A family of lithium-ion-conducting composite polymer-glass electrolytes containing the glass composition 14Li2O-9Al(2)O(3)-38TiO(2)-39P(2)O(5) (abbreviated as (LiAlTiP)(x)O-y) with high ionic conductivity, an excellent electrochemical stability range, and high compatibility with lithium insertion anodes is described. An optimized composition has a room temperature conductivity of 1.7 x 10(-4) S cm(-1), an Li+ transference number of 0.39, and an electrochemical stability window to +5.1 V versus Li/Li+. It also has good interfacial stability under both open-circuit and lithium metal plating-stripping conditions and provides good shelf-life.