Lithium-ion battery capacity can be vastly improved if, on the microscale, their electrodes have pores and channels. An interdigitated geometry, though it does allow lithium to transport through the battery efficiently during charging and discharging, is not optimal.

Rahul Panat, an associate professor of mechanical engineering at Carnegie Mellon University, and a team of researchers from Carnegie Mellon in collaboration with Missouri University of Science and Technology have developed a revolutionary new method of 3-D printing battery electrodes that creates a 3-D microlattice structure with controlled porosity. 3-D printing this microlattice structure, the researchers show in a paper published in the journal Additive Manufacturing, vastly improves the capacity and charge-discharge rates for lithium-ion batteries.

“In the case of lithium-ion batteries, the electrodes with porous architectures can lead to higher charge capacities,” says Panat. “This is because such architectures allow the lithium to penetrate through the electrode volume leading to very high electrode utilization, and thereby higher energy storage capacity. In normal batteries, 30-50% of the total electrode volume is unutilized. Our method overcomes this issue by using 3D printing where we create a microlattice electrode architecture that allows the efficient transport of lithium through the entire electrode, which also increases the battery charging rates.”

The additive manufacturing method presented in Panat’s paper represents a major advance in printing complex geometries for 3-D battery architectures, as well as an important step toward geometrically optimizing 3-D configurations for electrochemical energy storage. The researchers estimate that this technology will be ready to translate to industrial applications in about 2-3 years.

The microlattice structure (Ag) used as lithium-ion batteries’ electrodes was shown to improve battery performance in several ways such as a fourfold increase in specific capacity and a twofold increase in areal capacity when compared to a solid block (Ag) electrode. Furthermore, the electrodes retained their complex 3D lattice structures after forty electrochemical cycles demonstrating their mechanical robustness. The batteries can thus have high capacity for the same weight or alternately, for the same capacity, a vastly reduced weight — which is an important attribute for transportation applications.

The Carnegie Mellon researchers developed their own 3-D printing method to create the porous microlattice architectures while leveraging the existing capabilities of an Aerosol Jet 3-D printing system. The Aerosol Jet system also allows the researchers to print planar sensors and other electronics on a micro-scale, which was deployed at Carnegie Mellon University’s College of Engineering earlier this year.

Until now, 3-D printed battery efforts were limited to extrusion-based printing, where a wire of material is extruded from a nozzle, creating continuous structures. Interdigitated structures were possible using this method. With the method developed in Panat’s lab, the researchers are able to 3-D print the battery electrodes by rapidly assembling individual droplets one-by-one into three-dimensional structures. The resulting structures have complex geometries impossible to fabricate using typical extrusion methods.

“Because these droplets are separated from each other, we can create these new complex geometries,” says Panat. “If this was a single stream of material, as is in the case of extrusion printing, we wouldn’t be able to make them. This is a new thing. I don’t believe anybody until now has used 3-D printing to create these kinds of complex structures.”

This revolutionary method will be very important for consumer electronics, medical devices industry, as well as aerospace applications. This research will integrate well with the biomedical electronic devices, where miniaturized batteries are required. Non-biological electronic micro-devices will also benefit from this work. And on a bigger scale, electronic devices, small drones, and aerospace applications themselves can use this technology as well, due to the low weight and high capacity of the batteries printed using this method.

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Materials provided by College of Engineering, Carnegie Mellon University. Original written by Emily Durham. Note: Content may be edited for style and length.

The specifics of the deep geologic processes that occurred roughly 50 million years ago, when the Indian and Asian tectonics plates collided, have remained elusive. By collecting high-resolution earthquake data, geologists have generated a model that provides the clearest picture so far of the geology below the surface of the Tibetan Plateau. They report their findings in the Proceedings of the National Academy of Sciences.

“The continental collision between the Indian and Asian tectonic plates shaped the landscape of East Asia, producing some of the deadliest earthquakes in the world,” said Xiaodong Song, a geology professor at the University of Illinois and co-author of the new study. “However, the vast high plateau is largely inaccessible to geological and geophysical studies.”

Song and his colleagues reveal that the upper mantle layer of the Indian tectonic plate appears to be torn into four pieces that dive under Asia — each at a different angle and distance from the origin of the tear.

