Aqueous zinc‐ion batteries are promising alternatives to lithium‐ion batteries due to their cost‐effectiveness and improved safety. However, several challenges, including corrosion, dendrites, and water decomposition at the Zn anode, hinder their performance. Herein, an approach is proposed, that deviates from the conventional design by adding water into a propylene carbonate‐based organic electrolyte to prepare a non‐flammable “water‐in‐organic” electrolyte. The chaotropic salt Zn(ClO4)2exploits the Hofmeister effect to promote the miscibility of immiscible liquid phases. Interactions between propylene carbonate and water restrict water activity and mitigate unfavorable reactions. This electrolyte facilitates preferential Zn (002) deposition and the formation of solid electrolyte interphase. Consequently, the “water‐in‐organic” electrolyte achieves a 99.5% Coulombic efficiency at 1 mA cm−2over 1000 cycles in Zn/Cu cells, and constant cycling over 1000 h in Zn/Zn symmetric cells. A Na0.33V2O5/Zn battery exhibits impressive cycling stability with a capacity of 175 mAh g−1for 800 cycles at 2 A g−1. Additionally, this electrolyte enables sustainable cycling across a wide temperature range from −20 to 50 °C. The design of a “water‐in‐organic” electrolyte employing a chaotropic salt presents a potential strategy for high‐performance electrolytes in zinc‐ion batteries with a large stability window and a wide temperature range.
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Abstract The discovery of liquid battery electrolytes that facilitate the formation of stable solid electrolyte interphases (SEIs) to mitigate dendrite formation is imperative to enable lithium anodes in next‐generation energy‐dense batteries. Compared to traditional electrolyte solvents, tetrahydrofuran (THF)‐based electrolyte systems have demonstrated great success in enabling high‐stability lithium anodes by encouraging the decomposition of anions (instead of organic solvent) and thus generating inorganic‐rich SEIs. Herein, by employing a variety of different lithium salts (i.e., LiPF6,LiTFSI, LiFSI, and LiDFOB), it is demonstrated that electrolyte anions modulate the inorganic composition and resulting properties of the SEI. Through novel analytical time‐of‐flight secondary‐ion mass spectrometry methods, such as hierarchical clustering of depth profiles and compositional analysis using integrated yields, the chemical composition and morphology of the SEIs generated from each electrolyte system are examined. Notably, the LiDFOB electrolyte provides an exceptionally stable system to enable lithium anodes, delivering >1500 cycles at a current density of 0.5 mAh g−1and a capacity of 0.5 mAh g−1in symmetrical cells. Furthermore, Li//LFP cells using this electrolyte demonstrate high‐rate, reversible lithium storage, supplying 139 mAh g(LFP)−1at C/2 (≈0.991 mAh cm−2, @ 0.61 mA cm−2) with 87.5% capacity retention over 300 cycles (average Coulombic efficiency >99.86%).