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Abstract: Silicon/graphite/disordered carbon (Si/G/DC) is coated by Li2ZrO3 using Zr(NO3)4·5H2O and CH3COOLi·2H2O as coating reagents. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize Li2ZrO3-coated Si/G/DC composite. The Li2ZrO3-coated Si/G/DC composite exhibits a high reversible capacity with no capacity fading from 2nd to 70th cycle, indicating its excellent cycleability when used as anode materials for lithium ion batteries. A compact and stable solid-electrolyte interphase (SEI) layer is formed on the surface of Li2ZrO3-coated Si/G/DC electrode. Analysis of electrochemical impedance spectra (EIS) shows that the resistance of the coated material exhibits less variation during cycling, which indicates the integrity of electrode structure is kept during cycling. XPS shows that F and P elements do not appear in the SEI layers of Li2ZrO3-coated Si/G/DC electrode, while they have a relatively high content in SEI layers of Si/G/DC electrode. The improvement of Li2ZrO3-coated Si/G/DC is attributed to the decrease of lithium insertion depth and the formation of stable SEI film. [Copyright &y& Elsevier]

Abstract: Modified natural graphite is synthesized by surface coating and graphitizing process on the base of spherical natural graphite. The modified natural graphite is examined discharge capacity and coulombic efficiency for the initial charge–discharge cycle. Modification process results in marked improvement in electrochemical performance for a larger discharge capacity and better coulombic efficiency. The mechanism of the enhancement are investigated by means of X-ray powder diffraction, scan electron microscopy, and physical parameters examination. The proportion of rhombohedral crystal structure was reduced by the heat treatment process. The modified natural graphite exhibits 40mAhg−1 reduction in the first irreversible capacity while the reversible capacity increased by 16mAhg−1 in comparison with pristine graphite electrode. Also, it has an excellent capacity retention of ∼94% after 100 cycles and ∼87% after 300 cycles. [Copyright &y& Elsevier]