Valence study of Li(Ni0.5Mn0.5)1-xCox O2 and LiNi1-xCox O2: The role of charge transfer and charge disproportionation

Daisuke Takegami, Kosuke Kawai, Miguel Ferreira-Carvalho, Sahana Rößler, Cheng En Liu, Chang Yang Kuo, Chun Fu Chang, Atsusa Minamida, Tatsuya Miyazaki, Masashi Okubo, Liu Hao Tjeng, Takashi Mizokawa

研究成果: Article同行評審

摘要

The series of LiMO2 (M: transition metal) materials are highly relevant as cathode materials of Li-ion batteries. The stability of such systems remains an important factor for their usability in batteries, and depends strongly on the electronic configuration of the transition-metal ions. In particular, the promising class of multi-transition-metal systems exhibits complicated valence states due to intermetallic charge transfer and charge disproportionation. Here we perform a systematic study on the valence of the transition-metal ions using x-ray absorption spectroscopy on the M-L2,3 edges and O-K edges. In Li(Ni0.5Mn0.5)1-xCoxO2 we established that the valence is Co3+ and Ni0.52+Mn0.54+ throughout the whole series. Meanwhile, in LiNi1-xCoxO2 we found that the Ni displays a behavior consistent with a charge disproportionated negative charge transfer system, and that with increased concentration of Co3+, the disproportionation signal decreases. Since the number of O 2p holes also gets reduced, we infer that the material will also become more unstable.

原文English
文章編號055401
期刊Physical Review Materials
8
發行號5
DOIs
出版狀態Published - 5月 2024

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