Researchers at MIT have developed a new method of adding carbon nanotubes to lithium-ion batteries that give the batteries the best characteristics of both capacitors and traditional lithium-ion batteries while simultaneously increasing their energy storage.
The experimental batteries, which used layered carbon nanotubes as the positive electrode (the cathode) and a lithium titanium oxide as the negative electrode (the anode), demonstrated an impressive ability to deliver power at the very fast rates of capacitors while being able to store more energy and last much longer than even the best lithium-ion batteries available today.
To create the layered carbon nanotubes, the researchers dipped a base material repeatedly into a solution loaded with carbon nanotubes. The layers then built themselves up like a candle. To make the carbon nanotubes self-assemble onto the base material and stick together in even sheets, the scientists alternately charged them with positive and negative organic compounds. According to the researchers, the method could be adapted for spraying on the nanotubes which would then make the batteries ready for mass production on an assembly line.
All batteries are made up of three components: two electrodes (the negative anode and the positive cathode) separated by an electrolyte. When lithium ion batteries are producing energy, positively charged lithium ions move through the electrolyte and deposit at the cathode, which makes electricity. Alternatively when they are recharged, an external energy source (your outlet, regen braking, etc.) causes these lithium ions to move the back across the electrolyte and embed in the anode.
Because of the humongous surface area of the carbon nanotubes, the batteries can hold much more charge than traditional cathodes, enabling carbon nanotubes for the first time to serve as the positive electrode in lithium batteries, instead of just the negative electrode.
At an energy content of about 200 Watt hours per kilogram, these experimental batteries are way up there with the most advanced forms of lithium ion batteries on the horizon, yet they also can provide very high short bursts of energy — important for EVs that need to accelerate quickly. As an added benefit, the carbon nanotubes seem to provide the batteries with an incredible durability. After 1,000 charge/discharge cycles, the research team has seen no appreciable degradation in the battery’s function.
The research was published in Nature Nanotechnology. “High-power lithium batteries from functionalized carbon nanotube electrodes.” Seung Woo Lee, Naoaki Yabuuchi, Betar M. Gallant, Shuo Chen, Byeong-Su Kim, Paula T. Hammond, & Yang Shao-Horn. Nature Nanotechnology. 19 June 2010. doi:10.1038/nnano.2010.116
Source: EurekAlert!
PDF 
If I calculate right, with this technology, a 24kWh / 100 Mile battery (like the Nissan Leaf’s) would weigh 264 pounds. Or, a 53 kWh / 244 Mile mile battery (like the Tesla Raodster) would weigh about 583 pounds.
That would certainly help to make better EVs. I wonder how long it will take to get this technology to market?
Bret,
Your calculations are accurate. Keep in mind though, the 200 wh/kg measure is just of the cathode, so you have to add in some for the anode and associated battery managment features as well as packaging. Even so, I’d guess the battery would weigh around 500 pounds for the same 24 kWh that the LEAF accomplishes in about 900 pounds right now. The beauty of this battery is that is allows for very quick recharge and discharge times as well as adding very long lifespan.
If I calculate right, with this technology, a 24kWh / 100 Mile battery (like the Nissan Leaf’s) would weigh 264 pounds. Or, a 53 kWh / 244 Mile mile battery (like the Tesla Raodster) would weigh about 583 pounds.
That would certainly help to make better EVs. I wonder how long it will take to get this technology to market?
Bret,
Your calculations are accurate. Keep in mind though, the 200 wh/kg measure is just of the cathode, so you have to add in some for the anode and associated battery managment features as well as packaging. Even so, I’d guess the battery would weigh around 500 pounds for the same 24 kWh that the LEAF accomplishes in about 900 pounds right now. The beauty of this battery is that is allows for very quick recharge and discharge times as well as adding very long lifespan.
Sounds similar to the A123 battery also developed at MIT, which used nano-phosphate.
Hopefully we will see them in Dewalt’s power tool line before long!
http://biodiversivist.blogspot.com/2010/01/electric-bicycle-lessons-learned.html
Interesting times.
Sounds similar to the A123 battery also developed at MIT, which used nano-phosphate.
Hopefully we will see them in Dewalt’s power tool line before long!
http://biodiversivist.blogspot.com/2010/01/electric-bicycle-lessons-learned.html
Interesting times.
Hey Nick,
FYI, there’s an ad about cloud computing that covers up the first two comments.
I remember reading stories like this one about the A123 battery but I took it all with a grain of salt because as we all know, about 99.95 of research like this never results in a commercially marketable product.
Then one day I read that Dewalt was actually going to use the A123 in a battery in a power tool, which I also took with a grain of salt but finally, there they were in stores.
Time will tell.
Hey Nick,
FYI, there’s an ad about cloud computing that covers up the first two comments.
I remember reading stories like this one about the A123 battery but I took it all with a grain of salt because as we all know, about 99.95 of research like this never results in a commercially marketable product.
Then one day I read that Dewalt was actually going to use the A123 in a battery in a power tool, which I also took with a grain of salt but finally, there they were in stores.
