3. Deep Eutectic Solvents as Electrolytes for Nanomaterials-based high-performance Supercapacitors
In last decade, Supercapacitors (SCs) have attracted considerable interest in academia as well as in industry.
This has primarily been the result of three attractive characteristics of supercapacitors: high power density (>10 kW/kg),
rapid charging/discharging (milliseconds to seconds) and long-life cycles (> 10000 cycles).
Due to these, these devices can replace batteries when high power delivery or long cycling stability is required, or there is a need for intermittent energy with variable power demands.
Despite their promising features, the widespread use of supercapacitors is still limited due to their low energy density.
The energy density of supercapacitors (~5 Wh/kg) is significantly lower than that of widely used Li-ion batteries (~150 Wh/kg).
To overcome this challenge, extensive work has been devoted to increase the energy density of supercapacitors.
Since the energy density (E) of SCs is proportional to the capacitance (C) and the square of the voltage (V), increasing either or both of the capacitance and the cell voltage
is an effective way to increase the energy density. This can be achieved through the development of electrode materials with high capacitance and electrolytes with wide
potential windows. The operating cell voltage of the SCs is largely dependent on the electrochemical stable potential window (ESPW) of the electrolytes.
Aqueous electrolyte-based SCs are non-flammable, inexpensive, have higher ion conductivity and give often rise to higher capacitance due to smaller ions.
But usually have an operating potential window of 1.0-1.3 V. Commercial supercapacitors commonly use organic electrolytes.
The main advantage of organic electrolytes is their wide electrochemical stability window (~ 2.7 V).
However, the use of volatile, flammable, toxic and expensive solvents in electrolytes poses several safety problems upon long term application of the electrochemical devices.
In order to minimize the use of volatile solvents in the preparation of electrolytes, the concept of non-volatile solvent based electrolytes has been proposed by various researchers.
During last decade, intensive investigations have been carried out on using ionic liquids (ILs) as promising electrolytes for SCs due to their interesting properties such as low volatility, high thermal and chemical stability, high flame retardancy, high electrochemical stability, wide electrochemical windows, and high ionic conductivity.
ILs based SCs generally have potential windows of 3.5-4.0 V which makes ILs very suitable electrolytes for energy storage devices.
However, high-cost of ILs are of great concern. Thus, it is very important to find much cheaper, greener and safer electrolytes for supercapacitors.
Recently, deep eutectic solvents (DESs) have emerged as alternatives to ILs. This is because of the properties of DESs resemblance to ILs e.g. wide liquid range, low vapour pressure and non-flammability.
The preparation of DESs involves the mixing of low-cost and environmentally friendly starting materials.
This results in comparatively low production cost with respect to conventional ILs and permits large scale applications.
Also, the bio-compatible, bio-degradable and non-toxic nature of DESs encourage the usage of DESs in various applications.
This work will study the feasibility of deep eutectic solvents as a novel class of electrolytes for supercapacitors.
Please contact me if any one interesred in working on this project.(02 UG students are required. Work load: 06 hours per week only.