After five years and $50 million, 24M unveils new design for lithium ion batteries

24M founders Yet-Ming Chiang and Throop Wilder, outside the Cambridge company's "dry room" for battery production.
24M founders Yet-Ming Chiang and Throop Wilder, outside the Cambridge company's "dry room" for battery production.

Yet-Ming Chiang took an unusual approach to product testing last summer: He brought one of his company’s prototype batteries to a shooting range in Maynard, and peppered it with a half-dozen rounds from a deer rifle.

Not only did the battery not catch fire or explode — as would happen with many lithium ion batteries — but it continued pumping out power.
 “We think it’s the safest lithium ion battery ever made,” says Chiang, co-founder and chief scientist of Cambridge-based 24M Technologies. “You can penetrate it with a nail, crush it, deform it in a crash. It has unique abuse tolerance.”

The company also believes its new battery design will cut the cost of today’s lithium ion batteries in half. That’s a big deal for a product that is embedded in smartphones, laptops, electric vehicles, and used in power back-up systems. “We’re reinventing the lithium ion battery,” says Chiang, a professor at MIT who was also a founder of several prior companies, including A123 Systems. “The cost of the product is too high, and the manufacturing process is too complex.”

24M has been quiet since it originally spun out from A123 Systems in 2010. (A123 filed for bankruptcy in 2012, and was acquired at auction by the Chinese conglomerate Wanxiang Group.) But CEO Throop Wilder says 24M has hired 50 employees, and raised $50 million so far from venture capitalists including CRV and North Bridge Venture Partners, and PTT, a Bangkok-based energy company. The company has also received $4.5 million in Department of Energy grants, and been issued eight patents.

Wilder says that while he, Chiang, and the third co-founder, Craig Carter, are all interested in new kinds of battery chemistries, development of them is “taking forever.” In the meantime, lithium ion batteries are “turning out to be the world’s preferred kind.”

So what is so special about 24M’s approach? The company uses a semi-solid formulation that is, in fact, a ready-to-go battery the moment it is mixed. That eliminates a series of wet and dry manufacturing steps that are used in making batteries today, and it allows for a much simpler battery design. Instead of twenty or more layers of active and inactive material that are stacked vertically, in the same space 24M’s design has just a few — a cathode and an anode, separated by a thin film. That means that there’s less inactive material per millimeter of battery height. “Our core intellectual property,” Wilder says, “is about the semi-solid form of the electrolyte. You can make the layers thicker, and still get energy out of there.”

Wilder says the company has so far built about 10,000 prototype batteries in its Cambridge facility. Customers have been testing prototypes since last December. 24M expects to be producing limited quantities of batteries in 2017, and to begin high-volume production in 2020.

The company doesn’t plan to build its own large-scale battery facilities — as A123 did in Michigan. “We will work in partnership with manufacturers,” Wilder says.

24M plans to sell grid-scale batteries as its first product, choosing to wait for the electrical vehicle market to develop further. “A startup trying to tackle the EV market has a hard time,” Chiang says. “Been there, done that.” (A123 targeted that market, selling to automakers like Fisker Automotive, which filed for bankruptcy protection in 2013.) Grid-scale batteries are used by utilities to supply power at times of peak demand, or to store the energy generated by renewable sources like wind turbines or solar arrays. Each of those batteries is about the size of a large paperback book, Wilder says, and they are stored in large racks similar to those that house computer servers.

Below is a picture of a 24M prototype battery that had been folded like origami, but was still cranking out electricity.

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Scott Kirsner writes the Innovation Economy column every Sunday in the Boston Globe, in which he tracks entrepreneurship, investment, and big company activities around New England.
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