Flame‐Retarding Carbonate‐Based Electrolyte for High‐Nickel‐Based Lithium Metal Batteries

Li metal batteries (LMB) based on high‐nickel cathode are potential high‐energy‐density next‐generation batteries. The inherent issue of LMBs is the formation and growth of Li dendrite at Li anode and intensification of failure of Li anode under higher charge cut‐off voltage than 4.2 V, which causes short circuit and safety hazard. To address those issues, a fluorinated carbonate and sulfate‐based flame‐retarding (FR) liquid electrolyte formulation is reported that improves performance of a highly loaded (3.5 mAh cm −2 ) Li//LiNi 0.88 Co 0.08 Mn 0.04 O 2 (NCM‐88) LMB under a simultaneously aggressive condition of high voltage (4.3 V), high temperature (45 °C), and 1 C rate. Fluorine and sulfur‐containing robust cathode–electrolyte interphase species form, which provides high‐voltage and thermal stability, and suppresses metal dissolution. Highlighted is the surface passivation of Li anode with robust solid electrolyte interphase and prevention of Li dendrite, leading to excellent LMB cycling performance (capacity retention of 70% at 100 cycles) and safety. High stability of Li//Li symmetric cell is achieved with the FR electrolyte under current of 1 mA cm −2 (Li stripping‐plating in 1 h) for a prolonged time of 300 h. The present study gives an insight into the design of alternative electrolyte formulation to ether‐based one for safer high‐energy LMBs.