Surface chemical heterogeneous distribution in over-lithiated Li1+xCoO2 electrodes

Gang Sun; Fu-Da Yu; Mi Lu; Qingjun Zhu; Yunshan Jiang; Yongzhi Mao; John A McLeod; Jason Maley; Jian Wang; Jigang Zhou; Zhenbo Wang

doi:10.1038/s41467-022-34161-4

Surface chemical heterogeneous distribution in over-lithiated Li_1+xCoO₂ electrodes

Nat Commun. 2022 Oct 29;13(1):6464. doi: 10.1038/s41467-022-34161-4.

Authors

Gang Sun^#^{1

2}, Fu-Da Yu^#³, Mi Lu⁴, Qingjun Zhu¹, Yunshan Jiang⁵, Yongzhi Mao⁵, John A McLeod⁶, Jason Maley⁷, Jian Wang⁸, Jigang Zhou⁹, Zhenbo Wang^{10

11

12}

Affiliations

¹ College of Materials Science and Engineering, Shenzhen University, 518071, Shenzhen, China.
² College of Physics and Optoelectronic Engineering, Shenzhen University, 518060, Shenzhen, China.
³ College of Material Science and Engineering, Huaqiao University, 361021, Xiamen, China.
⁴ Key Laboratory of Functional Materials and Applications of Fujian Province, School of Materials Science and Engineering, Xiamen University of Technology, 361024, Xiamen, China.
⁵ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 150001, Harbin, China.
⁶ Department of Electrical & Computer Engineering, Western University, London, ON, N6A 5B9, Canada.
⁷ Department of Chemistry and Saskatchewan Structural Sciences Centre, University of Saskatchewan, Saskatoon, SK, S7N 5C9, Canada.
⁸ Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK, S7N 2V3, Canada. jian.wang@lightsource.ca.
⁹ Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK, S7N 2V3, Canada. jigang.zhou@lightsource.ca.
¹⁰ College of Materials Science and Engineering, Shenzhen University, 518071, Shenzhen, China. wangzhb@hit.edu.cn.
¹¹ College of Physics and Optoelectronic Engineering, Shenzhen University, 518060, Shenzhen, China. wangzhb@hit.edu.cn.
¹² School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 150001, Harbin, China. wangzhb@hit.edu.cn.

^# Contributed equally.

Abstract

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.

Abstract

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