AbstractBased on the preliminary investigation of the intermediate temperature sodium‐sulfur (IT‐NaS) battery (150 °C), herein we advance this energy storage system, by retuning the catholyte formulation; namely i) concentration, ii) layer thickness, and iii) cut‐off limits during galvanostatic charge‐discharge cycling, lowering the operating temperature and improving cell design. The systematic implementation of these strategies boosted the cell performance significantly, delivering 112 mAh/g‐sulfur, 90 % of its theoretical specific capacity (125 mAh/g‐sulfur), and 50 deep reversible charge‐discharge cycles with coulombic and round‐trip energy efficiencies of 97±3 % and 73±4 %, respectively. Along with the stability and improvement of cycle life, this study demonstrates, for the first time, the practicality of the tubular IT‐NaS technology at a temperature as low as 125 °C.