TY  - EJOUR
AU  - Li, Yongchun
AU  - Mazzio, Katherine
AU  - Yaqoob, Najma
AU  - Sun, Yanan
AU  - Freytag, Annica
AU  - Wong, Deniz
AU  - Schulz, Christian
AU  - Baran, Volodymyr
AU  - San Jose Mendez, Alba
AU  - Schuck, Götz
AU  - Zając, Marcin
AU  - Kaghazchi, Payam
AU  - Adelhelm, Philipp
TI  - Competing mechanisms determine oxygen redox in doped Ni-Mn based layered oxides for Na-ion batteries
M1  - PUBDB-2023-07449
PY  - 2023
AB  - 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<sub>0.67</sub>Ni<sub>0.33</sub>Mn<sub>0.67</sub>O<sub>2</sub>. 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<sub>2</sub> 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<sub>0.67</sub>Mg<sub>x</sub>Ni<sub>0.33−x</sub>Mn<sub>0.67</sub>O<sub>2</sub> (x<0<0.33). These findings provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxides.
LB  - PUB:(DE-HGF)25
DO  - DOI:10.26434/chemrxiv-2023-jfnmr
UR  - https://bib-pubdb1.desy.de/record/599477
ER  -