Increase of positive active material utilization in lead-acidbatteries using diatomaceous earth additives
2009-04-17 Journal of Power Sources, Vol.173, No.2, 882-886, 2007 McAllister SD, Ponraj R,
n this study we examined the use of diatomites toimprove the discharge capacity and utilization of the positiveelectrode of the lead-acid battery. A large fraction of thepositive electrode performance of this battery system(half-reaction shown below) is based on the ionic conduction ofsulfuric acid through the plate. PbO2(s) + HSO4- + 3H(+) + 2e(-)-> PbSO4(S) + 2H(2)O The porous diatomites improve the ionicconduction by providing channels in addition to the natural onesformed within the paste. The choice of diatomite is based on itsstability in the oxidative and corrosive environment of thelead-acid battery, as well as its naturally high porosity. Thediatomite particles were size sorted into 20-30 mu m, 30-53 mu m,53-74 mu m, and 74-90 mu m fractions, and the dischargeperformances of each were measured at 1%, 3%, and 5% weight ratios.The best performance was observed with 53-74 mu m particles with anoptimum weight ratio of 3%. At this size fraction and weight ratio,diatomites show a 12.7% increase in active material utilization anda 9.3% increase in specific capacity at high rate discharge (50 mAcm(-2)) relative to control samples without diatomites. (C) 2007Elsevier B.V. All rights reserved.