Article ID Journal Published Year Pages File Type
184562 Electrochimica Acta 2015 10 Pages PDF
Abstract

One of the drawbacks of ionic liquids is that some of them are solid or very viscous at room temperature; this prevents their use as electrolytes in energy storage systems. One solution consists of a binary mixture of pure, solid salts with the formation of a eutectic, allowing it to be used at room temperature. This work describes, for the first time, the formulation and use of a binary mixture of protic ionic liquids (PILs) based on the same H-bond donor, pyrrolidinium cation, with nitrate ([Pyrr][NO3]) and bis(trifluoromethanesulfonyl) imide ([Pyrr][TFSI]) anions as an electrolyte for carbon-based supercapacitors. The physico-chemical and thermal properties of mixtures as a function of composition and temperature were fully investigated and related to their electrochemical behavior as an electrolyte. The electrochemical characterization of some selected optimal compositions (x[Pyrr][NO3] = 0.64, 0.72, 0.80) shows, at first, good capacitive behavior (up to 148 F g−1) at a potential voltage of 2.0 V. Moreover, above 2.0 V, anion intercalation was observed, increasing the specific capacitance up to 209 F g−1. At 2.5 V during cycling, the characteristic peak of anion intercalation/deintercalation decreases, caused by saturation of the positive electrode by anions. Finally, accelerated aging tests showed good capacity retention (> 80%) at 2.0 V during 110 hours for x[Pyrr][NO3] = 0.72, at 25 °C. According to these results, the use of eutectic PIL binary mixtures is a promising way to design adapted electrolytes according to the material electrode for energy devices at room temperature.

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Physical Sciences and Engineering Chemical Engineering Chemical Engineering (General)
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