Hydrothermal synthesis and characterization of Li2FeSiO 4 as positive electrode materials for Li-Ion batteries

Abstract

Li2FeSiO4 was prepared by the hydrothermal method, and the influences of synthesis conditions (temperature, time, and lithium-ion concentration) were systematically examined. Low-temperature phase of Li 2FeSiO4 (space group; Pmn21, a = 6.23, b = 5.36, and c = 4.98 Å) was hydrothermally prepared from LiOH, FeCl 2, and amorphous SiO2 at 150 °C for 3 day. As-prepared Li2FeSiO4 (ca. 1 μm size) shows poor electrochemical reactivity with 20 mAh g-1 of discharge capacity at room temperature in aprotic Li cell. Electrochemical reactivity of the as-prepared Li 2FeSiO4 has been considerably improved by the ballmilling process with acetylene black because particle size of Li2FeSiO 4 is reduced to 50-200 nm size, and the individual particles are uniformly covered by acetylene black. The ballmilled Li2FeSiO 4 can deliver 130 mAh g-1 of the rechargeable capacity at room temperature or 150 mAh g-1 at 6°C.