INFLUENCE OF CYCLING ON THE NATURE OF THE POSITIVE ACTIVE MASS OF LEAD ACID BATTERIES AND EFFECT OF CASO4 ON THE BEHAVIOR OF THE POSITIVE PLATES/

Through cycling of tubular powder electrodes filled with positive acti ve mass (PAM) powder obtained from positive SLI plates with pure-lead grids, it has been established that during cycling PAM loses its abili ty to restore its skeleton structure. X-ray diffraction investigations have shown that the crystallinity of PAM increases on cycling. This i s probably the reason for the loss of PAM's ability to restore its ske leton structure. This ability is influenced by some metal ions called binders. The results of the present investigation indicate that Sn2+ i ons do not act as binders in contrast to Ca2+ ions, which have a notab le binder action. They facilitate the rebuilding process of the disint egrated PAM structure during discharge and, thus, improve the cycle li fe of positive plates with pure-lead grids. This effect of Ca2+ ions i s most pronounced when the positive paste contains 0.8% of CaSO4. Besi des, Ca2+ ions reduce the crystallinity of PAM particles and, hence, t heir proportion of gel (hydrated) zones increases. This yields a flexi ble skeleton structure of PAM. The effect of Ca2+ ions on the properti es of PAM is explained by the phenomena that occur in the gel/crystal structure of the PAM as a result of the electrochemical, chemical and crystallization processes.