Multi-layer microporous film
View Patent ↗Embodiments of the invention relate to microporous membranes that include first and second layers. The first layer includes ≦20.0 wt. % polymethylpentene and the second layer includes a compatibilizer. The invention also relates to methods for making such membranes and the use of such membranes as battery separator film.
1. A microporous membrane comprising:
(a) a first layer including ≧20.0 wt. % polymethylpentene based on the weight of the first layer;
(b) a second layer which (i) includes a compatibilizer and (ii) has a composition that is not substantially the same as that of the first layer; and
(c) a third layer located between the first and second layers;
wherein (i) the first and third layers have substantially the same composition and substantially the same thickness and each comprises 20.0 wt. % to 45.0 wt. % of the polymethylpentene, the polymethylpentene having an Mw of 1.0×10 4 to 4.0×10 6 and a Tm≧200.0° C.; 0.0 wt. % to 45.0 wt. % of an isotactic polypropylene having an Mw≧6.0×10 5 and a Tm≧162.0° C.; and ≧10.0 wt. % polyethylene, the weight percents being based on the weight of the layer, (ii) the second layer comprises ≧5.0 wt % of the compatibilizer based on the weight of the layer, the compatibilizer comprising poly(α-olefin) excluding polyethylene homopolymer, and (iii) at least one of the first or third layers is in layer-to-layer contact with the second layer.
2. A battery separator comprising the membrane of claim 1 .
3. A battery comprising an anode, a cathode, an electrolyte, and at least one separator located between the anode and cathode, the separator according to claim 2 .
4. The battery of claim 3 and a load electrically connected to the battery.
5. The battery of claim 3 , wherein the electrolyte contains lithium ions.
6. The battery of claim 5 , wherein the battery is a lithium ion secondary battery used as a power source for an electric vehicle or hybrid electric vehicle.