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The Lithium ion (Li-ion) battery is widely used as power source for consumer electronic devices due to its high energy density, large specific capacity. Recently, application of the Li-ion battery has been extended to aerospace, in which the outer space’s radiation environment has more stringent requirements for the battery performance. This type of battery also provides power for critical modern rescue, sampling equipment in nuclear environment, such as the robots deployed in the aftermath of Fukushima nuclear accident. As one of the most important components of these emergency response robots, the stability of the Li-ion battery under radiation is of crucial importance. The radiation effects on materials are generally categorized into four types: ionization, atomic displacement, impurity production, and energy release. To our knowledge, there has been no definitive study of such effects on Li-ion batteries and how ionizing radiation affects Li-ion batteries’ structure, strength, deformation, and electrical properties to final failure.In this work, the surface morphology of the Li-ion battery cathode before and after neutron and gamma ray radiation were characterized by atomic force microscopy (AFM). Distinct particle coarsening (size increase) of the cathode after irradiation was observed, which may primarily came from the crystal boundary migration driven by internal stress due to irradiation. There was a difference in the cathode particle size between thermal plus fast neutrons and fast neutrons alone and charge status of the Li-ion battery was also found to affect the cathode particle size change under radiations. X-ray diffraction (XRD) patterns of the Li-ion battery cathodes showed that a crystal structure disordering occurred during irradiation process. Electrical test was then carried and a substantial capacity loss of the battery after gamma irradiation was seen based on the discharge curves. The possible corresponding radiation effects on the Li-ion battery were discussed.