posted on 2023-12-13, 18:05authored byAngelica Petrongari, Vanessa Piacentini, Adriano Pierini, Paola Fattibene, Cinzia De Angelis, Enrico Bodo, Sergio Brutti
Lithium–oxygen
aprotic batteries (aLOBs) are highly
promising
next-generation secondary batteries due to their high theoretical
energy density. However, the practical implementation of these batteries
is hindered by parasitic reactions that negatively impact their reversibility
and cycle life. One of the challenges lies in the oxidation of Li2O2, which requires large overpotentials if not
catalyzed. To address this issue, redox mediators (RMs) have been
proposed to reduce the oxygen evolution reaction (OER) overpotentials.
In this study, we focus on a lithium iodide RM and investigate its
role on the degradation chemistry and the release of singlet oxygen
in aLOBs, in different solvent environments. Specifically, we compare
the impact of a polar solvent, dimethyl sulfoxide (DMSO), and a low
polarity solvent, tetraglyme (G4). We demonstrate a strong interplay
between solvation, degradation, and redox mediation in OER by LiI
in aLOBs. The results show that LiI in DMSO-based electrolytes leads
to extensive degradation and to 1O2 release,
affecting the cell performance, while in G4-based electrolytes, the
release of 1O2 appears to be suppressed, resulting
in better cyclability.