Research Team Discovers Way To Overcome Decline in Li-Sulfur Batteries

A team of researchers in the U.S. and China have worked together to identify a previously unknown reaction mechanism that causes the very short lifetimes of lithium-sulfur batteries. Their paper, published in the journal Nature, outlines the reaction and potential ways of overcoming it.

Li-sulfur batteries have almost three times the energy storage, by weight, when compared to other lithium-based battery formulas, and could be a key to unlocking longer ranges and faster charging. The batteries are also cheaper and do not require nickel, cobalt, and other expensive and rare materials.

The issue with li-sulfur batteries has been their short lifespans. In the laboratory at small scale, they are viable, but when scaled to commercial sizes, their capabilities decline rapidly. The reason for this was elusive, but the joint research between the U.S. and China believes it has found the cause and that it can be avoided.

The underlying cause lies in the dissolution of sulfur from the cathode during discharge. This leads to the formation of soluble lithium polysulfides. These compounds flow into the lithium metal negative electrode during charging, making the issue worse. The loss of sulfur from the cathode and alterations in the anode that result hinder the battery’s performance during cycling.

The solution for this problem was found by Argonne scientists who developed a catalytic material that in small amounts would eliminate the sulfur loss problem. But until now, how that worked was unknown. Now scientists have pinpointed the atomic-scale working mechanism and can thus further utilize it to improve lithium-sulfur battery compositions.

“Key is the formation of dense nanoscale bubbles of lithium polysulfides on the cathode surface, which do not appear without the catalyst. These lithium polysulfides rapidly spread throughout the cathode structure during discharge and transform to lithium sulfide consisting of nanoscale crystallites. This process prevents the sulfur loss and performance decline in commercial-size cells.” –Zhou, S, Shi, J, Liu, S, et al Nature, 2023

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