Classifications

• • 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
  • H01G11/22—Electrodes
  • H01G11/30—Electrodes characterised by their material
  • H01G11/32—Carbon-based
  • H01G11/38—Carbon pastes or blends; Binders or additives therein
• • 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
  • H01G11/54—Electrolytes
  • H01G11/58—Liquid electrolytes
  • H01G11/60—Liquid electrolytes characterised by the solvent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0569—Liquid materials characterised by the solvents
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/004—Details
  • H01G9/022—Electrolytes; Absorbents
  • H01G9/035—Liquid electrolytes, e.g. impregnating materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • 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
• • 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
  • Y02E60/13—Energy storage using capacitors

Definitions

• Fluoropolymers as binder for the electrodes in supercapacitors are Fluoropolymers as binder for the electrodes in supercapacitors
• the present invention relates to supercapacitors comprising
• fluoropolymers and to the use of fluoropolymers as binder materials for electrodes in supercapacitors.
• Supercapacitors comprise at least two electrodes which may be identical
• Active carbon electrodes are frequently used in supercapacitors of any type.
• the respective electrodes are thin electrodes generally obtained by depositing a paste on a current collector.
• the paste is usually a mixture of active material, diluent(s), percolator and binder(s).
• a well known binder for this purpose is polytetrafluoroethylene (PTFE).
• the binder serves to provide cohesion for the particles of active carbon which is usually in powder form, but without masking a large fraction of active surface area.
• the binder must furthermore enable the active material adhere to the current collector.
• the binder should confer a certain amount of flexibility, particularly while it is being assembled and while it is in operation.
• the binder during operation may be in contact with the electrolyte of the capacitor, the binder should be preferably inert relative to the components of the electrolyte.
• the insulating binder should support such double percolations.
• the binder does not interact excessively with the grains of the active carbon material in order to avoid reducing the active surface area which is important for the energy density of the capacitor. The compromise needs to be found so that the binder on one hand ensures the cohesion between the grains of the active material and on the other side does not detrimentally influence active surface area.
• a binder comprising a mixture of carboxy methyl cellulose and a copolymer of styrene and butadiene.
• the supercapacitors comprising fluoropolymers including at least one functional group (F1) capable of conferring adhesion properties on said polymer as binder materials for the electrodes.
• F1 functional group capable of conferring adhesion properties on said polymer as binder materials for the electrodes.
• Preferred fluoropolymers are defined in the dependent claims and described in the detailed specification hereinafter.
• the fluoropolymers which can be used in accordance with the present invention may either be grafted fluoropolymers grafted by at least one compound containing at least one functional group capable of configuring adhesion properties of the fluoropolymer or may be copolymers
• Fluoropolymers used in accordance with the present invention comprise at least one fluoropolymer (A).
• fluoropolymer is understood to mean a polymer for which more than 50 % by weight of the monomer units are derived from at least one fluoromonomer.
• the fluoropolymer may be a homopolymer; it may also be a copolymer formed by several
• copolymers with one another, or else a copolymer formed by one or more fluoromonomers with one or more non-fluorinated monomers.
• copolymers may, in particular, be random copolymers, block copolymers or grafted copolymers
• fluoromonomer is understood to mean any monomer that comprises at least one fluorine atom; it customarily comprises at least one ethylenic unsaturation.
• fluoromonomers mention may be made of fluorinated vinyl monomers, fluorinated styrene monomers such as 4-fluorostyrene, fluorinated (meth)acrylic monomers such as trifluoroethyl acrylate and fluorinated conjugated dienes such as 2- fluorobutadiene.
• the fluoromonomer is preferably a fluorinated vinyl monomer.
• fluorinated vinyl monomer is understood to denote the monoethylenically-unsaturated fluorinated monomers that are aliphatic and that have one or more fluorine atoms and optionally, in addition, one or more chlorine atoms, as the only heteroatom(s).
• fluorinated vinyl monomers mention may be made of vinyl monomers that are free of hydrogen atoms such as tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene, and partially
• hydrogenated fluorinated vinyl monomers such as vinyl fluoride, trifluoroethylene, 3,3,3-trifluoropropene and, with most particular mention, vinylidene fluoride.
• non-fluorinated monomer is understood to mean any monomer that is free of fluorine atoms; it customarily comprises at least one ethylenic unsaturation.
• non-fluorinated monomers are: a-monoolefins such as, for example, ethylene and propylene ; styrene and non-fluorinated styrene derivatives; non-fluorinated chloromonomers such as, for example, vinyl chloride and vinylidene chloride; non-fluorinated vinyl ethers; non-fluorinated vinyl esters such as, for example, vinyl acetate; (meth)acrylic esters, nitriles and amides such as acrylonitrile and acrylamide.
