FR3149612A1 - Composition comprising PVDF and use thereof for the preparation of an electrode - Google Patents

Abstract

The present invention relates to a composition comprising particles of a poly(vinylidene fluoride) polymer P1 comprising a compound C1 selected from the group consisting of a polymer P1 a comprising monomeric units derived from a monomer M1 selected from the group consisting of cellulose, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxypropylmethylcellulose and ethylmethylcellulose, a polymer P1 b comprising monomeric units derived from styrene and butadiene and a polymer P1 c comprising monomeric units derived from N-vinylpyrrolidone, or a mixture thereof.

Description

Composition comprising PVDF and use thereof for the preparation of an electrode

The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Li-ion type. More specifically, the invention relates to a composition comprising a recycled fluorinated polymer and used in the manufacture of an electrode.

Technological background of the invention

Halogenated polymers, especially semi-fluorinated ones, are widely used due to their unique properties such as thermal stability, chemical inertness (to solvents, oils, water, acids and bases) and mechanical properties. Therefore, they can be applied in many fields such as aerospace, microelectronic tubes, engineering, chemical industry, automobile industry and wiring insulation.

Semi-fluorinated polymers including vinylidene fluoride units are of particular importance because they can be used in a wide range of applications from piezoelectric materials, water treatment and energy storage.

An elementary cell of a Li-ion storage battery or a lithium battery comprises an anode (on discharge), and a cathode (also on discharge) generally composed of a lithium insertion compound of the metal oxide type, such as LiMn2O4, LiCoO2 or LiNiO2, between which is inserted an electrolyte which conducts the lithium ions.

Rechargeable or secondary cells are more advantageous than primary (non-rechargeable) cells because the associated chemical reactions that take place at the positive and negative electrodes of the battery are reversible. Secondary cell electrodes can be regenerated multiple times by applying an electrical charge. Many advanced electrode systems have been developed to store an electrical charge. In parallel, much effort has been devoted to the development of electrolytes capable of improving the capabilities of electrochemical cells.

For their part, the electrodes generally comprise at least one current collector on which is deposited, in the form of a film, a composite material consisting of a material called active material because it has electrochemical activity with respect to lithium, a polymer which acts as a binder, plus one or more electronically conductive additives which are generally carbon black or acetylene black, and possibly a surfactant.

Binders are classified as inactive components since they do not directly contribute to the cell capacity. However, their key role in electrode processing and their considerable influence on the electrochemical performance of electrodes have been widely described. The main relevant physical and chemical properties of binders are thermal stability, chemical and electrochemical stability, tensile strength (strong adhesion and cohesion), and flexibility. The main purpose of using a binder is to form stable networks of the solid components of the electrodes, i.e., active materials and conductive agents (cohesion). In addition, the binder must ensure the close contact of the composite electrode to the current collector (adhesion).

Polyvinylidene fluoride (PVDF) is used as a binder in lithium-ion batteries due to its excellent electrochemical stability, good binding capacity and strong adhesion to electrode materials and current collectors. As the market for electric vehicles and therefore lithium-ion batteries is expanding rapidly worldwide, the demand for binders is very high and PVDF is the reference binder for cathodes.

In an eco-design approach and a desire to build more sustainable and more environmentally friendly lithium-ion batteries, much research is underway on the recycling of the various elements of batteries, particularly on the active material. CN108736086 and CN105098281 also disclose methods for recovering materials present in a battery. There is therefore a need to improve and extend the life cycle of the elements present in a battery, particularly that of the binder. However, extending the life cycle of these components and their reuse presents a certain technical difficulty because the performance of the battery using these second-life components must not be reduced. In the case of the binder, it is therefore necessary to ensure that the recycled binder does not introduce impurities that could cause electrochemical degradation in the battery. The aim of the present invention is to overcome at least some of these drawbacks and to provide more efficient batteries.

According to a first aspect, the present invention relates to a composition comprising particles of a poly(vinylidene fluoride) polymer P1 comprising a compound C1 selected from the group consisting of a polymer P1 a comprising monomeric units derived from a monomer M1 selected from the group consisting of cellulose, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxypropylmethylcellulose and ethylmethylcellulose, a polymer P1 b comprising monomeric units derived from styrene and butadiene and a polymer P1 c comprising monomeric units derived from N-vinylpyrrolidone, or a mixture thereof; characterized in that the mass content of compound C1 in said poly(vinylidene fluoride) particles P1 is between 1 ppm and 5% based on the total weight of said particles P1 .

According to a preferred embodiment, said particles of polymer P1 are derived from a poly(vinylidene fluoride) polymer recycled from an electrochemical device or from a membrane containing the latter.

The introduction into an electrode binder composition of a composition according to the present invention does not deteriorate the final properties of the battery. On the contrary, certain properties of the battery are improved by the introduction of a portion of recycled PVDF into the electrode binder composition. The use of PVDF of recycled origin has several technical advantages: the addition of small quantities of C1 compounds resulting from the first life of the polymer, and which make it possible to improve the final properties of the electrode and of the battery containing this recycled binder. In addition to improving the properties of the battery, the use in part of a PVDF from a recycling sector to reduce its life cycle analysis.

According to a preferred embodiment, said polymer P1 is a homopolymer of poly(vinylidene fluoride) or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1a selected from the group consisting of vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof; and optionally said polymer P1 comprises monomeric units derived from a monomer M1 b selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

According to a preferred embodiment, said polymer P1 comprises monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1b selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate.

According to a preferred embodiment, said composition also comprises particles of a polymer P2 a comprising monomeric units derived from a monomer M2 a selected from the group consisting of vinylidene fluoride, vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

According to a preferred embodiment, said composition also comprises particles of a polymer P2 b comprising monomeric units derived from a monomer M2 b of formula R1R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of –NHC(CH3)2CH2C(O)CH3 or –OR' with R' selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more –OH group(s) or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain.

According to a preferred embodiment, said particles of polymer P1 also comprise a mass content of at least one lithium salt greater than 1 ppm based on the total weight of said particles P1 .

According to a preferred embodiment, said at least one lithium salt is selected from the group consisting of LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiBF ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiN(SO ₂ F)(SO ₂ C ₂ F ₅ ), LiN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), LiAsF ₆ , LiBF ₂ C ₂ O ₄ , LiNO ₃ , LiPF3(CF ₂ CF ₃ ) ₃ , LiBETI, LiTDI, NaTDI, KTDI, NaClO ₄ , KClO ₄ , NaPF ₆ , KPF ₆ , NaBF ₄ , KBF ₄ , NaAsF ₆ , KAsF ₆ , NaCF ₃ SO ₃ , KCF ₃ SO ₃ , NaN(CF ₃ SO ₂ ) ₂ , KN(CF ₃ SO ₂ ) ₂ , NaN(SO ₂ C ₂ F ₅ ) ₂ , NaN(SO ₂ F)(SO ₂ CF ₃ ), NaN(SO ₂ F)(SO ₂ C ₂ F ₅ ), NaN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), KN(SO ₂ C ₂ F ₅ ) ₂ , KN(SO ₂ F)(SO ₂ CF ₃ ), KN(SO ₂ F)(SO ₂ C ₂ F ₅ ), KN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), or a mixture of these.

According to a preferred embodiment, said particles of polymer P1 also comprise a mass content of solvent S1 of from 1 ppm to 10% by weight based on the total weight of said particles P1 ; said solvent S1 having a donor number greater than 4 kcal/mol.

According to a preferred embodiment, said particles of polymer P1 also comprise a mass content of carbon particles P3 of between 1 ppm and 5% by weight based on the total weight of said particles P1 ; said carbon particles P3 being selected from the group consisting of graphite, such as natural or artificial graphite, graphene, carbon fibers or carbon nanotubes or carbon black.

According to another aspect, the present invention provides a composition comprising particles of a poly(vinylidene fluoride) polymer P1 comprising a mass content of carbon particles P3 of between 1 ppm and 0.1% by weight based on the total weight of said particles P1 ; said carbon particles P3 being selected from the group consisting of graphite, such as natural or artificial graphite, graphene, carbon fibers or carbon nanotubes or carbon black.

According to a preferred embodiment, said particles of polymer P1 are derived from a poly(vinylidene fluoride) polymer recycled from a positive electrode containing the latter.

According to a preferred embodiment, said particles of polymer P1 also comprise a mass content of at least one lithium salt greater than 1 ppm based on the total weight of said particles P1 .

