WO2023182090A1 - Secondary battery electrode composition - Google Patents

Secondary battery electrode composition Download PDF

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Publication number
WO2023182090A1
WO2023182090A1 PCT/JP2023/010029 JP2023010029W WO2023182090A1 WO 2023182090 A1 WO2023182090 A1 WO 2023182090A1 JP 2023010029 W JP2023010029 W JP 2023010029W WO 2023182090 A1 WO2023182090 A1 WO 2023182090A1
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group
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secondary battery
mol
battery electrode
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PCT/JP2023/010029
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French (fr)
Japanese (ja)
Inventor
祐太郎 浅羽
潤 佐々木
遼 坂本
啓祐 竹中
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積水化学工業株式会社
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Publication of WO2023182090A1 publication Critical patent/WO2023182090A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present invention relates to a composition for secondary battery electrodes.
  • fibrous carbon materials such as carbon nanotubes and VGCF have been expected to be put to practical use in a wide range of fields such as electronics because they exhibit excellent electrical properties.
  • research has been carried out on adding it as a conductive additive to electrodes for secondary batteries and transparent electrodes.
  • Patent Document 1 discloses a composition containing fine particles made of polyvinyl acetal resin, a fibrous conductive substance, and a liquid dispersion medium containing 50% by weight or more of water.
  • Patent Document 2 discloses a fine carbon fiber dispersion liquid comprising fine carbon fibers, a dispersion medium, a polymer dispersant such as polyvinyl acetal, and a basic compound having a pKa of 7.5 or more. There is.
  • JP2014-209435A Japanese Patent Application Publication No. 2014-181140
  • fibrous carbon materials have a problem in that they have low solubility and dispersibility and cannot maintain a stable dispersion state in a solvent. Furthermore, although fibrous carbon materials have excellent electrical, thermal, and mechanical properties, their very large aspect ratio makes them easy to tangle, making it difficult to obtain high-performance composite materials that take full advantage of their properties. There is a problem. In order to solve the above problem, it is necessary to add a large amount of a resin component as a dispersant, but there is a problem that the properties of the fibrous carbon material are impaired. Furthermore, when a dispersion medium with a high moisture content is used as in Patent Document 1, there is a problem that the calculated dispersion state due to the hydrophobic interaction of the fibrous carbon material cannot be maintained sufficiently. Furthermore, the composition disclosed in Patent Document 2 has a problem in that it gels when mixed with a basic active material.
  • the present invention has excellent coating properties and adhesive properties, and is capable of achieving both high electronic conductivity and dispersibility and dispersion stability of fibrous carbon materials, and suppresses gelation.
  • An object of the present invention is to provide a composition for a secondary battery electrode that can produce a high-performance secondary battery.
  • the present disclosure (1) contains an active material, a hydrophobic solvent, a fibrous carbon material, and a polyvinyl acetal resin, the water content is 10% by weight or less, and the polyvinyl acetal resin has a hydroxyl group content. is 30 mol% or less.
  • the present disclosure (2) is the composition for a secondary battery electrode according to the present disclosure (1), wherein the polyvinyl acetal resin has a structural unit having an acidic functional group.
  • the present disclosure (3) provides a secondary battery electrode according to the present disclosure (1) or (2), wherein the acidic functional group is at least one selected from the group consisting of a carboxylic acid group, a sulfur-containing group, and a phosphorus-containing group. It is a composition.
  • the present disclosure (4) is the present disclosure (2) or (3), wherein the content of the structural unit having an acidic functional group with respect to all the structural units of the polyvinyl acetal resin is 0.01 mol% or more and 10 mol% or less.
  • This is a composition for secondary battery electrodes.
  • the present disclosure (5) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (4), in which the average degree of polymerization of the polyvinyl acetal resin is 150 or more and 1500 or less.
  • the present disclosure (6) provides the present disclosure (2) to (5), wherein the acidic functional group is a Br ⁇ nsted acidic group, and the Br ⁇ nsted acid amount in the polyvinyl acetal resin is 0.2 mg/g or more and 250 mg/g or less.
  • the present disclosure (7) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (6), further containing polyvinylidene fluoride.
  • the present disclosure (8) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (7), in which the fibrous carbon material is a carbon nanotube.
  • the present disclosure (9) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (8), in which the pH of the active material is 9 or more and 12 or less. The present invention will be explained in detail below.
  • the present inventors have found that by combining an active material, a fibrous carbon material, a hydrophobic solvent, and a polyvinyl acetal resin having a specific structure, and further reducing the water content to a predetermined amount or less, In addition to having excellent coating properties and adhesive properties, it is possible to achieve both high electronic conductivity and dispersibility and dispersion stability of the fibrous carbon material, suppressing gelation and manufacturing high-performance secondary batteries. This discovery led to the completion of the present invention.
  • the secondary battery electrode composition contains an active material.
  • the active material include a positive electrode active material and a negative electrode active material.
  • the positive electrode active material include lithium nickel oxide (e.g., LiNiO 2 ), lithium cobalt oxide (e.g., LiCoO 2 ), lithium manganese oxide (e.g., LiMn 2 O 4 ), and lithium nickel manganese oxide (e.g., LiNi 0 ) . .5 Mn 1.5 O 4 ), lithium nickel cobalt manganese oxide (e.g. LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), lithium nickel cobalt aluminum oxide (e.g.
  • LiNi 0.8 Co 0.15 examples include particles of an oxide (lithium transition metal oxide) containing lithium and a transition metal element as constituent metal elements, such as Al 0.05 O 2 ). Further, examples include particles of phosphates containing lithium and a transition metal element as constituent metal elements, such as lithium manganese phosphate (LiMnPO 4 ) and lithium iron phosphate (LiFePO 4 ). Note that these may be used alone or in combination of two or more.
  • negative electrode active material for example, materials conventionally used as negative electrode active materials of lithium secondary batteries can be used, such as carbon-based materials such as graphite, natural graphite, graphite carbon, amorphous carbon, lithium transition Examples include metal oxides, lithium transition metal nitrides, silicon, and silicon compounds such as silicon oxide.
  • the composition ratio of metal elements in the lithium transition metal oxide containing nickel is preferably such that the composition ratio of Ni atoms is 30 at% or more, and 50 at% It is more preferably at least 98 atom %, more preferably at most 95 atom %.
  • the composition ratio of the Ni atoms is preferably 30 to 98 atomic %, more preferably 50 to 95 atomic %.
  • the above active material is required to contain a large amount of Li in its structure in order to increase battery capacity. Since the manufacturing method differs depending on the active material, the pH of the obtained active material changes depending on the amount of basic compound such as Li hydroxide used.
  • the pH of the active material is preferably 9 or higher, more preferably 10 or higher, preferably 12 or lower, and preferably 11 or lower.
  • the above pH is preferably 9 to 12, more preferably 10 to 11.
  • the pH of the active material can be determined by measuring the pH of an aqueous solution in which the active material is added to water at a concentration of 1.0% by weight using a pH meter.
  • the average particle diameter of the active material is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more, even more preferably 1.0 ⁇ m or more, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and even more preferably 20 ⁇ m or less.
  • the average particle diameter is preferably 0.1 to 100 ⁇ m, more preferably 0.5 to 50 ⁇ m, and even more preferably 1.0 to 20 ⁇ m.
  • the average particle diameter can be determined, for example, by measuring the maximum diameter of 50 arbitrary active materials observed using a scanning electron microscope and calculating the average value.
  • the density of the active material is preferably 3.0 g/cm 3 or more, more preferably 3.5 g/cm 3 or more, preferably 6.0 g/cm 3 or less, and more preferably 5.5 g/cm 3 or less.
  • the density is preferably 3.0 to 6.0 g/cm 3 , more preferably 3.5 to 5.5 g/cm 3 .
  • the above density can be measured by a method based on JIS Z8807.
  • the specific surface area of the active material is preferably 0.1 m 2 /g or more, more preferably 0.2 m 2 /g or more, preferably 5.0 m 2 /g or less, and more preferably 4.5 m 2 /g or less.
  • the specific surface area is preferably 0.1 to 5.0 m 2 /g, more preferably 0.2 to 4.5 m 2 /g.
  • the specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
  • the secondary battery electrode composition contains a hydrophobic solvent.
  • a hydrophobic solvent By containing a hydrophobic solvent, it is possible to prevent moisture from entering and suppress side reactions in the battery.
  • the hydrophobic solvent refers to a "solvent having an octanol/water partition coefficient of 0.1 or more.” The above distribution coefficient can be measured by a method based on JIS Z7260-117:2006.
  • hydrophobic solvent examples include organic solvents such as ketones, alcohols, aromatic hydrocarbons, esters, carbonates, and amides.
  • ketones include acetone, methyl ethyl ketone, dipropyl ketone, diisobutyl ketone, and the like.
  • alcohols include methanol, ethanol, isopropanol, butanol, and the like.
  • aromatic hydrocarbons include toluene and xylene.
  • esters include methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, Examples include butyl hexanoate, 2-ethylhexyl acetate, butyl butyrate, 2-ethylhexyl butyrate, and the like.
  • methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, dihydroterpineol acetate, etc. can also be used.
  • the carbonates include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and the like.
  • the amides include dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, diethylformamide, and the like.
  • the content of the hydrophobic solvent in the secondary battery electrode composition is preferably 20.0% by weight or more, more preferably 25.0% by weight or more, and preferably 50.0% by weight or less.
  • the content of the hydrophobic solvent is preferably 20.0 to 50.0% by weight, more preferably 25.0 to 50.0% by weight.
  • the secondary battery electrode composition contains a fibrous carbon material. By containing the fibrous carbon material, conductive properties can be improved.
  • the above-mentioned fibrous carbon material means a carbon material having an aspect ratio (average fiber length/average fiber diameter) of 30 or more.
  • the aspect ratio (average fiber length/average fiber diameter) of the above-mentioned fibrous carbon material is preferably 50 or more, more preferably 100 or more, still more preferably 200 or more, and even more preferably 400 or more. more preferably 500,000 or less, more preferably 300,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 20,000 or less.
  • the aspect ratio is preferably 30 to 500,000, more preferably 50 to 300,000, even more preferably 100 to 100,000, even more preferably 200 to 50,000, and particularly preferably 400 to 20,000.
  • Examples of the fibrous carbon material include carbon fibers and carbon nanotubes.
  • Examples of the carbon fibers include PAN carbon fibers, pitch carbon fibers, cellulose carbon fibers, vapor grown carbon fibers (VGCF), and the like.
  • the carbon nanotube is a cylindrical carbon material, and includes single-walled carbon nanotubes, multi-walled carbon nanotubes, and the like. Among these, carbon nanotubes are preferred because they have high crystallinity and excellent conductivity.
  • the average fiber diameter of the fibrous carbon material is preferably 0.40 nm or more, more preferably 0.50 nm or more, still more preferably 1.00 nm or more, and 5.00 nm or more from the viewpoint of increasing the conductivity per unit weight. It is even more preferably 200.00 nm or less, more preferably 150.00 nm or less, even more preferably 100.00 nm or less.
  • the average fiber diameter is preferably 0.40 to 200.00 nm, more preferably 0.50 to 150.00 nm, and even more preferably 1.00 to 100.00 nm.
  • the average fiber diameter can be measured using, for example, a scanning laser microscope or a transmission laser microscope.
  • the average fiber length of the fibrous carbon material is preferably 0.10 ⁇ m or more, more preferably 0.50 ⁇ m or more, even more preferably 1.00 ⁇ m or more, and 5.00 ⁇ m or more from the viewpoint of increasing the conductivity per unit weight. It is even more preferably 500.00 ⁇ m or less, more preferably 250.00 ⁇ m or less, even more preferably 200.00 ⁇ m or less, and even more preferably 100.00 ⁇ m or less.
  • the average fiber length is preferably 0.10 to 500.00 ⁇ m, more preferably 0.50 to 250.00 ⁇ m, and even more preferably 1.00 to 100.00 ⁇ m.
  • the average fiber length can be measured using, for example, a scanning laser microscope or a transmission laser microscope.
  • the density of the fibrous carbon material is preferably 1.0 g/cm 3 or more, more preferably 1.1 g/cm 3 or more, and still more preferably 1.2 g/cm 3 or more from the viewpoint of increasing the conductivity per unit weight. It is preferably 1.8 g/cm 3 or more, even more preferably 2.5 g/cm 3 or less, more preferably 2.3 g/cm 3 or less, and even more preferably 2.1 g/cm 3 or less.
  • the above density is preferably 1.0 to 2.5 g/cm 3 , more preferably 1.1 to 2.3 g/cm 3 , even more preferably 1.2 to 2.1 g/cm 3 , and still more preferably 1.8 to 2 .1 g/cm 3 is even more preferred.
  • the above density can be measured by a method based on JIS Z8807.
  • the specific surface area of the fibrous carbon material is preferably 8 m 2 /g or more, more preferably 13 m 2 /g or more, even more preferably 100 m 2 /g or more, and 200 m 2 /g from the viewpoint of increasing the conductivity per unit weight. It is even more preferable that the area is at least 3000 m 2 /g, more preferably at most 1500 m 2 /g, even more preferably at most 1200 m 2 /g, and even more preferably at most 1000 m 2 /g.
  • the specific surface area is preferably 8 to 3000 m 2 /g, more preferably 13 to 1500 m 2 /g, even more preferably 100 to 1200 m 2 /g, and even more preferably 200 to 1000 m 2 /g.
  • the specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
  • the peak intensity ratio (G/D ratio) between the G band and the D band in the fibrous carbon material is preferably 0.1 or more, and 0.5 or more, since the higher the crystallinity, the higher the conductivity. More preferably, it is 100 or less, and even more preferably 95 or less.
  • the above G/D ratio is preferably 0.1 to 100, more preferably 0.5 to 95.
  • the above G/D ratio can be determined, for example, by measuring a Raman spectrum using Raman spectroscopy. When the above fibrous carbon material was measured by Raman spectroscopy, two peaks were clearly observed: the G band (near 1580 cm -1 ) corresponding to sp2 bonds and the D band (near 1360 cm -1 ) corresponding to sp3 bonds. Ru.
  • the carbon material is crystalline
  • one of the two bands described above becomes minimum.
  • the G band near 1580 cm -1 is hardly observed.
  • the D band near 1360 cm ⁇ 1 hardly appears.
  • the fibrous carbon material may be a discontinuous fiber whose fibers are intermittently divided, or a continuous fiber which is not divided.
  • the shape of the fibers is not particularly limited, but may be, for example, in addition to fibers, sheet shapes such as woven fabrics, knitted fabrics, and nonwoven fabrics.
  • the content of the fibrous carbon material in the secondary battery electrode composition is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, even more preferably 0.5% by weight or more, 1. It is even more preferably 5% by weight or more, preferably 15.0% by weight or less, and even more preferably 10.0% by weight or less.
  • the above content is preferably 0.05 to 15.0% by weight, more preferably 0.1 to 10.0% by weight, even more preferably 0.5 to 10.0% by weight, and even more preferably 1.5 to 10.0% by weight. % by weight is even more preferred.
  • the surface area (specific surface area (m 2 /g) x content (g)) of the active material is X
  • the surface area (specific surface area (m 2 /g)) of the fibrous carbon material is x content (g))
  • the surface area ratio (X/Y) is preferably 0.01 or more, preferably 6.0 or less, and more preferably 0.05 or more, from the viewpoint of conductivity. It is more preferably 4.5 or less, and even more preferably 3.0 or less.
  • the surface area ratio (X/Y) is preferably 0.01 to 6.0, more preferably 0.05 to 4.5, and even more preferably 0.05 to 3.0.
  • the secondary battery electrode composition may contain particulate carbon material in addition to the fibrous carbon material.
  • particulate carbon materials include graphite such as artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, and expanded graphite, acetylene black, Ketjen black, thermal black, and furnace black.
  • carbon black such as black and channel black.
  • the average particle diameter of the particulate carbon material is preferably 10 nm or more, more preferably 15 ⁇ m or more, even more preferably 20 ⁇ m or more, preferably 100 ⁇ m or less, more preferably 75 ⁇ m or less, and even more preferably 50 ⁇ m or less.
  • the average particle diameter is preferably 10 to 100 ⁇ m, more preferably 15 to 75 ⁇ m, and even more preferably 20 to 50 ⁇ m.
  • the density of the particulate carbon material is preferably 1.0 g/cm 3 or more, more preferably 1.1 g/cm 3 or more, even more preferably 1.2 g/cm 3 or more, and even more preferably 1.8 g/cm 3 or more. It is more preferably 2.5 g/cm 3 or less, more preferably 2.3 g/cm 3 or less, even more preferably 2.1 g/cm 3 or less.
  • the above density is preferably 1.0 to 2.5 g/cm 3 , more preferably 1.1 to 2.3 g/cm 3 , even more preferably 1.2 to 2.1 g/cm 3 , and still more preferably 1.8 to 2 .1 g/cm 3 is even more preferred.
  • the above density can be measured by a method based on JIS Z8807.
  • the specific surface area of the particulate carbon material is preferably 20 m 2 /g or more, more preferably 50 m 2 /g or more, preferably 1000 m 2 /g or less, and more preferably 800 m 2 /g or less.
  • the specific surface area is preferably 20 to 1000 m 2 /g, more preferably 50 to 800 m 2 /g.
  • the specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
  • the total content of the fibrous carbon material and the particulate carbon material in the secondary battery electrode composition is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and 0.5% by weight. % or more, still more preferably 1.5% by weight or more, preferably 15.0% by weight or less, and more preferably 10.0% by weight or less.
  • the above total content is preferably 0.05 to 15.0% by weight, more preferably 0.1 to 10.0% by weight, even more preferably 0.5 to 10.0% by weight, and even more preferably 1.5 to 10.0% by weight. Even more preferred is 0% by weight.
  • the secondary battery electrode composition contains a polyvinyl acetal resin.
  • the polyvinyl acetal resin has a hydroxyl group content of 30 mol% or less.
  • the above-mentioned polyvinyl acetal resin usually contains a structural unit having a hydroxyl group represented by the following formula (1-1), a constitutional unit having an acetyl group represented by the following formula (1-2), and a structural unit having a hydroxyl group represented by the following formula (1-2), and a structural unit having a hydroxyl group represented by the following formula (1-2). It has a structural unit having an acetal group represented by 3).
  • R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
  • R 1 is an alkyl group having 1 to 20 carbon atoms
  • examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group.
  • the content of the structural unit having a hydroxyl group represented by the above formula (1-1) (hereinafter also referred to as "hydroxyl group amount”) is 30 mol% or less.
  • hydroxyl group amount is preferably 10 mol% or more, more preferably 15 mol% or more, preferably 30 mol% or less, more preferably 28 mol% or less, and even more preferably 25 mol% or less.
  • the amount of hydroxyl groups is preferably 10 to 30 mol%, more preferably 15 to 28 mol%, even more preferably 15 to 25 mol%.
  • the amount of hydroxyl groups can be measured, for example, by NMR.
  • the content of the structural unit having an acetyl group represented by the above formula (1-2) is preferably 0.1 mol % or more, and 5 mol %. % or more, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less.
  • the amount of acetyl groups is preferably 0.1 to 30 mol%, more preferably 5 to 20 mol%, even more preferably 5 to 15 mol%.
  • the amount of acetyl groups can be measured, for example, by NMR.
  • the content of the structural unit having an acetal group represented by the above formula (1-3) (hereinafter also referred to as "acetal group amount”) is more preferably 60 mol% or more, and 70 mol%.
  • the above is more preferable, 80 mol% or less is more preferable, and even more preferably 75 mol% or less.
  • the amount of acetal groups is preferably 60 to 80 mol%, more preferably 70 to 75 mol%. Within the above range, the dispersibility of the fibrous carbon material can be further improved.
  • the structural unit having an acetal group is replaced by the structural unit having a hydroxyl group.
  • Calculate the amount of acetal groups by counting by converting into two parts.
  • the amount of acetal groups can be measured, for example, by NMR.
  • the polyvinyl acetal resin may have an ionic functional group.
  • ionic functional groups include sulfur-containing groups such as carboxylic acid groups, sulfonic acid groups, sulfinic acid groups, and sulfenic acid groups, phosphorus-containing groups such as phosphoric acid groups and phosphonic acid groups, amino groups, and salts thereof. It will be done. Among these, it is preferable to have a structural unit having an acidic functional group, and it is more preferable to have a structural unit having a Br ⁇ nsted acidic group.
