Dresden 2017 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 31: SYLI: Symposium Interfacial Challenges in Solid-State Li Ion Batteries - Structure - property relationships I
MM 31.3: Talk
Tuesday, March 21, 2017, 12:15–12:30, IFW A
Ion transport and phase transformation in thin film LiFePO4 intercalation electrodes — •Guido Schmitz1, Fabian Wunde2, and Frank Berkemeier2 — 1Institut für Materialwissenschaft, Univ. Stuttgart, Heisenbergstr. 3, 70569 Stuttgart — 2formerly: Institut für Materialphysik, Univ. Münster
Thin film battery materials have an important potential to be applied in all-solid-state batteries. From the view point of physics, they offer a clearer model geometry than the usual particle-binder-compound electrodes. The phase diagram of LiFePO4 predicts a phase separation in the Li intercalation. However, it is controversial whether phase separation might be suppressed in nanosystems due to elastic or kinetic constraints.
We study the intercalation kinetics of thin films under variation of the intercalation rate over more than 4 orders of magnitude. Also the layer thickness has been systematically varied. We show i) that the miscibility gap of the bulk system is essentially understood by elastic interaction, ii) that nanometric thin films clearly reveal phase separation and therefore undergo significant plastic relaxation, iii) that the grain boundaries represent fast transport paths with the electrochemical characteristics of an ion-conductor and iv) how the classic Randles-Sevcik analysis has to be modified in the case of a phase-separating material to derive proper diffusion coefficients.