Provided is a rechargeable alkali metal-selenium cell comprising an anode active material layer, an electrolyte, and a cathode active material layer containing multiple particulates of a selenium-containing material selected from a selenium-carbon hybrid, selenium-graphite hybrid, selenium-graphene hybrid, conducting polymer-selenium hybrid, a metal selenide, a Se alloy or mixture with Sn, Sb, Bi, S, or Te, a selenium compound, or a combination thereof and wherein at least one of the particulates comprises one or a plurality of selenium-containing material particles being embraced or encapsulated by a thin layer of an elastomer having a recoverable tensile strain no less than 5% when measured without an additive or reinforcement, a lithium ion conductivity no less than 10−7 S/cm at room temperature, and a thickness from 0.5 nm to 10 μm This battery exhibits an excellent combination of high selenium content, high selenium utilization efficiency, high energy density, and long cycle life.