Si@Co2SiO4/Reduced Graphene Oxide Nanocomposite Anodes for High Performance Lithium Ion Batteries

Abstract

Silicon (Si) has regarded as one of the most promising anode materials for next-generation Li-ion batteries (LIBs) because of its high theoretical capacity (4200 mAh/g), which is over 10 times higher than that of conventional graphite anodes (372 mAh/g). However, Si anode suffers from drastic volume expansion (~300%) upon Li alloying/dealloying, resulting in the structural collapse of the electrode. Therefore, Si anode loses electrical contacts with current collector and among the anode structures leading in rapid capacity fading. To overcome these obstacles, metal silicates (e.g. Co2SiO4, Zn2SiO4, Fe2SiO4, and Mn2SiO4) have been considered as good additive to suppress the structural changes and maintain electrochemical performance of Si anodes. In this study, Si@Co2SiO4/reduced graphene oxide (rGO) ternary nanocomposite was prepared by mixing Si nanoparticles, cobalt nitrate, and GO nanosheets, followed by hydrothermal treatment to create the Si@Co2SiO4 core-shells wrapped with multilayered rGO nanosheets. In particular, Co2SiO4 hollow structures of the composite enlarged the contact area of the electrode with electrolyte thereby facilitating fast transportation of electrons and Li ions during cycling. Moreover, void spaces between the Si@Co2SiO4 accommodated the huge volume change of Si during cycling. Furthermore, rGO nanosheets uniformly surrounding the core-shells enhanced the specific capacity and cycling stability of the anodes due to their good structural flexibility and electrical conductivity. As a result, the Si@Co2SiO4/rGO ternary nanocomposite achieved the significantly improved reversible capacity, steady cycleability, and excellent rate capability. We expect that this ternary system would further be extended to other nanocomposites as high-performance anode materials for next-generation LIBs.