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  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
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  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
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  • Y02E60/10—Energy storage using batteries

Definitions

• Carbon nanotubes are excellent in various properties such as mechanical strength, optical properties, electrical properties, thermal properties, and molecular adsorption ability, so they are used in electronic circuits such as logic circuits. , DRAM, SRAM, NRAM and other memories, semiconductor devices, interconnects, complementary MOS, bipolar transistors and other electronic components; chemical sensors such as trace gas detectors; biosensors such as DNA and protein measuring instruments; used in various electronic products.
• secondary battery electrodes used for forming electrode mixture layers provided in electrodes of non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as "secondary batteries") CNTs are also used as a conductive material for slurries.
• the electrode of a secondary battery expands and contracts greatly due to charging and discharging, which reduces the conductivity of the electrode and reduces the cycle characteristics of the secondary battery. It is possible to obtain a secondary battery in which a decrease in conductivity is suppressed and which is excellent in cycle characteristics.
• Patent Document 1 a conductive material dispersion containing CNTs, a dispersant, and an organic solvent as a dispersion medium, wherein the Hansen Solubility Parameter (HSP) distance between the CNTs and the dispersant is a predetermined value or less.
• HSP Hansen Solubility Parameter
• Patent Document 2 discloses a CNT dispersion containing CNTs, carboxymethyl cellulose or a salt thereof, and water, wherein the carboxymethyl cellulose or a salt thereof has a weight average molecular weight of 10,000 to 100,000.
• the degree of etherification is 0.5 to 0.9
• the product (X ⁇ Y) of the complex elastic modulus X (Pa) and the phase angle Y (°) of the CNT dispersion is 100 or more and 1,500 or less.
• CNT dispersions have been proposed.
• an object of the present invention is to provide a carbon nanotube dispersion having excellent dispersibility and storage stability of carbon nanotubes. Another object of the present invention is to provide a slurry for a non-aqueous secondary battery negative electrode containing the carbon nanotube dispersion. Another object of the present invention is to provide a negative electrode for a non-aqueous secondary battery using the slurry for a non-aqueous secondary battery negative electrode. Another object of the present invention is to provide a non-aqueous secondary battery comprising the negative electrode for a non-aqueous secondary battery.
• the inventor of the present invention has made intensive studies with the aim of solving the above problems. Then, the present inventors discovered that carbon nanotubes and a water-soluble polymer having an acid functional group (hereinafter, the "water-soluble polymer having an acid functional group” may be simply referred to as a "water-soluble polymer”).
• a water-soluble polymer having an acid functional group may be simply referred to as a "water-soluble polymer”
• water wherein the HSP distance (R a ) between the Hansen solubility parameter (HSP c ) of the carbon nanotube and the Hansen solubility parameter (HSP d ) of the water-soluble polymer is a predetermined value or less.
• the present inventors have newly found that the carbon nanotube dispersion is excellent in dispersibility and storage stability of carbon nanotubes, and completed the present invention.
• an object of the present invention is to advantageously solve the above problems, and the present invention provides a carbon nanotube dispersion containing carbon nanotubes, a water-soluble polymer having an acid functional group, and water. carbon, wherein the HSP distance (R a ) between the Hansen solubility parameter (HSP c ) of the carbon nanotube and the Hansen solubility parameter (HSP d ) of the water-soluble polymer is 7.0 MPa 1/2 or less Nanotube dispersion.
• HSP distance (R a ) between the Hansen solubility parameter (HSP c ) of the carbon nanotube and the Hansen solubility parameter (HSP d ) of the water-soluble polymer is 7.0 MPa 1/2 or less Nanotube dispersion.
• the “Hansen solubility parameter of carbon nanotubes (HSP c )” is composed of the polar term ⁇ p1 , the dispersion term ⁇ d1 and the hydrogen bonding term ⁇ h1
• the “Hansen solubility parameter of water-soluble polymers (HSP d )” consists of a polar term ⁇ p2 , a dispersion term ⁇ d2 and a hydrogen bonding term ⁇ h2 .
• ⁇ p1 ", “ ⁇ d1 " and “ ⁇ h1 ", and “ ⁇ p2 ", “ ⁇ d2 " and “ ⁇ h2 " are can be identified.
• the polymer being “water-soluble” means that when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25° C., the insoluble content is less than 1.0% by mass. do.
• the unit of the polar term ⁇ p , the dispersion term ⁇ d and the hydrogen bonding term ⁇ h is “MPa 1/2 ”, which may be omitted below.
• the Hansen solubility parameter (HSP d ) of the water-soluble polymer is 10.7 MPa 1/2
• the dispersion term ⁇ d3 is 18.6 MPa 1/2
• hydrogen bonding The HSP distance (R b ) to the Hansen solubility parameter (HSP m ) of the material with the term ⁇ h3 of 7.0 MPa 1/2 is preferably 8.0 MPa 1/2 or less.
• HSP distance (R b ) is equal to or less than the above upper limit, when a non-aqueous secondary battery negative electrode is produced using the non-aqueous secondary battery negative electrode slurry containing the carbon nanotube dispersion, the electrode mixture layer is not collected. Peel strength from electrical bodies can be improved.
• ⁇ p3 ”, “ ⁇ d3 ” and “ ⁇ h3 ” are values specified using the method described in Examples.
• the carbon nanotube dispersion liquid of the present invention preferably has a pH of 6 or more and 10 or less. If the pH is within the above range, the viscosity stability of the non-aqueous secondary battery negative electrode slurry containing the carbon nanotube dispersion can be improved, and the non-aqueous secondary battery prepared using the non-aqueous secondary battery negative electrode slurry It is possible to improve the cycle characteristics of a non-aqueous secondary battery provided with a battery negative electrode.
• At least part of the acid functional groups of the water-soluble polymer are preferably alkali metal bases or ammonium bases. If at least part of the acid functional groups of the water-soluble polymer are alkali metal bases or ammonium bases, the dispersibility and storage stability of the carbon nanotube dispersion can be improved, and non-aqueous secondary The viscosity stability of the battery negative electrode slurry can be improved, and the cycle characteristics of a non-aqueous secondary battery comprising a non-aqueous secondary battery negative electrode produced using the non-aqueous secondary battery negative electrode slurry can be improved.
• the acid functional group is preferably a carboxylic acid group. If the acid functional group is a carboxylic acid group, the dispersibility and storage stability of the carbon nanotube dispersion can be improved, and the viscosity stability of the non-aqueous secondary battery negative electrode slurry containing the carbon nanotube dispersion can be improved. Furthermore, the cycle characteristics of the non-aqueous secondary battery provided with the non-aqueous secondary battery negative electrode produced using the non-aqueous secondary battery negative electrode slurry can be improved. In addition, regardless of the type of carbon nanotubes, the dispersibility and storage stability of the carbon nanotube dispersion can be maintained.
• the acid functional groups are preferably sulfonic acid groups. If the acid functional group is a sulfonic acid group, the dispersibility and storage stability of the carbon nanotube dispersion can be improved, and the viscosity stability of the non-aqueous secondary battery negative electrode slurry containing the carbon nanotube dispersion can be improved. Furthermore, the cycle characteristics of the non-aqueous secondary battery provided with the non-aqueous secondary battery negative electrode produced using the non-aqueous secondary battery negative electrode slurry can be improved.
• the water-soluble polymer preferably contains an ether group. If the water-soluble polymer contains an ether group, the dispersibility and storage stability of the carbon nanotube dispersion can be improved, and the viscosity stability of the non-aqueous secondary battery negative electrode slurry containing the carbon nanotube dispersion can be improved. Furthermore, the cycle characteristics of the non-aqueous secondary battery provided with the non-aqueous secondary battery negative electrode produced using the non-aqueous secondary battery negative electrode slurry can be improved.
• the mass ratio of the carbon nanotubes to the water-soluble polymer is preferably 0.1 or more and 10 or less. If the mass ratio of carbon nanotubes to the water-soluble polymer is within the above range, the storage stability of the carbon nanotube dispersion can be improved.
• Another object of the present invention is to advantageously solve the above-mentioned problems, and the present invention is a negative electrode slurry for a non-aqueous secondary battery comprising a negative electrode active material and the carbon nanotube dispersion. .
• a non-aqueous secondary battery negative electrode slurry has excellent viscosity stability and can form a negative electrode capable of exhibiting excellent cycle characteristics in a non-aqueous secondary battery. can be
• the negative electrode active material preferably contains a silicon-based negative electrode active material. If the negative electrode active material includes a silicon-based negative electrode active material (silicon-containing negative electrode active material), a non-aqueous secondary battery comprising a non-aqueous secondary battery negative electrode prepared using a non-aqueous secondary battery negative electrode slurry can be obtained. It is possible to increase the capacity. Since the silicon-based negative electrode active material expands and contracts significantly during charging and discharging, the negative electrode slurry of the present invention is prepared using the above-described carbon nanotube dispersion of the present invention. Even in the case of using a silicon-based negative electrode active material as a negative electrode, it is possible to suppress deterioration of the conductivity of the electrode mixture layer and form a negative electrode capable of exhibiting excellent cycle characteristics in a non-aqueous secondary battery.