According to a preferred embodiment, said particles of polymer P1 also comprise a mass content of organic solvent S1 of from 1 ppm to 10% by weight based on the total weight of said particles P1 ; said organic solvent S1 having a donor number greater than 4 kcal/mol.

According to a preferred embodiment, said composition has a clarity L* of between 10 and 99; the L* value is derived from the luminance of the surface of said particle defined according to the CIELAB color space and is measured according to the CIE D65 standard.

According to another aspect, the present invention provides an electrode binder comprising said composition according to the present invention.

According to another aspect, the present invention provides an electrode composition comprising said binder according to the present invention, an active material and optionally a conductive agent.

According to another aspect, the present invention provides an electrode comprising said electrode composition according to the present invention deposited on at least one face of a current collector.

According to another aspect, the present invention provides a battery comprising at least one electrode according to the present invention.

According to another aspect, the present invention provides a separator disposed between two electrodes and comprising said composition according to the present invention.

According to another aspect, the present invention provides a battery comprising said separator according to the present invention.

Brief description of the figures

There is a graph illustrating the discharge capacity of a battery comprising an electrode according to a particular embodiment of the present invention and according to a comparative embodiment.

Detailed description of the invention

The present invention consists in providing a composition suitable for use as a binder in electrodes or as a separator between a positive electrode and a negative electrode. According to a first aspect, the present invention provides a composition comprising particles of a polymer P1 of poly(vinylidene fluoride). Said composition comprises, in addition to the particles of polymer P1 , a compound C1 selected from the group consisting of:

- a polymer P1 comprising monomeric units derived from a monomer M1 selected from the group consisting of cellulose, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxypropylmethylcellulose and ethylmethylcellulose,

- a polymer P1 b comprising monomeric units derived from styrene and butadiene, and

- a polymer P1 c comprising monomeric units derived from N-vinylpyrrolidone,

- or a mixture of these.

Preferably, the mass content of compound C1 in said particles of a polymer P1 of poly(vinylidene fluoride) is between 1 ppm and 5% based on the total weight of said particles of a polymer P1 .

The mass content of compound C1 in said particles of a polymer P1 of poly(vinylidene fluoride) may be greater than 5 ppm, advantageously greater than 10 ppm, preferably greater than 15 ppm, more preferentially greater than 20 ppm, in particular greater than 25 ppm, more particularly greater than 50 ppm, preferably greater than 75 ppm, advantageously more preferentially greater than 100 ppm.

The mass content of compound C1 in said particles of a polymer P1 of poly(vinylidene fluoride) may be less than 5%, advantageously less than 4.8%, preferably less than 4.6%, more preferably less than 4.4%, in particular less than 4.2%, more particularly less than 4.0%.

Thus, the mass content of compound C1 in said particles of a polymer P1 of poly(vinylidene fluoride) may be greater than 5 ppm, advantageously greater than 10 ppm, preferably greater than 15 ppm, more preferably greater than 20 ppm, in particular greater than 25 ppm, more particularly greater than 50 ppm, preferably greater than 75 ppm, advantageously more preferably greater than 100 ppm; and the mass content of compound C1 in said particles of a polymer P1 of poly(vinylidene fluoride) may be less than 5%, advantageously less than 4.8%, preferably less than 4.6%, more preferably less than 4.4%, in particular less than 4.2%, more particularly less than 4.0%.

In the contents as indicated above, the presence of the compound C1 in said composition makes it possible to improve the final performances of the battery, for example the adhesion to the current collector. This improvement is even more marked when the compounds C1 are intimately linked to the particles of a polymer P1 of poly(vinylidene fluoride).

This is observed in particular when the particles of a poly(vinylidene fluoride) polymer P1 come from a recycling step, that is to say that these particles of said polymer P1 have already been used in a device. Thus, preferably, said particles of the polymer P1 come from a recycled poly(vinylidene fluoride) polymer. Said particles of said polymer P1 may come from the recycling of an electrochemical device or a membrane containing the latter. The electrochemical device is not limited and may be a battery or a fuel cell. The membrane is not limited and may be, for example, a membrane previously used in a filtration device.

Polymer P1

Said polymer P1 may be a homopolymer of poly(vinylidene fluoride) or a copolymer thereof with another comonomer copolymerizable with vinylidene fluoride.

According to one embodiment, the polymer P 1 is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from at least one other comonomer copolymerizable with vinylidene fluoride. The comonomers compatible with vinylidene fluoride may be halogenated (fluorinated, chlorinated or brominated) or non-halogenated.

Thus, said polymer P 1 comprises monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1a selected from the group consisting of vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the monomer of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the monomer of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the monomer of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the monomer of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the monomer of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); trifluoropropene, tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Trifluoropropenes include 3,3,3-trifluoropropene. Tetrafluoropropenes include 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene. Pentafluoropropenes include 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene. Chlorofluoroethylene may refer to either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. The chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene.

Preferably, the polymer P 1 is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1a selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene or a mixture thereof. In the polymer P 1 , the mass content of the vinylidene fluoride units is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.

In particular, the polymer P 1 is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from hexafluoropropylene; preferably the mass content of the monomeric units derived from vinylidene fluoride is at least 50%, preferably at least 60%, more preferably greater than 70% and advantageously greater than 80%.

More particularly, the polymer P 1 is a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from hexafluoropropylene; the mass content of the vinylidene fluoride units is greater than 65% and the mass content of the hexafluoropropylene units is less than 35%.

According to one embodiment, the polymer P 1 consists of a mixture of a vinylidene fluoride homopolymer (PVDF) and at least one VDF copolymer, with a mass content of PVDF homopolymer ranging from 0.1 to 20% based on the weight of said mixture.

According to one embodiment, said polymer P 1 consists of a mixture of a PVDF homopolymer and a copolymer P(VDF-HFP).

According to one embodiment, said polymer P 1 consists of a mixture of two VDF copolymers of different structures.

According to a particular embodiment, the polymer P 1 is functionalized in whole or in part, which allows it to improve adhesion to metal. Thus, said polymer P 1 can comprise monomer units carrying at least one of the functions selected from the group consisting of carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups such as glycidyl, amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic; preferably at least one carboxylic acid or hydroxyl function.

The function is introduced by a chemical reaction which may be grafting, or a copolymerization with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with vinylidene fluoride, according to techniques well known to those skilled in the art. The content of functional groups in the polymer P1 is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

According to another embodiment, the functional group carries a carboxylic acid function which is a group of (meth)acrylic acid type chosen from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxypropylsuccinate. According to one embodiment, the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus. Thus, said polymer P1 may be for example a copolymer of vinylidene fluoride and a monomer M1 b selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxypropylsuccinate. Preferably, the content of monomer M1 b in said polymer P1 is from 0.01% to 5 mol%.

The polymer P1 preferably has a high molecular weight. By high molecular weight, as used herein, is meant a polymer P1 having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to ASTM D-3835 measured at 232°C and 100 sec ^-1 .

Compound C1

As mentioned above, the polymer P1 may comprise a compound C1 in small proportions. Preferably, this compound C1 comes from the first life of the polymer P1 when the latter is recycled.

Said compound C1 may be a polymer P1 a , a polymer P1 b or a polymer P1 c or a mixture thereof.

Preferably, said polymer P1a is a cellulose derivative. In particular, said polymer P1a may comprise monomeric units derived from a monomer M1 selected from the group consisting of cellulose, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxypropylmethylcellulose and ethylmethylcellulose. More particularly, said polymer P1a may comprise monomeric units derived from carboxymethylcellulose.

Preferably, said polymer P1 b comprises monomeric units derived from styrene, butadiene or a mixture thereof. Said polymer P1 b may be selected from the group consisting of poly(styrene-butadiene-styrene) (SBS), poly(styrene-isoprene-styrene) (SIS), poly(styrene-ethylene/propylene-styrene) (SEPS), poly(styrene-ethylene/butylene-styrene) (SEBS), styrene-butadiene rubber (SBR), poly(ethylene propylene diene) (EPDM) rubber, polybutadiene (PBD), polystyrene (PS), poly(acrylonitrile-co-styrene-co-butadiene) (ABS), poly(styrene-co-acrylonitrile) (SAN), poly(styrene-co-maleic anhydride), poly(butadiene-co-acrylate) and poly(butadiene-co-acrylic acid-co-acrylonitrile). More particularly, said polymer P1 b may be styrene-butadiene rubber (SBR).

