Effect of lithium difluoro (oxalato) borate on LiMn2O4-activated carbon hybrid capacitors

Abstract

The effect of lithium difluoro (oxalate) borate (LiDFOB) used as an electrolyte additive on the electrochemical performance of a LiMn2O4/activated carbon hybrid capacitor is investigated at a 10C charge/discharge current rate and a 0 - 2.5 V potential range. While the initial reversible capacitance of a LiDFOB-containing electrolyte cell is 44 F/g, in this study, the capacitance increased by 3.7 F/g after only 700 cycles. This can be explained by the role of the additive, which leads to retardation of the phased transition of LiMn2O4 during repeated chargingdischarging cycles. X-ray photoelectron spectroscopy analysis revealed that the oxalato functional group at the O1s was formed on the surface of the LiMn2O4 cathode electrode due to the electrochemical reaction between the LiDFOB and the organic electrolyte. We also found that the addition of LIDFOB to the electrolyte plays an important role in reducing the charge transfer resistance in the LiDFOB-containing electrolyte cell.