Core@shell silicon-carbon nanoparticles with a tunable shell thickness: performances as battery anodes

Abstract

International audienceSymposium: Battery and energy storage devices Nanometric silicon appears as an interesting candidate to improve the capacity of lithium-ion batteries anodes because its theoretical specific capacity is over 10 times that of CUITent commercial graphite electrodes. A major issue with nanosilicon anodes is the continuous formation of solid electrolyte interphase (SEI) due to the significant volume changes in the material during lithiation-delithiation. Coating the silicon surface with carbon has proved to protect it, as a more stable SEI is obtained. For this purpose, we synthesize core@shell silicon-carbon nanoparticles by a using a double-stage laser pyrolysis reactor. This gas-phase technique allows one-step synthesis of a silicon core coated by a carbon shell. The size and the size distribution, as well as the shell's thickness, can be controlled by the modification ofparameters. This wall-1ess process leads to clean interfaces. In this work the synthesis of carbon coated crystalline nanosilicon (30 nm) with various carbon contents, up to 20 % w/w, will be presented. These Si@C particles present a clear silicon-carbon interface as shown by STEM-EELS. The ga1vanostatic performance comparison indicates that the coulombic efficiency is improved by a greater carbon content and power rate experiments indicate that an optimum exists. Finally, by using electrochemical impedancespectroscopy (EIS), a comparison of SEI resistances for coated and non-coated parti cl es will be presented