Preferably, said polymer P1 c comprises monomeric units derived from N-vinylpyrrolidone. Said polymer P1 c may be polyvinylpyrrolidone. Polyvinylpyrrolidone is understood to mean a homopolymer of vinylpyrrolidone and/or a copolymer of vinylpyrrolidone and another polymerizable vinyl monomer such as for example a hydrophilic monomer M2b as described below. There is no particular limitation on the molecular weight of the polyvinylpyrrolidone. However, the weight average molecular weight is preferably between 10 and 5000 kD.

Lithium salt

According to a preferred embodiment, said particles of said polymer P1 comprise at least one lithium salt. Said alkali metal salt is preferably selected from the group consisting of LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiBF ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiN(SO ₂ F)(SO ₂ C ₂ F ₅ ), LiN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ),LiAsF ₆ , LiBF ₂ C ₂ O ₄ , LiNO ₃ , LiPF3(CF ₂ CF ₃ ) ₃ , LiBETI, LiTDI, NaTDI, KTDI, NaClO ₄ , KClO ₄ , NaPF ₆ , KPF ₆ , NaBF ₄ , KBF ₄ , NaAsF ₆ , KAsF ₆ , NaCF ₃ SO ₃ , KCF ₃ SO ₃ , NaN(CF ₃ SO ₂ ) ₂ , KN(CF ₃ SO ₂ ) ₂ , NaN(SO ₂ C ₂ F ₅ ) ₂ , NaN(SO ₂ F)(SO ₂ CF ₃ ), NaN(SO ₂ F)(SO ₂ C ₂ F ₅ ), NaN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), KN(SO ₂ C ₂ F ₅ ) ₂ , KN(SO ₂ F)(SO ₂ CF ₃ ), KN(SO ₂ F)(SO ₂ C ₂ F ₅ ), KN(SO ₂ CF ₃ (SO ₂ C ₂ F ₅ ), or a mixture of these. Preferably, said alkali metal salt is selected from the group consisting of LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiBF ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiN(SO ₂ F)(SO ₂ C ₂ F ₅ ), LiN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ),LiAsF ₆ , LiBF ₂ C ₂ O ₄ , LiNO ₃ , LiPF3(CF ₂ CF ₃ ) ₃ , LiBETI, LiTDI, or a mixture of these. Preferably, said particles of said polymer P1 have a mass content of at least one lithium salt greater than 1 ppm based on the total weight of said particles P1 . Preferably, said particles of said polymer P1 have a mass content of at least one lithium salt greater than 5 ppm, advantageously greater than 10 ppm, preferably greater than 15 ppm, more preferably greater than 20 ppm, in particular greater than 25 ppm, more particularly greater than 30 ppm. According to a preferred embodiment, said particles of said polymer P1 comprise a mass content of lithium salt less than 5%, advantageously less than 3%, preferably less than 1% based on the total weight of said particles P1 .

Solvent S1

According to a preferred embodiment, said particles of said polymerP1include an organic solventS1. Preferably, the mass content of organic solvent S1is comprised from 1 ppm to 10% by weight based on the total weight of said particlesP1. According to a preferred embodiment, said organic solventS1having a donor number greater than 4 kcal/mol. Preferably, said organic solventS1has a donor number greater than 5 kcal/mol. The donor number of a solvent represents the value -ΔH, ΔH being the enthalpy of the interaction between the solvent and antimony pentachloride (according to the method described inJournal of Solution Chemistry, vol. 13, n°9, 1984). According to a preferred embodiment, said organic solvent S1has a donor number greater than 6 kcal/mol, advantageously greater than 7 kcal/mol, preferably greater than 8 kcal/mol, more preferably greater than 9 kcal/mol, in particular greater than 10 kcal/mol. According to a particular embodiment, said organic solventS1 has a donor number of between 5 and 30 kcal/mol, advantageously between 5 and 25 kcal/mol, preferably between 10 and 20 kcal/mol. Said organic solvent S1may be chosen in particular esters, carbonates, nitriles or dinitriles, ethers or diethers, ketones provided that it has a donor number as provided in the present application and the saturated vapor pressure as described in the present application; and preferably the flash point as described in the present application. Combinations of these may also be used as organic solvent. By way of non-limiting example, the following may be mentioned as organic solvent:S1according to the present invention: N,N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, propanone, 2-butanone, 1,2-dimethoxyethane, 1,3-dioxolane, 2,3-butanedione, 2-methylpentan-3-one, 2-methyltetrahydrofuran, 2-pentanone, methyl cyanide, 3,3-dimethyl-2-butanone, 3-methyl-2-butanone, 3-pentanone, butyl acetate, cyclohexanone, cyclopentanone, 4-methylpentan-2-one, dibutyl ether, 1,4-dioxane, dipropyl ether, ethyl acetate, ethyl butanoate, methyl propanoate, tetrahydrofuran, N-butyl-2-pyrrolidone or a mixture thereof.

Carbon particles P3

According to a preferred embodiment, said particles of said polymer P1 comprise carbon particles P3 . Preferably, said particles P3 may be selected from the group consisting of graphite, such as natural or artificial graphite, graphene, carbon fibers or carbon nanotubes or carbon black.

According to a preferred embodiment, said particles of polymer P1 comprise a mass content of carbon particles P3 of between 1 ppm and 5% by weight based on the total weight of said particles P1 .

According to a preferred embodiment, said particles of polymer P1 comprise a mass content of carbon particles P3 of between 1 ppm and 0.1% by weight based on the total weight of said particles P1 . In the latter case, said particles of polymer P1 are derived from a recycled poly(vinylidene fluoride) polymer from cathodes containing the latter.

Compound C2

Said particles of said polymer P1 may also comprise one or more compound(s) C2 which are preferably residual organic compounds from synthesis or from the first life thereof in a battery such as chain transfer agents, pH regulators, electrolyte solvents and paraffin waxes. The total mass content of compound C2 in said polymer P1 is less than 1%, advantageously less than 0.9%, preferably less than 0.8%, more preferably less than 0.7%, in particular less than 0.6%, more particularly less than 0.5%. As examples, the paraffin waxes may be saturated long-chain hydrocarbon waxes and oils. As examples, the pH regulators may be phosphate or acetate buffer solutions.

Obtaining polymer P1

As mentioned above, said polymer P1 can be obtained by recycling it into membranes or electrochemical devices such as batteries.

There are currently several types of recycling for Li-ion batteries, including pyrometallurgical and hydrometallurgical. Pyrometallurgical uses furnaces and reducers to produce metal alloys of Co, Cu, Fe and Ni. Its main advantages over hydrometallurgy are its ability to handle different battery chemistries and cell types, limited need for pre-treatment (mechanical or pre-discharge), and process safety. The main disadvantages are high operating costs due to high energy input, reduced recycling efficiency, as Al, Li and Mn are lost in the final waste and are recycled in the concrete industry, and also the emission of harmful gases. A crushing and separation step can also be performed to separate metallic elements such as aluminium and copper. In the case of pyrolysis, the extraction of Pvdf is done upstream of the thermal treatment to avoid polymer degradation. Hydrometallurgy involves the use of aqueous solutions to leach target metals from the cathode. The cells must first be opened and handled; lithium-ion batteries under gaseous atmosphere have proven to be the optimal method of treating used cells. Many pilot-scale hydrometallurgical processes have been operated and recoveries of 75% of the active material have been reported. The complexity of the cell design involves an initial fragmentation step, followed by a series of leaching and mechanical separation steps using density, ferromagnetism and hydrophobicity to separate the “black mass” (active material separated from the current collectors). Froth flotation can also be used to separate carbons from metal oxides, however pre-sorting and labeling of batteries prior to recycling could reduce the need for these steps, while increasing the quality of the recycled materials. A separation step for metals such as aluminum and copper can be performed upstream of the leaching treatments. The extraction of polymer P1 can be carried out before the separation steps or before the leaching steps.

Another recycling technique is to couple the two previous techniques to improve leaching efficiencies. The cells are crushed. The aluminum, copper and polymers of the separator can be separated. A pyrolysis step is then carried out at a lower temperature than the classic pyrometallurgical process. This black mass is then leached in a classic hydrometallurgical process. In this third case, the extraction of the Pvdf is carried out before the separation steps or before the pyrolysis steps. The relative advantages of the different recycling techniques have been summarized by Lv et al. (W. Lv, Z. Wang, H. Cao, Y. Sun, Y. Zhang and Z. Sun, A Critical Review and Analysis on the Recycling of Spent Lithium-Ion Batteries, ACS Sustainable Chem. Eng., 2018, 6, 1504–1521).

