LAUSR

The room‐temperature sodium‐sulfur (RT Na‐S) batteries have been seriously hindered in their practical application due to the sluggish redox kinetics and incomplete conversion of polysulfides. In this study, a structure‐determined Keggin‐type heteropolyvanadotungstate of H5PW10V2O40·30H2O (PW10V2) is engineered and reveal its catalytic mechanism in RT Na‐S system. With the assistance of precise V sites and highly reversible multi‐electron redox properties, PW10V2 as a bidirectional molecular catalyst expedites the complete conversions between polysulfides and the insoluble sodium sulfide, while undergoing the reversible transformation between its reduced and oxidized states. Furthermore, PW10V2 with multicenter active sites can capture polysulfides efficiently. Consequently, the cell with the constructed PW10V2‐based modified separator achieves the perdurable cyclability up to 4000 loops even at 10 C toward an exceptionally low capacity decay rate of 0.012% per cycle, far surpassing those of current state‐of‐the‐art RT Na‐S batteries that employ the functional materials based on separator. This work first demonstrates the underlying electrochemical reaction processes of polyoxometalate‐based functional materials, which guides solving the challenging issues related to sodium polysulfides in RT Na‐S batteries.