Polythiourea Superionic Conductors for Solid-State Batteries

Abstract

Polymer electrolytes are considered as solid-state ionic conductors for the next generation of lithium metal batteries. Particularly, poly(ethylene oxide)-based electrolytes have been extensively studied due to their excellent ion conductivity and interfacial compatibility. Since the lithium-ion transport is strongly coupled with segmental motion of polymer chains, there usually exists a dilemma between the ion conductivity and mechanical strength enhancement. Other problems of low ion conductivity at low temperature and low cation transference number further impede their practical applications in batteries. Here, we report a type of polythiourea solid-state electrolyte, which exhibits a superionic ion conducting behavior. The strong supramolecular interaction between the thiourea group and perchlorate anions promotes the dissolution of high concentration lithium salts in polythiourea. The conducting channel composed of high-density thiourea and percolating polar groups enables rapid cation transport along the polymer chain and even working at the glass state. The combined merits of high transference number, good ion conductivity, and excellent mechanical strength are achieved in this class of superionic ionic conductors, shedding light on alternative solutions for solid-state electrolytes in batteries.