Originally published June 18 2011
Battery breakthrough could double range of electric vehicles
by Nicole Parsons
(NaturalNews) In the ongoing quest to find cheaper and more energy effective alternatives to gasoline, researchers at MIT have developed a radical new approach to the design of batteries. This new development could provide an inexpensive alternative to existing batteries for electric vehicles and the power grid. The new technology will potentially make "refuelling" these batteries as simple as pumping gas into a contemporary car.
The research was carried out by Mihai Duduta and graduate student Bryan Ho under the leadership of professors of W. Craig Carter and Yet-Ming Chiang. The key insight by Chiang's team was that it would be possible to combine the basic structure of aqueous-flow batteries with the proven chemistry of lithium-ion batteries by reducing the batteries' solid materials into tiny particles that could be carried in a liquid suspension. "We're using two proven technologies, and putting them together." Carter says.
The new battery relies on a semi-solid flow cell. Solid particles are suspended in liquid and pumped through the system. The battery's positive and negative electrodes are made of particles suspended in a liquid electrolyte. The two different liquids are pumped through, separated by a thin porous membrane that acts as a filter.
The two fundamental functions of a battery are storing energy and discharging it. The new design separates the two fundamental functions into separate physical structures, which is a new characteristic not found in conventional batteries. By separating these functions, "the batteries can be designed more efficiently" Chiang says.
This layout makes it possible to reduce the size, and cost, of a complete battery system. The reduction could be the key to making electric vehicles a fully viable option and real competition with gasoline or diesel powered vehicles.
Flow batteries have been around for some time; however the liquids in them typically have had a very low energy density. Since the amount of energy stored has been exponentially lower than what is found in this new system, existing flow batteries would take up much more space than current fuel cells and require rapid pumping of their energy rich liquid which compounds inefficiency.
This new semi-solid flow system provides a 10-fold improvement in energy density over current liquid flow-batteries at a lower manufacturing cost than lithium-ion batteries. Additionally, they create the possibility of "refuelling" the battery by pumping out the old liquid slurry and pumping in fully charged liquid.
Chiang's team realized the possibility of combining the basic structure of an aqueous-flow battery with the reliable chemistry of the lithium-ion battery by reducing the solid materials down to tiny particles able to be carried in a liquid suspension. "We're using two proven technologies and putting them together", Carter remarks.
This new system could be scaled up at low cost and would be well suited for making unpredictable energy sources such as wind and solar energy viable for powering a grid. "The demonstration of a semi-solid lithium-ion battery is a major breakthrough that shows that slurry-type active materials can be used for storing electrical energy" that "has tremendous importance for the future of energy production and storage," Yury Gogotsi, Professor at Drexel University and director of Drexel's Nanotechnology Institute says.
There are some problems that have arisen, though, such as the need to find better cathode and anode materials and electrolytes. Gogotsi adds "I don't see fundamental problems that cannot be addressed - those are primarily engineering issues. Of course, developing working systems that can compete with currently available batteries in terms of cost and performance may take years."
The goal for the team's three-year project, launched in September 2010, is to have a functioning prototype ready to go as a replacement for existing electric-car batteries.
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