Electrospun Silicon Micropowders and Titanium Dioxide Composite Nanofibers for Advanced Lithium Ion Batteries

Lithium ion batteries (LIBs) have been widely viewed as one of the most promising green technologies in the field of energy storage. However, high cost and limited electrochemical performance seriously limits their broader applications. Titanium dioxide (TiO 2 ) possesses the advantages of low-cost and structural stability. But its theoretical gravimetric capacity is low (330 mAh g -1 ), compared to that of Si (4,200 mAh g -1 ). Unfortunately, the structure of Si is unstable during the charging/discharging process, mainly due to unstable surface electrolyte interphase and huge volume variation ( ~ 400%) during cycling. Herein, structurally unstable & high capacity silicon micro-powders and template materials were wrapped in structurally stable & low capacity titanium oxide nanofibers using an electro-spinning technique combined with sol-gel chemistry. The removal of the template materials results in the formation of TiO 2 /Si void structure, thus allowing the silicon expansion by providing extra free volume. The morphology and elemental composition of these fibers were analyzed by scanning electron microscope attached with an energy dispersive X-ray analyzer, thermogravimetry analysis, and X-ray diffractometer. These nanofibers were employed as anode materials to fabricate LIB half cells, which demonstrated an excellent electrochemical performance, including a high capacity of 580 mAh g -1  and a high cycle life (>80% capacity can be maintained after 100 cycles). The usage of silicon micro-powders instead of Si nanocrystals can significantly reduce the LIB fabrication cost, thus paving a solid way for their practical applications.