Preparation of C-LiFePO4/polypyrrole lithium rechargeable cathode by consecutive potential steps electrodeposition

In this work carbon coated lithium iron phosphate (C-LiFePO4)/polypyrrole (PPy) composite preparation has been carried out using electrochemical techniques. This composite has been deposited on a stainless steel mesh in order to use it as a cathode in a lithium-ion battery. When an oxidation potential is applied to the working electrode, the pyrrole monomer is polymerized and the C-LiFePO4 particles are incorporated into the polymer matrix and bound to the polymer and mesh. An experimental procedure was performed in order to understand how the composite formation is carried out and what the oxidation state of the composite material is during the charge–discharge process. As the electrochemical method of synthesis has a big influence in the electrochemical properties of the polymer, the use of consecutive potential steps has been studied in order to improve the charge-storage capacity of the composite material. The influence on the final composite properties of the oxidation-deposition time and potential and the effect of the number of cycles has been analyzed. An improvement of about 20% has been achieved using short oxidation times (3 s) at 0.9 V vs. Ag/AgCl. The reasons for this improvement are discussed and analyzed using different experimental techniques.