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MM: Fachverband Metall- und Materialphysik

MM 42: Functional Materials I

MM 42.5: Talk

Thursday, March 17, 2011, 18:45–19:00, IFW B

Investigation of Lithium diffusion in sputtered layers of lithium titanat — •Fabian Wunde and Guido Schmitz — Institut für Materialphysik, WWU Münster, Deutschland

Lithium titanate (LTO) is used as an anode material for lithium ion batteries, as it reveals both, electronic as well as Li-ion conductivity. To investigate its ionic properties, ion-beam sputter-deposited thin films of LTO have been analysed by means of galvanostatic charge-discharge measurements. It has been observed that the measured charge capacities show a strong dependence on the charge/discharge current densities, i.e the charge capacity decreases when increasing the current. In order to explain this decrease in capacity, the kinetics of Li insertion into the LTO films is described by diffusion. Solving Fick`s diffusion law with finite diffusion space while assuming a constant electrical current as boundary condition, leads to theoretical concentration profiles. Subsequent combination of these profiles with the well-known Nernst equation shows that the observed loss of capacity is due to a gradient of the Li concentration and therefore depends on the diffusion coefficient of Li in LTO. By evaluating the measured capacity loss as a function of current the diffusion coefficient is determined.