Direct Detection and Visualization of the H<sup>+</sup> Reaction Process in a VO<sub>2</sub> Cathode for Aqueous Zinc-Ion Batteries
Shiyong Zuo, Jun Liu, Jun Liu, Weixin He, Sahar Osman, Zhengbo Liu, Xijun Xu, Jiadong Shen, Wei Jiang, Jiangwen Liu, Jiangwen Liu, Zhiyuan Zeng, Min Zhu
Abstract
Because they are safer and less costly than state-of-the-art Li-ion batteries, aqueous zinc-ion batteries (AZIBs) have been attracting more attention in stationary energy storage and industrial energy storage. However, the electrochemical reaction of H+ in all of the cathode materials of AZIBs has been puzzling until now. Herein, highly oriented VO2 monocrystals grown on a Ti current collector (VO2–Ti) were rationally designed as the research model, and such a well-aligned VO2 cathode also displayed excellent zinc-ion storage capability (e.g., a reversible capacity of 148.4 mAh/g at a current density of 2 A/g). To visualize the H+ reaction process, we used time-of-flight secondary-ion mass spectrometry. With the benefit of such a binder-free and conductor-free electrode design, a clear and intuitive reaction of H+ in a VO2 cathode is obtained, which is quite significant for unraveling the accurate reaction mechanism of VO2 in AZIBs.