Electrochemical and thermal properties of LiNi0.74Co0.26O2 cathode material with 5, 13 and 25μm-sized particles have been studied by using a coin-type half-cell Li/LiNi0.74Co0.26O2. The specific capacity of the material ranges from 205 to 210mAhg−1, depending on the particle size or the Brunauer, Emmett and Teller (BET) surface area. Among the particle sizes, the cathode with a particle size of 13μm shows the highest specific capacity. Even though the material with a particle size of 5μm exhibits the smallest capacity value of 205mAhg−1, no capacity fading was observed after 70 cycles between 4.3 and 2.75V at the 1C rate. Differential scanning calorimetry (DSC) studies of the charged electrode at 4.3V show a close relationship between particle size (BET surface area) and thermal stability of the electrode, namely, a larger particle size (smaller BET surface area) leads to a better thermal stability of the LiNi0.74Co0.26O2 cathode.