A Solid-State and Flexible Supercapacitor that Operates Across a Wide Temperature Range Ardalan Chaichi1,†, Gokul Venugopalan2,†, Ram Devireddy1, Christopher Arges2,*, Manas Ranjan Gartia1,* 1Department of Mechanical Engineering, Louisiana State University, Baton Rouge, USA 70803 2Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, USA 70803 † Equal contribution * Correspondence:
[email protected];
[email protected] Abstract Electrochemical properties of most supercapacitor devices degrade quickly when the operating temperature deviates from room temperature. In order to exploit the potential of rGO in supercapacitors at extreme temperatures, a resilient electrolyte that is functional over a wide- temperature range is also required. In this study, we have implemented a flexible, low-resistant solid-state electrolyte membrane (SSEM) into symmetric rGO electrodes to realize supercapacitor devices that operate in the temperature range of -70 °C to 220 °C. The SSEM consists of a polycation-polybenzimidazole blend that is doped with phosphoric acid (H3PO4) and this material displays uniquely high conductivity values that range from 50 mS cm-1 to 278 mS cm-1 in the temperature range of -25 °C to 220 °C. The fabricated supercapacitor produced a maximum capacitance of 6.8 mF cm-2 at 100 °C. Energy and power densities ranged from 0.83 to 2.79 mW h cm-2 and 90 to 125 mW cm-2, respectively. The energy storage mechanism with a SSEM occurs by excess H3PO4 migrating from the membrane host into the electrochemical double layer in rGO electrodes. The high temperature operation is enabled by the polycation in the SSEM anchoring phosphate type of anions preventing H3PO4 evaporation.