New solvent-free preparation method for catholytes and solid electrolyte layers

Abstract

The present application relates to solvent-free formulations based on sulfide solid electrolyte and fluoropolymer, suitable for solid electrolyte layers or an electrode layer for all-solid-state batteries.

Description

[0001] DESCRIPTION

[0002] TITLE: NEW SOLVENT-FREE PREPARATION PROCESS FOR CATHOLYTES AND SOLID ELECTROLYTE LAYERS

[0003] The present invention relates to the field of energy storage, and more specifically to accumulators, in particular of the lithium type.

[0004] The operation of lithium accumulators is based on the reversible exchange of lithium ions between a positive electrode and a negative electrode, separated by a separator containing an electrolyte, with the lithium being inserted into the negative electrode during charging.

[0005] Typically, electrodes consist of a metal foil to which an electrode formulation consisting of active material and optionally binder and conductive material is applied.

[0006] Due to the constant increase in energy and battery needs, it is necessary to improve their manufacturing, to facilitate industrialization, reduce costs and improve their environmental impact.

[0007] Currently, a very significant part of the manufacturing cost of an electrode is linked to its manufacturing process. Indeed, the solvent used to prepare the ink (based on active material, possible conductive fillers and binder) which will be coated on the strip to design the electrode, must be evaporated. This step therefore involves the use of energy-intensive ovens.

[0008] It is also desirable to limit the use of harmful solvents as part of an environmental approach.

[0009] In an effort to eliminate these solvents and reduce electrode manufacturing costs, new so-called solvent-free processes are currently being developed.

[0010] All-solid-state technology is based on replacing the liquid electrolyte with a non-flammable and more thermally stable solid electrolyte, and therefore offers increased safety. In all-solid-state batteries, a solid electrolyte layer (SEL) acts as a separator and solid electrolyte particles are present at the cathode, and possibly at the anode.

[0011] Solid sulfide electrolytes represent a preferred development path.

[0012] It is therefore desirable to provide solvent-free processes for the preparation of formulations comprising such electrolytes.

[0013] Thus, CN 105489931 describes a process for preparing formulations of solid sulfide electrolyte and PTFE, by mixing powders, grinding and compressing. However, the process described presents risks of reactivity of the solid electrolyte with the environment, and results in a highly heterogeneous mixture.

[0014] It is therefore necessary to provide a more suitable and / or easily industrializable process.

[0015] The present invention thus relates to a new solvent-free route for the improved preparation of formulations for all-solid-state electrochemical elements.

[0016] According to a first object, the present invention relates to a process for the solvent-free preparation of a formulation for an all-solid type electrochemical element with a sulfide electrolyte, said process comprising:

[0017] - The preparation of a premix comprising the mixture of a solid sulfide electrolyte;

[0018] A fluoropolymer type binder.

[0019] Fibrillation of the obtained premix, said fibrillation being carried out by extrusion with an extruder or by mixing with an internal or planetary mixer;

[0020] The premix preparation and fibrillation steps are carried out under an inert atmosphere.

[0021] Also disclosed is a process for the solvent-free preparation of a formulation for an all-solid-state electrochemical element with a sulfide electrolyte, said process comprising:

[0022] - The preparation of a premix comprising the mixture of o a solid sulfide electrolyte; o A fluoropolymer type binder.

[0023] - Fibrillation of the premix obtained; the steps of preparation of the premix and fibrillation being carried out under an inert atmosphere.

[0024] The method according to the invention aims to prepare a formulation based on solid sulfide electrolyte, suitable for an all-solid electrochemical element.

[0025] Said formulation can thus be suitable for a solid electrolyte layer (SEL), or a positive electrode layer or a negative electrode layer.

[0026] According to the invention, the process is solvent-free in that it does not use an organic or aqueous solvent, requiring a drying step. In the absence of solvent, problems related to reactivity between the solid sulfide electrolyte and the solvent residues can be avoided.

[0027] The term "solid sulfide electrolyte" refers to solid sulfur-based electrolytes typically used for all-solid-state batteries.

[0028] By way of illustration, said sulfide electrolyte may in particular be chosen from:

[0029] • all phases [(Li2S)y (Li2O)t(P2S5)iyt](iz)(LiX) z , with X representing one or more halogen elements; 0 <y<1 ; 0<z<1 ; 0<t<1

[0030] • compounds having an argyrodite structure such as Li6PS5X, with X = Cl, Br, I, or Li7P3Sn;

[0031] • sulfide electrolytes having the crystallographic structure equivalent to the compound Li GeP2Si2 including for example substitutions, dopings and / or vacancies;

[0032] • Li3PS4.

