Sodium is a very cheap and earth-abundant alternative to using lithium-ion batteries that is also known to turn purple and combust if exposed to water — even just water in the air.

Worldwide efforts to make sodium-ion batteries just as functional as lithium-ion batteries have long since controlled sodium’s tendency to explode, but not yet resolved how to prevent sodium-ions from “getting lost” during the first few times a battery charges and discharges. Now, Purdue University researchers made a sodium powder version that fixes this problem and holds a charge properly.

“Adding fabricated sodium powder during electrode processing requires only slight modifications to the battery production process,” said Vilas Pol, Purdue associate professor of chemical engineering. “This is one potential way to progress sodium-ion battery technology to the industry.”

The study was made available online in June 2018 ahead of print on August 31, 2018 in the Journal of Power Sources.

This work aligns with Purdue’s giant leaps celebration, acknowledging the university’s global advancements made in health, space, artificial intelligence and sustainability as part of Purdue’s 150th anniversary. Those are the four themes of the yearlong celebration’s Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.

Even though sodium-ion batteries would be physically heavier than lithium-ion technology, researchers have been investigating sodium-ion batteries because they could store energy for large solar and wind power facilities at lower cost.

The problem is that sodium ions stick to the hard carbon end of a battery, called an anode, during the initial charging cycles and not travel over to the cathode end. The ions build up into a structure called a “solid electrolyte interface.”

“Normally the solid electrolyte interface is good because it protects carbon particles from a battery’s acidic electrolyte, where electricity is conducted,” Pol said. “But too much of the interface consumes the sodium ions that we need for charging the battery.”

Purdue researchers proposed using sodium as a powder, which provides the required amount of sodium for the solid electrolyte interface to protect carbon, but doesn’t build up in a way that it consumes sodium ions.

They minimized sodium’s exposure to the moisture that would make it combust by making the sodium powder in a glovebox filled with the gas argon. To make the powder, they used an ultrasound — the same tool used for monitoring the development a fetus — to melt sodium chunks into a milky purple liquid. The liquid then cooled into a powder, and was suspended in a hexane solution to evenly disperse the powder particles.

Just a few drops of the sodium suspension onto the anode or cathode electrodes during their fabrication allows a sodium-ion battery cell to charge and discharge with more stability and at higher capacity — the minimum requirements for a functional battery.

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About 16 million years ago, this happened.

Lava erupted in pulses, ultimately burying the region to the height of a 30-story building. If the lava had been spread evenly over the lower 48 states instead of staying concentrated in the northwest, it would cover the country to a depth of about 80 feet.

Before now, most geologists believed that it took almost 2 million years to erupt all that lava, collectively known as “the Columbia River flood basalts.” But Princeton researchers are publishing findings today that show it happened more than twice as fast as previously believed, with 95 percent erupting within a 750,000-year window.

Flood basalts have fascinated geologists for centuries. As the largest volcanic events on Earth, they have been implicated in mass extinctions, such as the largest extinction event in Earth history, 252 million years ago. There was no mass extinction 16 million years ago, but there was a major climate event about that time, known as the Mid-Miocene Climate Optimum (MMCO), a global warming event with high temperatures and elevated atmospheric carbon dioxide levels.

The same volcanoes that erupt liquid rock also belch out greenhouse gases, so geologists have wondered if there was a connection between the flood basalts and the MMCO global warming event. Just one problem: Before now, no one was quite sure about the timing of the Columbia River flood basalts.

“In order to answer the question of whether the Columbia River flood basalts caused the MMCO, we need to know the timing of eruptions and climate shifts as precisely as possible,” said Blair Schoene, associate professor of geosciences.

“To put it simply, people didn’t know exactly when or over how long the Columbia River Basalt Group erupted, which made it difficult to explore a causal relationship with the MMCO,” said Jennifer Kasbohm, a graduate student and lead author of the paper appearing today in the journal Science Advances.

To help explain the scale of the eruptions, Kasbohm drew a parallel to the 2010 Eyjafjallajökull eruption in Iceland. “The Icelandic eruption shut down airports in Europe for a week, affecting 10 million travelers, and there were periodic airline disruptions for the following month,” she said. “Now imagine having one of those Icelandic eruptions every 8 months for 750,000 years in a row, and that would give you our predicted eruption rate for the Columbia River basalts.”

Three undergraduates accompanied Kasbohm and Schoene in the lab and the field, contributing to their research while completing projects of their own: Josh Murray of the Class of 2018, Sam Bartusek ’20 and Kyle Duffey ’19. “The project involved seven weeks of fieldwork, with many days over 100 degrees Fahrenheit,” said Kasbohm. “We encountered a handful of rattlesnakes, numerous spiders, friendly and helpful locals, and we managed to stay one step ahead of the forest fires in the region.”

