Effects of polypyrrole and chemically reduced graphene oxide on electrochemical properties of lithium iron (II) phosphate

It is still challenging to improve the electrochemical properties of lithium iron (II) phosphate used as cathode for lithium ion batteries (LIBs). In the work, we describe the composites of lithium iron (II) phosphate/polypyrrole/chemically reduced graphene oxide (LFP/PPy/CRGO) prepared simply through a one-pot chemical procedure. We demonstrated that using pyrrole as monomer and graphene oxide as oxidant, PPy and CRGO sheets can be deposited simultaneously on the surface of LiFePO4 nanoparticles forming a uniform coating layer. As cathode for LIBs, the as-prepared composites show improved electrochemical properties and the rate capability and cycling stability of the LIBs can be increased dramatically. Electrochemical impedance spectroscopy and cyclic voltammetry measurements illustrated that the as-coated PPy and CRGO can decrease the charge transfer resistance and increase the Li+ diffusivity of the LiFePO4 particles. The elaboration of the underneath mechanism on the pronounced electrochemical properties of the composites was also attempted and discussed.