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

Fabrication of supercapacitor devices with the carbon cloth supported W2N@carbon ultrathin layer core-shell structures (W2N@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 W2N over WO3-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.