Classifications

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  • C09D127/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers
  • C09D127/02—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
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  • C09D127/16—Homopolymers or copolymers of vinylidene fluoride
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  • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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  • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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  • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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• • C—CHEMISTRY; METALLURGY
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  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
  • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
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  • H01M2300/0085—Immobilising or gelification of electrolyte
• • 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
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  • 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
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  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention generally relates to the field of the storage of electrical energy in rechargeable secondary batteries of the Li-ion type. More specifically, the invention relates to a cathode composition comprising an intrinsically incorporated catholyte. The invention also relates to a quasi-solid Li-ion battery comprising said cathode, an anode and a separator, and a method of manufacturing said Li-ion battery.
• a Li-ion battery includes at least a negative electrode or anode coupled to a copper current collector, a positive electrode or cathode coupled to an aluminum current collector, a separator, and an electrolyte.
• the electrolyte consists of a lithium salt, generally lithium hexafluorophosphate, mixed with a solvent which is a mixture of organic carbonates, chosen to optimize the transport and dissociation of ions.
• a high dielectric constant favors the dissociation of ions, and therefore the number of ions available in a given volume, while a low viscosity favors ionic diffusion which plays an essential role, among other parameters, in the velocities of charging and discharging of the electrochemical system.
• Rechargeable or secondary batteries are more advantageous than primary (non-rechargeable) batteries because the associated chemical reactions that take place at the positive and negative electrodes of the battery are reversible. Secondary cell electrodes can be regenerated multiple times by applying an electrical charge. Many advanced electrode systems have been developed to store electrical charge. At the same time, many efforts have been devoted to the development of electrolytes capable of improving the capacities of electrochemical cells.
• Lithium-ion batteries conventionally use liquid electrolytes composed of solvent(s), lithium salt(s) and additive(s). These electrolytes have good ionic conductivity but are prone to leaking or igniting if the battery is damaged.
• the use of solid or quasi-solid electrolytes overcomes these difficulties.
• the advantage of solid or quasi-solid electrolytes is also to allow the use of lithium metal at the negative electrode, by preventing the formation of dendrites which can cause short circuits during cycling.
• the use of lithium metal allows a gain in energy density compared to the negative electrodes of insertion or alloy.
• solid or quasi-solid electrolytes are generally less conductive than liquid electrolytes, especially in the cathode and anode.
• the solid or quasi-solid electrolyte incorporated in the cathode is called catholyte.
• a recurring problem with all-solid or quasi-solid batteries is to obtain a catholyte that is chemically and electrochemically compatible with the cathode, while having sufficient conductivity and low resistivity at the interfaces with the cathode.
• Document FR 3049114 describes an all-solid battery comprising a solid polymer electrolyte, a negative electrode comprising lithium metal or a lithium metal alloy, and a positive electrode comprising an ion-conductive polymer.
• the disadvantage of this battery is that the ionic conductivity of the solid electrolyte incorporated in the cathode is low at room temperature, and the lithium-ion cell must be heated to 80°C to have good electrochemical performance.
• PVDF Poly(vinylidene fluoride)
• P(VDF-co-HFP) copolymer copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP)
• VDF vinylidene fluoride
• HFP hexafluoropropylene
• a secondary battery cell 20 comprising a cathode 21, an anode 22, a separator 23 and an electrolyte 24.
• the latter comprises a high molecular weight compound and a solution of electrolyte prepared by dissolving an electrolyte salt in a solvent, and the electrolyte solution is held in the high molecular weight compound to gel the electrolyte solution.
• Said high molecular weight compound comprises a first compound having a weight average molecular weight of 550,000 or more; and a second compound having a weight average molecular weight of 1000 or more but not exceeding 300,000.
• the first high molecular weight compound functions to improve the adhesion between the electrolyte 24, the cathode 21 and the anode 22.
• the second high molecular weight compound is believed to improve the permeability of the electrolyte 24 in the cathode 21 and the anode 22.
• a third high molecular weight compound can be incorporated into the electrolyte.
• Each of these compounds is chosen from PVDF and P(VDF-co-HFP) copolymers.
• the copolymers are block copolymers, and the mass content of HFP in the copolymer varies from 3% to 7.5%.