• the slurry for a non-aqueous secondary battery negative electrode of the present invention further comprises a particulate polymer, and the particulate polymer comprises a carboxylic acid group-containing monomer unit, an aromatic vinyl monomer unit and a conjugated diene monomer. It preferably contains units.
• the non-aqueous secondary battery negative electrode slurry described above can improve the cycle characteristics of a non-aqueous secondary battery having a non-aqueous secondary battery negative electrode prepared using the non-aqueous secondary battery negative electrode slurry.
• the polymer "comprising a monomer unit” means that "a repeating unit derived from the monomer is contained in the polymer obtained using the monomer". do.
• the content ratio of the carboxylic acid group-containing monomer unit in the particulate polymer is 100% by mass of all repeating units contained in the particulate polymer, It is preferably 3% by mass or more and 30% by mass or less. If the content ratio of the carboxylic acid group-containing monomer unit in the particulate polymer is within the above range, a non-aqueous secondary battery negative electrode prepared using the non-aqueous secondary battery negative electrode slurry is prepared. Cycle characteristics of the secondary battery can be further improved.
• the content of repeating units (monomer units) in the polymer can be measured using nuclear magnetic resonance (NMR) methods such as 1 H-NMR and 13 C-NMR.
• the HSP distance (R c ) between the Hansen solubility parameter (HSP d ) of the water-soluble polymer and the Hansen solubility parameter (HSP b ) of the particulate polymer is , 7.0 MPa 1/2 or less.
• the HSP distance (R c ) is equal to or less than the above upper limit, the cycle characteristics of a non-aqueous secondary battery having a negative electrode for a non-aqueous secondary battery produced using the slurry for a non-aqueous secondary battery negative electrode can be improved.
• HSP b the "Hansen Solubility Parameter (HSP b ) of a particulate polymer" is composed of the polar term ⁇ p4 , the dispersion term ⁇ d4 and the hydrogen bonding term ⁇ h4 .
• ⁇ p4 ”, “ ⁇ d4 ” and “ ⁇ h4 ” can be specified using the method described in the Examples.
• an object of the present invention is to advantageously solve the above-mentioned problems, and the present invention comprises a current collector and the slurry for a non-aqueous secondary battery negative electrode on the current collector. and a formed negative electrode mixture layer.
• a negative electrode for a non-aqueous secondary battery can be a negative electrode for a non-aqueous secondary battery that can exhibit excellent cycle characteristics in the non-aqueous secondary battery.
• the current collector is preferably an electrolytic copper foil. If the current collector is an electrolytic copper foil, the peel strength of the electrode mixture layer from the current collector can be improved.
• Another object of the present invention is to advantageously solve the above problems, and the present invention is a non-aqueous secondary battery comprising the negative electrode for a non-aqueous secondary battery.
• a non-aqueous secondary battery can be a non-aqueous secondary battery with excellent cycle characteristics.
• the carbon nanotube dispersion liquid which is excellent in the dispersibility and storage stability of a carbon nanotube can be provided.
• the slurry for nonaqueous secondary battery negative electrodes containing this carbon nanotube dispersion liquid can be provided.
• the CNT dispersion of the present invention is not particularly limited, and is used as a material for producing, for example, a non-aqueous secondary battery negative electrode slurry (hereinafter sometimes simply referred to as "negative electrode slurry").
• the negative electrode slurry of the present invention is prepared using the CNT dispersion of the present invention.
• the negative electrode for a non-aqueous secondary battery of the present invention (hereinafter sometimes simply referred to as "negative electrode”) is characterized by comprising a negative electrode mixture layer formed using the negative electrode slurry of the present invention.
• a non-aqueous secondary battery of the present invention is characterized by comprising the negative electrode of the present invention.
• the CNT dispersion of the present invention can be used as a raw material for composite materials containing resin and CNT, and for manufacturing electronic products.
• the CNT dispersion of the present invention contains CNTs, a water-soluble polymer having acid functional groups, water, and optionally other ingredients. Note that the CNT dispersion does not normally contain electrode active materials (positive electrode active material, negative electrode active material).
• the HSP distance (R a ) between the Hansen solubility parameter (HSP c ) of the CNT and the Hansen solubility parameter (HSP d ) of the water-soluble polymer is 7.0 MPa 1/2 or less. is.
• the CNT dispersion has excellent dispersibility and storage stability. Further, with the above CNT dispersion, it is possible to obtain a negative electrode slurry that is excellent in viscosity stability and capable of forming a negative electrode capable of exhibiting excellent cycle characteristics in a secondary battery.
• the HSP distance (R a ) is the HSP c of the CNT (polar term ⁇ p1 , the dispersion term ⁇ d1 , the hydrogen bond term ⁇ h1 ) and the HSP d of the water-soluble polymer (polar term ⁇ p2 , dispersion term ⁇ d2 , It can be adjusted by appropriately changing the hydrogen bond term ⁇ h2 ).
• the HSP of the polymer can be adjusted by appropriately selecting and combining monomers with known HSPs and polymerizing them. For HSPs of monomers, for example, the database of "HSPiP ver.5.3.04" can be referred to.
• the HSP distance (R a ) is preferably 6.0 MPa 1/2 or less, more preferably 5.0 MPa 1/2 or less, and even more preferably 4.5 MPa 1/2 or less. If the HSP distance (R a ) is at least the above lower limit, the dispersibility and storage stability of the CNT dispersion can be improved, and the viscosity stability of the negative electrode slurry containing the CNT dispersion can be improved. Cycle characteristics of a secondary battery including a negative electrode produced using slurry can be improved. On the other hand, the HSP distance (R a ) is, for example, 0.1 MPa 1/2 or more, and may be 1.0 MPa 1/2 or more.
• the CNT dispersion of the present invention has a Hansen solubility parameter (HSP d ) of a water-soluble polymer, a polarity term ⁇ p3 of 10.7, a dispersion term ⁇ d3 of 18.6, and a hydrogen bonding term ⁇ h3 of 7.0.
• the HSP distance (R b ) to the Hansen solubility parameter (HSP m ) of the material is preferably 8.0 MPa 1/2 or less, more preferably 5.0 MPa 1/2 or less, and 4.0 MPa 1 /2 or less is more preferable.
• HSP d Hansen solubility parameter close to the Hansen solubility parameter
• the HSP distance (R b ) is, for example, 0.1 MPa 1/2 or more, and may be 1.0 MPa 1/2 or more.
• the HSP distance (R b ) can be adjusted by appropriately changing the HSP d (polar term ⁇ p2 , dispersion term ⁇ d2 , hydrogen bonding term ⁇ h2 ) of the water-soluble polymer.
• HSP d polar term ⁇ p2 , dispersion term ⁇ d2 , hydrogen bonding term ⁇ h2
• Examples of materials having a polar term ⁇ p3 of 10.7, a dispersion term ⁇ d3 of 18.6, and a hydrogen bonding term ⁇ h3 of 7.0 include electrolytic copper foil. Electrodeposited copper foil means that, for example, a metal drum is immersed in an electrolytic solution in which copper ions are dissolved, and an electric current is applied while rotating the drum to deposit copper on the surface of the drum. It is a copper foil obtained by peeling.
• the CNT dispersion of the present invention preferably has a pH of 6 or more, more preferably 7 or more, still more preferably 7.5 or more, preferably 10 or less, and 9 or less. It is more preferably 8.5 or less. If the pH is within the above range, the viscosity stability of the negative electrode slurry containing the CNT dispersion can be improved, and the cycle characteristics of the secondary battery including the negative electrode produced using the negative electrode slurry can be improved.
• CNTs may be single-walled CNTs or multi-walled CNTs. Moreover, as CNTs, single-walled CNTs and multi-walled CNTs may be used in combination.
• the average diameter of CNTs is obtained by observing CNTs with a transmission electron microscope (TEM), measuring the diameter (outer diameter) of 50 CNTs from the obtained TEM image, and calculating the arithmetic mean of these measured values. can be obtained as a value.
• TEM transmission electron microscope
• the CNT preferably has a ratio of G-band peak intensity to D-band peak intensity in the Raman spectrum (G/D ratio) of 0.4 or more, more preferably 0.5 or more, and 0.6 or more. It is even more preferable to have If the G/D ratio of CNT is equal to or higher than the lower limit, the cycle characteristics of the secondary battery can be further improved.
• the upper limit of the G/D ratio of CNT is not particularly limited, it is, for example, 200 or less.
