Evaluation of performance metrics for high energy density rechargeable lithium-oxygen batteries

The demand for practical implementation of rechargeable lithium-oxygen batteries (LOBs) has grown owing to their extremely high theoretical energy density. However, the factors determining the performance of cell-level high energy density LOBs remain unclear. In this study, LOBs with a stacked-cell configuration were fabricated and their performance evaluated under different experimental conditions to clarify the unique degradation phenomenon under lean-electrolyte and high areal capacity conditions. First, the effect of the electrolyte amount against areal capacity ratio (E/C) on the battery performance was evaluated, revealing a complicated voltage profile for an LOB cell operated under high areal capacity conditions. Second, the impact of different kinds of gas-diffusion layer materials on the "sudden death" phenomenon during the charging process was investigated. The results obtained in the present study reveal the importance of these factors when evaluating the performance metrics of LOBs, including cycle life, and round-trip energy efficiency. We believe that adopting a suitable experimental setup with appropriate technological parameters is crucial for accurately interpreting the complicated phenomenon in LOBs with cell-level high energy density. The ratio of electrolyte amount against areal capacity (E/C) has a large impact on the performance of stacked-type lithium-oxygen batteries. The unique cell degradation behavior during the charging process under low E/C conditions was also demonstrated.