Disodium Terephthalate Ultrafine Fibers as High Performance Anode Material for Sodium-Ion Batteries under High Current Density Conditions

An aqueous mixture of poly(vinyl alcohol) (M.W. ∼ 8.9 × 104–9.8 × 104 g mol−1, 14% w/v) and disodium terephthalate (Na2TP) powders (6% w/v) was electrospun at 14 kV with a fiber collection distance and a feed rate of 12 cm and 0.5 mL h−1. Then, the obtained fibers were calcined at 350°C with a heating rate of 1°C min−1 under air for 7 h. Diameters of hollow Na2TP fibers, composed of grains with sizes of 76 ± 27 nm, are 189 ± 32 nm. Na2TP fibers are composed of ∼16% w/w Na2CO3. Na2TP structure is orthorhombic and can be indexed in a space group of Pbc21. Degree of crystallinity of Na2TP fibers is less than that of Na2TP powders. Galvanostatic curves display stable reversible capacities of Na2TP powders and fibers at ∼140 mA h g−1 and ∼110 mA h g−1, respectively, after 50 cycles at 25.5 mA g−1. On the other hand, at 255 mA g−1 and after 100 cycles, those of the powders and the fibers are ∼48 mA h g−1 and ∼70 mA h g−1, respectively. Thus, the eco-friendly Na2TP fibers are potentially used as anode materials of sodium-ion batteries under high current density.