Enhanced electrochemical performances via introducing LiF electrolyte additive for lithium ion batteries

摘要

High working potential and temperature put nonnegligible threats on electrochemical stability and safety performance of lithium ion batteries (LIBs). In this paper the carbonate-based electrolyte is modified with LiF additive to improve the comprehensive properties of cells in which a metallic lithium anode is paired with a LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode under the extreme conditions of high cut-off potential, high current rate or even high temperature (55 degrees C). The tests of self-discharge behavior and chronoamperometry present that the introduction of LiF additive contributes to relieving self-discharge of cells and side reactions on the surface of electrodes. The cells with 100 ppm exhibit the improved cyclic performance (81.6% of initial capacity 195.4 mAh g(-1)), high-rate capability (150.6 mAh g(-1) at 8 C) and high-temperature performance. Additionally after 100 cycles over 3.0-4.6 V, the results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) on electrodes reveal that the cathodes in LiF-reinforced electrolyte retain more stable layered structure and more intact spherical secondary particles than those in original electrolyte.