Recent solid-state battery announcements by Volkswagen and QuantumScape are raising hopes in the electric-vehicle market, but automotive battery experts are warning that the road to widespread, solid-state success is still a long and arduous one. A single breakthrough, as if from above, is not likely to turn the whole industry on its nose anytime soon.

“Solid-state is a great technology,” noted Bob Galyen, owner of Galyen Energy and former chief technology officer for the Chinese battery giant Contemporary Amperex Technology Ltd. (CATL). “But it’s going to be just like lithium-ion was in terms of the length of time it will take to hit the market. And lithium-ion took a long time to get there.”

“I haven’t seen cost numbers that are even close to competing with liquid-state, lithium-ion batteries.“ —Bob Galyen, Galyen Energy

Galyen and other experts consulted by IEEESpectrum noted that recent announcements by Volkswagen, QuantumScape, Toyota, and NIO have resulted in impressive stock market performance. However, these same experts noted a pointed skepticism toward the technical merits of these announcements. None could isolate anything on the horizon indicating that solid-state technology can escape the engineering and “production hell” that lies ahead.

The remaining hurdles will involve validating existing solid-state battery technologies (currently in use for more limited, often medical, applications) for cars and trucks. The adoption curve, experts say, will depend on the product’s ability to be validated in terms of performance, life, and cost characteristics.

Solid-state cells, so-named for their use of a solid electrolyte, are seen as a key to the future of the electric car because they potentially offer greater safety and energy, as well as much faster recharge times. Solid-state cells differ from conventional lithium-ion batteries in their use of a glass or ceramic electrolyte, instead of a liquid composed of lithium salts. Automakers are keen on solid-state batteries’ future, because the technology offers greater thermal stability than liquid-based batteries, thus allowing for substantially faster recharge, among other advantages.

Solid-state has also been the subject of recent announcements from battery manufacturers and mainstream automakers alike. In early January, Volkswagen Group’s PowerCo SE battery company said it tested lithium-metal cells from QuantumScape, achieving 1,000 charging cycles with 95 percent of the cell’s capacity still intact. The company said in a statement that the cell’s life-performance was analogous to “an electric car that could drive more than 500,000 kilometers (300,000 miles) without any noticeable loss of range.”

“What happens when you’re driving down I-75 and you hit a big pit in the road? What kind of damage would be done to the solid-state matrix?” —Bob Galyen, Galyen Energy

Similarly, Toyota announced in October that it plans to incorporate solid-state batteries in an unnamed number of production vehicles by 2027. The automaker said it is targeting a 1,000-km (600-mile) range with 80 percent DC fast-charge in 10 minutes or less. In December, Chinese automaker NIO also got in the game, saying it is introducing a 150-kilowatt-hour “semi-solid-state battery” that would theoretically offer a 1,000-km range as soon as this summer.

Experts were quick to point out, however, that NIO’s battery, made by WeLion New Energy Technology Co., is not solid-state. “This is in fact a fairly conventional NMC (nickel manganese cobalt) cell with a gel electrolyte that has been in production for 15 years and is typically referred to as lithium-polymer,” noted Sam Abuelsamid, principal research analyst for Guidehouse Insights. “Technically the gel is considered a semi-solid because it has properties of both a solid and liquid. But in a cell, it lacks the properties of a true solid-state electrolyte.” Notably, he said, semi-solid-state cells can be punctured on impact, which is closer to the nature of a traditional lithium-ion battery—and in contrast with actual solid-state cells, which would fracture. He also noted that semi-solid-state cells, with a manganese spinel chemistry, were used on a Hyundai Sonata hybrid in 2009.

Engineering challengeThe big challenge facing true solid-state cells, however, is the long climb to engineering validation. Galyen cites five “golden rules” of batteries–safety, performance, life, cost, and environmental–which must be met for solid-state cells to achieve industry-wide adoption.

The process is reminiscent of Elon Musk’s reference to “manufacturing hell” in 2018.

“Most of the solid-state battery companies fall short on at least three of the five golden rules,” he said. “I haven’t seen anyone publish life numbers that make any sense. And I haven’t seen cost numbers that are even close to competing with liquid-state, lithium-ion batteries.” Solid-state costs, he said, are about where conventional lithium-ion batteries were a decade ago.

Automakers also still need to verify the “performance rule” in three key areas–performance at temperature, performance at altitude, and performance under shock and vibration. Of those, Galyen said, shock and vibration are particularly concerning. “What happens when you’re driving down I-75 and you hit a big pit in the road?” he said. “What kind of damage would be done to the solid-state matrix?”

Automakers will not move to broad adoption until they are able to verify the new technology’s abilities in all those key areas, Galyen added. “None of these batteries have been validated yet,” he said. “So how do you plan on putting something into automotive production when it hasn’t been validated?”

Validation will take time, while automakers test factory-built cells in real-world conditions. To do that, manufacturers will first need to build battery factories, which could take two years, and then run a half-year of prototype products and distribute them to customers, who put them through their duty cycles. “Then you put the products into production and find out what your ‘gotchas’ are,” Galyen said of the inevitable problems.

The process is reminiscent of Elon Musk’s reference to “manufacturing hell” in 2018. Back then, Musk declared his company was about enter into six months of the so-called “hell” as it struggled to work out the kinks in its Model 3 production line. He told reporters at the time that a flood, a tornado, or even a ship sinking anywhere on earth could disrupt his company’s plans.

Galyen said that such headaches are commonplace in manufacturing, but particularly so in battery production. “There’s not one battery I’ve ever seen that doesn’t have a ton of ‘gotchas,’” he said.

To do the build-out, production, and validation could easily take seven or more years, Galyen said.

Science nearly readyExperts expect the science to keep evolving during that period. Today, there are numerous versions of solid-state batteries using everything from traditional graphite to silicon to lithium metal in the anode, and there are cathodes made from traditional NMC and nickel-rich materials.

Most experts assume that more time is needed to run the gauntlet o
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