Critical SiO2 nanolayers for improving corrosion resistance and lithium storage performances of core-shell nano-Si/C composites

Core-shell nano-Si/C composites are promising anodes for Li-ion batteries due to the unique structures of encapsulating Si nanoparticles in highly conducting carbon matrixes. However, such single carbon shells coated Si nanostructures still suffer from LiPF6-based electrolyte corrosions on the Si cores, limiting the lithium storage capability. To improve corrosion resistance, core dual-shell nano-Si@SiO2/C composites are synthesized by sequential coatings with similar to 2 nm of SiO2 interlayers followed by similar to 6 nm of outermost carbon shells. The effects of such SiO2 interlayers on electrolyte corrosion resistance and lithium storage performances of the achieved nano-Si@SiO2/C composites are investigated for the first time. The extra SiO2 nanolayers effectively protect nano-Si against LiPF6-based battery electrolyte corrosions, i.e., the formation of layers containing the insulating Li2SiF6 on Si cores, as confirmed by the techniques of XRD and TEM. Compared to the core-shell nano-Si/C, the unique core dual-shell nano-Si@SiO2/C electrodes (with similar to 2 nm of SiO2 interlayers) exhibit remarkably improved lithium storage performances (similar to 1369 mAh g(-1) after 50 cycles at 50 mA g(-1)), showing similar to 45% higher reversible capacities. This can be ascribed to the unique core dual-shell nanostructures of the SiO2 interlayers and outermost carbon nanolayers, better managing volume variations and protecting nano-Si cores against electrolyte corrosions. This study helps us further understand the critical roles of SiO2 nanolayers on corrosion resistance and lithium storage performances of core-shell Si/C nanostructures. (C) 2018 Elsevier B.V. All rights reserved.