WO2021015230A1 - 結着剤、固体電池用スラリー、固体電池用電極及び二次固体電池 - Google Patents
結着剤、固体電池用スラリー、固体電池用電極及び二次固体電池 Download PDFInfo
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- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
- C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
- C09D127/12—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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- C08F14/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
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- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
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- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08L27/16—Homopolymers or copolymers or vinylidene fluoride
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Definitions
- the present disclosure relates to binders, solid-state battery slurries, solid-state battery electrodes and secondary solid-state batteries.
- Solid-state batteries are being studied as batteries with excellent safety.
- Sulfide-based and oxide-based solid conductors are known as solid-state conductors used in solid-state batteries, and solid-state batteries using these are being studied.
- an electrode is produced by preparing a slurry containing an electrolyte and a binder, and applying and drying the slurry.
- Patent Document 1 discloses that butyl butyrate is used as a solvent and a copolymer of vinylidene fluoride and hexafluoropropylene is used as a binder in a method for producing a positive electrode for a solid-state battery.
- Patent Document 2 discloses that butyl butyrate is used as a solvent and a copolymer of vinylidene fluoride and hexafluoropropylene is used as a binder in a method for producing a negative electrode for a solid-state battery.
- Patent Document 3 discloses a slurry for a positive electrode for a sulfide-based solid-state battery, which contains a fluorine-based polymer containing a vinylidene fluoride monomer component.
- Patent Document 4 describes a slurry for a sulfide-based electrode containing a fluorine-based polymer containing a vinylidene fluoride monomer component and a nitrile solvent.
- the present disclosure is a binder used in a slurry for a solid battery containing sulfide-based solid electrolyte particles.
- the binder has a resin terminal functional group of 0.01 ⁇ ([-CH 2 OH] + [-COOH]) / ([-CH 3 ] + [-CF 2 H] + [-CH 2 OH] + [ -CH 2 I] + [-OC (O) RH] + [-COOH] ⁇ 0.25 (In the formula, R represents an alkyl group having 1 to 20 carbon atoms.) It is a binder characterized by being a fluorine-containing elastomer satisfying the above conditions.
- the fluorine-containing elastomer is preferably composed of a vinylidene fluoride (VdF) monomer unit and a copolymerization unit.
- VdF vinylidene fluoride
- the above-mentioned fluoroelastomer has a copolymerization unit of hexafluoropropylene (HFP), 2,3,3,3-tetrafluoropropylene, 1,3,3,3-tetrafluoropropylene, perfluoroalkyl vinyl ether (PAVE), and tetra. It is preferably at least one copolymer unit selected from the group consisting of fluoroethylene (TFE).
- TFE fluoroethylene
- the copolymerization unit of the fluorine-containing elastomer is hexafluoropropylene (HFP), perfluoroalkyl vinyl ether (PAVE), or tetrafluoroethylene (TFE).
- the fluorine-containing elastomer preferably has a fluorine content of 60 to 71% by mass.
- the fluorine-containing elastomer preferably has a glass transition temperature of 25 ° C. or lower.
- the fluorine-containing elastomer is preferably amorphous.
- the present disclosure is a solid-state battery slurry containing sulfide-based solid electrolyte particles, a binder and a solvent.
- the binder is preferably any of the above-mentioned binders.
- the solvent is preferably a low polar solvent.
- the solvent preferably contains at least one compound selected from the group consisting of aromatic compounds and ester compounds.
- the solid-state battery slurry preferably further contains active material particles.
- the active material particles are preferably negative electrode active materials.
- the present disclosure is also an electrode for a solid-state battery having an electrode active material layer formed by a slurry containing the active material particles and a current collector.
- the solid-state battery electrode is preferably a negative electrode. It is preferable that the electrode active material contains at least a part of a carbonaceous material. The electrode active material preferably contains a silicon-containing compound at least in part.
- the present disclosure is also a lithium ion secondary solid-state battery, which comprises the above-mentioned electrode for a solid-state battery.
- the binder of the present disclosure has excellent solubility in a low-polarity solvent, and has excellent adhesion and flexibility, and is suitably used when manufacturing an electrode in a sulfide-based solid-state battery. can do.
- the present disclosure is a binder mainly used for forming electrodes for solid-state batteries.
- a method is known in which a slurry containing sulfide-based solid electrolyte particles, a binder and a solvent is applied, dried, and then pressed.
- it is important to select a binder or a solvent to be used in combination with the sulfide-based solid electrolyte particles.
- a binder having a suitable dissolving ability in a solvent as the binder.
- most of the known binders have low solubility in a solvent. Therefore, it could not be sufficiently dissolved in the slurry containing the sulfide-based solid electrolyte particles, and the function as a binder could not be sufficiently exhibited.
- a binder having good dissolving performance can be obtained by using the polymer having the above-mentioned specific composition. This makes it possible to obtain a good slurry suitable for manufacturing a battery.
- the resin terminal functional group is 0.01 ⁇ ([-CH 2 OH] + [-COOH]) / ([-CH 3 ] + [-CF 2 H] + [-CH 2 OH] + [-CH 2 I] + [-OC ( O) RH] + [-COOH] ⁇ 0.25
- R represents an alkyl group having 1 to 20 carbon atoms.
- the polymer is excellent in performance such as heat resistance and flexibility, and is also excellent in that it has high solubility in a low polar solvent. This also has the advantage that a slurry in which the sulfide-based solid electrolyte particles do not react can be obtained.
- the range of solvents that can be used is widened, it is possible to use different solvents according to the purpose. In particular, it is particularly preferable that the amount of the resin terminal functional group satisfies the above, because the flexibility becomes good.
- the polymer of the present disclosure is a fluorine-containing elastomer.
- the fluorine-containing elastomer is a fluorine-based polymer that is amorphous or low crystallinity and has a low glass transition temperature.
- the fluorine-containing elastomer preferably has a glass transition temperature of 25 ° C. or lower. More preferably, the glass transition temperature is 0 ° C. or lower. The glass transition temperature is more preferably ⁇ 5 ° C. or lower, and most preferably ⁇ 10 ° C. or lower. Further, the temperature can be set to ⁇ 20 ° C. or lower.
- the glass transition temperature is a DSC curve by cooling to ⁇ 75 ° C. using a differential scanning calorimeter (X-DSC823e manufactured by Hitachi Technoscience Co., Ltd.) and then raising the temperature of 10 mg of the sample at 20 ° C./min. The temperature indicating the intersection of the extension of the baseline before and after the quadratic transition of the DSC curve and the tangent at the turning point of the DSC curve was defined as the glass transition temperature.
- the fluorine-containing elastomer is preferably amorphous.
- Amorphous means that the melting point peak does not exist in the DSC curve described above.
- Such a fluorine-containing elastomer having a low Tg and being amorphous is particularly preferable in that it is easily dissolved in a solvent, and when used as a binder, it gives flexibility to the electrode and makes it easy to process. is there.
- the polymer has the following inequality: 0.01 ⁇ ([-CH 2 OH] + [-COOH]) / ([-CH 3 ] + [-CF 2 H] + [-CH 2 OH] + [-CH 2 I] + [-OC (O) RH] + [-COOH]) ⁇ 0.25
- R represents an alkyl group having 1 to 20 carbon atoms. It is preferable to satisfy.
- the terminal functional group satisfies the above formula, the adhesion is good and the binder has an excellent function.
- [-CH 2 OH] and [-COOH] have functional groups having high affinity such as hydroxyl groups and carboxyl groups. Therefore, the resin having these has excellent dissolving ability in the hydrophilic solvent used for slurry preparation. Further, if the amount of these functional groups is excessive or too small, the resin becomes inflexible, so that sufficient physical properties required as a binder cannot be ensured. Further, when the amount of these functional groups is contained in a ratio of a certain amount or more, it is preferable in that a binder having excellent adhesion is obtained. From this point of view, it is preferable that [-CH 2 OH] and [-COOH] are within the above-mentioned range.
- the abundance of each terminal group of the resin can be determined by analysis by NMR.
- the method of setting [-CH 2 OH] and [-COOH] within the above-mentioned predetermined range is not particularly limited, and a known method (for example, selection and amount of initiator to be used) is used. Can be controlled.
- the end group analysis of NMR was measured by a solution NMR method of protons. The analysis sample was adjusted to a 20 wt% solution using Ace tone-d6 as a solvent, and the measurement was performed.
- the reference peak is a measuring device with the peak top of acetone as 2.05 ppm: VNMRS400 manufactured by Varian.
- the amount of terminal groups in the fluorine-containing elastomer can be controlled by a known general method. Specifically, the above-mentioned predetermined range can be obtained by adjusting the selection and usage amount of the initiator, the selection and usage amount of the chain transfer agent, and the like.
- the composition of the fluorine-containing elastomer of the present disclosure is not particularly limited as long as it has the above-mentioned terminal group amount, and a fluorine-containing polymer can be used.
- the fluoroelastomer of the present disclosure includes a vinylidene fluoride unit, a monomer unit having a structure represented by the following general formula (1), and a monomer having a structure represented by the following general formula (2). It may be other than a polymer having at least one copolymerization unit (A) selected from the group consisting of units.
- Rf 1 and Rf 2 are linear or branched fluorinated alkyl groups or fluorinated alkoxy groups having 1 to 12 carbon atoms, and when the number of carbon atoms is 2 or more, carbon-carbon atoms. It may contain an oxygen atom in between.
- fluorine-containing elastomer for example, vinylidene fluoride (VdF) -based fluorine-containing elastomer, TFE / propylene (Pr) -based fluorine-containing elastomer, TFE / Pr / VdF-based fluorine-containing elastomer, ethylene (Et) / HFP.
- VdF vinylidene fluoride
- Pr propylene
- Et ethylene
- Examples thereof include based fluorine-containing elastomers, Et / HFP / VdF-based fluorine-containing elastomers, Et / HFP / TFE-based fluorine-containing elastomers, fluorosilicone-based fluorine-containing elastomers, and fluorophosphazene-based fluorine-containing elastomers.
- they can be used in any combination as long as the effects of the present disclosure are not impaired.
- the VdF-based fluorine-containing elastomer is a fluorine-containing elastomer having a VdF repeating unit.
- the VdF repeating unit is preferably 20 mol% or more and 90 mol% or less, preferably 40 mol% or more, of the total number of moles of the VdF repeating unit and the repeating unit derived from other comonomers. More preferably, it is 85 mol% or less. A more preferable lower limit is 45 mol%, and a particularly preferable lower limit is 50 mol%. A more preferred upper limit is 80 mol%.
