Anode materials for lithium ion batteries obtained by mild and uniformly controlled oxidation of natural graphite

Modification of natural graphite for anode materials has been a recent focus of research and development. Here we report that a common natural graphite, whose electrochemical performance is very poor, can be modified by solutions of (NH₄)₂S₂O₈, concentrated nitric acid solution, or green chemical solutions such as aqueous solutions of hydrogen peroxide and ceric sulfate. All treatments result in marked improvement of the electrochemical performance, including reversible capacity, coulombic efficiency in the first cycle, and cycling behavior. The main reason is the effective removal of active defects in natural graphite, formation of a new dense surface film consisting of oxides, improvement of the graphite stability, and introduction of more nanochannels/micropores. As a result, these changes inhibit the decomposition of electrolytes, prevent the movement of graphene planes along the a-axis direction, and provide more passages and storage sites for lithium. They are mild and the uniformity of the product can be well controlled. Pilot experiments show economic promise for their application in industry to manufacture anode materials for lithium ion batteries.