Hierarchically structured silicon/graphene composites wrapped by interconnected carbon nanotube branches for lithium‐ion battery anodes

Summary Despite a high theoretical capacity, relatively low potential, and natural abundance, the practical application of Si anode is limited by a drastic volume change and low electrical conductivity. To resolve these issues, herein, we demonstrated a hierarchically structured composite, consisting of Si microparticle/reduced graphene oxide (rGO) wrapped by interconnected carbon nanotube (CNT) branches (CNT@NiNP@Si/rGO), for lithium‐ion battery (LIB) anodes. Chemical vapor deposition is used to in situ grow CNT branches integrated onto the rGO and to encapsulate Ni nanoparticles (NiNP) at the tip of CNTs for the construction of three‐dimensional (3D) hierarchical complex structures. Moreover, ultrasonication is required for achieving uniform dispersion of NiNP catalyst for the growth of well‐defined CNT branches. The resulting CNT@NiNP@Si/rGO composites deliver the high rate capacity of 806 mAh g−1 at 8,400 mA g−1 and high capacity of 973 mAh g−1 after 250 cycles. Consequently, these improved performances of CNT@NiNP@Si/rGO composites are attributed to the effect of stress delocalization and facilitated charge transfer of Si arising from the hierarchical structure and covalent SiC bonds. The three‐dimensional hierarchical CNT@NiNP@Si/rGO composite structure is constructed using chemical vapor deposition to in situ grow CNT branches from well‐dispersed NiNP catalyst to encapsulate Si/rGO. Thus, CNT@NiNP@Si/rGO composite greatly improved cyclic stability and rate capability of the pristine Si microparticles owing to the effect of stress delocalization and facilitated charge transfer of Si arising from the hierarchical structure and covalent SiC bonds.