• fluoropolymers mention may especially be made of the homopolymers of vinylidene fluoride, vinyl fluoride, trifluoroethylene or chlorotrifluoroethylene, and the copolymers that these fluoromonomers form with one another or with at least one other fluoromonomer as defined above (including a fluoromonomer that does not contain hydrogen atoms, such as tetrafluoroethylene or hexafluoropropylene).
• copolymers and terpolymers mention may be made of the copolymers and terpolymers of vinylidene fluoride and the copolymers and terpolymers of chlorotrifluoroethylene with at least one other fluoromonomer as defined above (including a fluoromonomer that does not contain hydrogen atoms, such as tetrafluoroethylene or hexafluoropropylene). Mention may also be made of the copolymers and terpolymers of at least one of the
• the fluoropolymer (A) according to the invention is preferably chosen from vinylidene fluoride polymers.
• a vinylidene fluoride polymer is a fluoropolymer (i.e. a polymer for which more than 50 % by weight of the monomer units are derived from at least one fluoromonomer), comprising monomer units derived from vinylidene fluoride.
• vinylidene fluoride polymers mention may especially be made of homopolymers of vinylidene fluoride, and copolymers thereof with other ethylenically unsaturated monomers, whether they are fluorinated (examples of other ethylenically unsaturated fluoromonomers are vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene and hexafluoropropylene) or non-fluorinated (examples of ethylenically unsaturated non-fluorinated monomers are a-monoolefins such as ethylene and propylene; styrene and non-fluorinated styrene derivatives; non-fluorinated chloromonomers such as vinyl chloride and vinylidene chloride; non-fluorinated vinyl ethers; non-fluorinated vinyl esters such as vinyl acetate; non-fluor
• the vinylidene fluoride polymers preferably contain more than 50 % by weight of monomer units derived from vinylidene fluoride.
• Particularly preferred vinylidene fluoride polymers are vinylidene fluoride homopolymers and random copolymers of vinylidene fluoride that contain 3 to 30, preferably 10 to 20 % by weight of a fluorinated comonomer chosen from hexafluoropropylene and chlorotrifluoroethylene.
• the fluoropolymer (A) is functionalized by grafting with at least one compound (a) - defined and described in detail hereinafter - which contains at least one functional group (fl) capable of conferring adhesion properties on said
• the fluoropolymer (A) can be obtained by copolymerisation or by various coupling reactions during the
• the functional group (fl) may be any group having a reactivity or a polarity such that it enables the fluoropolymer to develop adhesion forces, even with respect to materials that it is not normally possible to adhere to this polymer.
• the group (f1) is generally chosen from the groups bearing at least one reactive function that does not take part in radical mechanisms. It is usually chosen from
• acid groups the carboxylic acids from which these groups originate may be monocarboxylic or dicarboxylic acids,
• the epoxy groups (f1.5), the alcohol groups (f1.6) and the carbonyl groups (f1.7) are preferred. More particularly, the epoxy groups and the alcohol groups derived from diols are preferred. The alcohol groups derived from diols give the best results.
• the embodiment is carried out by grafting, to this polymer, at least one compound (a) that contains at least one functional group (f1).
• the functional group(s) (f1) borne by the compound(s) (a) may belong to the same family or to different families. Thus, it is in no way excluded to use both one compound (a) containing an epoxy group and another compound (a) containing one or more alcohol groups; similarly, it is in no way excluded to use a compound (a) containing both an ester group and another group, for example an epoxy or alcohol group.
• the compound (a) In order to be able to be grafted to the fluoropolymer (A), the compound (a) must also contain at least one group (g) that makes the grafting of said compound (a) to this polymer possible.
• This group (g) is generally chosen from:
• radical mechanisms such as additions or associations of radicals
• bromine groups and chlorine groups can be attached to the polymer backbone before grafting.
• the group (g) is chosen from organic groups having at least one ethylenically unsaturated carbon-carbon bond, from amino groups and from peroxy groups.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one acid or anhydride group as group (f1) are unsaturated monocarboxylic or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, bicyclo[2.2.1]hept-2-ene-5,6-dicarboxylic acid, maleic anhydride, itaconic anhydride, crotonic anhydride and citraconic anhydride.
• Maleic anhydride is generally preferred, in particular for reasons of accessibility.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as groups (g) and at least one ester group as group (f1) are vinyl acetate, vinyl propionate, monomethyl maleate, dimethyl maleate, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, diethyl fumarate, dimethyl itaconate and diethyl citraconate.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one amide group as group (f1) are acrylamide and methacrylamide.
