WO2020111027A1 - Séparateur pour élément électrochimique - Google Patents

Séparateur pour élément électrochimique Download PDF

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Publication number
WO2020111027A1
WO2020111027A1 PCT/JP2019/046067 JP2019046067W WO2020111027A1 WO 2020111027 A1 WO2020111027 A1 WO 2020111027A1 JP 2019046067 W JP2019046067 W JP 2019046067W WO 2020111027 A1 WO2020111027 A1 WO 2020111027A1
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Prior art keywords
particles
separator
hydroxide
less
hydrophilic
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PCT/JP2019/046067
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English (en)
Japanese (ja)
Inventor
小川　賢
弘子 原田
康行 高澤
進治 高崎
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株式会社日本触媒
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Priority to JP2020557717A priority Critical patent/JP7161547B2/ja
Publication of WO2020111027A1 publication Critical patent/WO2020111027A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • 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

Definitions

  • the present invention relates to a separator for electrochemical device. More specifically, it relates to a separator used for an electrochemical element such as a battery, a capacitor, a capacitor, a sensor and an electrolyzer.
  • a zinc-alkaline secondary battery in which a porous layer of magnesium oxide that acts as a barrier layer that blocks acicular zinc crystals (dendrites) generated during charging is adhered (see, for example, Patent Document 1). ..
  • the porous layer of magnesium oxide described in the above Patent Document 1 has room for further devising to prolong the life of the battery. Further, it is desired to extend the life of electrochemical devices other than batteries.
  • the present invention has been made in view of the above circumstances, and an object thereof is to provide a method for extending the life of an electrochemical device.
  • the present inventors have conducted various studies on methods for extending the life of an electrochemical device and focused on a separator used for the electrochemical device. Then, the inventors of the present invention can extend the life of an electrochemical device by including a hydrophobic particle and a hydrophilic particle each in a certain ratio or more, and by using a separator for an electrochemical device in which the content of a binder component is less than a certain ratio.
  • the present invention has been made, and the present invention has been achieved by realizing that the above problems can be solved satisfactorily.
  • the present invention is a separator used in an electrochemical device, wherein the separator contains hydrophobic particles, hydrophilic particles, and optionally a binding component, and hydrophobic particles/(hydrophilic particles and binding component Volume ratio of more than 20/80, the volume ratio of hydrophilic particles/(hydrophobic particles and binding component) exceeds 20/80, and of binding component/(hydrophobic particles and hydrophilic particles) The volume ratio is less than 30/70 for the electrochemical device separator.
  • the present invention has the above-mentioned structure and can prolong the life of the electrochemical device.
  • FIG. 4 is a triangular diagram showing the relationship between the cycle ratio and the volume ratio of hydrophobic particles, hydrophilic particles, and a binding component.
  • 3 is a SEM photograph showing a cross section of the separator of Example 1 (40% by volume of hydrophobic particles, 50% by volume of hydrophilic particles, 10% by volume of a binding component).
  • 5 is an SEM photograph showing a cross section of a separator (hydrophobic particles 0% by volume, hydrophilic particles 80% by volume, binder component 20% by volume) of Comparative Example 1-1.
  • 9 is a SEM photograph showing a cross section of a separator of Comparative Example 3.
  • 5 is a SEM photograph showing a cross section of the separator of Example 3.
  • 5 is a SEM photograph showing a cross section of the separator of Example 4-4 before immersion in the electrolytic solution. 5 is an SEM photograph showing a cross section of the separator of Example 4-4 after immersion in the electrolytic solution. It is a schematic diagram of a water permeability test.
  • the electrochemical device separator of the present invention is a member that secures ionic conductivity between the positive electrode and the negative electrode while separating the positive electrode and the negative electrode, but as described above, the hydrophobic particles and the hydrophilic particles are respectively used. It is contained in a certain proportion or more and the content of the binding component is less than the certain proportion.
  • the separator for an electrochemical device of the present invention has excellent durability due to its configuration, and particularly when used in an electrochemical device including an electrode that undergoes a morphological change with charge and discharge, a certain proportion of hydrophobic particles.
  • the electrochemical device of the present invention due to the water repellency of the hydrophobic particles, the substantial amount of the electrolytic solution in the separator is limited, and the free active material derived from the separator is used. Since the ion (for example, zincate ion) concentration is low, it is possible to sufficiently suppress the growth of dendrites that occur during the process of the dissolution and precipitation reaction of the active material component (for example, zinc component), and the electrochemical device The life can be extended.
  • the separator for electrochemical device of the present invention contains hydrophilic particles in a certain proportion or more, and the content of the binding component is less than the certain proportion, so that the hydrophilic particle surface serves as an ion conduction path and binds. It is possible to sufficiently prevent the gap between particles from being filled with the component when binding the particles, and it is possible to make the ionic conductivity of the separator sufficiently high. By making the ionic conductivity inside the electrochemical device sufficiently high and by using the electrochemical device having a low internal resistance, the electrochemical device can be appropriately driven, which contributes to a longer life.
