LiTi2(PO4)3/C 复合材料的制备及电化学性能

采用聚乙烯醇(PVA)辅助溶胶-凝胶法合成了具有Na+超离子导体(NASICON)结构的LiTi2(PO4)3/C复合材料.运用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等对其结构形貌和电化学性能进行表征.实验结果表明:合成的LiTi2(PO4)3/C具有良好的NASICON结构,首次放电容量为144mAh·g-1.电化学阻抗谱测试结果显示,LiTi2(PO4)3/C复合材料电极在首次嵌锂过程中分别出现了代表固体电解质相界面(SEI)膜及接触阻抗、电荷传递阻抗和相变阻抗的圆弧,并详细分析了它们的变化规律.计算了Li+在LiTi2(PO4)3中嵌入/脱出时的扩散系数,分别为2.40×10-5和1.07×10-5cm2·s-1.

Preparation and Electrochemical Performance of LiTi2(PO4)3/C Composite Cathode for Lithium Ion Batteries

LiTi 2(PO 4) 3 /C composite with a Na + superionic conductor(NASICON)-type structure was prepared by a sol-gel method.The LiTi 2(PO 4) 3 /C composite had a good NASICON structure and good electrochemical properties as revealed by X-ray diffraction(XRD),scanning electron microscopy(SEM),charging/discharging tests,cyclic voltammetry(CV),and electrochemical impedance spectroscopy(EIS).The first discharge capacity was 144 mAh·g-1.The EIS results indicated that there appeared semicircles respectively representing the solid electrolyte interface(SEI)film as well as the contact resistance,charge transfer resistance,and phase transformation resistance in the initial lithiation process of LiTi 2(PO 4) 3 /C composite electrode.The chemical diffusion coefficients of intercalation and de-intercalation of Li + in the LiTi 2(PO 4) 3 cathode material were calculated to be 2.40×10-5 and 1.07×10-5 cm 2 ·s-1,respectively.