Alleviating the stability-energy density dilemma via electron-donor-mediated orbital symmetry regulation in sodium phosphate cathodes.

Electron-donor-mediated Fe3+ and V3+ incorporation in manganese-based sodium super ionic conductor cathodes suppresses Mn3+-linked octahedral distortion while keeping high-spin behavior.

• Why it matters: Mn3+ formation with asymmetric eg orbital occupancy breaks octahedral symmetry, creating a stability–energy density tradeoff that is difficult to reconcile for sodium-ion battery cathodes.
• What they did: The study uses electron-donor-mediated orbital symmetry regulation by incorporating Fe3+ and V3+ to promote partial delocalization of Mn3+ 3d electrons and enhance orbital interactions via the transition metal–oxygen framework.
• The result: The modified cathode reaches 492.06 Wh kg-1 and delivers 178.8 mAh g-1 at 0.1 C, retaining 80.2% capacity after 2000 cycles at 10 C.

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