Variant‐Localized High‐Concentration Electrolyte without Phase Separation for Low‐Temperature Batteries

Abstract Dual‐ion batteries (DIBs) present great application potential in low‐temperature energy storage scenarios due to their unique dual‐ion working mechanism. However, at low temperatures, the insufficient electrochemical oxidation stability of electrolytes and depressed interfacial compatibility impair the DIB performance. Here, we design a variant‐localized high‐concentration solvation structure for universal low‐temperature electrolytes ( ν ‐LHCE) without the phase separation via introducing an extremely weak‐solvating solvent with low energy levels. The unique solvation structure gives the ν ‐LHCE enhanced electrochemical oxidation stability. Meanwhile, the extremely weak‐solvating solvent can competitively participate in the Li + ‐solvated coordination, which improves the Li + transfer kinetics and boosts the formation of robust interphases. Thus, the ν ‐LHCE electrolyte not only has a good high‐voltage stability of >5.5 V and proper Li + transference number of 0.51 but also shows high ionic conductivities of 1 mS/cm at low temperatures. Consequently, the ν ‐LHCE electrolyte enables different types of batteries to achieve excellent long‐term cycling stability and good rate capability at both room and low temperatures. Especially, the capacity retentions of the DIB are 77.7 % and 51.6 %, at −40 °C and −60 °C, respectively, indicating great potential for low‐temperature energy storage applications, such as polar exploration, emergency communication equipment, and energy storage station in cold regions.