Biphase Cobalt–Manganese Oxide with High Capacity and Rate Performance for Aqueous Sodium‐Ion Electrochemical Energy Storage |
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Authors: | Xiaoqiang Shan Daniel S. Charles Wenqian Xu Mikhail Feygenson Dong Su Xiaowei Teng |
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Affiliation: | 1. Department of Chemical Engineering, University of New Hampshire, Durham, NH, USA;2. X‐ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA;3. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA;4. Juelich Centre for Neutron Science, Forschungszentrum Juelich GmbH, Juelich, Germany;5. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA |
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Abstract: | Manganese‐based metal oxide electrode materials are of great importance in electrochemical energy storage for their favorable redox behavior, low cost, and environmental friendliness. However, their storage capacity and cycle life in aqueous Na‐ion electrolytes is not satisfactory. Herein, the development of a biphase cobalt–manganese oxide (Co? Mn? O) nanostructured electrode material is reported, comprised of a layered MnO2?H2O birnessite phase and a (Co0.83Mn0.13Va0.04)tetra(Co0.38Mn1.62)octaO3.72 (Va: vacancy; tetra: tetrahedral sites; octa: octahedral sites) spinel phase, verified by neutron total scattering and pair distribution function analyses. The biphase Co? Mn? O material demonstrates an excellent storage capacity toward Na‐ions in an aqueous electrolyte (121 mA h g?1 at a scan rate of 1 mV s?1 in the half‐cell and 81 mA h g?1 at a current density of 2 A g?1 after 5000 cycles in full‐cells), as well as high rate performance (57 mA h g?1 a rate of 360 C). Electrokinetic analysis and in situ X‐ray diffraction measurements further confirm that the synergistic interaction between the spinel and layered phases, as well as the vacancy of the tetrahedral sites of spinel phase, contribute to the improved capacity and rate performance of the Co? Mn? O material by facilitating both diffusion‐limited redox and capacitive charge storage processes. |
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Keywords: | aqueous Na‐ion storage biphase cobalt– manganese oxide capacitive and diffusion‐limited redox capacities in situ X‐ray diffraction pair distribution function |
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