Solar Energy

Researchers discover a surprising way to jump-start battery performance

Published

3 months ago

September 1, 2024

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Researchers discover a surprising way to jump-start battery performance

by Glennda Chui for SLAC News

Stanford CA (SPX) Sep 01, 2024

A lithium-ion battery’s very first charge is more momentous than it sounds. It determines how well and how long the battery will work from then on – in particular, how many cycles of charging and discharging it can handle before deteriorating.

In a study published in Joule, researchers at the SLAC-Stanford Battery Center report that giving batteries this first charge at unusually high currents increased their average lifespan by 50% while decreasing the initial charging time from 10 hours to just 20 minutes.

Just as important, the researchers were able to use scientific machine learning to pinpoint specific changes in the battery electrodes that account for this increase in lifespan and performance – invaluable insights for battery manufacturers looking to streamline their processes and improve their products.

The study was carried out by a SLAC/Stanford team led by Professor Will Chueh in collaboration with researchers from the Toyota Research Institute (TRI), the Massachusetts Institute of Technology and the University of Washington. It is part of SLAC’s sustainability research and a broader effort to reimagine our energy future leveraging the lab’s unique tools and expertise and partnerships with industry.

“This is an excellent example of how SLAC is doing manufacturing science to make critical technologies for the energy transition more affordable,” Chueh said. “We’re solving a real challenge that industry is facing; critically, we partner with industry from the get-go.”

This was the latest in a series of studies funded by TRI under a cooperative research agreement with the Department of Energy’s SLAC National Accelerator Laboratory.

The results have practical implications for manufacturing not just lithium-ion batteries for electric vehicles and the electric grid, but for other technologies, too, said Steven Torrisi, a senior research scientist at TRI who collaborated on the research.

“This study is very exciting for us,” he said. “Battery manufacturing is extremely capital, energy and time intensive. It takes a long time to spin up manufacturing of a new battery, and it’s really difficult to optimize the manufacturing process because there are so many factors involved.”

Torrisi said the results of this research “demonstrate a generalizable approach for understanding and optimizing this crucial step in battery manufacturing. Further, we may be able to transfer what we have learned to new processes, facilities, equipment and battery chemistries in the future.”

A “squishy layer” that’s key to battery performance

To understand what happens during the battery’s initial cycling, Chueh’s team builds pouch cells in which the positive and negative electrodes are surrounded by an electrolyte solution where lithium ions move freely.

When a battery charges, lithium ions flow into the negative electrode for storage. When a battery discharges, they flow back out and travel to the positive electrode; this triggers a flow of electrons for powering devices, from electric cars to the electricity grid.

The positive electrode of a newly minted battery is 100% full of lithium, said Xiao Cui, the lead researcher for the battery informatics team in Chueh’s lab. Every time the battery goes through a charge-discharge cycle, some of the lithium is deactivated. Minimizing those losses prolongs the battery’s working lifetime.

Oddly enough, one way to minimize the overall lithium loss is to deliberately lose a large percentage of the initial supply of lithium during the battery’s first charge, Cui said. It’s like making a small investment that yields good returns down the road.

This first-cycle lithium loss is not in vain. The lost lithium becomes part of a squishy layer called the solid electrolyte interphase, or SEI, that forms on the surface of the negative electrode during the first charge. In return, the SEI protects the negative electrode from side reactions that would accelerate the lithium loss and degrade the battery faster over time. Getting the SEI just right is so important that the first charge is known as the formation charge.

“Formation is the final step in the manufacturing process,” Cui said, “so if it fails, all the value and effort invested in the battery up to that point are wasted.”

High charging current boosts battery performance

Manufacturers generally give new batteries their first charge with low currents, on the theory that this will create the most robust SEI layer. But there’s a downside: Charging at low currents is time-consuming and costly and doesn’t necessarily yield optimal results. So, when recent studies suggested that faster charging with higher currents does not degrade battery performance, it was exciting news.

But researchers wanted to dig deeper. The charging current is just one of dozens of factors that go into the formation of SEI during the first charge. Testing all possible combinations of them in the lab to see which one worked best is an overwhelming task.

To whittle the problem down to manageable size, the research team used scientific machine learning to identify which factors are most important in achieving good results. To their surprise, just two of them – the temperature and current at which the battery is charged – stood out from all the rest.

Experiments confirmed that charging at high currents has a huge impact, increasing the lifespan of the average test battery by 50%. It also deactivated a much higher percentage of lithium up front – about 30%, compared to 9% with previous methods – but that turned out to have a positive effect.

