Advanced flexible supercapacitors: vertical 2D MoS₂ and WS₂ nanowalls on graphenated carbon nanotube cotton

Flexible supercapacitors (SCs), which are mostly produced from carbon-based materials, are emerging devices for lightweight, portable, miniaturized, and wearable electronic products. However, it is important to improve the energy density, power density and durability of flexible SCs, for which newly developed materials and composites are required. In this study, we developed flexible SCs with enhanced capacitance and stability using the advantages of high volume/surface ratio of vertical two-dimensional MoS₂ and WS₂ structures. Electrodes were grown on graphenated carbon nanotube (G-CNT) cotton using Radio Frequency (RF) magnetron sputtering in a time varying manner to investigate the impact on the vertical structure densities on the performance of the as-developed SCs. Galvanostatic charge-discharge (GCD) measurements revealed a maximum aerial capacitance value of 131.2 mF cm^-2 for the best WS₂ electrode and a value of 97.60 mF cm^-2 for the best MoS₂ electrode. The flexibilities of the SC devices were examined using angle-dependent CV measurements, which revealed almost no change. Stability tests for 10 000 cycles showed a retention rate of over 96% capacitance for both electrodes. This research demonstrates the potential of integrating the conductivity, large surface/volume ratio, and processability of G-CNTs with the unique features of transition metal dichalcogenides to develop SCs with improved efficiencies and flexibilities.