Synthesis of SnSb-embedded carbon-silica fibers via electrospinning : Effect of TEOS on structural evolutions and electrochemical properties

We demonstrate a facile one-pot synthesis of porous SnSb-embedded carbon-silica (SnSb-CS) fibers via electrospinning and subsequent calcination, using SnCl₂/SbCl₃ as Sn/Sb co-sources, polyvinylpyrrolidone (PVP) as carbon source and tetraethylorthosilicate (TEOS) as silica precursor. The introduction of TEOS promotes the complete encapsulation of SnSb alloy particles within carbon fibers with simultaneous formation of porous channels, and the in-situ generated silica species are uniformly distributed within the carbon fibers. When examined as anodes for lithium ion batteries, the SnSb-CS exhibits much enhanced electrochemical properties including higher reversible capacity, better cycle stability and rate capability than that of the counterpart SnSb-C without silica (namely, no introduction of TEOS during synthesis). The resulting SnSb-CS after annealed at 800 °C exhibits high specific capacity and excellent cycle stability (660 mA h/g at 200 mA/g after 100 cycles with ∼100% capacity retention). As revealed by the ex-situ TEM analysis, the confinement of SnSb into the porous carbon-silica matrix effectively buffers the volume changes of Li-Sn and Li-Sb alloying-dealloying upon cycling, and the incorporation of silica into carbon matrix increases the structural integrity of the composite electrodes, which synergistically contribute to the superior electrochemical performance. More importantly, the strategy of using TEOS-derived silica as reinforcing agent can be generally extended to the fabrication of various functional composites owing to its facileness.