Lithium ion battery technology is an alternative energy supply for portable equipment, electronics devices and high power applications such as electric vehicle and power storage for renewable energy. Electrolyte of lithium ion battery plays an important role in determining battery performance. It consists of lithium salt, commonly use lithium hexafluorophosphate (LiPF6), dissolved in organic carbonate solvent and additives. However, LiPF6 is thermally unstable and influence battery performance significantly. Moreover, the standard solvent also has some disadvantages on the electrical vehicle application. Because of this drawback, the selection of another lithium salt, lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) combined with ionic liquid BMIMTFSI become a great importance. Therefore, in this study, ionic conductivity characteristics of liquid electrolyte based on LiTFSI was investigated. The ionic conductivity measurement of lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) electrolyte in carbonate solvents with and without ionic liquid BMIMTFSI as an additive have been investigated. The ionic conductivity of LiTFSI with ionic liquid is larger than LiTFSI without ionic liquid as an additive, namely 3.1 mS/cm and 2.7 mS/cm.