  • the hydrophobic particles can remarkably exhibit the above-mentioned water repellency in that they have a particle shape rather than a fibrous shape having a small specific surface area. Similarly, the hydrophilic particles have a particle shape, so that the ionic conductivity of the separator can be made very excellent.
  • the volume ratio of the hydrophobic particles/(hydrophilic particles and binder component) is preferably 25/75 or more, and more preferably 37/63 or more.
  • the volume ratio of the hydrophobic particles/(hydrophilic particles and binding component) is 80/20 because the volume ratio of the hydrophilic particles/(hydrophobic particles and binding component) exceeds 20/80. It is less than 70, preferably less than 70/30.
  • the volume ratio of the hydrophilic particles/(hydrophobic particles and binding component) is preferably 30/70 or more.
  • the volume ratio of the hydrophilic particles/(hydrophobic particles and binding component) is 80/20 because the volume ratio of the hydrophobic particles/(hydrophilic particles and binding component) exceeds 20/80.
  • the volume ratio of the binder component/(hydrophobic particles and hydrophilic particles) is preferably 20/80 or less, more preferably 10/90 or less.
  • the binder component is an arbitrary component, and the lower limit of the volume ratio of the binder component/(hydrophobic particles and hydrophilic particles) is preferably 0/100, more preferably 0.1/99. 9 and more preferably 1/99.
  • hydrophobic particles the hydrophobic particles, the hydrophilic particles, the binding component which is an optional component, and the like contained in the separator for electrochemical device of the present invention will be described in order.
  • the electrochemical device separator of the present invention contains hydrophobic particles.
  • the hydrophobic particles mean particles having a water permeability of 0.01 g or less calculated by the following water permeability test.
  • the hydrophobic particles are not particularly limited as long as the water permeation amount is 0.01 g or less, and for example, the entire particles may be particles composed of a hydrophobic material, or the surface thereof may be coated with a hydrophobic material. It may be a particle.
  • the water permeability of the hydrophobic particles is preferably 0.001 g or less.
  • the lower limit of the amount of water permeation in the hydrophobic particles is 0 g.
  • the hydrophobic particles preferably maintain an independent particle shape.
  • ⁇ Water permeability test method> As shown in FIG. 8, at room temperature and under normal pressure, a hydrophilic (fluorine-treated) polypropylene non-woven fabric 8 is placed under a cylindrical container 6 having an inner diameter of 1.5 cm, and ⁇ -cellulose is used as a water absorber. 3 cm ⁇ 3 cm, thickness 1 mm, and weight 400 mg of filter paper 7 is installed, and sample powder 5 (1 g) is gently charged from the upper part of the cylindrical container 6. After that, water 9 (2 g) is gently introduced from the vicinity of the upper part of the cylindrical container 6, and after 1 hour, the amount of water absorbed by the filter paper 7 is measured to calculate the amount of water permeation per hour. The water content can be measured from the weight change of the filter paper 7.
  • the hydrophilic non-woven fabric 8 made of polypropylene is inserted between the filter paper 7 and the sample powder 5 so that the sample powder 5 does not adhere to the filter paper 7 and cause a weight error.
  • the lower part of the cylindrical container 6 is capped and charged so that the solid content weight of the dispersion is 1 g, and after drying, the lower cap is removed and hydrophilic treatment is completed.
  • water 9 is added as described above to conduct the water permeability test. The results of the water permeability test performed on various particles are shown in Examples.
  • the hydrophobic particles preferably have a surface glass transition temperature of 60° C. or higher, and more preferably the entire glass transition temperature of 60° C. or higher.
  • the glass transition temperature is a differential scanning calorimeter (device name: thermal analysis device DSC3100S, BRVKER, for the dried body obtained by applying a material such as a polymer on a glass plate and drying at 120° C. for 1 hour. ) Is used for measurement.
  • the hydrophobic particles are preferably polymer particles (organic polymer particles).
  • various hydrophobic materials can be suitably used, and may be thermoplastic or thermosetting.
  • halogen-containing atom ethylene polymer, polysulfone polymer examples thereof include polyether ketone, and among them, halogen-containing atom ethylene-based polymers and/or polysulfone-based polymers are preferable.
  • the above-mentioned halogen-containing ethylene-based polymer has a structure in which at least a part of polyethylene hydrogen atoms are replaced with halogen atoms, and in particular, a fluorine-containing structure having a structure in which at least a part of polyethylene hydrogen atoms is replaced with fluorine atoms.
  • Atomic ethylene polymers are preferable, and preferred examples thereof include polyvinylidene fluoride and polytetrafluoroethylene.
