S-M(M=Cu, Co, Ti)复合掺杂层状LiMnO2 的合成及其电化学性能

用水热法合成了锂离子电池正极材料正交结构LiMnO2材料, 并对其进行S2－、大尺寸阳离子(Cu2＋, Co3＋, Ti4＋)以及硫-金属离子复合掺杂改性. 用X射线衍射(XRD)、X光电子能谱分析(XPS)、透射电子显微镜(TEM)、恒电流充放电、交流阻抗谱(EIS)等测试技术进行表征. 实验结果表明: 当掺入离子的含量较低时, 得到的产物能保持完整的正交结构, 并表现出较好的电化学性能. S2－和非Jahn-Teller效应大尺寸阳离子的掺入使材料的循环稳定性能大幅度提高, 而这种提高是源于这些离子对LiMnO2结构的稳定作用. 电极材料Li1.02Mn0.988Ti0.012O1.989S0.011显示了最优的电化学性能, 在50 mA?g－1放电速率下, 其初始放电容量为142.6 mAh?g－1, 60次循环后放电容量为213.4 mAh?g－1. 硫-金属阳离子复合掺杂, 综合了大尺寸阳离子可以提高材料中Li＋的扩散能力和S2－掺杂抑制Jahn-Teller畸变两方面优势, 使层状结构LiMnO2正极材料既保持了较高的容量又获得良好的循环性能.

Synthesis and Electrochemical Properties of S-M (M=Cu, Co, Ti) Co-doped Layered LiMnO_2 Cathode Materials

Orthorhombic structure LiMnO2 compounds used as cathode materials for lithium-ion batteries were synthesized by a hydrothermal method, and modified by doping with sulphur ion (S~(2-)), large-sized cation (Cu~(2+), Co_(3+), Ti~(4+)) and co-doping with S-M (M=Cu, Co, Ti). The structure and electrochemical per-formances of the as-prepared materials were studied by X-ray powder diffraction (XRD), X-ray photoelec-tron microscopy (XPS), transmission electron microscopy (TEM), chronoamperometry and electrochemical impedance spectroscopy (EIS). The synthesized materials exhibit a standard orthorhombie structure and good electrochemical performance after the doping with a spot of above-mentioned ions. The beneficial ef-fect of these cations on improving cyclability was demonstrated, due to that the stability of LiMnO_2 ortho-rhombic structure is enhanced by the doping with these non-Jahn-Teller ions. The electrode of Li_1.02Mn_0.98Ti_0.012O_1.989S_0.011 shows excellent electrochemical properties with the first discharge capacity of cal results reveal that the co-doping of S-M (M=Cu, Co, Ti) combines the advantages of the improvement of Li~+ diffusion by cation doping, with the suppression of Jahn-Teller distortion by S~(2-) doping. In the mean-time, the co-doped materials also achieve higher capacity and better cyclic performance than the pristine LiMnO_2.