Sodium-ion battery vs. redox flow - which technology will prevail?

At a time when sustainable energy storage is becoming increasingly important, various battery technologies are taking centre stage. Two promising solutions are the sodium-ion battery and the redox flow battery. Both offer specific advantages, but which is the better choice? In this article, we compare the two technologies and show why the sodium-ion battery is considered a promising alternative.

How do they work - A Comparison

Sodium-ion (salt) batteries store energy using sodium ions as charge carriers, which move back and forth between the cathode and anode in an organic electrolyte. These batteries do not require scarce raw materials such as lithium or cobalt. Thanks to the high availability of sodium, they offer a sustainable and cost-effective alternative to conventional lithium-ion batteries.

Redox-Flow-Batteries work with liquid electrolytes that are stored in external tanks. The energy is released through chemical reactions within the cell by pumping it through a membrane. This technology is characterised by its scalability and is particularly suitable for stationary storage applications.

Technology comparison: sodium-ion vs. redox flow batteries

Properties	Sodium-Ion Battery	Redox Flow Battery
Safety	High level of safety thanks to available materials	Safe technology, but use of liquid, potentially toxic electrolytes
Energy Density	200-350 Wh/l	15 - 80 Wh/l
Charing speed	Very fast (1- 10 C)	Slow (< 0,5 C)
Voltage Range	1,5–4 V	1,0–2,2 V
Efficiency	90-95 %	50 - 80%
Operating temperature	Wide temperature range	Limitations at low temperatures
Costs	Cost-effective materials and production	Higher acquisition costs due to complex systems
Environmental friendliness	Sustainable raw materials, low CO₂ footprint	No rare materials, but electrolytes such as vanadium oxide, sodium bromide, polysulphide bromide, zinc bromide

Anwendungsbereiche

• Redox flow batteries are ideal for large, stationary energy storage systems such as grid stabilisation or industrial applications, as their scalability enables a high storage capacity.

• Sodium-ion (salt) batteries are suitable for both stationary and mobile applications due to their higher energy density, high level of safety and lower costs.
  

Conclusion

While redox flow batteries score with their unlimited scalability, sodium-ion batteries offers decisive advantages in terms of energy density, charging speed, temperature tolerance, cost-effectiveness and environmental friendliness, making it the preferred choice for future-proof energy storage solutions.

The decision for the right technology ultimately depends on the specific requirements - redox flow could continue to play a role for large-scale stationary storage systems, while sodium-ion batteries are becoming increasingly attractive as a versatile and cost-effective solution for the broad market.