Electrolyte additives have been widely used to address critical issues in current metal (ion) battery technologies. While their functions as solid electrolyte interface forming agents are reasonably well-understood, their interactions in the liquid electrolyte environment remain rather elusive. This lack of knowledge represents a significant bottleneck that hinders the development of improved electrolyte systems. Here, the key role of additives in promoting cation (e.g., Li
+) desolvation is unraveled. In particular, nitrate anions (NO
3−) are found to incorporate into the solvation shells, change the local environment of cations (e.g., Li
+) as well as their coordination in the electrolytes. The combination of these effects leads to effective Li
+ desolvation and enhanced battery performance. Remarkably, the inexpensive NaNO
3 can successfully substitute the widely used LiNO
3 offering superior long-term stability of Li
+ (de-)intercalation at the graphite anode and suppressed polysulfide shuttle effect at the sulfur cathode, while enhancing the performance of lithium–sulfur full batteries (initial capacity of 1153 mAh g
−1 at 0.25C) with Coulombic efficiency of ≈100% over 300 cycles. This work provides important new insights into the unexplored effects of additives and paves the way to developing improved electrolytes for electrochemical energy storage applications.
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