Decoupling TM–O Antibonding via Targeted Orbital Engineering Enables High‐Voltage and Long‐Life Sodium Polyanionic Cathodes

ABSTRACT

Polyanionic cathode materials based on Mn/V redox couples offer high‐voltage plateaux and high theoretical energy density for sodium‐ion batteries (SIBs). However, they suffer from severe degradation in rate capability and cycling stability under high‐voltage, whose microscopic origin remains elusive on the electronic‐level. Herein, we reveal the strong coupling between Mn/V–O antibonding orbitals at elevated voltages induces significant lattice strain, leading to kinetic hysteresis. Thus, we propose a targeted orbital engineering regulation strategy aiming to disentangle the strong coupling among (TM–O)* orbitals. By introducing Ti ⁴⁺ (3d ⁰ ) and Fe ³⁺ (3d ⁵ ) as the stable electronic configurations, and electron‐donating Si, we modulate (TM–O)* orbital occupancy at the electronic level, markedly alleviating structural stress and stabilizing Na ⁺ diffusion pathways. The optimized Na ₄ Mn _0.7 V _0.7 Ti _0.4 Fe _0.2 (PO ₄ ) _2.9 (SiO ₄ ) _0.1 cathode delivers high energy density (415.03 Wh/kg) and exceptional long‐cycle performance, retaining 80.3% capacity after 8,000 cycles at 20 C. This strategy demonstrates a feasible orbital engineering approach to develop stable high‐energy‐density cathodes for SIBs.