Process for preparing an electrode by extrusion

Abstract

Method for preparing an electrode by extrusion The invention relates to a method for preparing an electrode material comprising at least one step consisting of homogeneously mixing: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents; - at least one electrochemically active material; and - optionally at least one electronically conductive additive; said mixture being obtained in the presence of less than 1% by mass of solvent relative to its total mass. It also relates to a method for preparing an electrode by extrusion using one or more electrode materials.It also relates to an electrode comprising at least one electrochemically active layer having a porosity less than or equal to 20% and comprising at least one polypropylene, at least one additional polymer, at least one electrochemically active material, and optionally at least one electronically conductive additive. Figure for the abstract: None.

Description

Title of the invention: Method for preparing an electrode by extrusion Technical field

[0001] The present invention relates to the field of electrodes used in electrochemical elements. More specifically, it relates to a method for preparing an electrode by extrusion which can be carried out without solvent, and to the electrode thus obtained.

[0002] Such electrodes can be used in various electrochemical elements or devices, in particular in third generation batteries (metal-ion batteries), in particular sodium-ion, lithium-ion, potassium-ion, magnesium-ion batteries. Prior art

[0003] Conventionally, the operating principle of an electrochemical generator is based on the insertion and removal, also called "deinsertion", of an alkali or alkaline-earth metal ion or a proton, most often the lithium cation, into and from the positive electrode, and the deposition or extraction of this ion, onto and from the negative electrode. In the case of a lithium accumulator for example, the lithium cation extracted from the positive electrode during the charging of the battery is deposited on the negative electrode, and conversely, it is extracted from the negative electrode to be inserted into the positive electrode during the discharge.

[0004] The electrochemical cell, for example of a lithium accumulator, is thus conventionally formed of a negative electrode and a positive electrode, separated by an electrolyte (called a separator electrolyte). Each of the positive and negative electrodes comprises an electrochemically active layer and a current collector which are in contact with each other, the current collector ensuring the transport of electrons to an external electrical circuit.

[0005] Electrodes for batteries, particularly lithium batteries, are generally designed so that the electrochemical reaction is distributed in the volume of the electrochemically active layer on the surface of the particles of active material. The composition of the electrochemically active layer must therefore allow the conduction of both alkali or alkaline-earth ions and electrons, so that each of the grains of the active material is easily accessible to these reactants.

[0006] These electrodes are generally prepared by coating an ink comprising a powdery electrochemically active material, a polymeric binder and an electronically conductive additive, dispersed and / or solubilized in an organic or aqueous solvent, on a current collector, then evaporating the solvent. The polymeric binder allows the electrochemically active layer to be given cohesion of the various components and its mechanical strength on the current collector, while the electronically conductive additive ensures the conduction of electrons. In addition, the coating process, possibly followed by a calendering step, makes it possible to obtain an electrochemically active layer that is sufficiently porous so that its impregnation with a liquid electrolyte ensures the conduction of alkali or alkaline-earth ions.

[0007] However, the coating process has several drawbacks. It uses a solvent which is most often toxic and / or classified as CMR (carcinogenic, mutagenic and reprotoxic) such as N-methyl-2-pyrrolidone (NMP). In addition, this process includes a step of evaporation of the solvent and therefore of treatment of the solvent vapors. Finally, the evaporation step can lead to defects in the electrochemically active layers such as cracks or poor adhesion to the current collector.

[0008] Thus, it would be advantageous to have electrode preparation processes that do not require the use of solvents, in order to reduce the environmental impact of the process and to avoid the evaporation step, and therefore to simplify the process and reduce its cost and duration.

[0009] Several strategies have already been proposed. For example, US 2010 / 0263910 and US 2015 / 0303481 propose the preparation of solvent-free electrodes.

[0010] Extrusion is also a known process for shaping polymer-based materials in the absence of solvent by melting the polymer. However, this process has two major drawbacks in the context of the preparation of electrodes.

[0011] On the one hand, during extrusion, the pressures inside the extruder and in the dies are high, involving compression of the extruded material. Thus, the electrochemically active layer of the recovered electrode has low porosity, and therefore low ionic conductivity after impregnation with a liquid electrolyte, compared to electrochemically active layers of electrodes obtained by a conventional process in the presence of a solvent such as a coating method.

[0012] On the other hand, the viscosity of the mixture to be extruded must allow it to remain within pressure and torque ranges that can be supported by the equipment during the flow of the mixture in the extruder and the die. Thus, a high molten polymer content relative to the electrochemically active material content is generally selected to allow flow, which is detrimental to energy density.

[0013] An example of an extrusion process for forming an electrode with minimal or no use of solvent is shown in EP 1 360 732.

[0014] Therefore, there is a need for a method of preparing an electrode easy to implement, not requiring the use of solvent.

[0015] There is also a need for an extrusion process that can be carried out in the absence of solvent, making it possible to form electrodes exhibiting good performance after impregnation with an electrolyte.

[0016] The invention aims to satisfy these needs. Statement of the invention

[0017] Thus, the present invention relates to a method for preparing an electrode material, comprising at least the steps of: (i) mix homogeneously: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof; - at least one electrochemically active material, also called “active material”; and - possibly at least one electronically conductive additive; said mixture being obtained in the presence of less than 1% by mass of solvent relative to its total mass, and (ii) recovering the electrode material obtained at the end of step (i).

[0018] In particular, step (i) is carried out by extrusion.

[0019] Advantageously, the method for preparing an electrode material according to the invention uses less than 0.5% by mass, or even less than 0.1% by mass of solvent, relative to the total mass of the mixture. Preferably, the method for preparing an electrode material according to the invention does not use a solvent.

[0020] Preferably, the ancillary polymer is a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP).

[0021] Hereinafter, the term "annex polymer according to the invention" or "annex polymer" is intended to designate more simply the polymer capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof.

[0022] In particular, step (i) is carried out using an extruder or a mixer, in particular an internal one.

[0023] Thus, the present invention also relates to an electrode material obtained by the method of preparing an electrode material according to the invention.

[0024] The electrode material can be obtained in the form of an electrochemical layer- uniquely active at the end of the process according to the invention, or can be subjected to subsequent steps to form an electrochemically active layer, or even an electrode.

[0025] The present invention also relates to the use of an electrode material, in particular obtained by the process for preparing an electrode material according to the invention, comprising, or even consisting of: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - possibly at least one electronically conductive additive; for the preparation of an electrode.

[0026] Preferably, the use uses less than 1% by mass, in particular less than 0.5% by mass, more particularly less than 0.1% by mass of solvent, relative to the total mass of the electrode material, or even does not use any solvent.

