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'Cambridge crude' could let EVs refuel like gas-powered vehicles


June 14, 2011

The liquid suspension that has been dubbed "Cambridge crude" (Image: Dominick Reuter)

The liquid suspension that has been dubbed "Cambridge crude" (Image: Dominick Reuter)

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With consumers used to the convenience of refueling their vehicle at the gas station in a few minutes, one of the biggest disadvantages of electric vehicles is the time it takes to recharge their batteries. Now, by separating the energy storage and energy discharging functions of the battery into separate physical structures, researchers at MIT have achieved a breakthrough that could allow EVs to be recharged in the same time it takes to refuel a conventional car. The technology could also provide an inexpensive alternative for energy storage for intermittent, renewable energy sources such as wind and solar.

The new battery employs an architecture known as a "semi-solid flow cell," which sees the battery's positive and negative electrodes (cathodes and anodes) made up of solid particles suspended in a liquid electrolyte. These oppositely charged particles are pumped through systems separated by a filter, such as a thin porous membrane.

The MIT researchers say that by separating the energy storage and energy discharge functions of the battery into separate physical structures allows them to design more efficient batteries. This should allow for a complete battery system - including all its structural support and connectors - that is half the size and cost of existing rechargeable batteries.

"Recharge" in a jiffy

While such size and cost reductions alone would make them attractive for use in EVs, it is the possibility of "refueling" the battery by pumping out the discharged liquid and pumping in a fully charged replacement that could be the real game changer and make EVs more competitive with conventional gas- or diesel-powered vehicles. The technology also allows for the liquid to be recharged in the usual way when time isn't a factor.

Although flow batteries have been around for a while, they have used liquids with very low energy density. This has resulted in batteries that are much bigger than fuel cells and require rapid pumping of the fluid, which also reduced their efficiency.

The liquids in the new semi-solid flow batteries developed under the leadership of MIT materials science professors W. Craig Carter and Yet-Ming Chiang, provide a 10-fold improvement in energy density over present liquid flow batteries. This means the liquid suspensions - which have been dubbed 'Cambridge crude' as they look and flow like thick black goo and could take the role of petroleum in transportation - don't have to be pumped rapidly to deliver their power.

Grid storage

The researchers say the new battery could also be scaled up to very large sizes at low cost, making it suitable for large-scale energy storage for utilities faced with the often difficult task of matching electricity production to demand. The technology could also help overcome the problem of storing energy from intermittent renewable energy sources such as wind and solar.

At the moment the battery is built around the proven chemistry of lithium-ion batteries and better anode and cathode materials and electrolytes are needed before a practical, commercial version of the battery is viable. But Chiang says because the design architecture of the new battery "is not linked to any particular chemistry," it can be used with different chemical combinations. He and his colleagues are now exploring different possibilities and as better materials are discovered, they can be adapted to the battery's architecture.

Under a three-year ARPA-E grant awarded in September 2010, the team's target is to have a "fully-functioning, reduced-scale prototype system" that is ready to be engineered for production as a replacement for existing EV batteries by the end of 2013.

Chang and Carter have also founded a company called 24M, which has licensed the technology and has raised over US$16 million in venture capital and federal research funding.

Source: MIT News

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

Why not fuel cells? Electrolysis is only about 60% efficient and fuel cells are maybe 70% efficient.

LiOn battery tech is already in the 90\'s % in charge/discharge efficiency.

William Volk

Now we\'re talkin\' - I\'m already in the market for this one! MIT!


Why can\'t they just use hydrogen fuel cells, large amount of gas can be stored with a high energy to weight ratio. Use the power source that recharges these batteries for electrolysis and you have overcome all the problems.

Yusuf Khan

^^ The electrolysis fuel cell cycle efficiency is \"maybe 40%\" (per the Strategic Electrochemistry Research Center). Lithium-ion batteries have a 97-99% charge/discharge efficiency.

True, H2 energy to weight ratio is high, but energy to volume ratio is as low as it gets.

Since the energy source is electricity anyway, it makes more sense to store it in a battery at ~98% efficiency than to utilize a 40% efficient process that involves a lot of additional equipment.


