An Amphiphilic Molecule Induced Anion-Enrichment Interface for Next-Generation Lithium Metal Batteries

The electrolyte engineering enables the fabrication of robust electrode/electrolyte interphase with excellent electrochemical stability for reliable lithium (Li) metal batteries (LMBs). Herein, an amphiphilic molecule nonafluoro-1-butanesulfonate (NFSA) is employed in electrolytes to realize anion-enrichment interfacial design. The functions of such an amphiphilic molecule in the electrolyte and anode/electrolyte interphases of LMBs are elucidated via theoretical and experimental analyses. The polar lithophilic segments (-SO₃-) present a capability to solvate Li⁺, while the perfluoroalkyl chains (-CF₂CF₂CF₂CF₃) exhibit a solvent-phobic, which alters the Li⁺ solvation environment in the electrolyte and thus building a favorable interphase enriched with anion-derived inorganic compositions on Li electrode. As a result, the designed electrolyte enables stable operation of the Li||Cu cells for more than 200 cycles with a cumulative irreversible capacity loss of only 2.4 mAh cm^-2, and the long-term cycle life of the Li||Li cells is extended to more than 1500 h with a small overpotential (36.5 mV). Moreover, prolonged cycle life of the full cell assembled with commercial LiFePO₄ cathode (over 80% capacity retention after 500 cycles at 0.5 C) is achieved even under the limiting Li source (≈5 mAh cm^-2), high cathode loading (≈12 mg cm^-2), and lean electrolyte (≈2.5 µL mg^-1).