[0027] The present invention also relates to a method for preparing an electrode comprising at least the steps of: (a) having a composition consisting of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to the total mass of the composition, of one or more electrode materials, in particular obtained by the process for preparing an electrode material according to the invention, comprising, or even consisting of: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - possibly at least one electronically conductive additive, with said composition comprising less than 1% by mass of solvent relative to the total mass of said composition; (b) Extruding said composition to form it into an electrochemically active layer;

[0028] (c) depositing said electrochemically active layer obtained in step (b), in par particular after rolling, on a current collector; and (d) recovering said electrode thus formed.

[0029] Advantageously, the method for preparing an electrode according to the invention uses less than 0.5% by mass, or even less than 0.1% by mass of solvents, relative to the total mass of the composition. Preferably, the method for preparing an electrode according to the invention does not use a solvent.

[0030] In particular, the method for preparing an electrode material according to the invention is carried out prior to step (a).

[0031] The electrode material according to the invention or implemented in the method or use according to the invention may be in the form of granules or powder, in particular granules.

[0032] Against all expectations, the inventors have discovered that the combination of polypropylene with an additional polymer as defined above, used as a polymeric binder, makes it possible to form by extrusion an electrochemically active layer having on the one hand a limited content of polymeric binder due to the fluidity of the polypropylene, and therefore good performance in terms of energy density, and on the other hand an ability to be impregnated by a liquid electrolyte due to the presence of the additional polymer, and therefore good performance in terms of ionic conductivity. In addition, when the electronically conductive additive is present, the extrusion makes it possible to improve its dispersion and therefore the electronic conductivity of the electrochemically active layer.

[0033] Indeed, as is clear from the example below, an electrode formed by the method according to the invention has good charging and discharging capacities, despite a porosity of the electrochemically active layer of only 10%.

[0034] Thus, the invention also relates to an electrode comprising at least one electrochemically active layer, in particular cathodic, and a current collector, in particular cathodic, the electrochemically active layer having a porosity less than or equal to 20% and comprising, or even consisting of: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - possibly at least one electronically conductive additive.

[0035] The electrochemically active layer may be in contact with the current collector.

[0036] An electrode according to the invention can advantageously be manufactured without using a solvent, in particular by extrusion. In particular, an electrode according to the invention can be obtained by the method of preparing an electrode according to the invention.

[0037] The invention also relates to an electrochemical element comprising at least one electrode according to the invention or obtained by the method of preparing an electrode according to the invention, the electrochemically active layer of the electrode being in particular impregnated with a liquid electrolyte.

[0038] As indicated above, the methods and use according to the invention can advantageously be implemented with little or no solvent. In particular, the term "solvent" includes organic and inorganic solvents, in particular usually used in inks intended to form electrodes.

[0039] By "extrusion of a material" or "extruding a material" is meant a process of extrusion of only said material, without the use of additional additives or solvents. Brief description of the drawings

[0040] [Fig.l] shows the torque measured in example 1 after its stabilization during mixing in an internal mixer at a temperature of 190°C, at a rotor rotation speed of 30 revolutions per minute.

[0041] [Fig.2] shows the curves of the evolution of the pressure expressed in bars (triangles), of the torque expressed as a percentage in relation to the maximum value supported by the extruder (cross) and of the temperature expressed in °C (circles) during the extrusion described in example 2 to form the electrode material.

[0042] [Fig.3] shows the potential evolution curves (in V vs Li+ / Li0) as a function of the capacity (in mAh / g) during the 1st charge-discharge cycle at a C / 50 rate for two cells as prepared in example 2 with the same electrodes, implementing an electrode in accordance with the invention. Detailed description Process for preparing an electrode material

[0043] Step (i) consists of homogeneously mixing at least one polypropylene, at least one additional polymer according to the invention, at least one electrochemically active material and optionally at least one electronically conductive additive, to obtain the expected mixture.

[0044] In particular, step (i) is carried out by extrusion. According to this embodiment, at least one polypropylene, at least one additional polymer according to the invention, at least one electrochemically active material and optionally at least one electronically conductive additive are introduced into an extruder, to form the expected mixture therein.

[0045] Polypropylene

[0046] Polypropylene is advantageously a polymer having a high fluidity at the molten state. It thus allows, unlike a polymer such as PVDF usually used as a binder in batteries, to achieve a viscosity of the mixture suitable for its extrusion when it is in the molten state, even at polypropylene contents of less than 20% by mass relative to the total mass of the mixture.

[0047] The polypropylene used in the process according to the invention may be a homopolymer.

[0048] Polypropylene can be isotactic, or syndiotactic, in particular isotactic.

[0049] In particular, the polypropylene has a number-average molar mass ranging from 10 g / mol to 100 g / mol, more particularly from 20 g / mol to 70 g / mol, in particular from 30 g / mol to 55 g / mol. The number-average molar mass can be determined by high-temperature size exclusion chromatography (SEC) in trichlorobenzene.

[0050] In particular, the polypropylene has a melting temperature ranging from 150°C to 175°C, in particular from 160°C to 170°C, for example from 163°C to 167°C.

[0051] Preferably, the polypropylene has a melt flow index, measured according to the ISO 1133 standard at 230°C for a load of 2.16 kg, of at least 15 g / 10 min, in particular at least 25 g / 10 min, more particularly at least 35 g / 10 min, in particular at least 40 g / 10 min, or even ranging from 40 g / 10 min to 50 g / 10 min, in particular from 40 g / 10 mm to 45 g / 10 min.

[0052] In particular, the polypropylene has a density, measured according to the ISO 1183 standard, ranging from 0.7 to 1.1 g / cm3, in particular from 0.8 to 1 g / cm3, more particularly from 0.85 to 0.95 g / cm3.

[0053] The mixture in step (i) can be obtained in the presence of at least 1% by mass, in particular at least 3% by mass of polypropylene, relative to its total mass.

[0054] The mixture in step (i) can be obtained in the presence of at most 20% by mass, in particular at most 15% by mass, more particularly at most 10% by mass, or even at most 7% by mass of polypropylene, relative to its total mass.

[0055] In particular, the mixture is obtained in the presence of 1% to 15% by mass, in particular 1% to 10% by mass, more particularly 3% to 7% by mass of polypropylene, relative to its total mass.

[0056] Annex polymer

[0057] As specified above, this term designates a polymer capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, i.e. conducive to the absorption of organic solvent molecules in its polymer network. The organic solvents considered according to the invention, being usually used in liquid electrolytes, an additional polymer according to the invention is advantageously generously capable of swelling in the presence of a liquid electrolyte.

