Preparation of SiO @TiO2@N-doped carbon composite using chitin as carbon precursor for high-performance lithium storage

Abstract SiOx is regarded as a promising anode material for the next-generation lithium-ion batteries (LIBs) because of its high theoretical capacity. In order to relieve the volume variation and enhance the electronic and ionic conductivity, a SiOx@TiO2@N-doped carbon (NC) composite is prepared using biopolymer chitin as carbon precursor. The TiO2 coating layer shields the SiOx in the alkaline chitin solution, enabling the homogeneous and stable dispersion of the SiOx during the synthesis process. After emulsion, freeze-drying, and carbonization, the SiOx@TiO2@NC composite is obtained. The dual-confinement of TiO2 and NC effectively buffers the volume variation of SiOx and enhances the electronic/ionic conductivity. The enhanced structural integrity and conductivity guarantee the superior rate capability and the stable long-term cyclability of the SiOx@TiO2@NC composite. After 650 cycles at 0.5 and 1 A g−1, SiOx@TiO2@NC maintains reversible capacities of 633 and 540 mA h g−1, showing capacity retentions of 92.3% and 96.9%, respectively. After 100 cycles at 0.5 C, the assembled SiOx@TiO2@NC//LiFePO4 full cells can retain a discharge capacity of 121 mA h g−1, maintaining 90% of the third capacity. This work provides a chance for the industrial application of biopolymer chitin in LIBs, and may alleviate the pressure of environmental protection.