New Lithium-Air Battery Delivers 10 Times the Energy Density

Al writes "A company called PolyPlus has developed lithium metal-air batteries that have 10 times the energy density of regular lithium-ion batteries. The anode is made up entirely of lithium metal, and the surrounding air acts as the cathode, making the batteries incredibly energy dense. Previous efforts to make lithium metal batteries have been stymied by the sensitivity of lithium to water in the air. The new batteries use a sophisticated membrane to protect the lithium anode and PolyPlus has even created a version that works underwater, by drawing oxygen through the membrane. Lithium metal-air batteries could be light-weight power sources for demand for plug-in hybrid vehicles and consumer electronics; IBM also recently announced that it would develop lithium metal-air batteries for the energy grid and for transportation."

Comments

Same old story...

[abigsmurf]

"it expects these batteries to be on the market within a few years"

Just like those ultra efficient, cheap, solar panels we've been promised 'next year' each year for the last decade.

Re:Same old story...

[Rei]

Your pessimism is misplaced. Don't you remember cell phones from the early 90s? Those giant bricks? When the then top-of-the-line NiMH battery was introduced in 1989, it boasted 45Wh/kg energy density. Now we have li-ions widely available at 200Wh/kg (4.5x the energy density) and 10x the power density.

For any given tech advance, the odds of it making it to market are low. But there are so many tech advances, many of which you never hear about, that the tech continues to advance at a good clip.

That said, I'm not a really big fan of any X-air batteries. They tend to be inefficient, low power, expensive, and have poor cycle life. There are literally dozens of li-ion advances working toward commercialization that can each 1.5 to 8x the density of either the anode or cathode, so regular li-ion still looks to have a lot of life in it. Also, I'm particularly interested in the recent advancements in lithium-sulfur. Practical lithium sulfur cells are 3-4x the energy density of current li-ion and are efficient and with reasonable power (excepting the unimpressive "stabilized" ones), but they tend to have very short cycle lifes. The University of Waterloo came up with a really interesting approach of wicking the sulfur into the pores of mesoporous carbon, baking it off the outside, and then functionalizing the carbon surface with PEG to repel the hydrophobic sulfur and keep it trapped in the pores so it can't migrate across the membrane and precipitate useless lithium polysulfates (the normal means of capacity loss in LiS). Their results were pretty astounding. In one experiment, they deliberately used an electrolyte known for dissolving polysulfates, thus facilitating capacity loss -- and compared their electrode with a traditional one. In a couple dozen cycles, the traditional electrode lost something like 96% of its capacity. Theirs lost only about a quarter of its capacity.

Re:Explosions

[MyLongNickName]

Or if you even looked at the article, you would see a demo of it running underwater.

Re:Double edged sword

[evilviper]

Energy density is a double edged sword.

No, it isn't.

But there are inherent dangers. The current Lithium-Ion batteries are pretty dangerous when they are mistreated.

Lithium-Ion batteries are dangerous because of very low internal resistance. ie. They can dump a large amount of current in a very short time. This is completely independent of energy density, and future designs could well have higher energy density with less danger of thermal runaway.

Re:Explosions

[Locklin]

Diesel fuel has a very high energy density and very little explosive potential. The danger comes not from the contained energy, but how fast that energy can be released.

Energy Density Fears

[Burning1]

A lot of people are raising concerns about the risk associated with increasing the energy density of the battery.

I would like to point out that it's difficult to directly compare the risks of two fuel sources without knowing how quickly the energy can be released, and under what conditions it can happen.

For instance, I enjoy working with motorcycles, which typically carry 2 major energy sources: A battery, which supplies starting and auxiliary power, and gasoline, which supplies primary power (including the power required to charge the battery.)

The gasoline in the tank has a far greater energy density and far higher energy potential than the battery, but of the two, the battery poses the greatest risk of injury and explosion.

The gasoline can certainly burn, but will only explode under very specific conditions. The conditions required to set it burning are also very easily removed. In fact, I'm far more concerned about the chemical damaged caused by exposing fuel to skin than I am about the risk of fire or explosion.

On the other hand, I work around the battery with wrenches that are typically grounded against the frame while in use. Even with a disconnected battery, I've had cases (while working on a car) where the wrench contacts the positive terminal of the disconnected battery, creating very heavy gauge short circuit between the terminals. The resulting release of energy will cut through metal and cause severe burns. Likewise, if overdrawn, the battery can release hydrogen which can either vent and ignite, or build internal pressure causing the battery to explode.

An interesting example of a substance that is explosive, has a high energy density, and is safe is C4, which can actually be used to cook food if burned, but will not explode without a blasting cap.

So... Are these batteries a risk? Perhaps. We should look into that. But it's best not to cry about the sky falling without first investigating the matter.

Re:Explosions

[Anonymous Coward]

I believe the summary is the first time I've ever seen "sensitivity" used as a synonym for "tendency to explode violently."

My former girlfriend was a very sensitive person.

It never occurred to me before, but now that you mention it, I think this is exactly what she meant by the term.