WO2025023017A1 - 蓄電デバイス用バインダー組成物、蓄電デバイス電極用スラリー、蓄電デバイス電極、及び蓄電デバイス - Google Patents

蓄電デバイス用バインダー組成物、蓄電デバイス電極用スラリー、蓄電デバイス電極、及び蓄電デバイス Download PDF

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WO2025023017A1
WO2025023017A1 PCT/JP2024/024839 JP2024024839W WO2025023017A1 WO 2025023017 A1 WO2025023017 A1 WO 2025023017A1 JP 2024024839 W JP2024024839 W JP 2024024839W WO 2025023017 A1 WO2025023017 A1 WO 2025023017A1
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storage device
polymer
mass
binder composition
parts
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French (fr)
Japanese (ja)
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卓哉 中山
香奈 増田
一将 森
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Eneos Materials Corp
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Eneos Materials Corp
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Priority to KR1020267003346A priority Critical patent/KR20260048262A/ko
Priority to JP2025535709A priority patent/JPWO2025023017A1/ja
Priority to CN202480046201.7A priority patent/CN121488331A/zh
Publication of WO2025023017A1 publication Critical patent/WO2025023017A1/ja
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • the present invention relates to a binder composition for an electricity storage device, a slurry for an electricity storage device electrode, an electricity storage device electrode, and an electricity storage device.
  • Lithium-ion batteries and lithium-ion capacitors are expected to be such power storage devices.
  • the electrodes used in such energy storage devices are manufactured by applying and drying a composition (slurry for energy storage device electrodes) containing an active material and a polymer that functions as a binder to the surface of a current collector.
  • a composition slurry for energy storage device electrodes
  • the properties required of the polymer used as a binder include the ability to bind active materials together and to adhere to the current collector, and resistance to powder fall-off so that fine powder of the active material does not fall off from the active material layer when the applied and dried composition coating film (hereinafter also referred to as the "active material layer") is cut.
  • Such binder materials exhibit good adhesion and reduce the internal resistance of the battery caused by the binder material, thereby imparting good charge and discharge characteristics to the energy storage device.
  • the electrode binders disclosed in the above Patent Documents 1 to 5 do not have sufficient adhesion for practical use of new active materials, such as silicon materials, which have a large lithium ion storage capacity and a large volume change associated with the storage and release of lithium ions.
  • active materials such as silicon materials
  • the active material falls off due to repeated charging and discharging, causing the electrode to deteriorate, and there is an issue that the durability required for practical use is not sufficiently obtained.
  • Some aspects of the present invention provide a binder composition for an electricity storage device that can produce an electricity storage device electrode that has excellent adhesion and suppresses electrode expansion due to repeated charging and discharging, and can improve the cycle life characteristics of the electricity storage device.
  • the present invention has been made to solve at least some of the above problems, and can be realized in any of the following forms.
  • One aspect of the binder composition for an electrical storage device is Contains a polymer (A) and a liquid medium (B), When the total amount of repeating units contained in the polymer (A) is 100 parts by mass, the polymer (A) 50 to 80 parts by mass of a repeating unit (a1) derived from a conjugated diene compound; 15 to 49 parts by mass of a repeating unit (a2) derived from an aromatic vinyl compound; 0.1 to 10 parts by mass of a repeating unit (a3) derived from an unsaturated carboxylic acid; Contains the polymer (A) has one peak top of dynamic viscoelasticity tan ⁇ (loss modulus/storage modulus) in the range of ⁇ 50° C. or more and 10° C.
  • the proton relaxation time of the polymer (A) may be 1500 ms or more when a latex having a solid content concentration of 10% is measured by a CPMG method of pulse NMR.
  • the total amount of the repeating units (a1), (a2) and (a3) may be 80 parts by mass or more.
  • the polymer (A) may further contain 0.1 to 10 parts by mass of a repeating unit (a4) derived from an unsaturated carboxylate.
  • the polymer (A) may further contain 0.1 to 10 parts by mass of a repeating unit (a5) derived from an ⁇ , ⁇ -unsaturated nitrile compound.
  • the polymer (A) may have a degree of swelling in an electrolyte of 100 to 350%.
  • the polymer (A) is a polymer particle,
  • the polymer particles may have a number average particle size of 50 nm or more and 500 nm or less.
  • the polymer particles may have a surface acid amount of 0.05 mmol/g or more and 1 mmol/g or less.
  • the liquid medium (B) may be water.
  • One embodiment of a slurry for an electric storage device electrode according to the present invention is The binder composition for an electricity storage device according to any one of the above aspects and an active material are contained.
  • the active material may contain a silicon material.
  • the electrode comprises a current collector, and an active material layer formed by applying the slurry for an electricity storage device electrode according to any one of the above aspects to the surface of the current collector and drying the applied active material layer.
  • the power storage device includes the electrode according to the above aspect.
  • the binder composition for electricity storage devices according to the present invention makes it possible to produce electricity storage device electrodes that have excellent adhesion and suppress electrode expansion caused by repeated charging and discharging, thereby improving the cycle life characteristics of the electricity storage device.
  • FIG. 1 is a graph showing the relationship between the measurement temperature and tan ⁇ in the dynamic viscoelasticity measurement of the film prepared in Example 5.
  • (meth)acrylic acid ⁇ refers to “acrylic acid ⁇ " or “methacrylic acid ⁇ ”
  • ⁇ (meth)acrylate refers to “ ⁇ acrylate” or “ ⁇ methacrylate”
  • (meth)acrylamide refers to "acrylamide” or "methacrylamide”.
  • a numerical range described as "X to Y" is interpreted as including the numerical value X as the lower limit and the numerical value Y as the upper limit.
  • a binder composition for an electricity storage device contains a polymer (A) and a liquid medium (B).
  • the polymer (A) contains 50 to 80 parts by mass of repeating units (a1) derived from a conjugated diene compound, 15 to 49 parts by mass of repeating units (a2) derived from an aromatic vinyl compound, and 0.1 to 10 parts by mass of repeating units (a3) derived from an unsaturated carboxylic acid, relative to 100 parts by mass of the total repeating units contained in the polymer (A).
  • the polymer (A) has one peak top of dynamic viscoelasticity tan ⁇ (loss modulus/storage modulus) in the range of -50°C to 10°C and one peak top in the range of 150°C to 250°C, and when the tan ⁇ of the peak top in the range of -50°C to 10°C is tan ⁇ (Tp1) and the tan ⁇ of the peak top in the range of 150°C to 250°C is tan ⁇ (Tp2), the relationship of the following formula (1) is satisfied. tan ⁇ (Tp2)/tan ⁇ (Tp1) ⁇ 0.5 (1)
  • the binder composition for electricity storage devices according to this embodiment can be used as a material for producing an electrode (active material layer) for an electricity storage device with improved bonding ability between active materials, improved adhesion ability between the active material and the current collector, and improved resistance to powder shedding, and can also be used as a material for producing a protective film for suppressing short circuits caused by dendrites that occur during charging and discharging.
