Improved conducting states induced by an electrochemical charging process in polyaniline film doped with new dopants

We study the electrode characteristics of Li//polyaniline cells by using polyaniline films as positive electrodes. Two mechanisms for charging in a Li/polyaniline-Li salt cell are suggested; charge separation mechanism and intercalation mechanism. In the charge separation mechanism, the electrical conductivity, the peak area of N⁺ site in X-ray photoelectron spectroscopy (XPS) data, and the intensity of the electron spin resonance (ESR) signal increase as the concentration of unpaired electrons increases. We compare XPS and ESR signals, and dc conductivity for the polyaniline before and after charging. From the results of XPS experiments, the polyaniline samples after electrochemical treatment have more N⁺ state or more polarons, resulting in higher conductivity and larger ESR signal. The Li⁺ and counterions exist deep inside the Pani-LiPF₆ and Pani-LiBF₄ samples by charging process. Based on these results, we propose the charge separation mechanism in Li//polyaniline cells by using the polyaniline films as the positive electrodes.