# Sodium-ion batteries: Engineering and performance

The cold-proof, fire-resistant battery that ships fully discharged

Source page: https://www.materialinsights.org/energy/e_sodium_ion/sg-eng/

What this tab covers Engineering and operating performance: round-trip efficiency, whether power and energy can be scaled separately, footprint and siting, and safety.

Sodium-ion is efficient, works over a wider temperature range than lithium-ion and carries less fire risk, but needs more space for the same energy.

#### Round-trip efficiency
Favourable

IRENA puts sodium-ion round-trip efficiency at about 92%, within the 85 to 95% lithium-ion range. Cells can reach 80% charge in about 15 minutes.^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf)
 Round-trip efficiency about 92%^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf) Fast charge to 80% about 15 minutes^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf)

#### Power and energy decoupling
Mixed

As with lithium-ion, energy and power scale together with the number of cells, and only inverters and grid connections are sized independently. No published cost split for sodium-ion grid systems was found; because the cells drop into the same kind of containers, inverters and grid connections as lithium-ion, the power-related costs per kW should be similar.^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf)

#### Footprint and siting flexibility
Favourable

Sodium-ion cells hold 250 to 375 kWh per cubic metre, which is within the lithium-ion range but below its upper end, so a grid site needs somewhat more space than for nickel-rich cells. The bigger siting advantage is temperature: it works from about -40 C to 80 C and keeps about 90% of capacity at -40 C, which suits very cold sites and reduces cooling needs in hot climates such as much of India.^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf)^[2](https://iea.org/reports/global-ev-outlook-2026/electric-vehicle-batteries)
 Volumetric energy density 250-375 kWh/m3^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf) Operating temperature range -40 to 80 C^[1](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf) Capacity retained at -40 C about 90%^[2](https://iea.org/reports/global-ev-outlook-2026/electric-vehicle-batteries)

#### Safety and thermal runaway risk
Favourable

Sodium-ion cells can be stored and shipped at zero charge, whereas lithium-ion usually travels at 30 to 50% charge, which removes a major source of transport and warehouse fires. The study for the European Economic and Social Committee (EESC) reports a lower thermal runaway risk and a safe operating ceiling of about 100 C against about 60 C for lithium-ion. The organic electrolyte is still flammable, so grid systems need the same NFPA 855 fire testing and design as lithium-ion.^[3](https://www.eesc.europa.eu/sites/default/files/2026-06/qe-01-26-008-en-n.pdf)^[5](https://www.energy-storage.news/nfpa-855-2026-edition-updates-and-what-they-mean-for-energy-storage-projects/)
 Shipping state of charge, sodium vs lithium-ion 0% vs 30-50%^[3](https://www.eesc.europa.eu/sites/default/files/2026-06/qe-01-26-008-en-n.pdf) Approximate safe operating ceiling, sodium vs lithium-ion about 100 C vs about 60 C^[3](https://www.eesc.europa.eu/sites/default/files/2026-06/qe-01-26-008-en-n.pdf)

#### Sources

1. [Sodium-ion batteries: Technology brief](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Nov/IRENA_TEC_Sodium-ion_batteries_2025.pdf) IRENA, 2025
2. [Global EV Outlook 2026: Electric vehicle batteries](https://iea.org/reports/global-ev-outlook-2026/electric-vehicle-batteries) International Energy Agency, 2026
3. [Energy resilience of households in a prepared union: the potential of a sodium battery-based solution (study by Milieu, WSP and CE Delft)](https://www.eesc.europa.eu/sites/default/files/2026-06/qe-01-26-008-en-n.pdf) European Economic and Social Committee, 2026
4. [NFPA 855: 2026 edition updates and what they mean for energy storage projects](https://www.energy-storage.news/nfpa-855-2026-edition-updates-and-what-they-mean-for-energy-storage-projects/) Energy-Storage.news, 2026

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_sodium_ion/index.md)
- [Overview](https://www.materialinsights.org/energy/e_sodium_ion/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_sodium_ion/correlation/index.md)
- [Science and technology](https://www.materialinsights.org/energy/e_sodium_ion/sg-sci/index.md)
- [Economics](https://www.materialinsights.org/energy/e_sodium_ion/sg-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_sodium_ion/sg-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_sodium_ion/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_sodium_ion/links/index.md)