Hydrothermal synthesis of lithium iron phosphate using pyrrole as an efficient reducing agent

Highlights: ► Pyrrole is used as efficient reducing agent for hydrothermal synthesis of LiFePO4. ► Addition of pyrrole reduces Fe3+ to Fe2+. ► Pyrrole polymerizes to polypyrrole, creating a carbon source. ► LiFePO4 has high electrochemical performance in lithium-ion batteries. - Abstract: Lithium iron phosphate (LiFePO4) is synthesized by a hydrothermal process using pyrrole as an efficient reducing agent and a subsequent calcination. Observations through a scanning electron microscope and a transmission electron microscope (TEM) show that LiFePO4 has a diameter and length of 500 nm and 3 μm, respectively. The results of TEM and X-ray diffraction confirm that the structure of LiFePO4 is orthorhombic olivine. Raman and X-ray photoelectron spectroscopy results indicate that Fe3+ oxidized from reactant Fe2+ by air reacts with pyrrole, generating polypyrrole (PPy), and reduces to Fe2+. PPy that is generated can also serve as a carbon source in the subsequent calcination. In addition, the electrochemical measurement results show that the energy capacity of calcined LiFePO4/PPy is 153 mAh g−1 at 0.2 C. Calcined LiFePO4/PPy offers promising cycle-life performance in lithium-ion batteries.