Pseudocapacitive Performance of Freestanding Ni₃V₂O₈ Nanosheets for High Energy and Power Density Asymmetric Supercapacitors

Binder-free 2D nanosheet Ni3V2O8/Ni-foam (NVO/Ni) and Ni3V2O8 (NVO) nanoparticles were synthesized using a facile hydrothermal technique for electrochemical capacitor applications. Both the NVO and NVO/Ni samples, produced using 1 M LiOH as a reducing agent during the synthesis, belong to the Ni3V2O8 phase. The electrochemical traits of these electrodes revealed that the NVO/Ni electrodes performed significantly better than the 3D NVO electrodes. The NVO/Ni electrode provided a specific capacitance of 1300 F/g at a current density of 1 A/g with high cycling stability (80.62% at 4 A/g) after 7000 cycles due to structural advantages. Moreover, the NVO/Ni//AC asymmetric supercapacitor device delivered a high energy density of 33.2 Wh/kg at a power density of 2.4 kW/kg and high cycling stability over 10,000 cycles in the 1.2 V working potential window. The device also showed a considerably high maximum power density of 7.2 kW/kg at a 13.62 Wh/kg energy density and remained stable even after 10,000 cycles. The energy–power performance depicted nearly 200% power gain over a mere 59% energy expense, indicating its potential applications in practical devices.