Lithium−sulfur (Li−S) batteries have high theoretical energy density but low sulfur utilization due to the inherent insulating nature of sulfur and the shuttle effect of polysulfides. Herein, the CO 2 -activation carbon paper was prepared by poly(pphenylenebenzobisoxazole) (PBO) nanofiber and was first applied as an interlayer for efficiently alleviating the shuttle effect of polysulfides in Li−S batteries. This interlayer exhibits good flexibility and strength with rich −C�O and −COOH functional groups on the three-dimensional porous structure, which improves chemical adsorption on Li 2 S x species and ion rapid diffusion via interconnected diffusion channels and thus enhances the electrochemical kinetics. The initial specific capacity is 1367.4 mAh g −1 and remains 999.8 mAh g −1 after 200 cycles at 0.2C and 780.1 mAh g −1 at 5C, and the Coulombic efficiency is high, up to 99.8%, which is much better than that for the carbon paper without CO 2 activation. The highly conductive flexible PBO carbon paper may bring breakthroughs in performance and thus lead to more practical applications of Li−S batteries.

Herein, we reported that KOH impregnation can generate a large number of porous structures with fruitful nitrogen self-doped groups during the carbonized process for poly (p-phenylene terephthalamide) fiber and poly (p-phenylene benzobisoxazole) fiber (denoted as PPTA and PBO, respectively). The intrinsical insulation, volume change, and shuttle effect of polysulfides then can be more significantly improved for the PBO-coated separator than the PPTA case. The discharge capacity primary achieves 1,322 mA h/g, which retains 827 mA h/g even after 200 cycles at 0.2 C for the cell with PBO-coated separator. The reversible specific discharge capacity maintains 841 mA h/g with a Coulomb efficiency of 99.7% at 5 C. The nitrogen self-doped nanocarbon particles are etched by KOH with the simple one-step preparation, which has promising application as Li-S battery cathode.