Binder composition for secondary batteries

Abstract

The present invention relates to a composition comprising amorphous (per)fluorinated polymer powders and to its use for the manufacture of components for secondary batteries.

Description

Binder composition for secondary batteriesCross reference to previous applications

[0001] This application claims priority to European application No. 24183852.3 filed on 21 June 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present invention relates to a composition comprising amorphous (per)fluorinated polymer powders and to its use for the manufacture of components for secondary batteries.Background

[0003] Lithium ion batteries with liquid electrolytes are currently dominating the market of rechargeable energy storage devices, despite some intrinsic limitations. Among them, severe safety concerns and intrinsic low energy densities for high power applications. Conventional Li-ion battery liquid electrolytes are indeed based on organic carbonates that undergo leakage, generate volatile gaseous species and are flammable.

[0004] Solid state batteries (SSBs) promise to be the next generation of energy storage devices as they provide higher energy density, longer cycle life, improved safety and lower costs. In a SSB the highly flammable liquid electrolyte is replaced by a solid electrolyte, removing virtually all risk of ignition and / or explosion. Despite these intrinsic theoretical advantages over conventional batteries, also easy-handling and scalable processing is needed for their successful commercialization.

[0005] Among solid electrolytes, composite electrolytes composed of solid ionic (Li+) conductor inorganic materials dispersed into a polymeric binder, offer the possibility to combine high ionic conductivity with good mechanical properties.

[0006] State of the art composite electrolytes are usually produced through a wet casting method. In this method, the inorganic material powder is dispersed into a solution of a binder in a solvent to form a slurry which is cast on a support and subsequently dried to remove the used solvent.

[0007] The use of polymeric binders in solid state batteries is also interesting at cathode side, where active materials, conductive agent and inorganic solid electrolytes (eg. sulfides) are kept together in a continuous matrix thanks to the binder itself.

[0008] Among processing routes, both for electrodes and solid electrolytes, tape casting is the one most widely adopted, due to both similarities with conventional battery components processing and to its intrinsic versatility, which allows it to finely tune thickness and other processing parameters. With this method slurries are prepared by dispersing inorganic conductor particles into a polymeric solution and casting the obtained dispersion on the desired layer.

[0009] The use of specific inorganic materials in composite electrolytes and in electrodes poses limitations in the choice of solvents as well as in that of binders: highly conductive sulfides, in particular, limit the range of available compatible solvents, which should not react with them, not reduce their ionic conductivity and not create by-products that could interfere with battery operation. Binders have to be also compatible with sulfides and soluble or dispersible in available solvents.

[0010] Some reports suggest the use of fluorinated binders for sulfide composites. However, the use of commercially adopted crystalline fluorinated binders is limited by solubility issues to few solvents compatible with inorganics.

[0011] As an example, US 2019 / 296393 (in the name of TOYOTA JIDOSHA KK) discloses the preparation of solid electrolyte layers for SSB containing a sulfide solid electrolyte, polyvinylidene fluoride (PVdF), ethyl cellulose (EC) and butyl butyrate as solvent.

[0012] On the contrary, amorphous fluorinated polymers (e.g. Tecnoflon® FKM) can be solubilized in several compatible solvents. The use of these polymers asbinders has however intrinsic drawbacks, which can limit their real application in solid state battery components and pave the path to the development and use of new and alternative products. In particular, amorphous fluorinated polymers are mainly produced in the form of slabs, which have to be cut in small pieces before the dissolution process takes place. This results in time losses and additional processing operational costs, and also problems in obtaining a fine polymeric dispersion in selected compatible solvent.

[0013] Some amorphous fluorinated polymers in powder form currently exist on the market, e.g. Tecnoflon® NM powder. Nevertheless, usual additives such as organic anti-sticking agents present in said powders are not stable at the voltages at which the batteries operate, creating by-products and negatively impacting battery operation.

[0014] In document US 2010 / 174011 (in the name of E.l. DU PONT DE NEMOURS AND CO.), in particular in sections

[0042] to

[0047] , mention is made of cryogenic grinding as technology for downsizing fluoroelastomer crumbs or pellets; also in this case, the addition of a dusting agent to prevent massing is taught as an essential requirement for obtaining a free-flowing compound. However, said dusting agent is not stable in the voltage range where the battery operates.

[0015] US 9,518,178 (in the name of Solvay Specialty Polymers Italy Spa) discloses the addition of thermoplastic vinylidene fluoride polymers in (per)fluoroelastomer compositions during cryogenic milling, to advantageously provide for micronized pellets possessing free-flowing behaviour, maintaining these advantageous flowing properties even after long storage at room temperature, and providing excellent mechanical properties in cured compounds deriving therefrom.

[0016] WO 2024 / 033092, WO 2024 / 033089 and WO 2024 / 033090 (all in the name of Solvay Specialty Polymers Italy Spa) disclose solid composite electrolytes comprising (a) at least one fluoroelastomer comprising VDF and of at least one other halogenated fluorolefin, and (b) at least one sulfide-based solid ionic conducting inorganic particle different from lithium salt.

[0017] WO 2023 / 285511 (in the name of Solvay Specialty Polymers Italy Spa) discloses a binder composition for use in the preparation of components for electrochemical devices, including SSBs, said composition comprising (a) micronized pellets of a (per)fluoroelastomer composition comprising at least one (per)fluoroelastomer and at least one thermoplastic semicrystalline vinylidene fluoride polymer having average particle size (D50) below 500 pm (as measured according to ISO 13320 with a Beckman Coulter LS 13 320) and (b) at least one non-aqueous solvent (S). The micronized pellets comprised the at least one thermoplastic vinylidene fluoride polymer in an amount of at least 2% and lower than 5% by weight relative to the total weight of the (per)fluoroelastomer and of the thermoplastic semicrystalline vinylidene fluoride polymer. Such micronized pellets were prepared by a process comprising preparing slabs of the (per)fluoroelastomer, cooling such slabs in liquid nitrogen below the glass temperature, grinding the slabs at a temperature from -20°C to -50°C in combination with the required amount of thermoplastic semi crystalline vinylidene fluoride polymer.Summary of the invention

[0018] The Applicant is aware that there is still the need for non conductive binders compatible with inorganic materials suitable for use in the manufacture of battery components such as electrodes and of solid electrolyte layers through efficient fabrication processes.

[0019] In particular, the Applicant is aware that cooling the amorphous polymers below their glass transition temperature requires a high energy consumption.

[0020] Also, the Applicant is well aware that a lower amount of the thermoplastic semi crystalline vinylidene fluoride polymer in the composition would provide advantages in terms of compatibility of the solvent to be used for providing SSBs comprising sulfides.

[0021] Facing the above mentioned challenges, the Applicant surprisingly and unexpectedly, developed a new composition suitable for the manufacture ofbinders for use in particular in SSBs, which can be prepared via an easy process without the need for expensive steps, such as the cryogenic treatment or the exposure at temperatures below 0°C.

