Synthesis of Free‐Standing Tin Phosphide/Phosphate Carbon Composite Nanofibers as Anodes for Lithium‐Ion Batteries with Improved Low‐Temperature Performance

Abstract

AbstractFree‐standing tin phosphide/phosphate carbon composite nanofiber mats of unique nanostructure have been successfully synthesized by electrospinning and partially reducing the phosphate‐containing precursors. An unusual effect of the Sn:P molar ratio in the precursor solution on the structure and physical‐electrochemical properties of the material is observed. Physical characterizations, including X‐Ray diffraction (XRD), Raman spectroscopy, X‐Ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), confirm the formation of tin phosphide/phosphate nanoparticles of P‐rich inner SnxP layer and Sn‐rich outer layer uniformly distributed within carbon nanofiber matrix when the Sn:P=1:1. The prepared material is tested as an anode material for lithium‐ion batteries and it retains 1141 mAh g−1 charge capacity after 300 cycles at a current density of 250 mA g−1 with almost 100% Coulombic efficiency at room temperature. Furthermore, it demonstrates six times higher capacity (846 mAh g−1) at 0 °C compared to a commercial graphite anode and stable cyclability at −20 °C and 50 mA g−1. Post‐mortem ex situ XRD and SEM analyses confirm the structural stability of the designed material and the formation of a uniform stable solid electrolyte interphase layer even after 100 cycles at 50 mA g−1.