Flexible Anion Microbatteries: Towards Construction of a Hybrid Battery-Capacitor Device.

A proof-of-principle study is presented on the rechargeable anion storage capability of ferrocyanide immobilized in a polysilsesquioxane (PSQ)-modified flexible/rigid film for aqueous battery applications. This electrode material delivers high power density up to 140 μWh cm-2 and energy density of 9.4 μWh cm-2 with a long cycle life of more than 200 cycles in chloride ion medium. The proposed energy storage mechanism of this system is based on insertion and extraction of the anion into the [Fe(CN)6 ]4- -PSQ film during charging and discharging processes, respectively. Moreover, a hybrid battery-capacitor device comprising a graphite rod (capacitor) and the ferrocyanide-immobilized PSQ film as a faradaic electrode shows enhanced electrochemical performance.