Battery separator and method of manufacturing same

Patent metadata

Field	Value
Publication number	US-2018366709-A1
Application number	US-201615781429-A
Country	US
Kind code	A1
Filing date	Nov 14, 2016
Priority date	Dec 4, 2015
Publication date	Dec 20, 2018
Grant date	—

Abstract

A battery separator includes a polyolefin microporous membrane having a width of 100 mm or more, and a porous layer laminated on at least one surface of the polyolefin microporous membrane. The polyolefin microporous membrane has a variation range of an F25 value in a width direction of 1 MPa or less, and the F25 value indicates a value obtained by dividing a load value measured at 25% elongation of a specimen with use of a tensile tester by a cross-sectional area of the specimen. The porous layer contains a fluorine-based resin and an inorganic particle.

First claim

1 .- 7 . (canceled)

8 . A battery separator comprising a polyolefin microporous membrane having a width of 100 mm or more, and a porous layer laminated on at least one surface of the polyolefin microporous membrane, wherein the polyolefin microporous membrane has a variation range of an F25 value in a width direction of 1 MPa or less (wherein the F25 value indicates a value obtained by dividing a load value measured at 25% elongation of a specimen with use of a tensile tester by a cross-sectional area of the specimen), and the porous layer contains a fluorine-based resin and an inorganic particle.

9 . The battery separator according to claim 8 , wherein the porous layer has a thickness variation range (R) in a width direction of 1.0 μm or less.

10 . The battery separator according to claim 8 , wherein the fluorine-based resin contains at least one member selected from a polyvinylidene fluoride and a polyvinylidene fluoride-hexafluoropropylene copolymer.

11 . The battery separator according to claim 8 , wherein a width of the battery separator is 500 mm or more.

12 . A battery separator roll of the battery separator according to claim 8 , wherein a length of the battery separator is 500 m or more.

13 . A method of producing the battery separator according to claim 8 , the method comprising steps (a) to (g) in the following order:
(a) a step of melt-kneading a polyolefin resin and a forming solvent, thereby preparing a polyolefin resin solution; (b) a step of extruding the polyolefin resin solution into a sheet shape via an extruder and cooling an extrudate thereof, thereby forming an unstretched gel-like sheet; (c) a step of passing the unstretched gel-like sheet between at least two pairs of longitudinal stretching roller groups and stretching the sheet in a longitudinal direction based on a peripheral speed ratio of the two pairs of roller groups, thereby forming a longitudinally stretched gel-like sheet, wherein a longitudinal stretching roller and a nip roller parallelly contacting therewith are designated as a pair of longitudinal stretching roller group, and a contact pressure of the nip roller to the longitudinal stretching roller is 0.05 MPa or more and 0.5 MPa or less; (d) a step of stretching the longitudinally stretched gel-like sheet in a transverse direction while holding the sheet to allow a clip-to-clip distance to be 50 mm or less at a tenter outlet, thereby obtaining a biaxially stretched gel-like sheet; (e) a step of extracting the forming solvent from the biaxially stretched gel-like sheet and drying the sheet; (f) a step of heat-treating the dried sheet, thereby obtaining a polyolefin microporous membrane; and (g) a step of coating the polyolefin microporous membrane with a coating solution containing a fluorine-based resin and an inorganic particle by a reverse gravure coating method, passing the membrane through a coagulation bath, and then, subjecting to water washing and drying, thereby laminating a porous layer on the polyolefin microporous membrane.

14 . The method according to claim 13 , wherein the coating solution has a solution viscosity of 50 to 200 mPa·s.

15 . The battery separator according to claim 9 , wherein the fluorine-based resin contains at least one member selected from a polyvinylidene fluoride and a polyvinylidene fluoride-hexafluoropropylene copolymer.

16 . The battery separator according to claim 9 , wherein a width of the battery separator is 500 mm or more.

17 . The battery separator according to claim 10 , wherein a width of the battery separator is 500 mm or more.

