Sodium Ion Layered Transition Metal Oxides

This is the most mature sodium ion cathode technology due to its high theoretical capacity and structural similarity to commercial lithium-ion cathodes. These materials are classified by the sodium coordination environment (Octahedral ‘O’ or Prismatic ‘P’) and the number of transition metal layers (e.g., 2 or 3).

  • O3-Type Layered Oxides: These typically have high sodium content (x≥0.8) and offer high initial capacity but suffer from sluggish kinetics and air instability.
    • NFM: Na[Nix​Fey​Mnz​]O2​ is a standard low-cost model.
    • NFMMT: A modified version, Na[Ni0.4​Fe0.1​Mn0.4​Mg0.05​Ti0.05​]O2​, incorporates Magnesium (Mg) and Titanium (Ti) doping to mitigate adverse phase transitions.
    • Surface-Coated Variants: Examples include NFMMT coated with NaCaPO4​ to improve air/thermal stability and rate performance.
    • High-Entropy Oxides (HEO): These incorporate five or more transition metals (e.g., Ni, Mn, Cu, Ti, Sn) to suppress phase transitions and improve cycling stability through configurational entropy.
  • P2-Type Layered Oxides: These generally have lower sodium content (0.6≤x≤0.7) but feature open prismatic pathways that facilitate rapid sodium-ion transport for high-power applications.
    • High Na-Content P2: Novel compositions like Na45/54​Li4/54​Ni16/54​Mn34/54​O2​ have been synthesized to combine the stability of P2 structures with the higher capacity of high sodium content.
    • Mn/Ni-based P2: Prototypical materials like P2−Na0.67​Ni0.33​Mn0.67​O2​.
  • Biphasic Materials: These are hybrids designed to leverage the high capacity of O3 and the fast kinetics of P2, such as P2/O3 composites.

References

  1. Liang, X., Song, X., Sun, H. H., Kim, H., Kim, M.-C., & Sun, Y.-K. (2025). High-energy and long-life O3-type layered cathode material for sodium-ion batteries. Nature Communications, 16(1).
  2. Zhang, Y., Zhang, R., & Huang, Y. (2019). Air-Stable NaxTMO2 Cathodes for Sodium Storage. Frontiers in Chemistry, 7.
  3. Zhao, C. et al. (2020). Revealing High Na-Content P2-Type Layered Oxides as Advanced Sodium-Ion Cathodes. Journal of the American Chemical Society, 142(12), 5742–5750.

See also

Sodium Ion Cathodes, Polyanionic Compounds, Prussian Blue Analogues, Organic Cathode Materials