Shutdown functionalized nonwoven separator with improved thermal and electrochemical properties for lithium ion batteries
Abstract A shutdown functionalized nonwoven separator (SFNS) with improved thermal and electrochemical stabilities is prepared by a simple dip coating method for use in lithium ion battery (LiB) applications. The SFNS shows thermal stability at 200 degC, while providing shutdown functionality at approximately 140 degC, similar to commercial porous polyethylene separators. The surface coated polymer prevents leakage current problems and in addition, shows air permeability values similar to that of bare nonwoven separators, while maintaining a thickness of about 20 mm, which is a desired attribute of effective separators for LiBs. The SFNS also shows increased electrolyte uptake and higher conductivity, compared to a bare polyethylene separator. Therefore, a cell with the SFNS exhibits higher discharge capacity and better cycle property than that with a porous polyethylene separator. These results suggest that SFNS is an effective separator for high performance LiBs.