- the comonomer in the VdF-based elastomer is not particularly limited as long as it can be copolymerized with VdF.
- VdF tetrafluoroethylene
- HFP hexafluoropropylene
- PAVE perfluoroalkyl vinyl ether
- CTFE Chlorotrifluoroethylene
- trifluoroethylene trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, vinyl fluoride, iodine-containing fluorinated vinyl ether, general formula (1) -1)
- CH 2 CFRf 1 (1-1) (In the formula, Rf 1 is a linear or branched fluorinated alkyl group or fluorinated alkoxy group having 1 to 12 carbon atoms, and when the number of carbon atoms is 2 or more, oxygen is oxygen between carbon atoms.
- Fluorine-containing monomer represented by (which may contain an atom), General formula (2-1) CHF CHRf 2 (2-1) (In the formula, Rf 2 is a linear or branched fluorinated alkyl group or fluorinated alkoxy group having 1 to 12 carbon atoms, and when the number of carbon atoms is 2 or more, it is between carbon-carbon atoms.
- a fluorine-containing monomer such as a fluorine-containing monomer represented by (may contain an oxygen atom); a fluorine-free monomer such as ethylene (Et), propylene (Pr), alkyl vinyl ether, etc. Examples thereof include a monomer giving a crosslinkable group (cure site) and a reactive emulsifier, and one or a combination of two or more of these monomers and compounds can be used.
- Rf 1 is a linear or branched fluorinated alkyl group having 1 to 12 carbon atoms, or a linear or branched fluorinated alkoxy group having 1 to 12 carbon atoms. Both the fluorinated alkyl group and the fluorinated alkoxy group can contain an oxygen atom (—O—) between carbon atoms when the number of carbon atoms is 2 or more.
- the fluorinated alkyl group of Rf 1 may be a partially fluorinated alkyl group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom are fluorine atoms. It may be a perfluorinated alkyl group substituted with. Further, the fluorinated alkyl group of Rf 1 may have a hydrogen atom substituted with a substituent other than the fluorine atom, but preferably does not contain a substituent other than the fluorine atom.
- the fluorinated alkoxy group of Rf 1 may be a partially fluorinated alkoxy group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom may be used. It may be a perfluorinated alkoxy group substituted with a fluorine atom. Further, in the fluorinated alkoxy group of Rf 1 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but it is preferable that the fluorinated alkoxy group does not contain a substituent other than the fluorine atom.
- the carbon number of Rf 1 is preferably 1 to 10, more preferably 1 to 6, still more preferably 1 to 4, and particularly preferably 1.
- Rf 1 the general formula: -(Rf 11 ) m- (O) p- (Rf 12- O) n-Rf 13
- Rf 11 and Rf 12 are independently linear or branched fluorinated alkylene groups having 1 to 4 carbon atoms, and Rf 13 is linear or branched chain having 1 carbon atom. Fluorinated alkyl groups of -4, p is 0 or 1, m is an integer of 0-4, n is an integer of 0-4).
- the fluorinated alkylene group of Rf 11 and Rf 12 may be a partially fluorinated alkylene group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all of the hydrogen atoms bonded to the carbon atom. May be a perfluorinated alkylene group substituted with a fluorine atom. Further, in the fluorinated alkylene group of Rf 11 and Rf 12 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but it is preferable that the fluorinated alkylene group does not contain a substituent other than the fluorine atom. Rf 11 and Rf 12 may be the same or different at each appearance.
- the fluorinated alkylene groups of Rf 11 include -CHF-, -CF 2- , -CH 2- CF 2- , -CHF-CF 2- , -CF 2- CF 2-, -CF (CF 3 )-, -CH 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CF (CF 3) -CF 2 -, - CF 2 -CF (CF 3) -, - C (CF 3) 2 -, - CH 2 -CF 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2 -, -CF 2 -CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2
- the fluorinated alkylene groups of Rf 12 include -CHF-, -CF 2- , -CH 2- CF 2- , -CHF-CF 2- , -CF 2- CF 2-, -CF (CF 3 )-, -CH 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CF (CF 3) -CF 2 -, - CF 2 -CF (CF 3) -, - C (CF 3) 2 -, - CH 2 -CF 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2 -, -CF 2 -CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2
- the fluorinated alkyl group of Rf 13 may be a partially fluorinated alkyl group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom are fluorine. It may be an alkyl perfluorinated group substituted with an atom. Further, in the fluorinated alkyl group of Rf 13 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but the substituent other than the fluorine atom (for example, -CN, -CH 2 I, -CH 2 Br. Etc.) are not included.
- the alkylated alkyl groups of Rf 13 include -CH 2 F, -CHF 2 , -CF 3 , -CH 2- CH 2 F, -CH 2- CHF 2 , -CH 2- CF 3 , -CHF-CH 2.
- -CF 3, -CHF-CF 3 , - CF 2 -CHF 2, -CF 2 -CF 3, -CF 2 -CF 2 -CF 3, -CF (CF 3) -CF 3, -CF 2 -CF 2 -CF 2 -CF 3, -CH (CF 3 ) -CF 2- CF 3 or -CF (CF 3 ) -CF 2- CF 3 is preferred.
- n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0. Further, when p is 0, it is preferable that m is also 0.
- n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.
- the compound represented by the above formula (2-1) includes Rf 2 is a linear or branched fluorinated alkyl group having 1 to 12 carbon atoms, or a linear or branched fluorinated alkoxy group having 1 to 12 carbon atoms. Both the fluorinated alkyl group and the fluorinated alkoxy group can contain an oxygen atom (—O—) between carbon atoms when the number of carbon atoms is 2 or more.
- the fluorinated alkyl group of Rf 2 may be a partially fluorinated alkyl group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom are fluorine atoms. It may be a perfluorinated alkyl group substituted with. Further, the fluorinated alkyl group of Rf 2 may have a hydrogen atom substituted with a substituent other than the fluorine atom, but preferably does not contain a substituent other than the fluorine atom.
- the fluorinated alkoxy group of Rf 2 may be a partially fluorinated alkoxy group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom may be used. It may be a perfluorinated alkoxy group substituted with a fluorine atom. Further, in the fluorinated alkoxy group of Rf 2 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but it is preferable that the fluorinated alkoxy group does not contain a substituent other than the fluorine atom.
- the number of carbon atoms of Rf2 is preferably 1 to 10, more preferably 1 to 6, still more preferably 1 to 4, and particularly preferably 1.
- Rf 21 and Rf 22 are independently linear or branched fluorinated alkylene groups having 1 to 4 carbon atoms, and Rf 23 is linear or branched chain having 1 carbon atoms.
- the fluorinated alkylene group of Rf 21 and Rf 22 may be a partially fluorinated alkylene group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all of the hydrogen atoms bonded to the carbon atom. May be a perfluorinated alkylene group substituted with a fluorine atom. Further, in the fluorinated alkylene group of Rf 21 and Rf 22 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but it is preferable that the fluorinated alkylene group does not contain a substituent other than the fluorine atom. Rf 21 and Rf 22 may be the same or different at each appearance.
- the fluorinated alkylene groups of Rf 21 include -CHF-, -CF 2- , -CH 2- CF 2- , -CHF-CF 2- , -CF 2- CF 2-, -CF (CF 3 )-, -CH 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CF (CF 3) -CF 2 -, - CF 2 -CF (CF 3) -, - C (CF 3) 2 -, - CH 2 -CF 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2 -, -CF 2 -CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2
- the fluorinated alkylene groups of Rf 22 include -CHF-, -CF 2- , -CH 2- CF 2- , -CHF-CF 2- , -CF 2- CF 2-, -CF (CF 3 )-, -CH 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CF (CF 3) -CF 2 -, - CF 2 -CF (CF 3) -, - C (CF 3) 2 -, - CH 2 -CF 2 -CF 2 -CF 2 -, - CHF-CF 2 -CF 2 -CF 2 -, - CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2 -, -CF 2 -CF 2 -CF 2 -CF 2 -, - CH (CF 3) -CF 2 -CF 2
- the fluorinated alkyl group of Rf 23 may be a partially fluorinated alkyl group in which a part of the hydrogen atom bonded to the carbon atom is replaced by the fluorine atom, or all the hydrogen atoms bonded to the carbon atom are fluorine. It may be an alkyl perfluorinated group substituted with an atom. Further, in the fluorinated alkyl group of Rf 23 , the hydrogen atom may be substituted with a substituent other than the fluorine atom, but the substituent other than the fluorine atom (for example, -CN, -CH 2 I, -CH 2 Br. Etc.) are not included.
- the alkylated alkyl groups of Rf 23 include -CH 2 F, -CHF 2 , -CF 3 , -CH 2- CH 2 F, -CH 2- CHF 2 , -CH 2- CF 3 , and -CHF-CH 2.
- -CF 3, -CHF-CF 3 , - CF 2 -CHF 2, -CF 2 -CF 3, -CF 2 -CF 2 -CF 3, -CF (CF 3) -CF 3, -CF 2 -CF 2 -CF 2 -CF 3, -CH (CF 3 ) -CF 2- CF 3 or -CF (CF 3 ) -CF 2- CF 3 is preferred.
- n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0. Further, when p is 0, it is preferable that m is also 0.
- n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.
- the copolymerization units are hexafluoropropylene (HFP), tetrafluoroethylene (TFE), 2,3,3,3-tetrafluoropropylene, 1,3,3,3-tetrafluoropropylene, and perfluoroalkyl vinyl ether ( It is preferably made of PAVE). Furthermore, it is most preferable that at least a part of the copolymerization unit is hexafluoropropylene (HFP).
- the vinylidene fluoride-based elastomer in which at least a part of the copolymerization unit is hexafluoropropylene (HFP) includes a binary elastomer composed of vinylidene fluoride and hexafluoropropylene, vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene.
- a ternary elastomer or the like can be mentioned.
- PMVE perfluoro (methyl vinyl ether)
- PPVE perfluoro (propyl vinyl ether)
- CF 2 CFOCF 2 ORf c
- Rf c is a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms, a cyclic perfluoroalkyl group having 5 to 6 carbon atoms, or a carbon number containing 1 to 3 oxygen atoms.
- Perfluorovinyl ether represented by (2 to 6 linear or branched perfluorooxyalkyl groups) can also be used.
