In this paper, we investigate the use of paste additives to improve the performance of a horizontal plate, lead-acid battery. The horizontal plate battery can deliver high power for electric and hybrid electric vehicle applications. We develop a series of designs having different paste additives to continuously improve the specific energy (W h/kg) performance of this battery. Computer models, previously developed and reported, are used to estimate the specific energy performance of these designs. The baseline, horizontal plate battery containing no additives has a specific energy of 30-35 W h/kg. The final design in our design progression uses both porous and conductive paste additives to provide an estimated specific energy of 60-70 W h/kg. (C) 2000 Elsevier Science S.A. All rights reserved.