大功率LiFePO4/C复合材料的简易合成

本文采用碳热还原法,以廉价的FeCl3.6H2O、LiOH.H2O和NH4H2PO4为原料,以淀粉为还原剂和碳源,经600℃烧结制备了LiFePO4/C复合材料,方法重现性好且易规模化生产.采用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)测试材料结构,观察材料形貌.结果表明,经600℃烧结10 h所得产物具有纯相的橄榄石型晶体结构,良好的结晶性和规整的球状形貌,粒径为60～100 nm.包覆LiFePO4晶粒的碳层厚度为2 nm左右,碳含量为5%(by mass).材料的振实密度高达1.3 g·cm-3,在0.2C倍率下首次放电比容量为162 mAh·g-1,在0.5C、1C、2C、5C和10C倍率下首次放电比容量分别为143、135、127、116和105 mAh·g-1,10C倍率下500周期循环,其比容量仍有81 mAh·g-1.

A Facile Approach to Prepare LiFePO4/C Composite with High-Rate Performance

The LiFePO4/C composite electrode material was synthesized by a moderate in situ carbothermal reduction method at 600 ℃ using FeCl3·6H2O,LiOH·H2O and NH4H2PO4 as starting materials,soluble starch sol as a carbon source and a reducing agent.This method is readily reproducible and possibly feasible to carry out large-scale synthesis.The structure and morphology of the LiFePO4/C samples were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The synthesized LiFePO4/C composite was in pure phase of olivine-type,shows highly crystalline and spherical morphology with the particle sizes in the range of 60～100 nm.The thickness of the carbon film could be as thin as about 2 nm for the isolated LiFePO4/C particles,and the amount of carbon introduced into the composite was about 5%(by mass).The measured tap density of LiFePO4/C composite was as high as 1.3 g·cm-3 and the initial discharge capacities of LiFePO4/C composite reached 162,143,135,127,116 and 105 mAh·g-1 at 0.2C,0.5C,1C,2C,5C and 10C rates,respectively.Remarkably,even after 500 cycles at 10C,the capacity of 81 mAh·g-1 could be obtained.