High-energy solid-state asymmetric supercapacitor based on nickel vanadium oxide/NG and iron vanadium oxide/NG electrodes

Solid-state supercapacitors (SCs) are well-known as one of the most competitive power sources for modern electronics. However, most of the reported solid-state SCs suffer from low specific capacitance and energy density. Herein, a novel strategy for the synthesis of nickel vanadium oxide (Ni₃V₂O₈) and iron vanadium oxide (Fe₂VO₄) nanoparticles (NPs) anchored nitrogen doped graphene (NG) for high energy solid-state asymmetric SC (ACS) through a simple and cost-effective hydrothermal technique was demonstrated. SEM and TEM analysis reveals that active Ni₃V₂O₈ and Fe₂VO₄ NPs with uniform size are anchored on NG sheets. Electrochemical performance of Ni₃V₂O₈/NG and Fe₂VO₄/NG electrodes showed that both have ultra-high specific capacitances (∼1898 F g⁻¹ and 590 F g⁻¹ at current density of 1 A g⁻¹, respectively), tremendous rate capabilities, and superior cycling stabilities. Most significantly, solid-state ASC consisting of Ni₃V₂O₈/NG as a cathode and Fe₂VO₄/NG as an anode which achieves a high energy density of ∼77.2 W h kg⁻¹ at a power density of 863 W kg⁻¹ and an ultra-long cycle life (capacitance retention of ∼83.3% after 20,000 cycles). This study emphasizes the development of a wide variety of energy storage systems for modern electronics.