An electrolyte composite including a first block copolymer and a lithium ion conductor, wherein the first block copolymer includes i) a structural domain and ii) at least one of a rubbery domain and an ion conductive domain, wherein the structural domain includes a polymer segment including a structural repeating unit, wherein the rubbery domain includes a polymer segment including a rubbery repeating unit, and wherein the ion conductive domain includes a polymer segment including an ion conductive repeating unit.