Wednesday, February 21, 2024

This energy-dense battery could almost double the range of electric vehicles

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Scientists have long regarded lithium metal batteries as an ideal technology for energy storage, harnessing the lightest metal on the periodic table to provide cells filled with energy.

But researchers and companies have tried and failed for decades to produce affordable rechargeable versions that don’t have a bad habit of catching fire.

Then earlier this year, Jagdeep Singh, CEO of QuantumScape, said in an interview with The Mobilist that the stealthy and heavily funded Silicon Valley company had solved the major technical challenges. He added that VW expects to have the batteries in its cars and trucks by 2025, promising to cut costs and increase the range of its electric vehicles.

After its IPO in November, QuantumScape is now valued at around $ 20 billion, although it does not yet have any product or revenue (and no expectation whatsoever until 2024). VW has invested more than $ 300 million in the company and has formed a joint venture with QuantumScape to manufacture the batteries. The company has also raised hundreds of millions of other major investors.

Yet, so far, Singh has revealed few details about the battery, prompting researchers, rivals and reporters to scour patent filings, investor documents and other sources for clues. on exactly what the company had achieved – and how.

In a press announcement on Tuesday, December 8, QuantumScape finally provided the technical results of the lab tests. Its technology is a partially solid battery, which means it uses a solid electrolyte instead of the liquid that most batteries rely on to promote the movement of charged atoms through the device.

Many researchers and companies are exploring solid state technology for a variety of battery chemistries, as this approach has the potential to improve safety and energy density, although the development of a practical version has occurred. turned out to be difficult.

The San Jose, California-based company is still withholding certain details about its battery, including some of the key materials and processes it uses to keep it running. And some experts remain skeptical that QuantumScape really tackled the delicate technical challenges that would make a lithium metal battery possible in commercial vehicles over the next five years.

Test results

In an interview with MIT Technology Review, Singh said the company has shown that its batteries will effectively address five key consumer needs that have so far kept EVs from outperforming. 2% of new car sales in the United States: lower costs, greater autonomy, shorter charging times, longer total life on the road and improved safety.

“Any battery that can meet these requirements can really open up the 98% market in a way that you can’t do today,” he says.

Jagdeep Singh, CEO of QuantumScape


Indeed, the performance of QuantumScape is remarkable.

The batteries can be recharged to 80% of their capacity in less than 15 minutes. (MotorTrend found Tesla’s V3 Supercharger took a Model 3 from 5% to 90% in 37 minutes, in a test last year). And they retain over 80% of their capacity over 800 charge cycles, which is roughly the equivalent of going 240,000 miles. In fact, the battery shows little degradation even when subjected to aggressive charge and discharge cycles.

Finally, the company says the battery is designed to achieve a range that could exceed that of electric vehicles with standard lithium-ion batteries by more than 80%, although this has not yet been directly tested.

“The data from QuantumScape is quite impressive,” says Paul Albertus, assistant professor of chemical and biomolecular engineering at the University of Maryland and previously program director of the IONICS Solid State-Focused Program at ARPA-E, which no. has neither affiliation nor financial relationship. with the company.

The company “has gone a lot further than the other things I have seen” in lithium metal batteries, he adds: “They ran a marathon while everyone else did a 5 km.”

How it works

So how did they manage all of this?

In a standard lithium-ion battery in a car today, one of the two electrodes (the anode) is mostly graphite, which easily stores lithium ions that commute between the battery. In a lithium-metal battery, this anode is made of lithium itself. This means that almost all electrons can be put to work to store energy, which explains the potential for higher energy density.

But that creates some big challenges. The first is that metal is very reactive, so if it comes in contact with any liquid, including the electrolyte that supports the movement of these ions in most batteries, it can trigger side reactions that degrade the battery or burn it. The second is that the flow of lithium ions can form needle-like formations called dendrites, which can pierce the separator in the middle of the battery, bypassing the cell.

Over the years, these problems have led researchers to try to develop solid state electrolytes that are unreactive with lithium metal, using ceramics, polymers, and other materials.

One of the main innovations of QuantumScape was the development of a solid state ceramic electrolyte which also serves as a separator. Only a few tens of micrometers thick, it suppresses the formation of dendrites while allowing lithium ions to pass easily in both directions. (The electrolyte at the other end of the battery, cathode side, is a gel of some form, so it is not a solid state battery).

Singh refuses to specify the material they use, claiming it is one of their most closely-kept trade secrets. (Some battery experts suspect, based on patent filings, that it is an oxide known as LLZO.) It took five years; developing the right composition and manufacturing process to avoid defects and dendrites required five more.

The company believes the switch to solid-state technology will make batteries safer than the lithium-ion variety on the market today, which sometimes still catch fire themselves in extreme circumstances.

The other big advantage is that the battery is made without a separate anode. (See QuantumScape’s video here to get a better idea of ​​its “anode-less” design.)

As the battery charges, lithium ions on the cathode side pass through the separator and form a perfectly flat layer between it and the electrical contact at the end of the battery. Most of this lithium then returns to the cathode during the discharge cycle. This eliminates the need for any “host” anode material that does not directly aid in the work of energy storage or current transport, further reducing the weight and volume required. It should also reduce manufacturing costs, the company says.

Remaining risks

There is one catch, however: QuantumScape results come from lab tests performed on monolayer cells. A real car battery should have dozens of layers all working together. Moving from pilot line to commercial manufacturing is a big challenge in energy storage, and the point to which many once promising battery startups have failed.

Albertus notes that there is a rich history of premature drum breakthrough claims, so any news is met with skepticism. He would like to see QuantumScape subject the company’s cells to the kinds of independent tests that national labs perform, under standardized conditions.

Other industry watchers have expressed doubts the company could complete the scaling and safety tests needed to get batteries into vehicles on the road by 2025, if the company had so far only rigorously tested single-layer cells.

Sila Nanotechnologies, a rival battery startup in development another type of energy dense anode materials for lithium-ion batteries, published a white paper a day before the story of The Mobilist which highlights a litany of technical challenges for lithium-metal solid-state batteries. He notes that many of the theoretical benefits of lithium metal are narrowing as companies turn to commercial batteries, given all the extra steps needed to make them work.

But the document points out that the hardest part will be meeting the market challenge: competing with the massive global infrastructure already in place to source, produce, ship and install lithium-ion batteries.

Massive paris

Other observers say, however, that recent advancements in the field indicate both lithium-metal batteries will significantly exceed the energy density of lithium-ion technology and that the issues that delay the field can be solved.

“Previously it was about whether we will have lithium metal batteries, now it is about when we will have them,” says Venkat Viswanathan, associate professor at Carnegie Mellon, research lithium-metal batteries (and has done consulting work for QuantumScape).

Singh acknowledged that the company still faces challenges, but he insists that they relate to engineering and scaling up manufacturing. He doesn’t think further breakthroughs in chemistry are needed.

He also noted that the company now has over $ 1 billion, which gives it a considerable lead on its way to commercial production.

Asked why journalists should be confident in the company’s results without benefiting from independent conclusions, Singh stressed that he was sharing as much data as possible to be transparent. But he adds that QuantumScape is not “in the realm of academic research”.

“Not to offend you, but we don’t really care what you think,” he said. “The people we care about are our customers. They saw the data, they performed the tests in their own lab, they saw that it works, and as a result, they are making massive bets on this company. VW has done everything possible. “

In other words, the real test of whether QuantumScape has solved the problems as completely as it claims is whether the German auto giant is putting battery-powered cars on the road by 2025.


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