A novel design idea of high-stability silicon anodes for lithium-ion batteries: Building in-situ "high-speed channels" while reserving space

As one of the most promising anode materials for high-performance lithium-ion batteries, the commercial application of Si faces many dilemmas. In this paper, a facile method is developed to substantially improve the cycling stability of Si-based anodes. Firstly, based on the Kirkendall effect, the Si nanoparticle was transformed into multi-Si-void@SiO2 by heat-treatment. Then, the acid precipitation process was used to coat the lignin on the surface of the multi-Si-void@SiO2 structure via the hydrogen-bond interaction, and after in-situ carbonization, multi-Si-void@SiO2@lignin-based carbon composite was formed. The optimum electrode material maintained the specific capacity of 759 mA h g-1 after 1300 cycles at the current density of 1.0 A/g. The great electrochemical performance is attributed to the four components of voids, Si, SiO2 and lignin-based carbon (LC) performing their duties and synergistically, making the electrode exhibit excellent cycle stability. After long-term charge/discharge process, SiO2 layer is fully activated to construct Li4SiO4 and Li2O "high-speed channels", providing a "bridge" for Si to connect with the outside. And the reserved space inside the structure is conducive to the free expansion and contraction of Si. Meanwhile, lignin, as a cheap and renewable carbon source, greatly reduces the cost of material preparation. Consequently, the multi-Si-void@SiO2@LC composite presented here provides a feasible strategy for the large-scale development of highly stable Si-based anodes.