The present invention relates to an improved secondary battery having high weight energy density and good reversibility, more specifically, a battery containing i) a positive electrode comprising a reversible positive electrode material containing an organosulfur compound wherein sulfur-sulfur bond is formed upon oxidation and sulfur-sulfur bond is cleaved upon electrolytic reduction, an electroactive component selected from main group elements compound, electrically conductive ingredients and a current collector containing copper metal; ii) a polymer electrolyte having lithium salt; and iii) a negative electrode made of lithium metal, lithium alloy or lithium intercalating carbon.