Radiation effects on the electrode and electrolyte of a lithium-ion battery

The performance degradation and durability of a Li-ion battery is a major concern when it is operated under radiation conditions, for instance, in deep space exploration, in high radiation field, or rescuing or sampling equipment in a post-nuclear accident scenario. This paper examines the radiation effects on the electrode and electrolyte materials separately and their effects on a battery's capacity loss and resistance increase. A⁶⁰Co irradiator (34.3 krad/h) was used to provide 0.8, 4.1, and 9.8 Mrad dose to LiFePO₄ electrodes and 0.8, 1.6, and 5.7 Mrad to 1 M LiPF₆ in 1:1 wt% EC:DMC electrolytes. This study shows that the coin cells assembled with irradiated components have higher failure rate (ca. 70%) than that of control group (ca. 14%). A significant battery capacity fade post irradiation was observed. The electrolyte also shows a darkened color a few weeks or months after irradiation. The discovery of this latent effect may be significant because a battery may degrade significantly even showing no sign of degradation immediately after exposure. We investigated electrolyte composition by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and nuclear magnetic resonance spectroscopy prior and post irradiation. Polymerization reactions and HF formation are considered as the cause of the discoloration.