High-Performance Sodium-Ion Hybrid Supercapacitor Based on Nb2O5@Carbon Core-Shell Nanoparticles and Reduced Graphene Oxide Nanocomposites

Sodium-ion hybrid supercapacitors (Na-HSCs) have potential for mid- to large-scale energy storage applications because of their high energy/power densities, long cycle life, and the low cost of sodium. However, one of the obstacles to developing Na-HSCs is the imbalance of kinetics from different charge storage mechanisms between the sluggish faradaic anode and therapid non-faradaic capacitive cathode. Thus, to develop high-power Na-HSC anode materials, this paper presents the facile synthesis of nanocomposites comprising Nb2O5@Carbon core-shell nanoparticles (Nb2O5@C NPs) and reduced graphene oxide (rGO), and an analysis of their electrochemical performance with respect to various weight ratios of Nb2O5@C NPs to rGO (e.g.,Nb2O5@C, Nb2O5@C/rGO-70, -50, and -30). In a Na half-cell configuration, the Nb2O5@C/rGO-50 shows highly reversible capacity of approximate to 285 mA h g(-1) at 0.025 A g(-1) in the potential range of 0.01-3.0 V (vs Na/Na+). In addition, the Na-HSC using the Nb2O5@C/rGO-50 anode and activated carbon (MSP-20) cathode delivers high energy/power densities (approximate to 76 W h kg(-1) and approximate to 20 800 W kg(-1)) with a stable cycle life in the potential range of 1.0-4.3 V. The energy and power densities of the Na-HSC developed in this study are higher than those of similar Li- and Na-HSCs previously reported.