Xiao Biwei, Liu Hanshuo, Chen Ning, Banis Mohammad Norouzi, Yu Haijun, Liang Jianwen, Sun Qian, Sham Tsun-Kong, Li Ruying, Cai Mei, Botton Gianluigi A, Sun Xueliang
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, N6A 6B9, Canada.
Department of Materials Science and Engineering, McMaster University, Hamilton, ON, L8S 4L8, Canada.
Angew Chem Int Ed Engl. 2020 Aug 17;59(34):14313-14320. doi: 10.1002/anie.202005337. Epub 2020 Jun 30.
Li- and Mn-rich layered oxides are among the most promising cathode materials for Li-ion batteries with high theoretical energy density. Its practical application is, however, hampered by the capacity and voltage fade after long cycling. Herein, a finite difference method for near-edge structure (FDMNES) code was combined with in situ X-ray absorption spectroscopy (XAS) and transmission electron microscopy/electron energy loss spectroscopy (TEM/EELS) to investigate the evolution of transition metals (TMs) in fresh and heavily cycled electrodes. Theoretical modeling reveals a recurring partially reversible LiMn O -like sub-nanodomain formation/dissolution process during each charge/discharge, which accumulates gradually and accounts for the Mn phase transition. From the modeling of spectra and maps of the valence state over large regions of the cathodes, it was found that the phase change is size-dependent. After prolonged cycling, the TMs displayed different levels of inactivity.
富锂锰层状氧化物是锂离子电池中最具潜力的正极材料之一，具有较高的理论能量密度。然而，其实际应用受到长循环后容量和电压衰减的阻碍。在此，将近边结构有限差分法（FDMNES）代码与原位X射线吸收光谱（XAS）以及透射电子显微镜/电子能量损失光谱（TEM/EELS）相结合，以研究新鲜和深度循环电极中过渡金属（TMs）的演变。理论建模揭示了在每次充电/放电过程中反复出现的类似LiMnO的部分可逆亚纳米域形成/溶解过程，该过程逐渐累积并导致Mn的相变。通过对阴极大面积区域的价态光谱和图谱进行建模，发现相变与尺寸有关。长时间循环后，过渡金属表现出不同程度的惰性。