[0033] Preferably, said solid sulfide electrolyte is an electrolyte of the Li6PS5X type, with X = Cl, Br, I.

[0034] According to the invention, the inert atmosphere designates an atmosphere of gas inert with respect to the solid sulfide electrolyte and refers, for example, to an atmosphere of nitrogen (N2) or argon.

[0035] The term "electrochemical element" means an elementary electrochemical cell consisting of the positive electrode / solid electrolyte layer / negative electrode assembly, allowing the electrical energy supplied by a chemical reaction to be stored and released in the form of current.

[0036] The chemical elements according to the invention can be adapted to different battery technologies and types of electrolytes.

[0037] The electrochemical element can be of the all-solid type, the term "solid" refers to elements with solid electrolyte.

[0038] The term "fluoropolymer" as used herein refers to fluoropolymers whose repeating unit is a fluorocarbon, comprising multiple carbon-fluorine bonds. Among these fluoropolymers, mention may be made in particular of polytetrafluoroethylene (PTFE) and its derivatives, in particular its copolymers such as chlorofluoroethylene, perfluoroalkoxy (PFA), polychlorotrifluoroethylene (PCTFE or PTFCE), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene or poly(ethylene-co-tetrafluoroethylene) (ETFE), tetrafluoroethylene perfluoromethylvinylether (MFA), more particularly PTFE. Preferably, said fluoropolymers are of the fibrillable type. The term "fibrillable" is understood to mean the types of fluoropolymers which are capable of fibrillating, i.e. which can form a network of fibers in the mixture with the premix, under extrusion conditions. Fluoropolymer types can be of different shapes and / or grades.

[0039] “Premix” means a preliminary composition previously prepared; in this case the premix comprises the mixture of powders of the solid sulfide electrolyte and the fluoropolymer.

[0040] The premix may also further include additional ingredients, such as active material, a conductive element, a co-binder, in particular depending on the nature and purpose of the formulation envisaged.

[0041] Thus, according to one embodiment, the preparation of the premix and / or the fibrillation may further comprise the addition of a co-binder.

[0042] The term "co-binder" means a material that provides the electrode with cohesion of the various components and mechanical strength on the current collector, and / or provides a certain flexibility to the electrode for its implementation in a cell. More particularly, the co-binder according to the invention ensures cohesion between the various constituents. The co-binder may be amorphous or semi-crystalline.

[0043] According to one embodiment, the co-binder is chosen from thermoplastic polyurethane (TPU), poly(vinylidene fluoride) (PVDF) or its copolymers, cellulose and its derivatives, poly(oxyethylene) (POE), standard or modified cellulose, poly(styrene-butadiene-styrene) (SBS), poly(styrene-ethylene-butadiene-styrene) (SEBS), thermoplastic elastomers (TPE), vulcanized thermoplastics (TPV), polyamides, thermoplastic copolyesters (TPC), polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS), butadiene-acrylonitrile copolymers also called “nitrile rubbers” (NBR), hydrogenated butadiene-acrylonitrile copolymers, also called “hydrogenated nitrile rubbers” (HNBR), elastomers, thermoplastics or ethylene-acrylate terpolymers.

[0044] More particularly, the co-binder is chosen from HNBR, POE, PVDF and its copolymers, cellulose and its derivatives.

[0045] The co-binder can be added at the premix preparation step and / or at the fibrillation step.

[0046] According to another embodiment, the preparation of the premix may further comprise the mixing of active material and optionally of electronically conductive material, with the mixture of the solid sulfide electrolyte, the binder and the optional co-binder.

[0047] The preparation of the premix can be carried out by simply mixing the constituents, typically in the form of powders, under agitation. It can in particular be carried out with a planetary type mixer.

[0048] According to one embodiment, the step of preparing the premix can advantageously be carried out at a temperature below 40°C.

[0049] The active electrode material can be chosen from electrochemically active materials. It depends in particular on the type of electrode (positive or negative), the nature of the solid sulfide electrolyte and / or the type of battery considered.

[0050] Fibrillation is a process of mixing under mechanical stress to fibrillate the fluoropolymer binder. This fibrillation can typically be carried out by extrusion with an extruder, or by mixing with an internal mixer.

[0051] Extrusion is a thermomechanical process in which the formulation is forced through a barrel under the action of pressure and heat.

