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 β_I 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.