A strongly complexed solid polymer electrolyte enables a stable solid state high-voltage lithium metal battery

A solid-state electrolyte with a wide electrochemical window, high Li-ion conductivity, and anti-dendritic growth properties are required for high-energy-density solid-state batteries. Here, we reported a polyglycol oxide-based solid electrolyte constructed by incorporating a deep eutectic solvent within a dual crosslinked network. The combination of N-methylurea shielding the active ether group in the polyglycol chain and the quadruple hydrogen bond interactions result in the formation of an all solid polyglycol oxide-based electrolyte (ASPE) with an electrochemical window of 5.2 V. The newly developed ASPE demonstrates high ionic conductivity, uniform Li deposition, and high Li plating/stripping efficiencies. Facile in situ polymerization applications of ASPE in Li-LiFePO4, Li-LiCoO2, and Li-Li1.2Ni0.13Co0.13Mn0.54O2 batteries further show the diversity of the ASPE and its ability to achieve a high Coulombic efficiency and long life. Our finding deviates from the conventional wisdom of designing polymer electrolytes, demonstrating a promising direction for safe, high-energy, and long-life solid-state Li metal batteries.