• the "G/D ratio" of CNTs is the Raman spectrum obtained by measuring the Raman spectrum of CNTs using a microscopic laser Raman spectrophotometer (Nicolet Almega XR manufactured by Thermo Fisher Scientific Co., Ltd.). can be calculated as a ratio of the intensity of the G band peak observed near 1590 cm ⁇ 1 and the intensity of the D band peak observed near 1340 cm ⁇ 1 .
• the content of CNTs in the CNT dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and more preferably 0.1% by mass or more, based on the total mass of the CNT dispersion as 100% by mass. It is more preferably 7% by mass or more. If the content of CNTs in the CNT dispersion is at least the above lower limit, the productivity of products obtained using the CNT dispersion can be improved. On the other hand, the content of CNTs in the CNT dispersion is, for example, 10.0% by mass or less, may be 5.0% by mass or less, or 2.0% by mass or less, where the mass of the entire CNT dispersion is 100% by mass. can be
• the CNTs are not particularly limited, and those synthesized using known CNT synthesis methods such as the arc discharge method, laser ablation method, and chemical vapor deposition method (CVD method) can be used.
• the polarity term ⁇ p1 of CNT is, for example, 5 or more, may be 5.5 or more, or may be 6.0 or more, and may be, for example, 8.0 or less, may be 7.5 or less, or may be 7.0 or less.
• the dispersion term ⁇ d1 of CNT is, for example, 15.0 or more, may be 17.0 or more, may be 18.5 or more, may be 23.0 or less, may be 21.0 or less, or may be 19.4 It can be below.
• the hydrogen bonding term ⁇ h1 of CNT is, for example, 3.0 or more, may be 4.0 or more, or may be 4.5 or more, for example, may be 7.0 or less, or may be 5.5 or less. It may be 8 or less.
• the water-soluble polymer has acid functional groups and can function as a dispersant.
• the CNT dispersion of the present invention may contain a dispersant other than the water-soluble polymer.
• a water-soluble polymer having an HSP distance (R a ) exceeding 7.0 MPa 1/2 or a HSP distance of 7.0 MPa 1/2 is used as a dispersing agent other than the water-soluble polymer. It may further comprise a water-soluble polymer with no acid functionality below.
• the polar term ⁇ p2 of the water-soluble polymer is, for example, 3.0 or more, may be 3.5 or more, or may be 6.0 or more, and may be, for example, 10.0 or less, or may be 9.0 or less. It may be 0 or less.
• the dispersion term ⁇ d2 of the water-soluble polymer is, for example, 15.0 or more, may be 17.0 or more, or may be 18.0 or more, and may be, for example, 23.0 or less, or may be 21.0 or less. It may be 0 or less.
• the hydrogen bond term ⁇ h2 of the water-soluble polymer is preferably 5.0 or more, more preferably 6.0 or more, and even more preferably 6.5 or more.
• the hydrogen bond term ⁇ h2 is at least the above lower limit, the dispersibility and storage stability of the CNT dispersion can be improved. Although the reason for this has not been clarified, it is presumed that it becomes easier to form hydrogen bonds with water molecules, thereby improving the affinity with water.
• the hydrogen bond term ⁇ h2 of the water-soluble polymer is, for example, 12.0 or less, may be 10.0 or less, or may be 9.5 or less.
• the "acid functional group" possessed by the water-soluble polymer includes a salt neutralized with a base.
• acid functional groups include --COOH as well as neutralized forms such as the lithium carboxylate group (-COO ⁇ Li + ).
• the water-soluble polymer can improve the dispersibility and storage stability of the CNT dispersion, can improve the viscosity stability of the negative electrode slurry containing the CNT dispersion, and can improve the negative electrode produced using the negative electrode slurry.
• At least a portion of the acid functional groups are preferably alkali metal bases or ammonium bases, since the cycle characteristics of the provided secondary battery can be improved. All of the acid functional groups may be alkali metal bases or ammonium bases.
• Alkali metal bases include, for example, lithium metal bases, sodium metal bases, potassium metal bases, and the like. You may combine two or more types of these.
• the acid functionality of the water-soluble polymer is preferably a sulfonic acid group. If the acid functional group is a sulfonic acid group, the dispersibility and storage stability of the CNT dispersion can be improved, and the viscosity stability of the negative electrode slurry containing the CNT dispersion can be improved. It is possible to improve the cycle characteristics of the secondary battery including the negative electrode produced by the method.
• the water-soluble polymer contained in the CNT dispersion of the present invention will be described by exemplifying the first mode, the second mode, and the third mode, but the water-soluble polymer is limited to these. not a thing
• the first form of water-soluble polymer comprises carboxylic acid group-containing monomeric units and conjugated diene monomeric units.
• the water-soluble polymer of the first form may contain repeating units (other repeating units) other than the carboxylic acid group-containing monomer units and the conjugated diene monomer units.
• a carboxylic acid group-containing monomeric unit is a repeating unit containing a carboxylic acid group (--COOH).
• carboxylic acid groups of the carboxylic acid group-containing monomer units are sodium carboxylate groups (-COO - Na + ), lithium carboxylate groups (-COO - Li + ).
• carboxylate ammonium group (—COO ⁇ NH 4 + ).
• the dispersibility and storage stability of the CNT dispersion can be further improved, and the viscosity stability of the negative electrode slurry containing this CNT dispersion can be improved. can be further improved, and the cycle characteristics of a secondary battery including a negative electrode produced using this negative electrode slurry can be further improved.
• Carboxylic acid group-containing monomers capable of forming the carboxylic acid group-containing monomer units of the water-soluble polymer of the first embodiment include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives and the like.
• Monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid and the like.
• Monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxyacrylic acid and the like.
• Dicarboxylic acids include maleic acid, fumaric acid, itaconic acid and the like.
• Dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoro maleate.
• Examples include maleic acid monoesters such as alkyl.
• Acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
• an acid anhydride that produces a carboxylic acid group by hydrolysis can also be used.
• the carboxylic acid group-containing monomers may be used singly or in combination of two or more.
• acrylic acid and methacrylic acid are preferable from the viewpoint of improving the cycle characteristics of the secondary battery. That is, the water-soluble polymer of the first form preferably contains at least one of an acrylic acid unit and a methacrylic acid unit as the carboxylic acid group-containing monomer unit.
• the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the first form is 30% by mass or more based on 100% by mass of the total repeating units contained in the water-soluble polymer of the first form. is preferably 40% by mass or more, more preferably 50% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, 80% by mass is more preferably 70% by mass or less. Further, the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the first embodiment is 30 mol% or more based on 100 mol% of all repeating units contained in the water-soluble polymer of the first embodiment.
• the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the first embodiment is within the above range, the dispersibility and storage stability of the CNT dispersion can be further improved, and the CNT dispersion can be The viscosity stability of the negative electrode slurry containing the liquid can be further improved, and the cycle characteristics of the secondary battery including the negative electrode produced using this negative electrode slurry can be further improved.
• Conjugated diene monomers capable of forming the conjugated diene monomer unit of the water-soluble polymer of the first form include, for example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2 ,3-dimethyl-1,3-butadiene and 1,3-pentadiene. These may be used individually by 1 type, and may be used in combination of 2 or more types. Among these, 1,3-butadiene and isoprene are preferred, and isoprene is more preferred. That is, the water-soluble polymer of the first form preferably contains at least one of 1,3-butadiene units and isoprene units as conjugated diene monomer units, and more preferably contains isoprene units.
• the content of the conjugated diene monomer unit in the water-soluble polymer of the first form is 5% by mass or more when the total repeating units contained in the water-soluble polymer of the first form is 100% by mass. It is preferably 10% by mass or more, still more preferably 20% by mass or more, still more preferably 30% by mass or more, preferably 70% by mass or less, and 60% by mass or less. It is more preferable that the content is 50% by mass or less. Further, the content of the conjugated diene monomer unit in the water-soluble polymer of the first form is 10 mol% or more with respect to 100 mol% of the total repeating units contained in the water-soluble polymer of the first form.
• the content of the conjugated diene monomer unit in the water-soluble polymer of the first embodiment is within the above range, the dispersibility and storage stability of the CNT dispersion can be further improved, and the CNT dispersion can be It is possible to further improve the viscosity stability of the negative electrode slurry containing the negative electrode slurry, and further improve the cycle characteristics of the secondary battery provided with the negative electrode produced using this negative electrode slurry.
• the other repeating units that the water-soluble polymer of the first embodiment may contain are not particularly limited, and the above-described carboxylic acid group-containing Monomer units derived from known monomers (other monomers) copolymerizable with monomers and conjugated diene monomers are included. Other monomers may be used singly or in combination of two or more.
• the content of other repeating units in the water-soluble polymer of the first form is 100% by mass, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and 0 % by weight is particularly preferred.
