Bi-layered calcium vanadium oxide as a cathode material for wet organic electrolyte-based rechargeable Zn-ion batteries

Zn-ion batteries attract considerable attention as a promising option for large-scale energy storage owing to their many benefits, including safety, high abundance of zinc, low fabrication costs, and ease of handling in air. However, to improve their effectiveness, three key technical challenges must be overcome: low electrolyte performance, metal dendrite formation, and a limited choice of host materials. This study introduces a new cathode material for Zn-ion batteries — double-layered Ca_0.26V₂O₅·H₂O — that exhibits outstanding performance in a wet organic electrolyte. The cathode material demonstrates an initial discharge capacity of 268.76 mAh g⁻¹ at a rate of 0.2C and average operating voltage of 0.82 V (vs. Zn²⁺/Zn) with excellent capacity retention. A reversible Zn intercalation/crystal water extraction reaction is confirmed by conducting elemental and structural analyses, including powder X-ray diffraction. Furthermore, the results of bond valence sum calculations support the formation of a two-dimensional network of Zn-ion conduction pathways along the a-axis and b-axis, illustrating the electrochemical zinc intercalation into the wet organic electrolyte. Overall, this study not only introduces double-layered Ca_0.26V₂O₅·H₂O as a new cathode material for Zn-ion batteries but also provides valuable insights into the electrochemical zinc intercalation/crystal water extraction in wet organic electrolytes.