  • an electrode active material layer
  • the binder composition for electricity storage devices according to this embodiment can be used as a material for producing an electrode (active material layer) for an electricity storage device with improved bonding ability between active materials, improved adhesion ability between the active material and the current collector, and improved resistance to powder shedding, and can also be used as a material for producing a protective film for suppressing short circuits caused by dendrites that occur during charging and discharging.
  • the binder composition for a storage battery device contains a polymer (A).
  • the polymer (A) may be in a latex state dispersed in a liquid medium (B) described later, or may be dissolved in the liquid medium (B), but is preferably in a latex state dispersed in the liquid medium (B).
  • the stability of a slurry for a storage battery device electrode hereinafter also referred to as "slurry" prepared by mixing the polymer (A) with an active material is improved, and the coating property of the slurry on a current collector is also improved, which is preferable.
  • repeating units constituting polymer (A) When the total of the repeating units contained in the polymer (A) is taken as 100 parts by mass, the polymer (A) contains 50 to 80 parts by mass of repeating units (a1) (hereinafter also simply referred to as “repeating units (a1)”) derived from a conjugated diene compound, 15 to 49 parts by mass of repeating units (a2) (hereinafter also simply referred to as “repeating units (a2)”) derived from an aromatic vinyl compound, and 0.1 to 10 parts by mass of repeating units (a3) (hereinafter also simply referred to as "repeating units (a3)”) derived from an unsaturated carboxylic acid.
  • the polymer (A) may contain repeating units derived from other monomers copolymerizable therewith.
  • Repeating unit (a1) derived from a conjugated diene compound The content of the repeating unit (a1) derived from the conjugated diene compound is 50 to 80 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content of the repeating unit (a1) is preferably 52 parts by mass, more preferably 55 parts by mass.
  • the upper limit of the content of the repeating unit (a1) is preferably 78 parts by mass, more preferably 75 parts by mass.
  • the dispersibility of the active material and the filler is improved, and a homogeneous active material layer and a protective film can be prepared, so that the structural defects of the electrode plate are eliminated and good repeated charge and discharge characteristics are exhibited.
  • the polymer (A) covering the surface of the active material can be given elasticity, and the polymer (A) can be stretched and stretched to improve adhesion, so that good charge and discharge durability characteristics are exhibited.
  • Aromatic vinyl compounds include, but are not limited to, styrene, ⁇ -methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, etc., and one or more selected from these can be used. Among these, styrene is particularly preferred.
  • the polymer (A) may contain a repeating unit (a3) derived from an unsaturated carboxylic acid.
  • the content ratio of the repeating unit (a3) derived from an unsaturated carboxylic acid is preferably 0.1 to 10 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content ratio of the repeating unit (a3) is preferably 0.5 parts by mass, more preferably 1 part by mass.
  • the upper limit of the content ratio of the repeating unit (a3) is preferably 9 parts by mass, more preferably 8 parts by mass.
  • the unsaturated carboxylic acid is not particularly limited, but includes monocarboxylic acids and dicarboxylic acids (including anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc., and one or more selected from these can be used. Among these, it is preferable to use one or more selected from acrylic acid, methacrylic acid, and itaconic acid.
  • repeating unit (a4) derived from an unsaturated carboxylic acid ester
  • repeating unit (a5) derived from an ⁇ , ⁇ -unsaturated nitrile compound
  • repeating unit (a6) derived from (meth)acrylamide
  • repeating unit (a7) derived from a compound having a sulfonic acid group
  • repeating unit (a7) derived from a cationic monomer.
  • the polymer (A) may contain a repeating unit (a4) derived from an unsaturated carboxylic acid ester.
  • the content ratio of the repeating unit (a4) is preferably 0.1 to 10 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content ratio of the repeating unit (a4) is preferably 1 part by mass, more preferably 2 parts by mass.
  • the upper limit of the content ratio of the repeating unit (a4) is preferably 9 parts by mass, more preferably 8 parts by mass.
  • the affinity between the polymer (A) and the electrolyte solution is improved, and an increase in internal resistance due to the binder becoming an electric resistance component in the electricity storage device may be suppressed.
  • (meth)acrylic acid esters can be preferably used.
  • Specific examples of (meth)acrylic acid esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tri( ...propylene glycol di(
  • One or more selected from these can be used.
  • one or more selected from methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylene glycol di(meth)acrylate, and 2-hydroxyethyl (meth)acrylate are preferred, and methyl (meth)acrylate is particularly preferred.
  • the polymer (A) may contain a repeating unit (a5) derived from an ⁇ , ⁇ -unsaturated nitrile compound.
  • the content ratio of the repeating unit (a5) is preferably 0.1 to 10 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content ratio of the repeating unit (a5) is preferably 1 part by mass, more preferably 2 parts by mass.
  • the upper limit of the content ratio of the repeating unit (a5) is preferably 9 parts by mass, more preferably 8 parts by mass.
  • the dissolution of the polymer (A) in the electrolyte can be reduced, the affinity between the polymer (A) and the electrolyte can be improved, and an increase in internal resistance due to the binder becoming an electric resistance component in the electricity storage device can be suppressed in some cases.
  • the ⁇ , ⁇ -unsaturated nitrile compound is not particularly limited, but includes acrylonitrile, methacrylonitrile, ⁇ -chloroacrylonitrile, ⁇ -ethylacrylonitrile, vinylidene cyanide, etc., and one or more selected from these can be used. Among these, one or more selected from the group consisting of acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is particularly preferred.
  • the polymer (A) may contain a repeating unit (a6) derived from (meth)acrylamide.
  • the content ratio of the repeating unit (a6) is preferably 0 to 8 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content ratio of the repeating unit (a6) is preferably 0.5 parts by mass, more preferably 1 part by mass.
  • the upper limit of the content ratio of the repeating unit (a6) is preferably 7 parts by mass, more preferably 6 parts by mass.
  • the polymer (A) contains the repeating unit (a6) within the above range, the dispersibility of the active material and the filler in the slurry may be improved. In addition, the flexibility of the obtained active material layer may become appropriate, and the adhesion between the current collector and the active material layer may be improved.
  • (Meth)acrylamides include, but are not limited to, acrylamide, methacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diacetone acrylamide, maleic acid amide, and the like, and one or more selected from these can be used.
  • the polymer (A) may contain a repeating unit (a7) derived from a compound having a sulfonic acid group.
  • the content ratio of the repeating unit (a7) is preferably 0 to 8 parts by mass when the total of the repeating units contained in the polymer (A) is 100 parts by mass.
