A two-dimensional nanochannel facilitates ionic conductivity of a deep eutectic solvent for an efficient supercapacitor

Abstract

As an environmentally benign promising emerging class of versatile solvents, deep eutectic solvents (DESs) are inexpensive, non-corrosive, compatible with electrodes and eco-friendly, and attractive for cost-efficient energy storage systems. However, the limited ionic conductivity and liquid state constrict the wide application of bulk DESs in energy storage. Herein, we present a nanoconfined system by confining a common DES, choline chloride-ethylene glycol, into the two-dimensional nanochannel of graphene oxide (GO) membranes. Under infusing DES into GO nanochannels, the ionic conductivity of DESs has increased 64 times as that of the bulk one. The molar ratio and temperature influence of DES components on the ionic conductivity of nanoconfined GO-DES membranes have been investigated. As a proof of conception, the resulting GO-DES membranes were utilized as quasi-solid liquid electrolytes for supercapacitors. The GO-DES-based supercapacitor demonstrates a 50.88% energy density improvement than bulk one. The nanoconfined system of GO-DES10 exhibits high specific capacitance of 120 F g−1 at 1 A g−1 and an energy density of 10.23 Wh kg−1 at power density of 1 kW kg−1. These are the best performance among similar ionic liquid supercapacitors. This enhanced ionic conductivity in nanoconfined DESs will offer a new way for DESs in the electrochemical area.