Time will tell.
Nick, I doubt the Leaf’s battery weighs in at 900 pounds. Google “Nissan battery pounds” and you get a lot of different numbers ranging from 440 to 660 pounds. Most sources report below 500 pounds which makes sense. The lithium manganese technology should be able to get about 150 WH/Kg at the cell level and about 100WH/KG at the pack level.
Chris O,
The 900 pound number is accurate. But it is for the whole battery, including the metal casing surrounding it and the associated BMS.
Nick, I doubt the Leaf’s battery weighs in at 900 pounds. Google “Nissan battery pounds” and you get a lot of different numbers ranging from 440 to 660 pounds. Most sources report below 500 pounds which makes sense. The lithium manganese technology should be able to get about 150 WH/Kg at the cell level and about 100WH/KG at the pack level.
Chris O,
The 900 pound number is accurate. But it is for the whole battery, including the metal casing surrounding it and the associated BMS.
Russ, it is a electrode fabrication technique…not necessarily a marketable product (at the moment)
100kW/kg without significant aging effects? unless their process is extremely ineffective $$-wise it is hard to ignore
for reference A123 26650 (your dewalt batteries) are ~2-2.5kW/Kg, A123′s prismatic 20Ah cells are allegedly 5-6kW/kg
commercially available ultracapacitors are 5-6 kW/kg with the expectation that they can get to 20kW/kg over the next 5-10years
Russ, it is a electrode fabrication technique…not necessarily a marketable product (at the moment)
100kW/kg without significant aging effects? unless their process is extremely ineffective $$-wise it is hard to ignore
for reference A123 26650 (your dewalt batteries) are ~2-2.5kW/Kg, A123′s prismatic 20Ah cells are allegedly 5-6kW/kg
commercially available ultracapacitors are 5-6 kW/kg with the expectation that they can get to 20kW/kg over the next 5-10years
Hi Nick,
I think your figures are incorrect. I don’t think 200mAH g works out to 200 wh/kg.
Quoted from the original article:
“The electrode, which is several micrometres thick, can store lithium up to a reversible gravimetric capacity of ~200 mA h g−1electrode while also delivering 100 kW kgelectrode−1 of power and providing lifetimes in excess of thousands of cycles”
If it does why doesn’t the original make the same claim (the claim ENERGY 5x conventional electrochemical capacitors and POWER 10x conventional lithium-ion batteries):
“A device using the nanotube electrode as the positive electrode and lithium titanium oxide as a negative electrode had a gravimetric energy ~5 times higher than conventional electrochemical capacitors and power delivery ~10 times higher than conventional lithium-ion batteries.”
Energy 5x conventional electrochemical capacitors isn’t a hard target (for batteries) to hit. Power greater than current lithium-ion batteries might be nice but its not currently a major issue .
Mitchell,
Before writing the article, I was able to download and read the original paper. Although I can’t post the entirety here due to copyright, here’s a snippet that should help clear it up:
“Here, we report the use of an entirely different class of electrodes for lithium storage, which are based on functionalized multiwalled carbon nanotubes (MWNTs) that include stable pseudo-capacitive functional groups, and are assembled using the layer-by-layer (LBL) technique. These additive-free LBL-MWNT electrodes exhibit high gravimetric energy (200 Wh/kg) delivered at an exceptionally high power of 100 kW/kg in Li/LBL-MWNT cells when normalized to the single-electrode weight, with no loss observed after completing thousands of cycles. LBL- MWNT electrodes show significantly higher gravimetric energy not only over electrochemical capacitor electrodes, but also over high-power lithium battery electrodes, with gravimetric powers greater than approximately 10 kW/kg.”
Usually when scientists are running experimental batteries they use voltages per cell of 1 volt, which is why 200 mAh/g = 200 wh/kg.
Hi Nick,
I think your figures are incorrect. I don’t think 200mAH g works out to 200 wh/kg.
Quoted from the original article:
“The electrode, which is several micrometres thick, can store lithium up to a reversible gravimetric capacity of ~200 mA h g−1electrode while also delivering 100 kW kgelectrode−1 of power and providing lifetimes in excess of thousands of cycles”
If it does why doesn’t the original make the same claim (the claim ENERGY 5x conventional electrochemical capacitors and POWER 10x conventional lithium-ion batteries):
“A device using the nanotube electrode as the positive electrode and lithium titanium oxide as a negative electrode had a gravimetric energy ~5 times higher than conventional electrochemical capacitors and power delivery ~10 times higher than conventional lithium-ion batteries.”
Energy 5x conventional electrochemical capacitors isn’t a hard target (for batteries) to hit. Power greater than current lithium-ion batteries might be nice but its not currently a major issue .
