Two-dimensional porous carbon-coated sandwich-like mesoporous SnO2/graphene/mesoporous SnO2 nanosheets towards high-rate and long cycle life lithium-ion batteries

Two-dimensional (2D) carbon-coated sandwich-like mesoporous SnO2/graphene/mesoporous SnO2 nanosheets (C@SnO2-rGO-SnO2) is conceived and synthesized as a novel anode material towards advanced lithium-ion battery. The nanocrystals size of SnO2 could efficiently manipulate using sandwich-like mesoporous SiO2/graphene/ mesoporous SiO2 (SiO2-rGO-SiO2) nanosheets as template. The existence large quantity of mesoporous nanostructure not only could provide sufficient buffer space for alleviating volume change of SnO2 during the discharge/charge process, but also supply more surface reaction sites for facilitating the penetration of electrolyte into electrode and enhancing surface lithium storage capacity. The graphene acts as mini-current collector provides rapid Li+ diffusion and transportation, and the carbon-coated protection layer prevents SnO2 aggregation effectively, which contributes to form stable solid electrolyte interface (SEI) film during cycling. Furthermore, the synergistic effect of graphene and carbon-coated shell constitutes excellent conductive network, which overcomes low electrical conductivity shortage of SnO2. The C@SnO2-rGO-SnO2 electrode exhibits excellent reversibility (1211 mAh g(-1) after 300 cycles at 0.2 A g(-1)), good rate capability (545 mAh g(-1) at 5 A g(-1), 315 mAh g(-1) at 10 A g(-1)) and superior long-cycle stability (703 mAh g(-1) after 1200 cycles at 1 A g(-1), 525 mAh g(-1) after 1200 cycles at 2 A g(-1)).