[0052] The extrusion step can be adapted according to several parameters, such as mixing temperature, extruder screw profile type, extruder die type, rotation speed and / or screw length.

[0053] According to one embodiment, the fibrillation can be carried out with a single- or twin-screw type extruder, preferably a co-rotating twin-screw.

[0054] According to one embodiment, the screw profile used in the extruder is of the shear type in order to fibrillate the fluoropolymer in the extruder. The screw profile may contain one or more mixing zones. The number of mixing zones typically depends on the number of introduction zones. The position of the mixing zones in the extruder generally depends on the number of material introduction zones. After each material introduction zone, a mixing zone may be added.

[0055] Typically, the type of screw element used to shear the material can be adapted to the type of active ingredient in the premix. If the active ingredient is shear-sensitive, it is preferable to use low- or medium-shear elements. If the active ingredient is not very shear-sensitive, it is possible to use low-, medium-, or high-shear elements.

[0056] The screw rotation speed is generally the same throughout the screw. It is generally recommended to rotate it between 100 rpm and 1000 rpm, especially between 100 and 750 rpm. The screw rotation speed is generally adapted according to the desired material flow rate at the extruder outlet. The lower the screw rotation speed, the lower the output flow rates will be. Note that low rotation speeds result in longer residence times in the extruder. In such cases, if the material input flow rate is high, there may be a risk of clogging the extruder. In the case of a high screw rotation speed, the output flow rates may fluctuate if the incoming material flow rates are too low.

[0057] The fibrillation step can advantageously be carried out at a temperature between 40°C and the degradation temperature of the fluoropolymer, more particularly when a co-binder is present between the melting temperature of the co-binder and the melting temperature of the fluoropolymer under the extrusion conditions, it being understood that the degradation and / or melting temperatures of the fluoropolymer under the extrusion conditions can be reduced due to the mechanical stresses exerted. By way of illustration, for PTFE, the degradation temperature is approximately 350°C (under shear) and the melting temperature is approximately 330°C (this value can vary depending on the grade of PTFE), it being understood that due to the stresses exerted, the extrusion temperature is preferably less than or equal to 260°C.

[0058] In the case where the fibrillation is carried out by an internal mixer, the same conditions as for the extruder can be implemented.

[0059] The formulation obtained at the end of the fibrillation step is typically in the form of granules or agglomerated powder.

[0060] According to one embodiment, the method according to the invention comprises one or more subsequent steps. Thus, said method may further comprise one or more steps of shaping the formulation in the form of a film, and / or of depositing the film thus obtained.

[0061] Shaping may typically be accomplished by calendering using a heated roller calender, typically having a different roller speed, or an external roller mixer.

[0062] The film thus obtained can then be deposited either on a current collector to form an electrode or on a liner with a view to subsequently adhering to an SEL in the case of an electrode formulation, or in the case of an SEL formulation deposited on a liner to then be transferred to an electrode.

[0063] According to another object, the present invention also relates to a formulation capable of being obtained by the process according to the invention.

[0064] It can be an electrode formulation, positive or negative, or a solid electrolyte layer (SEL).

[0065] Thus, according to one embodiment, when it is a solid electrolyte layer formulation, said formulation generally comprises, in addition to the solid sulfide electrolyte and the binder, an optional co-binder. Typically, such a formulation may comprise, by way of illustration (by weight):

[0066] From 70 to 99.8% solid sulfide electrolyte;

[0067] - From 0.1 to 30% PTFE;

[0068] From 0.1 to 14.9% of co-binder. According to another object, the present invention also relates to a layer of solid sulfide electrolyte comprising said formulation.

[0069] According to an alternative embodiment, when the formulation is an electrode formulation, said formulation generally comprises, in addition to the solid sulfide electrolyte and the binder, an optional co-binder, active material and optionally electronically conductive material. Thus, typically, such a formulation may comprise, by way of illustration (by weight):

[0070] From 50 to 95% active ingredient;

[0071] From 4.9 to 49.9% solid sulfide electrolyte;

[0072] - From 0.1 to 15% PTFE;

[0073] From 0 to 14.9% co-binder;

[0074] From 0 to 10% electronic conductor.

[0075] Typically, the binder content can be adjusted to improve the homogeneity of the mixture and / or the mechanical strength, particularly in the absence of a co-binder.

[0076] The formulation can thus be a positive electrode formulation (catholyte). Alternatively, the formulation can also be a negative electrode formulation (anolyte), particularly when the negative electrode is silicon-based.

