Sodium-Ion

Sodium-ion batteries operate analogously to lithium-ion batteries, with both chemistries relying on the intercalation of ions between host structures. In addition, sodium based cell construction is almost identical with those of the commercially widespread lithium-ion battery types. However, sodium-ion batteries are characterised by several fundamental differences with lithium-ion, bringing both advantages and disadvantages:

Advantages:

  • Environmental abundance: Sodium is over 1000 times more abundant than lithium and more evenly distributed worldwide.
  • Safety: Sodium-ion cells can be discharged to 0V for transport, avoiding thermal run-away hazards which have plagued lithium-ion batteries.
  • Low cost: Sodium precursors (such as Na2CO3) are far cheaper than the equivalent lithium compounds.

Disadvantages:

  • Sodium-ion cells have lower energy densities than lithium-ion. This is due to sodium being significantly heavier and larger than lithium, as well as Na+/Na having a higher reduction potential than Li+/Li.
  • Sodium-ion technology is not as well established as lithium-ion.

Sodium-Ion Battery Materials

Many of the battery components in both sodium-ion and lithium-ion batteries are similar due to the similarities of the two technologies. This post provides a high-level overview for the constituent cell parts in Sodium-ion batteries.

Sodium-Ion Cell Characteristics

  • An energy density of 100 to 160 Wh/kg and 290Wh/L at cell level.
  • A voltage range of 1.5 to 4.3V. Note that cells can be discharged down to 0V and shipped at 0V, increasing safety during shipping.
  • 20-30% lower cell BOM cost than LFP.
  • A wider operating temperature than lithium-ion cells (-20°C to +60°C).
  • Typical Energy efficiency 92% at C/5.

Hard Carbon Anodes in Sodium-ion

  • Emerging battery technology – promising cost, safety, sustainability, and performance advantages over current commercialised lithium-ion batteries1,2.
  • Advantages:
    • widely available
    • inexpensive raw materials
    • rapidly scalable technology
    • meeting global demand for carbon-neutral energy storage solutions3,4.
  • Adding metals would increase the overall energy density, but results in volumetric changes leading to failure.
optimization of hard carbon for sodium ion - poster

Sodium-Ion Degradation

  • Over-voltage Charging
  • Presence of Hydrogen
    • causes irreversible degradation of α-NaMnO2 when used as the cathode in Na-ion batteries [1].
  • Defects in the Cathode Atomic Structure
    • these form during the steps involved in synthesizing the cathode material. These defects eventually lead to a structural earthquake in the cathode, resulting in catastrophic performance decline during battery cycling [2].

References

  1. Zhen Zhu, Hartwin Peelaers, Chris G. Van de Walle, Supporting Information: Hydrogen-induced degradation of NaMnO2, Chem. Mater. 2019, 31, 14, 5224–5228, June 21, 2019
  2. Xu, GL., Liu, X., Zhou, X. et al. Native lattice strain induced structural earthquake in sodium layered oxide cathodes. Nat Commun 13, 436 doi: 10.1038/s41467-022-28052-x
  3. Behrooz Mosallanejad et al, Cycling degradation and safety issues in sodium-ion batteries: Promises of electrolyte additives, Journal of Electroanalytical Chemistry, Volume 895, 15 August 2021, 115505