RESEARCH ON SECONDARY BATTERY MATERIALS BY FFT IMPEDANCE METHOD

近年来，<pi - > -共轭导电聚合物作为大功率电池蓄电材料的候选材料受到了广泛的关注。在这些聚合物中，我们主要研究了聚吡咯和聚苯胺作为可充电锂电池正极活性材料的可能性。我们主要利用高速FFT阻抗法来获得这些电极阻抗的频散，以表征这些电极上发生的阴离子掺杂-卸载过程。通过该方法对聚合物电极进行评价，证明了聚吡咯和聚苯胺在阴离子掺杂-脱掺杂反应的平稳性上优于聚乙炔。然后，通过改变成膜条件，如膜厚度或电解质阴离子，详细地研究了聚吡咯的电化学性能。不同电解质阴离子形成的聚吡咯膜内阴离子的掺杂率为：<PF(_6^-)> > <CF_3> <SO(_3^-)> > <ClO(_4^-)>。Li/LiClO4/聚吡咯的充放电性能与聚吡咯电极作为单一电极时的电化学性能完全一致，即当聚吡咯与<PF(_6^-)>阴离子形成时，电池性能最佳，且在电流密度约2.5 mA <cm^(-2)>时库仑产率保持100%。这些电池性能的差异不是由于键合方式的差异，而肯定是由于形态的差异。聚合物薄膜的傅里叶变换红外光谱证实了这一点。

Recently <pi> -cojugated electro-condctive polymer has been gathering much attentions especially as a candidate of chargestoring material of high-power battery. Among these polymers, we mainly investigated polypyrrole and polyaniline for their possibility as a cathode active material of rechargeable lithium battery. We mainly utilized the high-speed FFT impedance method to obtain the frequency dispersion of these electrode impedance, in order to characterize the anion doping-undoping process occurred at these electrodes. By evaluating polymer electrodes by this method, polypyrrole and polyaniline were proved to surpass polyacetylene in their smoothness of anion doping-undoping reaction.Then, by varying film formation conditions such as film thickness or electrolyte anions, the electrochemical properties of polypyrrole have been minutely investigated. The doping rate of anions within polypyrrole films formed with various kinds of electrolyte anions is as follows; <PF(_6^-)> > <CF_3> <SO(_3^-)> > <ClO(_4^-)> . The charging-discharging performances of Li/LiClO4/polypyrrole show perfect consistences with the electrochemical property of polypyrrole electrode as a sigle electrode, i.e., the battery performace was the best when polypyrrole was formed with <PF(_6^-)> anions and kept 100% of coulombic yield up to current density of ca. 2.5 mA <cm^(-2)> .These difference in battery performances is not ascribed to the difference in bonding manner, but is surely responsive for the morphology difference. This has been eidenced by FT-IR spectra of polymer films.