Patent ID: 6878491

Claim:
A solid polymer electrolyte comprising: (I) a crosslinked material of a polyether copolymer; (II) an electrolyte salt compound; and (III) a plasticizer which may be added if necessary and is selected from the group consisting of an aprotic organic solvent, a derivative or a metal salt of a linear or branched polyalkylene glycol, and a metal salt of said derivative, wherein the polyether copolymer having a weight-average molecular weight of 10 5 to 10 7 , comprises as a main chain: A) 3 to 30% by mol of a repeating unit (I′), derived from propylene oxide; B) 96 to 69% by mol of a repeating unit (II′), derived from ethylene oxide; and CH 2 —CH 2 —O (II′) C) 0.01 to 15% by mol of a repeating unit (III′-1) and/or (III′-2), derived from a crosslinkably reactive monomer; wherein R 1 and R 2 are groups each having a reactive functional group.