Design and Construction of Sodium Polysulfides Defense System for Room-Temperature Na-S Battery.

Room-temperature Na-S batteries are facing one of the most serious challenges of charge/discharge with long cycling stability due to the severe shuttle effect and volume expansion. Herein, a sodium polysulfides defense system is presented by designing and constructing the cathode-separator double barriers. In this strategy, the hollow carbon spheres are decorated with MoS (HCS/MoS) as the S carrier (S@HCS/MoS). Meanwhile, the HCS/MoS composite is uniformly coated on the surface of the glass fiber as the separator. During the discharge process, the MoS can adsorb soluble polysulfides (NaPSs) intermediates and the hollow carbon spheres can improve the conductivity of S as well as act as the reservoir for electrolyte and NaPSs, inhibiting them from entering the anode to make Na deteriorate. As a result, the cathode-separator group applied to room-temperature Na-S battery can enable a capacity of ≈1309 mAh g at 0.1 C and long cycling life up to 1000 cycles at 1 C. This study provides a novel and effective way to develop durable room-temperature Na-S batteries.