Physical and Electrochemical Characterization of Quaternary Ammonium Ionic Liquids and Polar Solvent Mixture as Electrolyte for Lithium Batteries

Due to their unique properties like nonvolatility, non-flammability, high thermal stability, wide liquid range and wide electrochemical window, ionic liquids (ILs) have a great potential as components of lithium batteries [1-3]. However, the high viscosity of ILs based quaternary ammonium remains big challenge for application as lithium electrolyte. Many attempts to decrease the ILs viscosity such as: tailoring the cation and anion structures, using eutectic mixtures of ionic liquids, addition of molecular additive (organic solvent such as: EC, acetonitrile,…) [4-9].

In our previous report, the incorporation of 20 wt% EC has no positive effect on the pure IL dissociation, but decreases the viscosity as well as improves the electrochemical window stability [8, 9]. Thus, the IC-ILs mixture constitutes an interesting alternative and safe solvents for application in lithium batteries. To further explore the potential application of ammonium quaternary (QA) based ILs, we investigate here the cycling behavior and evolution of impedance characteristics of lithium cell (Li metal//ILs + 0.25M LiTFSI or ILs-EC + 0.25M LiTFSI //LiMn₂O₄, LiCoO₂) using Swagelok prototype. The Li⁺insertion/desinsertion into electrode materials has also studied by cyclic voltammetry in lithium electrolyte based ILs.

Keywords:Electrolyte, ionic liquids, lithium battery

Acknowledgement: This work was supported by Vietnam National Foundation for Science and Technology Development (NAFOSTED) through Project Fund granted of 104.03-2012.46.

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