An Orthogonal Investigation in Structures and Performances of Vanadium Modified Li2FeSiO4

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
X. Wei, X. Luo, H. Chen, X. Cheng, L. Huang, and Y. Zhang (Xiamen University)
A series of vanadium modified carbon coated lithium iron silicate (Li2Fe1-xVxSiO4/C) composites were prepared by sol-gel precursor and solid-state reaction using ammonium metavanadate (NH4VO3) as a vanadium source material. The effects of vanadium content (x), sucrose amount (y), sol-gel time (t) and type of carboxylate acid on crystal structure, surface morphology, elemental composition and electrochemical performance of Li2Fe1-xVxSiO4/C composites were investigated through orthogonal design experiments. The preparation parameters were optimized to be x=35%, y=80%, t=2 h and use of citric acid as a pH regulator. The initial discharge capacity of 216.7 mAh/g (corresponding to 1.30 moles per formula unit) was achieved at 0.1C and room temperature with the Li2Fe0.65V0.35SiO4/C composite synthesized under the abovementioned optimized condition. A mixed Pmn21 and P21 phase was identified as the main structure, while metallic iron and lithium silicate (Li2SiO3) as the impure phases. The elemental analysis result revealed that 10.7% carbon was introduced. The elemental vanadium was detected by performing energy dispersive X-ray spectroscopic (EDX) analysis.