Battery separator and method of making same
A battery separator comprises a multi-layered film, individual layers of said film having been bonded together by heat and pressure, having a peel strength of greater than or equal to 40 grams per inch (1.6 g/mm) and a thickness of ≦25 microns. A method for making a battery separator comprises the steps of: extruding and winding up a first precursor film, extruding and winding up a second precursor film, unwinding the first and second precursor films, stacking up the first and second precursor films to form a single stacked precursor, laminating the single stacked precursor film, winding up the laminated single stacked precursor film, stacking up a plurality of laminated single stacked precursor films, and making microporous the stacked plurality of laminated single stacked precursor films.
1 . A battery separator comprising
a multi-layered microporous film, individual layers of said film having been bonded together by heat and pressure, having a peel strength of greater than 40 grams per inch (1.6 g/mm) and a thickness of ≦25 microns.
2 . The battery separator of claim 1 wherein said multi-layered microporous film being a tri-layered film.
3 . The battery separator of claim 2 wherein said tri-layered film having a polypropylene-polyethylene-polypropylene structure.
4 . The battery separator of claim 1 wherein said film having a thickness of less than or equal to 20 microns.
5 . The battery separator of claim 1 wherein said film having a thickness of less than or equal to 15 microns.
6 . A battery separator comprising:
a multi-layered microporous film, individual layers of said film having been bonded together by heat and pressure, having a peel strength of greater than 40 grams per inch (1.6 g/mm) wherein at least one layer being substantially polypropylene, another layer being substantially polyethylene, and the film having a thickness of less than or equal to 15 microns.
7 . A method of making a battery separator comprising the steps of:
extruding and winding up a first precursor film;
extruding and winding up a second precursor film;
unwinding the first and second precursor film;
stacking up the first and second precursor films to form a single stacked precursor;
laminating the single stacked precursor film;
winding up the laminated single stacked precursor film;
stacking up a plurality of laminated single stacked precursor films; and
making microporous said plurality of laminated single stacked precursor films.
8 . The method of claim 7 wherein extruding the first or second precursor further comprises extruding with a slot die, T die, or a blown film die.
9 . The method of claim 7 wherein the single stacked precursor being a tri-layer precursor.
10 . The method of claim 9 wherein the tri-layer precursor being a polypropylene-polyethylene-polypropylene precursor.
11 . The method of claim 7 wherein laminating being at speeds greater than 100 ft/min (30.5 m/min).
12 . The method of claim 11 wherein laminating being at speeds greater than 125 ft/min (38.1 m/min).
13 . The method of claim 12 wherein laminating being at speeds greater than 150 ft/min (45.7 m/min).
14 . The method of claim 13 wherein laminating being at speeds greater than 200 ft/min (61.0 m/min).
15 . The method of claim 7 wherein laminating being conducted between heated nip rollers.
16 . The method of claim 15 wherein the nip roller temperature ranging from 145° C. to 170° C.
17 . The method of claim 16 wherein the nip roller temperature ranges from 155° C. to 165° C.
18 . The method of claim 15 wherein the nip roller pressure ranges from 100 to 800 pounds per linear inch (pli).
19 . The method of claim 18 wherein the nip roller pressure ranges from 100 to 300 pli.
20 . The method of claim 7 wherein a chill roll following the nip rollers.
21 . The method of claim 20 wherein the chill roll temperature ranges from 20° C. to 45° C.
22 . The method of claim 21 wherein the chill roll temperature ranges from 25° C. to 40° C.
23 . The method of claim 20 wherein an air knife being placed between the nip rollers and the chill roll.
24 . The method of claim 20 wherein edge trim knives follow the chill roll.
25 . The method of claim 7 wherein the plurality of laminated single stacked precursor films being at least six laminated single stacked precursor films.
26 . The method of claim 25 wherein the plurality of laminated single stacked precursor films being at least twelve laminated single stacked precursor films.
27 . The method of claim 26 wherein the plurality of laminated single stacked precursor films being at least sixteen laminated single stacked precursor films.
28 . The method of claim 7 wherein making microporous said plurality of laminated single stacked precursor films being selected from the group consisting of a dry process and a wet process.
29 . A method of making a battery separator comprising the steps of:
extruding a precursor film,
laminating together two or more precursor films to form a multi-layered precursor film,
stacking up at least twelve multi-layered precursor films, and
making microporous the stacked multi-layered precursor films.
30 . The method of claim 29 wherein at least sixteen multi-layered precursor films are stacked up.
31 . The method of claim 29 wherein making microporous the stacked multi-layered precursor films being selected from the group consisting of a dry process and a wet process.