The fire incidents triggered by the thermal runaway of Li-ion batteries (LIBs) have aroused widespread concerns, as the instabilities of the delithiated cathode materials are generally accepted as one of the reasons for the ignition of LIBs. Herein, the electrochemical performance and the thermal stability of single-crystal and polycrystalline LiNi0.6Co0.2Mn0.2O2 electrode were investigated, trying to explore a novel, advanced approach for the thermal and cyclic stability of LiNi0.6Co0.2Mn0.2O2. Our results showed that the collapses of the layer structures and the cracks of polycrystalline particles occurred during charge; compared with the polycrystalline materials, the single-crystal particles efficiently improved the thermal stability, cyclic performance, and collapse of the layer structures. Additionally, the single-crystal material could maintain the structure and morphology even under a high charging voltage of 4.95 V. After 800 cycles at 45 degrees C, 92.5% of the initial capacity was maintained for the single-crystal LiNi0.6Co0.2Mn0.2O2, while the capacity retention of the polycrystalline materials was below 90.5% after 300 cycles. (c) 2018 The Electrochemical Society.