Elon Musk is well known for trying to disrupt old industries. He builds spacefaring rockets in-house and makes them reusable, dramatically lowering the cost to leave Earth. He showed electric vehicles can be made and sold in large quantities, because if they’re fun to drive, people will want to buy them. But when the question of batteries was raised on a Tesla earnings call in the summer of 2017, Musk asked for help:

“Can someone please come up with a battery breakthrough? We’d love it.”

Musk was being a little facetious — he and Tesla CTO JB Straubel had just been asked about then-recent news that Toyota was reportedly in the “production engineering phase” of an electric car powered by a still relatively unproven technology: solid-state batteries.

“Can someone please come up with a battery breakthrough?”

Calling it the “battery breakthrough du jour,” Musk quipped that any company working on solid-state tech should send Tesla samples, or at least have their claims verified by an independent lab. “Otherwise, STF[U],” he said.

At least one other EV startup CEO claims he is close to that breakthrough, though: Henrik Fisker, the famed automotive designer behind Fisker Automotive, the flashy hybrid sports car startup that arrived on the startup scene in the mid aughts and wound up bankrupt just a few years later.

Fisker recently started another eponymous car company — this time called Fisker, Inc. — that is focused on all-electric vehicles. And while he flirted with using LG’s automotive lithium-ion batteries to power his forthcoming electric supercar, dubbed “Emotion,” Fisker tells The Verge his new company is now just a few months away from putting the finishing touches on the final design for a scalable solid-state battery that will power the sedan instead.

While most current electric cars are powered by “wet” lithium-ion batteries — essentially bigger version of the ones that power your phone, or your laptop — some corners of the automotive industry are turning their attention to the concept of solid-state batteries, which don’t use liquid electrolytes to move energy around. Instead, the cells are made of solid and “dry” conductive material.

Solid-state batteries are less likely to catch fire than lithium-ion batteries. In lithium-ion batteries, the motion of the liquid electrolytes generates heat, and in certain situations, this can slip into a “runaway” effect that results in a fire. Solid-state batteries, then, would let you make it safer to quickly draw power from (or add it back to) the battery, meaning you could theoretically charge a battery-powered car faster. It also could mean, structurally, less room has to be devoted to temperature control, which could allow companies to squeeze more battery cells into the same size pack.

Solid-state batteries haven’t yet made it out of the lab and into production settings — not even in phones. Even Toyota, which was the spark for Musk’s cheeky remark, ran into problems trying to mass produce the batteries last fall. It has since partnered with other Japanese automakers — and Panasonic, which makes batteries with Tesla — to help solve some of the bottlenecks. But the head of the company’s powertrain division recently said he doesn’t expect the technology to reach mass-market scale until 2030; Panasonic has said it’s committed to lithium-ion until at least 2025. Volkswagen AG is considering pursuing solid-state batteries, but has not fully committed to the idea, and instead recently opted to merely invest in a company that’s working on the idea instead.

There’s plenty of room for improvement in the battery technology that powers electric cars, though. Tesla’s cars boast impressive speed and performance, and up to around 330 miles range in the most expensive models. But there are still shortcomings. It’s not possible to fully charge the car in under an hour, even at one of the company’s many so-called “Supercharger” stations. You can’t go more than about 150 miles without worrying if you’ll be able to make it back to your point of origin on one full charge.

Lithium-ion batteries also degrade over time, which means an electric car will never travel as far as it can when it’s brand new. And some Tesla battery packs have caught fire in accidents — some even more than once. It speaks to why small developments and even dubious claims about solid-state batteries tend to generate so much buzz. The technology could, in theory, take away almost all the headaches of electric cars.

It’s worth remembering that part of Fisker Automotive’s downfall was that the company had to recall the batteries in their hybrid cars in 2011, thanks to a problem with the supplier. These days, though, Fisker sounds sure about the solid-state battery being developed in-house. He believes he’s closer to production than anyone else because of the way it’s designed, and because of a new manufacturing process Fisker will employ.

To understand why Fisker feels so confident, it’s helpful to know a little about solid-state batteries. Some of the more promising solid-state batteries that are being developed in the lab are what’s known as “thin-film” — a name that comes from the fact that they’re made in the same way as solar panel cells. They’re smaller and more flexible than traditional lithium-ion cells, and are more energy dense, even though they carry less fire risk due to the “dry” composition. But they currently struggle to output as much power, the development process is still very expensive, and no one has shown that the technology can scale up to automotive levels.

Fisker’s solution is, roughly, like a three-dimensional layered version of these thin solid-state batteries, where they’re stacked together in each cell. The 3D structure of the cells allows for about 27 times more surface area, Fisker says, which means the battery is capable of far greater energy density than a single solid-state strip, and more than twice the energy density of current lithium-ion technology. He also claims his solid-state batteries will last “well over 1,000” charge cycles. (For reference, Tesla’s batteries are rated for about half that.)

