Revealing the correlation between structure evolution and electrochemical performance of high-voltage lithium cobalt oxide

Lithium cobalt oxide (LCO) is the dominating cathode materials for lithium-ion batteries (LIBs) deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances. The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies. However, the corresponding modification mechanism, especially the influence of the long- and short-range structural transitions at high-voltage on electrochemical performance, is still not well understood and needs further exploration. Based on ss-NMR, in-situ X-ray diffraction, and electrochemical performance results, it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO, thereby determining the electrochemical performance. The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level, leading to better reversibility of the H1-3 phase and smaller lattice strain, and significantly improved cycle performance. Such a comprehensive long-range, local, and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO, providing a guiding principle for developing high-voltage LCO for high energy density LIBs. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

The introduction of La and Al ions can delay the appearance of the H1-3 phase, induce various local environments, adapt better to volume changes at the atomic level, improve reversibility of the H1-3 phase and reduce lattice strain, resulting in significantly enhanced cycle performance.