[0022] Surprisingly, the Applicant found that a composition comprising a (per)fluoroelastomer and at least one thermoplastic vinylidene fluoride polymer [polymer (F)] having an average particle size (Dso) smaller than 40 pm, as measured by laser diffraction can be used for the manufacture of a binder for SSBs.Brief description of drawings

[0023] Figure 1 is a SEM picture obtained at magnification of 5.00 KX showing particles of polymer (F) adsorbed on the surface of (per)fluoroelastomer (A) as prepared according to Example 2 of the present invention.Disclosure of the invention

[0024] In the present application:- the numerical ranges includes the limits, unless otherwise specified;- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention;- where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed element components may be omitted from such list;- the expression “percent by weight” or “wt.%” is intended to indicate the content of a specific component in a mixture, calculated as the ratio between the weight of the specific component and the total weight of the mixture;- the expression “electrochemical cell” is intended to denote an electrochemical cell comprising a positive electrode, a negative electrode and an electrolyte, wherein a monolayer or multilayer separator is adhered to at least one surface of one of said electrodes. Non-limitative examples of electrochemical cells include batteries, in particular secondary batteries, and electric double layer capacitors;- the expression “secondary battery” is intended to indicate a rechargeable battery. Non-limitative examples of secondary batteries include alkaline or alkaline-earth secondary batteries;- the term “(per)fluoroelastomer” is intended to indicate a partially or fully fluorinated polymer serving as a base constituent for obtaining a true elastomer, said partially or fully fluorinated polymer comprising more than 10 wt.%, preferably more than 30 wt.%, of recurring units derived from at least one ethylenically unsaturated monomer comprising at least one fluorine atom (also referred to as (per)fluorinated monomer, or in other words partially or fully fluorinated monomer), optionally comprising recurring units derived from at least one ethylenically unsaturated monomer free from fluorine atoms (also referred to as hydrogenated monomer);- the expression “true elastomer” is intended to indicate an fluoropolymer resin defined by the ASTM, Special Technical Bulletin, No. 184 standard, as a material capable of being stretched at room temperature to twice their length and which, once released after being held under tension for 5 minutes, return to within 10% of their initial length in the same time;- the expression “fluorinated monomer” is intended to denote an ethylenically unsaturated monomer comprising at least one fluorine atom;- the expression “hydrogenated monomer” is intended to denote an ethylenically unsaturated monomer comprising at least one hydrogen atom and free from fluorine atoms;- the expression “electrode active material [material (AM)]” is intended to indicate a compound that is able to incorporate or insert into its structure and substantially release therefrom alkaline or alkaline-earth metal ions during thecharging phase and the discharging phase of an electrochemical device. Such material (AM) is preferably able to incorporate or insert and release lithium ions;- the expression “sulfide-based solid electrolyte” is intended to indicate an inorganic solid state material that conducts Li+ions but is substantially electronically insulating;- the expression “composite solid electrolyte film” is intended to indicate a composite film having lithium ionic conductivity, which may be in the form of a foldable and flexible film, and in some embodiments may have a freestanding shape at room temperature without a support.

[0025] In a first aspect, the present invention relates to a solid composition [composition (C1 )] comprising:- at least one (per)fluoroelastomer [(per)fluoroelastomer (A)] in the form of pellets having at least one dimension higher than 1 mm or solid particles having an average particle size (Dso) higher than 1 mm as measured by dry sieving, and- at least one thermoplastic vinylidene fluoride polymer [polymer (F)] having an average particle size (Dso) smaller than 40 pm, as measured by laser diffraction.

[0026] Composition (C1 ) is preferably in the form of granules, pellets or extrudates.

[0027] Preferably, (per)fluoroelastomer (A) is in the form of pellets.

[0028] As said above, such pellets of (per)fluoroelastomer (A) have at least one dimension, said dimension being the diameter and / or the length of the pellet, higher than 1 mm.

[0029] Preferably, such pellets have a length from about 1 .00 to about 15.00 mm, more preferably from about 1 .00 to about 10.00 mm, even more preferably from about 1 .00 to about 8.00 mm and still more preferably from about 1 .00 to about 6.00 mm.

[0030] Preferably, such pellets have a diameter from about 0.25 mm to about 8.00 mm, more preferably from about 1 .00 mm to about 6.50 mm.

[0031] Preferably, (per)fluoroelastomer (A) is in the form of solid particles.

[0032] The geometry of the solid particles of (per)fluoroelastomer (A) is not limited. Such solid particles can be spherical, cylindrical or asymmetrically shaped.

[0033] Preferably, such solid particles of (per)fluoroelastomer (A) have an average particle size (Dso) of at least 1.1 mm, more preferably 1 .2 mm and even more preferably 1 .5 mm, as measured by dry sieving.

[0034] Preferably, (per)fluoroelastomer (A) is in the form of solid particles having a Dso up to 15.0 mm, more preferably up to 10.0 mm and even more preferably 8.0 mm as measured by dry sieving. More preferably, the solid particles of (per)fluoroelastomer (A) have a D50 up to 5.0 mm, more preferably 4.0 mm and even more preferably 3.5 mm as measured by dry sieving.

[0035] As disclosed in more detail in the examples, the method for measuring the D50 of the solid particles of the (per)fluoroelastomer (A) encompasses dry sieving of the particles using 9 sieves with the following decreasing mesh size: 4750 - 4000 - 3360 - 2800 - 2380 - 2000 - 1400 - 1000 - 710 pm.

[0036] Preferably, said polymer (F) has an average particle size (D50) lower than 40 pm, more preferably up to 39 pm, even more preferably up to 35 pm, as measured by laser diffraction.

[0037] Preferably, said polymer (F) as a D50 from 0.10 pm, more preferably from 0.50 pm and even more preferably from 1 .00 pm, as measured by laser diffraction.

[0038] Advantageously, said polymer (F) has a D50 in the range from 0.75 to 35.00 pm, as measured by laser diffraction.

[0039] The calculation of the average particle size for polymer (F) can be made according to the methods known in the art, such as for example according to ISO 13320.

[0040] Preferably, said polymer (F) is in an amount lower than 4 wt.%, such as up to3.99 wt.%, more preferably up to 2.99 wt.% and even more preferably up to1 .99 wt.% and still more preferably up to 1 .95 wt.% based on the total weight of (per)fluoroelastomer (A) and polymer (F).

[0041] Preferably, polymer (F) is in an amount of at least 0.005 wt.%, more preferably at least 0.075 wt.% and even more preferably of at least 0.095 wt.% based on the total weight of (per)fluoroelastomer (A) and polymer (F).

[0042] Preferably, said polymer (F) is in an amount from 0.080 to 1 .98 wt.%, more preferably from 0.085 to 1 .92 wt.% and even more preferably from 0.090 to 1 .90 wt.% and still more preferably from 0.090 to 1 .80 or 1 .75 wt.% based on the total weight of (per)fluoroelastomer (A) and polymer (F).

[0043] Preferably, said polymer (F) is in the form of powder or agglomerate / aggregate. Advantageously, said polymer (F) is in the form of powder.

[0044] Preferably, (per)fluoroelastomer (A) comprises at least one (per)fluorinated monomer.