• the content of other repeating units in the water-soluble polymer of the first form is 20 mol% or less when the total repeating units contained in the water-soluble polymer of the first form are taken as 100 mol%. It is preferably 10 mol % or less, still more preferably 5 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol %.
• the total content of the carboxylic acid group-containing monomer unit and the conjugated diene monomer unit in the water-soluble polymer of the first form is the total repeating units contained in the water-soluble polymer of the first form.
• 100% by mass it is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 99% by mass or more. % is particularly preferred.
• the total content ratio of the carboxylic acid group-containing monomer unit and the conjugated diene monomer unit in the water-soluble polymer of the first form is 100% of all repeating units contained in the water-soluble polymer of the first form.
• the mol% is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 99 mol% or more, and 100 mol%. is particularly preferred.
• the second form of water-soluble polymer contains a sulfonic acid group-containing monomer unit and an alkylene oxide structure-containing monomer unit.
• the water-soluble polymer of the second form may contain repeating units (other repeating units) other than the sulfonic acid group-containing monomer units and the alkylene oxide structure-containing monomer units.
• a sulfonic acid group-containing monomer unit is a repeating unit containing a sulfonic acid group (--SO 3 H).
• some or all of the sulfonic acid groups of the sulfonic acid group-containing monomer units are sodium sulfonate groups (—SO 3 ⁇ Na + ), lithium sulfonate groups (—SO 3 ⁇ Li + ) and ammonium sulfonate group (—SO 3 ⁇ NH 4 + ).
• the dispersibility and storage stability of the CNT dispersion can be further improved, and the viscosity stability of the negative electrode slurry containing this CNT dispersion can be improved. can be further improved, and the cycle characteristics of a secondary battery including a negative electrode produced using this negative electrode slurry can be further improved.
• Examples of the sulfonic acid group-containing monomer capable of forming the sulfonic acid group-containing monomer unit of the water-soluble polymer of the second form include vinylsulfonic acid, methylvinylsulfonic acid, (meth)allylsulfonic acid, Styrenesulfonic acid, ethyl (meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, salts thereof, and the like.
• (meth)allyl means allyl and/or methallyl.
• the sulfonic acid group-containing monomers may be used singly or in combination of two or more.
• styrenesulfonic acid is preferable from the viewpoint of improving the cycle characteristics of the secondary battery. That is, the water-soluble polymer of the second form preferably contains styrenesulfonic acid units as the sulfonic acid group-containing monomer units.
• the content of the sulfonic acid group-containing monomer unit in the water-soluble polymer of the second form is 40% by mass or more when the total repeating units contained in the water-soluble polymer of the second form is 100% by mass. is preferably 50% by mass or more, more preferably 55% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, 80% by mass is more preferably 70% by mass or less.
• the content of the sulfonic acid group-containing monomer units in the water-soluble polymer of the second form is 40 mol% or more based on 100 mol% of the total repeating units contained in the water-soluble polymer of the second form.
• the dispersibility and storage stability of the CNT dispersion can be further improved, and the CNT dispersion can be The viscosity stability of the negative electrode slurry containing the liquid can be further improved, and the cycle characteristics of the secondary battery including the negative electrode produced using this negative electrode slurry can be further improved.
• alkylene oxide structure-containing monomer unit The alkylene oxide structure-containing monomer unit of the water-soluble polymer of the second form is a monomer unit containing a structure represented by the following general formula (I). [In Formula (I), m is an integer of 1 or more, and n is an integer of 1 or more. ]
• the dispersibility and storage stability of the CNT dispersion can be further improved, and a negative electrode slurry containing this CNT dispersion can be provided. Further, the viscosity stability of the negative electrode slurry can be further improved, and the cycle characteristics of a secondary battery having a negative electrode produced using this negative electrode slurry can be further improved.
• the integer m is preferably 2 or more and 5 or less, more preferably 2 or 3, and even more preferably 2.
• the monomer unit containing the structural unit represented by general formula (I) is called the ethylene oxide structure-containing monomer unit.
• the monomer unit containing the structural unit represented by the general formula (I) is referred to as the propylene oxide structure-containing monomer unit.
• the integer m is equal to or less than the above upper limit, the dispersibility and storage stability of the CNT dispersion can be further improved, and the viscosity stability of the negative electrode slurry containing the CNT dispersion can be further improved. It is possible to further improve the cycle characteristics of the secondary battery including the negative electrode produced using the slurry.
• the integer m is 2 that is, when the ethylene oxide structure-containing monomer unit is contained in the water-soluble polymer of the second form, the water-soluble polymer of the second form has an appropriate hydrophilicity.
• the water-soluble polymer of the second form can be enhanced in affinity for water.
• the dispersibility and storage stability of the CNT dispersion can be particularly improved.
• the viscosity stability of the negative electrode slurry containing the liquid can be particularly improved, and the cycle characteristics of the secondary battery including the negative electrode produced using this negative electrode slurry can be particularly improved.
• the water-soluble polymer of the second form may contain multiple types of alkylene oxide structure-containing monomer units.
• both the ethylene oxide structure-containing monomer unit and the propylene oxide structure-containing monomer unit may be contained in the water-soluble polymer of the second form.
• the integer n that defines the repeating number of the monomer units containing the structure that can be represented by the formula (I) is preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. Preferably, it is 2 or more. That is, the alkylene oxide structure-containing monomer unit contained in the water-soluble polymer of the second embodiment preferably contains a polyalkylene oxide structural unit in which the alkylene oxide structural unit is repeated n times. In addition, some or all of the hydrogen atoms in the alkylene oxide structural unit may be substituted with optional substituents.
• the repeating number n for each alkylene oxide structure-containing monomer unit may be the same or different.
• the number average value of all repetition numbers n is preferably within the preferred range described above, and more preferably all repetition numbers n are within the preferred range described above.
• Examples of the alkylene oxide structure-containing monomer capable of forming the alkylene oxide structure-containing monomer unit of the water-soluble polymer of the second form include monomers represented by the following general formula (II). .
• R 1 is a (meth)acryloyl group
• R 2 represents a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms.
• the number of carbon atoms in the alkyl group is preferably 2 or more and 5 or less, preferably 2 or 3, more preferably 2.
• m and n are the same as m and n in general formula (I).
• Examples of linear or branched alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups. More specifically, the monomer represented by the general formula (II) is not particularly limited and includes ethoxypolyethylene glycol (meth)acrylate such as methoxypolyethyleneglycol (meth)acrylate and ethoxydiethyleneglycol (meth)acrylate. Acrylate, polypropylene glycol mono(meth)acrylate, methoxypolypropylene glycol (meth)acrylate and the like.
• the monomer represented by formula (II) is preferably ethoxypolyethylene glycol (meth)acrylate, more preferably ethoxydiethyleneglycol (meth)acrylate, and particularly preferably ethoxydiethyleneglycol acrylate.
• (meth)acrylate means acrylate or methacrylate
• (meth)acryloyl means acryloyl or methacryloyl.
• the content of the alkylene oxide structure-containing monomer unit in the water-soluble polymer of the second form is 5% by mass or more based on 100% by mass of all repeating units contained in the water-soluble polymer of the second form. is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, preferably 60% by mass or less, 50% by mass It is more preferably 45% by mass or less, more preferably 45% by mass or less. Further, the content ratio of the alkylene oxide structure-containing monomer unit in the water-soluble polymer of the second form is 5 mol% or more based on 100 mol% of the total repeating units contained in the water-soluble polymer of the second form.
• the content of the alkylene oxide structure-containing monomer unit in the water-soluble polymer of the second embodiment is within the above range, the dispersibility and storage stability of the CNT dispersion can be further improved, and the CNT dispersion can be The viscosity stability of the negative electrode slurry containing the liquid can be further improved, and the cycle characteristics of the secondary battery including the negative electrode produced using this negative electrode slurry can be further improved.
• the other repeating units that the water-soluble polymer of the second embodiment may contain are not particularly limited, and the above-described sulfonic acid Examples thereof include monomer units derived from known monomers (other monomers) copolymerizable with group-containing monomer units and alkylene oxide structure-containing monomer units. Other monomers may be used singly or in combination of two or more.
• the content of other repeating units in the water-soluble polymer of the second form should be 100% by mass, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and 0 % by weight is particularly preferred.
• the content of other repeating units in the water-soluble polymer of the second form is 20 mol% or less when the total repeating units contained in the water-soluble polymer of the second form are taken as 100 mol%. It is preferably 10 mol % or less, still more preferably 5 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol %.
• the total content of the sulfonic acid group-containing monomer units and the alkylene oxide structure-containing monomer units in the water-soluble polymer of the second form is the total number of repeats contained in the water-soluble polymer of the second form.
• the unit is 100% by mass, it is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 99% by mass or more, 100% by mass is particularly preferred.