- CF 2 CFOCF 2 OCF 3
- CF 2 CFOCF 2 OCF 2 CF 3
- CF 2 CFOCF 2 OCF 2 CF 2 OCF 3 .
- VdF-based fluorine-containing elastomer examples include VdF / HFP copolymers, VdF / TFE / HFP copolymers, VdF / CTFE copolymers, VdF / CTFE / TFE copolymers, VdF / PAVE copolymers, and VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, VdF / TFE / Pr copolymer, VdF / Et / HFP copolymer and VdF / formula (1) At least one copolymer selected from the group consisting of copolymers of fluorine-containing monomers represented by -1) or (2-1) is preferable. Further, as the co-monomer other than VdF, it is more preferable to have at least one co-monomer selected from the group consisting of TFE
- VdF / HFP copolymer VdF / TFE / HFP copolymer, VdF / copolymer of fluorine-containing monomer represented by formula (1-1) or (2-1), VdF At least one copolymer selected from the group consisting of / PAVE copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer and VdF / HFP / TFE / PAVE copolymer is preferable.
- VdF / HFP copolymer VdF / TFE / HFP copolymer
- At least one copolymer selected from the group consisting of coalescing is more preferable, and at least one selected from the group consisting of VdF / HFP copolymer, VdF / TFE / HFP copolymer and VdF / PAVE copolymer.
- Species copolymers are particularly preferred.
- the VdF / HFP copolymer preferably has a VdF / HFP composition of (45 to 85) / (55 to 15) (mol%), more preferably (50 to 80) / (50 to 20). It is (mol%), more preferably (60 to 80) / (40 to 20) (mol%).
- the composition of VdF / HFP is also preferably (50 to 78) / (50 to 22) (mol%).
- the VdF / TFE / HFP copolymer preferably has a composition of VdF / TFE / HFP of (30 to 80) / (4 to 35) / (10 to 35) (mol%).
- the VdF / PAVE copolymer preferably has a VdF / PAVE composition of (65 to 90) / (35 to 10) (mol%). Further, it is also one of the preferable forms that the composition of VdF / PAVE is (50 to 78) / (50 to 22) (mol%).
- the VdF / TFE / PAVE copolymer preferably has a composition of VdF / TFE / PAVE of (40 to 80) / (3 to 40) / (15 to 35) (mol%).
- the VdF / HFP / PAVE copolymer preferably has a composition of VdF / HFP / PAVE of (65 to 90) / (3 to 25) / (3 to 25) (mol%).
- VdF / HFP / TFE / PAVE copolymer As a VdF / HFP / TFE / PAVE copolymer, the composition of VdF / HFP / TFE / PAVE is (40 to 90) / (0 to 25) / (0 to 40) / (3 to 35) (mol%). Is preferable, and (40 to 80) / (3 to 25) / (3 to 40) / (3 to 25) (mol%) is more preferable.
- the fluorine-containing monomer (1-1) or (2-1) -based copolymer represented by the VdF / formula (1-1) or (2-1) is a VdF / fluorine-containing monomer (1).
- -1) or (2-1) unit is 87/13 to 20/80 (mol%), VdF and fluorine-containing monomer (1-1) or other monomer other than (2-1).
- the unit is preferably 0 to 50 mol% of all monomer units, and the mol% ratio of VdF / fluorine-containing monomer (1-1) or (2-1) unit is 80/20 to 20/80. More preferably.
- the composition of the VdF / fluorine-containing monomer (1-1) or (2-1) unit is 78/22 to 50/50 (mol%).
- the VdF / fluorine-containing monomer (1-1) or (2-1) unit is 87/13 to 50/50 (mol%), and VdF and the fluorine-containing monomer (1-1) or ( It is also preferable that the monomer unit other than 2-1) is 1 to 50 mol% of the total monomer unit.
- Examples of the monomer other than VdF and the fluorine-containing monomer (1-1) or (2-1) include TFE, HFP, PMVE, perfluoroethyl vinyl ether (PEVE), PPVE, CTFE, trifluoroethylene, and the like.
- Monomers exemplified as co-monomers of the above VdF such as hexafluoroisobutene, vinyl fluoride, Et, Pr, alkyl vinyl ether, a monomer giving a crosslinkable group, and a reactive emulsifier are preferable, and PMVE, among them, More preferably, it is CTFE, HFP, or TFE.
- the TFE / Pr-based fluorine-containing elastomer refers to a fluorine-containing copolymer composed of TFE 45 to 70 mol% and Pr 55 to 30 mol%.
- a specific third component for example, PAVE may be contained in an amount of 0 to 40 mol%.
- the composition of Et / HFP is preferably (35 to 80) / (65 to 20) (mol%), and (40 to 75) / (60 to 25) (mol). %) Is more preferable.
- the Et / HFP / TFE copolymer preferably has a composition of Et / HFP / TFE of (35 to 75) / (25 to 50) / (0 to 15) (mol%), preferably (45 to 75). ) / (25 to 45) / (0 to 10) (mol%) is more preferable.
- Examples of the perfluorofluorine-containing elastomer include those made of TFE / PAVE.
- the composition of TFE / PAVE is preferably (50 to 90) / (50 to 10) (mol%), more preferably (50 to 80) / (50 to 20) (mol%). More preferably, it is (55 to 75) / (45 to 25) (mol%).
- PAVE examples include PMVE, PPVE, and the like, and these can be used alone or in any combination.
- the fluorine-containing elastomer preferably has a fluorine content of 50% by mass or more, more preferably 55% by mass or more, and further preferably 60% by mass or more.
- the upper limit of the fluorine content is not particularly limited, but is preferably 71% by mass or less.
- the fluorine content is a value calculated by calculation from the composition of the fluorine-containing elastomer measured by 19F-NMR. The molecular weight was calculated from the composition ratio, the mass of the fluorine atom contained therein was determined, and the fluorine content was calculated.
- the composition ratio of each repeating unit of the fluorine-containing elastomer is a value measured by an NMR method. Specifically, it is a value measured by the following solution NMR method.
- Measuring device: VNMRS400 manufactured by Varian Resonance frequency: 376.04 (Sfrq) Pulse width: 30 ° (pw 6.8)
- the non-perfluorofluorine-containing elastomer and the perfluorofluorine-containing elastomer described above can be produced by conventional methods such as emulsion polymerization, suspension polymerization, and solution polymerization.
- emulsion polymerization suspension polymerization
- solution polymerization emulsion polymerization
- iodine (bromine) compound known as iodine (bromine) mobile polymerization a fluorine-containing elastomer having a narrow molecular weight distribution can be produced.
- the polymer may have a structural unit other than the vinylidene fluoride unit and the copolymerization unit (A).
- the content of the other polymer is preferably 50 mol% or less.
- it may consist only of a vinylidene fluoride unit and a copolymerization unit (A).
- the content of the other polymer is more preferably 30 mol% or less, and further preferably 15 mol% or less.
- the polymer may use a monomer that provides a cross-linking site as the other monomer.
- X 2 is an iodine atom or a bromine atom), an iodine or bromine-containing monomer
- CF 2 CFO (CF 2 CF (CF 3 ) O) m (CF 2 ) n-X 3
- m is an integer of 0 to 5
- n is an integer of 1 to 3
- X 3 is a cyano group
- CH 2 CFCF 2 O (CF (CF 3 ) CF 2 O) m (CF (CF 3 )) n-X 4
- m is an integer of 0 to 5
- n is an integer of 1 to 3
- X 4 is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom
- CF 2 CFOCF 2 CF (CF 3 ) OCF 2 CF 2 CN
- CF 2 CFOCF 2 CF (CF 3 ) OCF 2 CF 2 COOH
- CF 2 CFOCF 2 CF 2 CH 2 I
- CF 2 CFOCF 2 CF (CF 3 ) OCF 2 CF 2 CH 2 I
- CH 2 CFCF 2 OCF (CF 3 ) CF 2 OCF (CF 3 ) CN
- CH 2 CFCF 2 OCF (CF 3 ) CF 2 OCF (CF 3 )
- It may also contain a repeating unit based on a monomer that provides a cross-linking site, but in one embodiment of the present disclosure, it does not contain a cross-linking agent.
- the fluorine-containing elastomer preferably has a number average molecular weight (Mn) of 7,000 to 5,000, and a mass average molecular weight (Mw) in order to have good adhesion and flexibility and good solubility in a solvent.
- Mn number average molecular weight
- Mw mass average molecular weight
- the number average molecular weight (Mn), the mass average molecular weight (Mw), and Mw / Mn are values measured by the GPC method.
- the fluorine-containing elastomer has a Mooney viscosity (ML1 + 10 (121 ° C.)) at 121 ° C. of preferably 2 or more, more preferably 5 or more, further preferably 10 or more, and 30 or more. Is particularly preferable. Mooney viscosity is a value measured in accordance with ASTM-D1646-15 and JIS K6300-1: 2013.
- the fluorine polymer can be produced by a general radical polymerization method.
- the polymerization form may be any of bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization, but emulsion polymerization is preferable because it is industrially easy to carry out.
- a polymerization initiator In the polymerization, a polymerization initiator, a chain transfer agent, a surfactant, and a solvent can be used, and conventionally known ones can be used for each. In the polymerization of the copolymer, an oil-soluble radical polymerization initiator or a water-soluble radical initiator can be used as the polymerization initiator.
- the oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, dialkyl peroxy carbonates such as diisopropyl peroxy dicarbonate and disec-butyl peroxy dicarbonate, and t-butyl per.
- Peroxyesters such as oxyisobutyrate and t-butylperoxypivalate, dialkyl peroxides such as dit-butyl peroxide, and di ( ⁇ -hydro-dodecafluoroheptanoid) peroxides, Di ( ⁇ -hydro-tetradecafluoroheptanoyl) peroxide, di ( ⁇ -hydro-hexadecafluorononanoyl) peroxide, di (perfluorobutyl) peroxide, di (perflupareryl) peroxide, di (per) Fluorohexanoyl) peroxide, di (perfluoroheptanoil) peroxide, di (perfluorooctanoyl) peroxide, di (perfluorononanoyl) peroxide, di ( ⁇ -chloro-hexafluorobutyryl) peroxide , Di ( ⁇ -chloro-decafluorohexan
- the water-soluble radical polymerization initiator may be a known water-soluble peroxide, for example, ammonium salts such as persulfate, perboric acid, perchloric acid, perphosphoric acid, and percarbonate, potassium salts, and sodium salts. , T-butyl permalate, t-butyl hydroperoxide and the like. Reducing agents such as sulfites and sulfites may also be included, and the amount used may be 0.1 to 20 times that of the peroxide.
