Effects of Li3PO4 additive on the electrochemical properties of Li2FeSiO4 as cathode material for lithium-ion batteries

Abstract

Li2FeSiO4/C is successfully modified by Li3PO4 additive to achieve excellent electrochemical properties. In comparison with bare Li2FeSiO4/C, the samples with Li3PO4 show no changes in the morphology and structure, which are verified by X-ray powder diffraction and scanning electron microscopy results. High resolution transmission electron microscopy image confirms that Li2FeSiO4/C and Li3PO4 exist in the form of nanocomposites. When used as LIB cathodes, the Li2FeSiO4/Li3PO4/C composites show notably improved electrochemical performance with outstanding high rate performance and superior cyclability than those of Li2FeSiO4/C. The sample with 6 mmol% (LFS-6) exhibits a large discharge capacity of 114.1 mAh g−1 with a remarkable capacity retention of 104.2% over 100 cycles at 10 C, which are much better than those of Li2FeSiO4/C (89.0 mAh g−1 and capacity retention of 75.9%). The enhancement in the electrochemical properties of Li2FeSiO4/C may be attributed to the existence of Li3PO4 additive with high ionic conductivity, which can accelerate the lithium ions diffusion capability and facilitate the charge transfer process.