The effects of morphology and size on performances of Li2FeSiO4/C cathode materials

The morphology-controlled Li2FeSiO4/C cathode material is successfully synthesized by a sol-gel method, in which commercial, spherical and cubic Fe2O3 are respectively used as iron sources. By controlling the Fe2O3 precursors' morphologies, the morphology and grain size of the Li2FeSiO4/C materials can be purposefully controlled via morphology-inheritance strategy. The morphologies, sizes, elemental distributions and structures of the as-prepared Li2FeSiO4/C materials are confirmed by field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results show that the as-synthesized Li2FeSiO4/C samples exhibit well-defined morphologies due to the homogeneous and well-crystallized Fe2O3 precursors. Comparing with Li2FeSiO4/C synthesized by commercial Fe2O3 precursor, the Li2FeSiO4/C materials prepared by spherical or cubic Fe2O3 precursors exhibit eminent electrochemical properties, e.g., high initial reversible capacities of 214.1 mAh g−1 for LFS/C-S and 206.5 mAh g−1 for LFS/C-C at 0.1 C and good cyclic stability (93.1% for LFS/C-S and 91.5% for LFS/C-C). In particular, the spherical LFS/C-S material with better fluidity and less agglomeration displays excellent rate capability of 105.4 mAh g−1 at 10 C. Therefore, the control of the morphology and size during preparation process of Li2FeSiO4/C cathode materials will open a new route for the development of high performances lithium-ion batteries.