Modification for Improving the Electrochemical Performance of Spherically-Shaped Natural Graphite as Anode Material for Lithium-Ion Batteries

A modified spherically-shaped natural graphite (M-SNG) material is prepared, and its physical and electrochemical properties for use as an anode material in lithium-ion batteries are reported. M-SNG is obtained by ultrasonication in a carbon precursor solution, followed by heat-treatment at 1,200°C under argon atmosphere. A gap between the flaky NG fragments forms on the surface and inside the M-SNG particles; amorphous carbon is present in this gap and on the M-SNG particle surface. The M-SNG anode exhibits superior electrochemical performance compared to a commercial carbon-coated SNG (C-SNG) anode, with high charge/discharge rate capability and stable capacity retention. The enhanced charge/discharge rate capability is attributed to the good soaking ability of the M-SNG anode, which allows the electrode to maintain low polarization even at high current density. The amorphous carbon coating on the surface and inside of the M-SNG suppresses side reactions with the electrolyte during charge–discharge cycles, facilitating excellent cycling stability, good thermal stability, and adequate dimensional stability.