Co-insertion of K+ and Ca2+ in vanadium oxide as high-performance aqueous zinc-ion battery cathode material

Inserting metal ions into vanadium oxides can effectively improve their electrochemical properties, and the insertion of different single metal ions into vanadium-based compounds can enhance their electrochemical performance in different ways. Moreover, the insertion of multiple metal ions into vanadium-based compounds may provide a synergistic effect. Therefore, in this work a K0.02Ca0.18V2O5·0.7H2O (KCaVOH) cathode material was obtained by co-inserting the monovalent metal ion K+ and the divalent metal ion Ca2+ into vanadium oxide through a one-step hydrothermal method. The insertion of K+ enhances the structural stability of the cathode material, while the insertion of Ca2+ increases the layer spacing between the V-O layers and improves the specific capacity of the cathode material. The co-insertion of K+ and Ca2+ effectively enhances the electrochemical performance of V2O5·1.6H2O, and the KCaVOH cathode provides a high specific capacity of 410 mAh·g-1 at 0.3 A·g-1. Moreover, the capacity still reaches 265 mAh·g-1 after 1800 cycles at 5 A·g-1. This method provides a strategy for significantly enhancing the electrochemical performance of vanadium-based cathode materials.