  • the polysulfone-based polymer is a polymer having a sulfonyl group as a repeating unit, and examples thereof include polysulfone (PSU), polyether sulfone (PESU), and polyphenyl sulfone (PSSU).
  • the polyetherketone is a polymer having an ether bond and a ketone bond, and examples thereof include polyetherketoneketone and polyetheretherketone.
  • the above-mentioned polymer can be produced by copolymerizing a monomer component forming a structural unit contained in the polymer in the presence of a radical generator and, if necessary, graft-modifying the same.
  • the method for polymerizing the monomer component is not particularly limited, and examples thereof include an aqueous solution polymerization method, an emulsion polymerization method, a reverse phase suspension polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk polymerization method.
  • the shape of the hydrophobic particles examples include fine powder, powder, granules, granules, scales, polyhedra, rods, and curved surface-containing shapes.
  • the hydrophobic particles preferably have an average particle size of 50 nm or more.
  • the average particle diameter is more preferably 100 nm or more, further preferably 200 nm or more. Further, the average particle diameter is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and further preferably 10 ⁇ m or less.
  • the average particle size is an average particle size in a volume-based particle size distribution. About 10 mL of an aqueous dispersion of hydrophobic particles is sampled in a glass cell, and this is measured by a dynamic light scattering method (Particle Sizing Systems [Particle Sizing Systems], trade name: NICOMP Model 380).
  • the hydrophobic particles may have an aspect ratio (longitudinal/horizontal) of 1 or more.
  • the aspect ratio (vertical/horizontal) is preferably 8 or less.
  • the aspect ratio (vertical/horizontal) is more preferably 5 or less, still more preferably 2 or less, and particularly preferably 1.5 or less.
  • the aspect ratio (vertical/horizontal) can be obtained from the shape of the particles observed by SEM. For example, when the particles have a rectangular parallelepiped shape, it can be determined by dividing the vertical length by the horizontal length with the longest side being the vertical and the second longest side being the horizontal.
  • one point is placed on the bottom surface so that the aspect ratio is maximized, and when a part is projected from the direction that maximizes the aspect ratio, a certain point is formed. It is calculated by measuring the length of one point farthest from, the longest one is vertical, and the shortest one of the straight lines passing through the vertical center points is horizontal, and the vertical length is divided by the horizontal length. be able to.
  • the particles having an aspect ratio (longitudinal/horizontal) in the above range are, for example, a method of selecting particles having such an aspect ratio, or optimization of preparation conditions at the stage of producing particles to optimize the particles. It can be obtained by a method of obtaining selectively.
  • the separator includes hydrophilic particles.
  • the hydrophilic particles are particles having a water permeability of more than 0.01 g calculated by the water permeability test, and are usually inorganic compound particles having no glass transition temperature.
  • the hydrophilic particles are not particularly limited as long as the amount of water permeation exceeds 0.01 g, and for example, the entire particles may be particles composed of a hydrophilic material, or particles whose surface is coated with a hydrophilic material. May be
  • the water permeability of the hydrophilic particles is preferably 0.1 g or more.
  • the upper limit of the amount of water permeation through the hydrophilic particles is 2 g.
  • the hydrophilic particles are preferably inorganic compound particles.
  • various hydrophilic materials can be preferably used, for example, selected from the group consisting of oxides, hydroxides, layered double hydroxides, and phosphoric acid compounds. It is preferable that it is at least one kind.
  • a hydroxide is a compound having a hydroxy group and refers to a compound other than the layered double hydroxide.
  • the oxide examples include lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, barium oxide, scandium oxide, yttrium oxide, lanthanoid oxide, titanium oxide, zirconium oxide, niobium oxide, ruthenium oxide, nickel oxide, Palladium oxide, copper oxide, cadmium oxide, boron oxide, aluminum oxide, gallium oxide, indium oxide, thallium oxide, silicon oxide, germanium oxide, tin oxide, lead oxide, phosphorus oxide, bismuth oxide, and the like. Alternatively, two or more kinds can be used.
  • magnesium oxide, calcium oxide, titanium oxide, zirconium oxide, and aluminum oxide are preferable, and magnesium oxide and oxide are preferable.
  • Titanium and zirconium oxide are more preferable.
  • the zirconium oxide may be, for example, a solid solution of an element such as yttrium, scandium, or ytterbium, or may have an oxygen defect.
  • hydroxide examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, scandium hydroxide, yttrium hydroxide, lanthanoid hydroxide, titanium hydroxide, and water.
  • germanium oxide, tin hydroxide, lead hydroxide, phosphoric acid and bismuth hydroxide examples thereof include germanium oxide, tin hydroxide, lead hydroxide, phosphoric acid and bismuth hydroxide, and one or more of these can be used.
  • those having a low solubility under alkaline conditions are preferable, for example, magnesium hydroxide, calcium hydroxide, titanium hydroxide and zirconium hydroxide are preferable, and magnesium hydroxide is more preferable.
