Nav: Home

Researchers peer into atom-sized tunnels in hunt for better battery

December 08, 2016

Battery researchers seeking improved electrode materials have focused on "tunneled" structures that make it easier for charge-carrying ions to move in and out of the electrode. Now a team led by a researcher at the University of Illinois at Chicago has used a special electron microscope with atomic-level resolution to show that certain large ions can hold the tunnels open so that the charge-carrying ions can enter and exit the electrode easily and quickly.

The finding is reported in Nature Communications.

"Significant research has been done to increase the energy density and power density of lithium ion battery systems," says Reza Shahbazian-Yassar, associate professor of mechanical and industrial engineering at UIC.

The current generation, he said, is useful enough for portable devices, but the maximum energy and power that can be extracted is limiting.

"So for an electric car, we need to increase the energy and power of the battery -- and decrease the cost as well," he said.

His team, which includes coworkers at Argonne National Laboratory, Michigan Technological University and the University of Bath in the U.K., has focused on developing a cathode based on manganese dioxide, a very low cost and environmentally-friendly material with high storage capacity.

Manganese dioxide has a lattice structure with regularly spaced tunnels that allow charge carriers -- like lithium ions -- to move in and out freely.

"But for the tunnels to survive for long-lasting function, they need support structures at the atomic scale," Shahbazian-Yassar said. "We call them tunnel stabilizers, and they are generally big, positive ions, like potassium or barium."

But the tunnel stabilizers, being positively charged like the lithium ions, should repel each other.

"If lithium goes in, will the tunnel stabilizer come out?" Shahbazian-Yassar shrugged. "The research community was in disagreement about the role of tunnel stabilizers during the transfer of lithium into tunnels. Does it help, or hurt?"

The new study represents the first use of electron microscopy to visualize the atomic structure of tunnels in a one-dimensional electrode material -- which the researchers say had not previously been possible due to the difficulty of preparing samples. It took them two years to establish the procedure to look for tunnels in potassium-doped nanowires of manganese dioxide down to the single-atom level.

Yifei Yuan, a postdoctoral researcher working jointly at Argonne National Laboratory and UIC and the lead author on the study, was then able to use a powerful technique called aberration-corrected scanning transmission electron microscopy to image the tunnels at sub-ångstrom resolution so he could clearly see inside them -- and he saw they do change in the presence of a stabilizer ion.

"It's a direct way to see the tunnels," Yuan said. "And we saw that when you add a tunnel stabilizer, the tunnels expand, their electronic structures also change, and such changes allow the lithium ions to move in and out, around the stabilizer."

The finding shows that tunnel stabilizers can help in the transfer of ions into tunnels and the rate of charge and discharge, Shahbazian-Yassar said. The presence of potassium ions in the tunnels improves the electronic conductivity of manganese dioxide and the ability of lithium ions to diffuse quickly in and out of the nanowires.

"With potassium ions staying in the center of the tunnels, the capacity retention improves by half under high cycling current, which means the battery can hold on to its capacity for a longer time," he said.
-end-
Co-authors on the Nature Communications paper are Kun He, Soroosh Sharifi-Asl, Boao Song and Anmin Nie of UIC; Chun Zhan, Zhenzhen Yang, Xiangyi Luo, Hao Wang, Khalil Amine and Jun Lu of Argonne; Hungru Chen, Stephen M. Wood and M. Saiful Islam of the University of Bath; and Wentao Yao of Michigan Tech.Funding was provided by the National Science Foundation and the U.S. Department of Energy.

University of Illinois at Chicago

Related Lithium Articles:

An air-stable and waterproof lithium metal anode
The instability of lithium metal anode in air and the dendrite growth limit its applications.
Expanding the temperature range of lithium-ion batteries
Electric cars struggle with extreme temperatures, mainly because of impacts on the electrolyte solutions in their lithium-ion batteries.
Toward a low-cost industrialization of lithium-ion capacitors
Combining two additives instead of one to facilitate the incorporation of lithium within capacitors: that is the solution proposed by researchers from l'Institut des matériaux Jean Rouxel (CNRS/Université de Nantes), in collaboration with Münster Electrochemical Energy Technology, in order to promote the low-cost, simple, and efficient development of the lithium-ion capacitors used to store electrical energy.
A close look at lithium batteries
Batteries with metallic lithium anodes offer enhanced efficiency compared to conventional lithium-ion batteries because of their higher capacity.
Graphene coating could help prevent lithium battery fires
Researchers from the University of Illinois at Chicago College of Engineering report that graphene -- wonder material of the 21st century -- may take the oxygen out of lithium battery fires.
New approach could boost energy capacity of lithium batteries
Researchers at MIT and in China have found a new way to make cathodes for lithium batteries, offering improvements in the amount of power for both a given weight and a given volume.
Lithium-matrix anode protected by a solid electrolyte layer for stable lithium metal batteries
A house-like Li anode was designed. The house matrix was composed of carbon fiber and affords a stable structure to relieve the volume change.
Whiskers, surface growth and dendrites in lithium batteries
Researchers at Washington University in St. Louis take a closer look at lithium metal plating and make some surprising findings that might lead to the next generation of batteries.
3D-printed lithium-ion batteries
Electric vehicles and most electronic devices, such as cell phones and laptop computers, are powered by lithium-ion batteries.
The cosmological lithium problem
This problem is one of the still unresolved questions of the current standard description of the Big Bang.
More Lithium News and Lithium Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.