Host-Guest Synergistic Regulation in Functionalized Metal-Organic Frameworks for Efficient Aqueous Zinc-Ion Batteries

Vanadium-based metal-organic framework (V-MOF) cathodes in aqueous zinc-ion batteries (AZIBs) are prone to be pronounced volumetric expansion during charging/discharging processes, which causes structural collapse, capacity fading, and compromised cycling stability. Herein, a series of novel hybrid nanomaterials (Br@P-X) are successfully prepared via a one-step solution method by confining polyoxometalates (POMs) within the pores of the V-MOF and precisely controlling the POMs loadings. The synergistic structural and functional interactions between the porous MOF framework and the uniformly dispersed POMs, as well as the precise tuning of guest POM clusters endow the system with unique electrochemical behavior. The Br@P-16 cathode possesses excellent structural and chemical stability, thus demonstrating outstanding electrochemical performance in AZIBs. The coordination environment of Br@P-16 is investigated using X-ray absorption fine structure spectroscopy. In-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy/Fourier transform infrared analyses reveal the structural evolution during the electrochemical cycling process. This study provides a novel perspective for the design and synthesis of high-performance cathode nanomaterials for AZIBs through the confinement strategy.