From O 2 − to HO 2 − : Reducing By‐Products and Overpotential in Li‐O 2 Batteries by Water Addition

The development of aprotic Li‐O 2 batteries, which are promising candidates for high gravimetric energy storage devices, is severely limited by superoxide‐related parasitic reactions and large voltage hysteresis. The fundamental reaction pathway of the aprotic Li‐O 2 battery can be altered by the addition of water, which changes the discharge intermediate from superoxide (O 2 − ) to hydroperoxide (HO 2 − ). The new mechanism involving HO 2 − intermediate realizes the two‐electron transfer through a single step, which significantly suppresses the superoxide‐related side reactions. Moreover, addition of water also triggers a solution‐based pathway that effectively reduces the voltage hysteresis. These discoveries offer a possible solution for desirable Li‐O 2 batteries free of aggressive superoxide species, highlighting the design strategy of modifying the reaction pathway for Li‐O 2 electrochemistry.