  • Examples of the Bronsted acidic group include a carboxylic acid group, a sulfonic acid group, a sulfinic acid group, a sulfenic acid group, a phosphoric acid group, a phosphonic acid group, or salts thereof.
  • a carboxylic acid group, a sulfur-containing group, and a phosphorus-containing group is preferable from the viewpoint of being able to increase adsorption to fibrous carbon materials, and carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are preferred. At least one selected from the group is more preferred. Since the modified polyvinyl acetal resin has the structural unit having the acidic functional group, the dispersibility of the fibrous carbon material can be improved even with a small amount added.
  • the above structural unit having an ionic functional group may have a structure in which an ionic functional group as a side chain is directly bonded to carbon constituting the main chain, or an ionic functional group may be bonded directly to carbon constituting the main chain through an alkylene group. It may also have a structure in which a sexual functional group is bonded. Further, the above structural unit having an ionic functional group may have a structure in which the ionic functional group is bonded to carbon forming the main chain via an acetal bond.
  • the above structural unit having an ionic functional group may have a three-dimensional structure in which two ionic functional groups are bonded to the same carbon constituting the main chain, or one ionic functional group is bonded to the same carbon constituting the main chain. It may be a three-dimensional structure in which two bonds are made. Alternatively, it may be a three-dimensional structure in which one ionic functional group is bonded to each adjacent carbon that makes up the main chain, or an ionic functional group is bonded to only one of the adjacent carbons that make up the main chain. It may be a three-dimensional structure.
  • it has a three-dimensional structure in which two ionic functional groups are bonded to the same carbon that makes up the main chain, or a three-dimensional structure in which one ionic functional group is bonded to each adjacent carbon that makes up the main chain. is preferred.
  • the above-mentioned structural unit having an ionic functional group may have a three-dimensional structure in which the ionic functional group is bonded in the same direction to the carbon constituting the main chain, which is an isotactic configuration. It may have a syndiotactic three-dimensional structure in which ionic functional groups are alternately bonded to carbon atoms on opposite sides. Furthermore, it may have a three-dimensional structure in which the ionic functional groups are randomly bonded in an atactic configuration.
  • the alkylene group is an alkylene group having 1 to 10 carbon atoms. It is preferably an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.
  • Examples of the alkylene group having 1 to 10 carbon atoms include a linear alkylene group, a branched alkylene group, and a cyclic alkylene group.
  • Examples of the linear alkylene group include a methylene group, a vinylene group, an n-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group.
  • Examples of the branched alkylene group include methylmethylene group, methylethylene group, 1-methylpentylene group, and 1,4-dimethylbutylene group.
  • cyclic alkylene group examples include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group.
  • a linear alkylene group is preferred, a methylene group, a vinylene group, and an n-propylene group are more preferred, and a methylene group and a vinylene group are even more preferred.
  • Examples of the above-mentioned structural units having an ionic functional group include structural units represented by the following formulas (2-1) to (2-4).
  • R 2 , R 4 , R 6 , R 8 , R 10 and R 12 are each independently a single bond or an alkylene group having 1 to 10 carbon atoms.
  • R 3 , R 5 , R 7 , R 9 , R 11 and R 13 each represent an ionic functional group.
  • the above R 2 , R 4 , R 6 , R 8 , R 10 and R 12 are preferably a single bond or an alkylene group having 1 to 5 carbon atoms, and are a single bond or an alkylene group having 1 to 3 carbon atoms. More preferably, it is an alkylene group.
  • Examples of the alkylene group having 1 to 10 carbon atoms include a linear alkylene group, a branched alkylene group, and a cyclic alkylene group.
  • Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group.
  • Examples of the branched alkylene group include methylmethylene group, methylethylene group, 1-methylpentylene group, and 1,4-dimethylbutylene group.
  • cyclic alkylene group examples include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group.
  • a linear alkylene group is preferred, a methylene group, an ethylene group, and a trimethylene group are more preferred, and a methylene group and an ethylene group are even more preferred.
  • examples of the structural unit having a carboxylic acid group include structural units represented by the following formulas (3-1) to (3-3).
  • R 14 to R 18 are each independently a single bond or an alkylene group having 1 to 10 carbon atoms
  • X 1 to X 5 are each independently , represents a hydrogen atom, a metal atom or a methyl group.
  • Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
  • the metal atoms include sodium atoms, lithium atoms, potassium atoms, and the like. Among these, a sodium atom is preferred.
  • Examples of the structural unit having a sulfonic acid group include a structural unit represented by the following formula (4).
  • R 19 represents a single bond or an alkylene group having 1 to 10 carbon atoms
  • X 6 represents a hydrogen atom, a metal atom, or a methyl group.
  • Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
  • Examples of the metal atom include those similar to X 1 in the above formula (3-1).
  • Examples of the above-mentioned structural unit having a phosphonic acid group include a structural unit represented by the following formula (5).
  • R 20 is a single bond or an alkylene group having 1 to 10 carbon atoms
  • X 7 and X 8 each independently represent a hydrogen atom, a metal atom, or a methyl group.
  • Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
  • Examples of the metal atom include those similar to X 1 in the above formula (3-1).
  • Examples of the above-mentioned structural unit having an amino group include a structural unit represented by the following formula (6).
  • R 21 represents a single bond or an alkylene group having 1 to 10 carbon atoms.
  • Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
  • the content of the structural unit having an ionic functional group with respect to all the structural units of the polyvinyl acetal resin is preferably 0.01 mol% or more, and 0.1 mol% or more from the viewpoint of dispersibility of the fibrous carbon material. It is more preferably 0.5 mol% or more, still more preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, and even more preferably 5 mol% or less.
  • the content of the structural unit having an ionic functional group is preferably 0.01 to 20 mol%, more preferably 0.1 to 15 mol%, even more preferably 0.5 to 10 mol%, and even more preferably 0.5 to 20 mol%. Even more preferred is 5 mol%.
  • the content of the structural unit having an ionic functional group can be measured, for example, by NMR.
  • the amount of Bronsted acid in the polyvinyl acetal resin is preferably 0.2 mg/g or more, more preferably 10 mg/g or more, and preferably 350 mg/g or less, and 250 mg/g. The following is more preferable, and 150 mg/g or less is still more preferable.
  • the amount of Br ⁇ nsted acid is preferably 0.2 to 350 mg/g, more preferably 10 to 250 mg/g, even more preferably 10 to 150 mg/g.
  • the above-mentioned amount of Bronsted acid means the amount of potassium hydroxide required to neutralize the Bronsted acid contained in the polyvinyl acetal resin.
  • the amount of Br ⁇ nsted acid can be measured, for example, by acid-base titration according to a method based on JIS K0070-1992.
  • the polyvinyl acetal resin has an acetal group having an ionic functional group represented by the above formula (2-4) as a structural unit having an ionic functional group
  • the polyvinyl acetal resin has an acetal group having an ionic functional group represented by the above formula (2-4).
  • -4) and the content of structural units having an acetal group represented by the above formula (1-3) (hereinafter referred to as "total acetal group content").
  • total acetal group content is preferably 45 mol% or more, more preferably 60 mol% or more, preferably 85 mol% or less, and more preferably 75 mol% or less.
  • the total amount of acetal groups is preferably 45 to 85 mol%, more preferably 60 to 75 mol%.
  • the average degree of polymerization of the polyvinyl acetal resin is preferably 150 or more, more preferably 200 or more, even more preferably 300 or more, since it can sufficiently improve the dispersibility of the fibrous carbon material and exhibit high electronic conductivity. It is preferably 1,500 or less, more preferably 1,200 or less, and even more preferably 900 or less.
  • the average degree of polymerization is preferably from 150 to 1,500, more preferably from 200 to 1,200, even more preferably from 300 to 900.
  • the average degree of polymerization can be measured, for example, by gel permeation chromatography (GPC).
  • the content of the polyvinyl acetal resin in the secondary battery electrode composition is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 30.0% by weight or less, and 15.0% by weight. % or less is more preferable.
  • the above content is preferably 0.1 to 30.0% by weight, more preferably 0.5 to 15.0% by weight.
  • the ratio of the content of the polyvinyl acetal resin to the content of the fibrous carbon material in the composition for secondary battery electrodes is 0.1 or more. is preferable, 0.2 or more is more preferable, 2 or less is preferable, and 1.5 or less is more preferable.
  • the above ratio is preferably 0.1 to 2, more preferably 0.2 to 1.5.
  • the fibrous carbon material has good dispersibility, making it easier to form conductive paths. As a result, electronic conductivity becomes even more excellent.
  • the ratio of the content (g) of the polyvinyl acetal resin to the surface area (specific surface area (m 2 /g) x content (g)) of the fibrous carbon material Resin content/surface area of fibrous carbon material) is preferably 0.0001 or more, preferably 0.04 or less, more preferably 0.001 or more, more preferably 0.035 or less, and still more preferably 0.005 or more. It is preferably 0.03 or less, and more preferably 0.03 or less.
  • the above ratio is preferably 0.0001 to 0.04, more preferably 0.001 to 0.035, and even more preferably 0.005 to 0.03.
  • a polyvinyl acetate resin obtained by polymerizing a monomer such as vinyl acetate is saponified by adding an acid or an alkali, and purified to contain Na ions.
  • Examples include a method of acetalizing polyvinyl alcohol resin in an adjusted amount.
  • polyvinyl alcohol resin conventionally known polyvinyl alcohol resins such as resins produced by saponifying polyvinyl acetate resin with alkali, acid, aqueous ammonia, etc. can be used.
  • the above-mentioned polyvinyl alcohol resin may be completely saponified, but it is completely saponified if there is at least one unit having a double hydroxyl group in the meso or racemo position at least at one location in the main chain. It is not necessary, and a partially saponified polyvinyl alcohol resin may be used.
  • polyvinyl alcohol resin a copolymer of vinyl alcohol and a monomer that can be copolymerized with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin, may also be used. be able to.
  • the polyvinyl acetate resin include ethylene-vinyl acetate copolymer.
  • polyvinyl acetal resin having a structural unit having an ionic functional group for example, polyvinyl acetate obtained by copolymerizing a monomer having an ionic functional group and vinyl acetate is saponified.
  • examples include a method of acetalizing the obtained polyvinyl alcohol by a conventionally known method.
  • an ionic functional group may be introduced by post-modifying a polyvinyl acetal resin obtained by acetalizing unmodified polyvinyl alcohol by a conventionally known method.
  • Examples of the monomer having a carboxylic acid group include monocarboxylic acids such as acrylic acid, crotonic acid, methacrylic acid, and oleic acid, methylene malonic acid, itaconic acid, 2-methylene glutaric acid, 2-methylene adipic acid, -Dicarboxylic acids such as methylene sebacic acid, maleic anhydride, and metal salts thereof.
  • Examples of the monomer having a sulfonic acid group include vinylsulfonic acid, sodium vinylsulfonate, beta-styrenesulfonic acid, and the like.
  • Examples of the monomer having a phosphonic acid group include vinyl phosphoric acid, sodium vinyl phosphate, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and the like.
  • Examples of the above-mentioned monomer having an amino group include vinylamine, allylamine, and the like.
  • the amount of residual acetyl groups in the polyvinyl alcohol resin is preferably 0.1 mol% or more and 20.0 mol% or less, more preferably 5.0 mol% or more and 15.0 mol% or less.
  • the acetalization can be carried out using a known method, and is preferably carried out in an aqueous solvent, in a mixed solvent of water and an organic solvent with which water is compatible, or in an organic solvent.
  • an organic solvent that is compatible with water for example, an alcohol-based organic solvent can be used.
  • the organic solvent include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffinic solvents, ether-based solvents, amide-based solvents, amine-based solvents, and the like.
  • the alcoholic organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol.
  • Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, methyl benzoate, and the like.
  • Examples of the aliphatic ester solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate.
  • Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone.
  • Examples of the lower paraffinic solvent include hexane, pentane, octane, cyclohexane, decane, and the like.
  • Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, and the like.
  • Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethyltesetamide, N-methylpyrrolidone, acetanilide, and the like.
  • amine solvent examples include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine. These solvents can be used alone or in a mixture of two or more. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoint of solubility in the resin and ease of purification.
  • the acetalization is preferably performed in the presence of an acid catalyst.
  • the above acid catalysts are not particularly limited, and include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, carboxylic acids such as formic acid, acetic acid, and propionic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and paratoluenesulfonic acid. Examples include sulfonic acids such as acids.
  • These acid catalysts may be used alone or in combination of two or more kinds of compounds. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.
  • aldehyde used in the acetalization examples include aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. As these aldehydes, conventionally known aldehydes can be used.
  • the aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include aliphatic aldehydes, aromatic aldehydes, and the like.
  • Examples of the aliphatic aldehydes include formaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, and n-octylaldehyde.
  • Examples include octeraldehyde, n-nonylaldehyde, n-decylaldehyde, amylaldehyde and the like.
  • aromatic aldehyde examples include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylbutyraldehyde, and ⁇ -phenylpropionaldehyde.
  • aldehydes examples include aldehydes.
  • cyclic multimers such as paraldehyde and metaldehyde can be used. These aldehydes may be used alone or in combination of two or more.
  • aldehydes examples include formaldehyde, butyraldehyde, butyraldehyde, and 2-ethylhexylaldehyde, which have excellent acetalization reactivity and can provide a sufficient internal plasticizing effect to the resulting resin, resulting in good flexibility.
  • n-nonylaldehyde and paraldehyde are preferred.
  • formaldehyde, n-butyraldehyde, and paraldehyde are more preferred because they yield an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.
  • the amount of the aldehyde added can be appropriately set depending on the amount of acetal groups in the target polyvinyl acetal resin. In particular, it is preferable to use 10 to 65 mol %, preferably 15 to 60 mol %, based on 100 mol % of polyvinyl alcohol, because the acetalization reaction can be carried out efficiently and unreacted aldehyde can be easily removed.
  • the secondary battery electrode composition has a water content of 10% by weight or less. By setting it as the said range, the dispersion stability of a fibrous carbon material can be improved.
  • the water content is preferably 5% by weight or less, more preferably 1% by weight or less. Further, the lower limit is not particularly limited, and is, for example, 0% by weight or more.
  • the water content is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and even more preferably 0 to 1% by weight.
  • the water content can be measured using, for example, an infrared moisture meter.
  • the secondary battery electrode composition further contains a binder resin.
  • the binder resin include fluorine-containing resins such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), and polymethyl acrylate (PMA).
  • acrylic resins such as polymethyl methacrylate (PMMA), polyvinyl acetate, polyimide (PI), polyamide (PA), polyvinyl chloride (PVC), polyethernitrile (PEN), polyethylene (PE), polypropylene (PP),
  • PMMA polymethyl methacrylate
  • PMMA polyvinyl acetate
  • PA polyamide
  • PVC polyvinyl chloride
  • PEN polyethernitrile
  • PE polyethylene
  • PP polypropylene
  • PAN polyacrylonitrile
  • PAN acrylonitrile-butadiene rubber
  • styrene-butadiene rubber poly(meth)acrylic acid
  • carboxymethyl cellulose hydroxyethyl cellulose
  • polyvinyl alcohol polyvinyl alcohol
  • the ratio of the content of the polyvinyl acetal resin to the content of the binder resin in the composition for secondary battery electrodes improves electrical properties and improves dispersibility.
  • it is preferably 0.1 or more, more preferably 0.2 or more, preferably 2.0 or less, and more preferably 1.0 or less.
  • the above ratio is preferably 0.1 to 2.0, more preferably 0.2 to 1.0.
  • the secondary battery electrode composition may further contain additives such as a conductive additive, a flame retardant additive, an antifoaming agent, a leveling agent, and an adhesion imparting agent, within a range that does not impair the effects of the present invention. Good too.
  • the method for producing the secondary battery electrode composition is not particularly limited, and for example, a polyvinyl acetal resin obtained by acetalizing raw material polyvinyl alcohol, an active material, and a fibrous carbon material are added to a hydrophobic solvent.
  • a polyvinyl acetal resin obtained by acetalizing raw material polyvinyl alcohol, an active material, and a fibrous carbon material are added to a hydrophobic solvent.
  • Examples include a method of mixing. Examples of the above-mentioned mixing method include methods using various mixers such as a ball mill, a blender mill, and a three-roll mixer.
  • a lithium secondary battery electrode can be formed by applying the composition for a secondary battery electrode onto a conductive substrate and drying the composition, for example.
  • various coating methods can be employed, including, for example, an extrusion coater, a reverse roller, a doctor blade, an applicator, and the like.
  • a composition for a secondary battery electrode that can be used to manufacture a secondary battery can be provided.
  • Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 1.0 mol%, content of structural units represented by formula (3-1) (R 14 is a methylene group, X 1 is a hydrogen atom) content 1 0 mol %) was added to 2500 g of pure water and stirred at 90° C. for 2 hours to dissolve. This solution was cooled to 40°C, 10g of hydrochloric acid with a concentration of 35% by weight was added thereto, the temperature was lowered to 5°C, 85g of n-butyraldehyde was added, and this temperature was maintained to carry out the acetalization reaction. The reaction product was precipitated.
  • the reaction was completed by keeping the liquid temperature at 65° C. for 5 hours, and 40 g of an aqueous sodium hydroxide solution was added to perform a neutralization reaction. Thereafter, 5000 g of pure water was added and stirred, and then 5000 g of water was removed by decantation. Furthermore, the process of adding 5000 g of pure water, stirring, and removing water by decantation was repeated three times in total. Thereafter, the solid content of the resin was adjusted to 20% by weight using ion-exchanged water to obtain a polyvinyl acetal resin (PVB-A1).
  • PVB-A1 polyvinyl acetal resin
  • the amount of acetal groups, the amount of hydroxyl groups, and the amount of acetyl groups were measured using 1 H-NMR (nuclear magnetic resonance spectrum), and the results were as shown in Table 1.
  • 1 H-NMR measurement used heavy DMSO as a solvent.
  • the amount of Br ⁇ nsted acid was measured by acid-base titration method in accordance with JIS K0070-1992. Specifically, it was measured by the following method. First, as a main test, about 1 g of the obtained polyvinyl acetal resin was accurately weighed into an Erlenmeyer flask, and 40 ml of a mixed solvent of ethanol/water (volume ratio 9:1) was added and dissolved by shaking.
  • Br ⁇ nsted acid amount [(AB) x f x (1/50) x (C/1000)] x 100/D
  • n - A polyvinyl acetal resin (PVB-A14) was obtained in the same manner as in Production Example 1 except that the amount of butyraldehyde added was 75 g.
  • Examples 1 to 18, Comparative Examples 1 to 8 An active material, a hydrophobic solvent, a carbon material, a polyvinyl acetal resin, a binder resin, and water were mixed according to the formulation shown in Table 2 to obtain a composition for a secondary battery electrode. Note that the following were used as the active material, hydrophobic solvent, carbon material, and binder resin. Further, the pH of the active material was measured by adding the active material into water at a concentration of 1.0% by weight, and measuring the pH of the resulting aqueous solution using a pH meter (manufactured by Horiba, Ltd.). Moreover, the water content was measured using an infrared moisture meter (manufactured by KETT).
  • LFP-1 Lithium iron phosphate (LiFePO 4 ) (pH 9, average particle size 1.0 ⁇ m, density 3.4 g/cm 3 , specific surface area 10.7 m 2 /g)
  • LFP-2 Lithium iron phosphate (LiFePO 4 ) (pH 10, average particle size 1.5 ⁇ m, density 3.7 g/cm 3 , specific surface area 12.0 m 2 /g)
  • LFP-3 Lithium iron phosphate (LiFePO 4 ) (pH 9, average particle size 5.5 ⁇ m, density 3.6 g/cm 3 , specific surface area 0.8 m 2 /g)
  • NCM-1 Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) (pH 12, average particle size 10.0 ⁇ m, density 3.5 g/cm 3 , specific surface area 0.5 m 2 /g)
  • NCM-2 Lithium nickel cobalt manganese oxide
  • the obtained secondary battery electrode composition was coated onto a glass plate using a doctor blade, and dried at 150° C. for 5 minutes in an air circulating oven to obtain a coating film.
