Composite electrodes

1. An electrode-forming composition [composition (C1)] comprising:

at least one partially fluorinated fluoropolymer [polymer (F)], wherein polymer (F) is a functional partially fluorinated polymer [polymer (FF-2)] comprising recurring units derived from at least one fluorinated monomer [monomer (F)] and at least one hydrogenated monomer comprising at least one hydroxyl end group [monomer (H OH )],

at least one electro-active compound [compound (EA)],

at least one metal compound [compound (M)] of formula (V):

X 4-m AY m   (V)

wherein m is an integer from 1 to 4, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group, optionally comprising one or more functional groups,

an electrolyte medium comprising at least one metal salt [medium (EL)],

at least one organic solvent [solvent (S)] selected from the group consisting of alcohols, ketones, linear or cyclic esters, linear or cyclic amides and dimethyl sulfoxide, and

optionally, at least one conductive agent [compound (C);

wherein at least one of the metal compounds (M) is grafted to polymer (FF-2) by at least one of the hydroxyl end groups of the hydrogenated monomer (H OH ) through at least one —O-A bond.

2. The composition (C1) according to claim 1 , wherein the polymer (F) is selected from the group consisting of:

polymers (F-1) comprising recurring units derived from vinylidene fluoride (VDF) and, optionally, at least one fluorinated monomer [monomer (F)] different from VDF, and

polymers (F-2) comprising recurring units derived from at least one per(halo)fluorinated monomer [monomer (FX)] selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE), at least one hydrogenated monomer [monomer (H)] selected from ethylene, propylene and isobutylene and, optionally, at least one monomer (F) different from said monomer (FX).

3. The composition (C1) according to claim 1 , wherein the compound is of formula (VI):

R A 4-m′ A(OR B ) m′   (VI)

wherein m′ is an integer from 1 to 4, A is a metal selected from the group consisting of Si, Ti and Zr, R A and R B , equal to or different from each other and at each occurrence, are independently selected from C 1 -C 18 hydrocarbon groups, optionally comprising one or more functional groups.

4. The composition (C1) according to claim 1 , wherein the compound is either a non-functional compound (M) or a functional compound (M).

5. The composition (C1) according to claim 1 , wherein the medium (EL) comprises the at least one metal salt and at least one organic carbonate.

6. The composition (C1) according to claim 1 , wherein the medium (EL) comprises the at least one metal salt, at least one ionic liquid and, optionally, at least one organic carbonate.

7. A process for the manufacture of a composite electrode [electrode (CE)], said process comprising:

(i) providing an electrode [electrode (E)] comprising:

a metal substrate and

directly adhered onto one surface of said metal substrate, at least one layer [layer (L1)] made from a composition comprising at least one functional partially fluorinated fluoropolymer [polymer (FF)], at least one electro-active compound [compound (EA)] and, optionally, at least one conductive agent [compound (C)];

(ii) providing the electrode-forming composition [composition (C1)] according to claim 1 ;

(iii) applying the composition (C1) provided in step (ii) onto the surface of the electrode (E) provided in step (i) thereby providing a surface-coated electrode; and

(iv) drying the surface-coated electrode provided in step (iii).

8. The process according to claim 7 , wherein the electrode [electrode (E)] is obtainable by:

(j) providing a metal substrate;

(jj) applying onto one surface of the metal substrate provided in step (j) an electrode-forming composition [composition (C2)] comprising:

at least one functional partially fluorinated fluoropolymer [polymer (FF)],

at least one electro-active compound [compound (EA)],

at least one organic solvent [solvent (S)] and

optionally, at least one conductive agent [compound (C)]

thereby providing a surface-coated electrode; and

(jjj) drying the surface-coated electrode provided in step (jj).

9. The process according to claim 8 , wherein the composition (C2) is free from an electrolyte medium comprising at least one metal salt [medium (EL)].

10. The process according to claim 7 , wherein the polymer (FF) is a functional partially fluorinated fluoropolymer [polymer (FF-1)] comprising recurring units derived from vinylidene fluoride (VDF), at least one hydrogenated monomer comprising at least one functional end group [monomer (HF)], said monomer (HF) comprising at least one functional end group selected from a hydroxyl end group and a carboxylic acid end group, and, optionally, at least one monomer (F) different from VDF.

11. The process according to claim 10 , wherein the monomer (HF) is of formula (III-A):

wherein R′1, R′2 and R′3 are hydrogen atoms and R″X is a hydrogen atom or a C1-C5 hydrocarbon group comprising at least one hydroxyl group.

12. A composite electrode [electrode (CE)] obtained by the process according to claim 7 .

13. The electrode (CE) according to claim 12 , comprising:

a metal substrate,

directly adhered onto one surface of said metal substrate, at least one layer [layer (L1)] made from a composition comprising at least one functional partially fluorinated fluoropolymer [polymer (FF)], at least one electro-active compound [compound (EA)] and, optionally, at least one conductive agent [compound (C)] and

directly adhered to said layer (L1), at least one layer [layer (L2)] made from a composition comprising at least one partially fluorinated fluoropolymer [polymer (F)], at least one electro-active compound [compound (EA)], an electrolyte medium comprising at least one metal salt [medium (EL)] and, optionally, at least one conductive agent [compound (C)].

14. A secondary battery comprising:

a positive electrode,

a negative electrode and

between said positive electrode and negative electrode, a membrane,

wherein at least one of the positive electrode and the negative electrode is the composite electrode [electrode (CE)] according to claim 12 .