Journal of Power Sources, Vol.244, 63-71, 2013
Synthesis and electrochemical properties of xLiFePO(4)center dot(1-x)LiVPO4F composites prepared by aqueous precipitation and carbothermal reduction
Phosphate-based compounds with the high working voltage, such as Li3V2(PO4)(3), LiVPO4F and LiMnPO4, have been proposed as a new class of cathode materials for lithium-ion batteries. To improve the operating voltage of LiFePO4, we introduce LiVPO4F to prepare xLiFePO(4)center dot(1 - x)LiVPO4F (LFP-LVPF) composites through an aqueous precipitation and carbothermal reduction method. A series of LFP-LVPF composites have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and total organic carbon (TOC) analysis. The discharge capacity of LFP-LVPF composites for x:(1 x) = 1:0, 0.99:0.01, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0:1 at a 0.2 C-rate is 153, 160, 132, 106, 92 and 78 mAh g(-1), respectively. The discharge capacity decreases with increasing mole fraction of LVPF. Moreover, the operating voltage of LFP-LVPF composites for x:(1 - x) = 0.75:0.25, 0.5:0.5 or 0.25:0.75 is higher than that of LFP, and the charge/discharge plateaus around 4.35/4.15 V for LFP-LVPF composites become longer as the value of x decreases. (C) 2013 Elsevier B.V. All rights reserved.
Keywords:Lithium iron phosphate;Lithium vanadium fluorophosphate;Lithium ion batteries;Cathode material