Solar Energy

Cobalt-free batteries could power cars of the future

Published

9 months ago

January 19, 2024

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Cobalt-free batteries could power cars of the future

by Anne Trafton | MIT News

Boston MA (SPX) Jan 19, 2024

Many electric vehicles are powered by batteries that contain cobalt – a metal that carries high financial, environmental, and social costs.

MIT researchers have now designed a battery material that could offer a more sustainable way to power electric cars. The new lithium-ion battery includes a cathode based on organic materials, instead of cobalt or nickel (another metal often used in lithium-ion batteries).

In a new study, the researchers showed that this material, which could be produced at much lower cost than cobalt-containing batteries, can conduct electricity at similar rates as cobalt batteries. The new battery also has comparable storage capacity and can be charged up faster than cobalt batteries, the researchers report.

“I think this material could have a big impact because it works really well,” says Mircea Dinca, the W.M. Keck Professor of Energy at MIT. “It is already competitive with incumbent technologies, and it can save a lot of the cost and pain and environmental issues related to mining the metals that currently go into batteries.”

Dinca is the senior author of the study, which appears in the journal ACS Central Science. Tianyang Chen PhD ’23 and Harish Banda, a former MIT postdoc, are the lead authors of the paper. Other authors include Jiande Wang, an MIT postdoc; Julius Oppenheim, an MIT graduate student; and Alessandro Franceschi, a research fellow at the University of Bologna.

Alternatives to cobalt

Most electric cars are powered by lithium-ion batteries, a type of battery that is recharged when lithium ions flow from a positively charged electrode, called a cathode, to a negatively electrode, called an anode. In most lithium-ion batteries, the cathode contains cobalt, a metal that offers high stability and energy density.

However, cobalt has significant downsides. A scarce metal, its price can fluctuate dramatically, and much of the world’s cobalt deposits are located in politically unstable countries. Cobalt extraction creates hazardous working conditions and generates toxic waste that contaminates land, air, and water surrounding the mines.

“Cobalt batteries can store a lot of energy, and they have all of features that people care about in terms of performance, but they have the issue of not being widely available, and the cost fluctuates broadly with commodity prices. And, as you transition to a much higher proportion of electrified vehicles in the consumer market, it’s certainly going to get more expensive,” Dinca says.

Because of the many drawbacks to cobalt, a great deal of research has gone into trying to develop alternative battery materials. One such material is lithium-iron-phosphate (LFP), which some car manufacturers are beginning to use in electric vehicles. Although still practically useful, LFP has only about half the energy density of cobalt and nickel batteries.

Another appealing option are organic materials, but so far most of these materials have not been able to match the conductivity, storage capacity, and lifetime of cobalt-containing batteries. Because of their low conductivity, such materials typically need to be mixed with binders such as polymers, which help them maintain a conductive network. These binders, which make up at least 50 percent of the overall material, bring down the battery’s storage capacity.

About six years ago, Dinca’s lab began working on a project, funded by Lamborghini, to develop an organic battery that could be used to power electric cars. While working on porous materials that were partly organic and partly inorganic, Dinca and his students realized that a fully organic material they had made appeared that it might be a strong conductor.

This material consists of many layers of TAQ (bis-tetraaminobenzoquinone), an organic small molecule that contains three fused hexagonal rings. These layers can extend outward in every direction, forming a structure similar to graphite. Within the molecules are chemical groups called quinones, which are the electron reservoirs, and amines, which help the material to form strong hydrogen bonds.

Those hydrogen bonds make the material highly stable and also very insoluble. That insolubility is important because it prevents the material from dissolving into the battery electrolyte, as some organic battery materials do, thereby extending its lifetime.

“One of the main methods of degradation for organic materials is that they simply dissolve into the battery electrolyte and cross over to the other side of the battery, essentially creating a short circuit. If you make the material completely insoluble, that process doesn’t happen, so we can go to over 2,000 charge cycles with minimal degradation,” Dinca says.

Strong performance

Tests of this material showed that its conductivity and storage capacity were comparable to that of traditional cobalt-containing batteries. Also, batteries with a TAQ cathode can be charged and discharged faster than existing batteries, which could speed up the charging rate for electric vehicles.

To stabilize the organic material and increase its ability to adhere to the battery’s current collector, which is made of copper or aluminum, the researchers added filler materials such as cellulose and rubber. These fillers make up less than one-tenth of the overall cathode composite, so they don’t significantly reduce the battery’s storage capacity.

These fillers also extend the lifetime of the battery cathode by preventing it from cracking when lithium ions flow into the cathode as the battery charges.

The primary materials needed to manufacture this type of cathode are a quinone precursor and an amine precursor, which are already commercially available and produced in large quantities as commodity chemicals. The researchers estimate that the material cost of assembling these organic batteries could be about one-third to one-half the cost of cobalt batteries.