  • the resulting coating film was visually observed and evaluated based on the following criteria. ⁇ : There were no cracks or fissures on the coating film surface, and the film thickness was uniform. ⁇ : Slight cracks and fissures were observed on the surface of the coating film. ⁇ : Cracks and fissures were observed on the coating film surface, and there were variations in film thickness.
  • Viscosity change rate is less than 150%
  • Viscosity change rate is 150% or more and less than 250%
  • Viscosity change rate is 250% or more
  • the storage modulus of the obtained secondary battery electrode composition was measured using RHEOSTRESS (manufactured by Thermo Scientific) at 25°C and a strain of 0.1, and the storage elastic modulus was measured according to the following criteria. It was evaluated by ⁇ : Storage modulus is less than 1000 ⁇ : Storage modulus is 1000 or more, less than 5000 ⁇ : Storage modulus is 5000 or more If the viscoelasticity evaluation is high, the paste has excellent fluidity and is difficult to gel.
  • a composition for a secondary battery electrode that can be used to manufacture a secondary battery can be provided.

Abstract

The present invention provides a secondary battery electrode composition with which it is possible to manufacture high-performance secondary batteries while suppressing gelation, which exhibits excellent coatability and adhesive properties, and which can achieve both high electron conductivity and dispersibility and dispersion stability of a fibrous carbon material. This secondary battery electrode composition contains an active material, a hydrophilic solvent, a fibrous carbon material, and a polyvinyl acetal resin, and has a water content of 10 wt% or less. The amount of hydroxyl groups in the polyvinyl acetal resin is 30 mol% or less.

Description

二次電池電極用組成物Composition for secondary battery electrodes
本発明は、二次電池電極用組成物に関する。 The present invention relates to a composition for secondary battery electrodes.
近年、カーボンナノチューブやＶＧＣＦ等の繊維状炭素材料は、優れた電気特性を示すことから、エレクトロニクス分野などの幅広い分野へ実用化が期待されている。例えば、二次電池用電極や、透明電極において、導電助剤として添加すること等が研究されている。 In recent years, fibrous carbon materials such as carbon nanotubes and VGCF have been expected to be put to practical use in a wide range of fields such as electronics because they exhibit excellent electrical properties. For example, research has been carried out on adding it as a conductive additive to electrodes for secondary batteries and transparent electrodes.
繊維状炭素材料は、水中又は有機溶剤中に分散させた組成物が一般的に用いられている。
例えば、特許文献１には、ポリビニルアセタール樹脂からなる微粒子、ファイバー状の導電性物質及び水を５０重量％以上含有する液状分散媒を含有する組成物が開示されている。
また、特許文献２には、微細炭素繊維と、分散媒と、ポリビニルアセタール等のポリマー系分散剤と、ｐＫａが７．５以上である塩基性化合物とからなる微細炭素繊維分散液が開示されている。 A composition in which the fibrous carbon material is dispersed in water or an organic solvent is generally used.
For example, Patent Document 1 discloses a composition containing fine particles made of polyvinyl acetal resin, a fibrous conductive substance, and a liquid dispersion medium containing 50% by weight or more of water.
Further, Patent Document 2 discloses a fine carbon fiber dispersion liquid comprising fine carbon fibers, a dispersion medium, a polymer dispersant such as polyvinyl acetal, and a basic compound having a pKa of 7.5 or more. There is.
特開２０１４－２０９４３５号公報JP2014-209435A 特開２０１４－１８１１４０号公報Japanese Patent Application Publication No. 2014-181140
しかしながら、繊維状炭素材料は、溶解性及び分散性が低く、溶剤中で安定した分散状態を保持できないという問題がある。また、繊維状炭素材料は、優れた電気的、熱的、機械的特性を有する半面、アスペクト比が非常に大きいため絡まりやすく、その特性を充分に活かした高性能の複合材料を得ることが難しいという問題がある。
上記問題に対して、分散剤である樹脂成分を多量に添加する必要があるが、繊維状炭素材料の特性を阻害してしまうという問題がある。また、特許文献１のように水分率が高い分散媒を用いると、繊維状炭素材料の疎水性相互作用により算定した分散状態を充分に維持できないという問題がある。また、特許文献２に開示の組成物では、塩基性である活物質と混合するとゲル化してしまうという問題がある。 However, fibrous carbon materials have a problem in that they have low solubility and dispersibility and cannot maintain a stable dispersion state in a solvent. Furthermore, although fibrous carbon materials have excellent electrical, thermal, and mechanical properties, their very large aspect ratio makes them easy to tangle, making it difficult to obtain high-performance composite materials that take full advantage of their properties. There is a problem.
In order to solve the above problem, it is necessary to add a large amount of a resin component as a dispersant, but there is a problem that the properties of the fibrous carbon material are impaired. Furthermore, when a dispersion medium with a high moisture content is used as in Patent Document 1, there is a problem that the calculated dispersion state due to the hydrophobic interaction of the fibrous carbon material cannot be maintained sufficiently. Furthermore, the composition disclosed in Patent Document 2 has a problem in that it gels when mixed with a basic active material.
本発明は、上記課題に鑑みて、塗工性、接着性に優れるとともに、高い電子伝導性と繊維状炭素材料の分散性、分散安定性とを両立することができ、ゲル化を抑制して高性能の二次電池を製造可能な二次電池電極用組成物を提供することを目的とする。 In view of the above-mentioned problems, the present invention has excellent coating properties and adhesive properties, and is capable of achieving both high electronic conductivity and dispersibility and dispersion stability of fibrous carbon materials, and suppresses gelation. An object of the present invention is to provide a composition for a secondary battery electrode that can produce a high-performance secondary battery.
本開示（１）は、活物質と、疎水性溶剤と、繊維状炭素材料と、ポリビニルアセタール樹脂とを含有し、水の含有量が１０重量％以下であり、前記ポリビニルアセタール樹脂は、水酸基量が３０モル％以下である二次電池電極用組成物である。
本開示（２）は、ポリビニルアセタール樹脂は、酸性官能基を有する構成単位を有する、本開示（１）の二次電池電極用組成物である。
本開示（３）は、酸性官能基が、カルボン酸基、硫黄含有基及びリン含有基からなる群から選ばれる少なくとも１種である、本開示（１）又は（２）の二次電池電極用組成物である。
本開示（４）は、ポリビニルアセタール樹脂の全構成単位に対する酸性官能基を有する構成単位の含有量が、０．０１モル％以上１０モル％以下である、本開示（２）又は（３）の二次電池電極用組成物である。
本開示（５）は、ポリビニルアセタール樹脂の平均重合度が１５０以上１５００以下である、本開示（１）～（４）の何れかとの任意の組み合わせの二次電池電極用組成物である。
本開示（６）は、酸性官能基はブレンステッド酸性基であり、ポリビニルアセタール樹脂中のブレンステッド酸量が０．２ｍｇ／ｇ以上２５０ｍｇ／ｇ以下である、本開示（２）～（５）の何れかとの任意の組み合わせの二次電池電極用組成物である。
本開示（７）は、更に、ポリフッ化ビニリデンを含有する、本開示（１）～（６）の何れかとの任意の組み合わせの二次電池電極用組成物である。
本開示（８）は、繊維状炭素材料が、カーボンナノチューブである、本開示（１）～（７）の何れかとの任意の組み合わせの二次電池電極用組成物である。
本開示（９）は、活物質のｐＨが９以上１２以下である、本開示（１）～（８）の何れかとの任意の組み合わせの二次電池電極用組成物である。
以下に本発明を詳述する。 The present disclosure (1) contains an active material, a hydrophobic solvent, a fibrous carbon material, and a polyvinyl acetal resin, the water content is 10% by weight or less, and the polyvinyl acetal resin has a hydroxyl group content. is 30 mol% or less.
The present disclosure (2) is the composition for a secondary battery electrode according to the present disclosure (1), wherein the polyvinyl acetal resin has a structural unit having an acidic functional group.
The present disclosure (3) provides a secondary battery electrode according to the present disclosure (1) or (2), wherein the acidic functional group is at least one selected from the group consisting of a carboxylic acid group, a sulfur-containing group, and a phosphorus-containing group. It is a composition.
The present disclosure (4) is the present disclosure (2) or (3), wherein the content of the structural unit having an acidic functional group with respect to all the structural units of the polyvinyl acetal resin is 0.01 mol% or more and 10 mol% or less. This is a composition for secondary battery electrodes.
The present disclosure (5) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (4), in which the average degree of polymerization of the polyvinyl acetal resin is 150 or more and 1500 or less.
The present disclosure (6) provides the present disclosure (2) to (5), wherein the acidic functional group is a Brønsted acidic group, and the Brønsted acid amount in the polyvinyl acetal resin is 0.2 mg/g or more and 250 mg/g or less. A composition for a secondary battery electrode in any combination with any of the above.
The present disclosure (7) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (6), further containing polyvinylidene fluoride.
The present disclosure (8) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (7), in which the fibrous carbon material is a carbon nanotube.
The present disclosure (9) is a composition for a secondary battery electrode in any combination with any of the present disclosures (1) to (8), in which the pH of the active material is 9 or more and 12 or less.
The present invention will be explained in detail below.
本発明者らは、鋭意検討の結果、活物質と、繊維状炭素材料と、疎水性溶剤と、特定構造を有するポリビニルアセタール樹脂を組み合わせ、更に水の含有量を所定量以下とすることで、塗工性、接着性に優れるとともに、高い電子伝導性と繊維状炭素材料の分散性、分散安定性とを両立することができ、ゲル化を抑制して高性能の二次電池を製造できることを見出し、本発明を完成させるに至った。 As a result of extensive studies, the present inventors have found that by combining an active material, a fibrous carbon material, a hydrophobic solvent, and a polyvinyl acetal resin having a specific structure, and further reducing the water content to a predetermined amount or less, In addition to having excellent coating properties and adhesive properties, it is possible to achieve both high electronic conductivity and dispersibility and dispersion stability of the fibrous carbon material, suppressing gelation and manufacturing high-performance secondary batteries. This discovery led to the completion of the present invention.
上記二次電池電極用組成物は、活物質を含有する。
上記活物質としては、正極活物質、負極活物質が挙げられる。
上記正極活物質としては、例えば、リチウムニッケル酸化物（例えばＬｉＮｉＯ２）、リチウムコバルト酸化物（例えばＬｉＣｏＯ２）、リチウムマンガン酸化物（例えばＬｉＭｎ２Ｏ４）、リチウムニッケルマンガン酸化物（例えばＬｉＮｉ０．５Ｍｎ１．５Ｏ４）、リチウムニッケルコバルトマンガン酸化物（例えばＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２）、リチウムニッケルコバルトアルミ酸化物（例えばＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２）等の、リチウムと遷移金属元素とを構成金属元素として含む酸化物（リチウム遷移金属酸化物）の粒子が挙げられる。また、リン酸マンガンリチウム（ＬｉＭｎＰＯ４）、リン酸鉄リチウム（ＬｉＦｅＰＯ４）等のリチウムと遷移金属元素とを構成金属元素として含むリン酸塩等の粒子が挙げられる。
なお、これらは単独で用いてもよく、２種以上を併用してもよい。
上記負極活物質としては、例えば、従来からリチウム二次電池の負極活物質として用いられている材料を用いることができ、例えば黒鉛、天然黒鉛、グラファイトカーボン、アモルファスカーボン等の炭素系材料、リチウム遷移金属酸化物、リチウム遷移金属窒化物、ケイ素、酸化ケイ素等のシリコン化合物等が挙げられる。 The secondary battery electrode composition contains an active material.
Examples of the active material include a positive electrode active material and a negative electrode active material.
Examples of the positive electrode active material include lithium nickel oxide (e.g., LiNiO 2 ), lithium cobalt oxide (e.g., LiCoO 2 ), lithium manganese oxide (e.g., LiMn 2 O 4 ), and lithium nickel manganese oxide (e.g., LiNi 0 ) . .5 Mn 1.5 O 4 ), lithium nickel cobalt manganese oxide (e.g. LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), lithium nickel cobalt aluminum oxide (e.g. LiNi 0.8 Co 0.15 Examples include particles of an oxide (lithium transition metal oxide) containing lithium and a transition metal element as constituent metal elements, such as Al 0.05 O 2 ). Further, examples include particles of phosphates containing lithium and a transition metal element as constituent metal elements, such as lithium manganese phosphate (LiMnPO 4 ) and lithium iron phosphate (LiFePO 4 ).
Note that these may be used alone or in combination of two or more.
As the negative electrode active material, for example, materials conventionally used as negative electrode active materials of lithium secondary batteries can be used, such as carbon-based materials such as graphite, natural graphite, graphite carbon, amorphous carbon, lithium transition Examples include metal oxides, lithium transition metal nitrides, silicon, and silicon compounds such as silicon oxide.
上記活物質のうち、ニッケルを含むリチウム遷移金属酸化物における金属元素の組成比は、電池容量を高めることができることから、Ｎｉ原子の組成比が３０原子％以上であることが好ましく、５０原子％以上であることがより好ましく、９８原子％以下であることが好ましく、９５原子％以下であることがより好ましい。上記Ｎｉ原子の組成比は、３０～９８原子％が好ましく、５０～９５原子％がより好ましい。 Among the above active materials, the composition ratio of metal elements in the lithium transition metal oxide containing nickel is preferably such that the composition ratio of Ni atoms is 30 at% or more, and 50 at% It is more preferably at least 98 atom %, more preferably at most 95 atom %. The composition ratio of the Ni atoms is preferably 30 to 98 atomic %, more preferably 50 to 95 atomic %.
上記活物質は、電池容量を高めるために、構造中にＬｉを多く含有することが求められる。活物質毎に製造方法が異なるため、Ｌｉ水酸化物等の塩基性化合物を用いる量に応じて、得られた活物質のｐＨが変化する。上記活物質のｐＨは９以上であることが好ましく、１０以上であることがより好ましく、１２以下であることが好ましく、１１以下であることが好ましい。上記ｐＨは、９～１２が好ましく、１０～１１がより好ましい。
上記活物質のｐＨは、活物質を水中に濃度１．０重量％となるように添加した水溶液のｐＨをｐＨメーターにより測定することで求めることができる。 The above active material is required to contain a large amount of Li in its structure in order to increase battery capacity. Since the manufacturing method differs depending on the active material, the pH of the obtained active material changes depending on the amount of basic compound such as Li hydroxide used. The pH of the active material is preferably 9 or higher, more preferably 10 or higher, preferably 12 or lower, and preferably 11 or lower. The above pH is preferably 9 to 12, more preferably 10 to 11.
The pH of the active material can be determined by measuring the pH of an aqueous solution in which the active material is added to water at a concentration of 1.0% by weight using a pH meter.
上記活物質の平均粒子径は、０．１μｍ以上が好ましく、０．５μｍ以上がより好ましく、１．０μｍ以上が更に好ましく、１００μｍ以下が好ましく、５０μｍ以下がより好ましく、２０μｍ以下が更に好ましい。上記平均粒子径は、０．１～１００μｍが好ましく、０．５～５０μｍがより好ましく、１．０～２０μｍが更に好ましい。
上記平均粒子径は、例えば、走査型電子顕微鏡を用いて観察される任意の５０個の活物質の最大径を測定し、その平均値を算出することにより求めることができる。 The average particle diameter of the active material is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less. The average particle diameter is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, and even more preferably 1.0 to 20 μm.
The average particle diameter can be determined, for example, by measuring the maximum diameter of 50 arbitrary active materials observed using a scanning electron microscope and calculating the average value.
上記活物質の密度は、３．０ｇ／ｃｍ３以上が好ましく、３．５ｇ／ｃｍ３以上がより好ましく、６．０ｇ／ｃｍ３以下が好ましく、５．５ｇ／ｃｍ３以下がより好ましい。上記密度は、３．０～６．０ｇ／ｃｍ３が好ましく、３．５～５．５ｇ／ｃｍ３がより好ましい。
上記密度は、ＪＩＳ　Ｚ８８０７に準拠した方法により測定することができる。 The density of the active material is preferably 3.0 g/cm 3 or more, more preferably 3.5 g/cm 3 or more, preferably 6.0 g/cm 3 or less, and more preferably 5.5 g/cm 3 or less. The density is preferably 3.0 to 6.0 g/cm 3 , more preferably 3.5 to 5.5 g/cm 3 .
The above density can be measured by a method based on JIS Z8807.
上記活物質の比表面積は、０．１ｍ２／ｇ以上が好ましく、０．２ｍ２／ｇ以上がより好ましく、５．０ｍ２／ｇ以下が好ましく、４．５ｍ２／ｇ以下がより好ましい。上記比表面積は、０．１～５．０ｍ２／ｇが好ましく、０．２～４．５ｍ２／ｇがより好ましい。
上記比表面積は、例えば、比表面積測定装置（島津製作所社製「ＡＳＡＰ－２０００」）を用いること等により測定することができる。 The specific surface area of the active material is preferably 0.1 m 2 /g or more, more preferably 0.2 m 2 /g or more, preferably 5.0 m 2 /g or less, and more preferably 4.5 m 2 /g or less. The specific surface area is preferably 0.1 to 5.0 m 2 /g, more preferably 0.2 to 4.5 m 2 /g.
The specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
上記二次電池電極用組成物は、疎水性溶剤を含有する。
疎水性溶剤を含有することで、水分の混入を防ぎ、電池の副反応を抑制することができる。
なお、本明細書中、上記疎水性溶剤とは「オクタノール／水分配係数が０．１以上である溶剤」をいう。
上記分配係数は、ＪＩＳ　Ｚ７２６０－１１７：２００６に準拠した方法により測定することができる。 The secondary battery electrode composition contains a hydrophobic solvent.
By containing a hydrophobic solvent, it is possible to prevent moisture from entering and suppress side reactions in the battery.
In this specification, the hydrophobic solvent refers to a "solvent having an octanol/water partition coefficient of 0.1 or more."
The above distribution coefficient can be measured by a method based on JIS Z7260-117:2006.
上記疎水性溶剤としては、ケトン類、アルコール類、芳香族炭化水素類、エステル類、カーボネート類、アミド類等の有機溶剤が挙げられる。
上記ケトン類としては、アセトン、メチルエチルケトン、ジプロピルケトン、ジイソブチルケトン等が挙げられる。
上記アルコール類としては、メタノール、エタノール、イソプロパノール、ブタノール等が挙げられる。
上記芳香族炭化水素類としては、トルエン、キシレン等が挙げられる。
上記エステル類としては、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸ブチル、ブタン酸メチル、ブタン酸エチル、ブタン酸ブチル、ペンタン酸メチル、ペンタン酸エチル、ペンタン酸ブチル、ヘキサン酸メチル、ヘキサン酸エチル、ヘキサン酸ブチル、酢酸２－エチルヘキシル、酪酸ブチル、酪酸２－エチルヘキシル等が挙げられる。
また、メチルセルソルブ、エチルセルソルブ、ブチルセルソルブ、テルピネオール、ジヒドロテルピネオール、ブチルセルソルブアセテート、ブチルカルビトールアセテート、テルピネオールアセテート、ジヒドロテルピネオールアセテート等を用いることもできる。
上記カーボネート類としては、プロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート等が挙げられる。
上記アミド類としては、ジメチルアセトアミド、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ－メチルピロリドン、ジエチルホルムアミド等が挙げられる。 Examples of the hydrophobic solvent include organic solvents such as ketones, alcohols, aromatic hydrocarbons, esters, carbonates, and amides.
Examples of the ketones include acetone, methyl ethyl ketone, dipropyl ketone, diisobutyl ketone, and the like.
Examples of the alcohols include methanol, ethanol, isopropanol, butanol, and the like.
Examples of the aromatic hydrocarbons include toluene and xylene.
The above esters include methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, Examples include butyl hexanoate, 2-ethylhexyl acetate, butyl butyrate, 2-ethylhexyl butyrate, and the like.
Further, methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, dihydroterpineol acetate, etc. can also be used.
Examples of the carbonates include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and the like.
Examples of the amides include dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, diethylformamide, and the like.
上記二次電池電極用組成物における上記疎水性溶剤の含有量は、２０．０重量％以上が好ましく、２５．０重量％以上がより好ましく、５０．０重量％以下が好ましい。上記疎水性溶剤の含有量は、２０．０～５０．０重量％が好ましく、２５．０～５０．０重量％がより好ましい。 The content of the hydrophobic solvent in the secondary battery electrode composition is preferably 20.0% by weight or more, more preferably 25.0% by weight or more, and preferably 50.0% by weight or less. The content of the hydrophobic solvent is preferably 20.0 to 50.0% by weight, more preferably 25.0 to 50.0% by weight.
