LiNO3–DMAc synergistic regulation of anion-rich solvation for dual-interphase stabilization in Li-metal batteries

Abstract

Lithium nitrate (LiNO₃) is a potent interphase-forming salt for Li-metal anodes; however, its low solubility in conventional carbonate solvents has limited its application. Strongly coordinating solvents dissolve LiNO₃ but often intensify parasitic reactions with reactive Li metal. Here, we report a LiNO₃–N,N-dimethylacetamide (DMAc) synergistically regulated localized high-concentration electrolyte (LNDT) that reconciles salt dissolution with interfacial stability. In LNDT, DMAc enables LiNO₃ to serve as the primary lithium salt, while extensive incorporation of NO₃^- into the Li⁺ solvation sheath weakens DMAc–Li⁺ coordination and redirects interfacial reduction from solvent decomposition toward nitrate-derived reactions. This nitrate-rich solvation chemistry generates a gradient inorganic-rich SEI composed of Li₃N/LiN_xO_y, Li₂O, and LiF on Li metal, together with an ultrathin, uniform 1.6–1.9 nm CEI on LFP. The resulting dual-interphase stabilization improves Li plating/stripping reversibility, interfacial kinetics, and deposition uniformity. Consequently, Li||LFP cells retain 80.4% of their capacity after 1100 cycles at 1 C and 85.8% after 500 cycles at 3 C, while supporting high-loading LFP cathodes and thin Li-metal anodes. This work establishes a salt–solvent regulation strategy that converts strong solvation from an interfacial liability into an enabler of durable Li-metal batteries.