Relationship between the intermolecular interactions of carbonyl (PC) with nitrile (HNBR) functional groups and the flash point of a gel polymer electrolyte

Abstract

Gel polymer electrolytes have been widely studied in lithium batteries as they present a desirable compromise between the ionic conductivity of liquid electrolytes and the mechanical strength and low flammability of solid polymer electrolytes. However, few studies investigating the contribution of the polymer matrix to the overall flammability of the gel polymer electrolyte have been performed. In this work, a relationship between the intermolecular interactions of the nitrile groups in hydrogenated nitrile rubber (HNBR) and the carbonyl groups of propylene carbonate (PC) and the value of the flash point is determined. This was done by analyzing HNBR samples with different percentages of acrylonitrile (0, 17, 36, 50 and 100%) (with and without added lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)) doped with 20 wt% PC. Flash points were determined using a closed cup instrument paired with a thermal imaging camera, FLIR A700. The study gives valuable insight on the safety of the gel polymer system by providing thermogravimetry analysis (formation of gas) and flash point temperature, along with the corresponding electrochemical performance.