2026-10-14T13:47:01Z https://www.scidb.cn/oai

10.57760/sciencedb.02714 2022-11-14T09:51:16Z

2022-11-14 Surface chemical heterogeneous distribution in over-lithiated Li1+xCoO2 electrodes doi:10.57760/sciencedb.02714 en In commercial Li-ion batteries, the internal short circuits or over-lithiation often cause structural transformation in electrodes and may lead to safety risks. Herein, we investigate the over-discharged mechanism of LiCoO2/graphite pouch cells, especially spatially resolving the morphological, surface phase, and local electronic structure of LiCoO2 electrode. With synchrotron-based X-ray techniques and Raman mapping, together with spectroscopy simulations, we demonstrate that over-lithiation reaction is a surface effect, accompanied by Co reduction and surface structure transformation to Li2CoO2/Co3O4/CoO/Li2O-like phases. This surface chemical distribution variation is relevant to the depth and exposed crystalline planes of LiCoO2 particles, and the distribution of binder/conductive additives. Theoretical calculations confirm that Li2CoO2-phase has lower electronic/ionic conductivity than LiCoO2-phase, further revealing the critical effect of distribution of conductive additives on the surface chemical heterogeneity evolution. Our findings on such surface phenomena are non-trivial and highlight the capability of synchrotron-based X-ray techniques for studying the spatial chemical phase heterogeneity. LiCoO2 electrode; Overlithiation; X-PEEM; Non-uniform distribution; Degradation mechanism; Surface heterogeneity Sun Gang PUBLIC https://creativecommons.org/publicdomain/zero/1.0/ dataset http://www.doi.org/10.1038/s41467-022-34161-4 Science Data Bank