Sodium Ion Cell

The sodium ion cell offers a sustainable energy storage alternative to lithium ion cells. With sodium based layered metal oxide cathode and a hard carbon anode. Sodium cells are still in the development stage with some small scale productions.

The main benefits of the Sodium Ion cell are:

1. Environmental abundance of Sodium
2. Safety
3. Low cost

An overview of the cell properties:

• 100 to 160 Wh/kg and 290Wh/litre at cell level
  • Faradion are targeting 190Wh/kg
  • A sodium metal anode could increase this to 230Wh/kg
• 1000 W/kg and 1300 W/litre at cell level
• Voltage range 1.5 to 4.3V
  • cells can be discharged down to 0V and shipped at 0V
• 20-30% lower cell BOM cost than LFP
• Temperature range -20°C to +60°C
• Typical cathode materials: NaNi_0.68Mn_0.22Co_0.10O₂
• Typical electrolytes: NaTFSI or NaPF6 dissolved in ethylene and propylene carbonate (EC and PC), and linear carbonates e.g. dimethyl, ethyl methyl, and diethyl carbonate (DMC, EMC and DEC) as solvents [3]
• Electrodes: aluminium anode and aluminium cathode
• Energy efficiency 92% at C/5 [4]

“The biggest thing going for sodium batteries is their use of abundant, cheap, and benign materials. There is over one-thousand times more sodium than lithium in the Earth’s crust. It also costs less to extract and purify. Moreover, sodium metal oxide cathodes typically used in batteries—the anodes are carbon just like lithium-ion batteries—can be made from plentiful metals such as iron and manganese. Lithium-ion cathodes, by contrast, use cobalt, a metal with limited geological reserves and an iffy supply chain centered on a handful of countries.

Sodium batteries are also more stable and safe than lithium-ion. They have a wider temperature range, are nonflammable, and there is no thermal runaway—which can cause lithium-ion batteries to catch fire—under any condition, says Pouchet.”

IEEE Spectrum

Discharge down to zero volts is possible and this also is interesting from a cell shipment perspective. The aluminium anode circumvents issues seen with over-discharging graphite-based Li-ion cells [6].

The performance and cost benefits of this technology show it has potential [5]:

• to replace lead acid
• to be competition for LFP
• to replace NMC in stationary applications

References

1. IEEE Spectrum – Sodium-Ion Batteries Poised to Pick Off Large-Scale Lithium-Ion Applications
2. K. M. Abraham, “How Comparable Are Sodium-Ion Batteries to Lithium-Ion Counterparts?“, ACS Energy Letters
3. Damien Monti, Erlendur Jónsson, Andrea Boschin, M. Rosa Palacín, Alexandre Ponrouch and Patrik Johansson, Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents, Physical Chemistry Chemical Physics, Issue 39, 2020
4. Faradion – sodium ion performance
5. 2021 roadmap for sodium-ion batteries, JPhys Energy
6. Ashish Rudola , Christopher J. Wright , Jerry Barker, Reviewing the Safe Shipping of Lithium-Ion and Sodium-Ion Cells: A Materials Chemistry Perspective, Energy Material Advances. vol. 2021

Lithium Ion Cell

When discharge begins the lithiated carbon releases a Li⁺ ion and a free electron.

Electrolyte, that can readily transports ions, contains a lithium salt that is dissolved in an organic solvent. The Li⁺ ion, which moves towards the electrolyte, replaces another Li + ion from the electrolyte, which moves towards the cathode. At the cathode/electrolyte interface, Li⁺ ions then become intercalated into the cathode and the associated electron is used by the external device.