Synthesized yttrium aluminum garnet (YAG) sol was coated on the surface of the LiCoO2 cathode particles by an in situ sol–gel process, followed by calcination at 923K for 10h in air. Based on XRD, TEM, and ESCA data, a compact YAG kernel with an average thickness of ∼20nm was formed on the surface of the core LiCoO2 particles, which ranged from ∼90 to 120nm in size. The charge–discharge cycling studies for the coated materials suggest that 0.3wt.% YAG-coated LiCoO2 heated at 923K for 10h in air, delivered a discharge capacity of 167mAhg−1 and a cycle stability of about 164 cycles with a fading rate of 0.2mAhcycle−1 at a 0.2C-rate between 2.75 and 4.40V vs. Li/Li+. The differential capacity plots revealed that impedance growth was slower for YAG surface treated LiCoO2, when cells were charged at 4.40V. DSC results exemplified that the exothermic peak at ∼468K corresponded to the release of much less oxygen and greater thermal-stability.