Issue 13, 2013

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

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

Supplementary files

Article information

Article type
Paper
Submitted
09 Jan 2013
Accepted
07 Feb 2013
First published
07 Feb 2013

J. Mater. Chem. A, 2013,1, 4207-4214

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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