- the amount of the radical polymerization initiator added is not particularly limited, but an amount (for example, several ppm to water concentration) or more that does not significantly reduce the polymerization rate is collectively, sequentially, or continuously at the initial stage of polymerization. And add it.
- the upper limit is the range in which the heat of the polymerization reaction can be removed from the device surface.
- a nonionic surfactant an anionic surfactant, a cationic surfactant and the like can be used, and a linear chain having 4 to 20 carbon atoms such as ammonium perfluorooctanoate and ammonium perfluorohexanate can be used.
- a branched fluorine-containing anionic surfactant is preferable.
- the amount added (against polymerized water) is preferably 10 to 5000 ppm. More preferably, it is 50 to 5000 ppm.
- a reactive emulsifier can be used as the surfactant.
- the amount added is preferably 10 to 5000 ppm. More preferably, it is 50 to 5000 ppm.
- the solvent is preferably a solvent having no chain transfer.
- dichloropentafluoropropane R-225
- water, a mixture of water and a water-soluble organic solvent, or water and a water-insoluble organic solvent The mixture can be mentioned.
- examples of the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate and dimethyl succinate, as well as isopentane, methane, ethane, propane, isopropanol and acetone. , Various mercaptans, carbon tetrachloride, cyclohexane and the like.
- a bromine compound or an iodine compound may be used as the chain transfer agent.
- Examples of the polymerization method using a bromine compound or an iodine compound include a method of performing emulsion polymerization in an aqueous medium under pressure in the presence of a bromine compound or an iodine compound in a substantially anoxic state. (Iodine transfer polymerization method).
- Typical examples of the bromine compound or iodine compound used include, for example, the general formula: R2IxBry (in the formula, x and y are integers of 0 to 2, respectively, and satisfy 1 ⁇ x + y ⁇ 2, and R2 is a saturated or unsaturated fluorohydrocarbon group having 1 to 16 carbon atoms or chlorofluoro. Examples thereof include a compound represented by a hydrocarbon group, or a hydrocarbon group having 1 to 3 carbon atoms, which may contain an oxygen atom).
- Examples of the iodine compound include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, and 1,5-.
- 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, and 2-iodoperfluoropropane are used from the viewpoints of polymerization reactivity, cross-linking reactivity, availability, and the like. Is preferable.
- the copolymer may be in any form such as an aqueous dispersion or powder.
- the copolymer powder can be obtained by coagulating the dispersion liquid after polymerization, washing with water, dehydrating, and drying. The coagulation can be carried out by adding an inorganic salt or an inorganic acid such as aluminum sulfate, applying a mechanical shearing force, or freezing the dispersion.
- suspension polymerization it can be obtained by recovering from the dispersion after polymerization and drying.
- solution polymerization it can be obtained by drying the solution containing the fluoropolymer as it is, or by dropping a poor solvent and purifying it.
- copolymer one kind may be used, or two or more kinds may be used. In particular, two types of copolymers having different molecular structures may be used in combination.
- the binder of the present disclosure is used in a slurry for a solid battery containing sulfide-based solid electrolyte particles. Specifically, it is used for a slurry for forming a layer constituting a solid-state battery. Further, specifically, it is used in a slurry for a solid battery containing sulfide-based solid electrolyte particles, a binder and a solvent.
- the slurry of the present disclosure preferably has a low polar solvent. It is preferable to use a low-polarity solvent because it is less likely to cause a reaction with sulfide-based solid electrolyte particles.
- a low-polarity solvent is defined in the present disclosure as a low-polarity solvent having a relative permittivity of less than 20 at a frequency of 100 kHz. More preferably, it is less than 10.
- the solvent preferably contains at least one compound selected from the group consisting of aromatic compounds, ester compounds, aliphatic hydrocarbon compounds, ether compounds and carbonate compounds. Aromatic compounds and ester compounds are preferable, and ester compounds are most preferable.
- the low polar solvent is not particularly limited, and is not particularly limited, and is n-octane, n-nonane, n-decane, n-butyl ether, diisopentyl ether, ethylbenzene, ethyl acetate, ethyl butyrate, butyl butyrate, propyl propionate, butyl methacrylate.
- At least one solvent selected from the group consisting of propyl propionate, butyl methacrylate, ethyl acetate, ethyl butyrate, and butyl butyrate can be more preferably used.
- a mixed solvent in which two or more of these are used in combination may be used.
- the slurry of the present disclosure contains a sulfide-based solid electrolyte.
- the sulfide-based solid electrolyte is not particularly limited, Li 2 S-P 2 S 5, Li 2 S-P 2 S 3, Li 2 S-P 2 S 3 -P 2 S 5, Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 S-P 2 S 5 , LiI-Li 2 S-P 2 O 5 , LiI-Li 3 PO 4- P 2 S 5 , LiI-Li 2 S -SiS 2- P 2 S 5 , Li 2 S-SiS 2 -Li 4 SiO 4 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 3 PS 4- Li 4 GeS 4 , Li 3.4 P 0.
- the water content is preferably low, specifically, 1000 ppm or less, more preferably 500 ppm or less, still more preferably 100 ppm or less. ..
- the slurry of the present disclosure can be a positive electrode slurry or a negative electrode slurry. Further, it can be used as a slurry for forming a solid electrolyte. Of these, when the slurry for electrodes is used, it further contains active material particles.
- the active material particles can be a positive electrode active material and a negative electrode active material.
- the slurry of the present disclosure can be more preferably used as a slurry for a negative electrode using a negative electrode active material.
- a positive electrode active material is blended in the slurry.
- a positive electrode active material known as a positive electrode active material of a solid-state battery can be applied.
- the positive electrode active material includes LiCoO 2 , Li (Ni, Co, Al) O 2 , Li 1 + x Ni 1/3 Mn 1/3 Co 1/3 O 2 (x is a real number of 0 or more).
- LiCoO 2 Li (Ni, Co, Al) O 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2
- a positive electrode active material coated on the surface of each of these materials may be used.
- the coating material that can be used in the present disclosure may contain a substance that has lithium ion conductivity and can maintain the morphology of the coating layer on the surface of the active material. Examples of the coating material include LiNbO 3 , Li 4 Ti 5 O 12 , Li 3 PO 4, and the like.
- the shape of the positive electrode active material is not particularly limited, but is preferably in the form of powder.
- the average particle size of the positive electrode active material is, for example, 1 to 50 ⁇ m, particularly preferably 1 to 20 ⁇ m, particularly preferably 3 to 7 ⁇ m. If the average particle size of the positive electrode active material is too small, the handling may be poor, and if the average particle size of the positive electrode active material is too large, it may be difficult to obtain a flat positive electrode active material layer. Because.
- the average particle size of the positive electrode active material can be obtained by measuring and averaging the particle size of the active material carrier observed by, for example, a scanning electron microscope (SEM).
- the negative electrode active material is not particularly limited, and for example, artificial graphite, graphite carbon fiber, resin calcined carbon, thermally decomposed vapor phase grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin calcined carbon, polyacene, pitch.
- MCMB mesocarbon microbeads
- a mixture of two or more types can be mentioned.
- those containing at least a part of a carbonaceous material and silicon-containing compounds can be particularly preferably used.
- the slurry for a sulfide-based solid-state battery of the present disclosure may further contain a conductive auxiliary agent, if necessary.
- the conductive auxiliary agent used in the present disclosure is not particularly limited as long as it can improve the conductivity in the target positive electrode for sulfide-based solid-walled batteries, but is, for example, carbon such as acetylene black and ketjen black. Black; carbon fibers such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, and vapor-grown carbon fibers (VGCF); metal powders such as SUS powder and aluminum powder can be mentioned.
- the slurry may contain a material other than the above materials.
- the content ratio of the material is preferably 8% by mass or less, and more preferably 4% by mass or less, when the volume of the entire slurry is 100% by mass.
- each of the above-mentioned components is mixed to obtain a slurry.
- the mixing order of each component is not particularly limited, and each component may be added to a solvent and mixed. However, from the viewpoint of obtaining a slurry in which the binder is dissolved, it is preferable to mix by the following method.
- the step of preparing the slurry it is desirable to prepare a binder solution in which the above-mentioned binder is previously dissolved in the above-mentioned solvent, and then mix with other materials.
- a slurry by the following procedure.
- (1) The above-mentioned binder is dissolved in a solvent to obtain a "binding agent solution”.
- a sulfide-based solid electrolyte prepared separately from the binder solution obtained in (1), or a positive electrode active material or a negative electrode active material to be used as necessary is added, and dispersion treatment (for example, ultrasonic waves) is performed.
- dispersion treatment for example, ultrasonic waves
- a sulfide-based solid electrolyte or an electrode active material is added to the "active material / binder slurry" or “solid electrolyte / binder slurry” obtained in (2).
- a dispersion treatment for example, ultrasonic treatment
- an "electrode slurry” in which the electrode active material and the sulfide-based solid electrolyte are highly dispersed in the solvent is obtained.
- the binder, the sulfide-based solid electrolyte, and the electrode active material to be used as needed are added stepwise, and the sequential dispersion treatment is performed, so that each component is highly dispersed in the solvent. Can be easily obtained.
- the slurry is subjected to the dispersion treatment. It is possible to obtain.
- the form of the dispersion treatment the above-mentioned ultrasonic treatment can be mentioned. In addition, distribution using high-speed disks is also conceivable.
- the “solution” of the present disclosure refers to a "binding agent solution” in which the binder obtained by the above-mentioned step (1) is dissolved in a solvent.
- the mixing ratio of the binder, the sulfide-based solid electrolyte, and the electrode active material used as needed should be such that the mixing ratio functions appropriately when each layer is formed. Any known mixing ratio can be adopted. It is particularly preferable that the above-mentioned binder is contained in an amount of 0.5 parts by mass or more and 4.5 parts by mass or less based on 100 parts by mass of the total solid content in the slurry. If the amount of the binder is too small, the adhesion between particles such as an electrolyte and the adhesion between the current collector and the particles such as an electrolyte may be inferior when the electrode is used, and it may be difficult to handle the electrode. On the other hand, if the amount of the binder is too large, the resistance of the electrode becomes large, and it may not be possible to obtain a solid-state battery having sufficient performance.
