Atmosphere Adaptive Lithium-Air Batteries Enabled by Thermodynamically Self-Limiting Salt-Free Electrolytes

The practical viability of lithium-air batteries (LABs) in semi-open systems is severely hindered by the hygroscopic nature of extrinsic lithium salts, which trigger parasitic reactions. Herein, we report a shift from traditional salt addition to an intrinsic ion-generation strategy by designing a thermodynamically self-limiting, salt-free electrolyte (SLE). By harnessing the interfacial reactivity between EMIMTFSI and the lithium anode, we elucidate a dual-pathway mechanism involving radical cleavage and dealkylation coordination. This in situ self-lithiation kinetically halts after involving only ∼11% of the EMIM⁺ species, while metallic lithium oxidation generates intrinsic Li⁺ carriers and constructs an organic-inorganic mosaic solid electrolyte interphase enriched with lithium carbide-related species, LiF, and Li₃N. This hydrophobic microenvironment regulates the permeation of atmospheric species and modulates discharge-product chemistry through trace moisture and CO₂. Consequently, SLE-based batteries exhibit atmosphere-adaptive electrochemistry, delivering a lifespan exceeding 280 h in ambient air and outperforming the pure-oxygen system (218 h). Mechanistic analyses further indicate that terminal cell failure is associated with solvation-induced kinetic freezing rather than dominant chemical degradation. This work establishes a framework for exploiting controlled interfacial reactivity toward self-adaptive energy storage in ambient environments.