Organic ionic plastic crystal enhanced interface compatibility of PEO-based solid polymer electrolytes for lithium-metal batteries

Abstract

Polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) are appealing solid electrolytes for lithium-metal batteries (LMBs) due to their high safety, low cost and flexibility. However, PEO'snarrow electro-chemical potential window and poor interfacial compatibility with the electrode restrict PEO-based SPE development. Herein, we used a solution-casting method to prepare PEO-based SPE membranes reinforced with an organic ionic plastic crystal—N,N-diethylpyrrolidinium bis(fluorosulfonyl)amide (C2epyrFSI). The as-prepared SPE exhibits high ionic conductivity of 3.02 × 10−4 S cm−1 at 50 °C, an extremely wide electro-chemical window (5.1 V) and flexible mechanical properties. Using SPE, the Li symmetric cells can cycle for 2000 h at a current density of 0.1 mA cm−2 without short circuiting at 50 °C. Furthermore, the Li|SPE|LiFePO4 all-solid-state LMBs have a high initial discharge specific capacity of 157.3 mAh g−1 at 0.2C and a capacity retention rate of 96% after 120 cycles. This study shows that the PEO-C2epyrFSI SPE is a promising electrolyte for all-solid-state LMBs.