18 . A battery separator roll of the battery separator according to claim 9 , wherein a length of the battery separator is 500 m or more.

19 . A battery separator roll of the battery separator according to claim 10 , wherein a length of the battery separator is 500 m or more.

20 . A battery separator roll of the battery separator according to claim 11 , wherein a length of the battery separator is 500 m or more.

21 . A method of producing the battery separator according to claim 9 , the method comprising steps (a) to (g) in the following order:
(a) a step of melt-kneading a polyolefin resin and a forming solvent, thereby preparing a polyolefin resin solution; (b) a step of extruding the polyolefin resin solution into a sheet shape via an extruder and cooling an extrudate thereof, thereby forming an unstretched gel-like sheet; (c) a step of passing the unstretched gel-like sheet between at least two pairs of longitudinal stretching roller groups and stretching the sheet in a longitudinal direction based on a peripheral speed ratio of the two pairs of roller groups, thereby forming a longitudinally stretched gel-like sheet, wherein a longitudinal stretching roller and a nip roller parallelly contacting therewith are designated as a pair of longitudinal stretching roller group, and a contact pressure of the nip roller to the longitudinal stretching roller is 0.05 MPa or more and 0.5 MPa or less; (d) a step of stretching the longitudinally stretched gel-like sheet in a transverse direction while holding the sheet to allow a clip-to-clip distance to be 50 mm or less at a tenter outlet, thereby obtaining a biaxially stretched gel-like sheet; (e) a step of extracting the forming solvent from the biaxially stretched gel-like sheet and drying the sheet; (f) a step of heat-treating the dried sheet, thereby obtaining a polyolefin microporous membrane; and (g) a step of coating the polyolefin microporous membrane with a coating solution containing a fluorine-based resin and an inorganic particle by a reverse gravure coating method, passing the membrane through a coagulation bath, and then, subjecting to water washing and drying, thereby laminating a porous layer on the polyolefin microporous membrane.

22 . A method of producing the battery separator according to claim 10 , the method comprising steps (a) to (g) in the following order:
(a) a step of melt-kneading a polyolefin resin and a forming solvent, thereby preparing a polyolefin resin solution; (b) a step of extruding the polyolefin resin solution into a sheet shape via an extruder and cooling an extrudate thereof, thereby forming an unstretched gel-like sheet; (c) a step of passing the unstretched gel-like sheet between at least two pairs of longitudinal stretching roller groups and stretching the sheet in a longitudinal direction based on a peripheral speed ratio of the two pairs of roller groups, thereby forming a longitudinally stretched gel-like sheet, wherein a longitudinal stretching roller and a nip roller parallelly contacting therewith are designated as a pair of longitudinal stretching roller group, and a contact pressure of the nip roller to the longitudinal stretching roller is 0.05 MPa or more and 0.5 MPa or less; (d) a step of stretching the longitudinally stretched gel-like sheet in a transverse direction while holding the sheet to allow a clip-to-clip distance to be 50 mm or less at a tenter outlet, thereby obtaining a biaxially stretched gel-like sheet; (e) a step of extracting the forming solvent from the biaxially stretched gel-like sheet and drying the sheet; (f) a step of heat-treating the dried sheet, thereby obtaining a polyolefin microporous membrane; and (g) a step of coating the polyolefin microporous membrane with a coating solution containing a fluorine-based resin and an inorganic particle by a reverse gravure coating method, passing the membrane through a coagulation bath, and then, subjecting to water washing and drying, thereby laminating a porous layer on the polyolefin microporous mem

Assignees

• Toray Industries

Inventors

• Mizuno Naoki
• Sugata Masami

Classifications

• B01D69/02

  characterised by their properties · CPC title

• C08J7/0427

  with only one layer of a composition containing a polymer binder (with more layers C08J7/042) · CPC title

• B29K2027/16

  PVDF, i.e. polyvinylidene fluoride · CPC title

• C08J9/365

  Coating · CPC title

• C08J2201/0502

  the liquid phase being organic · CPC title