Planetary explorations of human beings necessitate the research of the influence of γ-radiation on lithium-ion cells. In this study, the radioactive Co-60 was used as the radiation source. The electrochemical performances of LiCoO2/graphite full cells and LiCoO2/Li half-cells with a LiPF6-based electrolyte were measured before and after the radiation. The structural and compositional changes of the cell components were evaluated by means of X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and 1H nuclear magnetic resonance spectroscopy (1H NMR). The experimental results indicate that the cell performance is substantially deteriorated after the radiation due to two aspects of changes, i.e. radiation-induced defects in LiCoO2 and production of carboxyl in the electrolyte. The cell degradation is more pronounced for the LiCoO2/C full cells than for LiCoO2/Li half-cells owing to the reaction between active lithium and the carboxyl.