Layered Li[Ni0.5Co0.2Mn0.3]O2-Li2MnO3 core-shell structured cathode material with excellent stability

In order to improve the performance of the Li[Ni0.5Co0.2Mn0.3]O-2, a novel spherical Li[Ni0.5Co0.2Mn0.3] O-2-Li2MnO3 core-shell composite has been successfully synthesized by a simple sol-gel deposition method. It is found that the core shell composite consists of Li[Ni0.5Co0.2Mn0.3]O-2 as the core and Li2MnO3 as the outer shell according to examination by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction (XRD). The core-shell composite delivers a high capacity of 180.4 mAh g(-1) at a rate of 0.1 C in the voltage range of 2.0-4.4 V. Most importantly, the core-shell composite exhibits excellent capacity retention of 98.8% after 200 cycles at a rate of 0.5 C, and 93.8% capacity retention after 100 cycles at a rate of 5 C at room temperature. When cycled at an elevated 55 degrees C, the prepared sample exhibits only 2.3% capacity loss after 100 cycles. Meanwhile, the core-shell composite shows significantly improved thermal stability relative to that of the pristine Li[Ni0.5Co0.2Mn0.3]O-2. The improved stability of the core-shell composite is ascribed to the stable Li2MnO3 outer shell, which can prevent the Li[Ni0.5Co0.2Mn0.3]O-2 core from direct contact with the electrolyte, and the core material could operate with no risk of structural disruption at high voltages and high temperatures. (C) 2013 Elsevier B.V. All rights reserved.