Pentagon Defects Accelerating Polysulfides Conversion Enabled High-Performance Sodium–Sulfur Batteries

Abstract

Porous carbon materials with high electrical conductivity and superior mechanical strength have been demonstrated to be one of most promising sulfur hosts for room-temperature sodium–sulfur (RT Na–S) batteries. However, the nonpolar surface of intact graphite lattice displays weak interaction toward the polar polysulfides, thereby resulting in the notorious shuttle effect and poor sulfur conversion kinetics. Herein, pentagon defects are designed into the graphite lattice to break the integrity of π-conjugation, making the localized electron distribution to simultaneously enhance the polysulfide affinity and accelerate sulfur conversion kinetics. Notably, the as-synthesized carbon materials as the sulfur host exhibit a high reversible capacity of 1275 mAh g−1 at 0.1 C after 100 cycles and long-term cycling stability with low-capacity decay of only 0.035% per cycle at 3 C over 600 cycles. Density functional theory calculations and electrochemical experiments confirm that pentagon defects could efficiently accelerate the chemical interaction between pentagon carbon atoms and polysulfides, and markedly lower the sulfur conversion kinetics in comparison with intact graphene. This research offers a basis for designing intrinsic pentagon defects in carbon materials as efficient catalysts for RT Na–S batteries.