Researchers at Argonne National Laboratory have advanced lithium-sulfur (Li-S) battery research by creating a redox-active interlayer within the battery that adds energy storage capacity while nearly eliminating a traditional problem with sulfur batteries. An open-access paper on their work was published in the journal Nature Communications.

Lithium-sulfur batteries have theoretical specific energy higher than state-of-the-art lithium-ion batteries. However, from a practical perspective, these batteries exhibit poor cycle life and low energy content owing to the polysulfides shuttling during cycling. To tackle these issues, researchers proposed the use of redox-inactive protective layers between the sulfur-containing cathode and lithium metal anode. However, these interlayers provide additional weight to the cell, thus, decreasing the practical specific energy.

Here, we report the development and testing of redox-active interlayers consisting of sulfur-impregnated polar ordered mesoporous silica. Differently from redox-inactive interlayers, these redox-active interlayers enable the electrochemical reactivation of the soluble polysulfides, protect the lithium metal electrode from detrimental reactions via silica-polysulfide polar-polar interactions and increase the cell capacity.

Indeed, when tested in a non-aqueous Li-S coin cell configuration, the use of the interlayer enables an initial discharge capacity of about 8.5 mAh cm⁻² (for a total sulfur mass loading of 10 mg cm⁻²) and a discharge capacity retention of about 64% after 700 cycles at 335 mA g⁻¹ and 25 °C.

—Lee et al.

a–c, Illustration of Li-S batteries with (a) electrical conductive, (b) polar, and (c) S-containing polar interlayers (ILs). Lee et al.

Early lithium-sulfur (Li-S) batteries did not perform well because sulfur species (polysulfides) dissolved into the electrolyte, causing corrosion of the lithium anode. 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 sulfur cathode and lithium anode. However, 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.

Image shows microstructure and elemental mapping (silicon, oxygen and sulfur) of porous sulfur-containing interlayer after 500 charge-discharge cycles in lithium-sulfur cell. (Image by Guiliang Xu/Argonne National Laboratory.)

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. The cells with the active interlayer maintained high capacity over 700 charge-discharge cycles.

To further study the redox-active layer, the team conducted experiments at the 17-BM beamline of Argonne’s Advanced Photon Source (APS), 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.

Going forward, the team wants to evaluate the growth potential of the redox-active interlayer technology.

This research was sponsored by the DOE’s Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office Battery Materials Research Program and the National Research Foundation of Korea.

Resources

• Lee, BJ., Zhao, C., Yu, JH. et al. (2022) “Development of high-energy non-aqueous lithium-sulfur batteries via redox-active interlayer strategy.” Nat Commun 13, 4629 doi: 10.1038/s41467-022-31943-8