[0058] As is apparent from the above, after impregnation of an electrochemically active layer comprising an additional polymer according to the invention with a liquid electrolyte, the ionic conductivity is ensured both by the electrolyte present in the porosity and by the electrolyte present in the additional polymer. An electrode comprising such an electrochemically active layer can therefore achieve satisfactory ionic conductivities even with an electrochemically active layer of low porosity.

[0059] Preferably, the additional polymer is electrochemically stable in the usual potential ranges of battery electrodes, in particular lithium batteries.

[0060] The ancillary polymer(s) may be chosen from a polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), a polyester, in particular a polycaprolactone, a polycarbonate, in particular a poly(trimethylene carbonate), a poly(propylene carbonate), a poly(ethylene carbonate) or a copolymer of trimethylene carbonate, propylene carbonate and / or ethylene carbonate, a polyether, in particular a polyethylene glycol derivative such as a polyethylene glycol dialkylene ether, a polyethylene glycol dialkylene ester, a polyoxide comprising a poly(oxymethyleneoligooxyethylene), a poly(ethylene oxide) or a poly(propylene oxide), a poly(vinyl acetate), a poly(vinyl-pyrrolidone-vinyl acetate), a polymethyl methacrylate, and mixtures thereof.

[0061] In particular, the additional polymer(s) may be chosen from a polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), a polyester, a polycarbonate, a polyether, and mixtures thereof.

[0062] Preferably, the ancillary polymer is a PVDF-HFP.

[0063] In particular, the vinylidene fluoride (VDF) and hexafluoropropylene (HFP) units are present in the copolymer in a VDF / HFP mass ratio ranging from 92 / 8 to 82 / 18.

[0064] In particular, the ancillary polymer, in particular PVDF-HFP, has a melting temperature ranging from 120°C to 150°C, in particular from 125°C to 140°C, or even from 130 to 136°C.

[0065] Preferably, the additional polymer, in particular PVDF-HFP, has a melt flow index, measured according to the ISO 1133 standard at 230°C for a load of 5 kg, of at least 1 g / 10 min, in particular at least 3 g / 10 min, more particularly ranging from 3 g / 10 min to 13 g / 10 min, or even ranging from 3 g / 10 min to 9 g / 10 min.

[0066] In particular, the ancillary polymer, in particular PVDF-HFP, has a density, measured according to ISO 1183, ranging from 1.5 to 2.1 g / cm3, in particular from 1.6 to 2 g / cm3, more particularly from 1.70 to 1.85 g / cm3, or even from 1.75 to 1.80 g / cm3.

[0067] The mixture in step (i) can be obtained in the presence of at least 1% by mass, in particular at least 3% by mass of additional polymer, in particular PVDF-HFP, relative to the total mass of the mixture.

[0068] The mixture in step (i) can be obtained in the presence of at most 20% by mass, in particular at most 15% by mass, more particularly at most 10% by mass, or even at most 7% by mass of additional polymer, in particular PVDF-HFP, relative to the total mass of the mixture.

[0069] In particular, the mixture is obtained in the presence of 1% to 15% by mass, in particular 1% to 10% by mass, more particularly 3% to 7% by mass of additional polymer, in particular PVDF-HFP, relative to the total mass of the mixture.

[0070] Adjusting the mass ratio between the polypropylene and the ancillary polymer advantageously makes it possible to optimize the compromise between fluidity of the polymer binder in the molten state and capacity for impregnation by an electrolyte of the electrochemically active layer of the electrode obtained from the electrode material. Preferably, the polypropylene and the ancillary polymer are used in step (i) in a polypropylene / ancillary polymer mass ratio ranging from 75 / 25 to 25 / 75, in particular from 60 / 40 to 40 / 60, or even from 55 / 45 to 45 / 55.

[0071] Adjusting the total content of polymeric binder, combining polypropylene and one or more additional polymers according to the invention, advantageously makes it possible to optimize the compromise between, on the one hand, the viscosity of the electrode material in the molten state and, on the other hand, the energy density of the electrode formed from the electrode material. The mixture can be obtained in the presence of less than 20% by mass of the sum of the polypropylene and the additional polymer(s), relative to its total mass. The mixture can be obtained in the presence of more than 2% by mass of the sum of the polypropylene and the additional polymer(s), relative to its total mass. In particular, the mixture is obtained in the presence of 2% to 20% by mass, more particularly 5% to 15% by mass, of the sum of the polypropylene and the additional polymer(s), relative to its total mass.

[0072] Electrochemically active material

[0073] Electrochemically active materials for a positive electrode may be, for example, selected from lithium intercalation materials such as lithium phosphates, for example compounds of formula LixFei yMyP04 where M is selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; and 0.8 <x<l,2 ; 0<y<0,6 ; des composés de formule LixMni y zM’yM” ZPO4 (LMP) où M’ et M” sont différents l’un de l’autre et sont choisis dans le groupe consistant en B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb et Mo, avec 0.8 <x<l,2 ; 0<y<0,6 et 0<z<0,2 ; tels que LiFePO4 (LFP), LiMnPO4, LiMnyFei yPO4 avec0,8<x<l,2 ; 0<y<0,6 ;des composés lamellaires, comme l’oxyde de cobalt lithié LiCoO2, l’oxyde de manganèse lithié LiMn2O4, l’oxyde de nickel lithié LiNiO2 ou des matériaux à base de lithium-nickel-cobalt-manganèse LiNixMnyCozO2 avec x+y+z=l (aussi appelé NMC), tel que LiNioj33Mnoj33Cooj3302 ou LiNio,6Mn0,2Co0,202 (aussi appelé NMC622), ou un matériau à base de LiNixCoyAlzO2 avec x+y+z=l (aussi appelé NCA), ou encore des composés de structure spinelle tels que le spinelle LiNioj5Mni> 504 or LiMn2O4; Na3V2(PO4)2F3 (NVPF); Prussian white and blue; organic active materials; and mixtures thereof.

[0074] Advantageously, the active materials for a positive electrode are chosen from NMCs and LiCoO2, in particular from NMCs, preferably LiNi0>6 Mn0j2Co0j2O2.

[0075] The active materials for a negative electrode may be, for example, carbon, graphite, lithiated titanium oxide (Li4Ti50i2) or titanium and niobium oxide (TiNb2O7). They may also be materials based on silicon or based on lithium or sodium, or based on tin and their alloys. They may also be organic active materials.

[0076] Preferably, the electrochemically active material comprises an electrochemically active material for a positive electrode, in particular comprises lithium-nickel-cobalt-manganese LiNixMnyCozO2 with x+y+z=l, preferably comprises LiNioj6Mn0j2Cooj202.

