优化碳包覆对正极材料LiFePO4/C高倍率性能的影响

碳包覆层的结构和形态对LiFePO4正极材料的电子电导率影响很大. 本文以聚丙烯和葡萄糖为碳源, 二茂铁为催化剂前驱体, 采用原位固相法合成LiFePO4/C复合材料, 并对其微观结构和形貌, 碳的结构与含量, 电化学性能进行分析. 结果表明, 聚丙烯热解形成的碳包覆层石墨化程度高, 可提高材料的高倍率放电性能. 二茂铁的加入有助于优化包覆层的碳结构. 制备的LiFePO4/C复合材料具有优异的高倍率电化学性能, 10C (1C=170 mA·g-1)放电比容量达到145 mAh·g-1.

Effects of Optimized Carbon-Coating on High-Rate Performance of LiFePO4/C Composites

The structure and morphology of coating carbon play an important role in improving the electronic conductivity of lithium iron phosphate. LiFePO_4/C composites were synthesized using an in-situ solid state method while polypropylene and glucose were used as carbon sources. Ferrocene was used as a catalyst precursor to graphitize the pyrolytic carbon. The microstructure and morphology of lithium iron phosphate together with the amounts and structure of the coating carbon were investigated in detail. It is shown that the pyrolysis of polypropylene forms well graphitized carbon-coatings and thus improves the high-rate performance of the material. Ferrocene is effective in optimizing the carbon structure. A LiFePO_4/C composite with an excellent high-rate capacity of 145 mAh·g~(-1) at 10C (1C=170 mA·g~(-1)) was synthesized.