High density polyethylene microporous membranes

Microporous polymer membranes are the most commonly used separators in lithium-ion batteries. Majority of the microporous polymer membrane separators are based on semicrystalline polyolefin materials, such as polyethylene (PE), polypropylene (PP), PE-PP blends and high-density polyethylene (HDPE)-ultrahigh molecular polyethylene (UHMWPE). 

Polyolefin materials used for the battery separator are based on a homopolymer or a blend of polyethylene (PE) and polypropylene (PP) in a number of combinations between high density polyethylene (HOPE) and ultrahigh molecular weight polyethylene (UHMWPE). The methods for manufacturing the microporous polyolefin membranes can be divided into the dry process and wet process. Both processes contain an extmsion step to produce a thin film, and employ one or more orientation steps to impart porosity and increase tensile strength. The membranes made by diy process show a distinct slit-pore microstmcmre, while those by wet process feamre interconnected spherical or elliptical pores. 

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