The process for recycling polymer P1 consists in bringing the material to be recycled obtained in the various steps described above into contact with at least one polar solvent with a donor number > 10. For example, a polar solvent with a donor number > 10 may be 1,3-dimethylurea, 1,3-dioxolan-2-one, 1,3-dioxolane, 2,2,2-trifluoro-N,N-dimethylacetamide, 2,2,4,4-tetramethyl-3-pentanone, 2,2,4-trimethylpentan-3-one, 2,2,5,5-tetramethylhexan-3-one, 2,2,6,6-tetramethyl-4-heptanone, 2,2-dimethylpentan-3-one, 2,3-butanedione, 2,4-dimethyl-3-pentanone, 2,6-dimethyl-4-heptanone, 2-butanone, 2-methyl-1-propanol, 2-methyl-2-butanol, 2-methyl-2-propanamine, 2-methyl-2-propanol, 2-methylpentan-3-one, 2-methylpropanenitrile, 2-methyltetrahydrofuran, 2-pentanone, 2-phenylacetonitrile, 2-phenylethanol, 2-propanol, 2-propanone, 3,3-dimethyl-2-butanone, 3-methyl-1-butanol, 3-methyl-2-butanone, acetonitrile, cyclohexanol, cyclohexanone, cyclopentanone, methyl acetate, methyl benzoate, methyl propanoate, methyl propyl ether, ethyl 2,2-dimethylpropanoate, ethyl 2-methylpropanoate, ethyl acetate, ethyl benzoate, ethyl butanoate, ethyl chloroacetate, ethyl chloroformate, N,N-diethylacetamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-dimethylaniline, N,N-dimethylbenzylamine, N,N-dimethylcarbamoyl chloride, N,N-dimethylformamide, N-methylaniline, N-methylformamide, N-methylpyrrolidone, tetrahydrofuran, tert-butyl acetate, sulfolane. The contact can be carried out at a temperature between 10 and the boiling point of the solvent under the pressure conditions of the process. The extraction can be carried out under a pressure ranging from 1 bar to 150 bars absolute. This extraction can be carried out in batch or continuous mode to improve yields and contact times. Contact times can range from 1 min to 15 days. The solution obtained can optionally be concentrated by any method known to those skilled in the art. At least one non-polar solvent with a donor number < 9 is added to the solution to precipitate the polymer described in the invention. For example, a non-polar solvent with a donor number < 9 may be trichloromethane, thionyl chloride, toluene, tetrachloromethane, styrene, propanoyl chloride, methoxybenzene, hexane, ethylbenzene, fluorobenzene or dichloromethane. This polymer is then recovered and dried by any methods known to those skilled in the art. The extraction steps may be repeated until said polymer P1 as described in the present application is obtained, i.e. with the contents defined in the present application.

When the polymer P1 comes from membrane recycling, it is obtained by a membrane grinding step, possibly preceded by a cleaning step. The grinding step is followed by a regranulation step according to techniques known to those skilled in the art.

The polymer P1 may also be derived from cathode production scrap, or from mechanically separated cathodes if they are derived from production cells possibly already soaked in electrolytes, or from end-of-life cathodes mechanically separated during a first recycling step. The cathodes thus recovered are subjected to dissolution, precipitation and washing steps until the composition described in the present application is obtained. Mechanical recycling is a method under development, even if it is less widespread than hydrometallurgy and pyrometallurgy.

Polymer P2a and P2b

As mentioned above, said composition may comprise, in addition to polymer P1 , a polymer P2a or a polymer P2b as described below. When said composition comprises a blend between said polymer P1 and said polymer P2a , P2b or both, said composition preferably comprises at least 1% by weight of said polymer P1 , advantageously at least 5% by weight of said polymer P1 , preferably at least 10% by weight of said polymer P1 , more preferably at least 20% by weight of said polymer P1 , in particular at least 30% by weight of said polymer P1 , more particularly at least 40% by weight of said polymer P1 , more preferably at least 50% by weight of said polymer P1 based on the total weight of said polymers P1 , P2a and P2b therein.

According to a preferred embodiment, said polymer P2a comprises monomeric units derived from a monomer selected from the group consisting of vinylidene fluoride, vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof.

According to one embodiment, the polymer P 2 a is a homopolymer of vinylidene fluoride.

According to another embodiment, the polymer P 2 a is a copolymer of vinylidene fluoride with at least one comonomer compatible with vinylidene fluoride. The comonomers compatible with vinylidene fluoride can be halogenated (fluorinated, chlorinated or brominated) or non-halogenated. Examples of suitable fluorinated comonomers are: vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes and in particular 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene, perfluoroalkylvinylethers and in particular those of general formula Rf-O-CF-CF2, Rf being an alkyl group, preferably C1 to C4 (preferred examples being perfluoropropylvinylether and perfluoromethylvinylether). The fluorinated comonomer may comprise a chlorine or bromine atom. It may in particular be chosen from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene may denote either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene or 2-chloro-3,3,3-trifluoropropene. The VDF copolymer may also comprise non-halogenated monomers such as ethylene, and/or acrylic or methacrylic comonomers.

The polymer P 2a preferably contains at least 50 mol% vinylidene fluoride, advantageously at least 60 mol% vinylidene fluoride, preferably at least 70 mol% vinylidene fluoride. The comonomer may be present in a content of 1 to 50%, advantageously 2 to 30% by weight relative to the weight of said polymer P2a .

According to one embodiment, the polymer P 2a is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a weight percentage of hexafluoropropylene monomer units of 2 to 30%, advantageously of 2 to 25%, preferably of 2 to 20%, preferably of 4 to 15% by weight relative to the weight of said polymer P2a . According to another embodiment, the polymer P2a is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P(VDF-HFP)), having a weight percentage of hexafluoropropylene monomer units of 10 to 30%, advantageously of 10 to 25% by weight relative to the weight of said polymer P2a .

According to one embodiment, the polymer P2a is a copolymer of vinylidene fluoride and tetrafluoroethylene (TFE).

According to one embodiment, the polymer P2a is a copolymer of vinylidene fluoride and chlorotrifluoroethylene (CTFE).

According to one embodiment, the polymer P2a is a VDF-TFE-HFP terpolymer. According to one embodiment, the polymer P2a is a VDF-TrFE-TFE terpolymer (TrFE being trifluoroethylene). In these terpolymers, the mass content of VDF is at least 10%, the comonomers being present in variable proportions.

According to one embodiment, the polymer P2a comprises monomeric units carrying at least one of the following functions: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. The function is introduced by a chemical reaction which can be grafting, or a copolymerization of the vinylidene fluoride (VDF) monomer with a monomer carrying at least one of said functional groups and a vinyl function capable of copolymerizing with the VDF monomer, according to techniques well known to those skilled in the art.

According to one embodiment, the functional group carries a carboxylic acid function which is a group of (meth)acrylic acid type chosen from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate and hydroxyethylhexyl(meth)acrylate. Thus, said polymer P2a may comprise monomeric units derived from a monomer selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxyethylhexyl methacrylate.

According to one embodiment, the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus.

According to one embodiment, the functionality is introduced via the transfer agent used during the synthesis process. The transfer agent is a polymer with a molar mass of less than or equal to 20,000 g/mol and bearing functional groups chosen from the groups: carboxylic acid, carboxylic acid anhydride, carboxylic acid esters, epoxy groups (such as glycidyl), amide, hydroxyl, carbonyl, mercapto, sulfide, oxazoline, phenolic, ester, ether, siloxane, sulfonic, sulfuric, phosphoric, phosphonic. An example of a transfer agent of this type is acrylic acid oligomers. The content of functional groups in said polymer P2a is at least 0.01 mol%, preferably at least 0.1 mol%, and at most 15 mol%, preferably at most 10 mol%.

According to another embodiment, the functional group carries a carboxylic acid function which is a group of (meth)acrylic acid type chosen from acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxypropylsuccinate. According to one embodiment, the units carrying the carboxylic acid function further comprise a heteroatom chosen from oxygen, sulfur, nitrogen and phosphorus. Thus, said polymer P 2a may be for example a copolymer of vinylidene fluoride and a monomer M 2a selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxypropylsuccinate. Preferably, the content of monomer M 2a in said polymer P 2a is from 0.01% to 5 mol%. In this embodiment, at least 40% of the units resulting from the monomer M2a are distributed between two vinylidene fluoride units.

