Developing Shunt-Current Minimized Soluble-Lead-Redox-Flow-Batteries

Abstract

Shunt currents in membrane-less soluble-lead-redox-flow-batteries (SLRFB) are observed in open-circuit condition and found to depend on size of the stack, manifolds, flow rates and charge/discharge parameters. Ramifications of shunt currents on the performance of membrane-less SLRFB stacks with internal and external manifolds are reported. In the case of stacks with 3, 5 and 7-cells and internal manifold design, the charge current for the middle cell decreases by 3.3%, 6%, and 8.5%, while the discharge current increases by 2.6%, 5.5%, and 6.6%, respectively, for 3 A charge/discharge current. By contrast, no such adverse effect is observed for external manifold design. The current—potential studies show that while the stacks comprising 3 and 5-cells deliver a maximum power density of 35 mW cm −2 , which declines to 15 mW cm −2 for the 7-cell stack with internal manifold design, while the power density remains invariant at 50 mW cm −2 for stacks with external manifold design. An 8-cell stack of 12 V, 50 mAh/cm 2 specific capacity and 273 Wh energy storage capacity with 64% energy efficiency is also reported which shows good cyclability over 100 cycles with 95% coulombic efficiency when cycled at 20 mA cm −2 current density for 1 h duration.