Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 31, Issue 2, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202001812
Keywords
lithium-sulfur batteries; poly(ethylene oxide); polyvinylidene fluoride; reaction mechanisms; solid-state electrolytes
Categories
Funding
- Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program (Battery500 Consortium) [DE-EE0007762]
- TAFEL [UTA18-000175]
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The study found that the cycling performance of solid-state Li-S batteries improved significantly with a PVDF coating, which suppresses the formation of polysulfides and changes the reaction mechanism of sulfur. Introducing a polymer with low solvent properties in the sulfur cathode shows promise for increasing the cycling life of Li-S batteries.
The shuttle effect of long-chain polysulfides (Li2Sn, n = 4-8) from the multistep reactions reduces the cycling life of solid-state lithium-sulfur (Li-S) batteries with a poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE). Moreover, the ambiguous reaction mechanism of polysulfides in an SPE also limits the development of high-performance solid-state Li-S batteries. Here, a solid-state Li-S cell with a much-improved cycling performance is reported by coating the sulfur cathode with a layer of polyvinylidene fluoride (PVDF), which not only suppresses the formation of soluble polysulfides, but also changes the reaction mechanism of the sulfur from a multistep solid-liquid-solid reaction to a single-step solid-solid reaction. These results show that long-chain polysulfides are insoluble and unstable in PVDF polymers with a low solvent property, which facilitates the direct transformation of elemental sulfur to solid Li2S2/Li2S without the formation of intermediary products. However, the strong PEO-Li2Sn (n = 4-8) attraction causes a dissolution of polysulfides in PEO. The introduction of a polymer with a low solvent property in the sulfur cathode would be promising for the development of solid-state Li-S batteries with a long cycling life.
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