Electronic Cloud Topology-Driven Electrostatic Decoupling: To Suppress High-Voltage Parasitic Reactions of Phosphate Cathode in Sodium-Ion Batteries.

The polyanionic structure cathodes with synergistic Mn/V redox couples enables high-voltage platform and delivers considerable theoretical energy density in sodium-ion battery. However, achieving stable and reversible high-voltage redox reactions remain challenging due to the inactivation of redox couples during discharge. Herein, we found that coupled redox behavior triggered by orbitals with similar energy levels leads to high-voltage irreversibility and parasitic reactions. To overcome this, we propose a strategy of adjusting the electron cloud topology by altering the electrostatic field, thereby changing the orbital energy gap between the t2g state of V and the eg state of Mn, effectively decoupling the electrochemical reactions. As a model system, the Na3.5MnV0.5Ti0.5(PO4)3 (NMVTP) cathode significantly stabilizes the high-voltage Mn4+/3+ and V5+/4+ pairs, and increases the reversible capacity from 99.41 to 123.9 mAh g-1. This strategy opens new paths for developing high-energy density batteries through orbital bandgap modification.