[0045] Non limitative examples of suitable (per)fluorinated monomers are selected in the group comprising:- C2-C8 fluoro- and / or perfluoroolefins, such as tetrafluoroethylene (TFE), tetrafluoropropylene (TFP), hexafluoropropene (HFP), pentafluoropropylene, and hexafluoroisobutylene;- C2-C8 hydrogenated monofluoroolefins, such as vinyl fluoride; 1 ,2- difluoroethylene, vinylidene fluoride (VDF) and trifluoroethylene (TrFE);- (per)fluoroalkylethylenes complying with formula CH2=CH-Rro, in which Rro is a Ci-Ce (per)fluoroalkyl or a Ci-Ce (per)fluorooxyalkyl having one or more ether groups;- chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins, like chlorotrifluoroethylene (CTFE);- fluoroalkylvinylethers complying with formula CF2=CFORfi in which Rn is a Ci-Ce fluoro- or perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7 ;- hydrofluoroalkylvinylethers complying with formula CH2=CFORfi in which Rn is a Ci-Ce fluoro- or perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7 ;- fluoro-oxyalkylvinylethers complying with formula CF2=CFOXo, in which Xo is a C1-C12 oxyalkyl, or a C1-C12 (per)fluorooxyalkyl having one or more ether groups, like perfluoro-2-propoxy-propyl;- fluoroalkyl-methoxy-vinylethers complying with formula CF2=CFOCF2ORf2 in which Rt2 is a Ci-Ce fluoro- or perfluoroalkyl, e.g. -CF3, -C2F5, -C3F7 or a Ci- Ce (per)fluorooxyalkyl having one or more ether groups, like -C2F5-O-CF3;- functional fluoro-alkylvinylethers complying with formula CF2=CFOYo, in which Yo is a C1-C12 alkyl or (per)fluoroalkyl, or a C1-C12 oxyalkyl or a C1-C12 (per)fluorooxyalkyl, said Yo group comprising a carboxylic or sulfonic acid group, in its acid, acid halide or salt form;- fluorodioxoles, of formula :wherein each of Rf3, Rf4, Rfs, Rf6, equal or different each other, is independently a fluorine atom, a Ci-Ce fluoro- or per(halo)fluoroalkyl, optionally comprising one or more oxygen atom, e.g. -CF3, -C2F5, -C3F7, -OCF3, -OCF2CF2OCF3.

[0046] Examples of hydrogenated monomers are notably hydrogenated alphaolefins, including ethylene, propylene, 1 -butene, diene monomers, styrene monomers, alpha-olefins being typically used.

[0047] (Per)fluoroelastomers (A) are amorphous products or products having very low degree of crystallinity (heat of fusion of less than 4 J / g, preferably less than 3 J / g, when measured according to ASTM D 3418) and a glass transition temperature (Tg) below room temperature. In most cases, the fluoroelastomer (A) has advantageously a Tgbelow 10°C, preferably below 5°C, more preferably below 0°C.

[0048] The (per)fluoroelastomer (A) is preferably a fluoroelastomer.

[0049] In a preferred embodiment, the fluoroelastomer (A) is a VDF-based copolymer, in which VDF is copolymerized with at least one comonomer selected from the group consisting of:(a) C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), hexafluoroisobutylene;(b) hydrogen-containing C2-C8 olefins, such as vinyl fluoride (VF), trifluoroethylene (TrFE), perfluoroalkyl ethylenes of formula CH2 = CH-Rf, wherein Rf is a Ci-Ce perfluoroalkyl group;(c) C2-C8 chloro and / or bromo and / or iodo-fluoroolefins such as chlorotrifluoroethylene (CTFE);(d) (per)fluoroalkylvinylethers (PAVE) of formula CF2 = CFORf, wherein Rf is a Ci-Ce (per)fluoroalkyl group, e.g. CF3, C2F5, C3F7;(e) (per)fluoro-oxy-alkylvinylethers of formula CF2 = CFOX, wherein X is a Ci- 012 ((per)fluoro)-oxyalkyl comprising catenary oxygen atoms, e.g. the perfluoro-2-propoxypropyl group;(f) (per)fluorodioxoles having formula :wherein Rf3, Rf4, Rfs, Rf6, equal or different from each other, are independently selected among fluorine atoms and Ci-Ce (per)fluoroalkyl groups, optionally comprising one or more than one oxygen atom, such as notably -CF3, -C2F5, -C3F7, -OCF3, -OCF2CF2OCF3; preferably, perfluorodioxoles;(g) (per)fluoro-methoxy-vinylethers (MOVE, hereinafter) having formula: CFX2 = CX2OCF2OR"f wherein R"f is selected among Ci-Ce (per)fluoroalkyls , linear or branched; Cs-Ce cyclic (per)fluoroalkyls; and C2-C6 (per)fluorooxyalkyls, linear or branched, comprising from 1 to 3 catenary oxygen atoms, and X2 = F, H; preferably X2is F and R"fis -CF2CF3 (M0VE1 ); -CF2CF2OCF3 (M0VE2); or - CF3 (M0VE3);(h) C2-C8 non-fluorinated olefins (Ol), for example ethylene and propylene.

[0050] Optionally, (per)fluoroelastomers (A) of the present invention also comprises recurring units derived from a bis-olefin [bis-olefin (OF)] having general formula :wherein Ri, R2, R3, R4, Rs and Re, equal or different from each other, are H or C1-C5 alkyl; Z is a linear or branched C1-C18 alkylene or cycloalkylene radical, optionally containing oxygen atoms, preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene radical, e.g. as described in EP 661304 A (AUSIMONT SPA) 7 / 5 / 1995 .

[0051] The bis-olefin (OF) is preferably selected from the group consisting of those complying with formulae (OF-1 ), (OF-2) and (OF-3) : (OF-1 )wherein j is an integer between 2 and 10, preferably between 4 and 8, and R1 , R2, R3, R4, equal or different from each other, are H, F or C1-5 alkyl or (per)fluoroalkyl group;(OF-2)wherein each of A, equal or different from each other and at each occurrence, is independently selected from F, Cl, and H; each of B, equal or different from each other and at each occurrence, is independently selected from F, Cl, H and ORB, wherein RB is a branched or straight chain alkyl radical which can be partially, substantially or completely fluorinated orchlorinated; E is a divalent group having 2 to 10 carbon atom, optionally fluorinated, which may be inserted with ether linkages; preferably E is a - (CF2)m- group, with m being an integer from 3 to 5; a preferred bis-olefin of (OF-2) type is F2C=CF-O-(CF2)5-O-CF=CF2.(OF-3)wherein E, A and B have the same meaning as above defined; R5, R6, R7, equal or different from each other, are H, F or C1-5 alkyl or (per)fluoroalkyl group.

[0052] Among specific VDF-based copolymers of fluoroelastomers (A) suitable for the purpose of the invention, mention can be made of the following copolymers with monomer content expressed in mol %:(i) vinylidene fluoride (VDF) 35-85 %, hexafluoropropene (HFP) 10-45 %, tetrafluoroethylene (TFE) 0-30 %, perfluoroalkyl vinyl ethers (PAVE) 0-15 %, bis-olefin (OF) 0-5 %;(ii) vinylidene fluoride (VDF) 50-80 %, perfluoroalkyl vinyl ethers (PAVE) 5- 50 %, tetrafluoroethylene (TFE) 0-20 %, bis-olefin (OF) 0-5 %;(iii) vinylidene fluoride (VDF) 20-30 %, C2-C8 non-fluorinated olefins (Ol) I Q- 30 %, hexafluoropropene (HFP) and / or perfluoroalkyl vinyl ethers (PAVE) 18- 27 %, tetrafluoroethylene (TFE) 10-30 %, bis-olefin (OF) 0-5 %;(iv) vinylidene fluoride (VDF) 35-85 %, fluorovinyl ethers (MOVE) 5-40 %, perfluoroalkyl vinyl ethers (PAVE) 0-30 %, tetrafluoroethylene (TFE) 0-40 %, hexafluoropropene (HFP) 0-30 %, bis-olefin (OF) 0-5 %;(v) vinylidene fluoride (VDF) 20-85 %, at least one C2-C8 chloro and / or bromo and / or iodo fluoroolefin selected from the group consisting of 1 , 1 - chlorofluoroethylene (CFE), chlorodifluoroethylene (CDFE), bromotri- fluoroethylene, chlorotrifluoroethylene (CTFE), 1 ,2-dichloro-1 ,2-difluoro- ethylene, iodotrifluoroethylene, and combinations thereof 15-80 %;(vi) vinylidene fluoride (VDF) 20-85 %, at least one C2-C8 chloro and / or bromo and / or iodo fluoroolefin selected from the group consisting of 1 ,1 -chlorofluoroethylene (CFE), chlorodifluoroethylene (CDFE), bromotrifluoroethylene, chlorotrifluoroethylene (CTFE), 1 ,2-dichloro-1 ,2-difluoro- ethylene, iodotrifluoroethylene, and combinations thereof 15-80 %, and at least one other comonomer selected from (a) to (f) above 1-30 %.

