Characterization of Lithium Transport in Lithium Titanate Thin Films & their Utilization for Transference Number Measurements of Electrolytes for Lithium-Ion Batteries
The relative conductivity of Li+-ions in lithium-ion battery electrolytes is quantified by the transference number, which can be assessed by applying electrochemical impedance spectroscopy under anion-blocking conditions. However, many electrolytes are not stable against the typically used lithium e...
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| Format: | Doctoral Thesis |
| Language: | English |
| Published: |
Philipps-Universität Marburg
2024
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| Online Access: | PDF Full Text |
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| Summary: | The relative conductivity of Li+-ions in lithium-ion battery electrolytes is quantified by the transference number, which can be assessed by applying electrochemical impedance spectroscopy under anion-blocking conditions. However, many electrolytes are not stable against the typically used lithium electrodes, so that an influence on the measurements because of unstable interfaces cannot be ruled out. The aim of this work was therefore to utilize an alternative thin-film electrode with wide electrolyte compatibility, which still fulfills the method-specific requirements of reversible Li+ incorporation and symmetric polarizability. These conditions are feasible with the typical anode material lithium titanate (Li4Ti5O12, LTO), which exhibits a two-phase transition to Li7Ti5O12 upon lithiation.
In this work, LTO was successfully produced as a thin-film electrode via spin-coating and thoroughly characterized by means of electrochemical and materialchemical methods regarding cyclability, stoichiometry, homogeneity. Moreover, inaccuracies in the preparation and measurement of the electrodes are considered, specifically the coverage of heterogeneous margins and the voltage-amplitude sensitivity for the impedance measurement. The impedance behavior of LTO was investigated at different states of (de)lithiation to understand the very-low frequency impedance
contribution of those electrodes. Here, an asymmetry between charge and discharge process was identified for the diffusion behavior, indicating differing phase distribution and propagation mechanisms, which are discussed in context with literature (values) and state-specific material chemical measurements. Further, the thin-film LTO electrodes were optimized to allow a reliable differentiation to electrolyte processes in transference number measurements, and primal approaches for a setup combining preconditioning and transference number measurements have been developed. |
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| DOI: | 10.17192/z2025.0078 |