Interfacial control through fluorinated co-solvent electrolytes for enabling uniform Li metal plating and long-term stability in high-voltage lithium metal batteries

Lithium metal batteries (LMBs) are considered promising candidates for next-generation energy storage due to their high theoretical energy density. However, their practical application is hindered by uncontrolled lithium plating, which leads to dendrite formation, severe interfacial instability, and safety concerns. Herein, we report a fluorinated co-solvent strategy by incorporating 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether into carbonate-based electrolytes to regulate lithium deposition behavior. The optimized co-solvent electrolyte significantly enhances Li⁺ transport at the lithium metal[sbnd]electrolyte interface, facilitating uniform and dendrite-free lithium plating with a dense solid electrolyte interphase layer. This interfacial modulation enables stable cycling of LMBs employing a single-crystal LiNi_0.8Co_0.15Al_0.05O₂ (SC-NCA) cathode and a thin Li metal anode (≈ 40 µm), achieving 80 % capacity retention over 300 cycles at an areal capacity of 3.5 mAh cm⁻². Furthermore, combined surface and structural analyses reveal that controlled Li plating behavior correlates with homogeneous charge/discharge reactions in the SC-NCA cathode. This work highlights the critical role of electrolyte design in governing both lithium metal stability and cathode reaction uniformity, offering a practical pathway toward high-energy-density and long-cycle LMBs.