【摘要】 应用慢扫描循环伏安法研究磷酸铁锂化合物在水溶液体系中的电极过程,并通过交流阻抗法探讨了其在不同电位条件下的脱嵌锂过程。对不同频率区域的电化学行为进行分析表明,高频圆弧归属于体相电阻和电容;中低频区的半圆反映了Li+在电解液和活性物质界面发生的电荷转移;低频区部分的斜线说明了锂离子在电极材料内部的扩散行为。提出了等效电路模型,并以此对实验结果进行了拟合。在此基础上分析了磷酸铁锂在饱和硝酸锂溶液中的电极反应机理。研究表明,磷酸铁锂在水溶液体系中具有良好的电化学可逆性。更多还原

【Abstract】 The electrode process of LiFePO4 in aqueous system was investigated by slow scan rate cyclic voltammetry (SSCV). Lithium-ion insertion and extraction process under a wide range of potentials was investigated by electrochemical impedance spectroscopy (EIS). The results of analysis on different frequency regions show that the first semicircle in the high-frequency region is related to bulk resistance and capacity,the second semicircle in the high-to-medium frequency is contributed to the charge-transfer reaction on the interface of electrolyte and active materials,and the impedance in the low-frequency region is related to the diffusion of lithium ion in solid electrode directly. New equivalent circuit was presented to fit the experimental electrochemical impedance spectroscopy. The electrode reaction mechanism of LiFePO4 in saturated LiNO3 was investigated. The results show that lithium ion has good electrochemical reversibility in the compound during insertion and extraction.更多还原