  • the layered double hydroxide has the following general formula: [M 1 1-x M 2 x (OH) 2 ] (A n- ) x/n ⁇ mH 2 O
  • M 1 represents a divalent metal ion which is any one of Mg, Fe, Zn, Ca, Li, Ni, Co, Cu and Mn.
  • M 2 represents Al, Fe, Mn, Co, Cr and In. .
  • a n-is representative of the trivalent metal ion is any one, Cl -, NO 3 -, CO 3 2-, COO -. 1 or more valences such as, represents a trivalent following anions Among them, a n-is It is preferable to represent a divalent or less anion.
  • m is a number of 0 or more
  • n is a number of 1 or more and 3 or less
  • x is a number of 0.20 or more and 0.40 or less.
  • layered double hydroxides include, for example, hydrotalcite, manassite, motucoreite, stichtite, schogrenite, barbernite, pyroaurite, iomite, chloromagarminite, hydro.
  • Calumite, green last 1, bercherin, tacobite, ribesite, honesite, eardrite, mayxenerite and the like can be mentioned, and one or more of these can be used.
  • hydrotalcite in which M 1 in the above general formula is Mg and M 2 in the above formula is Al is preferable because it is industrially easy to use.
  • these layered hydroxides are, for example, compounds dehydrated by firing at 150° C. or higher and 900° C. or lower, compounds in which anions in the layers are decomposed, and anions in the layers to hydroxide ions and the like. It may be an exchanged compound.
  • a compound having a functional group such as a hydroxyl group, an amino group, a carboxy group or a silanol group may be coordinated with the layered double hydroxide.
  • the layered double hydroxide may have an organic substance between the layers.
  • Examples of the phosphoric acid compound include hydroxyapatite (Ca 10 (PO4) 6 (OH) 2 ), magnesium hydroxyapatite in which part or all of calcium ions of hydroxyapatite are replaced with magnesium, strontium hydroxyapatite in which strontium is replaced, Examples include barium hydroxyapatite substituted with barium. Of these, hydroxyapatite and magnesium hydroxyapatite are preferable.
  • the inorganic compound is preferably a magnesium-containing compound.
  • the inorganic compound is preferably a hydroxide, a layered double hydroxide or a phosphoric acid compound, more preferably a layered double hydroxide and/or a hydroxide.
  • the inorganic compound is more preferably a hydroxide from the viewpoint of making the strength of the separator more excellent, and from the viewpoint of making the ion conductivity of the separator more excellent, the layered double hydroxide.
  • Magnesium hydroxide is more preferable, and from the viewpoint of further improving the durability of the separator, magnesium hydroxide is particularly preferable.
  • the hydrophilic particles examples include fine powder, powder, granules, granules, scales, polyhedrons, rods, and curved surface-containing shapes.
  • the hydrophilic particles preferably have an average particle diameter of 2 ⁇ m or less.
  • the average particle diameter is more preferably 1 ⁇ m or less, still more preferably 0.5 ⁇ m or less. Further, the average particle diameter is preferably 0.001 ⁇ m or more, more preferably 10 nm or more, and further preferably 100 nm or more.
  • the average particle diameter is an average particle diameter in a volume-based particle size distribution
  • the hydrophilic particles are diluted with a dispersion medium (ion exchanged water containing 0.2% sodium hexametaphosphate) to obtain a diluted solution of about 10 mL.
  • a dispersion medium ion exchanged water containing 0.2% sodium hexametaphosphate
  • the particles having a volume average particle diameter in the above range are, for example, a method of pulverizing the particles with a ball mill or the like, dispersing the obtained coarse particles in a dispersant to obtain a desired particle diameter, and then drying to dryness.
  • a method of pulverizing the particles with a ball mill or the like dispersing the obtained coarse particles in a dispersant to obtain a desired particle diameter, and then drying to dryness.
  • the hydrophilic particles may have an aspect ratio (longitudinal/horizontal) of 1 or more.
  • the aspect ratio (vertical/horizontal) is preferably 8 or less.
  • the aspect ratio (vertical/horizontal) is more preferably 5 or less, still more preferably 2 or less, and particularly preferably 1.5 or less.
  • the aspect ratio (vertical/horizontal) is obtained as described above. Further, particles having an aspect ratio (longitudinal/horizontal) in the above range can be obtained by the method described above.
  • the separator is preferably, for example, as described above, an anion conductive membrane containing polymer particles as hydrophobic particles and inorganic compound particles as hydrophilic particles.
  • the anion conductive film refers to a film which is permeable to anions such as hydroxide ions involved in the reaction of the electrochemical element and which contains polymer particles and inorganic compound particles.
  • the anion conductive membrane has selectivity of anions to be transmitted by the action of the inorganic compound particles described later.
