Observation on sodium p-toluenesulfonate-doped polypyrrole cathode for sodium ion battery

Sodium p-toluenesulfonate (TsONa)-doped polypyrrole (PPy) was synthesized as the cathode active material of sodium ion battery by way of facile one-step electrodeposition on iron (Fe) foil. The micro-morphology and micro-structure of as-synthesized TsONa/PPy/iron cathode were characterized in terms of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction; furthermore, the electrochemical Na-storage activity of TsONa/PPy/iron cathode was investigated by methods of, galvanostatic charge/discharge, cyclic voltammetry and alternating current impedance. As expected, the cauliflower-like TsONa-doped PPy particles tightly combined with the surface of the iron foil without any additional polymer binders; and also, the resultant TsONa/PPy/iron cathode delivered satisfactory electrochemical performances, mainly attributed to high Na-storage activity of PPy matrix and high electronic conductivity induced by doping of TsONa. For example, the reversible discharge capacity of TsONa/PPy/iron cathode remained about 98 mAh/g after at least 50 cycles and the corresponding coulombic efficiency was 92%, indicating high cyclic stability and reversibility of TsONa/PPy/iron cathode for sodium ion battery.