Review of zinc-based hybrid flow batteries : from fundamentals to applications

Zinc-based hybrid flow batteries are one of the most promising systems for medium- to large-scale 82 energy storage applications, with particular advantages in terms of cost, cell voltage and energy den- 83 sity. Several of these systems are amongst the few flow battery chemistries that have been scaled up and 84 commercialized. The existing zinc-based systems rely on zinc electrodeposition in flowing electrolytes as 85 the negative electrode reaction, which is coupled with organic or inorganic positive active species in 86 either solid, liquid or gaseous phases. These reactions are facilitated with specific cell architectures under 87 certain circumstances. To improve the performance and cycle life of these batteries, this review provides 88 fundamental information on zinc electrodeposition and summarizes recent developments in the relevant 89 flow battery chemistries, along with recent applications. The future challenges and opportunities for this 90 technology are discussed.