  • the selectivity of the anion is such that a hydroxide ion or other anion easily permeates, and even an anion has a large ionic radius and is a metal-containing ion derived from an active material (for example, Zn(OH) 4 2 ⁇ ). Sufficiently prevent the penetration of such substances.
  • anion conductivity means that an anion having a small ionic radius such as a hydroxide ion is sufficiently permeated or that the anion is permeated.
  • Anions having a large ionic radius such as metal-containing ions are more difficult to permeate and may not permeate at all.
  • the separator may further include a binder component.
  • the binder component usually means a component having a glass transition temperature of less than 60° C., and by binding the particles, it is possible to contribute to the structural stability of the separator.
  • the binder component preferably has a glass transition temperature of 50° C. or lower.
  • the binding component is preferably non-particulate. Further, the binding component is preferably bound to other components around it (hydrophobic particles, hydrophilic particles, porous support, etc.).
  • the binder component is preferably a non-crystalline binder polymer having a glass transition temperature of less than 60°C. Being non-crystalline, it is easy to form a bond with the surrounding members, and it suitably functions as a binding component.
  • the binder polymer is preferably fibrous. Examples of the binder polymer include conjugated diene-based polymers and (meth)acrylic polymers, and among them, conjugated diene-based polymers are preferable.
  • the conjugated diene-based polymer has a monomer unit derived from a conjugated diene-based monomer.
  • the conjugated diene polymer include styrene-butadiene polymer, carboxy-modified styrene-butadiene polymer, polybutadiene polymer, carboxy-modified polybutadiene polymer, polyisoprene polymer, carboxy-modified polyisoprene polymer, acrylonitrile-butadiene polymer, One kind or two or more kinds of carboxy-modified acrylonitrile-butadiene-based polymer and the like can be preferably used.
  • styrene-butadiene-based polymers and carboxy-modified styrene-butadiene-based polymers are preferable, and carboxy-modified styrene-butadiene-based polymers are particularly preferable.
  • the conjugated diene-based polymer is a monomer unit derived from an aliphatic conjugated diene-based monomer, a monomer unit derived from an aromatic vinyl monomer, a monomer unit derived from an unsaturated monomer having a carboxylate group and/or a carboxylate group which is a salt thereof. , And may have monomer units derived from other unsaturated monomers.
  • the mass ratio of the monomer units derived from other unsaturated monomers is preferably 30% by mass or less, more preferably 5% by mass or less, and 0.1% by mass. The following is more preferable.
  • the (meth)acrylic polymer may be any polymer having a monomer unit derived from a monomer having a (meth)acryloyl group, but a typical example thereof is mainly a monomer unit derived from a (meth)acrylic acid ester monomer. (Meth)acrylic acid ester-based polymers are included.
  • the term “mainly composed of a monomer unit derived from a (meth)acrylic acid ester monomer” means that the content of the monomer unit derived from a (meth)acrylic acid ester monomer is 50% by mass or more in 100% by mass of the (meth)acrylic acid ester-based polymer.
  • Specific examples of the (meth)acrylate monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate.
  • T-butyl (meth)acrylate pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth) Examples include nonyl acrylate and decyl (meth)acrylate.
  • the (meth)acrylic polymer is a monomer unit derived from an unsaturated monomer having a carboxylate group and/or a carboxylate group which is a salt thereof in addition to the monomer unit derived from a (meth)acrylic acid ester monomer, and other unsaturated compounds. It may have a monomer unit derived from a monomer.
  • the mass ratio of the monomer units derived from other unsaturated monomers is preferably 30% by mass or less, more preferably 5% by mass or less, and 0.1% by mass or less. It is more preferable that the content is not more than mass %.
  • the binder polymer is preferably fibrous as described above, and may be in a fibrous state by heat or pressure. By making the polymer into fibers, the strength of the separator, the anion conductivity and the like can be suitably adjusted.
  • the separator for electrochemical device of the present invention further has a porous support (porous substrate) made of a polyolefin-based polymer or the like, and the porous support has hydrophobic particles, hydrophilic particles, and, if necessary,
  • the resin-impregnated layer may be a resin-impregnated layer impregnated with a mixture of binder components (dispersion liquid), and has a laminated structure obtained by bringing the mixture into contact with a porous substrate and drying the mixture as necessary. May be.
  • the porous support is not particularly limited, but is, for example, a polyolefin-based polymer such as polyethylene, polypropylene, an ethylene-propylene copolymer, or a cyclic polyolefin-based polymer; a polyvinyl alcohol-based polymer such as vinylon; an aliphatic polyamide; an aromatic polyamide; Non-woven fabrics, woven fabrics, microporous films and the like made of resin materials such as styrene-based polymers; polyester-based polymers; polyphenylene sulfide-based polymers are preferred, and among them, polyolefin-based polymers and polyvinyl alcohol-based polymers are more preferable. preferable.