[0053] The (per)fluoroelastomers (A) can be prepared by any known method, such as emulsion or micro-emulsion polymerization, suspension or microsuspension polymerization, bulk polymerization and solution polymerization.

[0054] Advantageously, polymer (F) is semicrystalline, i.e. it has an at least partially crystalline structure. Such semicrystalline polymer (F) generally has a heat of fusion, measured according to ASTM standard D3418, of at least 5 J / g, preferably of at least 15 J / g and more preferably of at least 25 J / g.

[0055] Polymer (F) used in the present invention is advantageously chosen from vinylidene fluoride (VDF) homopolymers and copolymers of VDF with one or more fluorinated monomer and / or, hydrogenated monomer.

[0056] For example, said polymer (F) comprises recurring units derived VDF and recurring units derived from at least one hydrogenated monomer comprising at least one carboxylic acid or a derivative thereof end group [monomer (MA)] and / or recurring units derived from at least one fluorinated monomer different from VDF.

[0057] Non-limiting examples of said monomer (MA) are, notably, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxyethylacrylate, hydroxypropylmethacrylate, hydroxypropylacrylate, hydroxyethylhexyl methacrylate, hydroxyethylhexylacrylate, and mixtures thereof.

[0058] The method for the manufacture of composition (C1 ) according to the present invention is not limited.

[0059] For example, composition (C1 ) according to the present invention can manufactured via a process comprising the following steps:(l-a) providing at least one (per)fluoroelastomer (A) in the form of at least one solid slab and(I l-a) reducing said at least one solid slab into solid particles having an average particle size (Dso) higher than 1 .00 mm as measured by dry sieving using 9 sieves, or(l-b) providing at least one (per)fluoroelastomer (A) in the form of solid particles having an average particle size (Dso) higher than 1 .00 mm as measured by dry sieving using 9 sieves;(III) contacting the solid particles of (per)fluoroelastomer (A) obtained in step (I l-a) or (l-b) and polymer (F);(IV) mixing said solid particles of (per)fluoroelastomer (A) and said polymer (F), thus obtaining composition (C1 ).

[0060] The solid slab of (per)fluoroelastomer (A) as used in step (l-a) can be manufactured, for example, by extrusion and / or using an open roller mill.

[0061] The method for reducing the at least one solid slab in step (ll-a) is not limited and can be performed in any device designed to break a solid material into smaller pieces. Preferably, such a device is equipped with a shaft and at least one rotating blade. Also, the geometry of the particles thus obtained is not limited. Such particles can be spherical, cylindrical or being asymmetrically shaped.

[0062] Preferably, step (ll-a) is performed by grinding or cutting or milling. More preferably, step (ll-a) is performed using a cutting mill.

[0063] In another preferred embodiment, step (l-a) is performed by extrusion. For example, according to this embodiment (per)fluoroelastomer (A) is kneaded in an extruder at elevated temperature, passed through a die to form strands of regular shape. Then, under step (ll-a), such strands are chopped into pellets of desired length using a cutting device.

[0064] Advantageously, when the method of the present invention comprises steps (l-a) and (ll-a), such step (ll-a) is performed at a temperature around room temperature, such as from 15 to 25°C.

[0065] Indeed, the Applicant surprisingly found that it is not necessary to perform step (ll-a) at a temperature below the glass transition temperature of(per)fluoroelastomer (A), thus providing for a process that is more efficient and less expensive in terms of energy consumption.

[0066] Preferably, under step (l-b), (per)fluoroelastomer (A) is provided in the form of aggregated particles obtained by spray drying or controlled coagulation or the like.

[0067] Preferably, polymer (F) is obtained by emulsion polymerization. Emulsion polymerization is advantageously performed according to methods known in the art.

[0068] Preferably, step (III) is performed by blending the solid particles of (per)fluoroelastomer (A) and the polymer (F).

[0069] Under step (III), polymer (F) is added to (per)fluoroelastomer (A) or (per)fluoroelastomer (A) is added to polymer (F).

[0070] The method for mixing under step (IV) is not limited. Preferably, step (IV) is performed with a high shear mixer or blender.

[0071] In another aspect, the present invention relates to a binder composition [composition (CB)] comprising:- composition (C1 ) as defined above, and- at least on non-aqueous solvent [solvent (S)] selected from the group consisting of nitrile-containing solvents, ethers, esters, thiols, thioethers, ketones, tertiary amines and cyclic carbonate esters.

[0072] Preferably, said solvent (S) is substantially free of water. More preferably, solvent (S) contains water in an amount up to 100 ppm, more preferably up to 80 ppm, as measured by known methods, such as Karl-Fisher titration.

[0073] The choice of solvent (S) is not particularly limited, as long as it is able to dissolve (per)fluoroelastomer (A).

[0074] In addition, when composition (CB) is used to prepare a composite solid electrolyte film, such solvent (S) must be compatible with the sulfide-based solid electrolyte, in other words, solvent (S) should have no negative impact on the ionic conductivity of the solid electrolyte.

[0075] Suitable nitrile-containing solvents have the general formula R-CN, where R represents an alkyl group. Non-limiting examples of nitrile-containing solvents are acetonitrile, butyronitrile, valeronitrile, isobutylnitrile and the like.

[0076] Suitable ethers have the general formula R1-O-R2, where each of R1 and R2 represents independently an alkyl group. Included in the ether solvents are cyclic ethers based on 3, 5 or 6-membered rings. The cyclic ethers can be substituted with alkyl groups, can have unsaturations and can have additional functional elements such as nitrogen or oxygen atoms inside the ring. Nonlimiting examples of (cyclic) ether solvents are diethylether, 1 ,2- dimethoxyether, cyclopentyl methyl ether, dibutyl ether, anisole, tetrahydrofuran, methyl tetrahydrofuran, tetrahydropyran and the like.

[0077] Suitable esters have the general formula of R3-COOR4, where each of R3 and R4 represents independently an alkyl group. Non-limiting examples of ester solvents are butyl acetate, butyl butyrate, ethyl benzoate and the like.

[0078] Suitable ketones have the general formula of RsReCO, where each of Rs and Re represents independently an alkyl group. Non-limiting examples of ketone solvents are methyl ethyl ketone, methyl isobutyl ketone, di-isobutyl ketone, acetophenone, benzophenone and the like.

