Even After You Fix the Explosions, Superbatteries Are Hard to Make
By: Steve Levine
Tags: Battery, Electric Vehicles, Transportation, Lithium Battery, Quantumscape

Even After You Fix the Explosions, Superbatteries Are Hard to Make

QuantumScape has released its first data, and battery scientists are impressed

Photo: Jan Woitas/picture alliance/Getty Images

A half century ago, Exxon pioneered, then abandoned a blockbuster new battery based on pure metallic lithium, a light element that packed the most energy punch of anything on the market, but also ignited dangerous explosions. Over the subsequent decades, numerous companies and labs tried to resurrect Exxon’s effort but foundered on the same shoal — the propensity of metallic lithium batteries to short-circuit and catch fire.

That long history of failure lies behind the release of data this week by two high-profile companies claiming metallic lithium breakthroughs that could lead to electric vehicles priced well below gasoline-fueled cars. The disclosures — today by VW-backed QuantumScape, which went public in a reverse merger last week; and this coming Thursday by Denver-based Solid Power, backed by Ford — won’t put to rest skepticism about the reality of commercializing metallic lithium batteries. But several leading researchers who examined QuantumScape’s data said in interviews that they were impressed with what they saw, especially that the company’s battery was depicted as working at normal temperature and charging in 15 minutes or less.

Among other companies also in the chase, GM last month said it was working on a metallic lithium battery that, if further development pans out, could power its mid-decade EV models. Two other high-profile competitors are South Korea’s Samsung, which published a much-discussed paper on metallic lithium in the prestigious journal Nature Energy in March; and the startup Sion Power.

All together, we have a scrum competing to at last deliver the metallic lithium superbattery.

“The holy grail of lithium-ion batteries is to go back to lithium metal,” Stan Whittingham, who shared the Nobel Prize in chemistry last year as the inventor of Exxon’s abortive metallic lithium battery, told me in a video interview. Whittingham, who serves as a paid member of a scientific advisory committee at QuantumScape, said the company seems to be ahead of the competition in terms of metallic lithium development.

The frenzy around metallic lithium is because of the enormous added energy it could confer. Because of metallic lithium’s volatility and its proclivity for growing sharp, short-circuit-producing spikes called dendrites, battery-makers have always used just sprinkles of lithium in a cell. This concept was developed in the 1980s by John Goodenough, an American physicist working at the time at Oxford University, and Bell Labs. The idea was to shuttle ions of lithium between the battery’s two electrodes: It would be stored within a graphite-based negative electrode, called an anode. On discharge, the lithium would move to the positive electrode, the cathode. When charging up again, the lithium would shuttle back for storage in the graphite anode, and so on.

By using such small amounts of lithium, the Goodenough-Bell battery, commercialized by Sony in 1991, was much safer than using pure metallic lithium. But it also lost the big umph of pure metallic lithium. In the three decades since, the field has been working to get that umph back.

QuantumScape’s solution has been to use a solid electrolyte — the layer separating the two cathodes — comprised of a flexible ceramic material that cordons off the lithium from any liquid or allowing any dendrites to protrude into the rest of the battery. In an interview, QuantumScape CEO Jagdeep Singh would not disclose the composition of the material, but the consensus in the field is that it is a garnet-based ceramic known as LLZO.

QuantumScape spent its first five years of existence identifying the right hybrid of material to serve as its solid electrolyte, then five more years to confirm that the material could be produced using standard equipment, a must if it were to gain wide acceptance.

The result is single-layer, hand-assembled cells the size of playing cards. The data show a large volume of lithium — 15 to 20 microns — shuttling back and forth in the cells 800 times at the normal warm temperature of 30 degrees Celsius, and at the end of this exercise maintaining at least 80% of the battery’s capacity. That equates to 240,000 miles of life.

Until now, the use of metallic lithium has required slow charge ranging up to 10 hours in order not to stress the material and trigger dendrite growth. But Singh suggested that with QuantumScape’s design, a vehicle’s owner could fast charge in 15 minutes or less an unlimited number of times without creating dendrites. “We can actually charge it as fast as the cathode can deliver, basically floor it and do a 15-minute charge … which is really remarkable,” Singh said.

Now the company must figure out how to produce these cells in large sheets at high speed in the industry’s long, factory-size, roll-to-roll, continuously operating machines. And to produce its ceramic material essentially free of defects — no bumps, pinches, holes or other imperfections through which some pure metallic lithium could poke and short circuit the battery. And do so not in single layers, but in 100-layer stacks.

Singh plays down the scale of the task left. The hard part was the material, he said. What is left is “not chemistry. It’s engineering/manufacturing.” Of course, Elon Musk, speaking of his own projects on Tesla Battery Day in September, said the opposite — that the hard part is the manufacturing. “It’s at least 10 to 100 times harder to do the factory than the prototype,” Musk said. “That’s why you see a lot of companies out there or startups, they’ll bring out a prototype but they just can’t get it over the hump for manufacturing. Because manufacturing of new technology especially is the hardest thing by far. The prototype is at best 10% of the difficulty and probably closer to 1%.”

Another thing that Singh said gives him confidence is that he has a war chest of about $1.1 billion, offering considerable latitude for experimentation and mistakes.

Other problems could arise. Michael Fetcenko, executive chairman of Sion Power, a Tuscon-based metallic lithium battery maker, said his company holds patents that others in the field will have to license. He did not say how much such licenses would cost, but judging by other major technologies, licenses can be expensive. “Everybody working in this field is likely to run into our patents,” he told me. He said that includes QuantumScape.

In addition, now that QuantumScape is publicly listed, it is vulnerable to public opinion, and must figure out how to balance its penchant for secrecy with what is necessary to tamp down skepticism. Last week, Mark Newman, an analyst from Sanford Bernstein, initiated coverage of QuantumScape with an underperform rating, saying that the company’s manufacturing risk is quite high. QuantumScape’s share price plunged more than 24%.

Finally, battery development is a moving target. Workhorse lithium-ion is becoming cheaper and cheaper, accelerated by Musk’s aim of cutting his battery costs well below $100 per kWh at the pack level, which if he succeeds would seriously undercut the price of conventional gasoline-driven cars. If he and others do succeed with such slashes in lithium-ion costs, they would diminish the importance of QuantumScape’s advances. “Is that enough to spend billions to try to realize it at scale?” said Paul Albertus, a professor at the University of Maryland whom QuantumScape briefed on its battery before today’s announcement.

Still, if we focus just on what’s done to date, much has been accomplished, suggests Venkat Srinivasan, director of the Collaborative Center for Energy Storage Science at Argonne National Laboratory. He said that when he first saw the data, “My gut reaction was, ‘That’s pretty cool.’” Questions have arisen since then in Srinivasan’s mind, such as how QuantumScape will deal with the unavoidable factor of defects in the ceramic material. “When you make it in large volumes, are you getting the same quality every time?” he asked. But overall, he said, “It seems like they are able to get high current charging without dendrites, good plating/stripping efficiency, and are able to move a lot of lithium using the right thinness of the separator. All this seems very impressive.”