Lithium-metal batteries exhibit microstructural growth when cycled with a conventional lithium battery electrolyte (left). Adding potassium ions to the electrolyte modulates degradation during battery operation, preventing the growth of microstructures and leading to safer, longer lasting batteries (right). Image: Lauren Marbella/Columbia Engineering.Electric vehicles (EVs) hold great promise for an energy-efficient, sustainable future, but among their limitations is the lack of a long-lasting, high-energy-density battery that can power them over long distances. The same is true for houses during blackouts and power grid failures – small, efficient batteries able to power a home for more than one night without electricity don't yet exist.
Next-generation lithium batteries that offer lightweight, long-lasting and low-cost energy storage could revolutionize the industry, but a host of challenges have prevented successful commercialization. A major issue is that while lithium-metal anodes play a key role in this new wave of lithium batteries, during battery operation these anodes are highly susceptible to the growth of lithium dendrites, which can lead to the batteries short-circuiting, catching fire or even exploding.
Now, in a paper in Cell Reports Physical Science, researchers at Columbia Engineering report their discovery that alkali metal additives, such as potassium ions, can prevent the growth of lithium dendrites during battery use. Using a combination of microscopy, nuclear magnetic resonance (NMR) spectroscopy and computational modelling, the researchers discovered that adding small amounts of potassium salt to a conventional lithium battery electrolyte produces unique chemistry at the lithium/electrolyte interface.
"Specifically, we found that potassium ions mitigate the formation of undesirable chemical compounds that deposit on the surface of lithium metal and prevent lithium ion transport during battery charging and discharging, ultimately limiting microstructural growth," explains Lauren Marbella, assistant professor of chemical engineering.
Her team's discovery that alkali metal additives suppress the growth of non-conductive compounds on the surface of lithium-metal anodes differs from traditional electrolyte manipulation approaches, which have focused on depositing conductive polymers on the anode's surface. This work is one of the first in-depth characterizations of the surface chemistry of lithium-metal anodes using NMR spectroscopy, and demonstrates the power of this technique to design new electrolytes for lithium-metal batteries. Marbella's results were complemented by density functional theory (DFT) calculations performed by collaborators in the Viswanathan group in mechanical engineering at Carnegie Mellon University.
"Commercial electrolytes are a cocktail of carefully selected molecules," Marbella notes. "Using NMR and computer simulations, we can finally understand how these unique electrolyte formulations improve lithium-metal battery performance at the molecular level. This insight ultimately gives researchers the tools they need to optimize electrolyte design and enable stable lithium-metal batteries."
The team is now testing these alkali metal additives in combination with more traditional additives that encourage the growth of conductive layers on lithium metal. They are also actively using NMR spectroscopy to directly measure the rate of lithium transport through these layers.
This story is adapted from material from Columbia Engineering, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.