[0077] The active material of the positive electrode is not particularly limited. It can be selected from the following groups or their mixtures:

[0078] - nickel-manganese-cobalt (NMC) type compounds, in particular lamellar oxides with a high nickel content, i.e. typically those for which the molar ratio of nickel, relative to the total of the elements nickel, manganese and cobalt, is greater than or equal to 0.6, in particular greater than or equal to 0.8;

[0079] - lithium-iron-phosphate (LFP) type compounds;

[0080] - lithium vanadium fluorophosphate compounds (LVPF) in particular those of formula LixVPC F with 0.8 <x<1 ,2, ou l’un de ses dérivés de formule LixVi.yMyPC Fz où 0,8<x<1 ,2 ; 0<y<0,5 ; 0,8<z<1 ,2 et M est choisi dans le groupe consistant en Ti, Al, Y, Cr, Cu, Mg, Mn, Fe, Co, Ni, et Zr ;

[0081] - lithium-iron-metal-phosphate (LFMP) type compounds, notably of the formula Li x Fei- y MyPO4(LFMP) 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<1 ,2 ; 0<y<0,6 ; - les composés de type Lithium-métal-polymère (LMP), notamment de formule Li x Mni. y . Z M ' y M ” Z PC>4 (LMP), where M' and M” are different from each other and are selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo, with 0.8 <x<1 ,2 ; 0<y<0,6 ; 0,0<z<0,2 ;

[0082] - nickel-cobalt-aluminum (NCA) type compounds.

[0083] A conductive element can also be added for the preparation of positive electrode. It can be selected from electronically conductive materials, such as graphite, carbon black, acetylene black, soot, graphene, carbon fibers, carbon nanotubes or a mixture thereof.

[0084] According to one embodiment, the electrode formulations according to the invention may further comprise one or more additives chosen from lubricants such as oils or waxes or graphite.

[0085] In addition, the formulations according to the invention may also comprise a carbon additive. This additive is distributed in the electrode so as to form an electronic percolating network between the active material and the current collector.

[0086] When present, the carbon additive may be up to about 10% (by weight), including 1 to 6% (by weight) of the total formulation content.

[0087] According to another object, the present invention also aims at an electrode comprising the electrode formulation according to the invention shaped.

[0088] According to one embodiment, said electrode may consist of a conductive support used as a current collector which is coated with the formulation according to the invention in a shaped form.

[0089] The term "negative electrode" refers to the electrode functioning as an anode when the battery is discharging, and the electrode functioning as a cathode when the battery is charging. The anode is defined as the electrode where an electrochemical oxidation reaction (emission of electrons) takes place, while the cathode is the site of reduction. The term negative electrode also refers to the electrode from which electrons leave, and from which cations (Li+) are released during discharge. The term "positive electrode" refers to the electrode where electrons enter, and where cations (Li+) arrive during discharge.

[0090] A current collector is an element such as a pad, plate, sheet or other, made of conductive material, connected to the positive or negative electrode, and ensuring the conduction of the flow of electrons between the electrode and the terminals of the battery.

[0091] The current collector is preferably a two-dimensional conductive support such as a solid or perforated metal-based strip.

[0092] In the case of the positive electrode, the current collector is typically an aluminum strip, notably covered with a carbon coating.

[0093] According to another object, the present invention also relates to an electrochemical element comprising at least one electrode and / or layer of solid sulfide electrolyte comprising a formulation according to the invention.

[0094] According to another object, the present invention also relates to an electrochemical module comprising the stack of at least two elements according to the invention, each element being electrically connected with one or more other element(s). The term "module" therefore designates here the assembly of several electrochemical elements, said assemblies being able to be in series and / or parallel.

[0095] Another object of the invention is still a battery comprising one or more modules according to the invention.

[0096] The term “battery” or accumulator means the assembly of several modules according to the invention.

[0097] Figures

[0098] [Fig 1] Figure 1 schematically represents an all-solid electrochemical element with in enlargement: the structure of the formulation of the solid electrolyte layer (SEL) consisting of sulfide solid electrolyte particles (2) dispersed within a network of binder fibrils (3); and the structure of the formulation of the positive electrode layer consisting of sulfide solid electrolyte particles (2) and active material particles (1), dispersed within a network of binder fibrils (3). [Fig 2] Figure 2 schematically represents an all-solid electrochemical element according to another embodiment further comprising optional elements such as an electronically conductive material (5) and a co-binder (4), for illustrative purposes.Thus, the enlargements represent respectively: the structure of the formulation of the solid electrolyte layer (SEL) consisting of particles of sulfide solid electrolyte (2) and co-binder (4), dispersed within a network of binder fibrils (3); and the structure of the formulation of the positive electrode layer consisting of particles of sulfide solid electrolyte (2), conductive material (5), and particles of active material (1), dispersed within a network of binder fibrils (3).

