All-solid-state sodium-sulfur battery showing full capacity with activated carbon MSP20-sulfur-Na3SbS4 composite

The need for an effective design of composite electrodes in all-solid-state Na-S batteries is warranted because of their slow charge-discharge reactions. By employing a composite of activated carbon MSP20, sulfur, and Na3SbS4 as the positive electrode material, we developed an effective all-solid-state Na-S battery that demonstrated the advantages of exhibiting a high capacity and good cyclability. Further, we discovered that filling the carbon micropores with sulfur and combining with highly conductive Na3SbS4, results in a reversible two-electron reaction between S and Na2S. This all-solid-state Na-S battery, operating at room temperature, demonstrates a high capacity of 1560 mAh per gram of sulfur (ca. 330 mAh per gram of positive electrode) and a capacity retention of 93% after 50 cycles. Decreasing the size of the S-MSP20 particles coated with Na3SbS4 in a liquid phase process was observed to reduce the volume change of the particles during charge and discharge cycles, which resulted in an excellent electrochemical performance.