PNNL

Abstract

Rational design of silicon and carbon nanocomposite with a special topological feature has been demonstrated to be a feasible way for mitigating the capacity fading associated with the large volume change of silicon anode in lithium ion batteries. Although the lithiation behavior of silicon and carbon as individual component has been well understood, lithium ion transport behavior across a network of silicon and carbon are still lacking. In this paper, we probe the lithiation behavior of silicon nanoparticles attached to and embedded in a carbon nanofiber using in-situ TEM and continuum mechanical calculation. We found that aggregated silicon nanoparticles show contact flattering upon initial lithiation, which is characteristically analogous to the classic sintering of powder particles by neck-growth mechanism. As compared with the surface-attached silicon particle, particles embedded in the carbon matrix show delayed lithiation. Depending on the strength of the carbon matrix, lithiation of the embedded silicon nanoparticle can lead to the fracture of the carbon fiber. These observations provide insights on lithium ion transport in the network structured composite of silicon and carbon, and ultimately provide fundamental guidance for mitigating the failure of battery due to the large volume change of silicon anode.