  • a polyolefin-based polymer such as polyethylene, polypropylene, an ethylene-propylene copolymer, or a cyclic polyolefin-based polymer
  • a polyvinyl alcohol-based polymer such as vinylon
  • the separator is a resin-impregnated layer obtained by impregnating a porous support with the dispersion liquid according to the present invention and a porous support at least partially integrated.
  • the solid content of the dispersion according to the present invention fills at least some of the pores in the porous support.
  • the mass ratio of the porous support is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more in 100% by mass of the separator. Further, the mass ratio is preferably 60 mass% or less, more preferably 50 mass% or less, and further preferably 40 mass% or less.
  • the density of the porous support in view of the time the paint impregnation, 0.05 g / cm 3 or more preferably, 0.1 g / cm 3 or more is more preferable. Further, the density is preferably 2.0 g/cm 3 or less, and more preferably 1.0 g/cm 3 or less.
  • the film thickness of the porous support is preferably 300 ⁇ m or less, and more preferably 200 ⁇ m or less, from the viewpoints of excellent electrochemical device performance and strength, and suppression of separation from inorganic components during impregnation.
  • the film thickness is preferably 5 ⁇ m or more, more preferably 20 ⁇ m or more.
  • the separator for electrochemical device of the present invention may further contain other components such as a conventionally known dispersant, thickener, conductive carbon, conductive ceramics and the like.
  • the content ratio of the other components in the separator is preferably 10% by mass or less in 100% by mass of the separator. It is more preferably 5% by mass or less, further preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.
  • the electrochemical device separator of the present invention preferably has an average film thickness of 10 ⁇ m to 1 mm. When it is 10 ⁇ m or more, the durability can be further improved. Further, when it is 1 mm or less, it is advantageous from the viewpoint of cost and the ion permeation ability is sufficiently excellent.
  • the average film thickness is more preferably 20 ⁇ m or more. Further, the average film thickness is more preferably 500 ⁇ m or less.
  • the average film thickness is an average value obtained by measuring arbitrary 10 points using a Digimatic micrometer (manufactured by Mitutoyo).
  • the electrochemical device separator of the present invention is preferably gas permeable.
  • the gas permeability is sufficient if the air permeability is a Gurley value of 10,000 seconds or less.
  • the Gurley value is preferably 9500 seconds or less.
  • the Gurley value is preferably 500 seconds or more, more preferably 1000 seconds or more.
  • the Gurley value is measured by the Gurley method described in the examples.
  • the Gurley value is an index indicating the ease with which gas passes, and the larger the value, the more difficult it is for gas to pass.
  • the Gurley value is the Gurley value measured for the laminate when the separator is a laminate in which a plurality of layers are laminated.
  • the porosity of the separator for electrochemical device of the present invention is preferably 20% by volume or more, and more preferably 30% by volume or more. Further, the porosity is preferably 90% by volume or less, and more preferably 80% by volume or less. The porosity is represented by the volume of the voids of the separator with respect to the volume of the separator, and can be measured by a mercury porosimeter.
  • hydrophilic particles As an example of the method for producing the separator for an electrochemical device of the present invention, first, hydrophilic particles, a known dispersant, and water are mixed and a dispersion liquid of hydrophilic particles is produced using a dispersing device.
  • a dispersion device such as an ultrasonic wave, a ball mill, or a paint shaker can be used.
  • a hydrophobic component hydrophobic particles
  • a dispersed state dispersed state
  • binder component a binder component
  • the viscosity is such that the coating composition is not subjected to shear stress.
  • the mixing may be performed under mild conditions such that the shear stress is low enough to maintain the particle shape of the hydrophobic particles and the like.
  • the paint can be mixed by stirring with a stirring blade.
  • a magnetic stirrer, a vibration stirrer, etc. can be used for stirring.
  • a mixing method such as a kneader that has high shearing stress at the time of mixing
  • the hydrophobic component is polymer particles, depending on the type of polymer (material, thermoplastic resin or crosslinked resin, etc.)
  • the polymer most of the particle morphology changes to a morphology other than particles such as fiber morphology.
  • a porous support for example, a non-woven fabric
  • the electrochemical device separator of the present invention is obtained by coating the above-mentioned mixed solution on a release base material, contacting it with a porous support, drying the film, and then peeling it from the release base material. You can also
  • the present invention is also an electrochemical device including the electrochemical device separator of the present invention.
  • the electrochemical device of the present invention is usually configured to include a positive electrode, a negative electrode, and an electrolyte together with a separator. Below, the positive electrode, the negative electrode, and the electrolyte which comprise the electrochemical element of this invention are demonstrated in order.
  • the electrochemical device of the present invention is usually configured to include a positive electrode.
  • the active material of the positive electrode is not particularly limited, and any of those used as a positive electrode active material of an electrochemical device can be used, and examples thereof include activated carbon, porous metal oxides, porous metals, and conductive heavy metals. It is preferable to use a combination, and activated carbon is particularly preferable.
