Polyaspartate as a gelled electrolyte additive to improve the performance of the gel valve-regulated lead-acid batteries under 100 % depth of discharge and partial-state-of charge conditions

The effect of polyaspartate (PASP) on the gel properties and performance of gel valve-regulated lead-acid (VRLA) batteries is reported. The presence of PASP in the gelled electrolyte has a marginal effect on the gelling process and gel strength. Cyclic voltammetry indicates that the addition of PASP does not affect the main reaction of the VRLA battery, but slightly suppresses the hydrogen evolution reaction. However, a concentration level of PASP seems not to affect the degree of suppression. The battery performance was evaluated under a 100 % depth of discharge (100 % DoD) over a wide temperature range (0-60 degrees C), and after a 3-month storage period and under partial-state-of charge (PSoC) conditions at normal and high charge/discharge rates. The addition of 0.005 % (w/v) PASP in the gelled electrolyte slows down the growth of lead sulfate crystals on the negative plate during the battery operation leading to a substantial improvement in the performance of the gel VRLA batteries. By combining the advantages of the gelled electrolyte structure and the presence of PASP in the gelled electrolyte, the gel VRLA batteries provide a superior discharge capacity and long cycle life under all 100 % DoD and PSoC conditions studied.