• the total content of the sulfonic acid group-containing monomer units and the alkylene oxide structure-containing monomer units in the water-soluble polymer of the second form is the total repeating units contained in the water-soluble polymer of the second form. 100 mol%, preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, even more preferably 99 mol% or more, 100 Mole % is particularly preferred.
• the water-soluble polymer of the third form contains a carboxylic acid group-containing monomer unit and a (meth)acrylic acid alkyl ester monomer unit.
• the water-soluble polymer of the third embodiment may contain repeating units (other repeating units) other than the carboxylic acid group-containing monomer units and the (meth)acrylic acid alkyl ester monomer units.
• (meth)acryl means acryl and/or methacryl.
• Examples of the carboxylic acid group-containing monomer capable of forming the carboxylic acid group-containing monomer unit of the water-soluble polymer of the third embodiment include the carboxylic acids described above in the section of "Water-soluble polymer of the first embodiment" Examples thereof include those similar to the group-containing monomer.
• the carboxylic acid group-containing monomers may be used alone or in combination of two or more.
• the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the third form is 10% by mass or more, with the total repeating units contained in the water-soluble polymer of the third form being 100% by mass. is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and 35% by mass More preferably: Further, the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the third embodiment is 10 mol% or more based on 100 mol% of the total repeating units contained in the water-soluble polymer of the third embodiment.
• the content of the carboxylic acid group-containing monomer unit in the water-soluble polymer of the third embodiment is within the above range, the dispersibility and storage stability of the CNT dispersion can be further improved.
• the viscosity stability of the negative electrode slurry containing the liquid can be further improved, and the cycle characteristics of the secondary battery including the negative electrode produced using this negative electrode slurry can be further improved.
• Examples of (meth)acrylic acid alkyl ester monomers capable of forming the (meth)acrylic acid alkyl ester monomer units of the water-soluble polymer of the third embodiment include methyl acrylate, ethyl acrylate, and n-propyl acrylate.
• Acrylic acid alkyl ester methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl Examples include methacrylic acid alkyl esters such as methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate.
• the (meth)acrylic acid alkyl ester monomers may be used singly or in combination of two or more. And among these, ethyl acrylate is preferable. That is, the water-soluble polymer of the third form preferably contains an ethyl acrylate unit as a (meth)acrylic acid alkyl ester monomer unit.
• the content ratio of the (meth)acrylic acid alkyl ester monomer unit in the water-soluble polymer of the third form is 50% by mass when the total repeating units contained in the water-soluble polymer of the third form is 100% by mass. is preferably 60% by mass or more, more preferably 65% by mass or more, more preferably 65% by mass or more, preferably 90% by mass or less, more preferably 80% by mass or less, It is more preferably 75% by mass or less.
• the content ratio of the (meth)acrylic acid alkyl ester monomer unit in the water-soluble polymer of the third embodiment is 50, assuming that the total repeating units contained in the water-soluble polymer of the third embodiment is 100 mol%.
• the content of the (meth)acrylic acid alkyl ester monomer unit in the water-soluble polymer of the third embodiment is within the above range, the dispersibility and storage stability of the CNT dispersion can be further improved, and The viscosity stability of the negative electrode slurry containing this CNT dispersion can be further improved, and the cycle characteristics of a secondary battery having a negative electrode produced using this negative electrode slurry can be further improved.
• the other repeating units that the water-soluble polymer of the third embodiment may contain are not particularly limited, and may be any of the above-described repeating units.
• Other monomers may be used singly or in combination of two or more.
• the content of other repeating units in the water-soluble polymer of the third form is 100% by mass, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and 0 % by weight is particularly preferred.
• the content of other repeating units in the water-soluble polymer of the third embodiment is 20 mol% or less when the total repeating units contained in the water-soluble polymer of the third embodiment are taken as 100 mol%. It is preferably 10 mol % or less, still more preferably 5 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol %.
• the total content of the carboxylic acid group-containing monomer unit and the (meth)acrylic acid alkyl ester monomer unit in the water-soluble polymer of the third embodiment is It is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and 99% by mass or more, based on the total repeating units containing 100% by mass. More preferably, it is particularly preferably 100% by mass.
• the total content of the carboxylic acid group-containing monomer unit and the (meth)acrylic acid alkyl ester monomer unit in the water-soluble polymer of the third embodiment is Based on 100 mol% of all repeating units, the content is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, and even more preferably 99 mol% or more. 100 mol % is particularly preferred.
• the method for preparing the water-soluble polymer is not particularly limited.
• a water-soluble polymer can be obtained, for example, by polymerizing a monomer composition containing one or more monomers in an aqueous solvent. The resulting polymer may optionally be hydrogenated. The content ratio of each monomer in the monomer composition can be determined according to the content ratio of desired repeating units (monomer units) in the polymer.
• the polymerization mode is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method and an emulsion polymerization method can be used.
• any reaction such as ionic polymerization, radical polymerization, living radical polymerization, various types of condensation polymerization, and addition polymerization can be used.
• known emulsifiers and polymerization initiators can be used as necessary.
• Hydrogenation can also be carried out by known methods.
• neutralization is performed with an aqueous sodium hydroxide solution, an aqueous lithium hydroxide solution, an aqueous ammonia, or the like to prepare the above-mentioned water-soluble polymer having a neutralized acid functional group. good.
• the content of the water-soluble polymer in the CNT dispersion is not particularly limited. more preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 0.8% by mass or less. If the content of the water-soluble polymer in the CNT dispersion is at least the above lower limit, the dispersibility of the CNT dispersion can be improved. On the other hand, when the content of the water-soluble polymer in the CNT dispersion is equal to or less than the above upper limit, the storage stability of the CNT dispersion can be improved.
• CNT dispersion may contain other than the CNTs, the water-soluble polymer, and water are not particularly limited, but include a conductive material other than the CNTs, a dispersion medium other than water, and the "non-aqueous secondary battery negative electrode slurry.” components other than the negative electrode active material, which will be described later in the section above.
• the conductive material other than CNT is not particularly limited, but carbon black (acetylene black, Ketjenblack (registered trademark), furnace black, etc.), graphite, carbon flakes, and carbon nanofibers can be used, for example.
• a dispersion medium other than water a known organic solvent compatible with water can be used.
• another component may be used individually by 1 type, and may be used in combination of 2 or more types.
• a method for preparing the CNT dispersion is not particularly limited.
• a CNT dispersion can be prepared by mixing CNTs, a predetermined water-soluble polymer, water, and other components used as necessary.
• a known mixing device such as a disper, a homomixer, a planetary mixer, a kneader, a ball mill, or a bead mill can be used.
• the negative electrode slurry of the present invention contains the above-described CNT dispersion and a negative electrode active material, and optionally contains optional components such as a binder.
• the negative electrode slurry of the present invention contains CNTs, a water-soluble polymer, and water, and optionally contains optional components such as a binder.
• the negative electrode slurry containing the above-described CNT dispersion can form a negative electrode that has excellent viscosity stability and allows the secondary battery to exhibit excellent cycle characteristics.
• ⁇ Negative electrode active material> A known negative electrode active material can be used without particular limitation as the negative electrode active material to be mixed in the negative electrode slurry.
• negative electrode active materials used in lithium ion secondary batteries are not particularly limited, but include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials combining these.
• the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton and capable of inserting lithium (also referred to as “doping”).
• Examples of carbon-based negative electrode active materials include carbonaceous materials and graphite quality materials.
• Examples of the carbonaceous material include graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
• graphitizable carbon includes, for example, carbon materials made from tar pitch obtained from petroleum or coal. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolytic vapor growth carbon fibers.
• Examples of the non-graphitic carbon include phenolic resin sintered material, polyacrylonitrile-based carbon fiber, pseudoisotropic carbon, furfuryl alcohol resin sintered material (PFA), and hard carbon.
• examples of graphite materials include natural graphite and artificial graphite.
• artificial graphite for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB obtained by heat-treating MCMB at 2000 ° C. or higher, mesophase pitch-based carbon fiber at 2000 ° C.
• examples thereof include graphitized mesophase pitch-based carbon fibers heat-treated as described above.
• the metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of intercalating lithium in its structure, and the theoretical electric capacity per unit mass when lithium is intercalated is 500 mAh / g or more.
• the metal-based active material for example, lithium metal, elemental metals capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn , Sr, Zn, Ti, etc.) and alloys thereof, and their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. are used.
• a silicon-based negative electrode active material (a negative electrode active material containing silicon) is preferable as the metal-based negative electrode active material. This is because the use of the silicon-based negative electrode active material can increase the capacity of the secondary battery.
• the silicon-based negative electrode active material expands and contracts significantly during charging and discharging, the negative electrode slurry of the present invention is prepared using the above-described CNT dispersion of the present invention. Even when a silicon-based negative electrode active material is used, a decrease in the conductivity of the electrode mixture layer is suppressed, and a negative electrode capable of exhibiting excellent cycle characteristics in a secondary battery can be formed.
