Redox Targeting of Energy Materials for Energy Storage and Conversion

Abstract

The redox‐targeting (RT) process or redox‐mediated process, which provides great operation flexibility in circumventing the constraints intrinsically posed by the conventional electrochemical systems, is intriguing for various energy storage and conversion applications. Implementation of the RT reactions in redox‐flow cells, which involves a close‐loop electrochemical–chemical cycle between an electrolyte‐borne redox mediator and an energy storage or conversion material, not only boosts the energy density of flow battery system, but also offers a versatile research platform applied to a wide variety of chemistries for different applications. Here, the recent progress of RT‐based energy storage and conversion systems is summarized and great versatility of RT processes for various energy‐related applications is demonstrated, particularly for large‐scale energy storage, spatially decoupled water electrolysis, electrolytic N2 reduction, thermal‐to‐electrical conversion, spent battery material recycling, and more. The working principle, materials aspects, and factors dictating the operation are highlighted to reveal the critical roles of RT reactions for each application. In addition, the challenges lying ahead for deployment are stated and recommendations for addressing these constraints are provided. It is anticipated that the RT concept of energy materials will provide important implications and eventually offer a credible solution for advanced large‐scale energy storage and conversion.

Molecular engineering of dihydroxyanthraquinone-based electrolytes for high-capacity aqueous organic redox flow batteries

“…Organic redox molecules frequently suffer from low solubility resulting in a poor EES performances 9 – 11 , for which the single molecule redox targeting (SMRT) reaction provides an elegant means to solve the problem without sacrificing battery performance 33 . The SMRT reaction proceeds between a sole soluble redox species and solid capacity-boosting materials via a closed-loop electrochemical-chemical cycle, which effectively exploits the capacity of solid materials and promotes the battery performance.…”

Flow batteries with solid energy boosters

“…Among the most significant recent developments from PR China was a demonstration of Zn-MnO2 battery with a positive Br2 posolyte mediator [228] and lithium-sulfur ROTS-RFB [209,229]. Several reviews about SEB-RFBs were also published during this period [230][231][232][233].…”

High‐Power Near‐Neutral Aqueous All Organic Redox Flow Battery Enabled with a Pair of Anionic Redox Species

“…With the silent features of superior scalability, operation flexibility (decoupled energy storage and power generation) and safety, redox flow battery (RFB) is regarded as a promising candidate for large-scale energy storage applications. [2] Among various RFB technologies, all-vanadium flow battery (VFB), as the most developed one, has been demonstrated in megawatt scales. [3] However, the limited vanadium resources which render high materials cost, along with other hurdles such as the use of corrosive electrolyte and poor thermal stability, impede the widespread applications of VFB.…”