Study of the Electronic Structure of Alkali Peroxides and Their Role in the Chemistry of Metal-Oxygen Batteries.

Sergio Brutti,Adriano Pierini,Enrico Bodo

doi:10.1021/acs.jpca.1c07255

Sergio Brutti, Adriano Pierini + Show 1 more

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https://doi.org/10.1021/acs.jpca.1c07255

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Abstract

We use a multiconfigurational and correlated ab initio method to investigate the fundamental electronic properties of the peroxide MO2– (M = Li and Na) trimer to provide new insights into the rather complex chemistry of aprotic metal–O2 batteries. These electrochemical systems are largely based on the electronic properties of superoxide and peroxide of alkali metals. The two compounds differ by stoichiometry: the superoxide is characterized by a M+O2– formula, while the peroxide is characterized by [M+]2O22–. We show here that both the peroxide and superoxide states necessarily coexist in the MO2– trimer and that they correspond to their different electronic states. The energetic prevalence of either one or the other and the range of their coexistence over a subset of the MO2– nuclear configurations is calculated and described via a high-level multiconfigurational approach.

Highlights

IntroductionLi and possibly on opportunity and, at tOhe2/sNama eelteimctero, achteecmhinstorlyogaircealachtraelmlenenged.o4−u8s
Aprotic metal−oxygen batteries[1−3] based on the O2/Li and possibly on opportunity and, at tOhe2/sNama eelteimctero, achteecmhinstorlyogaircealachtraelmlenenged.o4−u8sWhile their theoretical performance overcomes all other proposed battery chemistries, their practical implementation in real devices is still hampered by several unsolved issues, among which the parasitic release of several degrading byproducts is one of the foremost
The evolution of the potential energy surfaces (PESs) of the electronic states along the geometric changes is described by the series of plots reported in the right panels of Figure 3, where we show three cuts through the electronic states that are taken at fixed b

Summary

Introduction

Li and possibly on opportunity and, at tOhe2/sNama eelteimctero, achteecmhinstorlyogaircealachtraelmlenenged.o4−u8s While their theoretical performance overcomes all other proposed battery chemistries, their practical implementation in real devices is still hampered by several unsolved issues, among which the parasitic release of several degrading byproducts is one of the foremost. In aLOBs based on lithium metal, the electroactive process is a two-step reaction that involves the consecutive reduction of molecular oxygen to superoxide and peroxide anions. This simple reactive pathway is puzzled by the precipitation of both lithium superoxide and lithium peroxide, the chemical disproportionation of lithium superoxide, as well as the concurrent electrochemical/chemical degradation chemistries of the electrolytes and carbonaceous electrodes, leading to the accumulation of byproducts (e.g., lithium carbonate) or gas release (e.g., CO2).[1−3]. We have explored the superoxide disproportionation reaction when catalyzed by protons or Li ions using multiconfigurational methods.[14]

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