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

Superoxide (O-2(-)) species play a crucial role in determining the charge kinetics for aprotic lithium-oxygen (Li-O-2) batteries. However, the growth of O-2-rich lithium peroxide (Li2O2) is challenging since O-2(-) is thermodynamically unfavorable and unstable in an O-2 atmosphere. Herein, we reported the synthesis of defective Li2O2 with tunable O-2(-) via K+ doping. The K+ dopants can successfully stabilize O-2(-) species and induce the coordination of Li+ with O-2, leading to increased Li vacancies. Compared to the pristine Li2O2, the as-prepared defective Li2O2 can be charged at a lower overpotential in Li-O-2 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 O-2-species in Li2O2 by K+ dopants and provide insights into the K+ effects on charge mechanism in Li-O-2 batteries.