Preparation and characterization of Six-Co0.6B0.6Al0.2/modified graphite sphere composites as anodes for lithium-ion batteries

In order to improve the cyclic property of Si as anode for lithium-ion battery, Si-x-Co0.6B0.6Al0.2/modified graphite sphere composites (labeled as Si-x-Co0.6B0.6Al0.2/MGS, x = 0.72, 1.12, 1.68) were synthesized using high energy ball milling (HEBM) technique. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the compositions and morphology of composite materials. The electrochemical behaviors of Si-x-Co0.6B0.6Al0.2/MGS were investigated by galvanostatic charge-discharge technique and electrochemical impedance spectroscopy (EIS). The results indicate that Co, B, Al and MGS have a good synergistic effect in improving the electrochemical performance of Si powder-based electrode. Compared to Si/MGS and Si-1.12-Co0.6B0.6Al0.2, the cyclic performance and coulombic efficiency of Si-1.12-Co-0.6 B0.6Al0.2/MGS are significantly enhanced from the 2nd cycle. The first reversible capacity of Si-1.12-Co0.6B0.6Al0.2/MGS is 533 mAh g(-1) and 90% of the capacity may be obtained after 80 cycles. EIS and SEM measurements indicate that the microstructural stability of the composite during cycling appears to be the main reason contributing to the good cycleability. (C) 2009 Elsevier Ltd. All rights reserved.