off the solvent on the surface with a wiping paper, measure the mass, subtract the mass of the above-mentioned polyester sieve alone, and thus calculate the mass of the film pieces after swelling. Let the mass at this time be W1. Then, use the following mathematical formula (F2) to calculate the swelling degree.

[0146] Swelling degree (%) = {(W1 - W0) / W0} × 100 ··· (F2)

[0147] In the mathematical formula (F2), W0 represents the mass of the film sheet before being wrapped by the polyester sieve, and W1 represents the mass of only the film sheet after swelling.

[0148] [Ionic conductivity measurement]

[0149] For the lithium half-cells obtained in the following respective examples and comparative examples, measurement was performed by an alternating current impedance method for measuring the resistance component by applying an alternating current (applied voltage: 10 mV) between the electrodes. The ionic conductivity was calculated from the real impedance intercept of the obtained Cole-Cole plot. Note that a potentiostat / galvanostat (VMP-300, manufactured by Biologic) was used for the measurement.

[0150] Ionic conductivity (σ A ) is obtained by the following mathematical formula (F3).

[0151] σ A = L A / (R A ×S A ) ··· (F3)

[0152] In the mathematical formula (F3), σ A represents the ionic conductivity (unit: S·cm -1 ), R A represents the resistance (unit: Ω), S A represents the cross-sectional area at the time of measuring the solid electrolyte membrane (unit: cm 2 ), and L A represents the distance between the electrodes (unit: cm).

[0153] The measurement temperature was 25°C. In addition, the ionic conductivity (σ A ) was calculated from the measurement results of the complex impedance.

[0154] [Example 1]

[0155] (Synthesis of polymerization catalyst)

[0156] (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexanecobalt(II) and pentafluorobenzoic acid were weighed in a molar ratio of 1:1.1, placed in a flask, and dehydrated toluene was added thereto. The flask was shielded from light with aluminum foil and allowed to react at room temperature for 20 hours. The chemical reaction formula is as described below. After completion of the reaction, the solvent was removed under reduced pressure and washed several times with an excess of hexane. Then, vacuum drying was performed at room temperature to obtain a cobalt Salen complex.

[0157] [Chemical formula 9]

[0158]

[0159] (Synthesis of Copolymer A)

[0160] As the epoxide monomer, a substance obtained by mixing propylene oxide and allyl glycidyl ether in a molar ratio of 97:3 was used. The cobalt Salen complex synthesized as a polymerization catalyst and bis(triphenylphosphonium) ammonium chloride as a cocatalyst were weighed in a molar ratio of epoxide monomer:catalyst:cocatalyst = 2000:1:1 and placed in a pressure-resistant container. After further adding 200 ppm of phenothiazine, ethyl acetate was added in a ratio of monomer:ethyl acetate = 50:50 (mass ratio). All of the above operations were carried out by replacing the inside of the pressure vessel with argon. Then, after purging the inside of the pressure vessel, carbon dioxide was introduced into the pressure vessel through a liquid delivery pump to make the pressure inside the pressure vessel 2.0 MPa, and a polymerization reaction was carried out at 25 °C for 20 hours.

[0161] After the reaction was completed, chloroform was added to the content of the pressure vessel to prepare a chloroform solution, and 1M hydrochloric acid was added. Then, the chloroform solution was dropped into the stirring methanol to precipitate the product. Then, for the product, vacuum drying was carried out in a dryer using a diaphragm pump, and then vacuum drying was carried out at 60 °C to obtain copolymer A.

[0162] By nuclear magnetic resonance spectroscopy ( 1 1H-NMR, Biospin Avance 500, manufactured by Bruker Corporation), using (CDCl3, containing 0.03 vol% tetramethylsilane) as a solvent, the structure of the obtained copolymer A was confirmed. As a result, the molar ratio of the structural unit represented by the general formula (1) (hereinafter also referred to as structural unit (1)), the structural unit represented by the general formula (2) (hereinafter also referred to as structural unit (2)), the structural unit represented by the general formula (3) (hereinafter also referred to as structural unit (3)), and the structural unit represented by the 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 (refer to Figure 3 ).

[0163] In addition, the number-average molecular weight Mn of the obtained copolymer A was 24000, and the molecular weight distribution Mw / Mn was 1.1.

[0164] (Fabrication of Thin Film)

[0165] For the obtained copolymer A, 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator was added in such a manner that the copolymer:initiator = 97:3 mass %, and after further dilution with ethyl acetate and stirring, a solution for forming a film with a solid content concentration of 30 mass % was prepared. A first release film (manufactured by Lintec Corporation, product name "SP-PET381031") was prepared, and the prepared solution for forming a film was coated on the release-treated surface of this release film and dried at 120 °C for 1 minute to form a film layer with a thickness of 10 μm. A second release film (manufactured by Lintec Corporation, product name "SP-PET382150") was further prepared, and the release-treated surface of this release film was adhered to the surface of the film layer. Then, the laminate of the film sandwiched between the first release film and the second release film was placed on a stainless steel plate, and ultraviolet irradiation was performed under heating at 50 °C [using illuminance: 200 mW / cm 2 and cumulative light quantity: 1000 mJ / cm 2 , and measurement was performed using an illuminance and light quantity meter manufactured by EYE GRAPHICS (control unit: EYE UVMETER UVPF-A2, light-receiving unit: EYE UV METER PD-365A2), and thus a film with a thickness of 10 μm was obtained. The obtained film was a negative electrode protective film. The dissolution amount and swelling degree of the obtained film were measured by the above method.

