H⁺‐Insertion Boosted α‐MnO₂ for an Aqueous Zn‐Ion Battery

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.201905842. 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. www.advancedsciencenews.com

Mn2+ Ions Confined by Electrode Microskin for Aqueous Battery beyond Intercalation Capacity

“…In order to further emphasize the importance of this work, Table 1 shows the comparison of the maximum specific capacity between this work and some recent reports. [ 53–59 ] It is obvious that the maximum discharge capacity and cycle life of the ZMBs in this work are better than that of most literatures published in the year of 2020.…”

Self-assembled α-MnO2 urchin-like microspheres as a high-performance cathode for aqueous Zn-ion batteries

“…In Fig. 2e, the O 1s contribute to the electrochemical performances of the AUM-based AZIBs [29]. As shown in Fig.…”

Unraveling the Dissolution‐Mediated Reaction Mechanism of α‐MnO2 Cathodes for Aqueous Zn‐Ion Batteries

“…Despite its thermodynamic stability, however, the presence of ZnMn 2 O 4 is unwelcome for Zn/MnO 2 electrochemistry; strong electrostatic repulsion of Zn 2+ ions from ZnMn 2 O 4 makes their insertion into its lattice extremely difficult [28] and thus contributes to gradual capacity loss of a Zn/MnO 2 cell, reported in several literature reports. [11] For a few MnO 2 nanorods aggravated with severe Mn dissolution, parts of their outer surface detach from the bulk. As the surface detaches, the rod becomes torn out as shown in Figure S6a, Supporting Information.…”