Nanoporous composite separators with increased thermal conductivity
Nanoporous composite separators are disclosed for use in batteries and capacitors comprising a nanoporous inorganic material and an organic polymer material. The inorganic material may comprise Al 2 O 3 , AlO(OH) or boehmite, AlN, BN, SiN, ZnO, ZrO 2 , SiO 2 , or combinations thereof. The nanoporous composite separator may have a porosity of between 35-50%. The average pore size of the nanoporous composite separator may be between 10-90 nm. The separator may be formed by coating a substrate with a dispersion including the inorganic material, organic material, and a solvent. Once dried, the coating may be removed from the substrate, thus forming the nanoporous composite separator. A nanoporous composite separator may provide increased thermal conductivity and dimensional stability at temperatures above 200° C. compared to polyolefin separators.
1. A flexible porous composite battery separator, comprising:
a first group and a second group of inorganic particles, wherein
the first group of inorganic particles comprises boehmite particles having a first particle size and
the second group of inorganic particles comprises boehmite particles having a second particle size that is different from the first particle size; and
a polymeric binder, wherein
the first group of inorganic particles and the second group of inorganic particles are dispersed in the polymeric binder to form the flexible porous composite battery separator,
the flexible porous composite battery separator does not comprise an additional polymeric separator layer, and
the flexible porous composite battery separator exhibits less than 1% shrinkage when exposed to a temperature of 200° C. for one hour.
2. The flexible porous composite battery separator of claim 1 , wherein a thermal conductivity of said flexible porous composite battery separator is higher at 50° C. than at 25° C.
3. The flexible porous composite battery separator of claim 1 , wherein a ratio (weight/weight) of the first group and the second group of inorganic particles to the polymeric binder is about 4.5:1.
4. The flexible porous composite battery separator of claim 1 , wherein the boehmite particles having the first particle size are grouped around a first mode and the boehmite particles having the second particle size are grouped around a second mode that differs from the first mode.
5. The flexible porous composite battery separator of claim 4 , wherein the first mode is between 100 nm and 200 nm.
6. The flexible porous composite battery separator of claim 1 , wherein a porosity of the flexible porous composite battery separator is between 35% and 50%.
7. The flexible porous composite battery separator of claim 1 , wherein the polymeric binder comprises polyvinylidene difluoride (PVdF) and/or copolymers thereof.
8. The flexible porous composite battery separator of claim 7 , wherein the polymeric binder comprises high molecular weight grade PVdF and/or copolymers thereof.
9. The flexible porous composite battery separator of claim 1 , wherein the polymeric binder comprises a polymer selected from the group consisting of polyvinyl ethers, urethanes, acrylics, cellulosics, styrene-butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, and polyphosphazenes.
10. The flexible porous composite battery separator of claim 1 , wherein the polymeric binder further comprises a co-monomer.
11. The flexible porous composite battery separator of claim 1 , wherein a dimensional stability of the flexible porous composite battery separator is constant at temperatures from 50° C. to 250° C.
12. The flexible porous composite battery separator of claim 1 , wherein the first group and the second group of inorganic particles comprise at least 90% boehmite by weight.
13. The flexible porous composite battery separator of claim 1 , wherein the first group and the second group of inorganic particles comprise at least 95% boehmite by weight.
14. The flexible porous composite battery separator of claim 1 , wherein the first group and the second group of inorganic particles comprise at least 99% boehmite by weight.
15. The flexible porous composite battery separator of claim 1 , wherein a tensile stress of the flexible porous composite battery separator is 1500 psi or greater at 2% extension.
16. The flexible porous composite battery separator of claim 1 , wherein a tensile stress of the flexible porous composite battery separator is 1000 psi or greater at 0.5% extension.
17. The flexible porous composite battery separator of claim 1 comprising pores having an average pore size between 10 nm and 50 nm.
18. The flexible porous composite battery separator of claim 1 , wherein greater than 90% of a pore volume of the flexible porous composite battery separator comprises pores having a pore diameter of less than 100 nm.
19. The flexible porous composite battery separator of claim 1 , wherein the first group and the second group of inorganic particles comprise only boehmite.
20. An electrochemical cell comprising:
an anode;
a cathode:
an organic electrolyte comprising a lithium salt; and
a flexible porous composite battery separator, comprising:
a first group and a second group of inorganic particles, wherein
the first group of inorganic particles comprises boehmite particles having a first particle size and
the second group of inorganic particles comprises boehmite particles having a second particle size that is different from the first particle size; and
a polymeric binder;
wherein the flexible porous composite battery separator exhibits less than 1% shrinkage when exposed to a temperature of 200° C. for one hour, and
wherein the first group of inorganic particles and the second group of inorganic particles are dispersed in the polymeric binder to form the flexible porous composite battery separator, and
wherein the flexible porous composite battery separator does not comprise an additional polymeric separator layer.
21. The electrochemical cell of claim 20 , wherein a thermal conductivity of said flexible porous composite battery separator is higher at 50° C. than at 25° C.
22. The electrochemical cell of claim 20 , wherein a ratio (weight/weight) of the first group and the second group of inorganic particles to the polymeric binder is about 4.5:1.
23. The electrochemical cell of claim 20 , wherein the boehmite particles having the first particle size are grouped around a first mode and the boehmite particles having the second particle size are grouped around a second mode that differs from the first mode.
24. The electrochemical cell of claim 23 , wherein the first mode is between 100 nm and 200 nm.
25. The electrochemical cell of claim 20 , wherein a porosity of the flexible porous composite battery separator is between 35% and 50%.
26. The electrochemical cell of claim 20 , wherein the polymeric binder comprises polyvinylidene difluoride (PVdF) and/or copolymers thereof.
27. The electrochemical cell of claim 26 , wherein the polymeric binder comprises high molecular weight grade PVdF and/or copolymers thereof.
28. The electrochemical cell of claim 20 , wherein the polymeric binder comprises a polymer selected from the group consisting of polyvinyl ethers, urethanes, acrylics, cellulosics, styrene-butadiene copolymers, natural rubbers, chitosan, nitrile rubbers, silicone elastomers, PEO or PEO copolymers, and polyphosphazenes.
29. The electrochemical cell of claim 20 , wherein the polymeric binder further comprises a co-monomer.
30. The electrochemical cell of claim 20 , wherein a dimensional stability of the flexible porous composite battery separator is constant at temperatures from 50° C. to 250° C.
31. The electrochemical cell of claim 20 , wherein the first group and the second group of inorganic particles comprise at least 90% boehmite by weight.
32. The electrochemical cell of claim 20 , wherein the first group and the second group of inorganic particles comprise at least 95% boehmite by weight.
33. The electrochemical cell of claim 20 , wherein the first group and the second group of inorganic particles comprise at least 99% boehmite by weight.
34. The electrochemical cell of claim 20 , wherein a tensile stress of the flexible porous composite battery separator is 1500 psi or greater at 2% extension.
35. The electrochemical cell of claim 20 , wherein a tensile stress of the flexible porous composite battery separator is 1000 psi or greater at 0.5% extension.
36. The electrochemical cell of claim 20 comprising pores having an average pore size between 10 nm and 50 nm.
37. The electrochemical cell of claim 20 , wherein greater than 90% of a pore volume of the flexible porous composite battery separator comprises pores having a pore diameter of less than 100 nm.
38. The electrochemical cell of claim 20 , wherein the first group and the second group of inorganic particles comprise only boehmite.