Tim McNally

Numerous investigations have demonstrated charge acceptance and life of lead batteries in PSOC operation can be improved by the addition of high levels of specialty carbon additives to the NAM. Unfortunately, in some investigations an undesirable increase in water loss and diminished cold crank performance occurred at high carbon black-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. In this work, we investigated the interaction of lignosulfonate expanders Vanisperse A and Vanisperse DCA with eight commercially available carbons. The carbon’s specific surface area ranged from 75 m2/g to 1400 m2/g. While a general correlation is established between carbon´s specific surface area and effective dose, nonlinearities in lignosulfonate adsorption suggest secondary factors – such as carbon surface groups or size exclusion due to carbon pore structure may also play a role. Furthermore, the relative mass of the lignosulfonates adsorbed varied with the carbon suggesting lignosulfonate structure may also influence adsorption.

EN DCA, EN MHT, SAE J2801, cold crank and capacity testing 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, we conclude the effective dose of lignosulfonate is contingent on the carbon´s specific surface area and that a minimum threshold effective dose of lignosulfonate is necessary to preserve or improve key battery performance.