In this study, we examined the sulfonation reaction of polyolefin nonwovens and their properties as battery separators. The occurrence of the sulfonation was confirmed by means of X-ray photoelectron spectroscopy, and the influences of the temperature and time of the sulfonation reaction on the properties of polyolefin nonwoven battery separators were studied. The results show that the process method for producing the separators of sulfonation was capable of realizing high water conservation properties and improving the water absorption rate and K+ exchange capacity while maintaining tensile strength. The nickel-metal hydride batteries with the sulfonated polyolefin as separators had a similar capacity but a lower internal impedance compared to batteries with H&V commercial separators. Furthermore, their properties were stable after 300 charge-discharge cycles. (C) 2008 Wiley Periodicals, Inc.