The carbon additive effect on electrochemical performance of LiFe_0.5 Mn_0.5 PO₄ /C composites by a simple solid-state method for lithium ion batteries

This work reported a solid-state method to prepare LiFe_0.5 Mn_0.5 PO₄ /C (LFMP/C) composite cathode materials by using LiH₂ PO₄, MnO₂, Fe₂ O₃, citric acid (C₆ H₈ O₇), and sucrose (C₁₂ H₂₂ O₁₁). The citric acid was used as a complex agent and C₁₂ H₂₂ O₁₁ was used as a carbon source. Two novel hollow carbon sphere (HCS) and nanoporous graphene (NP-GNS) additives were added into the LFMP/C composite to enhance electrochemical performance. The HCS and NP-GNS were prepared via a simple hydrothermal process. The characteristic properties of the composite cathode materials were examined by micro-Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis (EA), and alternating current (AC) impedance methods. The coin cell was used to investigate the electrochemical performance at various rates. It was found that the specific discharge capacities of LFMP/C + 2% NP-GNS + 2% HCS composite cathode materials were 161.18, 154.71, 148.82, and 120.00 mAh¨ g^´1 at 0.1C, 0.2C, 1C, and 10C rates, respectively. Moreover, they all showed the coulombic efficiency ca. 97%–98%. The advantage of the one-pot solid-state method can be easily scaled up for mass-production, as compared with the sol-gel method or hydrothermal method. Apparently, the LFMP/C composite with HCS and NP-GNS conductors can be a good candidate for high-power Li-ion battery applications.