They were looking for zircons, tiny minerals containing trace amounts of uranium. Over time, the naturally radioactive material decays into lead, so geologists can use the ratio of uranium to lead to calculate exactly how old the zircon is. Unfortunately for geologists, basaltic lava flows like the Columbia River flood basalts don’t have the right chemistry to make zircons, so until now, geologists have had to settle for dates with uncertainties of over a million years, produced through other dating methods.

“To test for a causal link between climate and eruptions, a million years is not good enough,” said Schoene.

The researchers got around the lack of zircons in the lava rocks by looking at layers of volcanic ash between the basalt layers. The ash came from the nearby Cascade volcanoes (including Mount Saint Helens), which do contain zircon and were erupting about the same time as the massive lavas.

In their lab at Princeton, Kasbohm and Schoene separated 0.1 mm sized zircons from the 16-million-year-old rocks, measured the isotopic ratios of uranium and lead, and pinned down the ages of individual lava flows to within a few tens of thousands of years. “That precision is basically the best you can do with any chronometer for samples of this age — even though 10,000 years sounds like a lot — so our method is the gold standard,” she said.

“This is the most significant paper to come out about the Columbia River flood basalts in a decade or two,” said Stephen Reidel, a research professor of geology at Washington State University-Tri-Cities, who has studied these lava flows since 1972 and contributed to the analysis of this research. “Jenn and Blair deserve a lot of compliments for thinking to look at the zircons in the ash beds between the flows…. Of course, now we’re going to have to go back and re-calculate everything that used the old timeline or eruption rate. That’s okay — that’s part of the fun.”

With their more precise timeline, Kasbohm and Schoene have now shown that the prehistoric climate change did start very close in time to the beginning of the eruptions, but further work is needed to pin down the connection between them.

This 16-million-year-old climate change event is the last time that carbon dioxide concentrations in the atmosphere shot above 400 parts per million — until the last decade.

“The MMCO could be a parallel to our current climate, and further work investigating the timing and duration of that event will tell us more about how we can expect Earth to recover from anthropogenic climate change,” Kasbohm said. For instance, if the climate stayed warm for a million years after the volcanoes stopped erupting, as now looks possible, that could have significant implications for predicting how long the atmosphere will respond to human-caused global warming.

“Time matters,” said Kasbohm, “whether we’re trying to learn about Earth’s past or its future. It’s very empowering to use tiny minerals to tell the story of these voluminous rocks.”

Developed in the lab of Rebecca Kramer-Bottiglio, assistant professor of mechanical engineering & materials science, robotic skins enable users to design their own robotic systems. Although the skins are designed with no specific task in mind, Kramer-Bottiglio said, they could be used for everything from search-and-rescue robots to wearable technologies. The results of the team’s work are published today in Science Robotics.

The skins are made from elastic sheets embedded with sensors and actuators developed in Kramer-Bottiglio’s lab. Placed on a deformable object — a stuffed animal or a foam tube, for instance — the skins animate these objects from their surfaces. The makeshift robots can perform different tasks depending on the properties of the soft objects and how the skins are applied.

“We can take the skins and wrap them around one object to perform a task — locomotion, for example — and then take them off and put them on a different object to perform a different task, such as grasping and moving an object,” she said. “We can then take those same skins off that object and put them on a shirt to make an active wearable device.”

Robots are typically built with a single purpose in mind. The robotic skins, however, allow users to create multi-functional robots on the fly. That means they can be used in settings that hadn’t even been considered when they were designed, said Kramer-Bottiglio.

Additionally, using more than one skin at a time allows for more complex movements. For instance, Kramer-Bottiglio said, you can layer the skins to get different types of motion. “Now we can get combined modes of actuation — for example, simultaneous compression and bending.”

To demonstrate the robotic skins in action, the researchers created a handful of prototypes. These include foam cylinders that move like an inchworm, a shirt-like wearable device designed to correct poor posture, and a device with a gripper that can grasp and move objects.

Kramer-Bottiglio said she came up with the idea for the devices a few years ago when NASA put out a call for soft robotic systems. The technology was designed in partnership with NASA, and its multifunctional and reusable nature would allow astronauts to accomplish an array of tasks with the same reconfigurable material. The same skins used to make a robotic arm out of a piece of foam could be removed and applied to create a soft Mars rover that can roll over rough terrain. With the robotic skins on board, the Yale scientist said, anything from balloons to balls of crumpled paper could potentially be made into a robot with a purpose.

“One of the main things I considered was the importance of multifunctionality, especially for deep space exploration where the environment is unpredictable,” she said. “The question is: How do you prepare for the unknown unknowns?”

For the same line of research, Kramer-Bottiglio was recently awarded a $2 million grant from the National Science Foundation, as part of its Emerging Frontiers in Research and Innovation program.

Next, she said, the lab will work on streamlining the devices and explore the possibility of 3D printing the components.

WATCH VIDEO: https://youtu.be/uuAY5Y_INYQ

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