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Beyond lithium-ion technologies, lithium−sulfur batteries stand out because of their multielectron redox reactions and high theoretical specific energy (2500 Wh kg−1). However, the intrinsic irreversible transformation of soluble lithium polysulfides to solid short-chain sulfur species (Li2S2 and Li2S) and the associated large volume change of electrode materials significantly impair the long-term stability of the battery. Here we present a liquid sulfur electrode consisting of lithium thiophosphate complexes dissolved in organic solvents that enable the bonding and storage of discharge reaction products without precipitation. Insights garnered from coupled spectroscopic and density functional theory studies guide the complex molecular design, complexation mechanism, and associated electrochemical reaction mechanism. With the novel complexes as cathode materials, high specific capacity (1425 mAh g−1 at 0.2 C) and excellent cycling stability (80% retention after 400 cycles at 0.5 C) are achieved at room temperature. Moreover, the highly reversible all-liquid electrochemical conversion enables excellent low temperature battery operability (>400 mAh g−1 at −40 °C and >200 mAh g−1 at −60 °C). This work opens new avenues to design and tailor the sulfur electrode for enhanced electrochemical performance across a wide operating temperature range.
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Stable Lithium Sulfur Battery Based on In Situ Electrocatalytically Formed Li 2 S on Metallic MoS 2 –Carbon Cloth Support
A stable lean‐electrolyte operating lithium–sulfur (Li–S) battery based on a cathode of Li2S in situ electrocatalytically deposited from L2S8 catholyte onto a support of metallic molybdenum disulfide (1T‐MoS2) on carbon cloth (CC) is created. The 1T‐MoS2 significantly accelerates the conversion Li2S8 catholyte to Li2S, chemically adsorbs lithium polysulfide (LiPSs) from solution, and suppresses crossover of the LiPSs to the anode. These experimental findings are explained by density functional theory calculations that show that 1T‐MoS2 gives rise to strong adsorption of polysulfides on its surface and is electrocatalytic for the targeted reversible Li–S conversion reactions. The CC/1T‐MoS2 electrode in a Li–S battery delivers an initial capacity of 1238 mAh g−1, with a low capacity fade of only 0.051% per cycle over 500 cycles at 0.5 C. Even at a high sulfur loading (4.4 mg cm−2) and low electrolyte/S (E/S) ratio of 3.7 µL mg−1, the battery achieves an initial reversible capacity of 1176 mA h g−1 at 0.5 C, with 87% capacity retention after 160 cycles. The post 500 cycles Li metal opposing 1T‐MoS2 is substantially smoother than the Li opposing CC, with XPS supporting the role of 1T‐MoS2 in inhibiting LiPSs crossover.
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- Award ID(s):
- 1938833
- PAR ID:
- 10189578
- Date Published:
- Journal Name:
- Small Methods
- ISSN:
- 2366-9608
- Page Range / eLocation ID:
- 2000353
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/smtd.202000353
