A new class of polymer electrolytes based on poly(tetrafluoroethylene) and fluoro-functionalized ionic liquids with the intent of improved stability of advanced lithium ion batteries
This proposal presents a new class of electrolytes based on fluorinated polymers that have high thermal- and electrochemical-stability for use in advanced high-voltage lithium ion batteries (LIBs). Fluorinated polymers, such as poly(tetrafluoroethylene) (PTFE), will be chosen as a matrix for electrolyte solutions with respect to their extreme chemical inertness and thermal stability. PTFE-based polymer electrolytes are desired but have not yet made successful in their preparation because the extreme inertness of PTFE restricts the absorption of electrolytes. Meanwhile, we have focused on ionic liquids (ILs), an inflammable molten salt, as electrolytes for fluorinated polymers. Because ILs are composed of organic ions having structural diversity, we can deem that ILs are imbued with the possibility for showing a high compatibility so as to avoid the repellence of ILs from PTFE. Some fluoro-functionalized ILs originally prepared in my research last year have successfully resulted in the formation of homogeneous composites with PTFE. Taking advantages of this achievement, this year I propose ternary composites based on PTFE, commercialized electrolyte solutions, and fluorinated-ILs, where fluorinated-ILs are expected to play a crucial role as a binder between PTFE and the electrolyte solution. At the same time, fluorinated-ILs are also expected to act as an excellent flame-retardant and an additive to broaden the electrochemical stability window. With respect to the aim of this research, the ratio of all components will be optimized in terms of thermal- and electrochemical-stability. The applicability of the composites to advanced-high voltage LIBs (>5V) will be discussed by evaluating real batteries with the composites. The composites are expected to enable the safe use of high voltage cathodes which cannot be attained by using conventional electrolytes. Throughout this research, I intend to establish peculiar PTFE as a unique and reliable matrix for LIBs.