Concentrated “ionogel-in-ceramic” and “ionogel-in-polymer” bilayer electrolyte membrane for high-voltage quasi-solid-state lithium metal batteries

Abstract

A crucial challenge for next-generation batteries depends on development of ideal electrolyte that is expected to demonstrate peculiarity of free-standing membrane with superior conductivity and controlled thickness, along with interface compatibility toward both Li metal anode and high-voltage cathodes. We describe a unique concentrated bilayer electrolyte membrane and validate an electrolyte design strategy based on the integration of ionogel-in-ceramic layer (∼30 μm) and ionogel-in-polymer layer (∼7 μm) that establishes well-percolated Li+ transport and tackles interface issues to address the requirements for electrolyte. The concentrated bilayer electrolyte membrane shows a superior ionic conductivity of 8 × 10−4 S cm−1 at 25 °C, pretty low electronic conductivity of 2.69 × 10−11 S cm−1, and wide electrochemical stability window of 5.5 V vs Li/Li+. It is revealed that the electrolyte membrane enhances Coulombic efficiency to ∼92%, which is ascribed to flat Li plating/stripping and mixed-lithiophobic-conductive LiF-Li3N solid electrolyte interphase. Application of the electrolyte membrane in LiǁLiNi0.8Co0.1Mn0.1O2 quasi-solid-state lithium metal batteries further demonstrates improved cycling performance. Our study, therefore, provides an alternative electrolyte design strategy and a promising electrolyte membrane for high-energy-density quasi-/solid-state batteries.