Lithium batteries dominate, but need to improve a lot, researchers agree at StorageX Symposium

When Stanley Whittingham was in Stockholm, Sweden late last year to accept a Nobel prize for his pioneering work on lithium-ion batteries, astronauts on the International Space Station were replacing all of the station’s nickel metal hydride batteries with lithium-ion batteries.

Whittingham, who is a professor of chemistry and of materials science at State University of New York–Binghamton, got to talk with the astronauts. “They used half the number of batteries they used to use and the batteries would last twice as long, so they were very happy with lithium-ion,” Whittingham recalled during the inaugural Stanford StorageX International Symposium Series on May 21.

Despite lithium-ion’s dominance of renewable batteries today, lithium based battery technologies have much room for improvement, Whittingham and his fellow guest speaker Jun Liu agreed.

“The lithium-ion battery has revolutionized how we work and live, and the revolution continues. Many, many other innovations will come along,” said Liu, who is the director of the U.S. Department of Energy’s $50-million Battery500 research program at the Pacific Northwest National Laboratory. He is also a professor of materials science and of chemical engineering at the University of Washington.

More than 3,000 people around the world–mostly scientists, students, industry executives and investors–watched and were able to ask questions the inaugural StorageX symposium, which will be held weekly. The second StorageX International Symposium will feature Khalil Amine, head of the Technology Development group in the Electrochemical Energy Storage Department of Argonne National Lab, and Prof. Peter Bruce of the University of Oxford. It will be Friday, May 29, at 7:00am PT (14:00 GMT). All the symposia are free and open to the public, though registration is required. 

Without the lithium-ion battery, the virtual event would not have been possible, said Liu. It is the backbone of electric vehicles, personal computers, phones, many other consumer electronics, and some systems that store wind and solar power for use after the sun has set and the winds have died down.

The basic technology moves lithium ions, rather than electrons, from the negative side of the battery to the positive side via an electrolyte to produce an electric charge. The ions move back during charging.  The positive electrodes are made of a lithium compound, while the negative electrodes are typically carbon-based. Compared with other rechargeable technologies, lithium-ion batteries store a lot of energy for their size and they do not lose much of their charge while idle. Manufacturing costs have fallen 80 percent in 10 years.

Nevertheless, when “we actually look at what we get out of today's batteries, it is not all that impressive,” said Whittingham.

Today’s commercially available lithium-ion batteries achieve much less than 30 percent of their theoretical capacity, he explained. One of the main culprits is the carbon anode, which requires 70 grams of carbon to store seven grams of lithium.

“So, the ideal will be to try to make lithium metal work,” Whittingham said. “Maybe an intermediate stage would be to go to silicon, but it's not working too well.”

One technology under development, layered oxides, leaves about 12 percent of the material unused. If that material were used, the battery would fairly easily get to 400 Watt-hours per kilogram from the current level of about 200Wh/kg, Whittingham said. Even though that would mean the battery is attaining just 50 percent of its capacity, it would go a long way toward lowering costs and solving the problem, for example, of range anxiety with electric vehicles.

Getting to lithium-metal

The Battery500 Consortium that Liu leads is developing next-generation lithium-metal anode cells with a goal of delivering up to 500 Wh/kg. The team is composed of scientists and engineers from four national laboratories and five universities: SUNY–Binghamton, Stanford, the University of Texas–Austin, the University of Washington and the University of California–San Diego. Whittingham is on the team, as are the co-directors of the Stanford StorageX Initiative, professors Yi Cui and William Chueh.

The battery pack of a new Tesla car costs about $20,000, Liu said. That cost needs to be cut in half for electric vehicles to get to, say, a third of new car sales, which would represent a significant reduction in transportation-related greenhouse gas emissions and other pollutants.

“We want to reduce the cost to half so that not only professors from Stanford University can buy Teslas, but professors from other universities, students and graduate students can all buy electric cars at the same cost of gasoline cars,” said Liu.

Related to reducing cost, Liu’s team seeks to increase the energy density of the next generation lithium-based battery, while maintaining lithium-metal’s superior safety. The consortium is more than three years into a planned five-year project life.

Liu turned philosophical toward the end of the symposium in response to a question from Cui, who moderated the discussion. Liu advised students and junior professors to not have goals like winning notoriety or even a Nobel, which one cannot control.

“My life's lesson is really try to make a difference in people's lives, try to make not only myself feel better, but make people around us feel better, do better work and be able to really communicate why we are doing certain things,” he concluded.

Cui said the goals of the symposium series is to bring scientists around the world together to present and discuss results on ideas in energy storage, and to create a platform for academia and industry to interact and for students to learn.

The StorageX Symposium is funded by the Stanford StorageX Initiative research program and the university’s Precourt Institute for Energy.