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Structural transformations in Li2MnSiO4: Evidence that a Li intercalation material can reversibly cycle through a disordered phase

Abstract

Li2MnSiO4 is a promising high capacity cathode material due to the potential to extract two Li ions per formula unit. In practice, however, the use of Li2MnSiO4 is restricted by a low discharge capacity, which has been attributed to an irreversible structural change in the first charge cycle. Here, we use density functional theory calculations to explore this structural change; our central result is that it should be viewed as having two distinct components. First, we find that the material undergoes a structural collapse upon partial-delithiation. Remarkably, while this transformation is to a disordered structure, our calculations show that it is reversible upon relithiation. The calculated reversibility of the phase change is consistent with recent experimental x-ray diffraction measurements showing that peaks associated with crystalline MnSiO4 order, which disappear upon delithiation, are restored upon lithiation. Experiments showing reversibility of the material during cycling are also described here. We argue that the irreversible structural degradation is caused by oxygen evolution in the high delithiation state. Experimentally observed voltage profile shifts of Li2MnSiO4 during the first few cycles, as well as the different electrochemical behavior exhibited in Li2FeSiO4 can be explained by this oxygen redox model.

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Publication details

The article was received on 08 Apr 2017, accepted on 10 Jul 2017 and first published on 11 Jul 2017


Article type: Paper
DOI: 10.1039/C7TA03049E
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Structural transformations in Li2MnSiO4: Evidence that a Li intercalation material can reversibly cycle through a disordered phase

    Q. Chen, P. Xiao, Y. Pei, Y. Song, C. Xu, L. Zhen and G. Henkelman, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA03049E

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