Pumpable electrons to drive gasoline into oblivion?

The second biggest award, $6.9 million, was for another grid-battery project at MIT. Called Electroville, the liquid battery technology is designed to buffer usage fluctuations in neighborhoods, much as a bypass capacitor does for printed-circuit boards.

Arizona State University, meanwhile, has a $5 million Arpa-E-funded project under way to perfect metal-air ionic liquid batteries that substitute earth-abundant materials for the rare lithium used in hybrid vehicles today, with a promise to increase the range of electric vehicles to almost 1,000 miles while potentially decreasing the cost compared with those incurred by today's grid-charged vehicles.

Two other Arpa-E-funded efforts are aimed at improving the performance and lowering the cost of today's state-of-the-art Li-ion batteries. A $4 million project at Envia Systems aims to increase the energy density of Li-ion from 150 Wh/kg to more than 400 Wh/kg through the use of nanopatterned silicon-carbon electrodes. And a nearly $2 million project at Inorganic Specialists Inc. is developing silicon-coated carbon nanofiber paper material that promises to boost the storage capacity of Li-ion batteries fourfold.

None of these efforts, however, hold a candle to the promise of Cambridge Crude, a $2.5 million Arpa-E funded effort at 24M Technologies Inc. to perfect a battery technology for all-electric vehicles that would turn electrons into a fuel that could be pumped like diesel or gas. The ultimate aim is to render gasoline obsolete.

Why now?
Electric vehicles' popularity is tempered today by their limited range, their long recharge times and the poor long-term reliability of their batteries compared with that of internal-combustion engines. Cambridge Crude aims to solve all three problems with a synthetic fuel that can be stored in a tank, comparable in driving-range capacity to gasoline tanks, and pumped at a "gas" station using existing infrastructure. The technology offers reliability rivaling that of internal-combustion engines by moving into the liquid fuel the parts that wear out in batteries.

EcoVoltz Inc. is developing a flow battery that targets large power generating facilities such as wind farms. Source: EcoVoltz

24M Technologies, a spinoff of nearby Watertown-based A123 Systems Inc., is working feverishly to commercialize Cambridge Crude under the tutelage of MIT professor Yet-Ming Chiang, who founded both companies.

Chiang's aim is nothing less than to reinvent the rechargeable battery through liquid-fuel technology. "Cambridge Crude has a chemical composition designed to simultaneously allow the exchange of lithium ions internally between the cathode and the anode of the battery, and then transfer those electrons to the current collectors and out to an external circuit, where they perform useful electrical work," he said.

In collaboration with MIT and Rutgers University, 24M will use its Arpa-E funding to perfect the basic liquid-battery technology. The company also recently landed $10 million in Series A financing from Charles River Ventures and North Bridge Venture Partners to commercialize its efforts, bringing its total startup funding thus far to around $16 million.

With that initial funding, 24M promises to produce prototypes that double the energy density at half the cost of lithium-ion batteries, with a goal of 500Wh/kg energy densities at $250/kWh for vehicles and $100/kWh for grid applications.

The company also claims its flow battery design has lower materials and manufacturing costs than the advanced Li-ion batteries made by A123 and even the most efficient fuel-cell technologies, by virtue of an architecture that does not require cell-based subassemblies or per-unit operations, such as nanoparticle electrode coating, calendaring, slitting, tabbing and module assembly.

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