Issue 3, 2021

Towards a high MnO2 loading and gravimetric capacity from proton-coupled Mn4+/Mn2+ reactions using a 3D free-standing conducting scaffold

Abstract

We highlight 3D free-standing electrospun CNF electrodes as superior conductive scaffolds for the highly reversible proton-coupled MnIV(s) ↔ MnII(aq) conversion in a mild aqueous buffered electrolyte (pH 5). An electrochemical quartz crystal microbalance is used to in situ monitor these conversion reactions on the non-transparent CNF electrodes. Free-standing CNFs allow for a remarkably high relative MnO2 loading (63%, equivalent to an mMnO2/mCNF ratio of 1.7) at a maximal charge of 1.4 mA h cm−2, while keeping the C.E. ≥ 95% over 300 cycles. The gravimetric capacity of the complete cathode is thus as high as 338 mA h gMnO2+CNF−1 (i.e., 534 mA h gMnO2−1), outperforming the current state-of-the-art cathodes based on conventional graphite/carbon felts as substrates (<30% MnO2 loading, <0.4 mMnO2/mCNF ratio and <150 mA h gMnO2+substrate−1) or composite electrodes. Furthermore, the buffered electrolyte allows for remarkably highly constant deposition–dissolution potentials with a low hysteresis (0.16 V). Pairing 3D electrospun CNFs (diameter ≤ 200 nm) and mild aqueous buffered electrolytes is thus a striking approach towards the development of MnO2-based mild aqueous batteries with high energy efficiency.

Graphical abstract: Towards a high MnO2 loading and gravimetric capacity from proton-coupled Mn4+/Mn2+ reactions using a 3D free-standing conducting scaffold

Supplementary files

Article information

Article type
Communication
Submitted
02 Nov. 2020
Accepted
24 Dec. 2020
First published
24 Dec. 2020

J. Mater. Chem. A, 2021,9, 1500-1506

Towards a high MnO2 loading and gravimetric capacity from proton-coupled Mn4+/Mn2+ reactions using a 3D free-standing conducting scaffold

A. Singh, O. Sel, H. Perrot, V. Balland, B. Limoges and C. Laberty-Robert, J. Mater. Chem. A, 2021, 9, 1500 DOI: 10.1039/D0TA10685B

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