Formation of Stable Interphase of Polymer-in-Salt Electrolyte in All-Solid-State Lithium Batteries

The integration of solid-polymer electrolytes into all-solid-state lithium batteries is highly desirable to overcome the limitations of current battery configurations that have a low energy density and severe safety concerns.Polyacrylonitrile is an appealing matrix for solid-polymer electrolytes;however,the practical utilization of such polymer electrolytes in all-solid-state cells is impeded by inferior ionic conductivity and instability against a lithium-metal anode.In this work,we show that a polymer-in-salt electrolyte based on polyacrylonitrile with a lithium salt as the major component exhibits a wide electrochemically stable window,a high ionic conductivity,and an increased lithium-ion transference number.The growth of dendrites from the lithium-metal anode was suppressed effectively by the polymer-in-salt electrolyte to increase the safety features of the batteries.In addition,we found that a stable interphase was formed between the lithium-metal anode and the polymer-in-salt electrolyte to restrain the uncontrolled parasitic reactions,and we demonstrated an all-solid-state battery configuration with a LiFePO4 cathode and the polymer-in-salt electrolyte,which exhibited a superior cycling stability and rate capability.