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Insight into fast Li diffusion in Li-excess spinel lithium manganese oxide

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Abstract

Li-excess cathode materials are expected to have great potential for applications in lithium-ion batteries owing to their high energy density. In addition to the extensive studies on the anionic redox activity in lithium-ion batteries, their Li-ion diffusion properties have also attracted much interest. Using ab initio calculations, herein, we systematically explored Li diffusion properties in both stoichiometric and Li-excess phases of spinel lithium manganese oxide (LMO). Our results showed that there is a type of structural unit (six Mn ions forming a cation ring for Li-ions to pass through during migration) that acts as “gate sites” and the Li-excess configuration could introduce two types of fast Li-ion migration channels to enhance the Li-ion diffusivity. The first type of fast channels resulted from the decreased repulsive coulombic interactions between the cations at the gate site and the mobile Li-ions due to the substitution of Mn3+ by Li+. The second type of fast channels originated because the excess Li could induce more gate sites with symmetrical distribution of Mn4+ surrounding the Li diffusion channel, which is proved to be able to enhance the Li-ion mobility. Interestingly, it was also found that in slow Li diffusion channels for both stoichiometric and Li-excess LMO, a simultaneous polaron hopping process around the gate sites would be coupled with the Li migration process, which accounts for the high energy barriers for Li-ion diffusion.

Graphical abstract: Insight into fast Li diffusion in Li-excess spinel lithium manganese oxide

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Publication details

The article was received on 10 Feb 2018, accepted on 27 Mar 2018 and first published on 29 Mar 2018


Article type: Paper
DOI: 10.1039/C8TA01428K
Citation: J. Mater. Chem. A, 2018, Advance Article
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    Insight into fast Li diffusion in Li-excess spinel lithium manganese oxide

    W. Xiao, C. Xin, S. Li, J. Jie, Y. Gu, J. Zheng and F. Pan, J. Mater. Chem. A, 2018, Advance Article , DOI: 10.1039/C8TA01428K

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