Bifunctional NaCl template for the synthesis of Si@graphitic carbon nanosheets as advanced anode materials for lithium ion batteries

Abstract

Si has received much attention as an anode material for high performance LIBs due to its high theoretical capacity. Nevertheless, the serious volume changes during the lithiation/delitaiation process and poor electrical conductivity result in fast capacitative decay and poor rate performance, which seriously limit its practical applications. Herein, a 2D Si@graphitic carbon (GC) nanosheets composite was synthesized through the facile ball-milling method using NaCl as a bifunctional template, which not only served as a hard template but also stabilized the Si nanoparticles during the fabrication process. In this rationally designed architecture, Si nanoparticles are embedded into carbon nanosheets and encapsulated by a graphitic carbon wall. Therefore, the 2D Si@GC nanosheets composite as an anode for LIBs with outstanding cycling and rate performance, delivered a high capacity of 1450.7 mA h g⁻¹ after 400 cycles at 0.5 A g⁻¹, and maintained high reversible capacity of 877.4 mA h g⁻¹ even at 3.0 A g⁻¹. This outstanding electrochemical performance can be ascribed to the carbon nanosheets effectively buffering the volume change of the Si nanoparticles, graphitic carbon wall improving the electrical conductivity and 2D nanosheets facilitating the transport of Li⁺ during the charge/discharge process. Thus, the Si@GC nanosheet composite exhibited an outstanding rate and cycling performance.