A new generation of highly efficient expander products and correlation between their chemical composition and the performance of the lead-acid battery

A family of eight lignosulphonates produced by Borregaard LignoTech (Norway) is investigated with the aim to determine their efficiency as expanders in the negative plates of SLI lend-acid batteries. The lignosulphonates are introduced during preparation of the paste from which the negative active mass is formed. All battery tests were performed employing the DIN43539-2 test protocol. Besides the battery tests, all lignosulphonates were characterized with regard to their chemical composition (i.e., the content of various functional groups such as -COOH, Ar-OH, -O . CH3 and organic sulphur in the structure of the lignins), average molecular weight and purity. It has been found that the lignins UP-393, M, D, Vaniperse-A (VS-A) and UP-414 have a very strong beneficial effect as expanders on the performance of the negative plates. It has also been established that the cycle life of the batteries is limited by the conversion of the energetic NAM structure into skeleton one. As a result of this conversion, large shapeless lead crystals were formed with small surface area and large macropores in-between. The beneficial effect of the expander has been found to correlate positively with low number average molecular weight of the lignins and their derivatives, high -COOH content, low -O . CH3 and organic S content, optimum Ar-OH content and high lignin purity. Expanders with different chemical composition should be selected for different battery type applications. (C) 2000 Elsevier Science S.A. All rights reserved.