• An example of compound (a) that contains at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one epoxy group as group (f1) is allyl glycidyl ether.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one alcohol group as group (f1 ) are allyl alcohol and 3-allyloxy-1 ,2-propanediol.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one carbonyl group as group (f1) are organic heterocyclic compounds containing a vinyl or allyl group attached to the heteroatom and the heterocycle of which bears the carbonyl bond, such as N-vinylpyrrolidone and N-vinylcaprolactam.
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least one hydrolysable group containing a silyl group as group (fl) are vinyltrimethoxysilane, vinyltriethoxysilane,
• Examples of compounds (a) that contain at least one organic group having at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond as group (g) and at least two functional groups (f1 ) of different nature are: glycidyl acrylate and methacrylate (an ester group and an epoxy group as groups (f1)); hydroxyethyl acrylate and methacrylate and hydroxypropyl acrylate and methacrylate (an ester group and an alcohol group as groups (fl )), N-methylolmethacrylamide (an alcohol group and an amide group as groups(fl)).
• the compounds containing at least one functional group (f1) chosen from epoxy groups, alcohol groups and carbonyl groups, more particularly from alcohol groups derived from diols are preferred.
• Allyl glycidyl ether, 3-allyloxy-1 ,2-propanediol, N- vinylpyrrolidone and N-vinylcaprolactam give good results. The best results were obtained with 3-allyloxy-1 ,2-propanediol.
• the grafting of the compound (a) to the fluoropolymer (A) may be carried out by any method known for this purpose. Depending on the chemical properties and the physical state of the compound (a), this grafting may be carried out in the solid state, in solution, in suspension, in an aqueous medium or within an organic solvent. This grafting may also be carried out by irradiation, for example by means of an electron beam or by gamma radiation.
• the grafting of the compound (a) to the fluoropolymer (A) is most generally carried out on a molten blend of the compound and polymer. It is possible to operate in batch mode, in kneaders, or continuously, in extruders.
• radical generator usually promoted and initiated by a radical generator, at least when the group (g) of the compound (a) is not itself a group capable of easily forming free radicals, such as peroxy and azo groups.
• a radical generator use is generally made of compounds having a decomposition temperature between 120 and 350°C and a half life, in this temperature zone, of around one minute.
• the radical generator is preferably an organic peroxide, and more particularly an alkyl or aryl peroxide.
• benzoyl peroxide dichlorobenzoyl peroxide, dicumyl peroxide, di(i-butyl) peroxide, /-butylcumyl peroxide, 1 ,3-di(2-/- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(i-butylperoxy)hexane and 2,5-dimethyl-2,5-di(f-butylperoxy)-3-hexyne. 2,5-Dimethyl-2,5-di(i- butylperoxy)hexane and dicumyl peroxide are particularly preferred.
• the radical generator and the compound (a) may be introduced in any manner so long as they are introduced continuously over time and they are well dispersed in the molten material.
• the radical generator and the compound (a) may be introduced by spraying, for example by means of a spray-type injector or an atomizer or by injection into the molten mass.
• the introduction of the radical generator and the compound (a) via a masterbatch with the powdered fluoropolymer (A) or via a masterbatch with a filler can also be envisaged.
• the compound (a) is introduced before the radical generator.
• reaction in molten mass is understood to mean, for the purposes of the present invention, any reaction in the substantial absence of solvent or of diluent and at a temperature at least equal to the melting point of the fluoropolymer (A).
• extruder is understood to mean any continuous device
• the discharge zone may additionally be followed by a granulating device or by a device that gives the extruded material its final shape.
• extruders based on the work of a single screw or of two screws which, in the latter case, may cooperate in a co-rotating or counter-rotating manner (same direction of rotation or opposite directions of rotation).
• the extruder used according to the present invention is
• each of these zones has a very specific function and is at a very specific temperature.
• the feed zone has the role of carrying out the feeding of the fluoropolymer (A). It is customarily at a temperature less than or equal to 50°C.
• the material melting zone has the role of carrying out the melting of the material.
• the homogenization zone has the role of homogenizing the molten
• the reaction zone has the role of carrying out the reaction.
• the temperature in the melting zone and in the zone for homogenization of the material is customarily greater than or equal to the melting point of the fluoropolymer (A).
• the temperature in the reaction zone is customarily greater than or equal to the temperature at which the half life of the radical generator is less than the residence time of the material in this zone.
• the zone for introducing additives has the role of carrying out the introduction of additives when the latter are added into the extruder.
• the temperature of this zone is generally a function of the viscosity of the material and the nature of the additives added.
