Mechanism of High-Rate Cycling Stability of Anthraquinone Cathode for Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) are an appealing rechargeable battery technology for next-generation energy storage devices, known for their low cost and high safety. Among the promising cathode materials used for aqueous ZIBs, anthraquinone (AQ) stands out due to its high theoretical specific capacity, low cost, and environmental friendliness. In this study, we investigate the cyclic stability of AQ in aqueous ZIBs. We demonstrate that AQ exhibits a good capacity retention at a high current density even after 1000 charge–discharge cycles, while more obvious capacity fading is observed at a low current density. Density functional theory calculations reveal that the mechanism of the rapid capacity fading under a low current density is due to the significant structural deformation of AQ crystal during Zn insertion into the AQ bulk. Furthermore, the energy barrier of Zn ions that diffuse into the AQ bulk is much higher than the diffuse on the AQ surface, leading to an irreversible Zn insertion. However, under a high current density, Zn ions prefer to adsorb and diffuse on the AQ surface without bulk insertion and structural deformation, rending a higher cycling stability. These insights into the factors influencing the cycling stability of AQ-based electrodes offer a guidance to improve their performance for practical applications.