Structural and mechanistic insights into fast lithium-ion conduction in Li4SiO4-Li3PO4 solid electrolytes

Yue Deng, Christopher Eames, Jean Noël Chotard, Fabien Laleìre, Vincent Seznec, Steffen Emge, Oliver Pecher, Clare P. Grey, Christian Masquelier, M. Saiful Islam

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Abstract

Solid electrolytes that are chemically stable and have a high ionic conductivity would dramatically enhance the safety and operating lifespan of rechargeable lithium batteries. Here, we apply a multi-technique approach to the Li-ion conducting system (1–z)Li4SiO4–(z)Li3PO4 with the aim of developing a solid electrolyte with enhanced ionic conductivity. Previously unidentified superstructure and immiscibility features in high-purity samples are characterized by X-ray and neutron diffraction across a range of compositions (z = 0.0–1.0). Ionic conductivities from AC impedance measurements and large-scale molecular dynamics (MD) simulations are in good agreement, showing very low values in the parent phases (Li4SiO4 and Li3PO4) but orders of magnitude higher conductivities (10–3 S/cm at 573 K) in the mixed compositions. The MD simulations reveal new mechanistic insights into the mixed Si/P compositions in which Li-ion conduction occurs through 3D pathways and a cooperative interstitial mechanism; such correlated motion is a key factor in promoting high ionic conductivity. Solid-state 6Li, 7Li, and 31P NMR experiments reveal enhanced local Li-ion dynamics and atomic disorder in the solid solutions, which are correlated to the ionic diffusivity. These unique insights will be valuable in developing strategies to optimize the ionic conductivity in this system and to identify next-generation solid electrolytes.

Original languageEnglish
Pages (from-to)9136-9145
Number of pages10
JournalJournal of the American Chemical Society
Volume137
Issue number28
Early online date14 Jul 2015
DOIs
Publication statusPublished - 22 Jul 2015

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    Deng, Y., Eames, C., Chotard, J. N., Laleìre, F., Seznec, V., Emge, S., Pecher, O., Grey, C. P., Masquelier, C., & Islam, M. S. (2015). Structural and mechanistic insights into fast lithium-ion conduction in Li4SiO4-Li3PO4 solid electrolytes. Journal of the American Chemical Society, 137(28), 9136-9145. https://doi.org/10.1021/jacs.5b04444