Multi-layer microporous membrane, battery separator and battery

摘要

The invention relates to a particular multi-layer microporous membrane having a good balance of important properties, including excellent electrochemical stability and low heat shrinkage, while maintaining high permeability and heat resistance, with good mechanical strength, compression resistance and electrolytic solution absorption. Of particular importance when used as a battery separator, the present multi-layer microporous membrane exhibits excellent heat shrinkage, melt down temperature and thermal mechanical properties, i.e. low maximum shrinkage in the molten state. The multi-layer microporous membrane of the present invention is manufactured by layering, such as for example by coextrusion, one or more microporous membrane first layers and one or more microporous membrane second layers, such as on one or both sides of a first layer. The invention further relates to battery separators comprising the multi-layer microporous membrane and batteries utilizing the battery separators.

主权项

1. A multi-layer microporous membrane comprising:
at least two first microporous membrane skin layers comprising;
(a) from about 30 to about 70% of a first polyethylene,(b) from about 20 to about 40% of a first polypropylene, the first polypropylene having a weight average molecular weight of from about 0.8×106 to about 1.5×106, a molecular weight distribution of from about 1 to about 100 and a heat of fusion of 80 J/g or higher and(c) from about 10 to about 30% of a second polypropylene, the second polypropylene having a weight average molecular weight of from about 4×105 to about 7.5×105, a molecular weight distribution of from about 5 to about 100 and a heat of fusion of 80 J/g or higher, percentages based on the weight of the first microporous membrane skin layer; and at least one second microporous membrane layer in planar contact with the first microporous membrane comprising a high density polyethylene and an ultrahigh molecular weight polyethylene; wherein the first and second microporous membrane layers are formed into first layer/second layer/first layer or first layer/second layer/first layer/second layer/first layer structures.