- Number 367 |
- July 16, 2012
PNNL materials scientist focuses on the depth of field
The panorama of science and life is
important to Liu. Like his photos, where a
small flower captures the eye in a desert
landscape, his scientific contributions have
called attention to the urgent national need
for a grand effort in energy solutions.
Surrounded by white walls, a whiteboard, and standard-issue bland office furniture, Dr. Jun Liu of DOE’s Pacific Northwest National Laboratory contemplates a collection of his desert photos lining one office wall. Holding the broad desert southeastern Washington State landscape in focus, the composition directs his eye to a particular bolt of color or detail in the foreground. Keeping the big picture in perspective is nothing unusual for Liu. In addition to focusing a camera lens on desert charms, he is a soft-spoken materials scientist with an intense and compelling vision for the nation’s future. His wide angle view, evident in his photographs, is essential for determining how science can help meet the world’s growing needs for energy, hungry for the juice to power billions of cars, homes, and industries.
“If we can replace gasoline with electricity in our cars, we will reduce the amount of carbon we release into the atmosphere. But, electric and hybrid vehicles depend on how good the battery is,” said Liu. “On a high level, we need to replace fossil fuels with renewable energy—wind or solar. This energy is intermittent, so how do you store that energy? How do you make it reliable and available for the electrical grid? We will need gigawatts of electricity—ready when we need it.”
At PNNL, Liu is leading teams that have gained significant recognition in battery innovation, whether that’s for storing renewable energy or powering laptop computers. By focusing on the fundamental science and obtaining insights for different energy storage systems, Liu and his colleagues have pushed the frontiers of batteries, from conventional lithium-ion systems to high-capacity vanadium systems to cutting-edge lithium-air batteries.
The mainstay of cell phones and laptop computers, lithium-ion batteries are a common energy storage system with a host of challenges. Chief among these challenges is the lack of capacity or energy density. Liu leads an interdisciplinary team that has devised a way to improve the storage capacity by upgrading the materials inside. The team devised an electrode that self assembles at the molecular level, with the metal oxide and graphene sheets folding and binding together. Graphene sheets are ultra-thin layers of honeycombed carbon, which have intriguing properties inside batteries. This new graphene and metal oxide makes the electrode more stable and charge-discharge rate faster. And working with a high-resolution transmission electron microscopy expert, PNNL also developed the first working device to directly observe the charge-discharge in a battery, a technique that holds promise for others who want to see battery material changes as they occur.
Liu is also working with a team that is taking vanadium redox flow batteries to the next level. Vanadium batteries are a promising option for storing renewable power. These batteries can quickly generate power when it's needed as well as sit idle for long periods of time without losing capacity. Unfortunately, the redox battery's use has been limited by its cost and inability to work well in the wide range of temperatures, such as those near solar and wind farms. The team determined that by adding hydrochloric acid to the sulfuric acid typically used in the battery, they could increase the storage capacity by 70 percent and expand the temperature range in which the battery operates.
Another area of innovation is understanding and advancing the lithium-air battery, an idea that has been around for more than 40 years and continues to draw interest because it has an energy density that could rival traditional gasoline-fueled engines. The PNNL team designed an alternative to the smooth graphene sheet electrode. Their graphene structures resemble broken eggshells and provide this cutting-edge battery with very high energy capacity. This new material does not produce clogged particles, like the conventional electrode does, therefore greatly increasing the capacity.
Liu’s passion for a long-term challenge is palpable. He believes the challenges must include working with partners across all organizations, with people from different disciplines and backgrounds, and across the wide spectrum of science and engineering. Besides paying attention to the details, essential to any scientific endeavor, Liu has a sense of urgency about where we need to be in 50 years.
“I want to know that I’m making a difference in something greater than what I can do myself,” said Liu. “I want to work off the strengths of partners, trusting in each to push beyond. We don’t believe there is one technology that will solve every problem. A few times, the progress we made was from out-of-the box thinking. There is tremendous value in what you get from diverse teams, disparate ideas. Sometimes you put it together totally differently—and it works.” The energy Liu communicates in such a conversation is contagious.Liu’s office wall gives a clue to how he approaches his work. His desert photographs, each one with a small detail of color or unusual outcropping, relates a strong sense of how he balances the wide view with a sharp central focus. His critical eye captures hidden surprises in unusual landscapes. He has an appreciation for perspective and working on gathering a larger picture. Liu wants to expose a sum greater than the individual parts.
Submitted by DOE's Pacific Northwest National Laboratory