A nanotubular TiO2/SiOx/Si composite derived from cellulosic cotton as an anode material for lithium-ion batteries with enhanced electrochemical performance

A TiO2/SiOx/Si composite derived from cellulosic cotton as the structural template was biomimetically synthesized. Modified sol-gel deposition processes were performed to coat each cellulose nanofiber with a SiO2 thin gel layer, followed by layer-by-layer self-assembly processes to form an external TiO2 coating with controllable thickness. The resulted matter was calcined in air to obtain the TiO2/SiO2 composite, which was successively put in N-2 atmosphere and treated with magnesiothermic reduction reaction, resulting in the final TiO2/SiOx/Si composite. The composite possessed a typical hierarchical three-dimensional (3D) nanotubular network microstructure precisely inherited from the cellulosic cotton template, and each nanotube had a core-shell nanostructure with Si-based matters as the core and TiO2 coating as the shell. Compared with the bare nanotubular SiOx/Si material, the TiO2/SiOx/Si composite showed a highly enhanced electrochemical performance as an anode material for lithium-ion batteries (LIBs), delivering an initial discharge capacity of 2370 mAh g(-1) at a current density of 0.2 A g(-1) (an initial Coulombic efficiency of 56.4%), a reversible capacity of 682 mAh g(-1) after 100 discharge/charge cycles, and a discharge capacity of 241 mAh g(-1) at a high current density of 2.0 A g(-1). The excellent specific capacity, cycling stability and rate capability are ascribed to the synergistic effect of the unique 3D porous nanotubular network structure and the uniform TiO2 coating layer, which accommodates the volume variation of Si-based components during cycling, offers sufficient ion transport pathways and improves the electron transfer efficiency. This work provides a facile biomass-based strategy for fabrication of metal oxide/Si composites with well-defined microstructures that exhibit significant potential as anode materials for LIBs.