Bi-intercalated vanadium pentoxide synthesized via hydrogen peroxide-induced phase transition for highly stable cathode in aqueous zinc ion batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) have attracted significant attention as alternatives to lithium-ion batteries. In this case, vanadium pentoxide is a promising cathode material for aqueous zinc ion batteries. However, the small interlayer spacing of traditional vanadium oxide cathodes results in poor electrochemical performances, while their complex preparation steps also limit their applications. Herein, a simple and effective hydrothermal method was developed for the synthesis of K⁺ and H₂O intercalated vanadium pentoxide (KVOH), which was realized by hydrogen peroxide-induced conversion from the vanadium oxide phase to a hydrated vanadium oxide phase. This bi-intercalated structure possesses a large interlayer spacing (10.2 Å), promoting the embedding and detachment of Zn²⁺. The enhanced diffusion kinetics was explained by the fact that the intercalated water shields the electrostatic interactions between Zn²⁺ and the vanadium oxide skeleton, which was demonstrated by the bonding distribution in the molecular structure of KVOH. The strong electronegativity of K⁺, strong K–O bonding, and the pillar interaction of K⁺ synergistically enhanced the structural stability and ionic diffusion kinetics (6.13 × 10⁻¹⁴ cm² s⁻¹, which is two orders of magnitude higher compared with V₂O₅). KVOH showed excellent capacity and rate performance, with a discharge specific capacity of up to 414.7 mA h g⁻¹ (95.9%) at a current density of 0.1 A g⁻¹ and up to 284 mA h g⁻¹ (76.4%) after 800 cycles at a high current density of 1 A g⁻¹. The present work provides an effective solution for the construction of vanadium-based cathode materials for ZIBs as well as for the development of high-efficiency aqueous energy storage devices.