Lithium-based batteries aren't the only ones that hold promise. Donald Sadoway, an MIT professor who has teamed up with Bill Gates on a storage battery for grid applications, is also working on an aluminum-ion chemistry for EVs. The aluminum battery, which employs a solid polymer electrolyte, is probably the most novel idea on the battery horizon -- and possibly the riskiest. But Sadoway told us he sees tremendous potential: 500Wh/kg at $100/kWh.
"Aluminum is the third most abundant element in the earth's crust, 8,000 times more abundant than lithium, and available in the US," he said. "This means cheap raw materials and a secure supply chain."
Back to the future
Not all solutions are targeted at the distant future. Energy Power Systems (EPS) is reaching back to the age-old lead-acid chemistry in its effort to change the future of the EV. Instead of developing a high-energy battery and then reducing the cost, the startup is starting with low-cost lead-acid chemistry and then adding power density and life.
Subhash Dhar, who has notably served in executive roles with Energy Conversion Devices and Ener1, founded EPS with the idea of developing a battery with the same power density as nickel-metal hydride at about a third of the cost. Right now, his battery appears to be one of the strongest short-term solutions. It reportedly offers about six times the power density and almost 10 times the life of traditional lead-acid, and it does so for about $100/kWh -- a figure that's little more than a dream for most EV battery companies.
As Dhar told us last month:
The concept has always been to start with a chemistry that gives you high energy density, and then hope you can reduce the cost. But the industry has never made much progress in terms of cost. So we turned it upside down -- we started with low cost and improved the technology, so we can get the performance without disturbing the cost structure.
In truth, the EPS battery doesn't offer traditional high performance. Its energy density is 40Wh/kg -- a tiny fraction of what lithium-based batteries offer. But Dhar said he isn't worried. He anticipates the battery being used in full hybrids, mild hybrids, and start-stop applications, where power density matters far more than energy density. He also foresees it employed in plug-in cars, in tandem with lithium-ion batteries. Using Dhar's setup, the lithium-ion battery would supply the range, while his lead-acid design would produce the power. The bottom line, he said, is automakers might be able to build hybrids and plug-in cars for less money.
Most people aren't ready to make the transition away from lithium-ion. Many say lithium-ion costs will drop sharply in the coming decade, possibly hitting $250/kWh for EV battery packs and $150/kWh for cells by 2025.
Still, boosting energy density may be a more difficult task. Despite claims by US Energy Secretary Steven Chu that energy density will double or triple while battery costs drop 50 percent in the next three to four years, many in the battery community are doubtful.
Most experts say that the wait for $5,000 batteries and 300-mile ranges will be a long one. History has shown that battery development often takes 20 years or more of serious, well-funded effort, they say. "It can take a very, very long time to bring research in the lab to a strong commercial position," Cairns said.
That's why most material scientists are openly rooting for lithium-ion to succeed, even if lithium-ion is a competitor. "We want to see lithium-ion be successful," said Kopera of Sion Power. "It paves the way for our higher-energy batteries down the road."