Crown Ether Electrolyte Induced Li 2 O 2 Amorphization for Low Polarization and Long Lifespan Li-O 2 Batteries.

Lithium-oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next-generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor life, which lay a significant gap between laboratory research and commercial applications. In this work, we adopt 15-crown-5 ether (C15) as solvent to regulate the generation of discharge products in lithium-oxygen batteries. The coronal structure endows C15 with strong affinity to Li + , firmly stabilizes the intermediate LiO 2 and discharge product Li 2 O 2 . Thus, the crystalline Li 2 O 2 is amorphized into easily decomposable amorphous products. The lithium-oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm -2 to 5.7 mAh cm -2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm -2 . The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li 2 O 2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li 2 O 2 amorphization and reduce charge overpotential in lithium-oxygen batteries.