上記二次電池電極用組成物は、繊維状炭素材料を含有する。
繊維状炭素材料を含有することで、導電特性を向上させることができる。 The secondary battery electrode composition contains a fibrous carbon material.
By containing the fibrous carbon material, conductive properties can be improved.
上記繊維状炭素材料とは、アスペクト比（平均繊維長／平均繊維径）が３０以上である炭素材料を意味する。
上記繊維状炭素材料のアスペクト比（平均繊維長／平均繊維径）は、電子伝導性を高めることができることから、５０以上が好ましく、１００以上がより好ましく、２００以上が更に好ましく、４００以上が更により好ましく、５００，０００以下が好ましく、３００，０００以下がより好ましく、１００，０００以下が更に好ましく、５０，０００以下が更により好ましく、２０，０００以下が特に好ましい。上記アスペクト比は、３０～５００，０００が好ましく、５０～３００，０００がより好ましく、１００～１００，０００が更に好ましく、２００～５０，０００が更により好ましく、４００～２０，０００が特に好ましい。 The above-mentioned fibrous carbon material means a carbon material having an aspect ratio (average fiber length/average fiber diameter) of 30 or more.
The aspect ratio (average fiber length/average fiber diameter) of the above-mentioned fibrous carbon material is preferably 50 or more, more preferably 100 or more, still more preferably 200 or more, and even more preferably 400 or more. more preferably 500,000 or less, more preferably 300,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, particularly preferably 20,000 or less. The aspect ratio is preferably 30 to 500,000, more preferably 50 to 300,000, even more preferably 100 to 100,000, even more preferably 200 to 50,000, and particularly preferably 400 to 20,000.
上記繊維状炭素材料としては、例えば、炭素繊維、カーボンナノチューブ等が挙げられる。
上記炭素繊維としては、ＰＡＮ系炭素繊維、ピッチ系炭素繊維、セルロース系炭素繊維、気相成長系炭素繊維（ＶＧＣＦ）等が挙げられる。
上記カーボンナノチューブは、筒状の炭素材料であり、単層カーボンナノチューブ、多層カーボンナノチューブ等が挙げられる。
なかでも、結晶性が高く、導電性に優れることから、カーボンナノチューブが好ましい。 Examples of the fibrous carbon material include carbon fibers and carbon nanotubes.
Examples of the carbon fibers include PAN carbon fibers, pitch carbon fibers, cellulose carbon fibers, vapor grown carbon fibers (VGCF), and the like.
The carbon nanotube is a cylindrical carbon material, and includes single-walled carbon nanotubes, multi-walled carbon nanotubes, and the like.
Among these, carbon nanotubes are preferred because they have high crystallinity and excellent conductivity.
上記繊維状炭素材料の平均繊維径は、単位重量当たりの導電性を高める観点から、０．４０ｎｍ以上が好ましく、０．５０ｎｍ以上がより好ましく、１．００ｎｍ以上が更に好ましく、５．００ｎｍ以上が更により好ましく、２００．００ｎｍ以下が好ましく、１５０．００ｎｍ以下がより好ましく、１００．００ｎｍ以下が更に好ましい。上記平均繊維径は、０．４０～２００．００ｎｍが好ましく、０．５０～１５０．００ｎｍがより好ましく、１．００～１００．００ｎｍが更に好ましい。
上記平均繊維径は、例えば、走査型レーザー顕微鏡や透過型レーザー顕微鏡により測定することができる。 The average fiber diameter of the fibrous carbon material is preferably 0.40 nm or more, more preferably 0.50 nm or more, still more preferably 1.00 nm or more, and 5.00 nm or more from the viewpoint of increasing the conductivity per unit weight. It is even more preferably 200.00 nm or less, more preferably 150.00 nm or less, even more preferably 100.00 nm or less. The average fiber diameter is preferably 0.40 to 200.00 nm, more preferably 0.50 to 150.00 nm, and even more preferably 1.00 to 100.00 nm.
The average fiber diameter can be measured using, for example, a scanning laser microscope or a transmission laser microscope.
上記繊維状炭素材料の平均繊維長は、単位重量当たりの導電性を高める観点から、０．１０μｍ以上が好ましく、０．５０μｍ以上がより好ましく、１．００μｍ以上が更に好ましく、５．００μｍ以上が更により好ましく、５００．００μｍ以下が好ましく、２５０．００μｍ以下がより好ましく、２００．００μｍ以下が更に好ましく、１００．００μｍ以下が更により好ましい。上記平均繊維長は、０．１０～５００．００μｍが好ましく、０．５０～２５０．００μｍがより好ましく、１．００～１００．００μｍが更に好ましい。
上記平均繊維長は、例えば、走査型レーザー顕微鏡や透過型レーザー顕微鏡により測定することができる。 The average fiber length of the fibrous carbon material is preferably 0.10 μm or more, more preferably 0.50 μm or more, even more preferably 1.00 μm or more, and 5.00 μm or more from the viewpoint of increasing the conductivity per unit weight. It is even more preferably 500.00 μm or less, more preferably 250.00 μm or less, even more preferably 200.00 μm or less, and even more preferably 100.00 μm or less. The average fiber length is preferably 0.10 to 500.00 μm, more preferably 0.50 to 250.00 μm, and even more preferably 1.00 to 100.00 μm.
The average fiber length can be measured using, for example, a scanning laser microscope or a transmission laser microscope.
上記繊維状炭素材料の密度は、単位重量当たりの導電性を高める観点から、１．０ｇ／ｃｍ３以上が好ましく、１．１ｇ／ｃｍ３以上がより好ましく、１．２ｇ／ｃｍ３以上が更に好ましく、１．８ｇ／ｃｍ３以上が更により好ましく、２．５ｇ／ｃｍ３以下が好ましく、２．３ｇ／ｃｍ３以下がより好ましく、２．１ｇ／ｃｍ３以下が更に好ましい。上記密度は、１．０～２．５ｇ／ｃｍ３が好ましく、１．１～２．３ｇ／ｃｍ３がより好ましく、１．２～２．１ｇ／ｃｍ３が更に好ましく、１．８～２．１ｇ／ｃｍ３が更により好ましい。
上記密度は、ＪＩＳ　Ｚ８８０７に準拠した方法により測定することができる。 The density of the fibrous carbon material is preferably 1.0 g/cm 3 or more, more preferably 1.1 g/cm 3 or more, and still more preferably 1.2 g/cm 3 or more from the viewpoint of increasing the conductivity per unit weight. It is preferably 1.8 g/cm 3 or more, even more preferably 2.5 g/cm 3 or less, more preferably 2.3 g/cm 3 or less, and even more preferably 2.1 g/cm 3 or less. The above density is preferably 1.0 to 2.5 g/cm 3 , more preferably 1.1 to 2.3 g/cm 3 , even more preferably 1.2 to 2.1 g/cm 3 , and still more preferably 1.8 to 2 .1 g/cm 3 is even more preferred.
The above density can be measured by a method based on JIS Z8807.
上記繊維状炭素材料の比表面積は、単位重量当たりの導電性を高める観点から、８ｍ２／ｇ以上が好ましく、１３ｍ２／ｇ以上がより好ましく、１００ｍ２／ｇ以上が更に好ましく、２００ｍ２／ｇ以上が更により好ましく、３０００ｍ２／ｇ以下が好ましく、１５００ｍ２／ｇ以下がより好ましく、１２００ｍ２／ｇ以下が更に好ましく、１０００ｍ２／ｇ以下が更により好ましい。上記比表面積は、８～３０００ｍ２／ｇが好ましく、１３～１５００ｍ２／ｇがより好ましく、１００～１２００ｍ２／ｇが更に好ましく、２００～１０００ｍ２／ｇが更により好ましい。
上記比表面積は、例えば、比表面積測定装置（島津製作所社製「ＡＳＡＰ－２０００」）を用いること等により測定することができる。 The specific surface area of the fibrous carbon material is preferably 8 m 2 /g or more, more preferably 13 m 2 /g or more, even more preferably 100 m 2 /g or more, and 200 m 2 /g from the viewpoint of increasing the conductivity per unit weight. It is even more preferable that the area is at least 3000 m 2 /g, more preferably at most 1500 m 2 /g, even more preferably at most 1200 m 2 /g, and even more preferably at most 1000 m 2 /g. The specific surface area is preferably 8 to 3000 m 2 /g, more preferably 13 to 1500 m 2 /g, even more preferably 100 to 1200 m 2 /g, and even more preferably 200 to 1000 m 2 /g.
The specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
上記繊維状炭素材料におけるＧバンドとＤバンドとのピーク強度比（Ｇ／Ｄ比）は、結晶性が高いほど導電性を高めることができることから、０．１以上が好ましく、０．５以上がより好ましく、１００以下が好ましく、９５以下がより好ましい。上記Ｇ／Ｄ比は、０．１～１００が好ましく、０．５～９５がより好ましい。
上記Ｇ／Ｄ比は、例えば、ラマン分光法によりラマンスペクトルを測定することで求めることができる。
上記繊維状炭素材料をラマン分光法で測定した場合、ｓｐ２結合に対応したＧバンド（１５８０ｃｍ－１付近）及びｓｐ３結合に対応したＤバンド（１３６０ｃｍ－１付近）の２つのピークが明確に観察される。なお、炭素材料が結晶性の場合には、上記の２バンドのうち、何れかのバンドが極小化してゆく。例えば、単結晶ダイヤモンドの場合は１５８０ｃｍ－１付近のＧバンドが殆ど観察されない。一方、高純度グラファイト構造の場合は、１３６０ｃｍ－１付近のＤバンドが殆ど現れない。 The peak intensity ratio (G/D ratio) between the G band and the D band in the fibrous carbon material is preferably 0.1 or more, and 0.5 or more, since the higher the crystallinity, the higher the conductivity. More preferably, it is 100 or less, and even more preferably 95 or less. The above G/D ratio is preferably 0.1 to 100, more preferably 0.5 to 95.
The above G/D ratio can be determined, for example, by measuring a Raman spectrum using Raman spectroscopy.
When the above fibrous carbon material was measured by Raman spectroscopy, two peaks were clearly observed: the G band (near 1580 cm -1 ) corresponding to sp2 bonds and the D band (near 1360 cm -1 ) corresponding to sp3 bonds. Ru. Note that when the carbon material is crystalline, one of the two bands described above becomes minimum. For example, in the case of single crystal diamond, the G band near 1580 cm -1 is hardly observed. On the other hand, in the case of a high-purity graphite structure, the D band near 1360 cm −1 hardly appears.
上記繊維状炭素材料は、繊維が断続的に分断された非連続繊維であってもよく、分断されていない連続繊維であってもよい。
また、上記繊維の形状は、特に限定されないが、例えば、繊維状の他、織物、編物、不織布等のシート状等であってもよい。 The fibrous carbon material may be a discontinuous fiber whose fibers are intermittently divided, or a continuous fiber which is not divided.
Further, the shape of the fibers is not particularly limited, but may be, for example, in addition to fibers, sheet shapes such as woven fabrics, knitted fabrics, and nonwoven fabrics.
上記二次電池電極用組成物における上記繊維状炭素材料の含有量は、０．０５重量％以上が好ましく、０．１重量％以上がより好ましく、０．５重量％以上が更に好ましく、１．５重量％以上が更により好ましく、１５．０重量％以下が好ましく、１０．０重量％以下がより好ましい。上記含有量は、０．０５～１５．０重量％が好ましく、０．１～１０．０重量％がより好ましく、０．５～１０．０重量％が更に好ましく、１．５～１０．０重量％が更により好ましい。 The content of the fibrous carbon material in the secondary battery electrode composition is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, even more preferably 0.5% by weight or more, 1. It is even more preferably 5% by weight or more, preferably 15.0% by weight or less, and even more preferably 10.0% by weight or less. The above content is preferably 0.05 to 15.0% by weight, more preferably 0.1 to 10.0% by weight, even more preferably 0.5 to 10.0% by weight, and even more preferably 1.5 to 10.0% by weight. % by weight is even more preferred.
上記二次電池電極用組成物において、上記活物質の表面積（比表面積（ｍ２／ｇ）×含有量（ｇ））をＸ、上記繊維状炭素材料の表面積（比表面積（ｍ２／ｇ）×含有量（ｇ））をＹとしたとき、表面積比（Ｘ／Ｙ）は、導電性の観点から、０．０１以上が好ましく、６．０以下が好ましく、０．０５以上がより好ましく、４．５以下がより好ましく、３．０以下が更に好ましい。上記表面積比（Ｘ／Ｙ）は、０．０１～６．０が好ましく、０．０５～４．５がより好ましく、０．０５～３．０が更に好ましい。 In the secondary battery electrode composition, the surface area (specific surface area (m 2 /g) x content (g)) of the active material is X, and the surface area (specific surface area (m 2 /g)) of the fibrous carbon material is x content (g)) is Y, the surface area ratio (X/Y) is preferably 0.01 or more, preferably 6.0 or less, and more preferably 0.05 or more, from the viewpoint of conductivity. It is more preferably 4.5 or less, and even more preferably 3.0 or less. The surface area ratio (X/Y) is preferably 0.01 to 6.0, more preferably 0.05 to 4.5, and even more preferably 0.05 to 3.0.
上記二次電池電極用組成物は、上記繊維状炭素材料以外に粒子状炭素材料を含有していてもよい。
上記粒子状炭素材料としては、例えば、人造黒鉛、鱗片状黒鉛、薄片化黒鉛、天然黒鉛、酸処理黒鉛、膨張性黒鉛、膨張化黒鉛等の黒鉛、アセチレンブラック、ケッチェンブラック、サーマルブラック、ファーネスブラック、チャンネルブラック等のカーボンブラック等が挙げられる。 The secondary battery electrode composition may contain particulate carbon material in addition to the fibrous carbon material.
Examples of the particulate carbon materials include graphite such as artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, and expanded graphite, acetylene black, Ketjen black, thermal black, and furnace black. Examples include carbon black such as black and channel black.
上記粒子状炭素材料の平均粒子径は、１０ｎｍ以上が好ましく、１５μｍ以上がより好ましく、２０μｍ以上が更に好ましく、１００μｍ以下が好ましく、７５μｍ以下がより好ましく、５０μｍ以下が更に好ましい。上記平均粒子径は、１０～１００μｍが好ましく、１５～７５μｍがより好ましく、２０～５０μｍが更に好ましい。 The average particle diameter of the particulate carbon material is preferably 10 nm or more, more preferably 15 μm or more, even more preferably 20 μm or more, preferably 100 μm or less, more preferably 75 μm or less, and even more preferably 50 μm or less. The average particle diameter is preferably 10 to 100 μm, more preferably 15 to 75 μm, and even more preferably 20 to 50 μm.
上記粒子状炭素材料の密度は、１．０ｇ／ｃｍ３以上が好ましく、１．１ｇ／ｃｍ３以上がより好ましく、１．２ｇ／ｃｍ３以上が更に好ましく、１．８ｇ／ｃｍ３以上が更により好ましく、２．５ｇ／ｃｍ３以下が好ましく、２．３ｇ／ｃｍ３以下がより好ましく、２．１ｇ／ｃｍ３以下が更に好ましい。上記密度は、１．０～２．５ｇ／ｃｍ３が好ましく、１．１～２．３ｇ／ｃｍ３がより好ましく、１．２～２．１ｇ／ｃｍ３が更に好ましく、１．８～２．１ｇ／ｃｍ３が更により好ましい。
上記密度は、ＪＩＳ　Ｚ８８０７に準拠した方法により測定することができる。 The density of the particulate carbon material is preferably 1.0 g/cm 3 or more, more preferably 1.1 g/cm 3 or more, even more preferably 1.2 g/cm 3 or more, and even more preferably 1.8 g/cm 3 or more. It is more preferably 2.5 g/cm 3 or less, more preferably 2.3 g/cm 3 or less, even more preferably 2.1 g/cm 3 or less. The above density is preferably 1.0 to 2.5 g/cm 3 , more preferably 1.1 to 2.3 g/cm 3 , even more preferably 1.2 to 2.1 g/cm 3 , and still more preferably 1.8 to 2 .1 g/cm 3 is even more preferred.
The above density can be measured by a method based on JIS Z8807.
上記粒子状炭素材料の比表面積は、２０ｍ２／ｇ以上が好ましく、５０ｍ２／ｇ以上がより好ましく、１０００ｍ２／ｇ以下が好ましく、８００ｍ２／ｇ以下がより好ましい。上記比表面積は、２０～１０００ｍ２／ｇが好ましく、５０～８００ｍ２／ｇがより好ましい。
上記比表面積は、例えば、比表面積測定装置（島津製作所社製「ＡＳＡＰ－２０００」）を用いること等により測定することができる。 The specific surface area of the particulate carbon material is preferably 20 m 2 /g or more, more preferably 50 m 2 /g or more, preferably 1000 m 2 /g or less, and more preferably 800 m 2 /g or less. The specific surface area is preferably 20 to 1000 m 2 /g, more preferably 50 to 800 m 2 /g.
The specific surface area can be measured, for example, using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).
上記二次電池電極用組成物における上記繊維状炭素材料と上記粒子状炭素材料との合計含有量は、０．０５重量％以上が好ましく、０．１重量％以上がより好ましく、０．５重量％以上が更に好ましく、１．５重量％以上が更により好ましく、１５．０重量％以下が好ましく、１０．０重量％以下がより好ましい。上記合計含有量は、０．０５～１５．０重量％が好ましく、０．１～１０．０重量％がより好ましく、０．５～１０．０重量％が更に好ましく、１．５～１０．０重量％が更により好ましい。 The total content of the fibrous carbon material and the particulate carbon material in the secondary battery electrode composition is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and 0.5% by weight. % or more, still more preferably 1.5% by weight or more, preferably 15.0% by weight or less, and more preferably 10.0% by weight or less. The above total content is preferably 0.05 to 15.0% by weight, more preferably 0.1 to 10.0% by weight, even more preferably 0.5 to 10.0% by weight, and even more preferably 1.5 to 10.0% by weight. Even more preferred is 0% by weight.
上記二次電池電極用組成物は、ポリビニルアセタール樹脂を含有する。
上記ポリビニルアセタール樹脂は、水酸基量が３０モル％以下である。
上記ポリビニルアセタール樹脂を含有することで、活物質と併用した際の組成物のゲル化を抑制できる。また、繊維状炭素材料の分散性を充分に向上でき、高い電子伝導性と繊維状炭素材料の分散性とを両立できる。 The secondary battery electrode composition contains a polyvinyl acetal resin.
The polyvinyl acetal resin has a hydroxyl group content of 30 mol% or less.
By containing the polyvinyl acetal resin, gelation of the composition when used in combination with an active material can be suppressed. Further, the dispersibility of the fibrous carbon material can be sufficiently improved, and high electronic conductivity and dispersibility of the fibrous carbon material can be achieved at the same time.
上記ポリビニルアセタール樹脂は、通常、下記式（１－１）で表される水酸基を有する構成単位、下記式（１－２）で表されるアセチル基を有する構成単位、及び、下記式（１－３）で表されるアセタール基を有する構成単位を有する。 The above-mentioned polyvinyl acetal resin usually contains a structural unit having a hydroxyl group represented by the following formula (1-1), a constitutional unit having an acetyl group represented by the following formula (1-2), and a structural unit having a hydroxyl group represented by the following formula (1-2), and a structural unit having a hydroxyl group represented by the following formula (1-2). It has a structural unit having an acetal group represented by 3).
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
上記式（１－３）中、Ｒ１は水素原子又は炭素数１～２０のアルキル基を表す。 In the above formula (1-3), R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
上記式（１－３）中、Ｒ１が炭素数１～２０のアルキル基である場合、該アルキル基としては、例えば、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、ｉｓｏ－ブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ペンチル基、へキシル基、へプチル基、２－エチルヘキシル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、オクタデシル基等が挙げられる。なかでも、メチル基、ｎ－プロピル基が好ましい。 In the above formula (1-3), when R 1 is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group. , iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, Examples include a tetradecyl group, a pentadecyl group, an octadecyl group, and the like. Among these, methyl group and n-propyl group are preferred.
