中文摘要：

采用粉末X射线衍射法（XRD）和电化学阻抗谱（EIS）来研究LiFePO4充/放电过程的结构变化和界面行为。XRD测试表明,在充/放电过程中LiFePO4/FePO4处于两相共存相互转换的状态。确定了LiFePO4的脱/嵌锂过程中的等效电路,对LiFePO4不同充放电时期试样进行电化学阻抗测试,计算出了交换电流I0和锂离子扩散DLi＋。并讨论随充放电过程的进行i0和DLi＋的变化规律。

英文摘要：

The X-ray diffraction and electrochemical impedance spectrum were used to study the structural changes and interface behaviors during charge and discharge processes in LiFePO4.The XRD test results showed that the charge and discharge process was in a two-phase coexistence and conversion state between LiFePO4/FePO4.Equivalent circuit of the LiFePO4during intercalation and disintercalation was determined.The exchange current（I0） and lithium-ion diffusion coefficient（DLi＋） were calculated and electrochemical impedance spectrum was tested at different charge and discharge stage.The variation laws during the charge and discharge processes were also investigated.