Tracking electrochemical reactions inside organic electrodes by operando IR spectroscopy

Jan Bitenc,Alen Vizintin,Jože Grdadolnik,Robert Dominko

doi:10.1016/j.ensm.2019.05.038

Jan Bitenc, Alen Vizintin + Show 2 more

Open Access

https://doi.org/10.1016/j.ensm.2019.05.038

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Abstract

IR spectroscopy can be a non-destructive and straightforward probing tool in the battery research. However, its application has been limited due to the difficulties related to the handling and interpretation of ex situ samples along with the lack of widely applicable in situ and operando cells. Herein, we show a simple, operando ATR-IR two electrode pouch cell with an IR-transmissive silicon window and discuss its advantages and limitations. This setup is applied to the study of the polyanthraquinone (PAQ) reaction mechanism in Li- and Mg-organic batteries. During the reduction/oxidation process of the PAQ, not only the conversion of both CO groups into C–O– species is observed, but also the formation of an intermediate semiquinone radical anion as an intermediate product. Furthermore, continuous measurement of IR spectra allows visualization of the gradual solid-electrolyte interphase (SEI) buildup on the cathode during cycling.

Highlights

To speed up the development of novel battery technologies (Li-rich, Na-ion, metal (Li, Ca, Mg, Al)-organic, metal-sulfur, metal-air batteries)[1,2,3,4,5], we need to develop new and improve current battery characterization techniques
In order to gain the information about the battery reaction mechanism, different spectroscopic techniques have already been applied, among others X-ray diffraction (XRD), X-ray absorption (XAS), nuclear magnetic resonance (NMR), transmission and scanning electron microscopy (TEM and SEM), Raman spectroscopy, ultraviolet–visible (UV–Vis) and IR spectroscopy [7,8,9,10,11]
One of the distinct advantages of IR spectroscopy is that the instruments are relatively inexpensive and broadly available

Summary

Introduction

To speed up the development of novel battery technologies (Li-rich, Na-ion, metal (Li, Ca, Mg, Al)-organic, metal-sulfur, metal-air batteries). An ideal battery characterization would be straightforward, non-invasive, non-destructive and optimized to probe specific battery chemistry It should provide information about the electrochemical mechanism, degradation of the electrodes and electrolyte during prolonged cycling and allow real-time (operando) monitoring of the battery state-of-health. In contrast with ex situ and in situ, the operando visualizes transitional changes that can be overlooked during ex situ or in situ investigation Such setups require specially constructed electrochemical cells that minimize IR absorption by the bulk electrolyte and maximize the signal coming from the working electrode/electrolyte interface. An improved method to probe the electrochemical mechanism of the organic cathodes within the metal-organic batteries was developed based on a new operando ATR-IR cell with Si wafer window, which allows measurements of the IR spectra during battery operation [9]. During prolonged cycling formation of an SEI on the cathode surface is visualized

Energy dispersive X-ray spectroscopy of ex situ cathodes

Spectro-electrochemical operando ATR-IR cell

IR characterization

Findings

Conclusion