Facile One-Pot Synthesis of Li1-xFe1+xP1-xSixO4/C Nanocomposites with Enhanced Electrochemical Performance

Lithium iron phosphosilicates, i.e. Li1-xFe1+xP1-xSixO4, are novel cathode materials for lithium ion batteries. In this study, a facile one-pot method was employed to prepare Li1-xFe1+xP1-xSixO4/C nanocomposites. The dry gel, which contained all the starting materials, was calcined in an inert atmosphere to form the final product. The variation of their structural, morphological and electrochemical characteristics with x (x = 0, 0.15, 0.25, 0.5, 0.75 and 1) is studied. Single phase Li1-xFe1+xP1-xSixO4 with well-defined diffraction peaks can be obtained at an appropriate calcination temperature that varies with x. The phosphosilicate nanoparticles are embedded in an interconnected carbon network when the Li1-xFe1+xP1-xSixO4/C nanocomposites are obtained at 700 degrees C. The carbon network is highly porous and electronically conductive, which is benefit to the deintercalation of lithium from the phosphosilicate particles. The discharge capacity of Li1-xFe1+xP1-xSixO4/C composite declines with an increase in x as well as calcination temperature. A discharge capacity of 70 mAh g(-1) is preserved even if x is as high as 0.25 when the calcination temperature is 700 degrees C. The particle growth and aggregation of Li1-xFe1+xP1-xSixO4 are severe when the calcination temperature is as high as 900 degrees C, which leads to the collapse of carbon network. The interconnected carbon network is effective to increase the electrochemical performance of Li1-xFe1+xP1-xSixO4. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.045302jes] All rights reserved.