• Silicon-based negative electrode active materials include, for example, silicon (Si), alloys containing silicon, SiO, SiO x , and composites of Si-containing materials and conductive carbon obtained by coating or combining Si-containing materials with conductive carbon. etc.
• the proportion of the silicon-based negative electrode active material in the negative electrode active material is preferably 1% by mass or more, more preferably 3% by mass or more, and more preferably 20% by mass, based on 100% by mass of the entire negative electrode active material. It is preferably 15% by mass or less, more preferably 15% by mass or less. If the ratio of the silicon-based negative electrode active material is 1% by mass or more, the capacity of the secondary battery can be sufficiently increased, and if it is 20% by mass or less, the cycle characteristics of the secondary battery can be further improved.
• the particle size of the negative electrode active material is not particularly limited, and may be the same as that of conventionally used negative electrode active materials. Also, the amount of the negative electrode active material in the negative electrode slurry is not particularly limited, and can be within the conventionally used range.
• One type of the negative electrode active material may be used alone, or two or more types may be used in combination. preferably contains both a carbon-based negative electrode active material made of a graphite material and a silicon-based negative electrode active material.
• the CNT dispersion As the CNT dispersion, the CNT dispersion of the present invention described above can be used.
• the content of CNTs in the negative electrode slurry is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more when the content of the negative electrode active material is 100 parts by mass. is more preferably 0.08 parts by mass or more, preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and 0.15 parts by mass or less is more preferred.
• the content of the water-soluble polymer in the negative electrode slurry is preferably 0.005 parts by mass or more, and is preferably 0.01 parts by mass or more when the content of the negative electrode active material is 100 parts by mass. More preferably 0.02 parts by mass or more, preferably 0.2 parts by mass or less, more preferably 0.1 parts by mass or less, and 0.05 parts by mass or less is more preferable.
• the negative electrode slurry examples include binders, viscosity modifiers, reinforcing materials, antioxidants, and electrolytic solution additives that have the function of suppressing decomposition of the electrolytic solution. These optional components may be used singly or in combination of two or more.
• the negative electrode slurry preferably contains a binder from the viewpoint of improving the cycle characteristics of the secondary battery.
• the binder is not particularly limited, and any binder that can be used as a negative electrode binder can be used.
• a binder a carboxylic acid group-containing monomer unit and an aromatic vinyl monomer unit are used, since the cycle characteristics of a secondary battery having a negative electrode prepared using the negative electrode slurry can be further improved. , and a conjugated diene monomer unit.
• a particulate polymer that can be used as a binder can be prepared by a known method.
• the HSP distance (R c ) between the Hansen solubility parameter (HSP d ) of the water-soluble polymer and the Hansen solubility parameter (HSP b ) of the particulate polymer is 7.0 MPa. It is preferably 1/2 or less, more preferably 5.0 MPa 1/2 or less.
• the HSP distance (R c ) is equal to or less than the above upper limit, the cycle characteristics of the secondary battery including the negative electrode produced using the negative electrode slurry can be further improved.
• the HSP distance (R c ) is, for example, 0.1 MPa 1/2 or more, and may be 1.0 MPa 1/2 or more.
• the HSP distance (R c ) is the HSP d of the water-soluble polymer (polar term ⁇ p2 , dispersion term ⁇ d2 , hydrogen bonding term ⁇ h2 ), and the HSP b of the particulate polymer (polar term ⁇ p4 , dispersion It can be adjusted by appropriately changing the term ⁇ d4 and the hydrogen bond term ⁇ h4 ).
• the polar term ⁇ p4 of the particulate polymer is, for example, 5.0 or more, may be 6.5 or more, and may be, for example, 8.0 or less, and may be 7.5 or less.
• the dispersion term ⁇ d4 of the particulate polymer is, for example, 17.0 or more, may be 18.5 or more, and may be, for example, 21.0 or less, and may be 19.5 or less.
• the hydrogen bond term ⁇ h4 of the particulate polymer is, for example, 3.0 or more, may be 4.0 or more, and may be, for example, 6.0 or less, and may be 5.0 or less.
• Carboxylic acid group-containing monomer unit Examples of the carboxylic acid group-containing monomer capable of forming the carboxylic acid group-containing monomer unit of the particulate polymer include the carboxylic acid group-containing monomers described above in the section "Water-soluble polymer of the first embodiment". and similar ones.
• the carboxylic acid group-containing monomers may be used alone or in combination of two or more.
• the content of the carboxylic acid group-containing monomer unit in the particulate polymer is preferably 3% by mass or more, preferably 5% by mass, based on 100% by mass of all repeating units contained in the particulate polymer. It is more preferably 30% by mass or less, and more preferably 20% by mass or less. If the content of the carboxylic acid group-containing monomer unit in the particulate polymer is within the above range, the cycle characteristics of the secondary battery having the negative electrode produced using the negative electrode slurry can be further improved.
• aromatic vinyl monomers capable of forming the aromatic vinyl monomer units of the particulate polymer include styrene, styrenesulfonic acid and salts thereof, ⁇ -methylstyrene, pt-butylstyrene, butoxystyrene. , vinyltoluene, chlorostyrene, and vinylnaphthalene.
• An aromatic vinyl monomer may be used individually by 1 type, and may be used in combination of 2 or more types.
• styrene is preferable because it can further improve the cycle characteristics of a secondary battery having a negative electrode produced using the negative electrode slurry. That is, the particulate polymer preferably contains styrene units as aromatic vinyl monomer units.
• the content of the aromatic vinyl monomer units in the particulate polymer is preferably 20% by mass or more, preferably 25% by mass or more, based on 100% by mass of all repeating units contained in the particulate polymer. is more preferably 80% by mass or less, and more preferably 75% by mass or less. If the content ratio of the aromatic vinyl monomer unit in the particulate polymer is within the above range, the cycle characteristics of the secondary battery provided with the negative electrode produced using the negative electrode slurry can be further improved.
• Conjugated diene monomers capable of forming the conjugated diene monomer units of the particulate polymer include those similar to the conjugated diene monomers described above in the section of "water-soluble polymer". Conjugated diene monomers may be used singly or in combination of two or more. As the conjugated diene monomer, 1,3-butadiene is preferable because it can further improve the cycle characteristics of a secondary battery having a negative electrode prepared using the negative electrode slurry. That is, the particulate polymer preferably contains 1,3-butadiene units as conjugated diene monomer units.
• the content of the conjugated diene monomer unit in the particulate polymer is preferably 15% by mass or more, preferably 20% by mass or more, based on 100% by mass of all repeating units contained in the particulate polymer. more preferably 50% by mass or less, and more preferably 45% by mass or less. If the content of the conjugated diene monomer unit in the particulate polymer is within the above range, the cycle characteristics of the secondary battery having the negative electrode produced using the negative electrode slurry can be further improved.
• the content of other repeating units in the particulate polymer is preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of all repeating units contained in the particulate polymer. , is more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass.
• the content of the particulate polymer in the negative electrode slurry is preferably 100 parts by mass or more, more preferably 500 parts by mass or more, and 5000 parts by mass or less per 100 parts by mass of CNTs. is preferred, and 2000 parts by mass or less is more preferred.
• the content of the particulate polymer is within the above range, it is possible to further improve the cycle characteristics of a secondary battery having a negative electrode produced using the negative electrode slurry.
• the negative electrode slurry of the present invention preferably has a pH of 6 or more, more preferably 7 or more, preferably 10 or less, and more preferably 9 or less.
• the pH is within the above range, the viscosity stability of the negative electrode slurry can be improved, and the cycle characteristics of a secondary battery having a negative electrode produced using the negative electrode slurry can be improved.
• the mixing method is not particularly limited, and the known mixing apparatus described above in the “Method for preparing CNT dispersion” can be used.
• a negative electrode of the present invention includes a current collector and a negative electrode mixture layer formed on the current collector using the negative electrode slurry.
• the negative electrode mixture layer contains a negative electrode active material, CNTs, a water-soluble polymer, and optionally a binder and the like.
• the negative electrode of the present invention includes the negative electrode mixture layer formed using the negative electrode slurry of the present invention described above, the secondary battery can exhibit excellent cycle characteristics.
• the current collector is made of a material that is electrically conductive and electrochemically durable.
• a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used.
• copper foil is preferable, and electrolytic copper foil is particularly preferable, because the peel strength of the electrode mixture layer from the current collector can be improved.
• one of the above materials constituting the current collector may be used alone, or two or more of them may be used in combination.
• the polarity term ⁇ p5 of the electrolytic copper foil used as the current collector is preferably 9.0 or more, more preferably 10.0 or more, and preferably 12.0 or less. , 11.0 or less.
• the polarity term ⁇ p5 of the electrolytic copper foil is particularly preferably 10.7.
