Application of Electrochemically Formed Polyazulene to Rechargeable Lithium Battery

An electrochemically formed polyazulene(PAz), one of the electroconductive polycyclic hydrocarbons, was studied for its electrochemical properties in order to examine the possibility of utilizing it as a cathode active material of rechargeable lithium battery. The electrode kinetics of PAz film electrode, especially the anion doping-undoping process, were investigated mainly with cyclic voltammetry and FFT impedance method. The cyclic voltammetric results of PAz film showed a highly reversible redox process. Cole-Cole plots for PAz electrode obtained by impedance measurement as a function of doping potential were also found to offer an indication that PAz can be an excellent battery material. The charging-discharging property, and the cyclability of a Li/LiClO₄-PC(propylene carbonate)/PAz battery were then studied as a function of the film thickness of PAz cathode. The charging-discharging behavior of Li/LiClO₄-PC/PAz was also compared with those of Li/LiClO₄-PC/polypyrrole and Li/LiClO₄-PC/polyaniline batteries, which had been examined earlier. When compared with Li/LiClO₄-PC/polypyrrole or Li/LiClO₄-PC/polyaniline batteries, a Li/LiClO₄/PAz battery showed fairly high and constant discharge voltage (ca. 3.2V), while keeping 100% of coulombic yield. Inspection by SEM showed that the surface condition of PAz film greatly resembled that of polypyrrole, however, a 10 C cm^-2PAz film was prepared with thicker than polypyrrole formed with the same amount of charge of 10 C cm^-2.