磷酸铁锂/石墨烯复合材料的合成及电化学性能

采用研磨、超声分散与搅拌干燥的工艺方法制备磷酸铁锂/石墨烯复合材料。利用TEM,SEM,XRD和Raman对材料组织结构进行表征,并组装成扣式电池进行电化学性能测试。SEM图像表明,在该工艺所制备的磷酸铁锂/石墨烯复合材料中,石墨烯贴附在磷酸铁锂颗粒表面,并且均匀地分散在复合材料中形成良好的导电网络。电化学测试结果显示,添加2%(质量分数)石墨烯后,磷酸铁锂的倍率性能和循环性能都得到明显提高。具体表现为:倍率性能方面,在5C充放电条件下,放电比容量提高到94.2mAh·g~(-1),是添加前的2.53倍;循环性能方面,100次循环(1C充放电)后容量衰减由添加前的43.5%下降到添加后的9.6%。这种简便的工艺能够实现石墨烯在电极材料中的均匀分散,充分发挥石墨烯优异的导电性,进而提升磷酸铁锂正极材料电化学性能。

Synthesis and Performance of LiFeP04-C/Graphene Composite

LiFePO4-C/graphene composite was successfully prepared by a facile approach of grinding, ultrasonic dispersion, stirring and drying and used as the cathode material for lithium-ion batteries. The structure and morpholgy of as-prepared LiFePO4-C/graphene composite material was characterized with transmission electron microscopy, scanning electron microscopy, X-ray diffraction and Raman spectroscopy, and the electrochemical performance was tested using coin cells assembled in an argon-filled glovebox. SEM images show that in the as-prepared material, graphene nanoflakes are adhered on the surface of LiFeP04-C particles, and uniformly dispersed in the composite material forming an effective 3D conducting network. Electrochemical tests show that after adding 2％ of graphene, rate and cycling performances of the LiFeP04 -C/graphene composite material are obviously improved. For the rate performance, a high reversible capacity of 94. 2mAh · g-1 is achieved at 5C rate, which is more than 2. 53 times higher than that of pristine LiFeP04-C; For cycling performance, the composite material shows a low capacity decay rate of 9. 6％ when cycles under 1C rate for 100 times, which is lower than pure LiFeP04-C (43. 5％). The electrochemical performance enhancement can be mainly ascribed to the effective 3D conducting network formed by graphene nanoflakes with superior conductivity.