We report direct evidence of soluble LiO 2 generation upon Li 2 O 2 oxidation and reveal a strong solvent-controlled Li 2 O 2-oxidation reaction mechanism in Li-O 2 batteries. In high-donicity solvents, Li 2 O 2 oxidation follows a solution pathway by forming soluble LiO 2 intermediate. While in low-donicity solvent, Li 2 O 2 oxidation follows a solid-solution pathway by forming solid Li 2Àx O 2 intermediate. The preferential formation of soluble LiO 2 promotes the charging kinetics but leads to poor cycling stability. Our work shows that bypassing the generation of soluble LiO 2 will improve the stability of Li-O 2 batteries.

No abstract

Rechargeable potassium-oxygen (K-O ) batteries promise to provide higher round-trip efficiency and cycle life than other alkali-oxygen batteries with satisfactory gravimetric energy density (935 Wh kg ). Exploiting a strong electron-donating solvent, for example, dimethyl sulfoxide (DMSO) strongly stabilizes the discharge product (KO ), resulting in significant improvement in electrode kinetics and chemical/electrochemical reversibility. The first DMSO-based K-O battery demonstrates a much higher energy efficiency and stability than the glyme-based electrolyte. A universal KO growth model is developed and it is demonstrated that the ideal solvent for K-O batteries should strongly stabilize superoxide (strong donor ability) to obtain high electrode kinetics and reversibility while providing fast oxygen diffusion to achieve high discharge capacity. This work elucidates key electrolyte properties that control the efficiency and reversibility of K-O batteries.

No abstract

A new photosensitizer-free visible light-mediated gold-catalysed cis-difunctionalization reaction is developed.