Sodium Vs Lithium Batteries

1. Environment

Lithium Ion

Lithium mining has high CO2 emissions, similar to fossil fuels.

Mining can poison local ecosystems with chemicals, such as sulfuric acid and sodium hydroxide, used in the extraction process. It harms the soil; causes air contamination; and impact the flora and fauna.

It is increasingly affecting communities where this harmful extraction takes place.

Sodium Ion

Also known as Na-ion batteries (NIB) and Sodium-ion batteries (SIB) batteries.

Sodium is the 6th most abundant element and is seen as a sustainable and environmentally safer alternative to lithium.

Large-scale recycling potential.

Available from sea water desalination plants.

Sodium batteries use iron oxide and magnesium oxide for their cathodes, which are sourced from industrial by-products and recycled materials.

Sodium chloride salts still need to be chemically processed to make it suitable for battery use. The process requires significant electrical and thermal energy.

2. Energy Density

Energy density is the ratio between the amount of energy a battery holds and the weight of the battery.

Sodium batteries do have a lower energy density than lithium batteries. However, for use in home batteries this is largely irrelevant, unless wall mounted.

Sodium has an energy density of 140-160Wh/kg with lithium around 180-250Wh/kg. In contrast CATL have developed a condensed battery with 500Wh/kg!!

3. Fire Safety

Sodium is less prone to overheating and catching fire. This is because sodium electrolytes have a higher flashpoint than lithium electrolytes, meaning sodium doesn’t catch fire so quickly.

Ultimately both technologies will require fire suppression solutions and be installed outside (or in a garage with an interconnected fire alarm).

4. Cycle Life

Time based warranty

The Eleven Energy sodium battery has a warranty of 10 years for retaining 75% of useable energy.

The SigEnergy lithium battery has a warranty of 10 years for retaining 65% of useable energy.

Throughput warranty

The Eleven Energy sodium battery warranty ends if the lifetime energy throughput reaches 40 MWh for a 5kWh battery.

The SigEnergy lithium battery warranty ends if the lifetime energy throughput reaches 18.20MWh for the 5kWh battery.

Conclusion

The Eleven Energy sodium ion warranty is better than the SigEnergy lithium ion warranty. This is despite the fact that sodium ion is scientifically shown to have a shorter life compared to lithium.

5. New technology

Like with all new technologies, there is a risk to early adoption of using sodium batteries. As of 16/11/25 there are about 100 sodium batteries installed in the UK, so it is a fairly new technology, which does come with a level of risk. For many people the environmental benefit may outweigh the risk?

6. Low temperature performance

Lithium

Lithium optimum temperature is around 20-30°C. At this temperature the battery can charge and discharge efficiently. Charging and discharging below 20°C reduces the battery life. To control this, a battery management system will reduce the output/input (kW) of the battery to prolong the life.

Charging below 0°C can cause lithium plating on the anode and can cause permanent damage. Therefore the BMS stops charging below 0°C. However, some batteries such as Fox, Dyness, SigEnergy and Tesla have heating pads between the battery cells to increase the temperature to around 15°C before starting to charge. The battery heating pads prolong the life of the battery and also allows higher charge and discharge rates.

Sodium
Sodium batteries on the other hand reduce their charge rates below 0°C rather than +20°C. At -20°C the charge speed is still x10 slower than at above 0°C, so they could still benefit from battery heating pads if installed outside.

6. Cost

The Eleven Energy sodium batteries are about £683 per kWh of installed capacity. This compares to £570 per kWh for a SigEnergy system.

Sodium batteries are less expensive to produce so, as the Chinese factories scale up, the cost of sodium batteries is likely to fall.

The Eleven Energy battery is a hybrid battery, but they are releasing an all-in-one modular solution similar to SigEnergy. Also the maximum size of the Eleven Energy hyrbid inverter is 6kW at the moment, but again they are releasing a 12kW hybrid inverter to match the SigEnergy solution shortly.