Synthesis of porous Si/C by pyrolyzing toluene as anode in lithium-ion batteries with excellent lithium storage performance

Abstract

Silicon (Si) has attracted researchers’ attention because of the high theoretical capacity of 4200 mAh g−1. However, the electrochemical performance of Si is often worsened by the structure deterioration originated from the huge volume variation during charge/discharge process. To improve the electrochemical performance, the porous structure is initially fabricated in Si by removing aluminum from Si-Al alloy powder with HCl solution, and then a carbon layer coats on the surface of porous Si by pyrolyzing toluene at 700 °C under nitrogen atmosphere, forming porous Si/C composite. In this composite, carbon helps greatly to transfer electrons and stabilize the structure of Si, resulting in an enhanced charge/discharge performance in comparison with porous Si. Porous Si/C presents an enhanced Li-storage performance; at 200 mA g−1, porous Si/C can deliver 1402 mAh g−1 after 100 charge/discharge cycles, but only 585.3 mAh g−1 for porous Si; and at 3200 mA g−1, the reversible specific capacity of Si/C is 505.1 mA h g−1, while that for porous Si is 41.7 mAh g−1.