Ionic Liquid-Organic Solvent Mixture-Based Polymer Gel Electrolyte with High Lithium Concentration for Li-Ion Batteries

摘要

In this paper, we have investigated the performance and solid electrolyte interphase formation (SEI) of a hybrid polymer gel electrolyte based on poly(vinylidene fluoride)-co-hexafluoropropylene, 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide ([Py-1,Py-4]FSI), and lithium bis(fluorosulfonyl)imide (LiFSI) for all solid-state lithium-ion batteries. The effect of the addition of acetonitrile (AN) and different concentrations of LiFSI to such a polymer gel electrolyte was also examined. Compared to 1 M LiFSI in the ionic liquid-polymer electrolyte, the addition of 4 M LiFSI along with acetonitrile led to higher lithium storage capacity. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy were performed to analyze the SEI formation on a Ge electrode. The difference in the mechanical properties and SEI composition was observed upon changing the components of the polymer electrolyte. XPS analysis revealed a difference in the composition/thickness of the SEI layer, which varies upon increasing the Li-salt concentration and upon adding AN to [Py-1,Py-4]FSI. Such differences might have led to better Li storage capacity on using the concentrated IL-organic polymer electrolyte. Our study clearly shows that the addition of an organic solvent and high concentration of Li salt to the polymer gel electrolyte improves the performance of LIBs.