TY - JOUR
T1 - Mechanism of mediated alkali peroxide oxidation and triplet versus singlet oxygen formation
AU - Petit, Yann K.
AU - Mourad, Eléonore
AU - Prehal, Christian
AU - Leypold, Christian
AU - Windischbacher, Andreas
AU - Mijailovic, Daniel
AU - Slugovc, Christian
AU - Borisov, Sergey M.
AU - Zojer, Egbert
AU - Brutti, Sergio
AU - Fontaine, Olivier
AU - Freunberger, Stefan A.
PY - 2021/5/15
Y1 - 2021/5/15
N2 - Aprotic alkali metal–O
2 batteries face two major obstacles to their chemistry occurring efficiently, the insulating nature of the formed alkali superoxides/peroxides and parasitic reactions that are caused by the highly reactive singlet oxygen (
1O
2). Redox mediators are recognized to be key for improving rechargeability. However, it is unclear how they affect
1O
2 formation, which hinders strategies for their improvement. Here we clarify the mechanism of mediated peroxide and superoxide oxidation and thus explain how redox mediators either enhance or suppress
1O
2 formation. We show that charging commences with peroxide oxidation to a superoxide intermediate and that redox potentials above ~3.5 V versus Li/Li
+ drive
1O
2 evolution from superoxide oxidation, while disproportionation always generates some
1O
2. We find that
1O
2 suppression requires oxidation to be faster than the generation of
1O
2 from disproportionation. Oxidation rates decrease with growing driving force following Marcus inverted-region behaviour, establishing a region of maximum rate. [Figure not available: see fulltext.]
AB - Aprotic alkali metal–O
2 batteries face two major obstacles to their chemistry occurring efficiently, the insulating nature of the formed alkali superoxides/peroxides and parasitic reactions that are caused by the highly reactive singlet oxygen (
1O
2). Redox mediators are recognized to be key for improving rechargeability. However, it is unclear how they affect
1O
2 formation, which hinders strategies for their improvement. Here we clarify the mechanism of mediated peroxide and superoxide oxidation and thus explain how redox mediators either enhance or suppress
1O
2 formation. We show that charging commences with peroxide oxidation to a superoxide intermediate and that redox potentials above ~3.5 V versus Li/Li
+ drive
1O
2 evolution from superoxide oxidation, while disproportionation always generates some
1O
2. We find that
1O
2 suppression requires oxidation to be faster than the generation of
1O
2 from disproportionation. Oxidation rates decrease with growing driving force following Marcus inverted-region behaviour, establishing a region of maximum rate. [Figure not available: see fulltext.]
UR - https://doi.org/10.1038/s41557-021-00643-z
UR - http://www.scopus.com/inward/record.url?scp=85102822983&partnerID=8YFLogxK
U2 - 10.1038/s41557-021-00643-z
DO - 10.1038/s41557-021-00643-z
M3 - Article
SN - 1755-4330
VL - 13
SP - 465
EP - 471
JO - Nature Chemistry
JF - Nature Chemistry
IS - 5
ER -