Boron nitride nanofibers enhanced composite PEO-based solid-state polymer electrolytes for lithium metal batteries

Polyethylene oxide (PEO)-based solid-state polymer electrolytes (SPEs) are limited by their poor cyclic stability and inferior ionic conductivity for applicating in high-safety, long-cycling and high-energy-density lithium metal batteries. Herein, porous boron nitride nanofibers (BNNFs) are filled into PEO-based SPE, which significantly suppresses Li dendrites growth and enhances the electrochemical performance of Li metal battery. BNNFs with high porosity have more active sites to connect with PEO, which can effectively reduce the crystallinity of the PEO matrix and enhance its ionic conductivity. Moreover, owing to the hardness and good stability of BNNFs, BNNFs/PEO/LiTFSI electrolyte exhibits a wider electrochemical window, better mechanical property and higher thermal stability compared with PEO/LiTFSI electrolyte. Consequently, the Li symmetric cell composed of 1% BNNFs/PEO/LiTFSI performs good cyclic stability (>1800 h), and the Li||1% BNNFs/PEO/LiTFSI||LFP full battery shows obviously improved performances in charge-discharge polarization voltage, discharge specific capacity, rate performance and cyclic stability than the Li||PEO/LiTFSI||LFP battery.