We here present four new fluorine-free ionic liquids (ILs) based on the non-nutritive sweetener saccharinate (Sac) anion coupled with pyrrolidinium, imidazolium, and phosphonium cations and their thermal, physicochemical, and electrochemical properties. The pyrrolidinium cation-based material is a solid at room temperature, whereas the other three materials are room-temperature ionic liquids (RTILs). By infrared spectroscopy, we find the ionic interactions to be controlled by the distinct conformers of the Sac anion, which in turn are cation-dependent. (P₄₄₄₄)(Sac) shows the lowest glass transition temperature, (T_g), the highest thermal stability and ionic conductivity, and the widest electrochemical stability window, up to 6 V. As an electrolyte in a symmetric supercapacitor, it enabled a specific capacitance of 204 F g^–1 at 1 mV s^–1, an energy density of 53 Wh kg^–1 and a power density of 300 W kg^–1 at a current density of 0.1 A g^–1, and the capacitor retained 81% of its initial capacitance after 10,000 cycles at 60 °C. Altogether, these fluorine-free electrolytes have electrochemical properties promising for application in supercapacitors operating at elevated temperatures over a wide voltage range.

中文翻译：

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作为高温和高压超级电容器电解质的甜离子液体


我们在这里介绍了四种基于非营养性甜味剂糖酸盐 （Sac） 阴离子与吡咯烷、咪唑和鏻阳离子偶联的新型无氟离子液体 （ILs） 及其热、物理化学和电化学性质。吡咯烷阳离子基材料在室温下是固体，而其他三种材料是室温离子液体 （RTIL）。通过红外光谱，我们发现离子相互作用受 Sac 阴离子的不同构象异构体控制，而这些构象异构体又是阳离子依赖性的。（第₄₄₄₄ 页）（Sac） 显示最低的玻璃化转变温度 （T_g）、最高的热稳定性和离子电导率以及最宽的电化学稳定性窗口，最高可达 6 V。作为对称超级电容器中的电解质，它在 1 mV ^s-1 时实现了 204 F ^g-1 的比电容，在 0.1 A ^g-1 的电流密度下，能量密度为 53 Wh ^kg-1，功率密度为 300 W ^kg-1，电容器在 60 °C 下循环 10,000 次后仍保留了 81% 的初始电容。 总而言之，这些无氟电解质具有电化学特性，有望应用于在高温和宽电压范围内工作的超级电容器。