The Rise Of The Cyborg

Researchers from UCLA and the University of Connecticut have designed a new biofriendly energy storage system called a biological supercapacitor, which operates using charged particles, or ions, from fluids in the human body. The device is harmless to the body’s biological systems, and it could lead to longer-lasting cardiac pacemakers and other implantable medical devices like artificial heart.

The UCLA team was led by Richard Kaner, a distinguished professor of chemistry and biochemistry, and of materials science and engineering, and the Connecticut researchers were led by James Rusling, a professor of chemistry and cell biology. A paper about their design was published this week in the journal Advanced Energy Materials.

Pacemakers — which help regulate abnormal heart rhythms — and other implantable devices have saved countless lives. But they’re powered by traditional batteries that eventually run out of power and must be replaced, meaning another painful surgery and the accompanying risk of infection. In addition, batteries contain toxic materials that could endanger the patient if they leak.

The researchers propose storing energy in those devices without a battery. The supercapacitor they invented charges using electrolytes from biological fluids like blood serum and urine, and it would work with another device called an energy harvester, which converts heat and motion from the human body into electricity — in much the same way that self-winding watches are powered by the wearer’s body movements. That electricity is then captured by the supercapacitor.

Combining energy harvesters with supercapacitors can provide endless power for lifelong implantable devices that may never need to be replaced,” said Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the study.


NonCarbon SuperCapacitor Produces More Power

Energy storage devices called supercapacitors have become a hot area of research, in part because they can be charged rapidly and deliver intense bursts of power. However, all supercapacitors currently use components made of carbon, which require high temperatures and harsh chemicals to produce. Now researchers at MIT and elsewhere have for the first time developed a supercapacitor that uses no conductive carbon at all, and that could potentially produce more power than existing versions of this technology.


We’ve found an entirely new class of materials for supercapacitors,” Dincă says.

Dincă and his team have been exploring for years a class of materials called metal-organic frameworks, or MOFs, which are extremely porous, sponge-like structures. These materials have an extraordinarily large surface area for their size, much greater than the carbon materials do. That is an essential characteristic for supercapacitors, whose performance depends on their surface area. But MOFs have a major drawback for such applications: They are not very electrically conductive, which is also an essential property for a material used in a capacitor.

One of our long-term goals was to make these materials electrically conductive,” Dincă says, even though doing so “was thought to be extremely difficult, if not impossible.” But the material did exhibit another needed characteristic for such electrodes, which is that it conducts ions (atoms or molecules that carry a net electric charge) very well.

All double-layer supercapacitors today are made from carbon,” Dincă says. “They use carbon nanotubes, graphene, activated carbon, all shapes and forms, but nothing else besides carbon. So this is the first noncarbon, electrical double-layer supercapacitor.”

The team’s findings are being reported in the journal Nature Materials, in a paper by Mircea Dincă, an MIT associate professor of chemistry; Yang Shao-Horn, the W.M. Keck Professor of Energy; and four others.


How To Increase By Six Times The Capacity Of Lithium-Ion Batteries

The capacity of lithium-ion batteries might be increased by six times by using anodes made of silicon instead of graphite. A team from the Helmholtz-Zentrum Berlin (HZB) Institute of Soft Matter and Functional Materials has observed for the first time in detail how lithium ions migrate into thin films of silicon. It was shown that extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.

The team was able to show through neutron measurements made at the Institut Laue-Langevin in Grenoble, France, that lithium ions do not penetrate deeply into the silicon. During the charge cycle, a 20-nm anode layer develops containing an extremely high proportion of lithium. This means extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.
lithium-ion battery

Lithium-ion batteries provide laptops, smart phones, and tablet computers with reliable energy. However, electric vehicles have not gotten as far along with conventional lithium-ion batteries. This is due to currently utilised electrode materials such as graphite only being able to stably adsorb a limited number of lithium ions, restricting the capacity of these batteries. Semiconductor materials like silicon are therefore receiving attention as alternative electrodes for lithium batteries. Bulk silicon is able to absorb enormous quantities of lithium. However, the migration of the lithium ions destroys the crystal structure of silicon. This can swell the volume by a factor of three, which leads to major mechanical stresses. Now a team from the HZB Institute for Soft Matter and Functional Materials headed by Prof. Matthias Ballauff has directly observed for the first time a lithium-silicon half-cell during its charging and discharge cycles. “We were able to precisely track where the lithium ions adsorb in the silicon electrode using neutron reflectometry methods, and also how fast they were moving”, comments Dr. Beatrix-Kamelia Seidlhofer, who carried out the experiments using the neutron source located at the Institute Laue-Langevin.

