Enabling Ultralow‐Temperature (−70 °C) Lithium‐Ion Batteries: Advanced Electrolytes Utilizing Weak‐Solvation and Low‐Viscosity Nitrile Cosolvent

Abstract Low‐temperature performance of lithium‐ion batteries (LIBs) has always posed a significant challenge, limiting their wide application in cold environments. In this work, the high‐performance LIBs working under ultralow‐temperature conditions, which is achieved by employing the weak‐solvation and low‐viscosity isobutyronitrile as a cosolvent to tame the affinity between solvents and lithium ions, is reported. The as‐prepared electrolytes exhibit a sufficiently high conductivity (1.152 mS cm −1 ) at −70 °C. The electrolytes enable LiCoO 2 cathode and graphite anode to achieve high Coulombic efficiency of >99.9% during long‐term cycling at room temperature, and to respectively achieve 75.8% and 100.0% of their room‐temperature capacities at −40 °C. Even the LiCoO 2 //graphite pouch cells can retain 68.7% of the room‐temperature capacity when discharged at −70 °C, and present stable cycling performance at −40 and 60 °C. This work provides a solution for the development of advanced electrolytes to enable LIBs working at wide‐temperatures range.