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Scalable Synthesis of Pre‐Intercalated Manganese(III/IV) Oxide Nanostructures for Supercapacitor Electrodes: Electrochemical Comparison of Birnessite and Cryptomelane Products

Daniel Raymond Jones Orcid Logo, Haytham E. M. Hussein, Eleri Worsley, Sajad Kiani, Kittiwat Kamlungsua, Thomas Fone, Christopher Phillips Orcid Logo, Davide Deganello Orcid Logo

ChemElectroChem, Volume: 10, Issue: 14

Swansea University Authors: Daniel Raymond Jones Orcid Logo, Eleri Worsley, Sajad Kiani, Thomas Fone, Christopher Phillips Orcid Logo, Davide Deganello Orcid Logo

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DOI (Published version): 10.1002/celc.202300210

Abstract

Manganese(III/IV) oxide is a promising pseudocapacitive material for supercapacitor electrodes due to favorable attributes such as its chemical resilience, high earth abundance and low specific cost. Herein, the morphological, compositional and electrochemical characteristics of co-precipitated mang...

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Published in: ChemElectroChem
ISSN: 2196-0216 2196-0216
Published: Wiley 2023
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URI: https://cronfa.swan.ac.uk/Record/cronfa63467
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Abstract: Manganese(III/IV) oxide is a promising pseudocapacitive material for supercapacitor electrodes due to favorable attributes such as its chemical resilience, high earth abundance and low specific cost. Herein, the morphological, compositional and electrochemical characteristics of co-precipitated manganese(III/IV) oxide products, each described by the general formula NaxKyMnOz, are investigated to establish how these properties are influenced by synthesis conditions. NaxKyMnOz growths in low-temperature (<100 °C) basic and acidic environments are shown to promote the formation of turbostratic birnessite and cryptomelane phases, respectively, with the latter polymorph containing a relatively low concentration of interstitial Na+ and K+ cations. It is demonstrated that K+ pre-insertion during synthesis yields lower initial charge-transfer resistances than equivalent Na+ intercalation, and that this parameter correlates strongly with storage performance. Accordingly, Na-mediated storage initially delivers inferior specific capacitances and Coulombic efficiencies than K-based mechanisms, but K+ intercalation/deintercalation causes faster capacitance decay during prolonged galvanostatic cycling. Furthermore, whilst crystallographic phase is shown to have a weaker effect on NaxKyMnOz storage properties than the choice of intercalating guest cations, cryptomelane electrodes are more susceptible to cycling-induced capacitance and efficiency losses than their birnessite counterparts. In combination, these insights provide an instructive foundation for the optimization of NaxKyMnOz in high-power storage applications.
Keywords: Birnessite, Cryptomelane, Intercalation, MnO2, Pseudocapacitance
College: Faculty of Science and Engineering
Funders: This study is partially funded by Enserv Power Co. Ltd., and the research contributes to the IMPACT operation which has been part-funded by the European Regional Development Fund through the Welsh Government and Swansea University. The authors are grateful for access to XPS and TEM instrumentation provided by the Advanced Imaging of Materials (AIM) facility, which is funded in part by EPSRC (EP/M028267/1), the European Regional Development Fund via the Welsh Government (80708), the Ser Solar project via Welsh Government, and Carl Zeiss Microscopy. Swansea University.
Issue: 14