Development and characterization of cathode materials for next-generation rechargeable sodium-ion batteries

In this thesis study, the effect of Ni doping on the battery performance of Mn-Fe based cathodes used in sodium ion batteries was investigated to improve their battery performance. Cathode materials of Na0.67Mn0.5-xNixFe0.43Al0.07O2 and Na0.67Mn0.5-xNixFe0.43Ti0.07O2 were prepared for x = 0.0 - 0.5 range using the solid-state reaction method. The chemical amounts used in each composition were calculated considering stoichiometric ratios and subjected to heat treatment at 900°C for 6 hours. For the structural characterization of the produced cathode materials, SEM, XRD, FTIR, RAMAN, XPS, and BET analyses were performed. For the electrochemical performance measurements, Electrical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge measurements, and C-rate measurements were conducted at room temperature. As a result of the measurements, the best battery performances after 100 cycles were observed for Na0.67Mn0.44Ni0.06Fe0.43Al0.07O2 (181 mAh/g, 55.49% capacity retention rate) and Na0.67Mn0.44Ni0.06Fe0.43Ti0.07O2 (184 mAh/g, 62.16% capacity retention rate) compositions indicating x=0.06 as the optimum Ni doping concentration for both systems.