US 11,728,546 B2
Microporous membrane separators for lithium ion rechargeable batteries and related methods
Xiaomin Zhang, Charlotte, NC (US); Kang Karen Xiao, Mississauga (CA); Robert A. Nark, Charlotte, NC (US); and Ron E. Smith, Huntersville, NC (US)
Assigned to Celgard, LLC, Charlotte, NC (US)
Filed by Celgard, LLC, Charlotte, NC (US)
Filed on Nov. 24, 2015, as Appl. No. 14/950,478.
Claims priority of provisional application 62/084,628, filed on Nov. 26, 2014.
Prior Publication US 2016/0149181 A1, May 26, 2016
Int. Cl. H01M 10/05 (2010.01); H01M 50/449 (2021.01); H01M 50/414 (2021.01); H01M 50/406 (2021.01); H01M 50/489 (2021.01); H01M 50/494 (2021.01); H01M 50/491 (2021.01); H01M 10/052 (2010.01)
CPC H01M 50/449 (2021.01) [H01M 50/406 (2021.01); H01M 50/414 (2021.01); H01M 50/489 (2021.01); H01M 50/491 (2021.01); H01M 50/494 (2021.01); H01M 10/052 (2013.01)] 9 Claims
 
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-cm2, 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)/106  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.