关键词: 锂离子电池, 正极材料, Li(Ni_0.5Co_0.2Mn_0.3)O₂, Ti-Nb共掺杂

Abstract: The cathode-active materials of layered Li(Ni_0.5Co_0.2Mn_0.3)_1-2xTi_xNb_xO₂（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(Ni_0.5Co_0.2Mn_0.3)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(Ni_0.5Co_0.2Mn_0.3)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(Ni_0.5Co_0.2Mn_0.3)O₂. The best overall performance of Li(Ni_0.5Co_0.2Mn_0.3)_1-2xTi_xNb_xO₂ 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.

Key words: lithium ion battery, cathode, Li(Ni_0.5Co_0.2Mn_0.3)O₂, Ti-Nb co-dopants