[0077] In particular, the mixture is obtained in the presence of at least 70% by mass, in particular at least 80% by mass, more particularly at least 85% by mass, of the electrochemically active material(s), relative to its total mass.

[0078] According to a particular embodiment, the mixture can be obtained in the presence of 80% to 95% by mass, in particular 85% to 90% by mass of the electrochemically active material(s), relative to its total mass.

[0079] Electronic conductive additive

[0080] Preferably, the mixture in step (i) is obtained in the presence of at least one electronically conductive additive.

[0081] The electronically conductive additives are implemented to improve the electronic conductivity of the electrochemically active layer of the electrode obtained from the electrode material. They can be chosen for example from carbon fibers, carbon black, carbon nanotubes and their mixtures.

[0082] In particular, the mixture is obtained in the presence of at least 1% by mass, in particular from 1% to 10% by mass, more particularly from 3% to 7% by mass of one or more electronically conductive additives, relative to its total mass.

[0083] Solvent

[0084] The mixture in step (i) is obtained in the presence of less than 1% by mass of solvent, in particular chosen from organic and aqueous solvents and their mixtures, relative to its total mass. Preferably, the mixture in step (i) is obtained in the presence of less than 0.5% by mass, more particularly less than 0.1% by mass, of solvent, in particular chosen from organic and aqueous solvents and their mixtures, relative to its total mass. More preferably, step (i) does not use a solvent, in particular chosen from organic and aqueous solvents and their mixtures.

[0085] According to a particular embodiment, step (i) consists of mixing homogeneously: - from 1% to 10% by mass, in particular from 3% to 7% by mass of polypropylene; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more additional polymers according to the invention, in particular PVDF-HFP; - from 70% to 97% by mass, in particular from 80% to 90% by mass of one or more electrochemically active materials, in particular chosen from lithium-nickel-cobalt-manganese LiNixMnyCozO2-based materials with x+y+z=l; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more electronically conductive additives; and

[0086] - less than 0.5% by mass of solvent, in particular chosen from gold solvents organic, aqueous and their mixtures, the mixture being in particular free of solvent, in particular chosen from organic, aqueous solvents and their mixtures; the contents being expressed in relation to the total mass of the polypropylene, the ancillary polymer(s), the electrochemically active material(s), the electronically conductive additive(s), and the solvent if present.

[0087] In step (i), the polypropylene may be in the molten state. In particular, the polypropylene and the ancillary polymer(s), in particular PVDF-HFP, are in the molten state in step (i).

[0088] Preferably, the polypropylene, the ancillary polymer(s), the active material(s), the optional electronically conductive additive(s) and the solvent if present are mixed hot in step (i). In particular, step (i) is carried out at a temperature greater than or equal to the melting temperature of the polypropylene, in particular at a temperature ranging from 170°C to 300°C, more particularly at a temperature ranging from 190°C to 230°C.

[0089] In particular, step (i) is carried out at a temperature greater than or equal to the melting temperature of the ancillary polymer(s), preferably at a temperature greater than or equal to the melting temperature of the polypropylene and greater than or equal to the melting temperature of the ancillary polymer(s).

[0090] In particular, step (i) consists of: - mix polypropylene, additional polymer(s), active material(s), if applicable electronically conductive additive(s) and the solvent if present at a temperature greater than or equal to the melting temperature of the polypropylene and greater than or equal to the melting temperature of the ancillary polymer(s), in particular at a temperature ranging from 190°C to 230°C, and

[0091] - cool the assembly.

[0092] In particular, the method may further comprise a step of grinding the mixture obtained at the end of step (i) to obtain the electrode material.

[0093] The electrode material can also be obtained directly at the end of step (i), in particular in the form of granules.

[0094] The electrode material can be recovered in step (ii) in the form of powder or granules, in particular granules.

[0095] Step (i) may be carried out with an internal mixer and / or by extrusion, preferably by extrusion.

[0096] The polypropylene, the additional polymer(s), the active material(s), the possible electronically conductive additive(s) and the solvent if present can be mixed hot, in particular at a temperature as described above, simultaneously with their extrusion.

[0097] Generally, the extrusion is carried out with an extruder allowing the material to be extruded to be conveyed to the outlet of the extruder, in particular to a die at the outlet of the extruder. In particular, the extruder comprises at least one mixing zone and at least one conveying zone. Preferably, the extruder used in step (i) is a co-rotating twin-screw extruder. The die may be a flat die or a rod die.

[0098] The constituents of the mixture may be introduced into the extruder individually or in the form of a premix. In particular, the polypropylene and the ancillary polymer(s) may be introduced in the form of granules or powder. The electrochemically active material(s) and the possible electronically conductive additive(s) may be introduced in the form of powder.

[0099] Preferably, the polypropylene is introduced into the extruder, and in particular brought to a temperature greater than or equal to its melting temperature, upstream of the introduction of the ancillary polymer(s), the electrochemically active material(s) and the possible electronically conductive additive(s). After their introduction into the extruder, the ancillary polymer(s), in particular brought to a temperature greater than or equal to its melting temperature, the electrochemically active material(s) and the possible electronically conductive additive(s) may be mixed with the polypropylene in the molten state. The ancillary polymer(s), the electrochemically active material(s) and the possible electronically conductive additive(s) may be introduced into the extruder simultaneously in the form of a premix.

[0100] The additional polymer(s) may also be introduced into the extruder, brought to the molten state and mixed with the molten polypropylene upstream of the introduction of the electrochemically active material(s) and the possible electronically conductive additive(s).

[0101] Alternatively, the polypropylene, the ancillary polymer(s), the electrochemically active material(s) and the optional electronically conductive additive(s) may be introduced into the extruder simultaneously in the form of a premix.

[0102] The electrode material can be recovered at the outlet of the die, in particular after shaping and cooling, for example in the open air, of the extruded mixture.

[0103] The electrode material can be recovered in step (ii) directly in the form of an electrochemically active layer, in particular intended to be deposited on a current collector, the extruder being in particular equipped with a flat die.

[0104] Preferably, the electrode material is recovered in step (ii) in the form of granules.

[0105] In particular, the extruder is equipped with a rod die and a granulation system.

[0106] According to another particular embodiment, step (i) is carried out with a mixer, in particular an internal one.

[0107] The polypropylene, the ancillary polymer(s), the active material(s), the possible electronically conductive additive(s) may be introduced simultaneously or independently in the form of granules and / or powder into the internal mixer. They may be mixed in the internal mixer while hot, in particular at a temperature as described above, in particular greater than or equal to the melting temperature of the polypropylene and the ancillary polymer(s). After cooling, the mixture thus obtained may be ground. The electrode material may be recovered in the form of a powder. Use of electrode material

[0108] The use of an electrode material, in particular as described above, comprising: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - optionally at least one electronically conductive additive, allows the preparation of an electrode.

