title: Understanding Inhomogeneous Reactions in Li-Ion Batteries: Operando Synchrotron X-Ray Diffraction on Two-Layer Electrodes.
abstract: To understand inhomogeneous reactions perpendicular to the current collector in an electrode for batteries, a method combining operando synchrotron X-ray diffraction and two-layer electrodes with different porosities is developed. The two layers are built using two different active materials (LiNi0.80Co0.15Al0.05O2and LiMn2O4), therefore, tracing each diffraction pattern reveals which active material is reacting during the electrochemical measurement in transmission mode. The results demonstrate that the active material close to the separator is obviously more active than that one close to the current collector in the case of low porosity electrodes. This inhomogeneity should be due to the rate-limitation and especially to low average ionic conductivity of the electrolyte in the porous electrode because the current flows first mainly into the electrode regions close to the separator. The inhomogeneity is found to be mitigated by the adjustment of the electrode density and thus porosity. Hence, the novel operando method reveals a clear inhomogeneous reaction perpendicular to the current collector.
authors.affiliation: Battery Laboratory Toyota Central R&D Labs, Inc. 41-1 Yokomichi Nagakute Aichi 480-1192 Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Electrochemical Energy Storage Section Paul Scherrer Institute CH-5232 Villigen PSI Switzerland.
authors.forename: Claire
authors.initials: C
authors.lastname: Villevieille
authors.affiliation: Battery Laboratory Toyota Central R&D Labs, Inc. 41-1 Yokomichi Nagakute Aichi 480-1192 Japan.
authors.forename: Yoji
authors.initials: Y
authors.lastname: Takeuchi
authors.affiliation: Electrochemical Energy Storage Section Paul Scherrer Institute CH-5232 Villigen PSI Switzerland.
authors.forename: Petr
authors.initials: P
authors.lastname: Novák
keywords: electrochemistry; homogeneity; in situ X‐ray diffraction; lithium‐ion batteries