WC Archive

Lithium-Top: The two most conventional developments come from MIT, and push the limits of the current generation of lithium-based batteries. The first is a change in the manufacturing process that could lead to lithium batteries that are more stable, cheaper and 2-3 times more capacious than current versions. The second, different approach, also results in lithium batteries that are more stable, although production cost and improvements to capacity are still uncertain. In and of themselves, these are notable in passing but hardly worldchanging; in the context of what follows, though, they're a reminder that the older technologies may still have some life in them, too.

Ultrapower: At the other end of the "how conventional is this technology" spectrum is a new ultracapacitor that can be used like a battery, also from MIT. Ultracapacitors are devices that store energy as an electric field, not as a chemical mix. They have a number of advantages over traditional batteries: longer storage life; indifference to temperature, shock and vibration; and a faster and more efficient discharge/recharge cycle. They have a big downside, though -- literally. Ultracapacitors require a great deal more volume than a battery to store an equivalent amount of power.

That is, until you add carbon nanotubes to the mix. Because the storage capacity of ultracapacitors is equivalent to the internal surface area, adding a covering of nanotubes -- nanometers in width, but a hundred thousand times longer than they are wide -- can increase the overall storage capacity by roughly 25 times, allowing the ultracapacitors to store as much power as a regular battery in the same volume. While this is good news for those wishing to replace batteries with something more robust, it's wonderful news for makers of hybrid and fuel-cell vehicles: all current designs use regular ultracapacitors to handle the cycle of charging and discharging, so this breakthrough could lead to hybrid/fc cars able to go significantly further on electricity alone.

Superpower: And if this all sounds familiar, it should. Last month, we mentioned similar work done at Cambridge on nanotube-enhanced supercapacitors (as far as I can tell, the same as "ultracapacitors" -- anyone have better info?). The Cambridge research may also have implications for (of all things) computer memory:

The nanoscale capacitors might also serve in advanced memory chips, said Manish Chhowalla, a materials scientist at Rutgers University in Piscataway, N.J., who did not participate in this study. He noted that nanocapacitor conductance was high when they stored charge and low when they did not, which could serve as the equivalent of zeroes and ones "that are the basis of any memory device." The advantage nanotube capacitors might have over competing memory storage methods is the fact that they take up most of their space vertically, allowing more of them to be packed together onto a surface.

Super-Batteries: If nano-enhanced capacitors are good, what about nano-enhanced batteries? Unsurprisingly, MIT is in the mix on this one, too. A new super-battery design could blow past both traditional batteries and even ultracapacitors:

The M1, based on the same lithium-ion technology used in your cell phone and laptop, is the first product from MIT spinoff A123 Systems. Cofounder Yet-Ming Chiang, a materials science professor, succeeded in shrinking to nanoscale the particles that coat the battery's electrodes and store and discharge energy. The results are electrifying: Power density doubles, peak energy jumps fivefold (the cells pack more punch than a standard 110-volt wall outlet), and recharging time plummets. Going nano also solves a safety problem. Regular high-capacity Li-ion batteries tend to explode under severe stress, like if they're dropped from a ladder.

The article asserts that a battery typical of those used in hybrid cars could see a weight reduction of up to 80% for the same power, but the big news is that the battery could be recharged up to 90% in five minutes. Remember the key factor required for consumer acceptance of advanced technology vehicles: the new vehicle has to be at least as convenient as the old, meaning equivalent (or better) range, carrying capacity and fueling time. Five minutes to "fill up" an electric car isn't too far off the time needed at a gas pump today, and the kind of power output and storage density described in the article would bring electrics a lot closer to being competitive with gasoline vehicles in overall utility.

Nanograss: Finally, there's the work done at mPhase Technologies (PDF) using novel nanoscale structures referred to as "nanograss" (which we first talked about way back in October 2004) and a somewhat bizarre physical property known as "electrowetting." The result is a battery that is ideally suited to some pretty worldchanging applications:

A droplet of electrolyte when placed on this surface does not stick to it but rather remains highly mobile as a consequence of small solid-liquid interface. In essence, the droplet is only supported by the very tips of the nanoposts and does not penetrate into the space between them.

Electrowetting gives one the ability to change the contact angle of the solid-liquid interface by applying voltage to the liquid. It has been successfully applied to create a variety of optical devices such as lenses, diffraction gratings and is now combines with nanostructures to create novel batteries and battery architecture with unique characteristics.

So what does that mean? It means the same 19th century chemical battery concept, when mixed with 21st century nanoscale materials, can produce a battery with an up to 15 year shelf life, a far better power density, a fast ramp up to full power, and a production model using well-understood semiconductor techniques. The researchers see this technology as having applications in: storage for intermittent/periodic power generation, like solar and wind; embedded power cells for emergency equipment; and micropower sources for "lab-on-a-chip" equipment.

(Via Knowprose)