What do an electric car, a laptop and an electric toothbrush have in common? They all run on a lithium-ion battery. These batteries are the most efficient on the market. In recent years, manufacturers have begun to use these batteries in more and more applications. As a result, prices will certainly increase if society switches to electric mobility. Extraction of raw materials is associated with high costs and emission of greenhouse gases.
Recycling of lithium
Recycling of lithium has so far not been successful because the current processes are inefficient. Nevertheless, recycling this material can contribute to a more sustainable production of batteries.
The growing amount of batteries means that the waste stream will also increase in the coming years. Although there are efficient ways to recycle cobalt, copper, nickel and other minerals used in batteries, recycling lithium (Li) is still not cost-effective.
Membrane for lithium ions
Researchers from the German chemical company Evonik are working on a new solution to this problem. They have designed a membrane to selectively capture lithium ions from used batteries.
“The design is key,” Elisabeth Gorman told Innovation Origins. She is business development manager at Evonik. “The composition of the membrane selects lithium ions and allows them to move through the crystal structure we built.”
German researchers chose membrane electrolysis. Basically, the process uses electricity to separate lithium ions through a permselective ceramic membrane. This is a layer that is both semipermeable and enables ion exchange. Electrolysis is best known for the production of hydrogen, where electricity is used to split water into oxygen and hydrogen.
For this you use an electrolyser whose main elements are a positive electrode – the anode – and a negative electrode – the cathode. An ion-conducting membrane separates the two, allowing ions to flow through when an electrical potential is applied. This part of Evonik’s method makes all the difference.
“Compared to conventional lithium recycling techniques, our electrochemical separation process can produce lithium hydroxide in one step and in a very pure, battery-grade form. The technique has the potential to replace the current chemical precipitation process, which uses large amounts of chemicals for solid-liquid separation,” emphasizes Gorman.
Initially, lithium-containing wastewater from the recycling process flows between the anode and the membrane. That waste water is a mixture of metals from shredded batteries. This happens in a recycling company after the plastic parts have been removed. That waste therefore also contains lithium.
When electricity is passed through this water current, lithium ions move through the ion-conducting ceramic membrane to the cathode chamber. Other ions and water molecules cannot pass through. Water then reacts on the negative electrode with electrons to form hydrogen and hydroxide ions. These react with lithium ions to form lithium hydroxide, the product needed to make new batteries.
“Lithium and rare earths will soon become more important than oil and gas. Our demand for rare earth metals alone will quintuple by 2030,” EU Commission President Ursula von der Leyen said when the Critical Raw Materials Act was introduced. In light of this, Europe requires – Commission greater efforts in lithium recycling It is currently estimated that more than 1.9 million tonnes are thrown away each year.
The recycling rate and collection varies depending on the battery type. According to the proposed regulation, lithium must be recovered by 35 percent by 2026 and double by 2030. Mandatory minimum levels of recycled content are also set. From 2030, the requirement for recycled lithium would be 4 percent and rise to 10 percent five years after that.
According to a study by the NGO Transport and Environment (T&E), the targets should be higher. “However, by requiring recyclers to recover these small amounts of lithium – only 35 percent by 2030 – policymakers are missing a huge opportunity. The European battery industry cannot wait to build a domestic supply of critical metals,” reads the analysis. T&E favors higher percentages as they are technically feasible according to industry best practices, citing an assessment by the Circular Economy Initiative Deutschland.
Recycling lithium is, in a way, the same as mining it a second time. However, Evonik’s concept can also be used for actual mining. Large deposits of lithium brine have been found in German soil. These are accumulations of saline groundwater enriched with dissolved lithium. These may be the next source of lithium in the near future. The extraction can proceed according to the same principle as for used batteries.
“That is the long-term vision. However, we are in a research and development phase. I don’t see the process adapting to this type of application happening in the next two or three years,” Gorman clarifies.
In an attempt to stop lithium imports from countries like Australia or Chile, tapping European reservoirs would help the European battery industry. Not to mention the fact that transportation from afar generates tons of greenhouse gas emissions.
For now, Evonik is concentrating on optimizing their method. After that, the team will work on some prototypes and trial designs to scale up the idea. For this purpose, the researchers will stack several electrolysis cells on top of each other, increasing the amount of treated wastewater.
In the future, electrolysis may take place in larger recycling or battery factories, closing the loop where it started. Several companies have announced plans for battery factories – so-called giga factories – in Europe to meet the growing demand. Some of these projects also provide for the recycling of batteries at the end of their life.
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