• the compression-discharge zone has the role of compressing the material and of carrying out the discharge of the latter.
• the temperature in the compression-discharge zone is generally a function of the viscosity of the material to be discharged.
• the compound (a) is preferably introduced into the extruder before the homogenization zone.
• the radical generator is preferably introduced into the reaction zone of the extruder.
• the amount of compound (a) grafted to the polymer (A) expressed as amount of compound (a), is advantageously greater than 0.01 % by weight, preferably 0.05 % by weight or, better still, 0.1 % by weight, relative to the weight of polymer (A). Moreover, this amount is advantageously less than or equal to 5.0 % by weight, preferably 3.0 % and better still 2.0 % by weight.
• the metering is customarily carried out by a chemical route (titration).
• Such grafted fluoropolymers are preferably vinylidene fluoride polymers.
• they contain more than 50 % by weight of monomer units derived from vinylidene fluoride.
• they are chosen from vinylidene fluoride homopolymers and random copolymers of vinylidene fluoride that contain 3 to 30, preferably 10 to 20 % by weight of a fluorinated comonomer chosen from hexafluoropropylene and chlorotrifluoroethylene.
• an organic group containing at least one terminal ( ⁇ , ⁇ ) ethylenically unsaturated carbon-carbon bond is chosen from vinyl, allyl, acryloyloxyalkyl and methacryloyloxyalkyl groups. Most particularly preferably, it is an allyl group.
• the compound (a) of such grafted preferred fluoropolymers contains at most four alcohol groups. Particularly preferably, it contains at most three thereof. Most particularly preferably, it contains two such groups.
• the compound (a) of the preferred grafted fluoropolymers is preferably chosen from aliphatic and cycloaliphatic compounds. Particularly preferably, it is chosen from aliphatic compounds.
• fluoropolymers according to the present invention was 3-allyloxy-1 ,2- propanediol, in particular when the grafted fluoropolymers in question were chosen from vinylidene fluoride homopolymers and random copolymers of vinylidene fluoride that contain 3 to 30, preferably 10 to 20 % by weight of a fluorinated comonomer chosen from hexafluoropropylene and chlorotrifluoroethylene.
• fluoropolymer including at least one functional group (f1) capable of conferring adhesion properties on said polymer is obtained by the copolymerization of a fluoromonomer as defined above and a compound bearing at least one functional group capable of conferring adhesion properties on the copolymer.
• the functional groups are as described above for the embodiment of grafting.
• the amount of repeat units derived from compound (a) copolymerized with the fluoromonomer(s) is advantageously greater than 0. 1% by weight, preferably 0. 5 % by weight or, better still, 1 % by weight. Moreover, this amount is advantageously less than or equal to 20.0 % by weight, preferably 10 %, more preferably less than 5 % and better still 2.0 % by weight.
• the metering is customarily carried out by a chemical route (titration).
• copolymerization and various coupling techniques can be achieved by any techniques known to the skilled person like e.g. suspension or emulsion or polymerization.
• Suitable copolymers usually comprise more than 50 % by weight of repeat units derived from the fluoromonomer and less than 50 wt% of repeat units derived from the compound bearing at least one functional group capable of conferring adhesion properties on the copolymer.
• a preferred group of copolymers which can be advantageously used in the supercapacitors of the present invention are copolymers comprising repeat units derived from vinylidene fluoride, 3-30 wt%, preferably 10 to 20 wt% of repeat units, based on the total weight of the repeat units, derived from at least one of hexafluoropropylene, chlorotrifluoroethylene and
• repeat units derived from at least one compound providing the functional group f1 The percentage of repeat units derived from compounds (a) is as given above for the embodiment of
• the electrodes are manufactured by first fabricating a paste from the electrode material, e.g. active carbon, a percolator and the binder and putting this into a solvent. Thereafter the paste is spread on a metal foil constituting the collector which may e.g. be a metal foil, in particular an aluminum foil, followed by drying at elevated temperatures and then calendaring the product to obtain the desired porosity.
• the electrode material e.g. active carbon, a percolator and the binder
• the paste is spread on a metal foil constituting the collector which may e.g. be a metal foil, in particular an aluminum foil, followed by drying at elevated temperatures and then calendaring the product to obtain the desired porosity.
• Electrodes with porosities of at least 50, preferably at least 70% usually yield the best performance properties for the supercapacitors.
• the supercapacitors in which the fluoropolymers in accordance with the present invention may be used as binder for the electrodes comprise the usual components of such supercapacitors besides the electrodes, namely also a separator and an electrolyte system. Respective products for these components have been described in the literature and are known to the skilled person. Accordingly, a detailed or exhaustive description of these components is not necessary here.
