Battery unpacked: This graphic illustrates the multilayered structure of a ReVolt rechargeable zinc-air battery. From top to bottom: the battery cover, which lets in air; a porous air electrode; the interface between electrodes; the zinc electrode; the casing.
ReVolt
Rechargeable zinc-air batteries can store three times the energy of a lithium-ion battery.
A Swiss company says it has developed rechargeable zinc-air batteries that can store three times the energy of lithium ion batteries, by volume, while costing only half as much. ReVolt, of Staefa, Switzerland, plans to sell small "button cell" batteries for hearing aids starting next year and to incorporate its technology into ever larger batteries, introducing cell-phone and electric bicycle batteries in the next few years. It is also starting to develop large-format batteries for electric vehicles.
The battery design is based on technology developed at SINTEF, a research institute in Trondheim, Norway. ReVolt was founded to bring it to market and so far has raised 24 million euros in investment. James McDougall, the company's CEO, says that the technology overcomes the main problem with zinc-air rechargeable batteries--that they typically stop working after relatively few charges. If the technology can be scaled up, zinc-air batteries could make electric vehicles more practical by lowering their costs and increasing their range.
Unlike conventional batteries, which contain all the reactants needed to generate electricity, zinc-air batteries rely on oxygen from the atmosphere to generate current. In the late 1980s they were considered one of the most promising battery technologies because of their high theoretical energy-storage capacity, says Gary Henriksen, manager of the electrochemical energy storage department at Argonne National Laboratory in Illinois. The battery chemistry is also relatively safe because it doesn't require volatile materials, so zinc-air batteries are not prone to catching fire like lithium-ion batteries.
Because of these advantages, nonrechargeable zinc-air batteries have long been on the market. But making them rechargeable has been a challenge. Inside the battery, a porous "air" electrode draws in oxygen and, with the help of catalysts at the interface between the air and a water-based electrolyte, reduces it to form hydroxyl ions. These travel through an electrolyte to the zinc electrode, where the zinc is oxidized--a reaction that releases electrons to generate a current. For recharging, the process is reversed: zinc oxide is converted back to zinc and oxygen is released at the air electrode. But after repeated charge and discharge cycles, the air electrode can become deactivated, slowing or stopping the oxygen reactions. This can be due, for example, to the liquid electrolyte being gradually pulled too far into the pores, Henriksen says. The battery can also fail if it dries out or if zinc builds up unevenly, forming branch-like structures that create a short circuit between the electrodes.
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Good bit of news! Now hurry up and make a practical EV battery so we can stop sending all our money to the middle east dictators.
Liquid?
That depends on WHICH liquid. Something that doesn't freeze until minus 40C would work.
Pure ethanol freezes at -114C
A few hundred cycles is not going to cut it for a vehicle battery. Also if you read "hearing aid" , read that as "expensive"
A few hundred cycles is indeed enough for an EV. As these batteries have greater energy densities than lithium batteries, cars with 300+ mile ranges should be possible. 300 miles times 400 charges is 120,000 miles. And according to the article, parts of the batteries can be replaced after this - not entire batteries.
I've been hearing about how the zinc slurry battery would replace the IC engine for nearly 4 decades. I am at a loss to explain as to why this would take this long to make such small progress.
Easy. Cheap Gasoline.
With gasoline being such a good energy carrier, and relatively cheap, there wasn't much impetus to develop the alternatives.
Where did you hear about a zinc slurry battery 40 years ago?
Did you also read something that week about a guy who found a way to network computers together over phone lines ? :)
It dilutes the Li resource risk. I suspect that Zn is available in larger volumes and is more accessible globally than Li.
Correct. The USA and Australia have good reserves of Zinc, and it's more common in the Earth's crust than Lithium.
"we only have 10 years of Li left"
is because when you have 10 years you don't go looking for more. The exact same thing happend with oil 50 years ago. Only now are we starting to pass peak oil. There are still are larg reserves, but each barrel now takes a good part of and ever increasing fraction of a barrel in energy and costs to extract.
Billions are being invested in extraction plants,
outside of bolivia and their peasants would likely be less revolting (a revolution approximately every year) if they had jobs mining salt flats for Lithium.
"Says it has developed," I would love to see a working prototype. If they can get it right, there is big money in store for them.
Brian Glassman
Ph.D in Innovation Management from Purdue University
Actually there have been two running prototypes, in late nineties, in Las vegas and Bremen, as city buses. Both projects have died silently.
I think the most crucial factor in EV introduction is its ability to recharge fast enough, ie. in few minutes. If recharging takes 2-3 times that of running the batteries empty, EV cars will not hit the streets.
Zinc-air has potential for fast recharging, by replacing cells/zinc slurry at service stations.
I have learned that energy recharge efficiency is about 50%, when deoxidation is done by electricity. But is it technically possible to regenerate zinc from zincoxide thermally also, without use of electricity? Some countries have large supplies of renewable energy resources for that purpose.
