Description of the Zn/Br RFB System

Abstract

In order to make beneficial changes to the Zn/Br flow battery system, it is necessary first to understand its present structure and functional status, including the level of performance for typical systems, the operating mechanisms as well as the conventional materials and methods of construction. The previous chapter introduced and discussed the need for reliable large-scale electrical energy storage and the role of redox flow batteries for such purposes. This chapter describes the physical architecture of the Zn/Br system (i.e. electrode stack, membrane separator, electrolyte flow schematic), as well as the conventional electrolyte solution employed and the dominant chemical redox reactions occurring during charge and discharge processes at each electrode. Design considerations are detailed, such as the safe storage and treatment of bromine evolved, together with important operating practices such as tracking state-of-charge. Finally, electrochemical and overall operational performance characteristics are discussed with regard to maximizing the specific energy of the Zn/Br flow battery and scaling-up next-generation systems from benchtop testing to commercial use.