Boosting the Li-O2 pouch cell beyond 860 Wh kg−1 with an O2-enriched localized high-concentration electrolyte

ABSTRACT Lithium-oxygen batteries (LOBs) are considered to be the next generation of high-specific-energy storage devices. To improve the practical specific energy, LOBs typically require thick cathode electrodes to achieve higher areal capacity. However, due to the inefficient O2 diffusion within the electrolyte-flooded thick cathodes, the practical discharge capacity of LOBs is significantly lower than their ultra-high theoretical value. Herein, we propose a strategy to solve the problem of limited O2 diffusion in the thick cathodes of LOBs by applying an O2-enriched localized high-concentration electrolyte (LHCE). With a thick cathode (10 mg cm−2), LOBs based on this O2-enriched LHCE deliver impressive discharge capacities of 50.4, 27.1 and 20.3 mAh cm−2 at current densities of 0.1, 0.3 and 0.5 mA cm−2, respectively. The discharge product Li2O2 is homogeneously distributed within the thick cathode due to the enhanced O2 diffusion conferred by the O2-enriched LHCE, indicating that the product storage space of the thick cathode is more efficiently utilized. Besides, the O2-enriched LHCE-based LOBs derive a stable solid electrolyte interphase to protect the Li anode from O2 corrosion. Additionally, a pioneering primary Li-O2 pouch cell with the O2-enriched LHCE achieves an exceptional specific energy of 860.6 Wh kg−1 (based on the total pouch cell weight), providing a promising technical pathway for the practical application of LOBs.