Spatial quantification of dynamic inter and intra particle crystallographic heterogeneities within lithium ion electrodes
Donal P. Finegan, Antonis Vamvakeros, Chun Tan, Thomas M. M. Heenan, Sohrab R. Daemi, Natalie Seitzman, Marco Di Michiel, Simon D. M. Jacques, Andrew M. Beale, Dan J. L. Brett, Paul R. Shearing, Kandler Smith
Abstract
Abstract The performance of lithium ion electrodes is hindered by unfavorable chemical heterogeneities that pre-exist or develop during operation. Time-resolved spatial descriptions are needed to understand the link between such heterogeneities and a cell’s performance. Here, operando high-resolution X-ray diffraction-computed tomography is used to spatially and temporally quantify crystallographic heterogeneities within and between particles throughout both fresh and degraded Li x Mn 2 O 4 electrodes. This imaging technique facilitates identification of stoichiometric differences between particles and stoichiometric gradients and phase heterogeneities within particles. Through radial quantification of phase fractions, the response of distinct particles to lithiation is found to vary; most particles contain localized regions that transition to rock salt LiMnO 2 within the first cycle. Other particles contain monoclinic Li 2 MnO 3 near the surface and almost pure spinel Li x Mn 2 O 4 near the core. Following 150 cycles, concentrations of LiMnO 2 and Li 2 MnO 3 significantly increase and widely vary between particles.