A cascade protection strategy from cathode to anode with high air stability for ultralong life Li-air batteries in ambient conditions

Li-air batteries (LABs) possess an ultrahigh theoretical energy density exceeding 3500 Wh/kg, but to date, only pure O2 is applied as the operating environment in most literature, which seriously limits its application po-tential. Under ambient air, water molecules would easily induce Li anode pulverization and electrolyte decomposition, which eventually lead to battery failure. Apart from the above issues, water will also cause the discharge product to convert into LiOH, which would decompose at a higher oxidation potential. Herein, to enable aprotic LABs to work in an actual air environment, a cascade cathode to anode protection strategy is developed. Generally, a highly water repulsive and controllable passivation layer on the Li surface is elaborated by D4, D4H and MM interaction, which serves as the first shield to prevent Li reaction with permeated water. Meanwhile, the second shield is constructed at the cathode side with non-polar D4 molecules to tolerate the penetration of polar water. As a consequence, the LABs exhibit extralong cycling life up to 375 cycles (1400 h) in ambient conditions with relative humidity (RH) of 60% after constructing the cascade protection from cathode to anode. The cycle life is 12 times higher than the pristine unprotected LABs. To the best of our knowledge, this is the first LABs with a cycle life exceeding 1400 h in an air environment of 60% RH, which provides new insight into LABs' practicability. As an example, the decorative lamps with the above LABs continuously illuminate up to 100 h in ambient conditions.