• a cathode active material and a binder (copolymer of VDF-HFP), and, optionally, an electrical conductor are mixed to prepare a cathode mixture, and the cathode mixture is dispersed in a solvent such as methyl -2-pyrrolidone to form a cathode mixture slurry. Then, after applying the cathode mixing slurry to one side or both sides of the cathode current collector 21A and drying it, the cathode active material layer 21B is formed by compression molding so as to form the cathode 21.
• an electrolyte solution obtained by mixing, on the one hand, a solution formed from said high molecular weight compounds dissolved in a solvent such as dimethyl carbonate, and on the other hand, a solvent comprising ethylene carbonate, propylene carbonate and LiPF6.
• the active material layer 21B of the cathode was allowed to stand at room temperature for 8 hours to volatilize the dimethyl carbonate, leading to the formation of the electrolyte 24.
• this preparatory method remains laborious, because it adds a step of coating the electrolyte solution, as well as a step of evaporating the dimethyl carbonate, which lengthen the time required to obtain the electrolyte and lead to additional costs. Manufacturing.
• cathode compositions comprising a catholyte, having a good compromise between ionic conductivity within the cathode at room temperature and low resistivity at the interfaces with the solid or quasi-solid electrolyte, and which are suitable to a simplified implementation, without requiring prior transformation steps. Additionally, the amount of catholyte in the cathode should be minimized in order to maximize the energy density of the Li-ion cell.
• the object of the invention is therefore to remedy at least one of the drawbacks of the prior art, namely to propose a cathode for a quasi-solid Li-ion battery comprising a catholyte infiltrated into the electrode material and which allows sufficient swelling polymer binder incorporated into said material without loss of cohesion within the cathode or adhesion to the current collector.
• Sufficient swelling means that the ionic conductivity at room temperature of the cathode containing the catholyte is such that the capacity delivered in discharge at C/10 is greater than or equal to 80% of the theoretical reversible capacity.
• the invention also relates to a rechargeable Li-ion secondary battery comprising such a cathode containing a catholyte, an anode and a separator.
• the invention relates to a process for preparing a Li-ion battery comprising said cathode containing a catholyte, and which is compatible with the usual industrial processes.
• the technical solution proposed by the present invention is a cathode comprising a catholyte intrinsically mixed with the electrode material.
• the invention relates to a cathode for a lithium-ion battery comprising an electrode active material, a conductive additive, an inorganic oxide, a polymer binder and a catholyte.
• said binder is a mixture of two fluorinated polymers: a fluorinated polymer A which comprises at least one copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) having an HFP content greater than or equal to 3% by weight, and a fluoropolymer B which comprises a VDF homopolymer and/or at least one VDF-HFP copolymer, said fluoropolymer B having a mass content of HFP lower by at least 3% by weight relative to the mass content of HFP from polymer A.
• VDF vinylidene fluoride
• HFP hexafluoropropylene
• the catholyte includes at least one solvent and at least one lithium salt.
• the subject of the invention is a rechargeable Li-ion secondary battery comprising a cathode, an anode and a separator, in which said cathode is as described above.
• the invention relates to a process for preparing a Li-ion battery comprising said cathode.
• the present invention makes it possible to overcome the drawbacks of the state of the art. It is characterized by good conductivity at ambient temperature of the catholyte within the cathode. The cohesion and adhesion of the cathode as well as its flexibility are maintained with the catholyte.
• the manufacture of the battery described by this invention does not require additional steps compared to the conventional manufacturing method used in the production of Li-ion cells: no catholyte coating step; no intense heat treatment, e.g. no sintering required in the case of solid oxide-based electrolytes, with temperatures above 500°C; no very high pressure compression step; does not require more humidity or atmosphere control than current processes.
• the advantage of this technology is to offer a better guarantee of safety compared to liquid electrolytes: no electrolyte leakage and reduced flammability due to the gelation of the catholyte.
• Figure 1 is a diagram representing the impedance spectra of cathodes in symmetrical stacks.
• Figure 2 is a diagram showing the capacitance performance of a cathode according to the invention and a cathode according to a comparative example, at an IC discharge current.
