Effect of SiO2 coating on polyethylene separator with different stretching ratios for application in lithium ion batteries

To enhance the properties of polyethylene separators in lithium ion batteries, we tested separators with uni-axial stretching ratios of 180% and 300%. We also tested stretched separators coated with SiO2 ceramic substance to increase ionic conductivity and thermal stability without sacrificing mechanical properties. To test the thermal and tensile properties, thermomechanical analyzer (TMA) is employed. CR 2032-type coin cells are prepared by sandwiching pristine and coated stretched separators, respectively, between the Li anode and Li[Ni1/3Co1/3Mn1/3]O-2 cathode to evaluate the AC impedance and cycling performance. The coated separators are observed with superior ionic conductivity, thermal and tensile properties. The cells prepared with coated separator have slightly higher discharge capacity and a better capacity retention ratio than the cells with pristine separators. These results suggest that the coated separator is a better option for lithium ion batteries. (C) 2014 Elsevier B.V. All rights reserved.