Phase and microstructural evolution of Sn particles embedded in amorphous carbon nanofibers and their anode properties in Li-ion batteries

Phase and microstructural evolution of Sn-Carbon composite nanofibers (NFs) under various heat treatment conditions was clearly demonstrated in this work. Amorphous carbon nanofibers (a-CNFs) that contained metallic Sn nanoparticles were prepared via electrospinning and subsequent calcination under a reducing atmosphere. The sizes of the metallic Sn particles, which were decorated inside and outside of a-CNFs, were precisely manipulated by varying the Sn precursor content and introducing a reinforced quenching step, i.e., controlling the cooling rate after high-temperature processing. Because of the low melting temperature of metallic Sn (231.9 °C), the nucleation and growth rates of the Sn nanoparticles were significantly influenced by the high-temperature processing and cooling condition. In particular, the stresses that originated from volume changes of the Sn nanoparticles during the lithium alloying and dealloying processes were effectively compensated by amorphous carbon containing Sn particles, which led to reduced structural damage. The morphologies of the fibers with incorporated Sn nanoparticles provided efficient permeability to allow the penetration of the electrolyte into the inner fiber structure while maintaining a high-capacity (950 mAh g^-1 at 0.5 C-rate) characteristics due to enhanced surface activity.