[0109] The polypropylene, the additional polymer(s), the active material(s) and the possible electronically conductive additive(s) may be as described previously and / or in the proportions as defined previously.

[0110] The electrode material can be implemented in the form of powder or granules, in particular granules.

[0111] The use may comprise shaping the electrode material. In particular, the electrode material may be shaped by any technique usually used for thermoplastic polymers which does not require the use of a solvent. In particular, shaping the electrode material may comprise melting the polypropylene, in particular the polypropylene and the ancillary polymer(s), flowing the electrode material in the molten state to give it a determined shape, and cooling it. In particular, the electrode material is rolled before cooling it in order to obtain an electrochemically active layer of controlled thickness.

[0112] In particular, less than 1% by mass, in particular less than 0.5% by mass, more particularly less than 0.1% by mass of solvent, relative to the total mass of the electrode material is used to prepare the electrode. Preferably, no solvent is used to prepare the electrode. Method of preparing an electrode

[0113] The method for preparing an electrode makes it possible to form an electrode by extrusion of a composition mainly comprising one or more electrode materials, in particular as described previously, comprising: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - possibly at least one electronically conductive additive.

[0114] The polypropylene, the additional polymer(s), the active material(s) and the possible electronically conductive additive(s) may be as described previously and / or in the proportions as defined previously.

[0115] In particular, the electrode material used in the method for preparing an electrode comprises, relative to its total mass, or even consists of: - from 1% to 10% by mass, in particular from 3% to 7% by mass of polypropylene; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more additional polymers according to the invention, in particular PVDF-HFP; - from 70% to 97% by mass, in particular from 80% to 90% by mass of one or more electrochemically active materials, in particular chosen from lithium-nickel-cobalt-manganese LiNixMnyCozO2 materials with x+y+z=l; and - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more electronically conductive additives.

[0116] The composition in step (a) is made up of at least 95% by mass, relative to the total mass of the composition, of the electrode material(s). Preferably, the composition is made up of at least 99% by mass, or even at least 99.5% by mass, or even at least 99.9% by mass, relative to the total mass of the composition, of the electrode material(s).

[0117] The composition in step (a) comprises less than 1% by mass of solvent, in particular chosen from organic and aqueous solvents and their mixtures, relative to the total mass of said composition. In particular, the composition in step (a) comprises less than 0.5% by mass, more particularly less than 0.1% by mass, of solvent, in particular chosen from organic and aqueous solvents and their mixtures, relative to the total mass of said composition, in particular the composition is free of solvent, in particular chosen from organic and aqueous solvents and their mixtures.

[0118] According to a preferred embodiment, the composition consists of the electrode material(s).

[0119] In step (b), the composition is formed into an electrochemically active layer by extrusion.

[0120] The extrusion in step (b) may be carried out at a temperature greater than or equal to the melting temperature of the polypropylene, in particular greater than or equal to the melting temperature of the polypropylene and the ancillary polymer(s). In particular, the extrusion in step (b) is carried out at a temperature ranging from 170°C to 300°C, more particularly at a temperature ranging from 190°C to 230°C.

[0121] The extrusion in step (b) can be carried out with a twin-screw or single-screw extruder, in particular a single-screw extruder. In particular, the extruder is equipped with a flat die.

[0122] In particular, in step (b), the composition may be extruded in the form of a strip, in particular with a thickness ranging from 0.1 mm to 5 mm, in particular from 0.5 mm to 2 mm.

[0123] Preferably, the method comprises a step (b') of rolling the electrochemically active layer obtained at the end of step (b) to reduce its thickness, in particular after step (b) and before step (c).

[0124] The rolling can be carried out between two rotating rollers. The electrochemically active layer can be rolled directly at the die outlet between the two rollers. It can also be first stretched by one of the two rollers at the die outlet and then rolled between the two rollers.

[0125] Preferably, the rolling of the electrochemically active layer makes it possible to reduce its thickness to a thickness less than or equal to 500 μm, in particular less than or equal to 200 μm, more particularly ranging from 50 μm to 150 μm, or even from 75 μm to 115 μm.

[0126] The method comprises a step (c) during which the electrochemically active layer obtained at the end of step (b), optionally after a rolling step (b'), is deposited on a current collector.

[0127] In particular, the deposition in step (c) is carried out by co-laminating said electrochemically active layer with the current collector, by calendering said electrochemically active layer with the current collector or by hot pressing said electrochemically active layer onto the current collector, in particular by co-laminating said electrochemically active layer with the current collector.

[0128] For example, copper, aluminum, nickel, carbon felt, or stainless steel may be used as a current collector for a positive electrode; and copper, or steel, processed into a cut sheet, foam metal, or laminated foil plate, for example, may be used as a current collector for a negative electrode. In particular, the current collector is made of copper, aluminum, nickel, carbon felt, or stainless steel, more particularly is made of aluminum.

[0129] In particular, the electrode prepared by the method is a positive electrode comprising a current collector for positive electrode, called cathodic, and an electrochemically active layer, called cathodic, comprising an electrochemically active material for positive electrode.

[0130] According to a particular embodiment, the method for preparing an electrode according to the invention, in particular as described previously, further comprises, prior to step (a), the preparation of the electrode material according to the method defined in the present invention.

[0131] Preferably, the method for preparing an electrode, in particular as defined above, comprises at least the steps consisting of:

[0132] (1) mix homogeneously: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof; - at least one electrochemically active material; and - possibly at least one electronically conductive additive; said mixture being obtained in the presence of less than 1% by mass of solvent relative to its total mass, in particular not using solvent, (2) recovering the electrode material obtained at the end of step (1);

[0133] (3) forming a composition consisting of at least 95% by mass, in particular less than 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to the total mass of the composition, of the electrode material obtained in step (2), with said composition comprising less than 1% by mass of solvent relative to the total mass of said composition, in particular being solvent-free; (4) extruding said composition to form it into an electrochemically active layer;

[0134] (5) optionally laminating said electrochemically active layer obtained in step (4);

[0135] (6) depositing said electrochemically active layer obtained in step (4), or the case applicable in step (5), on a current collector; and (7) recovering said electrode thus formed. Electrode

[0136] The invention also relates to an electrode, in particular obtained by the method of preparing an electrode according to the invention, comprising at least one electrochemically active layer, in particular cathodic, and a current collector, in particular cathodic, the electrochemically active layer having a porosity less than or equal to 20% and comprising, or even consisting of: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, in particular as defined above, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - possibly at least one electronically conductive additive.

