Breaking a world record makes for a good day at work. For the NEES team, this big win came from something small. Really small. They built a working battery that’s one-millionth the size of a grain of sand. While it was fun—and frustrating—the NEES team had a practical purpose in mind. They wanted to see how nano-sized structures acted when they charged the world’s smallest battery.
“From my perspective, other researchers were focused on making materials in various particulate forms, which is how batteries are made today,” said Gary Rubloff, who leads NEES, which stands for Nanostructures for Electrical Energy Storage Center. “We focus on understanding the science that underpins batteries by making model systems, such as those tiny batteries, where we have elegant ways of controlling the electrodes’ shape and position.”
In the scientific community, building such tiny structures was a radical idea when Rubloff and his collaborators, professors at the University of Maryland, proposed it in 2009. Typically, researchers focused on larger structures. In fact, he and his colleagues thought the idea was so radical that he thought the Department of Energy (DOE) wouldn’t fund it at first. Ruboff and his colleagues wanted to fold the work into a proposal for a larger battery research center, where their approach was just one of many. “But we couldn’t find one where we fit,” said Rubloff. “So we had to do it ourselves.”
In 2009, the DOE accepted the idea and funded it as one of the DOE Office of Science’s Energy Frontier Research Centers, and NEES became a reality. Rubloff became the director.
Over the years, the team has uncovered crucial architectural details in batteries. While others treat atoms and molecules as building blocks for batteries, the NEES team sculpts wires, films, and other shapes from various materials with exquisite precision to see how the structures affect batteries.
Revolutionizing batteries could change more than just how often you charge your phone. Wind turbines and solar farms produced just 9 percent of the nation’s electricity in 2018. Why such a low number? There isn’t an easy way to store the energy. Storing such renewable energy and releasing it when it’s needed demands safe, high-capacity options. “Energy is a precious resource,” said Martha Heil, NEES’ outreach coordinator. “We need to maximize our ability to get it and store it.”
Research rarely takes the direct route from problem to solution. Doctoral candidate Emily Sahadeo who has worked with NEES since 2014 says it quite succinctly: “Science surprises you.”
Those surprises often lead to new questions, and getting answers is a team effort. For Sahadeo, who’s finishing her doctoral degree at the University of Maryland, it took time to get used to the precise style of her well-known colleagues. At one meeting where she discussed her data, Henry White, a University of Utah professor who’s given talks on battery science on four continents and is a key player in NEES, spoke up. Instead of offering vague advice, he gave her the exact equation to consult. But what truly impressed Sahadeo was how he did it: “He gave me the exact page number.”
In the early years, the NEES team created forests of nanoscale wires and tubes, each involving multiple materials, to move ions and electrons rapidly in an electrode that could outperform commercial lithium-ion batteries. Then, they moved on to bigger questions. Notably, could they replace the flammable liquid in batteries with a solid film, creating a solid-state battery? In today’s lithium-ion batteries, a liquid separates the positive and negative electrodes. The liquid lets lithium ions travel back and forth between the electrodes as you charge and then use the battery in your cell phone, laptop computer, or tablet. That liquid is also corrosive and flammable.
Replacing the liquid with solid nonflammable films wasn’t a new idea, but the thick films had to allow ions to cross from one electrode to the other rapidly. NEES added an alternative approach. “Other institutions are making films fairly thick—at least 1 micron, or 1000 nanometers,” said Rubloff. “We are down to 30 or 40 nanometers. It changes everything.”
With these ultra-thin films and an understanding of their inner workings, the team began looking for partnerships with industry to advance the research. “We got more interest from companies than we dreamed of,” said Rubloff. “Several companies are now working with us and providing substantial funding, which is amazing given that our pathway to research advances is quite nontraditional.” Rubloff and the NEES team continue to work on solid-state battery research. “While there’s serendipity in our advances,” said Rubloff, “it’s not a meander—it’s been a conscious choice.”
The University of Maryland leads the center. The center has been operating for ten years and will wrap up its work in 2020. NEES members are from Michigan State University, Sandia National Laboratories, University of California at Los Angeles, and University of Utah.
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Kristin Manke is a Communications Specialist on detail with the Office of Science. To provide feedback, please email Shannon.Shea@science.doe.gov.