Microwave synthesis of molybdenum doped LiFePO4/C and its electrochemical studies

Abstract

A Mo-doped LiFePO₄ composite was prepared successfully from an iron carbonyl complex by adopting a facile and rapid microwave assisted solid state method. The evolution of gases from the iron precursor produces a highly porous product. The formation and substitution of Mo in LiFePO₄ were confirmed by X-ray diffraction; surface analysis was carried out by scanning electron microscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the substituted LiFePO₄ were examined by cyclic voltammetry, electrochemical impedance spectroscopy and by recording charge–discharge cycles. It was observed that the as prepared composites consisted of a single phase orthorhombic olivine-type structure, where Mo⁶⁺ was successfully introduced into the M₂(Fe) sites. Incorporation of supervalent Mo⁶⁺ introduced Li⁺ ion vacancies in LiFePO_4. The synthesized material facilitated lithium ion diffusion during charging/discharging due to the charge compensation effect and porosity. The battery performance studies showed that LiMo_0.05Fe_0.095PO₄ exhibited a maximum capacity of 169.7 mA h g⁻¹ at 0.1 C current density, with admirable stability retention. Even at higher current densities, the retention of the specific capacity was exceptional.