Production of V‐Doped P2‐type Na0.67Mn0.5Fe0.43Al0.07O2 Cathodes and Investigation of Na‐Ion Full Cells Performance

The Na 0.67 Mn 0.5− x V x Fe 0.43 Al 0.07 O 2 ( x = 0–0.1) samples are successfully produced and their structural properties are investigated by common techniques. The highest surface area is found as 4.94 m 2 g −1 for x = 0.04 V by the Brunauer–Elmet–Teller analysis. According to X‐ray photoelectron spectroscopy of x = 0.04 V‐doped sample,V 4+, and V 5+ ions are formed in the structure. The main phase is observed as P63/mmc symmetry with an impurity phase of V 6 O 13 for x ≥ 0.06 . According to the CV analysis, while the redox voltage decreases for the Mn 3+ /Mn 4+ , the intensity of the peaks of Fe 2+ /Fe 3+ redox reaction decreases. While the best capacity value of the half cells at C/3‐rate is obtained as 171 mAh g −1 for x = 0.04, the lowest capacity fade is found for x = 0.08 . It is mentioned the V 6 O 13 may contribute to the electrochemical process . The galvanostatic tests are investigated for the voltage windows of 3.5–1.5, 4–1.5, 4–2.5, 4–2, and 4–2.5 V and it is seen that the battery cells for 3.5–1.5 V have the best capacity fade (6%) among the others. The Na 0.67 Mn 0.46 V 0.04 Fe 0.43 Al 0.07 O 2 / hard carbon is used for the full cells with presodiated anode and the first capacity value of the full cell is obtained as 80.2 mAh g −1 for C/2‐rate.