Unraveling the triple synergy of Co doping in V6O13 nanobelts for enhanced supercapacitor performance

To address the low conductivity and poor cycling stability of V 6 O 13 for supercapacitors, Ni 2+ , Co 2+ , and Mn 2+ -doped V 6 O 13 (denoted as XVO, where X = Ni, Co, and Mn) nanomaterials were synthesized using a one-step solvothermal method. A systematic comparative investigation revealed a counterintuitive yet insightful finding: Mn doping induces the largest lattice expansion; however, MnVO delivers the poorest electrochemical performance, whereas CoVO with only moderate lattice expansion achieves the best performance. Through comprehensive characterization, we demonstrated that Co 2+ uniquely balances three critical functions: optimizing lattice expansion, maximizing V 4+ /oxygen vacancy concentration, and directing the formation of highly dispersed nanobelts, creating a triple synergy that neither Ni 2+ nor Mn 2+ can replicate. Consequently, the CoVO electrode exhibited exceptional cycling stability with 93.1% capacity retention after 10000 cycles at 100 A∙g −1 , along with a high specific capacitance (753.7 F∙g −1 at 1 A∙g −1 ). Furthermore, an assembled CoVO//CoVO symmetric supercapacitor operated stably at 0–1.6 V, achieving a maximum energy density of 91.1 Wh∙kg −1 at 400 W∙kg −1 and retaining 42.2 Wh∙kg −1 at 8000 W∙kg −1 . This study identifies Co 2+ as the optimal dopant for V 6 O 13 -based electrodes and establishes that optimal performance requires a multi-scale synergistic optimization of the structure, electronics, and morphology, rather than the sole pursuit of maximum interlayer spacing.