[0079] Suitably, thiols have formula R?=S-H and thioethers have general formula of Rs-S-Rg, where each of R7, Rs and R9 is independently an alkyl group. Included in the thioether solvents are cyclic thioethers based on 3, 5 or 6 membered rings. The cyclic thioethers can be substituted with alkyl groups, can have unsaturations and can have additional functional elements such as nitrogen or oxygen atoms inside the ring. Non-limiting examples of thiol solvents are ethanethiol, tert-dodecyl mercaptan, thiophenol, t-butyl mercaptan, octanethiol, dimethylsulfide, ethylmethylsulfide, methyl benzylsulfide and the like.

[0080] Suitable tertiary amines have the general formula of R10R11 R12N, where each of R10, R11 and R12 represents independently an alkyl group. The N atom of the tertiary amine can be buried inside a 3, 5 or 6 membered ring. Nonlimiting examples of tertiary amine solvents are triethylamine,dimethylbutylamine, tributylamine, cyclohexyldimethylamine, N-ethyl- piperidine and the like.

[0081] In the present invention, the alkyl groups of Ri to R12 respectively refer to “alkyl groups” including saturated hydrocarbons having one or more carbon atoms, including straight-chain alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclic alkyl groups (or "cycloalkyl" or "alicyclic" or "carbocyclic" groups), such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl, branched-chain alkyl groups, such as isopropyl, tert-butyl, sec-butyl, and isobutyl, and alkylsubstituted alkyl groups, such as alkyl-substituted cycloalkyl groups and cycloalkyl-substituted alkyl groups as defined above. Additionally, the alkyl groups may include functional groups such as 1 or more unsaturations, ethers, carbonyl, carboxyl, hydroxyl, thio, thiol, thioxy, sulfo, nitrile, nitro, nitroso, azo, amide, imide, amino, imino or halogen.

[0082] Composition (CB) may include additional co-solvents, such as cyclic, acyclic or aromatic hydrocarbons. Suitably, the co-solvent can be selected from the group consisting of heptane, toluene, xylene, anisole and mesitylene.

[0083] Composition (CB) can be prepared by dissolving composition (C1 ) in solvent (S).

[0084] Preferably, composition (CB) is prepared at a temperature between 10 °C and 100 °C, preferably at a temperature of about 20 to 80 °C.

[0085] Preferably, composition (CB) is prepared under stirring.

[0086] Composition (CB) according to the present invention is suitable for the manufacture of components for electrochemical devices, more preferably for the preparation of SSBs.

[0087] Composition (CB) according to the present invention can be advantageously used to manufacture an electrode-forming composition [composition (CE)], wherein composition (CB) works as the binder.

[0088] The proper amount of solvent (S) can be selected based on the boiling point of the at least one solvent (S) to achieve dissolution of composition (C1 ) andsuitable evaporation of the solvent (S), when composition (CE) is used in the process for manufacturing an electrode or a solid electrolyte film.

[0089] In one embodiment, composition (CB) is a solution of composition (C1 ) in solvent (S), wherein composition (C1 ) is present in composition (CB) in an amount comprised between 3 and 70 wt.%, more preferably between 5 and 20 wt.%, even more preferably between 5 and 15 wt.%, based on the total weight of composition (CB).

[0090] Thus, in still another aspect, the present invention relates to an electrodeforming composition [composition (CE)] comprising:- at least one electrode active material [material (AM)],- composition (CB) as defined above; and- optionally, at least one conductive agent.

[0091] The nature of the material (AM) in composition (CE) depends on the intended use of such composition. In particular, if composition (CE) is used for the manufacture of a positive electrode [electrode (AMp)] or of a negative electrode [electrode (AMn)].

[0092] In the case of forming a positive electrode (AMp) for a Lithium-ion secondary battery, the electrode active material (AM) may comprise a composite metal chalcogenide of formula LiMQ2, wherein M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr and V and Q is a chalcogen such as O or S. Preferred examples thereof may include:- LiCoO2(LCO),- LiNiO2,- LiNixCoi-xO2(0 < x < 1 ),- spinel-structured LiMn2O4,- Lithium nickel manganese cobalt oxide of formula LiNixMnyCozO2(NMC), in particular those wherein with x + y + z that is near 1 such as LiNio.333Mno.333Co o.33302(NMC111 ), LiNio.6Mno.2Coo.202(NMC622) and LiNio.8Mno.iCoo.i02(NMC811 ), and- lithium nickel cobalt aluminum oxides (NCA) of general formula LiNixCoyAlzO2with x + y + z = 1 .

[0093] As an alternative, still in the case of forming a positive electrode (AMp) for a Lithium-ion secondary battery, the electrode active material (AM) may comprise a lithiated or partially lithiated transition metal oxyanion-based electro-active material of formula MiM2(JO4)fEi-f, wherein Mi is lithium, which may be partially substituted by another alkali metal representing less than 20% of the Mi metals, M2 is a transition metal at the oxidation level of +2 selected from Fe, Mn, Ni or mixtures thereof, which may be partially substituted by one or more additional metals at oxidation levels between +1 and +5 and representing less than 35% of the M2 metals, including 0, JO4 is any oxyanion wherein J is either P, S, V, Si, Nb, Mo or a combination thereof, E is a fluoride, hydroxide or chloride anion, f is the molar fraction of the JO4 oxyanion, generally comprised between 0.75 and 1.

[0094] The MiM2(JO4)fEi-f electro-active material as defined above is preferably phosphate-based and may have an ordered or modified olivine structure.

[0095] More preferably, the electrode active material (AM) in the case of forming a positive electrode (AMp) has formula Li3-xM’yM”2-y(JO4)3 wherein 0<x<3, 0<y<2, M’ and M” are the same or different metals, at least one of which being a transition metal, JO4 is preferably PCM which may be partially substituted with another oxyanion, wherein J is either S, V, Si, Nb, Mo or a combination thereof. Still more preferably, the electrode active material (AM) is a phosphate-based electro-active material of formula Li(FexMm-x)PO4 wherein 0<x<1 , wherein x is preferably 1 (that is to say, lithium iron phosphate of formula LiFePCk).

[0096] In the case of forming a negative electrode (AMn) for a Lithium-ion secondary battery, the electrode active material (AM) may preferably comprise a carbonbased material and / or a silicon-based material.

[0097] In some embodiments, the carbon-based material may be, for example, graphite, such as natural or artificial graphite, graphene, or carbon black.

[0098] These materials may be used alone or as a mixture of two or more thereof.

[0099] The carbon-based material is preferably graphite.

[0100] The silicon-based compound may be one or more selected from the group consisting of chlorosilane, alkoxysilane, aminosilane, fluoroalkylsilane, silicon, silicon chloride, silicon carbide, silicon sulfide and silicon oxide. More particularly, the silicon-based compound may be silicon, silicon oxide, silicon sulfide or silicon carbide. The silicon-based compound can be used as such, or in combination with other materials such as in the case of silicon / carbon composite materials. The morphology of the silicon-based can be any of nanosized, micron sized powder, nanowire or nanotube or the like.

[0101] When present in electrode active material (AM), the at least one silicon- based compound is comprised in the electrode active material (AM) in an amount ranging from 1 to 100 % by weight with respect to the total weight of the electrode active material (AM).

[0102] An optional conductive agent may be added in order to improve the conductivity of a resulting electrode.

[0103] Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder multiwall or single wall carbon nanotubes, graphene, vapor grown carbon (nano)fibers (VGCF), or fiber, or fine powder or fibers of metals such as nickel or aluminum, silver. The optional conductive agent is preferably VGCF or carbon black. Carbon black is available, for example, under the brand names, Super P® or Ketjenblack®.