Hydrogen is difficult to store and transport.

Facebook User

Khan: I see two advantages over hydrogen. One is that this battery can easily be recharged directly within the battery with electricity, as well as pumped fuel. While it is true that hydrogen can be obtained by electrolysis, the process of producing, capturing, compressing, and storing it is a bit more complicated. The second is that hydrogen is explosive. Also, as a gas, it requires airtight, pressurized containers to transport and such. Just my quick take on this. I especially like the idea of being able to store energy from wind and solar with this. Since \"the wind doesn\'t always blow and the sun doesn\'t always shine\" is the biggest arguement against renewables, this could be a major step forward.


So much effort to make a more expensive, less effective replacement for a practical, safe, and cleaner energy source.



Hydrogen has low energy density. Whether in super-high pressure tanks, liquid form or in adsorption storage media like metal hydrides or carbon nanotubes, it doesn\'t begin to approach something like gasoline in terms of either volume or weight.


Slowburn, what is this magical practical safe and clean energy source?

Bryan Paschke

They are simply trying to avoid using the most abundant energy source in the world. Water. Water is highly available, renewable, and virtually inexhaustible. No wonder every researcher that gets \"Paid\" is looking for a way to provide energy that is patentable, commercially monopolistic, and difficult for the average person to reproduce. They want the be the only kids on the block that can make it. Thus, the cycle of power and greed continues. We will never see any technology go mainstream that cannot be greedily controlled. ie: Nickola Tesla - Wireless electricity. They didn\'t have the technology to put a faucet on it, so guess what? It never happened.

Raymond Johnson

Roger that, Bryan. I want some too!

Walt Stawicki

Slowburn: It has been shown many times that \"magic\" doesn\'t exist. Produce your super material or be quiet.

Raymond: Likewise. Water is not an energy source or a way of storing energy. It is what you get after you have released energy. Water is oxidised (burnt) hydrogen. We can use the potential energy in water that is above sea level, like the hoover dam, or we can use it to transmit energy like hydraulics (though we usually use oil for various reason) but we can\'t use water as an energy source or as an energy sink no matter what some nut job has told you. Wireless electricity is available, I can use it to charge my mobile phone. If you believe it possible to simply \"broadcast\" electricity so that anyone, anywhere with an aerial can receive it and power their home, you are misguided. Wireless electricity is a patented and money making set of inventions. Check out http://en.wikipedia.org/wiki/Space-based_solar_power Also, I assume Raymond that you work only for food and shelter, that you have no other aspirations in life and all your spare time is spent labouring for the love of it, giving freely of everything you can\'t immediately use. Of course those things that will generate profit are those things that people will pursue. That\'s because we like to live and want the best for ourselves, our family and our community.


Thank-You Scion, you last paragraph is right on, couldn\'t have said it better.

Bob Charsha

Now break them up even further and have one part being charged in the vehicle while the others are working- regenerative braking, shocks and solar plus others like thermal heat to electricity all charging the other part of the battery-then switch when needed. Most cars are parked in the sun all day while the owners are at work. Plug them in then also.


Thinking about what Bob said: It makes a lot of sense to me to just cover the cars with solar cells as well. No they are not going to make a huge difference but they WILL make a difference. Making just 1 of the idler wheels on your car electrically powered would help.

Sean Ellwood

when this goo can be made to recharge itself in the presence of sunlight, or other light, it might be useful. of course the power-to-weight ratio could be a factor too. and capacity-to-volume also. let\'s keep an eye on this, shall we? :) .

Joe Wesson

All most all H2 right now is made from natural gas with steam reformation very inefficently, and producing CO2. If you look at the whole enegry use cycle Itis more efficent and less costly to run the natural gas in the IC right now, than any fuel cell. This flow battery is a usefull solution, there is one problem that I forsee and that is, the solution is going to be abrasive. Meaning as it flows acrossed a thin membrain, or thru a pump it can and will erode thru, and if there is a leak when the two liquids come into contact together, thereare a good subistute for rocket fuel.

Lin Higley
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