Dipole-dipole interactions in electrolyte to facilitate Li-ion desolvation for low-temperature Li-ion batteries

Lithium-ion batteries are widely recognized as prime candidates for energy storage devices.Ethylene carbonate （EC） has become a critical component in conventional commercial electrolytes due to its exceptional film-forming properties and high dielectric constant.However,the elevated freezing point,high viscosity,and strong solvation energy of EC significantly hinder the transport rate of Li+ and the desolvation process at low temperatures.This leads to substantial capacity loss and even lithium plating on graphite anodes.Herein,we have developed an efficient electrolyte system specifically designed for lowtemperature conditions,which consists of 1.0 M lithium bis（fluorosulfonyl）imide （LiFSI） in isoxazole （IZ）with fluorobenzene （FB） as an uncoordinated solvent and fluoroethylene carbonate （FEC） as a filmforming co-solvent.This system effectively lowers the desolvation energy of Li+ through dipole-dipole interactions.The weak solvation capability allows more anions to enter the solvation sheath,promoting the formation of contact ion pairs （CIPs） and aggregates （AGGs） that enhance the transport rate of Li+ while maintaining high ionic conductivity across a broad temperature range.Moreover,the formation of inorganic-dominant interfacial phases on the graphite anode,induced by fluoroethylene carbonate,significantly enhances the kinetics of Li+ transport.At a low temperature of -20℃,this electrolyte system achieves an impressive reversible capacity of 200.9 mAh g-1in graphite half-cell,which is nearly three times that observed with conventional EC-based electrolytes,demonstrating excellent stability throughout its operation.