Mitchell,
Before writing the article, I was able to download and read the original paper. Although I can’t post the entirety here due to copyright, here’s a snippet that should help clear it up:
“Here, we report the use of an entirely different class of electrodes for lithium storage, which are based on functionalized multiwalled carbon nanotubes (MWNTs) that include stable pseudo-capacitive functional groups, and are assembled using the layer-by-layer (LBL) technique. These additive-free LBL-MWNT electrodes exhibit high gravimetric energy (200 Wh/kg) delivered at an exceptionally high power of 100 kW/kg in Li/LBL-MWNT cells when normalized to the single-electrode weight, with no loss observed after completing thousands of cycles. LBL- MWNT electrodes show significantly higher gravimetric energy not only over electrochemical capacitor electrodes, but also over high-power lithium battery electrodes, with gravimetric powers greater than approximately 10 kW/kg.”
Usually when scientists are running experimental batteries they use voltages per cell of 1 volt, which is why 200 mAh/g = 200 wh/kg.
Nick: 900 pound it is then, but that would make your claim the highest in the business. Any source references to back this up? Too bad Nissan doesn’t seem too forthcoming with this kind of data. For instance: what does the Leaf weigh? Or is that some kind of trade secret? People will put it on a scale you know once it hits the streets… As a result the bloggosphere is rife with conflicting numbers.
Back to the 900 pounds: doing the math it would appear that Nissan is at 58 WH/KG at the pack level which is almost lead acid territory, which has no need for elaborate casing structures. At 900 pounds one wonders why Nissan bothered with expensive Li-ion…
Nick: 900 pound it is then, but that would make your claim the highest in the business. Any source references to back this up? Too bad Nissan doesn’t seem too forthcoming with this kind of data. For instance: what does the Leaf weigh? Or is that some kind of trade secret? People will put it on a scale you know once it hits the streets… As a result the bloggosphere is rife with conflicting numbers.
Back to the 900 pounds: doing the math it would appear that Nissan is at 58 WH/KG at the pack level which is almost lead acid territory, which has no need for elaborate casing structures. At 900 pounds one wonders why Nissan bothered with expensive Li-ion…
Chris O,
My reference is a conversation with Mark Perry at the Nashville groundbreaking. As I said, the 900 pounds includes everything related to the battery pack. It is a self-contained, weather-sealed, crash-resistant metal pack that is about 6′x5′x9″. Inside that pack you have all of the battery cells (individually wrapped), the cells are inside metal packs, you also have the Battery Management system, and all associated wiring.
I think the basic problem here is that there is no standard by which to measure what a “pack” is. Does it include everything required to make that battery work, or is is simply the weight of the individual cells. If you just take the weight of the cells, the battery pack would weigh much less. You can say any number you want to to come up with a favorable kWh/kg, but in my view, the only honest one includes the entire weight of all the battery components and associated weather protection. So Nissan has said that their self-contained weather sealed pack weighs around 900 pounds.
As for the lead acid argument – lead acid has VERY poor cold weather and hot weather performance characteristics… meaning you might lose 70% of your range in the right circumstances. LA also discharges very quickly compared to Li-ion so no leaving your car at the airport for a week. LA also contains toxic materials in high quantities. LA also corrodes much more quickly and needs to be replaced much more often. LA also can’t deliver power nearly as quickly as Li-ion. And, finally, if you wanted to seal up a giant lead acid pack properly to protect against crashes, it would indeed weigh much more than a typical lead-acid battery.
Again, it all comes down to what you use as the basis for measuring how much the “battery pack” weighs.
Chris O,
My reference is a conversation with Mark Perry at the Nashville groundbreaking. As I said, the 900 pounds includes everything related to the battery pack. It is a self-contained, weather-sealed, crash-resistant metal pack that is about 6′x5′x9″. Inside that pack you have all of the battery cells (individually wrapped), the cells are inside metal packs, you also have the Battery Management system, and all associated wiring.
I think the basic problem here is that there is no standard by which to measure what a “pack” is. Does it include everything required to make that battery work, or is is simply the weight of the individual cells. If you just take the weight of the cells, the battery pack would weigh much less. You can say any number you want to to come up with a favorable kWh/kg, but in my view, the only honest one includes the entire weight of all the battery components and associated weather protection. So Nissan has said that their self-contained weather sealed pack weighs around 900 pounds.
As for the lead acid argument – lead acid has VERY poor cold weather and hot weather performance characteristics… meaning you might lose 70% of your range in the right circumstances. LA also discharges very quickly compared to Li-ion so no leaving your car at the airport for a week. LA also contains toxic materials in high quantities. LA also corrodes much more quickly and needs to be replaced much more often. LA also can’t deliver power nearly as quickly as Li-ion. And, finally, if you wanted to seal up a giant lead acid pack properly to protect against crashes, it would indeed weigh much more than a typical lead-acid battery.
Again, it all comes down to what you use as the basis for measuring how much the “battery pack” weighs.
Hey Nick — hats off for a clear and concise explanation of this new battery process. I know from experience that descriptions like this are hard to pull off.
Hey Nick — hats off for a clear and concise explanation of this new battery process. I know from experience that descriptions like this are hard to pull off.
I thought lithium batteries ran about 3.3-3.6 Volts per cell.
I thought lithium batteries ran about 3.3-3.6 Volts per cell.
I always love to read the names of the American scientists.
I always love to read the names of the American scientists.