Solar Energy

Electric vehicle batteries: The older they get, the safer they are

Published

4 years ago

May 4, 2021

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Electric vehicle batteries: The older they get, the safer they are

As part of the project “SafeBattery”, a team from Graz University of Technology (TU Graz) has been investigating the behaviour of lithium-based batteries in electric cars under crash loads for the past four years.

“”The performance of new battery cells is largely known, so we dealt with the entire life cycle,” explains project manager Christian Ellersdorfer at the Institute of Vehicle Safety. Together with industry partners such as AVL, Audi and Daimler, research was conducted into scenarios that a battery can experience in the course of its life: for example, vibrations and strong accelerations caused by parking bumps, serious accidents and the constant charging and discharging of batteries.

Changes due to charging and discharging

With the help of crash tests, simulation models and calculation methods, the researchers were able to determine that vibrations and accelerations hardly affect the behaviour of batteries. However, more significant mechanical and electrical changes were seen as a result of the constant charging and discharging of the battery.

Battery cells aged in this way have a higher stiffness under mechanical load. “But the changes don’t necessarily mean that batteries become more dangerous with age. On the contrary. The sum of the influences makes them safer over time because they also lose electrical energy,” says Ellersdorfer.

The investigations of Ellersdorfer et al show that cells with a strongly reduced capacity content have a weakened course of the so-called thermal runaway after an internal short circuit. Thus, the reduced energy potential of aged batteries decreases the likelihood of accidental battery fires.

Benefit for automotive industry

Thanks to the research results, manufacturers now know what they can expect from a battery cell. This enables material-saving designs and greater efficiency, as Ellersdorfer explains: “Until now, the battery was installed in such a way that deformations could be ruled out in every conceivable scenario. Now manufacturers can make better use of the installation space. And safety checks on a new cell are valid for the life of the battery.”

Approval of EVBs for a second life

In the timeline of a battery’s life, the SafeBattery consortium now goes one step further. In the recently launched COMET project SafeLIB, the changes in traction batteries for electric vehicles are being examined in even greater detail together with other partners (LIT Law LAB, Infineon, Fronius, Mercedes) in order to be able to derive safety factors for subsequent use.

“”Used batteries with a power capacity of 80 percent are no longer suitable for electric vehicles, but they are very suitable for stationary energy storage or for machine tools. For the first time, we are determining generally valid parameters in the area of safety,” says Ellersdorfer, describing the project.

The researchers will use the world’s only test bench technology for battery safety at the Battery Safety Center Graz, which opened at the end of 2020. There, the early life of a battery cell can be examined at an unprecedented level of detail. The legal framework for re-usability (e.g. the question of liability for consequential damage) is also taken into account.

In addition to the so-called “state of health”, which reflects the existing residual capacity and performance of a battery cell, a “state of safety” should ultimately be defined, by which the safety status of a battery can be assessed over the entire life cycle. SafeLIB runs for four years and ends in 2025. The Austrian Research Promotion Agency FFG is funding the project with a total of 6 million euros (see FFG Fact sheet).

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Solar Energy

Scientists Probe Declining Earbud Battery Longevity

Published

1 day ago

February 5, 2025

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Scientists Probe Declining Earbud Battery Longevity

by Clarence Oxford

Los Angeles CA (SPX) Feb 05, 2025

Have you ever noticed how electronic devices, including wireless earbuds, seem to lose battery capacity faster the longer you use them? An international research team from The University of Texas at Austin set out to examine this familiar issue, known as battery degradation, by focusing on the earbuds that many people rely on daily. Through a series of x-ray, infrared, and other imaging approaches, the researchers investigated the hidden complexities behind these tiny devices and revealed why their battery life declines over time.

“This started with my personal headphones; I only wear the right one, and I found that after two years, the left earbud had a much longer battery life,” said Yijin Liu, an associate professor in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering, who led the new research published in Advanced Materials. “So, we decided to look into it and see what we could find.”

Their analysis showed that crucial earbud features – like the Bluetooth antenna, microphones, and circuits – compete with the battery in a very confined space, producing a microenvironment that is less than ideal. This situation results in a temperature gradient that damages the battery over time, with different sections of the cell experiencing variable temperatures.

Real-world factors also complicate matters. Frequent changes in climate, shifts in air quality, and a host of other environmental variables challenge the battery’s resilience. While cells are generally designed to endure harsh conditions, constant fluctuations can take their toll.

These discoveries highlight the importance of considering how batteries interact with devices such as phones, laptops, and even electric vehicles. Packaging solutions, strategic design decisions, and adaptations for user habits may all play a role in extending battery performance.

“Using devices differently changes how the battery behaves and performs,” said Guannan Qian, the first author of this paper and a postdoctoral researcher in Liu’s lab. “They could be exposed to different temperatures; one person has different charging habits than another; and every electric vehicle owner has their own driving style. This all matters.”

In conducting this study, Liu and his team worked closely with UT’s Fire Research Group, led by mechanical engineer Ofodike Ezekoye. They paired infrared imaging methods with their in-house x-ray technology at UT Austin and Sigray Inc. To expand their scope, they then teamed up with some of the world’s most advanced x-ray facilities.