Removing more lithium ions up front is a bit like scooping water out of a full bucket before carrying it, Cui said. The extra headspace in the bucket decreases the amount of water splashing out along the way. In similar fashion, deactivating more lithium ions during SEI formation frees up headspace in the positive electrode and allows the electrode to cycle in a more efficient way, improving subsequent performance.

“Brute force optimization by trial-and-error is routine in manufacturing – how should we perform the first charge, and what is the winning combination of factors?” Chueh said. “Here, we didn’t just want to identify the best recipe for making a good battery; we wanted to understand how and why it works. This understanding is crucial for finding the best balance between battery performance and manufacturing efficiency.”

This research was funded by the Toyota Research Institute through its Accelerated Materials Design and Discovery program.

Research Report:Data-driven analysis of battery formation reveals the role of electrode utilization in extending cycle life

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Solar Energy

More energy and oil possible through combining photovoltaic plants with hedgerow olive groves

Published

2 days ago

November 20, 2024

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More energy and oil possible through combining photovoltaic plants with hedgerow olive groves

by Hugo Ritmico

Madrid, Spain (SPX) Nov 20, 2024

The integration of photovoltaic plants on agricultural land has long sparked debate over balancing energy production with crop cultivation. Now, the innovative approach of combining both has gained momentum with promising results. This “agrivoltaic” system, which involves placing solar panels within agricultural setups, has been examined by a University of Cordoba research team to see if solar energy and agricultural production could mutually enhance each other.

The research group, including Marta Varo Martinez, Luis Manuel Fernandez de Ahumada, and Rafael Lopez Luque from the Physics for Renewable Energies and Resources group, along with Alvaro Lopez Bernal and Francisco Villalobos from the Soil-Water-Plant Relations group, developed a model that simulates an agrivoltaic system in hedgerow olive plantations. This simulation model combined predictions for oil yield from olive hedgerows and energy generation from solar collectors to assess combined productivity. The study concluded that using both in tandem increased overall productivity, marking a potential shift in land-use strategy that could cater to the needs for both clean energy and food.

The key findings show that mutual benefits arise when solar panels provide shade, acting as windbreaks that don’t compete for water, enhancing agricultural production. Meanwhile, the cooling effect from plant evapotranspiration can improve the efficiency of solar collectors by reducing their temperature, boosting energy output.

This model allows researchers to experiment with various collector configurations, adjusting heights, widths, and spacing, to pinpoint the most effective designs. Despite generally positive outcomes, the team noted that overly dense arrangements might limit space for machinery or complicate maintenance of the olive grove. The approach underscores the importance of balancing land-use density and operational accessibility.

Research Report:Simulation model for electrical and agricultural productivity of an olive hedgerow Agrivoltaic system

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Solar Energy

New initiative empowers Native American women with solar training

Published

2 days ago

November 20, 2024

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New initiative empowers Native American women with solar training

by Clarence Oxford

Los Angeles CA (SPX) Nov 20, 2024

Native American women across the country are gaining access to hands-on training in photovoltaic panel installation aimed at empowering them to establish solar systems in their communities and homes on tribal land.

Sandra Begay, an engineer at Sandia National Laboratories and a Navajo Nation member, is one of four mentors guiding this effort.

This training initiative is part of a Cooperative Research and Development Agreement between Sandia and Red Cloud Renewable, a nonprofit organization in Pine Ridge, South Dakota, that focuses on advancing energy independence for tribal members and communities.

Known as the Bridging Renewable Industry Divides in Gender Equality, or BRIDGE, Program, the initiative provides a five-week immersive training experience that emphasizes practical skills in photovoltaic installation.

In August, Begay joined the first group of participants in South Dakota.

“Five weeks is a long time to be away from home,” Begay said. “I provided encouragement and reminded the women that they made the right choice to participate in this program. We also used the time to reflect on what they learned.”

Participants are taught the components of photovoltaic systems and how to install them safely and effectively.

Begay also provided insight into the energy challenges faced by tribal communities.

“There are more than 20,000 homes on the Navajo Nation and some rural homes on the Hopi reservation that don’t have electricity. These are off-grid homes,” Begay said, noting that many of these homes depend on diesel generators. “We’re looking at a clean energy future. We want to move away from those types of fuels and look at clean energy sources such as solar.”

She highlighted that large-scale solar projects are being developed by the Navajo Nation and the Mountain Ute Tribe in Colorado.

“This program will provide participants with new employment opportunities and a better understanding of where we’re headed with clean energy,” Begay said.