• the invention relates to a cathode for a lithium-ion battery comprising an active electrode material, a conductive additive, an inorganic oxide, a polymer binder and a catholyte, in which:
• said binder is a mixture of two fluorinated polymers: a fluorinated polymer A which comprises at least one copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) having an HFP content greater than or equal to 3% by weight, and a fluoropolymer B which comprises a VDF homopolymer and/or at least one VDF-HFP copolymer, said fluoropolymer B having a mass content of HFP lower by at least 3% by weight relative to the mass content of HFP polymer A, and
• VDF vinylidene fluoride
• HFP hexafluoropropylene
• - Said catholyte comprises at least one solvent and at least one lithium salt.
• said cathode comprises the following characters, possibly combined. The contents indicated are expressed by weight, unless otherwise indicated.
• Said active electrode material is chosen from compounds of the xLi2MnO3-(l-x)LiMO2 type where 0 ⁇ x ⁇ 1, of the LiMPCL type, of the Li2MPO3F type, of the Li2MSiO4 type, where M is Co, Ni, Mn, Fe or a combination of these, of the LiM Ch type, and of the Ss type.
• Said conductive additive is chosen from carbon blacks, graphites, natural or synthetic, carbon fibers, carbon nanotubes, metal fibers and powders, conductive metal oxides, or mixtures thereof.
• Said inorganic oxide is chosen from silicon oxides, titanium dioxide, aluminum oxides, zirconia, zeolites or mixtures thereof.
• the fluorinated polymer A comprises at least one VDF-HFP copolymer having an HFP content greater than or equal to 3% by weight, preferably greater than or equal to 8%, advantageously greater than or equal to 13%.
• Said VDF-HFP copolymer has a mass content of HFP less than or equal to 55%, preferably 50%.
• This very poorly crystalline copolymer swells easily in electrolyte solvents such as carbonates, nitriles, glymes, which gives the binder good ionic conductivity.
• the swelling can be quantified by the caking of the electrolyte binder.
• the caking of this copolymer is at least greater than or equal to 5% by weight.
• the fluorinated polymer A consists of a single VDF-HFP copolymer with an HFP content greater than or equal to 3%.
• the level of HFP in this VDF-HFP copolymer is between 13% and 55%, limits included, preferably between 15% and 50%, limits included.
• the fluoropolymer A consists of a mixture of two or more VDF-HFP copolymers, the HFP content of each copolymer being greater than or equal to 3%.
• each of the copolymers has an HFP content of between 13% and 55%, limits included, preferably between 15% and 50%, limits included.
• Fluorinated polymer B comprises at least one VDF-HFP copolymer having a mass content of HFP lower by at least 3% compared to the mass content of HFP of polymer A. This makes it possible to provide sufficient mechanical strength to the cathode after swelling. Sufficient mechanical strength means that the adhesion of the cathode to the current collector is maintained after swelling, as well as the cohesion between the particles of active material.
• the fluoropolymer B consists of a single VDF-HFP copolymer.
• the level of HFP in this VDF-HFP copolymer is between 1% and 5%, limits included.
• the level of HFP in this VDF-HFP copolymer is between 1% and 10%, limits included.
• the fluorinated polymer B is a mixture of PVDF homopolymer with a VDF-HFP copolymer or else a mixture of two or more VDF-HFP copolymers.
• the HFP content of the mixture of polymers A and B is greater than 7% by weight.
• the mixture of fluorinated polymers A and B has a melting point above 150°C.
• the molar composition of units in fluoropolymers can be determined by various means such as infrared spectroscopy or RAMAN spectroscopy. Conventional methods of elemental analysis in the elements carbon, fluorine and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, make it possible to calculate without ambiguity the mass composition of the polymers, from which the molar composition is deduced.
• At least one of the fluorinated polymers A and B comprises units bearing at least one of the following functionalities: carboxylic acid, carboxylic acid anhydride, carboxylic acid ester, epoxy group (such as glycidyl), amide, alcohol, carbonyl, mercapto, sulfide, oxazoline and phenol.
• Said functionality is introduced onto the fluoropolymer by a chemical reaction which may be grafting, or a copolymerization reaction of the fluoropolymer with a compound bearing at least one of said functionalities, using techniques known to those skilled in the art.
