Tesla's new 'tabless' cell design is 'brilliant,' said a top battery researcher

Tesla's new 4680 battery cell is an "A-plus," according to Shirley Meng, a scientist from the University of California San Diego.

• Tesla's new 4680 battery cell is an "A-plus" design according to Shirley Meng, a scientist from the University of California San Diego.
• But she added that Tesla can't achieve is ambitious goals by itself — to get to ten terawatts of worldwide capacity, other players will be required.
• "The world needs so many batteries," she said.
• Visit Business Insider's homepage for more stories.

Tesla's Battery Day this week brought big news to the metallurgy and chemical-engineering worlds: the company had developed a new cylindrical battery cell, dubbed the "4680," that's much larger than the 2170 cells it's currently using.

While the 4680 cells remain at the prototyping stage and shouldn't enter mass production until 2022, CEO Elon Musk and his engineers are confident enough in the new form factor to start rethinking the design of Tesla's cars, with the 4680 cells becoming a structural feature.

In a nutshell, the new design does away with a "tab" that connects the battery cell and allows it to discharge and recharge energy. The bigger 4680 cell can handle more power, and Tesla maintains that it will be faster and cheaper to produce. And because it's larger than the 2170 cell, which is now arranged in elaborate packs that form the floor of Tesla's vehicles, the 4680 cell can add stiffness to the middle of a vehicle, subtracting a bunch of complicated parts in the process.

The technology itself impressed at least one expert.

"I give it an A-plus," said Shirley Meng, who studies nano-engineering and materials science at the University of California San Diego, where she is also the founding director of the college's Sustainable Power and Energy Center.

The tab-less design of the new Tesla cell is "brilliant," she said. "It's really an engineering achievement."

"The tab side used to be the weakest link," she explained. "Tesla gets a 10 out of 10 for handing this difficult issue."

The new battery cell is highly innovative

Meng confessed that the 4680 design (so-named because of its 46-millimeter diameter and 80-millimeter length) had some aspects that eluded even her, a scientist who has been working in field for over a decade.

"I couldn't wrap my head around the pattern," she said of the cell's spiral internal structure. "But I look forward to studying it in more detail. And I hope there will be more testing coming out. Based on physics, they have a good point."

That's because, she said, having that many contact locations inside the cells distributes power better, instead of having "all the electrons rushing through a little tab." By eliminating that weak point, the cell also offers better thermal management than the 2170 cell it should replace.

Meng also pointed out that the 4680 cell is highly innovative. "It's completely new as far as I know," she said. "Academic groups haven't been looking at this design. We usually don't talk about batteries of this scale."

10 terawatts of battery capacity

Tesla's goal for the new cell is to slash manufacturing costs by more than 50% while greatly increasing the power that cells can store. Musk and Tesla vice-president Drew Baglino said in a presentation that coming up with a new, better cell was the only way for the company to achieve an ambitious objective: produce three terawatts of battery capacity by 2023.

That's a lot — all of humanity uses about 18 terawatts of electricity — and Musk estimated that to replace all current transportation with electrically-powered vehicles, ten terawatts are in order.

"If we reach that scale, there will be many choices," Meng said of the various battery designs that are currently in use or being developed, including solid-state, which she called the "dream solution." 

She outlined a world where, if we make good progress, Tesla accounts for 2 to 3 terawatts and other manufacturers contribute an additional 2 to 3 terawatts — not quite enough to get to the ten-terawatt threshold. According to Meng, that means there should be plenty of room for other designs, including the sort of pouch-type packs that General Motors has developed to undergird its Ultium technology.

"The world needs so many batteries," she said.

Interestingly, for Meng, rising to the challenge isn't just about training a host of new battery-makers.

"We need more government and public support," she said. "It isn't just about more engineers. It's about our whole society transforming."