A novel redox flow battery system, single flow zinc–nickel battery system, has been proposed by J. Cheng and Zhang et al.[4]. Unlike the flow battery systems illustrated above, the single flow zinc-nickel battery possesses only one flowing passage, therefore the complexity of the mechanical and hydraulic structures is greatly reduced. And more importantly, there would be no requirement for the expensive ion exchange membrane anymore, which will greatly reduce the cost of the battery. In addition, the battery uses only abundant and relatively green materials with low levels of toxicity, and a fairly high level of safety, making it a highly cost-efficient alternative to large-scale power system storage. Table I [1-3, 8] provides a comparison between the single flow zinc-nickel battery and three other types of batteries for energy storage system.