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.