Energy-Dispersive Inelastic X-Ray Scattering (EDIXS) spectroscopy as a new tool for energy materials characterization: application to lithiation of Li4Ti5O12 spinel

J. J. LEANI; CÁMARA, OSVALDO RAÚL; SUSANA CHAUQUE; H. J. SANCHEZ; JOSE. I. ROBLEDO; FABIANA Y. OLIVA

Antofagasta

Workshop; 7th International Workshop on Lithium, Industrial Minerals and Energy - IWLiME; 2020

Universidad de Antofagasta.

In the last decade, EDIXS has become a powerful technique for the discrimination and characterization of chemical environments in a variety of samples of interest [1]. This technique makes use of core-level Resonant Inelastic X-ray Scattering (RIXS) since the analysis of the RIXS peak enables to establish a correspondence between the peak?s fine structure and the chemical state of the atom under study. In addition, EDIXS exploits the benefits of an Energy Dispersive detection System (EDS) and multivariate methods for the data analysis. As a result, this novel methodology shows a fast acquisition, energy-scanning free experiments, low self-absorption effects and an objective interpretation of the results. As it has been widely probed, by applying EDIXS the local chemical environment of an element of interest can be studied in a variety of irradiation geometries and experimental setups commonly used by conventional techniques, such as total reflection [2], grazing incidence [3] and even confocal setups [4].The compound Li4Ti5O12 (also known as LTO) has been investigated as anode material of lithium ion batteries for several applications as energy storage for electric and hybrid vehicles due to its exceptional features [5-7]. This LTO compound has shown a remarkable Li-ion intercalation/de-intercalation reversibility, demonstrating also zero-strain volume change during the cycling process, with the addition of a notable safety performance. Furthermore, LTO has a high voltage plateau in comparison with other anode material candidates, helping to avoid the formation of metallic lithium [8]. Clearly, a deep knowledge regarding the behavior of this LTO compound is of interest.In this work, the EDIXS technique is applied for the study and characterization of different states of charge of LTO electrodes. The measurements were carried out in the IAEA end-station of the XRF beamline at Elettra Sincrotrone Trieste (Italy) using a monochromatic beam. Similar measurements were performed applying X-ray Absorption Near Edge Structure (XANES) technique as to cross check the results and comparing the performance of both techniques in this kind of samples as well.An outcome of the present study is that the results confirm the theoretical predictions regarding the composition of the different oxidation states of titanium (Ti4+ and Ti3+) associated to different states of lithiation of the LTO spinel during the charge/discharge process. In addition, the results show that the fine structure of the RIXS peaks are clearly correlated with the different LTO chemical compounds (Li4Ti5O12 and Li7Ti5O12), showing that EDIXS can be a reliable tool to perform chemical speciation analysis on energy storage materials. This kind of experimental study can provide new insights into the behaviour and performance of several others active electrode materials based on lithium, such as LiFePO4, LiMnPO4 and LiMnOF, in addition to the LTO discussed here and currently used as a negative electrode in LIBs. By the end, chemical state characterizations by EDIXS can be also extended beyond lithium-based materials, such as those based on sodium (Na) and novel technologies based on polyvalent cations as magnesium (Mg) and aluminium (Al).