• said functionality is a terminal group located at the end of the fluoropolymer chain.
• the monomer carrying a functional group is intercalated in the fluoropolymer chain.
• the acrylic acid functionality is a hydrophilic group of (meth)acrylic type chosen from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and (meth)acrylate. )hydroxyethylhexyl acrylate.
• the mass content of functional groups is at least 0.01%, and less than or equal to 5% based on the weight of the fluorinated polymers.
• the mass ratio between polymer A and polymer B is greater than 1. catholyte
• the catholyte includes at least one solvent and at least one lithium salt.
• said solvent is chosen from cyclic and acyclic alkyl carbonates, ethers, glymes, formates, esters, nitriles and lactones.
• ethers such as dimethoxyethane (DME), methyl ethers of oligoethylene glycols with 2 to 100 oxyethylene units, dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and mixtures thereof.
• DME dimethoxyethane
• methyl ethers of oligoethylene glycols with 2 to 100 oxyethylene units dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and mixtures thereof.
• esters mention may be made of phosphoric acid esters and sulfite esters. Mention may be made, for example, of methyl formate, methyl acetate, methyl propionate, ethyl acetate, butyl acetate or mixtures thereof.
• the glymes used are of general formula R1-O-R2-O-R3 where R1 and R3 are linear alkyls of 1 to 5 carbons and R2 a linear or branched alkyl chain of 3 to 10 carbons.
• lactones mention may in particular be made of gamma-butyrolactone.
• nitriles mention may be made, for example, of acetonitrile, pyruvonitrile, propionitrile, methoxypropionitrile, dimethylaminopropionitrile, butyronitrile, succinonitrile, isobutyronitrile, valeronitrile, pivalonitrile, isovaleronitrile, glutaronitrile, methoxyglutaronitrile , 2-methylglutaronitrile, 3-methylglutaronitrile, adiponitrile, malononitrile, and mixtures thereof.
• cyclic carbonates such as, for example, propylene carbonate (PC) (CAS: 108-32-7), butylene carbonate (BC) (CAS: 4437-85-8), dimethyl carbonate (DMC) (CAS: 616-38-6), diethyl carbonate (DEC) (CAS: 105-58-8), methyl ethyl carbonate (EMC) (CAS: 623-53-0 ), diphenyl carbonate (CAS 102-09-0), methyl phenyl carbonate (CAS: 13509-27-8), dipropyl carbonate (DPC) (CAS: 623-96-1), methyl and propyl carbonate (MPC) (CAS: 1333-41-1), ethyl and propyl carbonate (EPC), vinylene carbonate (VC) (CAS: 872-36-6), fluoroethylene carbonate ( FEC) (CAS: 114435-02-8), trifluoropropylene carbonate (CAS: 1679
• PC propylene carbonate
• BC butylene
• said lithium salt is chosen from: LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethane)sulfonimide), LiTDI (2 lithium -trifluoromethyl-4,5-dicyano-imidazolate), LiPO2F2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNCh, LiCICL and mixtures thereof.
• the catholyte further comprises salts having a melting point below 100° C. such as ionic liquids, which form liquids consisting solely of cations and anions.
• organic cations By way of examples of organic cations, mention may be made in particular of the cations: ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, lithium, guanidinium, piperidinium, thiazolium, triazolium, oxazolium, pyrazolium, and mixtures thereof.
• anions By way of example of anions, mention may in particular be made of imides, in particular bis(trifluoromethanesulfonyl)imide (abbreviated as NTf2-) or bis(fluorosulfonyl)imide; borates, in particular tetrafluoroborate (abbreviated BF4-); phosphates, in particular hexafluorophosphate (abbreviated PF6-); phosphinates and phosphonates, in particular alkyl-phosphonates; amides, in particular dicyanamide (abbreviated DCA-); aluminates, in particular tetrachloroaluminate (A1C14-), halides (such as bromide, chloride and iodide anions), cyanates, acetates (CH3COO-), in particular trifluoroacetate; sulphonates, in particular methanesulphonate (CH3SO3-), trifluoromethanesul
• the catholyte consists of a mixture of solvent and lithium salt and is devoid of polymer binder.
