Graphene nanotube technology company OCSiAl opened its industrial-scale factory for the mass synthesis of graphene nanotubes just outside Belgrade, Serbia, in October. This will further result in significant cost reductions to enable their economically feasible application across many industries. Vic Giles attended the opening and spoke with Andrej Seniut, head of OCSiAl Energy Projects.

Photo: Andrej Seniut (right) with chairman of the board of directors and ex-CEO of Marvel, Peter Cuneo, at the factory opening.

First observed in 1952, carbon nanotubes go back to the first forest fires and ancient Chinese ink. Decades of research have confirmed that graphene nanotubes can be a universal additive for most materials. However, it was not until 2013 that Luxembourg-based OCSiAl created the first industrial technology for synthesising graphene nanotubes, also known as single-wall carbon nanotubes (SWCNTs).

While multi-wall carbon nanotubes (MWCNTs) are similar to SWCNTs, the properties make a significant difference to the battery industry. MWCNTs are a short, rigid product. SWCNTs are long, flexible and highly conductive. SWCNTs are >3,000 times longer than they are wide.

The OCSiAl vision

Seniut said the vision was to improve and reduce material usage to make cars and materials lighter and more energy efficient. The company explored and found using graphene nanotubes could improve many materials, he said.

For the first five years, the company focused on creating technology to produce nanotubes at scale. Twelve industrial synthesis reactor prototypes were built. Around $100 million went into production technology. The company launched its first SWCNT manufacturing in 2014. Following a steep learning curve, OCSiAl was able realise a 100-fold drop in the price from $150,000 per kg of SWCNTs.

“When we developed the technology, the pilot production unit was producing one tonne of graphene nanotubes per year, it was already 97% of the market,” he said. “There was a big opening event at Imperial College, London, where we introduced nanotubes to the world. We shipped out nanotubes to many research institutions, one gramme for free, and it was something unimaginable.” But response was poor because nobody knew how to use the product.

Second-stage products

This was in 2013, when Seniut joined the company. It created the first second-stage product – accepted by the industry around 2018/19. It developed dispersions for the lithium-ion battery industry which are compatible with conventional anode and cathode materials. Customers could easily integrate this additive without additional CapEx.

Improving battery properties

“If we speak about application in batteries, there is a need to make more efficient, lighter batteries,” he said. “Energy density is always a target, as is charging time. In addition to that, the degree of the scrap during the production is very important.”

Battery energy density is increased by adding silicon to the anode. With a specific capacity of 4000mAh per gramme, versus 370mAh for graphite, silicon can store 10 times more lithium ions than graphite.

Another development is fast-charging graphite applications. Different particle size graphite and special carbon coatings allow fast-charging graphite to absorb lithium faster.

Seniut said: “Regarding the energy density, an interesting approach is to increase the thickness of the electrodes, because if you do that, you have better active and non-active material ratio in the cell. And the increase in energy density reduces the cost of the batteries as well.”

He said this is a popular development where customers see some improvement in performance that allows them to use single crystal NCM particles.

Polycrystal particle size is quite big at ~8µm compared to ~3µm for single crystal NCM. The finer the particles, the greater the overall surface area.

“Basically, you have more particles inside and you need to make sure that you’re able to connect these small particles together with electrical network,” he said. “Typically, you would need to add substantially higher amounts of conductive additive to ensure that your cathode works with single crystals.

“With SWCNTs, because they are long and flexible, they build these conductive networks at very low dosages. So, you add a little bit and you either maintain the same level of conductive additives inside your cathode or even reduce it, because you’re introducing more efficient additives on the anode side.”

In the fast-charging graphite and thicker cathode applications mentioned above, SWCNTs introduce an entanglement inside the anode, which reduces the spring-back after calendaring. This helps to stabilise production by ensuring the electrode has a uniform and minimum thickness, as well as high flexibility.

The current applications of SWCNTs in batteries already in production will be found in products from cars to consumer electronic devices, and from many top brands. The company said it is not that important which chemistry is used in the battery – SWCNTs work in a similar manner in any battery technology.

Nanotubes for lithium batteries

“So, our business started with silicon-containing anodes, because here it was very easy for customers to see the benefits. With more silicon, you have more expansion and contraction of particles inside your anode. First, there’s a cracking of the particles and due to that, there’s a loss of electrical contact between these kinds of particles and it was a very big challenge to introduce a high amount of silicon because of this problem. You add more and you have this expansion problem, and your battery degrades ever more rapidly.”

Message to the battery industry

When OCSiAl entered the lithium-ion battery market with this new material, it met a lot of scepticism.

“If I were to speak with European/US battery makers, I would encourage them to innovate faster in order to create the products that can be competitive with the existing products supplied from the Asian market, because now Asia dominates both in terms of existing production capacity and technologies.”

To create competitive local supply chains, European and US battery makers need to create something better and more efficient, he said.

Seniut adds its product can play a very important role in these emerging technologies. “I would also encourage the cooperation. We have enough nanotubes for basically any demand.” It claims to be a nanotube production centre for any purpose and will distribute wherever necessary.

Gigafactory economies of scale

Seniut said, “a very good mnemonic rule is one gigawatt of batteries typically needs one tonne of SWCNTs – if you were to use them both on the anode and cathode side. So, you do not need to ship so much of the product. It’s only one tonne for 10,000–20,000 cars.”

Lithium-ion battery makers buy dispersions. This is nanotubes mixed in water for anodes, stabilised with polymers or mixed with different solvents – NMP mostly, for cathodes and currently stabilised with some polymers. They can be used for dry technology – concentrates of nanotubes in PTFE, or some other polymer compatible with the recipe.

“So basically, our customers receive second-stage products. And in these second-stage products, you have dispersions with around 1% of single carbon nanotubes, like 1% polymer and the rest is water, or solvent. Obviously, you will need 100 times more of the material to enhance 1GWh of the batteries in comparison with dry powder. And in this case, if you speak about very big gigafactories, then we need to have our dispersion production facility as close as possible.

“So, it really makes sense to localise dispersion production. It’s why we created a plant here in Europe, even though we have our partner production facility for dispersion in Asia, and we still supply from Asia to the US and Europe, etc. But it makes sense to have a local supply chain, to have the lowest possible logistics route. It improves many things – costs and emissions – and it is in our strategy to build this kind of dispersion, or second-stage product version facilities close to the end consumption.”

The company plans to diversify where it produces nanotubes, because demand is substantially exceeding supply. This means building more graphene nanotube production factories, firstly in Serbia, and soon after, it is aiming to launch a factory in Luxembourg, its home patch.