posted on 2022-02-04, 20:37authored byZheng-Yao Li, Xiaobai Ma, Ivan A. Bobrikov, Kai Sun, Hongliang Wang, Linfeng He, Yuqing Li, Dongfeng Chen
Layered
cathodes have been recognized as potential advanced candidates
for sodium-ion batteries (SIBs), but the poor electrochemical performance
has seriously hindered their further development. Herein, an ordered
Na2/3[Ni2/9Mg1/9Mn5/9Ti1/9]O2 (NMMT) is designed and investigated as a
high-performance cathode for SIBs through the synergistic effect of
Mg and Ti codoping. Compared to the single Mg- or Ti-doped materials,
NMMT clearly exhibits superstructure ordering diffraction peaks, and
neutron diffraction further confirms that the diffraction peaks can
be well indexed by a larger supercell P63, rather than the common unit cell P63/mmc by X-ray diffraction (XRD). High-resolution
transmission electron microscopy also approves the ordering arrangement.
This material shows an obvious capacity activation process during
the first cycles, thus delivering 113 mA h g–1 specific
capacity at 0.1 C (close to the theoretical value). Excellent rate
capability even at 15 C and cycling stability after 500 cycles between
2.0 and 4.3 V can also be achieved, indicating that an ordered cathode
is still promising. Besides, a single-phase reaction mechanism is
revealed by ex situ/in situ XRD experiments. This study offers some
insights into the material design and characterization of layered
oxide cathodes for high-performance SIBs in the future.