In Situ TEM Study of Lithiation Behavior of Silicon Nanoparticles Attached to and Embedded in a Carbon Matrix

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 components has been well understood, lithium ion transport behavior across a network of silicon and carbon is 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 flattening upon initial lithiation, which is characteristically analogous to the classic sintering of powder particles by a neck-growth mechanism. As compared with the surface-attached silicon particles, particles embedded in the carbon matrix show delayed lithiation. Depending on the strength of the carbon matrix, lithiation of the embedded silicon nanoparticles 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 batteries due to the large volume change of silicon anodes.

Review—Promises and Challenges of In Situ Transmission Electron Microscopy Electrochemical Techniques in the Studies of Lithium Ion Batteries

“…This open-cell device provides the possibility of atomic-level spatial resolution and analytical ability to investigate Li ion intercalation mechanisms upon charge/discharge cycling. [104][105][106] It was found that the ionic liquid was spread along the nanowire surface and there was formation of a thin coating, which means that, to some extent, this device could imitate the actual cell configuration to study the formation of a conformal layer on the surface of the active component. 99 One defect of this strategy is the polymerization of the ionic liquid electrolyte caused by the imaging electron beam after only several time cycles, which is too short for disclosing the microstructural progress of the electrode materials related to a real cell.…”

TEM in situ lithiation of tin nanoneedles for battery applications

“…For NPs, however, the carbon acts as a support and the sole conduction mechanism (rather than simply facilitating conduction). Reports on Si NPs decorating and contained in C nanofibers [28] and Si NPs enveloped in rumpled graphene sheets [29] have been published recently. In the latter study, the lithiation process was shown to change from isotropic to anisotropic during the reaction, which was attributed to more uniform electrical contact with the NPs provided by the graphene sheets.…”

Mesoporous silicon sponge as an anti-pulverization structure for high-performance lithium-ion battery anodes

“…However, its large volume expansion (4300%) during the lithiation process leads to the pulverization of silicon particles (4200 nm) and subsequently results in fast capacity fade of the electrode 3 . Many in-situ studies have directly observed the intrinsic volume expansion and pulverization of Si particles [4][5][6] . To overcome/bypass the pulverization problem, tremendous effort has been made on the synthesis of ultra-fine Si nanoparticles (o50 nm), development of new binders, and design of novel nanostructured Si materials, such as nanowires, nanotubes, hollow spheres and core-shell structures .…”