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

Abstract

The Na0.67Mn0.5−xVxFe0.43Al0.07O2 (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 m2 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,V4+, and V5+ ions are formed in the structure. The main phase is observed as P63/mmc symmetry with an impurity phase of V6O13 for x ≥ 0.06 . According to the CV analysis, while the redox voltage decreases for the Mn3+/Mn4+ , the intensity of the peaks of Fe2+/Fe3+ 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 V6O13 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 Na0.67Mn0.46V0.04Fe0.43Al0.07O2/ 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.