  • the positive electrode is preferably a carbon electrode.
  • the positive electrode active material is one that undergoes a morphological change with charge and discharge of lithium or the like.
  • the positive electrode can be obtained by adding a binder, a conductive auxiliary agent, a catalyst, a solvent and the like to form a slurry, applying this on a substrate and drying.
  • the pellets may be formed by press molding.
  • the binder, conductive aid, and catalyst will be described later.
  • the electrochemical device of the present invention is usually configured to include a negative electrode.
  • the active material of the negative electrode there can be used carbon, lithium, sodium, magnesium, zinc, nickel, tin, cadmium, hydrogen storage alloy, silicon-containing materials and the like which are usually used as the negative electrode active material of batteries.
  • the negative electrode active material zinc, lithium, nickel, magnesium, cadmium and the like, a morphological change occurs with charging and discharging, even for an electrochemical element configured using a material that may generate dendrite,
  • the present invention can be preferably applied. Above all, it is preferable that the negative electrode active material contains elemental zinc and/or a zinc compound.
  • the positive electrode and the zinc negative electrode may contain, in the active material layer, other components such as a binder, a conductive aid, and a catalyst together with the active material, if necessary.
  • the binder Although various known polymers can be used as the binder, the above-mentioned adhesive components can be preferably used.
  • the binder may be used either individually or in combination of two or more.
  • the conductive additive is not particularly limited, but is, for example, one or more of conductive carbon, conductive ceramics, metals such as zinc, copper, brass, nickel, silver, bismuth, indium, lead and tin. Can be used.
  • the catalyst is not particularly limited, and a conventionally known catalyst can be used.
  • the average thickness of the active material layer according to the present invention is preferably 100 ⁇ m or more, more preferably 200 ⁇ m or more, even more preferably 500 ⁇ m or more, and it is possible to suppress the active material from dropping and the like to obtain a large amount of active material. From the viewpoint of being able to construct an electrochemical element having a high energy density, in which a substance is mounted, it is particularly preferably 1 mm or more.
  • the average thickness of the active material layer is, for example, preferably 10 mm or less, and more preferably 5 mm or less. The average thickness of the active material layer can be calculated by arbitrarily measuring 5 points with a micrometer.
  • the positive electrode and the zinc negative electrode preferably further include a current collector.
  • the current collector include (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloy such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil. , Corrosion resistant nickel, nickel mesh (expanded metal), punched nickel, metallic zinc, corrosion resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric with conductivity; Ni ⁇ Zn ⁇ Sn ⁇ Pb ⁇ Hg, Bi, In, Tl, brass, etc.
  • a solid electrolyte As the electrolyte used in the electrochemical device of the present invention, a solid electrolyte may be used, but an electrolytic solution usually used as an electrolytic solution of an electrochemical device (more preferably an aqueous electrolytic solution) is preferably used. it can.
  • the aqueous electrolyte include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, zinc acetate aqueous solution, and the like.
  • alkaline electrolytes such as potassium hydroxide aqueous solution, sodium hydroxide aqueous solution and lithium hydroxide aqueous solution are preferable.
  • the electrolyte in the aqueous electrolytic solution may be used alone or in combination of two or more.
  • the aqueous electrolytic solution may contain an organic solvent.
  • the electrochemical device of the present invention may be hermetically sealed. By sealing the electrochemical device of the present invention, it is possible to suppress the evaporation of the electrolytic solution and the mixing of water and carbon dioxide in the atmosphere. For example, the reaction between carbon dioxide in the atmosphere and hydroxide ion in the electrolytic solution can be suppressed.
  • the electrochemical device of the present invention can be manufactured by appropriately using a known method.
  • an electrochemical device can be prepared by disposing a negative electrode in a cell, introducing an electrolyte solution into the cell, and further disposing a positive electrode, a separator and the like.
  • the electrochemical device of the present invention is excellent in durability while having sufficient ionic conductivity, and in particular, can sufficiently suppress a short circuit between electrodes due to dendrite, and is an auxiliary power source for a hybrid vehicle or a regenerative power storage device. It can be suitably used for many applications such as a secondary battery alternative device and a solar energy buffer.
  • part means “part by weight” and “%” means “mass %”.
  • Example 1 Magnesium hydroxide (average particle size 250 nm) was used as the hydrophilic particles, PTFE (average particle size 300 nm, glass transition temperature 115° C.) was used as the hydrophobic particles, and SBR (glass transition temperature ⁇ 1° C.) was used as the binder.
  • the nonwoven fabric was impregnated with the dispersion liquid that was mixed and slurried to have a volume ratio of 5:4:1 to obtain a separator.
