Direct synthesis of homogeneous Li2CoSiO4/C for enhanced ionic transport properties in Li-ion battery

Lithium metal orthosilicates are attracting a lot of attention owing to their potential as high capacity and high energy-density cathode materials for Li-ion batteries. Although a number of studies have been performed on lithium metal silicates, understanding of the structure and electrochemical behaviour of Li2CoSiO4 has remained elusive. Herein, homogeneous nanocrystalline Li2CoSiO4/C composites have been synthesized directly by a sol-gel method using water-soluble silicon compounds. X-ray diffraction (XRD) analysis confirmed that the Li2CoSiO4 was well-crystallized in βI phase with Pbn21 space group. From the high resolution transmission electron microscopy (HRTEM) image, the lattice fringes of {001} and {100} are well-resolved. Selected area electron diffraction (SAED) pattern reveal the highly crystalline nature of Li2CoSiO4 and HRTEM image shows the carbon layer coating on particle surface. The Li2CoSiO4 cathode materials delivered an initial discharge capacity of 112 mAhg−1 at C/10 rate with good cyclic performance. The discharge profile of Li2CoSiO4 shows a plateau at 4.1 V, revealing its importance as high potential voltage cathode for high energy-density battery.