lithium

simple-voltage-pulse-can-restore-capacity-to-li-si-batteries

Simple voltage pulse can restore capacity to Li-Si batteries

The new work, then, is based on a hypothetical: What if we just threw silicon particles in, let them fragment, and then fixed them afterward?

As mentioned, the reason fragmentation is a problem is that it leads to small chunks of silicon that have essentially dropped off the grid—they’re no longer in contact with the system that shuttles charges into and out of the electrode. In many cases, these particles are also partly filled with lithium, which takes it out of circulation, cutting the battery’s capacity even if there’s sufficient electrode material around.

The researchers involved here, all based at Stanford University, decided there was a way to nudge these fragments back into contact with the electrical system and demonstrated it could restore a lot of capacity to a badly degraded battery.

Bringing things together

The idea behind the new work was that it could be possible to attract the fragments of silicon to an electrode, or at least some other material connected to the charge-handling network. On their own, the fragments in the anode shouldn’t have a net charge; when the lithium gives up an electron there, it should go back into solution. But the lithium is unlikely to be evenly distributed across the fragment, making them a polar material—net neutral, but with regions of higher and lower electron densities. And polar materials will move in an uneven electric field.

And, because of the uneven, chaotic structure of an electrode down at the nano scale, any voltage applied to it will create an uneven electric field. Depending on its local structure, that may attract or repel some of the particles. But because these are mostly within the electrode’s structure, most of the fragments of silicon are likely to bump into some other part of electrode in short order. And that could potentially re-establish a connection to the electrode’s current handling system.

To demonstrate that what should happen in theory actually does happen in an electrode, the researchers started by taking a used electrode and brushing some of its surface off into a solution. They then passed a voltage through the solution and confirmed the small bits of material from the battery started moving toward one of the electrodes that they used to apply a voltage to the solution. So, things worked as expected.

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Fracking wastewater has “shocking” amount of clean-energy mineral lithium

fracking operation in Pennsylvania

Enlarge / A hydro-fracking drilling pad for oil and gas operates October 26, 2017 in Robinson Township, Pennsylvania.

A fracking drilling pad operates in the Marcellus Shale formation near Robinson Township, Pa. Credit: Robert Nickelsberg/Getty Images

In 2007, a geoscientist at Penn State named Terry Engelder calculated that Pennsylvania could be sitting on more than 50 trillion cubic feet of accessible natural gas deposits. Engelder later revised his calculation upward, to 489 trillion cubic feet, enough to meet U.S. natural gas demand for 18 years. These massive numbers set off the fracking boom in Pennsylvania, leading to drilling across the state. Since the rush began, there have been 13,000 unconventional wells drilled in Pennsylvania.

Now, a new “astounding” calculation has caught the attention of the gas industry: A study from researchers at the National Energy Technology Laboratory shows the wastewater produced by Pennsylvania’s unconventional wells could contain enough lithium to meet 38 to 40 percent of current domestic consumption. Lithium is a critical mineral that’s an “essential component” of many clean energy technologies, including batteries for electric vehicles. 

The study used chemical and production compliance data from the Pennsylvania Department of Environmental Protection to estimate that approximately 1,160 metric tons of lithium per year could be extracted from this produced water, which is a combination of fluids used for fracking and water from natural formations underground that returns to the surface during the drilling process. The lithium in Pennsylvania’s produced water likely comes from ancient volcanoes that were erupting at the time the natural gas deposits were being formed. This volcanic ash contained lithium that eventually seeped into the water underground.

“The researcher community in the U.S. is really working hard to find the materials and methods that will enable us to meet our climate goals and decarbonize the economy,” said Justin Mackey, the study’s lead investigator. “Sometimes you might be surprised where that material actually comes from.” 

The Marcellus Shale Coalition, an industry trade group dedicated to the Marcellus Shale formation, the natural gas deposit beneath Pennsylvania, West Virginia, Ohio and New York, reacted to the news with enthusiasm. “This scientific analysis by one of the leading energy laboratories in the world shows once again how abundant Pennsylvania natural gas can enhance America’s energy, environmental and national security,” the coalition said in a statement. 

The United States currently relies on imports from Argentina, Chile and China to fully meet its lithium needs, and the demand for lithium is expected to rise dramatically as the clean energy transition accelerates. 

Mackey, a research geochemist at the National Energy Technology Laboratory, said he had focused on lithium because it is a strategic material for the American economy and defense industries and because it has insecure supply chains. “We’re reliant on foreign entities like China and Chile and Australia to source these raw materials, but they’re critical to our economies,” he said. “And more importantly, they’re critical to decarbonizing the U.S. automotive fleet.”

He said the researchers were “shocked” that the highest concentrations of lithium found in the Marcellus “are comparable to lithium brine, to water that is actually being mined for lithium.” 

“I think having more domestic sources of lithium is definitely a positive thing, especially if you don’t have to create a mine to exploit the resource,” Mackey said. Unconventional drilling waste is likely to be produced in large quantities for the foreseeable future, he said, and if remediating this waste safely could also be made economically valuable, that could be beneficial for the environment as well.

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