  • the lower limit of the content ratio of the repeating unit (a7) is preferably 0.5 parts by mass, more preferably 1 part by mass.
  • the upper limit of the content ratio of the repeating unit (a7) is preferably 7 parts by mass, more preferably 6 parts by mass.
  • the dispersibility of the active material and the filler is improved, and it may be possible to prepare a homogeneous active material layer or protective film. Furthermore, the adhesion with the current collector is also improved, and the structural defects of the electrode plate are reduced, which may result in good charge and discharge characteristics.
  • Compounds having a sulfonic acid group include, but are not limited to, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, sulfobutyl (meth)acrylate, 2-acrylamido-2-methylpropanesulfonic acid, acrylamido tert-butylsulfonic acid, 2-hydroxy-3-acrylamidopropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and alkali salts thereof, and one or more selected from these may be used.
  • the polymer (A) may contain a repeating unit derived from a cationic monomer.
  • the cationic monomer is not particularly limited, but is preferably at least one monomer selected from the group consisting of secondary amines (salts), tertiary amines (salts), and quaternary ammonium salts.
  • cationic monomer examples include 2-(dimethylamino)ethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate methyl chloride quaternary salt, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, 3-(diethylamino)propyl (meth)acrylate, 4-(dimethylamino)phenyl (meth)acrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl (meth)acrylate, 2-(0-[1'-methylpropylideneamino]carboxyamino)ethyl (meth)acrylate, 2-(1-aziridinyl)ethyl (meth)acrylate, methacryloylcholine chloride, tris(2-acryloyloxyethyl) isocyanurate, and 2-vinyl
  • antibacterial agent examples include lysine, quinaldine red, 1,2-di(2-pyridyl)ethylene, 4'-hydrazino-2-stilbazole dihydrochloride hydrate, 4-(4-dimethylaminostyryl)quinoline, 1-vinylimidazole, diallylamine, diallylamine hydrochloride, triallylamine, diallyldimethylammonium chloride, dichlormid, N-allylbenzylamine, N-allylaniline, 2,4-diamino-6-diallylamino-1,3,5-triazine, N-trans-cinnamyl-N-methyl-(1-naphthylmethyl)amine hydrochloride, trans-N-(6,6-dimethyl-2-hepten-4-ynyl)-N-methyl-1-naphthylmethylamine hydrochloride, and the like. One or more selected from these may be used.
  • the measurement sample in this dynamic viscoelasticity measurement is a film of polymer (A).
  • the film of polymer (A) is prepared by drying polymer (A) at 40°C for 24 hours to prepare a uniform film with a thickness of 1.0 ⁇ 0.3 mm, drying this film at 160°C for 30 minutes in a vacuum dryer, and then cutting it into a 10 mm x 10 mm strip.
  • the measurement sample is fixed with a parallel plate (product name "PP-12") and measured in the temperature range of -70°C to 250°C under the measurement conditions described below.
  • Measurement conditions shear mode, measurement frequency 0.01 to 1 Hz, heating speed 0.1°C/min
  • Dynamic viscoelasticity measuring device Anton Paar, model "MCR 301"
  • the value of "tan ⁇ (Tp2)/tan ⁇ (Tp1)" of the polymer (A) used in this embodiment is smaller than 0.5, preferably 0.48 or less, and more preferably 0.45 or less.
  • the value of "tan ⁇ (Tp2)/tan ⁇ (Tp1)" of the polymer (A) is within the above range, it indicates that there is a large amount of polymer components near the peak top temperature of tan ⁇ (Tp1).
  • the viscosity is high at temperatures near the peak top temperature of tan ⁇ (Tp1), and it is believed that this high viscosity can ensure adhesion to the active material mainly made of carbon materials.
  • the high cross-link i.e., the polymer (A)
  • the binder can maintain its particle shape without being crushed by the expansion and contraction during repeated charging and discharging of the Si active material, so it is believed that the adhesion to the active material can be maintained and the expansion of the electrode can be suppressed.
  • the internal resistance can be reduced, making it possible to produce an electrode that exhibits good repeated charge/discharge characteristics.
  • the polymer (A) used in this embodiment can improve adhesion, making it possible to produce an electrode that exhibits good charge/discharge durability characteristics.
  • the temperature Tp1 (°C) of the peak top of tan ⁇ in the dynamic viscoelasticity measurement of polymer (A) is preferably in the temperature range of -38°C or higher and 8°C or lower, more preferably -35°C or higher and 5°C or lower. It is also preferable that there is one peak top in the above temperature range. The presence of one Tp in the above temperature range indicates high viscosity in the same temperature range. It is believed that this high viscosity allows polymer (A) to maintain a high binding strength in the same temperature range, and allows good adhesion to be exhibited.
  • the temperature Tp2 (°C) of the peak top of tan ⁇ in the dynamic viscoelasticity measurement of polymer (A) is preferably in the temperature range of 155°C or higher and 245°C or lower, more preferably 160°C or higher and 240°C or lower. It is also preferable that there is one peak top in the above temperature range.
  • the presence of one Tp in the above temperature range indicates that a polymer with a high content of hydrophilic polymer has been formed in the same temperature range. It is believed that the high content of hydrophilic polymer in polymer (A) in the same temperature range makes polymer (A) hard and reduces its internal resistance.
  • the temperature Tp of the peak top of tan ⁇ can be adjusted by adjusting the monomer composition during polymerization of polymer (A).
  • the tan ⁇ (Tp1) of the polymer (A) is preferably 0.5 to 1.2, more preferably 0.55 to 1.15, and particularly preferably 0.6 to 1.10.
  • the fact that the tan ⁇ (Tp1) of the polymer (A) is within the above range indicates that the polymer (A) is viscous but not too hard, and has sufficient binding strength to maintain the electrode structure.
  • the tan ⁇ (Tp2) of polymer (A) is preferably 0.01 to 0.4, more preferably 0.03 to 0.38, and particularly preferably 0.05 to 0.35.
  • the fact that the tan ⁇ (Tp2) of polymer (A) is within the above range indicates that polymer (A) is not too soft, suppresses fusion between particles, and has sufficient hardness to withstand the expansion and contraction of Si.
  • Methods for adjusting tan ⁇ (Tp) include changing the glass transition temperature or gel content of polymer (A), or changing the method of adding monomers during polymerization of polymer (A).
  • the measurements are performed using a pulsed nuclear magnetic resonance device "BRUKER minispec mq20" with hydrogen nuclei as the measurement nuclei, and the transverse relaxation time (spin-spin relaxation time) of protons is measured by the CPMG method (Carr-Purcell Meiboom-Gill method) under the following measurement conditions: measurement temperature 25°C, frequency 20 MHz, 90-180° pulse interval 0.04 tau. Note that when performing the measurements, it is preferable to adjust the pH of the aqueous dispersion to 8.0.
