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Impact of Structural Transformation on Electrochemical Performances of Li-Rich Cathode Materials: The Case of Li₂RuO₃

Zheng, Feng, Zheng, Shiyao, Zhang, Peng, Zhang, Xiaofeng, Wu, Shunqing, Yang, Yong, Zhu, Zi-zhong
Journal of physical chemistry 2019 v.123 no.22 pp. 13491-13499
cathodes, cations, electric potential difference, electrochemistry, lithium batteries, oxidation, oxides, oxygen production, physical chemistry
Exploration of Li-rich transition-metal (TM) oxides with active anionic redox reaction has paved a promising way for the design of high-capacity Li-ion battery cathode materials. In the present work, we show that our predicted two-step structural transformation and resulted structural evolution for Li₂RuO₃ agree well with our experiments. The anionic oxidation occurs upon delithiation, and the reduction of structural stability would initiate cation migration from Li–Ru layers to adjacent Li layers, which can in turn restabilize the delithiated structures and suppress the oxygen evolution, providing a good explanation on the observed high reversible capacity. However, the gradual migration of cations will cause a serious voltage decay of Li₂RuO₃ upon cycling, as well as poor cycling kinetics because of the fact that migrating cations in Li layers impede the Li diffusion. Our finding significantly broadens the current understanding on the electrochemistry of Li₂RuO₃ and provides important guidelines for the future design of Li-rich TM oxides as high-capacity cathode materials.