简单固相法合成锂离子电池用Na2FePO4F/C复合材料（英文）

Na2FePO4F/C composite synthesized via a simple solid state route for lithium-ion batteries

选用二水合磷酸铁为铁源,经乙醇辅助球磨和固相反应制备了氟磷酸亚铁钠/碳复合材料。X-射线衍射证实产品有高的结晶度和相纯度。扫描电镜和透射电镜照片显示,球形氟磷酸亚铁钠粒子的粒径分布在50~300 nm之间;从高分辨透射电镜图可以看出,在氟磷酸亚铁钠/碳复合材料的表面包覆了一层厚度为3.6 nm的碳层。碳层的包覆能有效地遏制氟磷酸亚铁钠粒子的长大及粒子的团聚。以锂片作为负极组装半电池,在0.5C,1C,2C倍率下,复合材料的放电比容量分别为102.8,96.4,90.3 mA·h/g。0.5C循环100次后电池的放电比容量为98.9 mA·h/g,容量保持率为96.2%。从循环伏安曲线计算得到氟磷酸亚铁钠/碳复合材料的锂离子扩散系数为1.71×10^–9cm^2/s。显然,固相法是制备锂离子电池正极材料用氟磷酸亚铁钠/C复合材料的有效方法。

Using low-cost FePO4·2H2O as iron source,Na2FePO4F/C composite is prepared by alcohol-assisted ball milling and solid-state reaction method.The XRD pattern of Na2FePO4F/C composite demonstrates sharp peaks,indicating high crystalline and phase purity.The SEM and TEM images reveal that diameter of the spherical-like Na2FePO4F/C particles ranges from 50 to 300 nm,and HRTEM image shows that the surface of Na2FePO4F/C composite is uniformly coated by carbon layer with a average thickness of about 3.6 nm.The carbon coating constrains the growth of the particles and effectively reduces the agglomeration of nanoparticles.Using lithium metal as anode,the composite delivers a discharge capacities of 102.8,96.4 and 90.3 mA·h/g at rates of 0.5C,1C and 2C,respectively.After 100 cycles at 0.5C,a discharge capacity of 98.9 mA·h/g is maintained with capacity retention of 96.2%.The Li+diffusion coefficient(D)of Na2FePO4F/C composite is calculated as 1.71×10^–9 cm^2/s.This study reveals that the simple solid state reaction could be a practical and effective synthetic route for the industrial production of Na2FePO4F/C material.