New Polymer Blend Could Help Store Energy for the Grid and EVs

As electronics demand higher energy density, one component has proved challenging to shrink: the capacitor. Making a smaller capacitor usually requires thinning the dielectric layer or electrode surface area, which has often resulted in a reduction of power. A new polymer material could help change that. In a study published 18 February in Nature, a Pennsylvania State University-led team reported a capacitor crafted from a polymer blend that can operate at temperatures up to 250 °C while storing roughly four times as much energy as conventional polymer capacitors. Today’s advanced polymer capacitors typically function only up to about 100 °C, meaning engineers often rely on bulky cooling systems in high-power electronics. The research team has filed a patent for the polymer capacitors and plans to bring them to market. Capacitors deliver rapid bursts of energy and stabilize voltage in circuits, making them essential in applications ranging from electric vehicles and aerospace electronics to power-grid infrastructure and AI data centers. Yet while transistors have steadily shrunk with advances in semiconductor manufacturing, passive components such as capacitors and inductors have not scaled at the same pace. “Capacitors can account for 30 to 40 percent of the volume in some power electronics systems,” says Qiming Zhang, an electrical engineering researcher at Penn State and study author, explaining why it’s important to make smaller capacitors. A plastics blend more powerful than its parts The research team combined two commercially available engineered plastics: polyetherimide (PEI), originally developed by General Electric and widely used in industrial equipment, and PBPDA, known for strong heat resistance and electrical insulation. When processed together under controlled conditions, the polymers self-assemble into nanoscale structures that form thin dielectric films inside capacitors. Those structures help suppress electrical leakage while allowing the material to polarize strongly in an electric field, allowing greater energy storage. The resulting material exhibits an unusually high dielectric constant—a measure of how much electrical energy a material can store. Most polymer dielectrics have values around four, but the blended polymer dielectric in the new work had a value of 13.5. “If you look at the literature up to now, no one has reached this level of dielectric constant in this type of polymer system,” Zhang says. “Putting two commonly used polymers together and seeing this kind of performance was a surprise to many people.” Because the material can remain operational even at elevated temperatures—such as those from extreme environmental heat or hot spots in densely built components—capacitors built from this polymer could potentially store the same amount of energy in a smaller package. “With this material, you can make the same device using about [one-fourth as much] material,” Zhang says. “Because the polymers themselves are inexpensive, the cost does not increase. At the same time, the component can become smaller and lighter.” How the polymer mix improves capacitors The researchers’ finding is “a big advancement,” says Alamgir Karim, a polymer research director at the University of Houston who was not involved in the Penn State development. “Normally when you mix polymers, you don’t expect the dielectric constant to increase.” Karim says the effect likely arises from nanoscale interfaces created when the polymers partially separate. “At about a 50–50 mixture, the polymers don’t fully mix and instead create a very large interfacial area,” he says. “Those interfaces may be where the unusual electrical behavior comes from.” If the material can be produced at scale, it could help address a key bottleneck in high-power electronics. Higher-temperature capacitors could reduce cooling requirements and allow engineers to pack more power into smaller systems—an advantage for aerospace platforms, electric vehicles, the electric grid, and other high-temperature environments. But translating the concept from laboratory methods to commercial manufacturing may present challenges, says Zongliang Xie, a postdoctoral researcher at the Lawrence Berkeley National Laboratory. The Penn State team is now producing small dielectric films, but industrial capacitor manufacturing typically requires continuous rolls of material that can extend for kilometers. “Industry generally prefers extrusion-based processing because it’s easier and cheaper to control,” Xie says. “Scaling to produce great lengths of film while maintaining the same structure and performance could complicate matters. There’s potential, but it’s also challenging.” Still, researchers say the discovery demonstrates that new performance limits may still be unlocked using familiar materials. “Developing the material is only the first step,” Zhang says. “But it shows people that this barrier can be broken.”