NOVELTY - Solid polymer electrolyte comprises at least one polymer compound having a poly-or oligo-carbonated group (I) and at least one electrolyte salt.    USE - For lithium batteries, electric double layer capacitor (claimed) and for various electrochemical elements.    ADVANTAGE - The inorganic oxide improves strength and uniformity of the film thickness and generates fine vacancy between the inorganic oxide and the polymer. The inorganic oxide enables free dispersion of electrolytic solution into the solid polymer electrolyte into the vacancy resulting in elevated ion conductivity and ion mobility without impairing the effect of improving the strength. Viscosity of the polymerizable composition increases and separation of the polymer and the solvent is inhibited by adding the inorganic oxide. The polymer electrolyte has high strength even when formed into a thin film having a thickness on the order of tens of mum, high ion conductivity, excellent workability, high-temperature characteristics and large current characteristics. The battery or electric double layer capacitor using the solid polymer electrolyte can be used for long period of time, avoiding fear of liquid leakage. The battery has good cycle property, excellent safety, reliability and can work in high capacity and high current.    DETAILED DESCRIPTION - Solid polymer electrolyte comprises at least one polymer compound having a poly-or oligo-carbonated group of formula (I), and at least one electrolyte salt.    INDEPENDENT CLAIMS are also included for:    (i) a lithium battery comprising a cathode composed of lithium, lithium alloy or carbon material, inorganic oxide, inorganic chalcogenide or an electro-conductive polymer compound, each capable of occluding and releasing lithium ions;    (ii) an electric double layer capacitor comprising the polarizable electrodes, disposed through the solid polymer electrolyte as ion conductive material;    (iii) a process for producing a solid polymer electrolyte which involves disposing at least one heat and/or active ring polymerizable compound having the poly- or oligo- carbonate group, a polymerizable functional group and a polymerizable composition containing at least one electrolyte salt, or at least one organic solvent and/or at least one inorganic oxide on a support and polymerizing the polymerizable composition;    (iv) the process of producing a battery;    (v) the process for producing an electric double layer capacitor; and    (vi) a polymerizable compound (IV).    R1, R4 = 1-10C straight chain, branched and/or cyclic divalent group optionally containing a hetero atom;    m = 3-10;    n = 2-1000;    R2, R3 = H, 1-6C alkyl; and    R5 = 1-20C straight chain, branched and/or cyclic organic group optionally containing a hetero atom.