Chinese researchers have developed an iron-mediated strategy that improves the reversibility and stability of lattice-oxygen redox reactions in sodium-ion battery cathodes. A 15.8 Ah pouch cell using the cathode achieved an energy density of 206 Wh/kg, with lattice-oxygen redox reversibility reaching 99%.
A research group in China has developed an iron-mediated strategy to improve the stability and energy density of sodium-ion batteries. The researchers incorporated iron into a sodium-deficient manganese-magnesium-iron layered oxide (Na₂/₃Mn₇/₁₂Mg₁/₄Fe₁/₆O₂, or NMMF) cathode, making its lattice-oxygen reactions more reversible and reducing capacity loss during cycling.
“The iron in the NMMF compound is first found to show redox-mediated (RM) catalysis behavior,” co-author Shiyong Chu told pv magazine. “This is the first report of RM in classic alkali metal-ion batteries. Unlike traditional RMs that facilitate surface reactions, as observed in lithium-oxygen and sodium-oxygen (Li/Na-O₂), in this study, the iron-mediated catalytic reaction takes place within the bulk of the lattice-oxygen-activated cathode material, enabling the efficient utilization of lattice-oxygen redox.”
Chu said poor lattice-oxygen redox reversibility occurs in most anionic-redox cathodes, resulting in poor structural and electrochemical stability. The researchers therefore proposed an iron-mediated catalysis strategy to improve redox reversibility and used quantitative mapping of resonant inelastic X-ray scattering to determine the lattice-oxygen redox reversibility of NMMF.