• the catholyte also comprises solid electrolytes such as lithium ionic superconductors [Lithium superionic conductor (LISICON)] and derivatives, thio-LISICON, structures of the Li4SiO4-Li3PO4 type, ionic superconductors of sodium and derivatives [Sodium superionic conductor (NASICON)], Lii type structures. 3 Hello.
• solid electrolytes such as lithium ionic superconductors [Lithium superionic conductor (LISICON)] and derivatives, thio-LISICON, structures of the Li4SiO4-Li3PO4 type, ionic superconductors of sodium and derivatives [Sodium superionic conductor (NASICON)], Lii type structures. 3 Hello.
• the solid electrolyte included in the catholyte can be a combination of said solid electrolytes.
• the catholyte also comprises a conductive organic polymer such as polymers based on PEO, PAN, PMMA, PVA.
• the catholyte has a lithium salt concentration of 0.05 moles/liter to 5 moles/liter in the solvent.
• said cathode has the following mass composition:
• - 1% to 11% conductive additive preferably from 1.5% to 7.5%
• inorganic oxide preferably 0% to 1%
• catholyte preferably from 5% to 20%, the sum of all these percentages being 100%.
• the catholyte/polymer binder mass ratio is from 0.05 to 20, preferably from 0.1 to 10.
• said cathode has a ratio between the mass contents of the electronic conductive additive and of the polymer binder, greater than 0.7. Indeed, it was found that the contact resistance of the cathode increases when the rate of conductive additive decreases with respect to the rate of polymer binder.
• the cathode described above is manufactured by a method comprising the following steps: mixing an active electrode material, a conductive additive, an inorganic oxide and a polymer binder in a solvent, to obtain an ink.
• the mixture can be prepared using a planetary mixer or a dispersing disc.
• a solution of polymer binder in a solvent is prepared, having a solids content between 2% and 20%.
• the inorganic oxide is then dispersed in this solution.
• the conductive additive is then dispersed in this solution.
• the active material is then dispersed in this solution and the dry extract of the ink is adjusted by adding solvent, to reach a value of between 30% and 80%. coating said ink on a current collector support.
• This collector can be an aluminum sheet, coated or not with a layer of electronic conductor and/or of polymer, with a thickness of between 5 ⁇ m and 30 ⁇ m.
• the ink can be applied to one side or to both sides of the current collector. drying said ink to form a coating. The drying can be carried out on a heating plate or in an oven at a temperature varying in a range between 20°C and 150°C, with or without air flow. calendering the assembly formed by the coating and the collector so as to obtain a temperature of between 50° C. and 130° C.; impregnating said coating with an electrolyte comprising at least one solvent and at least one lithium salt.
• the cathode is impregnated in the Li-ion cell at the time of filling and before sealing the cell. Li-ion battery
• the subject of the invention is a rechargeable Li-ion secondary battery comprising a cathode, an anode and a separator, in which said cathode is as described above.
• the anode is a sheet of lithium metal.
• the anode comprises a lithium insertion material such as graphite, metal oxides, non-graphitizable carbon, pyrolytic carbon, coke, carbon fibers, activated carbon, a material of alloy such as based on the elements Si, Sn, Mg, B, As, Ga, In, Ge, Pb, Sb, Bi, Cd, Ag, Zn, Zr, or a mixture of said anode materials.
• a lithium insertion material such as graphite, metal oxides, non-graphitizable carbon, pyrolytic carbon, coke, carbon fibers, activated carbon
• a material of alloy such as based on the elements Si, Sn, Mg, B, As, Ga, In, Ge, Pb, Sb, Bi, Cd, Ag, Zn, Zr, or a mixture of said anode materials.
• said is a “conventional” separator comprising one or more porous layers of polypropylene and/or polyethylene, and optionally comprising a coating on one or both sides of the separator.
• Said coating comprises a polymeric binder and inorganic particles.
