Na-ion Cathodes
Our research on Na-ion cathodes explores how composition and structure influence redox behaviour and structural evolution, revealing pathways to high-energy density Na-ion materials.
Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes
This work shows that first-cycle voltage hysteresis in these oxygen-redox cathodes is determined by the superstructure in the transition-metal layers. Loss of honeycomb ordering on charge enables manganese migration and molecular O2 formation, whereas a ribbon superstructure suppresses these processes, stabilising oxygen redox and minimising hysteresis.
Delocalized electron holes on oxygen in a battery cathode
Oxidation of oxide ions in layered O-redox cathodes can initially produce delocalised electron holes in the O 2p band rather than localised species or molecular O2. Using ribbon-ordered Na0.6[Li0.2Mn0.8]O2 to suppress transition-metal migration, these holes are shown to be delocalised across O–Mn2 environments and to gradually condense into trapped molecular O2, leading to voltage hysteresis.
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Reversible Electron–Holes on O in P2-type Na0.67Li0.1Ni0.3Mn0.6O2
This work demonstrates a Na-ion cathode, P2-Na0.67Li0.1Ni0.3Mn0.6O2, in which reversible oxygen redox proceeds via stabilized electron holes on oxygen rather than molecular O2 formation. By suppressing honeycomb ordering through low Li content, the material preserves a high-voltage oxygen-redox plateau while also exploiting the Ni³⁺/Ni⁴⁺ redox couple, delivering high energy density in a Na-ion cathode.
Influence of ion size on structure and redox chemistry in Na-rich and Li-rich disordered rocksalt battery cathodes
This study compares the structural evolution and electrochemical behaviour of isostructural disordered rocksalt cathodes Li2MnO2F and Na2MnO2F, showing that the larger Na⁺ ion leads to lower-voltage Mn and O redox couples and a two-phase charging mechanism with significant amorphisation on charge, unlike the single-phase behaviour seen in the Li analogue.
