24M Unveils the Reinvented Lithium-Ion Battery

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A123 spinout says that a semi-solid lithium-ion material can pack energy into a much safer, cheaper, easier-to-make package.

Jeff St. John

Five years ago, 24M Technologies spun out from parent company A123 with plans to turn a mysterious, semi-solid electrode material into a revolution in how lithium-ion batteries are designed and built.

Back then, co-founder and Massachusetts Institute of Technology professor Yet-Ming Chiang described a “clean sheet of paper” approach, combining concepts from flow batteries and fuel cells, and stripping the modern lithium-ion battery architecture of all its inactive materials and complex manufacturing steps.

On Monday, the Cambridge, Mass.-based startup unveiled the results: a lithium-ion battery that the firm says can be built at $100 per kilowatt-hour at scale, or half the cost of today’s competition. And by using a fluid-like set of electrodes that can be formed into a working cell in one step, 24M says its manufacturing facilities could be one-tenth the cost of today’s battery plants, and come in much smaller, modular packages.

“Nobody has ever made a battery this way,” Chiang said in a phone interview last week. 24M has made about 10,000 test cells so far using a “single wet process from beginning to end,” he said. Compared to the multi-stage process used in today’s lithium-ion batteries, it’s “simplified, streamlined, with a lot of metrology, to make it as reliable and bulletproof as we can.”

24M’s approach can also incorporate a multitude of today’s various lithium-ion chemistries into its semi-solid materials process, he said. By early 2017, the startup intends to start producing utility-scale grid storage batteries, using lithium iron phosphate as the cathode and graphite as the anode. 

To scale up to this goal, 24M has raised $50 million in private investment, adding to the $10 million raised in 2010 from Charles River Ventures and North Bridge Venture Partners with new investment from these VCs and some new strategic investors, CEO Throop Wilder said.

These include Japan’s IHI, a major manufacturer of jet engines, power turbines and other heavy industrial equipment; PTT, Thailand’s state-owned oil and gas company; and a third, as-yet-unnamed investor that’s working on joint development of manufacturing systems for 24M’s technology, he said.

The startup expects to have sample cells available early next year and is in the midst of raising a Series C round to set up its first production facility with its anonymous manufacturing partner by the end of 2016, he said. “Our defining goal is to chop 50 percent out of the current cost of lithium-ion,” he said. “We will enter at a very competitive price, but the volumes will be lower. Once we get to high volumes, that’s where we get to this $100 per kilowatt-hour cost.”

24M is targeting a lithium-ion energy storage market that’s already being eyed by contenders like Tesla Motors, Boston-Power, and Alevo, as well as established battery giants like Samsung, Panasonic and LG Chem. Breakthroughs being promised by startups with new nano-structured materials and designs, such as Amprius, Nanosys, and the lawsuit-challengedEnvia Systems, could enable even greater performance and cost improvements for traditional battery designs. And outside lithium-ion batteries, a host of new chemistries from startups such as Aquion, Eos Energy Storage and a long list of flow battery contenders are promising low-cost, multi-hour energy storage solutions at utility scale.

Given the novelty of what 24M is promising, it’s likely to be met with a skeptical eye by the industry until it starts delivering a testable product at scale. As GTM Research analyst Ravi Manghani noted, “As with any new technology, it boils down to financeability and execution on the firm's end, both of which are yet to be determined for 24M.”

“It’s not easy to go from lab or prototype scale to large manufacturing,” he said. At the same time, the firm's “approach has been very cautious, not trying to push the product into the market directly, but through integrators.” 

So how does 24M’s approach make for an entirely new way of designing and building lithium-ion batteries? Chiang offered this step-by-step explanation, starting with the novel semi-solid material at its core.

A “liquid wire” for thicker electrodes and reduced inactive materials

During 24M’s early days, Chiang and startup co-founder and fellow MIT professor W. Craig Carter saw its semi-solid electrode material -- dubbed “Cambridge crude” for its MIT roots -- as a material to be used in flow batteries, or perhaps as a “fuel” for electric vehicles. These facts, and published papers from the two scientists, have fed much of the media coverage and speculation on the startup’s plans until now.

In simple terms, “It’s a fluid that can conduct electricity. A friend of mine referred to it as a 'liquid wire,'” Chiang said last week. “Furthermore, it stores a ton of energy.” The startup received early funding from the Department of Energy’s ARPA-E program to explore the potential uses for this material.

“We originally conceived of using this type of electrode in a flow battery,” he said. “But what we realized upon forming the company was that this semi-solid electrode capability had a much better [application]: reinventing how lithium-ion batteries are made.”

Chiang identified two main problems in today’s lithium-ion battery design. “One is that the current lithium-ion battery itself contains a great deal of material that doesn’t store any energy,” he said. He’s referring to the inactive material that’s layered between the super-thin electrodes that allow today’s lithium-ion batteries to charge and discharge quickly.

“Having a thin electrode means that the distance the lithium ion has to travel is short -- and in the beginning, this was really necessary,” he said. “But our semi-solid electrode design allows you to get around this problem, and to create a battery that has much thicker electrodes, and thus much less inactive materials.”


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