Theoretical Vibrational Assessments of Electrochemical mechanisms in Alkali-ion Accumulators (VASELinA) – VASELinA

For the realization of this project, quantum chemical calculations (DFT) have been used coupled with chemical bonding analysis tools. Several and pertinent models were built to discriminate all observed phenomena/events and proposed the most likely reaction intermediates.

With the modeling and the assignment of Raman signatures of the different entities and environments (O2)n-, MO4, MO6, ..., the competition between anionic and cationic redox, degassing and metal migration phenomena can be rapidly detected and above all rationalized without requiring sophisticated, time consuming and especially expensive experimental techniques.

This project has led to a large-scale study involving several laboratories in France. The objective is to better understand the real-time working of a Li-ion battery in order to improve its performance. To this end, an optical fiber was incorporated into this electrochemical device in order to measure the vibrational signatures of this device in functioning and to correlate them with the nature of the generated species.

This methodology based on the modeling the Raman spectra, in particular the intensities, is currently being extrapolated to other position and also negative electrodes materials.

C. Gervillie-Mouravieff, C. Boussard-Pledel, J. Huang, C. Leau, L. A. Blanquer, M. Ben Yahia, M.-L. Doublet, S. T. Boles, X. H. Zhang, J.-L. Adam and J.-M. Tarascon
Unlocking cell chemistry evolution with operando fibre optic infrared spectroscopy in commercial Na(Li)-ion batteries , Nat. Energy 7, pages 1157–1169 (2022)

VASELinA aims at developing a rapid and efficient characterization method to shed light on the electrochemical mechanisms occurring at positive electrodes in lithium-ion batteries. The method is to tap into the wealth of information provided by the in situ Raman spectroscopy, in particular intensities that are governed by polarizability variation, and to capture the chemical bond modifications taking place in electrode materials when Li is inserted/de-inserted in/from their host structure. The strategy is to develop pertinent descriptors issued from the electronic and mechanical properties of electrode materials to rationalize the Raman intensities and correlate them to the Li-driven local structural modifications occurring upon charge/discharge. Based on such novel developments, a quantitative monitoring of reaction products will be possible, thus allowing a full rationalization of the electrochemical processes. This methodology will be applied to Li-rich layered transition metal oxides. These materials are foreseen to replace current electrode materials due to their increased energy density arising from an original electrochemical activity combining cationic and anionic redox processes. However most of these compounds display voltage and capacity fading upon cycling which are attributed to structural instabilities, e.g. O2 gas release and cationic migration with no clear understanding of the underlying mechanisms. Given the world industrial stakes, these materials are in the heart of fierce battle led by different international research teams. This proposal will be an important step forward as it will open routes to counteract the structural instability of these materials in finding the never-to-exceed Li/metal ratio and/or the winning combination of transition metals for optimal electrochemical performances. Another more academic and fundamental goal of this project is to establish Raman spectral library as in Infra-Red spectroscopy and make them available to the scientific community to facilitate the interpretation of experimental data.