The superoxide disproportionation reaction is a key step in the chemistry of aprotic metal oxygen batteries that controls the peroxide formation upon discharge and opens the way for singlet oxygen release. Here we clarify the energy landscape of the disproportionation of superoxide in aprotic media catalyzed by group 1A cations. Our analysis is based on ab initio multireference computational methods and unveils the competition between the expected reactive path leading to peroxide and an unexpected reaction channel that involves the reduction of the alkaline ion. Both channels lead to the release of triplet and singlet O2. The existence of this reduction channel not only facilitates singlet oxygen release but leads to a reactive neutral solvated species that can onset parasitic chemistries due to their well-known reducing properties. Overall, we show that the application of moderate overpotentials makes both these channels accessible in aprotic batteries.
We explore the disproportionation reaction of superoxide anions in the presence of H+ and Li+ cations with high quality multiconfigurational ab‐initio methods. This reaction is of paramount importance in Li−O2 battery chemistry as it represents the source of a major degrading impurity, singlet molecular oxygen. For the first time, the thermodynamic and kinetic data of the reaction are drawn from an accurate theoretical model where the electronic structure of the reactant and products is treated at the necessary level of theory. Overall, the H+ catalyzed O2−+O2− disproportionation follows a very efficient thermodynamic and kinetic reaction path leading to neutral 3O2, 1O2 and peroxide anions. On the contrary, we have found that the Li+ catalysis promotes only the release of 3O2 whereas the 1O2 formation is energetically unfeasible at room temperature.
We
use a multiconfigurational
and correlated ab initio method to
investigate the fundamental electronic properties of the peroxide
MO
2
–
(M = Li and Na) trimer to provide
new insights into the rather complex chemistry of aprotic metal–O
2
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
+
O
2
–
formula, while the peroxide is characterized by [M
+
]
2
O
2
2–
. We show here that both
the peroxide and superoxide states necessarily coexist in the MO
2
–
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
MO
2
–
nuclear configurations is calculated
and described via a high-level multiconfigurational approach.
The Cover Feature illustrates the electronic energies along the Li+‐coordinated disproportionation of superoxide anions, a parasitic reaction that leads to the formation of the detrimental, highly reactive singlet oxygen molecules which limits the rechargeability and efficiency of lithium–O2 (air) batteries. More information can be found in the Article by E. Bodo and co‐workers.
Multivalent aprotic metal-oxygen batteries are a novel concept in the applied electrochemistry field. These systems are variants of the so-called Li-air batteries and up to present are in their research...
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