(Image: Chalmers University of Technolgy)

The transition to a society without fossil fuels means that the need for batteries is increasing at a rapid pace. At the same time, the increase will mean a shortage of lithium and cobalt — key components in the most common battery types. One option is a sodium-ion battery, where table salt and biomass from the forest industry make up the main raw materials.

Now, researchers from Chalmers University of Technology, Sweden, have shown in their study that sodium-ion batteries have an equivalent climate impact as their lithium-ion counterparts — without the risk of running out of raw materials.

“Li-ion batteries are becoming a dominant technology in the world and they are better for the climate than fossil-based technology is, especially when it comes to transport,” said Associate Professor of Environmental Systems Rickard Arvidsson. “But lithium poses a bottleneck. You can't produce lithium-based batteries at the same rate as you want to produce electric cars, and the deposits risk being depleted in the long term.”

“We came to the conclusion that sodium-ion batteries are much better than Li-ion batteries in terms of impact on mineral resource scarcity, and equivalent in terms of climate impact,” added Arvidsson. “Depending on which scenario you look at, they end up at between 60 and just over 100 kilograms of carbon dioxide equivalents per kilowatt hour theoretical electricity storage capacity, which is lower than previously reported for this type of sodium-ion battery. It’s clearly a promising technology.”

The researchers also identified a number of measures with the potential to further reduce climate impact, such as developing an environmentally better electrolyte, as it accounted for a large part of the battery's total impact.

“Energy storage is a prerequisite for the expansion of wind and solar power. Given that the storage is done predominantly with batteries, the question is what those batteries will be made from? Increased demand for lithium and cobalt could be an obstacle to this development,” said Arvidsson.

Rickard Arvidsson (Image: Chalmers University of Technolgy)

The study is a prospective lifecycle assessment of two different sodium-ion battery cells where the environmental and resource impact is calculated from cradle to gate, i.e., from raw material extraction to manufacturing a battery cell. The functional unit of the study is 1 kWh theoretical electricity storage capacity at the cell level.

Both types of battery cells are mainly based on abundant raw materials. The anode is made up of hard carbon from either bio-based lignin or fossil raw materials, and the cathode is made up of so-called "Prussian white" (consisting of sodium, iron, carbon, and nitrogen). The electrolyte contains a sodium salt. The production is modelled to correspond to a future, large-scale production. For example, the actual production of the battery cell is based on today's large-scale production of Li-ion batteries in gigafactories.

Two different electricity mixes were tested, as well as two different types of allocation methods — allocation of resources and emissions. One where the climate and resource impact is distributed between coproducts based on mass, and another method where all impact is allocated to the main product (the sodium-ion battery and its components and materials).

Here is an exclusive Tech Briefs interview with Arvidsson, edited for length and clarity.

Tech Briefs: The article says, “The research team chose to look at sodium-ion batteries … instead of lithium.” What made you choose sodium?

Arvidsson: Sodium is a cheap and abundant material worldwide, which suggests it would be preferable to lithium from a resource point of view. We wanted to assess whether this could be confirmed also in a lifecycle perspective, where we considered not only the battery materials themselves but also upstream energy and material requirements.

Tech Briefs: What was the biggest technical challenge you faced during the study?

Arvidsson: The biggest challenge was that there are no large-scale production facilities (“gigafactories”) for sodium-ion batteries yet. Therefore, we adapted a model of a gigafactory for Li-ion batteries to sodium-ion batteries based on their specifics. Still, data from an actual sodium-ion battery gigafactory would have been preferable.

Tech Briefs: How was the lifecycle assessment study conducted?

Arvidsson: We collected data on emissions and resource use from the sodium-ion battery cell production, the manufacturing of battery materials, and the raw material extraction. These emissions and resources were then converted to so-called impacts categories, with climate change (measured in carbon dioxide equivalents) being the most well-known one.

Tech Briefs: What are the pros and cons of sodium-ion batteries?

Arvidsson: The general benefit is the abundance of sodium. Furthermore, the main point of the specific sodium-ion battery cell we studied is the ambition to make it from abundant raw materials only. As we showed in our study, it also has climate change impacts in a similar range as current lithium-ion batteries. The main con is slightly lower energy storage capacity compared to most current Li-ion batteries.

Tech Briefs: How soon could we see sodium-ion batteries implemented on a commercial scale?

Arvidsson: We estimated that this could happen some time during 2025-2030 in the study. Since its publication, there has been high interest in sodium-ion batteries with several prototypes showcased and investments in production facilities. Considering this, it seems likely to happen in the earlier part of our time interval.

Tech Briefs: What are your next steps?

Arvidsson: We will now do a follow-up study where we also consider the end-of-life of the sodium-ion battery and additional future developments, such as the implementation of more renewables in the future global electricity mix.