• Li, Z.; Yu, Y.; Zhang, T.; Wong, D.; Schulz, C.; Zhang, N.; Ning, D.; Li, Q.; Zhang, J.; Liu, X.: Tuning Electronegativity-Difference Configuration to Construct Non-Bonded O 2p Orbitals for Reversible Anionic Redox in O3-Type Cathode. Advanced Functional Materials early view (2024), p. 2404797


How to tune the activity and reversibility of oxygen anion redox (OAR) is a critical issue for O3-type sodium-ion battery (SIB) cathodes. Herein, the key role of electronegativity-difference configuration on the activation of OAR is find out, and further tune electronegativity-difference configuration with La incorporation to construct non-bonded O 2p orbitals and achieve the reversible anionic redox in O3-type NaMn1/3Fe1/3Ni1/3O2. Owing to the special extranuclear electronic structure of La3+ [Xe], the La electron cloud is difficult to be disturbed by the O electron cloud, and some O electrons do not participate in the formation of ionic bonds, thus retaining the non-bonded electrons of O 2p and activating OAR. Moreover, La3+ doping also decreases the Coulomb force between Na+ and O2− favoring Na+ migration as well as strengthening the La─O bonds inhibiting the irreversible phase transition. La2O3 coating layer also plays a role on inhibiting the reaction between molecular oxygen and the electrolyte, and making OAR reversible. After modification, the cycling stability is significantly improved (86.9% vs 27.3%@2C@200cycles; 90.8% vs 52.9%@5C@300 cycles). This study presents some insights on OAR activation mechanism and offers a facile strategy to improve the activity and reversibility of OAR for designing high performance SIBs cathodes.