Si/C/B₂O₃ composite anode for lithium ion batteries

The Si/C/B₂O₃ composites were prepared by pyrolyzing the phenol-formaldehyde resin (PFR) mixed with silicon and boric acid powders. The phase structure and composition of the prepared Si/C/B₂O₃ composites were analyzed by X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). Using the prepared Si/C/B₂O₃ composites as negative electrodes in Li-ion batteries, their charge-discharge performance were tested, and the electrochemical reactions of the composites were also studied by cyclic voltammograms (CV) and charge-discharge curves. The results show that the element boron in the composite is in the form of boron oxide, and the initial reversible capacity and cycle performance of the Si/C/B₂O₃ composites prepared are improved significantly by the addition of the compound containing element boron into the silicon/carbon materials. The charge-discharge test results show that the Si/C/B₂O₃ composite prepared by pyrolysis at 900°C exhibits an initial capacity of 584 mA·h·g^-1 with a coulombic efficiency of 60%, and its reversible capacity remains 325 Ma·h·g^-1 after 40 cycles.