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Amorphous MoS3 as the sulfur-equivalent cathode material for room-temperature Li–S and Na–S batteries

  1. Jun Lub,2
  1. aInstitute of Functional Nano and Soft Materials, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China;
  2. bChemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439
  1. Edited by Richard Eisenberg, University of Rochester, Rochester, New York, and approved October 31, 2017 (received for review July 3, 2017)

Significance

We propose a concept of “sulfur-equivalent cathode materials,” and reason that instead of using problematic elemental sulfur, one can use sulfur-containing compounds as the alternatives with a comparable electrochemical property but free of any polysulfide generation. We demonstrate here the great potential of amorphous MoS3 as such a sulfur-equivalent cathode material for room-temperature Li–S and Na–S batteries. More remarkably, we find that MoS3 is fully cyclable in the carbonate electrolyte (which is known to kill conventional sulfur cathodes) under a relatively high temperature of 55 °C. MoS3 can also be used as the cathode material of even more challenging Na–S batteries to enable an impressive performance.

Abstract

Many problems associated with Li–S and Na–S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS3 as such a material for room-temperature Li–S and Na–S batteries. In Li–S batteries, MoS3 exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS3 can also be used as the cathode material of even more challenging Na–S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS3. It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Footnotes

  • ?1H.Y. and L.M. contributed equally to this work.

  • ?2To whom correspondence may be addressed. Email: yanguang{at}suda.edu.cn or junlu{at}anl.gov.
  • Author contributions: Y.L. and J.L. designed research; H.Y., L.M., Y.Z., L.W., and N.H. performed research; F.Z., J.D., and T.W. contributed new reagents/analytic tools; and H.Y., Y.L., and J.L. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1711917114/-/DCSupplemental.

Published under the PNAS license.

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