Understanding electrochemical performance improvement with Nb doping in lithium-rich manganese-based cathode materials

• Published in: Journal of power sources Vol. 462; p. 228185
• Main Authors: Dong, Shengde, Zhou, Yuan, Hai, Chunxi, Zeng, Jinbo, Sun, Yanxia, Shen, Yue, Li, Xiang, Ren, Xiufeng, Sun, Chao, Zhang, Guotai, Wu, Zhaowei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.06.2020
• Subjects: Density functional theory; Electrochemical performance; Li-ion battery; Lithium-rich manganese-based cathode materials; Nb doping; Nb doping; Electrochemical performance; Density functional theory; Lithium-rich manganese-based cathode materials; Li-ion battery
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2020.228185

This study synthesizes pristine and Nb-doped lithium-rich manganese-based cathode materials by solvothermal and high-temperature solid-phase methods. Analysis by focused ion beam scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy indicates successful Nb doping into the material's bulk structure. Electrochemical evaluation reveals that electrochemical performance is significantly enhanced by Nb doping. The discharge capacity of Nb-0.02 can maintain 271.7 mAh·g−1, and its cycle retention rate is up to 98.50% after 300 cycles at 0.2C; however, under the same parameters, the pristine material's discharge capacity and cycle retention rate are 212.8 mAh·g−1 and 86.68%. The initial coulombic efficiency and initial discharge capacity of Nb-0.02 is 86.94% and 287.5 mAh·g−1, while that of the pristine material is 73.59% and 234.2 mAh·g−1. Density functional theory calculations demonstrate that Nb doping accelerates Li-ion diffusion and stabilizes material structure due to stronger Nb–O bonds from reduced Li-ion migration barrier energy. Thus, the proposed modification strategy for Nb doping can illuminate the structural design of lithium-rich manganese-based cathode materials. •Nb elements are distributed across the surface and in the bulk material.•ICE and cycle performance are significantly enhanced by Nb doping.•DFT calculations confirm that Nb doping accelerates Li-ion diffusion.