Climate-friendly battery raw material: producing nickel with 84 percent less CO₂

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Nickel is considered one of the most climate-damaging elements in battery production. Researchers are therefore working on a better CO₂ balance and want to have found a way.

How quickly an electric car moves its carbon footprint into the green zone depends very much on the production of the battery raw materials. For example, nickel, which is used in the particularly long-range lithium-ion batteries of the NMC (nickel-manganese-cobalt) type. For the current annual production of around three million tons, 60 million tons of carbon dioxide are currently blown into the air – around twice as much as is produced by air traffic in Germany. According to current estimates, this figure could double due to the switch to electric cars.

A team from the Max Planck Institute (MPI) for Sustainable Materials in Düsseldorf now wants to remedy this situation. It has developed a process that could reduce greenhouse gas emissions in nickel production by 84 percent. Even ores such as nickel laterite with a nickel content of just one to two percent are suitable for this, according to the magazine Nature.

How nickel is extracted for batteries

In nature, nickel occurs in two rock forms: nickel-rich sulphides and nickel laterites, which contain nickel and iron as oxygen-containing compounds, silicates and oxides. These compounds make up around 60 percent of the world's deposits and can only be processed at great expense. To extract nickel from them, they are usually mixed with carbon and melted in a rotary kiln. The carbon binds the interfering oxygen in the ore – and "reduces" the nickel, as chemists say –, turning it into carbon dioxide.

Coal as a reducing agent is therefore one of the main reasons for the high greenhouse gas emissions in conventional production, says Ubaid Manzoor, a doctoral student at the MPI in Düsseldorf. In addition, several plants are required and the molten ore cools down repeatedly during transportation in between. The mixture has to be reheated several times. "We have now replaced the carbon with a hydrogen plasma as a reducing agent. This produces water instead of carbon dioxide," explains Manzoor. Electricity from renewable resources is used as the energy source. And the new process works in just one step, so it only requires one system.

In the laboratory, the researchers fill the dried and ground nickel ore into a 30-liter reactor, into which hydrogen is also blown. They then use high electrical voltages to ignite an electric arc, which melts the ore and gives the hydrogen in the reactor real superpowers.

Hydrogen is usually a molecule made up of two hydrogen atoms bonded together. "In the plasma, this bond is split and the electrons are also removed from the atoms," explains Manzoor. The result is highly reactive, charged hydrogen particles. They bind the oxygen bound in the ore at record speed and release a lot of energy in the process. "The temperature at the reaction interface is around 2000 degrees Celsius, depending on the current we use."

Bead of nickel and iron

The product from the arc furnace looks inconspicuous at first: a gray-brown stone about the size of a fist. But when it is broken open, a silvery pearl is revealed inside: a mixture of nickel and iron, known as ferronickel. "Ferronickel is also the product of conventional nickel production," says Manzoor. However, in contrast to production using coal as a reducing agent, which contains all kinds of impurities, it is highly pure. The ferronickel obtained in this way can be fed directly into stainless steel production as an alloy metal or – further processed – in the manufacture of lithium batteries and high-performance magnets.

Incidentally, there are purely physical reasons for the seemingly magical generation of beads. "We have two different types of melts in the reactor, from oxides and from pure metals. They are like oil and water. They don't mix," explains the MPI researcher. "The metal part separates and forms spherical droplets due to the surface tension."

The researchers used thermodynamic data to calculate the potential energy saving of 18% and a reduction in CO₂ emissions of 84% compared to conventional nickel production. "The remaining 16% of emissions result from extraction in the mines and transportation to the arc furnace," says Manzoor.

Mixing is possible: with stirring systems or gas bubbles

However, there are still a few hurdles to overcome before the process can make a career for itself on an industrial scale. Above all, sufficient green hydrogen must be available, the scientist emphasizes. It is also still unclear how well the molten ore can be moved in an industrial electric arc furnace. "The reduction of the ores only takes place at the reaction surface – not in the entire molten bath. It is therefore crucial that the unreduced melt continuously reaches the reaction surface." This can be achieved with electromagnetic stirring systems or by introducing gas bubbles, for example. Arc furnaces have been around for a long time. They are used in the recycling of scrap metal, for example.

Metal extraction in hydrogen plasma is also suitable for other battery metals, such as cobalt, and for recycling batteries, magnets or other electronic scrap, adds Manzoor. However, the most important pro argument remains the carbon footprint: "If we continue to produce nickel conventionally, we are simply shifting the environmental impact from the transport sector to the metallurgy sector," says the researcher. However, he is optimistic that producers will switch. "In view of the government regulations on CO₂ emissions and the fact that nickel is one of the most climate-damaging elements in battery production, companies will also try to go down this route."

This article first appeared on t3n.de .

(mma)