Exploring the frontiers of Li–air battery research: A review of in situ/operando measurement techniques

抄録

Over the past two decades, research on lithium–air batteries (LABs) has advanced significantly. Although many studies have used high-purity oxygen, the ultimate goal remains the development of batteries that can operate using oxygen directly from the air, while achieving an acceptable discharge–charge cycle performance. For this reason, these systems are referred to as LABs in this review. Among various research areas, the investigation of positive electrode materials has received the most attention. Recent years have seen a surge in the number of studies using in situ and operando measurement techniques, particularly those using time-resolved methods. As with other battery studies, relying solely on voltage and current data is insufficient to get the full picture. Instead, real-time monitoring of reaction states and structural changes in the electrodes, as well as the entire battery system, is imperative. A broad array of measurement techniques has been used for these analyses, including electrochemical methods, spectroscopic techniques, gravimetric analysis, X-ray analysis, imaging methods, and gas analysis. LABs are composed of three main components: the positive electrode, the negative electrode, and the electrolyte. The reactions occurring at the lithium surface and inside the positive electrode are highly complex. Therefore, selecting appropriate measurement methods that align with the research objectives is crucial for understanding these complex processes. LABs aim to achieve discharge–charge characteristics comparable to or surpassing those of lithium–ion batteries. This review focuses primarily on various in situ and operando measurements applied to the positive electrode, outlining how these methods help analyze the various phenomena in LABs and providing insights for future research directions.