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H + ‐Insertion Boosted α‐MnO 2 for an Aqueous Zn‐Ion Battery
Author(s) -
Gao Xu,
Wu Hanwen,
Li Wenjie,
Tian Ye,
Zhang Yun,
Wu Hao,
Yang Li,
Zou Guoqiang,
Hou Hongshuai,
Ji Xiaobo
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201905842
Subject(s) - materials science , cathode , aqueous solution , battery (electricity) , electrochemistry , electrolyte , energy storage , chemical engineering , ion , manganese , nanotechnology , electrode , metallurgy , chemistry , power (physics) , physics , organic chemistry , quantum mechanics , engineering
Abstract Rechargeable Zn/MnO 2 batteries using mild aqueous electrolytes are attracting extensive attention due to their low cost, high safety, and environmental friendliness. However, the charge‐storage mechanism involved remains a topic of controversy so far. Also, the practical energy density and cycling stability are still major issues for their applications. Herein, a free‐standing α‐MnO 2 cathode for aqueous zinc‐ion batteries (ZIBs) is directly constructed with ultralong nanowires, leading to a rather high energy density of 384 mWh g −1 for the entire electrode. Greatly, the H + /Zn 2+ coinsertion mechanism of α‐MnO 2 cathode for aqueous ZIBs is confirmed by a combined analysis of in situ X‐ray diffractometry, ex situ transmission electron microscopy, and electrochemical methods. More interestingly, the Zn 2+ ‐insertion is found to be less reversible than H + ‐insertion in view of the dramatic capacity fading occurring in the Zn 2+ ‐insertion step, which is further evidenced by the discovery of an irreversible ZnMn 2 O 4 layer at the surface of α‐MnO 2 . Hence, the H + ‐insertion process actually plays a crucial role in maintaining the cycling performance of the aqueous Zn/α‐MnO 2 battery. This work is believed to provide an insight into the charge‐storage mechanism of α‐MnO 2 in aqueous systems and paves the way for designing aqueous ZIBs with high energy density and long‐term cycling ability.