Hierarchical V₂O₅ microspheres: A pseudocapacitive cathode material for enhanced sodium ion storage

Vanadium oxides represent promising host materials for energy storage but suffer from sluggish ionic diffusion and poor cyclability. We here synthesize hierarchical V₂O₅ microspheres (HVMs) which demonstrate excellent electrochemical performance for sodium ion storage, especially at high discharge/charge rates. The HVMs deliver a high capacity of 254 mA h g⁻¹ at 0.1 A g⁻¹ with Coulombic efficiency of above 99.0%. Highly reversible capacities of 120–155 mA h g⁻¹ are well retained with limited decay for 500 cycles even under much high discharge/charge rates of 0.5–2.0 A g⁻¹. The robust performance is attributed to the fast Na⁺-ion diffusion in the unique hollow structure and enhanced reaction kinetics through a pseudocapacitive process.