Vertically Aligned Niobium Nanowire Arrays for Fast-Charging Micro-Supercapacitors

Planar micro-supercapacitors are attractive for system on chip technologies and surface mount devices due to their large areal capacitance and energy/power density compared to the traditional oxide-based capacitors. In the present work, a novel material, niobium nanowires, in form of vertically aligned electrodes for application in high performance planar micro-supercapacitors is introduced. Specific capacitance of up to 1 kF m^-2 (100 mF cm^-2 ) with peak energy and power density of 2 kJ m^-2 (6.2 MJ m^-3 or 1.7 mWh cm^-3 ) and 150 kW m^-2 (480 MW m^-3 or 480 W cm^-3 ), respectively, is achieved. This remarkable power density, originating from the extremely low equivalent series resistance value of 0.27 Ω (2.49 µΩ m² or 24.9 mΩ cm² ) and large specific capacitance, is among the highest for planar micro-supercapacitors electrodes made of nanomaterials.