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

This study presents the synthesis, physical characterization, and transport as well as electrochemical properties of a novel class of ten ionic liquids (ILs). The ILs are created with two biomass derived anions such as furan-2-carboxylate [FuA] and tetrahydrofuran-2-carboxylate [HFuA] coupled to a range of nitrogen heterocyclic cations, for which the nature of cation controlled their transport and electrochemical properties.

Abstract

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.

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