Study On The Sulfonation Treatment Of ES Nonwoven Fabrics As Battery Separator

With the development of scientific technology, Ni-MH battery is being employed in more areas than before. As one of the most important part in the battery, separators are positioned in order to prevent physical contact. They should also have adequate permeability for the electrolytes or electrolyte ions and so on. The quality of the separators will influence the discharge capacity and service life of the battery.Based on the study of the requirements, material selection, web-forming and modification technology, an insulating porous non-woven battery separator base fabric has been developed with polyolefin fibers by dry-laid non-woven process and bonded by area thermal bonding. The hydrophilic modification of the base fabric was improved by sulfonation process. Scanning electron microscopy(SEM) and IR was employed to characterize and analyze the physical and chemical properties of the separator.Problem of polyolefin fiber's poor electrolyte absorption ability was partly solved by a layer of hydrophilic finish. The optimal time of treatment using concentrated sulfuric acid or chromic acid is 20min, at the room temperature 25℃, the liquid absorption ratio using chromic acid reached 370.06%, and the liquid absorption speed reached 122mm/30min; the liquid absorption ratio using concentrated sulfuric acid reached 362.14%, and the liquid absorption speed reached 131mm/30min.If we change the temperature of the treatment, The optimal conditions of treatment using concentrated sulfuric acid were as following:temperature was 60℃,time was 20s. The liquid absorption ratio reached 355%, the liquid absorption speed reached 129.4mm/30min.As for comparison, the layer of hydrophilic finish was removed by some method. In this case, The optimal conditions of treatment using concentrated sulfuric acid were as following: temperature was 120℃, time was 120s. The liquid absorption ratio reached 466.94%, the liquid absorption speed reached 103mm/30min.The micro-analysis by SEM and IR indicated that etches and flaws had been developed on the surface of the diaphragm after sulfonation, and the sulfonic groups had been successfully introduced on the surface of membranes.