TY  - JOUR
AU  - Li, Yongchun
AU  - Mazzio, Katherine
AU  - Yaqoob, Najma
AU  - Sun, Yanan
AU  - Freytag, Annica I.
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
JO  - Advanced materials
VL  - 36
IS  - 18
SN  - 0935-9648
CY  - Weinheim
PB  - Wiley-VCH
M1  - PUBDB-2024-01425
SP  - 2309842
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. In this study, Mg and Sc are chosen as dopants in P2-Na<sub>0.67</sub>Ni<sub>0.33</sub>Mn<sub>0.67</sub>O<sub>2</sub>, and both have found to positively impact the cycling stability, but influence the high voltage regime in different ways. Through a combination of synchrotron-based methods and theoretical calculations it is shown that it is more than just suppression of the P2 to O2 phase transition that is critical for promoting the favorable properties, and that the interplay between Ni and O activity is also a critical aspect that dictates the performance. With Mg doping, the Ni activity can be enhanced 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. This contradiction is addressed by proposing a competing mechanism between Ni and Mg that impacts differences in O activity in Na<sub>0.67</sub>MgxNi<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)16
C6  - pmid:38269958
UR  - <Go to ISI:>//WOS:001150573000001
DO  - DOI:10.1002/adma.202309842
UR  - https://bib-pubdb1.desy.de/record/605338
ER  -