Anionic redox reaction triggered by trivalent Al<sup>3+</sup> in P3-Na<sub>0.65</sub>Mn<sub>0.5</sub>Al<sub>0.5</sub>O<sub>2</sub>
Ding-Ren Shi, Tian Wang, Zulipiya Shadike, Lu Ma, Xiao‐Qing Yang, Shufen Chu, Zhiwei Zhao, Zhangquan Peng, Zheng‐Wen Fu
Abstract
P3-Na0.65Mn0.5Al0.5O2 (NMAO) has been synthesized and studied as a cathode for sodium batteries, and shows anionic redox reaction (ARR) and exhibits a first charging capacity of ∼110 mA h g-1. The electrochemical mechanism of NMAO was comprehensively investigated by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and density functional theory (DFT) calculations. The reversible oxygen redox behaviour is triggered by Al3+ through oxygen quasi non-bonding states generated by the relatively ionic interaction of Al and O. Furthermore, the presence of Al3+ can suppress oxygen loss in ARR. This work provides new insights into the design and mechanism of anionic redox active cathode materials.