ZnO-coated LiNi0.5Mn1.5O4 powders with excellent electrochemical cyclability and structural stability at elevated temperature have been synthesized by a sol-gel method. The structural degradation of the as-prepared LiNi0.5Mn1.5O4 and ZnO-coated LiNi0.5Mn1.5O4 electrodes before and after cycling in the 5 V region has been studied. The ZnO-coated LiNi0.5Mn1.5O4 electrode showed almost no capacity loss and retained its original cubic spinel structure after 50 cycles. We found that ZnO played an important role in reducing the HF content in the electrolyte solution. (C) 2002 The Electrochemical Society.