Electrochemical and Magnetic Properties of Electrospun SrTi_1−xFe_xO₃ (x = 0, 0.05 and 0.10) Nanofibers for Anodes of Li-Ion Batteries

SrTi_1−xFe_xO₃ (x = 0, 0.05 and 0.1) nanofibers (NFs) were fabricated by electrospinning technique. As prepared products were calcined at 800 ^∘ C in argon atmosphere for 3 h to obtain a perovskite phase. The crystal structure and morphology of samples were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical and magnetic properties of calcined NFs were studied using a potentiostat/galvanostat electrochemical cell system and vibrating sample magnetometer (VSM), respectively. XRD results showed the cubic perovskite structure of calcined samples with the diameter estimated by TEM in the range of 137.4–141.3 nm SEM micrographs revealed the linkage of crystalline grains in NFs of porous and rough surfaces. Electrochemical properties performed on coin-cell-type Li-ion batteries (LIBs) with calcined SrTi_1−xFe_xO₃ (x = 0.05 and 0.10) NF-based anodes showed a significant increase of the specific capacity from 305 to 431 mAh/g for the first cycle with the reversible values of 100 and 130 mAh/g, respectively. VSM measurements at room temperature (RT) indicated that calcined SrTiO₃ NFs exhibited paramagnetic (PM) behavior, while calcined SrTi_1−xFe_xO₃ NFs displayed ferromagnetic (FM) behavior at RT with the increase of unsaturated magnetization at 10 kOe from 0.46 to 0.82 emu/g for samples with x = 0.05 and 0.10, respectively. The observed FM behavior in calcined SrTi_1−xFe_xO₃ (x = 0.05 and 0.1) NFs was suggested to originate from the face center exchange (FCE) mechanism owing to Fe³⁺ –Vo–Fe³⁺ couplings.