MAR 06

MIT is definitely a hot spot on the map of green innovation. Besides making a major breakthrough in hydrolysis catalysis this past summer, MIT has delivered many good technology concepts lately, such as power-generating shock absorbers, solar race cars and even self-propelling fish farms, just to name a few. The latest MIT idea comes from its materials chemistry department, where a professor has demonstrated a new kind of battery.

A conventional battery consists of two solid metal electrodes immersed in an electrolyte that is touching them both. As they react over time, electrons travel through the electrolyte as well as through the load. This battery uses liquid electrodes instead. Three liquids are poured into a vessel – molten magnesium, molten antimony and an electrolyte. Due to their different densities, the three liquids naturally separate; the antimony settles to the bottom, the electrolyte rests in between and the magnesium sits on top.

As the battery discharges, the molten metals react and slowly ionize, dissolving into the electrolyte solution. Thus, when discharged, the battery is mostly electrolyte, with only thin layers of metal remaining. When it is recharged, the magnesium ions are reduced and the antimony ions are oxidized – which, in this case, causes both the magnesium and antimony to go from ionic to metallic form. Thus, the recharged battery once again has thick liquid metal layers and a thin electrolyte layer.

This might not be more than an interesting chemistry experiment, were it not for the fact that such a liquid battery offers numerous advantages over conventional ones. The liquid metals and molten salt (used as the electrolyte) can absorb very high electrical currents – ten times higher than the best batteries we have today, according to the MIT professor heading the project. And the design of the battery allows it to be built quickly and cheaply (the team only used magnesium and antimony for the prototype - they have found better, cheaper materials to use for real-world versions, but are keeping the details quiet).

In other words, these batteries could be ideal for solar power storage. If so, they would be welcomed with open arms – solar proponents know that the biggest thing standing in the way of large, utility-scale solar power is the question of how it can be effectively stored. We don’t yet have any really promising answers to that question. Solar power can drive hydrolysis and generate hydrogen gas to be used as fuel, but it can be inefficient. Some have proposed to pump water up hills so that it can power turbines on the way down, but if you’re short on water, that isn’t the best option. And ultracapcitors are still a little way off.

MIT, keep ‘em coming.

Via MIT Tech Review

Comments (10)

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recharge cycles
written by Ben, March 06, 2009

I'm no expert, but it seems to be that these ought to be able to withstand more charge/discharge cycles than conventional batteries, too. Generally failure there is because the geometry of the electrodes is important, and tends to get worse as the electrodes are broken down and rebuilt. This format seems as though it might be less likely to cause such problems, and/or less susceptible to them.

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Energy consumed to keep the metals "molt
written by Foraker, March 06, 2009

One big problem here is that it will take quite a bit of energy to keep the metals in liquid form. Magnesium's melting point is 650 °C, 1202 °F, and antimony's melting point is close to the same.

The "better, cheaper" materials probably also have lower melting point temperatures.

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Maybe...
written by Jay Tee, March 06, 2009

@ Foraker,
What if you put the battery in a thermos, or if you have a solar-thermal installation, have the battery in molten salt..... just trying to throw out ideas here. I think this is VERY intriguing.

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Another Possibility
written by SolarLad, March 06, 2009

This is definitely a cool idea. I would wager, however, that lithium-ion may be a solar storage technology that hits the shelves a lot sooner. Sharp has recently committed to developing lithium-ion batteries for this purpose and they have up to 40 times the storage capacity of existing batteries.

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...
written by Carl, March 06, 2009

These are designed to be in buildings at a large scale, so only the outside walls of the building need insulation. No need for vacuum panels-- there is no problem adding a foot
or even meter of insulation around the core-- it would make an insignificant difference in size. The units in the article are wrong-- what is needed is the kWh/m3 not W/m2. Just doing some calculations (guessing 100 kWh/m3) there would be less than 1% loss (assuming 20% use/day) with R40 insulation and proportionally less with R80 or R120. It would probably make economic sense to install as much as R400 (maybe 3 meters thick). A large building with the capacity of a nuke plant might be the size of a football field. A small building the capacity of a few large wind turbines (size of a garage) would have 3-4 times the percentage heat loss for the same insulation.

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For transportation?
written by shek, March 09, 2009

It sounds like these batteries need to be kept hot, but does anyone know if these batteries can be cooled when not in use, and then heated up for later use without any complications? It seems to me that charge time is also a major hurdle for EV's and if these batteries can charge very quickly they might have applications there too, as long as the heating is worked out.

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Batteries for Solar
written by Uncle B, March 11, 2009

In a Post (GRD) great republican depression era, When the "Post Materialists" form their meritocracy, and millions of small scale vehicle battery backed, wind and solar installations come into existence, around scientifically designed "Zero operating cost Zero maintenance" GRD survival shelters, few people will require the huge "For Capitalist Industry" grid systems that provide power at night, and the daily race to an early coffin in a SUV, so why prepare, or even concern ourselves with the imagined problems we might have. The current system has collapsed, or been sent off-shore! The current "McMansion" lifestyle is foreclosed upon! The incandescent lightbulb has been epoched by a new cheap LED light(see:http://theinfochief.com/) and microwave cooking has replaced huge resistance type A.C. elements. Super-insulations exist and are rapidly replacing old poor ones, and as we speak, individual energy requirements are going down fast and cheap oil is running out as Solar, Wind, Wave, Hydro, Tidal and Geothermal perpetual or renewable (as you wish) energies are being developed. Our Battery cars will soon "ballast" variations in the grid by electronically sensed charging during surpluses, at lower rates. Night shifts at factories will disappear in this country, bunking at the factory will replace commuting, Asia will continue in our 19th century pattern for a very short while, until, enlightened by the exploitative nature of rampant, unbridled capitalism and consumer madness, they too resort to a more sane and sustainable lifestyle outside the pages of glossy magazines and slovenly TV advertisements. Mankind is growing up, at last, and will no longer tolerate mass exploitation as before - see Post-Soviet Russia for an example!

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air jordan
written by air jordan, June 27, 2009

IT SOUND INTERESTING.

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...
written by Fred, July 16, 2009

Liquid power is interesting i like this concepts

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"The Doc"
written by The Megabyte Doctor, December 28, 2009

Having been in the battery industry for over 10 years this is the single most exciting thing I have seen in a long time and it bodes well for the future of solar and other non base load power generation systems in the future. I have read a lot about this new technology and as far as I can see it is tailor made for large power storage while allowing short charge and discharge times combined with high current input and output. Keeping the unit hot is a minor engineering challenge in this day and age and as far as I can see the actual charging and discharging of the battery creates heat within the cell during the chemical process. One other benefit I can see is that unlike a "solid" type of storage system, Lithium-Ion...etc...etc... This system can be "topped-up" when the materials begin to be lost in the reaction over time. No matter how efficient a system is there will always be some loss and this will need to be addressed. There ain't no such thing as a free lunch, or the unfortunately mythical, perpetual motion machine. I'm no engineer but it would be nice to see this idea in a practical size of a small refrigerator for individual home use also for people with their own power generation systems. Fingers Crossed this may be the future solution to the base load power pollution problem or at least a shorter way to it that waiting for fusion power to eventuate. We need something clean to fill the job of Coal/Gas/Oil/Nuclear base load generation NOW.

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