Ionic Liquids (ILs)-based Electrolytes System for Lithium Ion Batteries

Electrolytes system plays an important part in Lithium Ion Batteries (LIBs) due to its role in lithium ion (Li⁺) transport between anode and cathode. Commercial LIBs use organic carbonates-based electrolytes system, but these electrolytes are flammable and volatile. For these reasons, replacement with non-flammable, non-volatile and high conductive compounds become recent research focus. Owing to the excellent properties, ILs are expected to cover the limitation of the organic-based electrolytes system in LIBs. The conductivity of electrolytes system which consists of dimethyl carbonate (DMC)/diethyl carbonate (DEC) (1:1, v/v) as organic solvent (OS) and imidazolium-based ILs is measured at various temperatures. Furthermore, the thermal stability of the electrolytes and the redox properties of lithium ion in IL-based electrolytes system are also investigated. [bmim][BF₄]-based electrolyte yields a conductivity of ~13 mS cm⁻¹ at 20 °C which is 10,000 times higher than DMC/DEC based only. Thermal analysis shows that the IL-based electrolytes decompose at 360 °C, much higher than the organic-based only (∼110 °C). Cyclic voltammetry measurement of the ILs-based electrolytes with [bmim][BF₄] : DEC: DMC (3:1:1) + LiBF₄ 0.2 M compositions displays reversible redox reaction. The presence of [bmim][BF₄] affects the redox reaction of Li+ ion, in both current and potential. Based on these results, a mixture of ILs and organic solvent has a potential as a new electrolytes system in the next LIBs.