RESEARCH ON SECONDARY BATTERY MATERIALS BY FFT IMPEDANCE METHOD

近年<pi>来，共轭导电聚合物作为高功率电池的电荷储存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。我们主要利用高速傅立叶变换阻抗法来获得这些电极阻抗的频散，以表征在这些电极上发生的阴离子掺杂-去掺杂过程。用该方法对聚合物电极进行评价，发现聚吡咯和聚苯胺在阴离子掺杂-去掺杂反应的平稳性上优于聚乙炔，并通过改变成膜条件如膜厚、电解质阴离子等，对聚吡咯的电化学性能进行了详细的研究。不同电解质阴离子在聚吡咯膜中的掺杂率为：&lt;PF（_6^-）&gt; &gt;<CF_3>&lt;SO（_3^-）&gt; &gt; &lt;ClO（_4^-）&gt;。Li/LiClO 4/聚吡咯电极的充放电性能与聚吡咯电极作为单一电极的电化学性能表现出很好的一致性，当聚吡咯与&lt;PF（6 ^-）&gt;阴离子形成时，电池性能最好，在电流密度约为100%时，仍保持100%的库仑产率。2.5电池性能的这些差异并不归因于键合方式的差异，而肯定是对形态差异的响应。聚合物薄膜的FT-IR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.