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.