New battery chemistries will reach the electric-car market over the next decade, but to be successful the new generation of products will need to have drop-in manufacturing capability, experts said last week.
"Whatever the chemistry is, it will have to be made in the same factory as today, with fundamentally the same equipment, and in the same amount of space," Sam Jaffe, principal research analyst for Navigant Research, tells Design News.
In a webinar last week called "Beyond Lithium-Ion: Next Generation Battery Technologies," Jaffe said that the leading alternatives to today’s lithium-ion batteries are lithium-sulfur and "metal-air" chemistries, which includes lithium-air, zinc-air, and sodium-air. All of those chemistries have the potential to boost the driving range of electric cars, but they still have technical issues that must be resolved before they can be placed in production vehicles, he said.
The chemistry closest to automotive production applications is lithium-sulfur, but even that is a minimum of five years away, he said. Lithium-sulfur offers about twice the specific energy of today’s best lithium-ion chemistries, but it still suffers from short cycle life. To date, most such chemistries have exhibited degradation caused by a breakdown of the sulfur. The result is that most lithium-sulfur batteries have offered about 100-200 charge/discharge cycles, far less than the 2,000 cycles automakers are seeking.
Makers of lithium-sulfur storage technology are making progress, however, he said. He pointed to efforts to bring the chemistry into aviation applications, and said he expects that technology to crack that market by 2016.
Similarly, a research team at Lawrence-Berkeley National Laboratory last year produced a lithium-ion coin cell that was said to offer 1,500 charge/discharge cycles. Hyundai and General Motors have also acknowledged that they are working on the technology.
Jaffe predicted that the first automotive applications of lithium-sulfur would surface in about 2019. "Lithium-sulfur will definitely be a player in the electric vehicle space," he said.
Metal-air batteries, which use an air cathode, are farther out, he said. Lithium-air offers tremendous potential, exhibiting specific energies of as much as 800 Wh/kg -- about four times that of the best lithium-ion products. "Looking purely from an energy density perspective, nothing beats lithium-air," he said. "It’s the only potential battery type that comes close to gasoline in terms of energy."
But lithium-air has been plagued by degradation problems, largely because it’s sensitive to the introduction of even the tiniest amounts of water. "You can’t have a single molecule of water, or carbon monoxide, inside there," he said. "Otherwise, it will wreak havoc in the battery."
He related stories told by automotive engineers who concluded that the amount of air-purification equipment needed onboard a vehicle to make a lithium-air battery work would in some cases be larger than the vehicle itself.
Still, he said, automakers are researching the technology and making headway. Volkswagen admitted earlier this year that it has plans for lithium-air. Toyota, Samsung, and IBM have also acknowledged that they are researching it. He said he believes the first production car to use a lithium-air battery could arrive as early as 2023.
To date, not all experts have been as optimistic, however. Elton Cairns of the University of California told Design News in 2012 that he believes lithium-air is still 20 years away. Earlier this year, noted battery developer Donald Sadoway of MIT told us that lithium-air simply doesn’t work. "The problem is the air electrode," he said. "It’s unstable and it doesn’t last."
What’s more, production batteries seldom hit the performance numbers that are publicized by labs. By the time manufacturing is reached, new terminals, covers, additives, binders, solvents, separators, and other inactive materials detract from the energy and boost the cost of the final products. As a result, performance can be compromised, even when the larger problems are resolved.
If and when battery developers solve all those problems, however, they will still face challenges bringing the new chemistries to market, Jaffe said. Material scientists who are successful won’t have the financial wherewithal to produce high-volume products and will have to team up with existing manufacturers to bring new technologies to market. "We’re expecting that when the next generation of battery chemistries are made, they will be made in the same factories, the same buildings, and even on the same equipment as today’s batteries," he said.