Numerous investigations have demonstrated that the charge acceptance and life of lead–acid batteries in PSoC operation can be improved by the addition of high levels of specialty carbon additives to the negative active material (NAM). Unfortunately, in some investigations an undesirable increase in water loss and diminished cold-cranking performance occurred at high carbon black and low organic expander pairings. Increasing the organic expander dosage and use of specialty organic expanders remedied the adverse responses. These complicated responses warrant a systematic investigation to elucidate the relationship between the carbon black, the organic expander and battery performance. This presentation concerns an investigation of the interaction of lignosulfonate expanders Vanisperse A and Vanisperse DCA with eight commercially available carbons. The carbon’s surface-area ranged from 75 m2 g-1 to 1400 m2 g-1. Whereas, a general correlation was established between the carbon specific surface-area and the effective dose, nonlinearities in lignosulfonate adsorption suggested secondary factors, for example, carbon surface groups or size exclusion due to carbon pore structure might also play a role. Furthermore, given that the relative mass of the lignosulfonates adsorbed varied with the carbon suggested that lignosulfonate structure might also influence adsorption. Subsequent battery tests also revealed strong correlations between effective lignosulfonate dose and battery performance, though again the extents of these correlations were complicated by secondary effects or intrinsic lignosulfonate / carbon synergies. Nevertheless, it can be concluded that (i) the effective dose of lignosulfonate is contingent on the carbon specific surface-area and (ii) a minimum threshold effective dose of lignosulfonate is necessary to preserve or improve key battery performance metrics.
Mr. Tim McNally –
Tim McNally joined Borregaard USA, Inc. in 1996 and is the Manager of Research and Development and the Technical Application Manager for Batteries. His group develops innovative organic expander additives to improve cold-cranking, charge acceptance, and high temperature life. He received his M.S. degree in Chemistry in 1987.