Anionic redox reaction triggered by trivalent Al3+ in P3-Na0.65Mn0.5Al0.5O2

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 similar to 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.

Automated summary

This study comprehensively investigated the electrochemical mechanism of the cathode material NMAO for sodium ion batteries through experimental and computational methods, revealing that the reversible oxygen redox behavior is triggered by Al3+ through the oxygen quasi non-bonding states. The presence of Al3+ is found to suppress oxygen loss in the anionic redox reaction, providing new insights into the design and mechanism of anionic redox active cathode materials.