TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Group: The chemically cross-linkable functional group is chosen from oxetane group and alicyclic epoxy group.Preferred Solvent: The solvent contains cyclic ester, cyclic carbonate, linear carbonate, cyclic ether, chain shaped ether and/or nitrile.Preferred Solute: The solute is a redox system constituent, which consists of iodine or iodine compound, preferably lithium salt.    TECHNOLOGY FOCUS - POLYMERS - Preferred Electrolyte: The molar ratio (m/n) of m mol of cross-linkable polymerizable monomer, and n mol of another polymerizable monomer, is 1-20-2/1.Preferred Monomer: The monomer which contains oxetane group has structure of formula (1), and monomer containing alicyclic epoxy group, has structure of formula (2). The other polymerizable monomer is vinyl type monomer having Q value of 0-1.5, solubility parameter of homopolymer of 17-30, and has structure of formula (3). The polymer (B) contains vinylidene fluoride as monomer component, such as vinylidene fluoride hexafluoro propylene copolymer. The weight ratio of polymer (A) and polymer (B) is 0.5-10 wt.% and 5-30 wt.% respectively, with respect to whole of gel-form electrolyte.R1,R3,R4=H or 1-3C alkyl;R2=1-6C alkyl; andR5=1-6C alkyl, hydroxyl alkyl group or alkylene oxide group. EXAMPLE - A polymerizable monomer of formula (1), and another polymerizable monomer of formula (3) of Q value 0.78, solubility parameter value 18.6, were copolymerized in a molar ratio of 1/3. The obtained cross-linkable polymer compound had weight average molecular weight of 3x105. Tetrapropyl ammonium iodide of 0.5 mol/dm3 and iodine of 0.01 mol/dm3, were dissolved in gamma-butyrolactone of SP value 26.2, and an electrolyte liquid was obtained. The cross-linkable polymer compound was dissolved in the electrolyte liquid and polymer solution (A) was obtained. Power Flex LGB1 (RTM: vinylidene fluoride-hexafluoro propylene copolymer) (20 weight parts), was mixed with the electrolyte liquid (A) (68 weight parts) and tricresyl borate (2 weight parts). The polymer solution (A) (10 weight parts) was added and the gel-form electrolyte precursor was produced. The precursor was cast to a thickness of 200 microns and heated at 75degreesC in closed state for 1 hour and cooled. A gel-form electrolyte film was obtained. The electrolyte film had excellent mechanical strength in normal temperature, shape stability and ionic conductivity.