Electrochemical Conversion of Silica Nanoparticles to Silicon Nanotubes in Molten Salts: Implications for High-Performance Lithium-Ion Battery Anode
Fan Wang, Yongsong Ma, Peng Li, Chuang Peng, Huayi Yin, Wei Li, Dihua Wang
Abstract
Understanding the material formation mechanism is critical to guide the material synthesis and exploitation. Herein, we reveal a different conversion mechanism of SiO2 particles to Si nanotubes (SNTs) in the molten salt electrolysis. Unlike conventional strategies employing templates and/or catalysts, the one-step electrochemical synthesis is template- and catalyst-free, which process involves lamination, exfoliation, and reduction. Specifically, SiO2 particles are first converted into layer-structured CaSiO3, from which CaO and O2– are subsequently extracted, causing the collapse of the layer structure and forming SiOx (0 < x < 2) layers. The newly formed SiOx layers are finally deeply reduced into SNTs. Besides, the morphology of silicon-based nanostructures can be controlled via altering the applied voltage between a SiO2 cathode and a graphite anode. In addition, the electrolytic SNTs show enhanced lithium-storage performances, such as a high specific capacity (2485 mAh g–1 at 0.2 A g–1) and an excellent rate capability (1362 mAh g–1 at 5 A g–1), which is benefited from the tube structure that can buffer the volume variation of Si. Overall, the revealed conversion mechanism will shed light on designing advanced Si-based nanomaterials for various applications.