Provided is lithium secondary battery comprising a cathode, an anode, and an electrolyte or separator-electrolyte assembly disposed between the cathode and the anode, wherein the anode comprises: (a) a foil or coating of lithium or lithium alloy; and (b) a thin layer of a high-elasticity polymer disposed between the foil/coating and the electrolyte (or separator-electrolyte assembly), 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 1 nm to 10 μm, wherein the high-elasticity polymer contains a cross-linked network of polymer chains having an ether linkage, nitrile-derived linkage, benzo peroxide-derived linkage, ethylene oxide linkage, propylene oxide linkage, vinyl alcohol linkage, cyano-resin linkage, triacrylate monomer-derived linkage, tetraacrylate monomer-derived linkage, or a combination thereof in the cross-linked network of polymer chains.