Design of d/p-Band Center Regulation Guided by Suppressing Electron Interference for Ultra-stable Iron/Manganese-based Mixed Phosphate Cathode

Abstract

Iron/manganese-based mixed phosphate, characterized by its remarkable energy density and structural stability, emerges as a formidable contender for the next generation of commercial sodium-ion battery cathode materials. However, due to the 3d⁵ electronic configuration of Mn²⁺, the d-orbitals are in a half-filled state, which results in uneven charge distribution. Therefore, we propose the design of d/p-band center regulation for Na₄Fe₂Mn(PO₄)₂(P₂O₇). As a result, the electronic interference resulting from electronic localization is effectively mitigated. Through lattice reconstruction, the internal strain within the material is alleviated, and the Mn Jahn-Teller synergistic distortion is effectively suppressed, thereby enhancing the structural stability and electronic transition capability. Furthermore, the introduction of defect engineering for charge compensation alleviates the restricted diffusion of sodium ions due to the exacerbation of P₂O₇ distortion. Based on this, the modified iron/manganese-based mixed phosphate shows high energy density and ultra-long cycle stability, indicating significant potential for large-scale applications in sodium-ion batteries.