- the amount of solid content (electrode active material, sulfide-based solid electrolyte and binder) with respect to the solvent is not particularly limited, but for example, the solid content in the slurry is 30 mass by mass. It is preferable that the content is% or more and 75% by mass or less. With such a solid content ratio, the electrode and the solid electrolyte layer can be produced more easily.
- the lower limit of the solid content ratio is more preferably 50% by mass or more, and the upper limit is more preferably 70% by mass or less.
- the slurry of the present disclosure can be used to form an electrode for a solid-state battery and / or an electrolyte layer for a sulfide-based solid-state battery.
- the method for manufacturing such an electrode for a solid-state battery is not particularly limited, but It can be carried out by (1) a step of preparing a base material, (2) a step of preparing a slurry, and (3) a step of coating the slurry to form an electrode for a sulfide-based solid-state battery.
- the above steps (1) to (3) will be described in order.
- Step (1) Step of preparing a base material The base material used in the present disclosure is not particularly limited as long as it has a flat surface to which a slurry can be applied.
- the base material may be in the form of a plate or in the form of a sheet. Further, the base material may be a prefabricated one or a commercially available product.
- the base material used in the present disclosure may be one used for a sulfide-based solid-state battery after forming an electrode for a sulfide-based solid-state battery and / or an electrolyte layer for a sulfide-based solid-state battery, or a sulfide-based solid-state battery. It may not be a material for a solid-state battery.
- Examples of the base material used for the sulfide-based solid-state battery include an electrode material such as a current collector and a material for a sulfide-based solid electrolyte layer such as a sulfide-based solid electrolyte membrane.
- the sulfide-based solid-state battery electrode and / or the sulfide-based solid-state battery electrolyte layer obtained by using the slurry of the present disclosure is used as a base material, and further, the sulfide-based solid-state battery electrode and / or Alternatively, an electrolyte layer for a sulfide-based solid-state battery can be formed.
- Examples of the base material that cannot be used as a material for the sulfide-based solid-state battery include a transfer base material such as a transfer sheet and a transfer substrate.
- the sulfide-based solid-state battery electrode and / or the sulfide-based solid-state battery electrolyte layer formed on the transfer substrate is thermally pressure-bonded to the sulfide-based solid-state battery electrode and / or the sulfide-based solid-state battery electrolyte layer.
- the electrode active material layer for a sulfide-based solid-state battery formed on the transfer substrate is bonded to the current collector by thermal pressure bonding or the like, and then the transfer substrate is peeled off to form the electrode active material layer on the electrode current collector.
- An electrode for a sulfide-based solid-state battery having an electrode active material layer formed therein can be obtained.
- Step (2) Step of preparing the slurry This step can be carried out according to the above-mentioned slurry preparation method.
- Step (3) Step of coating a slurry to form an electrode for a sulfide-based solid-state battery
- the slurry is coated on at least one surface of the above-mentioned base material for a sulfide-based solid-state battery.
- This is a step of forming an electrode.
- the electrode for a sulfide-based solid-state battery may be formed on only one side of the base material, or may be formed on both sides of the base material.
- the slurry coating method, drying method and the like can be appropriately selected.
- examples of the coating method include a spray method, a screen printing method, a doctor blade method, a bar coating method, a roll coating method, a gravure printing method, and a die coating method.
- examples of the drying method include vacuum drying, heat drying, vacuum heating drying and the like. There are no particular restrictions on the specific conditions for vacuum drying and heat drying, which may be set as appropriate.
- the amount of the slurry coated varies depending on the composition of the slurry, the intended use of the electrode for the sulfide-based solid-state battery, and the like, but it may be about 5 to 30 mg / cm 2 in the dry state.
- the thickness of the electrode for a sulfide-based solid-state battery is not particularly limited, but may be about 10 to 250 ⁇ m.
- the electrode for a sulfide-based solid-state battery according to the present disclosure may include a current collector and a lead connected to the current collector in addition to the active material layer.
- the thickness of the active material layer used in the present disclosure varies depending on the intended use of the sulfide-based solid-state battery and the like, but is preferably 10 to 250 ⁇ m, particularly preferably 20 to 200 ⁇ m. In particular, it is most preferably 30 to 150 ⁇ m.
- the current collector used in the present disclosure is not particularly limited as long as it has a function of collecting current in the above-mentioned active material layer.
- Examples of the material of the positive electrode current collector include aluminum, SUS, nickel, iron, titanium, chromium, gold, platinum, zinc and the like, and among them, aluminum and SUS are preferable.
- As the shape of the positive electrode current collector for example, a foil shape, a plate shape, a mesh shape and the like can be mentioned, and among them, the foil shape is preferable.
- the positive electrode for a sulfide-based solid-state battery according to the present disclosure is excellent by setting the content ratio of the binder to 0.5 to 10% by mass of the positive electrode for a sulfide-based solid-state battery (preferably the electrode active material layer).
- a sulfide-based solid-state battery using the positive electrode exhibits a high output.
- the present disclosure is also a secondary solid-state battery, which comprises the above-mentioned electrode for a solid-state battery.
- the secondary solid-state battery is preferably a lithium ion battery.
- the sulfide-based solid-state battery of the present disclosure is a sulfide-based solid-state battery including a positive electrode, a negative electrode, and a sulfide-based solid electrolyte layer interposed between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode are described above. It contains the binder of the present disclosure.
- FIG. 1 is a diagram showing an example of a laminated structure of a sulfide-based solid-state battery according to the present disclosure, and is a diagram schematically showing a cross section cut in the laminated direction.
- the sulfide-based solid-state battery according to the present disclosure is not necessarily limited to this example.
- the sulfide-based solid battery is sandwiched between the positive electrode 6 including the positive electrode active material layer 2 and the positive electrode current collector 4, the negative electrode 7 including the negative electrode active material layer 3 and the negative electrode current collector 5, and the positive electrode 6 and the negative electrode 7.
- the sulfide-based solid electrolyte layer 1 to be formed is provided.
- the positive electrode and negative electrode used in the present disclosure are the same as the above-mentioned electrodes for sulfide-based solid-state batteries.
- the negative electrode and the sulfide-based solid electrolyte layer used in the sulfide-based solid-state battery according to the present disclosure, and the separator and the battery case preferably used in the sulfide-based solid-state battery according to the present disclosure will be described in detail.
- the negative electrode current collector used in the present disclosure is not particularly limited as long as it has a function of collecting current in the negative electrode active material layer.
- Examples of the material of the negative electrode current collector include chromium, SUS, nickel, iron, titanium, copper, cobalt, zinc and the like, and copper, iron and SUS are preferable.
- the shape of the negative electrode current collector for example, a foil shape, a plate shape, a mesh shape and the like can be mentioned, and among them, the foil shape is preferable.
- the negative electrode for a sulfide-based solid-state battery according to the present disclosure is excellent by setting the content ratio of the binder to 0.5 to 10% by mass of the negative electrode for a sulfide-based solid-state battery (preferably the electrode active material layer).
- a sulfide-based solid-state battery using the negative electrode exhibits high output while exhibiting a strong adhesive force.
- the sulfide-based solid electrolyte layer used in the present disclosure is not particularly limited as long as it is a layer containing the above-mentioned sulfide-based solid electrolyte.
- the sulfide-based solid electrolyte layer used in the present disclosure is preferably a layer made of the above-mentioned sulfide-based solid electrolyte.
- the sulfide-based solid-state battery of the present disclosure may include a separator between the positive electrode and the negative electrode.
- the separator include a porous film such as polyethylene and polypropylene; a non-woven fabric made of resin such as polypropylene, and a non-woven fabric such as a glass fiber non-woven fabric.
- the sulfide-based solid-state battery of the present disclosure may further include a battery case.
- the shape of the battery case used in the present disclosure is not particularly limited as long as it can accommodate the above-mentioned positive electrode, negative electrode, electrolyte layer for sulfide-based solid-state battery, etc., but specifically, it is a cylindrical type. , Square type, coin type, laminated type and the like.
- the method for producing a sulfide-based solid-state battery of the present disclosure is a method for producing a sulfide-based solid-state battery including a positive electrode, a negative electrode, and an electrolyte layer for the sulfide-based solid-state battery interposed between the positive electrode and the negative electrode. , The step of preparing the electrolyte layer for the sulfide-based solid-state battery, the step of kneading the positive electrode or negative electrode active material, the sulfide-based solid electrolyte, the binder, and the solvent or dispersion medium to prepare the slurry, and the above.
- the slurry is applied to one surface of the electrolyte layer for a sulfide-based solid-state battery to form a positive electrode, and the negative electrode is formed on the other surface of the electrolyte layer for a sulfide-based solid-state battery to form a sulfide-based electrode. It is characterized by having a step of manufacturing a solid-state battery.
- Binder 2 (Manufacturing method of binder) (Binder 2; for examples) Put 1650 ml of pure water in a 3 L stainless steel autoclave, replace with nitrogen, slightly pressurize with hexafluoropropylene (HFP), adjust the temperature to 80 ° C while stirring at 380 rpm, press-fit HFP to 0.23 MPa, and further press vinylidene.
- a mixed solution monomer having a molar ratio of fluoride (VdF) and HFP of 78.2 / 21.8 was press-fitted to 1.472 MPa.
- the resulting polymer contained HFP and VdF in a molar ratio of 22.1 / 77.9.
- the Mooney viscosity (ML1 + 10 (121 ° C.)) of the obtained polymer was 140, and the Tg was determined by DSC to be -18 ° C. In addition, heat of fusion was not observed in the second run.
- Binder 7 for comparative example
- KF7200 manufactured by Kureha
- a mixed solution monomer having a molar ratio of 70.2 / 1 1.3 / 18.5 was press-fitted to 2.000 MPa. 0.0218 g of persulfate ammonium dissolved in 4 ml of pure water was press-fitted with nitrogen to start polymerization. When 12 g of continuous monomer was reached, 2.5022 g of 1,4-diiodoperfluorobutane was added. When the pressure dropped to 1.97 MPa, the pressure was increased to 2.03 MPa with a continuous monomer. This was repeated for about 5.0 hours, and when 572 g of continuous monomer was charged, the gas in the autoclave was released and cooled to recover 2302 g of the dispersion.
- the solid content of the dispersion was 23.5 wt%.
- Aluminum sulfate was added to this dispersion, coagulated, and dried to obtain 571 g of a polymer.
