Lithium Tetrafluoroborate as an Electrolyte Additive to Improve the High Voltage Performance of Lithium-Ion Battery

Lithium tetrafluoroborate (LiBF4) used as an electrolyte additive to improve the cycling performance of LiNi0.5Co0.2Mn0.3O2/graphite cell at higher operating voltage is investigated. With 1.0 wt% LiBF4 addition into the electrolyte, the capacity retention of lithium ion battery after 100 cycles was greatly improved from 29.2% to 90.1% in the voltage of 3.0 V-4.5 V. To understand the mechanism of the capacity retention enhancement at high voltage operation, the properties including the cell performance, the impedance behavior as well as the characteristics of the electrode interfacial properties are examined. It is found that LiBF4 was likely to participate in the formation of interface film on both electrodes. The improved performances of the cell are attributed to the modification of interface layer components on graphite anode and LiNi0.5Co0.2Mn0.3O2 cathode, which leading to lower the interfacial impedance.