Starfruit-like vanadium oxide with Co2+ pre-intercalation and amorphous carbon confinement as a superior cathode for supercapacitors

Abstract

The vanadium dioxide (VO2(D)), with ultra-high theoretical capacitance, has been considered as a boon for electrode materials of advanced supercapacitors (SCs). However, the VO2 has a series of shortcomings such as poor electrical conductivity, severe structural damage, and rapid capacity fading during cycles, resulting in unsatisfactory electrochemical performance. Herein, the Co2+ pre-intercalation and amorphous carbon confined vanadium dioxide (CoxVO2@C) with starfruit-like nanostructure is synthesized on a conductive Ni foam substrate via a versatile and cost-effective method. As a cathode for SCs, the obtained CoxVO2@C not only enables a small amount of Co2+ pre-intercalation layer to offer faster ion diffusion kinetics for VO2, but also utilizes a high-conductivity amorphous carbon to protect VO2 from dissolution in an alkaline electrolyte, thereby exhibiting the ultrahigh specific capacitance up to 4440.0 mF cm−2 at 5 mA cm−2 (525.2 F g−1 at 2 A g−1) and the prominent long-term stability performance of the electrode. Benefited from these excellent characteristics, a high-performance CoxVO2@C//V2O3 hybrid supercapacitor (HSC) device with an operating voltage of 1.7 V is further assembled. The HSC device delivers a superior energy density of 102.3 W h kg−1 at a power density of 6.1 kW kg−1, manifesting its practical feasibility.