Hasta La Gadget!

Left: diagram of a lithium-ion battery constructed using a nanostructured bicontinuous cathode. Right: scanning electron microscope image of the nanostructure, a three-dimensional metal foam current collector coated with a thin layer of active material. Image courtesy of Paul Braun, University of Illinois.

by John Timmer, Ars Technica

Batteries are an essential part of most modern gadgets, and their role is expected to expand as they’re incorporated into vehicles and the electric grid itself. But batteries can’t move charge as quickly as some competing devices like supercapacitors, and their performance tends to degrade significantly with time. That has sent lots of materials science types into the lab, trying to find ways to push back these limits, sometimes with notable success. Over the weekend, there was another report on a technology that enables fast battery charging. The good news is that it uses a completely different approach and technology than the previous effort, and can work with both lithium- and nickel-based batteries.

The previous work was lithium-specific, and focused on one limit to a battery’s recharge rate: how quickly the lithium ions could move within the battery material. By providing greater access to the electrodes, the authors allowed more ions to quickly exchange charge, resulting in a battery with a prodigious capacity. The researchers increased lithium’s transport within the battery by changing the structure of the battery’s primary material, LiFePO₄.

The new work is quite different. The authors, from the University of Illinois, don’t focus on the speed of the lithium ions in the battery; instead, they attempt to reduce the distance the ions have to travel before reaching an electrode. As they point out, the time involved in lithium diffusion increases with the square of the distance traveled, so cutting that down can have a very dramatic effect. To reduce this distance, they focus on creating a carefully structured cathode.

The process by which they do this is fairly simple, and lends itself to mass production. They started with a collection of spherical polystyrene pellets. By adjusting the size of these pellets (they used 1.8µm and 466nm pellets), they could adjust the spacing of the electrode features. Once the spheres were packed in place, a layer of opal (a form of silica) was formed on top of them, locking the pattern in place with a more robust material. After that, a layer of nickel was electrodeposited on the opal, which was then etched away. The porosity of the nickel layer was then increased using electropolishing.

When the process was done, the porosity — a measure of the empty space in the structure — was about 94 percent, just below the theoretical limit of 96 percent. The authors were left with a nickel wire mesh that was mostly empty space.

Into these voids went the battery material, either nickel-metal hydride (NiMH) or a lithium-treated manganese dioxide. The arrangement provides three major advantages, according to the authors: an electrolyte pore network that enables rapid ion transport, a short diffusion distance for the ions to meet the electrodes, and an electrode with high electron conductivity. All of these make for a battery that acts a lot like a supercapacitor when it comes to charge/discharge rates.

With the NiMH battery material, the electrodes could deliver 75 percent of the normal capacity of the battery in 2.7 seconds; it only took 20 seconds to recharge it to 90 percent of its capacity, and these values were stable for 100 charge/discharge cycles. The lithium material didn’t work quite as well, but was still impressive. At high rates of discharge, it could handle 75 percent of its normal capacity, and still stored a third of its regular capacity when discharged at over a thousand times the normal rate.

A full-scale lithium battery made with the electrode could be charged to 75 percent within a minute, and hit 90 percent within two minutes.

There are a few nice features of this work. As the authors noted, the electrodes are created using techniques that can scale to mass production, and the electrodes themselves could work with a variety of battery materials, such as the lithium and nickel used here. It may also be possible to merge them with the LiFePO₄used in the earlier work. A fully integrated system, with materials designed to work specifically with these electrodes, could increase their performance even further.

Of course, that ultimately pushes us up against the issue of supplying sufficient current in the short time frames needed to charge the battery this fast. It might work great for a small battery, like a cell phone, but could create challenges if we’re looking to create a fast-charge electric car.

Nature Nanotechnology, 2011. DOI: 10.1038/NNANO.2011.38 (About DOIs).

Originally published as Electrode lets lithium batteries charge in just two minutes on Ars Technica.

Want to stay connected with your family’s activities? Sync with your Google Calendar? Get a better week view? These apps offer that and more.

Originally posted at iPhone Atlas

It’s well known that advertisers track our web-surfing habits to tailor the ads we see, but they’d prefer to know exactly what’s going on inside of that brain of yours. NeuroFocus’ aptly named Mynd, a full-brain wireless EEG sensor headset, serves as a stylish and easy way to record your thoughts whilst gazing at logos and lusting after products. In addition to neuromarketing applications, the European Tools for Brain-Computer Interaction consortium (TOBI) see it as a tool to help develop new technology for those with neurological disabilities. Sporting looks straight off the Game Grid, the Mynd is made of medical-grade EEG sensors to capture brain activity 2,000 times per second and a Bluetooth radio to shoot your thoughts to the smartphone, tablet, or PC of your choice. The wireless bit represents a huge upgrade over traditional EEG caps because it makes the headset’s mind-reading powers available in shopping malls and living rooms instead of just hospitals. All so the sellers of things can know just how effective a spokesperson the ETrade baby really is. PR’s after the break.

Continue reading NeuroFocus makes first wireless EEG sensor headset, don’t call it a thinking cap

NeuroFocus makes first wireless EEG sensor headset, don’t call it a thinking cap originally appeared on Engadget on Wed, 23 Mar 2011 11:13:00 EDT. Please see our terms for use of feeds.

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Apple has apparently responded to the public outcry surrounding Exodus International’s controversial “gay cure” app. The app, which stirred up protest from gay rights groups earlier this month, culminating in a petition signed by nearly 150,000 people, has disappeared from the iPhone App Store.

Apple has long been a friend of the LGBT community, opposing California’s Proposition 8, removing the anti-gay Manhattan Declaration iPhone app, and earning a 100% score from the Human Rights Campaign’s Corporate Equality Index. I am shocked that this same company has given the green light to an app from a notoriously anti-gay organization like Exodus International that uses scare tactics, misinformation, stereotypes and distortions of LGBT life to recruit clients.

On Monday, Google expressed its belief that its email users in China were experiencing “a government blockage carefully designed to look like the problem is with Gmail.” Now, as is par for this thorny course, the Chinese state has come out with a terse rebuttal, saying simply that “this is an unacceptable accusation.” The retort was, says the BBC, part of a regular news conference on Tuesday and it doesn’t appear that any more time was spent on the subject. Which is odd since most people would tend to act to prevent something they see as unacceptable — but then we suppose China already has a pretty long list of folks it’d like to shut up, Google’s just gonna have to get in line and wait its turn. There’s a good citizen.

China, predictably, denies Google’s accusations of Gmail tampering originally appeared on Engadget on Wed, 23 Mar 2011 10:14:00 EDT. Please see our terms for use of feeds.

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