- the obtained polymer contained VdF, TFE and HFP in a molar ratio of 69.9 / 11.2 / 18.9.
- the Mooney viscosity (ML1 + 10 (121 ° C.)) of the obtained polymer was 48, and the Tg was determined by DSC to be ⁇ 20 ° C. In addition, heat of fusion was not observed in the second run.
- Binder 8 for comparative example
- the polymer composition was adjusted so as to have the composition of the binder 8 shown in Table 1, and this was obtained.
- Table 1 shows the binders used in Examples and Comparative Examples.
- slurries for negative electrodes according to Examples and Comparative Examples were prepared. Specifically, it is as follows. The solvent contained in the binder solution was added to the PET container together with the above-mentioned binder solution and graphite as the negative electrode active material, and ultrasonic treatment (50 seconds) was performed once using an ultrasonic homogenizer. Negative electrode active material / binder slurry ”was prepared.
- the negative electrode active material, the binder slurry obtained was further added a binder solution, solvent and sulfide-based solid electrolyte and (30LiI ⁇ 70 (0.75Li 2 S ⁇ 0.25P 2 S 5)), By performing ultrasonic treatment (30 seconds) three times using an ultrasonic homogenizer, a “negative electrode slurry” in which the negative electrode active material, the sulfide-based solid electrolyte, and the binder were highly dispersed was obtained.
- the solid content concentration of the binder in the final slurry was 3.0% by mass.
- the preparation of the solid electrolyte slurry was as follows. That is, a solid electrolyte and a binder solution are added to the solvent butyl butyrate, and ultrasonic treatment (30 seconds) is performed once using an ultrasonic homogenizer to highly dissolve or disperse the solid electrolyte and the binder. An electrolyte slurry was obtained. The solid content at this time was 49%.
- Glass-transition temperature According to ASTM E1356-98, the glass transition temperature is determined by the midpoint method from heat absorption in the second run using a DSC measuring device manufactured by METTLER TORDO. The results are shown in Table 1. Furthermore, the presence or absence of the crystal melting point in the second run was confirmed. Those having no crystal melting point in the second run are judged to be "amorphous”. Measurement condition Heating rate; 20 ° C / min Sample amount; 10 mg Heat cycle; -100 ° C to 220 ° C, temperature rise, cooling, temperature rise
- Electrode bending test The prepared electrode was cut into a length of 3 cm and a width of 6 cm, and then rolled with a roll press machine under a pressure of 10 tons. After folding 180 °, it was unfolded and the presence or absence of cracks in the electrodes was visually confirmed. When no crack was confirmed, it was evaluated as ⁇ , and when crack was confirmed, it was evaluated as ⁇ .
- the prepared electrolyte sheet was packed in a sample bottle and sealed. Deterioration was promoted by opening the sample in a chamber whose humidity was adjusted to 50% RH in advance and exposing it to the air moisture in the chamber. After 1 hour, a sample was taken out and the condition was observed. Further, for the solid electrolyte, a frequency of 10 MHz to 0.01 H is used using an impedance analyzer (manufactured by Solartron: SI-1260). The AC impedance was measured at z, and the conductivity was calculated based on the measurement result. The one using the binder (3) had a conductivity of 4 ⁇ 10 -4 S / cm before exposure.
- the binder of the present disclosure can be used as a binder for a slurry for a solid-state battery.
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Abstract
Description
特許文献2には、固体電池用負極の製造方法において、溶媒として酪酸ブチルを使用し、結着剤としてビニリデンフルオライド及びヘキサフルオロプロピレンの共重合体を使用することが開示されている。
特許文献3には、ビニリデンフルオライド単量体成分を含むフッ素系重合体を含む、硫化物系固体電池用正極用スラリーが開示されている。
特許文献4には、ビニリデンフルオライド単量体成分を含むフッ素系重合体及びニトリル溶媒を含む、硫化物系電極用スラリーが記載されている。
結着剤は、樹脂末端官能基が
0.01≦([-CH2OH]+[-COOH])/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC(O)RH]+[-COOH]≦0.25
(式中、Rは炭素数1~20のアルキル基を表す。)
を満たす含フッ素エラストマーであることを特徴とする結着剤である。
上記含フッ素エラストマーは、共重合単位がヘキサフルオロプロピレン(HFP)、2,3,3,3-テトラフルオロプロピレン、1,3,3,3-テトラフルオロプロピレン、 パーフルオロアルキルビニルエーテル(PAVE)、テトラフルオロエチレン(TFE)からなる群より選択される少なくとも一種の共重合単位であることが好ましい。
上記含フッ素エラストマーは、ガラス転移温度が25℃以下であることが好ましい。
上記含フッ素エラストマーは、非晶質であることが好ましい。
結着剤は、上述したいずれかの結着剤であることが好ましい。
上記溶媒は、低極性溶媒であることが好ましい。
上記固体電池用スラリーは、更に、活物質粒子を含有することが好ましい。
上記活物質粒子は、負極活物質であることが好ましい。
本開示は、上記活物質粒子を含有するスラリーによって形成された電極活物質層、及び、集電体を有する固体電池用電極でもある。
上記電極活物質は、少なくとも一部に炭素質材料を含むものであることが好ましい。
上記電極活物質は、少なくとも一部にシリコン含有化合物を含むものであることが好ましい。
本開示は、上述した固体電池用電極を備えることを特徴とするリチウムイオン二次固電池でもある。
本開示は、主に固体電池用の電極形成に使用される結着剤である。
硫化物系の固体電池用の電極形成においては、硫化物系固体電解質粒子、結着剤及び溶媒を含有するスラリーを塗布・乾燥し、その後プレスする方法が知られている。このような方法によって良好な電極を形成する場合には、硫化物系固体電解質粒子と組み合わせて使用される結着剤や溶媒の選択が重要となる。特に、硫化物系固体電解質粒子を使用する場合、硫化物系固体電解質粒子と反応しないものを選択する必要があり、使用可能な溶媒の種類が限定される。そして、このような溶媒を使用したスラリーを調製するためには、結着剤として当該溶媒に溶解するものを選択する必要がある。
0.01≦([-CH2OH]+[-COOH])/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC(O)RH]+[-COOH]≦0.25
(式中、Rは炭素数1~20のアルキル基を表す。)
を満たす含フッ素エラストマーを使用する。
好ましくは、0.03≦([-CH2OH]+[-COOH])/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC(O)RH]+[-COOH]≦0.20である。
上記重合体は、耐熱性、柔軟性等の性能に優れ、低極性溶媒への溶解能が高いという点でも優れている。これによって、硫化物系固体電解質粒子が反応を生じることのないスラリーを得ることができる、という利点も有する。また、使用することができる溶媒の幅も広くなるため、目的に応じて溶媒を使い分けることも可能となる。特に、樹脂末端官能基量を、上記を満たすものとすることで、柔軟性が良好なものとなる点で特に好ましい。
