S/N-codoped carbon nanotubes and reduced graphene oxide aerogel based supercapacitors working in a wide temperature range.

Among many supercapacitor electrode materials, carbon materials are widely used due to their large specific surface area, good electrical conductivity and high economic efficiency. However, carbon-based supercapacitors face the challenges of low energy density and limited operating environment. This work reports a facile self-assembled method to prepare three-dimensional carbon nanotubes/reduced graphene oxide (CNTs/rGO) aerogel material, which was applied as both positive and negative electrodes in a symmetric superacapacitor. The fabricated supercapacitor exhibited prominent capacitive performance not only at room temperature, but also at extreme temperatures (-20 ∼ 80 °C). The specific capacitances of the symmetric supercapacitors based on CNTs/rGO at a weight ratio of 2:5 respectively reached 107.8 and 128.2 F g at 25 °C and 80 °C with KOH as the electrolyte, and 80.0 and 144.6 F g at -20 °C and 60 °C with deep eutectic solvent as the electrolyte. Notably, the capacitance retention and coulombic efficiency of the assembled supercapacitors remained almost unchanged after 20,000 cycles of charge/discharge test over a wide temperature range. The work uncovered a possibility for the development of high-performance supercapacitors flexibly operated at extreme temperatures.