聚吡咯/磷酸铁锂复合正极材料的制备与表征

采用化学氧化法, 以吡咯为单体、 三氯化铁为氧化剂、 苯磺酸钠为掺杂剂在磷酸铁锂颗粒表面进行原位聚合, 制备了聚吡咯/磷酸铁锂(PPy/LiFePO₄)复合材料。用FTIR、 XRD和SEM对PPy/LiFePO₄复合材料进行了结构与形貌表征。用电化学工作站和充放电测试系统对复合材料的电化学性能进行了表征。结果表明: PPy/LiFePO₄复合材料作锂二次电池正极具有良好的充放电循环性能。当PPy质量分数为17%, 充放电电流为0.1 mA时, PPy/LiFePO₄复合材料最高放电比容量达163 mAh·g^-1, 50次循环之后放电比容量仍为初始时的94.9%; 与LiFePO₄相比, 当PPy的含量适当时, PPy/LiFePO₄复合正极材料的放电比容量会有明显提高。PPy的加入提高了LiFePO₄的电子电导率, 从而提高了活性物质有效利用率, 因此PPy/LiFePO₄复合材料的比容量和循环性能均得到了提升。

Preparation and characterization of PPy/LiFePO4 composite material as cathode

Polypyrrole was coated onto pure LiFePO4 particles to form polypyrrole/lithium iron phosphate(PPy/LiFePO4) composite material by chemical oxidative polymerization,with ferric trichloride(FeCl3) as oxidant,benzene sulfonic acid sodium salt as dopant.The molecular structure and morphology of PPy/LiFePO4 were characterized by FTIR,XRD and SEM.The electrochemical performances of composite were measured by electrochemical workstation and charge-discharge test system.It is found that the battery with PPy/LiFePO4 composite as cathode shows better charge-discharge performance.The discharge capacity of PPy/LiFePO4 composite is 163 mAh·g-1,which is higher than that of LiFePO4,when the mass fraction of PPy is 17.0% and the current is 0.1 mA.The discharge specific capacity of composite is still 94.9% of initial capacity after 50 cycles.Compared with pure LiFePO4,the coating of proper amount of PPy can improve the electronic conductivity of LiFePO4.As the effective utilization of LiFePO4 increases,both the specific capacity and cycle performance of PPy/LiFePO4 composite improves.