Though still a nascent technology, solid-state batteries are hot right now. Among the most prominent proponents is Toyota, which aims to commercialize solid-state batteries for electric cars by 2022.
Other auto competitors are close on Toyota’s heels in the rush to satisfy government mandates for emission-free alternatives to gasoline- and diesel-powered vehicles. BMW, for example, has also indicated a keen interest in developing solid-state batteries for their promise of better safety and higher energy density.
Today’s state-of-the-art batteries—those based on lithium-ion technology—have been honed to near perfection since they were introduced more than 25 years ago, but they are still heavy and occasionally explode and catch fire, as they did in Samsung’s Galaxy Note 7 phones so spectacularly last year. By getting flammable liquid electrolytes out of lithium-ion batteries and replacing them with solid electrolytes, solid-state battery makers hope to usher in an era of safer, more compact, higher-capacity energy storage devices.
Yet some patience is advised. With a few exceptions, like the solid polymer electrolyte batteries from French transportation firm Bolloré Group, solid-state batteries are just starting to be commercialized, mostly for low-power sensors connected to the internet. Firms like Ilika, Front Edge Technology, and Cymbet are making the small batteries in modest numbers. But they acknowledge that it will be years before solid-state batteries begin to show up in large numbers in consumer electronics, phones, and cars.
Toyota’s enthusiasm aside, solid-state batteries are likely to remain niche players unless some major breakthrough occurs, says Lorenzo Grande, a technology analyst with the consulting firm IDTechEx. Lithium-ion battery sales will reach $100 billion worldwide by 2027, he projects, compared to just $7 billion for solid-state batteries.
“Batteries are by definition unstable systems, and any improvement in energy storage comes with safety issues,” says Grande, who studied battery science at the University of Münster. But batteries with solid-state electrolytes may be inherently safer because they are solvent free, he says.
The potentially greater margin of safety in solid-state batteries has caught the attention of some pretty big players. In 2013, Apple acquired solid-state battery developer Infinite Power Solutions. In 2015, the cordless vacuum cleaner maker Dyson bought Sakti3, a University of Michigan spin-off. Founder James Dyson recently said he would pour $2.7 billion into developing a car with solid-state batteries. Also in 2015, the auto components maker Bosch Group bought Seeo, whose solid-state technology was licensed from Lawrence Berkeley National Laboratory.
Ilika, a materials research firm that has helped Toyota develop solid-state batteries, says the carmaker has been working on solid electrolyte technology for 10 years. “Toyota’s vision was to replace the flammable liquid electrolyte in a lithium-ion battery with a conductive ceramic material,” says Graeme Purdy, Ilika’s chief executive officer.
The firm, a spin-off from the University of Southampton, screened a number of materials using its high-throughput vapor deposition rig to assess solid electrolytes for Toyota. On its own, Ilika is harnessing the intellectual property it jointly owns with Toyota to make small solid-state batteries.
The batteries are intended to be combined with energy harvesters like solar cells to provide a constant energy source for small sensors used in the internet of things. Purdy says the company’s aim is to “get volume and grow in a niche where solid-state batteries can prove their capabilities.” Those capabilities include long life and the ability to operate in high-temperature and often hostile environments where lithium-ion batteries cannot.
Solid-state batteries have several pluses over traditional lithium-ion batteries
– Higher cost
+ Higher energy storage
– Nascent technology
+ Performs well at high temperatures
Sources: IDTechEx, industry sources
+ Lower cost
– Lower energy storage
+ Proven technology
– Decreased battery life at higher temperature
“Everyone involved in rechargeable batteries is investing in solid-state technology,” says Douglas Campbell, CEO of 10 Start-ups to watch Solid Power. A 2012 spin-off from the University of Colorado, Boulder, the firm is in the process of raising $15 million from investors including battery maker A123 Systems.
Solid Power licensed a portfolio of lithium sulfur electrolytes from Oak Ridge National Laboratory. By building on that technology, Campbell says, the firm has developed its own solid lithium-sulfide electrolyte.
The electrolyte is applied between a lithium metal anode and an iron disulfide cathode in a manufacturing process that could be run on existing battery lines, Campbell says. The electrolyte forms a mechanical barrier between the anode and cathode, blocking the formation of dendrites that can short the battery. The electrolyte also reduces both the mass and volume of the battery compared to one with a liquid electrolyte, he says.
