Mild preparation of anode materials by a salt-free green method

No current research on anode materials for lithium ion batteries is directed to the preparation by salt-free green methods. Here we report that H₂O₂ aqueous solution can act as an efficient oxidant to improve the electrochemical performance of common natural graphite including reversible capacity, coulombic efficiency in the first cycle and cycling behavior. Through investigation of X-ray photoelectron spectroscopy, thermogravimetry and differential thermal analysis and high resolution electron microscopy, it is found that the improvement is owning that this oxidation removes some imperfect structures with high reactivity, introduces more nano-channels, and replaces the surface by a dense layer of oxides. As a result, the stability of graphite crystal improves, the decomposition and the co-intercalation of electrolytes are prevented, more lithium can intercalate, and the movement of graphene planes along the a-axis direction is impeded. This method can be performed at low temperature (60 °C), is benign to the environment, and can well control the uniformity of products. In addition, there are no problems such as corrosion associated with salt-containing reactions. This salt-free green method is also exciting in economy and efficiency, and promising for industry.