Electrochemical Polymerization of Electroactive Polyaniline in Nonaqueous Solution and Its Application in Rechargeable Lithium Batteries

An electroactive polyaniline (PAn) was successfully prepared from nonaqueous propylene carbonate (PC) solution containing acid (CF₃ COOH) and electrolyte (LiC10₄). PAn deposition and the doping-undoping process of deposited PAn film were investigated by consecutive cyclic voltammetry in various electropolymerization solutions. It is confirmed by infrared spectral measurement that there is no essential difference in the manner of bonding between the electroactive PAn films deposited from aqueous and PC solutions. Inspection by scanning electron microscope revealed that PAn films deposited from aqueous HC10₄ solution had a fibrous structure, whereas the PAn film deposited from PC solution had a porous surface which resembled polypyrrole films. The shape of the electro-oxidation curve is found to be essentially different, depending on the solvent or the pK_a value of acid in an electropolymerization solution. An electroactive PAn film deposited from PC solution was applied to an effective cathode material of a rechargeable lithium battery (Li/LiClO₄-PC/ PAn). The Li/LiC10₄-PC/PAn (deposited from PC solution) battery showed a high coulombic efficiency and high-energy density in charging-discharging behavior. The electroactivity of PAn film deposited from PC solution was found to be as high as, or higher than, that of PAn film deposited from aqueous solution.