Review Article: Flow battery systems with solid electroactive materials

Abstract

Energy storage is increasingly important for a diversity of applications. Batteries can be used to store solar or wind energy providing power when the Sun is not shining or wind speed is insufficient to meet power demands. For large scale energy storage, solutions that are both economically and environmentally friendly are limited. Flow batteries are a type of battery technology which is not as well-known as the types of batteries used for consumer electronics, but they provide potential opportunities for large scale energy storage. These batteries have electrochemical recharging capabilities without emissions as is the case for other rechargeable battery technologies; however, with flow batteries, the power and energy are decoupled which is more similar to the operation of fuel cells. This decoupling provides the flexibility of independently designing the power output unit and energy storage unit, which can provide cost and time advantages and simplify future upgrades to the battery systems. One major challenge of the existing commercial flow battery technologies is their limited energy density due to the solubility limits of the electroactive species. Improvements to the energy density of flow batteries would reduce their installed footprint, transportation costs, and installation costs and may open up new applications. This review will discuss the background, current progress, and future directions of one unique class of flow batteries that attempt to improve on the energy density of flow batteries by switching to solid electroactive materials, rather than dissolved redox compounds, to provide the electrochemical energy storage.

Current Advances in TiO2-Based Nanostructure Electrodes for High Performance Lithium Ion Batteries

“…The redox-flow battery (RFB) is one of the most promising energy storage systems that provides high capacity and energy density suitable for numerous application e.g., in the automotive sector but is also heavily discussed for large-scale stationary power storage units for renewable power production and grid stability. A typical flow battery is composed of three components, (i) an electrochemical cell-power output unit in which, two adjacent electrochemical half cells, containing porous electrodes are separated by a semipermeable membrane, (ii) two energy storage tanks (anolyte and catholyte) each filled with redox-active species are dissolved in a solvent serving as electrolyte, (iii) a pumping unit which circulates the anolyte and catholyte between the power output cells and the energy storage tanks [76][77][78][79]. The operation principle is based on oxidation and reduction reactions between the electroactive transition metal ion species at the surface of a porous electrode in the electrochemical cells.…”

“…The operation principle is based on oxidation and reduction reactions between the electroactive transition metal ion species at the surface of a porous electrode in the electrochemical cells. The two electrolyte solutions, which represent the active electrode materials, are pumped into a membrane-divided stack allowing for ion migration of the conducting salt and not the redox-active species and the electron transfer [76][77][78]. The vanadium redox-flow battery is one of the famous flow battery examples established in the market for large-scale storage [80].…”

An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources

“…Zinc‐bromine (ZnBr) batteries are hybrid flow class of batteries wherein two aqueous solutions, based on zinc and bromine placed in two different tanks, are used which, during charging and discharging phases, flow through the electrolytic cells where the reversible electrochemical reactions take place . When the electrochemical reaction takes place, zinc and bromine ions move towards opposite electrolyte direction through the porous separator .…”

“…Zinc-bromine (ZnBr) batteries are hybrid flow class of batteries wherein two aqueous solutions, based on zinc and bromine placed in two different tanks, are used which, during charging and discharging phases, flow through the electrolytic cells where the reversible electrochemical reactions take place. 121,131 When the electrochemical reaction takes place, zinc and bromine ions move towards opposite electrolyte direction through the porous separator. 92,132 During charging, deposition of zinc takes place on the negative electrode and that of bromine on the positive electrode, while in discharging mode, reverse electrochemical reactions takes place and zinc deposited on the negative electrode gets dissolved into the electrolyte so as to be available for the next charging cycle 133 .…”

Interphases in Electroactive Suspension Systems: Where Chemistry Meets Mesoscale Physics

“…The concept of SSRFBs opened doors for a bounty of design possibilities at the level of redox chemistry, multiphase electrode, and cell architecture. This subject has been addressed in reviews and the last ten years show an explosion of diverging possibilities like flow capacitors, water desalination, incorporation of redox mediators, carbon‐free suspensions, polysulfide or metal‐ion based carbon suspensions, and semi‐solid metal‐air flow batteries . In the interest of brevity, this review is specifically focused on how the state of art of LiBs and particle suspensions impact SSRFBs.…”