A film capacitor that can take the heat
Scripps Research scientists and collaborators use an innovative set of machine-learning models to discover a record-breaking material for film capacitors, key components in many energy technologies.
December 05, 2024
- Content provided by Berkeley Lab, with light edits for stylistic purposes. -
LA JOLLA, CA – Scripps Research, the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), and several other collaborating institutions have successfully demonstrated a machine-learning technique to accelerate discovery of materials for film capacitors—crucial components in electrification and renewable energy technologies. The technique was used to screen a library of nearly 50,000 chemical structures to identify a compound with record-breaking performance.
The other collaborators include University of Wisconsin–Madison, University of California–Berkeley and University of Southern Mississippi.
Their research, reported in the journal Nature Energy on December 5, 2024, highlights the rapidly growing demand for film capacitors that can be used in high-temperature, high-power applications such as electric vehicles, electric aviation, power electronics and aerospace. Film capacitors are also essential components in the inverters that convert solar and wind generation into the alternating-current power that can be used by the electric grid.
This study builds on their previous work, in which K. Barry Sharpless, PhD, W.M. Keck Professor of Chemistry at Scripps Research; Scripps Research Molecular and Cellular Biology Professor Peng Wu, PhD; and Berkeley Lab Facility Director for Organic and Macromolecular Synthesis Yi Liu, PhD, discovered a new type of polysulfate compound to be used in polymer film capacitors. They found these thin polysulfate membranes shielded the capacitors from destruction by harsh conditions: high operating heat environment and high electric fields.
“As a chemist, our previous findings presented an existential challenge: How could a powerful electromagnetic energy wave from physics be tamed by passing through a thin polysulfate film?” says Sharpless, co-senior author of the new study. “Now, our new collaboration has enabled a significant advancement in this project, which seeks much better capacitor shields that could lead to crucial energy savings in common electric power applications. In short, our AI analysis quickly identified some key variables in the polymer design details that were predicted to add big improvements in the shielding properties of these polysulfate membranes. As reported in our new Nature Energy study, these earliest machine learning predictors for improving the capacitors are dramatically born-out by experiment.”
“For cost-effective, reliable renewable energy technologies, we need better performing capacitor materials than what are available today,” Liu adds, who is also a co-senior author of the new study. “This breakthrough screening technique will help us find these ‘needle-in-a-haystack’ materials.”
Film capacitors require heat-resistant materials
Batteries receive a lot of attention as a workhorse in renewable energy applications, but electrostatic film capacitors are also important. These devices consist of an insulating material sandwiched between two conductive metal sheets. While batteries use chemical reactions to store and release energy over long periods, capacitors use applied electric fields to charge and discharge energy much more quickly.
Film capacitors are used for regulating power quality in diverse types of power systems. For example, they can prevent ripple currents and smooth voltage fluctuations, ensuring stable, safe, reliable operations.
Polymers—large molecules with repeating chemical units—are well-suited for the insulating material in film capacitors because of their light weight, flexibility, and endurance under applied electric fields. However, polymers have a limited ability to tolerate the high temperatures in many power system applications. Intense heat can reduce the polymers’ insulating properties and cause them to degrade.
Narrowing down 49,700 polymers to three
Researchers have traditionally looked for high-performance polymers through trial and error, synthesizing a few candidates at a time and then characterizing their properties.
To accelerate discovery, the research team developed and trained a set of machine-learning models known as feedforward neural networks to screen a library of nearly 50,000 polymers for an optimal combination of properties, including the ability to withstand high temperatures and strong electric fields, high energy storage density, and ease of synthesis. The models identified three particularly promising polymers.
Interestingly, these three polymers had already been discovered by Sharpless, Liu and team in a previous study. They had synthesized the compounds using a powerful technique, known as click chemistry, that rapidly and efficiently links together molecular building blocks into high-quality products. Sharpless was one recipient of the 2022 Nobel Prize in Chemistry for his role in developing the click-chemistry concept.
At Berkeley Lab’s Molecular Foundry, the researchers fabricated film capacitors from these polymers and then evaluated both the polymers and capacitors. The team found that they had exceptional electrical and thermal performance. Capacitors made from one of the polymers exhibited a record-high combination of heat resistance, insulating properties, energy density and efficiency. (A high-efficiency capacitor wastes very little energy when it charges and discharges.) Additional tests on these capacitors revealed their superior material quality, operational stability, and durability.
Making even better models
The research team is considering several lines of follow-up research. One idea is to design machine learning models that provide more insights into how the structure of polymers influences their performance. Another potential research area is to develop generative AI models that can be trained to design high-performance polymers without having to screen a library.
The Molecular Foundry is a Department of Energy Office of Science user facility at Berkeley Lab.
The research was supported by the Department of Energy’s Office of Science (BES).
About Scripps Research
Scripps Research is an independent, nonprofit biomedical institute ranked one of the most influential in the world for its impact on innovation by Nature Index. We are advancing human health through profound discoveries that address pressing medical concerns around the globe. Our drug discovery and development division, Calibr-Skaggs, works hand-in-hand with scientists across disciplines to bring new medicines to patients as quickly and efficiently as possible, while teams at Scripps Research Translational Institute harness genomics, digital medicine and cutting-edge informatics to understand individual health and render more effective healthcare. Scripps Research also trains the next generation of leading scientists at our Skaggs Graduate School, consistently named among the top 10 US programs for chemistry and biological sciences. Learn more at www.scripps.edu.
About the Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory (Berkeley Lab) is committed to delivering solutions for humankind through research in clean energy, a healthy planet, and discovery science. Founded in 1931 on the belief that the biggest problems are best addressed by teams, Berkeley Lab and its scientists have been recognized with 16 Nobel Prizes. Researchers from around the world rely on the lab’s world-class scientific facilities for their own pioneering research. Berkeley Lab is a multiprogram national laboratory managed by the University of California for the U.S. Department of Energy’s Office of Science.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
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