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

Abstract 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 (‐SO ₃ ‐) present a capability to solvate Li ⁺ , while the perfluoroalkyl chains (‐CF ₂ CF ₂ CF ₂ CF ₃ ) 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 LiFePO ₄ 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 ).