A free-standing carbon nanofiber interlayer for high-performance lithium-sulfur batteries

Free-standing porous carbon nanofibers with tunable surface area and pore structure have been investigated as an interlayer between the sulfur cathode and the separator to inhibit the shuttling of the intermediate polysulfides in lithium-sulfur (Li-S) batteries. Specifically, the effects of thickness, surface area, and pore size distribution of carbon nanofiber (CNF) interlayers on the performance of Li-S batteries have been studied. The carbon nanofiber interlayer not only reduces the electrochemical resistance but also localizes the migrating polysulfides and traps them, thereby improving the discharge capacity as well as cyclability. It was found that the optimum thickness of the interlayer is a critical factor to achieve good cell performance, in addition to the surface area and pore structure. A high initial discharge capacity of 1549 mA h g(-1) at C/5 rate, which is 92% of the theoretical capacity of sulfur, with 98% average coulombic efficiency and 83% capacity retention after 100 cycles was obtained with a meso-microporous carbon nanofiber interlayer.