[0137] It is understood that the definition of the electrode does not include the liquid electrolyte. For example, the total mass of the electrochemically active layer does not include the mass of the impregnated electrolyte.

[0138] Preferably, the electrochemically active material(s) and the optional electronically conductive additive(s) are dispersed homogeneously in a mixture of the polypropylene and the additional polymer(s).

[0139] The weight of the electrode can be between 5 mg / cm2 and 100 mg / cm2, in par particularly between 10 mg / cm2 and 40 mg / cm2, more particularly between 15 mg / cm2 and 30 mg / cm2. The weight of the electrode corresponds to the surface mass of the electrochemically active layer.

[0140] The thickness of the electrochemically active layer may be between 20 pm and 300 pm, in particular between 50 pm and 150 pm.

[0141] In particular, the porosity of the electrochemically active layer is less than or equal to 15%, in particular between 5% and 15%, or even between 7% and 12%.

[0142] The porosity of the electrochemically active layer corresponds to the ratio of the volume occupied by the pores of the electrochemically active layer to the total volume of the electrochemically active layer.

[0143] The polypropylene, the ancillary polymer(s), the electrochemically active material(s) and the possible electronically conductive additive(s) may be as defined previously.

[0144] Preferably, the electrochemically active layer consists of at least 85% by mass, in particular at least 95% by mass, more particularly at least 99% by mass of the sum of the polypropylene, the ancillary polymer(s), the electrochemically active material(s) and the optional electronically conductive additive(s), relative to the total mass of the electrochemically active layer. Preferably, the electrochemically active layer consists of the polypropylene, the ancillary polymer(s), the electrochemically active material(s) and the optional electronically conductive additive(s).

[0145] The electrochemically active layer may comprise at least 1% by mass, in particular at least 3% by mass of polypropylene, relative to the total mass of the electrochemically active layer. The electrochemically active layer may comprise at most 20% by mass, in particular at most 15% by mass, more particularly at most 10% by mass, or even at most 7% by mass of polypropylene, relative to the total mass of the electrochemically active layer. In particular, the electrochemically active layer comprises from 1% to 15% by mass, in particular from 1% to 10% by mass, more particularly from 3% to 7% by mass of polypropylene, relative to the total mass of the electrochemically active layer.

[0146] The electrochemically active layer may comprise at least 1% by mass, in particular at least 3% by mass of ancillary polymer, in particular PVDF-HFP, relative to the total mass of the electrochemically active layer. The electrochemically active layer may comprise at most 20% by mass, in particular at most 15% by mass, more particularly at most 10% by mass, or even at most 7% by mass of ancillary polymer, in particular PVDF-HFP, relative to the total mass of the electrochemically active layer. In particular, the electrochemically active layer comprises from 1% to 15% by mass, in particular from 1% to 10% by mass, more particularly 3% to 7% by mass of additional polymer, in particular PVDF-HFP, relative to the total mass of the electrochemically active layer.

[0147] Preferably, the polypropylene / annealed polymer mass ratio in the electrochemically active layer is between 75 / 25 and 25 / 75, in particular between 60 / 40 and 40 / 60, or even between 55 / 45 and 45 / 55.

[0148] The electrochemically active layer may comprise less than 20% by mass of the sum of the polypropylene and the ancillary polymer(s), relative to the total mass of the electrochemically active layer. The electrochemically active layer may comprise more than 2% by mass of the sum of the polypropylene and the ancillary polymer(s), relative to the total mass of the electrochemically active layer. In particular, the electrochemically active layer comprises from 2% to 20% by mass, more particularly from 5% to 15% by mass, of the sum of the polypropylene and the ancillary polymer(s), relative to the total mass of the electrochemically active layer.

[0149] In particular, the electrochemically active layer comprises at least 70% by mass, in particular at least 80% by mass, more particularly at least 85% by mass, of the electrochemically active material(s), relative to the total mass of the electrochemically active layer. According to a particular embodiment, the electrochemically active layer may comprise from 80% to 95% by mass, in particular from 85% to 90% by mass, of the electrochemically active material(s), relative to the total mass of the electrochemically active layer.

[0150] Preferably, the electrochemically active layer comprises one or more electronically conductive additives. In particular, the electrochemically active layer comprises at least 1% by mass, in particular from 1% to 10% by mass, more particularly from 3% to 7% by mass of one or more electronically conductive additives, relative to the total mass of the electrochemically active layer.

[0151] According to a particular embodiment, the electrochemically active layer comprises, or even consists of: - from 1% to 10% by mass, in particular from 3% to 7% by mass of polypropylene; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more additional polymers according to the invention, in particular PVDF-HFP; - from 70% to 97% by mass, in particular from 80% to 90% of one or more electrochemically active materials, in particular chosen from lithium-nickel-cobalt-manganese LiNixMnyCozO2 materials with x+y+z=l; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more electronically conductive additives; the percentages being expressed relative to the total mass of the electrochemically active layer.

[0152] In particular, the electrode has a charging capacity at a C / 50 regime and at a temperature of 60°C of at least 190 mAh / g, in particular of at least 195 mAh / g.

[0153] In particular, the electrode has a discharge capacity at a C / 50 regime and at a temperature of 60°C of at least 150 mAh / g, in particular of at least 155 mAh / g- Electrochemical element

[0154] The invention also relates to an electrochemical element comprising at least one electrode according to the invention or obtained by the method according to the invention, the electrochemically active layer of the electrode being in particular impregnated with a liquid electrolyte.

[0155] In particular, the electrochemically active layer of the electrode is impregnated with a liquid electrolyte comprising at least one alkali or alkaline-earth metal salt, preferably at least one lithium or sodium-based salt, more preferably lithium-based, in one or more organic solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof.

[0156] In particular, the impregnation of the electrode by the liquid electrolyte is carried out after mounting the electrode in a cell of the electrochemical element, in particular in a glove box.

[0157] Preferably, the electrode according to the invention or obtained by the method according to the invention is present in the electrochemical element as a positive electrode.

[0158] The electrochemical element in which the electrode according to the invention is implemented may in particular be a rechargeable electrochemical accumulator, in particular a lithium accumulator or battery.

[0159] Preferably, this rechargeable electrochemical accumulator comprises, in addition to the positive or negative electrode according to the invention or obtained by the method according to the invention, respectively a negative or positive electrode, and, between the positive and negative electrodes, a porous separator impregnated with a liquid electrolyte. Preferably, the separator and the electrochemically active layer of the electrode according to the invention or obtained by the method according to the invention are impregnated with the same electrolyte.

[0160] Advantageously, an electrode according to the invention can be implemented in a battery in cation-ion configuration, in particular a lithium-ion, sodium-ion, potassium-ion, magnesium-ion battery; a battery in “dual-ion” configuration, in which both cations and anions are involved in the redox reaction; or even a battery in anion-ion configuration.

