Researchers from the Shanghai Institute of Technology, Naval University of Engineering and Liaoshen Industries Group have developed a highly porous NiCo₂V₂O₈@GO hollow sphere electrode material that could improve supercapacitor performance. This innovation tackles the persistent challenge of low energy density in supercapacitors, which excel in power delivery and cycle life but lag behind batteries in stored energy.
The team first explored a series of ternary metal vanadates - NiₓCo₃₋ₓV₂O₈, NiₓMn₃₋ₓV₂O₈, and NiₓCu₃₋ₓV₂O₈ (x = 1, 1.5, 2) - to pinpoint optimal metal combinations for electrochemical activity. They then refined NiCo₂V₂O₈@GO via anion exchange on metal glycerolate precursors, followed by annealing to form yolk-double-shell hollow nanospheres coated with graphene oxide (GO). This core-shell design leverages GO's 2D scaffold to prevent nanoparticle aggregation, boost electrical conductivity, and expand the electrochemically accessible surface area.
In three-electrode tests, NiCo₂V₂O₈@GO delivers a specific capacitance of 1683 C·g⁻¹ at 1 A·g⁻¹, retaining 1467.9 C·g⁻¹ (87.22% capacity) even at 20 A·g⁻¹, showcasing superior rate capability. After 5000 cycles at 10 A·g⁻¹, it maintains 90.8% of its initial capacity, thanks to the material's thermal stability and structural integrity.
These results stem from synergistic effects: multiple oxidation states in Ni, Co, and V enable rich redox reactions, while the hollow spheres provide high surface-to-volume ratios and pore channels for rapid ion diffusion. GO hybridization enhances conductivity (addressing a common vanadate weakness), suppresses volume changes during cycling, and maximizes electrolyte penetration, amplifying pseudocapacitive charge storage.
Assembled into a symmetric supercapacitor, the material achieves an energy density of 52.49 Wh·kg⁻¹ at a power density of 755.85 W·kg⁻¹, positioning it as a viable candidate for next-generation energy storage in high-power applications.
