SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 16: Energy Conversion

MM 16.9: Vortrag

Dienstag, 28. März 2023, 12:30–12:45, SCH A 215

Lithium diffusion visualized in Li4+xTi5O12 using optical microscopy (revealing slow-moving phase boundary) — •Yug Joshi, Robert Lawitzki, and Guido Schmitz — Chair of Materials Physics, Institute of Materials Science, University of Stuttgart, Stuttgart, Germany

Lithium titanate (Li4Ti5O12) undergoes a phase transformation from spinel structured (Li4Ti5O12) to rock-salt (Li7Ti5O12). The material has been reported to show sluggish mobility of lithium in fully lithiated and delihiated phases. This challenges the high-rate performance observed in this material. To elucidate this behavior, optical microscopy and the electrochromic character of the material have been used to visualize the phase transformation. The kinetics of lithium transport is observed in a constrained region of sputter-deposited thin-film samples. This enables a study of the lateral transport on the length scales of tens of micrometers. Furthermore, with a thermostatically controlled cell, the Arrhenius-like temperature dependence of lithium diffusivity is revealed. Our quantitative findings demonstrate that indeed the end phases have poor diffusivity. Surprisingly, the phase boundary moves slowly upon lithiation, which has been refuted in prior reports, however, it is confirmed here by the linear growth kinetics of the Li-rich phase in the initial stages of the lithium transport. Interestingly, the partial solubility of lithium in the spinel structured Li4/3+δTi5/3O4 phase increases the diffusivity of lithium drastically. This increase in diffusivity along with the reduction in size of the electrode seems to be compensating the kinetic hindrance induced by the phase boundary.