A process for manufacturing a polymer electrolyte separator based on a fluoropolymer hybrid organic/inorganic composite, said process comprising: (i) providing a mixture of: - at least one fluoropolymer comprising recurring units derived from at least one (meth)acrylic monomer [monomer] of formula: wherein each of R1, R2, R3, equal or different from each other, is independently a hydrogen atom or a C 1 -C 3 hydrocarbon group, and R OH is a C 1 -C 5 hydrocarbon moiety comprising at least one hydroxyl group [polymer]; - at least one metal compound [compound] of formula: X 4-m AY m 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, X is a hydrocarbon group, optionally comprising one or more functional groups; and - at least one electrolyte; and - at least one liquid plasticizer; (ii) reacting at least a fraction of hydroxyl groups of the R OH groups of said monomer of said polymer with at least a fraction of said compound, so as to obtain a grafted polymer comprising pendant -Y m-1 AX 4-m groups, with m, Y, A and X having same meaning as above detailed; (iii) hydrolyzing and/or polycondensing compound and/or pendant -Y m-1 AX 4-m groups, as above detailed to yield a liquid mixture comprising fluoropolymer hybrid organic/inorganic composite comprising inorganic domains and incorporating solvent and electrolyte; and (iv) casting a film from the liquid mixture obtained in (iii); (v) drying the film obtained in (iv) for obtaining the polymer electrolyte separator. (i) providing a mixture of: - at least one fluoropolymer comprising recurring units derived from at least one (meth)acrylic monomer [monomer] of formula: wherein each of R1, R2, R3, equal or different from each other, is independently a hydrogen atom or a C 1 -C 3 hydrocarbon group, and R OH is a C 1 -C 5 hydrocarbon moiety comprising at least one hydroxyl group [polymer]; - at least one metal compound [compound] of formula: X 4-m AY m 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, X is a hydrocarbon group, optionally comprising one or more functional groups; and - at least one electrolyte; and - at least one liquid plasticizer; - at least one fluoropolymer comprising recurring units derived from at least one (meth)acrylic monomer [monomer] of formula: - at least one metal compound [compound] of formula: X 4-m AY m 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, X is a hydrocarbon group, optionally comprising one or more functional groups; and - at least one electrolyte; and - at least one liquid plasticizer; (ii) reacting at least a fraction of hydroxyl groups of the R OH groups of said monomer of said polymer with at least a fraction of said compound, so as to obtain a grafted polymer comprising pendant -Y m-1 AX 4-m groups, with m, Y, A and X having same meaning as above detailed; (iii) hydrolyzing and/or polycondensing compound and/or pendant -Y m-1 AX 4-m groups, as above detailed to yield a liquid mixture comprising fluoropolymer hybrid organic/inorganic composite comprising inorganic domains and incorporating solvent and electrolyte; and (iv) casting a film from the liquid mixture obtained in (iii); (v) drying the film obtained in (iv) for obtaining the polymer electrolyte separator.