Aligned CNT Forests on Stainless Steel Mesh for Flexible Supercapacitor Electrode with High Capacitance and Power Density

Carbon nanotube-based hybrid materials integrated with conducting stainless steel mesh is of great importance for developing electrochemically stable and mechanically flexible supercapacitors. We report sweet spot tunable CVD growth of vertically aligned carbon nanotube coated with TiO2 on stainless steel mesh with remarkable supercapacitor performance. Aligned CNT forest growth is observed at certain distance from the upstream inside the heating zone. We find that residence time of the carbon precursor has significant influence on controlling the density and height of vertically aligned carbon nanotube forest. When the residence time is increased by reducing the carrier gas flow rate from 590 to 300 sccm, vertically aligned carbon nanotube forest height is increased significantly from ∼9 to ∼31 μm on stainless steel mesh. The developed vertically aligned CNT forest on stainless steel mesh found to be suitable for supercapacitor electrode but its superhydrophobic nature limits its energy storage performance. To tune its wettability for further improving the electrode performance, 3 nm TiO2 conformal coating is introduced on VACNT-SS mesh using atomic layer deposition. TiO2–VACNT hybrid shows superhydrophilic nature and able to achieve 16.24 mF/cm2 specific capacitance in particular current density of 1.67 mA/cm2. This CNT–TiO2 hybrid outperforms other CNT based supercapacitor electrodes and shows high power density of 1.18 mW/cm2. Around 99.7% capacitance was retained by the developed hybrid after 5000 charge–discharge cycles. Supercapacitor measurements performed in flexible geometry and after severe ultrasonication to ensure the mechanical stability and flexibility of the developed TiO2-coated CNT forest on SS mesh.