MnO2/carbon nanotube free-standing electrode recycled from spent manganese-oxygen battery as high-performance supercapacitor material.

Metal–oxygen batteries have been growing rapidly as an energy storage technology in light of their high specific energy density. However, waste metal–oxygen batteries will raise many environmental issues; therefore, the recycling and reusing of the spent metal–oxygen batteries has attracted great attention. Herein, we report the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) as a redox mediator for manganese–oxygen battery (MOB). Trace amounts of PTIO result in the discharge capacity of MOB increase to 2588 mAh g−1 and enhance the formation of manganese dioxide (MnO2) with toroidal appearance and high crystallinity on the cathode. After being used, the dismantled MnO2/carbon nanotube (CNT) cathode can be reused as an electrode for supercapacitor via simple calcining at mild temperature. The recycled free-standing MnO2/CNT electrode demonstrates an exceptional specific capacitance (253.86 F g−1) at a current density of 0.5 A g−1 in a 0.5 M Na2SO4 electrolyte. Moreover, we prepare an asymmetric supercapacitor fabricated with the recycled MnO2/CNT electrode and activated carbon (AC), which exhibits excellent energy density (32.00 Wh kg−1 at 413.70 W kg−1) with 78.26% retention over 6000 cycles. This work provides a promising strategy to derive high-quality and high-value MnO2/CNT electrode materials from the spent MOBs. It's the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) as a redox mediator for manganese-oxygen battery (MOB). The recycled manganese dioxide (MnO2)/carbon nanotube (CNT) cathode can be reused as an electrode for supercapacitor via simple calcining at mild temperature. The recycled MnO2/CNT electrode shows the toroidal appearance and high crystallinity. Furthermore, the asymmetric supercapacitor fabricated with the MnO2/CNT free-standing electrode displays high specific capacitance, superior energy density, and good cyclic ability. [ABSTRACT FROM AUTHOR]