Self-standing electrodes with core-shell structures for high-performance supercapacitors

Abstract Fabrication of supercapacitor devices with the carbon cloth supported W 2 N@carbon ultrathin layer core-shell structures (W 2 N@C CS/carbon cloth) were realized by aerosol-assisted chemical vapour deposition (AACVD) followed by an ammonia annealing process. The representative electrodes delivered excellent areal specific capacitance of 693.0 mF cm -2 at 5 mV s -1 in a three electrode testing system, good rate capability of ~ 78% retention when the scan rate increased 10 times and superior cycling stability with ~ 91% capacitance retention after 20,000 cycles. The self-standing electrodes were manufactured for flexible asymmetric supercapacitors and assembled into coin cells with ionic electrolyte for high working voltage applications. The primary origins for the outperformance of W 2 N over WO 3-x in acid aqueous electrolytes are uncovered by electrochemical analysis, simulation work and in-situ transmission electron microscope (TEM). This discovery paved the way of exploring and designing advanced metal nitride electrode materials for supercapacitors.