• said separator is a gelled polymer membrane comprising a fluorinated polymer film and an electrolyte comprising at least one solvent and at least one lithium salt, said fluorinated film comprising at least one layer, said layer consisting of a mixture of two fluorinated polymers: a fluorinated polymer A which comprises at least one copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) having an HFP content greater than or equal to 3% by weight, and a fluorinated polymer B which comprises a VDF homopolymer and/or at least one VDF-HFP copolymer, said fluorinated polymer B having a mass content of HFP lower by at least 3% by weight compared to the mass content of HFP of polymer A.
• VDF vinylidene fluoride
• HFP hexafluoropropylene
• said film consists of a single layer.
• said mixture comprises: i. a mass content of polymer A greater than or equal to 10% and less than or equal to 99%, preferably greater than or equal to 50% and less than or equal to 95%, advantageously greater than or equal to 25% and less than or equal to 95%, and ii. a mass content of polymer B less than or equal to 90% and greater than 1%, preferably less than 50% and greater than 5%.
• said monolayer fluoropolymer film has a thickness of 1 to 1000 ⁇ m, preferably from 1 ⁇ m to 500 ⁇ m, and even more preferably between 5 ⁇ m and 100 ⁇ m.
• said fluoropolymer film can be manufactured by a solvent process.
• Polymers A and B are dissolved in a solvent known for polyvinylidene fluoride or its copolymers.
• solvent known for polyvinylidene fluoride or its copolymers.
• solvent of n-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl formamide, methyl ethyl ketone, acetone.
• the film is obtained after deposition of the solution on a flat substrate and evaporation of the solvent.
• said fluoropolymer film is a multilayer film of which at least one of the layers is composed of a mixture of polymers A and B according to the invention.
• the overall thickness of the multilayer film is between 2 ⁇ m and 1000 ⁇ m, the thickness of the fluoropolymer layer according to the invention being between 1 ⁇ m and 999 ⁇ m.
• the additional layer or layers are chosen from the following polymer compositions: a composition consisting of a fluorinated polymer chosen from vinylidene fluoride homopolymers and VDF-HFP copolymers preferably containing at least 90% by weight of VDF; a composition consisting of a mixture of a fluorinated polymer, chosen from vinylidene fluoride homopolymers and VDF-HFP copolymers preferably containing at least 85% by weight of VDF, with a methyl methacrylate (MM A) homopolymer and the copolymers containing at least 50% by mass of MMA and at least one other monomer copolymerizable with the MMA.
• MM A methyl methacrylate
• the polymer (homopolymer or copolymer) of MMA comprises by mass from 0 to 20% and preferably 5 to 15% of a C1-C8 alkyl (meth)acrylate, which is preferably methyl acrylate and/or ethyl acrylate.
• the polymer (homopolymer or copolymer) of MMA can be functionalised, i.e. it contains, for example, acid, acid chloride, alcohol and anhydride functions.
• the functionality is in particular the acid function provided by the acrylic acid comonomer. It is also possible to use a monomer with two neighboring acrylic acid functions which can dehydrate to form an anhydride.
• the proportion of functionality can be from 0 to 15% by weight of the MMA polymer, for example from 0 to 10% by weight.
• said fluoropolymer film is manufactured by a process for transforming polymers in the molten state such as flat extrusion, extrusion by sheath blowing, calendering, thermocompression.
• the membrane forming the separator further comprises inorganic fillers such as silicon oxides, titanium dioxide, aluminum oxides, zirconia, zeolites or their mixture.
• the membrane also comprises solid electrolytes such as lithium ionic superconductors [Lithium superionic conductor (LISICON)] and derivatives, thio-LISICON, structures of the Li4SiO4-Li3PO4 type, ionic superconductors of sodium and derivatives [Sodium superionic conductor (NASICON)], Lii type structures.
• solid electrolytes such as lithium ionic superconductors [Lithium superionic conductor (LISICON)] and derivatives, thio-LISICON, structures of the Li4SiO4-Li3PO4 type, ionic superconductors of sodium and derivatives [Sodium superionic conductor (NASICON)], Lii type structures.
• the solid electrolyte included in the catholyte can be a combination of said solid electrolytes.
• said solvent is chosen from cyclic and acyclic alkyl carbonates, ethers, glymes, formates, esters, nitriles and lactones.
• ethers such as dimethoxyethane (DME), methyl ethers of oligoethylene glycols with 2 to 100 oxyethylene units, dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and mixtures thereof.
