To improve the electrochemical performance of Li2FeSiO4 with low electric conductivity, the Li2FeSiO4/C composites with different carbon content are synthesized by a vacuum solid-state method. The experimental results show that the introduced carbon decrease the crystallite sizes of final products, but still keep the serious aggregated particles and make the Li2SiO3 impurity further increased. The Li2FeSiO4 with 4.15 wt.% carbon delivers the initial discharge capacity of 108.9 mAhg(-1) at room temperature and retains 71.5% of the initial discharge capacity after 50 cycles. The transition phenomenon in charge-discharge curves and the variation in DLi+ values with the cycling number clearly indicate a transient process of phase transition for Li2FeSiO4, which requires at least 5-10 charge-discharge cycles. (C) 2013 Elsevier B.V. All rights reserved.