Investigation of expander formulation in the negative active material on key performance characteristics of lead-acid batteries

Lead-acid battery has been widely used for automotive yet, due to low cost, high power and 100% recyclable . the battery forms from sponge lead ( Pb/PbSO4) as negative electrode, with a lead dioxide (PbO2/PbSO4) as positive electrode in sulfuric acid solution. several additives introduced to modify negative active materials (NAM) to improve the batteries performance. Modern expander formulations are usually a blend of barium sulfate(BaSO4), lignosulfonate (LS) and carbon black(C). The function of BaSO4 is to act as a site for the precipitation of lead sulfate as the battery is discharged. C is added to the expander to increase the NAM electrochemical surface area. .[1] The most pronounced effect of LS on battery performance is the improvement in low-temperature performance at high rates of discharge.[2] The purpose of the present work was to examine various expander formulation on cold cranking test, dynamic charge acceptance, capacity as key performance characteristics of lead-acid batteries. It was made three series of expander : the first one containing 33% LS, 20% C, and 47% BaSO4.; the second one had 28% LS, 17% C, 55% BaSO4.; and the last one w 22% LS, 13% C, 65% BaSO4.Using 1% of the expanders, three pastes and subsequent three king of negative plate were produces. The plates were studied by scanning electron microscope (SEM) in two state: before charging the plates and after an charge-discharge cycle. SEM images indicated different morphology and particle size for plates with different expander . electrochemical impedance spectroscopy was used to investigate the discharge plates. The results have been shown that Rct in the first formulation is ten time more than the second one. but it was not considerable difference between Rct of the second plate and the last one. Using the different negative plates, three 74Ah batteries were made and standard testes were done over them. The results show that plates that prepared with second expander have best dynamic charge acceptance, capacity. Whereas the first plates that its expander with 33%LS, has best cold cranking result.