Reduced polysulfide shuttle in lithium-sulfur batteries using Nafion-based separators

Nafion-coated polypropylene separator (Celgard 2500) is used as cation-selective membrane for lithium sulfur batteries to suppress polysulfide diffusion enhancing the charge efficiency of the cells especially at low charge/discharge rates. The charge efficiency of the 10th cycle rises from about 70% to nearly 90% at a rate of C/20. The reduction of polysulfide penetration through the Nafion-coated Celgard 2500 is also proven by visual characterization. FTIR and SEM investigations verify a smooth and dense Nafion-coating on the porous polypropylene backbone of the separator. The influence of Nafion-loading on rate capability and discharge voltage is investigated by galvanostatic charge-discharge measurements. With the lowest Nafion-loading of 0.25 mg cm-2 we are able to achieve a rate capability comparable to uncoated Celgard 2500 up to current densities of 3 mA cm-2, whereas the functionality as polysulfide shuttle inhibitor is largely preserved.