New strategies for interrogation of redox flow batteries via Synchrotron radiation

Operando and in situ characterisation studies with the assistance of high energy light produced by synchrotrons are becoming increasingly attractive in the energy storage area, allowing for nondestructive investigations of material properties and device behaviour in realistic working environments, and with high temporal resolution afforded by the latest generation of high-flux beamlines. Many operando synchrotron techniques are well suited to redox flow batteries, which undergo redox changes of the active species in their electrolytes when flowed through porous electrodes. There is a large variety of redox flow battery designs and chemistries, spanning transition metal solutions, hybrid gas-liquid devices, plating and stripping mechanisms and organic redox species. This review presents an overview of recent progress and preponderance of synchrotron techniques in investigating the current issues of redox flow batteries. For each synchrotron X-ray analytical approach, practical examples and breakthrough findings are outlined and the potential applications on the newly developed redox flow batteries are discussed.