The team gathered geophysical data from various sources to generate seismic wave tomographic images of Tibet that extend roughly 160 kilometers deep. They found that these newly modeled images match well with historic earthquake activity and with geological and geochemical observations.

“The presence of these tears helps give a unified explanation as to why mantle-deep earthquakes occur in some parts of southern and central Tibet and not others,” Song said.

The intact regions of crust between the tears are strong enough to accumulate strain to generate earthquakes. The crustal areas above the torn regions are exposed to more of the heat from the mantle and are therefore more ductile, the researchers said. That ductile flexibility makes warmer crust less susceptible to earthquakes.

“What were previously thought of as unusual locations for some of the intercontinental earthquakes in the southern Tibetan Plateau seem to make more sense now after looking at this model,” said graduate student and co-author Jiangtao Li. “There is a striking correlation with the location of the earthquakes and the orientation of the fragmented Indian upper mantle.”

The model also explains some of the deformation patterns seen at the surface, including a series of unusual north-south rifts. Together, the earthquake locations and deformation patterns are evidence of a strongly coupled crust and upper mantle in southern Tibet, the researchers said.

Armed with this new information, geoscientists now have a clearer picture of what role the Indian upper mantle plays in shaping the Tibetan Plateau and why earthquakes happen where they do in this region. This could help assess earthquake risk, the researchers said.

“Overall, our new research suggests that we need to take a deeper view to understand the Himalayan-Tibetan continental deformation and evolution,” Song said.

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Materials provided by University of Illinois at Urbana-Champaign. Note: Content may be edited for style and length.

On September 6, three hurricanes advanced in a menacing line across the Atlantic Ocean. Category 5 Hurricane Irma ravaged Barbuda in the Caribbean’s Leeward Islands in the early morning and churned onward to St. Marin, St. Barthelemy, Anguilla and the Virgin Islands, causing massive damage. Tropical Storm Katia hovered in the Gulf of Mexico and Tropical Storm Jose approached from the open ocean. Both were upgraded to hurricane status later that day.

On the surface of the Sun, 150 million kilometers (93 million miles) away, another storm was brewing. A class X-2.2 and major class X-9.3 solar flare erupted on the morning of September 6 at about 8 a.m. local time. NOAA’s Space Weather Prediction Center warned of a strong radio blackout over most the sunlit side of Earth, including the Caribbean.

Amateur radio operators assisting with emergency communications in the islands reported to the Hurricane Watch Net that radio communications went down for most of the morning and early afternoon on September 6 because of the Sun’s activity, according to the new study. French civil aviation reported a 90-minute loss of communication with a cargo plane, according to the study’s authors, and NOAA reported on September 14 that high frequency radio, used by aviation, maritime, ham radio, and other emergency bands, was unavailable for up to eight hours on September 6.

Another large class-X flare erupted from the Sun on September 10, disrupting radio communication for three hours. The disruption came as the Caribbean community coped with Category 4 Hurricane Jose’s brush with the Leeward Islands and the Bahamas, and Irma’s passage over Little Inagua in the Bahamas on September 8 and passage over Cuba on September 9.

“Space weather and Earth weather aligned to heighten an already tense situation in the Caribbean,” said Rob Redmon, a space scientist with NOAA’s National Centers for Environmental Information in Boulder, Colorado, and the lead author of the new study. “If I head on over to my amateur radio operator, and they have been transmitting messages for me, whether it be for moving equipment or finding people or just saying I’m okay to somebody else, suddenly I can’t do that on this day, and that would be pretty stressful.”

Bobby Graves, an experienced ham radio operator who manages the Hurricane Watch Net from his home near Jackson, Mississippi, said the flares caused communications to go down for hours. The Hurricane Watch Net is a group of licensed amateur radio operators trained and organized to provide communications support to the National Hurricane Center during storm emergencies.

“You can hear a solar flare on the air as it’s taking place. It’s like hearing bacon fry in a pan, it just all of a sudden gets real staticky and then it’s like someone just turns the light completely off, you don’t hear anything. And that’s what happened this last year on two occasions,” Graves said. “We had to wait ’til the power of those solar flares weakened so that our signals could actually bounce back off the atmosphere. It was a helpless situation.”

