Battery separator with antistatic properties

Abstract

A battery separator comprising: a microporous polyolefin film having from 0.1% to 50% by weight of a block copolymer including a polyetheresteramide monomer. In this battery separator the polyolefin is selected from the group consisting of: polyethylene, polypropylene, polybutylene, polymethylpentene, mixtures thereof, and copolymers thereof. Preferably the polyolefin is polyethylene, mixtures of polyethylene and copolymers of polyethylene, or polypropylene, mixtures of polypropylene and copolymers of polypropylene and has less than or equal to 5% by weight of the block copolymer. In the battery separator of the invention, the microporous film generally has a thickness of no greater than 200 microns, a porosity in the range of 10 to 90%, and a pore size in the range of 0.005 micron to 1.5 micron.

Description

technical field

[0001] The present invention relates to battery separators having antistatic properties. Background technique

[0002] Static charges on microporous polyolefin films used as separators in batteries such as rechargeable lithium batteries often cause problems. First, during the manufacture of the separator, electrostatic charges can move or attract contaminants to the membrane. These contaminants can form defects such as spots, pinholes, etc. on the film. Also, during lamination of multilayer films, contaminants can become trapped between layers, which in turn can cause defects in the film. Second, static charges on the film can cause the battery to fail by drawing contaminants into the anode / separator / cathode structure (gel roll or prism) during battery fabrication. The most notable of these failures can cause short circuits in internal circuits. As far as battery manufacturing is concerned, the static charge generated in the dry (ie, low humidity) environ...