Li-S batteries show high energy storage capacity and have great potential to transform current energy landscape. However, sulfur cathode suffers issues like low electronic conductivity, lithiation induced volume expansion, and dissolution of polysulphides in organic electrolytes. We produce carbon/sulfur with sulfur host material encapsulated in mesovoids of carbon fibers to help solve these problems associated with Li-S batteries. A foaming/electrospinning strategy is adopted to produce such a yolk-shell configuration of composite nanofibers to sequester the intermediate polysulfide as well as accommodate the volume expansion during sulfur lithiation. Sublimation agents, such as aluminum acetylacetonate, (Al(C5H7O2)3 , or AACA) and element sulfur, are coated on lithium sulfide nanoparticles, prior to the loading into the electrospinning fluid. The produced polymer/sulfur nanofibers firstly go through an oxidative stabilization step to create conjugated ladder structure. Mesovoids are simultaneously generated in polymer fibers during this thermal treatment when AACA or sulfur is sublimated. After polymer is further carbonized in nitrogen gas, the produced sulfur/carbon composite nanofibers with mesovoids will serve as the cathode. Unlike other pore formation processes (i.e., using immiscible polymer or sacrificial nanoparticles), the foaming process is closely coupled with the nanofiber production in one step so that no special treatment or care is needed. The produced confined nanostructures effectively accommodate the aforementioned issues in Li-S batteries that induce capacity loss in sulfur electrodes so that remarkable improvement on the reversible capacity and cycling stability are achieved. Together with the low cost and high throughput features of the involved processes, this innovative manufacturing strategy is expected to facilitate the commercialization of Li-S batteries.

Lock sulfur in confined nanostructures to improve the performance of Li-S batteries

255th National Meeting (2018)

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