Fabrication of a Dendrite‐Free all Solid‐State Li Metal Battery via Polymer Composite/Garnet/Polymer Composite Layered Electrolyte

Abstract While all‐solid‐state Li metal batteries based on ceramic solid‐electrolytes offer higher energy density and better safety features over their liquid counterparts, critical challenges in their design such as high electrode–electrolyte interface resistance and formation of Li‐dendrites still remain unsolved. To address the issues, an intimate contact between Li and the solid‐state electrolyte is necessary. Herein, a flexible and mechanically robust polymer membrane comprising of poly(ethylene oxide), lithium perchlorate, and garnet particles is used as an interlayer between Li metal and garnet ceramic electrolyte. The Li salt enhances the ionic conductivity of the membranes and ensures their flexible nature while garnet particles enhance their mechanical strength. The cells comprising of composite membranes results in four times smaller charge transfer resistance at the interface and demonstrate stable and reversible Li plating/stripping voltage profiles. Further, the polymer composite membrane mechanically blocks the formation of Li dendrites at reasonably high currents (0.1 mA cm −2 ) in the structures even after prolonged cycling (140 h) owing to their enhanced toughness. With smaller charge transfer resistance (≈400 Ω cm 2 at room temperature), stability at extended periods of cycling and no Li‐dendrite formations, the structures can prove a viable electrolyte candidate for advanced solid‐state Li metal batteries.