Novel Polyoxovanadate and Its Phase Transition Product for Electrochemical Performance of Aqueous Zinc-Ion Batteries

As an innovative technique in the field of energy storage, aqueous zinc-ion batteries (AZIBs) have garnered considerable research interest over recent years. However, designing and developing high-performance cathode materials for AZIBs remains a primary challenge. In this study, a novel POV-based cathode material, [KV16O38]2[Zn2(en)5][Zn(en)2H2O]4·en·12H2O·6OH− (KZVO), was first synthesized using a hydrothermal method, demonstrating a high specific capacity of 255.9 mAh g−1 at 0.5 A g−1 and excellent long-term cycling performance, retaining 206.5 mAh g−1 after 2000 cycles at 4 A g−1, with a capacity retention of 77.6%. It is noteworthy that KZVO undergoes a gradual phase transition during electrochemical cycling. At 4 A g−1, the phase transformation is completed after approximately 580 cycles, and the newly formed phase remains stable during subsequent cycles. Additionally, ex situ XRD and XPS analyses were conducted to further investigate the phase evolution and Zn2+ storage mechanism. In summary, this work not only demonstrates the effective utilization of POV-based cathode materials but also provides a novel perspective for the design of future AZIB cathode materials.