Safe, Superionic Conductive and Flexible “Polymer-in-plastic salts” Electrolytes for Dendrite-free Lithium Metal Batteries

Abstract Solid polymer electrolytes (SPEs) garner tremendous attention for both enabling higher energy density battery chemistry and alleviating the safety concerns of liquid electrolytes, but the practical utilizations of SPEs are severely hindered by the limited room temperature ionic conductivity, low transference number and huge interface impedance. Unlike the polymer chain movement in traditional SPEs, in the present work, we develop novel “polymer-in-plastic salts” electrolytes (PIPSEs) via a high weight ratio of plastic salts to polymer in which polymer just function as framework so that non-flammable, superionic conductive and flexible SPEs can be obtained. Also, the high content of plastic salts in PIPSEs can wet electrodes and form compatible solid electrolyte interface (SEI) with lithium metal. As a consequence, solid-state dendrite-free symmetric Li cells with PIPSEs show ultralong cycle life over 1000 h under up to 2.0 mA cm−2 and Li/LiFePO4 and high-voltage Li/LiNi0.6Co0.2Mn0.2O2 cells utilizing above PIPSEs exhibit excellent cycle performance and appealing rate performance. It is anticipated that our work provides a new strategy for the next-generation solid-state batteries.