Silicon nanocrystals-embedded carbon nanofibers from hybrid polyacrylonitrile – TEOS precursor as high-performance lithium-ion battery anodes

Abstract

The high capacity of silicon (Si) for lithium incorporation makes it a promising anode material for lithium-ion batteries; however, pulverization of Si due to huge volume changes during lithiation/delithiation leads to significant capacity loss during cycling. To address challenges in low cyclability, nanostructured Si in carbon nanocomposites offers an attractive solution. In this study, we report an efficient method for the synthesis of a nanocomposite containing Si nanoparticles homogeneously embedded in an electrically conductive carbon nanofiber (CNF) network. Electrospinning of polyacrylonitrile (PAN) solution containing hydrolyzed tetraethyoxysilane (TEOS), as a Si precursor, and subsequent carbonization of hybrid nanofibers yielded a composite of SiO2 ultrafine nano-domains in the carbon network (C-SiO2). Low temperature molten salt-assisted aluminothermic reduction of C-SiO2 nanofibers allowed us to produce a C-Si/SiOx nanocomposite without forming detrimental SiC, which is thermodynamically favorable at high temperatures in a system with a high interfacial surface area between the carbon and SiO2 phases. The nanocomposite C-Si/SiOx anodes showed a reversible capacity of 860 mAh g−1 at a current rate of 200 mA g−1, retaining a capacity of 680 mAh g−1 after 100 cycles. In addition, the nanocomposite anodes delivered a reversible capacity of 569 mAh g−1 at a current rate of 400 mA g−1 while maintaining 95% of maximum capacity after subsequent 100 cycles. This study demonstrates the capability of designing nanocomposite anodes from reaction precursors combined with low-temperature aluminothermic reduction to produce a capacity-retaining anode composite of Si nanocrystals uniformly dispersed in the carbon matrix.