Potassium Doping Facilitated Formation of Tunable Superoxides in Li2O2 for Improved Electrochemical Kinetics.

Superoxide (O2-) species play a crucial role in determining the charge kinetics for aprotic lithium-oxygen (Li-O2) batteries. However, the growth of O2--rich lithium peroxide (Li2O2) is challenging since O2- is thermodynamically unfavorable and unstable in an O2 atmosphere. Herein, we reported the synthesis of defective Li2O2 with tunable O2- via K+ doping. The K+ dopants can successfully stabilize O2- species and induce the coordination of Li+ with O2-, leading to increased Li vacancies. Compared to the pristine Li2O2, the as-prepared defective Li2O2 can be charged at a lower overpotential in Li-O2 batteries, which is ascribed to further increased Li vacancies contributed by the depotassiation process at the onset of the charge process. Our findings suggest a new strategy to better control O2- species in Li2O2 by K+ dopants and provide insights into the K+ effects on charge mechanism in Li-O2 batteries.