A Novel Room Temperature Molten Salt Electrolyte Based on LiBOB and 2-Oxazolidinone for Electrochemical Capacitors

Abstract

Abstract In this paper, a novel room temperature molten salt electrolyte based on lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB) and 2-Oxazolidinone (C3H5NO2, OZO) has been prepared as the electrolyte of electrochemical capacitors (EDLCs). The conductivity, thermal stability and electrochemical stability of the LiBOB-OZO electrolytes are investigated. It shows excellent thermal stability, high ionic conductivity (up to 10.4mS cm−1) and a wide electrochemical stability window (4.5 V). The temperature dependence of conductivity for the electrolytes follows the VFT equation, which demonstrates a solvent-assisted ionic conductivity mechanism. Based on it, a specific recipe of the LiBOB-OZO electrolytes (with a molar ratio of 1:6) is evaluated by cylic voltammetry, AC impedance spectroscopy, and galvanostatic charging-discharging in a test EDLC capacitor. It is found that the EDLC with the LiBOB-OZO complex electrolyte can be charged up to 2.5 V, the specific capacitance based on an activated carbon electrode can reach 92.5 F g−1 at 50°C, the equivalent series resistance (ESR) decreases sharply from 18.2 Ω at 30 °C to 7.2 Ω at 70 °C. Then, an EDLC of higher energy density and power density can be obtained，especially in the temperatures above 50 °C