A short review of ionic liquids (ILs) and their applications as electrolytes for electrochemical devices, such as electric double layer capacitors, fuel cells, lithium batteries, and solar cells, are presented here. The properties of ILs, such as non-volatility, non-flammability, wide liquid temperature ranges, and wide electrochemical windows, have the potential to be improved, including improvements in durability and safety, extending the operational temperature ranges and enabling improvements in power and energy densities of the devices.