Organic Ionic Plastic Crystal‐polymer Solid Electrolytes with High Ionic Conductivity and Mechanical Ability for Solid‐state Lithium Ion Batteries

Abstract Solid electrolytes (SEs) would be an ideal solution to safety concerns, miniaturization and increase of energy density; however, SEs are difficult to have high ionic conductivity and mechanical properties simultaneously. In this work, we firstly synthesize a novel class of ammonium‐based organic ionic plastic crystals (OIPCs), then prepare SE system by blending synthesized OIPC with poly(vinylidenefluoride‐co‐hexafluoropropylene) (P(VDF‐HFP)) and lithium bis(fluorosulfonyl)imide (LiFSI). Such SEs overcome most of the limitations, with attractive ionic conductivity and lithium ion transference number, excellent mechanical properties, high electrochemical stability, as well as satisfactory interfacial stability with lithium metal. In particular, Li/LiFePO 4 cells employing as‐prepared SE exhibit high discharge capacity, favorable cycling and rate performance at 30 °C, which is comparable to those using liquid electrolytes. The reported SE system, combined with excellent overall performance, is expected to have great potential for application in solid‐state lithium ion batteries.