  • the transverse relaxation time TA of protons present in the aqueous dispersion of polymer (A) is preferably 1500 ms or more, more preferably 1550 ms or more, and particularly preferably 1600 ms or more.
  • the transverse relaxation time of protons measured by pulse NMR is measured as the relaxation time of the entire components of the measurement sample. Therefore, in the case of an aqueous dispersion of polymer (A) with a solid content concentration of 10%, the relaxation time TA is obtained as the average value of the relaxation times of protons present in 10% polymer (A) and 90% water.
  • the relaxation time TA becomes shorter as the interaction between the surface of the polymer (A) and water molecules becomes stronger. That is, the more hydrophilic the particle surface is, the shorter the relaxation time TA becomes, and the more hydrophobic the particle surface is, the longer the relaxation time TA becomes. Therefore, it is considered that the longer the relaxation time TA is, the more hydrophobic the surface of the polymer (A) is, and the more effectively it is adsorbed on the active material surface, thereby exhibiting excellent adhesion and the effect of suppressing the expansion of the electrode.
  • the number average particle size of the particles is preferably 50 nm or more and 500 nm or less, more preferably 70 nm or more and 480 nm or less, and particularly preferably 90 nm or more and 450 nm or less.
  • the number average particle size of the particles of the polymer (A) is within the above range, the particles of the polymer (A) are easily adsorbed on the surface of the active material, so that the particles of the polymer (A) can move along with the movement of the active material. As a result, migration can be suppressed, and the deterioration of electrical properties can be reduced in some cases.
  • the number average particle size of the particles of polymer (A) is the average particle size obtained from images of 50 particles observed with a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • An example of a transmission electron microscope is the "H-7650" manufactured by Hitachi High-Tech Corporation.
  • the surface acid amount of the particle is preferably 0.05 mmol/g or more and 1 mmol/g or less, more preferably 0.07 mmol/g or more and 0.95 mmol/g or less, and particularly preferably 0.10 mmol/g or more and 0.90 mmol/g or less.
  • the surface acid amount of the polymer (A) particles is within the above range, a stable and homogeneous slurry can be prepared.
  • an active material layer is prepared using such a homogeneous slurry, an active material layer with a small thickness variation in which the active material and the polymer (A) particles are uniformly dispersed can be obtained.
  • the surface acid amount of the polymer (A) can be measured by the method described in the examples described later.
  • Electrolyte swelling degree When the polymer (A) is immersed in a solvent consisting of ethylene carbonate and ethyl methyl carbonate at a volume fraction of 1:1 at 70°C for 24 hours, the swelling degree (hereinafter also referred to as “electrolyte swelling degree”) is preferably 100% or more and 350% or less, more preferably 110% or more and 250% or less, and particularly preferably 120% or more and 200% or less. When the electrolyte swelling degree of the polymer (A) is within the above range, the polymer (A) can swell appropriately by absorbing the electrolyte.
  • the solvated lithium ions can easily reach the active material, so that the electrode resistance can be effectively reduced and better charge/discharge characteristics can be realized.
  • the electrolyte swelling degree of the polymer (A) is within the above range, the polymer (A) does not undergo a large volume change even when it absorbs the electrolyte, and therefore has excellent adhesion.
  • the polymerization step for the polymer (A) is not particularly limited, but may be, for example, an emulsion polymerization method carried out in the presence of a known emulsifier, chain transfer agent, polymerization initiator, and the like.
  • emulsifiers include anionic surfactants such as sulfate salts of higher alcohols, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkyldiphenyletherdisulfonates, aliphatic sulfonates, aliphatic carboxylates, dehydroabietic acid salts, naphthalenesulfonic acid-formaldehyde condensates, and sulfate salts of nonionic surfactants; nonionic surfactants such as alkyl esters of polyethylene glycols, alkylphenyl ethers of polyethylene glycols, and alkyl ethers of polyethylene glycols; and fluorine-based surfactants such as perfluorobutylsulfonates, perfluoroalkyl group-containing phosphate esters, perfluoroalkyl group-containing carboxylates, and perfluoroalkylethylene oxide ad
  • chain transfer agents and polymerization initiators that can be used include the compounds described in Japanese Patent No. 5,999,399, etc.
  • the emulsion polymerization method for synthesizing polymer (A) may be carried out in a single-stage polymerization or in a multi-stage polymerization of two or more stages.
  • the mixture of the above monomers can be subjected to emulsion polymerization in the presence of a suitable emulsifier, chain transfer agent, polymerization initiator, etc., preferably at a temperature of 0 to 80°C, and for a polymerization time of preferably 4 to 36 hours.
  • polymer (A) is synthesized by two-stage polymerization
  • the proportion of the monomers used in the first-stage polymerization is preferably in the range of 20 to 99% by mass, and more preferably in the range of 25 to 99% by mass, based on the total mass of the monomers (the sum of the mass of the monomers used in the first-stage polymerization and the mass of the monomers used in the second-stage polymerization).
  • the type and proportion of monomers used in the second-stage polymerization may be the same as or different from the type and proportion of monomers used in the first-stage polymerization.
  • the polymerization conditions in each stage are preferably as follows.
  • First stage polymerization a temperature of preferably 0 to 80° C.; a polymerization time of preferably 2 to 36 hours; a polymerization conversion rate of preferably 50% by mass or more, more preferably 60% by mass or more.
  • Second stage polymerization preferably at a temperature of 0 to 80° C.; preferably at a polymerization time of 2 to 18 hours.
  • polymer (A) is synthesized by three-stage polymerization
  • the proportion of monomers used in the first-stage polymerization is preferably in the range of 20 to 90% by mass, and more preferably in the range of 25 to 80% by mass, based on the total mass of monomers (the sum of the mass of monomers used in the first-stage polymerization, the mass of monomers used in the second-stage polymerization, and the mass of monomers used in the third-stage polymerization).
  • the proportion of monomers used in the first-stage polymerization is preferably in the range of 20 to 90% by mass, and more preferably in the range of 25 to 80% by mass, based on the total mass of monomers (the sum of the mass of monomers used in the first-stage polymerization, the mass of monomers used in the second-stage polymerization, and the mass of monomers used in the third-stage polymerization).
  • the type and proportion of monomers used in the second-stage polymerization may be the same as or different from the type and proportion of monomers used in the first-stage polymerization.
  • the type and proportion of monomers used in the third-stage polymerization may be the same as or different from the type and proportion of monomers used in the first-stage polymerization and the type and proportion of monomers used in the second-stage polymerization.
  • the polymerization conditions in each stage are preferably as follows.
  • First stage polymerization a temperature of preferably 0 to 80° C.; a polymerization time of preferably 2 to 36 hours; a polymerization conversion rate of preferably 50% by mass or more, more preferably 60% by mass or more.
