Uniformly dispersed nano-crystallite graphite in a silicon-oxygen-carbon matrix for high rate performance lithium-ion batteries

Two important performance parameters for lithium ion battery applications are capacity and cycle life, especially on fast charging. In this study, nano-crystalline graphite (NCG) uniformly dispersed in SiOC (NCG@SiOC) was prepared via hydroboration of polysiloxane and acrylonitrile followed by heat treatment. The thermal annealing process has a significant effect on the NCG@SiOC structure due to carbon rearrangement during annealing, which in turn affected the electrochemical properties of materials. NCG@SiOC exhibited an excellent cycling and rate performance. The transformation of the carbon structure and formation of defects during heat treatment were investigated using Raman spectroscopy and electron paramagnetic resonance, and a relationship between the carbon structure and electrochemical properties was established. In-situ Raman spectroscopy indicated that lithiation sites are mainly on the surface of the NCG in the NCG@SiOC material, which leads to fast charge/discharge behavior and a long cycle life.