上記ポリビニルアセタール樹脂において、上記式（１－１）で表される水酸基を有する構成単位の含有量（以下、「水酸基量」ともいう）は、３０モル％以下である。
上記範囲とすることで、活物質と併用した際の組成物のゲル化を抑制できる。また、繊維状炭素材料の分散性、分散安定性を充分に向上できるとともに、高い電子伝導性を発揮できる。
上記水酸基量は、１０モル％以上が好ましく、１５モル％以上がより好ましく、３０モル％以下が好ましく、２８モル％以下がより好ましく、２５モル％以下が更に好ましい。上記水酸基量は、１０～３０モル％が好ましく、１５～２８モル％がより好ましく、１５～２５モル％が更に好ましい。
上記水酸基量は、例えば、ＮＭＲにより測定することができる。 In the polyvinyl acetal resin, the content of the structural unit having a hydroxyl group represented by the above formula (1-1) (hereinafter also referred to as "hydroxyl group amount") is 30 mol% or less.
By setting it as the said range, gelation of the composition when used together with an active material can be suppressed. Further, the dispersibility and dispersion stability of the fibrous carbon material can be sufficiently improved, and high electronic conductivity can be exhibited.
The amount of hydroxyl groups is preferably 10 mol% or more, more preferably 15 mol% or more, preferably 30 mol% or less, more preferably 28 mol% or less, and even more preferably 25 mol% or less. The amount of hydroxyl groups is preferably 10 to 30 mol%, more preferably 15 to 28 mol%, even more preferably 15 to 25 mol%.
The amount of hydroxyl groups can be measured, for example, by NMR.
上記ポリビニルアセタール樹脂において、上記式（１－２）で表されるアセチル基を有する構成単位の含有量（以下、「アセチル基量」ともいう）は、０．１モル％以上が好ましく、５モル％以上がより好ましく、３０モル％以下が好ましく、２０モル％以下がより好ましく、１５モル％以下が更に好ましい。上記アセチル基量は、０．１～３０モル％が好ましく、５～２０モル％がより好ましく、５～１５モル％が更に好ましい。
上記アセチル基量が上記範囲であると増粘を抑制して、塗工性をより高めることができる。
上記アセチル基量は、例えば、ＮＭＲにより測定することができる。 In the above polyvinyl acetal resin, the content of the structural unit having an acetyl group represented by the above formula (1-2) (hereinafter also referred to as "acetyl group amount") is preferably 0.1 mol % or more, and 5 mol %. % or more, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less. The amount of acetyl groups is preferably 0.1 to 30 mol%, more preferably 5 to 20 mol%, even more preferably 5 to 15 mol%.
When the amount of acetyl groups is within the above range, thickening can be suppressed and coating properties can be further improved.
The amount of acetyl groups can be measured, for example, by NMR.
上記ポリビニルアセタール樹脂において、上記式（１－３）で表されるアセタール基を有する構成単位の含有量（以下、「アセタール基量」ともいう）は、６０モル％以上がより好ましく、７０モル％以上が更に好ましく、８０モル％以下がより好ましく、７５モル％以下が更に好ましい。上記アセタール基量は、６０～８０モル％が好ましく、７０～７５モル％がより好ましい。
上記範囲であると、繊維状炭素材料の分散性をより向上させることができる。
なお、本明細書において、上記アセタール基量の計算方法としては、ポリビニルアセタール樹脂のアセタール基は２個の水酸基がアセタール化されて得られることから、アセタール基を有する構成単位を水酸基を有する構成単位２つ分と換算して数える方法を採用してアセタール基量を計算する。
上記アセタール基量は、例えば、ＮＭＲにより測定することができる。 In the above polyvinyl acetal resin, the content of the structural unit having an acetal group represented by the above formula (1-3) (hereinafter also referred to as "acetal group amount") is more preferably 60 mol% or more, and 70 mol%. The above is more preferable, 80 mol% or less is more preferable, and even more preferably 75 mol% or less. The amount of acetal groups is preferably 60 to 80 mol%, more preferably 70 to 75 mol%.
Within the above range, the dispersibility of the fibrous carbon material can be further improved.
In addition, in this specification, as a method for calculating the amount of acetal groups, since the acetal group of polyvinyl acetal resin is obtained by acetalizing two hydroxyl groups, the structural unit having an acetal group is replaced by the structural unit having a hydroxyl group. Calculate the amount of acetal groups by counting by converting into two parts.
The amount of acetal groups can be measured, for example, by NMR.
上記ポリビニルアセタール樹脂は、イオン性官能基を有していてもよい。
イオン性官能基としては、カルボン酸基、スルホン酸基、スルフィン酸基、スルフェン酸基等の硫黄含有基、リン酸基、ホスホン酸基等のリン含有基、アミノ基又はこれらの塩等が挙げられる。
なかでも、酸性官能基を有する構成単位を有することが好ましく、ブレンステッド酸性基を有する構成単位を有することがより好ましい。
上記ブレンステッド酸性基としては、カルボン酸基、スルホン酸基、スルフィン酸基、スルフェン酸基、リン酸基、ホスホン酸基又はこれらの塩等が挙げられる。
なかでも、繊維状炭素材料への吸着性を高めることができるという観点から、カルボン酸基、硫黄含有基及びリン含有基から選ばれる少なくとも１種が好ましく、カルボン酸基、スルホン酸基及びホスホン酸基から選ばれる少なくとも１種がより好ましい。
上記変性ポリビニルアセタール樹脂が上記酸性官能基を有する構成単位を有することにより、少ない添加量でも繊維状炭素材料の分散性を向上できる。 The polyvinyl acetal resin may have an ionic functional group.
Examples of ionic functional groups include sulfur-containing groups such as carboxylic acid groups, sulfonic acid groups, sulfinic acid groups, and sulfenic acid groups, phosphorus-containing groups such as phosphoric acid groups and phosphonic acid groups, amino groups, and salts thereof. It will be done.
Among these, it is preferable to have a structural unit having an acidic functional group, and it is more preferable to have a structural unit having a Brønsted acidic group.
Examples of the Bronsted acidic group include a carboxylic acid group, a sulfonic acid group, a sulfinic acid group, a sulfenic acid group, a phosphoric acid group, a phosphonic acid group, or salts thereof.
Among these, at least one selected from a carboxylic acid group, a sulfur-containing group, and a phosphorus-containing group is preferable from the viewpoint of being able to increase adsorption to fibrous carbon materials, and carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are preferred. At least one selected from the group is more preferred.
Since the modified polyvinyl acetal resin has the structural unit having the acidic functional group, the dispersibility of the fibrous carbon material can be improved even with a small amount added.
上記イオン性官能基を有する構成単位は、主鎖を構成する炭素に側鎖としてのイオン性官能基が直接結合した構造であってもよく、主鎖を構成する炭素にアルキレン基を介してイオン性官能基が結合した構造であってもよい。また、上記イオン性官能基を有する構成単位は、主鎖を構成する炭素にアセタール結合を介してイオン性官能基が結合した構造であってもよい。 The above structural unit having an ionic functional group may have a structure in which an ionic functional group as a side chain is directly bonded to carbon constituting the main chain, or an ionic functional group may be bonded directly to carbon constituting the main chain through an alkylene group. It may also have a structure in which a sexual functional group is bonded. Further, the above structural unit having an ionic functional group may have a structure in which the ionic functional group is bonded to carbon forming the main chain via an acetal bond.
上記イオン性官能基を有する構成単位は、主鎖を構成する同一の炭素に２つのイオン性官能基が結合した立体構造であってもよく、主鎖を構成する炭素にイオン性官能基が１つ結合した立体構造であってもよい。また、主鎖を構成する隣り合う炭素にイオン性官能基が１つずつ結合した立体構造であってもよく、主鎖を構成する隣り合う炭素のどちらか一方のみにイオン性官能基が結合した立体構造であってもよい。なかでも、主鎖を構成する同一の炭素に２つのイオン性官能基が結合した立体構造、又は、主鎖を構成する隣り合う炭素にイオン性官能基が１つずつ結合した立体構造を有することが好ましい。 The above structural unit having an ionic functional group may have a three-dimensional structure in which two ionic functional groups are bonded to the same carbon constituting the main chain, or one ionic functional group is bonded to the same carbon constituting the main chain. It may be a three-dimensional structure in which two bonds are made. Alternatively, it may be a three-dimensional structure in which one ionic functional group is bonded to each adjacent carbon that makes up the main chain, or an ionic functional group is bonded to only one of the adjacent carbons that make up the main chain. It may be a three-dimensional structure. In particular, it has a three-dimensional structure in which two ionic functional groups are bonded to the same carbon that makes up the main chain, or a three-dimensional structure in which one ionic functional group is bonded to each adjacent carbon that makes up the main chain. is preferred.
また、上記イオン性官能基を有する構成単位は、主鎖を構成する炭素にイオン性官能基が同一方向に結合したイソタクチック配置である立体構造を有するものであってもよく、主鎖を構成する炭素にイオン性官能基が交互に反対側に結合したシンジオタクチック配置である立体構造を有するものであってもよい。更に、上記イオン性官能基がランダムに結合したアタクチック配置である立体構造を有するものであってもよい。 Further, the above-mentioned structural unit having an ionic functional group may have a three-dimensional structure in which the ionic functional group is bonded in the same direction to the carbon constituting the main chain, which is an isotactic configuration. It may have a syndiotactic three-dimensional structure in which ionic functional groups are alternately bonded to carbon atoms on opposite sides. Furthermore, it may have a three-dimensional structure in which the ionic functional groups are randomly bonded in an atactic configuration.
上記イオン性官能基を有する構成単位が、主鎖を構成する炭素にアルキレン基を介してイオン性官能基が結合した構造を有する場合、上記アルキレン基としては、炭素数１～１０のアルキレン基であることが好ましく、炭素数１～５のアルキレン基であることがより好ましく、炭素数１～３のアルキレン基であることが更に好ましい。 When the above structural unit having an ionic functional group has a structure in which an ionic functional group is bonded to carbon constituting the main chain via an alkylene group, the alkylene group is an alkylene group having 1 to 10 carbon atoms. It is preferably an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms.
上記炭素数１～１０のアルキレン基としては、直鎖状アルキレン基、分岐鎖状アルキレン基、環状アルキレン基が挙げられる。
上記直鎖状アルキレン基としては、メチレン基、ビニレン基、ｎ－プロピレン基、テトラメチレン基、ペンタメチレン基、ヘキサメチレン基、オクタメチレン基、デカメチレン基等が挙げられる。
上記分岐鎖状アルキレン基としては、メチルメチレン基、メチルエチレン基、１－メチルペンチレン基、１，４－ジメチルブチレン基等が挙げられる。
上記環状アルキレン基としては、シクロプロピレン基、シクロブチレン基、シクロヘキシレン基等が挙げられる。
なかでも、直鎖状アルキレン基が好ましく、メチレン基、ビニレン基、ｎ－プロピレン基がより好ましく、メチレン基、ビニレン基が更に好ましい。 Examples of the alkylene group having 1 to 10 carbon atoms include a linear alkylene group, a branched alkylene group, and a cyclic alkylene group.
Examples of the linear alkylene group include a methylene group, a vinylene group, an n-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group.
Examples of the branched alkylene group include methylmethylene group, methylethylene group, 1-methylpentylene group, and 1,4-dimethylbutylene group.
Examples of the cyclic alkylene group include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group.
Among these, a linear alkylene group is preferred, a methylene group, a vinylene group, and an n-propylene group are more preferred, and a methylene group and a vinylene group are even more preferred.
上記イオン性官能基を有する構成単位としては、例えば、下記式（２－１）～（２－４）で表される構成単位が挙げられる。 Examples of the above-mentioned structural units having an ionic functional group include structural units represented by the following formulas (2-1) to (2-4).
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
上記式（２－１）～（２～４）中、Ｒ２、Ｒ４、Ｒ６、Ｒ８、Ｒ１０、Ｒ１２は、それぞれ独立して、単結合又は炭素数１～１０のアルキレン基を表し、Ｒ３、Ｒ５、Ｒ７、Ｒ９、Ｒ１１、Ｒ１３は、イオン性官能基を表す。
上記Ｒ２、Ｒ４、Ｒ６、Ｒ８、Ｒ１０、Ｒ１２としては、単結合、又は、炭素数１～５のアルキレン基であることが好ましく、単結合、又は、炭素数１～３のアルキレン基であることがより好ましい。 In the above formulas (2-1) to (2-4), R 2 , R 4 , R 6 , R 8 , R 10 and R 12 are each independently a single bond or an alkylene group having 1 to 10 carbon atoms. , and R 3 , R 5 , R 7 , R 9 , R 11 and R 13 each represent an ionic functional group.
The above R 2 , R 4 , R 6 , R 8 , R 10 and R 12 are preferably a single bond or an alkylene group having 1 to 5 carbon atoms, and are a single bond or an alkylene group having 1 to 3 carbon atoms. More preferably, it is an alkylene group.
上記炭素数１～１０のアルキレン基としては、直鎖状アルキレン基、分岐鎖状アルキレン基、環状アルキレン基が挙げられる。
上記直鎖状アルキレン基としては、メチレン基、エチレン基、トリメチレン基、テトラメチレン基、ペンタメチレン基、ヘキサメチレン基、オクタメチレン基、デカメチレン基等が挙げられる。
上記分岐鎖状アルキレン基としては、メチルメチレン基、メチルエチレン基、１－メチルペンチレン基、１，４－ジメチルブチレン基等が挙げられる。
上記環状アルキレン基としては、シクロプロピレン基、シクロブチレン基、シクロヘキシレン基等が挙げられる。
なかでも、直鎖状アルキレン基が好ましく、メチレン基、エチレン基、トリメチレン基がより好ましく、メチレン基、エチレン基が更に好ましい。 Examples of the alkylene group having 1 to 10 carbon atoms include a linear alkylene group, a branched alkylene group, and a cyclic alkylene group.
Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group.
Examples of the branched alkylene group include methylmethylene group, methylethylene group, 1-methylpentylene group, and 1,4-dimethylbutylene group.
Examples of the cyclic alkylene group include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group.
Among these, a linear alkylene group is preferred, a methylene group, an ethylene group, and a trimethylene group are more preferred, and a methylene group and an ethylene group are even more preferred.
上記イオン性官能基がカルボン酸基である場合、カルボン酸基を有する構成単位としては、例えば、下記式（３－１）～（３－３）で表される構成単位が挙げられる。 When the ionic functional group is a carboxylic acid group, examples of the structural unit having a carboxylic acid group include structural units represented by the following formulas (3-1) to (3-3).
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
上記式（３－１）～（３－３）中、Ｒ１４～Ｒ１８は、それぞれ独立して、単結合又は炭素数１～１０のアルキレン基、Ｘ１～Ｘ５は、それぞれ独立して、水素原子、金属原子又はメチル基を表す。
上記炭素数１～１０のアルキレン基としては、上記式（２－１）中、Ｒ２と同様のものが挙げられる。
上記金属原子としては、ナトリウム原子、リチウム原子、カリウム原子等が挙げられる。なかでも、ナトリウム原子が好ましい。 In the above formulas (3-1) to (3-3), R 14 to R 18 are each independently a single bond or an alkylene group having 1 to 10 carbon atoms, and X 1 to X 5 are each independently , represents a hydrogen atom, a metal atom or a methyl group.
Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
Examples of the metal atoms include sodium atoms, lithium atoms, potassium atoms, and the like. Among these, a sodium atom is preferred.
上記スルホン酸基を有する構成単位としては、下記式（４）で表される構成単位が挙げられる。 Examples of the structural unit having a sulfonic acid group include a structural unit represented by the following formula (4).
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
上記式（４）中、Ｒ１９は、単結合又は炭素数１～１０のアルキレン基、Ｘ６は水素原子、金属原子又はメチル基を表す。
上記炭素数１～１０のアルキレン基としては、上記式（２－１）中、Ｒ２と同様のものが挙げられる。
上記金属原子としては、上記式（３－１）中、Ｘ１と同様のものが挙げられる。 In the above formula (4), R 19 represents a single bond or an alkylene group having 1 to 10 carbon atoms, and X 6 represents a hydrogen atom, a metal atom, or a methyl group.
Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
Examples of the metal atom include those similar to X 1 in the above formula (3-1).
上記ホスホン酸基を有する構成単位としては、下記式（５）で表される構成単位が挙げられる。 Examples of the above-mentioned structural unit having a phosphonic acid group include a structural unit represented by the following formula (5).
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000005
上記式（５）中、Ｒ２０は、単結合又は炭素数１～１０のアルキレン基、Ｘ７及びＸ８はそれぞれ独立して、水素原子、金属原子又はメチル基を表す。
上記炭素数１～１０のアルキレン基としては、上記式（２－１）中、Ｒ２と同様のものが挙げられる。
上記金属原子としては、上記式（３－１）中、Ｘ１と同様のものが挙げられる。 In the above formula (5), R 20 is a single bond or an alkylene group having 1 to 10 carbon atoms, and X 7 and X 8 each independently represent a hydrogen atom, a metal atom, or a methyl group.
Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
Examples of the metal atom include those similar to X 1 in the above formula (3-1).
上記アミノ基を有する構成単位としては、下記式（６）で表される構成単位が挙げられる。 Examples of the above-mentioned structural unit having an amino group include a structural unit represented by the following formula (6).
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000006
上記式（６）中、Ｒ２１は、単結合又は炭素数１～１０のアルキレン基を表す。
上記炭素数１～１０のアルキレン基としては、上記式（２－１）中、Ｒ２と同様のものが挙げられる。 In the above formula (6), R 21 represents a single bond or an alkylene group having 1 to 10 carbon atoms.
Examples of the above alkylene group having 1 to 10 carbon atoms include those similar to R 2 in the above formula (2-1).
上記ポリビニルアセタール樹脂の全構成単位に対する上記イオン性官能基を有する構成単位の含有量は、繊維状炭素材料の分散性の観点から、０．０１モル％以上が好ましく、０．１モル％以上がより好ましく、０．５モル％以上が更に好ましく、２０モル％以下が好ましく、１５モル％以下がより好ましく、１０モル％以下が更に好ましく、５モル％以下が更により好ましい。上記イオン性官能基を有する構成単位の含有量は、０．０１～２０モル％が好ましく、０．１～１５モル％がより好ましく、０．５～１０モル％が更に好ましく、０．５～５モル％が更により好ましい。
上記イオン性官能基を有する構成単位の含有量は、例えば、ＮＭＲにより測定することができる。 The content of the structural unit having an ionic functional group with respect to all the structural units of the polyvinyl acetal resin is preferably 0.01 mol% or more, and 0.1 mol% or more from the viewpoint of dispersibility of the fibrous carbon material. It is more preferably 0.5 mol% or more, still more preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, and even more preferably 5 mol% or less. The content of the structural unit having an ionic functional group is preferably 0.01 to 20 mol%, more preferably 0.1 to 15 mol%, even more preferably 0.5 to 10 mol%, and even more preferably 0.5 to 20 mol%. Even more preferred is 5 mol%.
The content of the structural unit having an ionic functional group can be measured, for example, by NMR.
上記ポリビニルアセタール樹脂中のブレンステッド酸量は、繊維状炭素材料の分散性の観点から、０．２ｍｇ／ｇ以上が好ましく、１０ｍｇ／ｇ以上がより好ましく、３５０ｍｇ／ｇ以下が好ましく、２５０ｍｇ／ｇ以下がより好ましく、１５０ｍｇ／ｇ以下が更に好ましい。上記ブレンステッド酸量は、０．２～３５０ｍｇ／ｇが好ましく、１０～２５０ｍｇ／ｇがより好ましく、１０～１５０ｍｇ／ｇが更に好ましい。
上記ブレンステッド酸量とは、ポリビニルアセタール樹脂中に含まれるブレンステッド酸を中和するのに要する水酸化カリウムの量を意味する。
上記ブレンステッド酸量は、例えば、ＪＩＳ　Ｋ００７０－１９９２に準拠した方法による酸塩基滴定により測定することができる。 From the viewpoint of dispersibility of the fibrous carbon material, the amount of Bronsted acid in the polyvinyl acetal resin is preferably 0.2 mg/g or more, more preferably 10 mg/g or more, and preferably 350 mg/g or less, and 250 mg/g. The following is more preferable, and 150 mg/g or less is still more preferable. The amount of Brønsted acid is preferably 0.2 to 350 mg/g, more preferably 10 to 250 mg/g, even more preferably 10 to 150 mg/g.
