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Issue 13, 2013
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Defect chemistry and lithium-ion migration in polymorphs of the cathode material Li2MnSiO4

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Abstract

The search for new low-cost and safe cathodes for next-generation lithium batteries has led to increasing interest in silicate materials. Here, a systematic comparison of crystal properties, defect chemistry and Li-ion migration behaviour of four polymorphs of Li2MnSiO4 is reported based on the results of atomistic simulations. The four polymorphs examined have Pmn21, Pmnb, P21/n, and Pn symmetry. Lattice energies of all four polymorphs are very similar, with only a small energy preference for the two orthorhombic phases over the monoclinic phases, which explains the difficulty experimentalists have had preparing pure-phase samples. Defect formation energies of the polymorphs are also similar, with antisite Li/Mn defects the most energetically favourable. Detailed analysis of the Li-ion migration energy surfaces reveals high activation energies (around 0.9 to 1.7 eV) and curved trajectories. All four polymorphs are thus expected to be poor Li-ion conductors, requiring synthesis as nanoparticles to facilitate sufficient Li transfer. The results accord well with experimental reports on the structure, relative phase stabilities and electrochemical performance of materials in this system.

Graphical abstract: Defect chemistry and lithium-ion migration in polymorphs of the cathode material Li2MnSiO4

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Publication details

The article was received on 09 Jan 2013, accepted on 07 Feb 2013 and first published on 07 Feb 2013


Article type: Paper
DOI: 10.1039/C3TA00111C
Citation: J. Mater. Chem. A, 2013,1, 4207-4214
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    Defect chemistry and lithium-ion migration in polymorphs of the cathode material Li2MnSiO4

    C. A. J. Fisher, N. Kuganathan and M. S. Islam, J. Mater. Chem. A, 2013, 1, 4207
    DOI: 10.1039/C3TA00111C

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