Cobalt-induced charge redistribution and lattice distortion enable accelerated sodium storage kinetics in...

Cation substitution provides an effective route to regulate electrochemical kinetics in NASICON-type cathodes, yet the interplay between electronic structure and ion transport remains insufficiently clarified. Here, cobalt substitution is introduced into Na₃V₂(PO₄)₃ to simultaneously tailor electronic states and sodium diffusion pathways. The incorporation of Co²⁺ may induce local structural perturbation within the NASICON framework, leading to enhanced metal‑oxygen covalency and a continuous distribution of electronic states near the Fermi level. This modification promotes charge-transfer kinetics. Concurrently, the induced lattice distortion lowers the Na⁺ migration energy barrier from 0.36 to 0.21 eV, enabling faster ion transport. The optimized Na₃V_1.88Co_0.12(PO₄)₃ exhibits a discharge capacity of 96.04 mAh g^-1 at 2C (1C = 117 mAh g^-1) and maintains 91.34% of its capacity after 1000 cycles. A practical NVCP-15||hard carbon full cell demonstrates promising sodium-ion storage performance, achieving an initial discharge capacity of 73.58 mAh g^-1, stable cycling with 78.7% capacity retention after 300 cycles at 1C, and robust rate capability with 41.2 mAh g^-1 retained at 5C. This study establishes a coupling mechanism between lattice distortion, electronic reconstruction, and ion transport, providing a design strategy for high-performance NASICON cathodes.