Synthesis and Electrochemical Properties of Li(Ni_0.5Co_0.2Mn_0.3)_1-2xTi_xNb_xO₂

Abstract

The cathode-active materials of layered Li(Ni0.5Co0.2Mn0.3)1-2xTixNbxO2（x=0, 0.002, 0.005, 0.01, 0.02）composites were synthesized by the thermal treatment of the coprecipitated precursor at 900 oC in air. The effects of Ti-Nb co-dopants on the structural and electrochemical properties of Li(Ni0.5Co0.2Mn0.3)O2 were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical experiments. The results show that the small amounts of Ti-Nb co-dopants in Li(Ni0.5Co0.2Mn0.3)O2significantly decreased the degree of cation mixing in the layered structure. The lattice parameters increased as the doping contents increased. The Ti-Nb co-doped composite materials exhibited better electrical properties and high temperature performance compared to Li(Ni0.5Co0.2Mn0.3)O2. The best overall performance of Li(Ni0.5Co0.2Mn0.3)1-2xTixNbxO2 was achieved with square battery when x=0.005. The initial specific discharge capacity of 165.9 mAh·g-1 under 1C rate in a voltage range of 3.0 ~ 4.2 V was obtained with the capacity retention of 96.5% after 100th cycles at ambient temperature and the capacity retention of 92.6% after 300th cycles at 55 oC. The thickness swelling rate of the square battery was 9.8% when cooling down for two hours after being stored at 80 oC/6 h.