锂离子电池正极材料LiFePO_4的复合改性研究

Composite modification of LiFePO_4 as cathode material of lithium ion battery

为了提高LiFePO4的充放电性能,通过高温固相法合成了Li0.98M0.02FePO4/C(M=Cr、W)及Li1.03M0.02Fe0.98PO4/C(M=Zr、Ni)两类橄榄石型正极材料。运用X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、能量散射X射线谱(EDX)和电化学测试对合成产物的晶体结构、颗粒形貌和电化学性能进行了表征。结果表明:Li0.98Cr0.02FePO4/C的放电比容量最高达到157.3mAh/g,且多次循环后容量几乎无衰减;在大电流充放电倍率下,材料依然能保持优良的循环性能,Li0.98W0.02FePO4/C首次放电比容量可达130.2mAh/g,10次循环后容量保持率为97%。离子掺杂和碳包覆改性能有效地提高LiFePO4的比容量和循环性能。

In order to improve the electrochemical performance of LiFePO4,Li0.98M0.02FePO4/C （M=Cr,W）and Li1.03M0.02Fe0.98PO4/C （M=Zr,Ni）were prepared by solid state reaction method.The structure,morphology and electrochemical performance of composite cathode materials were characterized by XRD,SEM,EDX and charge-discharge tests.The results show that the maximum discharge capacities of Li0.98Cr0.02FePO4/C can reach 157.3 mAh/g and the capacity does not fade after several cycles.,the cycling performance of the material keeps excellent at high-current charge-discharge rate,the initial discharging capacity of Li0.98W0.02FePO4/C can reach 130.2 mAh/g and the capacity retention is 97% after 10 cycles.Composite modification can increase the capacity and cycle performances of LiFePO4.