Every September, European Researchers’ Night invites the public to meet the people behind science. On 25 September 2026, museums, universities and research institutions across 40 countries expected over a million visitors. This year, CIRCUBATT joined in online with a campaign on circular battery research. We opened the doors of four partner teams and followed one simple question through their work: what happens to a battery after its first life?
The answer takes us from computer models in Switzerland to whiteboards in the United Kingdom. It continues in chemistry labs in Slovenia and pilot equipment in Norway. This article brings those four stories together. Step by step, and without jargon, it explains how researchers work to “close the loop” on batteries.
What does “closing the battery loop” actually mean?
Most products follow a straight line. We make them, use them and throw them away. Researchers call this a linear model. A circular model bends that line into a loop. Products and materials stay in use for as long as possible, and they return to the system instead of becoming waste.
For batteries, the loop has several stops. A battery may be too tired for an electric car. Yet it can still handle an easier job, such as storing solar energy for a building. We call that a second life. When a battery has nothing left to give, recycling can recover its valuable materials. Manufacturers can then use those materials to make a brand new battery, which brings us back to the start. CIRCUBATT works on every one of these stops, from battery design to reuse and recycling.
First, a quick look inside a battery
To see why a used battery still has value, it helps to look inside one. Electric cars, phones and laptops all use lithium-ion batteries. Each one contains many small units called cells.
Every cell has two sides, or electrodes. The positive side is the cathode and the negative side is the anode. Between them sits a liquid or gel, the electrolyte. When you charge a battery, tiny charged lithium particles move from the cathode to the anode. When you use it, they travel back, and that movement powers your device.
The cathode holds many of the most valuable materials. Depending on the recipe, it can contain lithium, nickel, cobalt, manganese, iron and phosphorus. People often shorten these recipes to three letters. NMC stands for nickel manganese cobalt. LFP stands for lithium iron phosphate. LCO stands for lithium cobalt oxide, a chemistry that phones and laptops have long used. These materials cost a lot, and Europe imports several of them. That is exactly why throwing a battery away wastes so much.
Stage 1: Can a used battery live again?
Every battery ages. Each charge and discharge causes small changes inside the cells. Gradually, the battery holds a little less energy than it did when new. In an electric car, range matters, so at some point the battery stops being ideal. But “not ideal for a car” is very different from “useless”.
At Battronics in Switzerland, Dr Michael Hess and his colleagues study this in-between moment. Their work happens on computers, not in a lab. They build models that predict how batteries age. They also weigh up what reuse would cost and what environmental footprint it would leave.
“We assess the ageing, cost and footprint of battery reuse in Europe,” Michael explains. His team wants to know how much value remains in cells that have already powered electric vehicles. Those cells could then work in battery energy storage systems. A battery energy storage system is simply a large bank of batteries. It stores electricity, for example from solar panels, for later use. For Michael, the motivation is personal. Reusing batteries could save resources and create new value and business in Europe.
Can a second life battery really do a good job? Our article Second-Life Batteries: Do They Really Perform Poorly? looks at the evidence.
Stage 2: Can a second life pay its way?
A working battery is only half the story. For second life batteries to become normal, someone has to pay for them. The numbers also need to make sense for everyone involved. That is where the University of Greenwich comes in. It coordinates CIRCUBATT, and its team researches new business models for batteries.
One of these models is Battery as a Service. Instead of buying a battery, a customer pays to use it, a bit like a subscription. The provider keeps ownership and looks after the battery throughout its life. That gives the provider every reason to reuse and recycle it responsibly. You can read more in When Does Battery-as-a-Service Make Business Sense?
For Researchers’ Night, the team shared photos from a working session. Prof Li Zhou, the project coordinator, and her colleagues James, Jimmy, Maggie and Jacky were building a mathematical model. It covers one pathway: second life batteries that support the electricity grid. “What might surprise people is that circular battery innovation isn’t only about battery technology,” the team says. They also need business and revenue models that let second life batteries create real value in energy systems.
The team has shared this thinking with industry before, including at the Cambridge workshop on the battery second life value chain earlier this year.
Stage 3: What can we recover when a battery is finished?
Eventually, even a second life ends. At this point, the goal changes from using the battery to recovering what is inside it. Recycling a battery is not like recycling a glass bottle. The valuable metals sit mixed together in tiny particles. Getting them back out cleanly takes careful chemistry.
One common family of recycling methods is hydrometallurgy. In simple terms, chemists dissolve the metals in a liquid, then separate and recover them one by one. Finding the right liquids and conditions is the hard part. The process has to be both efficient and safe.
