Part 1: Exploring Sodium-Ion Batteries

Northvolt recently presented a new sodium-ion battery cell, developed together with Altris AB . Having had this article series in the making for quite some time, we think that it is the right time to explore sodium-ion batteries with you now. This will be a mini-series of articles presenting information about sodium-ion batteries, explaining their characteristics and potential use cases around the world. If any of the details triggers your attention or if you have any questions along the way, drop a comment and we will come back to you swiftly.

What are Sodium Batteries?

When you read about a new battery technology in media, at times you might expect that they will look very different from what you are used to. Like a new car or a new piece of technology with an updated new look. This is not necessarily the case for batteries, and is not the case here. Sodium-ion batteries refers to the cell chemistry used to store energy in a electrochemical way, where sodium ions are the charge carriers. From an outside perspective, they cannot be distinguished from a lithium-ion battery, used in electric vehicles and battery energy storage systems today.

Sodium-ion batteries are a type of rechargeable battery that use sodium ions (Na+) as the charge carriers, as previously mentioned. They have a lot of similarities with lithium-ion batteries, but lithium is exchanged for Sodium (latin: Natrium). These batteries are considered a promising alternative to lithium-ion batteries due to the abundance and lower cost of Sodium, as well as the ability to be transported fully discharged due to not being sensitive to deep discharge, with the potential to be an attractive alternative in several applications. Lithium and sodium are both alkali metals, being part of the first group of the periodic table, resulting in that they share a lot of properties; such as a high reduction potential. As sodium has a higher atomic number (11 for sodium vs 3 for lithium) it is a bulkier atom which will be important for its use in type batteries as we will come to later.

One of the main challenges in developing sodium-ion batteries is finding suitable electrolytes to facilitate the movement of sodium ions between the cathode and anode. The choice of electrolyte is essential for the battery's performance, safety, and stability during charge and discharge cycles. Because of its larger size, the sodium-ion is more difficult to move around in the electrolyte, thus potentially limiting the performance of the cell compared to lithium. This can be seen as a less rigid negative electrode, resulting in a lower cycle count before EOL of the battery cell.

Sodium - An abundant and available material

Sodium (Na), chemical element of the alkali metal group of the periodic table. A very soft silvery-white metal and the most common alkali metal and the sixth most abundant element on Earth, comprising 2.8 percent of Earth's crust. Compare this to lithium (0,01 %), and sodium is 280 times as common as lithium. This comes very handy in a society where the demand for batteries are rapidly growing to support the green transition. Not only is it important from a cost point of view, where lower cost of materials would result in a lower cost battery cells. But also from an availability point of view. Once large players in the world start chasing the same materials, supply chain issues occur. If materials such as sodium could then replace these scarce materials, those issues would be phased out. Additionally, sodium-ion batteries, such as the one that Altris has developed, do not depend on several other rare minerals essential for most lithium-ion batteries such as Cobalt, and graphite.

What will we see in the near future?

Researchers and scientists continue to work on improving the performance and safety of sodium-ion batteries, aiming to make them more competitive with lithium-ion batteries for various applications. And while we don't know what the future holds on details about technology, performance or exact cost. We can have a look at the development of lithium-ion batteries and their performance back in time.

Given the graph above and the interest in commercializing sodium-ion batteries as we can see. We think its is fair to say there are a lot of things that will happen during the coming years as research intensify around sodium-ion batteries. What that will be in details, we can not state. But we are sure that plenty of progress will be made to refine sodium-ion batteries, in the same way lithium-ion batteries has been refined since 2008.

About the authors

Dr Henrik Lundgren has a PhD in chemical engineering (applied electrochemistry) from KTH Royal Institute of Technology and has been working within battery development in both the automotive industry and stationary energy storage.

Johannes Löfgren holds an MSc in engineering (product & process development) together with an BSc in business administration. His work has been related different topics related to process engineering, operations management as well as establishments, profitability and performance of manufacturing units.

Together, Henrik and Johannes share an interest in new battery technology and use this set of articles as a channel to jointly explore and write about relevant subjects tickling their curiosity. As former colleges, this has become one interesting way to stay in contact, while also educating themselves and others along the way.