Highly Stable Sodium Metal Batteries Enabled by Manipulating the Fluorinated Organic Components of Solid-Electrolyte-Interphase

Na metal batteries (NMBs) stand at the forefront of advancing energy storage technologies, but are severely hampered by Na dendrite issues, especially when using carbonate electrolytes. Suppressing the growth of Na dendrites through constructing NaF-rich solid-electrolyte-interphase (SEI) is a commonly-used strategy to prolong the lifespan of NMBs. In contrast, fluorinated organic SEI components are often underutilized. Inspired by unveiling the adsorption configuration of fluorinated organic compounds on the surface of Na metal, an optimized SEI architecture for stabilizing NMBs is proposed by investigating the C4H9SO2F-/C4F9SO2F-treated Na metal anodes. It is revealed that the SEI built on a fluorinated inorganic/organic hybrid layer exhibit favorable Na passivation capability, significantly improving Na deposition behavior. As a result, the NMB with a high-loading cathode (15 mg cm-2) and a negative/positive capacity ratio (N/P) ratio of 4 shows a long-term life span over 1000 cycles with 92.8% capacity retention at 2 C. This work opens a new pathway for developing robust and high-energy-density NMBs. Stabilizing Na metal anodes is successfully achieved by using perfluoroalkane sulfonyl fluoride. Mechanism investigation reveals that constructing the SEI with a fluorinated inorganic/organic hybrid layer is beneficial to suppressing Na dendrite formation. The resulting Na metal anode enables the Na|Na3V2(PO4)3 full cell to deliver a remarkably enhanced cycling stability under high Na3V2(PO4)3 loading and low Na excess conditions. image