Tailoring Asymmetric Discharge‐Charge Rates and Capacity Limits to Extend Li‐O2 Battery Cycle Life

Widespread issues with the fundamental operation and stability of Li‐O2 cells impact cycle life and efficiency. While the community continues to research ways of mitigating side reactions and improving stability to realize Li‐O2 battery prospects, we show that limiting the depth‐of‐discharge while unbalancing discharge/charge rate symmetry can extend Li‐O2 battery cycle life by ensuring efficient reversible Li2O2 formation, markedly improving cell efficiency. Systematic variation of the discharge/charge currents shows that clogging from discharging the Li‐O2 cell at high current (250 μA) can be somewhat negated by recharging with a lower applied current (50 μA), with a marked improvement in cycle life achievable. Our measurements determined that specific reduction of the depth of discharge in decrements from equivalent capacities of 1000 mAhg−1 to 50 mAhg−1 under symmetric discharge/charge currents of 50 μA strongly affect the cumulative discharge capacity of each cell. A maximum cumulative discharge capacity occurs at ∼10 % depth of discharge (500 mAhg−1) and the cumulative discharge capacity of 39,500 mAhg−1 is significantly greater than that of cells operated at higher and lower depths of discharge. The results emphasize the importance of appropriate discharge/charge rate and depth of discharge selection for other cathode/electrolyte combinations for directly improving the cycle life performance of Li‐O2 batteries. Slow down! This work quantifies the influence of asymmetric charge‐discharge operation of Li‐O2 battery cells and demonstrates the importance of appropriate discharge/charge rate and depth of discharge selection for directly improving cycle life performance of Li‐O2 batteries. Limiting the depth‐of‐discharge while unbalancing discharge/charge rate symmetry controls the total capacity to extend Li‐O2 battery cycle life, and predicts that cycle life at a fixed capacity limit.