Unveiling the molecular mechanism of 1,3,2-dioxathiolane 2,2-dioxide in a propylene carbonate-based battery electrolyte

Abstract

Propylene carbonate (PC)-based electrolytes are gaining attention as next-generation electrolytes for use in high-voltage and high-temperature environments due to their superior stability at high voltages and their wide operating temperature range. However, commercialization is challenged by the exfoliation of the graphite anode, which is caused by the co-intercalation of PC. Various additives have been devised to address this issue. 1,3,2-dioxathiolane 2,2-dioxide (DTD) exhibits outstanding capacity retention and lifespan characteristics in lithium-ion batteries in which PC-based electrolytes are used, but a molecular-level understanding of its operating mechanism remains elusive. According to our quantum static and dynamics calculations, the Li+ binding energy of DTD is much lower than that of PC, rendering its coordination ability insufficient to compete with PC. As a result, the neutral DTD does not play a role in favoring the desolvation of PC from the solvation structure. However, DTD is reduced prior to PC and shows a strong reduction tendency accompanied by ring-opening. Based on this, DTD in its anionic form participates in the Li+ solvation sheath through a solvent–additive exchange reaction to promote the desolvation of PC. We reveal that the use of the charges of the oxygen atoms bonded to Li+ ions to interpret the Li+–solvent binding energies is inappropriate. Instead, we suggest the electrostatic potential minimum (ESPMin) as a useful and powerful descriptor. This work provides insights into the molecular characteristics and mechanisms of additives that enable PC-based electrolytes, offering guidance for the development of new additives.