Electric vehicle batteries get a longer lifespan when weak cells are bypassed
image:
Photo Ivan Radic licensed under CC BY 2.0.
view moreCredit: Photo Ivan Radic licensed under CC BY 2.0.
In today's electric vehicle batteries, a single weak cell can limit the life of the entire battery pack, even when the other cells are still working well. The goal is for future batteries to be able to bypass weak cells and make better use of the remaining capacity. A study, led by researchers at Chalmers University of Technology, in Sweden, now shows that a new ‘smart battery architecture’, under optimal conditions, can give electric vehicle batteries over 20 percent longer life in certain vehicles. At the same time, the total cost can be reduced over the battery's lifetime.
Battery packs in electric vehicles, or EVs, consist of many interconnected cells that do not age in the same way. In today's battery structure, the weakest cell can therefore set the limit for the entire package.
Albert Škegro, a doctoral student at the Department of Electrical Engineering at Chalmers University of Technology in Sweden, draws an analogy, describing the structure as the cells being connected by a rope, while they all try to move forward.
"Since they are bound to each other, everyone has to keep the same pace as the slowest cell and stop when that cell stops. With the solution in our study, the battery can instead bypass the cell that is causing problems and continue forward," says Albert Škegro, first author of the new study, which has been published in Nature Communications and conducted in collaboration with industry.
Previous research has shown how important differences between cells can be for the performance and lifespan of EV batteries. In a recently published study, co-authored by Chalmers researcher Changfu Zou, the researchers found that the weakest cells clearly limit the entire battery pack.
A battery that can adapt as cells age
In the new study, the researchers map the benefits of so-called reconfigurable battery packs, where switches and control systems can change the connections between the cells. These battery packs can bypass weaker cells so that more of the remaining capacity can be utilised.
In the researchers' models, the most advanced solution – where each cell can be controlled separately – can extend the lifespan by over 20 percent in some high-voltage vehicles, such as electric trucks and long-range electric cars. In practice, groups of cells are more likely to be controlled together, so the figure is a theoretical upper limit.
"Reconfiguration is not a question of 'on or off'. It is a spectrum, and where a manufacturer chooses to sit on that spectrum determines how much of the potential benefit can be realised," says Changfu Zou, Professor at the Department of Electrical Engineering at Chalmers and co-author of the study.
Longer lifespan can outweigh higher cost
To illustrate what the results can mean in practice, the researchers analysed an example with a typical 80 kilowatt-hour car battery and 12,000 kilometres of annual mileage. The example assumes that a conventional battery pack is replaced after 10 years, in line with current industry practice. In the model, the reconfigurable pack reaches the same point after about 11 years, so roughly 14 months longer. It also had a higher residual value because it had deteriorated less through aging.
"For a private electric car owner, it is a great advantage that the car's battery lasts longer. For a fleet with hundreds of battery packs, extending the battery life can mean significant savings," says Albert Škegro.
The technology is not yet available in series- or mass- produced vehicles but has been tested in research and industrial prototypes. Since it requires additional electronics, the technology has a higher initial cost, but the researchers also show that a longer service life and higher residual value can outweigh the additional cost under many realistic conditions. The potential is greatest in high-voltage vehicles with a long range and many series-connected cells.
In addition to the increased battery life, the researchers also point to more sustainability gains. Today, considerable resources are spent on testing and matching cells with similar characteristics during manufacturing. The new technology allows greater variation between cells and could therefore reduce the need for such precise matching. A larger part of the battery packs can also be given a second life, for example, as stationary energy storage.
"A battery pack that is taken out of service prematurely means both wasted material and wasted energy. Keeping battery packs in use for longer is therefore a sustainability argument even before you take the economy into account," says Albert Škegro.
More about the research:
The study System-level assessment of dynamic reconfiguration for lifetime and cost outcomes in electric vehicle battery packs | Nature Communications, published in Nature Communications.
The authors are Albert Škegro, Torsten Wik and Changfu Zou at Chalmers University of Technology; Bo Bijlenga at PHINIA Inc, Åmål; and Alexander Bessman at Scania CV AB, Södertälje.
Journal
Nature Communications
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
System-level assessment of dynamic reconfiguration for lifetime and cost outcomes in electric vehicle battery packs
Conceptual diagram visualising reconfigurable battery packs as the trunk of a tree. Graphic by Albert Škegro, Chalmers University of Technology
Credit
Albert Škegro / Chalmers University of Technology
Platinum in fuel cells lasts longer with nitrogen-enhanced graphene wrapper
Nagoya University
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A sample of the newly developed catalyst, Pt@N-FLG/SWCNT
view moreCredit: Sumeet Kulkarni, Nagoya University
Researchers from Nagoya University in Japan have developed a durable fuel-cell catalyst by wrapping platinum nanoparticles in nitrogen-containing graphene and placing them on carbon nanotubes. This design retained 96.9% of its active surface after 30,000 durability cycles, pointing towards fuel cells with longer lifespans and lower platinum demand.