• the dispersion term ⁇ d5 of the electrolytic copper foil used for the current collector is preferably 17.0 or more, more preferably 18.0 or more, and preferably 20.0 or less. It is more preferably 0 or less.
• the polarity term ⁇ d5 of the electrolytic copper foil is particularly preferably 18.6.
• the hydrogen bonding term ⁇ h5 of the electrolytic copper foil used for the current collector is preferably 5.0 or more, more preferably 6.0 or more, and preferably 9.0 or less. It is more preferably 0.0 or less.
• the hydrogen bonding term ⁇ h5 of the electrolytic copper foil is particularly preferably 7.0.
• the method for producing the negative electrode of the present invention is not particularly limited.
• the negative electrode of the present invention can be produced by applying the negative electrode slurry of the present invention described above to at least one surface of a current collector and drying it to form a negative electrode mixture layer.
• the manufacturing method includes a step of applying a negative electrode slurry to at least one surface of a current collector (application step), and drying the negative electrode slurry applied to at least one surface of the current collector. and a step of forming a negative electrode mixture layer on the current collector (drying step).
• the method for applying the negative electrode slurry onto the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the negative electrode slurry may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the negative electrode mixture layer obtained by drying.
• the method for drying the negative electrode slurry on the current collector is not particularly limited, and known methods can be used. drying method. By drying the negative electrode slurry on the current collector in this manner, a negative electrode mixture layer can be formed on the current collector, and a negative electrode including the current collector and the negative electrode mixture layer can be obtained.
• the negative electrode mixture layer may be pressurized using a mold press, a roll press, or the like.
• the pressure treatment allows the negative electrode mixture layer to adhere well to the current collector.
• the negative electrode mixture layer contains a curable polymer, the polymer may be cured after forming the negative electrode mixture layer.
• a secondary battery of the present invention includes the negative electrode of the present invention described above. And since the secondary battery of the present invention includes the negative electrode of the present invention, it has excellent cycle characteristics.
• the secondary battery of the present invention is preferably, for example, a lithium ion secondary battery.
• This lithium ion secondary battery includes a positive electrode, a negative electrode, an electrolytic solution, and a separator.
• the negative electrode is the above-described negative electrode for non-aqueous secondary batteries of the present invention.
• the positive electrode is not particularly limited, and known positive electrodes can be used.
• an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
• a lithium salt for example, is used as the supporting electrolyte.
• lithium salts include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi and the like.
• LiPF 6 , LiClO 4 and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable, because they are easily dissolved in a solvent and exhibit a high degree of dissociation.
• one electrolyte may be used alone, or two or more electrolytes may be used in combination at an arbitrary ratio.
• lithium ion conductivity tends to increase as a supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted depending on the type of supporting electrolyte.
• the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
• Examples include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (EMC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethylsulfoxide etc. are preferably used. A mixture of these solvents may also be used.
• carbonates are preferably used because they have a high dielectric constant and a wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is more preferably used.
• concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate, for example, it is preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and 5 to 10% by mass. is more preferred.
• known additives such as fluoroethylene carbonate and ethyl methyl sulfone may be added to the electrolytic solution.
• the separator is not particularly limited, and for example, those described in JP-A-2012-204303 can be used. Among these, the film thickness of the entire separator can be made thin, and as a result, the ratio of the electrode active material in the lithium ion secondary battery can be increased to increase the capacity per volume. Microporous membranes made of resins of the system (polyethylene, polypropylene, polybutene, polyvinyl chloride) are preferred.
• the lithium-ion secondary battery according to the present invention can be produced, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, winding or folding this according to the shape of the battery, if necessary, and putting it into a battery container. It can be produced by injecting an electrolytic solution into the container and sealing it. In order to prevent an increase in internal pressure of the secondary battery and the occurrence of overcharge/discharge, etc., a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary.
• the shape of the secondary battery may be, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, rectangular, or flat.
• HSP Hansen solubility parameters
• HSP distance dispersibility of CNT dispersion
• storage stability of CNT dispersion storage stability of CNT dispersion
• the viscosity stability of the negative electrode slurry and the cycle characteristics of the secondary battery were each evaluated using the following methods.
• Hansen Solubility Parameter (HSP)> [HSP c of CNT] 0.1 g of CNT was added to 10 ml each of 12 types of solvents (acetone, toluene, ethanol, tetrahydrofuran, dimethylformamide, methyl ethyl ketone, benzyl alcohol, ⁇ -butyrolactone, nitrobenzene, N-methyl-2-pyrrolidone, salicylaldehyde, methyl acetate). , 20 kHz, 200 W, and 10 minutes, to obtain a measurement solution. Pulse NMR measurements were performed on 12 kinds of solvents (pure solvents) and measurement solutions.
• HSP d of water-soluble polymer When the water-soluble polymer is a homopolymer, HSP d of the water-soluble polymer is HSPiP ver. It was obtained by the Y-MB method of 5.3.04. When the water-soluble polymer is a copolymer, the HSP d of the water-soluble polymer is HSPiP ver.
• the polar term ⁇ p , the dispersion term ⁇ d and the hydrogen bonding term ⁇ h of each homopolymer determined by the Y-MB method in 5.3.04, and the molar ratio of each monomer unit in the copolymer I asked for it in the internal division.
• the water-soluble polymer is a copolymer of monomer unit A and monomer unit B, the content of monomer unit A is 60 mol%, and the content of monomer unit B is 40 mol%.
• the polar term ⁇ p is A p
• the dispersion term ⁇ d is A d
• the hydrogen bonding term ⁇ h is Ah
• the monomer unit B alone when the polar term ⁇ p is B p , the dispersion term ⁇ d is B d
• the hydrogen bonding term ⁇ h is B h
• the HSP d of the water-soluble polymer was determined by the method described above. However, when the detailed structure of the water-soluble polymer is unknown, it can be determined by, for example, the following method. First, 10 ml each of 12 types of solvents (acetone, toluene, ethanol, tetrahydrofuran, dimethylformamide, methyl ethyl ketone, benzyl alcohol, ⁇ -butyrolactone, nitrobenzene N-methyl-2-pyrrolidone, salicylaldehyde, methyl acetate) were added at 25°C. After drying for 7 days, 0.5 g of a water-soluble polymer vacuum-dried at 60° C.
• solvents acetone, toluene, ethanol, tetrahydrofuran, dimethylformamide, methyl ethyl ketone, benzyl alcohol, ⁇ -butyrolactone, nitrobenzene N-methyl-2-pyrrolidone, sal
• HSP m of electrolytic copper foil The HSP m of the surface of the electrolytic copper foil was determined as follows. First, 12 types (aniline, benzyl benzoate, dimethyl sulfoxide, ⁇ -butyrolactone, benzyl alcohol, N-methyl-2-pyrrolidone, methyl ethyl ketone, salicylaldehyde, ethyl acetate, ethanol, 1,1,2,2-tetrabromoethane , formamide) was dropped on the surface of the electrolytic copper foil.
• 12 types aniline, benzyl benzoate, dimethyl sulfoxide, ⁇ -butyrolactone, benzyl alcohol, N-methyl-2-pyrrolidone, methyl ethyl ketone, salicylaldehyde, ethyl acetate, ethanol, 1,1,2,2-tetrabromoethane , formamide
• HSP b of particulate polymer (binder) 12 types of solvents (acetone, toluene, ethanol, tetrahydrofuran, dimethylformamide, methyl ethyl ketone, benzyl alcohol, ⁇ -butyrolactone, nitrobenzene N-methyl-2-pyrrolidone, salicylaldehyde, methyl acetate) in 10 ml each at 25°C for 7 days. After drying, 0.5 g of a particulate polymer vacuum-dried at 60° C. for 10 hours was added and allowed to stand at 25° C. for 24 hours to prepare an evaluation liquid. This evaluation liquid was visually observed and scored as follows.
• HSP distance (R a ) [HSP distance (R a )]
• HSP distance (R a ) was calculated according to the following formula (1).
• HSP distance (R a ) ⁇ ( ⁇ p1 ⁇ p2 ) 2 +4 ⁇ ( ⁇ d1 ⁇ d2 ) 2 +( ⁇ h1 ⁇ h2 ) 2 ⁇ 1/2 (1)
• volume average particle diameter D50 of the CNT dispersion was wet measured using a laser diffraction/scattering particle size distribution analyzer (Microtrac MT-3300EXII manufactured by Microtrac Bell) in accordance with JIS Z8825:2013.
