The separator-divided soluble lead flow battery

The soluble lead flow battery (SLFB) is conventionally configured with an undivided cell chamber. This is possible, unlike other flow batteries, because both electrode active materials are electroplated as solids from a common species, Pb 2+ , on the electrode surfaces during charging. Physically separating the active materials has the advantage that a single electrolyte and pump circuit can be used; however, failure mechanisms such as electrical shorting may be observed. In addition, a common electrolyte requires that any electrolyte additives are compatible with both half-cell reactions. This paper introduces two new configurations; semi- and fully divided for the SLFB. Cationic, anionic, and microporous separators are assessed for ionic conductivity in SLFB electrolytes, showing that their incorporation adds as little as a 20 mV to the cell voltage. Voltammetry shows the effect of additives on the equilibrium potential and stripping overpotential of PbO 2 . It is then demonstrated that the incorporation of a separator into the SLFB can reduce failure due to electrical shorting and permit electrode-specific additives to be used. A unit flow cell with electrode area of 100 cm 2 is shown to operate for over 300 Ah in the semi-divided configuration, more than doubling the previously reported cycle life for cells of similar size. Graphical Abstract