A new DMF-derived ionic liquid with ultra-high conductivity for high-capacitance electrolyte in electric double-layer capacitor

• Published in: Electrochimica acta 2019-10, Vol.319, p.843-848
• Main Authors: Chen, Zhengjian, Li, Zuopeng, Ma, Xiaoyun, Wang, Yu, Zhou, Quanbao, Zhang, Shiguo
• Format: Article
• Language: English
• Subjects: Activated carbon; Capacitance; Capacitors; DMF-Based ionic liquid; Electric double layer; Electrolyte; Electrolytes; High conductivity; Ion currents; Ionic liquids; Ionic mobility; Ions; Solvents; Supercapacitor
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.07.015

In this study, a new DMF-derived ionic liquid electrolyte [EDMF]BF4 was prepared, characterized and applied as a high-capacitance electrolyte for electric double-layer capacitors (EDLCs). [EDMF]BF4 was measured to have very high ionic conductivity and low viscosity (24.8 mS cm−1 and 21.6 mPa s at 25 °C), as well as a comparable electrochemical window (4.4 V, on a GC electrode) with [EMIm]BF4, which is one of the most widely studied ionic liquid electrolytes with high performance. Therefore, [EDMF]BF4 was used as a non-volatile electrolyte for activated carbon-based EDLCs. The [EDMF]BF4-based EDLCs are capable to operate stably over a voltage of 2.7 V, and the specific capacitance of activated carbon was determined to be 165 F g−1 (100th cycle at 1 mA cm−2 and 30 °C), which is much larger than in the case of [EMIm]BF4 (126 F g−1). Besides, [EDMF]BF4 showed lower ohmic resistance and double layer resistance than [EMIm]BF4 in EDLCs. The high performance of [EDMF]BF4 electrolyte should be related to the quasi-linear [EDMF] cation of moderate size, which is presumably more suitable for enhanced ion mobility and compact electric double layer.