Dynamic switching of Na⁺ transport via interphase channels of P2/O3 biphasic cathodes towards fast-charging sodium-ion batteries

The precise control of intergrowth structure is pivotal for enhancing structural stability of layered oxide cathodes due to the interlocking effect. However, the underlying kinetic mechanism governing the fast-charging ability of intergrowth structures remains underexplored, limiting the practical application of sodium-ion batteries (SIBs). Herein, we propose a dynamic switching kinetics mechanism and the corresponding triggering conditions via designing P2/O3 intergrowth structure, and confirm the rationality of this mechanism by comprehensive characterizations. Specifically, the rate-determining step of Na⁺ diffusion is dominated by kinetically more favorable diffusion between P2/O3 phases in the intergrowth structure. That is, the P2/O3 interface as unique dispersion region allows Na⁺ to autonomously choose migration path during Na⁺ (de)intercalation, ensuring that Na⁺ migration always occupies a kinetic advantage. Moreover, the interlocking effect in the P2/O3 intergrowth structure effectively mitigates lattice distortions, thereby enhancing the structural stability of P2/O3 biphasic cathodes. Consequently, the as-designed biphasic P2/O3-Na_0.8Ni_0.2Fe_0.2Mn_0.5Mg_0.1O₂ cathode exhibits a high initial capacity of 176.1 mAh g⁻¹ at 1 C and impressive rate performance of 85.7 mAh g⁻¹ at 10 C. This work proposes an unconventional kinetic mechanism in P2/O3 intergrowth structure and highlights the necessity of designing composite structure materials for high-performance and fast-charging SIBs.