Continuous Carbon Channels Enable Full Na-Ion Accessibility for Superior Room-Temperature Na–S Batteries

Porous carbon has been widely used as an efficient host to encapsulate highly active molecular sulfur (S) in Li–S and Na–S batteries. However, for these sub-nanosized pores, it is a challenge to provide fully accessible sodium ions with unobstructed channels during cycling, particularly for high sulfur content. It is well recognized that solid interphase with full coverage over the designed architectures plays critical roles in promoting rapid charge transfer and stable conversion reactions in batteries, whereas constructing a high-ionic-conductivity solid interphase in the pores is very difficult. Herein, unique continuous carbonaceous pores are tailored, which can serve as multifunctional channels to encapsulate highly active S and provide fully accessible pathways for sodium ions. Solid sodium sulfide interphase layers are also realized in the channels, showing high Na-ion conductivity toward stabilizing the redox kinetics of the S cathode during charge/discharge processes. This systematically designed carbon-hosted sulfur cathode delivers superior cycling performance (420 mAh g−1 at 2 A g−1 after 2000 cycles), high capacity retention of ≈90% over 500 cycles at current density of 0.5 A g−1, and outstanding rate capability (470 mAh g−1 at 5 A g−1) for room-temperature sodium–sulfur batteries.