[0161] It may be a lithium-ion, lithium-sulfur, lithium-air or supercapacitor battery, and preferably a lithium-ion battery.

[0162] The remainder of the battery can be formed by conventional methods.

[0163] Generally speaking, batteries have an architecture with two electrodes (a positive electrode and a negative electrode), arranged on either side of an organic or inorganic separator. The two most commonly used assembly techniques for this architecture are winding (winding the various components in a cylindrical or prismatic geometry) and stacking (stacking the various elements layer by layer). Of course, other assembly techniques for forming a battery are possible, such as printing techniques.

[0164] The invention will now be described by means of the following figures and examples, given of course for illustrative and non-limiting purposes of the invention. Material Examples

[0165] The following raw materials were used: - Polypropylene (molar mass of approximately 42g / mol) marketed under the name PPH 10012 by the company TotalEnergies; - PVDF-HFP marketed under the name SOLEF® 21510 by the company Solvay;

[0166] - LiNio,6Mn0,2Coo,202 (NMC) marketed under the name HX12TH by the Umicore company;

[0167] - Carbon black marketed under the name SUPER C65 by the company Imerys.

[0168] The properties of polypropylene and PVDF-HFP are reported in Table 1 below.

[0169] [Tables 1] Density Melting point (C'C) Melt flow index (g / Wmin) at PVDF-HFP 1.78 130 g / Wmin (5kg load) PP 0.965 165 (2.16kg load)

[0170] The twin-screw extruder used is a TSE24 extruder marketed by Ther-moElectron with a diameter of 24mm.

[0171] The single-screw extruder used is a Rheomex QC extruder marketed by ThermoElectron. Example 1: Mixing with an internal mixer

[0172] Hot mixing (fluidification) of five formulations A to E of PVDF and polypropylene, loaded or not with NMC, the compositions of which are provided in Table 2, is carried out. The proportions are indicated for the unloaded compositions in mass percentage relative to the total mass of polymer. The NMC is present in all the NMC-loaded mixtures at a mass content of 90% relative to the total mass of the mixture, which corresponds to a volume fraction of 70% in the mixture, except for formulation A where it was not possible to exceed a mass content of 87% in view of the increase in torque.

[0173] The formulations are mixed with an internal mixer from Ther-moElectron, the plates of which are heated to a temperature of 190°C. The rotation speed of the rotors in the internal mixer is kept constant at 30 revolutions per minute.

[0174] [Tables2] A [ B cw Ci PP (W |iw ​​50 25 | 16 PVDF 190 - 50 75 90

[0175] The torque in the internal mixer is measured during mixing for each of the formulations in Table 2, unfilled or filled with NMC. The torque obtained after stabilization is reported in [Fig.l]. It is observed that PP (formulation B) makes it possible to obtain a low torque for the filled formulation after stabilization, while PVDF (formulation A) leads to a high torque after stabilization for the filled formulation, such that it is not possible to achieve an NMC mass content of 90% by mass, and resulting in conditions not supported by the extruder for NMC mass contents greater than or equal to 60%. In addition, it is observed that the torque after stabilization for the filled formulation decreases when the polypropylene content in the formulation increases.

[0176] Example 2: Preparation and implementation of an electrode according to the invention

[0177] Preparation of an electrode material in accordance with the invention and its use to form an electrode

[0178] An electrode material is prepared in the twin-screw extruder described above, equipped with a rod die and a granulation system. The extruder barrel is heated to between 190°C and 230°C.

[0179] Polypropylene (PP) is introduced upstream of the extruder in the form of granules using a gravimetric granule feeder.

[0180] A premixture of PVDF-HFP, NMC and carbon black (SP), in the form powder, is introduced downstream of the polypropylene introduction zone, using a gravimetric doser, so that the PP is in the molten state at the pre-mix introduction zone.

[0181] PP, PVDF-HFP, NMC and carbon black are mixed in the extruder in the proportions indicated in Table 3 (formulation F) in mass percentage relative to the total mass of the mixture and extruded through the rod die.

[0182] The granulation system leads to the formation of granules of the electrode material.

[0183] The pressure, torque and temperature are measured at the extruder outlet and reported in [Fig.2]. The pressure and torque are within acceptable ranges for the extruder.

[0184] [Tables3]

[0185] The granules of the electrode material obtained are introduced into the single-screw extruder described above to be melted and extruded through a flat die. A strip of thickness 1 mm is obtained.

[0186] The strip is then rolled in a rolling mill between two rollers located at the exit of the flat die. The thickness of the strip after rolling is 95 μm.

[0187] This is then laminated onto an aluminum current collector to obtain the electrochemically active layer deposited on the current collector.

[0188] The weight of the electrode, measured by weighing a known surface, is 22 mg / cm2.

[0189] The thickness of the electrochemically active layer, measured by micrometer, is 90 pm.

[0190] The porosity of the electrochemically active layer, calculated from the weight of the electrode, the thickness of the electrode, and the densities of the constituents of the electrode, is 10%. Evaluation of electrochemical performances

[0191] In order to determine the electrochemical performances of the electrode obtained according to the invention, the latter is used as a positive electrode in a cell of a pouch-type lithium accumulator ("pouch-cell" according to the English terminology). Saxon), with a negative graphite electrode, a PP or PE separator coated with alumina, and an electrolyte consisting of a mixture of carbonates and LiPF 6. A pouch-cell type cell has a flexible packaging, for example aluminum-plastic. After assembly of the cell, it is filled with a controlled quantity of electrolyte using a syringe. The cell is then subjected to several vacuums. The cell is weighed before and after filling to determine the quantity of electrolyte added. It is then heat-sealed and placed on a rack between two plates which maintain it under pressure (1 bar).

[0192] Electrochemical tests are carried out in galvanostatic cycling at a C / 50 regime at a temperature of 60°C between IV and 4.2V vs Li.

[0193] [Fig.3] represents the curves of evolution of the potential as a function of the capacity during the 1st charge-discharge cycle at a rate of C / 50 for two “pouch-cell” type cells as prepared as described previously, implementing an electrode in accordance with the invention.

[0194] These cells have a charge capacity of 197 mAh / g and a discharge capacity of 158 mAh / g.

[0195] Example 3: Preparation and implementation of an electrode outside the invention

[0196] The process described in Example 2 is reproduced by replacing the PVDF-HFP with po- lypropylene. It is not possible to measure an electrochemical signal with the formed electrode.

