Microporous membrane separators for lithium ion rechargeable batteries and related methods

Patent metadata

Field	Value
Publication number	US-11728546-B2
Application number	US-201514950478-A
Country	US
Kind code	B2
Filing date	Nov 24, 2015
Priority date	Nov 26, 2014
Publication date	Aug 15, 2023
Grant date	Aug 15, 2023

Abstract

Several embodiments of a microporous battery separator for lithium rechargeable batteries and/or related methods of making and/or using such separators are disclosed. A dry process battery separator or membrane separator exhibits a thickness that is less than about 14 μm and has increased strength performance as defined by reduced splittiness. The mode of splitting failure has been investigated, and the improvement in splittiness quantified by a test method known as the Composite Splittiness Index (CSI).

First claim

We claim:

1. A separator for a lithium battery having a puncture strength (PS) first load peak of at least 130 gf, a composite splittiness index (CSI) of at least 29, a porosity of from 25% to 31%, and an electrical resistance (ER) value of less than or equal to 1.5 ohm-cm 2 , wherein the separator is a multilayer separator or a trilayer separator and has a total separator thickness of about 7 microns;
wherein the separator includes at least one microporous polyolefin membrane produced according to a dry process in which a polyolefin resin is extruded to form said at least one microporous polyolefin membrane, said polyolefin resin having a melt flow index (MFI) of less than or equal to about 0.8 grams/10 minutes, and wherein
the composite splittiness index (CSI) is defined by Equation 1:
CSI=( A−|B−A| 1.8 )× C ×( D×E )/10 6   Equation 1

where:
A=First Load Peak/Thickness×(1−% Porosity)
B=Second Load Peak/Thickness
C=TD Elongation
D=MD Tensile Strength
E=TD Tensile Strength
where First and Second Load Peak are in units of gram-force, thickness values are in microns, MD and TD tensile strength are in gram-force, and TD elongation is expressed as percentage.

2. The separator of claim 1 wherein the separator has a porosity in the range of 27% to 31%.

3. The separator of claim 1 wherein the separator is for energy cells.

4. The separator of claim 1 wherein the separator has a TD tensile strength of at least 150 kgf/cm 2 .

5. The separator of claim 1 wherein the composite splittiness index (CSI) is higher than 30.

6. The separator of claim 1 wherein the composite splittiness index (CSI) is at least 50.

7. The separator of claim 1 wherein the composite splittiness index (CSI) is at least 100.

8. The separator of claim 1 wherein the separator includes at least one microporous polyolefin membrane produced according to a dry process in which a polyolefin resin is extruded to form said at least one microporous polyolefin membrane, said polyolefin resin having a melt flow index (MFI) of less than or equal to about 0.5 grams/10 minutes.

9. A separator comprising:
at least one microporous membrane having a composite splittiness index (CSI) of at least 29 and being produced according to a dry stretch process in which a polyolefin resin, mix containing polyolefin resin or blend containing the polyolefin resin is extruded to form said at least one microporous membrane, said polyolefin resin having a melt flow index (MFI) of less than or equal to about 0.8 grams/10 minutes; and
said separator having a total thickness of about 7 μm, a porosity in the range of 25% to 30%, and an electrical resistance (ER) value of less than or equal to about 1.5 ohm-cm 2 .

Assignees

• Celgard Llc

Inventors

• Zhang Xiaomin
• Xiao Kang Karen
• Nark Robert A
• Smith Ron E

Classifications

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M50/406 Primary

  Moulding; Embossing; Cutting · CPC title

• H01M50/449 Primary

  having a layered structure · CPC title

• H01M50/489 Primary

  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

• H01M50/457

  comprising three or more layers · CPC title