The Rice University lab of chemist James Tour has shown that thin nanotube films effectively stop dendrites that grow naturally from unprotected lithium metal anodes in batteries. A paper on their work is published in the journal Advanced Materials.
Here, it is shown that lithiated multiwall carbon nanotubes (Li‐MWCNTs) act as a controlled Li diffusion interface that suppresses the growth of Li dendrites by regulating the Li+ ion flux during charge/discharge cycling at current densities between 2 and 4 mA cm−2.
A full Li‐S cell is fabricated to showcase the versatility of the protected Li anode with the Li‐MWCNT interface, where the full cells could support pulse discharges at high currents and over 450 cycles at different rates with coulombic efficiencies close to 99.9%. This work indicates that carbon materials in lithiated forms can be an effective and simple approach to the stabilization of Li metal anodes.—Salvatierra et al.
An illustration shows how lithium metal anodes developed at Rice University are protected from dendrite growth by a film of carbon nanotubes. Courtesy of the Tour Group.
Over time, dendrites can pierce the battery’s electrolyte core and reach the cathode, causing the battery to fail. That problem has both dampened the use of lithium metal in commercial applications and encouraged researchers worldwide to solve it.
One of the ways to slow dendrites in lithium-ion batteries is to limit how fast they charge. People don’t like that. They want to be able to charge their batteries quickly.—James Tour
The Rice team’s solution is simple, inexpensive and highly effective at stopping dendrite growth, Tour said.
What we’ve done turns out to be really easy. You just coat a lithium metal foil with a multi-walled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.—James Tour
Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions, explained Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva. The ions distribute themselves throughout the nanotube film.
When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.
Images of lithium metal anodes after 500 charge/discharge cycles in tests at Rice University show the growth of dendrites is quenched in the anode at left, protected by a film of carbon nanotubes. The unprotected lithium metal anode at right shows evidence of dendrite growth. Courtesy of the Tour Group.
The tangled-nanotube film effectively quenched dendrites over 580 charge/discharge cycles of a test battery with a sulfurized-carbon cathode the lab developed in previous experiments. The researchers reported the full lithium metal cells retained 99.8% of their coulombic efficiency, the measure of how well electrons move within an electrochemical system.
The research was supported by the Air Force Office of Scientific Research, the National Institutes of Health, the National Council of Science and Technology, Mexico; the National Council for Scientific and Technological Development, Ministry of Science, Technology and Innovation and Coordination for the Improvement of Higher Education Personnel, Brazil; and Celgard, LLC.
R. V. Salvatierra, G. A. López‐Silva, A. S. Jalilov, J. Yoon, G. Wu, A.‐L. Tsai, J. M. Tour (2018) “Suppressing Li Metal Dendrites Through a Solid Li‐Ion Backup Layer” Adv. Mater. doi: 10.1002/adma.201803869