April 29, 2019
Batteries can never last longer enough for my money. Whenever I need my flashlight or want to change a channel on the TV, guess who needs new batteries? Well, research scientists to the rescue! It seems they've discovered a way prolong battery life of lithium metal batteries. Power up!
Learn about this and more interesting stories from the scientific community in today's issue.
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*-- New additive yields longer-lasting lithium batteries --*
As electric vehicles and other battery-powered technologies proliferate, scientists are searching for ways to make energy storage safer and more resilient.
One team of researchers has found a way to prolong battery life of lithium metal batteries. When scientists added a nano-coating of boron nitride to the electrolytes in lithium metal batteries, the batteries were more stable and lasted longer.
Lithium ion batteries are used in everything from electric cars to smart phones, but they aren't very energy dense and the liquid electrolyte inside them is flammable. As a result of their instability, the batteries have a relatively short life.
Batteries with a lithium metal anode, instead of a graphite anode, can store more energy and deliver a more powerful charge. But the anode's lithium plating can birth deformities called dendrites. The branch-like growths can penetrate the membrane wall, the separator between the anode and cathode, compromising the battery's safety and performance.
"We decided to focus on solid, ceramic electrolytes. They show great promise in improving both safety and energy density, as compared with conventional, flammable electrolytes in lithium ion batteries," Yuan Yang, assistant professor of materials science and engineering at Columbia University, said in a news release. "We are particularly interested in rechargeable solid-state lithium batteries because they are promising candidates for next-generation energy storage."
Solid electrolytes are more powerful and stable than liquid electrolytes, and they can also curb lithium dendrite growth. But lithium causes most solid electrolytes to corrode.
"Lithium metal is indispensable for enhancing energy density and so it's critical that we be able to use it as the anode for solid electrolytes," said Qian Cheng, a postdoctoral research scientist at Columbia.
To successfully use lithium in a solid electrolyte battery, scientists had to find a chemically and mechanically stable interface -- an interface with a variety of qualities.
"It is essential that the interface not only be highly electronically insulating, but also ionically conducting in order to transport lithium ions," Cheng said. "Plus, this interface has to be super-thin to avoid lowering the energy density of batteries."
In the lab, scientists deposited a thin protective layer of a boron nitride nano-film between the lithium metal and the solid electrolyte, the ionic conductor. Researchers created the nano-film with intrinsic defects that allowed lithium ions to travel through it.
"It's the perfect material to function as a barrier that prevents the invasion of lithium metal to solid electrolyte," Cheng said. "Like a bullet-proof vest, we've developed a lithium-metal-proof 'vest' for unstable solid electrolytes and, with that innovation, achieved long cycling lifetime lithium metal batteries."
Researchers are now testing the boron nitride nano-film with several different types of solid electrolytes. They expect the new technology -- described this week in the journal Joule -- to be used in the near future to create solid-state batteries with improved performance and longer lifetimes.
*-- Tiny microbe-killing robots could be used to clean teeth --*
 In the near future, the war on plaque could be waged by an army of tiny robots.
Engineers, dentists and biologists at the University of Pennsylvania developed a system of microscopic robots that work catalytically to destroy biofilms.
"Treating biofilms that occur on teeth requires a great deal of manual labor, both on the part of the consumer and the professional," Penn engineer Edward Steager said in a news release. "We hope to improve treatment options as well as reduce the difficulty of care."
Biofilms feature bacteria entangled in protective scaffolding. The scaffolding holds together the bacteria and helps it bind to different types of surfaces, including water pipes, teeth, implants and catheters.
"Existing treatments for biofilms are ineffective because they are incapabale of simultaneously degrading the protective matrix, killing the embedded bacteria, and physically removing the biodegraded products," said Hyun Koo, researcher at Penn's School of Dental Medicine. "These robots can do all three at once very effectively, leaving no trace of biofilm whatsoever."
Prevoiusly, Koo and his colleagues have deployed iron-oxide-containing nanoparticles to destroy biofilm. The nanoparticles catalytically activate hydrogen peroxide to release bacteria-killing free radicals.
By chance, Steager and his colleagues have been using iron-oxide nanoparticles to develop microscopic robotic systems, or microbots.
Together, the two teams of researchers developed a pair of microbot systems to breakup and kill biofilms. Scientists dubbed the systems catalytic antimicrobial robots, or CARs.
The first system features iron-oxide nanoparticles suspended in a solution. When directed to move by a magnetic force, the microbots operate like a snowplow, clearing away the biofilm. The second system features nanoparticles embedded in 3D gel molds. Scientists used the microbot-filled gels to attack biofilms clogging pipes and tubing.
Both CARs effectively destroyed the biofilm scaffolding and killed bacteria. When scientists tested the two systems on plaque-plagued teeth, they microbot systems were able to destroy the biofilms on the surface of the teeth, as well as in the hard to reach crevices between root canals.
"Existing treatments for biofilms are ineffective because they are incapable of simultaneously degrading the protective matrix, killing the embedded bacteria, and physically removing the biodegraded products," said Koo. "These robots can do all three at once very effectively, leaving no trace of biofilm whatsoever."
Researchers described their new microbot technologies this week in the journal Science Robotics.
Steager, Koo and their research partners are currently working to improve their techniques for precisely directing the tiny robots with magnetic forces.
"We think about robots as automated systems that take actions based on actively gathered information," said Steager. "The motion of the robot can be informed by images of the biofilm gathered from microcameras or other modes of medical imaging."
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