• DME dimethoxyethane
• methyl ethers of oligoethylene glycols with 2 to 100 oxyethylene units dioxolane, dioxane, dibutyl ether, tetrahydrofuran, and mixtures thereof.
• esters mention may be made of phosphoric acid esters and sulfite esters. Mention may be made, for example, of methyl formate, methyl acetate, methyl propionate, ethyl acetate, butyl acetate or mixtures thereof.
• the glymes used are of general formula R1-O-R2-O-R3 where R1 and R3 are linear alkyls of 1 to 5 carbons and R2 a linear or branched alkyl chain of 3 to 10 carbons.
• lactones mention may in particular be made of gamma-butyrolactone.
• nitriles mention may be made, for example, of acetonitrile, pyruvonitrile, propionitrile, methoxypropionitrile, dimethylaminopropionitrile, butyronitrile, succinonitrile, isobutyronitrile, valeronitrile, pivalonitrile, isovaleronitrile, glutaronitrile, methoxyglutaronitrile , 2-methylglutaronitrile, 3-methylglutaronitrile, adiponitrile, malononitrile, and mixtures thereof.
• cyclic carbonates such as for example ethylene carbonate (EC) (CAS: 96-49-1), propylene carbonate (PC) (CAS: 108-32-7) , butylene carbonate (BC) (CAS: 4437-85-8), dimethyl carbonate (DMC) (CAS: 616-38-6), diethyl carbonate (DEC) (CAS: 105-58-8 ), methyl carbonate (EMC) (CAS: 623-53-0), diphenyl carbonate (CAS 102-09-0), methyl phenyl carbonate (CAS: 13509-27-8), dipropyl carbonate (DPC) ( CAS: 623-96-1), methyl propyl carbonate (MPC) (CAS: 1333-41-1), ethyl propyl carbonate (EPC), vinylene carbonate (VC) (CAS : 872-36-6), fluoroethylene carbonate (FEC) (CAS: 114435-02-8), trifluor
• said lithium salt present in the separator is chosen from: LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTDI (2-trifluoromethyl-4,5-dicyano -lithium imidazolate), LiTFSI (lithium bis(trifluoromethane)sulphonimide), LiPO2F2, LiB(C2O4)2, LiF2B(C2O4)2, LiBF4, LiNCh, LiClO4 or their mixture.
• the electrolyte present in the separator comprises, in addition to the solvent and the lithium salt, at least one additive.
• the additive can be selected from the group consisting of fluoroethylene carbonate (FEC), vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, pyridazine, vinyl pyridazine, quinoline , vinyl quinoline, butadiene, sebaconitrile, alkyl disulphide, fluorotoluene, 1,4-dimethoxytetrafluorotoluene, t-butylphenol, di-t-butylphenol, tris(pentafluorophenyl)borane, oximes, aliphatic epoxides , halogenated biphenyls, metacrylic acids, allyl ethyl carbonate, vinyl acetate, divinyl adipate, propanesultone, acrylonitrile, 2-vinylpyr
• the additive can also be chosen from salts having a melting point below 100° C. such as ionic liquids, which form liquids consisting solely of cations and anions.
• organic cations By way of examples of organic cations, mention may be made in particular of the cations: ammonium, sulfonium, pyridinium, pyrrolidinium, imidazolium, imidazolinium, phosphonium, lithium, guanidinium, piperidinium, thiazolium, triazolium, oxazolium, pyrazolium, and mixtures thereof.
• anions By way of example of anions, mention may in particular be made of imides, in particular bis(trifluoromethanesulfonyl)imide and bis(fluorosulfonyl)imide; borates, in particular tetrafluoroborate (abbreviated BF4); phosphates, in particular hexafluorophosphate (abbreviated PF ⁇ ); phosphinates and phosphonates, in particular alkyl-phosphonates; amides, in particular dicyanamide (abbreviated DCA); aluminates, in particular tetrachloroaluminate (AICI4), halides (such as bromide, chloride or iodide anions), cyanates, acetates (CEECOO- ), in particular trifluoroacetate; sulfonates, in particular methanesulfonate (CH3SO3), trifluoromethanesulfonate; and sulphates, especially hydrogen sulph
• said electrolyte has a salt concentration of 0.05 moles/liter to 5 moles/liter in the solvent.
