Work

Freeze‐Vulnerable Plastic Crystal to Cryogenic Liquid Electrolyte for Lithium Batteries by Deep Freezing‐Point Depression

Year: 2024

Type: article

Abstract: Low‐ T f solvents ( T f = freezing point) are considered and employed for low‐temperature lithium‐ion battery (LIB) electrolytes to keep electrolytes in the liquid phase at low temperatures. Unfortunately, T f is synchronized with T b (boiling point) so low T f brings T b down and therefore discourages the thermal stability of electrolytes using low‐ T f solvents. In this work, 1) the hot wing of LIB‐working temperature by employing a high‐ T b (inevitably high‐ T f ) solvent and 2) the cold wing by using a significant T f depression is secured. Sulfolane is employed as the high‐ T f (therefore, high‐ T b ) and high‐ K f ( K f = cryoscopic constant) solvent since its mesomorphic state between solid and liquid. That abnormally and significantly decreases the enthalpy of fusion, and resultantly grants extremely high K f at 66.4 K m −1 . By employing sulfolane with 2 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the liquid‐phase temperature window down to <−80 °C for the cold wing and simultaneously guaranteed its flash point at >+150 °C for the hot wing is successfully extended. LIB cells with lithium iron phosphate and lithium metal worked in a good stand with 2 m LiTFSI/sulfolane at room temperature, −30 °C as an ambient cold, −74 °C as a deep cold, and +80 °C as a deep hot.

Source: Small

DOI: 10.1002/smll.202404722