Thermal Stability Enhancement of Polyethylene Separators by Gamma-ray Irradiation for Lithium Ion Batteries

Abstract

The thermal stability of polyethylene (PE) separators irradiated by 50, 100, and 150 kGy dose gamma-rays is investigated when they are exposed to high-temperature environments. The gamma-ray irradiated separators have much lower Gurley numbers and higher ionic conductivity than a non-irradiated separator after storage at 100 and 120 degrees C. These results indicate that the thermal stability of PE separators can be drastically improved by gamma-ray irradiation. Even after storage at 120 degrees C for 1 h, the gamma-ray irradiated separator is maintaining its own structure. A cell assembled with a gamma-ray irradiated separator exhibits better rate-capability and cyclic performance than a pristine PE separator. The positive effects of gamma-ray irradiation are examined in detail with the purpose of improving battery performance. (c) 2012 The Japan Society of Applied Physics.