Preparation And Characterization Of Core-Shell Structured TiO_x/C@SnO_x/C Nanofibers As Anode Materials For Lithium-Ion Batteries

Lithium-ion batteries (LIBs) as the most promising energy storage technology in this century, have been widely used in electronics, electric vehicles and other other energy storage devices. However, the LIBs face the bottlenecks in increasing the energy density, and little improvement on the high power charge-discharge performance. The troules limited the power LIBs application. Inorder to solve these issues and to make the LIBs taking more market share of electric vehicles, many scientists have developed mew type electrode materias of LIBs. Anode materias as an important part of the LIBs, they achieve great progress.Sn-based anode materials have a high Lithium storage ability. The capacity (Sn990mAh·g-1、SnO2781mAh·g-1) is much higher than the graphite using in commerce (372mAh·g-1), which is good to increase the energy density of LIBs. But it has to face the pulverization caused by large volume expansion (>300%) which can fade the electrochemical performance. Ti-based anode materials show good abilities to improve the rate and safety performance because of its structure stability (<4%), Li+diffusion coefficient and high Li+embedded potiental (1.7V, vs. Li+/Li).In this work, SnOx/CNFs and TiOx/CNFs anode materials were fabricated by electrospinning method and following heat treatment. After30discharge-charge cycles, the SnOx/CNFs with25.8wt.%of Sn has the highest reversible capacity576.6mAh·g-1, much bigger than the pure amorphous CNFs. With Ti content and crystallinity increased in TiOx/CNFs, the capacity decreased to281mAh·g-1.The core-shell structured TiOx/C@SnOx/CNFs anode materials were fabricated by coaxial electrospinning method and following heat treatment. The TiOx nanoparticles were located in the core area, and the SnOx were distributed in the carbon nanofibers uniformly. Due to the synergy effect of SnOx, TiOx, and the core-shell structured carbon nanofibers, the TiOx/C@SnOx/CNFs present excellent electrochemical perforamnce. The sample with5.6wt.%of Ti and13.1wt.%of Sn present593mAh·g-1after100cycle times at a current density of100mA·g-1, and high initial coulombic efficiency76.4%. The rate performance is also outstanding. Its capacity is up to270mAh·g-1，two times capacity of SnOx/CNFs at2000mA·g-1.