Method for producing nonaqueous electrolyte secondary battery separator

Patent metadata

Field	Value
Publication number	US-10978767-B2
Application number	US-201916597961-A
Country	US
Kind code	B2
Filing date	Oct 10, 2019
Priority date	Mar 3, 2017
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

An embodiment of the present invention provides, as a nonaqueous electrolyte secondary battery separator excellent in cycle characteristic, a nonaqueous electrolyte secondary battery separator including a polyolefin porous film, wherein a ratio of a displacement amount of the nonaqueous electrolyte secondary battery separator at a 10th loading-unloading cycle to a displacement amount of the nonaqueous electrolyte secondary battery separator at a 50th loading-unloading cycle is in a range of 100% to 130%.

First claim

The invention claimed is:

1. A method for producing a nonaqueous electrolyte secondary battery separator containing a polyolefin porous film, comprising the steps of:
(A) melt-kneading a polyolefin-based resin powder and an additive in a kneader to obtain a polyolefin resin composition;
(B) extruding the polyolefin resin composition through a T-die of an extruder, and then shaping the polyolefin resin composition into a sheet while cooling the polyolefin resin composition, so that a sheet-shaped polyolefin resin composition is obtained;
(C) stretching the sheet-shaped polyolefin resin composition, so that a feed speed, an intermediate speed, and a discharge speed of the sheet-shaped polyolefin resin composition in a stretching apparatus meet a relation of feed speed<discharge speed<intermediate speed, and the sheet-shaped polyolefin resin composition has a stretching speed ratio of 0.1 to 0.7, the stretching speed ratio being defined by an equation below;
stretching speed ratio={(intermediate speed)−(discharge speed)}/(intermediate speed)

(D) cleaning, with use of a cleaning liquid, the polyolefin resin composition having been stretched in the step (C); and
(E) drying and/or heat fixing the polyolefin resin composition having been cleaned in the step (D), so that a polyolefin porous film is obtained.

2. The method as set forth in claim 1 , wherein in the step (A), the additive is a combination of an additive (i) that exists in a solid state at 25° C. and an additive (ii) that exists in a liquid state at 25° C.

3. The method as set forth in claim 1 , wherein in the step (E), the polyolefin resin composition having been cleaned in the step (D) is heat fixed at a heat fixing temperature of not lower than 110° C. and not higher than 130° C.

4. The method as set forth in claim 1 , wherein
the polyolefin porous film contains a high molecular weight component having a weight-average molecular weight of 3×10 5 to 15×10 6 ,
the polyolefin porous film has a thickness of 4 μm to 40 μm, and
the polyolefin porous film has a porosity of 20% by volume to 80% by volume.

5. A method for producing a nonaqueous electrolyte secondary battery laminated separator comprising a nonaqueous electrolyte secondary battery separator and an insulating porous layer,
said method comprising the steps of:
producing a nonaqueous electrolyte secondary battery separator by the method set forth in claim 1 ; and
providing an insulating porous layer on one surface or both surfaces of the nonaqueous electrolyte secondary battery separator.

6. A method for producing a nonaqueous electrolyte secondary battery member comprising: a positive electrode; a nonaqueous electrolyte secondary battery separator; and a negative electrode, the positive electrode, the nonaqueous electrolyte secondary battery separator, and the negative electrode being disposed in this order,
said method comprising the steps of:
producing a nonaqueous electrolyte secondary battery separator by the method set forth in claim 1 ; and
disposing the positive electrode, the nonaqueous electrolyte secondary battery separator, and the negative electrode in this order.

7. A method for producing a nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte secondary battery separator,
said method comprising the steps of:
producing a nonaqueous electrolyte secondary battery separator by the method set forth in claim 1 ;
disposing a positive electrode, the nonaqueous electrolyte secondary battery separator, and a negative electrode in this order to produce a nonaqueous electrolyte secondary battery member; and
placing the nonaqueous electrolyte secondary battery member in a container to serve as a housing of the nonaqueous electrolyte secondary battery, filling the container with a nonaqueous electrolyte, and then hermetically sealing the container while reducing a pressure inside the container.

8. A method for producing a nonaqueous electrolyte secondary battery member comprising: a positive electrode; a nonaqueous electrolyte secondary battery laminated separator; and a negative electrode, the positive electrode, the nonaqueous electrolyte secondary battery laminated separator, and the negative electrode being disposed in this order,
said method comprising the steps of:
producing a nonaqueous electrolyte secondary battery laminated separator by the method set forth in claim 5 ; and
disposing the positive electrode, the nonaqueous electrolyte secondary battery laminated separator, and the negative electrode in this order.

9. A method for producing a nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte secondary battery laminated separator,
said method comprising the steps of:
producing a nonaqueous electrolyte secondary battery laminated separator by the method set forth in claim 5 ;
disposing a positive electrode, the nonaqueous electrolyte secondary battery laminated separator, and a negative electrode in this order to produce a nonaqueous electrolyte secondary battery member; and
placing the nonaqueous electrolyte secondary battery member in a container to serve as a housing of the nonaqueous electrolyte secondary battery, filling the container with a nonaqueous electrolyte, and then hermetically sealing the container while reducing a pressure inside the container.

10. The method as set forth in claim 5 , wherein the insulating porous layer contains a polyamide-based resin.

Assignees

• Sumitomo Chemical Co

Inventors

• Kurakane Kosuke

Classifications

• H01M50/451

  comprising layers of only organic material and layers containing inorganic material · CPC title

• H01M50/417 Primary

  Polyolefins · CPC title

• H01M50/414

  Synthetic resins, e.g. thermoplastics or thermosetting resins · CPC title

• H01M50/449 Primary

  having a layered structure · CPC title

• H01M4/13

  Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof · CPC title