Nano power: The pores between the nanotubes in this transmission- electron microscopy image can store lithium ions in a high-power battery.
Nature Nanotechnology/NPG
Lithium-ion batteries with nanotube electrodes could go longer between charges.
A lithium-ion battery with a positive electrode made of carbon nanotubes delivers 10 times more power than a conventional battery and can store five times more energy than a conventional ultracapacitor. The nanotube battery technology, developed by researchers at MIT and licensed to an undisclosed battery company, could lead to batteries that improve heavy-duty hybrid vehicles and allow faster recharging for electronic gadgets, including smartphones.
Researchers have been trying to make electrodes for lithium-ion batteries from carbon nanotubes because their high surface area and high conductivity promise to improve both energy and power density relative to conventional forms of carbon. But working with the material has proved challenging--most methods for assembling carbon nanotubes require a binding agent that brings down the conductivity of the electrode, and lead to the formation of clumps of the material, reducing the surface area. The electrodes made by the MIT group, however, have a very high surface area for storing and reacting with lithium. This high surface area is critical both to the high storage capacity of the electrodes, as well as their high power: because lithium is stored on the surface, it can move in and out of the electrode rapidly, enabling faster charging and discharging of the battery.
The key to the performance of the MIT electrodes is an assembly process that creates dense, interconnected, yet porous carbon-nanotube films, without the need for any fillers. The group, led by chemical engineering professor Paula Hammond and mechanical engineering professor Yang Shao-Horn, create water solutions of carbon nanotubes treated so that one group is positively charged and the other is negatively charged. They then alternately dip a substrate, such as a glass slide, in the two solutions, and the nanotubes, attracted by differences in their charge, cling to one another very strongly in uniform, thin layers. The researchers had previously demonstrated that when heated and removed from the substrate, these dense yet porous films could store a lot of charge and release it quickly--acting like an electrode in an ultracapacitor.
A new method produces dense arrays of carbon nanotubes for digital logic.
The large facility is meant to reflect a change of direction for the bankrupt company.
Wording almost seemed to skirt around issue. Probably reflecting the wording in the press release.
Actually sounds very interesting and has lots of obvious advantages; Rapidity of discharging and perhaps charging being important, especially in hybrid applications, as well as durability.
If one adds increased energy density and high efficiency (most of what goes in comes out) and mass manufacturing and this could be revolutionary. Which is why the wording was so odd. Sounds like they've only got two or three out of four nailed down. Which is OK, a very respectable breakthrough. But if so, say so; adds to "your," whoever "you" is/are, credibility.
Actual power density is not the issue being skirted. The point almost being made is, the large surface area the electrons cross to get in/out of the anode/cathode reduces heat generated to negligible, thus preventing fire. This allows the battery to be filled/emptied quickly without paying the otherwise inevitable price : spontaneous ignition. Thus the unfortunate comparison to ultracapacitor.
The point not being made, and not just here, is the life cycle of SOME SORTS of Lithium Ion Batteries depends not only on how you use it, but also on the simple passage of time. A case of use it, because you are going to lose it. Not a sales point, in spades. You want to be careful about this as it DOES NOT apply to every type of LIon Battery.
The point being omitted intentionally is the manufacturers name. I think it is probably A123. It may be MIT has made a deal with another manufacturer, but they certainly have one with A123. I seem to recall GM does too.
Did I miss where they spoke about cycle life? Energy density and speed of discharge is useless if you can only use it a few times.
Re: No reference to cycle life??
the nature article report exceptional stability. it sounds like studying the stability is less mature than the energy density and power density analysis though. from the article:
The stability of the functional groups on these MWNTs is remarkable when compared to the considerable losses of carbonyl derivative molecules within 50 to 100 cycles reported recently34, 35, 43. We hypothesize that the cycling stability of the LBL-MWNT electrodes can be linked to the strong chemical covalent bonding of the surface functional groups on the MWNTs, in contrast to the gradual separation occurring between the active carbonyl groups and carbon additives in composite electrodes during cycling.
Still thinking in terms of hybrids for nano-tube Li batteries? If these batteries can make it to market with all the capability they claim the car would have sufficient range and quick charging capability to ditch the combustion engine all together.
Thank you to the other commenters for educating me on more of the technical questions. I'd like to add a very non-technical question: when are they projecting availability of this technology? Are they looking at producing these batteries in the next few years or is this yet another "5-10 year" technology that may or may not ever see the light of day?
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.
On Twitter
Become a Fan on Facebook
Subscribe to the Feed
tammons
8 Comments
what about energy density
I can see the logic that the carbon tubes can store and release ions faster thus increasing power density but what about energy density of the battery? Comparing it to an ultra capacitor is not very encouraging. Will it help to provide longer running time in a Lap Top or extending range over existing Lion batteries in an electric car?
Reply
yoatmon
30 Comments
Re: what about energy density
The following is a theoretical evaluation of a successful symbiosis of Graphene and CNTs. Practical R&D results from MIT support these theories.
Stacks of several µ-meter thick sheets (approx. the size of a standard sheet of paper) connected in series (strings) and parallel connected strings all stacked to approx. 1mm thick to produce a Ultra-Super Cap could reach an energy density approx. 20 to 25 times higher than present Li-Ion batteries.
Reply