LiNi1/3Co1/3Mn1/3O2 particles were coated with Al2O3 nanoparticles by means of a mechanochemical bonding process; SEM confirmed that the Al2O3 particles were uniformly coated over the surface of the LiNi1/3Co1/3Mn1/3O2 powder. During subsequent electrochemical testing using pouch cells, uncoated LiNi1/3Co1/3Mn1/3O2 exhibited a gradual capacity fading and an increase in area specific impedance (ASI) at a 50% state of charge. Under the same conditions, the increase in ASI of the Al2O3 modified samples was significantly suppressed, although the initial performance (charge/discharge capacity and ASI) slightly deteriorated. The Al2O3 coating was also effective in improving the cyclability of LiNi1/3Co1/3Mn1/3O2 at elevated temperatures by reducing the extent of cracking.