Kong, Junhua, et al. Nanoscale 5.7 (2013): 2967-2973.
Challenge: Silicon's exceptional lithium storage capacity is often offset by its poor electrical conductivity and drastic volume expansion during cycling, which lead to rapid capacity fade and electrode pulverization in lithium-ion batteries.
Solution: This case study examined a hybrid anode material-silicon nanoparticles encapsulated within hollow graphitized carbon nanofibers-to address silicon's conductivity and mechanical stability challenges.
Fabrication: Polyacrylonitrile (PAN) and silicon nanoparticle blends were electrospun into loose nanofiber mats collected on water, creating a suspended network with generous inter-fiber spacing. The wet fibers were uniformly coated in situ with a thin polydopamine (PDA) layer, serving as a carbon precursor. Subsequent etching removed sacrificial components, and high-temperature calcination graphitized the PDA shell and carbonized residual PAN, yielding hollow carbon nanofibers with silicon cores.
Key Results:
· When tested as anodes in half-cells, the graphitized carbon-silicon nanofibers retained over 70 % of silicon's theoretical capacity after 50 cycles, significantly outperforming non-graphitized controls. At a high current density of 5 A/g, the hybrid delivered ~500 mAh/g, demonstrating excellent rate capability.
· The graphitic carbon shell uniformly surrounding each fiber provides efficient electron pathways and mechanical support, while the hollow architecture and nanoparticulate silicon ensure rapid lithium insertion/extraction and accommodate volume changes. This design markedly improves cycle life and power performance.
Yli-Rantala, Elina, et al. Fuel Cells 11.6 (2011): 715-725.