Modification of lithium source in LiBOB salt of LiTFSI-LiBOB electrolyte to improve lithium-ion battery performance

Lithium bis(trifluoromethanesulfonyl)imide [LiTFSI, LiN(CF3SO2)2] can be used as an alternative electrolyte salt in Li-ion battery to replace LiPF6 because it has good tolerance to moisture and is thermally stable. However, LiTFSI can cause corrosion to current collectors in Li-ion batteries. To suppress the corrosion rate, mixing LiTFSI with LiBOB salt [lithium bis(oxalato)borate, LiB(C2O4)2] has been recommended. This study aims to determine the effect of different LiBOB salt on Li-ion battery performance. In this study, three types of LiBOB are used: i.e., commercial LiBOB (PA), LiBOB2 synthesized with lithium source from LiOH (PA), and LiBOB5 synthesized by substitution of lithium source using Li2CO3 and brine water (technical grade). Based on the cyclic voltammetry (CV) test results, the current value in the sample mixed with LiBOB is lower than that without LiBOB. The decrease occurs from about 1 mA in the LiTFSI to 0.5 mA, and 0.1 mA in the LiTFSI-LiBOB2 (Mix 2), LiTFSI-LiBOB5 (Mix 3), and commercial LiTFSI-LiBOB (Mix 1), respectively. This result shows that LiBOB addition as co-salt in the LiTFSI electrolyte reduces Cu corrosion. In contrast to the CV results, the results of the charge-discharge (CD) test show that Mix 1 produces the lowest capacity (about 70 mAH/g), while the highest capacity value is produced by Mix 3 (about 104 mAH/g). Based on the results of the electrochemical impedance spectroscopy (EIS), the highest conductivity is produced by Mix 2 (0.0674 mS/cm), while Mix 1 produces the lowest (0.0388 mS/cm).