Synthesis and electrochemical performance of Ti-Fe co-doped LiMnPO4/C as cathode material for lithium-ion batteries

摘要

LiMnPO4/C, LiMn0.85Fe0.15PO4/C, LiMn0.92Ti0.08PO4/C and Li(Mn0.85Fe0.15)(0.92)Ti0.08PO4/C are prepared by a solid-state reaction route and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical tests. All samples are single phase with similar morphologies, particle sizes and carbon contents. Ti4+ and Fe2+ co-doping at the Mn-site greatly enhances the performance of LiMnPO4/C due to the synergistic effect between Ti4+ and Fe2+, resulting in an improvement in the dynamic stability of the olivine structure, lithium ion diffusion and electrochemical kinetics. Compared with LiMn0.85Fe0.15PO4/C and LiMn0.92Ti0.08PO4/C, Li (Mn0.85Fe0.15)(0.92)Ti0.08PO4/C shows a much higher discharge capacity and a better rate capability. It delivers a capacity of 144.4 mA h g(-1) with a capacity retention ratio of approximately 100% after 50 cycles at 1 C. These results prove that Fe2+ and aliovalent ion co-doping at the Mn site is an effective way to improve the electrochemical properties of lithium manganese phosphate. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.