The new study detailing the activity on the Sun and its effects on radio communications from September 4 — 13 serves as an overview to a collection of journal articles in Space Weather investigating the solar activity of September 2017. The collision of Earth and space weather in September delivered a reminder that solar events can happen at any time and may coincide with other emergencies, according to the study’s authors.

The information in the study could help scientists improve space weather forecasting and response, according to the study’s authors. By understanding how the events on the Sun and Earth unfolded, scientists can better understand how to forecast and prepare for future events, they said.

The new study shows the solar flares affected shortwave radio communications, which were being used by amateurs and professionals in emergency response efforts, although it does not detail how emergency efforts may have been affected by the radio blackout.

“Safeguards put in place to prevent dangerous disruption to GPS from solar events worked,” said Mike Hapgood, head of space weather at Rutherford Appleton Laboratory in the United Kingdom, and a scientist not connected to the new study. “In many ways, we were ready. Some things that could have caused big problems didn’t, but shortwave radio is always tricky to use during solar events. But good radio operators are aware of the events and will work hard to overcome problems.”

“It’s the Sun reminding us that it’s there,” Hapgood added. “The Sun’s been very quiet for the last 10 years. It reminds people not to be complacent.”

Unexpected space weather

The 2017 flares were the largest since 2005 and the best documented solar storm to date, observed from a fleet of spacecraft between the Earth and the Sun, in Earth’s orbit, on Earth and Mars.

Solar flares release bursts of X-rays from the Sun that travel outwards in all directions at the speed of light. Strong flares can disrupt radio and aviation communications. Space weather forecasters have only minutes to broadcast warnings to spacecraft, aviation and other administrators before affects are felt on Earth.

X-rays from solar flares interact with Earth’s atmosphere 50-1000 kilometers (30-600 miles) above the Earth, in a region called the ionosphere. Shortwave radio communication works by bouncing signals off the ionosphere and refracting them back to Earth. When the Sun releases a burst of x-rays, like the flares released in early September, the extra energy delivered to the ionosphere can cause it to absorb high frequency radio signals, like those used by ham radio enthusiasts.

The September 6 and 10 flares were also accompanied by bursts of high energy solar material explosively ejected from the Sun in an expanding bubble much larger than the Earth. Such coronal mass ejections, which arrive within one to three days, have the potential to wreck the most havoc on human technology. The geomagnetic storms generated by coronal mass ejections can damage power grids, confuse GPS systems and damage or disrupt communication with spacecraft, including weather satellites.

NOAA’s Space Weather Prediction Center issued warnings for potentially severe geomagnetic storms for September 7-9.

An unlucky coincidence

The unexpected burst of space weather coincided with high hurricane activity in the Atlantic Ocean.

Irma, one of the most powerful Atlantic hurricanes on record with sustained winds of 287 kilometers per hour (175 miles per hour), hit the tiny island of Barbuda at maximum intensity, razing 95 percent of its buildings. The storm destroyed most homes and much infrastructure on St. Martin, Anguilla, Great Inagua and Crooked Island in the Bahamas, and the U.S. and British Virgin Islands. It caused power outages and damage in the Cuban Keys, Turks and Caicos and the southeastern United States. Wind and rain from the storm killed 37 people in the Caribbean and 10 on the U.S. mainland, according the National Hurricane Center.

During the September crisis, the Caribbean Emergency and Weather Net logged many “radiograms” relaying survival notes between anxious family members on the islands and the mainland via ham radio operators, Redmon said.

“Seeing that logbook really brought home to me the human dimension of the storm,” Redmon said. “It put the humanity in the science.”

Ham radio hobbyists routinely volunteer to disseminate hazard information from the National Weather Service to island communities and ships during major storms, report real-time ground conditions and damages back to the National Hurricane Center, and assist the Red Cross with communications.

Graves, the ham radio operator, said many people trapped by storms appreciate hearing a friendly voice over amateur radio relaying the latest weather update, even if they are not able to reply. During a storm, ham radio volunteers strain to listen for lone stations in the affected area that may still be transmitting, Graves said.

“A lot of folks in the area were asking us: We heard there’s Jose coming behind Irma, what’s this thing going to do?” he said.