Porous membranes filled with nano-particles, separators, batteries, and related methods
View Patent ↗A membrane includes a porous membrane or layer made of a polymeric material having a plurality of surface treated (or coated) particles (or ceramic particles) having an average particle size of less than about 1 micron dispersed therein. The polymeric material may be selected from the group consisting of polyolefins, polyamides, polyesters, co-polymers thereof, and combinations thereof. The particles may be selected from the group consisting of boehmite (AlOOH), SiO 2 , TiO 2 , Al 2 O 3 , BaSO 4 , CaCO 3 , BN, and combinations thereof, or the particles may be boehmite. The surface treatment (or coating) may be a molecule having a reactive end and a non-polar end. The particles may be pre-mixed in a low molecular weight wax before mixing with the polymeric material. The membrane may be used as a battery separator.
1. A method of making a membrane comprising the steps of:
mixing dried surface treated particles with a wax thereby forming a first mixture;
mixing the first mixture with a polymeric material thereby forming a second mixture; and
forming the second mixture into a porous membrane.
2. A battery comprising: a negative electrode, a positive electrode, a separator sandwiched between said negative electrode and said positive electrode, an electrolyte in communication between said negative electrode and said positive electrode, and said separator including a porous membrane or layer made by the method of claim 1 and made of a polymeric material having a plurality of wax-coated surface treated particles having an average particle size of less than about 1 micron dispersed therein.
3. The battery of claim 2 wherein said polymeric material being selected from the group consisting of polyolefins, polyamides, polyesters, co-polymers thereof, and combinations thereof.
4. The battery of claim 3 wherein said polyolefins being selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, co-polymers thereof, and combinations thereof.
5. The battery of claim 2 wherein said plurality of wax-coated surface treated particles comprising 0.1-30% by weight of said polymeric material.
6. The battery of claim 2 wherein said particles comprising ceramic particles being selected from the group consisting of boehmite (AlOOH), SiO 2 , TiO 2 , Al 2 O 3 , BaSO 4 , CaCO 3 , BN, and combinations thereof with a surface treatment or coating.
7. The battery of claim 2 wherein said surface treatment being a molecule having a reactive end and a non-polar end.
8. The battery of claim 2 wherein said average particle size being less than about 500 nanometers.
9. The battery of claim 2 wherein said membrane being a layer of a multi-layered separator.
10. The battery of claim 2 wherein said wax being a polyolefin wax coating.
11. The battery of claim 2 wherein said wax having a molecular weight in the range of 800-5000.
12. The battery of claim 2 being a lithium battery.
13. The battery of claim 2 being a secondary lithium battery.
14. The battery of claim 2 being a lead acid battery.
15. The method of claim 1 wherein the first mixing step including heating and the first mixture being a fluid.
16. The method of claim 1 wherein the wax having a molecular weight in the range of 800-5000.
17. The method of claim 1 wherein forming the second mixture into a porous membrane including:
extruding the second mixture into a sheet or tube,
annealing the sheet or tube, and
stretching the annealed sheet or tube.
18. A battery separator having a membrane made by the method of claim 1 .
19. The battery separator of claim 18 wherein said membrane being a layer of a multi-layered separator.
20. A battery having the battery separator of claim 18 .
21. The battery of claim 20 being a secondary lithium battery.
22. A battery separator having a microporous membrane made by the method of claim 1 .
23. A membrane made by the method of claim 1 comprising:
a porous membrane or layer made of a polymeric material having a plurality of wax-coated surface treated particles having an average particle size of less than about 1 micron dispersed therein, the wax having a molecular weight in the range of 800-5000.