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DOE OSTI · 3016010

Revealing key structures for reversible sulfur redox in amorphous polymeric sulfur

Wang, Nan [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000224500689)·Wang, Shen [Univ. of California, San Diego, CA (United States)]·Zheng, Yu [Texas A & M Univ., College Station, TX (United States)]·Kuai, Dacheng [Texas A & M Univ., College Station, TX (United States)]·Lee, Seungmin [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0009000088097780)·Tan, Sha [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:000000018277893X)·Yen, Dean [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000216910856)·Zhong, Hui [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000251579089)·Ghose, Sanjit [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000302458560)·Du, Yonghua [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:000000032655045X)·Balbuena, Perla [Texas A & M Univ., College Station, TX (United States)] (ORCID:0000000223583910)·Liu, Ping [Univ. of California, San Diego, CA (United States)]·Hu, Enyuan [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000218814534)
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Abstract

Amorphous polymeric sulfur cathodes, such as sulfurized polyacrylonitrile (SPAN), enable high-energy lithium-sulfur batteries without cobalt or nickel, leveraging abundant sulfur. However, the limited in situ understanding of their synthesis and electrochemistry has impeded targeted optimization. Here, in this study, we integrate operando high-energy total scattering with sulfur K-edge X-ray absorption spectroscopy to monitor SPAN's formation and cycling in real time. Our results show that S-C bond formation halts further fusion of cyclized polyacrylonitrile, fostering π-π stacking and a transition from long-chain to short-chain sulfur-critical for reversible sulfur redox. These features synergistically minimize polysulfide dissolution and charge-transfer resistance, enabling optimized SPAN to achieve high capacity retention over 1,000 cycles. Operando X-ray absorption spectroscopy reveals that residual protons drive thiol-thione tautomerism, with lithium replacement during the first discharge causing ~20% irreversible capacity loss. To enhance performance, minimizing -NH groups and expanding pyridine networks are key. These findings transform SPAN optimization from empirical tuning to mechanism‑guided engineering and point the way towards sulfur loadings and energy densities competitive with state‑of‑the‑art Li‑ion cathodes.

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25 ENERGY STORAGEOperando X-ray absorption spectroscopyirreversible capacity lossoperando high-energy total scatteringsulfurized polyacrylonitrile (SPAN)

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Wang, Nan [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000224500689), Wang, Shen [Univ. of California, San Diego, CA (United States)], Zheng, Yu [Texas A & M Univ., College Station, TX (United States)], Kuai, Dacheng [Texas A & M Univ., College Station, TX (United States)], Lee, Seungmin [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0009000088097780), Tan, Sha [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:000000018277893X), Yen, Dean [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000216910856), Zhong, Hui [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000251579089), Ghose, Sanjit [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000302458560), Du, Yonghua [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:000000032655045X), Balbuena, Perla [Texas A & M Univ., College Station, TX (United States)] (ORCID:0000000223583910), Liu, Ping [Univ. of California, San Diego, CA (United States)], Hu, Enyuan [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000218814534). 2026-01-28. Revealing key structures for reversible sulfur redox in amorphous polymeric sulfur. https://doi.org/10.1038/s41563-026-02484-y

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25 ENERGY STORAGE subjectLithium-ion batteries materialsulfurized polyacrylonitrile (SPAN) subject

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