A new concept of synergetic effects was developed with the synthesis of a spherical core-shell structure to effect a higher capacity from the LiNi0.8Co0.1Mn0.1O2 core and improved thermal stability from the Li[Ni0.5Mn0.5]O-2 shell. We now report the microscale spherical core-shell structure with LiNi0.8Co0.1Mn0.1O2 as the core and a Li[Ni0.5Mn0.5]O-2 as the shell. With these core-shell particles, a high capacity was delivered from the LiNi0.8Co0.1Mn0.1O2 core and a high thermal stability was achieved by the Li[Ni0.5Mn0.5]O-2 shell. The core-shell structured Li[(Ni0.8Co0.1Mn0.1)(0.8)(Ni0.5Mn0.5)(0.2)]O-2-carbon cell showed superior cyclability and thermal stability relative to the Li[Ni0.8Co0.1Mn0.1]O-2 alone at a 1 C rate for 600 cycles. As a new positive electrode material, the core-shell structure of Li[(Ni0.8Co0.1Mn0.1)(0.8)(Ni0.5Mn0.5)(0.2)]O-2 provides a significant breakthrough for the development of lithium batteries with high capacity, excellent cyclability, and high thermal stability. (c) 2006 The Electrochemical Society.