Enhanced rate performance of Li4Ti5O12 anodes with bridged grain boundaries

By Feng, Xu-Yong; Li, Xiang; Tang, Mingxue; Gan, Alberic; Hu, Yan-Yan
Published in Journal of Power Sources NULL 2017

Abstract

Abstract Excellent rate performance of Li4+xTi5O12 (0 < x < 3, LTO) electrodes results from mixed Li site occupancy and facile Li ion exchange at 8a and 16c sites. In this paper, we reveal that inter-particle connectivity within {LTO} electrodes affects 8a and 16c site occupancies upon discharge and impacts Li ion diffusion. {LTO} electrodes of the same primary crystal structure but of different grain boundary structures were prepared and they showed significantly different electrochemical performance. {LTO} electrodes with a percolated 3D structural network and bridged grain boundaries offered balanced 8a-16c occupancy, Li ion exchange at 8a and 16c sites upon discharge, high ionic conductivities, and good rate performance. While {LTO} electrodes with isolated clusters of particles showed strong rate dependence of 8a-16c occupancy, a lack of Li ion exchange at 8a and 16c sites, large over-potential, and substantial capacity decay upon fast charging. Bridged grain boundaries in {LTO} secondary particles facilitate apparent solid-solution process during electrochemical cycling by maintaining Li site exchange and thus enhance the rate performance of {LTO} electrodes.

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