Tunable Synthesis of Hierarchical Yolk/Double-Shelled SiO_x@TiO₂@C Nanospheres for High-Performance Lithium-Ion Batteries

This work reports the preparation of unique hierarchical yolk/double-shelled SiOx@TiO2@C nanospheres with different voids by a facile sol-gel method combined with carbon coating. In the preparation process, SiOx nanosphere is used as a hard template. Etch time of SiOx yolk affects the morphology and electrochemical performance of SiOx@TiO2@C. With the increase in etch time, the yolk/double-shelled SiOx@TiO2@C with 15 and 30 nm voids and the TiO2@C hollow nanospheres are obtained. The yolk/double-shelled SiOx@TiO2@C nanospheres exhibit remarkable lithium-ion battery performance as anodes, including high lithium storage capacity, outstanding rate capability, good reversibility, and stable long-term cycle life. The unique structure can accommodate the large volume change of the SiOx yolk, provide a unique buffering space for the discharge/charge processes, improve the structural stability of the electrode material during repeated Li+ intercalation/deintercalation processes, and enhance the cycling stability. The SiOx@TiO2@C with 30 nm void space exhibits a high discharge specific capacity of approximate to 1195.4 mA h g(-1) at the current density of 0.1 A g(-1) after 300 cycles and approximate to 701.1 mA h g(-1) at 1 A g(-1) for over 800 cycles. These results suggest that the proposed particle architecture is promising and may have potential applications in improving various high performance anode materials.