| Resumo: | In the present work, the effect of temperature and additives on the ionic conductivity of mixed organic/ionic liquid electrolytes (MOILEs) was investigated by conducting galvanostatic charge/discharge and ionic conductivity experiments. The mixed electrolyte is based on the ionic liquid (IL) (EMI/TFSI/LiTFSI) and organic solvents EC/DMC (1:1 <i>v</i>/<i>v</i>). The effect of electrolyte type on the electrochemical performance of a LiCoO<sub>2</sub> cathode and a SnO<sub>2</sub>/C composite anode in lithium anode (or cathode) half-cells was also investigated. The results demonstrated that the addition of 5 wt.% succinonitrile (SN) resulted in enhanced ionic conductivity of a 60% EMI-TFSI 40% EC/DMC MOILE from ~14 mS·cm<sup>−1</sup> to ~26 mS·cm<sup>−1</sup> at room temperature. Additionally, at a temperature of 100 °C, an increase in ionic conductivity from ~38 to ~69 mS·cm<sup>−1</sup> was observed for the MOILE with 5 wt% SN. The improvement in the ionic conductivity is attributed to the high polarity of SN and its ability to dissolve various types of salts such as LiTFSI. The galvanostatic charge/discharge results showed that the LiCoO<sub>2</sub> cathode with the MOILE (without SN) exhibited a 39% specific capacity loss at the 50th cycle while the LiCoO<sub>2</sub> cathode in the MOILE with 5 wt.% SN showed a decrease in specific capacity of only 14%. The addition of 5 wt.% SN to the MOILE with a SnO<sub>2</sub>/C composite-fiber anode resulted in improved cycling performance and rate capability of the SnO<sub>2</sub>/C composite-membrane anode in lithium anode half-cells. Based on the results reported in this work, a new avenue and promising outcome for the future use of MOILEs with SN in lithium-ion batteries (LIBs) can be opened.
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