Multidimensional structural regulation of layered oxide cathodes for sodium-ion batteries: from microstructural...

P2-type layered oxides are considered promising cathode materials for sodium-ion batteries owing to their high capacity potential and suitable operating voltage. However, their practical application is still limited by sluggish Na⁺ transport kinetics and insufficient long-term cycling stability. Herein, we propose a macro-to-micro structural regulation strategy that links microstructural design and facet regulation with local Na⁺/vacancy disordering. As a result, primary particles with a high proportion of exposed {010} active facets are closely packed and further assembled into a dense and uniform spherical secondary-particle architecture, thereby improving interparticle contact and preserving structural integrity. Meanwhile, local Na⁺/vacancy disordering facilitates Na⁺ extraction/insertion and improves Na⁺ transport kinetics, contributing to smoother charge/discharge profiles. Benefiting from this strategy, the P2-Na_2/3Ni_0.3Mn_0.7O₂ cathode prepared at 950 °C exhibits a high capacity retention of 94.06% after 300 cycles at 1C while maintaining a well-preserved particle morphology after cycling. Furthermore, selected-area electron diffraction, in situ X-ray diffraction, and focused ion beam analyses demonstrate that the optimized cathode possesses a locally disordered Na⁺/vacancy configuration, undergoes reversible P2 structural evolution, and maintains well-preserved particle integrity during cycling. This work highlights the synergistic correlation among secondary-particle architecture, primary-particle facet regulation, and local Na⁺/vacancy disordering, providing new insights into the rational design of high-performance P2-type layered oxide cathodes with enhanced Na⁺ transport kinetics and structural stability.