このような低Tgで非晶質である含フッ素エラストマーは、溶媒に溶けやすく、結着剤として使用した場合に、電極に柔軟性を与え、加工し易さを与えるという点で特に好ましいものである。
(式中、Rは炭素数1~20のアルキル基を表す。)
を満たすことが好ましい。
末端官能基が上記式を満たすものとすることで、密着性が良好なものとなり、結着剤として優れた機能を有するものとなる。
なお、NMRの末端基分析は、プロトンの溶液NMR法により測定した。分析サンプルはAce tone-d6を溶媒として、20wt% 溶液となるように調整し、測定を行った。
基準ピークはアセトンのピークトップを2.05ppmとする
測定装置:バリアン社製 VNMRS400
共鳴周波数:399.74(Sfrq)
パルス幅:45°
各末端は、以下のピーク位置のものに対応させた。
[-CH3]:1.72~1.86ppm
[-CF2H]:6.1~6.8ppm
[-CH2OH]:3.74~3.80ppm
[-CH2I]:3.87~3.92ppm
[-OC(O)RH]:1.09~1.16ppm
[-COOH]:10~15ppm
上述した測定によって特定された各ピークの積分値に基づいて、各ピーク強度から官能基量を算出し、その結果に基づいて下記式にて計算する。
([-CH2OH]+[-COOH])/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC(O)RH]+[-COOH])
なお、本開示のフッ素エラストマーは、ビニリデンフルオライド単位、並びに、下記一般式(1)で表される構造を有する単量体単位及び下記一般式(2)で表される構造を有する単量体単位からなる群より選択される少なくとも1つの共重合単位(A)を有する重合体以外のものであってもよい。
CH2=CFRf1 (1-1)
(式中、Rf1は炭素数1~12の直鎖状または分岐鎖状のフッ素化アルキル基またはフッ素化アルコキシ基であり、炭素数が2以上である場合は、炭素-炭素原子間に酸素原子を含むものであってもよい。)で表される含フッ素単量体、
一般式(2-1)
CHF=CHRf2 (2-1)
(式中、Rf2は、炭素数1~12の直鎖状または分岐鎖状のフッ素化アルキル基またはフッ素化アルコキシ基であり、炭素数が2以上である場合は、炭素-炭素原子間に酸素原子を含むものであってもよい。)で表される含フッ素単量体などのフッ素含有単量体;エチレン(Et)、プロピレン(Pr)、アルキルビニルエーテル等のフッ素非含有単量体、架橋性基(キュアサイト)を与える単量体、および反応性 乳化剤などが挙げられ、これらの単量体や化合物のなかから1種または2種以上を組み合わせて用いることができる。
Rf1は、炭素数1~12の直鎖状もしくは分岐鎖状のフッ素化アルキル基、または、炭素数1~12の直鎖状もしくは分岐鎖状のフッ素化アルコキシ基である。フッ素化アルキル基およびフッ素化アルコキシ基は、いずれも、炭素数が2以上ある場合には、炭素-炭素原子間に酸素原子(-O-)を含むことができる。
-(Rf11)m-(O)p-(Rf12-O)n-Rf13
(式中、Rf11およびRf12は、独立に、直鎖状もしくは分岐鎖状の、炭素数1~4のフッ素化アルキレン基、Rf13は、直鎖状もしくは分岐鎖状の、炭素数1~4のフッ素化アルキル基、pは0または1、mは0~4の整数、nは0~4の整数である)で表される基が好ましい。
-CH2-CF[-CF3]-、
-CH2-CF[-CF2CF3]-、
-CH2-CF[-CF2CF2CF3]-、
-CH2-CF[-CF2CF2CF2CF3]-、
-CH2-CF[-CF2-O-CF(CF3)-CF2-O-CHF-CF3]-、
-CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF2-CF3]-、
-CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF(CF3)-CF3]-、
-CH2-CF[-CF2-O-CF(CF3)-CF2-O-CH(CF3)-CF2-CF3]-、
-CH2-CF[-CF2-O-CF(CF3)-CF2-O-CF(CF3)-CF2-CF3]-、
-CH2-CF[-OCF2OCF3]-、
-CH2-CF[-OCF2CF2CF22OCF3]-、
-CH2-CF[-CF2OCFOCF3]-、
-CH2-CF[-CF2OCF2CF2CF2OCF3]-、または、
-CH2-CF[-O-CF2-CF3]-
が好ましく、
-CH2-CF[-CF3]-
がより好ましい。
Rf2は、炭素数1~12の直鎖状もしくは分岐鎖状のフッ素化アルキル基、または、炭素数1~12の直鎖状もしくは分岐鎖状のフッ素化アルコキシ基である。フッ素化アルキル基およびフッ素化アルコキシ基は、いずれも、炭素数が2以上ある場合には、炭素-炭素原子間に酸素原子(-O-)を含むことができる。
-(Rf21)m-(O)p-(Rf22-O)n-Rf23
(式中、Rf21およびRf22は、独立に、直鎖状もしくは分岐鎖状の、炭素数1~4のフッ素化アルキレン基、Rf23は、直鎖状もしくは分岐鎖状の、炭素数1~4のフッ素化アルキル基、pは0または1、mは0~4の整数、nは0~4の整数である。)で表される基が好ましい。
-CHF-CH[-CF3]-、
-CHF-CH[-CF2CF3]-、
-CHF-CH[-CF2CF2CF3]-、または、
-CHF-CH[-CF2CF2CF2CF3]-、
が好ましく、
-CHF-CH[-CF3]-
がより好ましい。
(式中、Rfcは、炭素数1~6の直鎖または分岐状パーフルオロアルキル基、炭素数5~6の環式パーフルオロアルキル基、又は、1~3個の酸素原子を含む炭素数2~6の直鎖または分岐状パーフルオロオキシアルキル基である)で表されるパーフルオロビニルエーテルを用いることもできる。例えば、CF2=CFOCF2OCF3、CF2=CFOCF2OCF2CF3、または、CF2=CFOCF2OCF2CF2OCF3を用いることが好ましい。
組成比から分子量を算出し、その中に含まれるフッ素原子の質量を求め、フッ素含有率を算出した。
測定装置:バリアン社製 VNMRS400
共鳴周波数:376.04(Sfrq)
パルス幅:30°(pw=6.8)
上記架橋部位を与える単量体としては特に限定されず、たとえば、一般式:
CX1 2=CX1-Rf1CHR1X2
(式中、X1は、水素原子、フッ素原子または-CH3、Rf1は、フルオロアルキレン基、パーフルオロアルキレン基、フルオロ(ポリ)オキシアルキレン基またはパーフルオロ(ポリ)オキシアルキレン基、R1は、水素原子または-CH3、X2は、ヨウ素原子または臭素原子である。)で表されるヨウ素または臭素含有単量体、一般式:
CF2=CFO(CF2CF(CF3)O)m(CF2)n-X3 (式中、mは0~5の整数、nは1~3の整数、X3は、シアノ基、カルボキシル基、アルコキシカルボニル基、ヨウ素原子、又は臭素原子である。)で表される単量体、一般式 :
CH2=CFCF2O(CF(CF3)CF2O)m(CF(CF3))n-X4
(式中、mは0~5の整数、nは1~3の整数、X4は、シアノ基、カルボキシル基、アルコキシカルボニル基、ヨウ素原子、臭素原子、又は-CH2OHである。)で表される 単量体を他の単量体として使用するものであってもよい。
R2IxBry (式中、xおよびyはそれぞれ0~2の整数であり、かつ1≦x+y≦2を満たすもので あり、R2は炭素数1~16の飽和もしくは不飽和のフルオロ炭化水素基またはクロロフルオロ炭化水素基、または炭素数1~3の炭化水素基であり、酸素原子を含んでいてもよい)で表される化合物があげられる。
(1)溶媒中に上述の結着剤を溶解させ「結着剤溶液」を得る。
(2)溶媒に、(1)で得られた結着剤溶液と別途用意した硫化物系固体電解質又は必要に応じて使用する正極活物質又は負極活物質を添加し、分散処理(例えば超音波処理)を施すことで、硫化物系固体電解質が溶媒中に高度に分散された「固体電解質・結着剤スラリー」又は活物質が溶媒中に高度に分散された「活物質・結着剤スラリー」を得る。
(3)電極用スラリーの場合は、(2)で得られた「活物質・結着剤スラリー」又は「固体電解質・結着剤スラリー」に、硫化物系固体電解質又は電極活物質を添加し、分散処理(例えば超音波処理)を施すことで、電極活物質と硫化物系固体電解質が溶媒中に高度に分散した「電極用スラリー」を得る。
ただし、溶媒中に、結着剤、硫化物系固体電解質及び必要に応じて使用する電極活物質、並びに、任意成分を一度に添加し、一度に分散処理を施した場合であっても、スラリーを得ることが可能である。
なお、分散処理の形態としては、一例として上記の超音波処理があげられる。また、他にも高速ディスクによる分散等も考えられる。
なお、スラリー中の固形分総質量100質量部に対して、上述の結着剤を0.5質量部以上4.5質量部以下含ませることが特に好ましい。結着剤が少なすぎると、電極にした場合において電解質等の粒子間の密着性及び集電体と電解質等の粒子間との密着性に劣り、電極のハンドリングが困難となる場合がある。一方、結着剤が多すぎると、電極の抵抗が大きくなって、十分な性能を有する固体電池を得ることができなくなる場合がある。
(1)基材を準備する工程、(2)スラリーを準備する工程、及び、(3)スラリーを塗工して硫化物系固体電池用電極を形成する工程
によって行うことができる。
以下、上記工程(1)~(3)について、順に説明する。
本開示に用いられる基材は、スラリーを塗工できる程度の平面を有するものであれば、特に限定されない。基材は、板状であってもよいし、シート状であってもよい。また、基材は、予め作製したものでもよいし、市販品でもよい。
また、転写用基材上に形成した硫化物系固体電池用電極活物質層は、集電体と熱圧着等により接合した後、転写用基材を剥離することにより、電極用集電体上に電極活物質層を形成した硫化物系固体電池用電極を得ることができる。
この工程については、上述したスラリーの調製方法に従って行うことができる。
本工程は、上記基材の少なくともいずれか一方の面に、上記スラリーを塗工して硫化物系固体電池用電極を形成する工程である。
硫化物系固体電池用電極は、基材の片面のみに形成されてもよいし、基材の両面に形成されてもよい。
スラリーの塗工量は、スラリーの組成や目的とする硫化物系固体電池用電極の用途等によって異なるが、乾燥状態で5~30mg/cm2程度となるようにすればよい。また、硫化物系固体電池用電極の厚さは、特に限定されないが、10~250μm程度とすればよい。
正極集電体の材料としては、例えばアルミニウム、SUS、ニッケル、鉄、チタン、クロム、金、白金、亜鉛等を挙げることができ、中でもアルミニウム及びSUSが好ましい。また、正極集電体の形状としては、例えば、箔状、板状、メッシュ状等を挙げることができ、中でも箔状が好ましい。
硫化物系固体電池は、正極活物質層2及び正極集電体4を備える正極6と、負極活物質層3及び負極集電体5を備える負極7と、上記正極6及び上記負極7に挟持される硫化物系固体電解質層1を備える。
本開示に用いられる正極、負極は、上述した硫化物系固体電池用電極と同様である。以下、本開示に係る硫化物系固体電池に用いられる負極及び硫化物系固体電解質層、並びに本開示に係る硫化物系固体電池に好適に用いられるセパレータ及び電池ケースについて、詳細に説明する。
負極集電体の材料としては、例えばクロム、SUS、ニッケル、鉄、チタン、銅、コバルト、及び亜鉛等を挙げることができ、中でも銅、鉄、及びSUSが好ましい。また、負極集電体の形状としては、例えば、箔状、板状、メッシュ状等を挙げることができ、中でも箔状が好ましい。
(結着剤2;実施例用)