[0099] For illustration purposes, Figures 1 and 2 have been shown with PTFE as the binder and carbon additive as the conductive material.

[0100] It is understood that the presence of electronic conductor in the cathode and co-binder in the SEL are not obligatory.

[0101] The void areas between the different components represent residual porosity. It should also be noted that the thicknesses of the different layers, namely the thickness of the negative electrode, the SEL or the positive electrode, are purely indicative.

[0102] Examples

[0103] Example 1: Production of a positive electrode

[0104] The active material, the binder, the solid sulfide electrolyte, and possibly the electronic conductor and co-binder are pre-mixed in a planetary mixer to distribute the different materials evenly. The introduction of the different materials into this mixer can be done either all at once or in several batches. In the latter case, the different materials can follow a specific order of introduction. Note that graphite, carbon black and graphene present a greater risk of reactivity with the solid electrolyte than other electronic conductors.

[0105] For illustration purposes, the following compositions were produced:

[0106] Positive electrode formulation:

[0107] NMC81 1 (75%), binder: PTFE (5%); argyrodite-type sulfide electrolyte (20%); electronic conductor carbon fibers (3%), PTFE (3%); argyrodite (20%) and NMC81 1 74% SEL formulation:

[0108] 97% solid electrolyte and 3% PTFE;

[0109] 94% solid electrolyte, 3% PTFE and 3% co-binder.

[0110] In a first configuration: the premix is ​​kept in this planetary mixer and is brought to high temperature (between 40°C and 150°C, preferably between 60 and 130°C) for the fibrillation of the PTFE. The texture of the recovered material can depend on the level of fibrillation of the PTFE but also on the formulation (presence or absence of co-binder and the particle size of the different components).

[0111] In a second alternative configuration: once the premix is ​​made, it can then be introduced into an extruder (preferably twin-screw) or an internal mixer in order to carry out the fibrillation of the binder (PTFE). This extruder is heated to a temperature between 40°C and 270°C. The temperature depends on the presence or absence of a co-binder and, if present, also on its chemical nature. In the absence of a co-binder in the premix, it can optionally be introduced into the extruder using a separate doser. The profile of the screws is chosen according to the desired level of fibrillation of the PTFE and according to the presence or absence of a co-binder in the formulation. The rotation speed of the screws is also adjusted according to these two criteria.

[0112] Note that this extruder as well as the planetary mixer are both used in an inert environment (nitrogen atmosphere) suitable for the use of a solid sulfide electrolyte exposed or not to thermo-mechanical stress. The material recovered from the extruder is then either in the form of agglomerated powder or in the form of granules.

[0113] Regardless of the chosen configuration, the material is then reworked or not before being introduced into a heated roller calender. This calender (composed of at least 2 rollers) has rollers rotating at the same or different speeds. One or more electrode films is / are then produced. These are either deposited directly onto a current collector or transfer material or recovered as self-supporting film(s).

[0114] Example 2: Production of a solid electrolyte layer The solid electrolyte type, the binder and any co-binder are pre-mixed using a planetary mixer in order to correctly disperse the different components.

[0115] In a first configuration: the pre-mix is ​​kept in this planetary mixer and is brought to high temperature (between 40°C and 150°C, preferably between 60 and 130°C) for the fibrillation of the PTFE. The texture of the recovered material depends on the level of fibrillation of the PTFE but also on the formulation (presence or absence of co-binder and the particle size of the different components).

[0116] In a second configuration: once the premix is ​​made, it is then introduced into an extruder (preferably twin-screw) or an internal mixer in order to carry out the fibrillation of the binder (PTFE). This extruder is heated to a temperature between 40°C and 270°C. The temperature depends on the presence or absence of a co-binder and, if present, also on its chemical nature. In the case of an absence of co-binder in the premix, it can optionally be introduced into the extruder using a separate doser. The profile of the screws is chosen according to the desired level of fibrillation of the PTFE and according to the presence or absence of a co-binder in the formulation. The rotation speed of the screws is also adjusted according to these two criteria.

