CO2-Activation Nanofiber Carbon Paper as a High-Performance Interlayer for Trapping Polysulfides in Li–S Batteries

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 CO2-activation carbon paper was prepared by poly(p-phenylenebenzobisoxazole) (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 Li2Sx 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 CO2 activation. The highly conductive flexible PBO carbon paper may bring breakthroughs in performance and thus lead to more practical applications of Li–S batteries.