Molecular Crowding Solid Polymer Electrolytes for Lithium Metal Battery by In Situ Polymerization

Abstract Solid‐state polymer electrolytes (SPEs) require high ionic conductivity and dense contact with the electrodes for high‐performance lithium‐metal solid‐state batteries. However, massive challenges such as poor ionic migration ability, low antioxidant ability, and lithium dendrite formation still remain unresolved. These issues severely restrict its practical applications. Herein, a new type of solid‐state polymer electrolyte with a molecular crowding feature is rationally designed by in situ polymerization of a precursor containing poly (ethylene glycol) diacrylate (PEGDA) and 1,2‐dimethoxyethane (DME). Noticeably, the prepared SPE expands the electrochemical window to 4.7 V with a high lithium‐ion transfer number of 0.55 and a superior ionic conductivity of 3.6 mS cm −1 at room temperature. As a result, the lithium symmetrical batteries achieve stable cycles with more than 3000 h with no lithium dendrites at a current density of 0.5 mA cm −2 . Importantly, this design provides dense contact of solid‐state polymer electrolytes with the porous cathode and lithium anode, allowing the assembled winding‐type solid‐state pouch cells with outstanding cycling stability of 81.7% retention for more than 340 cycles at room temperature. It shows excellent adaption to widely practical technology with large‐scale battery production, offering a new solution for the future development of solid‐state polymer lithium‐metal batteries.