The polymer P2a preferably has a high molecular weight. By high molecular weight, as used herein, is meant a polymer P2a having a melt viscosity greater than 100 Pa.s, preferably greater than 500 Pa.s, more preferably greater than 1000 Pa.s, according to ASTM D-3835 measured at 232°C and 100 sec-1.

In one embodiment, the polymer P2a bearing functional groups can crosslink either by self-condensation of its functional groups or by reaction with a catalyst and/or a crosslinking agent, such as melamine resins, epoxy resins and the like, as well as known low molecular weight crosslinking agents such as di- or higher polyisocyanates, polyaziridines, polycarbodiimides, polyoxazolines, dialdehydes such as glyoxal, acetoacetates, malonates, acetals, di- and trifunctional thiols and acrylates, cycloaliphatic epoxy molecules, organosilanes such as epoxysilanes and amino silanes, carbamates, diamines and triamines, inorganic chelating agents such as certain zinc and zirconium salts, titaniums, glycourils and other aminoplasts. In some cases, functional groups from other polymerization ingredients, such as surfactants, initiators, seed particles, may be involved in the crosslinking reaction. When two or more functional groups are involved in the crosslinking process, the complementary reactive group pairs are, for example, hydroxyl-isocyanate, acid-epoxy, amine-epoxy, hydroxyl-melamine, acetoacetate-acid. The acrylate and/or methacrylate monomers not containing functional groups capable of entering into crosslinking reactions after polymerization should preferably represent 70% or more by weight of the total monomer mixture, and more preferably, should be greater than 90% by weight. According to one embodiment, the polymer P1 comprises a crosslinking agent selected from the group consisting of isocyanates, diamines, adipic acid, dihydrazides and combinations thereof.

According to another embodiment, said composition may comprise a polymer P2b . As mentioned above, said polymer P2b comprises monomeric units derived from a monomer M2b of formula R ¹ R 2 C=C( R ³ )C(O)R in which the substituents R ¹ , R ² and R ³ are ^{independently} of each other selected from the group consisting of H and C ₁ -C ₅ alkyl; R is selected from the group consisting of –NHC(CH ₃ ) ₂ CH ₂ C(O)CH ₃ or –OR' with R' selected from the group consisting of H and C ₁ -C ₁₈ alkyl optionally substituted by one or more –OH group(s) or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. Said heterocycle may be saturated or unsaturated or aromatic. Said heterocycle may be monocyclic or bicyclic. Said heterocycle may be a pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, oxindole, isatin, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone ring. Said heterocycle may be substituted by one or more C ₁ -C ₅ alkyl groups. As mentioned above, the C ₁ -C ₁₈ alkyl is optionally substituted by said heterocycle. The latter may be linked to the alkyl chain by the nitrogen atom or any other atoms forming the heterocycle. Preferably the heterocycle is 2-pyrrolidone, delta-lactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

Preferably, said polymerP2 bcomprises monomeric units derived from a monomerM2 b of alkyl (meth)acrylate of formula R¹R²C=C(R³)C(O)R in which the substituents R¹, R²and R³are independently selected from the group consisting of H and C₁-C₅alkyl; R is selected from the group consisting of –NHC(CH₃)₂CH₂C(O)CH₃or –OR’ with R’ selected from the group consisting of H and C₁-C₁₈alkyl optionally substituted by one or more –OH group(s) a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. Preferably, the heterocycle is as defined above, in particular the heterocycle is 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. The expression “alkyl (meth)acrylate” includes alkyl acrylates and alkyl methacrylates. According to a preferred embodiment, the substituent R’ is selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, n-dodecyl, amyl, isoamyl, hexyl, 2-ethylhexyl, lauryl, n-octyl, hydroxybutyl, hydroxypropyl, ethyl substituted by a ureido group, hydroxy ethyl, hydroxy propyl, hydroxy butyl.

In particular, said polymerP2 bcomprises monomeric units derived from a monomerM2 b of alkyl (meth)acrylate of formula R¹R²C=C(R³)C(O)R in which the substituents R¹and R²are H; R³is H or CH₃; R is –OR’ with R’ selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxy propyl, hydroxy butyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone.

Thus the alkyl (meth)acrylate can be acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-dodecyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, methyl acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-dodecyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureido methacrylate and mixtures thereof. Among these, alkyl acrylates with an alkyl group having 1 to 8 carbon atoms are preferred, and alkyl acrylates with an alkyl group having 1 to 5 carbon atoms are more preferable. These compounds may be used alone or as a mixture of two or more. Thus, said polymer P2 b may be a homopolymer of a monomer M2 b as defined above or a copolymer derived from a mixture of one or more monomer M2 b as defined above.

The term “acrylate” herein includes both acrylates and methacrylates.

The optional ethylenically unsaturated compound copolymerizable with alkyl acrylate and alkyl methacrylate comprises:

- (A) an alkenyl compound containing a functional group, and

- (B) an alkenyl compound without a functional group.

The alkenyl compound (A) containing a functional group includes, for example, α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, crotonic acid, itaconic acid and the like; vinyl ester compounds such as vinyl acetate, vinyl neodecanoate and the like; amide compounds such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, diacetone acrylamide and the like; acrylic acid esters such as 2-hydroxyethyl acrylate, N-dialkylaminoethyl acrylate, glycidyl acrylate, n-dodecyl acrylate, fluoroalkyl acrylate and the like; methacrylic acid esters such as dialkylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate, n-octyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate and the like; maleic anhydride, and alkenyl glycidyl ether compounds such as allyl glycidyl ether and the like. Among these, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and allyl glycidyl ether are preferred. These compounds may be used alone or as a mixture of two or more.

The functional group-free alkenyl compound (B) includes, for example, conjugated dienes such as 1,3-butadiene, isoprene and the like; divinyl hydrocarbon compounds such as divinyl benzene and the like; and alkenyl cyanides such as acrylonitrile, methacrylonitrile and the like. Among these, preferred are 1,3-butadiene, and acrylonitrile. These compounds may be used alone or as a mixture of two or more.

It is preferable that the functional alkenyl compound (A) is used in an amount of less than 50% by weight relative to the weight of the monomer mixture and that the functional group-free alkenyl compound (B) is used in an amount of less than 30% by weight relative to the weight of the monomer mixture.

In some embodiments, polymers P1 , P2a , and P2b are composed of bio-based VDF. The term “bio-based” means “derived from biomass.” This improves the ecological footprint of the separator. The bio-based vinylidene fluoride may be characterized by a renewable carbon content, i.e. carbon of natural origin and originating from a biomaterial or biomass, of at least 1 atomic % as determined by the 14C content according to standard NF EN 16640. The term “renewable carbon” indicates that the carbon is of natural origin and originates from a biomaterial (or biomass), as indicated below. According to certain embodiments, the bio-carbon content of the VDF may be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50%, preferably greater than or equal to 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100%.

The vinylidene fluoride homopolymers and copolymers used in the invention can be obtained by known polymerization methods such as emulsion or suspension polymerization. According to one embodiment, they are prepared by an emulsion polymerization process in the absence of fluorinated surfactant.

The polymerization of vinylidene fluoride preferably results in a latex generally having a solids content of 10 to 60% by weight, preferably 10 to 50%, and having a weight average particle size of less than 1 micrometer, preferably less than 1000 nm, preferably less than 800 nm, and more preferably less than 600 nm. The weight average particle size is generally at least 20 nm, preferably at least 50 nm, and advantageously the average size is in the range of 100 to 400 nm. The polymer particles may form agglomerates having a weight average size of 1 to 30 micrometers, and preferably 2 to 20 micrometers. The agglomerates may break up into discrete particles during formulation and application to a substrate.

According to a particular embodiment, said composition comprises said polymer P1 and said polymer P2a , each comprising, independently of one another, monomeric units derived from vinylidene fluoride and optionally monomeric units of a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. In particular, said composition comprises said polymer P1 and said polymer P2a , each independently of the other being a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof. As mentioned above, in this composition, the mass content of polymer P1 is at least 1%, advantageously at least 5%, preferably at least 10%, more preferably at least 20%, in particular at least 30%, more particularly at least 40%, preferably at least 50% based on the total weight of said polymers P1 and P2a in said composition.

