Review—Ionic Liquids Applications in Flow Batteries

Abstract

Increasing energy demand throughout the world produces great environmental issues. Therefore, renewable and clean energy sources, such as tidal energy, wind energy, solar energy and geothermal energy, are greatly desired. Developing a new critical energy storage technology to balance the instantaneous energy supply and demand is urgent. Rechargeable flow batteries are solutions for storing electricity in the form of chemical energy, containing positive and negative electrodes reserved in two separate containers, which have the advantages of low self-discharge and independent scaling of power, making them promising energy storage technologies. Ionic liquids have been widely studied and used in energy storage devices, such as lithium ion batteries, for their unique prospective properties. Herein, the key role of ILs and their applications in supporting electrolytes, separators, and additives in flow batteries are highlighted. The approaches and challenges in developing ILs supported flow batteries are discussed, and a significative overview of the opportunities of ILs promote flow batteries is provided to help achieve further improvements in flow batteries.

Energy Applications of Ionic Liquids: Recent Developments and Future Prospects

“…112 Nevertheless, with the increasing demand for large-scale energy storage, the long cycle life of RFBs makes them well-suited for stationary energy storage, and their low mobility drawbacks are mitigated by the application scope. 112,198,199 Therefore, in recent years, research on ionic liquid electrolytes for these flexible, adjustable stationary batteries has been growing. Research on ILs in redox flow batteries mainly focuses on enhancing the power density and energy density of the electrolyte.…”

“…Research on ionic liquids in this area is relatively limited compared to the previous two types of batteries, as the driving force for the latter has been the demand for high energy density and high power density in mobile applications . Nevertheless, with the increasing demand for large-scale energy storage, the long cycle life of RFBs makes them well-suited for stationary energy storage, and their low mobility drawbacks are mitigated by the application scope. ,, Therefore, in recent years, research on ionic liquid electrolytes for these flexible, adjustable stationary batteries has been growing.…”

“…This modular design offers flexibility to meet various customized energy and power requirements . Moreover, RFBs exhibit outstanding performance in terms of energy storage duration and charge-discharge cycles . However, due to the concentration of charge carriers and the distinct design of tanks, cell stacks, and pumps, their energy density and power density are at a disadvantage compared to the other two types of batteries.…”

“…198 Moreover, RFBs exhibit outstanding performance in terms of energy storage duration and charge-discharge cycles. 199 However, due to the concentration of charge carriers and the distinct design of tanks, cell stacks, and pumps, their energy density and power density are at a disadvantage compared to the other two types of batteries. Research on ionic liquids in this area is relatively limited compared to the previous two types of batteries, as the driving force for the latter has been the demand for high energy density and high power density in mobile applications.…”

Redox Flow Batteries: Electrolyte Chemistries Unlock the Thermodynamic Limits

“…[70] Room temperature ionic liquids have been studied as supporting electrolytes for RFBs, as have been reviewed elsewhere. [71][72][73] Beyond the inherent feature to offer a broad electrochemical stability window (> 4 V), ionic liquids allowed a reversible reduction reaction of 2,2,6,6-tetramethylpiperidine 1oxyl (TEMPO) radical that is not achievable in conventional aqueous electrolytes. [74] Their applications are, however, largely limited by the low solubility of redox-active materials and high viscosity.…”