摘要
In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.
In order to obtain an in-depth insight into the mechanism of charge compensation and capacity fading in LiCoO2, the evolution of electronic structure of LiCoO2 at different cutoff voltages and after different cycles are studied by soft x-ray absorption spectroscopy in total electron（TEY） and fluorescence（TFY） detection modes, which provide surface and bulk information, respectively. The spectra of Co L2,3-edge indicate that Co contributes to charge compensation below 4.4 V.Combining with the spectra of O K-edge, it manifests that only O contributes to electron compensation above 4.4 V with the formation of local O 2 p holes both on the surface and in the bulk, where the surficial O evolves more remarkably. The evolution of the O 2 p holes gives an explanation to the origin of O2^-or even O2. A comparison between the TEY and TFY of O K-edge spectra of LiCoO2 cycled in a range from 3 V to 4.6 V indicates both the structural change in the bulk and aggregation of lithium salts on the electrode surface are responsible for the capacity fading. However, the latter is found to play a more important role after many cycles.
作者
Xing-Hui Long
Yan-Ru Wu
Nian Zhang
Peng-Fei Yu
Xue-Fei Feng
Shun Zheng
Jia-Min Fu
Xiao-Song Liu
Na Liu
Meng Wang
Lei-Min Xu
Jin-Ming Chen
Jenn-Min Lee
龙兴辉;吴颜如;张念;于鹏飞;冯雪飞;郑顺;傅佳敏;刘啸嵩;柳娜;王梦;徐磊敏;陈锦明;李振民(State Key Laboratory of Functional Materials for Informatics,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China;Center for Excellence in Superconducting Electronics,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China;University of Chinese Academy of Sciences,Beijing 100049,China;Advanced Light Source,Lawrence Berkeley National Laboratory,Berkeley,California 94720,USA;School of Physical Science and Technology,Shanghai Tech University,Shanghai 200031,China;NingDe Amperex Technology Limited,Ningde 352100,China;＂National＂ Synchrotron Radiation Research Centre,Hsinchu 30076,Taiwan,China)
基金
Project supported by the National Natural Science Foundation of China(Grant Nos.21503263,U1632269,21473235,and 11227902)
