Provided is a rechargeable alkali metal-sulfur cell comprising an anode active material layer, an electrolyte, and a cathode active material layer containing multiple particulates of a sulfur-containing material selected from a sulfur-carbon hybrid, sulfur-graphite hybrid, sulfur-graphene hybrid, conducting polymer-sulfur hybrid, metal sulfide, sulfur compound, or a combination thereof and wherein at least one of the particulates is composed of one or a plurality of sulfur-containing material particles being embraced or encapsulated by a thin layer of a high-elasticity ultra-high molecular weight polymer having a recoverable tensile strain no less than 2%, a lithium ion conductivity no less than 10−6 S/cm at room temperature, and a thickness from 0.5 nm to 10 μm This battery exhibits an excellent combination of high sulfur content, high sulfur utilization efficiency, high energy density, and long cycle life.