3Lのステンレス製オートクレーブに純水1650ml入れ窒素置換し、ヘキサフルオロプロピレン(HFP)で微加圧とし、380rpmで攪拌しながら80℃に温調して、HFPを0.23MPaまで圧入し、さらにビニリデンフルオライド(VdF)とHFPのモル比が78.2/21.8の混合液モノマーを1.472MPaまで圧入した。2-メチルブタンを0.097cc窒素で圧入し、過硫酸アンモニウム36.4gを純水80mlに溶解したものを窒素で圧入して重合スタートした。圧力が1.44MPaまで降下したところで連続モノマーにて1.50MPaまで昇圧した。これを繰り返し約9.3時間の後連続モノマーを607g仕込んだところでオートクレーブ内のガスを放出し、冷却して2299gの分散液を回収した。分散液の固形分含有量は26.9wt%であった。この分散液に塩化マグネシウムを加えて凝析し、乾燥することで610gのポリマーを得た。得られたポリマーはHFPとVdFをモル比で22.1/77.9の割合で含んでいた。得られたポリマーのムーニー粘度(ML1+10(121℃))は140で、TgはDSCにより-18℃と決定された。また、融解熱は、セカンドランでは認められなかった。
同様の方法で、表1に示した結着剤1、3~6の組成になるように、ポリマー組成を調整し、これを得た。
3Lのステンレス製オートクレーブに純水1716ml、CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4 50%水溶液を0.3432g、C5F11COONH4 50%水溶液を3.421g入れ窒素置換し、HFPで微加圧とし、560rpmで攪拌しながら80℃に温調して、HFPを0.56MPaまで圧入し、Vd Fを0.69MPaまで圧入し、さらにVdFとTFEとHFPのモル比が70.2/1 1.3/18.5の混合液モノマーを2.000MPaまで圧入した。過硫酸アンモニウ ム0.0218gを純水4mlに溶解したものを窒素で圧入して重合スタートした。連続モノマー12gに到達したときに1,4-ジヨードパーフルオロブタン2.5022g添加した。圧力が1.97MPaまで降下したところで連続モノマーにて2.03MPaまで昇圧した。これを繰り返し約5.0時間の後連続モノマーを572g仕込んだところでオートクレーブ内のガスを放出し、冷却して2302gの分散液を回収した。分散液の固形分含有量は23.5wt%であった。この分散液に硫酸アルミニウムを加えて凝析し、乾燥することで571gのポリマーを得た。得られたポリマーはVdFとTFEとHFPをモル比で69.9/11.2/18.9の割合で含んでいた。得られたポリマーのムーニー粘度(ML1+10(121℃))は48で、TgはDSCにより-20℃と決定された。また、融解熱は、セカンドランでは認められなかった。
同様の方法で、表1に示した結着剤8の組成になるように、ポリマー組成を調整し、これを得た。
3Lのステンレススチール製のオートクレーブに、純水1.7L、CH2=CFCF2OCF(CF3)CF2OCF(CF3)COONH4の50%水溶液を0.17g、F(CF2)5COONH4の50%水溶液を6.8g仕込み、系内を窒素ガスで充分に置換した。600rpmで攪拌しながら80℃に昇温した後、初期槽内モノマー組成をVdF/HFP=45/55(モル比)、1.52MPaとなるようにモノマーを圧入した。ついで過硫酸アンモニウム(APS)60mgを5mlの純水に溶解した重合開始剤溶液を窒素ガスで圧入し、反応を開始した。重合の進行に伴い内圧が1.42MPaに降下した時点でVdF/HFP=78/22(モル比)の追加混合モノマーを内圧が1.52MPaとなるまで圧入した。このとき、ジヨウ素化合物I(CF2)4Iを2.15g圧入した。昇圧、降圧を繰り返しつつ、3時間ごとにAPS60mgを5mlの純水に溶解した重合開始剤溶液を窒素ガスで圧入して、重合反応を継続した。混合モノマーを600g追加した時点で、未反応モノマーを放出し、オートクレーブを冷却して、固形分濃度25.8質量%のフッ素ゴムのディスパージョンを2364g得た。重合時間は7.1時間であった。NMR分析によりこのフッ素ゴムの共重合組成を調べたところ、VdF/HFP=78/22(モル比)であり、ムーニー粘度(ML1+10(121℃))は35であった。
結着剤を真空乾燥機にいれ、50℃ 12時間で真空乾燥を行った後に、
結着剤を溶媒中に添加し 、一晩攪拌した後で、超音波ホモジナイザーを用いて超音波処理(90秒)を3回繰り返し、結着剤溶液を調製した。ここで、結着剤溶液全体を100質量%として結着剤が5質量%含まれるようにした。実施例を行った結着剤の組成は表1に示す。また結着剤と溶媒の組み合わせは表2、3に示す。
本開示においては、以下の手順で正極、負極用スラリーおよび固体電解質層を作製した。
調製した結着剤溶液を用いて、実施例及び比較例に係る負極用スラリーを作製した。具体的には以下の通りである。
PET容器に、上記の結着剤溶液、負極活物質である黒鉛とともに結着剤溶液に含まれた溶媒を添加し、超音波ホモジナイザーを用いて超音波処理(50秒)を1回行い、「負極 活物質・結着剤スラリー」を調製した。得られた負極活物質・結着剤スラリーに、さらに結着剤溶液、溶媒と硫化物系固体電解質(30LiI・70(0.75Li2S・0.25P2S5))とを添加し、超音波ホモジナイザーを用いて超音波処理 (30秒)を3回行うことで、負極活物質と硫化物系固体電解質と結着剤とが高度に分散した「負極用スラリー」を得た。最終的なスラリー中の結着剤固形分濃度は3.0質量%となった。
各負極用スラリーを負極集電体である銅箔上にドクターブレードを用いて塗工し、乾燥させて、負極集電体の表面に厚み110μmの負極層が形成されてなる負極を得た。
負極についての評価結果を表2に示す。
溶媒として酪酸ブチルを、正極活物質として三元系活物質Li(NiMnCo)1/3O2を、固体電解質として上述の硫化物系固体電解質を、結着剤として上述の結着剤溶液を用いて、スラリー中の結着剤固形分濃度は5質量%となるように調整し正極用スラリーを得た。作製した正極用スラリーを正極集電体であるアルミニウム箔上にドクターブレードを用いて塗工し、乾燥させて、正極集電体の表面に厚み85μmの正極層が形成されてなる正極を得た。
正極についての評価結果を表3に示す。
溶媒として酪酸ブチルを、固体電解質として上述の硫化物系固体電解質を、結着剤溶液として結着剤として結着剤(3)または結着剤(9)を含む結着剤溶液を用いて、電解質スラリーを作製し、作製した電解質スラリーを剥離可能な基材(PTFEシート)上にドクターブレードを用いて塗工し、乾燥させたうえで、基材上に厚み45μmの固体電解質シートを形成した。固体電解質シートにおける固体電解質及び結着剤の質量比は固体電解質:結着剤=100質量部:1質量部とした。
(極性末端基量)
上述した方法によるNMRによる組成分析を行い、([-CH2OH]+[-COOH] )/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC( O)RH]+[-COOH])の割合を算出した。
ASTM E1356-98に従い、METLER TOLEDO製のDSC測定装置 を使用してセカンドランにおける熱吸収から中点法によってガラス転移温度を決定する。結果を表1に示す。さらに、セカンドランにおける結晶融点の有無について確認を行った。セカンドランにおいて結晶融点がないものについて、「非晶性」と判断する。
測定条件
昇温速度;20℃/min
試料量;10mg
ヒートサイクル;-100℃~220℃、昇温、冷却、昇温
表2に示す通り、溶媒としてプロピオン酸プロピル、酪酸ブチルを用いた場合は、溶媒と硫化物系固体電解質との反応を抑制しつつ、結着剤が溶解した。一方、比較例1および2では結着剤が溶解せず、均一なスラリーを作製することができなかった。
作製した電極を縦3cm、横6cmに切り取った後、ロールプレス機により、10t加圧で圧延した。180°折り畳んだ後広げて、電極の割れの有無を目視で確認した。割れが確認されない場合は○、割れが確認された場合は×と評価した。
作製した電解質シートをサンプル瓶につめて密封した。あらかじめ湿度を50%RHに調整したチャンバー内でサンプルを開封し、チャンバー内の気中水分に曝露させることで劣化を促進させた。1時間後、サンプルをとりだし、様態を観察した。また、固体電解質について、インピーダンスアナライザー
(Solartron社製:SI-1260)を用いて、周波数10MHz~0.01H
zで交流インピーダンス測定を行い、測定結果に基づいて導電率を算出した。結着剤(3)を用いたものは曝露前の導電率は4×10 -4 S/cmであった。
1.2×8.0cmに切った正極または負極の電極側を可動式治具に固定し、集電体側にテープを張り、そのテープ側を100mm/分の速度でテープを90度に引っ張った時の応力(N/mm)をオートグラフにて測定した。オートグラフのロードセルには1Nを用いた。 比較例4の結果を100として、相対比較した。正極活物質を用いた実施例8では比較例5を100として、相対評価した。 比較例1,2では結着剤が酪酸ブチルに溶解せず、電極の作製が困難であったため、密着性および柔軟性の評価は出来なかった。
また、長期信頼性の結果、結着剤(3)を用いたものは曝露後も形状を保っていたのに対し、結着剤(9)は脆性が生じておりピンセットでつまんで取り出すことが困難であった。また、結着剤(3)を用いたものは曝露後の導電率は4×10 -5 S/cmであった
2 正極活物質層
3 負極活物質層
4 正極集電体
5 負極集電体
6 正極
7 負極
Claims (17)
- 硫化物系固体電解質粒子を含有する固体電池用スラリーに使用される結着剤であって、
結着剤は、樹脂末端官能基が
0.01≦([-CH2OH]+[-COOH])/([-CH3]+[-CF2H]+[-CH2OH]+[-CH2I]+[-OC(O)RH]+[-COOH]≦0.25
(式中、Rは炭素数1~20のアルキル基を表す 。)
を満たす含フッ素エラストマーを含むことを特徴とする結着剤。 - 含フッ素エラストマーは、ビニリデンフルオライド(VdF)単量単位及び共重合単位からなるものである請求項1記載の結着剤。
- 含フッ素エラストマーは、共重合単位がヘキサフルオロプロピレン(HFP)、テトラフルオロエチレン(TFE)、2,3,3,3-テトラフルオロプロピレン、1,3,3,3-テトラフルオロプロピレン、パーフルオロアルキルビニルエーテル(PAVE)からなる群より選択される少なくとも一種の共重合単位である請求項2記載の結着剤。
- 含フッ素エラストマーは、共重合単位の少なくとも一部がヘキサフルオロプロピレン(HFP)である請求項2又は3記載の結着剤。
- フッ素含有率が60~71質量%である請求項1、2、3又は4記載の結着剤。
- ガラス転移温度は、25℃以下である請求項1、2、3、4又は5記載の結着剤。
- 硫化物系固体電解質粒子を含有する固体電池用スラリーに使用される溶液であって、結着剤及び溶媒を含み、 結着剤は、請求項1~6のいずれかに記載の結着剤であることを特徴とする溶液。
- 硫化物系固体電解質粒子、結着剤及び溶媒を含む固体電池用スラリーであって、結着剤は、請求項1~6記載のいずれかに記載の結着剤であることを特徴とする固体電池用スラリー。
- 溶媒は、低極性溶媒である請求項8記載の固体電池用スラリー。
- 溶媒は、芳香族系化合物、エステル系化合物からなる群より選択される少なくとも1の化合物を含む請求項8又は9記載の固体電池用スラリー。
- 更に、活物質粒子を含有する請求項8、9又は10記載の固体電池用スラリー。
- 活物質粒子は、負極活物質である請求項11記載の固体電池用スラリー 。
- 請求項11又は12記載のスラリーによって形成された電極活物質層、及び、集電体を有する固体電池用電極。
- 負極である請求項13に記載の固体電池用電極。
- 電極活物質は、少なくとも一部に炭素質材料を含むものである請求項14に記載の固体電池用電極。
- 電極活物質は、少なくとも一部にシリコン含有化合物を含むものである請求項14に記載の固体電池用電極。
- 請求項13~16のいずれか1項に記載の固体電池用電極を備えることを特徴とするリチウムイオン二次固体電池。
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