Revealing the Structural Evolution and Phase Transformation of O3-Type NaNi<sub>1/3</sub>Fe<sub>1/3</sub>Mn<sub>1/3</sub>O<sub>2</sub> Cathode Material on Sintering and Cycling Processes
Yingying Xie, Han Gao, Ross Harder, Linsen Li, Linsen Li, Jihyeon Gim, Haiying Che, Hong Wang, Yang Ren, Xiaoyi Zhang, Luxi Li, Luxi Li, Zonghai Chen, Khalil Amine, Zi‐Feng Ma
Abstract
O-type layered oxide cathode materials can be easily synthesized for a full sodium stoichiometry with high specific capacity, but they all suffer from a capacity fade on cycling. The sintering process control and optimization are critical to ensure a high quality and consistency of the prepared cathode materials with stable structure. Herein, in situ high-energy X-ray diffraction (HEXRD) was first employed to investigate the phase evolution of the oxides during the sintering process of O3-type NaNi1/3Fe1/3Mn1/3O2. The in situ HEXRD and both operando Bragg coherent diffraction (BCXD) and coherent multicrystal diffraction (CMCD) were utilized to investigate the phase transformation of the cathode materials during the sodiation/desodiation process. A composite structure comprised of O-type and P-type oxides was formed after the initial electrochemical activation of the cathode material, resulting in good structural and electrochemical stability. This finding implies that strain engineering can be a new design philosophy for the development of next generation high-performance sodium ion cathodes.