用电池级纳米层状磷酸铁制备磷酸铁锂研究

Preparation of lithium iron phosphate from nano-layered battery grade iron phosphate

利用三价铁盐为铁源,浓磷酸为磷源,在硝酸介质中通过加入表面活性剂十二烷基硫酸钠(SDS),制备出纳米层状电池级磷酸铁。通过高温固相还原法制备得到碳包覆的磷酸铁锂正极材料。对磷酸铁锂材料进行了X射线衍射光谱分析(XRD)、扫描电镜微观形貌观测(SEM)及材料电化学性能测试,结果表明,片层纳米结构磷酸铁制备的磷酸铁锂粒径变小且均匀分散,由粒径约为100nm的细小颗粒堆砌而成;样品的衍射峰与磷酸铁锂标准卡片衍射峰吻合度高;其首次充电比容量为164.70mAh/g,放电比容量为159.47mAh/g,库仑效率为96.82%,具有良好的循环可逆性能;通过交流阻抗测试并计算了扩散系数(DLi+)为4.13×10^-11cm^2/s,探讨了磷酸铁纳米层状结构对磷酸铁锂形貌的影响。

The nano-layered battery grade iron phosphate was prepared by adding surfactant sodium dodecyl sulfate (SDS) in nitric acid medium with ferric salt as iron source and concentrated phosphoric acid as phosphorus source. The carbon coated lithium iron phosphate cathode materials were prepared by solid state reduction at high temperature. The results of XRD, SEM and electrochemical analysis show that the prepared material is composed of fine particles with diameter of about 100 nm. The coincidence between the diffraction peaks of samples and those of lithium iron phosphate standard cards is high. The first charge and discharge specific capacity are 164.70 and 159.47 mAh/g, and the coulomb efficiency is 96.82%, exhibiting remarkable cyclic reversibility. The AC impedance test was conducted and the calculated diffusion coefficient of lithium ion (DLi+) is 4.13×10^-11 cm^2/s. The effect of nano-layered structure of iron phosphate on the morphology of lithium iron phosphate was discussed.