Resilient battery separator media and a battery including the resilient separator media

A resilient battery separator, especially suited for use in a starved electrolyte battery, is made of an air laid fibrous mat of randomly oriented, entangled microfibers having a mean diameter between 0.5 and 2.0 microns. The air laid mat weighs between 50 and 450 g/m2 and has a thickness between 0.01 and 0.5 inches. The fibrous mat may be essentially uniform in density throughout its thickness or may include one or two relatively high density, high tensile strength fibrous surface layer(s) and a relatively low density, more resilient fibrous layer integral with and, in one embodiment, intermediate the two surface layers. The microfibers in the surface layer(s) are more entangled than the microfibers in the resilient layer. In a starved electrolyte battery, the separator has a thickness, when subjected to a loading of 1.5 psi, that is equal to or greater than the spacing between the electrode plates of the battery and, preferably, at least 110% of the spacing between the electrode plates of the battery.