Synthesis of LiFePO_4 /C composite electrode with enhanced electrochemical performance

摘要

LiFePO_4/C composite was synthesized by high temperature solid-state reaction using iron( H ) oxalate, ammonium di-hydrogen phosphate and lithium carbonate with a kind of carbohydrate dissolved in the dispersant(eth-anol) as carbon sources added to the synthetic precursor. The samples were characterized by X-ray diffraction (XRD) , scanning electron microscopy observations(SEM) , charge/discharge test, cyclic voltammetry(CV) and carbon analysis. The results show that the synthesis of LiFePO_4/C has ordered olivine structure. The carbon has two advantages: optimizing particle size of LiFePO_4 and increasing the electronic conductivity and high Li+ diffusivity. The cathode material can demonstrate a charge/discharge flat voltage of 3. 4 V(vs Li+/Li). Especially the active material with 15 percent and 20 percent carbohydrate added according to the final product of lithium iron phosphate shows very good electrochemical performance delivering about initial 150. 2 mA centre dot h g~(-1) and 162. 0 mA centre dot h g~(-1) specific capacity respectively at 0. 1 C rate and the carbon contents in the final production are only 5. 17 percent and 5. 29 percent > respectively.