a rechargeable battery comprises lithium intercalation compound electrodes and an interposed electrolyte of flexible polymer containing a lithium salt dissolved in a polymer - compatible solvent . preferred components include tertiary lithium manganese oxide compound positive electrodes , carbon negative electrodes , and poly copolymer electrolyte layers containing about 20 to 70 % of a solution of lithium salt in a medium boiling solvent comprising such solvents as ethylene carbonate , propylene carbonate , and dimethyl carbonate . the electrolyte layers may be employed in the form of individual separator films or as a coated component of multilayer battery structures to provide electrical ionic conductivity up to about 10 - 3 s / cm .