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

Li‐O 2 batteries are promising candidates for next‐generation high‐energy‐density battery systems. However, the main problems of Li–O 2 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–O 2 battery. Versatile effects of this additive on the oxygen cathode and the Li metal anode became evident. The Li–O 2 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 Li 2 O 2 in the electrolyte and the increased diffusion rate of O 2 . 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 .