In Situ Infrared Micro and Nanospectroscopy for Discharge Chemical Composition Investigation of Non‐Aqueous Lithium–Air Cells

Abstract

Metal–air batteries, such as Li–air, may be the key for large‐scale energy storage as they have the highest energy density among all electrochemical devices. However, these devices suffer from irreversible side reactions leading to battery failure, especially when ambient air is used as the O2 source, so a deep understanding over the surface chemistry evolution is imperative for building better devices. Herein, a multi‐scale (nano‐micro) FTIR analysis is made over the electrode surface during cell discharge employing synchrotron infrared nanospectroscopy (SINS) for the first time, to track the chemical composition changes at the nanoscale which are successfully correlated with in operando micro‐FTIR characterization. The in situ results reveal homogeneous product distribution from the nano to the micro scale, and that the discharge rate does not interfere in chemical composition. In operando micro‐FTIR shows the atmosphere dependency over Li products formation; the presence of HCOO– species occurring due to CO2 electroreduction in water, LiOH and Li2CO3, are also detected and even the lowest concentration of CO2 and H2O affects the O2 reactions. Finally, evidence of the Li2O2 reaction with DMSO forming DMSO2 after just 140 s of cell discharge shows this new technique's relevance in aiding the search for stable electrolytes.

Tuning aprotic solvent properties with long alkyl chain ionic liquid for lithium-based electrolytes

“…The degradation of DMSO in potentials greater than 5.00 V is widely reported in the literature, 19,51,52 which is attributed to the organic solvent molecules reaction with water traces present in the samples. Mozhzhukhina et al 51 indicated the beginning of DMSO degradation at 4.30 V over a Pt electrode and the formation of dimethylsulfone.…”

Systematic Study of O2 Supply in Li–O2 Batteries with High and Low Doner Number Solvents

“…Moreover, there were no Raman bands related to dimethyl sulfoxone (DMSO 2 ) in the spectrum which indicates that no DMSO oxidation was detected. DMSO 2 Raman bands should appear at 500 and 1130 cm –1 …”

“…DMSO 2 Raman bands should appear at 500 and 1130 cm −1 . 48 The morphologies of the pristine air electrode and after the deep discharge using DMSO were analyzed by SEM, at the oxygen channel side, 49 and are shown in Figure 5. Comparing the electrodes from the best performance for the open (Figure 5b; Figure S9b) and closed system (Figure 5c; Figure S10b) with the pristine electrode (Figure 5a; Figure S11), the presences of spherical particles and flake-like agglomerated were observed and can be attributed to mixed LiOH and Li 2 O 2 , as reported by Zeng et al, 9 and identified through Raman analysis.…”

Exploring carbon electrode parameters in Li–O2 cells: Li2O2 and Li2CO3 formation

“…Li 2 O 2 is the main expected product for an aprotic Li–O 2 battery and the mechanism proposed by most studies involves an initial oxygen reduction (Eqn (1)), followed by Li + complexation (Eqn (2)) and lithium superoxide (LiO 2 ) disproportionation (Eqn (3)) to yield Li 2 O 2 . 6,20,38 Peng and co-workers highlighted LiO 2 intermediate formation using surface enhanced Raman spectroscopy (SERS) at a gold electrode in an acetonitrile-based electrolyte. 39 In our results, the characteristic superoxide band was not observed, probably because it remained in solution at low concentrations with a short lifetime.…”