The Study Of Polyethylene Oxide In Lithium-sulfur Batteries

Lithium-sulfur batteries which comprised of sulfur cathode and lithium anodehave a theoretical energy density of2600Wh/kg as well as high theoretical specificcapacity of1675mAh/g. In addition to, elemental sulfur is abundant, inexpensive andenvironmental friendly. However, series of problems such as “shuttle” effect causedby soluble polysulfides, structural change of cathode during cycling have impeded thepractical application of lithium-sulfur batteries.For these problems, we investigated the influence of different binders ofPolyethylene oxide （PEO）, polytetrafluoroethylene (PTFE) and Gelatin on theelectrochemical performance of lithium-sulfur batteries. The results showed thatgelatin and PTFE electrode achieved better electrochemical performance than PEOelectrode. The bad electrochemical performance of PEO is that PEO swells in theorganic electrolyte and leads to cathode damage. Gelatin, as a high dispersion andgood adhesion properties which attributed to its groups-COOH and-NH2showed thebest cycling stability. Gelatin electrode exhibited a specific capacity of788mAh/g at50thcycle at0.2C. PEO with different molecular weight and content had beeninvestigated as binder for lithium-sulfur batteries. PEO (Mw=1x105,1x106and9.5x106) coated sulfur/carbon composites were prepared by physical method. Comparedwith the non-coated ball milling sulfur/carbon composite (81wt%sulfur), thecomposite became more even and smooth because the PEO coating and elementalsulfur was no longer exposed on the surface of material. At the same time, S/C/PEOhad an improved conductive network due to the tighter contact between carbon andsulfur. PEO coating layer could adapt to the volume expansion of the sulfur duringcycling, more important, it could prevent the polysulfides from diffusing out of thesulfur cathode. S/C/PEO composite delivered an initial discharge capacity of989.6mAh/g at1C and remained648.3mAh/g at100th. Moreover, the Coulomb efficiencyof S/C/PEO was as high as~98%during the latter105cycles. PEO based solid-stateelectrolyte and electrolyte with PEO additive was prepared to investigate the cyclingperformance of lithium sulfur batteries.