Commercially obtained LiSr0.002Ni0.9Co0.1O2 was modified by overcoating its surface with MgO. As the surface was modified, onset temperature of thermal dissociation was increased about 10 degrees C, and heat dissipation during thermal decomposition was diminished to a substantial extent. Lithium-ion batteries whose cathodes were made from the surface-modified LiSr0.002Ni0.9Co0.1O2 exhibited improved performance, especially at the demanding rate of 1 C. Tendency toward explosion in the cylindrical battery was largely alleviated by the surface treatment, even though thr safety rating has not yet reached the industrial criterion.