High-energy density solid-state biredox energy storage device based on poly(ionic liquid)/ionic liquid redox electrolytes

In this work we have synthesized two redox-active poly(ionic liquid) / ionic liquid (PIL/IL) solid-state electrolytes based on the 2,2,6,6- tetramethylpiperidine-1-oxyl (TEMPO) and anthraquinone active molecules. We first characterized the two electrolytes to better understand their electrochemical behavior in a three-electrode configuration utilizing thermally reduced graphene oxide (Tr-GO) as working electrodes. An asymmetric supercapacitor (full cell) was then assembled with two Tr-GO electrodes and each redox-active PIL/IL electrolyte in one semi-cell, according to their redox active potentials: TEMPO as the catholyte and anthraquinone as the anolyte. The biredox solid-state supercapacitor showed excellent performance, with 81.4 F g^-1 capacitance at 0.25 A g^-1, and an energy density of 59.9 W h kg^-1, placing this device among the best in the literature for solid devices based on non-aqueous redox electrolytes, especially at low current densities. The supercapacitor retained 82.9% of its initial capacitance after 3000 charge/discharge cycles. This work presents a great advancement for the field of energy storage in applications that demand leakage-free high energy density devices.