Fluorine-Free Biomass-Derived Ionic Liquid Electrolytes: Ion Dynamics and Electrochemical Properties

Here we present the synthesis, physical characterization, and transport as well as electrochemical properties of a novel class of ten ionic liquids (ILs) derived from biomass. Two biomass derived anions such as furan-2-carboxylate [FuA] and tetrahydrofuran-2-carboxylate [HFuA] are coupled to a range of nitrogen heterocyclic cations to create the ILs, for which the nature of cation controlled their properties. For instance, the thermal decomposition temperature ranges from 183 to 259 °C, the glass transition temperature from - 47 to - 70 °C, and the ionic conductivity from 0.002 to 1.4 mS cm^-1 at 20 °C. The supercapacitors prepared using [EPy][FuA] and [EMPip][FuA] exhibited specific capacitances of 99 F g^-1 and 70 F g^-1 at 0.2 A g^-1, respectively. The [EPy][FuA]-based supercapacitor achieved an energy density of 56 Wh kg^-1 as well as a power density of 410 W kg^-1 at 0.2 A g^-1, while the [EMPip][FuA]-based supercapacitor achieved an energy density of 36 Wh kg^-1 and a power density of 360 W kg^-1 at 0.2 A g^-1. In addition, the supercapacitors retained 98% and 94% of their initial capacitances after 6000 cycles, for [EPy][FuA] and [EMPip][FuA] electrolytes, respectively.