An Argonne National Laboratory research team has built and tested a new interlayer to prevent dissolution of the sulfur cathode in lithium-sulfur batteries. This new interlayer increases Li-S cell capacity and maintains it over hundreds of cycles. With this new design, lithium-sulfur batteries could reach their full potential.
Batteries energize much of daily life, from cell phones and smart watches to the increasing number of electric vehicles. Most of these devices use the well-known battery chemistry known as lithium-ion battery technology. And while lithium-ion batteries have come a long way since they were first introduced, they have some familiar drawbacks as well, such as short lifetimes, overheating and supply chain challenges for certain raw materials.
Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory are researching solutions to these issues by testing new materials in battery construction. One such material is sulfur. Sulfur is extremely abundant and cost effective and can hold more energy than traditional ion-based batteries.
In the new study, researchers advanced sulfur-based battery research by creating a layer within the battery that adds energy storage capacity while nearly eliminating a traditional problem with sulfur batteries that caused corrosion.
Wenqian Xu, a beamline scientist at Argonne’s Advanced Photon Source noted, “These results demonstrate that a redox-active interlayer could have a huge impact on Li-S battery development. We’re one step closer to seeing this technology in our everyday lives.”
The promising battery design pairs a sulfur-containing positive electrode (cathode) with a lithium metal negative electrode (anode). In between those components is the electrolyte, or the substance that allows ions to pass between the two ends of the battery.
Early lithium-sulfur (Li-S) batteries did not perform well because sulfur species (polysulfides) dissolved into the electrolyte, causing its corrosion. This polysulfide shuttling effect negatively impacts battery life and lowers the number of times the battery can be recharged.
To prevent this polysulfide shuttling, previous researchers tried placing a redox-inactive interlayer between the cathode and anode. The term “redox-inactive” means the material does not undergo reactions like those in an electrode. But this protective interlayer is heavy and dense, reducing energy storage capacity per unit weight for the battery. It also does not adequately reduce shuttling. This has proved a major barrier to the commercialization of Li-S batteries.
To address this, researchers developed and tested a porous sulfur-containing interlayer. Tests in the laboratory showed initial capacity about three times higher in Li-S cells with this active, as opposed to inactive, interlayer. More impressively, the cells with the active interlayer maintained high capacity over 700 charge-discharge cycles.
Guiliang Xu, an Argonne chemist and co-author of the paper said, “Previous experiments with cells having the redox-inactive layer only suppressed the shuttling, but in doing so, they sacrificed the energy for a given cell weight because the layer added extra weight. By contrast, our redox-active layer adds to energy storage capacity and suppresses the shuttle effect.”
To further study the redox-active layer, the team conducted experiments at the 17-BM beamline of Argonne’s Advanced Photon Source, a DOE Office of Science user facility. The data gathered from exposing cells with this layer to X-ray beams allowed the team to ascertain the interlayer’s benefits.
The data confirmed that a redox-active interlayer can reduce shuttling, reduce detrimental reactions within the battery and increase the battery’s capacity to hold more charge and last for more cycles.
Wenqian Xu said, “These results demonstrate that a redox-active interlayer could have a huge impact on Li-S battery development. We’re one step closer to seeing this technology in our everyday lives.”
Going forward, the team wants to evaluate the growth potential of the redox-active interlayer technology. “We want to try to make it much thinner, much lighter,” Guiliang Xu said.
With this result at 700 cycles from the lab research samples, one can guess that more development might take the cycle count much higher. What is most curious is the weight vs. capacity ratio, a metric that will have a large impact on progress. That and the thought that lithium supplies might be extended could put quite a push into this technology’s marketability.
The commentary suggests there is more to come, which is needed, and it will be welcome indeed.
By Brian Westenhaus via New Energy and Fuel
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