Revisit of Polypyrrole as Cathode Material for Lithium-Ion Battery

Conducting polymer polypyrrole (PPy) was revisited as cathode material for lithium-ion battery. Synthesis condition, microstructure, doping effect and electrochemical performance were systematically investigated. Chemical polymerization was employed to synthesize PPy with sodium p-toluenesulfonate (pTSNa) as anionic dopant. Fe2(SO4)3·xH2O, ammonium persulfate (APS) and FeCl3·6H2O were used as oxidants respectively. The product was carefully characterized by elemental analysis, conductivity measurement, scanning electron microscopy, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. Experiments show that the oxidant and the molar ratio of pTSNa to monomer pyrrole (Py) strongly influence the yield, conductivity, composition, structure, morphology and electrochemical performance. As a cathode material, the PPy obtained with Fe2(SO4)3·xH2O as oxidant at [pTSNa]/[Py] = 2.0 exhibits the best performance, which gives a discharge capacity up to 122.5 mAh g−1 at current density of 7.2 mA g−1 and a capacity retention of 89.9% after 600 cycles at 72 mA g−1.