Boron-Doping Modification Of SnO_x/CNFs Composites As High Performance Lithium Ion Batterie Anode Materialas

Although lithium-ion batteries (LIBs) have been well used in daily life, they have limitations in all-electric vehicles. The key to successful development of more excellent performance LIBs is the electrode materials.Recently, tin-based materials have been made for research focus due to their high specific capacity and low cost, but tin-based materials have the fatal drawback of dramatic volumetric change during lithium alloying and de-alloying process, resulting inelectrical performance fading. Compositing tin-based active material with carbon matrix (SnOx/CNFs) is a very effective way to alleviate volume change in cycling. However, the nanocomposite still remains the unsatisfactory electrical performance, including low reversible capacityand shortened cycle life. Doping heteroatoms into SnOx/CNFs composite materials have been reported be helpful to improve the electrochemical performance.Boron-doped SnO,/CNFs composite materials (B-SnOx/CNFs) with different carbonized temperature and a varied amount of B-doping content have been successfulry fabricated by electrospinning technique and subsequent thermal treatment. In this study, scanning electron microscope, high resolution transmission electron microscopy, X-Ray diffraction, thermogravimetry, Raman, X-ray photoelectron spectroscopy and electrochemical testing for characterization of structure, composition and electrochemical performance were used to find the best carbonization temperature and boric acid amount. Meanwhile, the principle of doping boron has been researched. The results show that the increase of carbonization temperature and boron amount have arised graphitization of composites materials. B-SnO,/CNFs with carbonization temperature of 700℃ exhibits the best electrical performance, while sample with carbonization temperature of 900℃ exhibits the worst. The 1.5B-Snx/CNFs (the mass ratio of boric acid versus polyacrylonitrile is 1.5%) with carbonization temperature of 700℃exhibits the best capacity of 670.2mAhg-1 at the current density of 200 mA g-1 after 100 cycles, which is about 20% higher than that of undoped boron composite (565.7 mAh·g-1). More importantly, the 1.5B-SnOx/CNFs electrode shows a high capacity of 300 mAh g-1 at 2000 mA g-1, with keeping good fiber morphology after 100cycles. The improvement of electrochemical performance is attributed to the special network structure of non-bridging oxygens (NBO:B-O...Sn) in the matix material, which can buffer the large volume change of SnOx and prohibit the aggregation of Sn nanoparticles during the charge-discharge cycles.