【摘要】 以1~3μm金属铁粉和磷酸二氢锂为原料,采用高温固相法合成了无碳磷酸铁锂。通过X射线衍射(XRD),扫描电镜(SEM)和电化学测试等方法对合成的磷酸铁锂材料的结构、形貌和电化学性能进行了表征。研究结果表明,采用1~3μm的金属铁粉和磷酸二氢锂为原料,高温固相法合成了具有橄榄石晶体结构的磷酸铁锂材料,粉末近似球形,振实密度较高,一次颗粒200~300 nm。600℃合成的磷酸铁锂存在杂质相,650~750℃下合成的磷酸铁锂具有完整的橄榄石晶体结构,产物为纯相。无碳的磷酸铁锂呈浅灰色,600~750℃下合成的磷酸铁锂材料0.1C充放电存在平台,显示两相充放电特性,比容量均在100 mAh·g-1左右,且极化较大。用蔗糖对其进行包覆改性得到碳包磷酸铁锂,其颜色呈黑色,改性后的磷酸铁锂电化学性能有了较大的提高,0.1C比容量达到了154 mAh·g-1,充电平台和放电平台之间的极化明显降低,具有较好的循环稳定性。更多还原

【Abstract】 The cathode material of C free LiFePO4 was synthesized by solid-state method with 1 ~ 3 μm Fe powder and LiH2PO4. The crystalline structure,morphology of particles,and electrochemical performances of the samples were investigated by X-ray diffraction( XRD),scanning electron microscope( SEM) and charge discharge test. The results showed that cathode materials of C free LiFePO4 were near-spherical primary particles of 200 ~ 300 nm with the olivine type LiFePO4 structure and high tap density. Impurity was detected in the C free LiFePO4 prepared at 600 ℃. The XRD pattern indicated that pure phase for C free LiFePO4 prepared at 650 ~ 750 ℃had complete olivine type structure characteristic. The C free LiFePO4 prepared at 600 ~ 750 ℃ with light grey color had two phase charge-discharge feature both with the discharge capacity of 100 mAh·g- 1 and showed a discharge plateau when charge-discharge at0. 1C. The polarization between the charge and discharge plateau is serious for C free LiFePO4. After coating with sucrose,the electrochemical performance was greatly improved with discharge capacity of 154 mAh·g- 1,having good capacity retention. The polarization of the C coated LiFePO4 between the charge and discharge plateau was lower than that of LiFePO4.更多还原