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. (© 2024 Wiley-VCH GmbH)