  • Second stage polymerization preferably at a temperature of 0 to 80° C.; preferably at a polymerization time of 2 to 18 hours.
  • Third stage polymerization preferably at a temperature of 0 to 80° C.; preferably at a polymerization time of 2 to 9 hours.
  • the polymerization reaction can be carried out in a state in which the dispersion stability of the particles of the resulting polymer (A) is good.
  • This total solids concentration is preferably 45% by mass or less, and more preferably 40% by mass or less.
  • a neutralizing agent used here is not particularly limited, but examples include metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonia, etc.
  • the binder composition for a storage battery device contains a liquid medium (B).
  • the liquid medium (B) is preferably an aqueous medium containing water, and more preferably water.
  • the aqueous medium can contain a non-aqueous medium other than water. Examples of the non-aqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, and sulfone compounds, and one or more selected from these can be used.
  • the content of the non-aqueous medium in the aqueous medium is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably substantially free of the non-aqueous medium, per 100 parts by mass of the aqueous medium.
  • substantially free of the non-aqueous medium means that the non-aqueous medium is not intentionally added as a liquid medium, and may include a non-aqueous medium that is inevitably mixed in when preparing the binder composition for an electrical storage device.
  • the binder composition for an electrical storage device according to this embodiment may contain additives other than the above-mentioned components as necessary.
  • additives include polymers other than the polymer (A), preservatives, thickeners, etc.
  • the binder composition for a storage battery device may contain a polymer other than the polymer (A).
  • a polymer is not particularly limited, but may be an acrylic polymer containing an unsaturated carboxylic acid ester or a derivative thereof as a structural unit, a fluorine-based polymer such as PVDF (polyvinylidene fluoride), or the like. These polymers may be used alone or in combination of two or more. By containing these polymers, flexibility and adhesion may be further improved.
  • the binder composition for a storage battery device may contain a preservative.
  • a preservative By containing a preservative, it may be possible to suppress the proliferation of bacteria, mold, and the like and the generation of foreign matter when the binder composition for a storage battery device is stored.
  • Specific examples of the preservative include compounds described in Japanese Patent No. 5477610 and the like.
  • the binder composition for an electricity storage device may contain a thickener. By containing a thickener, it may be possible to further improve the coatability of the slurry and the charge/discharge characteristics of the obtained electricity storage device.
  • Thickeners include, for example, cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose; poly(meth)acrylic acid; the cellulose compounds or the ammonium salts or alkali metal salts of the poly(meth)acrylic acid; modified polyvinyl alcohol, polyethylene oxide; polyvinylpyrrolidone, polycarboxylic acid, oxidized starch, starch phosphate, casein, various modified starches, chitin, and chitosan derivatives. Among these, cellulose-based polymers are preferred.
  • thickeners include, for example, alkali metal salts of carboxymethylcellulose such as CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (all manufactured by Daicel Corporation).
  • the content of the thickener is preferably 5% by mass or less, and more preferably 0.1 to 3% by mass, relative to 100% by mass of the total solid content of the binder composition for an electricity storage device.
  • pH of the binder composition for an electrical storage device The pH of the binder composition for an electricity storage device according to this embodiment is preferably 6.0 to 9.5, more preferably 6.3 to 9.2, and particularly preferably 6.5 to 9.0. When the pH is within this range, the occurrence of insufficient leveling and dripping can be suppressed, and it becomes easy to manufacture an electricity storage device electrode that has both good electrical properties and good adhesion.
  • pH refers to a physical property measured as follows: It is a value measured at 25°C using a pH meter that uses a glass electrode calibrated with neutral phosphate standard solution and borate standard solution as pH standard solutions, in accordance with JIS Z8802:2011. Examples of such pH meters include the “HM-7J” manufactured by DKK-TOA Corporation and the “D-51” manufactured by Horiba, Ltd.
  • the pH of the binder composition for electrical storage devices is affected by the monomer composition constituting the polymer (A), it is not determined solely by the monomer composition. In other words, it is generally known that even with the same monomer composition, the pH of the binder composition for electrical storage devices changes depending on the polymerization conditions, etc., and the examples in this specification merely show one example.
  • the slurry for an electric storage device contains the above-mentioned binder composition for an electric storage device.
  • the above-mentioned binder composition for an electric storage device can be used as a material for producing a protective film for suppressing short circuits caused by dendrites that occur during charging and discharging, and can also be used as a material for producing an electrode for an electric storage device (active material layer) with improved binding ability between active materials, adhesion ability between an active material and a current collector, and resistance to powder falling off.
  • slurry for an electric storage device for producing a protective film hereinafter also referred to as “slurry for protective film”
  • slurry for an electric storage device electrode the slurry for an electric storage device for producing an active material layer of an electrode for an electric storage device
  • Slurry for protective film refers to a dispersion liquid used to prepare a protective film on the surface of an electrode or a separator or both by applying the slurry to the surface of an electrode or a separator or both and then drying the slurry.
  • the slurry for protective film according to this embodiment may be composed only of the binder composition for a storage battery device described above, or may further contain an inorganic filler. Examples of the inorganic filler include the inorganic fillers described in JP 2020-184461 A.
  • the "slurry for electricity storage device electrode” refers to a dispersion liquid used for preparing an active material layer on the surface of a current collector by applying the dispersion liquid to the surface of the current collector and then drying the dispersion liquid.
  • the slurry for electricity storage device electrode according to this embodiment contains the above-mentioned binder composition for electricity storage devices and an active material.
  • a slurry for an electricity storage device electrode often contains a binder component such as an SBR-based copolymer and a thickener such as carboxymethyl cellulose in order to improve adhesion.
  • the slurry for an electricity storage device electrode according to this embodiment can improve adhesion even when it contains only the above-mentioned polymer (A) as the polymer component.
  • the slurry for an electricity storage device electrode according to this embodiment may contain a polymer other than the polymer (A) or a thickener in order to further improve adhesion.
  • the components contained in the slurry for an electricity storage device electrode according to this embodiment are described below.
  • Polymer (A) The composition, physical properties, production method, etc. of the polymer (A) are as described above, so description thereof will be omitted.
  • the content of the polymer component in the slurry for the storage device electrode according to this embodiment is preferably 1 to 8 parts by mass, more preferably 1 to 7 parts by mass, and particularly preferably 1.5 to 6 parts by mass, relative to 100 parts by mass of the active material.
  • the content of the polymer component is within the above range, the dispersibility of the active material in the slurry is good, and the coating properties of the slurry are also excellent.
  • the polymer component includes the polymer (A), polymers other than the polymer (A) that are added as necessary, and a thickener, etc.
  • the active material used in the slurry for the electrode of the power storage device includes a positive electrode active material and a negative electrode active material.
