聚合电流对锂/聚吡咯电池正极电化学行为的影响

在Pt微盘电极上用恒电流技术在电流密度为0.05-10 mA·cm-2范围合成了1 滋m厚度的聚吡咯(PPy)膜. 采用循环伏安(CV)、计时电势、交流阻抗(EIS)技术考察了不同聚合电流下得到的聚吡咯的电化学行为. 结果表明, 最佳聚合电流区间为1-5 mA·cm-2, 对应的电势一般在3.9-4.1V (vs Li/Li+)之间, PPy的掺杂度为30%左右. 在这一聚合电流密度范围得到的PPy具有较大的电化学容量, 较佳的电化学反应可逆性能、较高的氧化还原电势数值和稳定性能. 处于氧化态的聚吡咯具有优良的导电性. 上述条件下得到的PPy适合于作为锂离子二次电池的正极材料. 适当选择电流, 可以得到有相对完整的共轭仔键的长链结构的PPy 膜.

Influence of Electropolymerized Current Density on Polypyrrole Electrode of Lithium Ion Cells

In this research, different polypyrrole (PPy) film samples with same thickness were electro-polymerized on Pt micro-disk electrode by method of chronopotentiometry at current densities, ranging from 0.05 mA·cm-2 to 10 mA·cm-2. The electrochemical behaviors of obtained PPy samples were investigated in lithium perchlorate-proylene carbonate electrolyte by electrochemical methods: cyclic voltammetry (CV), chronopotentionmetry and electrochemical impedance spectroscopy (EIS). The results indicated that the polyprrole samples fabricated at suitable current density,t hat was, 1-5 mA·cm-2, could exhibit better electrochemical behavior, such as, higher d egree of electrochemical redox reversibility, more positive redox potential, and larger capacity. It was found that each of the potential response signals was considerably stable and there was a clear linear relationship between corresponding potential response signal and used electro-polymerization current density in the process of electro-polymerization reaction. At the condition of suitable current density, corresponding potential signal was changed from3.9Vto 4.1 V (vs Li/Li+) with the increasing of used electro-polymerization current density. Moreover, each outstanding properties, for example, the most doping degree, 30%or so, lower membrane impedance and charge transfer impedance at oxidated state, could be achieved on the PPy samples fabricated at abovementioned suitable current density. It was also found that each kind of obtained polypyrrole sample exhibited excellent columbic efficiency and electrochemical reversibility during galvanostatic charge/discharge process in the electrolytes of Li-ion battery. Those polypyrrole samples obtained at abovementioned suitable electro-polymerization condition should be promising candidate for the fabrication of the positive electrode of secondary lithium/LiClO4 /polypyrrole battery.