Ionic liquid assisted quasi-solid-state polymer electrolyte for rechargeable lithium metal batteries operating at room temperature

Abstract

Solid-state electrolytes are emerging as a promising approach to improve the safety and cycle life of lithium metal batteries (LMBs). However, low ionic conductivity, narrow potential window and deficient interfacial contact with the electrodes greatly hinder their practical applications. Herein, an ionic liquid (IL)-assisted quasi-solid-state polymer electrolyte (QSPE) by incorporating functional Pyr14TFSI into the PVDF matrix is developed. Profitted from the inherent interaction between the IL and polymer, the optimizedly-designed QSPE holds favorable overall properties including ionic conductivity, electrochemical window, Li ion transfer number and mechanical strength. Moreover, the SEM, XPS and EIS analyses reveal that the released IL under external pressure during cell assembly serves as a in-situ electrode surface wetting agent to promote ionic transport and charge transfer, as well as a solid/electrolyte interphase modifier to mitigate the electrolyte degradation and homogenize Li deposition. Consequently, the assembled quasi-solid-state LMBs demonstrate superior cycle and rate capability at room temperature.