CNTs and rGO synergistically enhance the cycling stability of yolk-shell silicon anodes for efficient lithium storage

Abstract

Si-based anode materials have received a lot of attention from researchers due to their ultra-high theoretical specific capacity. However, poor conductivity and volume expansion during cycling have seriously hindered their further commercialization. To address the problems of Si-based materials, the multidimensional carbon materials constructed from Zeolitic imidazolate framework (ZIF) derived carbon and carbon nanotubes (CNTs) followed by the addition of reduced graphene oxide (rGO) are employed to encapsulate silicon nanoparticles (Si@C-ZIF@CNTs@rGO) to prepare a composite anode with a yolk-shell structure, which are prepared by mechanical stirring, electrostatic self-assembly and two-step calcination. The heat-treated ZIF materials not only form a unique yolk-shell structure that can effectively inhibit the volume expansion of silicon nanoparticles, but also derive rigid carbon shells and carbon nanotubes to improve the electrical conductivity of the anode materials, while rGO introduced by electrostatic self-assembly provides a large number of transport paths for electrons and ions. In a full battery test composed of LiFePO4 cathode, the composite cathode material loses only 2.4 % of its specific capacity after 100 cycles at 0.5 C current density. This work provides new ideas for multidimensional carbon structures to improve the lithium storage performance of silicon-based anodes.