中文摘要：

以Fe（NO3）3,LiNO3,NH4H2PO4和NaNO3为原料,采用简单的液相-碳热还原法合成Li0.97Na0.03FePO4/C复合正极材料.使用X射线衍射（XRD）、扫描电子显微镜（SEM）和充放电等测试技术研究了材料的结构及倍率充放电性能.通过循环伏安（CV）曲线和电化学阻抗谱（EIS）研究电极反应过程中的动力学特点.结果表明,Na掺杂形成了具有橄榄石结构的Li0.97Na0.03FePO4固溶体,并增大了晶格中Li＋一维扩散通道,使LiFePO4/C的电荷转移电阻减小了约2/3,Li＋扩散系数提高了3～4倍.因此,Li0.97Na0.03FePO4/C首次放电比容量在0.1 C和2 C倍率下分别达到152 mAh g-1和109 mAh g-1,比未掺杂的LiFePO4/C的放电比容量分别提高了4.83%和62.69%.

英文摘要：

Li0.97Na0.03FePO4/C composite cathode material was prepared by a simple wet chemistry- carbothermal reduction method using Fe（NO3）3, LiNO3, NH4H2PO4 and NaNO3 as starting materials. The structure and charging-discharging rate properties of the samples were studied by X-ray diffraction （XRD）, scanning electron microscope （SEM） and charge-discharge test. Furthermore, the kinetics of lithium-ion extraction and insertion at LiFePO4/C were evaluated from cyclic voltammetry （CV） curves and electrochemical impedance spectroscopy （EIS）. The results indicate that the Li0 97Na0.03FePO4 solid-solution with olivine structure is obtained. Na-doping enlarges one-dimensional lithium-ion diffusion pathway in the olivine structure. Consequently, the materials exhibit a decrease in the charge transfer resistance by 67% and an increase in the lithium-ion diffusion coefficient by 3 -4 times. The initial discharge capacities of Li0.97Na0.03FePO4/C sample at the rate of 0.1 C and 2 C are 152 mAh·g^-1 and 109 mAh·g^-1, respectively, which increase 4.83% and 62.69% compared with that ofun-doped LiFePO4/C.