Aluminum cobalt oxide-coated LiNi0.5Mn1.5O4 (LNMO) cathode materials are synthesized via a wet-coating method. The surface coating of the LNMO with cobalt aluminum oxide (CoAl2O4) does not alter its spinel structure, but greatly affects its thermostability. The complete, thin cobalt aluminum oxide coating layer strongly adheres to the host material and possesses a great thermal stability and electrochemical resistance, and it is not damaged in acid or alkali environments. The CoAl2O4 coating layer in this work successfully inhibits the dissolution of transition metal ions and maintain the stability of the LNMO structure. This CoAl2O4 coating layer also hold back the HF scavenger of the spinel structure in the electrolyte, which leads to enhanced electrochemical properties, especially at high temperatures. Furthermore, the coated LNMO exhibits an obviously improved thermostability compared with bare LNMO.