Lamborghini has licensed the patent on the technology. Dinca’s lab plans to continue developing alternative battery materials and is exploring possible replacement of lithium with sodium or magnesium, which are cheaper and more abundant than lithium.

Research Report:er: “A Layered Organic Cathode for High-Energy, Fast-Charging, and Long-Lasting Li-Ion Batteries”

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Solar Energy

Sandia evaluates heat shields for Mars Sample Return and Titan missions

Published

2 days ago

October 16, 2024

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Sandia evaluates heat shields for Mars Sample Return and Titan missions

by Clarence Oxford

Los Angeles CA (SPX) Oct 16, 2024

Sandia National Laboratories’ National Solar Thermal Test Facility is utilizing solar energy to simulate the intense heat experienced during atmospheric reentry and hypersonic flight. The latest tests aim to support NASA missions, including the Mars Sample Return campaign, a joint effort with the European Space Agency to bring Martian rock samples to Earth for analysis. These samples could reveal evidence of ancient life and aid preparations for future human missions to Mars.

As part of the Mars Sample Return mission, a Sample Retrieval Lander would carry the heaviest payload ever sent to Mars, along with a rocket for launching the collected samples into Martian orbit. Heat shield materials for the lander recently underwent testing at Sandia, said Sandia engineer and test director Ken Armijo. “This would be the first mission to return rocks from Mars to Earth; it’s got a bigger payload,” Armijo explained. “The heavier the payload and the bigger the entry vehicle, the hotter the vehicle gets during atmospheric entry, and the better the heat shield needs to be.”

Sandia’s solar testing facility uses hundreds of heliostat mirrors to focus sunlight on samples up to three feet wide, simulating atmospheric conditions on different planets. Unlike arc jets and lasers, which consume significant power, this approach saves between 15,000 to 60,000 kilowatts per test, equivalent to running 5,000 to 20,000 clothes dryers simultaneously.

The facility’s solar power tower, 200 feet tall and equipped with 212 heliostats, provides a unique environment for testing materials under high solar flux and heat. “We have high flux and high flux distribution on the Solar Tower,” said Armijo. The facility can simulate hypersonic flight conditions and accommodate large test samples, including full aircraft sections. Sunlight is concentrated up to 3,500 times its normal intensity, allowing precise control over heat exposure.

Compared to the $100,000-per-day cost of arc jet testing and the $150,000-per-day cost of laser testing, solar testing costs about $25,000 per day, Armijo noted. The intensity of sunlight can be adjusted by varying the number of heliostats focused on the sample, mimicking different reentry conditions. NASA’s lead engineer for the Sample Retrieval Lander’s heat shield, Brandon Smith, commented, “Sandia’s ability to test at this size nicely complements our other test facilities.”

Testing also supports NASA’s Dragonfly mission to Titan, Saturn’s largest moon, with heat shield materials made from Phenolic Impregnated Carbon Ablator, developed at NASA’s Ames Research Center. Previously used in missions like Stardust and Mars 2020, the material was tested on two-foot-wide samples at Sandia. The facility’s capability to test larger samples allowed NASA to simulate the stress and strain experienced during atmospheric entry.

Dragonfly, a rotorcraft designed to explore Titan’s methane-rich atmosphere, faces unique challenges due to Titan’s dense atmosphere, which is four times thicker than Earth’s. To recreate the thermal conditions of Martian and Titan atmospheric entry, nitrogen gas is blown over the heat shield samples during tests. A newly installed gas line running from the base to the top of the power tower ensures adequate gas flow, said Armijo.

Daniel Ray, a mechanical technologist at Sandia, was responsible for setting up the gas line and addressing issues during tests. “My role on every project is to make it work,” Ray said. He resolved an issue with the carbon felt catching fire by designing ceramic shields to protect the system.

In 2022, Sandia also supported the Applied Physics Laboratory’s tests on a heat exchanger prototype intended for future spacecraft. The prototype endured light levels equivalent to 2,000 suns, reaching temperatures of 3,100 degrees Fahrenheit, demonstrating its ability to withstand the intense heat of a close solar flyby.

The facility’s history includes various aerospace projects, such as testing radar protection domes and evaluating materials for space shuttles and military aircraft. Sandia has refined its solar testing methods over the years, said Armijo. “Because we can dial-in the profiles, we have more confidence that it’s going to survive and function well during a mission. Having confidence that it will make it to Mars, land and pick up the rocks safely is important.”

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Solar Energy

Computer simulations offer new insights into enhancing solar cell materials

Published

2 days ago

October 16, 2024

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Computer simulations offer new insights into enhancing solar cell materials

by Robert Schreiber

Berlin, Germany (SPX) Oct 16, 2024

Researchers from Chalmers University of Technology in Sweden have made progress in understanding halide perovskites, a promising class of materials for solar cells. These materials could serve as an efficient and cost-effective alternative to traditional silicon-based cells, but they face challenges with stability. The new insights are expected to aid the development of more reliable and efficient solar cells, key components in the transition to sustainable energy.