  • the mixing is performed by using a tank-type stirring device with a vertical stirrer equipped with a propeller-type stirring blade, at a rotation speed of 100 rpm with a sufficient distance between the propeller-type stirring blade and the inner wall of the container and no shear stress. I went for 5 minutes.
  • the Gurley value of the separator was about 5000 sec. No short circuit was observed even after 500 cycles.
  • Example 2-1 to 2-11, Comparative Examples 1-1 to 1-12 For the three components described in Example 1, the battery life was plotted against the composition shown in the triangular diagram of FIG.
  • Table 1 below shows specific compositions (hydrophilic particles, hydrophobic particles, and the volume ratio of the binding component) shown in the triangular diagram of FIG.
  • Example 2 In Example 1, mixing was performed by kneading using a kneader at a rotation speed of 100 rpm for 30 minutes in a state where shear stress was applied between the rotor and the chamber, and the composition of the material to be mixed was the same as in Example 1. A sheet (kneaded product) having a thickness of 0.3 mm was obtained. The kneaded material thus obtained was laminated with a non-woven fabric to form a separator. The Gurley value was 1200 sec, and the battery life was 100 cycles. When the cross section of the separator was observed by SEM, most of the PTFE particles were fibrillated.
  • Example 3 Magnesium oxide (average particle size 250 nm) was used as the hydrophilic particles, and PTFE dispersion (average particle size 300 nm, glass transition temperature 115° C.) was used as the dispersion of the hydrophobic particles so that the weight ratio of the solid content was 8:2. And mixed with water to adjust the slurry so that the solid content concentration becomes 50 wt %. The volume ratio of magnesium oxide particles and PTFE particles calculated from the specific gravity was 7:3. A non-woven fabric (“Papillon” manufactured by Sansho Co., Ltd.) was dipped in the slurry, sufficiently impregnated with the slurry, and then pulled up, and dried to prevent rolling stress and the like, and formed into a sheet. As a result of measuring the life, 500 cycles or more were confirmed.
  • PTFE dispersion average particle size 300 nm, glass transition temperature 115° C.
  • hydrophilic particles inorganic compound particles
  • PTFE average particle size 300 nm, glass transition temperature 115° C.
  • SBR glass transition temperature ⁇ 1° C.
  • the non-woven fabric was impregnated with the dispersion liquid mixed and slurried to prepare a separator.
  • the volume ratio of hydrophilic particles:hydrophobic particles:binding component was 5:4:1.
  • a charge/discharge test (charge/discharge rate 1C, charge/discharge depth SOC 50%) was performed by inserting the separator into a Ni—Zn battery using a Ni (nickel) electrode for the positive electrode and a Zn (zinc) electrode for the negative electrode. In all, performance of 500 cycles or more was observed.
  • the separator of Example 1 and the separator of Example 4-4 were each immersed in an aqueous potassium hydroxide solution adjusted to 6 mol/L, and the separator resistance after standing for 24 hours in a constant temperature bath at 70° C. was measured.
  • the separator resistance of Example 1 was 0.32 ⁇ , which was almost unchanged, whereas the separator resistance of Example 4-4 decreased to 0.11 ⁇ .
  • Observation of the cross section of the separator of Example 4-4 at this time revealed that the shape of the inorganic particles was smaller than that of the separator cross section (FIG. 6) before being left for 24 hours in a constant temperature bath at 70° C. as shown in FIG. With the change, the weight decreased by about 7%.
  • Table 3 shows the results of experiments in which the following particles were subjected to a water permeability test to determine their hydrophobicity/hydrophilicity.
  • the separator contains hydrophobic particles and hydrophilic particles each at a certain ratio or more, and the content of the binder component is When the ratio is less than a certain ratio, the ionic conductivity is sufficient, and the durability is excellent, and especially when the electrochemical device includes an electrode that undergoes a morphological change due to charge and discharge, a short circuit between electrodes due to dendrites. It was found that the above can be sufficiently suppressed, and as a result, the electrochemical device can have a long life. Among them, it was found that the separator of Example 1 using magnesium hydroxide as the hydrophilic particles was remarkably excellent in durability.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Cell Separators (AREA)

Abstract

La présente invention concerne un procédé d'allongement de la durée de vie d'un élément électrochimique. La présente invention concerne un séparateur pour un élément électrochimique, dans lequel : le séparateur comprend des particules hydrophobes, des particules hydrophiles et, comme souhaité, un constituant de liaison ; le rapport en volume de particules hydrophobes à (particules hydrophiles + constituant de liaison) dépasse 20/80 ; le rapport volumique des particules hydrophiles à (particules hydrophobes + constituant liant) dépasse 20/80 ; et le rapport volumique du constituant de liaison à (particules hydrophobes + particules hydrophiles) est inférieur à 30/70.
PCT/JP2019/046067 2018-11-26 2019-11-26 Séparateur pour élément électrochimique WO2020111027A1 (fr)

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