Fuel cells turn the chemical energy of hydrogen directly into electricity. Hydrogen is fed to one side of the cell, where it separates into protons and electrons. The electrons travel through an external circuit to provide power, while the protons cross a membrane. On the other side, they reunite with the electrons and oxygen from air, producing water.
Water is the only by-product here; no carbon dioxide is emitted at any point during this process. This makes fuel cells promising sources of clean energy that can be used to power vehicles and other applications. Fuel cells are particularly useful for heavy-duty vehicles and public transport since they require much larger conventional EV batteries.
However, broader commercial use of fuel cells is limited by cost. The reaction between oxygen, protons and electrons is slow. To speed it up, platinum, a scarce and expensive precious metal, is used as a catalyst.
To save costs, research fuel cell catalyst technology is currently targeting two fronts: increasing its performance and durability. “Durability is a critical problem especially for use in heavy-duty vehicles,” said Miftakhul Huda, a Designated Lecturer working in the Matsuo Lab at Nagoya University’s Department of Chemical Systems Engineering and a lead investigator of this study along with Professor Yutaka Matsuo. “In this work, we have increased the durability of both platinum and its carbon support in fuel cells,” he added.
Platinum’s protective shell: an accidental discovery
Platinum works by offering active sites that hold oxygen molecules, help break them apart and combine quickly with protons and electrons to form water. Making platinum particles smaller to the nano-scale exposes more surface for this reaction, allowing less platinum to do more work.
Current commercially available electrocatalsys typically consist of bare platinum nanoparticles supported on amorphous carbon materials. But these nanoparticles tend to clump into larger particles during operation, slowly degrading performance over time. Meanwhile, conventional carbon supports can still corrode during the repeated voltage changes experienced when a fuel-cell system starts and stops.
To solve this problem, the researchers encapsulated each platinum nanoparticle into a graphene shell. Normally, encapsulated nanoparticles do not make great catalysts because they offer fewer active sites for the reaction to occur. But by doping the graphene shell with nitrogen, the researchers found that the number of active sites actually exceeded their theoretical estimates. The nitrogen in the shell interacted with the platinum. This changed how the metal handled oxygen-containing molecules, helping the reaction proceed more efficiently rather than simply shielding the platinum from its surroundings.
Next, they needed something to load the particles on, for which Matsuo, Huda and their team obtained corrosion-resistant single-walled carbon nanotubes from Meijo Nano Carbon Co., Ltd., based in Nagoya, Japan. But something strange happened when they tried to attach platinum nanoparticles on it: they realized no linkers were needed!
“It was actually very accidental, we just decided to try directly loading the graphene-encapsulated platinum first and it attached well,” said Huda about the discovery, for which he credits his materials engineering background for not following the conventional chemistry approach of always using an intermediary to form metal-carbon bonds.
The new catalyst, named “Pt@N-FLG/SWCNT” for nitrogen-doped few-layer graphene-shell-encapsulated platinum electrocatalysts supported by single-walled carbon nanotubes, has been reported in the journal ACS Catalysis.
Built to endure
In laboratory measurements, Pt@N-FLG/SWCNT provided 96.3 square metres of active platinum surface per gram, compared to 60.6 square meters for a commercial catalyst.
The team next assembled the catalyst into a working fuel cell and subjected it to repeated voltage cycles designed to accelerate aging. After 30,000 cycles, it had lost only 3.1% of its active platinum surface and its voltage had dropped by 22.8 millivolts. In addition, no voltage loss was observed at 1.5 amperes after 5000 cycles of rigorous high-voltage triangular-wave cycling to simulate carbon corrosion. Both results surpassed the US Department of Energy’s 2025 targets for electrocatalysts.
Further imaging suggested that the nanotubes restricted how far the platinum could move. Instead of growing into the large clumps usually seen in aged catalysts, the particles aligned into slender wire-like structures, which may help preserve useful surface area.
Having achieved a desired level of durability, the Matsuo Lab wants to turn to the efficiency problem next. “We not only want to increase the performance, but also decrease the amount of platinum needed in fuel cells in order to scale up,” Huda said.
Journal
ACS Catalysis
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Pt–N Interactions and Nitrogen-Doped Graphene-Shell Encapsulation in Platinum Electrocatalysts Supported by SWCNTs for Enhanced ORR Activity and Durability
Transmission Electron Microscopy (TEM) photos show slender wire-like structures and no clumping of platinum nanoparticles in the new catalyst Pt@N-FLG/SWCNT after durability tests.
The structure of Pt@N-FLG/SWCNT and its performance metrics.
Credit
Yu et al., ACS catalysis, 2026.
Yu et al., ACS catalysis, 2026.
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