Iron-mediated cathode lifts sodium-ion pouch cell to 206 Wh/kg

A 15.8 Ah sodium-ion pouch cell built with an iron-mediated NMMF cathode reached an energy density of 206 Wh/kg, with lattice-oxygen redox reversibility of 99%.

Chinese researchers designed the iron-mediated strategy to improve the reversibility and stability of lattice-oxygen redox reactions in sodium-ion battery cathodes. Lattice-oxygen redox adds capacity beyond what transition-metal redox alone delivers, but the reaction degrades as oxygen fails to return to its original state across cycles.

That degradation is what the iron mediation addresses. Redox reversibility of lattice oxygen improved from 75% to 99% through the redox-mediated catalysis, according to pv magazine. The NMMF electrode delivers a specific capacity of 220 mAh/g from the lattice-oxygen redox.

The work was published in Nature Energy. Contributors included Nanjing University, Zhejiang University, Soochow University and HoNa New Energy Technology in China, alongside Lawrence Berkeley National Laboratory in the United States.

Sodium-ion chemistry competes with lithium iron phosphate on cost and raw-material availability rather than on energy density, where it has trailed. A pouch cell at 206 Wh/kg, reported by ESS News, puts a sodium-ion cell in a range that narrows that gap.