Failure analysis of nanoscale VO₂ used as the cathode electrode for aqueous zinc-ion batteries

In this study, VO₂ nanoparticles were synthesized in a single step using a simple and rapid low-temperature combustion synthesis method. When used as the cathode electrode material for aqueous zinc-ion batteries. It exhibited excellent rate performance, with maximum capacities of 415 mAh g⁻¹, 375 mAh g⁻¹, and 350 mAh g⁻¹ at current densities of 0.5 A g⁻¹, 1 A g⁻¹, and 2 A g⁻¹, respectively. However, the cyclic performance was subpar. This study was conducted to investigate the capacity degradation, revealing the formation of plate-like Zn₃V₂O₇(OH)₂·2H₂O (BZS) precipitates on the electrode surface during the cycling process. The H⁺ ions generated from the BZS precipitation co-intercalated with Zn²⁺ ions into the VO₂ structure, thereby enhancing the battery specific capacity. Nevertheless, excessive H⁺ ions altered the electrolyte pH, resulting in vanadium dissolution and capacity degradation. Furthermore, the excessive buildup of BZS during the cycling process severely impacted ion transport, leading to capacity loss.