Revealing the role of calcium ion intercalation of hydrated vanadium oxides for aqueous zinc-ion batteries

Exploring suitable high-capacity V 2 O 5 -based cathode materials is essential for the rapid advancement of aqueous zinc ion batteries (ZIBs). However, the typical problem of slow Zn 2+ diffusion kinetics has severely limited the feasibility of such materials. In this work, unique hydrated vanadates (CaVO, BaVO) were obtained by intercalation of Ca 2+ or Ba 2+ into hydrated vanadium pentoxide. In the CaVO//Zn and BaVO//Zn batteries systems, the former delivered up to a 489.8 mAh g −1 discharge specific capacity at 0.1 A g −1 . Moreover, the remarkable energy density of 370.07 Wh kg −1 and favorable cycling stability yard outperform BaVO, pure V 2 O 5 , and many reported cathodes of similar ionic intercalation compounds. In addition, pseudocapacitance analysis, galvanostatic intermittent titration (GITT) tests, and Trasatti analysis revealed the high capacitance contribution and Zn 2+ diffusion coefficient of CaVO, while an in-depth investigation based on EIS elucidated the reasons for the better electrochemical performance of CaVO. Notably, ex-situ XRD, XPS, and TEM tests further demonstrated the Zn 2+ insertion/extraction and Zn-storage mechanism that occurred during the cycle in the CaVO//Zn battery system. This work provides new insights into the intercalation of similar divalent cations in vanadium oxides and offers new solutions for designing cathodes for high-capacity aqueous ZIBs.