Red Cloud Renewable also supports the women with resume building, interview training, networking, and job placement services.

With over 30 years of experience championing renewable energy in Native American communities, Begay is committed to maintaining relationships with participants.

“I am making a long-term commitment to the women in the BRIDGE Program,” Begay said. “I will share any job openings I see with them and support them in their job searches.”

Teamwork for success

Begay emphasized the critical role teamwork plays in photovoltaic installations.

“Photovoltaic installation happens with a team of people. How do you work through that group dynamic? How do you work with each other as a team? Those questions are underemphasized in the work we do. They’re going to rely on each other when installing photovoltaic systems,” she said.

Alicia Hayden, Red Cloud Renewable’s communications manager, noted the strong bond formed among the participants.

“What stood out to me was the incredible camaraderie among the women,” Hayden said. “They were genuinely supportive of each other and grateful to be participating in this program alongside women who share similar backgrounds.”

Funded by the Department of Energy’s Solar Energy Technology Office, the project is set to continue over the next few years and aims to train two additional groups, eventually involving around 45 women.

“These women will be equipped to take on installer jobs within their own reservations, bringing valuable skills and opportunities for sustainable development to their people,” Hayden said.

Despite being highly underrepresented in the solar industry – comprising just 0.05% of the sector, according to Red Cloud Renewable – Native American women stand to gain from this initiative.

Begay expressed optimism about the impact of the BRIDGE Program.

“It’s very gratifying both professionally and personally to see where we can help women who are underrepresented in the workforce, let alone in a unique technology like photovoltaic installation,” Begay said. “We’re seeding ideas for the women that they would never have thought of doing. I think that’s what’s unique.”

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Solar Energy

Perovskite advancements improve solar cell efficiency and longevity

Published

2 days ago

November 20, 2024

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Perovskite advancements improve solar cell efficiency and longevity

by Sophie Jenkins

London, UK (SPX) Nov 20, 2024

A global team led by the University of Surrey, in collaboration with Imperial College London, has pioneered a method to enhance the efficiency and durability of solar cells constructed from perovskite by addressing an unseen degradation pathway.

The University of Surrey’s Advanced Technology Institute (ATI) detailed their findings in ‘Energy and Environmental Science’, showing that by employing specific design strategies, they successfully created lead-tin perovskite solar cells achieving over 23% power conversion efficiency (PCE) – a significant result for this material type. Notably, these improvements also boosted the operational lifespan of these cells by 66%. PCE measures the proportion of sunlight converted to usable energy by a solar cell.

While traditional silicon solar panels are already widely used, advancements are steering towards perovskite/silicon hybrid panels, and fully perovskite-based panels promise even higher efficiencies. However, improving the stability and efficiency of lead-tin perovskite cells remains a significant hurdle. This research by the University of Surrey sheds light on mechanisms contributing to these limitations and offers a pathway to overcoming them, aiding in the broader advancement of solar technology.

Hashini Perera, Ph.D. student and lead author at ATI, stated: “The understanding we have developed from this work has allowed us to identify a strategy that improves the efficiency and extends the operational lifetime of these devices when exposed to ambient conditions. This advancement is a major step towards high efficiency, long-lasting solar panels which will give more people access to affordable clean energy while reducing the reliance on fossil fuels and global carbon emissions.”

The team focused on minimizing losses caused by the hole transport layer, crucial for solar cell functionality. By introducing an iodine-reducing agent, they mitigated the degradation effects, enhancing both the cell’s efficiency and its lifespan. This innovation paves the way for more sustainable and economically feasible solar technology.

Dr. Imalka Jayawardena from the University of Surrey’s ATI, co-author of the study, said: “By significantly enhancing the efficiency of our perovskite-based solar cells, we are moving closer to producing cheaper and more sustainable solar panels. We are already working on refining these materials, processes and the device architecture to tackle the remaining challenges.”

Professor Ravi Silva, Director of the ATI, added: “This research brings us closer to panels that not only generate more power over their lifetime but are also longer lasting. Greater efficiency and fewer replacements mean more green energy with less waste. The University of Surrey are in the process of building a 12.5MW solar farm, where we can test some of these modules. We’re confident that our innovative perovskite research will accelerate the widespread commercial adoption of perovskite-based solar panels.”

This progress aligns with the UN Sustainable Development Goals, specifically Goals 7 (affordable and clean energy), 9 (industry, innovation, and infrastructure), and 13 (climate action).

Research Report:23.2% efficient low band gap perovskite solar cells with cyanogen management