The above-mentioned amount of Bronsted acid means the amount of potassium hydroxide required to neutralize the Bronsted acid contained in the polyvinyl acetal resin.
The amount of Brønsted acid can be measured, for example, by acid-base titration according to a method based on JIS K0070-1992.
また、上記ポリビニルアセタール樹脂が、イオン性官能基を有する構成単位として、上記式（２－４）で表されるイオン性官能基を有するアセタール基を有する場合、上記ポリビニルアセタール樹脂における上記式（２－４）で表されるイオン性官能基を有する構成単位の含有量と上記式（１－３）で表されるアセタール基を有する構成単位の含有量との合計（以下、「全アセタール基量」ともいう）は、４５モル％以上が好ましく、６０モル％以上がより好ましく、８５モル％以下が好ましく、７５モル％以下がより好ましい。上記全アセタール基量は、４５～８５モル％が好ましく、６０～７５モル％がより好ましい。 Further, when the polyvinyl acetal resin has an acetal group having an ionic functional group represented by the above formula (2-4) as a structural unit having an ionic functional group, the polyvinyl acetal resin has an acetal group having an ionic functional group represented by the above formula (2-4). -4) and the content of structural units having an acetal group represented by the above formula (1-3) (hereinafter referred to as "total acetal group content"). ) is preferably 45 mol% or more, more preferably 60 mol% or more, preferably 85 mol% or less, and more preferably 75 mol% or less. The total amount of acetal groups is preferably 45 to 85 mol%, more preferably 60 to 75 mol%.
上記ポリビニルアセタール樹脂の平均重合度は、繊維状炭素材料の分散性を充分に向上できるとともに、高い電子伝導性を発揮できることから、１５０以上が好ましく、２００以上がより好ましく、３００以上が更に好ましく、１５００以下が好ましく、１２００以下がより好ましく、９００以下が更に好ましい。上記平均重合度は、１５０～１５００が好ましく、２００～１２００がより好ましく、３００～９００が更に好ましい。
上記平均重合度は、例えば、ゲル浸透クロマトグラフィー（ＧＰＣ）により測定することができる。 The average degree of polymerization of the polyvinyl acetal resin is preferably 150 or more, more preferably 200 or more, even more preferably 300 or more, since it can sufficiently improve the dispersibility of the fibrous carbon material and exhibit high electronic conductivity. It is preferably 1,500 or less, more preferably 1,200 or less, and even more preferably 900 or less. The average degree of polymerization is preferably from 150 to 1,500, more preferably from 200 to 1,200, even more preferably from 300 to 900.
The average degree of polymerization can be measured, for example, by gel permeation chromatography (GPC).
上記二次電池電極用組成物における上記ポリビニルアセタール樹脂の含有量は、０．１重量％以上が好ましく、０．５重量％以上がより好ましく、３０．０重量％以下が好ましく、１５．０重量％以下がより好ましい。上記含有量は、０．１～３０．０重量％が好ましく、０．５～１５．０重量％がより好ましい。 The content of the polyvinyl acetal resin in the secondary battery electrode composition is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, preferably 30.0% by weight or less, and 15.0% by weight. % or less is more preferable. The above content is preferably 0.1 to 30.0% by weight, more preferably 0.5 to 15.0% by weight.
上記二次電池電極用組成物における上記ポリビニルアセタール樹脂の含有量と上記繊維状炭素材料の含有量との比（ポリビニルアセタール樹脂の含有量／繊維状炭素材料の含有量）は、０．１以上が好ましく、０．２以上がより好ましく、２以下が好ましく、１．５以下がより好ましい。上記比は、０．１～２が好ましく、０．２～１．５がより好ましい。
上記範囲であると、繊維状炭素材料の分散性が良好となり、導電パスを形成しやすくなる。その結果、電子伝導性がより一層優れるものとなる。 The ratio of the content of the polyvinyl acetal resin to the content of the fibrous carbon material in the composition for secondary battery electrodes (content of polyvinyl acetal resin/content of fibrous carbon material) is 0.1 or more. is preferable, 0.2 or more is more preferable, 2 or less is preferable, and 1.5 or less is more preferable. The above ratio is preferably 0.1 to 2, more preferably 0.2 to 1.5.
Within the above range, the fibrous carbon material has good dispersibility, making it easier to form conductive paths. As a result, electronic conductivity becomes even more excellent.
上記二次電池電極用組成物において、上記ポリビニルアセタール樹脂の含有量（ｇ）と上記繊維状炭素材料の表面積（比表面積（ｍ２／ｇ）×含有量（ｇ））との比（ポリビニルアセタール樹脂の含有量／繊維状炭素材料の表面積）は、０．０００１以上が好ましく、０．０４以下が好ましく、０．００１以上がより好ましく、０．０３５以下がより好ましく、０．００５以上が更に好ましく、０．０３以下が更に好ましい。上記比は、０．０００１～０．０４が好ましく、０．００１～０．０３５がより好ましく、０．００５～０．０３が更に好ましい。 In the secondary battery electrode composition, the ratio of the content (g) of the polyvinyl acetal resin to the surface area (specific surface area (m 2 /g) x content (g)) of the fibrous carbon material Resin content/surface area of fibrous carbon material) is preferably 0.0001 or more, preferably 0.04 or less, more preferably 0.001 or more, more preferably 0.035 or less, and still more preferably 0.005 or more. It is preferably 0.03 or less, and more preferably 0.03 or less. The above ratio is preferably 0.0001 to 0.04, more preferably 0.001 to 0.035, and even more preferably 0.005 to 0.03.
上記ポリビニルアセタール樹脂を作製する方法としては、例えば、酢酸ビニル等の単量体を重合して得られたポリ酢酸ビニル樹脂を酸またはアルカリを添加してケン化し、精製すること等によりＮａイオン含有量を調整したポリビニルアルコール系樹脂をアセタール化する方法等が挙げられる。 As a method for producing the polyvinyl acetal resin, for example, a polyvinyl acetate resin obtained by polymerizing a monomer such as vinyl acetate is saponified by adding an acid or an alkali, and purified to contain Na ions. Examples include a method of acetalizing polyvinyl alcohol resin in an adjusted amount.
上記ポリビニルアルコール系樹脂としては、例えば、ポリ酢酸ビニル系樹脂をアルカリ、酸、アンモニア水等によりケン化することにより製造された樹脂等の従来公知のポリビニルアルコール系樹脂を用いることができる。
上記ポリビニルアルコール系樹脂は、完全ケン化されていてもよいが、少なくとも主鎖の１カ所にメソ、ラセモ位に対して２連の水酸基を有するユニットが最低１ユニットあれば完全ケン化されている必要はなく、部分ケン化ポリビニルアルコール系樹脂であってもよい。また、上記ポリビニルアルコール系樹脂としては、エチレン－ビニルアルコール共重合体樹脂、部分ケン化エチレン－ビニルアルコール共重合体樹脂等、ビニルアルコールと共重合可能なモノマーとビニルアルコールとの共重合体も用いることができる。
上記ポリ酢酸ビニル系樹脂は、例えば、エチレン－酢酸ビニル共重合体等が挙げられる。 As the polyvinyl alcohol resin, conventionally known polyvinyl alcohol resins such as resins produced by saponifying polyvinyl acetate resin with alkali, acid, aqueous ammonia, etc. can be used.
The above-mentioned polyvinyl alcohol resin may be completely saponified, but it is completely saponified if there is at least one unit having a double hydroxyl group in the meso or racemo position at least at one location in the main chain. It is not necessary, and a partially saponified polyvinyl alcohol resin may be used. Furthermore, as the polyvinyl alcohol resin, a copolymer of vinyl alcohol and a monomer that can be copolymerized with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin, may also be used. be able to.
Examples of the polyvinyl acetate resin include ethylene-vinyl acetate copolymer.
上記イオン性官能基を有する構成単位を有するポリビニルアセタール樹脂を作製する方法としては、例えば、イオン性官能基を有する単量体と酢酸ビニルとを共重合させることによって得られるポリ酢酸ビニルをケン化し得られたポリビニルアルコールを、従来公知の方法によりアセタール化する方法が挙げられる。また、未変性のポリビニルアルコールを、従来公知の方法によりアセタール化して得られたポリビニルアセタール樹脂を後変性させることでイオン性官能基を導入したものであってもよい。
上記カルボン酸基を有する単量体として、例えば、クリル酸、クロトン酸、メタクリル酸、オレイン酸等のモノカルボン酸、メチレンマロン酸、イタコン酸、２－メチレングルタル酸、２－メチレンアジピン酸、２－メチレンセバシン酸等のジカルボン酸、無水マレイン酸等やその金属塩が挙げられる。
上記スルホン酸基を有する単量体としては、例えば、ビニルスルホン酸、ビニルスルホン酸ナトリウム、ベータスチレンスルホン酸等が挙げられる。
上記ホスホン酸基を有する単量体としては、例えば、ビニルリン酸、ビニルリン酸ナトリウム、ジメチルビニルホスホナート、ジエチルビニルホスホナート等が挙げられる。
上記アミノ基を有する単量体としては、例えば、ビニルアミン、アリルアミン等が挙げられる。 As a method for producing a polyvinyl acetal resin having a structural unit having an ionic functional group, for example, polyvinyl acetate obtained by copolymerizing a monomer having an ionic functional group and vinyl acetate is saponified. Examples include a method of acetalizing the obtained polyvinyl alcohol by a conventionally known method. Alternatively, an ionic functional group may be introduced by post-modifying a polyvinyl acetal resin obtained by acetalizing unmodified polyvinyl alcohol by a conventionally known method.
Examples of the monomer having a carboxylic acid group include monocarboxylic acids such as acrylic acid, crotonic acid, methacrylic acid, and oleic acid, methylene malonic acid, itaconic acid, 2-methylene glutaric acid, 2-methylene adipic acid, -Dicarboxylic acids such as methylene sebacic acid, maleic anhydride, and metal salts thereof.
Examples of the monomer having a sulfonic acid group include vinylsulfonic acid, sodium vinylsulfonate, beta-styrenesulfonic acid, and the like.
Examples of the monomer having a phosphonic acid group include vinyl phosphoric acid, sodium vinyl phosphate, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and the like.
Examples of the above-mentioned monomer having an amino group include vinylamine, allylamine, and the like.
上記ポリビニルアルコール系樹脂は、残存アセチル基量が０．１モル％以上２０．０モル％以下であることが好ましく、５．０モル％以上１５．０モル％以下であることがより好ましい。
上記ポリビニルアルコール系樹脂を用いることにより、繊維状炭素材料の分散性をより高めることができる。 The amount of residual acetyl groups in the polyvinyl alcohol resin is preferably 0.1 mol% or more and 20.0 mol% or less, more preferably 5.0 mol% or more and 15.0 mol% or less.
By using the above polyvinyl alcohol resin, the dispersibility of the fibrous carbon material can be further improved.
上記アセタール化は、公知の方法を用いることができ、水系溶剤中、水と水との相溶性のある有機溶剤との混合溶剤中、あるいは有機溶剤中で行うことが好ましい。
上記水との相溶性のある有機溶剤としては、例えば、アルコール系有機溶剤を用いることができる。
上記有機溶剤としては、例えば、アルコール系有機溶剤、芳香族有機溶剤、脂肪族エステル系溶剤、ケトン系溶剤、低級パラフィン系溶剤、エーテル系溶剤、アミド系溶剤、アミン系溶剤等が挙げられる。
上記アルコール系有機溶剤としては、例えば、メタノール、エタノール、ｎ－プロパノール、イソプロパノール、ｎ－ブタノール、ｔｅｒｔ－ブタノール等が挙げられる。
上記芳香族有機溶剤としては、例えば、キシレン、トルエン、エチルベンゼン、安息香酸メチル等が挙げられる。
上記脂肪族エステル系溶剤としては、例えば、酢酸メチル、酢酸エチル、酢酸ブチル、プロピオン酸メチル、プロピオン酸エチル、酪酸メチル、酪酸エチル、アセト酢酸メチル、アセト酢酸エチル等が挙げられる。
上記ケトン系溶剤としては、例えば、アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン、メチルシクロヘキサノン、ベンゾフェノン、アセトフェノン等が挙げられる。
上記低級パラフィン系溶剤としては、ヘキサン、ペンタン、オクタン、シクロヘキサン、デカン等が挙げられる。
上記エーテル系溶剤としては、ジエチルエーテル、テトラヒドロフラン、エチレングリコールジメチルエーテル、エチレングリコールジエチルエーテル、プロピレングリコールジエチルエーテル等が挙げられる。
上記アミド系溶剤としては、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルテセトアミド、Ｎ－メチルピロリドン、アセトアニリド等が挙げられる。
上記アミン系溶剤としては、アンモニア、トリメチルアミン、トリエチルアミン、ｎ－ブチルアミン、ジｎ－ブチルアミン、トリｎ－ブチルアミン、アニリン、Ｎ－メチルアニリン、Ｎ，Ｎ－ジメチルアニリン、ピリジン等が挙げられる。
これらは、単体で用いることもできるし、２種以上の溶剤を混合で用いることもできる。これらのなかでも、樹脂に対する溶解性及び精製時の簡易性の観点から、エタノール、ｎ－プロパノール、イソプロパノール、テトラヒドロフランが特に好ましい。 The acetalization can be carried out using a known method, and is preferably carried out in an aqueous solvent, in a mixed solvent of water and an organic solvent with which water is compatible, or in an organic solvent.
As the organic solvent that is compatible with water, for example, an alcohol-based organic solvent can be used.
Examples of the organic solvent include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffinic solvents, ether-based solvents, amide-based solvents, amine-based solvents, and the like.
Examples of the alcoholic organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol.
Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, methyl benzoate, and the like.
Examples of the aliphatic ester solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate.
Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone.
Examples of the lower paraffinic solvent include hexane, pentane, octane, cyclohexane, decane, and the like.
Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether, and the like.
Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethyltesetamide, N-methylpyrrolidone, acetanilide, and the like.
Examples of the amine solvent include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine.
These solvents can be used alone or in a mixture of two or more. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoint of solubility in the resin and ease of purification.
上記アセタール化は、酸触媒の存在下において行うことが好ましい。
上記酸触媒は特に限定されず、硫酸、塩酸、硝酸、リン酸等の鉱酸や、ギ酸、酢酸、プロピオン酸等のカルボン酸や、メタンスルホン酸、エタンスルホン酸、ベンゼンスルホン酸、パラトルエンスルホン酸等のスルホン酸が挙げられる。これらの酸触媒は、単独で用いられてもよく、２種以上の化合物を併用してもよい。なかでも、塩酸、硝酸、硫酸が好ましく、塩酸が特に好ましい。 The acetalization is preferably performed in the presence of an acid catalyst.
The above acid catalysts are not particularly limited, and include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, carboxylic acids such as formic acid, acetic acid, and propionic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and paratoluenesulfonic acid. Examples include sulfonic acids such as acids. These acid catalysts may be used alone or in combination of two or more kinds of compounds. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.
上記アセタール化に用いられるアルデヒドとしては、炭素数１～１０の鎖状脂肪族基、環状脂肪族基又は芳香族基を有するアルデヒドが挙げられる。これらのアルデヒドとしては、従来公知のアルデヒドを使用できる。上記アセタール化反応に用いられるアルデヒドは、特に限定されるものではなく、例えば、脂肪族アルデヒド、芳香族アルデヒド等が挙げられる。
上記脂肪族アルデヒドとしては、ホルムアルデヒド、プロピオンアルデヒド、ｎ－ブチルアルデヒド、イソブチルアルデヒド、ｎ－バレルアルデヒド、ｎ－ヘキシルアルデヒド、２－エチルブチルアルデヒド、２－エチルヘキシルアルデヒド、ｎ－ヘプチルアルデヒド、ｎ－オクチルアルデヒドオクテルアルデヒド、ｎ－ノニルアルデヒド、ｎ－デシルアルデヒド、アミルアルデヒド等が挙げられる。
上記芳香族アルデヒドとしては、ベンズアルデヒド、シンナムアルデヒド、２－メチルベンズアルデヒド、３－メチルベンズアルデヒド、４－メチルベンズアルデヒド、ｐ－ヒドロキシベンズアルデヒド、ｍ－ヒドロキシベンズアルデヒド、フェニルブチルアルデヒド、β－フェニルプロピオンアルデヒド等の芳香族アルデヒド等が挙げられる。
また、パラアルデヒド、メタアルデヒド等の環状の多量体等を用いることができる。
これらのアルデヒドは、１種を単独で使用してもよく、２種以上を併用してもよい。アルデヒドとしては、なかでも、アセタール化反応性に優れ、生成する樹脂に充分な内部可塑効果をもたらし、結果として良好な柔軟性を付与することができるホルムアルデヒド、ブチルアルデヒド、ブチルアルデヒド、２－エチルヘキシルアルデヒド、ｎ－ノニルアルデヒド、パラアルデヒドが好ましい。また、耐衝撃性及び金属との接着性に特に優れる接着剤組成物を得られることから、ホルムアルデヒド、ｎ－ブチルアルデヒド、パラアルデヒドがより好ましい。 Examples of the aldehyde used in the acetalization include aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. As these aldehydes, conventionally known aldehydes can be used. The aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include aliphatic aldehydes, aromatic aldehydes, and the like.
Examples of the aliphatic aldehydes include formaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, and n-octylaldehyde. Examples include octeraldehyde, n-nonylaldehyde, n-decylaldehyde, amylaldehyde and the like.
Examples of the aromatic aldehyde include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylbutyraldehyde, and β-phenylpropionaldehyde. Examples include aldehydes.
Further, cyclic multimers such as paraldehyde and metaldehyde can be used.
These aldehydes may be used alone or in combination of two or more. Examples of aldehydes include formaldehyde, butyraldehyde, butyraldehyde, and 2-ethylhexylaldehyde, which have excellent acetalization reactivity and can provide a sufficient internal plasticizing effect to the resulting resin, resulting in good flexibility. , n-nonylaldehyde and paraldehyde are preferred. Furthermore, formaldehyde, n-butyraldehyde, and paraldehyde are more preferred because they yield an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.
上記アルデヒドの添加量としては、目的とするポリビニルアセタール樹脂のアセタール基量にあわせて適宜設定することができる。特に、ポリビニルアルコール１００モル％に対して、１０～６５モル％、好ましくは１５～６０モル％とすると、アセタール化反応が効率よく行われ、未反応のアルデヒドも除去しやすいため好ましい。 The amount of the aldehyde added can be appropriately set depending on the amount of acetal groups in the target polyvinyl acetal resin. In particular, it is preferable to use 10 to 65 mol %, preferably 15 to 60 mol %, based on 100 mol % of polyvinyl alcohol, because the acetalization reaction can be carried out efficiently and unreacted aldehyde can be easily removed.
上記二次電池電極用組成物は、水の含有量が１０重量％以下である。
上記範囲とすることで、繊維状炭素材料の分散安定性を向上できる。
上記水の含有量は、５重量％以下が好ましく、１重量％以下がより好ましい。また、下限は特に限定されず、例えば０重量％以上である。上記水の含有量は、０～１０重量％が好ましく、０～５重量％がより好ましく、０～１重量％が更に好ましい。
上記水の含有量は、例えば、赤外水分計を用いて測定できる。 The secondary battery electrode composition has a water content of 10% by weight or less.
By setting it as the said range, the dispersion stability of a fibrous carbon material can be improved.
The water content is preferably 5% by weight or less, more preferably 1% by weight or less. Further, the lower limit is not particularly limited, and is, for example, 0% by weight or more. The water content is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and even more preferably 0 to 1% by weight.
The water content can be measured using, for example, an infrared moisture meter.
