Presently, nanocrystallization and carbon composite modification are two main strategies to mitigate the volume change of Sn and prolong the cycle life. Nanoscale Sn can reduce the absolute volume change and suppress the volume mismatch in a single granule and the particle breakage is significantly inhibited. Moreover, the small size can shorten the ions diffusion distance in the material and improve dynamic performance. Carbon is the ideal material to modify Sn anodes. On one hand, the soft and flexible carbon works as “buffer zone” to hold the volume change and inhibit the particles aggregation. On the other hand, it serves as the conductive network to accelerate the ions transport and electrons transfer, as a result, improving the rate capability of Sn based materials.
Taking the advantages of nanoscale Sn and carbon modification, we recently designed nano-Sn/reduced graphene oxide (Sn/RGO) composites with extra small Sn particles uniformly dispersing in the carbon matrix. The 3D few-layer stacked Sn/RGO composite shows a structural evolution phenomenon from a stratified structure to a curly Sn@Carbon nanocage-like structure after cycling. The nanocage-like Sn@C structure is stable and guarantees the ultralong cycle life of Sn/RGO. It can steadily cycle up to 1000 times without obvious attenuation at 0.2 C, the specific capacities remain stable above 550 mAh g-1.
Figure 1. Schematic illustration of structural evolution of Sn/RGO during cycling
This work is supported by the National Natural Science Foundation of China (Grant No. 51371186), the “Strategic Priority Research Program” of the Chinese Project Academy of Science (Grant No.XDA09010201), Ningbo 3315 International Team of Advanced Energy Storage Materials, Zhejiang Province Key Science and Technology Innovation Team (2013TD16).