Synergistic H+/Zn2+ dual ion insertion mechanism in high-capacity and ultra-stable hydrated VO2 cathode for aqueous Zn-ion batteries
By Kaiyue Zhu, Tao Wu, Shichen Sun, Wessel van den Bergh, M. Stefik, Kevin Huang. 2020
204 citations recorded by the source corpus.
Abstract Rechargeable aqueous zinc ion batteries (ZIB) with near-neutral electrolytes are a promising candidate for stationary energy storage owing to their high-energy-density, high-safety, low-cost and environmental-friendliness. However, the development of ZIBs is currently hindered by the lack of high-performance cathode materials and a good understanding of the true ionic storage mechanism in cathodes. Herein, using a promising ZIB cathode, hydrated VO2 (denoted as H-VO2), as a model material, we carried out a systematic experimental and theoretical work to elucidate the ionic storage mechanisms. We show strong evidence that H+ and Zn2+ are synergistically involved in the ionic storage in H-VO2. The H+-insertion/extraction, which leads to a pH swing of the electrolyte, can be viewed as an indirect Zn2+-storage through a reversible precipitation/dissolution of Zn(OH)2 on the surface of H-VO2 cathode. The first-principles DFT calculations further reveal that H+ and Zn2+ have their own favorable insertion sites and migration pathways, but H+-insertion predominates in the initial discharge stage whereas Zn2+-insertion controls in the late discharge stage. Because of the synergetic H+/Zn2+ co-insertion, H-VO2-based ZIB exhibits a high capacity and stability at both low and high rates, e.g. 410 and 200 mAh g-1, 88% and 70% retention rate for 200 (~1500 h) and 3000 cycles (~215 h) at 0.1 and 5.0 A g-1, respectively. The new fundamental insights gained from this study deepen the understanding of aqueous Zn-ion battery chemistry for future development of advanced ZIB cathodes.
Subfields: Electrical and Electronic Engineering, Electronic, Optical and Magnetic Materials
View Paper: https://www.semanticscholar.org/paper/43b761db377f17b7e31f4d5fdc428aac9ca9b3c1