Unveiling the Reversibility and Stability Origin of the Aqueous V2O5–Zn Batteries with a ZnCl2 “Water‐in‐Salt” Electrolyte

• Published in: Advanced science Vol. 8; no. 23
• Main Authors: Tang, Xiaoyu, Wang, Pan, Bai, Miao, Wang, Zhiqiao, Wang, Helin, Zhang, Min, Ma, Yue
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.12.2021; John Wiley and Sons Inc; Wiley
• Subjects: Crystal structure; Electrodes; Electrolytes; operando XRD; Phase transitions; proton insertion mechanism; self‐discharge; V2O5 cathode; water‐in‐salt electrolytes; Zinc
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202102053

Aqueous V2O5–Zn batteries, an alternative chemistry format that is inherently safer to operate than lithium‐based batteries, illuminates the low‐cost deployment of the stationary energy storage devices. However, the cathode structure collapse caused by H2O co‐insertion in aqueous solution dramatically deteriorates the electrochemical performance and hampers the operation reliability of V2O5–Zn batteries. The real‐time phase tracking and the density functional theory (DFT) calculation prove the high energy barrier that inhibits the Zn2+ diffusion into the bulk V2O5, instead the ZnCl2 “water‐in‐salt electrolyte” (WiSE) can enable the dominant proton insertion with negligible lattice strain or particle fragment. Thus, ZnCl2 WiSE enables the enhanced reversibility and extended shelf life of the V2O5–Zn battery upon the high temperature storage. The improved electrochemical performance also benefits by the inhibition of vanadium cation dissolution, enlarged voltage window, as well as the suppression of the Zn dendrite protrusion. This study comprehensively elucidates the pivotal role of a concentrated ZnCl2 electrolyte to stabilize the aqueous batteries at both the static storage and dynamic operation scenarios. The application of ZnCl2 “water‐in‐salt” electrolyte in V2O5—Zn battery can effectively enhance the electrochemical performance no matter in dynamic or static conditions. This improvement is ascribed to the inhibition of cathode dissolution, extended voltage window, and the suppression of the Zn dendrite protrusion. Moreover, it is proved that proton inertion contributes most of the capacity, benefiting the particle integrity.