Improved Reversibility of Fe3+/Fe4+ Redox Couple in Sodium Super Ion Conductor Type Na3Fe2(PO4)3 for Sodium‐Ion Batteries

The methodology employed here utilizes the sodium super ion conductor type sodium iron phosphate wrapped with conducting carbon network to generate a stable Fe³⁺ /Fe⁴⁺ redox couple, thereby exhibiting higher operating voltage and energy density of sodium-ion batteries. This new class of sodium iron phosphate wrapped by carbon also displays a cycling stability with >96% capacity retention after 200 cycles.