• C Volume average particle diameter D50 is 50 ⁇ m or more
• ⁇ Storage stability of CNT dispersion> The viscosity ⁇ 1 immediately after preparation of the CNT dispersion was measured using a Brookfield viscometer under conditions of a temperature of 25° C. and a spindle rotation speed of 60 rpm after 60 seconds had passed since the start of spindle rotation. After the measurement of ⁇ 1, the CNT dispersion was stored under static conditions at 25° C. for 10 days, and the viscosity ⁇ 2 after storage was measured in the same manner as the viscosity ⁇ 1. The ratio of ⁇ 2 to ⁇ 1 ( ⁇ 2/ ⁇ 1) was taken as the viscosity ratio of the dispersion and evaluated according to the following criteria.
• ⁇ Viscosity stability of negative electrode slurry The viscosity ⁇ 3 immediately after preparation of the negative electrode slurry was measured using a Brookfield viscometer under conditions of a temperature of 25° C. and a spindle rotation speed of 60 rpm after 60 seconds had passed since the start of spindle rotation. After the measurement of ⁇ 3, the negative electrode slurry was stored at 25° C. for 3 days under static conditions, and the viscosity ⁇ 4 after storage was measured in the same manner as the viscosity ⁇ 3. The ratio of ⁇ 4 to ⁇ 3 ( ⁇ 4/ ⁇ 3) was defined as the slurry viscosity ratio and evaluated according to the following criteria.
• a higher capacity retention rate indicates that the secondary battery is more excellent in cycle characteristics.
• Example 1 Preparation of water-soluble polymer (dispersant)>
• a reactor 473 parts of ion-exchanged water, 58 parts of methacrylic acid (carboxylic acid group-containing monomer), 0.6 parts of t-dodecylmercaptan, and ion-exchanged water were diluted to a solid content concentration of 10%. 3.0 parts of sodium dodecylbenzenesulfonate were charged. Then, the inside of the reactor was sealed, and nitrogen substitution was performed twice while stirring with a stirring blade. After completion of nitrogen substitution, 42 parts of nitrogen-substituted isoprene (conjugated diene monomer) was charged into the reactor.
• the second-stage polymerization was initiated by starting the addition of . That is, as a whole monomer composition, 57 parts of styrene, 33 parts of 1,3-butadiene and 10 parts of acrylic acid were used. Five and a half hours after the initiation of the second-stage polymerization, the addition of the entire amount of the mixture containing these monomer compositions was completed.
• the electrolytic copper foil coated with the negative electrode slurry was conveyed at a speed of 0.5 m/min in an oven at a temperature of 100° C.
• the negative electrode slurry on the foil was dried to obtain a negative electrode raw fabric.
• This negative electrode original fabric was rolled by a roll press to obtain a negative electrode having a negative electrode mixture layer with a thickness of 80 ⁇ m.
• the aluminum foil coated with the positive electrode slurry was conveyed at a speed of 0.5 m/min in an oven at a temperature of 60° C. for 2 minutes and then in an oven at a temperature of 120° C. for 2 minutes.
• the positive electrode slurry was dried to obtain a positive electrode raw fabric.
• This positive electrode material was rolled by a roll press to obtain a positive electrode having a positive electrode mixture layer with a thickness of 70 ⁇ m.
• a single-layer polypropylene separator (manufactured by a dry method, width 65 mm, length 500 mm, thickness 25 ⁇ m, porosity 55%) was prepared. This separator was cut into a square of 5 cm ⁇ 5 cm and used for manufacturing a secondary battery.
• An aluminum packaging material exterior was prepared as the exterior of the battery.
• the positive electrode was cut into a square of 4 cm ⁇ 4 cm, and placed so that the surface on the side of the current collector was in contact with the exterior of the aluminum packaging material.
• the square separator was placed on the surface of the positive electrode mixture layer of the positive electrode.
• the negative electrode was cut into a square of 4.2 cm ⁇ 4.2 cm, and this was placed on a separator so that the surface of the negative electrode mixture layer side faced the separator.
• Example 2 Various operations were performed in the same manner as in Example 1, except that in the preparation of the CNT dispersion, the amount of the water-soluble polymer used was changed so that the solid content concentration of the water-soluble polymer in the CNT dispersion was 1%. , was measured and evaluated. Table 1 shows the results.
• Example 4 Using 59 parts of sodium styrenesulfonate (sulfonic acid group-containing monomer) and 41 parts of ethoxydiethylene glycol acrylate (alkylene oxide structure-containing monomer) instead of isoprene and methacrylic acid in the preparation of the water-soluble polymer. , and the preparation of the CNT dispersion, various operations, measurements and evaluations were performed in the same manner as in Example 1, except that the pH of the CNT dispersion was adjusted to 7.7. Table 1 shows the results.
• Example 5 Various operations, measurements, and evaluations were performed in the same manner as in Example 4, except that single-walled CNTs (average diameter: 3 nm, G/D ratio: 5) were used instead of multi-walled CNTs in the preparation of the CNT dispersion. rice field. Table 1 shows the results.
• Example 7 Various operations, measurements and evaluations were performed in the same manner as in Example 4, except that the pH of the CNT dispersion was adjusted to 12.0 in the preparation of the CNT dispersion. Table 1 shows the results.
• Example 8 Various operations, measurements and evaluations were carried out in the same manner as in Example 7, except that in the preparation of the water-soluble polymer, the amount of sodium styrenesulfonate was changed to 77 parts and the amount of ethoxydiethylene glycol acrylate was changed to 23 parts. gone. Table 1 shows the results.
• Example 9 Various operations, measurements and evaluations were carried out in the same manner as in Example 1, except that a 5% aqueous sodium hydroxide solution was used in place of the 5% aqueous lithium hydroxide solution in the preparation of the water-soluble polymer and the CNT dispersion. gone. Table 1 shows the results.
• Example 10 In adjusting the CNT dispersion, the amounts of CNT and water-soluble polymer used are changed so that the solid concentration of CNT in the CNT dispersion is 0.4% and the solid concentration of the water-soluble polymer is 1%.
• Table 1 shows the results.
• Example 11 Example except that 70 parts of ethyl acrylate ((meth)acrylic acid alkyl ester monomer) and 30 parts of methacrylic acid were used instead of 42 parts of isoprene and 58 parts of methacrylic acid in the preparation of the water-soluble polymer.
• Various operations, measurements and evaluations were performed in the same manner as in 9. Table 1 shows the results.
• Example 12 In the preparation of the CNT dispersion, 70 parts of ethyl acrylate ((meth)acrylic acid alkyl ester monomer) and 30 parts of methacrylic acid were used instead of 42 parts of isoprene and 58 parts of methacrylic acid, and a water-soluble polymer and the preparation of the CNT dispersion, various operations, measurements and evaluations were performed in the same manner as in Example 10, except that a 5% sodium hydroxide aqueous solution was used instead of the 5% lithium hydroxide aqueous solution. Table 1 shows the results.
• Comparative Example 5 Various operations, measurements, and evaluations were performed in the same manner as in Comparative Example 4, except that single-walled CNTs (average diameter: 3 nm, G/D ratio: 5) were used instead of multi-walled CNTs in the preparation of the CNT dispersion. rice field. Table 1 shows the results.
• Example 6 A CNT dispersion was prepared in the same manner as in Example 1, except that the water-soluble polymer was not prepared and the water-insoluble hydrogenated nitrile rubber prepared as follows was used instead of the water-soluble polymer. tried. However, multi-layered CNTs were not dispersed, and a CNT dispersion that could be used to form a negative electrode mixture layer could not be produced. Therefore, various evaluations were not performed.
• TIBM 2,2′,4,6,6′-pentamethylheptane-4-thiol
• Emulsion polymerization was carried out at 30°C in the presence of 0.35 parts of potassium persulfate as a polymerization initiator to copolymerize the above monomers.
• potassium persulfate as a polymerization initiator to copolymerize the above monomers.
• 0.2 part of hydroxylamine sulfate per 100 parts of monomer was added to terminate the polymerization.
• the mixture is heated and steam-distilled at about 70°C under reduced pressure to recover residual monomers, and then 2 parts of alkylated phenol is added as an anti-aging agent to obtain an aqueous dispersion of the polymer. Obtained.
• the contents were returned to normal temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration reached 40% to obtain a hydrogenated nitrile rubber.
• the resulting hydrogenated nitrile rubber was water-insoluble.
• MW indicates multi-walled CNT
• SW indicates single-walled CNT
• IP indicates isoprene units
• MAA indicates a methacrylic acid unit
• SS indicates a sodium styrene sulfonate unit
• EA indicates an ethoxydiethylene glycol acrylate unit
• AA indicates an acrylic acid unit
• AAm indicates an acrylamide unit
• CMC indicates the sodium salt of carboxymethylcellulose
• HNBR denotes hydrogenated nitrile rubber.
• Li indicates a lithium base
• Na indicates a sodium base
• K indicates potassium base
• LIB indicates a lithium ion secondary battery.
• a CNT dispersion having excellent CNT dispersibility and storage stability can be provided.
• the slurry for nonaqueous secondary battery negative electrodes containing this CNT dispersion liquid can be provided.

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