Capturing O₂ ^•‒ Intermediate to Promote Oxygen-Reduction-Reaction Pathway for Li-O₂ Batteries with...

Oxygen reduction reaction (ORR) with two-electron transfer pathway is the key reaction for aprotic lithium-oxygen (Li-O₂) batteries with high theoretical energy density. Herein, we present that capturing ORR superoxide (O₂ ^•‒) intermediate can promote ORR rate and stability by using pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py-TFSI). Py⁺ cation can bind O₂ ^•‒ absorbed on the surface of solid catalyst and transfer it into electrolyte, in which the coordination chemistry not only inhibits the generation and disproportionation of LiO₂ on the electrode surface to enhance ORR rate, but also stabilize O₂ ^•‒ to inhibit its related side reactions for better ORR stability. Over fivefold enhancement of ORR activity is observed. Moreover, Py-TFSI promotes the uniform lithium deposition through enriching inorganics in solid-electrolyte-interphase and electrostatic shielding effect on Li metal surface, resulting in 2.5 times increase of cycling stability of Li electrode. As a result, the Li-O₂ batteries demonstrate a cycle lifespan of 47 days with a high areal capacity of 5 mAh cm^‒2. This study presents the deep understanding of intermediate manipulation mechanism for ORR and provides the effective way to improve the performance of metal-O₂ batteries.