Fisker says he’s also figured out how to bring down the cost, too, which he attributes to a manufacturing breakthrough. “We have solved how to produce [three-dimensional solid-state cells] accurately, repeatedly, and very fast,” Fisker says. “In a normal lithium-ion battery manufacturing, you’re looking at about 18 different steps of manufacturing, and you’re looking at, from the day the material comes in to the day you have a fully charged battery that you ship, it’s about 50 to 60 days. That’s an incredibly long time.” Fisker says his solid-state battery, meanwhile, will take “less than 10 days” from start to finish.

Fisker’s boasting about the specs of his solid-state battery, but isn’t sharing many specifics

But Fisker won’t say how his new company will manufacture solid-state batteries at this speed. He also won’t say what materials he’s using in the battery. (His company’s choice of electrolyte — likely from ceramics, glass, or polymers — will have a huge impact on characteristics like durability or ease of manufacturing.)

Of course, Fisker says, a real breakthrough would justify his choice of playing things close to the vest because of the pent up demand for higher-performance batteries. In fact, he says, the company is already in discussions with “selected” automakers with regards to the tech. He also claims he’s spoken with major battery manufacturers who might want to mass produce his solid-state cells and packs.

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It’s understandable why some might want to at least talk. Most major automakers are trying to figure out how to imbue their electric cars with more range while also driving down the cost of battery cells, which are still “by far most costly part of the battery pack.” And until a true technological breakthrough happens, these automakers are largely trying to use economies of scale to squeeze as much out of lithium-ion as possible.

Tesla (with Panasonic) has brought production of the lithium-ion battery cells and packs in-house at its Gigafactory in Nevada, and has spent the last few years optimizing the overall production process. (Musk has said Tesla is already the biggest buyer of lithium-ion battery cells in the world — and the company is also building a second Gigafactory in New York, and planning similar factories in China and Europe.)

While Volkswagen is still deciding whether to pursue solid-state technology, the company has pledged $48 billion to a number of the leading battery manufacturers in Asia order to help max out current battery tech (while also ensuring enough future supply for all of the EVs coming in the next decade from its sub-brands). Other German automakers are also heavily reliant on Asian battery manufacturers (like Samsung, LG Chem, or China’s state-run CATL) who can turn out lithium-ion batteries at the volumes required for fleet-sized orders. A recent Bloomberg New Energy Finance study estimated lithium-ion battery production capacity will nearly quadruple by 2021.

All those efforts will help further drive costs down, but there may not be much more runway on the technology side. Musk himself said at this summer’s annual Tesla shareholder meeting that he thinks he can only squeeze about 30 percent more performance out of the particular size of battery pack used in the company’s cars.

If Fisker’s company is truly as close to what he’s promising, then, he could have a hit on his hands. But he has to prove that it works. One reason to believe it’s not totally smoke and mirrors is that the head of the battery division of Fisker Inc. was the cofounder of Sakti3, a battery company that’s spent the last decade working at developing solid-state batteries.

Experts believe there is a wealth of reasons why solid-state battery technology is still many years away. Fisker’s goal, then, is to beat those expectations — and the other automakers to the punch. And, for what it’s worth, he says he’s aware of the skepticism that comes after what happened with his previous company.

“You could of course argue, ‘why should I believe him at this point?’”

“You could of course argue, ‘why should I believe him at this point?’ But we just don’t have the need to try and convince people. We’re working with companies under strict NDA to get into production, and that’s number one goal for us,” he says.

If Fisker’s bold solid-state battery promise comes true, don’t expect Tesla to come knocking. For one thing, Tesla and Fisker have a touchy history. In 2008, Tesla sued Henrik Fisker for alleged trade secret violations, arguing that he was using information he learned while consulting on the Model S to get Fisker Automotive off the ground. (Tesla lost the suit in arbitration.) As much as it might have sounded like Musk was issuing an open call for help in changing the battery game, his company is not simply waiting around.

”If there’s something better [than Tesla’s battery technology], I don’t know about it,” Tesla’s Straubel said at the shareholder meeting this summer. “And we’ve looked as hard as we possibly can. We try and talk to every single battery startup, every lab, every large manufacturer. We get quotes from them. We test cells from them. So if there’s something better, we’re all ears, we’d love to find it. But we haven’t found it yet.”

Musk, on the shareholder call last year, was more blunt in his skepticism. “Everything works on PowerPoint. I could give you a PowerPoint presentation about teleportation to the Andromeda Galaxy,” he said. “That doesn’t mean it works.”

Correction: Tesla lost its lawsuit against Fisker in arbitration. This article has been updated.