According to a particular embodiment, said composition comprises said polymerP1and said polymerP2 b, these being as defined in the present application. Preferably, said composition comprises said polymerP1and said polymerP2 b, wherein said polymerP1comprises monomeric units derived from vinylidene fluoride and optionally monomeric units of a monomer selected from the group consisting of vinyl fluoride; trifluoroethylene (VF₃); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF₂=CFOCF₂CF(CF₃)OCF₂CF₂X in which X is SO₂F, CO₂H, CH₂OH, CH₂OCN or CH₂OPO₃H; the product of formula CF₂=CFOCF₂CF₂SO₂F; the product of formula F(CF₂)nCH₂OCF=CF₂in which n is 1, 2, 3, 4 or 5; the product of formula R¹CH₂OCF=CF₂in which R¹is hydrogen or F(CF₂)m and m is 1, 2, 3 or 4; the product of formula R²OCF=CH₂in which R²is F(CF₂)p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof; and said polymerP2 bcomprises monomeric units derived from a monomerM2 bof formula R¹R²C=C(R³)C(O)R in which the substituents R¹, R²and R³are independently selected from the group consisting of H and C₁-C₅alkyl; R is selected from the group consisting of –NHC(CH₃)₂CH₂C(O)CH₃or –OR’ with R’ selected from the group consisting of H and C₁-C₁₈alkyl optionally substituted by one or more –OH group(s) or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. In particular, said composition comprises said polymerP1and said polymerP2 b, wherein said polymerP1is a homopolymer of vinylidene fluoride or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer selected from the group consisting of trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene or a mixture thereof; and the polymerP2bincludes includes monomeric units derived from a monomerM2 b of alkyl (meth)acrylate of formula R¹R²C=C(R³)C(O)R in which the substituents R¹and R²are H; R³is H or CH₃; R is –OR’ with R’ selected from the group consisting of H, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, hydroxy propyl, hydroxy butyl, 2-pyrrolidone, deltalactam, succinimide, 2-imidazolidinone, 4-imidazolidinone. As mentioned above, in this composition, the mass content of polymerP1is at least 1%, advantageously at least 5%, preferably at least 10%, more preferably at least 20%, in particular at least 30%, more particularly at least 40%, preferably at least 50% based on the total weight of said polymersP1AndP2 bin said composition.

According to a particular embodiment, said composition has a clarity L* of between 10 and 99; the L* value is derived from the luminance of the surface of said particle defined according to the CIELAB color space and is measured according to the CIE D65 standard. According to a particular embodiment, said composition has a clarity L* of between 10 and 98, advantageously between 10 and 97, preferably between 10 and 96, more preferably between 10 and 95, in particular between 10 and 94, more particularly between 10 and 93, preferably between 10 and 92, advantageously preferably between 10 and 91, preferably preferably between 10 and 90.

When said composition comprises, in addition to polymer P1 , said polymer P2a , P2b or a mixture of the two, the content of polymer P1 is from 1 to 99%, advantageously from 5 to 95%, preferably from 10 to 90% based on the total weight of polymers P1 , P2a and P2b .

Use

Said composition according to the present invention can be used as a binder for an electrode. To form said binder for the electrode, said composition can be used alone or in admixture with one or more other polymers. In particular, said binder can comprise said composition according to the present invention comprising said polymer P1 alone or in admixture with polymer P2a , P2b or a mixture P2a and P2b .

Thus, according to another aspect, the present invention provides an electrode composition comprising said binder according to the present invention, an active material and optionally a conductive agent.

In a preferred embodiment, the electrode has the following mass composition:

a. 50% to 99.9% active material, preferably 50% to 99%,

b. 25% to 0% conductive agent, preferably 25% to 0.5%,

c. 25% to 0.05% of said binder according to the invention, preferably 25% to 0.5%,

d. 0% to 5% of at least one additive selected from the group consisting of a plasticizer, an ionic liquid, a dispersing agent for conductive additive, and a flow aid;

the sum of all these percentages being 100%.

The conductive agents in the electrode are composed of one or more materials that can enhance the conductivity. Some examples include carbon blacks such as acetylene black, Ketjen black; carbon fibers, such as carbon nanotube, carbon nanofiber, vapor-grown carbon fiber; metal powders such as SUS powder, and aluminum powder.

Active materials in electrode compositions are materials that are capable of storing and releasing lithium ions.

In a preferred embodiment, said electrode is a negative electrode. In particular, for a negative electrode, said active material is selected from the group consisting of a lithium alloy, lithium metal, a metal oxide, a carbon material such as graphite or hard carbon, silicon, a silicon alloy and Li ₄ TiO ₁₂ . The shape of the negative electrode active material is not particularly limited but is preferably particulate.

In another preferred embodiment, said electrode is a positive electrode. Preferably, for a positive electrode, said active material is selected from the group consisting of LiCoO ₂ , Li(Ni, Co, AI)O ₂ , Li(1+ x), NiaMnbCoc (x represents a real number of 0 or more, a = 0.8, 0.6, 0.5, or 1/3, b = 0.1, 0.2, 0.3, or 1/3, c = 0.1, 0.2, or 1/3), LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₃ NiMn ₃ O ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) ₃ , a Li Mn spinel substituted by a different element having a composition represented by Li1+xMn2-x-yMyO4, M representing at least one metal selected from Al, Mg, Co, Fe, Ni, and Zn, x and y independently representing a real number between 0 and 2, lithium titanate LixTiOy – x and y independently representing a real number between 0 and 2, and a lithium metal phosphate having a composition represented by LiMPO4, M representing Fe, Mn, Co, or Ni. The shape of the positive electrode active material is not particularly limited but is preferably particulate. In addition, the surface of each of the materials described above can be coated. The coating material is not particularly limited as long as it has lithium ion conductivity and contains a material capable of being maintained as a coating layer on the surface of the active material. Examples of the coating material include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ .

Said electrode composition can be deposited on at least one face of a current collector to form said electrode. This deposition can be carried out in the presence of an organic solvent, water, a mixture of the two or by a solvent-free process, i.e. by a dry coated electrode production process.

According to another aspect of the present invention, a method for preparing the dry coated electrode is provided. Said method for preparing the dry coated electrode comprises the following steps:

- mixing the active material, said binder according to the present invention in powder form as described above, and the conductive agent using a process which provides an electrode formulation applicable to a metal substrate by a “solvent-free” process;

- depositing said electrode formulation on a substrate by a solvent-free process to obtain a Li-ion battery electrode, and

- consolidation of said electrode by a thermomechanical treatment step carried out at a temperature T1 between Tf – 50°C < T1 < Tf + 50°C or Tf – 50°C < T1 < Tg + 50°C when Tg > Tf or at a temperature T1 between Tg – 50°C < T1 < Tf + 50°C when Tf > Tg with Tf being the melting temperature of the fluorinated polymer P1 or P2a and Tg being the glass transition temperature of the acrylic polymer P2b . A “solvent-free” process is a process that does not require a residual solvent evaporation step after the deposition step. A thermomechanical treatment can be carried out for example by a calendering machine comprising rollers that can be heated or a plate press that can also be heated. As solvent-free mixing processes of the various constituents of the electrode formulation before the deposition phase on the collector, the following may be mentioned, without being exhaustive: mixing by stirring, mixing by air jet, high shear mixing, mixing by V mixer, mixing by screw mass mixer, mixing by double cone, mixing by drum, conical mixing, mixing by double Z arm, mixing in a fluidized bed, mixing in a planetary mixer, mixing by mechanical fusion, mixing by extrusion, mixing by calendering, mixing by grinding. The particle size of said binder can be adapted for easier implementation of the solvent-free process. According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free spraying process, by depositing the formulation on the metal substrate, by a pneumatic spraying process, by electrostatic spraying, by dipping in a fluidized powder bed, by spraying, by electrostatic screen printing, by deposition with rotating brushes, by deposition with rotating addition rollers, by calendering. According to one embodiment, the consolidation of the electrode after a solvent-free spray deposition process on the metal substrate (pneumatic spraying process, electrostatic spraying, dipping in a fluidized powder bed, sprinkling, electrostatic screen printing, deposition with rotating brushes, deposition with rotating addition rollers) is carried out by a calendering process. This process consists in applying pressure to the electrode using two optionally heated rollers. According to one embodiment, after the powder mixing step, the electrode is manufactured by a two-step solvent-free process. A first step consists in manufacturing a self-supporting film from the premixed formulation with a thermomechanical process such as extrusion, calendering or thermo-compression. In a second step, the self-supporting film is laminated on the metal substrate by a process combining temperature and pressure such as calendering or thermo-compression. According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free process using a calendering process that makes it possible to carry out the film-forming and coating transfer step on the current collector in a single step, i.e. without going through a step of manufacturing a self-supporting film. To do this, the calender used has several rollers (at least three). The powder obtained after the mixing step is introduced between the first two rollers, most often heated and having differential rotation speeds to shear the powder. The coating formed and remaining stuck on the fastest roller is then directly rolled onto the current collector with a third roller. The electrode thus obtained can be subsequently passed through a calender to adjust its porosity or thickness if necessary. The mass ratio of the conductive agents relative to the active material is preferably 0 to 10%, more preferably 0 to 7%. The mass ratio of binder to active material is preferably 0.1 to 10%, more preferably 0.5 to 7%. According to one embodiment, the electrode components are all mixed at once according to conventional methods, resulting in an electrode formulation. In one embodiment, said electrode formulation is applied to a substrate by electrostatic screen printing. Some examples of substrate are current collectors such as metal foil and metal mesh, polymer films, or a solid electrolyte layer of a solid-state battery. The preferred thickness of an electrode is 0.1 µm to 1000 µm, preferably 0.1 µm to 300 µm. Preferably, the solvent-free process is carried out from a binder comprising a composition comprising said polymer P1 in admixture with polymer P2a , P2b or a mixture P2a and P2b .

