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

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 LiCoO2 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 LiCoO2 //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.