The Light Side: Secret of Lithium-Ion Batteries Revealed

June 13, 2014

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There are plenty of things in the universe where we know they just work without fully understanding how it happens, but Massachusetts Institute of Technology researchers might have crossed lithium-ion batteries off that list.

Using in-situ transmission electron microscopy (TEM), MIT professor Ju Li and six colleagues were able to see exactly what happens to the electrode material in lithium-based rechargeable batteries -- lithium iron phosphate, or LiFePO4 -- during charging. And, as a result, they were pleased to have proven a longstanding theory behind why lithium-ion batteries are such fast-charging, high-powered performers.

The MIT researchers discovered that during battery charging, a solid-solution zone, or SSZ, forms at the boundary between lithium-rich and lithium-depleted areas in the LiFEPO4 electrode. The SSZ is where charging activity is concentrated, as lithium ions are pulled out of the electrode. Li says the SSZ "has been theoretically predicted to exist, but we see it directly for the first time."

LiFePO4 and, inherently, iron phosphate (FePO4) have very poor ionic and electrical conductivities. But after LiFePO4 is doped and carbon coated and used as nanoparticles in batteries, LiFePO4 shows rapid charging and discharging rates. "We directly observed a metastable random solid solution that may resolve this fundamental problem that has intrigued [material scientists] for many years," Li said.

The SSZ, which persists for several minutes at room temperature during battery charging, is also the key that explains why lithium-ion batteries have a high number of cycles before they can no longer hold a charge. It serves as a buffer that slows down electrode fatigue. Knowing this mechanism might allow fine-tuning of electrodes for even greater performance.

Despite an incomplete understanding to date, lithium iron phosphate nanoparticles are already used at an industrial scale for lithium-ion batteries. LiFePO4 is a promising material for applications ranging from large-scale grid storage to electric vehicle batteries to power tools. "Compared to traditional lithium-ion, LiFePO4 is environmentally friendly and very stable, but it's important for this material to be well understood," Li said.

He adds that the discovery of the SSZ can be applied in principle to other electrode materials. "People are looking for high-power electrode materials, and such metastable states could exist in other electrode materials that are inert in bulk form."

3D Printing 'Suits' RoboCop's Special Effects Wizards

Stratasys Ltd., in an announcement yesterday, revealed that the company's multimaterial Objet Connex 3D printing technology played a leading role in the production of the RoboCop suit for the iconic character's return in this year's blockbuster remake.

Tasked with realizing the 3D designs from RoboCop's production designer was Legacy Effects, a Hollywood special effects company. It has used Stratasys' 3D printing technology before to bring to life a number of recognizable movie characters.

robocopUsing Stratasys' high-resolution Objet Connex multimaterial 3D printing technology, Legacy Effects produced every aspect of the RoboCop suit -- from helmet to boots -- as master mold patterns. These pieces were then molded and cast in other materials to create variants of the suit depending on the requirements of each movie scene.

In addition, some versions of the suit used in the movie were composed of as much as 90 percent actual Stratasys 3D-printed parts. For example, the striking visor, which forms part of the helmet on the black version of the RoboCop suit, features a gleaming red strip; the entire visor used in the movie is 3D printed with Stratasys' transparent VeroClear material.

According to Jason Lopes, Legacy Effects' lead design engineer, RoboCop's chest-armor piece perhaps best exemplifies how the use of 3D printing technology overcomes certain challenges that can affect production methods.

"First, in terms of the size of RoboCop's chest piece specifically, only Stratasys' 3D printing technology would allow us to print something at the actual size; the part virtually fills the entire (machine) build-tray," Lopes explained.

"Second, the same part comprises a blend of smooth areas, as well as other areas that feature an extremely high level of detail, such as the police badge and other logos, which we needed to retain for the molding process," he added. "There isn't a technology currently available beyond that provided by Stratasys that affords us this level of intricate detail, together with the hard-surface modeling of the shells altogether in one print."

In addition to creating the RoboCop suit, Legacy Effects was also involved in 3D printing both master molds and prototype parts for the "Exo-suit" featured in the movie. These prototype pieces included fully-functional spring-operated fingers that were printed in a single build using multiple materials on Stratasys' printers.

Using Stratasys' 3D printing technology, the Legacy Effects team was able to work much faster and more efficiently than in the days when it produced parts by hand.

"Doing everything by hand meant that we couldn't run tests, as it would have taken forever," recalled Lopes. "Also, 3D printing allows us to work in symmetry, which enables us to build an entire left side of a suit, then mirror it and output the right side as well, all from one file with the click of a button. You can't do that by hand."

Despite the recent economic downturn still having an impact on Hollywood studio budgets, high expectation from customers requires shorter production times, regardless of the all-too-commonplace eleventh-hour changes. For Lopes, 3D printing's ability to speed up processes, as well as the capability to make late changes, has revolutionized the way Legacy Effects operates.

"This is where 3D printing comes to the fore, by meeting such pressures head on," said Lopes. "If we see something's not working, or we're asked to make a design change, we can make another iteration, go to an open 3D printer and be printing two simultaneous tests within an hour. We go to lunch, come back, and it's done. It doesn't get better than that!"

"Legacy Effects' use of multimaterial 3D printing is indicative of how the technology is becoming increasingly integral to filmmaking," said Bruce Bradshaw, director of marketing for Stratasys North America. "The ability to rapidly 3D print all materials together in one single print run meets the film industry prerequisite to save time and money. In the special effects world, fine detail and true-to-life models and parts are the industry standard."

[youtube]https://www.youtube.com/watch?v=sMEDln3Wex8[/youtube]

This article was originally published on Engineering.com and is adapted with permission. For more stories like this please visit Engineering.com.
It's the Stuff of Nightmares, Says Dream Study

A recent study by psychology professionals at the University of Montreal investigated the differentiators of "bad dreams" and "nightmares" as well as the different types of dreamscapes between men and women. While nightmares represent a somewhat rarer and more severe expression, they represent the same basic phenomenon as bad dreams. But men tend to dwell on themes of disasters, war, and calamities like floods and earthquakes, while women focus on interpersonal conflicts.

Those were the observations of Dr. Genevieve Robert and Dr. Antonio Zadra, who aimed to determine how nightmares are conceptualized. They collected about 10,000 dream reports from 572 test participants over a five-week period and investigated the content of 253 nightmares and 431 bad dreams. Most people forget their dreams, but heavy dreamers remember them more easily, and some even become aware that they're dreaming, a phenomenon called lucid dreaming.

"Nightmares are not a disease in themselves but can be a problem for the individual who anticipates them or who is greatly distressed by their nightmares," Zadra said. "People who have frequent nightmares may fear falling asleep." The two researchers defined nightmares as dreams so intense that they physically awaken sleepers and have greater emotional impact.

Whether it is a natural or man-made disaster, physical aggression is the most frequently reported theme in nightmares, followed by death and health concerns. Sometimes it could just be a threatening or ominous environment experienced by someone just before sleep that triggers a nightmare. "I'm thinking of one narrative, in which the person saw an owl on a branch and was absolutely terrified," Robert said.

Interpersonal conflicts predominated in bad dreams. When compared to bad dreams, nightmares were more bizarre and contained substantially more aggressions, failures, and "unfortunate endings," according to the study report's abstract.

Those who lucid dream can fight their nightmares through visualization techniques, such as learning to change the scenario or environment as the event goes down.

Happy Friday the 13th.

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