聚苯胺包覆法制备纳米LiFePO4/C核壳复合材料及其表征(英文)

Preparation and Characterization of LiFePO_4/Carbon Nanocomposite with Core-Shell Structure by a Polyaniline Coating Method

采用聚苯胺包覆法合成了具有核壳结构的纳米LiFePO_4/C复合材料。聚苯胺包覆层对限制先驱体FePO_4的粒径起着关键性的作用。反应热力学理论计算和实验结论都表明制备FePO_4/PANI最适宜的pH值约为5。FePO4/PANI复合物的粒径由苯胺添加量决定,当添加的苯胺与FePO_4摩尔比为0.44时,可以合成粒径约50 nm的FePO4/PANI复合物。经过碳热还原过程,FePO_4表面的聚苯胺层转化为LiFePO_4表面导电性良好的碳包覆层。采用优化工艺合成的LiFePO_4/C颗粒近似球体,粒径约为55 nm,碳包覆层厚度约为2 nm,0.2和1 C倍率下放电比容量约为136 mAh.g^(-1),在10、20、30和40 C倍率下放电比容量分别为118,103,94和87 mAh·g^(-1),高倍率下放电比容量和循环性能明显优于固相法合成的LiFePO_4材料。.

LiFePO_4/carbon nanocomposite with core-shell structure was synthesized by a polyaniline coating method.The polyaniline coating layer plays an important role in limiting the diameter of FePO_4 particles.Experiment and thermodynamic calculus present that suitable pH value for preparation of FePO_4/PANI is about 5.Diameter of partials is decided by aniline addition.The molar ratio(aniline:FePO_4=0.44:l) could be best to synthesize FePO_4/PANI composite with 50 nm diameter.After carbothermal process,the polyaniline layer on FePO_4 surface could transfer to carbon layer with high electronic conductivity on LiFePO_4 surface.By optimal technics,the crystal size of LiFePO_4/C is about 55 nm,and the coating layer is about 2 nm,approximate a sphere.The specific capacity of nano-LiFePO_4/C with core shell structure is about 136 mAh·g^(-1) at 1 and 0.2 C discharge rate.The specific capacity is respectively 118,103,94 and 87 mAh·g^(-1)at 10,20,30 and 40 C rate,showing higher specific capacity and better cycling performance at high discharge rate.