High Ion Transport within a Freeze-Casted Gel Film for High-Rate Integrated Flexible Supercapacitors

Gel electrolytes are important components in flexible solid-state supercapacitors. An urgent need exists for gel electrolytes that can store abundant electrolyte ions and provide high ionic conductivity, with performance characteristics similar to the liquid electrolyte, enabling high-power capability for devices. Herein, we have reported a general and scalable strategy toward various high-performance gel electrolytes including the first freeze of chemical cross-linked poly(vinyl alcohol) followed by infusing with different electrolytes (acid, neutral, and alkaline). The engineering not only endows robust electrolyte ion retention ability and outstanding ion migration rate but also strengthens the mechanical properties for gel electrolytes. As a proof of application, we demonstrate that an all-in-one supercapacitor with a H 2 SO 4 gel electrolyte can deliver excellent rate capability (58.2% retention under the 50-fold increase in current densities), high areal capacitance (644.4 mF cm –2 ), and long operating lifetime (63.6% retention after 50 000 cycles), representing the best performance among the previously reported all-in-one devices. Thus, we anticipate that the method has a potential application for flexible solid-state energy storage.