[0104] When present, the conductive agent is different from the carbon-based material described above.

[0105] Composition (CE) is also particularly suitable for manufacturing electrodes for solid state batteries, which comprise at least one sulfide-based solid electrolyte.

[0106] Thus, a further embodiment of the present invention relates to an electrodeforming composition [composition (CE-S)] comprising:- at least one material (AM) as defined above,- composition (CB) as defined above,- optionally, at least one conductive agent, and- at least one sulfide-based solid electrolyte.

[0107] Said sulfide-based solid electrolyte comprises, preferably consists of, sulfide- based solid ionic conducting inorganic particles.

[0108] The sulfide-based solid ionic conducting inorganic particle(s) is(are) not limited, as long as it is a solid electrolyte material containing sulfur atom(s) in the molecular structure or in the composition.

[0109] The sulfide-based solid ionic conducting inorganic particle preferably contains Li, X (with X being P, Si, Sn, Ge, Al, As, or B) and S, to increase Li-ion conductivity.[001 10] The sulfide-based solid electrolyte according to the present invention is more preferably selected from the group consisting of:- lithium tin phosphorus sulfide (“LSPS”) materials, such as Li SnP2Si2;- lithium phosphorus sulfide (“LPS”) materials, such as glasses, crystalline or glass-ceramic of those of formula (Li2S)x-(P2Ss)y, wherein x+y=1 and 0<x<1 , LiyPsSu , LiyPSe, Li4P2Se, Li9.6P3Si2 and LisPS4;- doped LPS, such as Li2CuPS4, Li Lii+2xZm-xPS4, wherein 0<x<1 , Li3.33Mgo.33P2S6, and Li4-3xScxP2Se, wherein 0<x<1 ;- lithium phosphorus sulfide oxygen (“LPSO”) materials of formula LixPySzO, where 0.33<x<0.67, 0.07<y<0.2, 0.4<z<0.55, 0<w<0.15;- lithium phosphorus sulfide materials including X (“LXPS”), wherein X is Si, Ge, Sn, As, Al, such as Li GeP2Si2 and LiioSiP2Si2;- lithium phosphorus sulfide oxygen including X (“LXPSO”), wherein X is Si, Ge, Sn, As, Al;- lithium silicon sulfide (“LSS”) materials;- lithium boron sulfide materials, such as LisBSs and Li2S- B2S3-LH;- lithium tin sulfide materials and lithium arsenide materials, such as Lio.8Sno.8S2, Li4SnS4, Li3.833Sno.833Aso.i66S4, LisAsS4-Li4SnS4, Ge-substituted LisAsS4; and- Argyrodite-type sulfide materials of general formula Liy-xPSe-xXx wherein:- Y represents at least one halogen element selected in the group of Cl, Br and I or a combination thereof; and x represents a positive number from 0.8to 2.0, such as the compounds being possibly deficient in sulfur, lithium or halogen, for instance Lie-xPSs-xCh+x with 0<x<0.5, or doped with a heteroatom.

[0111] Particularly preferred sulfide solid electrolytes are LPS materials, LSPS materials and Argyrodite-type sulfide materials.

[0112] A further object of the present invention is a process for manufacturing an electrode for secondary battery, such process comprising the steps of:(A) providing composition (CE) or composition (CE-S) as defined above,(B) providing a metal substrate having at least one surface,(C) applying said composition (CE) or composition (CE-S) provided in step(A) onto said at least one surface of the metal substrate provided in step (B), thereby providing for an assembly comprising a metal substrate at least partially coated with said composition (CE) or composition (CE-S) onto the at least one surface, and(D) drying the assembly as provided in step (C).

[0113] According to another object, the present invention provides for an electrode for a secondary battery, said electrode being obtainable by the process comprising at least steps (A) to (D) as defined above.

[0114] Preferably, when composition (CE-S) is used, the method comprises an additional step of compacting and optionally densification / sintering.

[0115] According to another embodiment, composition (CB) according to the present invention is suitable for preparing a composite solid electrolyte film.

[0116] Thus, a further object of the present invention relates to a composition [composition (C-F)] comprising:- at least one sulfide-based solid electrolyte, and- composition (CB) as defined above.

[0117] The method for manufacturing composition (C-F) is not limited.

[0118] For example, composition (C-F) can be prepared by a process comprising mixing composition (CB) as defined above with the sulfide-based solid electrolyte. Such mixing can be performed according to any method known in the art.

[0119] Preferably, composition (C-F) is manufactured via a process comprising- contacting such composition (CB) as defined above and said sulfide-based solid electrolyte, thus providing a mixture and- mixing such a mixture.

[0120] The amount of composition (CB) in composition (C-F) is such to provide a composite solid electrolyte film comprising composition (C1 ) in an amount preferably from 2 to 30 wt.%, more preferably from 2 to 20 wt.%, even more preferably from 2 to 15 wt.% based on the total weight of composition (C1 ) and the sulfide-based solid electrolyte.

[0121] If the amount of the composition (C1 ) is less than 2 wt.%, then the cohesion of the sulfide-based solid electrolyte in the composite solid electrolyte film will be not sufficient. On the other hand, if the amount of composition (C1 ) exceeds 30 wt.%, the ionic conductivity of the composite solid electrolyte film might be negatively affected.

[0122] Another object of the present invention relates to a process for manufacturing a composite solid electrolyte film for solid state batteries, said process comprising the steps of:(I) providing composition (C-F) as defined above,(II) processing composition (C-F) to form a wet film of a solid composite electrolyte, and(III) drying said wet film.

[0123] Preferably, step (II) is performed by applying composition (C-F) onto at least one foil of inert flexible support or directly onto the surface of at least one electrode.

[0124] Such step of applying is preferably performed via casting, spray coating, rotary spray coating, roll coating, doctor blading, slot die coating, gravure coating, inkjet printing, spin coating, screen printing, brush, squeegee, foam applicator, curtain coating, vacuum coating. Casting is particularly preferred.

[0125] The wet film thus obtained typically has a thickness between 10 pm and 400 pm, preferably between 40 pm and 400 pm.

[0126] Preferably, step (III) of the process of the invention can be performed at a temperature that can be selected based on the boiling point and vapor pressure of the solvent (S). For example, the wet film is preferably dried at a temperature preferably between 10°C and 250°C.

[0127] An additional drying step [step (lll-b)] in an oven, optionally under vacuum, and at a temperature preferably between 20°C and 150°C, preferably between 30°C and 120°C can be suitably carried out after step (III) to achieve complete solvent removal.

[0128] The duration and temperature of step (III) can be properly selected depending on the boiling point of the at least one solvent (S).

[0129] The dry film obtained in step (III), or after the additional drying step (lll-b), typically has a thickness between 10 pm and 150 pm, preferable between 10 pm and 100 pm and more preferable between 10 pm and 50 pm.

[0130] The process of the invention for preparing a composite solid electrolyte film may further include, after step (III) or step (lll-b), an additional step (IV) of subjecting the dry film to a compression step to lower the porosity and increase the density of the composite solid electrolyte film.

[0131] Preferably, such a compression step is performed via calendering or uniaxial compression process or isostatic pressing (either warm or cold).

[0132] In still another object, the present invention provides for a composite solid electrolyte film obtained by the process as defined above.

[0133] The solid state batteries according to the present invention includes a positive electrode and a negative electrode, wherein preferably at least one the negative electrode or the positive electrode is an electrode according to the present invention.

