Preparation And Performance Study Of Phosphorous-Doped SnO_x/C Nanofibers For Lithium Ion Batterie Anode Materialas

Significant progress in lithium-ion battery technology has been made in the past decade. However, so far, long-term performance targets for all-electric vehicles have not been met. The key to the success of development of novel and advanced rechargeable lithium-ion batteries (LIBs) are the materials. Tin-based materials have been widely recognized as appealing and competitive anode candidates for LIBs because of their intriguing features, including high theoretical capacities, safe working potentials, considerable cost-effectiveness and environmental benignity. However, tin-based materials have abominable disadvantages for practical use due to the dramatic volumetric change during cycling process. Dispersed SnOx into a carbon matrix is considered to be a very effective way to improve the reversible capacity and cycle life of SnOx/C electrode, But its still remains the unsatisfactory circulating capacity, lower initial Coulomb efficiency and shortened cycle life resulted from the poor conductivity and serious aggregation of tin-based materials. Doping the carbon and tin-based materials with heteroatoms has been researched and demonstrated to be an effective method to improve the electrochemical performance of SnOx/C electrode.Phosphorus-doped carbon nanotibers (P/C) and Phosphorus-doped SnOx/C nanotibers composite materials (P-SnOx/CNFs) with a varied amount of P-doping content have been successfully fabricated by electrospinning technique and subsequent thermal treatment. Physical characterization including SEM, EDX, TEM, Raman, XRD, XPS and electrochemical testing were used to characterize and investigate the morphology, composition, structure, crystallization behavior and electrochemical performance. For P/C materials, the results exhibit that phosphorus doping can induce a large number of defects sites and increase the degree of disorder of carbon materials. P-doped CNFs sample with the2.5wt%phosphoric acid exhibits a good specific capacity (581.3mAh·g-1) and rate performance. For P-SnOx/CNFs materials, P-doping can greatly enhance the reversible capacity and improve the cycling stability and rate capability of the SnOx/CNFs electrode. An P-SnOx/CNFs sample with the atomic ratio of P:Sn=0.25:1exhibits a greatly enhanced reversible capacity (676mAh·g-1after100cycles at200mA·g-1) compared to the pristine SnOx/CNFs electrode (565.7mAh·g-1) and show excellent cycling stability. Furthermore, at2000mA·g-1rate the composite can still obtain288mAh·g-1discharge specific capacity, moreover, its morphology and structure still maintain good and integrity after circulation. This outstanding enhancement in electrochemical performance of P-SnOx/CNFs is mainly originated from the P-doping effects such as the change of band structure of SnOx, inducement of a stable structure protection for tin particles, and the enhancement of lithium ion diffusion coefficient and electron kinetics of electrode materials.