Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 26: Materials for Energy Storage and Conversion

MM 26.2: Talk

Wednesday, April 3, 2019, 15:15–15:30, H43

Electrochromism and Phase Transformation in Lithium Titanate — •Yug Joshi, Efi Hadjixenophontos, and Guido Schmitz — Chair of Materials Physics, Institute of Material Science, University of Stuttgart, Stuttgart, Germany

Lithium titanate (LTO) is a well-known battery anode mainly due to its high rate capability, high cyclability and high power density. In the potential range between 1V-2V vs Li/Li+, intercalation appears between two phases i.e. Li7Ti5O12 (stable below ca. 1.55V) and Li4Ti5O12 (stable above ca. 1.55V). While there is negligible volumetric change, the two phases show contrasting dielectric constants and complex refractive indices. Our study is based on understanding the phase transformation mechanism of LTO by exploiting these contrasting properties in the two phases. To realize this, firstly the active LTO layer is deposited using ion beam sputtering and annealed appropriately. The crystal structure of the layers are probed using X-ray diffraction and transmission electron microscopy. Once the crystal structure is confirmed, the samples are electrochemically characterized. Finally, the electrochromic characterization is performed in-situ and ex-situ to visualize the electrochromic reversibility and to extract the complex refractive indices. The latter are used to calculate the dielectric constants in the single- and in the dual-phase regions. Describing the dielectric constant of the dual phase region as a combination of those of the pure phases, information is derived about the migration of the phase front during transformation.