Sodium-Ion battery

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.
  • Three major families of materials for cathode chemistry options:
    • layered transition metal oxides
    • polyanionic compounds
    • prussian blue analogs
  • Cathode materials can be synthesized from more sustainable transition metals such as Fe, Cu or Mn.

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
HiNa 32140 OCV curves versus other chemistry

Open Circuit Voltage

The OCV for the two cell datasets that we have to date are quite similar. The hysteresis between charge and discharge is small.

However, you can see that the voltage swing versus SoC is more significant than the other chemistries.

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].
HiNa 32140 2C / 2C cycle life

Hina NaCR32140-MP10 sodium ion cell 0.5C Charge / 0.5C Discharge and 98% capacity retention after 500 cycles.

Reduce the DoD to 90% and even at 2C / 2C cycling the capacity retention is 96% after 3850 cycles, expected life to 80% SOH is >25,000 cycles.

Sodium Ion Battery Pack

This low cot battery technology is approaching fast with lots of announcements.

Achieving 120Wh/kg at pack level.

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
  4. Comprehensive Inorganic Chemistry III, Reference Work • Third Edition • 2023