Electrospun nanofibers with a core–shell structure of silicon nanoparticles and carbon nanotubes in carbon for use as lithium-ion battery anodes

Abstract

Core–shell structured nanofibers, consisting of silicon nanoparticles and carbon nanotubes encased in carbon (SCNFs), were fabricated for use as an anode material in lithium-ion batteries (LIBs). This entailed first electrospinning of precursor solutions containing a blend of silicon nanoparticles (SiNPs), carbon nanotubes (CNTs), and polyvinylpyrrolidone (PVP) for the core, and polyacrylonitrile (PAN) for the shell. The final SCNF structure was obtained by carbonization at 1000 °C for 1 h under nitrogen; the core–shell structure achieved with varying carbon contents was determined by scanning electron microscopy, transmission electron microscopy, and water contact angle measurements. An evaluation of the electrochemical performance of SCNF-based anodes in LIBs found that a SCNF electrode with 1 wt% CNTs has an initial delithiation capacity as high as 1500 mA h g⁻¹ at C/10 rate and a retained capability of 50% at high rates (10C). Following the 100^th cycle at 1C, a capacity of 1000 mA h g⁻¹ and coulombic efficiency of 99% were achieved, the former representing 74.1% of the original capacity (1350 mA h g⁻¹). Thus, not only does the robust carbon shell of SCNFs minimize the effect of volume expansion in the SiNPs, but the CNTs in the core also provide a greater number of conductive pathways, both between SiNPs and to the carbon shell, which assist electrochemical reactions.