Layered oxide has been regarded as one of the most promising cathode materials for sodium-ion batteries (SIBs) owing to its high theoretical energy density. However, irreversible phase transitions at high voltages, lattice oxygen redox (O2−/O2n−, 1 ≤ n ≤ 3), and sluggish Na+ kinetics still hinder its practical application intrinsically. Herein, we manipulate the intra- and interlayer structure of layered oxide cathodes by hierarchically employing a modified gallic acid (GA) polyphenol-metal complex with multi-elements co-regulated (Ca, Li, and Cu). Benefitted from self-assembly of GA, the as-prepared GA-Na0.61Ni0.23Mn0.67Ca0.05Li0.05Cu0.05O2 (GA-NNM-CaLiCu) cathode reveals reduced oxygen vacancies (OVs) and enhanced crystallinity. The anchoring of interlayered Ca2+ generates a reinforced “pillar” effect and the strategically migration of Li+ into the transition-metal (TM) layer mitigates electrostatic repulsion. The redox active Cu2+ strengthens the interlayered Ni/Mn-O bonds, facilitating negligible structural strain under an extended voltage window (2-4.3 V). As a result, the GA-NNM-CaLiCu cathode delivers 144.8 mAh g-1 at 0.1 C and retains 85.2% of its capacity after 1000 cycles at 20 C. This work provides a comprehensive approach to improve structural stability and reaction kinetics of P2-type Na0.67Ni0.33Mn0.67O2 (NNM) cathodes in SIBs.
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