• the electrodes may be used as binder for the electrodes further comprise at least one percolator.
• the percolator allows typically for electrical percolation phenomena, and can be defined as a chemical agent is capable of facilitating the move of electron and/or ions, preferably of both, through the electrodes, more precisely through their active masses.
• the chemical nature of the percolator is not particularly limited. Suitable percolators include carbon black, especially highly porous carbon black, exfoliated graphite, graphene, carbon nanotubes, carbon nanohorns and mixtures thereof.
• separator also comprises a fluoropolymer of the type described above and thus supercapacitors of this type constitute another preferred embodiment of the present invention.
• the fluoropolymers are used as binder for electrodes in supercapacitors which comprise electrolyte system comprising organic solvents or mixtures of solvents which contain of from 0.1 to 30, preferably of from 0,2 to 20 and particularly preferably of from 0.5 to 10 wt%, based on the total weight of the electrolyte solvent, of a fluorinated carbonate of the general formulae I
• R 1 to R 4 which may be the same or different, are independently selected from hydrogen, fluorine, Ci to Cs -alkyl and Ci to Cs haloalkyl which the proviso that at least one of R to R 4 is a fluorine atom or comprises a fluorine atom and R 5 to R 6 , independently of one another are selected from hydrogen, Ci to Ce alkyl or d-Cs haloalkyl.
• Such electrolyte systems may comprise one or more than one fluorinated carbonate. If mixtures of fluorinated carbonates are used, the weight percentages given above are applicable for the entire weight of the mixture of fluorinated carbonates in the electrolyte system.
• fluorinated propylene carbonates (at least one of R 1 to R 4 is a methyl or a fluonnated methyl group) generally show a significantly higher viscosity than respective ethylene carbonates.
• the increased viscosity may lead to a decrease in ion conductivity of the electrolyte system, thus bearing the risk of deterioration of the
• the viscosity also generally increases with increasing number of fluorine atoms in the fluorinated carbonate, which is also a factor the skilled person will take into account.
• fluorinated carbonates for use in electrolyte systems.
• F1 EC represents monofluoro
• F1 EC, ethyl 1 -fluoroethyl carbonate and methyl 1-fluoroethyl carbonate, comprising one fluorine atom in the molecule are particularly preferred when a low viscosity is aimed at.
• non-cyclic carbonates generally are less viscous than cyclic carbonates which may be taken into account by the skilled person.
• the electrolyte may comprise 0.1 to 100, preferably 20-80 and more preferably 40-60 % by weight, based on the total weight of the electrolyte, of LITFSI
• LiTFSI can be used alone or in combination with a fluorinated carbonate as described above.
• the present invention can be particularly useful in hybrid supercapacitors, which comprise two different electrodes operating according to different electrochemical mechanisms (which is the reason for the term hybrid supercapacitor), one of which works in a similar albeit different way than the anode in lithium batteries.
• hybrid supercapacitors combine the energy storage principle of a lithium-ion secondary battery and an electric double-layer capacitor.
• a capacitive material is characterized by a potential swing during the charge and discharge of the capacitor.
• the initial output potential difference of a symmetric cell with capacitive electrodes is 0V and the potentials diverge linearly during charging of cell.
• the batterylike electrode is characterized by an almost constant potential during charging and discharging.
• Li-intercalation compounds Li Ti 5 0i2, WO2, L1C0O2, LiMn1.2Nio.5O4, etc.
• Li-intercalation compounds Li Ti 5 0i2, WO2, L1C0O2, LiMn1.2Nio.5O4, etc.
• Hybrid supercapacitors may comprise a graphite negative electrode wherein lithium ions are previously intercalated; the later is combined with a porous carbon positive electrode and for both electrodes the fluoropolymers can be used as a binder.
• Respective systems may comprise a positive electrode based on activated carbon and a negative electrode based on graphite or hard carbon and have been described in the literature as Li-ion capacitors.
• Hybrid supercapacitors comprising a positive electrode based on activated carbon and comprising at least 20, preferably at least 50 and most preferably at least 80 % activated carbon are preferred.
• the negative electrode of hybrid supercapacitors in accordance with the present invention is preferably based on graphite and comprises at least 20, preferably at least 50 and more preferably at least 80% of graphite.
• the potential of the negative electrode can be lowered and the potential window of the positive electrode can be extended.
• an additional lithium ion source has to be provided and a Li foil has been used for this purpose.

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• 2013
  • 2013-01-25 WO PCT/EP2013/051397 patent/WO2013110740A1/fr not_active Ceased

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