Uniform Si nanoparticle-embedded nitrogen-doped carbon nanofiber electrodes for lithium ion batteries

Preparing the homogeneous spinnable solutions with highly dispersed Li-electroactive nanoparticles has been of the crucial issues for electrospinning technique to develop nanocomposite with carbon nanofibers, because the particle aggregation can lead to a poor cyclic stability and formation of unstable solid electrolyte interface layers. Herein, we present that the commercial Si nanoparticles (≤50 nm in diameter), with using polyethylene glycol (PEG), are embedded uniformly into nitrogen-doped carbon nanofibers (w-Si@N-CNFs) through a facile electrospinning route, followed by carbonization at 800 °C. The PEG played a critical role as dispersion agent to prevent the aggregation of Si nanoparticles during electrospinning, which successfully leads to the high dispersion and incorporation of Si nanoparticles without any agglomeration on N-CNFs. As anode materials for Li-ion batteries, the electrochemical properties of w-Si@N-CNFs was evaluated and compared to the non-uniform Si@N-CNFs (wo-Si@N-CNFs) that is prepared without PEG. The w-Si@N-CNFs anodes exhibit not only the enhanced Li-storage performances with a high capacity-retention of 66.0% without any drastic capacity fading after 150 cycles at a current density of 200 mA g⁻¹, but also the notable rate performances with a reversible capacity of 1076.8 and 640.8 mA h g⁻¹ at current densities of 100 and 2000 mA g⁻¹, respectively. These results demonstrate that the uniformly embedded Si nanoparticles enhance the electrochemical performances of the Si@carbon nanofibers, which is attributed to the well-dispersed Si nanoparticles surrounded by carbon layers without aggregation, resulted in leading to the formation of stable solid electrolyte interface layers and the alleviation of volume expansion of Si nanoparticles. This simple and cost-effective process is expected as a platform for development of anode materials based on nanoparticles-embedded CNFs nanocomposite along with electrospinning technique.