According to another aspect, the present invention provides a method of preparing an electrode by solvent-based route comprising the steps of:

- mixing in the presence of a solvent of said binder according to the present invention, of an active material and optionally of a conductive agent;

- depositing the mixture obtained in the previous step on a current collector to obtain an electrode;

- drying of said electrode.

In this method, said solvent may be water or an organic solvent or a mixture of both. Said organic solvent may be selected from the group consisting of n-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), triethylphosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethylketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate (EA), butyl acetate (BA), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), gamma-butyrolactone and N-butylpyrrolidone; and mixtures thereof.

According to another aspect of the present invention, a Li-ion battery is provided. Preferably, the Li-ion battery comprises a positive electrode, a negative electrode and a separator, at least one electrode being an electrode according to the present invention.

According to another aspect of the present invention, said composition according to the present invention can be used as a coating in a separator arranged between two electrodes. Said separator according to the present invention comprises a coating comprising, preferably consisting of, said composition according to the present invention, optionally arranged on one or both faces of a porous support. In this case, the coating is used to coat the support of a separator, on at least one face, in the form of a monolayer or multilayers. There is no particular limitation in the choice of the support which is coated with the coating of the invention, as long as it is a porous substrate having pores. When it comprises several layers, the coating as described in the present invention is arranged on the external face of the support, that is to say on the face which will first be in contact with the electrolytic composition used in the battery. Advantageously, the application of the coating to the support is done by aqueous or solvent route. The porous substrate may be in the form of a membrane or a fibrous fabric. When the porous substrate is fibrous, it may be a nonwoven web forming a porous web, such as a web obtained by direct spinning or melt blowing (of the "spunbond" or "melt blown" type) or electro-spinning. Examples of porous substrates useful in the invention as a support include, but are not limited to: polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, poly(phenylene oxide), poly(phenylene sulfide), polyethylene naphthalene or mixtures thereof. However, other heat-resistant engineering plastics may be used without particular limitation. Nonwoven materials made of natural and synthetic materials may also be used as the substrate of the separator. The porous substrate generally has a thickness of 1 to 50 µm, and are typically membranes obtained by extrusion and stretching (wet or dry processes) or cast nonwovens. The porous substrate preferably has a porosity of between 5% and 95%. The average pore size (diameter) is preferably between 0.001 and 50 µm, more preferably between 0.01 and 10 µm. The support may also be aluminum or aluminum coated with a polymer layer.

In addition to said composition, the separator coating may contain inorganic particles that serve to form micropores in the coating (the interstices between inorganic particles). The addition of inorganic particles may also contribute to heat resistance or improve wettability. In one embodiment, said coating comprises from 50 to 99 weight percent inorganic particles, based on the weight of the coating. These inorganic particles must be electrochemically stable (not subject to oxidation and/or reduction in the range of voltages used). In addition, the powdered inorganic materials preferably have high ionic conductivity. Low density materials are preferred over higher density materials because the weight of the produced battery can be reduced. The dielectric constant is preferably equal to or greater than 5. According to one embodiment, said inorganic particles are selected from the group consisting of: BaTiO3, Pb(Zr,Ti)O3, Pb 1-x LaxZryO3 (0<x<1, 0<y<1), PBMg3Nb2/3)3,PbTiO3, hafnia (HfO (HfO2), SrTiO 3, SnO2, CeO2, MgO, NiO, CaO, ZnO, Y2O3, bohemite (y-AlO(OH)), Al2O3, TiO2, SiC, ZrO2, boron silicate, BaSO4, nano-clays, or mixtures thereof. The separator coating may optionally comprise from 0 to 15% by weight based on the polymer, and preferably 0.1 to 10% by weight of additives, selected from thickeners, agents pH adjustment agents, anti-sedimentation agents, surfactants, wetting agents, fillers, anti-foaming agents and fugitive or non-fugitive adhesion promoters. The fillers mentioned here in the additives are different from the inorganic particles mentioned above.

According to another aspect of the present invention, a Li-ion battery is provided. Preferably, the Li-ion battery comprises a positive electrode, a negative electrode and said separator according to the present invention.

Examples

Example 1

In this example, two binders were tested. Comparative binder A 1 is a poly(vinylidene fluoride) homopolymer. Binder B 1 according to the invention is a mixture comprising 75% by weight of binder A 1 and 25% by weight of a poly(vinylidene fluoride) homopolymer from the recycling of a battery and comprising 0.5% of carboxymethylcellulose (Mw between 100,000 and 900,000). The melt viscosity of the poly(vinylidene fluoride) homopolymer is 48 to 52.5 kPoise measured at 230°C, a shear rate of 100s-1 according to ASTM D3835. An electrode composition for a cathode was prepared by the wet mixing method. A binder solution was prepared by dissolving the binder composition in NMP (9% solution in NMP). The conductive agent (carbon black C65) was added, mixed, and then diluted with NMP. The wet-mix formulation was prepared using a Thinky ARE-310 mixer. Carbon black was added to a Thinky cup, followed by the binder composition in the NMP solution. Mixing was carried out at 2000 rpm. The active material (NMC 811) was added to the NMP. The total amount of NMP was 3.36 mL. The resulting electrode composition was cast onto an aluminum foil using a doctor blade. The electrode was dried in an oven at 120°C to evaporate the NMP. The electrode was calendered and its physical properties were tested. Adhesion was measured by a 180° peel test in accordance with ASTM D903. The results are shown in Table 1. The ratio of NMC811/Binder/C65 is 97/1.5/1.5.

Examples Membership (N/m) Binder A1 (comparison) 136 Binder B1 (Invention) 142

As can be seen, binder B1 according to the present invention makes it possible to obtain better adhesion than binder A1. Binder B1 comprising compounds C1 as defined in the present application has a surprising advantage over the binder devoid of compound C1 and not derived from recycling.

Example 2

In this example, two binders were tested. Comparative binder A2 is a poly(vinylidene fluoride) homopolymer. Binder B2 according to the invention is a mixture comprising 75% by weight of binder A2 and 25% by weight of a poly(vinylidene fluoride) homopolymer from the recycling of a membrane and comprising 0.5% of poly(N-vinylpyrrolidone). The melt viscosity of the poly(vinylidene fluoride) homopolymer is 48 to 52.5 kPoise measured at 230°C, a shear rate of 100s-1 according to ASTM D3835. An electrode composition for a cathode was prepared by the wet mixing method. A binder solution was prepared by dissolving the binder in NMP (8% solution in NMP). The conductive agent (carbon black C65) was added, mixed, and then diluted with NMP. The wet-mix formulation was prepared using a Thinky ARE-310 mixer. The carbon black was added into a Thinky cup, followed by the binder composition in the NMP solution. The mixing was carried out at 2000 rpm. The active material (LFP) was added to the NMP. The total amount of NMP was 3.36 mL. The resulting electrode composition was cast onto an aluminum foil using a doctor blade. The electrode was dried in an oven at 120°C to evaporate the NMP. The electrode was calendered and its physical properties were tested. Adhesion was measured by a 180° peel test according to ASTM D903. The results are shown in Table 2. The LFP/Binder/C65 ratio is 94/3/3.

