Operando Synchrotron-Based Fourier Transform Infrared Microspectroscopy of Metal-Ion Organic Battery Materials
Ashley P. Black, Deyana S. Tchitchekova, Nagaraj Patil, Nicolas Goujon, David Mecerreyes, Rebeca Marcilla, Ibraheem Yousef, Alexandre Ponrouch
Abstract
High Resolution Image Download MS PowerPoint Slide Operando synchrotron-based Fourier transform infrared (SR-μFTIR) microspectroscopy takes advantage of the high brilliance of synchrotron radiation to collect high-quality spectra with a superior signal-to-noise ratio (S/N) in subsecond timeframes. This technique achieves a spatial resolution finer than ten micrometers, enabling real-time operando mapping of electrode surfaces during battery operation, even under high C rate. The combination of both high temporal and spatial resolution makes (SR-μFTIR) a powerful tool for investigating dynamic electrochemical processes at the microscale. Operando SR-μFTIR microspectroscopy can be applied to the study of electrode materials, electrolytes, and electrode–electrolyte interfaces. It is especially valuable for the elucidation of reaction mechanisms taking place in noncrystalline and/or lightweight element-based electrodes, such as organic electrode materials. Herein, we show how a simple modification of the commercially available ECC-Opto-Std (ELCELL) cell allows unraveling the potential of operando SR-μFTIR microspectroscopy for investigating organic electrodes. This setup is applied to study the reaction mechanism of polyimide derived from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) in lithium, sodium, and calcium cells. During the charge/discharge process of the polyimide, a reversible change in the carbonyl bands intensities is observed with the concomitant appearance of two main new bands. Density functional theory calculations assign these bands to competing enolation/carbonylation processes with direct interactions between the aromatic ring and alkaline metal ions present in the electrolyte. Furthermore, the enhanced spectral resolution of synchrotron radiation provides a more detailed insight into the stepwise mechanism pathway in Na cells, as well as rate-dependent variations in the reaction mechanism.