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| Home > Publications database > Competing mechanisms determine oxygen redox in doped Ni-Mn based layered oxides for Na-ion batteries |
| Preprint | PUBDB-2023-07449 |
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2023
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Please use a persistent id in citations: doi:10.26434/chemrxiv-2023-jfnmr doi:10.3204/PUBDB-2023-07449
Abstract: Cation doping is an effective strategy for improving the cyclability of layered oxide cathode materials through suppression of phase transitions in the high voltage region (>~4.0V). In this study we choose Mg and Sc as representative dopants in P2- Na$_{0.67}$Ni$_{0.33}$Mn$_{0.67}$O$_2$. While both dopants have a positive effect on the cycling stability, they are found to influence the properties in the high voltage regime in different ways. Through a combination of RIXS, XRD, XAS, PDF analysis, and DFT, we show that it is more than just suppression of the P2 to O$_2$ phase transition that is critical for promoting the favorable properties, and that the interplay between Ni and O activity are also critical aspects that dictate the performance. With Mg doping, we could enhance the Ni activity while simultaneously suppressing the O activity. This is surprising because it is in contrast to what has been reported in other Mn-based layered oxides where Mg is known to trigger oxygen redox. We address this contradiction by proposing a competing mechanism between Ni and Mg that impacts differences in O activity in Na$_{0.67}$Mg$_x$Ni$_{0.33-x}$Mn$_{0.67}$O$_2$ (x<0<0.33). These findings provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxides.
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