Examples Membership (N/m) Binder A2 (comparison) 70 Binder B2 (Invention) 90

As can be seen, binder B2 according to the present invention makes it possible to obtain better adhesion than binder A2. Binder B2 comprising compounds C1 as defined in the present application has a surprising advantage over the binder devoid of compound C1.

A power test was also carried out using the electrodes prepared above. The power test is used to evaluate the amount of energy that the battery can restore when subjected to increasingly rapid charge and discharge cycles. The charge is carried out in 10 hours (C/10, C representing 1 hour), the discharge ranges from 5 hours to 12.5 minutes. The battery tested also includes, in addition to the cathode as detailed above, a lithium metal anode. The electrolyte used is LiPF6 (1M) in an EC/EMC mixture 3/7 by volume (EC: ethyl carbonate; EMC: ethyl methyl carbonate). The results are presented in . As can be seen, the binder B2 according to the invention has a better discharge capacity than the comparative binder not comprising recycled PVDF.

Example 3

Two binders A3 and A4 are prepared in this example. Both binders have the same composition detailed in Table 3 below. Binder A3 is prepared by mixing a homopolymer of poly(vinylidene fluoride) having a melt viscosity of 48 to 52.5 kPoise measured at 230°C, a shear rate of 100s-1 according to ASTM D3835, CMC, C65, LiPF6 and ethylene carbonate (EC) in the proportions described below. Binder A4 is obtained by recycling a Li-ion battery via a process described in the present application.

HSV900 CMC C65 LiPF6 EC 96.4 0.5% 1% 0.1% 2%

An electrode composition for a cathode was prepared by wet mixing method from binders A3 and A4. A binder solution was prepared by dissolving the binder in NMP (8% solution in NMP). The conductive agent (carbon black C65) was added, mixed, and then diluted with NMP. The wet mixing formulation was prepared using a Thinky ARE-310 mixer. Carbon black was added to a Thinky cup, followed by the binder composition in the NMP solution. Mixing was carried out at 2000 rpm. The active material (LFP) was added to the NMP. The total amount of NMP was 3.36 mL. The resulting electrode composition was cast onto an aluminum foil using a doctor blade. The electrode was dried in an oven at 120 °C to evaporate the NMP. The electrode was calendered and its electrochemical properties were tested.

A power test was also carried out using the electrodes prepared above. The power test is used to assess the amount of energy that the battery can restore when subjected to increasingly rapid charge and discharge cycles. Charging is carried out in 10 hours (C/10, C representing 1 hour), and discharging ranges from 5 hours to 12.5 minutes. The battery tested also includes, in addition to the cathode as detailed above, a lithium metal anode. The electrolyte used is LiPF6 (1M) in an EC/EMC mixture 3/7 by volume (EC: ethyl carbonate; EMC: ethyl methyl carbonate). The results are presented in Table 4.

Examples Capacity @ C/2 Capacity @ 2C A3 binder 130 mAh/g 20 mAh/g A4 binder 135 mAh/g 50 mAh/g

As can be seen, the binder A4 according to the invention and resulting from the recycling of a battery has a better discharge capacity than the binder A3 obtained by a simple mixture of the different constituents. Indeed, the intimacy of the mixture obtained after recycling allows a better interaction between the different constituents. Despite everything, the binder A3 has a better capacity than a comparative binder A2 resulting from a virgin polymer.

Claims (17)

A composition comprising particles of a poly(vinylidene fluoride) polymer P1 comprising a compound C1 selected from the group consisting of a polymer P1 a comprising monomeric units derived from a monomer M1 selected from the group consisting of cellulose, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxypropylmethylcellulose and ethylmethylcellulose, a polymer P1 b comprising monomeric units derived from styrene and butadiene and a polymer P1 c comprising monomeric units derived from N-vinylpyrrolidone, or a mixture thereof;
characterized in that the mass content of compound C1 in said particles P1 of poly(vinylidene fluoride) is between 1 ppm and 5% based on the total weight of said particles P1 . Composition according to the preceding claim, characterized in that said particles of polymer P1 come from a poly(vinylidene fluoride) polymer recycled from an electrochemical device or from a membrane containing the latter. Composition according to any one of the preceding claims, characterized in that said polymer P1 is a homopolymer of poly(vinylidene fluoride) or a copolymer comprising monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1a selected from the group consisting of vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof; and optionally said polymer P1 comprises monomeric units derived from a monomer M1 b selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate. Composition according to any one of the preceding claims 1 or 2, characterized in that said polymer P1 comprises monomeric units derived from vinylidene fluoride and monomeric units derived from a monomer M1b selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxyethylhexyl(meth)acrylate and acryloyloxy propylsuccinate. Composition according to any one of the preceding claims, characterized in that it also comprises particles of a polymer P2 a comprising monomeric units derived from a monomer M2 a selected from the group consisting of vinylidene fluoride, vinyl fluoride; trifluoroethylene (VF ₃ ); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methylvinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE) and perfluoro(propylvinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); the product of formula CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ X in which X is SO ₂ F, CO ₂ H, CH ₂ OH, CH ₂ OCN or CH ₂ OPO ₃ H; the product of formula CF ₂ =CFOCF ₂ CF ₂ SO ₂ F; the product of formula F(CF ₂ )nCH ₂ OCF=CF ₂ in which n is 1, 2, 3, 4 or 5; the product of formula R ¹ CH ₂ OCF=CF ₂ in which R ¹ is hydrogen or F(CF ₂ )m and m is 1, 2, 3 or 4; the product of formula R ² OCF=CH ₂ in which R ² is F(CF ₂ )p and p is 1, 2, 3 or 4; perfluorobutyl ethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene or a mixture thereof. Composition according to any one of the preceding claims, characterized in that it also comprises particles of a polymer P2 b comprising monomeric units derived from a monomer M2 b of formula R1R2C=C(R3)C(O)R in which the substituents R1, R2 and R3 are independently of each other selected from the group consisting of H and C1-C5 alkyl; R is selected from the group consisting of –NHC(CH3)2CH2C(O)CH3 or –OR' with R' selected from the group consisting of H and C1-C18 alkyl optionally substituted by one or more –OH group(s) or a five- or ten-membered heterocycle comprising at least one nitrogen atom in its cyclic chain. Composition according to any one of the preceding claims, characterized in that said particles of polymer P1 also comprise a mass content of at least one lithium salt greater than 1 ppm based on the total weight of said particles P1 . Composition according to the preceding claim, characterized in that said at least one lithium salt is selected from the group consisting of LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiBF ₄ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ F)(SO ₂ CF ₃ ), LiN(SO ₂ F)(SO ₂ C ₂ F ₅ ), LiN(SO ₂ CF ₃ )(SO ₂ C ₂ F ₅ ), LiAsF ₆ , LiBF ₂ C ₂ O ₄ , LiNO ₃ , LiPF3(CF ₂ CF ₃ ) ₃ , LiBETI, LiTDI, or a mixture of these. Composition according to any one of the preceding claims, characterized in that said particles of the polymerP1also include a mass content of organic solventS1comprised from 1 ppm to 10% by weight based on the total weight of said particlesP1; said organic solvent S1having a donor number greater than 4 kcal/mol. Composition according to any one of the preceding claims, characterized in that said particles of polymer P1 also comprise a mass content of carbon particles P3 of between 1 ppm and 5% by weight based on the total weight of said particles P1 ; said carbon particles P3 being selected from the group consisting of graphite, such as natural or artificial graphite, graphene, carbon fibers or carbon nanotubes or carbon black. Composition according to any one of the preceding claims, characterized in that it has a clarity L* of between 10 and 99; the L* value comes from the luminance of the surface of said particle defined according to the CIELAB chromatic space and is measured according to the CIE D65 standard. Electrode binder comprising said composition according to any one of the preceding claims. Electrode composition comprising said binder according to the preceding claim, an active material and optionally a conductive agent. Electrode comprising said electrode composition according to the preceding claim deposited on at least one face of a current collector. Battery comprising at least one electrode according to the preceding claim. Separator arranged between two electrodes and comprising said composition according to any one of the preceding claims 1 to 11. Battery comprising said separator according to the preceding claim.