  • a positive electrode active material includes carbon materials, silicon materials, oxides containing lithium atoms, sulfur compounds, lead compounds, tin compounds, arsenic compounds, antimony compounds, aluminum compounds, conductive polymers such as polyacene, composite metal oxides represented by A X B Y O Z (wherein A represents an alkali metal or transition metal, B represents at least one selected from transition metals such as cobalt, nickel, aluminum, tin, and manganese, O represents an oxygen atom, and X, Y, and Z are numbers in the ranges of 1.10>X>0.05, 4.00>Y>0.85, and 5.00>Z>1.5, respectively), and other metal oxides. Specific examples of these include compounds described in Japanese Patent No. 5999399 and the like.
  • the slurry for storage device electrodes according to this embodiment can be used to fabricate either positive or negative electrodes, but is particularly preferably used for negative electrodes.
  • a negative electrode among the active materials exemplified above, it is preferable to use one that contains a silicon material and/or a carbon material, and more preferably a mixture of a silicon material and a carbon material. Silicon materials have a larger amount of lithium absorbed per unit weight than other active materials, and therefore can increase the storage capacity of the resulting electricity storage device. As a result, the output and energy density of the electricity storage device can be increased. On the other hand, carbon materials have a smaller volume change during charging and discharging than silicon materials, so by using a mixture of silicon material and carbon material as the negative electrode active material, the effect of the volume change of the silicon material can be mitigated, and the adhesion ability between the active material layer and the current collector can be further improved.
  • silicon (Si) When silicon (Si) is used as an active material, while it has a high capacity, it undergoes a large change in volume when absorbing lithium ions. This causes silicon materials to pulverize due to repeated expansion and contraction, which can lead to peeling from the current collector and separation of active materials from each other, and can easily disrupt the conductive network inside the active material layer. This property causes the charge/discharge durability of the energy storage device to deteriorate drastically in a short period of time.
  • the electricity storage device electrode produced using the electricity storage device electrode slurry according to this embodiment can exhibit good electrical properties even when a silicon material is used, without the above-mentioned problems occurring.
  • the reason for this is believed to be that the polymer (A) can firmly bind the silicon material, and at the same time, even if the silicon material expands in volume by absorbing lithium, the polymer (A) can expand and contract, thereby maintaining the silicon material in a firmly bound state.
  • the content of silicon material in 100% by mass of active material is preferably 1% by mass or more, more preferably 2 to 50% by mass, even more preferably 3 to 45% by mass, and particularly preferably 10 to 40% by mass.
  • an electricity storage device can be obtained that has an excellent balance between improved output and energy density of the electricity storage device and the charge/discharge durability characteristics.
  • the negative electrode active material is preferably in the form of particles.
  • the average particle size of the negative electrode active material is preferably 0.1 to 100 ⁇ m, and more preferably 1 to 20 ⁇ m.
  • an oxide containing lithium atoms is preferable.
  • oxides containing lithium atoms include those represented by the following general formula (2) and selected from the group consisting of lithium manganese oxide, lithium nickel oxide, lithium cobalt oxide, and lithium manganese nickel cobalt oxide.
  • M is at least one selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn.
  • A is at least one metal ion selected from the group consisting of Si, S, P, and V, and x is a number satisfying the relationship 0 ⁇ x ⁇ 1.
  • the value of x in the general formula (2) is selected according to the valences of M and A so that the overall valence of the general formula (2) is zero.
  • olivine-type lithium-containing phosphate compounds examples include LiFePO4 , LiCoPO4 , LiMnPO4 , Li0.90Ti0.05Nb0.05Fe0.30Co0.30Mn0.30PO4 , etc.
  • LiFePO4 lithium iron phosphate
  • LiFePO4 is particularly preferred because the raw material iron compound is easily available and inexpensive .
  • the average particle size of the olivine-type lithium-containing phosphate compound is preferably in the range of 1 to 30 ⁇ m, more preferably in the range of 1 to 25 ⁇ m, and particularly preferably in the range of 1 to 20 ⁇ m.
  • the active material layer may contain the following active materials: conductive polymers such as polyacene, composite metal oxides represented by A X B Y O Z (wherein A is an alkali metal or a transition metal, B is at least one selected from transition metals such as cobalt, nickel, aluminum, tin, and manganese, O is an oxygen atom, and X, Y, and Z are numbers within the ranges of 1.10>X>0.05, 4.00>Y>0.85, and 5.00>Z>1.5, respectively), and other metal oxides.
  • Examples of the composite metal oxide include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and ternary lithium nickel cobalt manganese oxide.
  • the electricity storage device electrode produced using the electricity storage device electrode slurry according to this embodiment can exhibit good electrical properties even when an oxide containing lithium atoms is used as the positive electrode active material. This is thought to be because the polymer (A) can firmly bind the oxide containing lithium atoms and at the same time, can maintain the state in which the oxide containing lithium atoms is firmly bound even during charging and discharging.
  • the slurry for the power storage device electrode according to this embodiment may contain components such as a polymer other than the polymer (A), a thickener, a liquid medium, a conductive assistant, a pH adjuster, a corrosion inhibitor, an antioxidant, and cellulose fiber, as necessary.
  • the polymer other than the polymer (A) and the thickener can be appropriately selected from the compounds exemplified in the above section "1.3.
  • Other Additives and used for the same purpose and in the same content ratio.
  • a liquid medium may be further added to the slurry for an electric storage device electrode according to this embodiment in addition to the liquid medium carried over from the binder composition for an electric storage device.
  • the liquid medium to be added may be the same as or different from the liquid medium (B) contained in the binder composition for an electric storage device, but is preferably selected from the liquid media exemplified in the above section "1.2. Liquid medium (B)".
  • the content of the liquid medium (including the amount carried over from the binder composition for electricity storage devices) in the slurry for electricity storage device electrodes according to this embodiment is preferably such that the solids concentration in the slurry (meaning the proportion of the total mass of the components in the slurry other than the liquid medium to the total mass of the slurry; the same applies below) is 30 to 70 mass%, and more preferably 40 to 60 mass%.
  • a conductive assistant may be further added to the slurry for an electricity storage device electrode according to this embodiment for the purposes of imparting electrical conductivity and buffering the volume change of the active material caused by the ingress and egress of lithium ions.
  • conductive additives include activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, fullerene, carbon nanotubes, and other carbons.
  • acetylene black, ketjen black, and carbon nanotubes are preferably used.
  • the content of the conductive additive is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass, relative to 100 parts by mass of the active material.
  • a pH adjuster may be further added to the slurry for an electricity storage device electrode according to this embodiment for the purpose of suppressing corrosion of the current collector depending on the type of active material.
  • pH adjusters examples include hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, ammonium phosphate, ammonium sulfate, ammonium acetate, ammonium formate, ammonium chloride, sodium hydroxide, potassium hydroxide, etc.