[0117] Note that this extruder and the planetary mixer are both used in an inert environment (nitrogen atmosphere) suitable for the use of a solid sulfide electrolyte exposed or not to thermo-mechanical stress. The material recovered from the extruder is then either in the form of agglomerated powder or in the form of granules.

[0118] Whatever the configuration chosen, the material is then reworked or not before being introduced into a heated roller calender. This calender (composed of at least 2 rollers) has rollers rotating at the same or different speeds. One or more films of solid electrolyte layer is / are then produced. This (these) is / are either deposited directly on a positive electrode (itself being or not on a current collector) or on a negative electrode (itself being or not on a current collector) or on a transfer material (liner type) or recovered as a self-supporting film.

Claims

CLAIMS 1. Process for the solvent-free preparation of a formulation for an all-solid-type electrochemical element with a sulfide electrolyte, said process comprising: - The preparation of a premix comprising the mixture of o a solid sulfide electrolyte; o A fluoropolymer type binder. - Fibrillation of the premix obtained, said fibrillation being carried out by extrusion with an extruder or by mixing with an internal or planetary mixer; The premix preparation and fibrillation steps are carried out under an inert atmosphere.

2. A method according to claim 1 such that the preparation of the premix and / or fibrillation further comprises the addition of a co-binder to the mixture.

3. Method according to claim 1 or 2, such that the preparation of the premix further comprises the mixing of active material and optionally electronically conductive material, with the mixture of the electrolyte, the binder and the optional co-binder.

4. Method according to any one of the preceding claims such that said solid sulfide electrolyte is an electrolyte of the Li6PS5X type, with X = Cl, Br, I.

5. Method according to any one of the preceding claims, such that the step of preparing the premix is ​​carried out at a temperature below 40°C.

6. Method according to any one of the preceding claims such that the fluoropolymer binder is chosen from polytetrafluoroethylene (PTFE) and its copolymers, such as chlorofluoroethylene, perfluoroalkoxy (PFA), polychlorotrifluoroethylene (PCTFE or PTFCE), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene or poly(ethylene-co-tetrafluoroethylene) (ETFE), tetrafluoroethylene perfluoromethylvinylether (MFA).

7. Method according to any one of the preceding claims such that the fluoropolymer is PTFE.

8. Method according to claim 2 such that the co-binder is chosen from thermoplastic polyurethane (TPU), poly(vinylidene fluoride) (PVDF) or its copolymers, cellulose and its derivatives, poly(oxyethylene) (POE), standard or modified cellulose, poly(styrene-butadiene-styrene) (SBS), poly(styrene-ethylene-butadiene-styrene) (SEBS), thermoplastic elastomers (TPE), vulcanized thermoplastics (TPV), polyamides, thermoplastic copolyesters (TPC), polystyrene-b-poly(ethylene-butylene)-b-polystyrene (SEBS), butadiene-acrylonitrile copolymers also called “nitrile rubbers” (NBR), hydrogenated butadiene-acrylonitrile copolymers, also called “hydrogenated nitrile rubbers” (HNBR), elastomers, thermoplastics or ethylene-acrylate terpolymers.

9. Method according to any one of the preceding claims such that the fibrillation step is carried out at a temperature between 40°C and the degradation temperature of the fluoropolymer.

10. Method according to any one of the preceding claims further comprising the steps of forming into a film, and depositing the film thus obtained.

11. Formulation for an all-solid electrochemical element with a sulfide electrolyte capable of being obtained by the method according to any one of the preceding claims.

12. Formulation according to claim 11 as it is a sulfide solid electrolyte layer (SEL) formulation, a positive electrode (catholyte) formulation or a silicon-based negative electrode (anolyte) formulation.

13. Formulation according to claim 11 or 12 such that it is a catholyte formulation, and such that it comprises active material and optionally electronically conductive material, in addition to said solid sulfide electrolyte, the binder and the optional co-binder.

14. Formulation according to claim 13 such that it comprises (by weight): From 50 to 95% of active material; From 4.9 to 39.9% solid sulfide electrolyte; - From 0.1 to 15% PTFE; From 0 to 14.9% co-binder; From 0 to 10% electronic conductor.

15. Formulation according to claim 12 as it is a solid sulfide electrolyte formulation, and as it comprises (by weight): From 85 to 99.9% solid sulfide electrolyte; - From 0.1 to 15% PTFE; From 0 to 14.9% of co-binder.

16. Electrochemical element such that it comprises at least one electrode and / or the layer of solid sulfide electrolyte comprising the formulation according to any one of claims 1 to 15.

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