Fast-cure gel polymer electrolytes are prepared by trapping an oligo(alkylene glycol)siloxane or silane in a three dimensional polymer matrix. An ion-conducting phase of the electrolyte contains a siloxane or silane compound and a lithium salt. Such siloxanes or silanes include a silicon or silicon oxide group having four or less substituents that is an oligo(alkylene glycol), or cyclic carbonate moiety.