Dual-Functional Fluorinated Additive in Gel Polymer Electrolyte for High-Energy-Density Anode-Free Lithium Batteries With Enhanced Thermal Stability.

Anode-free lithium metal batteries offer high energy density and low cost, but their practical deployment is limited by unstable lithium-electrolyte interfaces and safety risks from dendrite growth and flammable electrolytes. Here, we report a dual-functional fluorinated additive that enables in situ gelation, forming a thin, inorganic-rich solid electrolyte interphase while simultaneously enhancing flame retardancy through radical capture. At 0.5 C discharge, the additive-enabled anode-free pouch cell delivers high specific capacities of 202.1 mAh/g (3.0-4.5 V) and 192.0 mAh/g (3.4-4.3 V), while retaining 80.3% and 80.1% of their initial values after 85 and 100 cycles, respectively. Moreover, Cu/NCA pouch cells with capacities of 1.4 Ah (3.0-4.5 V) and 200 mAh (3.6-4.3 V), incorporating the additive, retain 80.2% of initial capacity after 85 cycles and 92.9% after 100 cycles, respectively. Such performance is on par with or better than the best results in the literature. Impressively, such a 1.4 Ah cell shows no thermal runaway in a harsh drilling test at the fully charged state, even after 100 cycles. These results demonstrate that the dual-functional fluorine additive leads to both excellent electrochemical performance and enhanced safety, paving the way for the safe and practical application of anode-free lithium metal cells.