Effect of asphalt-decomposed soft carbon on the performance of Si-based anode material in lithium ion battery

The silicon (Si) was mixed with different amounts of asphalt (0%, 10%, 20%, 30% and 50% in mass fraction) as the soft carbon (C) source, respectively, to form the C/Si composites via the thermal decomposition method. As a result, the volume expansion of the Si material during the insertion/deinsertion process is effectively supressed, and the electric conductivity is improved at the same time, leading to the cycling stability and specific capacity increasing. For instance, a first-charge capacity as high as 2 356.7 mAhg^-1 is achieved for the C/Si sample synthesized using 20% asphalt. After 50 cycles, 726.4 mAhg^-1 of the capacity is retained, which is much higher than that of the commercial graphite and promising for industrial application. Moreover, the synthesis mechanism and effect of different amounts of asphalt on the morphology of obtained materials were also discussed.