K-Ion intercalated V6O13 with advanced high-rate long-cycle performance as cathode for Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) are regarded as potential candidates for large-scale energy storage devices due to their low cost, high safety, and abundant Zn resources. The cathode materials of AZIBs affect the overall electrochemical performance of the battery. Therefore, developing cathode materials that could rapidly accept/release Zn-ions and maintain structural stability has become the key to AZIBs. V6O13 exhibits metallic conductivity at room temperature and has a three-dimensional framework structure suitable for Zn-ion transport. In this study, to improve the high-rate properties of V6O13, the K-ion intercalation method was adopted. Combining the hydrothermal method with argon annealing, K-ion intercalated V6O13 (K-V6O13) was successfully prepared. K ions could act as the support in the material and expand the spacing of the (001) planes; meanwhile, K ions could cause charge redistribution between V atoms and O atoms and reduce the electrostatic interaction between Zn ions and O atoms during the Zn-ion migration, which facilitates the transport of Zn ions. The specific capacity of K-V6O13 was 367 mA h g(-1) at 0.5 A g(-1) and 198.8 mA h g(-1) at 10 A g(-1), and the capacity could be maintained at 90% after 2000 cycles at 10 A g(-1). Theoretical simulations show that the K-ion intercalation would not destroy the metallic conducting behavior of V6O13 and could reduce the Zn-ion diffusion barrier from 0.94 to 0.33 eV. This study is valuable in highlighting the potential role of K-ion intercalation in the design and development of novel vanadium oxide cathodes for AZIBs.