A Versatile Halide Ester Enabling Li-Anode Stability and a High Rate Capability in Lithium-Oxygen Batteries

Li-O₂ batteries are promising candidates for next-generation high-energy-density battery systems. However, the main problems of Li-O₂ batteries include the poor rate capability of the cathode and the instability of the Li anode. Herein, an ester-based liquid additive, 2,2,2-trichloroethyl chloroformate, was introduced into the conventional electrolyte of a Li-O₂ battery. Versatile effects of this additive on the oxygen cathode and the Li metal anode became evident. The Li-O₂ battery showed an outstanding rate capability of 2005 mAh g^-1 with a remarkably decreased charge potential at a large current density of 1000 mA g^-1 . The positive effect of the halide ester on the rate capacity is associated with the improved solubility of Li₂ O₂ in the electrolyte and the increased diffusion rate of O₂ . Furthermore, the ester promotes the formation of a solid-electrolyte interphase layer on the surface of the Li metal, which restrains the loss and volume change of the Li electrode during stripping and plating, thereby achieving a cycling stability over 900 h and a Li capacity utilization of up to 10 mAh cm^-2 .