Battery Innovation Uses Semi-Liquid Electrodes
A radical new battery developed by researchers at the Massachusetts Institute of Technology (MIT) could make “refueling” as quick and easy as pumping gas into a conventional car.
The “flow” battery suspends solid electrode particles in a liquid electrolyte that can be pumped through the system. Cathode and anode suspensions are separated by a filter, such as a thin, porous membrane.
The work was carried out by 2010 graduate Mihai Duduta and graduate student Bryan Ho, under the leadership of materials science professors W. Craig Carter and Yet-Ming Chiang. It is described in a paper published May 20, in the journal Advanced Energy Materials. The paper was co-authored by visiting research scientist Pimpa Limthongkul, postdoctoral student Vanessa Wood and graduate student Victor Brunini.
The new design separates the two functions of the battery — storing energy and discharging that energy — into separate physical structures. That may make it possible to reduce the size and the cost of a complete battery system by half, improving the efficiency of an electric vehicle (EV).
A flow-battery EV might be refueled by pumping out the liquid slurry and pumping in a fresh, fully charged replacement, or swapping out liquid-filled cartridges, while still preserving the option of simply recharging the existing material when time permits.
Flow batteries have existed for some time, but have used liquids with very low energy density. A key insight for the MIT team was to adapt the chemistry of lithium-ion batteries to semi-liquid state. That provides a tenfold improvement in energy density over present liquid flow batteries, and lower-cost manufacturing than conventional lithium-ion batteries.
Because the suspensions look and flow like black goo, Carter said, “We call it ‘Cambridge crude.’”
In addition to potential applications in vehicles, the new battery system could be scaled up for utility-scale storage.
Chiang and his colleagues are now exploring different chemical combinations that could be used within the semi-solid flow system. “We’ll figure out what can be practically developed today,” Chiang said, “but as better materials come along, we can adapt them to this architecture.”
Chiang, whose earlier insights on lithium-ion battery chemistries led to the 2001 founding of MIT spinoff A123 Systems, said the two technologies are complementary, and address different potential applications. For example, the new semi-solid flow batteries will probably never be suitable for smaller applications such as tools, or where short bursts of very high power are required — areas where A123’s batteries excel.
The new technology is licensed to 24M Technologies, founded last summer by Chiang and Carter along with entrepreneur Throop Wilder, who is the company’s president. The company has already raised more than $16 million in venture capital and federal research financing.
The development of the technology was partly funded by grants from the U.S. Department of Defense’s Defense Advanced Research Projects Agency and the Advanced Research Projects Agency – Energy (ARPA-E).
— DAVID CHANDLER, MIT NEWS OFFICE