Development of multi-component hybrid nanoarchitectured silicon/graphene/carbon nanofiber negative electrodes

The focus of this study is to investigate the role of different carbon materials on the mechanical integrity and electrochemical stability of silicon anodes during cycling tests. Because, the electrochemical performance of lithium ion cell strongly depends on the mechanical integrity of silicon during the lithium insertion process. Huge volume change of silicon (∼300%) causes undesirable mechanical pulverization of electrodes that results in electrical disconnection between the active materials and the current collector, and eventual fast capacity fading. To this aim, multi-component anode materials are designed with various combinations of silicon, carbon black, spherical amorphous carbon, reduced graphene oxide, and carbon nanofibers for high capacity and long stability electrodes. Firstly, the conductivity of electrode was improved with mechanical addition of carbon black. Then the silicon nanoparticles were trapped in spherical amorphous carbon with yolk-shell structure to control SEI formation and volume changes. Due to still observing some problems in electrochemical and mechanical performances, reduced graphene oxide was used in electrode to better protection against the aforementioned challenges. In order to better understand of improvement in electrochemical and mechanical behavior of electrodes, real-time stress measurements were studied for the first time on reduced graphene oxide based electrodes in this study. Furthermore, double protection was achieved with the combination of yolk-shell structure and reduced graphene oxide turbostatic packing on silicon. In addition, the stress generations in this electrode were calculated after fully expanded silicon using finite element method in ANSYS design modeler. This computational first report presented the contribution of the carbon shell between reduced graphene oxide layer to the deformation and stress generation in electrode. Finally, carbon nanofibers were strongly added to the system to highly improve the conductivity and better control the mechanical integrity. According to the experimental and computational findings obtained in this research, Si/C/rGO/CNFs electrode has exhibited the highest reversible capacity of about 2370 mAh/g after 500 cycles and the fairly good integral stability against lithium insertion-induced expansion of a silicon. Due to easy scaling-up possibility of the method, this multi-component hybrid nanocomposite is a great candidate for becoming a new electrode for electrochemical energy storage systems