  • sulfuric acid, ammonium sulfate, sodium hydroxide, and potassium hydroxide are preferred.
  • a neutralizing agent selected from those described in the production method for polymer (A) can also be used.
  • corrosion inhibitors include ammonium metavanadate, sodium metavanadate, potassium metavanadate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, potassium paratungstate, ammonium molybdate, sodium molybdate, potassium molybdate, etc., and among these, ammonium paratungstate, ammonium metavanadate, sodium metavanadate, potassium metavanadate, and ammonium molybdate are preferred.
  • the slurry for an electric storage device electrode according to this embodiment may further contain cellulose fibers.
  • cellulose fibers may be used.
  • the addition of cellulose fibers may improve the adhesion of the active material to the current collector. It is believed that the fibrous cellulose fibers bond adjacent active materials together in a fibrous form by linear adhesion or linear contact, thereby preventing the active material from falling off and improving the adhesion to the current collector.
  • the slurry for power storage device electrode according to this embodiment may be produced by any method as long as it contains the above-mentioned binder composition for power storage device and active material. From the viewpoint of producing a slurry having better dispersibility and stability more efficiently and inexpensively, it is preferable to produce the slurry by adding the active material and optional additive components used as necessary to the binder composition for power storage device and mixing them. Specific examples of the production method include the method described in Japanese Patent No. 5999399.
  • An electricity storage device electrode comprises a current collector and an active material layer formed by applying and drying the above-mentioned slurry for electricity storage device electrodes to the surface of the current collector.
  • Such an electricity storage device electrode can be manufactured by applying the above-mentioned slurry for electricity storage device electrodes to the surface of a current collector such as a metal foil to form a coating film, and then drying the coating film to form an active material layer.
  • the current collector is not particularly limited as long as it is made of a conductive material, but examples include the current collectors described in Patent No. 5999399, etc.
  • the content of silicon elements in 100% by mass of the active material layer is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and particularly preferably 3 to 10% by mass.
  • the content of silicon elements in the active material layer is within the above range, not only is the storage capacity of the electricity storage device produced using it improved, but an active material layer with a uniform distribution of silicon elements can be obtained.
  • the content of silicon elements in the active material layer can be measured by the method described in, for example, Patent No. 5999399.
  • the electricity storage device includes the above-mentioned electricity storage device electrode, further contains an electrolyte solution, and can be manufactured by a conventional method using components such as a separator.
  • a specific manufacturing method includes, for example, stacking a negative electrode and a positive electrode via a separator, and storing the stack in a battery container by rolling or folding the stack according to the battery shape, and injecting an electrolyte solution into the battery container and sealing it.
  • the shape of the battery can be any appropriate shape, such as a coin type, a cylindrical type, a square type, or a laminate type.
  • the above-mentioned electricity storage device can be applied to lithium ion secondary batteries, electric double layer capacitors, lithium ion capacitors, and the like, which require discharge at a high current density.
  • lithium ion secondary batteries are particularly preferred.
  • the components other than the binder composition for electricity storage devices can be publicly known components for lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors.
  • Example 1 5.1.1. Preparation of binder composition for an electricity storage device ⁇ Example 1> A binder composition for an electrical storage device containing a polymer (A1) was obtained by two-stage polymerization as shown below. A reactor was charged with 300 parts by mass of water, a monomer mixture consisting of 50 parts by mass of 1,3-butadiene, 35 parts by mass of styrene, 5 parts by mass of acrylonitrile, 1 part by mass of sodium styrenesulfonate, 1 part by mass of itaconic acid, and 1 part by mass of acrylamide, 0.1 parts by mass of tert-dodecyl mercaptan as a chain transfer agent, 0.1 parts by mass of sodium alkyl diphenyl ether disulfonate as an emulsifier, and 1.0 part by mass of potassium persulfate as a polymerization initiator, and the mixture was polymerized at 70° C.
  • a monomer mixture consisting of 50 parts by mass
  • the particle dispersion of polymer (A1) thus obtained was concentrated by removing unreacted monomers, and a 5% aqueous sodium hydroxide solution was added, and then moisture was removed using an evaporator to obtain a binder composition for an electrical storage device containing particles of polymer (A1) with a solid content concentration of 40% by mass and a pH of 7.0.
  • the binder composition for electric storage devices obtained above was diluted to 0.1 wt % and a drop of the latex was dropped onto a collodion support film with a pipette, and a drop of 0.02 wt % osmium tetroxide solution was dropped onto the collodion support film with a pipette and air-dried for 12 hours to prepare a sample.
  • the sample thus prepared was observed at a magnification of 10K (magnification) using a transmission electron microscope (TEM, Hitachi High-Tech Corporation, model number "H-7650”), and image analysis was performed using a HITACHI EMIP program to calculate the number average particle diameter of 50 randomly selected particles of polymer (A1). As a result, the number average particle diameter of polymer (A1) was 190 nm.
  • Table 1 The measurement results are shown in Table 1 below.
  • EC/EMC ethylene carbonate
  • EMC ethyl methyl carbonate
  • the insoluble matter was separated by filtration through a 300-mesh wire net, and the weight (Y (g)) of the residue obtained by evaporating and removing the soluble EC/EMC was measured.
  • the EC/EMC attached to the surface of the insoluble matter (film) separated by the above filtration was absorbed into paper and removed, and the weight (Z (g)) of the insoluble matter (film) was measured.
  • the surface acid amount of the particles of the polymer (A1) contained in the binder composition for a storage battery device obtained above was measured as follows. First, it was confirmed that 0.005 mol/L of sulfuric acid was filled in the titration burette of the potentiometric titration device (manufactured by Kyoto Electronics Manufacturing Co., Ltd., model "AT-510") and the reagent bottle at the top of the main body, and it was confirmed that the conductivity of the ultrapure water was 2 ⁇ S or less. Next, purging was performed to remove air from the burette, and further bubbles were removed from the nozzle.
  • the transverse relaxation time T A of protons present in an aqueous dispersion of polymer (A1) adjusted to a solid content concentration of 10% was measured by a pulsed NMR method.
  • the measurement was performed using a pulsed nuclear magnetic resonance apparatus "minispec mq20 manufactured by BRUKER Co., Ltd.”, with hydrogen nuclei as the measurement nuclei, and the transverse relaxation time (spin-spin relaxation time) of water protons was measured by the CPMG method (Carr-Purcell Meiboom-Gill method) under the measurement conditions of a measurement temperature of 25°C, a frequency of 20 MHz, and a 90-180° pulse interval of 0.04 tau.
