稀土Sm掺杂LiFePO4/C正极材料的结构和电化学性能

采用高温固相法制备LiFe1-xSmxPO4/C(x=0,0.06,0.08,0.10)锂离子电池正极材料,并用XRD,SEM,CV及EIS等方法进行结构和电化学性能的测试。结果表明,通过该法制得的样品均具有橄榄石型晶体结构。Sm的掺杂可明显细化颗粒,并导致LiFePO4晶格中c轴方向的P-O键长增加,其中x=0.08样品P-O键长最大(0.152 8 nm),明显大于未掺杂样品的键长(0.142 2nm)。电化学性能测试表明,掺杂后LiFePO4的放电容量增加,循环稳定性能提高。在-20～40℃的温度区间内,放电容量随温度的升高而增加,其中x=0.08的样品40℃时放电容量为159 mAh.g-1,但测试温度达到60℃时,放电容量急剧下降。EIS测试表明Sm的掺杂可以明显改善电极表面电化学反应的动力学性能,降低电荷转移电阻,提高交换电流密度。

Structure and Electrochemical Properties of Sm-Doped Lithium Iron Phosphate Cathode Materials

Microstructure and electrochemical properties of LiFe1-xSmxPO4 /C(x=0,0.06,0.08,0.10) have been investigated using XRD,SEM,CV,EIS measurements.All the samples have the crystal structure of olivine.With increasing Sm substitution content,the particles of synthesized LiFe1-xSmxPO4 /C are fine and homogeneous in size.The optimal doping content of Sm is that x=0.08 in the LiFe1-xSmxPO4 /C samples to achieve high discharge capacity and good cycle performances.The temperature effect indicates that the discharge capacity increases with the rise of temperature in-20～40 ℃.The sample with x=0.08 delivers the discharge capacity of 159 mAh·g-1 at 40 ℃,while the discharge capacity decreases drastically at 60 ℃.EIS test demonstrates that the doping of Sm can improve the dynamic performance,decreases the charge transfer resistance Rct and increases the exchange current density i0 greatly.