Altering the Electrochemical Pathway of Sulfur Chemistry with Oxygen for High Energy Density and Low Shuttling in a Na/S Battery

In this work, we demonstrate that intrinsically altering the reaction pathway of a sulfur-based cathode with designed additional redox activities could simultaneously suppress polysulfide shuttling and enhance energy density. A new hybrid sulfur–oxygen chemistry was described for room-temperature Na/S batteries, where the solvated sodium–oxygen reaction in the electrolyte redirected the cathode chemistry via the formation of NaO2–Na2Sn (1< n ≤ 4) clusters at the nanoscale. These intermediate oxy-sulfur species serve as an effective mediator to immobilize the polysulfide species and unlock high specific capacity from the hybrid cathode. This new cathode chemistry delivers a high reversible capacity of over 1400 mA h/g, low overpotential (∼250 mV), and stable cycling performance (over 800 mA h/g after 50 cycles). The judicious hybridization of oxygen and sulfur chemistries has resolved the persistent degradation that has been plaguing all sulfur-based cathodes and enabled a high energy and reversible Na/S battery at room temperature.