Preparation of polyaniline nanofibers and their use as a cathode of aqueous rechargeable batteries

Normal pulse voltammetric method was used to synthesize nanofibers of polyaniline (PANi) in HCl solution on a platinum electrode. The influences of the synthesis parameters, such as potential increment, pulse duration and monomer concentration on the electrochemical properties of the PANi films were investigated. Scanning electron microscopic micrographs clearly revealed the formation a nanofiber structure with average diameter in range 70-100 nm under optimum experimental conditions. The electrochemical properties of PANi films were studied with the impedance analysis, cyclic voltammetry and charge/discharge capacities. FT-IR results revealed that the PANi nanofibers were in emeraldine salt form. The film was employed as a positive electrode (cathode) for a PANi-Zn secondary battery containing 1.0 M ZnCl₂ and 0.5 M NH₄Cl as electrolyte. The cells were charged and discharged under a pulse current of 0.31 mA cm⁻². It was found that the maximum capacity of the PANi-Zn battery is 235.60 Ah kg⁻¹ with a columbic efficiency of 97-100% over a wide range of current density of 0.3-5.6 mA cm⁻². The specific energy was 287.43 Wh kg⁻¹ and the PANi cathode exhibited good recycleability.