Modification Of Copper Doping On Tin Oxides/Carbon Nanofibers Composite For Lithium-Ion Battery Anode Materials

For a long time, graphite has been used in commercial anode material for lithium ion batteries. However, due to the low theoretical specific capacity of graphite (372mAh·g-1), it is unable to meet the increasing demand nowadays. In order to adapt to the trend of electronic equipment becoming more and more lightweight and miniaturization, the development of lithium ion batteries of high capacity, high energy density has become animminent task. Tin-based materials is considered to be an ideal substitute for its high specific capacity, but the huge volume expansion during cycling leads to the pulverization of electrode. As a result, the cycle life of the electrode is poor. Moreover, the conductivity of tin oxides leads to poor rate performance, making the the practical application limited.In this study, amorphous Cu-doped SnOx/CNFs composite webs with different metail, diverse amount of Cu-doping, varied carbonization temperature and time were prepared by electrospinning technique and subsequent thermal treatment to observe the changes of morphology and the electrochemical properties and select the anode material with the best electrochemical performance. An optimal condition of Cu-doped SnOx/CNFs anode (SnOx-20%Cu/CNFs) under the carbonanization of 700℃ for 1h was obtained. Tin oxide and copper oxide are uniformly distributed in the carbon nano fiber with smooth surface and no particles loading on. Tin oxide and copper oxide exist in an amorphous form. At a current density of 200mA g-1, the reversible capacity of SnOx-20%Cu/CNFs is 743 mAh g-1, higher than that of SnOx/CNFs with the capacity of 652 mAh g-1. When cycled at 5A g-1, the capacity of 347 mAh g-1 was obtained in SnOx-20%Cu/CNFs, increased by 60% than that of SnOx/CNFs (214mAh g-1). Moreover, after a long-term cycle of 1000 at current density of 2 A g-1, the capacity of 411 mAh g-1 was still retained in SnOx-20%Cu/CNFs, much improved than that of SnOx/CNFs (244mAh g-1). The reversible capacity, rate capability and long cycle of such a high performance are mainly attributed to the following aspects. The formation of Cu nanoparticles dispersed in a lithiamatrix (Li2O), inhibits the aggregation of Sn particles in the following alloying-dealloying cycling. Meanwhile, the presence of Cu nanoparticles can not only improve the charge transfer ability of Li+ and the conductivity of the electrode, but also enhance the reversibility of Sn back to SnOx in the recharge process.