Antimony, added to the lead plates to facilitate casting, produces an ion migration resulting in a continuing reduction of end-of-charge Voltage of about 0.2 Volts. Test information shows the antimony poisoning to be reduced with rubber separators, so using a combination of analytical steps, Daramic, LLC produced a new material which has the antimony retardation of rubber, while maintaining the other superior performance properties of polyethylene separators. The material produces a cell which has an end of charge current below that of a rubber separator and three times less than that of a nonactive separator.
The Battery Man, June 2005, pp. 28-31