Microporous polymeric membranes, battery separators, and production methods therefor
A multilayer microporous membrane including polymer and having a shutdown temperature of ≦130.5° C. and a storage stability of 0.3V or less.
1. A multilayer microporous membrane comprising at least a first layer comprises a first polymer having a 115.0° C.≦Tm≦130.0° C. and an Mw of from 5.0×10 3 to 4.0×10 5 and a second layer comprising polyethylene having an amount of terminal unsaturation <0.20 per 10,000 carbon atoms, and having a shutdown temperature of ≦130.5° C. and a storage stability of 0.3V or less.
2. The membrane of claim 1 , wherein the first polymer is a polyolefin having a 115.0° C.≦Tm≦130.0° C.
3. The membrane of claim 1 , wherein the first layer includes a polyethylene having an Mw<1.0×10 6 and an amount of terminal unsaturation <0.20 per 10,000 carbon atoms.
4. The membrane of claim 1 , further comprising at least a third layer comprising an ethylene/α-olefin copolymer having a Tm of ranging from 121.0 to 125.0° C. and a polyethylene having an Mw<1.0×10 6 and an amount of terminal unsaturation <0.20 per 10,000 carbon atoms; wherein the first polymer is an ethylene/α-olefin copolymer having a Tm of ranging from 121.0 to 125.0° C.; wherein the second layer is located between the first and third layers and further comprises a polyethylene having an Mw≧1.0×10 6 .
5. The microporous membrane of claim 1 , wherein the shutdown temperature is ≦128.5° C.
6. The microporous membrane of claim 1 , wherein the storage stability is less than 0.2V and the membrane has a thickness greater than 18 μm.
7. The microporous membrane of claim 1 , wherein the membrane has a normalized pin puncture strength greater than or equal to 3900 mN/20 μm and a normalized air permeability less than or equal to 300 seconds/100 cm 3 /20μ.
8. The microporous membrane of claim 1 , wherein the membrane's thickness is in the range of 20 microns to 25 microns, the normalized pin puncture strength is in the range of 3900 to 4300 mN/20 μm, the normalized air permeability is in the range of 200 to 300 seconds/100 cm 3 /20 μm.
9. The microporous membrane of claim 1 , wherein the membrane has a TD heat shrinkage at 105° C. in the range of 1% to 5% and an MD heat shrinkage in the range of 2% to 10%, a porosity in the range of about 30% to about 45%, an MD tensile strength of 1000 Kg/cm 3 or more, an TD tensile strength of 1000 Kg/cm 3 or more, and a meltdown temperature of 145° C. or more.