Battery separators with controlled pore structure
Disclosed are battery separators comprising glass fibers and having a basis weight (gsm), a specific surface area (m 2 /g), a density (gsm/mm) and a mean pore size (μm), which satisfy the equation disclosed herein. Also disclosed are batteries comprising the battery separators, and processes for making the separators.
1. A battery separator comprising fibers, wherein the fibers comprise at least 5% glass fibers and wherein the fibers comprise fibers having an average fiber diameter of greater than or equal to 1 micron and less than or equal to 2 microns, and having a basis weight (in gsm), a specific surface area (in m 2 /g), a density (in gsm/mm) and a mean pore size (in μm), wherein the following equation is satisfied:
mean
pore
size
<
(
270
basis
weight
)
0.53
*
1.6
specific
surface
area
*
(
65
density
-
1.8
)
provided that:
the density is greater than 175 gsm/mm,
wherein:
the battery separator has an acid filling time of less than or equal to 500 seconds; and
the battery separator has a thickness greater than about 1 mm when loaded to a force of 20 kPa.
2. The battery separator of claim 1 , wherein the specific surface area is less than 2.0 m 2 /g.
3. The battery separator of claim 1 , wherein the fibers comprise about 5% to about 50% fibers having an average diameter less than or equal to 1.0 μm.
4. The battery separator of claim 3 , wherein the fibers comprise about 15% to about 35% fibers having an average diameter less than or equal to 1.0 μm.
5. The battery separator of claim 1 , wherein the mean pore size is less than 6 μm.
6. The battery separator of claim 5 , wherein the mean pore size is less than 5 μm.
7. The battery separator of claim 5 , wherein the mean pore size is less than 4 μm.
8. The battery separator of claim 1 , wherein the density is about 180 gsm/mm to about 400 gsm/mm.
9. The battery separator of claim 8 , wherein the density is about 180 gsm/mm to about 220 gsm/mm.
10. The battery separator of claim 1 , wherein the battery separator has a percent recovery, when compressed from 10 kPa to 100 kPa and recovered to 10 kPa, of greater than 84% when measured according to Battery Council International Battery Technical Manual BCIS-03 (Rev. September 2009) method number 1, and wherein the percent recovery is equal to (T rec /T comp )*100%, where T comp is the thickness of the battery separator at 20 kPa during compression and wherein T rec is the thickness at 20 kPa during recovery.
11. The battery separator of claim 1 , wherein the basis weight is between 150 gsm and 1000 gsm.
12. The battery separator of claim 1 , wherein the basis weight is from about 150 gsm to about 500 gsm.
13. The battery separator of claim 1 , wherein the basis weight is greater than or equal to about 160 gsm.
14. The battery separator of claim 1 , wherein the fibers comprise about 5% to about 50% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, and wherein the basis weight is between 150 gsm and 1000 gsm.
15. The battery separator of claim 1 , wherein the fibers comprise about 15% to about 30% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, and wherein the basis weight is between 150 gsm and 500 gsm.
16. The battery separator of claim 1 , wherein the specific surface area is less than 1.50 m 2 /g, wherein the fibers comprise about 5% to about 50% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, and wherein the basis weight is between 150 gsm and 1000 gsm.
17. The battery separator of claim 1 , wherein the specific surface area is less than 1.50 m 2 /g, wherein the fibers comprise about 15% to about 30% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, and wherein the basis weight is between 150 gsm and 500 gsm.
18. The battery separator of claim 1 , wherein the specific surface area is less than 1.50 m 2 /g, wherein the fibers comprise about 5% to about 50% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, wherein the basis weight is between 150 gsm and 1000 gsm, wherein the battery separator has a percent recovery, when compressed from 10 kPa to 100 kPa and recovered to 10 kPa, of greater than 84% when measured according to Battery Council International Battery Technical Manual BCIS-03 (Rev. September 2009) method number 1, and wherein the percent recovery is equal to (T rec /T comp )*100%, where T comp is the thickness of the battery separator at 20 kPa during compression and wherein T rec is the thickness at 20 kPa during recovery.
19. The battery separator of claim 1 , wherein the specific surface area is less than 1.50 m 2 /g, wherein the fibers comprise about 15% to about 30% fibers having an average diameter less than or equal to 1.0 μm, wherein the mean pore size is less than 6 μm, wherein the density is about 180 gsm/mm to about 400 gsm/mm, wherein the basis weight is between 150 gsm and 500 gsm, wherein the battery separator has a percent recovery, when compressed from 10 kPa to 100 kPa and recovered to 10 kPa, of greater than 84% when measured according to Battery Council International Battery Technical Manual BCIS-03 (Rev. September 2009) method number 1, and wherein the percent recovery is equal to (T rec /T comp )*100%, where T comp is the thickness of the battery separator at 20 kPa during compression and wherein T rec is the thickness at 20 kPa during recovery.
20. The battery separator of claim 1 , wherein the fibers having an average fiber diameter of greater than or equal to 1 micron and less than or equal to 2 microns make up greater than or equal to 20 wt % and less than or equal to 100 wt % of the battery separator.
21. The battery separator of claim 20 , wherein the fibers further comprise fibers having an average fiber diameter of less than 1 micron.
22. The battery separator of claim 21 , wherein the fibers having an average fiber diameter of less than 1 micron make up greater than or equal to 20 wt % of the battery separator.
23. The battery separator of claim 21 , wherein the fibers further comprise fibers having an average fiber diameter of greater than 2 microns.
24. The battery separator of claim 1 , wherein glass fibers make up 100 wt % of the fibers in the battery separator.
25. The battery separator of claim 1 , wherein the specific surface area is greater than 1.4 m 2 /g.
26. The battery separator of claim 1 , wherein the fibers comprise synthetic fibers.
27. The battery separator of claim 26 , wherein the synthetic fibers comprise bicomponent fibers.
28. A battery separator comprising fibers, wherein:
the fibers comprise at least 5% glass fibers and wherein the fibers comprise fibers having an average fiber diameter of greater than or equal to 1 micron and less than or equal to 2 microns, and having a basis weight (in gsm), a specific surface area (in m 2 /g), a density (in gsm/mm) and a mean pore size (in μm), wherein the following equation is satisfied:
mean
pore
size
<
(
270
basis
weight
)
0.53
*
1.6
specific
surface
area
*
(
65
density
-
1.8
)
provided that:
the density is greater than 175 gsm/mm,
wherein:
the battery separator has a wet tensile strength of greater than or equal to 0.01 kN/m; and
the battery separator has a thickness greater than about 1 mm when loaded to a force of 20 kPa.