In situ thermal conversion strategy derived from metal-organic framework for enhanced cathode performance in aqueous zinc-ion batteries

Abstract

The development of aqueous zinc-ion batteries as innovative energy storage devices has garnered significant attention due to their low cost, high safety, and environmental friendliness. However, achieving high-performance and excellent cycling reliability remains a challenge for cathode materials. This study introduces an innovative in-situ thermal conversion strategy using MIL-100(Fe) as the sacrificial template to introduce Fe metal ions into vanadium oxide. This strategy promotes the formation of FeVOx with reduced particle size and enhanced active surface area, facilitating the rapid diffusion of Zn2+. As a result, the FeVOx-1/2 cathode delivers a high specific capacity of 325 mAh/g at a current density of 0.05 A/g and maintains a high capacity retention of about 94.8 % after 4000 cycles at 1 A/g. In-situ electrochemical impedance spectroscopy (EIS) was employed to elucidate the changes in the electrode interface during the charge-discharge processes. Additionally, a series of ex-situ characterization methods were utilized to further deepen our understanding of the reversible structural changes in the cathode during charge-discharge processes, as well as the corresponding reversible insertion and extraction mechanism for Zn2+ storage. The introduction of Fe not only enhances electrical conductivity, but also provides further structural stabilization, as supported by theoretical calculation results. This study presents a novel approach to broaden the doping strategies for vanadium oxide cathodes by utilizing metal-organic frameworks as templates.