In Situ Synthesis of a Si/CNTs/C Composite by Directly Reacting Magnesium Silicide with Lithium Carbonate for Enhanced Lithium Storage Capability

Silicon is considered as an ideal anode material for the next generation of lithium-ion batteries (LIBs) owing to its high specific capacity, low lithiation potential, and high natural abundance. However, its potential application is greatly restricted by poor electrical conductivity and large volume expansion during lithiation/delithiation processes. Herein, a novel solid-state reaction route is developed to synthesize a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite by directly reacting magnesium silicide (Mg2Si) with lithium carbonate (Li2CO3). This method realizes synchronous formation of Si, CNTs, and amorphous carbon with a good interfacial configuration. Transmission electron microscopy (TEM) reveals that MgO may be responsible for the in situ growth of CNTs during the chemical reaction process. The crystalline Si particles are encapsulated by CNTs and the amorphous carbon matrix, which not only accommodates the volume expansion of Si but also enhances the integral electronic conductivity. Consequently, the Si/CNTs/C composite exhibits a high reversible capacity (702 mA h g–1 at 0.2 A g–1), excellent rate performance (420 mA h g–1 at 5 A g–1), and long cycling life (over 1500 cycles) when used as an anode for LIBs. Notably, this research might provide a new strategy for large-scale synthesis and utilization of Si/C composites in high-performance LIBs.