Weekend read: More than ‘an alternative’

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From pv magazine ISSUE 09/23

pv magazine: How did you come up with the idea of working on sodium-ion batteries and where are you at today, in terms of development?

Florian Kogler: Two people met. One wanted to establish a successful company and the other one was already working in the battery sector. They were talking one evening over a glass of beer about what they wanted to do with €1 million ($1.66 million) and came to the idea to invest in sodium-ion technology.

The idea was further developed and then they secured the funding from the Austrian Research Promotion Agency [the Österreichische Forschungsförderungsgesellschaft, or] (FFG) and got the ball rolling. Kite Rise was established in 2021 and named after Benjamin Franklin’s kite-in-a-thunderstorm experiment. Since then, the team has grown to nine people, most of whom have decades of experience in the battery sector.

Our first product is called KiteOne, a 6 kWh sodium-ion stationary battery with a nominal voltage range from 150 V to 830 V. It comes with a guarantee of 10 years and an expected lifetime of about 20 years and around 10,000 cycles. We focus on the residential market segment but our product can be easily scalable for commercial and industrial applications. Presently, we are actively working on the A sample and developing the B sample, which will likely be ready by the year’s end. Our goal is to launch series production in 2025.

Based on your user-experience research, how much do prospective customers know about this battery chemistry?

The technology is basically unknown. There are just a few people out there who know about it and these are usually the ones who are on the lookout for lithium-ion alternatives. In fact, prospective customers do not care about the cell technology as long as it is safe and sustainable. What they have in their mind are hazardous fires and safety incidents, as well as the amount of water needed to extract lithium, or human right abuses linked to cobalt extraction.

Sodium-ion batteries don’t need these raw materials and offer improved safety, the level of which depends on the type of the cathode material. Kite Rise uses a sodium-vanadium-phosphate-fluoride cathode so there are no oxides inside that can contribute to potential fires. We have seen the nail penetration tests with our cells and that was incredible. The first time the nail went through the cell, nothing happened. With the second penetration, the jelly fluid was broken up and the temperature went up to 150 C due to a shortcut over the nail. The little amount of gas venting in such a situation is not flammable at that temperature, unlike with lithium-ion [devices]. The gas is also not hazardous, although it does contain a negligible amount of carbon monoxide.

In which applications would sodium-ion batteries outdo lithium-ion systems?

What is great about sodium-ion is its high temperature range. For example, it is possible to install it in a hut in the Alps where temperature can get to -20 C at night in winter and the system would still operate at 85% of its capacity. This also means you can simply install the battery outside, of course with proper rain protection.

The technology is also great for all commercial applications where safety is a major concern, such as in data centres or mines. Sodium-ion batteries can also do higher power. Our product can do a full cycle at 2 C without cooling. We even estimate that our system could do one loading-unloading cycle, from 100 to 0, at 5 C without cooling.

They are also easier to recycle than lithium-ion batteries. Both electrodes in sodium-ion batteries are made of aluminium so there is only one metal, in addition to one transition metal – vanadium and, therefore, they are easier to separate. The way we assemble our product also allows it to be easily disassembled as we use no glue, which is also important for the efficiency of recycling.

Of course, there are also disadvantages. For instance, the energy density is a bit lower: around 115 Wh/kg as compared to lithium-iron phosphate, with 140 Wh/kg to 160 Wh/kg. With that said, sodium-ion is not the Holy Grail of batteries but it is the next storage technology which really looks promising.

In terms of raw material cost, sodium-ion is a clear winner but the challenge is bringing the technology to scale. How do the two battery technologies compare in terms of system prices?

There are numerous factors that affect system prices but we are calculating that the cost of our product will be around 20% higher per kilowatt-hour [of storage capacity] than the average lithium-ion battery. I was told recently that if we would assume that there is 50% sodium-ion and 50% lithium-ion production worldwide, then the former would be around 30% cheaper. This is because the cost of raw materials is some 30% lower on the cell level. This translates into around 20% lower cost at the storage level, and 10% at the system level.

Production would look the same with no upgrade to manufacturing lines to switch to sodium-ion. This is just a rough estimation, of course. But our analyses show that customers are willing to pay a bit more for a safe and sustainable system with the same amount of energy.

Given the current state of the market, you won’t have much competition in Europe for sodium-ion battery manufacturing. How do you plan to seize this opportunity?

We are aiming to build an entire supply chain in Europe. We are buying cells from a French company and our key inverter partner is a major German manufacturer. The [battery] housing is no problem to get in Europe and the electronic parts can be sourced here as well. Of course, if you go down to smaller component parts and analyse if certain chips of the control unit were manufactured in Europe or Asia, or where the raw materials for the electronics were mined, things might get difficult.

The bottom line is that we have the capabilities in Europe to manufacture sodium-ion batteries locally and that the cell, which is by far the most important part, comes from Europe. For instance, our cell provider sources their raw materials from a Belgian company. And then the remaining question is where the mines are located. Sodium, phosphor, fluoride can all be sourced in Europe. Vanadium is, today, mostly mined from Australia but it should be also possible to get it here. From the geopolitical point of view, Europe wants to have local battery manufacturing. So the funding possibilities within Europe can provide a springboard for sodium-ion businesses to overcome the scaling issue and finally stand shoulder to shoulder with lithium-based batteries.

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