Stable cycling of lithium metal electrode in nanocomposite solid polymer electrolytes with lithium bis(fluorosulfonyl)imide

Nanocomposite solid polymer electrolytes (NSPEs) comprising lithium salt based on two representative sulfonylimide anions (i.e., bis(fluorosulfonyl)imide ([N(SO2F)2]−, FSI−) and bis(trifluoromethanesulfonyl)imide ([N(SO2CF3)2]−, TFSI−)) have been prepared by simply dissolving the corresponding lithium salt in poly(ethylene oxide) matrix in the presence of inert nano-sized Al2O3 fillers. The physicochemical and electrochemical properties of the FSI- and TFSI-based NSPEs are investigated, in terms of phase transition, ion transport behavior, chemical and electrochemical compatibility with Li metal. With the addition of nano-sized Al2O3 fillers, a significant improvement in chemical and electrochemical compatibility with Li metal has been observed in both the FSI- and TFSI-based NSPEs. Particularly, the symmetric cell using the FSI-based NSPE can be continuously cycled for >1000h at 70°C. The Li|LiFePO4 cell with the FSI-based NSPEs shows good cycling stability and capacity retention. These promising results make them attractive electrolytes for safe and stable rechargeable Li metal batteries. [Display omitted] •Nanocomposite solid polymer electrolyte (NSPE) with Li[N(SO2F)2] is prepared.•The NSPE shows high conductivity and good compatibility with Li metal.•Highly stable cycling of the Li|LiFePO4 cell is obtained in the NSPE.