Battery separator

Abstract

Resinous fibers of nanometer to micrometer width dimensions are drawn from a multi-component system by a melt extrusion process. The process includes a step of combining a fiber resin with a water-soluble carrier resin to form a resinous mixture. The resinous mixture is extruded to form an extruded resinous mixture, the extruded resinous mixture having strands of the fiber resin with the carrier resin. The extruded resinous mixture is then contacted with water to separate the strands of the fiber resin from the carrier resin. A fibrous sheet is then formed from the strands of fiber resin. The fibrous sheets are useful in filtration, as battery separators in Li ion batteries and as diffusion layers in fuel cells.

Description

technical field

[0001] The present invention relates to porous mats useful for filtration and as separators for battery and fuel cell applications. Background technique

[0002] High-quality porous mats are used in filtration and in many electronic devices such as batteries and fuel cells. In such devices, the porous pad is advantageously permeable to the passage of gas or components dissolved in the liquid. Porous mats are made from microfibers, nanofibers and microporous membranes. Fibers of these dimensions are prepared by electrospinning in the case of solvent soluble polymers. However, polyolefins are difficult to form into solutions without maintaining high temperatures in high-boiling solvents. Cellular polyolefins are prepared by biaxially stretching films or sheets of these plastic polymers. Alternatively, porogens are added to the polyolefin sheet during manufacture and then extracted with a solvent or removed by heating. In the case of solvent soluble olefins...

Images