Synergistic N-O-containing anion-cation interaction for uniform lithium metal electrodeposition

Lithium metal batteries (LMBs) are recognized as one of the most promising next-generation energy storage systems due to their exceptionally high energy density and relatively low cost. However, the inevitable growth of lithium dendrites remains a critical challenge. Electrolyte additives have emerged as a straightforward and effective strategy for anode modification. Among these, nitrate salts (particularly LiNO 3 ) have been widely employed to suppress the polysulfide “shuttle effect” in lithium‑sulfur (Li S) batteries while enhancing Coulombic efficiency (CE). Nevertheless, the underlying reaction mechanisms remain insufficiently understood. To guide the rational design of high-performance electrolyte additives, this study systematically investigates the synergistic effects of different cationic nitrate additives (K + , Na + ) and N O bond anions (NO 3 − , NO 2 − ) on Li deposition behavior. The results demonstrate that NO 3 − can effectively participate in the Li + solvation process, facilitating the formation of an inorganic-rich, high-quality solid electrolyte interphase (SEI). In contrast, although NO 2 − exhibits stronger adsorption energy with both Li + and the Li (110) surface, which enables more uniform lithium deposition, it fails to construct a stable SEI structure. Furthermore, cations demonstrate distinct synergistic interactions with N O anions during electrochemical processes, significantly influencing Li + deposition kinetics. This work provides fundamental insights into the mechanistic roles of K + /Na + -based nitrate and nitrite additives in LMBs. Additionally, a novel characterization approach utilizing conventional transmission electron microscopy (TEM) is proposed to evaluate SEI quality, providing a practical tool for interfacial analysis. These findings present valuable guidelines for designing advanced electrolyte additives and controlling Li deposition behavior in high-energy-density battery systems.