[0134] In still a further object, the present invention provides for a solid state battery comprising a composite solid electrolyte film and / or at least one electrode according to the present invention.

[0135] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of thepresent application to the extent that it may render a term unclear, the present description shall take precedence.

[0136] The present invention will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.

[0137] Experimental section

[0138] Materials

[0139] Polymer A1 = vinylidene fluoride / hexafluoropropylene copolymer having 66.0% fluorine content; Mooney viscosity (ML 1 +10’) at 121 °C according to ASTM D1646 = 62 MU, having a Tg of about -18°C.

[0140] Polymer F1 = PVDF homopolymer, melting point (Tm2) = 158°C, melt viscosity = 31 Pa.s (measured by melting at 230°C and shear rate 100 Hertz), average particle size (Dso) = 4.5 pm.

[0141] Polymer F2 = copolymer VDF / acrylic acid, melting temperature = 160-168°C, average particle size (Dso) < 80 pm.

[0142] The following compositions were prepared:Example 1 and Example 2 according to the invention and Example 1 C of comparison were prepared using polymer A1 in the form of particles, prepared according to the method [I] disclosed below.Example 3 according to the invention and Example 2C and Example 5C of comparison comprised polymer A1 in the form of extruded pellets, prepared according to the method [II] described below.Example 3C and Example 4C of comparison comprised polymer A1 in the form of particles obtained after cryomilling [III] as described below.

[0143] Method [I] Preparation of polymer A1

[0144] Slabs of polymer A1 were cut into irregularly shaped medium dimension crumbs (diameter < 10 mm) with a cutting mill Retsch SM300 and then blended with polymer F1 using a high shear mixer, in the amount detailed inTable 1 .

[0145] Method [II] Preparation of polymer A1 in the form of pellets

[0146] Strands with a diameter of 3 mm of Polymer A1 were extruded using a 15cc double screw compounder from DSM, at a temperature of 180°C, and cut manually into small cylindrical pellets with a length of 2 mm to 6 mm.

[0147] Method [III] Preparation of polymer A1 via cryomilling

[0148] Slabs of polymer A1 were cut into irregularly shaped medium dimension crumbs (diameter < 10 mm) with a cutting mill Retsch SM300 and then blended with polymer F1 using a high shear mixer, in the amount detailed in Table 1 . The obtained crumbs were cryogenically milled using a Netzsch Condux CUM 150 impact mill into small sized crumbs / powder with a D50 below 1 mm.

[0149] Each of the compositions comprising polymer A1 prepared as described above was blended with polymer F1 or polymer F2, in the amounts described in Table 1 below.

[0150] The compositions comprising polymer A1 in the form of pellets were blended with polymer F1 in the amount disclosed in Table 1 , using a high shear mixer.

[0151] Evaluation of the physical form

[0152] Physical form of the compositions was evaluated by visual inspection.

[0153] Examples 1 , 2 and 3 according to the invention were easy flowing and did not aggregate. No aggregation was observed also after 3 months of storage of the compositions at room temperature, showing that the compositions were suitable for storage and for being transported.

[0154] Example 1 C of comparison showed highly sticky agglomerated blocks, which were not possible to be de-agglomerated. For this reason, this composition was not further analyzed.

[0155] Example 2C of comparison showed highly sticky pellets, which agglomerated after a few hours, showing that the composition was not suitable for storage. For this reason, this composition was not further analyzed.

[0156] Example 3C of comparison obtained via cryomilling but with an amount of polymer F1 lower than 2 wt.% was not easy flowing and showed agglomeration after about 24 hours, showing that the composition was not suitable for storage.

[0157] Example 4C of comparison obtained via cryomilling and with an amount of polymer F1 higher than 2 wt.% (as disclosed in the prior art) was easy flowing and non-stick.

[0158] Example 5C of comparison showed low sticky pellets, which could be easily de-agglomerated by mechanical means.

[0159] Evaluation of the particle size

[0160] The particle size of the compositions was evaluated according to the following methods.

[0161] Examples having a particle size below 2 mm, the particle size was determined with a Horiba LA-960V2 laser diffraction particle size distribution analyzer.The particle size distribution (PSD) was determined in the dry method with a PowderJet Dry feeder system, a feed speed of 100, using an air pressure of 0.3MPa and vacuum settings on automatic. For the calculation of the PSD, the fraunhofer model was used.

[0162] Examples having a particle size larger than 2 mm, the particle size was determined by sieving according to the following method.70 g of each composition was dry sieved (without the addition of anti-static agents) over a series of 9 sieves with decreasing mesh size (4750 - 4000 - 3360 - 2800 - 2380 - 2000 - 1400 - 1000 - 710 pm). For the analysis, theAnalysette equipment from Fritsch was used with a vibration amplitude of 10 for a time of 30 minutes. The particle size was determined based on the mass percentage of the samples retained / passing by the different sieves.

[0163] Example 1 C of comparison showed highly sticky agglomerated blocks, which were not possible to be de-agglomerated and hence the evaluation of the particle size was not possible.

[0164] Example 3C of comparison showed re-agglomeration. To determine its particle size, the composition was sieved over a 2000 pm sieve prior to the particle size determination.

[0165] The results measured as D50 and D90 are reported in Table 1 .

[0166] Evaluation of flowability factor

[0167] A bulk solid can be characterized numerically using a flowability factor (ffc), which is defined as the ratio of the consolidation stress (o1 ) to the unconfined yield stress (oc) and can be determined using a ring shear tester, using the following formula: ffc = o1 / oc

[0168] The higher the ffc number, the better the bulk solid flows. The Jenike(1964) classification of powder flowability by flow index is as follows: ffc < 1 not flowing1 < ffc < 2 very cohesive2 < ffc < 4 cohesive4 < ffc < 10 easy-flowing10 < ffc free-flowing

[0169] Flowability of the compositions of the examples was determined using the RST-XS.s ring shear tester, Dietmar Schulze. All flowability tests were performed at a preconsolidation stress of 5000 Pa.

[0170] The results are reported in Table 1.

[0171] Example 4C of comparison: small particles of polymer A1 with high amounts of polymer F1 (comp. Example 4) are easy flowing and as such suitable for storage, transportation and easy use.

[0172] Example 3C of comparison: Small particles of polymer A1 with low amounts of polymer F1 (comp. Example 3) on the other hand can be characterized as cohesive (ffc < 4) and are as such not suited for storage, transportation and handling.

[0173] Polymer A1 with larger particle size, on the other hand can be transformed into easy flowing materials using low amounts of polymer F1 (ex. 1 and 2).

[0174] Evaluation of solubility in sulfide-compatible solvents

[0175] Solutions comprising 10 wt.% of Examples 1 , 2 and 3 according to the invention and Example 5C of comparison were prepared in dehydrated butyl butyrate at room temperature and left to settle at room temperature for one week. Visual inspection was performed at the end of the one week.

[0176] All solutions obtained with Examples 1 , 2 and 3 according to the invention were transparent and clear, no deposit of insoluble fractions were observed.

[0177] Solution obtained with Example 5C of comparison showed undissolved floating polymer particles after such a solution was prepared. After one week, deposits of insoluble was found at the bottom of the reservoir, which made the solution not suitable for the final application.

