Effect of electrolyte on the performance of electrodes for an all lead flow battery

Abstract

The effect of Pb(II) and H+ concentrations on the electrochemical behavior of a PbO2 anode and a Pb cathode on a graphite composite was investigated. It is shown that the electrode process is under an electrochemical and diffusion mixed control. When a PbO2 deposit is formed, a nucleation loop occurs. The nucleation overpotential of a Pb cathode is rather small. The difference between charge and discharge potentials of the Pb cathode is much lower than that of the PbO2 anode. This indicates that the polarization in an all lead flow battery is attributed mainly to the PbO2 anode. An increase in H+ concentration is beneficial for a reduction in the polarization; however, side reactions producing oxygen and hydrogen, and corrosion also increase. An increase of Pb(II) concentration favors the suppression of oxygen evolution, however, the potential of the PbO2 electrode is increased. This results in an increase in the difference between potentials of the charged and discharged states. When the Pb(II) concentration is relatively low, PbO2 deposits shed from the substrate during charge and discharge. As a result, the charge potential is further reduced. Appropriate concentrations of HBF4 and Pb(II) were determined to be 2 mol · L-1 and greater than 0.9 mol̇ L-1, respectively. © Editorial office of Acta Physico-Chimica Sinica.