At the National Institute of Chemistry in Ljubljana, Slovenia, researcher Marko Gabrovšek works on the chemistry of battery recycling. His photos offer a rare glimpse of that work. Rows of neatly labelled vials carry battery chemistries such as NMC, LFP and LCO. Others carry the names of organic acids, including citric acid, the same acid you find in lemons. “As a researcher, I get to play a small part in closing the recycling loop,” Marko says. For him, each small part adds up to a greener future.
Recycling also raises fair questions about safety and cost. We explore them in Is Battery Recycling Actually Safe? and Why Battery Recycling Isn’t Profitable Yet in Europe.
Stage 4: Can old materials become a new battery?
Recovering materials only makes sense if we can use them again. The final step of the loop turns them back into ingredients for a new battery. Researchers must also prove these materials are as good as freshly mined ones.
At Shift Materials in Oslo, Norway, the team does exactly that. They use recovered materials to make new LFP cathode material. That is the lithium iron phosphate recipe we met earlier, which many electric vehicles and energy storage systems use. Then comes the real test. The team compares its material with benchmark LFP to check whether it meets the required quality and performance. A benchmark is simply a reference sample that shows what “good enough” looks like.
What might surprise people most? According to the team, “materials from an old battery can become part of a new one.” The team includes CEO Rune Wendelbo, CTO Azadeh Motealleh and CSO Maryam Modares. Their motivation is simple: “Valuable materials from end-of-life batteries should not become waste.” By reusing those materials to make high-quality cathodes, they aim to reduce the need for virgin resources. Virgin resources are raw materials mined fresh from the ground. In turn, their work helps build a more sustainable and resilient battery value chain.
Why this matters for Europe
Closing the battery loop is not just a good idea. EU law increasingly requires it. The EU Batteries Regulation sets rules for the whole life of a battery, from design to disposal. It aims for batteries with a low carbon footprint and minimal harmful substances. It also wants batteries to need fewer imported raw materials. And it wants Europe to collect, reuse and recycle them to a high degree.
The regulation also sets clear recycling targets. By the end of 2027, recyclers must recover 90% of the cobalt, copper, lead and nickel, and 50% of the lithium. By the end of 2031, those targets rise to 95% and 80%. Meeting them depends on exactly the kind of circular battery research in this article. You can read the official summary on EUR-Lex and the European Commission’s overview of the recycling rules.
Circular battery research looks different in every lab
If Researchers’ Night teaches one lesson, it is this: no single picture shows what a battery researcher looks like. Some write computer models all day. Some fill whiteboards with equations. Others work at fume hoods with gloves and goggles. Each holds one piece of the puzzle, and the loop only closes when all the pieces fit.
A warm thank you to the teams at Battronics, the University of Greenwich, the National Institute of Chemistry and Shift Materials. Thank you for opening your doors to us. You can meet all of CIRCUBATT’s partners, explore our work packages or follow us on LinkedIn.
Frequently asked questions
What is a second life battery?
A second life battery has finished its first job, usually in an electric vehicle. But it still has enough capacity for an easier one. A common example is storing solar energy for a home, a business or the electricity grid.
Why not recycle every used battery straight away?
Recycling recovers materials, but it also uses energy. It also ends the battery’s life as a working product. If a battery still works well enough, reusing it first gets more value from the resources that went into it. Recycling becomes the right choice once the battery can no longer work safely or usefully.
What is Battery as a Service?
Battery as a Service is a business model where customers pay to use a battery instead of buying it. The provider keeps ownership and responsibility for the battery throughout its life. This encourages reuse, repair and proper recycling.
What is a cathode, and what do NMC and LFP mean?
The cathode is the positive side of a battery cell. It contains many of the battery’s most valuable materials. NMC and LFP are two common cathode recipes. NMC stands for nickel manganese cobalt, and LFP stands for lithium iron phosphate.
Is battery recycling safe?
Recyclers follow strict safety procedures, because used batteries can still hold energy and contain reactive materials. Our article Is Battery Recycling Actually Safe? explains the main risks and how recyclers manage them.
What is European Researchers’ Night?
European Researchers’ Night is a Europe-wide public event funded by the Marie Skłodowska-Curie Actions. It brings researchers and the public together through experiments, talks and activities. It usually takes place on the last Friday of September.
What is CIRCUBATT?
CIRCUBATT is a Horizon Europe research project that runs from January 2025 to December 2027. It brings together 10 organisations from 8 countries. Together, they aim to make Europe’s battery value chain more circular, from design to reuse and recycling. Our FAQ section has more answers.