Pure bulk ion-conducting membrane for high-energy-density batteries

Abstract

Solid electrolytes (SE) are key components for the safe and continuous operation of high-energy lithium metal batteries. Metal oxide SEs, which are stable under ambient conditions, are used as separators in the form of thick and heavy plates; however, this reduces the specific energy of practical battery cells. Despite considerable efforts, the development of thin SE separators with high ionic conductivities has remained a significant challenge. This paper reports the scalable production of a thin membrane comprising single-crystal SE particles that are bicontinuously embedded in a polymer matrix to form ion-conducting channels. The membrane exhibits a high ionic conductivity of 6.0 × 10−4 S cm−1 with remarkably low activation energy (20-times greater than that of current membranes with polycrystalline SE particles), eliminating large grain boundary resistances. The high conductivity enables stable lithium metal stripping and plating, producing a homogeneous ion flow to the lithium metal. Furthermore, a lithium metal–air battery cell using the membrane demonstrates a high specific energy of 700 Wh kg−1.