Thermodynamic And Electrochemical Properties Of [C_nmmim][SCN] And [DEME][BF₄] Ionic Liquids And Their Mixtures

Issues related to environmental,health or safety have forced us to seek solutions from chemical research.Ionic liquids?ILs?is a new class of solvents that have great potential in many fields,including scientific and engineering research,due to their fluidity and designable.Therefore,systematic exploration of the basic properties of ionic liquids and their potential applications is particularly important.In recent years,in order to improve the disadvantage of high viscosity of ionic liquids,many scholars have tried to mix ionic liquids with organic solvents or other liquids to form a mixed system to improve the comprehensive properties of ionic liquids,and achieved remarkable results.Through the investigation of the literature,it is found that mixing ionic liquids with organic solvents to prepare a hybrid system is the simplest,most effective and cost-effective way to broaden the application of ionic liquids.The research on the thermodynamic properties and electrochemical properties of ionic liquid mixed systems is also very important.In this paper,two novel ionic liquids were designed and synthesized,namely 1-propyl-2,3-dimethylimidazolium thiocyanate?[C₃mmim][SCN]?and 1-butyl-2,3-dimethylimidazolium thiocyanate?[C₄mmim][SCN]?,then they were mixed with the organic solvent acetonitrile at a whole concentration to prepare a mixed system.A series of thermodynamic properties of the neat systems and two mixed systems at different temperatures,including density,viscosity and conductivity,were determined.The thermodynamic properties of the two ionic liquids were calculated using empirical equations.The relationship between conductivity,viscosity and temperature of the mixed system is described according to the Vogel-Fulcher-Tamman?VFT?equation and the Arrhenius equation.The excess molar volume V^E and viscosity deviation??were calculated from the experimental density and viscosity values,and the interactions of the mixed systems in different concentration ranges were discussed and the Redlich-Kister?R-K?equation was used for fitting.[DEME][BF₄]was mixed with?-butyrolactone at full concentration.The effects of solvent addition on the conductivity and viscosity properties were investigated by using Casteel-Amis equation and VFT equation,respectively.It was found that the addition of solvent broadened the anode potential of the mixed system and enhanced the electrochemical stability.These two components were used as the electrolyte of the button type supercapacitor,and cyclic voltammetry,alternating current impedance and constant current charge and discharge tests were carried out,and it was found that the mixed system has the potential to become a high performance supercapacitor electrolyte.