Objectively Evaluating the Cathode Performance of Lithium‐Oxygen Batteries

Abstract Lithium‐oxygen battery is a promising high specific energy electrochemical system for next generation energy storage. Many literatures have reported lithium‐oxygen battery cathodes with specific capacity higher than 1000 mA h g⁻¹ and cyclability of several hundred cycles in half‐cell tests. However, on the prototype cell level, high specific energy lithium‐oxygen batteries are still irreversible. In this report, the huge discrepancy between the half‐cell result and the prototype cell performance is carefully analyzed. Some methods and parameters to evaluate the cathode performances in lithium‐ion batteries are found to be unsuitable in lithium‐oxygen battery studies. More reliable half‐cell testing methods are discussed to objectively evaluate the cathode capacity and cyclability. Considering the latest progress, the lithium‐oxygen battery is still a promising energy storage system. But at this early stage, fundamental research on the battery chemistry is still the most important issue. Objective evaluating the electrochemical performance is the prerequisite to find the exact problems and thus deserves attention.