Rice husk derived silicon/carbon and silica/carbon nanocomposites as anodic materials for lithium-ion batteries

Abstract

The unique hierarchical structures over multiple length scales (micrometer-to-nanometer levels) possessed by the natural biosubstances make them to be ideal substrates for the syntheses of functional nanostructured artificial materials. In this work, nanostructured silicon/carbon and silica/carbon nanocomposites derived from rice husks were obtained, which showed enhanced electrochemical performances as being employed as anodic materials for lithium-ion batteries. The homogeneous silicon/carbon composite was synthesized via a one-pot carbonization/ magnesiothermic-reduction process of the rice husk, which was composed of fine silicon nanocrystals embedded in the carbon matrix. As being applied as an anodic material, it delivered a high reversible capacity of 560 mAh g−1 as cycled at a current density of 100 mA g−1 over 180 cycles with good structural stability. Direct carbonization of the rice husk resulted in the silica/carbon nanocomposite, and it was found that, as being employed as an anodic material, the higher carbonization temperature led to better electrochemical performances such as the cycling stability (650 mAh g−1 after 150 cycles at 100 mA g−1 for the sample carbonized at 900 °C) and rate capacity. Silver nanoparticles were further composited with the silicon/carbon and silica/carbon hybrids to make the corresponding ternary nanocomposites, resulting in improved electrochemical performances.