上記二次電池電極用組成物は、更にバインダー樹脂を含有することが好ましい。
上記バインダー樹脂としては、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリフッ化ビニリデン－ヘキサフルオロプロピレン共重合体（ＰＶＤＦ－ＨＦＰ）、ポリテトラフルオロエチレン（ＰＴＦＥ）等のフッ素含有樹脂、ポリメチルアクリレート（ＰＭＡ）、ポリメチルメタクリレート（ＰＭＭＡ）等のアクリル樹脂、ポリ酢酸ビニル、ポリイミド（ＰＩ）、ポリアミド（ＰＡ）、ポリ塩化ビニル（ＰＶＣ）、ポリエーテルニトリル（ＰＥＮ）、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリアクリロニトリル（ＰＡＮ）、アクリロニトリル・ブタジエンゴム、スチレンブタジエンゴム、ポリ（メタ）アクリル酸、カルボキシメチルセルロース、ヒドロキシエチルセルロース、ポリビニルアルコール等が挙げられる。なかでも、電気特性に優れるという観点から、ポリフッ化ビニリデンを含有することが好ましい。 It is preferable that the secondary battery electrode composition further contains a binder resin.
Examples of the binder resin include fluorine-containing resins such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), and polymethyl acrylate (PMA). , acrylic resins such as polymethyl methacrylate (PMMA), polyvinyl acetate, polyimide (PI), polyamide (PA), polyvinyl chloride (PVC), polyethernitrile (PEN), polyethylene (PE), polypropylene (PP), Examples include polyacrylonitrile (PAN), acrylonitrile-butadiene rubber, styrene-butadiene rubber, poly(meth)acrylic acid, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and the like. Among these, it is preferable to contain polyvinylidene fluoride from the viewpoint of excellent electrical properties.
上記二次電池電極用組成物における上記ポリビニルアセタール樹脂の含有量と上記バインダー樹脂の含有量との比（ポリビニルアセタール樹脂の含有量／バインダー樹脂の含有量）は、電気特性を向上し、分散性・密着性を高める観点から、０．１以上が好ましく、０．２以上がより好ましく、２．０以下が好ましく、１．０以下がより好ましい。上記比は、０．１～２．０が好ましく、０．２～１．０がより好ましい。 The ratio of the content of the polyvinyl acetal resin to the content of the binder resin in the composition for secondary battery electrodes (content of polyvinyl acetal resin/content of binder resin) improves electrical properties and improves dispersibility. - From the viewpoint of improving adhesion, it is preferably 0.1 or more, more preferably 0.2 or more, preferably 2.0 or less, and more preferably 1.0 or less. The above ratio is preferably 0.1 to 2.0, more preferably 0.2 to 1.0.
上記二次電池電極用組成物は、本発明の効果を損なわない範囲で、更に、導電助剤、難燃助剤、消泡剤、レベリング剤、密着性付与剤等の添加剤を含んでいてもよい。 The secondary battery electrode composition may further contain additives such as a conductive additive, a flame retardant additive, an antifoaming agent, a leveling agent, and an adhesion imparting agent, within a range that does not impair the effects of the present invention. Good too.
上記二次電池電極用組成物を作製する方法としては特に限定されず、例えば、原料ポリビニルアルコールをアセタール化したポリビニルアセタール樹脂と、活物質と、繊維状炭素材料とを疎水性溶剤に添加して混合する方法等が挙げられる。
上記混合する方法としては、例えば、ボールミル、ブレンダーミル、３本ロール等の各種混合機を用いる方法等が挙げられる。 The method for producing the secondary battery electrode composition is not particularly limited, and for example, a polyvinyl acetal resin obtained by acetalizing raw material polyvinyl alcohol, an active material, and a fibrous carbon material are added to a hydrophobic solvent. Examples include a method of mixing.
Examples of the above-mentioned mixing method include methods using various mixers such as a ball mill, a blender mill, and a three-roll mixer.
上記二次電池電極用組成物は、例えば、導電性基体上に塗布し、乾燥する工程を経ることで、リチウム二次電池電極が形成できる。
上記塗布方法としては、例えば、押出しコーター、リバースローラー、ドクターブレード、アプリケーターなどをはじめ、各種の塗布方法を採用することができる。 A lithium secondary battery electrode can be formed by applying the composition for a secondary battery electrode onto a conductive substrate and drying the composition, for example.
As the above-mentioned coating method, various coating methods can be employed, including, for example, an extrusion coater, a reverse roller, a doctor blade, an applicator, and the like.
本発明によれば、塗工性、接着性に優れるとともに、高い電子伝導性と繊維状炭素材料の分散性、分散安定性とを両立することができ、ゲル化を抑制して高性能の二次電池を製造可能な二次電池電極用組成物を提供できる。 According to the present invention, it is possible to achieve both excellent coating properties and adhesive properties, high electronic conductivity, dispersibility and dispersion stability of the fibrous carbon material, suppress gelation, and achieve high performance. A composition for a secondary battery electrode that can be used to manufacture a secondary battery can be provided.
以下に実施例を掲げて本発明を更に詳しく説明するが、本発明はこれら実施例のみに限定されるものではない。 The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.
（製造例１）
カルボン酸変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基１．０モル％、式（３－１）で表される構成単位（Ｒ１４がメチレン基、Ｘ１が水素原子）の含有量１．０モル％）５００ｇを純水２５００ｇに加え、９０℃で２時間攪拌し溶解させた。この溶液を４０℃に冷却し、これに濃度３５重量％の塩酸１０ｇを添加した後、液温を５℃に下げてｎ－ブチルアルデヒド８５ｇを添加し、この温度を保持してアセタール化反応を行い、反応生成物を析出させた。液温を６５℃として、５時間保持して反応を完了させ、水酸化ナトリウム水溶液４０ｇを加えて中和反応を行った。その後、純水５０００ｇを加え、攪拌した後、デカンテーションにより水５０００ｇを除去した。更に、純水５０００ｇを加え、攪拌した後、デカンテーションにより水を除去する工程を合計３回繰り返した。その後イオン交換水を用いて樹脂の固形分率を２０重量％に調整して、ポリビニルアセタール樹脂（ＰＶＢ－Ａ１）を得た。
得られたポリビニルアセタール樹脂について、１Ｈ－ＮＭＲ（核磁気共鳴スペクトル）を用いてアセタール基量、水酸基量、アセチル基量を測定したところ、結果は表１の通りであった。１Ｈ－ＮＭＲ測定は、溶剤として重ＤＭＳＯを用いた。
また、ＪＩＳ　Ｋ００７０－１９９２に準拠して酸塩基滴定法によりブレンステッド酸量を測定した。具体的には、以下の方法により測定した。まず、本試験として、得られたポリビニルアセタール樹脂を試料として、試料約１ｇを三角フラスコに精秤し、エタノール／水（体積比９：１）混合溶剤４０ｍｌを加えて振とう溶解する。溶解後、フェノールフタレイン１重量％溶液を指示薬として０．０２モル／Ｌエタノール性水酸化カリウム溶液を用い、マイクロビュレットで微紅色が３０秒以上保つ点まで滴定する。別に空試験を行い、次式によりブレンステッド酸量を測定した。結果は１９．２ｍｇ／ｇであった。
ブレンステッド酸量＝［（Ａ－Ｂ）×ｆ×（１／５０）×（Ｃ／１０００）］×１００／Ｄ
Ａ：本試験におけるエタノール性水酸化カリウム溶液の滴下量（ｍＬ）
Ｂ：空試験におけるエタノール性水酸化カリウム溶液の滴下量（ｍＬ）
Ｃ：酸性官能基を有する構成単位の分子量
Ｄ：試料の量（ｇ）
ｆ：０．０２モル／Ｌエタノール性水酸化カリウム溶液の力価 (Manufacturing example 1)
Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 1.0 mol%, content of structural units represented by formula (3-1) (R 14 is a methylene group, X 1 is a hydrogen atom) content 1 0 mol %) was added to 2500 g of pure water and stirred at 90° C. for 2 hours to dissolve. This solution was cooled to 40°C, 10g of hydrochloric acid with a concentration of 35% by weight was added thereto, the temperature was lowered to 5°C, 85g of n-butyraldehyde was added, and this temperature was maintained to carry out the acetalization reaction. The reaction product was precipitated. The reaction was completed by keeping the liquid temperature at 65° C. for 5 hours, and 40 g of an aqueous sodium hydroxide solution was added to perform a neutralization reaction. Thereafter, 5000 g of pure water was added and stirred, and then 5000 g of water was removed by decantation. Furthermore, the process of adding 5000 g of pure water, stirring, and removing water by decantation was repeated three times in total. Thereafter, the solid content of the resin was adjusted to 20% by weight using ion-exchanged water to obtain a polyvinyl acetal resin (PVB-A1).
Regarding the obtained polyvinyl acetal resin, the amount of acetal groups, the amount of hydroxyl groups, and the amount of acetyl groups were measured using 1 H-NMR (nuclear magnetic resonance spectrum), and the results were as shown in Table 1. 1 H-NMR measurement used heavy DMSO as a solvent.
Further, the amount of Brønsted acid was measured by acid-base titration method in accordance with JIS K0070-1992. Specifically, it was measured by the following method. First, as a main test, about 1 g of the obtained polyvinyl acetal resin was accurately weighed into an Erlenmeyer flask, and 40 ml of a mixed solvent of ethanol/water (volume ratio 9:1) was added and dissolved by shaking. After dissolution, using a 1% by weight solution of phenolphthalein as an indicator and a 0.02 mol/L ethanolic potassium hydroxide solution, titration is carried out using a microburette until a slight red color remains for 30 seconds or more. A blank test was conducted separately, and the amount of Brønsted acid was measured using the following formula. The result was 19.2 mg/g.
Brønsted acid amount = [(AB) x f x (1/50) x (C/1000)] x 100/D
A: Dropping amount (mL) of ethanolic potassium hydroxide solution in this test
B: Dropping amount (mL) of ethanolic potassium hydroxide solution in blank test
C: Molecular weight of the structural unit having an acidic functional group D: Amount of sample (g)
f: 0.02 mol/L titer of ethanolic potassium hydroxide solution
（製造例２）
スルホン酸変性ポリビニルアルコール樹脂（平均重合度１５０、残存アセチル基５．０モル％、式（４）で表される構成単位（Ｒ１９がメチレン基、Ｘ６が水素原子）の含有量１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を６９ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ２）を得た。 (Manufacturing example 2)
Sulfonic acid-modified polyvinyl alcohol resin (average degree of polymerization 150, residual acetyl group 5.0 mol%, content of the structural unit represented by formula (4) (R 19 is a methylene group, X 6 is a hydrogen atom) content 1.0 A polyvinyl acetal resin (PVB-A2) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 69 g.
（製造例３）
無変性ポリビニルアルコール樹脂（平均重合度９００、残存アセチル基１０．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を７５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ３）を得た。 (Manufacturing example 3)
Polyvinyl acetal resin (PVB-A3 ) was obtained.
（製造例４）
ホスホン酸基変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基１．０モル％、式（５）で表される構成単位（Ｒ２０がエチレン基、Ｘ７、Ｘ８が水素原子）の含有量５．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を７５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ４）を得た。 (Manufacturing example 4)
Phosphonic acid group-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 1.0 mol%, containing a structural unit represented by formula (5) (R 20 is an ethylene group, X 7 and X 8 are hydrogen atoms) A polyvinyl acetal resin (PVB-A4) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde was 75 g.
（製造例５）
無変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基１０．０モル％）２５０ｇと、カルボン酸変性ポリビニルアルコール樹脂（平均重合度１５０、残存アセチル基量１．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量１．０モル％）２５０ｇとを用いた。また、ｎ－ブチルアルデヒドの添加量を８０ｇとした。上記以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ５）を得た。 (Manufacturing example 5)
250 g of unmodified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 10.0 mol%) and carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 150, residual acetyl group amount 1.0 mol%, formula (2-1) 250 g of the structural unit represented by (R 2 is a methylene group, X 1 is a hydrogen atom) content: 1.0 mol %) was used. Further, the amount of n-butyraldehyde added was 80 g. Polyvinyl acetal resin (PVB-A5) was obtained in the same manner as in Production Example 1 except for the above.
（製造例６）
カルボン酸変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基２０．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量０．０１モル％）を用い、ｎ－ブチルアルデヒドの添加量を６５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ６）を得た。 (Manufacturing example 6)
Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 20.0 mol%, content of structural units represented by formula (2-1) (R 2 is a methylene group, X 1 is a hydrogen atom) content is 0 A polyvinyl acetal resin (PVB-A6) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 65 g.
（製造例７）
スルホン酸変性ポリビニルアルコール樹脂（平均重合度１５００、残存アセチル基１．０モル％、式（４）で表される構成単位（Ｒ１９がメチレン基、Ｘ６が水素原子）の含有量１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を８５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ７）を得た。 (Manufacturing example 7)
Sulfonic acid-modified polyvinyl alcohol resin (average degree of polymerization 1500, residual acetyl group 1.0 mol%, content of the structural unit represented by formula (4) (R 19 is a methylene group, X 6 is a hydrogen atom) content 1.0 A polyvinyl acetal resin (PVB-A7) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 85 g.
（製造例８）
カルボン酸変性ポリビニルアルコール樹脂（平均重合度１５００、残存アセチル基１．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量１５．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を７０ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ８）を得た。 (Production example 8)
Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 1500, residual acetyl group 1.0 mol%, content of structural units represented by formula (2-1) (R 2 is a methylene group, X 1 is a hydrogen atom) content 15 A polyvinyl acetal resin (PVB-A8) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 70 g.
（製造例９）
ホスホン酸基変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基１．０モル％、式（５）で表される構成単位（Ｒ２０がエチレン基、Ｘ７、Ｘ８が水素原子）の含有量１．０モル％）２５０ｇと、カルボン酸変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基量１．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量１．０モル％）２５０ｇとを用いた。また、ｎ－ブチルアルデヒドの添加量を７９ｇとした。上記以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ９）を得た。 (Manufacturing example 9)
Phosphonic acid group-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 1.0 mol%, containing a structural unit represented by formula (5) (R 20 is an ethylene group, X 7 and X 8 are hydrogen atoms) 250 g of carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group amount 1.0 mol%, structural unit represented by formula (2-1) (R 2 is a methylene group) , X 1 is a hydrogen atom) content of 1.0 mol %) was used. Further, the amount of n-butyraldehyde added was 79 g. Polyvinyl acetal resin (PVB-A9) was obtained in the same manner as in Production Example 1 except for the above.
（製造例１０）
無変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を８５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１０）を得た。 (Manufacturing example 10)
A polyvinyl acetal resin (PVB-A10 ) was obtained.
（製造例１１）
スルホン酸変性ポリビニルアルコール樹脂（平均重合度１５０、残存アセチル基５．０モル％、式（４）で表される構成単位（Ｒ１９がメチレン基、Ｘ６が水素原子）の含有量１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を７９ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１１）を得た。 (Production example 11)
Sulfonic acid-modified polyvinyl alcohol resin (average degree of polymerization 150, residual acetyl group 5.0 mol%, content of the structural unit represented by formula (4) (R 19 is a methylene group, X 6 is a hydrogen atom) content 1.0 A polyvinyl acetal resin (PVB-A11) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 79 g.
（製造例１２）
無変性ポリビニルアルコール樹脂（平均重合度２０００、残存アセチル基１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を８５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１２）を得た。 (Production example 12)
A polyvinyl acetal resin (PVB-A12 ) was obtained.
（製造例１３）
カルボン酸変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基３０．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量１．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を５０ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１３）を得た。 (Manufacturing example 13)
Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 30.0 mol%, content of structural units represented by formula (2-1) (R 2 is a methylene group, X 1 is a hydrogen atom) content 1 A polyvinyl acetal resin (PVB-A13) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 50 g.
（製造例１４）
アミン変性ポリビニルアルコール樹脂（平均重合度９００、残存アセチル基５．０モル％、式（６）で表される構成単位（Ｒ２１が単結合）の含有量５．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を７５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１４）を得た。 (Manufacturing example 14)
Using an amine-modified polyvinyl alcohol resin (average degree of polymerization 900, residual acetyl group 5.0 mol%, content of the structural unit represented by formula (6) (R 21 is a single bond) 5.0 mol%), n - A polyvinyl acetal resin (PVB-A14) was obtained in the same manner as in Production Example 1 except that the amount of butyraldehyde added was 75 g.
（製造例１５）
カルボン酸変性ポリビニルアルコール樹脂（平均重合度１５００、残存アセチル基５．０モル％、式（２－１）で表される構成単位（Ｒ２がメチレン基、Ｘ１が水素原子）の含有量２０．０モル％）を用い、ｎ－ブチルアルデヒドの添加量を６０ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ａ１５）を得た。 (Production example 15)
Carboxylic acid-modified polyvinyl alcohol resin (average degree of polymerization 1500, residual acetyl group 5.0 mol%, content of structural units represented by formula (2-1) (R 2 is a methylene group, X 1 is a hydrogen atom) content 20 A polyvinyl acetal resin (PVB-A15) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde added was 60 g.
（製造例１６）
スルホン酸変性ポリビニルアルコール樹脂（平均重合度６００、残存アセチル基５．０モル％、式（４）で表される構成単位（Ｒ１９がメチレン基、Ｘ６が水素原子）の含有量０．０１モル％）を用い、ｎ－ブチルアルデヒドの添加量を６５ｇとした以外は製造例１と同様にしてポリビニルアセタール樹脂（ＰＶＢ－Ｂ１）を得た。 (Production example 16)
Sulfonic acid-modified polyvinyl alcohol resin (average degree of polymerization 600, residual acetyl group 5.0 mol%, content of the structural unit represented by formula (4) (R 19 is a methylene group, X 6 is a hydrogen atom) content 0.01 A polyvinyl acetal resin (PVB-B1) was obtained in the same manner as in Production Example 1, except that the amount of n-butyraldehyde was changed to 65 g.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
（実施例１～１８、比較例１～８）
活物質、疎水性溶剤、炭素材料、ポリビニルアセタール樹脂、バインダー樹脂及び水を表２に示す配合の通りに混合し、二次電池電極用組成物を得た。
なお、活物質、疎水性溶剤、炭素材料、バインダー樹脂として、以下のものを用いた。
また、活物質のｐＨは活物質を濃度１．０重量％となるように水中に投入して得られた水溶液のｐＨをｐＨメーター（堀場製作所社製）を用いて測定した。また、水の含有量は赤外水分計（ＫＥＴＴ社製）を用いて測定した。
＜活物質＞
ＬＦＰ－１：リン酸鉄リチウム（ＬｉＦｅＰＯ４）（ｐＨ９、平均粒子径１．０μｍ、密度３．４ｇ／ｃｍ３、比表面積１０．７ｍ２／ｇ）
ＬＦＰ－２：リン酸鉄リチウム（ＬｉＦｅＰＯ４）（ｐＨ１０、平均粒子径１．５μｍ、密度３．７ｇ／ｃｍ３、比表面積１２．０ｍ２／ｇ）
ＬＦＰ－３：リン酸鉄リチウム（ＬｉＦｅＰＯ４）（ｐＨ９、平均粒子径５．５μｍ、密度３．６ｇ／ｃｍ３、比表面積０．８ｍ２／ｇ）
ＮＣＭ－１：リチウムニッケルコバルトマンガン酸化物（ＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２）（ｐＨ１２、平均粒子径１０．０μｍ、密度３．５ｇ／ｃｍ３、比表面積０．５ｍ２／ｇ）
ＮＣＭ－２：リチウムニッケルコバルトマンガン酸化物（ＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２）（ｐＨ１２、平均粒子径１０．２μｍ、密度３．１ｇ／ｃｍ３、比表面積０．４ｍ２／ｇ）
ＮＣＭ－３：リチウムニッケルコバルトマンガン酸化物（ＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２）（ｐＨ１２、平均粒子径１１．７μｍ、密度３．４ｇ／ｃｍ３、比表面積０．４ｍ２／ｇ）
ＮＣＭ－４：リチウムニッケルコバルトマンガン酸化物（ＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２）（ｐＨ１０、平均粒子径５．５μｍ、密度３．８ｇ／ｃｍ３、比表面積０．６ｍ２／ｇ）
ＬＣＯ－１：リチウムコバルト酸化物（ＬｉＣｏＯ２）（ｐＨ９、平均粒子径１４．３μｍ、密度４．０ｇ／ｃｍ３、比表面積０．４ｍ２／ｇ）
ＮＣＡ－１：リチウムニッケルコバルトアルミ酸化物（ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２）（ｐＨ１２、平均粒子径１．５μｍ、密度３．６ｇ／ｃｍ３、比表面積１．８ｍ２／ｇ）
＜疎水性溶剤＞
ＮＭＰ：Ｎ－メチルピロリドン
ＭＥＫ：メチルエチルケトン
酪酸ブチル
＜炭素材料＞
ＭＷ－１：多層カーボンナノチューブ（シグマアルドリッチ社製、平均繊維径９ｎｍ、平均繊維長１３μｍ、密度１．８ｇ／ｃｍ３、比表面積２００ｍ２／ｇ）
ＭＷ－２：多層カーボンナノチューブ（Ｃｎａｎｏ社製、平均繊維径１０ｎｍ、平均繊維長１５０μｍ、密度１．９ｇ／ｃｍ３、比表面積３０００ｍ２／ｇ）
ＭＷ－３：多層カーボンナノチューブ（Ｃｎａｎｏ社製、平均繊維径１０ｎｍ、平均繊維長１５μｍ、密度１．８ｇ／ｃｍ３、比表面積２５０ｍ２／ｇ）
ＶＧＣＦ：気相成長系炭素繊維（昭和電工株式会社製、平均繊維径１５０ｎｍ、平均繊維長１５μｍ、密度２．１ｇ／ｃｍ３、比表面積１３ｍ２／ｇ）
ＳＷ：単層カーボンナノチューブ（ＯＣＳＩＡＬ社製、平均繊維径１．２±０．５ｎｍ、平均繊維長４μｍ以上、密度１．３ｇ／ｃｍ３、比表面積１９００ｍ２／ｇ）
ＡＢ：アセチレンブラック（デンカ株式会社製、平均粒子径３５ｎｍ、比表面積６８ｍ２／ｇ）
ＫＢ：ケッチェンブラック（ライオンスペシャリティケミカルズ社製、平均粒子径３５ｎｍ、比表面積１２００ｍ２／ｇ）
＜バインダー樹脂＞
ＰＶＤＦ：ポリフッ化ビニリデン（クレハ社製）
ＰＶＰ：ポリビニルピロリドン（東京化成社製）
ＣＭＣ：カルボキシメチルセルロース（第一工業製薬社製） (Examples 1 to 18, Comparative Examples 1 to 8)
An active material, a hydrophobic solvent, a carbon material, a polyvinyl acetal resin, a binder resin, and water were mixed according to the formulation shown in Table 2 to obtain a composition for a secondary battery electrode.
