Core-shell structured Si@Cu nanoparticles encapsulated in carbon cages as high-performance lithium-ion battery anodes

Rationally surface optimization is considered to improve both energy capacity and structure stability in rechargeable batteries. A novel structure of copper coated silicon nanoparticles encapsulated in carbon cages (Si@Cu@CC) is synthesized by feasible methods of reduction and pyrolysis. The obtained composite exhibits a superior reversible capacity of 1724.3 mAh g−1 after 50 cycles at 0.1 A g−1, and the coulombic efficiency (CE) is 98.13%. It also maintains 1201.6 mAh g−1 even at the current density of 2 A g−1. The copper shell as a mechanical support layer wraps around the silicon nanoparticle can relieve the inner stress caused by the volumetric change. The exterior of Si@Cu particles is continuous network of carbon cages, which not only improves the conductivity of electrodes but also provides abundant transport channels for electrons and ions. The particular structure and the synergistic effect of copper and carbon have very important influence on the gorgeous properties of this composites.