NOVELTY - Fluorinated but not perfluorinated ionomers with a polyethylene backbone and pendant fluoroalkoxy sulfonic acid and sulfonic acid salt groups provide a solution to the long-standing problem of obtaining ionomers comprising monomer vinylidene fluoride (VDF) units resistant to attack by bases.    USE - The ionomers are useful in electrochemical applications, e.g. batteries, fuel cells, electrolysis cells, ion exchange membranes, sensors, electrochemical capacitors, and modified electrodes.    ADVANTAGE - In contrast to previous ionomers, the new ionomers in combination with preferably 50 - 200 wt.% of solvents suitable for electrochemical applications, especially lithium batteries, show good melt processability with no decrease in optimum battery performance.    DETAILED DESCRIPTION - An ionomer (preferably having a melting point of more than 150 degreesC) comprises monomer VDF units and a perfluoroalkenyl monomer having an ionic pendant group of formula (I): -(O-CF2CFR)aO-CF2(CFR')bSO3-M+ where    R, R' = F, Cl, or perfluorinated 1 - 10C alkyl;    a = 0 - 2;    b = 0 - 6; and    M+ = H+ or a univalent metal cation.    INDEPENDENT CLAIMS are included for:    (1) an ionomer formation process involving contacting a polymer comprising monomer VDF units and a perfluoroalkenyl monomer having a pendant group of formula: -(O-CF2CFR)aCF2(CFR')bSO2F, where R and R' = as above, with a mixture of alkali metal salt and solvent for time sufficient to obtain required degree of conversion to alkali metal sulfonate form of polymer;    (2) a process for forming ionically functionalized olefin comprising contacting a functionalized olefin of formula: CF2=CF-(O-CF2CFR)aO-CF2(CFR')bSO2F, where R and R = as above with a mixture of alkali metal salt and solvent for time sufficient to obtain required degree of conversion to alkali metal sulfonate form of olefin;    (3) a process for forming an ionomer comprising polymerization of the above ionically functionalized olefin with vinylidene fluoride in aqueous medium in which olefin concentration in the medium is about 1 - 50 %;    (4) an ionically conductive composition comprising above ionomer and liquid imbibed in it;    (5) an ionically conductive electrically insulating polymer film or sheet with a gel imbibed in its micropores;    (6) an electrode comprising at least 1 electrode active material, the above ionomeric polymer mixed in it, and a liquid imbibed in it;    (7) an electrochemical cell comprising positive and negative electrode, a separator between them, and a means for connecting the cell to an outside load or source wherein at least 1 of the separator and two electrodes comprises the above ionically conductive composition;    (8) a process for forming shaped articles by combining above ionomer with solvent, melting, forming and cooling the shaped article.