Cu/Zn dual-site-specific co-doping for stabilizing P2-layered oxide cathodes towards advanced sodium-ion batteries

P2-type layered oxide cathode materials suffer from severe challenges for practical application in sodium-ion batteries (SIBs), such as irreversible detrimental phase transitions, sluggish Na + diffusion kinetics, and poor air stability. To address these issues, a dual-site synergistic doping strategy is rationally designed and implemented in this work, enabling the successful synthesis of the P2-Na 0.65 Ni 0.09 Fe 0.16 Mn 0.67 Cu 0.05 Zn 0.05 O 2 (NFMCZO) cathode material. Atom-level energy-dispersive X‑ray spectroscopy (EDS) mapping directly confirms the precise dual-site occupation of Cu/Zn. Specifically, Zn 2+ occupies the Na sites to form a “pillar effect” to stabilize the interlayer structure, prevent the intrusion of H 2 O and CO 2 , and hinder transition metal (TM) migration. Meanwhile, both Zn 2+ and Cu 2+ are doped into the TM layer, which strengthens the TM–O bonds, avoids cracks, and expands the Na + transport pathways. Ex-situ X-ray diffraction (XRD) results further demonstrate that the detrimental P2-O2 phase transition is effectively suppressed during repeated charge-discharge cycling. Benefiting from the synergistic doping effect, the NFMCZO cathode shows excellent electrochemical performance. It achieves a capacity retention of 75.16% after 200 cycles at 1 C, along with outstanding rate capability (78.36 mAh g −1 at 5 C) and remarkable air stability (almost no structural change after 30 days of exposure). This work provides feasible design insights into the development of SIBs with long cycling life and excellent air stability, which can be extended to the construction of more stable layered oxide compounds and further promote the enhancement of their electrochemical performances. Cu/Zn dual-site-specific synergistic doping stabilizes P2-type layered oxide cathodes, in which Zn acts as an interlayer pillar to expand the Na + transport pathway; meanwhile, both Cu and Zn strengthen TM–O bonds to inhibit phase transitions, thus enabling fast Na + diffusion, excellent cycling stability, and exceptional air stability. Download: Download high-res image (195KB) Download: Download full-size image