Carnegie Mellon University
May 30, 2019

Enabling Safe, Low-Temperature Operation In Batteries

By Anne Boyle

Lisa Kulick
Carnegie Mellon University's Venkat Viswanathan and a graduate students Shashank Sripad and Dilip Krishnamurthy are working to improve the safety of lithium ion batteries, which are common in devices such as smartphones, hearing aids and digital cameras.

Viswanathan, an assistant professor in mechanical engineering, researches how designing materials can create novel energy conversion and improve storage capabilities.

Lithium-ion batteries "are basically the most energy dense batteries you can find," Sripad said. "For many portable electronics, they are the only battery that you can use."

Unfortunately, they also have been known to unexpectedly short out, causing fires and other safety issues.

These shortages are caused by dendrites, miniscule branches of ions in the interior of the battery. When a battery charges, lithium ions travel between the positive and negative end, also known as the cathode and anode. Sometimes the ions don't travel into the anode, instead depositing on its surface. They stack over time, creating dendrites. If the dendrites reach the cathode, the battery shorts out and a fire can start.

Viswanathan and his team hope to improve battery safety by preventing dendrite growth at its source - the anode. They are focusing specifically on dendrite growth in lower temperatures. When the battery's environment is cold, "the energetic barriers become more important," Krishnamurthy said. "Meaning it will take not be as easy to push the lithium ions into the anode."

In order to prevent barriers, the "battery spends its own energy heating up," Sripad said. Needless to say, this uses up energy and decreases the battery's effectiveness.

For this research, Viswanathan received a 2019 Young Investigator Award from the Office of Naval Research (ONR). The Young investigator Program supports young academic scientists and engineers in researching topics that could benefit the goals of the Navy and Marine Corps. As the recipient of the award, Viswanathan will work closely with other NRL researchers, to make the work relevant for naval applications.

Viswanathan and his team said they hope that the collaboration will result in a practical way to mitigate dendrite growth. If they succeed, the improved battery safety could have a tangible impact in both the Navy and the public sector.

"Think of submarines, or even cruise ships," Sripad said. "All of them are exposed to low temperatures. This will definitely improve the reliability and safety of most of their energy storage systems."

For Viswanathan and his team, the coming years will likely hold challenges and triumphs. And lots and lots of batteries.