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Enabling stable MnO₂ matrix for aqueous zinc-ion battery cathodes

Jiao, Y; Kang, L; Berry-Gair, J; McColl, K; Li, J; Dong, H; Jiang, H; ... Parkin, IP; + view all (2020) Enabling stable MnO₂ matrix for aqueous zinc-ion battery cathodes. Journal of Materials Chemistry A 10.1039/d0ta08638j. (In press). Green open access

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Abstract

The primary issue faced by MnO2 cathode materials for aqueous Zn-ion batteries (AZIBs) is the occurrence of structural transformations during cycling, resulting in unstable capacity output. Pre-intercalating closely bonded ions into the MnO2 structures has been demonstrated as an effective approach to combat this. However, mechanisms of the pre-intercalation remain unclear. Herein, two distinct δ-MnO2 (K0.28MnO2·0.1H2O and K0.21MnO2·0.1H2O) are prepared with varying amounts of pre-intercalated K+ and applied as cathodes for AZIBs. The as-prepared K0.28MnO2·0.1H2O cathodes exhibit relatively high specific capacity (300 mA h g−1 at 100 mA g−1), satisfactory rate performance (35% capacity recovery at 5 A g−1) and competent cyclability (ca. 95% capacity retention after 1000 cycles at 2 A g−1), while inferior cyclability and rate performance are observed in K0.21MnO2·0.1H2O. A stable δ-MnO2 phase is observed upon cycling, with the reversible deposition of Zn4SO4(OH)6·5H2O (ZSH), ion migration between electrodes and synchronous transition of Mn valence states. This work firstly and systematically reveals the role of the pre-intercalated ions via density functional theory simulations and show that above a threshold K/Mn ratio of ca. 0.26, the K ions suppress structural transformations by stabilizing the δ phase. To demonstrate its commercial potential, AZIBs with high-loading active materials are fabricated, which deliver adequate energy and power densities compared with most commercial devices.

Type: Article
Title: Enabling stable MnO₂ matrix for aqueous zinc-ion battery cathodes
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/d0ta08638j
Publisher version: https://doi.org/10.1039/d0ta08638j
Language: English
Additional information: This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence (http://creativecommons.org/licenses/by-nc/3.0/).
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10113373
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