BATTERIES New research could extend the lives of next-gen batteries

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Researchers have found that cation engineering could be the answer to solving the problem of lithium microstructure proliferation during battery use, potentially paving the way for the development of safer, longer-lasting next-generation batteries.

The growth of microstructures in lithium batteries is a problem that researchers have been fighting for years. These microstructures, known as dendrites, are tiny, rigid tree-like structures that feature needle-like projections, and they’re seriously problematic both inside and outside of the battery.

One notable problem is that dendrites can pierce through separator films inside of battery cells and cause failure through a short circuit. In extreme scenarios where a battery is dense enough, such as in an Electric Vehicle (EV) application, this could lead to combustion. Indeed, the growth of microstructures is a problem that’s very much holding back the development of revolutionary next-gen, long-lasting lithium batteries and their commercialization.

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Now, in a study published in mid-November, researchers at the Columbia University School of Engineering and Applied Science say that a solution may be found in alkali metal additives such as potassium ions.

Alkali metal additives

In their study, the researchers report that such alkali metal additives can prevent lithium microstructure growth during battery use.

To investigate this, the researchers used a combination of microscopy, nuclear magnetic resonance, and computational modeling to demonstrate that by adding very small amounts of potassium salt to a lithium battery electrolyte, unique chemistries at the interface of lithium and the battery’s electrolyte are produced.

"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," said Lauren Marbella, an assistant professor of chemical engineering who is working on the project.

A first-of-its-kind study

The research team’s discovery that alkali metal additives like potassium ions are capable of suppressing the growth of dendrites and other non-conductive compounds on the surface of lithium metal is very different from other approaches to manipulating electrolytes, which have focused on depositing conductive polymers on lithium’s surface.

In this vein, the study represents one of the first of its kind: An in-depth characterization of the surface chemistry of lithium metal using nuclear magnetic resonance. It demonstrates the power of this technique for the design of new electrolytes for lithium metal. Marbella’s results were backed up with Density Functional Theory (DFT) calculations carried out by colleagues from the Viswanathan group at Carnegie Mellon University.

Commenting on the study, Marbella refers to commercial electrolytes as a “cocktail of carefully selected molecules.” She added: “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."

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Marbella’s team at Columbia University now plans to test alkali metal additives that stop the formation of harmful surface layers in combination with more traditional additives that promote the growth of conductive layers on lithium metal.

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