I believe the company you're thinking of is Arotech. They had a full size city bus running on 9 of their zinc air fuel cells. That program died, but at the time they reached 127 miles on a single charge moving a fully loaded bus. Each cell weighed about 180 lbs and could be recycled in a proprietary process that converted the zinc oxide back into zinc. The process used electricity, but that could easily be done off peak when it was cheaper. I seem to recall the cost of a recharging facility was only $250k. Not sure what recycling capacity that yielded. It seems to me the zinc air process is safer than having a huge, high pressure hydrogen tank onboard. I think too much big money was pushing hydrogen, and a small company like Arotech didn't have a chance.
This raises the possibility of exploring other fuel cell chemistries. A battery that can "burn" a fuel using air as an oxidizer has great potential in making electric propulsion a practical reality.
The ability to recharge is not a requirement if an external reducing system is possible. The advantage that only half the problem (discharging) must be solved in a compact device demands more attention to this approach. Ironically, hydrogen as a fuel seems a rather poor choice to pursue considering the storage problem.
we have trillions of gallons of hydrogen stored so safely we even put out fires with it.
Why would you even WANT to store more than a little free hydrogen given its flammability?
Reducing metals as others mentioned is the easiest way to produce hydrogen on demand.
Al + H20 -> Aluminum oxide plus hydrogen to fuel your car. Aluminum reacts with water at room temperature (really, powdered aluminum is incredibly reactive) in presence of gallium which keeps a surface film of aluminum oxide from froming)
a tank full of aluminum pellets and 35 gallons of water would give you 300+ miles range in a car and you could exchange your used up oxide slurry for new pellets at a refueling station. aluminum is the 7th most abundant element in the crust and we have vast efficient plants that make aluminum from oxide ore. the electricity from the grid used to reform the oxide back to aluminum to put back in your car can be from any source including renewable.
http://www.fuelcellsworks.com/Supppage7355.html
same process can be done using magnesium instead of aluminum in a small reactor at temps around standard car engine temps:
http://www.techbriefs.com/component/content/article/3498
http://www.physorg.com/news98556080.html
the hydrogen can be burned in an internal combustion engine
or
in a fuel cell, converted directly to electricity to drive the car
the fuel cell option is twice as efficient as the internal combustion engine so less fuel taken and range extended
Batteries for electric vehicles have requirements that are different than other applications such as PCs, PDAs, hearing aids, etc.
1. Safety - Battery pack must be designed with safety as the primary concern in the event of crash and/or a "thermal event" in a cell. The more immune the cell chemistry is to explosion, leaking dangerous chemicals, etc., the easier it is to design the battery pack. For small battery systems this is much easier than for massive EV battery systems.
2. Cost - the overall cost of a battery pack is the key to making EVs a reality. Today's EV battery technologies run from $250/kW-h for AGM batteries to $1000/kW-h for Li-ion. EVs become practical when the cost approaches the AGM pricing. Keep in mind that these are system prices, not cell prices. System includes BMS, packaging, etc. for EV.
3. Power - EVs require a lot of power capability for acceleration and fast charging. The ideal battery should support 20C or more in both directions continuous.
4. Specific energy - EV batteries need to have high specific energy in both volume and weight. This is why AGM batteries are only good enough for golf carts and not full size EVs. Size and weight of the battery system really matter when car designers are trying to fit the battery into the volumes available in a car.
5. Cycle life - EV batteries need to last the life of the car. That means 10 years/150k miles. 10 years of recharging once a day = 3560 recharge cycles. If a cell can do that at 100% DOD, it's a winner. However, most cannot so battery packs have to be designed so that the batteries experience a much lower DOD, like 60%. This results in batteries that are larger, heavier, and more expensive than are actually required for the application. Chevy Volt is an example: it has a 16kW-h battery of which only 8kW-h is used day-to-day in order to prolong its life.
My last comment is that virtually all cells that are available on the market today have been developed for the portable electronics industry. The portable electronics industry cares a lot about doubling the specific energy but doesn't care at all about cost since the battery represents a small part of the overall cost of the device. Car manufacturers, on the other hand, care a lot about cost because the battery is so large that it represents a substantial part of the cost of an EV. Cell manufacturers who want to be successful in the EV industry need to focus on radically driving down costs.
Mharrigan: Regarding point 5...
Surely, even normal car batteries now last 3-5 years; can you fairly expect a 10 year life cycle from EV batteries?
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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ArtInvent
67 Comments
Sounds very interesting but . . .
. . . it's a very very long way from a button cell for hearing aids to a large capacity EV battery. The slurry pumping from one part of the battery to another - actually sounds quite ingenious. But it's so novel that I can see a lot of problems to work out in mass production. I would be very surprised to see a zinc air bicycle battery in five years. Whereas we'll be seeing large cell lithium EV batteries in cars like the Volt and the Nissan Leaf in only about a year. In five years lithium will probably have developed substantially and it's energy and current capacities and longevity increase, charge times decrease, etc.
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Jkirk3279
5 Comments
Re: Sounds very interesting but . . .
The primary problem with Lithium, other than the whole "explosion" bit, is it's limited.
The biggest reserves are in Bolivia.
In five years, we'll have much better lithium technology. And we'll be hurting for lithium.
This Zinc/Air battery tech could make for a handy backup plan.
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