Microporous film, process for production of the film, and use of the film
View Patent ↗The invention relates to microporous polymeric membranes suitable for use as battery separator film. The membrane comprises polyethylene, polypropylene, and polymethylpentene. The invention also relates to a method for producing such a membrane, batteries containing such membranes as battery separators, methods for making such batteries, and methods for using such batteries.
1. A membrane comprising a layer containing a polymer blend, the polymer blend comprising 45.0 wt. % to 77.0 wt % polypropylene, 1.0 wt % to 18.0 wt. % polymethylpentene, and 5.0 wt. % to 54.0 wt. % polyethylene, based on the weight of the polymer blend, wherein the membrane is microporous and has an electrochemical stability ≦50.0 mAh.
2. The membrane of claim 1 , wherein the membrane further comprises a second layer, wherein the second layer is microporous and comprises a second polymer blend.
3. The membrane of claim 1 , wherein the membrane has a thickness ≦50.0 μm, a meltdown temperature ≧170.0° C., and a normalized air permeability ≦50.0 seconds/100 cm 3 /μm.
4. The membrane of claim 1 , wherein the polypropylene has an Mw in the range of from 0.90×10 6 to 2.0×10 6 , an MWD≦20.0, and a ΔHm≧90.0 J/g.
5. The membrane of claim 1 , wherein the polymethylpentene has an MFR in the range of from 0.1 dg/min to 28.0 dg/min and a Tm in the range of 223.0° C. to 235.0° C.
6. The membrane of claim 2 , wherein the second polymer blend comprises 55.0 wt. % to 75.0 wt % of a first polyethylene and 25.0 wt. % to 45.0 wt % of a second polyethylene, based on the weight of the second polymer blend, and wherein the first polyethylene has a an Mw in the range of 1.0×10 5 to about 0.90×10 6 and an MWD≦20.0 and the second polyethylene has an Mw≧1.0×10 6 , an MWD≦20.0, and a Tm≧134° C.
7. The membrane of claim 2 , wherein the membrane further comprises a third layer, the third layer having a composition substantially the same as that of the first layer, the second layer being located between the first and third layers.
8. The membrane of claim 7 , wherein:
(a) the second layer is in contact with the first layer and the third layer;
(b) the membrane's total thickness is in the range of 10.0 μm to 25.0 μm;
(c) the second layer has a thickness of 70.0% to 90.0% of the membrane's total thickness; and
(d) the thicknesses of the first and third layers are each in the range of 5.0% to 15.0% of the membrane's total thickness.
9. The membrane of claim 1 , wherein the membrane has one or more of a porosity ≧20.0%, a normalized pin puncture strength ≧1.0×10 2 mN/μm, and a 105° C. heat shrinkage ≦10.0% in at least one direction.
10. A membrane comprising a first layer containing a first polymer blend and a second layer containing a second polymer blend, wherein the first polymer blend comprising 45.0 wt. % is to 77.0 wt. % polypropylene, 1.0 wt. % to 18.0 wt. % polymethylpentene, and 5.0 wt. % to 54.0 wt. % polyethylene, based on the weight of the polymer blend, the polypropylene has an Mw in the range of from 0.90×10 6 to 2.0×10 6 , an MWD≦20.0, and a ΔHm≧90.0 J/g and the polymethylpentene has an MFR in the range of from 0.1 dg/min to 28.0 dg/min and a Tm in the range of 223.0° C. to 235.0° C., wherein the second polymer blend comprises 55.0 wt. % to 75.0 wt. % of a first polyethylene and 25.0 wt. % to 45.0 wt. % of a second polyethylene, based on the weight of the second polymer blend, and wherein the first polyethylene has a an Mw in the range of 1.0×10 5 to about 0.90×10 6 and an MWD≦20.0 and the second polyethylene has an Mw≧1.0×10 6 , an MWD≦20.0, and a Tm≧134° C., wherein the membrane is microporous and has an electrochemical stability ≦50.0 mAh, one or more of a porosity ≧20.0%, a normalized pin puncture strength ≧1.0×10 2 mN/μm, and a 105° C. heat shrinkage ≦10.0% in at least one direction, 130° C. TD heat shrinkage ≦25.0%, a 170° C. TD heat shrinkage ≦55.0%, and a normalized pin puncture strength ≧1.4×10 2 mN/μm.