Halide perovskites refer to a group of materials recognized for their potential in flexible, lightweight solar cells and various optical applications, such as LEDs. They exhibit high efficiency in light absorption and emission, making them suitable for next-generation solar technologies. However, understanding the causes of rapid degradation remains a hurdle in optimizing these materials.

Advanced computer simulations reveal material behavior

The research team employed advanced computer simulations and machine learning to study 2D perovskite materials, which are typically more stable than their 3D counterparts. The findings, published in *ACS Energy Letters*, provide new insights into the factors that influence the materials’ properties.

“By mapping out the material in computer simulations and subjecting it to different scenarios, we can draw conclusions about how the atoms in the material react when exposed to heat, light, and so on,” explained Professor Paul Erhart from the research team. “We now have a microscopic description of the material that is independent of what experiments have shown, but which we can show to lead to the same behavior as the experiments.”

Simulations allow researchers to analyze material behaviors at a detailed level, offering a unique view that complements experimental data. This approach has made it possible to observe what leads to specific outcomes in experiments, deepening the understanding of 2D perovskites’ functionality.

Machine learning enables broader and deeper analysis

The integration of machine learning techniques allowed the researchers to study larger systems over longer durations than was previously feasible.

“This has given us both a much broader overview than before, but also the ability to study materials in much more detail,” said Associate Professor Julia Wiktor. “We can see that in these very thin layers of material, each layer behaves differently, and that’s something that is very difficult to detect experimentally.”

The composition and interaction of layers in 2D perovskites

2D perovskites consist of inorganic layers separated by organic molecules, which play a crucial role in determining the material’s stability and optical properties. Understanding the atomic movements within these layers and their connection to the organic linkers is essential for designing efficient devices.

“In 2D perovskites, you have perovskite layers linked with organic molecules. What we have discovered is that you can directly control how atoms in the surface layers move through the choice of the organic linkers,” noted Erhart. “This movement is crucial to the optical properties, creating a domino effect that extends deep inside the material.”

Future research directions

The study’s results pave the way for developing more stable and efficient optoelectronic devices by identifying which molecular configurations could enhance performance. The researchers aim to extend their work to more complex systems, focusing on interfaces that are essential for device functionality.

“Our next step is to move to even more complex systems and in particular interfaces that are fundamental for the function of devices,” Wiktor added.

Research Report:Impact of Organic Spacers and Dimensionality on Templating of Halide Perovskites

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Solar Energy

Bright future for solar panels and screens with new nanocrystal research

Published

2 days ago

October 16, 2024

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Bright future for solar panels and screens with new nanocrystal research

by Simon Mansfield

Sydney, Australia (SPX) Oct 16, 2024

Curtin University researchers have made a significant discovery that could enhance everyday technology, from TV screens to solar panels and medical diagnostics. The study, led by Associate Professor Guohua Jia, revealed how to increase the number of molecules, known as ligands, that adhere to zinc sulfide nanocrystals by manipulating the shape of these tiny particles.

Associate Professor Jia from Curtin’s School of Molecular and Life Sciences explained that ligands are essential for influencing the behavior and performance of zinc sulfide nanocrystals across various applications. “Ligands play an important role in controlling the behaviour and performance of zinc sulfide nanocrystals in various important technologies,” Jia said.

The research found that flatter, more uniform particles, termed nanoplatelets, can accommodate a greater number of tightly bound ligands compared to other shapes such as nanodots and nanorods. “In a discovery that could open new possibilities for developing smarter, more advanced devices, our study found flatter, more even particles called nanoplatelets allow more ligands to attach tightly, compared to other shapes like nanodots and nanorods,” Jia explained.

By tailoring the shapes of these nanocrystals, the researchers were able to enhance their interactions with surrounding environments, boosting the efficiency of a wide range of applications. Jia highlighted that these findings could potentially transform the efficiency and performance of products such as LED lights, screens, solar panels, and medical imaging devices.

The discovery also holds promise for advancing optoelectronic devices, which either generate light or utilize it to perform various functions. “Optoelectronics are important in many modern technologies, including telecommunications, medical devices and energy production,” Jia noted. The ability to control the manipulation of light and electricity is vital for the development of faster, more efficient, and compact electronic systems.

The applications include LEDs used in light bulbs and TV screens, solar cells that convert sunlight into electrical power, photodetectors in cameras and sensors, and laser diodes in fiber-optic communication systems.

Research Report:Deciphering surface ligand density of colloidal semiconductor nanocrystals: Shape matters