Tris(pentafluorophenyl)borane as an Electrolyte Additive to Improve the High Temperature Cycling Performance of LiFePO4 Cathode

Abstract

The capacity fading of batteries using ethylene carbonate/dimethyl carbonate electrolyte with tris(pentafluorophenyl)borane (TPFPB) additive at is investigated by cyclic voltammetry, cyclability, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The cyclability results show that the cell with the TPFPB additive electrolytes exhibits high discharge capacity and good cycling performance at . The electrode cycled at without the TPFPB additive shows a significant increase in charge-transfer resistance by EIS analysis. The TPFPB additive in the electrolyte reduces the difference in the charge-transfer resistance before and after 100 cycles at elevated temperatures. SEM results show that after 100 cycles at in an electrolyte without TPFPB additive, the electrode forms a visible material on the electrode surface. The observed material is presumably related with capacity fading in the cell. The results indicate that TPFPB in the electrolyte prevents the formation of the observed material on the electrode, reduces charge-transfer resistance, and enhances cycling performance of the cells at .