Reversible Oxygen Redox Chemistry in Aqueous Zinc‐Ion Batteries

• Published in: Angewandte Chemie International Edition Vol. 58; no. 21; pp. 7062 - 7067
• Main Authors: Wan, Fang, Zhang, Yan, Zhang, Linlin, Liu, Daobin, Wang, Changda, Song, Li, Niu, Zhiqiang, Chen, Jun
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 20.05.2019
• Edition: International ed. in English
• Subjects: Aquatic plants; Batteries; Cathodes; Crystal structure; Electric potential; electrochemistry; Electrolytes; Energy storage; Flux density; Organic chemistry; Oxygen; oxygen redox chemistry; Rechargeable batteries; Storage batteries; vanadium redox chemistry; Voltage; Zinc; zinc-ion batteries; zinc-ion batteries; electrochemistry; vanadium redox chemistry; energy storage; oxygen redox chemistry
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201902679

Rechargeable aqueous zinc‐ion batteries (ZIBs) are promising energy‐storage devices owing to their low cost and high safety. However, their energy‐storage mechanisms are complex and not well established. Recent energy‐storage mechanisms of ZIBs usually depend on cationic redox processes. Anionic redox processes have not been observed owing to the limitations of cathodes and electrolytes. Herein, we describe highly reversible aqueous ZIBs based on layered VOPO4 cathodes and a water‐in‐salt electrolyte. Such batteries display reversible oxygen redox chemistry in a high‐voltage region. The oxygen redox process not only provides about 27 % additional capacity, but also increases the average operating voltage to around 1.56 V, thus increasing the energy density by approximately 36 %. Furthermore, the oxygen redox process promotes the reversible crystal‐structure evolution of VOPO4 during charge/discharge processes, thus resulting in enhanced rate capability and cycling performance. Rezinking zinc batteries: Aqueous zinc‐ion batteries based on VOPO4 cathodes and a water‐in‐salt electrolyte displayed highly reversible oxygen redox chemistry at high voltages (see graph). The oxygen redox process not only led to increased capacity and a higher average operating voltage of the Zn/VOPO4 batteries, but also improved rate capability and cycling performance.