FUNDAMENTAL-STUDIES TO DEVELOP THE MAINTE NANCE FREE LEAD-ACID-BATTERIES .7. OPTIMIZATIONS OF LEAD POWDERS FOR POSITIVE ACTIVE MATERIAL ANDCONCENTRATION OF SULFURIC-ACID-SOLUTION OF THIN SEALED LEAD-ACID-BATTERIES

In order to produce the thin-type sealed lead-acid batteries with high energy density, characteristics of lead powders as the raw materials of positive active material were examined, and then the optimum concen tration of sulfuric acid solution was determined. Fine lead powder cru shed from ordinary powder was better for the positive material of the thin-type battery, which has one positive and one negative plates on b oth side of retainer. PbO2 active positive material formed from fine l ead powder was formed by the secondary powders combined firmly with un iform and fine primary powders and had many macropores with large surf ace area. Thus, since the electrolyte diffused in active material easi ly and the active material was utilized effectively, the large energy density was obtained by the use of fine lead powder. alpha-PbO2 had th e important role for the mutual combination between lead powders, so t he optimum ratio of PbSO4 in the positive paste (16 wt %) was existed for long charge . discharge cycles. Concentrated sulfuric acid solutio n led to high energy density of battery, but led to low utilization of active materials by the formation of inactive PbSO4. Thus, optimum co ncentration of sulfuric acid solution (6.15 M) was existed for the hig h energy density and the long cycle life.