Constructing Heterotransition Metal Ligand Field Clusters with a Compact Spatial Structure for Maintaining Unimpeded Sodium-Ion Migration.

Wang, Hanlin; An, Jiajia; Zhao, Wenxi; Yu, Binkai; Li, Ye; Hu, Jinqiao; Jiang, Shikang; Gu, Qinfen et al. · ACS Nano · 2025

basic_science · Level V

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Abstract

Revealing the mechanism of Mn doping in polyanionic NaFePO<sub>4</sub> materials advances our fundamental understanding of electrochemical reactions. Herein, we propose the concept of heterotransition metal ligand field clusters (H-TMLFC) as a framework to investigate the structural evolution of transition metal (TM) ligand fields at the microscopic level. The introduced [MnO<sub>6</sub>] octahedra exhibit a distinctive half-filled frontier orbital configuration, thereby strengthening σ-bonding interactions and modulating the charge distribution between adjacent [FeO<sub>6</sub>] units. The redistribution of charge density around the edge-sharing oxygen atoms in [FeO<sub>6</sub>]-[MnO<sub>6</sub>] pairs enhances Fe-O covalency and mitigates Fe/Na antisite defects. As a result, H-TMLFC-derived NaFe<sub>0.95</sub>Mn<sub>0.05</sub>PO<sub>4</sub> achieves an exceptional capacity of 148.9 mAh·g<sup>-1</sup> (96.7% of the theoretical capacity) and exhibits superior long-term cycling stability. This work introduces a novel approach for designing high-performance sodium-ion batteries through TM doping, offering atomic-scale insights into the optimization of polyanionic cathode materials.