Synthesis Of Metal Nitride Materials And Their Applications In All-solid-state Supercapacitors

Nowadays,in the context of the severe energy and environmental crisis,people demand the adjustment of existing energy structures,chasing for the clean and high-efficient energy conversion and storage systems.As one of the promising candidates,supercapacitors attract much attention,owning to the merits of high power density,long cycle life and low maintenance cost.However,the relatively low energy density is still the important barrier that limits large-scale applications of supercapacitors.The key point to cope with this knotty problem is to enhance the performance of electrode materials.Recently,metal nitrides are highlighted as one the promising candidates for supercapacitors,depending on their advantages like relatively high specific capacitance,well stability and comparatively good conductivity.Herein,the research purposes of our work are focusing on the fabrication for metal nitrides of electrode materials and their practical applications in supercapacitors.The main contents are shown as followed.1.NbN thin film electrodes were synthesized via facile reactive magnetron sputtering,and their electrochemical performances were optimized by adjusting experimental parameters.The NbN thin film electrode presents high areal capacitance that can up to 181.7 mF/cm2 in 0.5M H2SO4 electrolyte,and excellent cycling life remaining 92.2%after 20,000 cycles,outperforming than other similar materials.Furthermore,symmetric NbN all-solid-state supercapacitor(SSC),consisting of the H2SO4/PVA solid electrolyte and two NbN thin film electrodes,which possessing an areal capacitance of 49.4 mF/cm2 at a current density of 0.5 mA/cm2.Besides,the SSC can achieve an energy density of 1.34 mWh/cm3 and reserve 85%of the initial capacitance after 20,000 cycles testing.2.We successfully prepared stacked polyhedral Cu3N directly on carbon paper substrates by reactive magnetron sputtering.Such Cu3N samples have abundant pores dispersed on the surface and,thus,relatively high specific area.Moreover,we also study the influence of experimental parameters,determining the appropriate condition that the pure Cu3N can be synthesized.While tested in 1M KOH electrolyte,the Cu3N electrode shows outstanding performances,which have an areal capacitance of 151.1 mF/cm2,and the capacitance loss less than 3%after 20,000 cycles.For the practical application,the Cu3N//AC all-solid-state supercapacitor(ASC)were assembled as the asymmetric configuration,in which the KOH/PVA solid-electrolyte were sandwiched by the Cu3N positiv e electrode and the AC negative electrode.Thanks to the asymmetric configuration,the working potential window is greatly improved to 1.6 V of the whole device.According to the results of electrochemical performances,the ASC possess an energy density of 1.32 mWh/cm3,and retains 89.5%of the initial capacitance after 20,000 cycles.