Nanostructured silicon/porous carbon spherical composite as a high capacity anode for Li-ion batteries

A nanostructured silicon/porous carbon spherical composite was prepared by a simple hydrothermal method using glucose as a carbon source and Pluronic F127 as a soft template/pore forming agent in the presence of silicon nanoparticles, and a subsequent carbonization process. In this composite, silicon nanoparticles were individually and separately coated with a porous carbon shell with a thickness of 15–20 nm and a pore size of 3–5 nm. The composite electrode exhibited excellent cycling stability and rate capability, delivering a stable capacity of 1607 mA h g−1 at a current density of 0.4 A g−1 after 100 cycles, and a reversible capacity of 1050 mA h g−1 even at a high current density of 10 A g−1. Detailed analysis of cyclic voltammetry and electrochemical impedance spectroscopy revealed that the composite showed favorable electrochemical kinetics due to the nano-sized porous carbon shell, which facilitated the formation of a solid electrolyte interface film and the transportation of Li ions and electrons, and decreased the charge transfer resistance, thus significantly improving the electrochemical performance compared with the bare nano-Si electrode.