ABSTRACT
One of the significant challenges common to the lithium and “beyond lithium” battery technologies is the development of a safe and reliable electrolyte. Conventional electrolytes have some safety concerns, especially due to their flammability and volatility. Under the right circumstances, the electrolyte in a Li–ion battery can ignite or even explode. Ionic liquids (ILs) are liquids consisting entirely of ions and can be further as molten salts having melting points lower than 100°C. Unlike most organic solvents, they do not vaporize unless heated to the point of thermal decomposition, typically 200–300°C or more. In addition, they have no flash point and could be considered as nonflammable compounds. As a result, ILs have been undoubtedly applied for energy storage and conversion materials and devices, because there is a continuously increasing demand for clean and sustainable energy. So far, single ILs did not fully satisfy the requirements and/or operative conditions of practical devices, although their properties can be finely tuned by properly modifying their architecture. Other disadvantages are their cost compared to carbonate solvents, and the lack of specified purity grade, which must be assessed in order to be able to evaluate the reliability of the cycling tests. These drawbacks explain their current limited use at industrial level.
In this chapter, an overview of the use of ionic liquids as electrolytes for different chemistry batteries is presented. The systematic investigation of physical, chemical, and electrochemical properties of IL-based electrolytes has been reported to emphasize not only their advantages but also their challenges. Finally, the idea of electrolyte development based on the understanding of why they work the way they do is highlighted.
