Anion-Containing Solvation Structure Reconfiguration Enables Wide-Temperature Electrolyte for High-Energy-Density Lithium-Metal Batteries

The demand for high-energy-density lithium batteries (LBs) that work under a wide temperature range (-40 to 60 degrees C) has been increasing recently. However, the conventional lithium hexafluorophosphate (LiPF6)-based ester electrolyte with a solvent-based solvation structure has limited the practical application of LBs under extreme temperature conditions. In this work, a novel localized high-concentration electrolyte (LHCE) system is designed to achieve the anion-containing solvation structure with less free solvent molecules using lithium difluorophosphate (LiPO2F2) as a lithium salt, which enables wide-temperature electrolyte for LBs. The optimized solvation structure contributes to the cathode-electrolyte interface (CEI) with abundant LiF and P-O components on the surface of the LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode, effectively inhibiting the decomposition of electrolyte and the dissolution of transition-metal ions (TMIs). Moreover, the weakened Li+-dipole interaction is also beneficial to the desolvation process. Therefore, the 4.3 V Li parallel to NCM523 cell using the modified electrolyte maintains a high capacity retention of 81.0% after 200 cycles under 60 degrees C. Meanwhile, a considerable capacity of 70.9 mAh g(-1) (42.0% of that at room temperature) can be released at an extremely low temperature of -60 degrees C. This modified electrolyte dramatically enhances the electrochemical stability of NCM523 cells by regulating the solvation structure, providing guidelines for designing a multifunctional electrolyte that works under a wide temperature range.

Automated summary

The demand for high-energy-density lithium batteries (LBs) that can work under extreme temperatures has been increasing. However, the conventional ester electrolyte structure limits the practical application of LBs under these conditions. In this study, a localized high-concentration electrolyte (LHCE) system was designed using lithium difluorophosphate (LiPO2F2) as a lithium salt to achieve the desired solvation structure and enable wide-temperature electrolyte for LBs. The optimized solvation structure contributes to the stability and performance of the LBs, allowing them to maintain high capacity retention even under extreme temperatures.