Double-shelled hollow carbon nanospheres as enclosed electrochemical reactors to enhance the lithium storage performance of silicon nanodots

Abstract

An ingenious design is applied to synthesise unique double shelled hollow carbon nanospheres encapsulated with silicon nanodots (SiNDs@DSHC). As a promising anode for lithium ion batteries, this rationally designed carbon/silicon composite can offer several attractive advantages: (a) silicon nanodots with ultrasmall size can shorten lithium ion paths considerably, enable intimate electrolyte contact with the Si active materials and accommodate lithiation-induced strain without fracture outstandingly. (b) The double-shelled hollow carbon with high mesoporosity can serve as a chemical reactor to confine silicon nanodots, thereby improving the thermodynamic stability and minimizing the structural instability. (c) The synergistic effect of the double shell hollow structure carbon and numerous mesopores on the carbon shell can be helpful for buffering the volume expansion of silicon and the diffusion of electrolyte into the hollow void to allow intimate contact with Si nanodots. The SiNDs@DSHC composite exhibits excellent performance. The reversible capacity is 1350 mA h g⁻¹ after 400 cycles at a current density of 0.3 A g⁻¹ and 750 mA h g⁻¹ after 2000 cycles at a current density of 1 A g⁻¹, respectively. In addition, the SiNDs@DSHC‖LiCoO₂ lithium full-cell battery displays a stable capacity of 532 mA h g⁻¹ after 500 cycles at a current density of 0.4 A g⁻¹.