Synthesis and characterization of LiFePO4 and LiFePO4/C cathode material from lithium carboxylic acid and Fe3+

Olivine LiFePO4 and LiFePO4/C are successfully prepared by a simple solid-state reaction using FePO4·2H2O, lithium oxalate and glucose (bare LiFePO4 without adding glucose) as raw materials. The structure of the LiFePO4 and LiFePO4/C is investigated by X-ray diffraction (XRD). The micromorphology of LiFePO4 and LiFePO4/C is observed using scanning electron microscopy (SEM) and BET, and the in situ coating of carbon on the particles is observed by transmission electron microscopy (TEM) and Raman spectrum. Furthermore, the electrochemical properties are evaluated by cyclic voltammograms (CVs), electrochemical impedance spectra (EIS) and constant current charge/discharge cycling tests. The results show that carbon coated LiFePO4 can deliver better battery performance than the bare LiFePO4. It exhibits initial discharge capacities of 162, 142 and 112 mA h g−1 at rates of 0.1, 1 and 10 C, respectively, and it presents excellent capacity retention as there is tiny capacity fade after 100 cycles. Moreover, the reductive mechanism of using lithium carboxylic acid to synthesize LiFePO4 is firstly mentioned.

► This study reports a simple, effective and environmentally friendly synthetic route to prepare LiFePO4/C composite that can be applied in industrial production.
► This study reports a simple way to synthesize bare LiFePO4 from lithium carboxylic acid and Fe3+.
► The effects of carbon coating on materials are investigated in detail by using XRD, SEM, TEM, BET, Raman spectrum, CV, EIS and constant current charge/discharge cycling tests.