Operando probing of Li-insertion into LiMn₂O₄cathodes by spectroscopic ellipsometry

Abstract

A novel operando spectroscopic ellipsometry tool for the characterization of battery materials that combines high spatial resolution with multi-layer and time-resolved capabilities.

Nanoscaled LiMn2O4 for Extended Cycling Stability in the 3 V Plateau

“…In this way, the layer permittivity is obtained in the acquisition spectral range, and the volume changes will be known by the variation of the dense bottom layer thickness. The optical absorption extracted at 2.8 eV in Figure d is expected to follow the Li (de-) insertion in the layer, providing an indicator of the state-of-charge along the complete cycle . While this is clearly the case for the delithiation sweep, there are some deviations during the first lithiation which could be attributed to the investment of the introduced current in the generation of an SEI or some other process not related to the TF reduction …”

“…The optical absorption extracted at 2.8 eV in Figure 5d is expected to follow the Li (de-) insertion in the layer, providing an indicator of the state-ofcharge along the complete cycle. 29 While this is clearly the case for the delithiation sweep, there are some deviations during the first lithiation which could be attributed to the investment of the introduced current in the generation of an SEI or some other process not related to the TF reduction. 14 Interestingly, it is also possible to accurately infer the thickness variation along the galvanostatic sweep, Figure 5e.…”

“…A deeper understanding of the complex Li−Mn−O compositional landscape is provided for the lithiation/delithiation during overdischarge, and the real-time state-of-charge (SOC) is followed by spectroscopic ellipsometry (SE). Operando SE has only recently proven to be a powerful technique in monitoring real-time changes in optical transitions 29 and holds generally broad acceptance in determining TF and material properties. 30…”

Ion Intercalation in Lanthanum Strontium Ferrite for Aqueous Electrochemical Energy Storage Devices

“…In this work, the concentration of Fe Fe • during the ion intercalation process was successfully measured by in situ ellipsometry on thin films. This in situ ellipsometry methodology has been recently proposed by the authors for successfully tracking defect chemistry and ion insertion in thin films under real electrochemical operation conditions. , Ellipsometry is a widely employed non-destructive spectroscopic technique, mainly used for the estimation of optical constants and thicknesses, which is based on the change of the polarization state of the light beam reflected on a thin film sample . In combination with ellipsometry, the mechanism of ion intercalation in LSF was investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS), positron annihilation lifetime spectroscopy (PALS), and ex situ ellipsometry.…”

In situ and operando characterisation techniques for solid oxide electrochemical cells: recent advances

“…This topical review aims to provide a snapshot of the most recent developments in this field, now that improvements in in situ and operando measurement environments are step by step approaching realistic operation conditions. Although it focuses on SOCs applications, it is noteworthy mentioning that similar advances are being undertaken in other types of electrochemical and optoelectronic devices such as batteries and solar cells [7]- [11]. Targeting the main source of polarisation losses is critical for achieving real breakthroughs of the SOC technologies.…”