Design and performance improvement of SiNPs@graphene@C composite with a popcorn structure

Silicon anodes are considered to be the most promising alternatives owing to their theoretical specific capacity, which is almost 10 times higher than that of graphite anodes. However, huge volume changes during charging and discharging affect their interface stability, which strongly limits their application in commercial batteries. Herein, a popcorn-structured silicon-carbon composite ([email protected]@C), composed of silicon nanoparticles (SiNPs), graphene spheres and pitch-based carbon, is prepared by spray-drying followed by a wet process. The resulting [email protected]@C composite has good flexibility and elastic-strain capacity due to the graphene substrate, and it possesses macrostructural integrity and mechanical stability during cycling due to the rigid carbon–carbon chemical bonds. As a result, it shows a discharge-specific capacity of 481.3 mAh g−1 and a capacity retention of 82.9% after 500 cycles at 1 A g−1. Besides, the initial coulomb efficiency is increased from 65.7% to 86.5% by pre-lithiation, which improves the feasibility of commercialising the [email protected]@C composite.