This work demonstrates the effect of coating LiMn1.5Ni0.5O4 with MgO and ZnO by a sono-chemical method. It was found that the sonochemical process results in a coating that serves as a buffer, yet allows the easy transport of Li+ ions to and from the active mass. Both the ZnO and MgO coatings modify the particles' surface chemistry and help to inhibit the dissolution of Mn and Ni ions from the active mass into the solution phase at elevated temperatures and thus managed to improve the stability of LiMn1.5Ni0.5O4 as an high voltage cathode material. MgO was found to be more effective than ZnO in this regard. The MgO coated cathodes demonstrated better electrochemical performance than the uncoated material. Lastly, the ZnO-coated material indicated a reduction in thermal stability in standard solutions, while the MgO coating did not affect the material's thermal stability. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.032203jes] All rights reserved.