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August 19th, 2010

A123’s launching new lithium flow battery project: ’24M’

Published on August 19th, 2010 | By: pwray@ceramics.org

Chiang at 2009 Materials Challenge for Alternative and
Renewable Energy meeting. Credit: ACerS.

When I interviewed Yet Ming Chiang, one of the brains behind A123 System’s lithium-ion battery technology, in 2009, he recalled a time when business opportunities weren’t yet a major interest:

“So, as the academic researcher, I wasn’t involved in A123 for my business acumen, right? But what happened was that my other co-founder, Ric Fulop, catalyzed the whole thing by coming to my office one day and announcing to me that he was interested in developing a venture based on new battery technology, and he wanted to know if I was working on anything that had that potential. What he really did when he arrived at my office was to prompt me to start to commercialize things that I might otherwise have waited longer to do, waited for a higher level of development . . . Part of the pitch [to venture capital companies] is, how do you convince an investor that even the technical guys understand what the impact of this can be? Over time the boundaries blurred a great deal. Ric became an expert in the technology very quickly, and I learned a lot about the business side, and it was mutually beneficial. So, I was able to help with the business development side as well as the technology.

Indeed, it became news in a conference call last week that Chiang and A123 Systems are working with venture investors on spin-off project to develop a new lithium-based battery design on flow battery principles. The new business is called 24M Technologies. According to a story by Technology Review, the name is a reference to 24 molar, a “concentration levels that Chiang cryptically calls ‘technically significant’ to the company.”

I shed more light on the “24 molar” reference below, although coincidentally there is a old chemistry joke:

Q: How do you make a 24-molar solution?
A: Put your artificial teeth in water.

Chiang, an ACerS member, tells TR that the new battery technology – initially developed at A123 and improved upon at MIT – involves a semisolid design that could cut production costs by 85 percent.

Chiang also tells TR that the battery design incorporates some concepts and elements of traditional batteries, fuel cells and flow batteries. He is quoted as saying, “In a typical rechargeable battery, only half of it is actual energy-storing materials. The rest is supporting materials. . . That’s a problem I’ve been thinking about for years – how do you improve the efficiency of the design?”

If his thinking goes back years, it might be worth noting that Chiang’s original battery concepts – before A123 – involved controlling colloid chemistry to get batteries to self organize. He thinks of self organization in the sense that the cathode and anode materials might repel themselves and spontaneously form an electrochemical junction. At the time, the hard part, for Chiang, was finding materials for the positive side of the junction. He spent a lot of time looking at olivines, “because,” he told me, “of all of the compounds, they were known to be useful as electrode materials. We screened them and found they had useful refractive indexes. So, that led to some work we did looking at olivines – lithium-ion phosphate, lithium manganese phosphate, nickel cobalt phosphate, that family of compounds – in order to see if we could use the properties in a way to produce a self-organizing system. In the end, we were able to produce an interesting laboratory demonstration of that concept. It has not proceeded, at this point, to full-scale device development.”

Building on this – and more on point – Chiang and three others at MIT filed a fascinating patent in 2009 regarding a design of a “redox flow” battery with a semisolid electrode:

“Redox flow devices are described in which at least one of the positive electrode or negative electrode-active materials is a semisolid or is a condensed ion-storing electroactive material, and in which at least one of the electrode-active materials is transported to and from an assembly at which the electrochemical reaction occurs, producing electrical energy. The electronic conductivity of the semisolid is increased by the addition of conductive particle to suspensions and the surface modification of the solid in semisolids: coating the solid with a more electron conductive coating material to increase the power of the device. High energy density and high power redox flow devices are disclosed.

. . .

“By “semisolid” it is meant that the material is a mixture of liquid and solid phases, for example, such as a slurry, particle suspension, colloidal suspension, emulsion, gel, or micelle. “Condensed ion-storing liquid” or “condensed liquid” means that the liquid is not merely a solvent as it is in the case of an aqueous flow cell catholyte or anolyte, but rather, that the liquid is itself redox-active. Of course, such a liquid form may also be diluted by or mixed with another, non-redox-active liquid that is a diluent or solvent, including mixing with such a diluent to form a lower-melting liquid phase, emulsion or micelles including the ion-storing liquid.”

Redox flow batteries are also known as a “flow cells” or “reversible fuel cells.” They are energy storage devices in which the positive and negative electrode reactants are soluble metal ions in liquid solution that are oxidized or reduced during the operation of the cell. Using two reversible redox couples, liquid state redox reactions are carried out at the positive and negative electrodes. In a flow battery, the nonelectrochemically active components at which the redox reactions take place and electrons are transported to or from the external circuit are known as electrodes, whereas in a conventional primary or secondary battery they are known as current collectors.

The patent goes on to describe a device that includes a storage tank for storing a flowable semisolid or condensed liquid ion-storing redox composition. The storage tank is in “flow communication” with the redox flow energy storage device using a peristaltic pump to transport the fluid. (A peristaltic pump is what you’ve seen used in hospitals with IV medicines: A roller moves along a length of flexible tubing, so that the fluid inside the tubing never comes into contact with anything outside of the tubing.)

The patent goes on to say that the the flowable semisolid or condensed liquid ion-storing redox composition provides a specific energy of more than about 150 Wh/kg at a total energy of less than about 50 kWh; 200 Wh/kg at total energy less than about 100 kWh; or 250 Wh/kg at total energy less than about 300 kWh.

Translating that into actual application in something like an electric vehicle or hybrid-electric vehicle, the patent notes that a semisolid redox flow battery that supplies a 200-mile range may weigh 225 to 300 kg mass, much less than the mass (and volume) of advanced lithium ion batteries providing the same range.

The patent seems to address the mystery of the “24M” name:

One distinction between a conventional flow battery anolyte and catholyte and the ion-storing solid or liquid phases as exemplified herein is the molar concentration or molarity of redox species in the storage compound. For example, conventional anolytes or catholytes that have redox species dissolved in aqueous solution may be limited in molarity to typically 2M to 8M concentration. Highly acidic solutions may be necessary to reach the higher end of this concentration range. By contrast, any flowable semi-solid or condensed liquid ion-storing redox composition as described herein may have, when taken in moles per liter or molarity, at least 10M concentration of redox species, preferably at least 12M, still preferably at least 15M, and still preferably at least 20M.

I deduce here that, apparently, the sweet spot is at 24M.

In the recent conference call with investment analysts, A123 officials described the new battery design as a “significant long-term project” and a “significant change from lithium ion technology.” They said they spun off the new company to “get enough focused management time and funding to get it move aggressively to marketplace. By using VC funding and management approach, probability of success will be much greater in a short period of time.”

One surprise, however, is that they see the new flow battery not just for electric vehicles but more importantly as a low-cost energy storage solution for the electric grid. The new company has already received $10 million in funding from private investors and $6 million from ARPA-E.

Adding: For reference purposes, the estimated weight of the battery for a Nissan Leaf is ~660+ pounds.


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