[0178] The results are summarized in Table 1.Table 1(*) of comparison np = not performed ffc = flowability factor

Claims

Claims1 . A solid composition [composition (C1 )] comprising:- at least one (per)fluoroelastomer [(per)fluoroelastomer (A)] in the form of pellets having at least one dimension higher than 1 mm or solid particles having an average particle size (Dso) higher than 1 mm as measured by dry sieving, and- at least one thermoplastic vinylidene fluoride polymer [polymer (F)] having an average particle size (Dso) smaller than 40 pm, as measured by laser diffraction.

2. The composition (C1 ) according to Claim 1 , wherein said polymer (F) has an average particle size (Dso) lower than 40 pm, more preferably up to 39 pm, even more preferably up to 35 pm, as measured by laser diffraction; and / or from 0.10 pm, more preferably from 0.50 pm and even more preferably from 1.00 pm, as measured by laser diffraction.

3. The composition (C1 ) according to Claim 1 or 2, wherein said polymer (F) is in an amount lower than 4 wt.%, preferably up to 3.99 wt.%, more preferably up to 2.99 wt.%, even more preferably up to 1 .99 wt.% and still more preferably up to 1 .95 wt.% based on the total weight of (per)fluoroelastomer (A) and polymer (F); and / or in an amount of at least 0.005 wt.%, more preferably at least 0.075 wt.% and even more preferably of at least 0.095 wt.% based on the total weight of (per)fluoroelastomer (A) and polymer (F).

4. The composition (C1 ) according to any one of Claims 1 to 3, wherein said polymer (F) is in the form of powder or agglomerate or aggregate.

5. The composition (C1 ) according to any one of the preceding Claims, wherein (per)fluoroelastomer (A) comprises at least one (per)fluorinated monomerselected in the group comprising:- C2-C8 fluoro- and / or perfluoroolefins;- C2-C8 hydrogenated monofluoroolefins;- (per)fluoroalkylethylenes complying with formula CH2=CH-Rfo, in which Rro is a Ci-Ce (per)fluoroalkyl or a Ci-Ce (per)fluorooxyalkyl having one or more ether groups;- chloro- and / or bromo- and / or iodo-C2-Ce fluoroolefins;- fluoroalkylvinylethers complying with formula CF2=CFORfi in which Rn is a Ci-Ce fluoro- or perfluoroalkyl ;- hydrofluoroalkylvinylethers complying with formula CH2=CFORfi in which Rn is a Ci-Ce fluoro- or perfluoroalkyl ;- fluoro-oxyalkylvinylethers complying with formula CF2=CFOXo, in which Xo is a C1-C12 oxyalkyl, or a C1-C12 (per)fluorooxyalkyl having one or more ether groups;- fluoroalkyl-methoxy-vinylethers complying with formula CF2=CFOCF2ORf2 in which Rt2 is a Ci-Ce fluoro- or perfluoroalkyl or a Ci-Ce (per)fluorooxyalkyl having one or more ether groups;- functional fluoro-alkylvinylethers complying with formula CF2=CFOYo, in which Yo is a C1-C12 alkyl or (per)fluoroalkyl, or a C1-C12 oxyalkyl or a C1-C12 (per)fluorooxyalkyl, said Yo group comprising a carboxylic or sulfonic acid group, in its acid, acid halide or salt form;- fluorodioxoles, of formula :wherein each of Rf3, Rf4, Rfs, Rf6, equal or different each other, is independently a fluorine atom, a Ci-Ce fluoro- or per(halo)fluoroalkyl, optionally comprising one or more oxygen atom.

6. The composition (C1 ) according to any one of the preceding Claims, wherein polymer (F) is semicrystalline.

7. The composition (C1 ) according to any one of the preceding Claims, wherein polymer (F) is selected from vinylidene fluoride (VDF) homopolymers and copolymers of VDF with one or more fluorinated monomer and / or, hydrogenated monomer.

8. A binder composition [composition (CB)] comprising:- composition (C1 ) according to any one of Claims 1 to 7, and- at least on non-aqueous solvent [solvent (S)] selected from the group consisting of nitrile-containing solvents, ethers, esters, thiols, thioethers, ketones, tertiary amines and cyclic carbonate esters.

9. An electrode-forming composition [composition (CE)] comprising:- at least one electrode active material [material (AM)],- composition (CB) according to Claim 8; and- optionally, at least one conductive agent.

10. An electrode-forming composition [composition (CE-S)] comprising:- composition (CE) according to Claim 9, and- at least one sulfide-based solid electrolyte.

11. The composition (CE-S) according to Claim 10, wherein said at least one sulfide-based solid electrolyte is selected from:- lithium tin phosphorus sulfide (“LSPS”) materials, such as Li SnP2Si2;- lithium phosphorus sulfide (“LPS”) materials, such as glasses, crystalline or glass-ceramic of those of formula (Li2S)x-(P2Ss)y, wherein x+y=1 and 0<x<1 , LiyPsSu , LiyPSe, Li4P2Se, Li9.6P3Si2 and LisPS4;- doped LPS, such as Li2CuPS4, Li Lii+2xZm-xPS4, wherein 0<x<1 , Li3.33Mgo.33P2S6, and Li4-3xScxP2Se, wherein 0<x<1 ;- lithium phosphorus sulfide oxygen (“LPSO”) materials of formula LixPySzO, where 0.33<x<0.67, 0.07<y<0.2, 0.4<z<0.55, 0<w<0.15;- lithium phosphorus sulfide materials including X (“LXPS”), wherein X is Si, Ge, Sn, As, Al, such as Li GeP2Si2 and LiioSiP2Si2;- lithium phosphorus sulfide oxygen including X (“LXPSO”), wherein X is Si, Ge, Sn, As, Al;- lithium silicon sulfide (“LSS”) materials;- lithium boron sulfide materials, such as I 3BS3 and l_i2S- B2Ss-Lil;- lithium tin sulfide materials and lithium arsenide materials, such as Lio.8Sno.8S2, Li4SnS4, Li3.833Sno.833Aso.i 66S4, Li3AsS4-Li4SnS4, Ge-substituted LisAsS4; and- Argyrodite-type sulfide materials of general formula Liy-xPSe-xXx wherein:- Y represents at least one halogen element selected in the group of Cl, Br and I or a combination thereof; and x represents a positive number from 0.8 to 2.0, such as the compounds being possibly deficient in sulfur, lithium or halogen, for instance Lie-xPSs-xCh+x with 0<x<0.5, or doped with a heteroatom.

12. A process for manufacturing an electrode for secondary battery, such process comprising the steps of:(A) providing composition (CE) according to Claim 9 or composition (CE-S) according to Claims 10 and 11 ,(B) providing a metal substrate having at least one surface,(C) applying said composition (CE) or composition (CE-S) provided in step (A) onto said at least one surface of the metal substrate provided in step (B), thereby providing for an assembly comprising a metal substrate at least partially coated with said composition (CE) or composition (CE-S) onto the at least one surface, and(D) drying the assembly as provided in step (C).

13. An electrode for a secondary battery, said electrode being obtainable by the process comprising at least steps (A) to (D) according to Claim 12.

14. A composition [composition (C-F)] comprising:- at least one sulfide-based solid electrolyte, and- composition (CB) according to Claim 8.

15. A process for manufacturing a composite solid electrolyte film for solid state batteries, said process comprising the steps of:(I) providing composition (C-F) according to Claim 14,(II) processing composition (C-F) to form a wet film of a solid composite electrolyte, and(III) drying said wet film.

16. A composite solid electrolyte film obtained by the process according to Claim 15.

17. A solid state battery comprising a composite solid electrolyte film as defined in Claim 16 and / or at least one electrode as defined in Claim 13.

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