Effect of HF in LiPf_6 based electrolytes on the rpoperties of surface passivation films formed on graphite electrodes in Li scondary batteries

摘要

The effect of hydrofluoric acid (HF) concentration in conventional LiPF_6EC+DEC electrolyte on the properties of solid electrolyte interphase (SEI) films formed on synthetic graphite electrode and the electrode and the electrochemical performance were studied using x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), elemental analysis and electrochemical measurement. The morphology and composition of SEI are affected by a small amount of HF in the electrolyte. Higher F content in The SEI was observed when high HF electrolyte were used, although the irreversible capacities used for formation of SEI were nearly the same value. The cycleability o f the s ynthetic graphite electrode was greatly improved when surface film contains larger amount of LiF.