Sn–Co nanoalloys embedded in porous N-doped carbon microboxes as a stable anode material for lithium-ion batteries

For improving the capacity and stability of Sn-based anode materials, a novel Sn–Co nanoalloy embedded in porous N-doped carbon was synthesized using the metal–organic framework ZIF-67 as both the template and carbon source, and SnCl4 as the tin source through carbonization. This composite shows the shape of a microbox with the diameter of about 2 μm in which about 10 nm of Sn–Co nanoalloy particles were uniformly embedded. When used as the anode material for lithium-ion batteries, it exhibits a high capacity of 945 mA h g−1, and 86.6% capacity retention after 100 cycles at 100 mA g−1 as well as an excellent rate capacity of 472 mA h g−1 at a high current density of 2 A g−1. The superior electrochemical performance can be ascribed to the well-dispersed, nano-sized alloy and the buffering effect of porous N-doped carbon coating. Moreover, the uniform particles remain intact upon cycling which gives the material enhanced electrochemical stability.