High Temperature Lithium Ion Capacitors Fabricated with Peglyated Polysilsesquioxane Ionogel Polymer Electrolytes

A PEGylated polysilsesquioxane, ladder-like structured poly(methacryloxypropyl-co-polyethyleneoxide)silsesquioxane (LMAPEOSQ) was synthesized and investigated as high temperature ionogel polymer electrolytes for lithium ion capacitors. By utilizing a small weight percent of LMAPEOSQ crosslinker concentration (5 wt%), we were able to obtain mechanically pliant gel-state ionogels with high thermal stability (~400 ^oC), high ionic conductivities comparable to the liquid state ionic liquid, and non-leaking properties, even at high temperatures. Lithium ion capacitors fabricated with these hybrid ionogel polymer electrolytes revealed excellent cell performance at various C-rates at a variety of temperatures, comparable with those of neat liquid electrolyte, and superior over ionogels fabricated with organic crosslinkers without PEO-moeities. Moreover, these ionogel polymer electrolytes exhibited excellent cycling performance during 50 cycles at 80 °C, sustaining over 99% coulombic efficiency. High ionic conductivity in the gel state, thermal stability, excellent C-rate performance, cyclability and nonflammability offer opportunities for applications as high temperature electrolytes.