Electrospray Synthesis of Silicon/Carbon Nanoporous Microspheres as Improved Anode Materials for Lithium-Ion Batteries

An optimized nanostructure design of Si-based anode material for high-performance lithium-ion batteries is realized in the form of Si/C nanoporous microspheres. Self-assembled Si/C nanoporous microspheres are synthesized by a programmed method and are investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, N-2 adsorption-desorption isotherms, and electrochemical experiments. The programmed synthesis steps involve electrojetting Si nanoparticle-containing sodium alginate aqueous solution followed by calcination, carbon coating, and final etching. The electrospray step is the key step toward the formation of the microspheres in which sodium alginate acts as a dispersant and a carbon precursor for nano-Si particles as well as a coagulant together with Cu2+. The Si/C nanoporous microspheres exhibit remarkably enhanced cycling performance and rate performance compared with nano-Si particles when used as anode materials in lithium-ion batteries. The improved electrochemical performances benefit from the advanced nano/microstructure with proper size, carbon coating, and porosity as well as from the as-formed Cu3Si with good electronic conductivity and surface stability.