Suppressing the high-voltage phase transition in O3-type layered cathode enables ultra-stable sodium-ion batteries
M. K. Yu, Ming Ma, Lina Yang, Qingling Guo, Shanshan Ye, Nazir Ahmad, Zixuan Jiang, Jiacheng Liang, Jing Xia, Bo Peng, Wenxiu He, Liang Shi, Genqiang Zhang
Abstract
O3-type transition metal layer oxide cathode materials are promising candidates for sodium-ion batteries, owing to their high theoretical capacity and ample sodium availability. However, they are challenged for operating at higher voltage (≥4.2 V) to realize high use of capacity with long cyclability, limited by the phase transition at high voltage. Herein, we show that the high-voltage phase transition of typical O3-NaFe 0.5 Mn 0.5 O 2 cathode can be well suppressed, by means of high entropy design strategy. As proof of concept, the designed low-cost O3-Na 0.8 Ni 0.2 Fe 0.25 Al 0.05 Mg 0.05 Ti 0.05 Mn 0.4 O 2 (HE-NFMO) cathode material exhibits suppressed high-voltage phase transition, which displays excellent electrochemical properties operated at high-voltage of 4.2 V. Consequently, the HE-NFMO cathode achieves a high capacity of 131.9 mAh g −1 at 0.1 C and long cycling life over 900 cycles at 5.0 C. Advanced characterizations combined with theoretical calculations confirm that the HE-NFMO could maintain a stable structural framework and show low Na + diffusion barrier, which demonstrate suppressed phase transition with ultra-low strain and fast Na + transfer kinetics. This study offers valuable insights for the design of ultra-stable cathode operated at high cut-off voltage.