Low electrical resistance microporous battery separator membranes, separators, cells, batteries, and related methods

Patent metadata

Field	Value
Publication number	US-2019237733-A1
Application number	US-201916378841-A
Country	US
Kind code	A1
Filing date	Apr 9, 2019
Priority date	Jun 3, 2015
Publication date	Aug 1, 2019
Grant date	—

Abstract

Novel or improved microporous battery separator membranes, separators, cells, batteries including such membranes, separators, or cells, and/or methods of making such membranes and/or separators, and/or methods of using such membranes and/or separators. In accordance with at least certain embodiments, an improved or novel battery separator for a secondary or rechargeable lithium battery may have low Electrical resistance of less than 0.95 ohm-cm 2 , or in some cases, less than 0.8 ohm-cm 2 . Furthermore, the inventive battery separator membrane may provide a means to achieve an improved level of battery performance in a rechargeable or secondary lithium battery based on a possibly synergistic combination of low Electrical resistance, low Gurley, low tortuosity, and/or a unique trapezoid shaped pore. In accordance with at least certain multilayer embodiments (by way of example only, a trilayer membrane made of two polypropylene layers with a polyethylene layer in between), the inventive microporous membrane or battery separator may have excellent onset and rate of thermal shutdown performance.

First claim

We claim:

1 . A microporous membrane comprising:
a dry stretch microporous polyolefin membrane with non-round, trapezoid shaped pores, and having: a Gurley less than 500 sec/100 cc, and a tortuosity less than 1.5.

2 . The microporous membrane of claim 1 wherein the dry stretch microporous polyolefin membrane has:
a Gurley less than 150 sec/100 cc,
a tortuosity less than 1.3, and/or
said dry stretch microporous polyolefin membrane consists of a polypropylene, polyethylene, mixtures thereof, or co-polymers thereof.

3 . The microporous membrane of claim 1 where said dry stretch microporous polyolefin membrane is a monolayer membrane or a multilayer membrane with a thermal shutdown function.

4 . The microporous membrane of claim 1 where said dry stretch microporous polyolefin membrane is a multilayer membrane consisting of a trilayer of polypropylene/polyethylene/polypropylene.

5 . The microporous membrane of claim 1 where said dry stretch microporous polyolefin membrane has a thickness less than 25 μm.

6 . The microporous membrane of claim 1 , where said dry stretch microporous polyolefin membrane is made by a process comprising:
extruding a polypropylene which has a melt flow index less than 1.0 g/10 minutes to form a monolayer nonporous polypropylene precursor membrane, and machine direction stretching the monolayer nonporous polypropylene precursor membrane to form a semi-porous intermediate membrane having a puncture strength>350 gf and TD elongation>600%, and transverse direction stretching the semi-porous intermediate membrane using a stretch ratio of 15 to 400% to form the dry stretch microporous polyolefin membrane of the microporous membrane.

7 . The microporous membrane of claim 6 where said stretch ratio is from 25 to 100%.

8 . The microporous membrane of claim 4 , where said trilayer of polypropylene/polyethylene/polypropylene is made by a process comprising:
extruding a polyethylene which has a melt flow index less than 1.0 g/10 minutes to form a monolayer nonporous polyethylene precursor membrane, and extruding a polypropylene which has a melt flow index less than 1.0 g/10 minutes to form a monolayer nonporous polypropylene precursor membrane, and laminating two plies of polypropylene precursor membrane as outer plies or layers sandwiching one inner ply or layer of polyethylene precursor membrane to form a trilayer polypropylene/polyethylene/polypropylene nonporous precursor, machine direction stretching a nonporous polypropylene/polyethylene/polypropylene precursor membrane to form a semi-porous intermediate membrane having a puncture strength>350 gf and TD elongation>600%, and transverse direction stretching the semi-porous intermediate membrane using a stretch ratio of 15 to 400% to form the trilayer of polypropylene/polyethylene/polypropylene which is microporous.

9 . The microporous membrane of claim 8 where said stretch ratio is 25 to 100%.

10 . A microporous membrane comprising:
a dry stretch microporous polyolefin membrane with non-round, trapezoid shaped pores, and having: an electrical resistance less than 0.95 ohm-cm 2 , and a tortuosity less than 1.5.

11 . A microporous membrane comprising:
a dry stretch microporous polyolefin membrane with non-round, trapezoid shaped pores, and having:
an electrical resistance less than 0.95 ohm-cm 2 , and
a Gurley less than 500 sec/100 cc.

12 . The microporous membrane of claim 1 , where said dry stretch microporous polyolefin membrane is a monolayer membrane.

13 . The microporous membrane of claim 10 , where said dry stretch microporous polyolefin membrane is a monolayer membrane.

14 . The microporous membrane of claim 11 , where said dry stretch microporous polyolefin membrane is a monolayer membrane.

15 . The microporous membrane of claim 12 , where said dry stretch microporous polyolefin membrane is a polypropylene membrane.

16 . The microporous membrane of claim 13 , where said dry stretch microporous polyolefin membrane is a polypropylene membrane.

17 . The microporous membrane of claim 14 , where said dry stretch microporous polyolefin membrane is a polypropylene membrane.

18 . A battery separator comprising the microporous membrane of claim 1 .

19 . A battery separator comprising the microporous membrane of claim 10 .

20 . A battery separator comprising the microporous membrane of claim 11 .

Assignees

• Celgard Llc

Inventors

• Zhang Xiaomin
• Shi Lie

Classifications

• B32B27/08 Primary

  of synthetic resin · CPC title

• H01M50/457

  comprising three or more layers · CPC title

• H01M50/417 Primary

  Polyolefins · CPC title

• H01M50/491

  Porosity · CPC title

• H01M50/489

  Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties · CPC title