• the electrolyte/fluorinated polymers ratio is from 0.05 to 20, preferably from 0.1 to 10.
• said film has a caking at least greater than or equal to 5% by weight, preferably ranging from 10% to 1000%.
• the separator in the form of a gelled polymer membrane is non-porous, which means that the gas permeability of the separator is 0 ml/min, as detected by the gas permeability test (when the surface of the separator is of 10 cm 2 , the gas pressure difference between the two sides is 1 atm, and the time is 10 minutes).
• said separator contains a single gelled polymer membrane.
• said separator consists of a multilayer film, each layer of which has the composition of the film described above.
• the membrane is not supported by a support.
• the invention relates to a process for preparing a Li-ion battery comprising said cathode.
• the Li-ion cell is prepared by assembling the anode, separator and cathode.
• a liquid electrolyte comprising at least one solvent and at least one lithium salt is introduced into the cell before sealing the cell in order to form the catholyte by swelling the binder in the cathode.
• the cell can be heated between 30°C and 90°C, and preferentially between 40°C and 70°C for 5 min to 24 h, and preferentially for 30 min to 12 h to promote the swelling of the binder of the cathode impregnated with the catholyte, and polymer gel in the separator (if applicable).
• the Li-ion cell can also be pressurized by 0.01 MPa to 3 MPa to promote the impregnation of the catholyte in the cathode.
• the cathode containing the catholyte is assembled with a separator and an anode, the separator possibly being a solid or quasi-solid electrolyte such as a polymer gel electrolyte.
• PVDF 1 Copolymer of vinylidene fluoride (VDF) and vinylidene hexafluoride (HFP) with 25% by weight of HFP, characterized by a viscosity in the molten state of 1000 Pa.s at 100 s 1 and 230 °C.
• PVDF 2 Homopolymer of vinylidene fluoride characterized by a melt viscosity of 1000 Pa.s at 100 s 1 and 230°C.
• PVDF 3 Acid functionalized vinylidene fluoride homopolymer with a functionality rate of approximately 1% by mass, characterized by a viscosity of 547 cP at 5 s -1 and 25°C in a 10% NMP solution of dry extract.
• LiFSI Lithium bis(fluorosulfonyl)imide
• quasi-solid cathodes are prepared by mixing the active material, the carbon black electronic conductor, and the binder, which can be a mixture of a copolymer and a homopolymer of PVDF, in the solvent N-methyl pyrrolidone.
• the ink is smeared onto an aluminum current collector, which is then dried to evaporate the solvent.
• the electrode is then calendered to reduce the porosity.
• Impedance measurements are carried out in a button cell containing two similar cathodes, separated by a three-layer PP/PE/PP separator.
• the appended figure 1 presents the impedance spectra obtained with the cathodes of table 1.
• the diameter of the semi-circle is proportional to the contact resistance at the interface between the cathode and the aluminum current collector.
• the cathodes of Examples 1 and 2 have a relatively low contact resistance close to that of Comparative Example 1.
• the contact resistance increases when the carbon black content relative to the binder decreases, as shown by the NC/PVDE ratio values in Table 1.
• the cathode of example 2 is assembled as a button cell facing a lithium metal anode.
• the separator is a membrane made up of PVDE 1 and PVDE 2. 20 ⁇ L of liquid electrolyte containing 0.75M LiESI in the dimethoxyethane solvent is injected into the button cell before it is sealed. The battery is then placed in an oven at 45°C for 2 hours so that the electrolyte swells the polymer and forms a gel in the separator and the catholyte.
• the cathode of comparative example 1 is assembled as a button cell facing a lithium metal anode.
• the separator is a tri-layer PP/PE/PP and the electrolyte contains IM LiPE6 in EC/EMC (3:7, vol).
• FIG. 2 shows the capacitance delivered by the cathodes E2 and EC1 at a discharge current of IC.
• the quasi-solid cathode of Example 2 assembled with a polymer gel electrolyte has similar IC performance to the cathode of Comparative Example 1 operating with a liquid electrolyte.

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