Novel insights into the charge storage mechanism in pseudocapacitive vanadium nitride thick films for high-performance on-chip micro-supercapacitors

Abstract

The Internet of Things, enabled by a worldwide network of interconnected sensors, is limited in its large-scale deployment of nomadic miniaturized devices due to the bounds of energy self-sufficiency. One possible solution, albeit challenging, is constructing on-chip pseudocapacitive micro-supercapacitors. Herein, we achieve the collective fabrication of micro-supercapacitors based on sputtered bi-functional vanadium nitride films acting as the electrode material and as the current collector. The reported surface and volumetric capacitance values (1.2 F cm⁻² and >700 F cm⁻³, respectively) of the 16 μm-thick vanadium nitride film obtained via production-compatible microelectronic deposition methods compete well with those of cutting-edge transition metal oxide/nitride materials, and exceed those of standard carbon electrodes. An arsenal of advanced techniques has been deployed to investigate the pseudocapacitive behavior of sputtered vanadium nitride films in aqueous electrolyte in order to unveil the charge storage process explaining their high capacitance and their improved cycling behavior.