Multifunctional Separator with Porous Carbon/Multi-Walled Carbon Nanotube Coating for Advanced Lithium−Sulfur Batteries

Graphical Divide and conquer : A porous carbon (PC) with a high specific surface area and large pore volume, prepared from an abundant industrial byproduct (coal tar pitch, CTP), is composited with multi-walled carbon nanotubes (MWCNTs) through a heat-treatment method. The PC/MWCNT composite is deposited onto one side of a polypropylene (PP) separator by using a slurry coating method. The modified separator is then applied in Li−S batteries with promising results. An issue associated with lithium−sulfur (Li−S) batteries is polysulfide dissolution, leading to the serious crossover of polysulfide to the Li anode. To address this issue, we report on a multifunctional separator prepared by introducing a porous carbon/multi-walled carbon nanotube (PC/MWCNT) composite into a commercial separator. It shows that the PC/MWCNT composite is able to enhance the interfacial interaction between the coating and the polysulfide and provides a large surface area for absorbing the polysulfide, thus improving the electrical conductivity. It has been demonstrated that the Li−S cell constructed with the PC/MWCNT composite separator results in a reversible capacity as high as 659 mAh g −1 after 200 cycles at 0.5 C, and the average capacity fading rate of the cell is about 0.138 % per cycle. The performance improvement is attributed to a reduction in the crossover rate of polysulfide through the composite separator as a result of the polysulfide absorption by PC/MWCNT layer.