A pilot line to produce car batteries will be on-line in the next 12 months, Campbell says. “We’re on the cusp of showing relevance to the automotive industry,” he says.
Battery maker Front Edge Technology licensed lithium phosphorus oxynitride (LiPON) patents from Oak Ridge, setting its sights on small batteries to power internet of things sensors and medical implants. Front Edge Technology’s LiPON electrolyte is “an amorphous material that is quite flexible when it is thin,” says Simon Nieh, the firm’s chief technology officer.
The company is now producing its thin-film batteries on a pilot line in California. “Solid-state batteries are mostly directed at small-volume niche applications now,” Nieh says. “But I think you’ll see them used on a much larger scale in five years.”
Also producing batteries in a pilot plant is Cymbet. “We are building micro-batteries. Large-format batteries are not yet cost-effective,” says Jeff Sather, vice president of technology. The 5- by 5-mm batteries can be readily soldered on a printed circuit board. Getting to this point has taken 17 years, during which Cymbet has raised about $100 million. Investors include Dow Chemical, Intel, and Texas Instruments.
The firm, also an Oak Ridge licensee, vacuum sputters a lithium phosphate electrolyte between the anode and cathode. The battery is assembled on a silicon wafer made in a photolithographic process similar to the one in which computer chips are put together, Sather says.
In addition to internet of things sensors, “our biggest opportunity is in the medical device market,” Sather says. “We’ve also been approached by computer makers for scale-up of our battery technology for laptop devices.”
But Sather doesn’t see LiPON as suitable for devices that draw a lot of current, like laptops and car batteries. Another firm, Ionic Materials, says it has a solid electrolyte that would in fact work well with high-current-draw devices. The brainchild of Tufts University material scientist Michael Zimmerman, the company describes its electrolyte as a solid-state polymer that is safer, cheaper, and higher performing than current electrolytes.
Batteries based on solid-state polymers are already on the market from France’s Bolloré. They power vehicles rented through the firm’s Autolib car-sharing service. But the downside of the batteries in those vehicles is that they operate efficiently only above 60 °C, notes Grande, the IDTechEx consultant.
Ionic Materials’ polymer, in contrast, conducts at room temperature, says Erik Terjesen, the firm’s strategy director. Admittedly secretive about the polymer’s composition, he claims it has the “highest lithium-ion diffusivity of any know solid at room temperature.”
The firm has no plans to make batteries on its own and instead wants to sell its polymers to battery makers. “We are working with influential battery cell makers and original equipment manufacturers of note right now,” Terjesen says.
Savvy investors think Ionic Materials may have something. Backers include Silicon Valley investment firm Kleiner Perkins Caufield & Byers and Bill Joy, cofounder of Sun Microsystems.
A difficulty impeding the rapid adoption of solid-state batteries is that they are hard to analyze, researchers in the academic community say. Because the components of a solid-state battery adhere so tightly to one another, “you can’t take them apart in any sensible way,” says New York University chemistry professor Alexej Jerschow. He is developing a nondestructive magnetic resonance imaging technique to measure ion mobility in the laminated batteries.
Instrument makers are also helping analyze the new batteries. Thermo Fisher Scientific, for instance, is “pushing the imaging performance of our electron microscopes and has made the characterization of small defects and small-scale interfaces” in solid-state batteries possible, says Herman Lemmens, a business development manager for the firm.
Despite the attention solid-state batteries are receiving, their commercial viability is “not clear,” maintains M. Stanley Whittingham, a chemist who has been at the forefront of lithium-ion battery development for over 40 years.
Whittingham, now a professor at Binghamton University, suggests that the best-performing lithium batteries will have a solid electrolyte with just a touch of liquid electrolyte surrounding the electrodes. That way battery makers will get the advantage of good contact between the electrolyte, anode, and cathode while retaining the safety advantage of a solid electrolyte.
The biggest challenge for solid-state batteries, he argues, is getting their prices down to where they can compete with the incumbent technology. That will take a while. For many uses, but especially for electric cars, Whittingham says, traditional lithium-ion batteries won’t have any competition for the next five to 10 years.
CORRECTION: This article was updated on Nov. 22, 2017, to correctly identify the patents Solid Power licensed from Oak Ridge National Laboratory.