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Title: A comprehensive picture of the current rate dependence of the structural evolution of P2-Na2/3Fe2/3Mn1/3O2
Authors: Sharma, N
Han, MH
Pramudita, JC
Gonzalo, E
Brand, HEA
Rojo, T
Keywords: Cathodes
Electric batteries
Sodium ions
Electric discharges
Issue Date: 2-Sep-2015
Publisher: Royal Society of Chemistry
Citation: Sharma, N., Han, M. H., Pramudita, J. C., Gonzalo, E., Brand, H. E. A., & Rojo, T. (2015). A comprehensive picture of the current rate dependence of the structural evolution of P2-Na 2/3 Fe 2/3 Mn 1/3 O 2. Journal of Materials Chemistry A, 3(42), 21023-21038.doi:10.1039/C5TA04976H
Abstract: Cathodes that feature a layered structure are attractive reversible sodium hosts for ambient temperature sodium-ion batteries which may meet the demands for large-scale energy storage devices. However, crystallographic data on these electrodes are limited to equilibrium or quasi-equilibrium information. Here we report the current-dependent structural evolution of the P2-Na2/3Fe2/3Mn1/3O2 electrode during charge/discharge at different current rates. The structural evolution is highly dependent on the current rate used, e.g., there is significant disorder in the layered structure near the charged state at slower rates and following the cessation of high-current rate cycling. At moderate and high rates this disordered structure does not appear. In addition, at the slower rates the disordered structure persists during subsequent discharge. In all rates examined, we show the presence of an additional two-phase region that has not been observed before, where both phases maintain P63/mmc symmetry but with varying sodium contents. Notably, most of the charge at each current rate is transferred via P2 (P63/mmc) phases with varying sodium contents. This illustrates that the high-rate performance of these electrodes is in part due to the preservation of the P2 structure and the disordered phases appear predominantly at lower rates. Such current-dependent structural information is critical to understand how electrodes function in batteries which can be used to develop optimised charge/discharge routines and better materials. © 2015 The Royal Society of Chemistry. This article is Open Access.
Description: This article is licenced under a Creative Commons Attribution-Non Commercial 3.0 Unported licence.
ISSN: 2050-7488
Appears in Collections:Journal Articles

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