Customized Design of LiF‐Rich SEI Layer on Lithium Metal Anode for High Flame Retardant Electrolyte

ABSTRACT Gel polymer electrolytes (GPEs) with high flame‐retardant concentration can remarkably reduce the thermal runaway risk of lithium metal batteries (LMBs). However, higher flame‐retardant content in GPEs always leads to increased leakage of active component and severe lithium corrosion, which greatly hinders the service life of LMBs. Herein, GPEs with high‐loading triphenyl phosphate (TPP) are originally fabricated by coaxial electrospinning and stabilized by dual confinement effects, including chemisorption of polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP), and physical encapsulation of polyacrylonitrile (PAN)/PVDF‐HFP. These effects arise from the strong polar interactions between the −CF 3 group in PVDF‐HFP and P=O group in TPP, as well as the superior anti‐swelling property of PAN. To mitigate TPP‐induced corrosion during cycling, the optimized Li anode is armored with LiF‐rich solid electrolyte interphase (SEI) layer through immersing it in fluoroethylene carbonate‐containing electrolyte. As expected, the corresponding Li||Li symmetric cells deliver long‐term stable cycling behavior over 2400 h at 0.5 mA cm −2 , and the LiFePO 4 ||Li batteries hold a high‐capacity retention ratio of 81.7% after 6000 cycles at 10 C with excellent flame retardancy. These findings offer new insight into designing the SEI layer for lithium metal in flame‐retardant electrolytes, thus promoting the development and application of high‐security LMBs.