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.