Understanding the Origin of Irreversible Capacity loss in Non-Carbonized Carbonate − based Metal Organic Framework (MOF) Sulfur hosts for Lithium − Sulfur battery

• Published in: Electrochimica acta Vol. 229; no. C; pp. 208 - 218
• Main Authors: Shanthi, Pavithra M., Hanumantha, Prashanth J., Gattu, Bharat, Sweeney, Matthew, Datta, Moni K., Kumta, Prashant N.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2017; Elsevier BV; Elsevier
• Subjects: Batteries; Cathodes; Cathodic dissolution; Chemical bonds; Density; Dissolution; Encapsulation; Energy storage; Flux density; Lithium; Lithium sulfur batteries; Lithium-Sulfur; Metal organic framework; Oxidation; Polysulfide; Polysulfides; Scanning electron microscopy; Separators; Spectroscopic analysis; Storage batteries; Studies; Surface stability; X ray photoelectron spectroscopy; Metal organic framework; Polysulfide; Encapsulation; Lithium-Sulfur
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2017.01.115

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•Sulfur was vapor infiltrated into nanoporous metal organic framework (S – MOFs).•XPS analysis of S – MOFs shows binding of sulfur to MOF.•Specific capacities ∼609mAh/g with very low fade rate of 0.0014%/cycle obtained.•Post cycling XPS analysis shows complete trapping of polysulfide in S – MOFs.
Li-Sulfur (Li-S) batteries are emergent next-generation energy storage devices due to their very high specific energy density (∼2567Whg−1) but are limited by polysulfide dissolution issues. In this work, chemically synthesized sulfur containing non-carbonized metal organic framework (S-MOF) cathodes show initial specific capacities of 1476mAhg−1 stabilizing at ∼609mAhg−1 with almost no fade for over 200 cycles. Post-cycled separators of the S – MOF cathodes display complete absence of polysulfides after cycle 1, 20 and 200, respectively. It was identified that the occurrence of carbonate species in the MOF structure resulted in the formation of C-S bonded species causing retention of polysulfide at the electrode surface ensuring long-term stability. However, this observed capacity drop during the first 10 cycles is attributed to the oxidation of some of the infiltrated sulfur by the MOF as determined by electrochemical and X-ray photoelectron spectroscopy (XPS) analyses. Nevertheless, the negligible fade rate (0.0014% cycle−1) and complete prevention of polysulfide dissolution renders these cathodes most promising candidates for Li-S batteries. Understanding of this transformation behavior in sulfur-containing MOF is essential to engineer chemically-bonded host-structures capable of efficient polysulfide trapping, a key pathway to establishing novel platforms for achieving high power Li – S batteries.