Phase-selective synthesis of nanoshell hollow V2O3 and V3O5 microspheres as high-performance cathodes for aqueous Zn-ion batteries

Divanadium trioxide (V2O3) microspheres having nano-sized shells were produced by a facile and cost-efficient solvothermal method. Thermal treatment of V2O3 yielded trivanadium pentoxide (V3O5) microspheres. After the synthesis, the structural and electrochemical characterizations were performed in detail. Cathodes produced with the V2O3 and V3O5 materials reached specific capacities of 388 and 320 mAh g-1, respectively, at a current density of 0.1 A g-1. Aqueous zinc-ion batteries (ZIBs) fabricated with V2O3 and V3O5 cathodes demonstrated high-rate capability and capacity retention. The V2O3 microspheres, which possess a rhombohedral corundum-type structure, showed outstanding rate capability (412 mAh g-1 at 0.1 A g-1; 149 mAh g-1 at 20 A g-1) and notable cycling stability (95.6 % capacity retention after 1200 cycles at 2 A g-1; 80 % retention at the 2400th cycle at 5 A g-1). Conversely, monoclinic V3O5 provided a comparable initial capacity (374 mAh g-1 at 0.1 A g-1) but faced rapid capacity decline at high current (26 % retention after 6000 cycles at 5 A g-1). These results emphasize the significance of crystal structure in achieving stable and high-rate Zn2+ storage. In summary, the rhombohedral V2O3 phase exhibits superior Zn2+ transport kinetics and mechanical strength compared to the monoclinic V3O5, which accounts for the differences observed in their electrochemical performance.