“We’ve almost doubled the cycle life of our cell, the core lifetime metric for any advanced battery technology, and because of that and its lighter weight, it is now sufficient to support the expected flight range and lifetime requirements of all typical eVTOLs coming to market.”
This is the latest news from California-based Cuberg, announced this week by Dr. Richard Wang, CEO and founder.
This achievement puts Cuberg’s lithium metal cells among the highest performing and longest-lived lithium metal cells in the world.
Yes, many other advanced lithium battery technologies have been created in the last 10 years, but because Cuberg’s technology was designed to integrate with existing battery manufacturing processes, it’s affordably scalable — as these other technologies have not been.
Looking forward, Cuberg expects that commercial production of about 100,000 of its commercial-sized 20 amp-hour (Ah) cells per month — which will supply batteries for about 400 typical eVTOL aircraft per year — will begin in 2026.
This aligns with the certification and commercial production timelines of many eVTOL companies. Cuberg customers already include Beta Technologies and Boeing.
Scale-up to commercial production will require a great deal of precise refining of manufacturing processes in order to meet battery certification standards and ensure quality control at the extremely high level of aviation manufacturing.
Cuberg was acquired by Sweden-based battery manufacturer Northvolt in March 2021.
Independent testing of Cuberg’s 5 Ah “pouch” cells has confirmed that cycle life has been extended from 370 to 672 cycles with 80% capacity retention, Wang explained.
It’s the first time a lithium metal cell has exceeded the cycle life of the most advanced similarly-sized lithium-ion cells. Cycle life has historically been an issue with lithium metal cells, which are prized in battery development due to their high-energy density and high-power output.
Lithium metal cells are also much, much lighter than Li-ion cells.
“The weight issue has been something of an elephant in the room or an Achilles heel in the aviation battery world,” Wang said. “With lithium-ion cells, eVTOLs would be too heavy to fly more than a short range, and much shorter than what many companies have publicly claimed. This is due to battery safety requirements from the FAA [U.S. Federal Aviation Administration] and EASA [European Union Aviation Safety Agency] evolving to become increasingly difficult to meet. It’s something that no one wants to talk about. A lot of firms have been planning to go to market with conventional Li-ion technology, but it’s not going to satisfy most commercial use cases. In our view, this fact has not been fully grasped by the industry.”
As a reminder, a battery consists of a cathode and anode, between which ions flow (in an electrolyte medium) across a separator.
Wang explained that Cuberg’s design swaps the anode from traditional graphite, which is heavy, to lithium metal, which is vastly lighter and more energy dense. “We have also innovated with the electrolyte,” he said, “developing a novel liquid electrolyte that doesn’t introduce any new critical material supply requirements to battery manufacturing.”
The Cuberg electrolyte is also non-flammable and chemically very stable, which stabilizes lithium metal (a highly-reactive element) and thereby achieves a heightened safety level in the cell (and in batteries containing these cells).
Wang explained that the reactivity of lithium metal has historically been a big challenge in battery development. Over the lifetime of a typical lithium metal battery, the lithium metal degrades the electrolyte and causes thin spindles of lithium (called dendrites) to grow outward into the cell. This generally results in severe cell degradation or complete failure.
One solution for this has been to use a solid electrolyte in place of the conventional liquid electrolyte.
“In theory, it works but there is a big problem in effectively manufacturing solid-state batteries on a commercial scale in a cost-effective way,” Wang said. “There is also a second problem in attaining the performance in commercial-sized cells rather than demonstrations in forced laboratory conditions. This has not been achieved to date.”
Scalability is key
During his Ph.D. at Stanford, Wang took a close look at these problems.
“Manufacturing scalability is a difficult aspect for many new technologies but especially for battery technologies,” he explained. “There have been many innovations in batteries that started coming on the scene in about 2010, but because they were not compatible with existing manufacturing systems, commercialization was not possible. The cost and manufacturing capital requirements are too aggressive.”
Manufacturing processes for batteries have been innovated and refined to some extent by companies like Tesla over the last decade, but that has taken investments of tens of billions of dollars. In Wang’s view, it’s safe to say at this point that the manufacturing end of batteries has been thoroughly examined and optimized.
“So, it was clear to me that to get a new type of battery to market, your design must fully integrate with existing manufacturing processes,” he said. “We did that from the start. It was clear that the chemistry of the battery is a much more solvable problem than trying to create new battery manufacturing processes.”
Northvolt, Wang said, saw the value in Cuberg’s “manufacturing-compatible” design and moved to purchase the company last year.
For Cuberg, the purchase meant having a parent company that would take its innovation to market.
“Northvolt is a mature manufacturing company with extensive global supply chain expertise and experience in terms of product certification, quality assurance and so on,” Wang said.
“Northvolt has also worked hard with regard to securing critical materials. They have pioneered battery recycling, reclaiming lithium, nickel and other raw materials, and have been securing virgin supplies of these materials from the mining industry in Europe and North America. Northvolt does not want to have to depend on mining and processing firms in China, where most of the mining and processing capacity investments for lithium and nickel have been made in recent years. We need companies around the world to make more investments in mining and processing these metals.”
Working with partners
Cuberg has to some degree developed its technology in collaboration with many other companies, delivering 5 Ah sample cells to over 20 customers, including Beta Technologies, with which Cuberg has worked closely since 2019.
“We are currently making about 1,000 5-Ah cells a month, sending out a lot to customers for their evaluation and also for our own internal research and development,” Wang said. “We’ve also begun shipping out 20 Ah cells to customers. We have the strongest relationships with Beta and four other companies, including several prominent eVTOL OEMs [original equipment manufacturers] and an electric propulsion OEM that is working with a number of eCTOL and eVTOL programs.”
With its partners, Cuberg is now entering a second phase toward commercialization, working on how to package its cells into battery modules. Stay tuned for further developments.