Sambandam Balaji, Alfaruqi Muhammad H, Park Sunhyeon, Lee Seunggyeong, Kim Sungjin, Lee Jun, Mathew Vinod, Hwang Jang-Yeon, Kim Jaekook
Department of Materials Science and Engineering, Chonnam National University, Gwangju 61186, South Korea.
ACS Appl Mater Interfaces. 2021 Nov 17;13(45):53877-53891. doi: 10.1021/acsami.1c15394. Epub 2021 Nov 6.
In this study, magnesium-ion-substituted, sodium-deficient, P3- and P2-layered manganese oxide cathodes (NaMgMnO) were synthesized through a facile polyol-assisted combustion technique for applications in sodium-ion batteries. The electrochemical reaction pathways, structural integrity, and long cycling ability at low current rates of the P3- and P2-phases of the NaMgMnO cathodes were investigated using time-consuming techniques, such as galvanostatic titration and series cyclic voltammetry. The results obtained from these techniques were supported by those obtained from operando X-ray diffraction (XRD) analysis. Particularly, the P2-phase provided excellent structural stability owing to its intrinsic crystal structure, thereby exhibiting a reversible capacity retention of 82.6% after 262 cycles at a low rate of 0.1 C; in contrast, the P3-phase exhibited a capacity retention of 38.7% after 241 cycles at a similar current rate. The air stability of these as-prepared powders, which were stored under ambient conditions, was progressively analyzed over a period of 6 months through XRD without conducting any special experiments. The results suggest that in the P3-phase, the formation of NaHCO and hydrated phase impurities, resulting from Na/H exchange and hydration reactions, respectively, was likely to occur more quickly, that is, within a few days, compared to that in the P2-phase.
