Grain BoundariesPerovskite manganites with general formula RE 1−x B x MnO 3±δ (where RE stands for a trivalent rare-earth element and B for a divalent alkaline ion) have been extensively investigated for their wide variety of intriguing properties, such as oxygen electrocatalysis in solid oxide fuel cell (SOFC), [1,2] The ORCID identification number(s) for the author(s) of this article can be found under https://doi.
The kinetics of the reversible insertion of lithium ions assisted by aqueous environment into LiMn 2 O 4 thin film fabricated by multi-layer pulsed laser deposition is studied using dynamic multi-frequency analysis (DMFA). This method allowed us to acquire time resolved impedance spectra in the range of 210 kHz to 11.5 Hz during cyclic voltammetry. The impedance spectra obtained comprises of two RC time constants (semi-circles) indicating that the reversible insertion process of lithium ions in LiMn 2 O 4 thin films in aqueous media follows a two-stage intercalation process with the first stage as the (de)solvation step of the lithium ions and the second stage as a (de)insertion process with a concurrent change in the oxidation state of manganese. The temporal development of the kinetic parameters with the state of charge during the voltage sweep was investigated and reported in this work.
Grain boundaries in Sr-doped LaMnO3±δ thin films have been shown to strongly influence the electronic and oxygen mass transport properties, being able to profoundly modify the nature of the material. The unique behaviour of the grain boundaries can be correlated with substantial modifications of the cation concentration at the interfaces, which can be tuned by changing the overall cationic ratio in the films. In this work, we study the electronic properties of La0.8Sr0.2Mn1-yO3±δ thin films with variable Mn content. The influence of the cationic composition on the grain boundary and grain bulk electronic properties is elucidated by studying the manganese valence state evolution using spectroscopy techniques and by confronting the electronic properties of epitaxial and polycrystalline films. Substantial differences in the electronic conduction mechanism are found in the presence of grain boundaries and depending on the manganese content. Moreover, the unique defect chemistry of the nanomaterial is elucidated by measuring the electrical resistance of the thin films as a function of oxygen partial pressure, disclosing the importance of the cationic local nonstoichiometry on the thin films behavior. † Institute of Engineering Univ. Grenoble Alpes
A novel operando spectroscopic ellipsometry tool for the characterization of battery materials that combines high spatial resolution with multi-layer and time-resolved capabilities.
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