Weak Solvation Engineering of Reduction-Stable Electrolytes for Durable Continuous Lithium-Mediated Ammonia Electrosynthesis

Continuous lithium-mediated nitrogen reduction reaction (Li-NRR), which integrates anodic hydrogen oxidation with cathodic nitrogen fixation, opens a viable pathway for ambient ammonia synthesis. Nevertheless, its long-term and efficient operation remains tremendously challenging due to severe solvent issues including polymerization, volatilization, and reductive decomposition. Here, we fundamentally uncover the intrinsic reductive decomposition mechanism of solvent molecules in ion-solvent complex-dominated electrolytes, and develop a weak-solvent modulation strategy to significantly enhance the reduction stability of solvent frameworks toward durable and efficient Li-NRR operation. The optimized weakly solvating electrolyte attenuates solvent molecule distortion by Li⁺ and promotes the formation of an anion‑enriched solvation sheath and a nanocrystalline LiF‑rich solid electrolyte interphase (SEI). Such a functional SEI layer effectively suppresses solvent decomposition on the cathode and constructs a fast Li⁺ transport network via abundant surface pathways and grain boundaries, which synergistically improves Li plating kinetics and nitrogen fixation efficiency, as well as stability. Benefiting from these optimizations, we achieve stable and continuous N₂ electroreduction over 300 h. Meanwhile, the system delivers a high NH₃ Faradaic efficiency of 69.5% and an improved energy efficiency up to 23.2%. This work provides an effective molecular design strategy that significantly enhances the energy efficiency and stability of Li-NRR.