Originally published in Physics Today by Alex Lopatka
John Goodenough, M. Stanley Whittingham, and Akira Yoshino will receive the 2019 Nobel Prize in Chemistry for developing lithium-ion batteries, the Royal Swedish Academy of Sciences announced on Wednesday. Goodenough (University of Texas at Austin), Whittingham (Binghamton University in New York), and Yoshino (Asahi Kasei Corp and Meijo University in Japan) will each receive one-third of the 9 million Swedish krona (roughly $900 000) prize. Their research not only allowed for the commercial-scale manufacture of lithium-ion batteries, but it also has supercharged research into all sorts of new technology, including wind and solar power.
At the heart of any battery is a redox reaction. During the discharge phase, the oxidation reaction at the anode frees ions to travel through a liquid electrolyte solution to the cathode, which is undergoing a reduction reaction. Meanwhile, electrons hum through a circuit to power a connected electronic device. For the recharge phase, the redox processes reverse, and the ions go back to the anode so that it’s ready for another discharge cycle.
The now ubiquitous lithium-ion battery that powers smartphones, electric vehicles, and more got its start shortly before the 1973 oil crisis. The American Energy Commission asked Goodenough, who was then at MIT’s Lincoln Laboratory, to evaluate a project by battery scientists at the Ford Motor Company. They were looking into the feasibility of molten-salt batteries, which used sodium and sulfur, to replace the standard but outdated lead–acid batteries developed about a century earlier. But by the late 1960s, it became clear that high operating temperatures and corrosion problems made those batteries impractical (see the article by Matthew Eisler, Physics Today, September 2016, page 30).
Whittingham, then a research scientist at Exxon, instead considered low-temperature, high-energy batteries that could not only power electric vehicles but also store solar energy during off-peak hours. To that end he developed a battery in 1976 with a titanium disulfide cathode paired with a lithium metal anode. Lithium’s low standard reduction potential of −3.05 V makes it especially attractive for high-density and high-voltage battery cells. Critically, Whittingham’s design employed lithium ions that were intercalated—that is, inserted between layers of the TiS2 structure—and provided a means to reversibly store the lithium during the redox reactions.
Lithium’s high reactivity, however, means that it must be isolated from air and water to avoid dangerous reactions. Whittingham solved that problem by using nonaqueous electrolyte solutions that had been carefully designed and tested by other researchers in lithium electrochemistry experiments conducted a few years earlier. The proof of concept was a substantial improvement: Whittingham’s lithium-ion battery had a higher cell potential than the lead–acid battery’s—2.5 V compared with 2 V.
Whittingham’s lithium-ion battery, though, wasn’t particularly stable. After repeated discharging and recharging, whisker-like crystals of lithium would grow on the anode. Eventually the wispy threads would grow large enough to breach the barrier separating the anode from the cathode, and the battery would short-circuit or even explode.
In 1980 Goodenough didn’t solve that problem, but he did come up with a much better material for the cathode. Along with Koichi Mizushima and colleagues at Oxford University, he found that lithium cobalt oxide could be used for the cathode. As with the TiS2, the cobalt oxide structure was tightly intercalated with lithium and could thus provide the cathode with sufficient energy density. Goodenough’s insight into the relationship between the cobalt oxide structure and voltage potential resulted in better battery performance; the voltage increased from 2.5 V to 4 V. Although the new battery was an improvement over Whittingham’s design, the system still used highly reactive lithium metal as the anode, so companies couldn’t safely manufacture the batteries on a commercial scale.
The final piece of the puzzle fell into place in 1985 when Yoshino, working at the Asahi Kasei Corp, replaced the anode material with graphite. It was stable in the required electrochemical conditions and accommodated many lithium ions in graphite’s crystal structure. With Goodenough’s lithium cobalt oxide cathode and the graphite anode, Yoshino, “came up with two materials you could put together without a glove box” in a chemistry laboratory, says Clare Grey, a chemist at the University of Cambridge. Importantly, the graphite anode is lightweight and capable of being recharged hundreds of times before its performance deteriorates. Soon after, Sony teamed up with Asahi Kasei and replaced all the nickel–cadmium batteries in its consumer electronics with lithium-ion ones.
“The story of the lithium-ion battery, like so many stories about innovation, is about contributions from many sources over many years, conditioned by changing economic and social circumstances,” says Matthew Eisler, a historian of science at the University of Strathclyde in Glasgow, UK. When the 1979 oil crisis ended, the automotive industry’s interest in batteries drained, but in 1991 they were commercialized for use in cameras, laptops, smartphones, and other handheld electronics enabled by advancements in microprocessor technology.
To develop transportation that doesn’t rely on fossil fuels, the US Department of Energy in 2013 set an ambitious goal for its Joint Center for Energy Storage Research: Make a battery for electric vehicles that has five times the energy density and is one-fifth the cost of currently available batteries. DOE’s goal hasn’t been reached yet, but the program was renewed in September 2018, with dedicated funding of $120 million over the next five years. In a story on the center, Goodenough told Physics Today (June 2013, page 26), “People are working hard, and I believe the problem is solvable, but to get to the next stage, it’s going to take a little luck and some cleverness.”
Editor’s note: This post was updated at 7:15pm EDT from an earlier summary.