Boosting the Low-Temperature Performance for Li-Ion Batteries in LiPF₆-Based Local High-Concentration Electrolyte

Abstract

LiPF6-based commercial electrolytes are widely used in lithium-ion batteries (LIBs). However, due to the low ion conductivity that originated from the high freezing point of EC, sluggish desolvation process, and large interface resistance, LIBs with the currently commercial electrolyte based on LiPF6 demonstrate unsatisfactory performance in low-temperature operation. Herein, a LiPF6-based local high-concentration electrolyte with lithium difluorobis(oxalato)phosphate (LiDFBOP) additive is designed to enhance the performance of LIBs at low temperature. Higher-concentration LiPF6 in EC-free solvent improve the overall ionic conductivity of electrolyte. The Li+–solvent–PF6– structure can be obtained to reduce the desolvation energy; meanwhile, LiDFBOP is introduced to construct an effective SEI film with high ionic conductivity and cycle stability. The graphite/Li cells demonstrate good rate performance and low-temperature performance (ca. 240 mAh g–1 at −20 °C (0.1 C)). This work provides a feasible strategy for developing a commercial LiPF6-based electrolyte to improve the operation of LIBs at low temperature.