Role of Electrolytes in Sustainable Supercapacitors

Renewable energy sources and technologies with zero emissions are given top priority worldwide, due to which energy storage (ES) materials with efficient performance are rigorously developed. In this context, ES devices like supercapacitors and batteries are paramount choices because of their superior performance, stability, and green credentials. Supercapacitors, also known as electrochemical capacitors, are the favored option for applications requiring high power due to their higher specific power (PS > 10 kW kg -1 ), ability to charge and discharge quickly (within seconds), and superior cycling stability (>105 cycles) in comparison with batteries. Sustainable supercapacitors are still an increasingly popular research topic, with ongoing efforts to boost their performance, long-term viability, and economical value. These advances are critical to achieving a more efficient and sustainable energy storage scenario. Sustainable supercapacitors are energy storage devices that are designed to enable high-capacity, quick energy storage and release while minimizing environmental effect. They are intended to be more environmentally friendly than traditional supercapacitors by utilizing eco-friendly materials, lowering consumption of resources, and focusing on end-of-life disposal concerns. Electrolytes are crucial components of electrochemical devices, and their morphological and electrochemical properties influence device performance such as rate performance, cyclability, capacity, power density, and safety. The interaction between electrodes and electrolytes is fundamental to supercapacitor performance, which is outlined in this chapter. The chapter also discusses factors such as mobility, diffusion coefficient, ionic conductivity, ion solvation, thermal stability, viscosity, ionic size, electrochemical stability, dielectric constant, and dispersion interaction that affect the overall performance of the devices. Given the requirements for developing superior electrolytes, along with the hurdles that must be addressed, this research push extends beyond fundamental understanding, aiming to translate those insights into practical improvements for supercapacitors that can compete in the energy storage market.