One step synthesis of Si@C nanoparticles by laser pyrolysis: high capacity anode material for lithium ion batteries
Résumé
Carbon covered silicon nanoparticles (Si@C) were synthesized for the first time by a one-step continuous process in a novel two stages laser pyrolysis reactor. Crystallized silicon cores formed in the first stage were covered in the second stage by a continuous shell mainly consisting in low organized sp² carbon. At the Si/C interface silicon carbide is absent and the presence of silicon oxide is subsequently reduced, allowing the use of such material as promising anode material in lithium-ion batteries (LIB). Auger Electron Spectroscopy (AES) analysis of the samples at both SiKLL and SiLVV edges proved the uniformity of the carbon coating. In half-cell configuration, Si@C active material exhibits a high and stable capacity of 2400 mAh.g-1 at C/10 and up to 500 mAh.g-1 over 500 cycles at 2C. Cyclic voltammetry was used in order to compare the stability of Si and Si@C materials. The retention of the capacity is attributed to the protective effect of the carbon shell which limits the Si pulverization and avoids direct contact between the silicon surface and the electrolyte.