She discovered two different zones during her investigations. Near the boundary to the electrolytes, a roughly 20-nm layer formed having extremely high lithium content: 25 lithium atoms were lodged among 10 silicon atoms. A second adjacent layer contained only one lithium atom for ten silicon atoms. Both layers together are less than 100 nm thick after the second charging cycle.

After discharge, about one lithium ion per silicon node in the electrode remained in the silicon boundary layer exposed to the electrolytes. Seidlhofer calculates from this that the theoretical maximum capacity of these types of silicon-lithium batteries lies at about 2300 mAh/g. This is more than six times the theoretical maximum attainable capacity for a lithium-ion battery constructed with graphite (372 mAh/g).

The results ar published in the journal ACSnano (DOI: 10.1021/acsnano.6b02032).


Nanotechnologies Boost Electric Car Batteries

On a drizzly, gray morning in April, Yi Cui weaves his scarlet red Tesla in and out of Silicon Valley traffic. Cui, a materials scientist at Stanford University here, is headed to visit Amprius, a battery company he founded 6 years ago. It’s no coincidence that he is driving a battery-powered car, and that he has leased rather than bought it. In a few years, he says, he plans to upgrade to a new model, with a crucial improvement: “Hopefully our batteries will be in it.” Cui and Amprius are trying to take lithium–ion batteries—today’s best commercial technology—to the next level. They have plenty of company. Massive corporations such as Panasonic, Samsung, LG Chem, Apple, and Tesla are vying to make batteries smaller, lighter, and more powerful. But among these power players, Cui remains a pioneering force.
Unlike others who focus on tweaking the chemical composition of a battery’s electrodes or its charge-conducting electrolyte, Cui is marrying battery chemistry with nanotechnology. He is building intricately structured battery electrodes that can soak up and release charge-carrying ions in greater quantities, and faster, than standard electrodes can, without producing troublesome side reactions.

Tesla Model 3

“He’s taking the innovation of nanotechnology and using it to control chemistry,” says Wei Luo, a materials scientist and battery expert at the University of Maryland, College Park.
In a series of lab demonstrations, Cui has shown how his architectural approach to electrodes can domesticate a host of battery chemistries that have long tantalized researchers but remained problematic. Among them: lithium-ion batteries with electrodes of silicon instead of the standard graphite, batteries with an electrode made of bare lithium metal, and batteries relying on lithium-sulfur chemistry, which are potentially more powerful than any lithium-ion battery. The nanoscale architectures he is exploring include silicon nanowires that expand and contract as they absorb and shed lithium ions, and tiny egglike structures with carbon shells protecting lithium-rich silicon yolks.


Electric Car: Safer, Cheaper Rechargeable Batteries

By chemically modifying and pulverizing a promising group of compounds, scientists at the National Institute of Standards and Technology (NIST) have potentially brought safer, solid-state rechargeable batteries two steps closer to reality.

sodiumChunks of this sodium-based compound (Na2B12H12) (left) would function well in a battery only at elevated temperatures, but when they are milled into far smaller pieces (right), they can potentially perform even in extreme cold, making them even more promising as the basis for safer, cheaper rechargeables.

These compounds are stable solid materials that would not pose the risks of leaking or catching fire typical of traditional liquid battery ingredients and are made from commonly available substances. Since discovering their properties in 2014, a team led by NIST scientists has sought to enhance the compounds’ performance further in two key ways: Increasing their current-carrying capacity and ensuring that they can operate in a sufficiently wide temperature range to be useful in real-world environments.

Considerable advances have now been made on both fronts, according to Terrence Udovic of the NIST Center for Neutron Research, whose team has published a pair of scientific papers that detail each improvement.  The first advance came when the team found that the original compounds — made primarily of hydrogen, boron and either lithium or sodium — were even better at carrying current with a slight change to their chemical makeup. Replacing one of the boron atoms with carbon improved their ability to conduct charged particles, or ions, which are what carry electricity inside a battery. As the team reported in February in their first paper, the switch made the compounds about 10 times better at conducting.

But perhaps more important was clearing the temperature hurdle. The compounds conducted ions well enough to operate in a battery — as long as it was in an environment typically hotter than boiling water. Unfortunately, there’s not much of a market for such high-temperature batteries, and by the time they cooled to room temperature, the materials’ favorable chemical structure often changed to a less conductive form, decreasing their performance substantially. One solution turned out to be crushing the compounds’ particles into a fine powder.

This approach can remove worries about whether batteries incorporating these types of materials will perform as expected even on the coldest winter day,” said Udovic, whose collaborators on the most recent paper include scientists from Japan’s Tohoku University, the University of Maryland and Sandia National Laboratories. “We are currently exploring their use in next-generation batteries, and in the process we hope to convince people of their great potential.”