Claims

Claims

1. A method for preparing an electrode material, comprising at least the steps of: (i) homogeneously mixing: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof; - at least one electrochemically active material; and - optionally at least one electronically conductive additive; said mixture being obtained in the presence of less than 1% by mass of solvent relative to its total mass, and (ii) recovering the electrode material obtained at the end of step (i).

2. Method according to the preceding claim, step (i) being carried out by extrusion.

3. Process according to claim 1 or 2, wherein said mixture is obtained in the presence of less than 0.5% by mass, more particularly less than 0.1% by mass, of solvent relative to its total mass, in particular step (i) does not use solvent.

4. A method according to any one of the preceding claims, wherein the ancillary polymer(s) are selected from polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), a polyester, in particular polycaprolactone, a polycarbonate, in particular poly(trimethylene carbonate), poly(propylene carbonate), poly(ethylene carbonate) or a copolymer of trimethylene carbonate, propylene carbonate and / or ethylene carbonate, a polyether, in particular a polyethylene glycol derivative such as a polyethylene glycol dialkylene ether, a polyethylene glycol dialkylene ester, a polyoxide comprising poly(oxymethyleneoligooxyethylene), poly(ethylene oxide) or poly(propylene oxide), poly(vinyl acetate), poly(vinyl-pyrrolidone-vinyl acetate), polymethyl methacrylate, and mixtures thereof, preferably the ancillary polymer is a PVDF-HFP.

5. A method according to any preceding claim, in in which the polypropylene and the additional polymer are used in step (i) in a polypropylene / additional polymer mass ratio ranging from 75 / 25 to 25 / 75, in particular from 60 / 40 to 40 / 60, or even from 55 / 45 to 45 / 55.

6. A method according to any one of the preceding claims, wherein the mixture is obtained in the presence of at least 1% by mass, in particular from 1% to 15% by mass, more particularly from 1% to 10% by mass, in particular from 3% to 7% by mass of polypropylene, relative to its total mass.

7. A method according to any preceding claim, wherein the electrochemically active material comprises an electrochemically active material for a positive electrode, in particular comprises lithium-nickel-cobalt-manganese LiNixMnyCozO2 with x+y+z=l.

8. Method according to any one of the preceding claims, the mixture being obtained in the presence of at least 70% by mass, in particular at least 80% by mass, more particularly at least 85% by mass, of the electrochemically active material(s), relative to its total mass.

9. A method according to any preceding claim, wherein the electronically conductive additive(s) are selected from carbon fibers, carbon black, carbon nanotubes and mixtures thereof.

10. A method according to any one of the preceding claims, wherein the mixture is obtained in the presence of less than 20% by mass, in particular from 2% to 20% by mass, more particularly from 5% to 15% by mass, of the sum of the polypropylene and the ancillary polymer(s), relative to its total mass.

11. A method according to any one of the preceding claims, wherein step (i) is carried out at a temperature greater than or equal to the melting temperature of the polypropylene, in particular at a temperature ranging from 170°C to 300°C, more particularly at a temperature ranging from 190°C to 230°C.

12. A method according to any one of the preceding claims, the electrode material being recovered in step (ii) in the form of powder or granules, in particular granules.

13. Electrode material obtained by the method of any one of the preceding claims.

14. Use of an electrode material, in particular according to the preceding claim, comprising: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, in particular according to claim 4, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - optionally at least one electronically conductive additive, for the preparation of an electrode.

15. A method for preparing an electrode comprising at least the steps of: (a) providing a composition consisting of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to the total mass of the composition, of one or more electrode materials, in particular according to claim 13, comprising: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, in particular according to claim 4, preferably at least one PVDF-HFP; - at least one electrochemically active material;and - optionally at least one electronically conductive additive, with said composition comprising less than 1% by mass of solvent relative to the total mass of said composition; (b) extruding said composition to form it into an electrochemically active layer; (c) depositing said electrochemically active layer obtained in step (b), in particular after rolling, on a current collector; and (d) recovering said electrode thus formed.;

16. Method according to the preceding claim, in which the composition comprises less than 0.5% by mass, more particularly less than 0.1% by mass, of solvent relative to the total mass of said com- position, in particular the composition is solvent-free.

17. Method according to claim 15 or 16, in which the extrusion is carried out in step (b) at a temperature greater than or equal to the melting temperature of the polypropylene, in particular at a temperature ranging from 170°C to 300°C, more particularly at a temperature ranging from 190°C to 230°C.

18. A method according to any one of claims 15 to 17, wherein the deposition in step (c) is carried out by co-laminating said electrochemically active layer with the current collector, by calendering said electrochemically active layer with the current collector or by hot pressing said electrochemically active layer onto the current collector, in particular by co-laminating said electrochemically active layer with the current collector.

19. Electrode comprising at least one electrochemically active layer, in particular cathodic, and a current collector, in particular cathodic, the electrochemically active layer having a porosity less than or equal to 20% and comprising: - at least one polypropylene; - at least one additional polymer, capable of swelling in the presence of one or more organic electrolyte solvents chosen from carbonate solvents, linear or cyclic ether solvents, nitrile solvents, lactone solvents, amide solvents, ester solvents and mixtures thereof, in particular according to claim 4, preferably at least one PVDF-HFP; - at least one electrochemically active material; and - optionally at least one electronically conductive additive.

20. Electrode according to the preceding claim, the electrochemically active layer having a porosity less than or equal to 15%, in particular between 5% and 15%.

21. Electrode according to claim 19 or 20, the electrochemically active layer being made up of at least 85% by mass, in particular at least 95% by mass, more particularly at least 99% by mass of the sum of the polypropylene, of the said additional polymer(s), of the electrochemically active material(s) and of the possible electronically conductive additive(s), relative to the total mass of the electrochemically active layer.

22. An electrode according to any one of claims 19 to 21, the layer electrochemically active comprising, or even consisting of: - from 1% to 10% by mass, in particular from 3% to 7% by mass of polypropylene; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more additional polymers, preferably PVDF-HFP; - from 70% to 97% by mass, in particular from 80% to 90% by mass of one or more electrochemically active materials, in particular according to claim 7, in particular chosen from lithium-nickel-cobalt-manganese LiNixMnyCozO2 materials with x+y+z=l; - from 1% to 10% by mass, in particular from 3% to 7% by mass of one or more electronically conductive additives; the percentages being expressed relative to the total mass of the electrochemically active layer.

23. An electrode according to any one of claims 19 to 22, the electrode being obtained by the method defined in any one of claims 15 to 18.

24. Electrochemical element comprising at least one electrode according to any one of claims 19 to 23 or obtained by the method according to any one of claims 15 to 18, the electrochemically active layer of the electrode being in particular impregnated with a liquid electrolyte.

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