Constructing stable ordered ion channels for a solid electrolyte membrane with high ionic conductivity by combining the advantages of liquid crystal and ionic liquid

Abstract

The advantages of solid-state polymer electrolytes (SPEs) such as ease of fabrication, high safety, good compatibility with Li metals make SPEs one of the most promising electrolyte materials for next generation high-performance and high-safety lithium-ion batteries (LIBs). However, the traditionally used PEO-based electrolytes usually exhibit very low ionic conductivity due to the high crystallinity of PEO, which impedes the commercialization of solid-state LIBs using PEO-based polymer electrolytes. In this study, an ‘alternative’ solid electrolyte material was prepared using a nematic liquid crystal (LC) and an ionic liquid (IL). Specifically, the LC with ordered layered nanostructures was polymerized and immobilized via UV-irradiation, while IL was sufficiently inserted into the ordered ion channels for fast transport ions. It should be noted that such a free-standing electrolyte film with stable ordered channels has been confirmed through the characterizations of DSC, POM, SEM and XRD. As a result, the solid electrolyte film shows superior comprehensive electrochemical performance in terms of a very high room temperature ionic conductivity (2.14 × 10⁻² S cm⁻¹), wide electrochemical window (4.8 V), and very good compatibility with lithium metal. Furthermore, the LiFePO₄/Li cell using the ordered electrolyte film shows an average discharge capacity of 150 mA h g⁻¹. Undoubtedly, our study provides a new solid electrolyte material that has the potential to be used in the next generation of high safety and high energy density LIBs.