BiVO4/V2O5 Heterostructures for Durable and Highly Reversible Calcium- and Zinc- Ion Batteries

Abstract

The potential of BiVO4/V2O5 (BVO/VO) heterostructures for Ca2+ and Zn2+ ion storage is demonstrated. BVO micro-clusters and VO micro-platelets, characterized by large vacant voids and wide inter-layer spacings enable facile Zn2+ ion intercalation via diffusion mechanism, owing to its small size and ease of de-solvation at the electrolyte/BVO/VO interface. Zn-ion battery (ZIB) fabricated with the following architecture: BVO/VO/carbon nanotubes (CNTs)/Zn2+/Zn- activated carbon (AC), delivers an initial discharge capacity of ~162 mAh g-1, and retains nearly 100% of its original capacity after 100 cycles at 30 mA g-1. Accelerated cycling at 2 A g-1, showed this ZIB to retain ~82% of its initial capacity after 2500 cycles. The highly stable and reversible response is attributed to the formation of robust interphases at the cathode and anode that allow facile Zn2+ ion diffusion and prevent any Zn-ion consuming decomposition reactions, as both the electrodes maintain their structural integrity with cycling. In a similar vein, Ca-ion battery (CIB) with a BVO/VO/CNTs/Ca2+/AC configuration provides an initial capacity of 120 mAh g-1, with 100% retention after 100 cycles. The large size of Ca2+ ion and its large solvation shell inhibits direct intercalation into BVO/VO, allowing only surface Faradaic reactions at the cathode/electrolyte interface and anion adsorption/desorption at the AC anode. The consistent storage capacity maintained by the cell with cycling is attributed to the stability of the BVO/VO heterostructures and AC, which are largely unaffected by the back-and-forth movement of Ca2+ ions during charge-discharge.