[0166] [Example 2]

[0167] (Polymerization of copolymer B)

[0168] As the epoxide monomer, a substance obtained by mixing propylene oxide and allyl glycidyl ether in a molar ratio of 90:10 was used, and polymerization was carried out in the same manner as in Example 1 except for this. In the same manner as in Example 1, 1 the structure of the obtained copolymer B was confirmed by 1H-NMR. As a result, 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.

[0169] In addition, the number average molecular weight Mn of the obtained copolymer B was 25000, and the molecular weight distribution Mw / Mn was 1.2.

[0170] (Production of film)

[0171] Copolymer B was used, and except for this, a film with a thickness of 10 μm was obtained by the same method as in Example 1.

[0172] [Example 3]

[0173] (Polymerization of Copolymer C)

[0174] As the epoxide monomer, a substance obtained by mixing propylene oxide and glycidyl acrylate 4 - hydroxybutyl ether in a molar ratio of up to 98:2 was used. Except for this, the polymerization was carried out in the same manner as in Example 1. In the same way as in Example 1, through 1 1H - NMR, the structure of the obtained copolymer C was confirmed. As a result, 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 (refer to Figure 4 ).

[0175] In addition, the number - average molecular weight Mn of the obtained copolymer C was 38000, and the molecular weight distribution Mw / Mn was 1.2.

[0176] (Fabrication of Thin Film)

[0177] Copolymer C was used. Except for this, a thin film with a thickness of 10 μm was obtained by the same method as in Example 1.

[0178] [Example 4]

[0179] (Polymerization of Copolymer D)

[0180] As the epoxide monomer, a substance obtained by mixing propylene oxide and glycidyl acrylate 4 - hydroxybutyl ether in a molar ratio of up to 95:5 was used. Except for this, the polymerization was carried out in the same manner as in Example 1. In the same way as in Example 1, through 1 1H - NMR, the structure of the obtained copolymer D was confirmed. As a result, 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.

[0181] In addition, the number - average molecular weight Mn of the obtained copolymer D was 41000, and the molecular weight distribution Mw / Mn was 1.1.

[0182] (Fabrication of Thin Film)

[0183] Copolymer D was used. Except for this, a thin film with a thickness of 10 μm was obtained by the same method as in Example 1.

[0184] [Comparative Example 1]

[0185] (Fabrication of Thin Film)

[0186] The poly(ethylene carbonate) (trade name "QPAC25", manufactured by EMPOWER MATERIALS) was diluted with chloroform to prepare a solution with a solid component concentration of 30% by mass. The prepared solution was coated on the release-treated surface of a release film (manufactured by Lintec Corporation, product name "SP-PET381031") and dried at 90 °C for 1 minute to obtain a film with a thickness of 10 μm.

[0187] [Comparative Example 2]

[0188] (Fabrication of the film)

[0189] The poly(propylene carbonate) (trade name "QPAC40", manufactured by EMPOWER MATERIALS) was diluted with ethyl acetate to prepare a solution with a solid component concentration of 30% by mass. The prepared solution was coated on the release-treated surface of a release film (manufactured by Lintec Corporation, product name "SP-PET381031") and dried at 120 °C for 1 minute to obtain a film with a thickness of 10 μm.

[0190]

[0191]

[0192] From the results shown in Table 2, it can be seen that although the films obtained in Examples 1 to 4 had a high degree of swelling, the amount of elution was small. Thus, it was confirmed that the copolymers obtained in Examples 1 to 4 had crosslinkability.

Claims

1. A resin composition comprising a copolymer containing 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% or more and 20.0 mol% or less, ， 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 are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, and X 1 is any reactive group among the groups represented by the following structural formula (2-1) and the following structural formula (2-2). 。 2. The resin composition according to claim 1, wherein, the copolymer further contains at least one structural unit selected from the structural unit represented by the following general formula (3) and the structural unit represented by the following general formula (4) in an amount of 0.1 mol% or more and 30.0 mol% or less, ， 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 are each independently a single bond or an alkylene group having 1 to 3 carbon atoms, and X 2 is any reactive group among the groups represented by the following structural formula (4-1) and the following structural formula (4-2). 。 3. The resin composition according to claim 1 or 2, wherein, in the crosslinked product of the resin composition, the amount of the copolymer dissolved in ethyl acetate is 10% or less, the swelling ratio of the copolymer in a mixed solvent having a volume ratio of ethylene carbonate to dimethyl carbonate of 1:1 is 100% or more.

4. An adhesive resin comprising the resin composition according to claim 1 or 2.

5. A battery comprising the adhesive resin according to claim 4.

6. A polymer film comprising the resin composition according to claim 1 or 2.

7. A battery comprising the polymer film according to claim 6.

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