11. A battery separator film comprising the membrane of claim 1 .
12. A battery separator film comprising a layer containing a polymer blend, the polymer blend comprising 60.0 wt. % to 70.0 wt. % polypropylene, 3.0 wt. % to 6.0 wt. % polymethylpentene, and 24.0 wt. % to 37.0 wt. % of a polyethylene, based on the weight of the polymer blend, wherein battery separator film has an Electrochemical Stability ≦55.0 mAh, a thickness ≦50.0 μm and a normalized air permeability ≦40.0 seconds/100 cm 3 /μm.
13. A battery separator film comprising a layer containing a polymer blend, the polymer blend comprising 57.0 wt. % to 67.0 wt. % polypropylene, more than 6.0 wt. % and 12.0 wt. % or less polymethylpentene, and 21.0 wt. % to 37.0 wt. % of a polyethylene, based on the weight of the polymer blend, wherein battery separator film has an electrochemical stability ≦25.0 mAh and a thickness ≦50.0 μm.
14. The battery separator film of claim 12 , wherein the battery separator film has a 130° C. TD heat shrinkage ≦25.0%, a 170° C. TD heat shrinkage ≦55.0%, and a normalized pin puncture strength ≧1.4×10 2 mN/μm.
15. The battery separator film of claim 12 , wherein the layer is a skin layer.
16. The battery separator film of claim 12 further comprising: (i) a second skin layer having substantially the same composition as the first skin layer and (ii) a core layer comprising polyethylene, wherein the battery separator film has a 130° C. TD heat shrinkage ≦25.0%, a 170° C. ID heat shrinkage ≦55.0%, and a normalized pin puncture strength ≧1.4×10 2 mN/μm.
17. The battery separator film of claim 13 , further comprising: (i) a second skin layer having substantially the same composition as the first skin layer and (ii) a core layer comprising polyethylene, wherein the battery separator film has a 130° C. TD heat shrinkage ≦25.0%, a 170° C. TD heat shrinkage ≦55.0%, and a normalized pin puncture strength ≧1.4×10 2 mN/μm.
18. A lithium ion battery comprising the battery separator film of claim 12 .
19. The membrane of claim 2 , wherein the membrane has a thickness ≦50.0 μm, a meltdown temperature ≧170.0° C., and a normalized air permeability ≦50.0 seconds/100 cm3/μm.
20. The membrane of claim 4 , wherein the polymethylpentene has an MFR in the range of from 0.1 dg/min to 28.0 dg/min and a Tm in the range of 223.0° C. to 235.0° C.
21. The membrane of claim 4 , wherein the membrane further comprises a third layer, the third layer having a composition substantially the same as that of the first layer, the second layer being located between the first and third layers.
22. The membrane of claim 6 , wherein the membrane further comprises a third layer, the third layer having a composition substantially the same as that, of the first layer, the second layer being located between the first and third layers.
23. The membrane of claim 2 , wherein the membrane has one or more of a porosity ≧20.0%, a normalized pin puncture strength ≧1.0×102 mN/μm, and a 105° C. heat shrinkage ≦10.0% in at least one direction.
24. The membrane of claim 4 , wherein the membrane has one or more of a porosity ≧20.0%, a normalized pin puncture strength ≧1.0×102 mN/μm, and a 105° C. heat shrinkage ≦10.0% in at least one direction.
25. The membrane of claim 4 , wherein the membrane has one or more of a porosity ≧20.0%, a normalized pin puncture strength ≧1.0×102 mN/μm, and a 105° C. heat shrinkage ≦10.0% in at least one direction.
26. A battery separator film comprising the membrane of claim 2 .
27. A battery separator film comprising the membrane of claim 4 .
28. A battery separator film comprising the membrane of claim 6 .
29. The battery separator film of claim 13 , wherein the battery separator film has a 130° C. TD heat shrinkage ≦25.0%, a 170° C. TD heat shrinkage ≦55.0%, and a normalized pin puncture strength ≧1.4×102 mN/μm.
30. The battery separator film of claim 13 , wherein the layer is a skin layer.
31. A lithium ion battery comprising the battery separator film of claim 12 .
32. A lithium ion battery comprising the battery separator film of claim 16 .
33. A lithium ion battery comprising the battery separator film of claim 17 .