Imidazolium salt ionic liquids have the advantages of low volatility, high thermal stability, stable chemical properties, excellent electrical conductivity and wide electrochemical window. They are a class of alternative energy materials and have attracted extensive attention of scientists in recent years. Due to the above characteristics of imidazolium salt ionic liquids, they are very suitable as electrolytes for various batteries. Replacing the traditional electrolyte with imidazolium salt ionic liquid can improve the environmental protection of the battery, which is beneficial to the sustainable development.
Figure 1. A general formula of imidazolium salt ionic liquid.
- Fuel cell: Electrolyte is the main component of fuel cell, and imidazolium salt ionic liquids with excellent ionic conductivity and rich designability are very suitable for the creation of new fuel cell. Different structures of imidazolium salt ionic liquid electrolytes have different effects on the performance of fuel cells. For example, 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate can improve the performance of hydrogen fuel cells. Moreover, bromide-1-butyl-3-methylimidazole, 1-butyl-3-methylimidazole hydrogen sulfate and chloride-1-butyl-3-methylimidazole can improve the performance of methane fuel cells.
Figure 2. An example of imidazolium salt ionic liquid used in fuel cell.
- Lithium-air battery: Lithium-air batteries have high specific capacity, stable charge-discharge cycles and long discharge times, and are the focus of research on green batteries in recent years. Although lithium-air batteries have great potential, many challenges remain before practical application. In the composition of lithium-air battery, the electrolyte has a crucial impact on its performance. The electrolyte of lithium-air battery mainly acts as the main body of conducting ions and oxygen, and is required to have the characteristics of low volatility and high ionic conductivity. Imidazolium salt ionic liquid is considered to be a very promising electrolyte for lithium-air battery due to its higher ionic conductivity, more stable flame retardancy and lower vapor pressure, which can reduce the free volatilization of organic solvents and the occurrence of self-discharge reactions.
- Others: In addition to the above applications, imidazolium salt ionic liquids can also be used in solar cells, lithium-ion batteries and others. For example, solar energy is the cleanest and inexhaustible natural energy. The rational use and development of solar energy is an effective way to solve the current energy crisis. Dye-sensitized solar cells are a new type of efficient and inexpensive thin-film solar cells. The dye-sensitized solar cell consists of three parts including dye-sensitized nanoporous TiO2 photoanode, electrolyte solution containing redox couples and counter electrode. At present, most of the electrolyte solutions of dye-sensitized solar cells use I3- and I- as redox couples. It is worth noting that the electrolyte of dye-sensitized solar cells composed of ionic liquid alkylimidazolium iodide as the I- donor has the best photovoltaic performance.
- Singh J K, Sharma R K, Ghosh P, et al. Imidazolium Based Ionic Liquids: A Promising Green Solvent for Water Hyacinth Biomass Deconstruction[J]. Frontiers in Chemistry, 2018, 6.
- Zhang W, Liu X, He B, et al. Interface Engineering of Imidazolium Ionic Liquid toward Efficient and Stable CsPbBr3 Perovskite Solar Cells[J]. ACS Applied Materials & Interfaces, 2020.