Hydrothermal synthesis and electrochemical properties of Li2FexMnxCo1-2xSiO4/C cathode materials for lithium-ion batteries

Abstract

Crystallographic and morphological data and the galvanostatic cycling and rate performance of the cobaltsubstituted Li2Fe0.5Mn0.5SiO4/C compounds Li2FexMnxCo1-2xSiO4/C (x = 0.33, 0.40, 0.45) were evaluated and compared with those of unsubstituted Li2Fe0.5Mn0.5SiO4/C. The hydrothermally synthesized Li2FexMnxCo1-2xSiO4, consisting of uniform nanosized primary particles and no impurities, were indexed on the basis of the orthorhombic unit cell in space group Pmn21 and exhibited a solid solution at least beyond x = 0.33. The primary particle sizes of Li2FexMnxCo1-2xSiO4 decreased because of the substitution of cobalt for iron and manganese. In addition, although the capacity fades of Li2FexMnxCo1-2xSiO4/C were similar to those of Li2Fe0.5Mn0.5SiO4/C, the discharge capacity and rate capability of Li2Fe0.5Mn0.5SiO4/C were improved by the substitution of cobalt for iron and manganese. Li2FexMnxCo1-2xSiO4/C (x = 0.45) exhibited the best electrochemical performance with first discharge capacities of 242.5 and 163.6mAhg-1 at current rates of 3.3 and 165mAg-1, respectively. The good electrochemical performance of Li2FexMnxCo1-2xSiO4/C cathode materials is attributed to their smaller primary particle size compared with that of Li2Fe0.5Mn0.5SiO4/C.