Morphological and structural evolution of Si-Cu nanocomposites by an instantaneous vapor-liquid-solid growth and the electrochemical lithiation/delithiation performances

摘要

Polymorphic Si-Cu nanocomposites of Si@Cu3Si nanowires, Si@Cu3Si nanorods, and Si@Cu3Si(Cu) nanocapsules are synthesized via the high-energy arc-discharge plasma. Electrochemical performances of these materials as anodes for lithium-ion batteries are also investigated. It is found that the morphologies and structures of above Si-Cu nanocomposites are alterable by the composition of the raw target and synthetic conditions. Optical emission spectroscopy is adopted to reveal the energetic states of excited atoms in plasma; thus, the temperature of working plasma as well as the evaporation rate of each element can be evaluated, in which both favor to control the composition of Si-Cu nanopowder product and the aborative nanostructures. Formation of multifarious Si-Cu nanostructures is understood from the in situ nucleation and anisotropic growth processes, induced by an instantaneous vapor-liquid-solid mechanism within the robust plasma. The optimal composition and microstructure of Si@Cu3Si nanorods are found for the excellent electrochemical behaviors, typically a stable discharge capacity of 783mAhg(-1) with the coulombic efficiency of 98.51% at 100mAg(-1) after 100 cycles. Good performances are attributed to one-dimensional Si-Cu nanostructure, which favors to promote Li+ ion diffusion. Metallic Cu component released from Cu3Si precursor enhances the conductivity, buffers the volume change, and facilitates the stabilization in cycling.