Their collaborators included researchers from SLAC National Accelerator Laboratory’s Stanford Synchrotron Radiation Lightsource, Brookhaven National Laboratory’s National Synchrotron Light Source II, Argonne National Laboratory’s Advanced Photon Source, and the European Synchrotron Radiation Facility (ESRF) in France. These partnerships allowed them to observe battery behavior under more authentic operating conditions.

“Most of the time, in the lab, we’re looking at either pristine and stable conditions or extremes,” said Xiaojing Huang, a physicist at Brookhaven National Laboratory. “As we discover and develop new types of batteries, we must understand the differences between lab conditions and the unpredictability of the real world and react accordingly. X-ray imaging can offer valuable insights for this.”

Looking ahead, Liu says his team will continue analyzing battery performance in the settings people experience every day. They plan to expand their approach to larger batteries, such as those in smartphones, laptops, and electric vehicles, to learn more about their degradation patterns.

Research Report:In-device Battery Failure Analysis

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Solar Energy

Quantum factors elevate plant energy transport efficiency

Published

1 day ago

February 5, 2025

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Quantum factors elevate plant energy transport efficiency

by Robert Schreiber

Munich, Germany (SPX) Feb 05, 2025

For countless engineers, converting sunlight into easily stored chemical energy stands as an enduring goal. Yet nature perfected this challenge billions of years ago. A recent study reveals that quantum mechanics, once thought to be limited to physics, is also essential for key biological processes.

Green plants and other photosynthetic organisms draw on quantum mechanical mechanisms to capture the sun’s energy. According to Prof. Jurgen Hauer: “When light is absorbed in a leaf, for example, the electronic excitation energy is distributed over several states of each excited chlorophyll molecule; this is called a superposition of excited states. It is the first stage of an almost loss-free energy transfer within and between the molecules and makes the efficient onward transport of solar energy possible. Quantum mechanics is therefore central to understanding the first steps of energy transfer and charge separation.”

Classical physics alone cannot completely describe how this phenomenon unfolds throughout green plants and in certain photosynthetic bacteria. Although the exact details remain only partly understood, Prof. Hauer and first author Erika Keil consider their new findings an important step toward uncovering how chlorophyll, the pigment behind leaf coloration, functions. Applying these insights to engineered photosynthesis devices could unlock unprecedented solar energy conversion efficiencies for both power production and photochemical applications.

In their investigation, the researchers focused on two portions of the light spectrum absorbed by chlorophyll: the low-energy Q band (yellow to red) and the high-energy B band (blue to green). In the Q region, two electronic states are quantum mechanically coupled, promoting virtually loss-free energy movement. The system subsequently relaxes via “cooling”, i.e. by releasing energy in the form of heat. These observations demonstrate that quantum mechanical processes can play a major role in shaping key biological functions.

Research Report:Reassessing the role and lifetime of Qx in the energy transfer dynamics of chlorophyll a

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Solar Energy

HZB sets new efficiency record for CIGS perovskite tandem solar cells

Published

2 days ago

February 5, 2025

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HZB sets new efficiency record for CIGS perovskite tandem solar cells

by Robert Schreiber

Berlin, Germany (SPX) Feb 05, 2025

Researchers at Helmholtz Center Berlin for Materials and Energy (HZB) and Humboldt University Berlin have developed a CIGS-perovskite tandem solar cell that has set a new world record for efficiency, achieving 24.6%. The performance of the cell has been officially certified by the Fraunhofer Institute for Solar Energy Systems.

Thin-film solar cells, such as those based on copper, indium, gallium, and selenium (CIGS), require minimal material and energy to manufacture, making them an environmentally friendly alternative to conventional silicon-based solar cells. CIGS thin films can also be applied to flexible substrates, expanding their potential applications.

The new tandem solar cell developed by HZB and Humboldt University combines a CIGS bottom cell with a perovskite top cell. By optimizing the contact layers between these two components, the research team successfully increased efficiency to a record-breaking 24.6%. This milestone was confirmed by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany.

This achievement was made possible through a collaborative effort among researchers. The top cell was developed by Thede Mehlhop, a master’s student at TU Berlin, under the supervision of Stefan Gall. The perovskite absorber layer was created in the joint laboratory of HZB and Humboldt University Berlin, while the CIGS sub-cell and contact layers were fabricated by HZB researcher Guillermo Farias Basulto. Additionally, the KOALA high-performance cluster system at HZB was used to deposit the perovskite and contact layers in a vacuum.

“At HZB, we have highly specialized laboratories and experts who are top performers in their fields. With this world record tandem cell, they have once again shown how fruitfully they work together,” said Prof. Rutger Schlatmann, spokesman for the Solar Energy Department at HZB.

HZB has a strong track record in achieving world records in solar cell efficiency, including past accomplishments in silicon-perovskite tandem cells and now in CIGS-perovskite tandem technology.

“We are confident that CIGS-perovskite tandem cells can achieve much higher efficiencies, probably more than 30%,” said Prof. Rutger Schlatmann.