  • CPMG method Carr-Purcell Meiboom-Gill method
  • the polymer (A1) obtained above was dried at 40°C for 24 hours to prepare a uniform film having a thickness of 1.0 ⁇ 0.3 mm. This film was dried in a vacuum dryer at 160°C for 30 minutes. The film was removed from the vacuum dryer and cut into strips of 10 mm x 10 mm to prepare a measurement sample.
  • FIG. 1 shows a graph showing the relationship between the measurement temperature and tan ⁇ in the dynamic viscoelasticity measurement of the film produced in Example 5 as an example.
  • ⁇ Slurry stability test> About 1 mL of a C/Si 90/10 slurry was measured using a Physica MCR301 manufactured by Anton Paar, and a 25 mm diameter cone plate was used under the conditions of a GAP of 1 mm and 25° C. The shear rate was started from 1 (1/s), and when it reached 1000 (1/s), the shear rate was slowed down again to 1 (1/s) to obtain the slurry viscosity behavior. The measurement was defined as going from 1 to 1000 (1/s) and as returning from 1000 to 1 (1/s), and the evaluation criteria were as follows.
  • ⁇ 5 points The viscosity at 100 (1/s) of the return is within ⁇ 8% of the viscosity at 100 (1/s) of the forward flow.
  • ⁇ 4 points The viscosity at 100 (1/s) of the return is within ⁇ 10% of the viscosity at 100 (1/s) of the forward flow.
  • ⁇ 3 points The viscosity at 100 (1/s) of the return is within ⁇ 15% of the viscosity at 100 (1/s) of the forward flow.
  • ⁇ 2 points The viscosity at 100 (1/s) of the return is within ⁇ 20% of the viscosity at 100 (1/s) of the forward flow.
  • ⁇ 1 point The viscosity at 100 (1/s) of the return is greater than ⁇ 20% of the viscosity at 100 (1/s) of the forward flow.
  • NMP NMP was added to the obtained paste, and the solid content concentration was adjusted to 65% by mass. Then, using a stirring and defoaming machine (manufactured by Thinky Corporation, product name "Awatori Rentaro"), the mixture was stirred and mixed at 200 rpm for 2 minutes, 1800 rpm for 5 minutes, and further at 1800 rpm for 1.5 minutes under reduced pressure (about 2.5 ⁇ 10 4 Pa), to prepare a positive electrode slurry.
  • the positive electrode slurry was uniformly applied to the surface of a current collector made of aluminum foil by a doctor blade method so that the film thickness after solvent removal was 80 ⁇ m, and the solvent was removed by heating at 120 ° C. for 20 minutes. Thereafter, the active material layer was pressed with a roll press machine so that the density of the active material layer was 3.0 g / cm 3 , thereby obtaining a counter electrode (positive electrode).
  • the positive electrode produced above was punched out to a diameter of 15.95 mm and placed on the cell, and the exterior body of the two-electrode coin cell was sealed with screws to assemble a lithium-ion battery cell (electricity storage device).
  • Capacity retention rate (%) (discharge capacity at 100th cycle) / (discharge capacity at 1st cycle) (6) (Evaluation Criteria) ⁇ 5 points: Capacity retention is 95% or more. 4 points: Capacity retention is between 90% and 95%. 3 points: Capacity retention is between 85% and 90%. ⁇ 2 points: Capacity retention is between 80% and 85%. ⁇ 1 point: Capacity retention is between 75% and 80%. 0 points: Capacity retention is less than 75%.
  • ⁇ 5 points Resistance increase rate is 100% or more but less than 150%.
  • ⁇ 4 points Resistance increase rate is 150% or more but less than 200%.
  • ⁇ 3 points Resistance increase rate is 200% or more but less than 250%.
  • ⁇ 2 points Resistance increase rate is between 250% and 300%.
  • ⁇ 1 point Resistance increase rate is between 300% and 350%.
  • ⁇ 0 points Resistance increase rate is 350% or more.
  • a contact sensor manufactured by Keyence Corporation, product name "GT2-H12KLF" was attached to the electricity storage device, and the thickness of the film at that point was taken as the film thickness after chemical formation. Then, charging was started at a constant current (0.2C), and charging was continued at a constant voltage (4.2V) when the voltage reached 4.2V, and charging was completed (cut-off) when the current value reached 0.01C. Thereafter, discharge was started at a constant current (0.2 C) in a thermostatic chamber adjusted to 25° C., and discharge was completed (cut off) when the voltage reached 2.5 V.
  • the film thickness at the 10th discharge cycle was measured to calculate the plate expansion coefficient according to the following formula (8) and evaluated according to the following criteria.
  • Plate expansion rate (%) ((film thickness at 10th discharge cycle) - (film thickness after formation)) / (initial film thickness) x 100 ...
  • ⁇ 5 points The expansion rate of the electrode plate is 40% or less.
  • ⁇ 4 points Plate expansion rate is over 40% to 43% or less.
  • ⁇ 3 points The electrode plate expansion rate is more than 43% and less than 46%.
  • ⁇ 2 points The electrode plate expansion rate is more than 46% and less than 50%.
  • ⁇ 1 point The expansion rate of the electrode plate is more than 50%.
  • Examples 2 to 15 and Comparative Examples 1 to 6 In Examples 2 to 15 and Comparative Examples 1 and 3 to 6, the types and amounts of monomers were as shown in Tables 1 to 3 below, respectively, and each polymer was synthesized by two-stage polymerization in the same manner as in Example 1 to obtain each binder composition for an electricity storage device.
  • Comparative Example 2 the types and amounts of monomers were as shown in Table 3 below, and the polymer was synthesized by one-stage polymerization to obtain a binder composition for an electricity storage device. All other steps were carried out in the same manner as in Example 1.
  • the slurry for the storage device electrode contains the binder composition for the storage device of the present invention and an active material containing a silicon material.
  • the binder particles were not destroyed by the active material, which has a large volume change due to charging and discharging, and the particle shape was maintained.
  • the active materials can be favorably bonded to each other, the electrode plate expansion rate can be reduced, and the adhesion between the active material layer and the current collector can be well maintained.
  • the binder particles can maintain their particle shape, so that the permeability of the electrolyte is increased and the resistance increase rate can be suppressed.
  • a storage device electrode with good cycle characteristics was obtained that suppresses peeling of the active material layer and reduces electrode plate expansion, even when the volume of the active material is repeatedly expanded and contracted by repeated charging and discharging.
  • the present invention is not limited to the above-mentioned embodiment, and various modifications are possible.
  • the present invention includes configurations that are substantially the same as those described in the embodiment (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect).
  • the present invention also includes configurations in which non-essential parts of the configurations described in the above-mentioned embodiment are replaced with other configurations.
  • the present invention also includes configurations that have the same action and effect as the configurations described in the above-mentioned embodiment, or that can achieve the same purpose.
  • the present invention also includes configurations in which publicly known technology is added to the configurations described in the above-mentioned embodiment.

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