Facile fabrication of Si-embedded amorphous carbon@graphitic carbon composite microspheres via spray drying as high-performance lithium-ion battery anodes

Silicon-nanoparticle-embedded amorphous carbon-graphitic carbon composite microspheres (denoted as Si/AC@GC) with numerous empty voids are synthesized using a spray drying process. Spray dried composite microspheres consisting of Si nanopowders, dextrin, and iron salt are transformed to uniquely structured Si/AC@GC microspheres via one-step carbonization followed by acid etching. The in situ formation of graphitic carbon with high electrical conductivity within the Si-C composite at a low carbonization temperature (700 °C) is achieved by applying a metallic Fe nanocatalyst. The Si/AC@GC microspheres exhibit higher electrochemical properties than bare Si nanopowders and Si/amorphous carbon composite microspheres (denoted as Si/AC) with filled structures. The synergistic effects of structural merits owing to the spherical morphology with empty nanovoids for liquid electrolyte penetration and a graphitic carbon layer with high electrical conductivity result in the superior lithium-ion storage performances of Si/AC@GC microsphere. The composite-based electrode delivers a high reversible capacity of 803 mA h g⁻¹ after 200 cycles at 1.0 A g⁻¹, indicating long-term cycling stability. Even at 5.0 A g⁻¹, the electrode exhibits stable reversible discharge capacity of 589 mA h g⁻¹ without significant capacity loss.