Our new review in Journal of Energy Storage takes on a problem that has quietly held back high-energy sodium cathodes: oxygen redox produces extra charge, but that charge only matters if it comes back on discharge as usable energy. Too often it does not — the voltage sags, hysteresis grows, and the apparent capacity gain never becomes deliverable energy.
The review reframes lattice oxygen redox as a mechanism-informed design challenge rather than a capacity headline, and organizes the evidence around a descriptor triad.
A — Accessibility. Is oxygen participation actually reached within practical voltage windows, rates, and protocols — without being dominated by parasitic high-voltage charge?
R — Reversibility (bulk). Does the lattice return on discharge, with limited defect accumulation, cation rearrangement, and irreversible phase or stacking evolution?
C — Containment (interfacial). Can a thin, ion-conducting interphase confine high-voltage reactivity, suppress electrolyte oxidation and surface reconstruction, and prevent rapid impedance growth?
Around this triad, the review proposes evidence tiers that pair electrochemical fingerprints (extra capacity, high-voltage plateaus, dQ/dV features) with oxygen- and structure-sensitive validation — and, crucially, with explicit constraints on oxygen loss and interfacial parasitics. The aim is to separate intrinsic lattice oxygen redox from interfacial artifacts that can masquerade as it, and to make claims comparable across the O3, O2, P2, P3, and intergrowth families.
The through-line is one this group returns to often: judge a cathode by discharge-energy retention, not capacity alone, and report the conditions that let the comparison be trusted. Read that way, oxygen redox shifts from a source of instability toward a design variable that can be engineered deliberately for durable, high-energy sodium cathodes.
The work is an international collaboration led from the Department of Chemical Engineering, Chulalongkorn University, with partners in South Korea, Taiwan, Hong Kong, and Japan: M. Gopalakrishnan, P. Tangthuam, W. Kao-ian, I. In, W.-R. Liu, R. Zhang, T. Yonezawa, and S. Kheawhom.
Read the review
Gopalakrishnan M., Tangthuam P., Kao-ian W., In I., Liu W.-R., Zhang R., Yonezawa T., Kheawhom S. From oxygen redox to usable energy: Evidence hierarchies, design principles, and reporting standards for Na-layered oxides. Journal of Energy Storage 177 (2026) 123460. DOI 10.1016/j.est.2026.123460
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