锂离子电池LiFePO_4/C复合正极材料掺杂金属离子的制备及改性研究

Study on Preparation and Modification of LiFePO_4/C Cathode Material for Lithium Rechargeable Batteries Doping Metal Ions

以碳酸锂、草酸亚铁、磷酸氢二铵、碳酸镁、碳酸锰为原料,葡萄糖为碳源,采用两步球磨高温固相法合成了锂离子电池正极LiMgxFe1-xPO4/C、LiMnxFe1-xPO4/C、LiFe1-x-yMnxMgyPO4/C复合材料。讨论了镁、锰金属离子对LiFePO4/C结构和性能的影响。利用X射线衍射、扫描电子显微镜、X射线能谱仪等方法研究了镁、锰金属离子掺杂对LiFePO4/C晶体结构和表面形貌的影响;利用电化学方法研究了镁、锰掺杂对LiFePO4/C充放电性能和循环稳定性的影响。结果表明,镁、锰金属离子掺杂合成的LiFePO4/C具有单一的橄榄石结构,颗粒尺寸均匀,具有良好的电化学性能和循环稳定性。掺杂的LiMg0.1Fe0.9PO4/C、LiMn0.1Fe0.9PO4/C、LiFe0.8Mn0.1Mg0.1PO4/C在0.1C下首次放电比容量分别为128.4mAh/g、110.8mAh/g、131.8mAh/g。

LiMgxFe1-xPO4/C、LiMnxFe1-xPO4/C、LiFe1-x-yMnxMgyPO4/C cathode materials were synthesized for lithium rechargeable batteries by two step ball-milling and high temperature solid-state reaction, using Li2CO3, FeC4O4 ·2H2O, （NH4）2HPO4, MnCO3, （MgCO3）4 ·Mg（OH）2 · 5H2O as raw materials and glucose as carbon source. Effect of doping Mg2＋ and Mnz＋ on the structure and performance of the samples was discussed. Effect of do- ping Mg2＋ and Mnz＋ on crystal structure and surface morphology of LiFePO4/C composite material was investigated by using X-ray diffraction, scanning electron microscope, and X-ray energy dispersive spectroscopy. Electrochemical measurements were used to study effect of doping Mn2＋ and Mg2＋ on charge/discharge performance and cycle stability of LiFePO4/C composite material. Results indicated that the prepared samples by doping Mn2＋ and Mg2＋ have single olivine structures and uniform particle sizes, and exhibited an excellent electrochemical performance and enhanced sta- bilities. Among them, the first specific discharge capacity of LiMg0.1Fe0.9 PO4/C was 128.4mAh/g at 0. 1C; the first specific discharge capacity of LiMno. lFeo,9 PO4/C was 110. 8mAh/g at 0. 1C; the fist specific discharge capacity of LiFeo.gMgo. lMno. xPO4/C was 131.8mAh/g at 0. 1C.