Physical and electrochemical characterization of PbO2 electrode prepared at different H2SO4/H2O/PbO ratios

The influence of pastes from various H2SO4/H2O/PbO ratios on the material structure and electrochemical characteristics of PbO2 electrodes is studied. The structural and electrochemical characteristics of these electrodes are investigated by scanning electron microscopy (SEM), X-ray diffraction, mercury intrusion porosimetry (MIP), ac impedance, and charge–discharge curves. Three pastes (A, B, and C) are studied to assess the influence of H2SO4/H2O/PbO ratios. Paste A, prepared with more water, has a larger specific surface-area and pore-size. The group A plates have a greater porosity, which gives higher active material utilization and higher initial capacity. The plates have poor mechanical strength, however, which results in a high capacity loss for each cycle. In studies on ac impedance, the appearance of a high-frequency inductive loop in the group A plates indicates that these plates have active materials of greater porosity during the electrode processing reactions. The group C plates, prepared with more H2SO4, contained more α-PbO2 crystals which results in a smaller charge-transfer resistance, and a larger exchange current.