Billaud, Juliette and Eames, Christopher and Tapia Ruiz, Nuria and Roberts, Matthew R. and Naylor, Andrew J. and Armstrong, A. Robert and Islam, M. Saiful and Bruce, Peter G. (2017) Evidence of enhanced ion transport in Li-rich silicate intercalation materials. Advanced Energy Materials, 7 (11): 1601043. ISSN 1614-6832
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Abstract
The silicate compounds Li2MSiO4 (where M = Mn, Fe, Co) have received significant attention recently as Li intercalation electrodes. Overwhelmingly they exhibit relatively poor kinetics of ion intercalation. By synthesizing Li-rich solid solutions of the form Li2+2xFe1−xSiO4 (with 0 ≤ x ≤ 0.3), the structural requirements for fast ion transport and hence relatively fast intercalation have been identified. Specifically the presence of additional Li+ in interstitial sites, not normally occupied in the stoichiometric Li2FeSiO4 compound, enhances ion transport by more than two orders of magnitude. The results, obtained by combining electrochemical measurements, with powder X-ray and neutron diffraction and atomistic modeling of the ion dynamics, provide valuable guidance in designing future intercalation electrodes with high Li-ion transport and, hence, fast electrode kinetics.