Note that the following were used as the active material, hydrophobic solvent, carbon material, and binder resin.
Further, the pH of the active material was measured by adding the active material into water at a concentration of 1.0% by weight, and measuring the pH of the resulting aqueous solution using a pH meter (manufactured by Horiba, Ltd.). Moreover, the water content was measured using an infrared moisture meter (manufactured by KETT).
<Active material>
LFP-1: Lithium iron phosphate (LiFePO 4 ) (pH 9, average particle size 1.0 μm, density 3.4 g/cm 3 , specific surface area 10.7 m 2 /g)
LFP-2: Lithium iron phosphate (LiFePO 4 ) (pH 10, average particle size 1.5 μm, density 3.7 g/cm 3 , specific surface area 12.0 m 2 /g)
LFP-3: Lithium iron phosphate (LiFePO 4 ) (pH 9, average particle size 5.5 μm, density 3.6 g/cm 3 , specific surface area 0.8 m 2 /g)
NCM-1: Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) (pH 12, average particle size 10.0 μm, density 3.5 g/cm 3 , specific surface area 0.5 m 2 /g)
NCM-2: Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) (pH 12, average particle size 10.2 μm, density 3.1 g/cm 3 , specific surface area 0.4 m 2 /g)
NCM-3: Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) (pH 12, average particle size 11.7 μm, density 3.4 g/cm 3 , specific surface area 0.4 m 2 /g)
NCM-4: Lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) (pH 10, average particle size 5.5 μm, density 3.8 g/cm 3 , specific surface area 0.6 m 2 /g)
LCO-1: Lithium cobalt oxide (LiCoO 2 ) (pH 9, average particle size 14.3 μm, density 4.0 g/cm 3 , specific surface area 0.4 m 2 /g)
NCA-1: Lithium nickel cobalt aluminum oxide (LiNi 0.8 Co 0.15 Al 0.05 O 2 ) (pH 12, average particle size 1.5 μm, density 3.6 g/cm 3 , specific surface area 1.8 m 2 /g)
<Hydrophobic solvent>
NMP: N-methylpyrrolidone MEK: Methyl ethyl ketone butyl butyrate <carbon material>
MW-1: Multi-walled carbon nanotube (manufactured by Sigma-Aldrich, average fiber diameter 9 nm, average fiber length 13 μm, density 1.8 g/cm 3 , specific surface area 200 m 2 /g)
MW-2: Multi-walled carbon nanotube (manufactured by Cnano, average fiber diameter 10 nm, average fiber length 150 μm, density 1.9 g/cm 3 , specific surface area 3000 m 2 /g)
MW-3: Multi-walled carbon nanotube (manufactured by Cnano, average fiber diameter 10 nm, average fiber length 15 μm, density 1.8 g/cm 3 , specific surface area 250 m 2 /g)
VGCF: Vapor-grown carbon fiber (manufactured by Showa Denko K.K., average fiber diameter 150 nm, average fiber length 15 μm, density 2.1 g/cm 3 , specific surface area 13 m 2 /g)
SW: Single-wall carbon nanotube (manufactured by OCSIAL, average fiber diameter 1.2±0.5 nm, average fiber length 4 μm or more, density 1.3 g/cm 3 , specific surface area 1900 m 2 /g)
AB: Acetylene black (manufactured by Denka Corporation, average particle diameter 35 nm, specific surface area 68 m 2 /g)
KB: Ketjen black (manufactured by Lion Specialty Chemicals, average particle diameter 35 nm, specific surface area 1200 m 2 /g)
<Binder resin>
PVDF: Polyvinylidene fluoride (manufactured by Kureha)
PVP: Polyvinylpyrrolidone (manufactured by Tokyo Kasei Co., Ltd.)
CMC: Carboxymethyl cellulose (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
＜評価＞
実施例及び比較例で得られた二次電池電極用組成物について以下の評価を行った。結果を表３に示した。 <Evaluation>
The secondary battery electrode compositions obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Table 3.
（１）分散性
離型処理されたポリエチレンテレフタレート（ＰＥＴ）フィルム上に得られた二次電池電極用組成物を乾燥後の膜厚が２０μｍとなるように塗工し、乾燥してＰＥＴフィルムから剥離してシートを作製した。
得られたシートについて、ＪＩＳ　Ｂ　０６０１（１９９４）に基づいて平均表面粗さＲａを測定し、以下の基準で評価した。
〇：Ｒａが５μｍ未満であった。
△：Ｒａが５μｍ以上、８μｍ未満であった。
×：Ｒａが８μｍ以上であった。
平均表面粗さＲａが低い値であると円滑性や分散性に優れているといえる。 (1) Coat the resulting secondary battery electrode composition on a polyethylene terephthalate (PET) film that has been subjected to dispersion release treatment so that the film thickness after drying is 20 μm, dry it, and release it from the PET film. A sheet was prepared by peeling.
The average surface roughness Ra of the obtained sheet was measured based on JIS B 0601 (1994) and evaluated according to the following criteria.
Good: Ra was less than 5 μm.
Δ: Ra was 5 μm or more and less than 8 μm.
×: Ra was 8 μm or more.
It can be said that when the average surface roughness Ra is a low value, smoothness and dispersibility are excellent.
（２）接着性
アルミ箔（厚み２０μｍ）の上に、乾燥後の膜厚が２０μｍとなるように得られた二次電池電極用組成物を塗工、乾燥し、アルミ箔上に二次電池電極用組成物のシートが形成された試験片を得た。
この試験片を縦１ｃｍ、横２ｃｍに切り出し、ＡＵＴＯＧＲＡＰＨ（島津製作所社製、「ＡＧＳ－Ｊ」）を用い、試験片を固定しながらシートを引き上げ、アルミ箔から完全にシートが剥離するまでに要する剥離力（Ｎ）を計測した後、以下の基準で判定した。
〇：剥離力が８．０Ｎ以上であった。
△：剥離力が５．０Ｎ以上、８．０Ｎ未満であった。
×：剥離力が５．０Ｎ未満であった。 (2) Coat the obtained secondary battery electrode composition on adhesive aluminum foil (thickness 20 μm) so that the film thickness after drying is 20 μm, dry it, and apply the secondary battery electrode composition on the aluminum foil. A test piece on which a sheet of the electrode composition was formed was obtained.
Cut this test piece into 1 cm long and 2 cm wide pieces, and use AUTOGRAPH (Shimadzu Corporation, "AGS-J") to pull up the sheet while fixing the test piece. It takes until the sheet completely peels off from the aluminum foil. After measuring the peeling force (N), it was judged based on the following criteria.
○: Peeling force was 8.0N or more.
Δ: Peeling force was 5.0N or more and less than 8.0N.
×: Peeling force was less than 5.0N.
（３）塗工性
得られた二次電池電極用組成物をガラス板上にドクターブレードを用いて塗工し、空気巡回式オーブン中、１５０℃で５分間乾燥して塗膜を得た。得られた塗膜を目視にて観察し、以下の基準で評価した。
〇：塗膜表面にひび割れや亀裂がなく、膜厚が均一であった。
△：塗膜表面に僅かにひび割れや亀裂が確認できた。
×：塗膜表面にひび割れや亀裂が確認でき、膜厚にばらつきがあった。 (3) Coating properties The obtained secondary battery electrode composition was coated onto a glass plate using a doctor blade, and dried at 150° C. for 5 minutes in an air circulating oven to obtain a coating film. The resulting coating film was visually observed and evaluated based on the following criteria.
○: There were no cracks or fissures on the coating film surface, and the film thickness was uniform.
△: Slight cracks and fissures were observed on the surface of the coating film.
×: Cracks and fissures were observed on the coating film surface, and there were variations in film thickness.
（４）分散安定性
得られた二次電池電極用組成物について、コーンプレート型粘度計Ｇｅｍｉｎｉ（Ｂｏｈｌｉｎ　Ｉｎｓｔｒｕｍｅｎｔｓ製）を用いて、２５℃、せん断速度２０ｓ－１における初期粘度（Ｐａ・ｓ）を測定した。 (4) Dispersion stability For the obtained secondary battery electrode composition, the initial viscosity (Pa・s) at 25° C. and a shear rate of 20 s −1 was measured using a cone-plate viscometer Gemini (manufactured by Bohlin Instruments). It was measured.
得られた二次電池電極用組成物について、初期粘度測定より３０日後の粘度（Ｐａ・ｓ）を同様にして測定して粘度の変化率（％）を確認し、以下の基準で評価した。
〇：粘度変化率が１５０％未満
△：粘度変化率が１５０％以上、２５０％未満
×：粘度変化率が２５０％以上 Regarding the obtained secondary battery electrode composition, the viscosity (Pa·s) 30 days after the initial viscosity measurement was measured in the same manner to confirm the rate of change (%) in viscosity, and evaluated according to the following criteria.
〇: Viscosity change rate is less than 150% △: Viscosity change rate is 150% or more and less than 250% ×: Viscosity change rate is 250% or more
（５）導電性
離型処理されたポリエチレンテレフタレート（ＰＥＴ）フィルム上に得られた二次電池電極用組成物を乾燥後の膜厚が２０μｍとなるように塗工し、乾燥してＰＥＴフィルムから剥離してシートを作製した。
得られたシートについて、電極抵抗測定器（日置電機株式会社製）を用いて電極抵抗値を測定し、以下の基準で評価した。
〇：電極抵抗値が１００Ω／ｓｑ未満であった。
△：電極抵抗値が１００Ω／ｓｑ以上、２００Ω／ｓｑ未満であった。
×：電極抵抗値が２００Ω／ｓｑ以上であった。
表面抵抗値が低い値であると電子伝導性に優れているといえる。 (5) Coat the resulting secondary battery electrode composition on a conductive release-treated polyethylene terephthalate (PET) film so that the film thickness after drying is 20 μm, dry and remove the PET film. A sheet was prepared by peeling.
The electrode resistance value of the obtained sheet was measured using an electrode resistance measuring device (manufactured by Hioki Electric Co., Ltd.) and evaluated according to the following criteria.
○: Electrode resistance value was less than 100Ω/sq.
Δ: The electrode resistance value was 100Ω/sq or more and less than 200Ω/sq.
×: The electrode resistance value was 200Ω/sq or more.
It can be said that a low surface resistance value indicates excellent electronic conductivity.
（６）粘弾性
得られた二次電池電極用組成物について、ＲＨＥＯＳＴＲＥＳＳ（サーモサイエンティフィック社製）を用い、２５℃、ひずみが０．１の条件における貯蔵弾性率を測定し、以下の基準で評価した。
〇：貯蔵弾性率が１０００未満
△：貯蔵弾性率が１０００以上、５０００未満
×：貯蔵弾性率が５０００以上
粘弾性評価が高いとペーストの流動性に優れ、ゲル化しにくいといえる。 (6) Viscoelasticity The storage modulus of the obtained secondary battery electrode composition was measured using RHEOSTRESS (manufactured by Thermo Scientific) at 25°C and a strain of 0.1, and the storage elastic modulus was measured according to the following criteria. It was evaluated by
○: Storage modulus is less than 1000 Δ: Storage modulus is 1000 or more, less than 5000 ×: Storage modulus is 5000 or more If the viscoelasticity evaluation is high, the paste has excellent fluidity and is difficult to gel.
（７）電池特性
（ａ）コイン電池の作製
得られた二次電池電極用組成物を厚さ１５μｍのアルミ箔に均一に塗布、乾燥し、これをφ１６ｍｍに打ち抜いて正極層を得た。
電解液としてＬｉＰＦ６（１Ｍ）を含有するエチレンカーボネートとジエチルカーボネートとの混合溶媒（体積比１：１）を用い、該電解液を正極層に含浸させた後、この正極層を正極集電体上に置き、さらにその上に電解液を含浸させた厚さ２５ｍｍの多孔質ＰＰ膜（セパレータ）を置いた。
更に、この上に負極層となるリチウム金属板を置き、この上に絶縁パッキンで被覆された負極集電体を重ね合わせた。この積層体を、かしめ機により圧力を加え、密閉型のコイン電池を得た。 (7) Battery characteristics (a) Preparation of coin battery The obtained composition for a secondary battery electrode was uniformly applied to a 15 μm thick aluminum foil, dried, and punched out to a diameter of 16 mm to obtain a positive electrode layer.
A mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1:1) containing LiPF 6 (1M) was used as the electrolytic solution, and after impregnating the positive electrode layer with the electrolytic solution, the positive electrode layer was used as a positive electrode current collector. A porous PP membrane (separator) impregnated with an electrolytic solution and having a thickness of 25 mm was placed on top of the membrane.
Furthermore, a lithium metal plate serving as a negative electrode layer was placed on top of this, and a negative electrode current collector covered with insulating packing was superimposed on this. Pressure was applied to this laminate using a caulking machine to obtain a sealed coin battery.
（ｂ）放電容量評価、及び、充放電サイクル評価
得られたコイン電池について、充放電試験装置（宝泉社製）を用いて放電容量評価、及び、充放電サイクル評価を行った。
この放電容量評価、充放電サイクル評価は電圧範囲２．７～４．２Ｖ、評価温度は２５℃と５０℃で行った。なお、充放電サイクル評価は、初回の放電容量に対する３０サイクル目の放電容量の割合（容量維持率）を算出し、以下の基準で評価した。
〇：容量維持率が９０％以上であった。
△：容量維持率が７０％以上９０％未満であった。
×：容量維持率が７０％未満であった。 (b) Discharge capacity evaluation and charge/discharge cycle evaluation The obtained coin batteries were subjected to discharge capacity evaluation and charge/discharge cycle evaluation using a charge/discharge test device (manufactured by Hosensha).
The discharge capacity evaluation and charge/discharge cycle evaluation were performed in a voltage range of 2.7 to 4.2V and at evaluation temperatures of 25°C and 50°C. In addition, the charge/discharge cycle evaluation was performed by calculating the ratio of the discharge capacity at the 30th cycle to the initial discharge capacity (capacity retention rate), and evaluated based on the following criteria.
○: Capacity retention rate was 90% or more.
Δ: Capacity retention rate was 70% or more and less than 90%.
×: Capacity retention rate was less than 70%.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
本発明によれば、塗工性、接着性に優れるとともに、高い電子伝導性と繊維状炭素材料の分散性、分散安定性とを両立することができ、ゲル化を抑制して高性能の二次電池を製造可能な二次電池電極用組成物を提供できる。

  According to the present invention, it is possible to achieve both excellent coating properties and adhesive properties, high electronic conductivity, dispersibility and dispersion stability of the fibrous carbon material, suppress gelation, and achieve high performance. A composition for a secondary battery electrode that can be used to manufacture a secondary battery can be provided.

Claims (9)

  1. 活物質と、疎水性溶剤と、繊維状炭素材料と、ポリビニルアセタール樹脂とを含有し、
    水の含有量が１０重量％以下であり、
    前記ポリビニルアセタール樹脂は、水酸基量が３０モル％以下である、二次電池電極用組成物。     Contains an active material, a hydrophobic solvent, a fibrous carbon material, and a polyvinyl acetal resin,
    The water content is 10% by weight or less,
    The polyvinyl acetal resin is a secondary battery electrode composition in which the amount of hydroxyl groups is 30 mol% or less.
  2. ポリビニルアセタール樹脂は、酸性官能基を有する構成単位を有する、請求項１に記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to claim 1, wherein the polyvinyl acetal resin has a structural unit having an acidic functional group.
  3. 酸性官能基が、カルボン酸基、硫黄含有基及びリン含有基からなる群から選ばれる少なくとも１種である、請求項１又は２に記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to claim 1 or 2, wherein the acidic functional group is at least one selected from the group consisting of a carboxylic acid group, a sulfur-containing group, and a phosphorus-containing group.
  4. ポリビニルアセタール樹脂の全構成単位に対する酸性官能基を有する構成単位の含有量が、０．０１モル％以上１０モル％以下である、請求項２又は３の何れかに記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to claim 2 or 3, wherein the content of the structural unit having an acidic functional group with respect to all the structural units of the polyvinyl acetal resin is 0.01 mol% or more and 10 mol% or less. thing.
  5. ポリビニルアセタール樹脂の平均重合度が１５０以上１５００以下である、請求項１～４の何れかに記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to any one of claims 1 to 4, wherein the polyvinyl acetal resin has an average degree of polymerization of 150 or more and 1,500 or less.
  6. 酸性官能基はブレンステッド酸性基であり、ポリビニルアセタール樹脂中のブレンステッド酸量が０．２ｍｇ／ｇ以上２５０ｍｇ／ｇ以下である、請求項２～５の何れかに記載の二次電池電極用組成物。 The secondary battery electrode according to any one of claims 2 to 5, wherein the acidic functional group is a Brønsted acidic group, and the Brønsted acid amount in the polyvinyl acetal resin is 0.2 mg/g or more and 250 mg/g or less. Composition.
  7. 更に、ポリフッ化ビニリデンを含有する、請求項１～６の何れかに記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to any one of claims 1 to 6, further comprising polyvinylidene fluoride.
  8. 繊維状炭素材料が、カーボンナノチューブである、請求項１～７の何れかに記載の二次電池電極用組成物。 The composition for a secondary battery electrode according to any one of claims 1 to 7, wherein the fibrous carbon material is a carbon nanotube.
  9. 活物質のｐＨが９以上１２以下である、請求項１～８の何れかに記載の二次電池電極用組成物。

          The composition for a secondary battery electrode according to any one of claims 1 to 8, wherein the active material has a pH of 9 or more and 12 or less.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009098779A1 (en) * 2008-02-08 2009-08-13 Meijo Nano Carbon Co., Ltd. Carbon nanotube dispersion and utilization of the same
JP2018535284A (en) * 2015-09-25 2018-11-29 エルジー・ケム・リミテッド Carbon nanotube dispersion and method for producing the same
JP2018206675A (en) * 2017-06-07 2018-12-27 積水化学工業株式会社 Slurry for power storage device electrode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009098779A1 (en) * 2008-02-08 2009-08-13 Meijo Nano Carbon Co., Ltd. Carbon nanotube dispersion and utilization of the same
JP2018535284A (en) * 2015-09-25 2018-11-29 エルジー・ケム・リミテッド Carbon nanotube dispersion and method for producing the same
JP2018206675A (en) * 2017-06-07 2018-12-27 積水化学工業株式会社 Slurry for power storage device electrode

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